Application Note: SSC2100 Series Power Factor Correction Discontinuous Conduction Mode Controller

Application Information
SSC2100 Series Power Factor Correction
Continuous Conduction Mode Controller
Introduction
The SSC2100 series devices are controller ICs intended
to implement a Discontinuous Conduction Mode (DCM)
interleaved Power Factor Correction (PFC) circuit. Using
the two-phase interleaved control incorporated in this IC,
it is possible to achieve a low cost, high performance PFC
system with low input / output ripple currents, low noise, and
few external components.
Features and benefits include the following:
▪ Interleaved Discontinuous Conduction Mode (DCM)
operation: low peak current, low ripple current, and low
noise; for medium- to high-power applications
▪ Constant Voltage Mode control: no auxiliary windings
required on inductors because of the built-in arithmetic
circuit; achieves a simple PFC system
• Maximum on-time: 15 μs (typ)
▪ Built-in Soft Start function: reduces stress on power
devices at startup
▪ Built-in High Speed Response (HSR): suppression of
output voltage changes during dynamic load transients
▪ Error Amplifier reference voltage: 3.5 V (typ)
▪ Protection Functions
▫ Soft Overvoltage Protection (SOVP): output voltage
reduction
▫ Output Overvoltage Protection (OVP): gate drive on/off
on a pulse-by-pulse basis, with auto-restart
▫ Overcurrent Protection (OCP): dual-level OCP, with
auto-restart
▫ Output Open Loop Detection (OLD): switching
operation stop and transition to standby mode
▫ Open Terminal Protection (OTP): switching operation
stop or output voltage reduction, during open condition
on VFB, VIN, or IS terminals
▫ Thermal Shutdown (TSD): auto-restart with hysteresis
SSC2100-AN
Figure 1. The SSC2100 series devices are provided in a compact,
standard package, a surface mount SOP8.
Contents
Introduction
Electrical Characteristics
Functional Description
Parameters Design
Design Notes
SANKEN ELECTRIC CO., LTD.
http://www.sanken-ele.co.jp/en/
1
4
7
14
16
Functional Block Diagram
–
Peak Current
Limitation
COMP 1
VCC
Gain
Control
–
VFB 3
3.5 V
+
8 IS
+
gm
–
+
R
Q
S
Q
7 OUT1
6 GND
–
3.72 V
OVP
+
–
+
R
Q
S
Q
5 OUT2
–
0.7 V or
0.5 V
+
Phase
Management
VIN 2
VCC
OVP
UVLO
VCC 4
TSD
VREG5V
Pin-out Diagram
COMP 1
8 IS
VIN 2
7 OUT1
VFB 3
6 GND
VCC 4
5 OUT2
Terminal List Table
Name
1
SSC2100-AN
Number
COMP
Function
Error Amplifier output and phase compensation terminal
2
VIN
AC mains rectified voltage monitoring input terminal
3
VFB
Feedback control terminal, input for: Constant Voltage Mode control signal,
Overvoltage Protection signal, and Open Loop Detection signal
4
VCC
IC power supply input terminal
5
OUT2
Gate drive 2 output terminal
6
GND
IC ground terminal
7
OUT1
Gate drive 1 output terminal
8
IS
Peak current detection signal input terminal
SANKEN ELECTRIC CO., LTD.
2
Typical Application Diagram
D1
85 to
264 VAC
RC1
L1
D2
L2
D3
EMI
Filter
VOUT
C1
R7
R1
7
4
OUT1
External
power
supply
R3
VCC
SSC2100
5
3
OUT2
VFB
Q1
R8
Q2
2
VIN
COMP
C2
1
R4
IS
8
R2
R5
R6
GND
6
C4
GND
C3
Package Outline Drawing
10º
0º
5.2 ±0.3
8
0.15
+0.1
–0.05
A
B
4.4 ±0.2
Branding:
6.2 ±0.3
A. Type number (abbreviation): SC21xx
C
0.4 ±0.2
B. Lot number
1st letter: Last digit of year
1
0.695 TYP
0.10
1.27 ±0.05
SSC2100-AN
2nd letter: Month
2
1 to 9 for January to September
O for October
N for November
D for December
0.4 ±0.1
0.12 M
3rd letter: Week
1 for dates 1 through 10
2 for dates 11 through 20
3 for dates 21 through 31
1.5 ±0.1
0.05 ±0.05
Dimensions in mm
SANKEN ELECTRIC CO., LTD.
