Fairchild FAN9611 Interleaved dual bcm pfc controller Datasheet

FAN9611 / FAN9612
Interleaved Dual BCM PFC Controllers
Features

Sync-Lock™ Interleaving Technology for 180°
Out-of-Phase Synchronization Under All Conditions


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


Automatic Phase Disable at Light Load




Minimum Restart Frequency to Avoid Audible Noise




Open-Feedback Protection
Dead-Phase Detect Protection
2.0A Sink, 1.0A Source, High-Current Gate Drivers
High Power Factor, Low Total Harmonic Distortion
Voltage-Mode Control with (VIN)2 Feedforward
Closed-Loop Soft-Start with User-Programmable
Soft-Start Time for Reduced Overshoot
Maximum Switching Frequency Clamp
Brownout Protection with Soft Recovery
Non-Latching OVP on FB Pin and Latching SecondLevel Protection on OVP Pin
Power-Limit and Current Protection for Each Phase
Low Startup Current of 80µA Typical
Works with DC and 50Hz to 400Hz AC Inputs
Applications
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100-1000W AC-DC Power Supplies
Large Screen LCD-TV, PDP-TV, RP-TV Power
High-Efficiency Desktop and Server Power Supplies
Networking and Telecom Power Supplies
Solar Micro Inverters
Description
The FAN9611/12 family of interleaved dual BoundaryConduction-Mode (BCM) Power-Factor-Correction (PFC)
controllers operate two parallel-connected boost power
trains 180° out of phase. Interleaving extends the
maximum practical power level of the control technique
from about 300W to greater than 800W. Unlike the
continuous conduction mode (CCM) technique often
used at higher power levels, BCM offers inherent zerocurrent switching of the boost diodes, which permits the
use of less expensive diodes without sacrificing
efficiency. Furthermore, the input and output filters can
be smaller due to ripple current cancellation and effective
doubling of the switching frequency.
The converters operate with variable frequency, which is
a function of the load and the instantaneous input /
output voltages. The switching frequency is limited
between 16.5kHz and 525kHz. The Pulse Width
Modulators (PWM) implement voltage-mode control with
input voltage feedforward. When configured for PFC
applications, the slow voltage regulation loop results in
constant on-time operation within a line cycle. This PWM
method, combined with the BCM operation of the boost
converters, provides automatic power factor correction.
The controllers offers bias UVLO (10V / 7.5V for
FAN9611 and 12.5V / 7.5V for FAN9612), input
brownout, over-current, open-feedback, output overvoltage, and redundant latching over-voltage protections.
Furthermore, the converters’ output power is limited
independently of the input RMS voltage. Synchronization
between the power stages is maintained under all
operating conditions.
Figure 1. Simplified Application Diagram
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
April 2011
Part Number
Package
Packing Method
Packing
Quantity
FAN9611MX
16-Lead, Small Outline Integrated Circuit (SOIC)
Tape and Reel
2,500
FAN9612MX
16-Lead, Small Outline Integrated Circuit (SOIC)
Tape and Reel
2,500
This device passed wave soldering test by JESD22A-111.
Package Outlines
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Ordering Information
Figure 2. SOIC-16 (Top View)
Thermal Resistance Table
Thermal Resistance
Package
16-Lead SOIC
Suffix
M
ΘJL(1)
ΘJA(2)
35°C/W
50 – 120°C/W(3)
Notes:
1. Typical ΘJL is specified from semiconductor junction to lead.
2. Typical ΘJA is dependent on the PCB design and operating conditions, such as air flow. The range of values
covers a variety of operating conditions utilizing natural convection with no heatsink on the package.
3. This typical range is an estimate; actual values depend on the application.
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
2
V IN
L2a
D2
V OUT
V LINE
L2b
R ZCD2
C IN
RIN1
L1a
D1
R ZCD1
L1b
AC IN
EMI Filter
RIN2
C 5VB
1
ZCD1
CS1 16
2
ZCD2
CS2 15
3
5VB
VDD 14
4
MOT
DRV1 13
5
AGND
DRV2 12
6
SS
PGND 11
7
COMP
8
FB
R MOT
R INHYST
C SS
R FB1
V BIAS
R FB2
Q1
RG1
Q2
RG2
R OV1
R COMP
VIN 10
C COMP,LF
C COMP,HF
RCS1
OVP 9
C VDD1
C VDD2
C INF
Figure 3. Typical Application Diagram
Block Diagram
RCS2
R OV2
C OUT
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Typical Application Diagram
Figure 4. Block Diagram
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
3
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Pin Configuration
Figure 5. Pin Layout (Top-View)
Pin Definitions
Pin #
Name
Description
1
ZCD1
Zero Current Detector for Phase 1 of the interleaved boost power stage.
2
ZCD2
Zero Current Detector for Phase 2 of the interleaved boost power stage.
3
5VB
5V Bias. Bypass pin for the internal supply, which powers all control circuitry on the IC.
4
MOT
Maximum On-Time adjust for the individual power stages.
5
AGND
Analog Ground. Reference potential for all setup signals.
6
SS
7
COMP
8
FB
9
OVP
Output Voltage monitor for the independent, second-level, latched OVP protection.
10
VIN
Input Voltage monitor for brownout protection and input-voltage feedforward.
11
PGND
Power Ground connection.
12
DRV2
Gate Drive Output for Phase 2 of the interleaved boost power stage.
13
DRV1
Gate Drive Output for Phase 1 of the interleaved boost power stage.
14
VDD
External Bias Supply for the IC.
15
CS2
Current Sense Input for Phase 2 of the interleaved boost power stage.
16
CS1
Current Sense Input for Phase 1 of the interleaved boost power stage.
Soft-Start Capacitor. Connected to the non-inverting input of the error amplifier.
Compensation Network connection to the output of the gM error amplifier
Feedback pin to sense the converter’s output voltage; inverting input of the error amplifier.
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
4
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be
operable above the recommended operating conditions and stressing the parts to these levels is not recommended.
In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability.
The absolute maximum ratings are stress ratings only.
Symbol
Parameter
Min.
Max.
Unit
VDD
Supply Voltage to AGND & PGND
-0.3
20.0
V
VBIAS
5VB Voltage to AGND & PGND
-0.3
5.5
V
Voltage On Input Pins to AGND (Except FB Pin)
-0.3
VBIAS + 0.3
V
Voltage On FB Pin (Current Limited)
-0.3
VDD + 0.8
V
Voltage On Output Pins to PGND (DRV1, DRV2)
-0.3
VDD + 0.3
V
Gate Drive Peak Output Current (Transient)
2.5
A
Gate Drive Output Current (DC)
0.05
A
TL
Lead Soldering Temperature (10 Seconds)
+260
ºC
TJ
Junction Temperature
-40
+150
ºC
TSTG
Storage Temperature
-65
+150
ºC
IOH, IOL
Recommended Operating Conditions
The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended
operating conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not
recommend exceeding them or designing to Absolute Maximum Ratings.
Symbol
Parameter
Min.
Typ.
Max.
Unit
12
18
V
5
V
VDD
Supply Voltage Range
9
VINS
Signal Input Voltage
0
ISNK
Output Current Sinking (DRV1, DRV2)
1.5
2.0
A
ISRC
Output Current Sourcing (DRV1, DRV2)
0.8
1.0
A
(4)
LMISMATCH Boost Inductor Mismatch
TA
±5%
Operating Ambient Temperature
-40
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Absolute Maximum Ratings
±10%
+125
ºC
Note:
4. While the recommended maximum inductor mismatch is ±10% for optimal current sharing and ripple-current
cancellation, there is no absolute maximum limit. If the mismatch is greater than ±10%, current sharing is
proportionately worse, requiring over-design of the power supply. However, the accurate 180° out-of-phase
synchronization is still maintained, providing current cancellation, although its effectiveness is reduced.
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
5
Unless otherwise noted, VDD = 12V, TJ = -40°C to +125°C. Currents are defined as positive into the device and
negative out of the device.
Symbol
Parameter
Conditions
Min.
Typ.
Max.
Unit
VDD = VON – 0.2V
80
110
µA
Output Not Switching
3.7
5.2
mA
4
6
mA
9.5
10.0
10.5
V
12.0
12.5
13.0
V
7.0
7.5
8.0
V
Supply
ISTARTUP
IDD
IDD_DYM
VON
VOFF
VHYS
Startup Supply Current
Operating Current
Dynamic Operating Current
(5)
UVLO Start Threshold, FAN9611
UVLO Start Threshold, FAN9612
UVLO Stop Threshold Voltage
UVLO Hysteresis, FAN9611
UVLO Hysteresis, FAN9612
fSW = 50kHz; CLOAD = 2nF
VDD Increasing
VDD Decreasing
VON – VOFF
2.5
V
5.0
V
Bias Regulator (C5VB = 0.1µF)
TA = 25°C; ILOAD = 1mA
V5VB
IOUT_MAX
5VB Output Voltage
Total Variation Over Line,
Load, and Temperature
Maximum Output Current
5.0
4.8
5.2
5.0
V
mA
Error Amplifier
TA = 25°C
2.95
Total Variation Over Line,
Load, and Temperature
2.91
3.075
Input Bias Current
VFB = 1V to 3V;
|VSS – VFB| ≤ 0.1V
–0.2
0.2
µA
IOUT_SRC
Output Source Current
VSS = 3V; VFB = 2.9V
-13.7
-8
-4
µA
IOUT_SINK
Output Sink Current
VSS = 3V; VFB = 3.1V
4
8
12
µA
VOH
Output High Voltage
4.5
4.7
V5VB
V
VOL
Output Low Voltage
0.0
0.1
0.2
V
gM
Transconductance
50
78
115
µmho
120
195
270
mV
0
µs
VEA
Voltage Reference
IBIAS
ISINK < 100µA
3.00
3.05
V
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Electrical Characteristics
PWM
VRAMP,OFST PWM Ramp Offset
tON,MIN
Minimum On-Time
TA = 25°C
VFB > VSS
Maximum On-Time
VMOT
tON,MAX
Maximum On-Time Voltage
R = 125k
1.16
1.25
1.30
V
Maximum On-Time
R = 125k; VVIN = 2.5V;
VCOMP > 4.5V; TA = 25°C
3.4
5.0
6.6
µs
VFB > VPWM_OFFSET
12.5
16.5
20.0
kHz
400
525
630
kHz
Restart Timer (Each Channel)
fSW,MIN
Minimum Switching Frequency
Frequency Clamp (Each Channel)
fSW,MAX
Maximum Switching Frequency(5)
Continued on the following page…
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
6
Unless otherwise noted, VDD = 12V, TJ = -40°C to +125°C. Currents are defined as positive into the device and
negative out of the device.
Symbol
Parameter
Conditions
Min.
Typ.
Max.
Unit
0.19
0.21
0.23
V
0.2
µA
85
100
ns
–0.1
0
0.1
V
IZCD = 0.5mA
0.8
1.0
1.2
V
IZCD = –0.5mA
–0.7
–0.5
–0.3
V
Current Sense
VCS
CS Input Threshold Voltage Limit
ICS
CS Input Current
VCSX = 0V to 1V
CS to Output Delay
CS Stepped from 0V to 5V
tCS_DELAY
–0.2
Zero Current Detection
VZCD_IN
Input Voltage Threshold(4)
VZCD_H
Input High Clamp Voltage
VZCD_L
Input Low Clamp Voltage
(4)
IZCD_SRC
Source Current Capability
1
mA
IZCD_SNK
Sink Current Capability(4)
10
mA
tZCD_DLY
Turn-On Delay(5)
ZCDx to OUTx
180
ns
VOUTx = VDD/2; CLOAD = 0.1µF
2.0
A
VOUTx = VDD/2; CLOAD = 0.1µF
1.0
A
Rise Time
CLOAD = 1nF, 10% to 90%
10
25
ns
Fall Time
CLOAD = 1nF, 90% to 10%
5
20
ns
Output Voltage During UVLO
VDD = 5V; IOUT = 100µA
1
V
Output
ISINK
ISOURCE
tRISE
tFALL
VO_UVLO
IRVS
OUTx Sink Current (5)
OUTx Source Current
(5)
Reverse Current Withstand
(5)
500
mA
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Electrical Characteristics (Continued)
Soft-Start (CSS = 0.1µF)
ISS_MAX
Maximum Soft-Start Current
VCOMP < 3.0V
–7
–5
–3
µA
ISS_MIN
Minimum Soft-Start Current
VCOMP > 4.5V
–0.40
–0.25
–0.10
µA
0.76
0.925
1.10
V
0.2
µA
(5)
Input Brown-Out Protection
VIN_BO
IVINSNK
Input Brownout Threshold
VVIN > 1.1V
–0.2
VVIN < 0.8V
1.4
2
2.5
µA
VIN Feedforward Upper Limit (5)
3.1
3.7
4.3
V
VFF_UL / VIN_BO
3.6
4.0
4.3
VIN Sink Current
Input-Voltage Feedforward Range
VFF_UL
VFF_RATIO
(5)
Phase Management
VPH,DROP
Phase Dropping Threshold
VCOMP Decreasing, Transition
from 2 to 1 Phase, TA = 25°C
0.66
0.73
0.80
V
VPH,ADD
Phase Adding Threshold
VCOMP Increasing, Transition
from 1 to 2 Phase, TA = 25°C
0.86
0.93
1.00
V
3.15
3.25
3.35
V
Over-Voltage Protection Using FB Pin – Cycle-by-Cycle (Input)
VOVPNL
Non-Latching OVP Threshold
(+8% above VOUT_NOMINAL)
VOVPNL_HYS OVP Hysteresis
TA = 25°C
DRV1=DRV2=0V
FB Decreasing
0.24
V
Over-Voltage Protection Using OVP Pin – Latching (Input)
VOVPLCH
Latching OVP Threshold (+15%)
DRV1=DRV2=0V
3.36
3.50
3.65
V
Note:
5. Not tested in production.
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
7
There are many fundamental differences in CCM and
BCM operations and the respective designs of the boost
converter.
1. Boundary Conduction Mode
The boost converter is the most popular topology for
power factor correction in AC-to-DC power supplies.
This popularity can be attributed to the continuous input
current waveform provided by the boost inductor and to
the fact that the boost converter’s input voltage range
includes 0V. These fundamental properties make close
to unity power factor easier to achieve.
The FAN9611/12 utilizes the boundary conduction mode
control algorithm. The fundamental concept of this
operating mode is that the inductor current starts from
zero in each switching period, as shown in the lower
waveform in Figure 7. When the power transistor of the
boost converter is turned on for a fixed amount of time,
the peak inductor current is proportional to the input
voltage. Since the current waveform is triangular, the
average value in each switching period is also
proportional to the input voltage. In the case of a
sinusoidal input voltage waveform, the input current of
the converter follows the input voltage waveform with
very high accuracy and draws a sinusoidal input current
from the source. This behavior makes the boost
converter in BCM operation an ideal candidate for
power factor correction.
This mode of control of the boost converter results in a
variable switching frequency. The frequency depends
primarily on the selected output voltage, the
instantaneous value of the input voltage, the boost
inductor value, and the output power delivered to the
load. The operating frequency changes as the input
voltage follows the sinusoidal input voltage waveform.
The lowest frequency operation corresponds to the peak
of the sine waveform at the input of the boost converter.
Even larger frequency variation can be observed as the
output power of the converter changes, with maximum
output power resulting in the lowest operating
frequency. Theoretically, under zero-load condition, the
operating frequency of the boost converter would
approach infinity. In practice, there are natural limits to
the highest switching frequency. One such limiting factor
is the resonance between the boost inductor and the
parasitic capacitances of the MOSFET, the diode, and
the winding of the choke, in every switching cycle.
Figure 6. Basic PFC Boost Converter
The boost converter can operate in continuous
conduction mode (CCM) or in boundary conduction
mode (BCM). These two descriptive names refer to the
current flowing in the energy storage inductor of the
boost power stage.
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Theory of Operation
Another important characteristic of the BCM boost
converter is the high ripple current of the boost inductor,
which goes from zero to a controlled peak value in every
switching period. Accordingly, the power switch is
stressed with high peak current. In addition, the high
ripple current must be filtered by an EMI filter to meet
high-frequency
noise
regulations
enforced
for
equipment connecting to the mains. The effects usually
limit the practical output power level of the converter.
Figure 7. CCM vs. BCM Control
As the names indicate, the current in Continuous
Conduction Mode (CCM) is continuous in the inductor;
while in Boundary Conduction Mode (BCM), the new
switching period is initiated when the inductor current
returns to zero.
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
8
The FAN9611/12 control IC is configured to control two
boost converters connected in parallel, both operated in
boundary conduction mode. In this arrangement, the
input and output voltages of the two parallel converters
are the same and each converter is designed to process
approximately half the total output power.
The pulse width modulator implements voltage mode
control. This control method compares an artificial ramp
to the output of the error amplifier to determine the
desired on-time of the converter’s power transistor to
achieve output voltage regulation.
Figure 9. PWM Operation
Figure 8. Interleaved PFC Boost Operation
In FAN9611/12, there are two PWM sections
corresponding to the two parallel power stages. For
proper interleaved operation, two independent 180degree out-of-phase ramps are needed; which
necessitates the two pulse width modulators. To ensure
that the two converters process the same amount of
power, the artificial ramps have the same slope and use
the same control signal generated by the error amplifier.
Parallel power processing is penalized by the increased
number of power components, but offers significant
benefits to keep current and thermal stresses under
control and to increase the power handling capability of
the otherwise limited BCM PFC control solution.
Furthermore, the switches of the two boost converters
can be operated 180 degrees out of phase from each
other. The control of parallel converters operating 180
degrees out of phase is called interleaving. Interleaving
provides considerable ripple current reduction at the
input and output terminals of the power supply, which
favorably affects the input EMI filter requirements and
reduces the high-frequency RMS current of the power
supply output capacitor.
4. Input-Voltage Feedforward
Basic voltage-mode control, as described in the
previous section, provides satisfactory regulation
performance
in most cases. One important
characteristic of the technique is that input voltage
variation to the converter requires a corrective action
from the error amplifier to maintain the output at the
desired voltage. When the error amplifier has adequate
bandwidth, as in most DC-DC applications, it is able to
maintain regulation within a tolerable output voltage
range during input voltage changes.
There is an obvious difficulty in interleaving two BCM
boost converters. Since the converter’s operating
frequency is influenced by component tolerances in the
power stage and in the controller, the two converters
operate at different frequencies. Therefore special
attention must be paid to ensure that the two converters
are locked to 180-degree out-of-phase operation.
Consequently, synchronization is a critical function of an
interleaved boundary conduction mode PFC controller.
It is implemented in the FAN9611/12 using proprietary
and dedicated circuitry called Sync-Lock™ interleaving
technology.
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
a sine square function. Eliminating the line frequency
component from the feedback system is imperative to
maintain low total harmonic distortion (THD) in the input
current waveform.
2. Interleaving
On the other hand, when voltage-mode control is used
in power factor corrector applications; the error amplifier
bandwidth, and its capability to quickly react to input
voltage changes, is severely limited. In these cases, the
input voltage variation can cause excessive overshoot
or droop at the converter output as the input voltage
goes up or down.
To overcome this shortcoming of the voltage-mode
PWM circuit in PFC applications, input-voltage
feedforward is often employed. It can be shown
mathematically that a PWM ramp proportional to the
square of the input voltage rejects the effect of input
voltage variations on the output voltage and eliminates
the need of any correction by the error amplifier.
3. Voltage Regulation, Voltage Mode Control
The power supply’s output voltage is regulated by a
negative feedback loop and a pulse width modulator.
The negative feedback is provided by an error amplifier
that compares the feedback signal at the inverting input
to a reference voltage connected to the non-inverting
input of the amplifier. Similar to other PFC applications,
the error amplifier is compensated with high DC gain for
accurate voltage regulation, but very low bandwidth to
suppress line frequency ripple present across the output
capacitor of the converter. The line frequency ripple is
the result of the constant output power of the converter
and the fact that the input power is the product of a
sinusoidal current and a sinusoidal voltage thus follows
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
9
Figure 10. Input-Voltage Feedforward
Figure 12. PWM Cycle Start
When the PWM ramp is made proportional to the input
voltage squared, the system offers other noteworthy
benefits. The first is the input voltage-independent small
signal gain of the closed loop power supply, which
makes compensation of the voltage regulation loop
much easier. The second side benefit is that the output
of the error amplifier becomes directly proportional to
the input power of the converter. This phenomenon is
very significant and it is re-visited in Section 9
describing light-load operation.
6. Terminating the Conduction Interval
Terminating the conduction period of the boost
transistor in boundary conduction mode controllers is
similar to any other pulse width modulator. During
normal operation, the PWM comparator turns off the
power transistor when the ramp waveform exceeds the
control voltage provided by the error amplifier. In the
FAN9611/12 and in similar voltage-mode PWMs, the
ramp is a linearly rising waveform at one input of the
comparator circuit.
5. Starting a PWM Cycle
Maximum
On-Time
The principle of boundary conduction mode calls for a
pulse width modulator able to operate with variable
frequency and initiate a switching period whenever the
current in the boost inductor reaches zero. Therefore,
BCM controllers cannot utilize a fixed frequency
oscillator circuit to control the operating frequency.
Instead, a zero current detector is used to sense the
inductor current and turn on the power switch once the
current in the boost inductor reaches zero. This process
is facilitated by an auxiliary winding on the boost
inductor. The voltage waveform of the auxiliary winding
can be used for indirect detection of the zero inductor
current condition of the boost inductor. Therefore it
should be connected to the zero current detect input, as
shown in Figure 11.
S
Current Limit
DRV
Q
RD Q
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
At startup condition and in the unlikely case of missing
zero current detection, the lack of an oscillator would
mean that the converter stops operating. To overcome
these situations, a restart timer is employed to kick start
the controller and provide the first turn-on command, as
shown in Figure 12.
PWM
Figure 13. Conduction Interval Termination
In addition to the PWM comparator, the current limit
circuit and a timer circuit limiting the maximum on-time
of the boost transistor can also terminate the gate drive
pulse of the controller. These functions provide
protection for the power switch against excessive
current stress.
7. Protecting the Power Components
In general, power converters are designed with
adequate margin for reliable operation under all
operating conditions. However, it might be difficult to
predict dangerous conditions under transient or certain
fault situations. Therefore, the FAN9611/12 contains
dedicated protection circuits to monitor the individual
peak currents in the boost inductors and in the power
transistors. Furthermore, the boost output voltage is
sensed by two independent mechanisms to provide
over-voltage protection for the power transistors,
rectifier diodes, and the output energy storage capacitor
of the converter.
Figure 11. Simple Zero-Current Detection Method
The auxiliary winding can also be used to generate bias
for the PFC controller when an independent bias power