C. Sanken tracking number
3
Electrical Characteristics
Absolute Maximum Ratings* TA = 25°C unless otherwise specified
Characteristics
VCC Terminal Voltage
Symbol
Notes
Terminals
Rating
Unit
A
VCC
4–6
−0.3 to 30
VCOMP
1–6
−0.3 to 5.5
A
VFB
3–6
−0.3 to 5.5
V
VFB Terminal Current
IFB
3–6
−1 to 1
mA
VIN Terminal Voltage
VIN
2–6
−0.3 to 5.5
V
VIN Terminal Current
IIN
2–6
−1 to 1
mA
IS Terminal Voltage
VIS
8–6
−16.0 to 5.5
V
COMP Terminal Voltage
VFB Terminal Voltage
IIS
8–6
−1.75 to 1
mA
OUT2 Terminal Voltage
IS Terminal Current
VOUT2
5–6
−0.3 to 30
V
OUT1 Terminal Voltage
VOUT1
7–6
−0.3 to 30
V
Operating Frame Temperature
TFOP
–
−40 to 85
°C
Storage Temperature
Tstg
–
−40 to 125
°C
Junction Temperature
Tj
–
−40 to 125
°C
*Current polarity is defined relative to the IC: sink as positive, source as negative.
ELECTRICAL CHARACTERISTICS Valid at TA = 25°C, unless otherwise specified
Characteristics
Symbol
Test Conditions
Terminals
Min.
Typ.
Max.
Unit
Power Supply Start-up Operation
VCC Operation Start Voltage
VCC(ON)
4–6
10.8
11.6
12.4
V
VCC Operation Stop Voltage
VCC(OFF)
4–6
9.8
10.6
11.4
V
VCC Undervoltage Lockout Hysteresis
VCC(HYS)
4–6
0.8
1.0
1.2
V
VCC Circuit Current in Pre-operation
ICC(OFF)
4–6
–
40
100
μA
VCC Circuit Current in Operation
ICC(ON)
4–6
–
11.0
15.0
mA
VCC Circuit Current During OVP
ICC(OVP)
4–6
–
8.0
10.0
mA
ICC(Standby)
4–6
–
100
200
μA
Maximum On-Time
tONMAX
7–6
14
15
16
μs
OUT1 to OUT2 On-Time Matching
tRATIO
5–6
7–6
−5
0
5
%
OUT1 to OUT2 Phase Difference
∆PHASE
5–6
7–6
170
180
190
deg.
VCC Circuit Current During Standby
Oscillator Operation
Continued on the next page…
SSC2100-AN
SANKEN ELECTRIC CO., LTD.
4
ELECTRICAL CHARACTERISTICS (continued) Valid at TA = 25°C, unless otherwise specified
Characteristics
Symbol
Test Conditions
Terminals
Min.
Typ.
Max.
Unit
Protection Operation
VFB Output Open Loop Stop Voltage
VFB(OLDL)
3–6
0.46
0.50
0.54
V
VFB Output Open Loop Start Voltage
VFB(OLDH)
3–6
0.64
0.70
0.76
V
VFB Output Overvoltage Protection
Voltage
VFB(OVP)
3–6
3.64
3.72
3.80
V
VFB Output Soft Overvoltage
Protection Voltage
VFB(SOVP)
3–6
3.60
3.68
3.76
V
IS Lower Overcurrent Protection
Voltage
VIS(OCPL)
8–6
−0.48
−0.42
−0.36
V
IS Upper Overcurrent Protection
Voltage
VIS(OCPH)
8–6
−0.62
−0.55
−0.48
V
COMP Sink Current During
Protection Mode
ICOMP(SK)
1–6
80
100
120
μA
Upper Thermal Shutdown Protection
Threshold Temperature
TJTSDH
Not tested, guaranteed by design
–
150
–
–
°C
Lower Thermal Shutdown Protection
Threshold Temperature
TJTSDL
Not tested, guaranteed by design
–
140
–
–
°C
TJTSDHYS
Not tested, guaranteed by design
–
–
10
–
°C
VFB(REF)
3–6
3.4
3.5
3.6
V
gmEA
–
80
100
120
μS
COMP Error Amplifier Maximum
Source Current
ICOMP(SO)
1–6
–36
–30
–24
μA
COMP Error Amplifier Maximum
Output Voltage
VCOMP(MAX)
1–6
4.00
4.12
4.25
V
VFB High Speed Response
Enable Voltage
VFB(HSR)enable Not tested, guaranteed by design
3–6
3.3
3.4
3.5
V
VFB High Speed Response
Active Voltage
VFB(HSR)active
3–6
3.1
3.2
3.3
V
COMP High Speed Response
Source Current
ICOMP(SOHSR)
1–6
–120
–100
–80
μA
IFB(bias)
3–6
–
–
1.5
μA
VCOMP(OLD)
1–6
0.7
0.9
1.1
V
Thermal Shutdown Protection
Hysteresis
Error Amplifier Operation
VFB Error Amplifier Reference
Voltage
VFB Error Amplifier Transconductance
Gain
VFB Input Bias Current
COMP Voltage During Output Open
Loop Detection
Continued on the next page…
SSC2100-AN
SANKEN ELECTRIC CO., LTD.