supply is not present in the system.
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
10
The architecture and operating principle of FAN9611/12
also provides inherent input power limiting capability.
Figure 15. Automatic Phase-Control Operation
10. Brownout Protection with Soft Recovery
An additional protection function usually offered by PFC
ICs is input brownout protection to prevent the converter
from operating below a user-defined minimum input
voltage level. For this function to work, the input voltage
of the converter is monitored. When the voltage falls
below the brownout protection threshold, the converter
stops working. The output voltage of the boost converter
falls until the load stops drawing current from the output
capacitor or until the input voltage gets back to its
nominal range and operation resumes.
Figure 14. On-Time vs. VIN_RMS
When the slope of the PWM ramp is made proportional
to the square of the input RMS voltage, the maximum
on-time of the boost power switch becomes inversely
proportional to the square of VIN,RMS, as represented in
Figure 14. In boundary-conduction mode, the peak
current of the boost transistor is proportional to its on
time. Therefore, controlling the maximum pulse width of
the gate drive signal according to the curve shown is an
effective method to implement an input-voltage
independent power limit for the boost PFC.
As the output falls, the voltage at the feedback pin falls
proportionally, according to the feedback divider ratio.
To facilitate soft recovery after a brownout condition, the
soft-start capacitor – which is also the reference voltage
of the error amplifier – is pulled lower by the feedback
network. This effectively pre-conditions the error
amplifier to provide closed-loop, soft-start-like behavior
during the converter’s recovery from a brownout
situation. Once the input voltage goes above the
brownout protection threshold, the converter resumes
normal operation. The output voltage rises back to the
nominal regulation level following the slowly rising
voltage across the soft-start capacitor.
9. Light-Load Operation (Phase Management)
One of the parameters determining the operating
frequency of a boundary conduction mode converter is
the output power. As the load decreases, lower peak
currents are commanded by the pulse width modulator
to maintain the output voltage at the desired set point.
Lower peak current means shorter on-time for the power
transistor and shorter time interval to ramp the inductor
current back to zero at any given input voltage. As a
result, the operating frequency of the converter
increases under light load condition.
11. Soft Starting the Converter
As the operating frequency and corresponding switching
losses increase, conduction losses diminish at the same
time. Therefore, the power losses of the converter are
dominated by switching losses at light load. This
phenomenon is especially evident in a BCM converter.
During startup, the boost converter peak charges its
output capacitor to the peak value of the input voltage
waveform. The final voltage level, where the output is
regulated during normal operation, is reached after the
converter starts switching. There are two fundamentally
different approaches used in PWM controllers to control
the startup characteristics of a switched-mode power
supply. Both methods use some kind of soft-start
mechanism to reduce the potential overshoot of the
converter’s output after the desired output voltage level
is reached.
To improve light-load efficiency, FAN9611/12 disables
one of the two interleaved boost converters
automatically when the output power falls below
approximately 13% of the maximum power limit level.
By managing the number of phases used at light load,
the FAN9611/12 can maintain high efficiency for a wider
load range of the power supply.
The first method is called open-loop soft-start and relies
on gradually increasing the current or power limit of the
converter during startup. In this case, the voltage error
amplifier is typically saturated, commanding maximum
current until the output voltage reaches its final value. At
that time, the voltage between the error amplifier inputs
changes polarity and the amplifier slowly comes out of
saturation. While the error amplifier recovers and before
it starts controlling the output voltage, the converter
operates with full power. Thus, output voltage overshoot
is unavoidable in converters utilizing the open-loop softstart scheme.
Normal interleaved operation of the two boost
converters resumes automatically once the output
power exceeds approximately 18% of the maximum
power limit level of the converter.
By adjusting maximum on-time (using RMOT), the phase
management thresholds can be adjusted upward,
described in the “Adjusting the Phase-Management
Thresholds” section of this datasheet.
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
8. Power Limit
www.fairchildsemi.com
11
FAN9611/12 employs closed-loop soft-start where the
reference voltage of the error amplifier is slowly
increased to its final value. When the current and power
limits of the converter are properly taken into
consideration, the output voltage of the converter
follows the reference voltage. This ensures that the
error amplifier stays in regulation during soft start and
the output voltage overshoot can be eliminated.
Functional Description
1. Detecting Zero Inductor Current
(ZCD1, ZCD2)
Each ZCD pin is internally clamped close to 0V (GND).
Any capacitance on the pin is ineffective in providing
any delay in ZCD triggering. The internal sense circuit is
a true differentiator to catch the valley of the drain
waveforms. The resistor between the auxiliary winding
of the boost inductor and the ZCD pin is only used for
current limiting. The maximum source current during
zero current detection must be limited to 0.5mA. Source
and sink capability of the pin is about 1mA, providing
sufficient margin for the higher source current required
during the on-time of the power MOSFETs.
Figure 17. 5V Bias
3. Maximum On-Time Control (MOT)
Maximum on-time, MOT, (of the boost MOSFET) is set
by a resistor to analog ground (AGND). The
FAN9611/12 implements input-voltage feedforward. The
maximum on-time is a function of the RMS input
voltage. The voltage on the MOT pin is 1.25V during
operation (constant DC voltage). The maximum on-time
of the power MOSFETs can be approximated by:
tON , MAX  RMOT 120 1012 
Figure 16. Zero-Current Detect Circuit
The RZCD resistor value can be approximated by:
R ZCD 
V
N AUX
1
 O 
0.5 mA 2 N BOOST
2.4
1
 2
1.25 VINSNS
, PK
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
This method is especially dangerous in power-factorcorrector applications because the error amplifier’s
bandwidth is typically limited to a very low crossover
frequency. The slow response of the amplifier can
cause considerable overshoot at the output.
(2)
where VINSNS,PK is the peak of the AC input voltage as
measured at the VIN pin (must be divided down, see the
VIN pin description).
(1)
2. 5V Bias Rail (5VB)
This is the bypass capacitor pin for the internal 5V bias
rail powering the control circuitry. The recommended
capacitor value is 220nF. At least a 100nF, good-quality,
high-frequency, ceramic capacitor should be placed in
close proximity to the pin.
The 5V rail is a switched rail. It is actively held LOW
when the FAN9611/12 is in under-voltage lockout. Once
the UVLO turn-on threshold is exceeded at the VDD pin,
the 5V rail is turned on, providing a sharp edge that can
be used as an indication that the chip is running.
Potentially, this behavior can be utilized to control the
inrush current limiting circuit.
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
Figure 18. Maximum On-Time Control (MOT)
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12
Analog ground connection (AGND) is the GND for all
control logic biased from the 5V rail. Internally, the
AGND and PGND pins are tied together by two antiparallel diodes to limit ground bounce difference due to
bond wire inductances during the switching actions of
the high-current gate drive circuits. It is recommended to
connect AGND and PGND pins together with a short,
low-impedance trace on the PCB (right under the IC).
Furthermore, during brownout condition, the output
voltage of the converter might fall, which is reflected at
the FB pin. When FB voltage goes 0.5V below the
voltage on the SS pin, it starts discharging the soft-start
capacitor. The soft-start capacitor remains 0.5V above
the FB voltage. When the brownout condition is over,
the converter returns to normal operation gracefully,
following the slow ramp up of the soft-start capacitor at
the non-inverting input of the error amplifier.
PGND is the reference potential (0V) for the highcurrent gate-drive circuit. Two bypass capacitors should
be connected between the VDD pin and the PGND pin.
One is the VDD energy storage capacitor, which provides
bias power during startup until the bootstrap power
supply comes up. The other capacitor shall be a goodquality ceramic bypass capacitor, as close as possible
to PGND and VDD pins to filter the high peak currents
of the gate driver circuits. The value of the ceramic
bypass capacitor is a strong function of the gate charge
requirement of the power MOSFETs and its
recommended value is between 1µF and 4.7µF to
ensure proper operation.
5. Soft-Start (SS)
Soft-start is programmed with a capacitor between the
SS pin and AGND. This is the non-inverting input of the
transconductance (gM) error amplifier.
At startup, the soft-start capacitor is quickly pre-charged
to a voltage approximately 0.5V below the voltage on
the feedback pin (FB) to minimize startup delay. Then a
5µA current source takes over and charges the soft-start
capacitor slowly, ramping up the voltage reference of
the error amplifier. By ramping up the reference slowly,
the voltage regulation loop can stay closed, actively
controlling the output voltage during startup. While the
SS capacitor is charging, the output of the error
amplifier is monitored. In case the error voltage (COMP)
ever exceeds 3.5V, indicating that the voltage loop is
close to saturation, the 5µA soft-start current is reduced.
Therefore, the soft start is automatically extended to
reduce the current needed to charge the output
capacitor, reducing the output power during startup.
This mechanism is integrated to prevent the voltage
loop from saturation. The charge current of the soft-start
capacitor can be reduced from the initial 5µA to as low
as 0.5µA minimum.
Figure 19. Soft-Start Programming
6. Error Amplifier Compensation (COMP)
COMP pin is the output of the error amplifier. The
voltage loop is compensated by a combination of RS
and CS to AGND at this pin. The control range of the
error amplifier is between 0.195V and 4.3V. When the
COMP voltage is below about 0.195V, the PWM circuit
skips pulses. Above 4.3V, the maximum on-time limit
terminates the conduction of the boost switches.
Due to the input-voltage feedforward, the output of the
error amplifier is proportional to the input power of the
converter, independent of the input voltage. In addition,
also due to the input-voltage feedforward, the maximum
power capability of the converter and the loop gain is
independent of the input voltage. The controller’s phasemanagement circuit monitors the error amplifier output
and switches to single-phase operation when the COMP
voltage falls below 0.73V and returns to two-phase
operation when the error voltage exceeds 0.93V. These
thresholds correspond to about 13% and 18% of the