5
ELECTRICAL CHARACTERISTICS (continued) Valid at TA = 25°C, unless otherwise specified
Characteristics
Symbol
Test Conditions
Terminals
Min.
Typ.
Max.
Unit
Drive Circuit
OUTx Gate Voltage (Low)
VOUT(L)
5–6
7–6
–
–
0.3
V
OUTx Gate Voltage (High)
VOUT(H)
5–6
7–6
–
10.2
–
V
OUTx Rise Time
tr
5–6
7–6
–
70
–
ns
OUTx Fall Time
tf
5–6
7–6
–
35
–
ns
OUTx Peak Source Current
IOUT(SO)
Not tested, guaranteed by design
5–6
7–6
–
–0.5
–
A
OUTx Peak Sink Current
IOUT(SK)
Not tested, guaranteed by design
5–6
7–6
–
0.5
–
A
Terminals
Min.
Typ.
Max.
Unit
–
–
65
85
ºC/W
*Current polarity is defined relative to the IC: sink as positive, source as negative.
Thermal Characteristics Valid at TA = 25°C
Characteristics
Symbol
Package Thermal Resistance (Junction
to Internal Leadframe)
RθJF
SSC2100-AN
Test Conditions
Internal leadframe temperature (TF) is
measured at the root of pin 6, the GND
terminal.
SANKEN ELECTRIC CO., LTD.
6
Functional Description
Interleaved Discontinuous Conduction Mode (DCM)
The well-known single-phase Discontinuous Conduction Mode
(DCM) technique achieves low switching noise because the drain
current increase starts at zero when a power MOSFET turns on,
and the rate of drain current increase is not steep, as shown by
the waveforms in Figure 1. However, the usable power level of
single-phase DCM is limited by the very high input / output ripple
currents that are generated.
The SSC2100 series provides two-phase interleaved DCM (see
Figure 2). This advanced technique incorporates two boost
converters working together to cancel input ripple currents and
to reduce output ripple currents. This result is based on a phase
difference of 180° between the two converters.
Interleaved DCM also achieves a PFC system with lower switching noise and smaller input filter footprint in comparison to
single-phase DCM. This is because reducing input / output ripple
currents increases the filtering effectiveness of the EMI filter and
also reduces switching noise.
ID
L1
VOUT
MOSFET
Drain Current
IL
IL
Q1
ID
0
Inductor
Current
0
Figure 1. External circuit and current waveforms for single-phase DCM
L1
IL(Q1)
ID(Q1)
VOUT
L2
ID
MOSFET
Drain Current
ID(Q2)
I D(Q1
0
Q1
IL(Q2)
)
)
I D(Q2
Q2
IL
IL
CM
P
Inductor
Current
0
)
I L(Q2
)
I L(Q1
ILCMP = Composite Inductor Current
Figure 2. External circuit and current waveforms for two-phase interleaved DCM
SSC2100-AN
SANKEN ELECTRIC CO., LTD.
7
Startup Operation
Soft Start Function
VCC is the external power supply input to the SSC2100 IC. The
external circuit for the VCC terminal is shown in Figure 3.
Soft start is adjusted by the external circuits on the VFB and
COMP terminals, as shown in Figure 5. At startup, when the
input voltage increases to approximately 20% of the rated output voltage, VOUT , and the VCC terminal voltage increases to
VCC(ON) = 11.6 V (typ), soft start operation begins.
When AC mains and VCC external voltage are applied, after the
VFB terminal voltage increases to VFB(OLDH) = 0.7 V (typ) or
more and the VCC terminal voltage increases to VCC(ON) = 11.6 V
(typ) or more, the control circuit starts switching operation.