maximum power capability of the design.
In addition to modulating the soft-start current into the
SS capacitor, the SS pin is clamped 0.2V above the FB
pin. This is useful in preventing the SS capacitor from
running away from the FB pin and defeating the closedloop soft-start. During the zero crossing of the input
source waveform, the input power is almost zero and
the output voltage can not be raised. Therefore the FB
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
voltage stays flat or even decays while the SS voltage
keeps rising. This is a problem if closed-loop soft-start
should be maintained. By clamping the SS voltage to
the FB pin, this problem can be mitigated.
4. Analog Ground (AGND) and Power Ground
(PGND)
www.fairchildsemi.com
13
7. Output Voltage Feedback (FB)
8. Secondary Output Voltage Sense (OVP)
The feedback pin receives the divided-down output
voltage of the converter. In regulation, the FB pin should
be 3V, which is the reference used at the non-inverting
input of the error amplifier. Due to the gM type error
amplifier, the FB pin is always proportional to the output
voltage and can be used for over-voltage protection as
well. A non-latching over-voltage detection circuit
monitors the FB pin and prevents the boost MOSFETs
from turning on when the FB voltage exceeds 3.25V.
Operation resumes automatically when the FB voltage
returns to its nominal 3V level.
A second-level latching over-voltage protection can be
implemented using the OVP pin of the controller. The
threshold of this circuit is set to 3.5V. There are two
ways to program the secondary OVP.
Option 1, as shown in Figure 22, is to connect the OVP
pin to the FB pin. In addition to the standard nonlatching OVP (set at ~8%), this configuration provides a
second OVP protection (set at ~15%), which is latched.
In the case where redundant over-voltage protection is
preferred (also called double-OVP protection), a second
separate divider from the output voltage can be used, as
shown by Option 2 in Figure 22. In this case, the
latching OVP protection level can be independently
established below or above the non-latching OVP
threshold, which is based on the feedback voltage (at
the FB pin).
The open feedback detection circuit is also connected to
the FB pin. Since the output of the boost converter is
charged to the peak of the input AC voltage when power
is applied to the power supply, the detection circuit
monitors the presence of this voltage. If the FB pin is
below 0.5V, which would indicate a missing feedback
divider (or wrong value causing dangerously-high
regulation voltage), the FAN9611/12 does not send out
gate drive signals to the boost transistors.
External
Components
Internal
Circuits
To SS
VOUT
+200 mV,
–500 mV,
Clamp
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Figure 20. Error Amplifier Compensation Circuitry
If latching OVP protection is not desired at all, the OVP
pin should be grounded (Option 3).
To Phase /
Gain
Control
gM Error
Amplifier
8
FB
Figure 22. Secondary Over-Voltage Protection
Circuit
Figure 21. Output-Voltage Feedback Circuit
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
14
The input AC voltage is sensed at the VIN pin. The input
voltage is used in three functions: input under-voltage
lockout (brownout protection), input over-voltage
protection, and input voltage feedforward in the PWM
control circuit. All the functions require the RMS value of
the input voltage waveform. Since the RMS value of the
AC input voltage is directly proportional to its peak, it is
sufficient to find the peak instead of the more
complicated and slower method of integrating the input
voltage over a half line cycle. The internal circuit of the
VIN pin works with peak detection of the input AC
waveforms. One of the important benefits of this
approach is that the peak indicates the correct RMS
value even at no load when the HF filter capacitor at the
input side of the boost converter is not discharged
around the zero crossing of the line waveform. Another
notable benefit is that during line transients, when the
peak exceeds the previously measured value, the inputvoltage feedforward circuit can react immediately,
without waiting for a valid integral value at the end of the
half line period. Furthermore, lack of zero crossing
The valid range for the peak of the AC input is between
approximately 0.925V and 3.7V. This range is optimized
for universal input voltage range of operation. If the
peak of the sense voltage remains below the 0.925V
threshold, input under-voltage or brownout condition is
declared and the FAN9611/12 stops operating. When
the VIN voltage exceeds 3.7V, the FAN9611/12 input
voltage sense circuit saturates and the feedforward
circuit is not able to follow the input any higher.
Consequently, the slope of the PWM ramp remains
constant corresponding to the VIN = 3.7V level
amplitude for any VIN voltage above 3.7V.
The input voltage is measured by a tracking analog-todigital converter, which keeps the highest value (peak
voltage) of the input voltage waveform. Once a
measurement is taken, the converter tracks the input for
at least 12ms before a new value is taken. This delay
ensures at least one new peak value is captured before
the new value is used.
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
detection could fool the integrator while the peak
detector works properly during light-load operation.
9. Input Voltage Sensing (VIN)
Figure 23. Input Voltage Sensing Circuit
The measured peak value is then used in the following
half-line cycle while a new measurement is executed to
be used in the next half line cycle. This operation is
synchronized to the zero crossing of the line waveform.
Since the input voltage measurement is held steady
during the line half periods, this technique does not feed
any AC ripple into the control loop. If line zero crossing
detection is missing, the FAN9611/12 measures the
input voltage in every 32ms; it can operate from a DC
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
input as well. The following figures provide detail about
the input voltage sensing method of the controller.
As shown in the waveforms, input voltage feedforward is
instantaneous when the line voltage increases and has
a half line cycle delay when the input voltage decreases.
Any increase in input voltage would cause output over
voltage due to the slow nature of the voltage regulation
loop. This is successfully mitigated by the immediate
action of the input-voltage feedforward circuit.
www.fairchildsemi.com
15
The purpose of the MillerDrive™ architecture is to
speed switching by providing high current during the
Miller plateau region when the gate-drain capacitance of
the MOSFET is being charged or discharged as part of
the turn-on / turn-off process.
10. Gate Drive Outputs (DRV1; DRV2)
High-current driver outputs DRV1 and DRV2 have the
capability to sink a minimum of 2A and source 1A. Due
to the low impedance of these drivers, the 1A source
current must be actively limited by an external gate
resistor. The minimum external gate resistance is:
The output pin slew rate is determined by VDD voltage
and the load on the output. It is not user adjustable, but
if a slower rise or fall time at the MOSFET gate is
needed, a series resistor can be added.
VDD
(3)
1A
To take advantage of the higher sink current capability
of the drivers, the gate resistor can be bypassed by a
small diode to facilitate faster turn-off of the power
MOSFETs. Traditional fast turn-off circuit using a PNP
transistor instead of a simple bypass diode can be
considered as well.
RGATE 
VDD
It is also imperative that the inductance of the gate drive
loop is minimized to avoid excessive ringing. If optimum
layout is not possible or the controller is placed on a
daughter card, it is recommended to use an external
driver circuit located near the gate and source terminals
of the boost MOSFET transistors. Small gate charge
power MOSFETs can be driven by a single 1A gate
driver, such as the FAN3111C; while higher gate charge
devices might require higher gate drive current capable
devices, such as the single-2A FAN3100C or the dual2A FAN3227C family of drivers.
VOUT
11. MillerDrive™ Gate Drive Technology
Figure 25. Current-Sense Protection Circuits
FAN9611/12 output stage incorporates the MillerDrive™
architecture shown in Figure 25. It is a combination of
bipolar and MOS devices which are capable of providing
large currents over a wide range of supply voltage and
temperature variations. The bipolar devices carry the
bulk of the current as OUT swings between 1/3 to 2/3
VDD and the MOS devices pull the output to the high
or low rail.
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Figure 24. Input Voltage Sensing Waveforms
www.fairchildsemi.com
16
This is the main bias source for the FAN9611/12. The
operating voltage range is between 8V and 18V. The
VDD voltage is monitored by the under-voltage lockout
(UVLO) circuit. At power-up, the VDD voltage must
exceed 10.0V (±0.5V) for FAN9611 and exceed 12.5V
(±0.5V) for FAN9612 to enable operation. Both the
FAN9611 and the FAN9612 stops operating when the
VDD voltage falls below 7.5V (±0.5V). See PGND pin
description for important bypass information.
13. Current-Sense Protection (CS1, CS2)
The FAN9611/12 uses independent over-current
protection for each of the power MOSFETs. The
current-sense thresholds at the CS1 and CS2 pins are
approximately 0.2V. The current measurements are
strictly for protection purposes and are not part of the
control algorithm. The pins can be directly connected to
the non-grounded end of the current-sense resistors
because the usual R-C filters of the leading-edge
current spike are integrated in the IC.
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
Figure 26. Current-Sense Protection Circuits
The time constant of the internal filter is approximately:
  27k  5pF  130ns
or
P 
1
 1.2MHz
2    27k  5 pF
(4)
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
12. Bias Supply (VDD)
www.fairchildsemi.com
17
2. FAN9612 Startup with 12V Bias (Less than
UVLO)
1. Synchronization and Timing Functions
The
FAN9611/12
employs
a
sophisticated
synchronization sub-system. At the heart of the system
is a dual-channel switching-frequency detector that
measures the switching period of each channel in every
switching cycle and locks their operating phase 180
degrees out of phase from each other. The slower
operating frequency channel is dominant, but there is no
master-slave arrangement. Moreover, as the frequency
constantly changes due to the varying input voltage,
either channel can be the slower dominant channel.
The FAN9612 (not FAN9611) is designed so that the
controller can start even if the auxiliary bias voltage is
less than the controller’s under-voltage lockout start
threshold. This is useful if the auxiliary power is 12V or
below. This configuration also allows bias power
designs using a bootstrap winding to start the FAN9612
without a dedicated startup resistor.
In the boost PFC topology, the output voltage is precharged to the peak line voltage by the boost diode. As
soon as voltage is present at the output of the boost
converter, current starts to flow through the feedback
resistors from the boost output to GND. Using an
external low-voltage MOSFET in series with the lower
resistor in the feedback divider, as shown in Figure 27;
this current can be diverted to charge the VDD bypass
capacitor of the controller. The upper resistor becomes
a current source to charge the capacitor. To accomplish
this, a small external diode should be connected
between the VDD and FB pins.
As opposed to the most common technique, where the
phase relationship between the channels is provided by
changing the on-time of one of the MOSFETs, the
FAN9611/12 controls the phase relationship by inserting
a turn-on delay before the next switching period starts
for the faster running phase. As shown in the
[1]
literature , the on-time modulation technique is not
stable under all operating conditions, while the off-time
modulation (or delaying the turn-on) is unconditionally
stable under all operating conditions.
a.
As VDD rises past the under-voltage lockout threshold of
the IC, the 5V reference is turned on, which turns on the
external MOSFET and connects the resistor of the
feedback divider to ground. The IC checks if the FB
voltage is below 3.22V, ensuring that the FB pin is in its
normal operating voltage range, before enabling the rest
of the IC operation. The diode between the FB pin and
the VDD pin is reverse biased and the FB pin reverts to
its normal role of output voltage sensing. A simplified
circuit implementation for this proprietary startup method
is shown in Figure 27.
Restart Timer and Dead-Phase Detect
Protection
The restart timer is an integral part of the Sync-Lock™
synchronizing circuit. It ensures exact 180-degree outof-phase operation in restart timer operation. This is an
important safety feature. In the case of a non-operating
phase due to no ZCD detection, missing gate drive
connection (for example no gate resistor), one of the
power components failing in an open circuit, or similar
errors, the other phase is locked into restart timer
operation, preventing it from trying to deliver full power
to the load. This is called the dead-phase detect
protection.
If, for whatever reason, the bias to the IC drops below
the under-voltage lockout level, the startup process is
repeated.
The restart timer is set to approximately 16.5kHz, just
above the audible frequency range, to avoid any
acoustic noise generation.
b.
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Application Information
Frequency Clamp
Just as the restart timer, the frequency clamp is
integrated into the synchronization and ensures exact
180-degree out-of-phase operation when the operating
frequency is limited. This might occur at very light-load
operation or near the zero crossing region of the line
voltage waveform. Limiting the switching frequency at
light load can improve efficiency, but has a negative
effect on power factor since the converter also enters
true DCM operation. The frequency clamp is set to
approximately 525kHz.
Figure 27. Simplified FAN9612 Startup Circuit Using
the Output Feedback Resistors to Provide a
Charging Current
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
18
In some applications, the output voltage of the PFC
boost converter is decreased at low power levels to
boost the light load efficiency of the power supply.
Implementing this function with a circuit external to the
FAN9611/12 is straightforward because the error
amplifier reference (the positive input) is available on
the soft-start (SS) pin, as shown in Figure 28. In the
FAN9611/12 architecture, the power of the converter is
proportional to the voltage on the COMP pin, minus a
small offset. The voltage on the COMP pin is monitored
to determine the operating power of the supply.
Therefore the voltage on the SS pin can be adjusted
lower to achieve the desired lower output voltage.
Several possible implementations to adjust the output
voltage of the boost stage at light load are described in
the application note AN-8021. It includes the universal
output voltage adjust implementation which is
modulated by input voltage to avoid the boost converter
becoming a peak rectifier at high line and light load.
Figure 29. Adjusting Phase Management Thresholds
Since the phase management threshold is fixed at 13%
and 18% of the maximum power limit level, the actual
power management threshold as a percentage of
nominal output power can be adjusted by the ratio
between nominal power and maximum power limit level
as shown in Figure 29. The second plot shows an
example where the maximum power limit level is 1.4
times of nominal output power. By adjusting the
maximum on-time (using RMOT), the phase management
thresholds can be adjusted upward.
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
The default thresholds can be adjusted upward based
on the application requirement; for example, to meet the
Energy STAR 5.0 or the Climate Savers Computing
efficiency requirements at 20% of the load. The phase
drop threshold can be adjusted upward (for example to
25%) by adjusting the maximum on time.
3. Adjusting the Output Voltage with Load
Phase management is implemented such that the
output of the error amplifier (VCOMP) does not have to
change when the system toggles between single-phase
and two-phase operations, as shown in Figure 30. The
output of the error amplifier is proportional to the output
power of the converter independently, whether one or
both phases are operating in the power supply.
Furthermore, because the maximum on-time limit is
applied independently to each pulse-width modulator,
the power handling capability of the converter with only
one phase running is approximately half of the total
output power that can be delivered when both phases
are utilized.
Figure 28. FAN9611/12 Error Amplifier Configuration
4. Adjusting the Output Voltage with Input
Voltage
In some applications, the output voltage of the PFC
boost converter is adjusted based on the input voltage
only. This boost follower implementations increases the
efficiency of the downstream DC-DC converter and
therefore of the overall power supply.
Implementations for both the two-level boost and the
linear boost follower (or tracking boost) are described in
application note AN-8021.
Additional details on adjusting phase management are
provided in the application note AN-6086.
5. Adjusting the Phase-Management
Thresholds
In any power converter, the switching losses become
dominant at light load. For an interleaved converter
where there are two or more phases, light-load
efficiency can be improved by shutting down one of the
phases at light load (also known as phase-shedding or
phase-dropping operating).
The initial phase-management thresholds are fixed at
approximately 13% and 18% of the maximum load
power level. This means when the output power
reaches 13%, the FAN9611/12 automatically goes from
a two-phase to a single-phase operation (phase shed or
phase drop). When the output power comes back up to
18%, the FAN9611/12 automatically goes from the
single-phase to the two-phase operation (phase-add).
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
Figure 30. VCOMP vs. tONMAX
www.fairchildsemi.com
19
d.
There are four ways to disable the FAN9611/12. It is
important to understand how the part reacts for the
various shutdown procedures.
a.
Pull the SS Pin to GND. This method uses the error
amplifier to stop the operation of the power supply.
By pulling the SS pin to GND, the error amplifier’s
non-inverting input is pulled to GND. The amplifier
senses that the inverting input (FB pin) is higher
than the reference voltage and tries to adjust its
output (COMP pin) to make the FB pin equal to the
reference at the SS pin. Due to the slow speed of
the voltage loop in PFC applications, this might take
several line cycles. Thus, it is important to consider
that by pulling the SS pin to GND, the power supply
is not shut down immediately. Recovery from a shut
down follows normal soft-start procedure when the
SS pin is released.
b.
Pull the FB Pin to GND. By pulling the FB pin below
the open feedback protection threshold of
approximately 0.5V, the power supply can be shut
down immediately. It is imperative that the FB is
pulled below the threshold very quickly since the
power supply keeps switching until this threshold is
crossed. If the feedback is pulled LOW softly and
does not cross the threshold, the power supply tries
to deliver maximum power because the FB pin is
forced below the reference voltage of the error
amplifier on the SS pin. Eventually, as FB is pulled
to GND, the SS capacitor is pulled LOW by the
internal clamp between the FB and SS pins. The
SS pin stays approximately 0.5V higher than the FB
pin itself. Therefore, recovery from a shut down
state follows normal soft-start procedure when the
FB pin is released as the voltage across the SS
capacitor starts ramping from a low value.
c.
7. Layout and Connection Guidelines
For high-power applications, two or more PCB layers
are recommended to effectively use the ground pattern
to minimize the switching noise interference.
The FAN9611/12 incorporates fast-reacting input
circuits, short propagation delays, and strong output
stages capable of delivering current peaks over 1.5A to
facilitate fast voltage transition times. Many high-speed
power circuits can be susceptible to noise injected from
their own output or external sources, possibly causing
output re-triggering. These effects can be especially
obvious if the circuit is tested in breadboard or nonoptimal circuit layouts with long input or output leads.
The following guidelines are recommended for all layout
designs, but especially strongly for the single-layer PCB
designs. (For example of a 1-layer PCB design, see the
Application Note AN-6086.)
Pulling the COMP Pin to GND. When the COMP
pin is pulled below the PWM ramp offset,
approximately 0.195V, the FAN9611/12 stops
sending gate drive pulses to the power MOSFETs.
This condition is similar to pulse skipping under noload condition. If any load is still present at the
output of the boost PFC stage, the output voltage
decreases. Consequently, the FB pin decreases
and the SS capacitor voltage is pulled LOW by the
internal clamp between the FB and SS pins. At that
point, the operation and eventual recovery to
normal operation is similar to the mechanism
described above. If the COMP pin is held LOW for
long enough to pull the SS pin LOW, the recovery
follows normal soft-start procedure when the COMP
pin is released. If the SS capacitor is not pulled
LOW as a result of a momentary pull-down of the
COMP pin, the recovery is still soft due to the fact
that a limited current source is charging the
compensation capacitors at the output of the error
amplifier. Nevertheless, in this case, output voltage
overshoot can occur before the voltage loop enters
closed-loop operation and resumes controlling the
output voltage again.
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
Pull the VIN Pin to GND. Since the VIN sense
circuit is configured to ride through a single line
cycle dropout test without shutting down the power
supply, this method results in a delayed shutdown
of the converter. The FAN9611/12 stops operation
approximately 20ms to 32ms after the VIN pin is
pulled LOW. The delay depends on the phase of
the line cycle at which the pull-down occurs. This
method triggers the input brownout protection (input
under-voltage lockout), which gradually discharges
the compensation capacitor. As the output voltage
decreases, the FB pin falls, pulling LOW the SS
capacitor voltage. Similarly to the shutdown, once
the VIN pin is released, operation resumes after
several milliseconds of delay needed to determine
that the input voltage is above the turn-on
threshold. At least one line cycle peak must be
detected above the turn-on threshold before
operation can resume at the following line voltage
zero-crossing. The converter starts following normal
soft-start procedure.
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
6. Disabling the FAN9611/12
General

Keep high-current output and power ground paths
separate from analog input signals and signal
ground paths.

For best results, make connections to all pins as
short and direct as possible.
Power Ground and Analog Ground

Power ground (PGND) and analog ground (AGND)
should meet at one point only.

All the control components should be connected to
AGND without sharing the trace with PGND.

The return path for the gate drive current and VDD
capacitor should be connected to the PGND pin.

Minimize the ground loops between the driver
outputs (DRV1, DRV2), MOSFETs, and PGND.

Adding the by-pass capacitor for noise on the VDD
pin is recommended. It should be connected as
close to the pin as possible.
www.fairchildsemi.com
20

To minimize switching noise, current sensing
should not make a loop.
Input Voltage Sensing (VIN)
The gate drive pattern should be wide enough to
handle 1A peak current.

Keep the controller as close to the MOSFETs as
possible. This minimizes the length and the loop
area (series inductance) of the high-current gate
drive traces. The gate drive pattern should be as
short as possible to minimize interference.
Current Sensing

Current sensing should be as short as possible.
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3

Since the impedance of voltage divider is large and
FAN9611/12 detects the peak of the line voltage,
the VIN pin can be sensitive to the switching noise.
The trace connected to this pin should not cross
traces with high di/dt to minimize the interference.

The noise bypass capacitor for VIN should be
connected as close to the pin as possible.
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers

Gate Drive
www.fairchildsemi.com
21
The FAN9611/12 can be configured following the next
steps outlined in this section. This Quick Setup Guide
refers to the schematic diagram and component
references of Figure 33. It uses the equations derived
and explained in Application Note AN-6086.
Input Voltage Sense Divider
In preparation to calculate the setup component values,
the power supply specification must be known.
Furthermore, a few power stage components must be
pre-calculated before the controller design begins as
their values determine the component selections. An
Excel design tool is also available to ease calculations.
Bypass Capacitor for VDD_HF
Description
Name
VLINE.ON
Minimum AC RMS Input (Turn-Off)
VLINE.OFF
Minimum Line Frequency
fLINE,MIN
Nominal DC Output
VOUT,RIPPLE
Latching Output OVP
VOUT,LATCH
Nominal Output Power (to Load)
POUT
Desired Hold-Up Time
tHOLD
Minimum DC Output (End of tHOLD)
Gate Drive Resistor
RG1, RG2
Gate Drive Speed-Up Diode
DG1, DG2
Current Sense Resistor
CVDD1
2.2μ
CVDD2
47μ
RCS1, RCS2
Step 1: Input Voltage Range
Value
FAN9611/12 utilizes a single pin (VIN) for input voltage
sensing. The VIN pin must be above 0.925V (VIN_BO) to
enable operation. The converter turns on at a higher
VIN voltage (VIN_ON) set independently by the designer.
The input voltage information is used for feedforward in
the control algorithm as well. The input-voltage
feedforward operates over a four-to-one range from
0.925V (VIN_BO) to 3.7V (VFF_UL), as measured at the VIN
pin.
VOUT
Output Voltage Ripple (2 · fLINE)
RINHYST
Startup Energy Storage for VDD
From Power Supply Specification:
Minimum AC RMS Input (Turn-On)
RIN2
Brownout Hysteresis Set
VOUT,MIN
Minimum Switching Frequency
fSW,MIN
Maximum DC Bias (for FAN9611/12)
VDDMAX
Pre-Calculated Power Stage Parameters:
Estimated Conversion Efficiency
Maximum Output Power per Channel
Output Capacitance
Boost Inductance per Channel
Maximum On-Time per Channel
Turns Ratio (NBOOST / NAUX)
η
0.95
PMAX,CH
Figure 31. VIN Turn-on and Turn-off Thresholds
COUT
At VIN voltages above the 3.7V upper limit (VFF_UL), input
voltage feedforward is not possible. The input voltagesense circuitry saturates at this point and the PWM
ramp is modulated any longer. Above VFF_UL, the
converter’s output power becomes a function of the
input voltage as shown in Figure 32. It can also be
expressed analytically as:
L
tON,MAX
N
10
Other Variables Used During the Calculations:
Peak Inductor Current
Maximum DC Output Current (to Load)
IL,PK
 VIN 
POUT_NO_FF  PMAX  

 3.7 
IO,MAX
Calculated Component Values:
Zero Current Detect Resistor
RZCD1,
RZCD2
Bypass Capacitor for 5V Bias
C5VB
Maximum On-Time Set
RMOT
Soft-Start Capacitor
CSS
Compensation Capacitor
Compensation Resistor
Compensation Capacitor
Feedback Divider
2
(5)
where VIN is the voltage at the VIN pin and PMAX is the
desired maximum output power of the converter which
will be maintained constant while the input voltage
feedforward circuit is operational.
0.15μ
CCOMP,LF
RCOMP
CCOMP,HF
RFB1
Feedback Divider
RFB2
Over Voltage Sense Divider
ROV1
Over Voltage Sense Divider
ROV2
Input Voltage Sense Divider
RIN1
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Quick Setup Guide
Figure 32. VIN Feedforward Range
As can be seen, the converter’s output power capability
will follow a square function above VFF_UL.
www.fairchildsemi.com
22
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Figure 33. Interleaved BCM PFC Schematic Using FAN9611/12
Step 2: Estimated Conversion Efficiency
Step 3: Maximum Output Power per
Channel
Use the estimated full-load power conversion efficiency.
Typical value for an interleaved BCP PFC converter is in
the 0.92 to 0.98 range. The efficiency is in the lower half
of the range for low-power applications. Using state-ofthe-art semiconductors, good quality ferrite inductors
and selecting lower limit for minimum switching
frequency positively impacts the efficiency of the
system. In general, the value of 0.95 can be used
unless a more accurate power budget is available.
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
PMAX, CH  1.2 
POUT
2
(6)
A margin of 20% has been added to the nominal output
power to cover reference inaccuracy, internal
component tolerances, inductance mismatch, and
current-sense resistor variation to the per-channel
power rating.
www.fairchildsemi.com
23
C OUT(RIPPLE) 
C OUT(HOLD) 
Step 9: Zero Current Detect Resistors
POUT
4  fLINE,MIN  VOUT  VOUT,RIPPLE
(7)
R ZCD1  R ZCD2 
2  POUT  t HOLD
V

 VOUT  OUT,RIPPLE

2

2

2
  VOUT,MIN


Step 10: Maximum On-Time Setting
Resistor
RMOT  4340  10 6  t ON,MAX
Step 11: Output Voltage Setting Resistors
(Feedback)
RFB2 
L LINE,MAX 
2  fSW, MIN  VOUT  PMAX, CH

2
η  VLINE,MAX
 VOUT  2  VLINE,MAX


2  fSW,MIN  VOUT  PMAX,CH
(9)
(10)
The minimum switching frequency can occur either at
the lowest or at the highest input line voltage.
Accordingly, two boost inductor values are calculated
and the lower of the two inductances must be selected.
This L value keeps the minimum operating frequency
above fSW,MIN under all operating conditions.
2  L  PMAX, CH
2
η  VLINE,
OFF
RFB2 
2  VLINE,OFF
L
 t ON,MAX
(12)
2  PMAX, CH
VOUT
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
 2 V
LINE, ON

 12.5V  3  0.7V 
0.12mA  VOUT
V

RFB1   OUT  1  RFB2
 3V

Step 8: Maximum DC Output Current
IOUT,MAX 
3V 
(17)
where 3V is the reference voltage of the error amplifier
at its non-inverting input; 12.5V is the controller’s UVLO
turn-on threshold; 0.12mA is the worst-case startup
current required to start operation; and 3·0.7V accounts
for the forward voltage drop of three diodes in series of
the startup current. Once the value of RFB2 is
determined, RFB1 is given by the following formula:
(11)
Step 7: Peak Inductor Current per Channel
IL,PK 
(16)
If the feedback divider is used to provide startup power
for the FAN9611/12 (see AN-6086 for implementation
details), the following equation is used to calculate RFB2:
Step 6: Maximum On-Time per Channel
t ON,MAX 
3V  VOUT 3V

PFB
IFB
where 3V is the reference voltage of the error amplifier
at its non-inverting input and PFB or IFB are selected by
the designer. If the power loss associated to the
feedback divider is critical to meet stand-by power
consumption regulations, it might be beneficial to start
the calculation by choosing PFB. Otherwise, the current
of feedback divider, IFB should be set to approximately
0.4mA at the desired output voltage set point. This value
ensures that parasitic circuit board and pin capacitances
do not introduce unwanted filtering effect in the
feedback path.
Step 5: Boost Inductance per Channel

(15)
where RMOT should be between 40k and 130k.
The second expression yields the minimum output
capacitance based on the required hold-up time based
on the power supply specification. Ultimately, the larger
of the two values satisfies both design requirements and
has to be selected for COUT.
2
η  VLINE,
OFF  VOUT  2  VLINE, OFF
(14)
where 0.5·VOUT is the maximum amplitude of the
resonant waveform across the boost inductor during
zero current detection; N is the turns ratio of the boost
inductor and the auxiliary winding utilized for the zero
current detection; and 0.5mA is the maximum current of
the ZCD pin during the zero current detection period.
(8)
The output capacitance must be calculated by two
different methods. The first equation determines the
capacitor value based on the allowable ripple voltage at
the minimum line frequency. It is important to remember
that the scaled version of this ripple is present at the FB
pin. The feedback voltage is continuously monitored by
the non-latching over voltage protection circuit. Its
threshold is about 8% higher the nominal output voltage.
To avoid triggering the OVP protection during normal
operation, VOUT,RIPPLE should be limited to less 12% of
the nominal output voltage, VOUT.
L LINE, OFF 
0.5  VOUT
N  0.5mA
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Step 4: Output Capacitance
(18)
RFB1 can be implemented as a series combination of two
or three resistors; depending on safety regulations,
maximum voltage, and or power rating of the selected
resistor type.
(13)
www.fairchildsemi.com
24
C SS
5 μA  C OUT  R FB1  R FB2 

0.3  IOUT, MAX  R FB2
converter so noise can be effectively attenuated. The
recommended fHFP frequency is around 120Hz in PFC
applications.
(19)
Step 14: Over-Voltage Protection Setting
(OVP)
where 5μA is the charge current of the soft-start
capacitor and 0.3·IOUT,MAX is the maximum output
current charging the output capacitor of the converter
during the soft-start process. It is imperative to limit the
charge current of the output capacitor to be able to
maintain closed-loop soft-start of the converter. The 0.3
factor used in the CSS equation can prevent output over
voltage at the end of the soft-start period and provides
sufficient margin to supply current to the load while the
output capacitor is charging.
R OV2 
CCOMP,LF 
4.1V  COUT  2  π  f0 
2
RFB2

RFB1  RFB2
(24)
POVP
where 3.5V is the threshold voltage of the OVP
comparator and POVP is the total dissipation of the
resistive divider network. Typical POVP power loss is in
the 50mW to 100mW range.
Step 13: Compensation Components
gM  IOUT,MAX
3.5V  VOUT, LATCH
 VOUT, LATCH

R OV1  
 1  R OV2
3.5V


(20)
(25)
ROV1 can be implemented as a series combination of
two or three resistors; depending on safety regulations,
maximum voltage, and or power rating of the selected
resistor type.
where 4.1V is the control range of the error amplifier
and f0 is the desired voltage loop crossover frequency. It
is important to consider that the lowest output ripple
frequency limits the voltage loop crossover frequency. In
PFC applications, that frequency is two times the AC
line frequency. Therefore, the voltage loop bandwidth
(f0), is typically in the 5Hz to 15Hz range.
Step 15: Input Line Voltage Sense
Resistors
0.925 V  V
2
LINE,MAX
To guarantee closed-loop soft-start operation under all
conditions, it is recommended that:
R IN2 
C COMP,HF  4  C SS
where 0.925V is the brown-out protection threshold at
the VIN pin. VLINE,MIN is the minimum input RMS
operating voltage. Its divided down level at the VIN pin
corresponds to the 0.925V brown out protection
threshold. VLINE,MAX is the maximum input RMS voltage
anticipated in the design and PINSNS is the total power
dissipation of the RIN1 - RIN2 divider when the input
voltage equals VLINE,MAX. Typical PINSNS power loss is in
the 50mW to 100mW range.
(21)
This relationship is determined by the ratio between the
maximum output current of the gM error amplifier to the
maximum charge current of the soft-start capacitor.
Observing this correlation between the two capacitor
values ensures that the compensation capacitor voltage
can be adjusted faster than any voltage change taking
place across the soft-start capacitor. Therefore, during
startup the voltage regulation loop’s response to the
increasing soft-start voltage is not limited by the finite
current capability of the error amplifier.
RCOMP 
1
2  π  f0  CCOMP,LF
CCOMP,HF 
1
2  π  fHFP  RCOMP
 2  VLINE,MIN

 1  RIN2
RIN1  
 0.925V



(27)
RIN1 can be implemented as a series combination of two
or three resistors; depending on safety regulations,
maximum voltage, and or power rating of the selected
resistor type.
(22)
(23)
RINHYST
where fHFP is the frequency of a pole implemented in the
error amplifier compensation network against highfrequency noise in the feedback loop. The pole should
be placed at least a decade higher than f0 to ensure that
it does not interfere with the phase margin of the voltage
regulation loop at its crossover frequency. It should also
be sufficiently lower then the switching frequency of the
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
(26)
2  VLINE,MIN  PINSNS
 2  VLINE,ON  RIN2


 0.925V 


RIN1  RIN2


2μA
(28)
where 0.925V is the threshold voltage of the line undervoltage lockout comparator and 2μA is the sink current
provided at the VIN pin during line under-voltage
(brownout) condition. The sink current, together with the
terminating impedance of the VIN pin determines the
hysteresis between the turn-on and turn-off thresholds.
www.fairchildsemi.com
25
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Step 12: Soft-Start Capacitor
It is recommended to place at least a 15 resistor
between each of the gate drive outputs (DRV1, DRV2)
and their corresponding power devices. The gate drive
resistors have a beneficial effect to limit the current
drawn from the VDD bypass capacitor during the turn-on
of the power MOSFETs and to attenuate any potential
oscillation in the gate drive circuits.
R G1  R G2 
VDDMAX
1.0 A
In addition to the high-speed turn-off, another advantage
of this circuit is that the FAN9611/12 does not have to
sink the high peak discharge current from the MOSFET,
reducing the internal power dissipation in the gate drive
circuitry by a factor of two. Instead, the current is
discharged locally in a tighter, more controlled loop,
minimizing parasitic trace inductance while protecting the
FAN9611/12 from injected disturbances associated with
ground bounce and ringing due to high-speed turn-off.
(29)
where 1.0A is the recommended peak value of the gate
drive current.
Step 17: Current-Sense Resistors
R CS1  R CS2 
Figure 34. Recommended Gate Drive Schematic
0.18V
IL,PK
(30)
where 0.18V is the worst-case threshold of the current
limit comparator. The size and type of current sense
resistors depends on their power dissipation and
manufacturing considerations.
A speed-up discharge diode that feeds switching current
back into the IC is not recommended.
 1 4 2 V
LINE,OFF
2
 R CS1   
PRCS1  1.5  IL,PK
6
9  π  VOUT





FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
The FAN9611/12 sources high peak current to the
MOSFET gate through RG and DON, where RG is used to
control the turn-on transition time. When the MOSFET is
commanded to turn off, QOFF conducts, shorting the gate
to the source, where the turn-off speed can be
controlled by the value of ROFF. Where maximum turnoff time is desired, the value of ROFF can be 0Ω. DON
serves the dual purpose of protecting the QOFF baseemitter junction and blocking the MOSFET discharge
current from sinking back through the FAN9611/12.
Step 16: Gate Resistors
(31)
where the 1.5 factor is used for the worst-case effect of
the current-limit threshold variation. When the currentsense resistor is determined, the minimum currentsense threshold must be used to avoid activating overcurrent protection too early as the power supply
approaches full-load condition. The worst-case power
dissipation of the current sense resistor occurs when the
current-sense threshold is at its maximum value defined
in the datasheet. The ratio between the minimum and
maximum thresholds squared (since the square of the
current determines power dissipation) yields exactly the
1.5 factor used in the calculation.
Figure 35. Discharge Diode is Not Recommended
In cases where it is desirable to control the MOSFET
turn-on and turn-off transition times independently, the
circuit of Figure 36 can be used.
Figure 36. Gate Drive Schematic with Independent
Turn-On and Turn-Off
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
26
Typical characteristics are provided at TA = 25°C and VDD = 12V unless otherwise noted.
Figure 37. ISTARTUP vs. Temperature
Figure 38. Operating Current vs. Temperature
Figure 39. UVLO Thresholds vs. Temperature
Figure 40. UVLO Hysteresis vs. Temperature
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
27
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Typical Performance Characteristics — Supply
Typical characteristics are provided at TA = 25°C and VDD = 12V unless otherwise noted.
Figure 41. Transfer Function
(Maximum On Time vs. VIN)
Figure 42. Maximum On Time vs. Temperature
Figure 43. EA Transconductance (gM) vs.
Temperature
Figure 44. EA Reference vs. Temperature
Figure 45. 5V Reference vs. Temperature
Figure 46. Soft-Start Current vs. Temperature
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Typical Performance Characteristics — Control
www.fairchildsemi.com
28
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Typical Performance Characteristics — Control
Typical characteristics are provided at TA = 25°C and VDD = 12V unless otherwise noted.
Figure 47. Phase-Control Thresholds vs. Temperature
Gate Drive 1
Gate Drive 1
Gate Drive 2
Gate Drive 2
Inductor Current 1
Inductor Current 1
Inductor Current 2
Inductor Current 2
Figure 48. Phase-Dropping Operation
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
Figure 49. Phase-Adding Operation
www.fairchildsemi.com
29
Typical characteristics are provided at TA = 25°C and VDD = 12V unless otherwise noted.
Figure 50. CS Threshold vs. Temperature
Figure 51. CS to OUT Delay vs. Temperature
Figure 52. Restart Timer Frequency vs. Temperature
Figure 53. Maximum Frequency Clamp
vs. Temperature
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Typical Performance Characteristics — Protection
Figure 54. Brownout Threshold vs. Temperature
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
30
Typical characteristics are provided at TA = 25°C and VDD = 12V unless otherwise noted.
Figure 55. Non-Latching OVP vs. Temperature
Figure 56. Latching OVP vs. Temperature
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Typical Performance Characteristics — Protection
Figure 57. OVP Hysteresis vs. Temperature
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
31
Typical characteristics are provided at TA = 25°C and VDD = 12V unless otherwise noted.
IL1
IL1
IL2
IL2
IL1 + IL2
IL1 + IL2
Figure 58. Ripple-Current Cancellation (110VAC)
Figure 59. Ripple-Current Cancellation (110VAC)
VGATE
VGATE
VOUT
VOUT
Line Current
Line
Current
Figure 60. No-Load Startup at 115VAC
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Typical Performance Characteristics — Operation
Figure 61. Full-Load Startup at 115VAC
Line
Vol
VOUT
110VAC
220VAC
COMP
Line
Current
Figure 62. Input Voltage Feedforward
Note:
6. For full performance operational characteristics at both low line (110VAC) and high line (220VAC), as well as at noload and full-load, refer to FEB279 Evaluation Board User Guide: 400W Evaluation Board using FAN9612.
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
32
FEB388: 400W Evaluation Board Using FAN9611/12
FEB388 is an evaluation board for an interleaved dual
boundary-conduction-mode PFC converter rated at
400W (400V/1A) power. With phase management, the
efficiency is maintained above 96% even down at 10%
of the rated output power. The efficiencies for full-load
condition exceed 96% as shown below.
Figure 63 and Figure 64 show the phase management
with the default minimum threshold values of the IC.
They can be adjusted upwards to achieve a different
efficiency profile (Figure 65 and Figure 66) where phase
management thresholds are adjusted to 30% / 44% of
the full load. For full specification, design schematic, bill
of materials and test results; see FEB388 — FAN9611/12
400W Evaluation Board User Guide (AN-9717).
Input Voltage
Rated Output Power
Output Voltage (Rated Current)
VIN Nominal: 85V~264VAC
VDD Supply: 13V~18VDC
400W
400V (1A)
FIGURE 63.
Measured Efficiency at 115VAC
(Default Thresholds)
FIGURE 64.
Measured Efficiency at 230VAC
(Default Thresholds)
FAN9612 Efficiency vs. Load
FAN9612 Efficiency vs. Load
(230 VAC Input, 400 VDC Output, 400W)
(115 VAC Input, 400 VDC Output, 400W)
95
95
Efficiency (%)
100
100
Efficiency (%)
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Evaluation Board
With Phase Management
With Phase Management
90
90
Without Phase Management
Without Phase Management
85
85
0
10
20
30
40
50
60
70
80
90
0
100
Figure 65. Measured Efficiency at 115VAC
(Adjusted Thresholds)
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
10
20
30
40
50
60
70
80
90
100
Output Power (%)
Output Power (%)
Figure 66. Measured Efficiency at 230VAC
(Adjusted Thresholds)
www.fairchildsemi.com
33
Related Products
Part
Number
FAN6961
Description
Green Mode PFC
FAN7527B Boundary Mode PFC Control IC
PFC Control
Number
of Pins
Comments
Industry Standard Pin-Out with
Green Mode Functions
Single BCM (CRM)
8
Single BCM (CRM)
8
Industry Standard Pin-Out
FAN7528
Dual Output Critical Conduction
Mode PFC Controller
Single BCM (CRM)
8
Low THD for Boost-Follower
Implementation
FAN7529
Critical Conduction Mode PFC
Controller
Single BCM (CRM)
8
Low THD
FAN7530
Critical Conduction Mode PFC
Controller
Single BCM (CRM)
8
Low THD, Alternate Pin-Out of
FAN7529 (Pins 2 and 3 Reversed)
FAN7930
Critical Conduction Mode PFC
Controller
Single BCM (CRM)
8
PFC Ready pin, Frequency Limit,
AC-Line-Absent Detection, SoftStart to Minimize Overshoot,
Integrated THD Optimizer, TSD
FAN9611
Interleaved Dual BCM PFC
Controller
Dual BCM (CRM)
16
Dual BCM (CRM), 180°
Out-of-Phase, 10.0V UVLO
FAN9612
Interleaved Dual BCM PFC
Controller
Dual BCM (CRM)
16
Dual BCM (CRM), 180°
Out-of-Phase, 12.5V UVLO
Related Resources



AN-6086: Design Consideration for Interleaved Boundary Conduction Mode (BCM) PFC Using FAN9612
AN-9717: Fairchild Evaluation Board User Guide FEB388: 400W Evaluation Board using FAN9611/12
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Table 1.
AN-8021: Building Variable Output Voltage Boost PFC Converters Using FAN9612
References
1.
2.
L. Huber, B. Irving, C. Adragna and M. Jovanovich, “Implementation of Open-Loop Control for Interleaved
DCM/BCM Boundary Boost PFC Converters”, Proceedings of APEC ’08, pp. 1010-1016.
C. Bridge and L. Balogh, “Understanding Interleaved Boundary Conduction Mode PFC Converters”,
Fairchild Power Seminars, 2008-2009.
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
34
10.00
9.80
A
8.89
16
9
B
4.00
3.80
6.00
PIN ONE
INDICATOR
1.75
1
5.6
8
0.51
0.35
1.27
(0.30)
0.25
M
1.27
C B A
0.65
LAND PATTERN RECOMMENDATION
1.75 MAX
1.50
1.25
SEE DETAIL A
0.25
0.10
C
0.25
0.19
0.10 C
0.50
0.25 X 45°
(R0.10)
NOTES: UNLESS OTHERWISE SPECIFIED
GAGE PLANE
A) THIS PACKAGE CONFORMS TO JEDEC
MS-012, VARIATION AC, ISSUE C.
B) ALL DIMENSIONS ARE IN MILLIMETERS.
C) DIMENSIONS ARE EXCLUSIVE OF BURRS, MOLD
FLASH AND TIE BAR PROTRUSIONS
D) CONFORMS TO ASME Y14.5M-1994
E) LANDPATTERN STANDARD: SOIC127P600X175-16AM
F) DRAWING FILE NAME: M16AREV12.
(R0.10)
0.36
8°
0°
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Physical Dimensions
SEATING PLANE
0.90
0.50
(1.04)
DETAIL A
SCALE: 2:1
Figure 67. 16-Lead SOIC Package
Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner
without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify or
obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions, specifically the
warranty therein, which covers Fairchild products.
Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings:
http://www.fairchildsemi.com/packaging/.
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
35
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
www.fairchildsemi.com
36
Revision History
Revision
Date
1.0.0
July 2009
Initial Release of FAN9612
Description
1.0.1
Aug 2009
Preliminary release of FAN9611 product added to the FAN9612 Released datasheet.
1.1.0
Apr 2010
Updated FB-SS Clamp operation text and input voltage range section. Updated min and
max frequency specs.
1.1.1
May 2010
Added note 4 to Max Switching Frequency pg 4.
1.1.2
Oct 2010
1. Page 26/ Step 16: Change from "It is recommended to place a low-value resistor..." to
"It is recommended to place at least a 15-Ohm resistor between each of the gate drive
outputs (DRV1, DRV2) and their corresponding power devices. "
2. Removed ESD data (leaving only the website data, maintained dynamically).
3. Added Figure 35.
4. Modified FEB279 references to FEB388.
5. Added FAN7930 into the Related Products table.
1.1.3
Mar 2011
Removed the preliminary status of FAN9611 from ordering information
© 2008 Fairchild Semiconductor Corporation
FAN9611 / FAN9612 • Rev. 1.1.3
FAN9611 / FAN9612 — Interleaved Dual BCM PFC Controllers
Table 2.
www.fairchildsemi.com
37