Note: One of the startup conditions is that the input voltage must
reach 20% or more of the rated value for VOUT . This value of
VOUT is equivalent to approximately VFB(OLDH) = 0.7 V (typ).
As shown in Figure 6, during the soft start period, the COMP
terminal is charged by ICOMP(SO) = −30 μA. In this way, the output
power increases gradually, reducing stress on the power devices.
8176
When the VCC terminal voltage subsequently decreases to
VCC(OFF) = 10.6 V (typ) or less, the control circuit stops switching operation. It does so by enabling the UVLO (undervoltage
lockout) circuit, and then reverting to the standby mode that is the
state of the IC before startup.
When the VFB terminal voltage subsequently decreases to
VFB(OLDL) = 0.5 V (typ) or less, the control circuit stops switching
operation and reverts to pre-startup standby mode, even if VCC
terminal voltage has increased to VCC(ON) or more.
Because the regulation range of the VCC internal circuit is very
wide, between VCC(OFF) = 11.4 V (max) and the VCC absolute
maximum rating of 30 V (max), a wide input voltage range
from the external power supply can be applied. The behaviors of
ICC during startup and when switching is stopped are shown in
Figure 4.
%
4
55%
%1/2
Ǵ#
4
%
%
%
4
+5
8+0
176
8($
)0&
8%%
176
Figure 5. External circuits of VFB and COMP terminals
IDS(Q1,Q2)
SSC2100
IS 8
1 COMP
power supply
2 VIN
OUT1 7
3 VFB
GND 6
4 VCC
C6
VFB
VFB(REF)
OUT2 5
Cf
Time
Soft start period Constant voltage operation
3.5 V
≈ 3.2 V
VOUT=100%
≈ 90% of VOUT
0.7 V
0
Figure 3. External circuit of VCC terminal
Time
ICOMP
ICC
ICC(ON)
11 mA(typ )
0
Stop
Startup
ICOMP(SO)
Time
VCC
ICC(OFF)
40 μA(typ)
VCC(ON)
11.6 V(typ)
External power supply
for VCC
10.6 V(typ)
VCC(OFF)
11.6V(typ) VCC
VCC(ON)
Figure 4. Relationship of VCC and ICC at startup and stopping
SSC2100-AN
㧙30ǴA
0
Time
Figure 6. Soft Start operation
SANKEN ELECTRIC CO., LTD.
8
using the voltage-mode control method. Thus, a PFC system used
with this IC has no requirement for an auxiliary winding to detect
zero crossings of the inductor current. This allows simple circuits
with few external components.
Voltage Control Operation
A generic PFC circuit for implementing single-phase DCM is
shown in Figure 7. The circuit is composed of a boost inductor (L1), a switching device (Q1), a rectifier diode (D2), and an
output capacitor (C2). A control circuit would monitor the C2
voltage and generate an error amplifier output signal to operate
Q1. When the control circuit detects an off-time at the L1 Zero
Current Detection (ZCD) winding, it turns on Q1 for a period
of time. When Q1 is later turned off, the energy stored in L1 is
transferred through D2 to C2. After all of the energy stored in L1
is transferred to C2, the control circuit would again turn on Q1,
repeating the process.
In the boost PFC converter, tON is a function of load power and
tOFF is a function of both the input voltage, EIN , and the rated
output voltage, VOUT . The relationship between tON and tOFF is
given by the following:
EIN
(1)
tOFF >
× tON
VOUT – EIN
The VIN terminal voltage is monitored internally and used to calculate the internal tOFF . The typical relationship between tON and
the VIN terminal voltage, VIN , is shown in Figure 8. The maximum tON occurs at VIN = 0 V. The values shown assume VCOMP =
4 V , where VCOMP is the COMP terminal voltage.
The SSC2100 series two-phase interleaved DCM uses the VIN
terminal to monitor the AC mains rectified input voltage, the
VFB terminal to monitor output voltage, and the COMP terminal
to monitor phase compensation. This IC internally generates the
on-time, tON , and off-time, tOFF , and it controls output voltage
'+0
&
.
As shown in Figure 9, the rectified input voltage is divided by
R1 and R2, and input to the VIN terminal. The output voltage is
divided by R3 and R4, and input to the VFB terminal. Because of
the way in which the VIN terminal voltage and the VFB terminal voltage are used for internal calculations, the two dividers
should be well matched. Thus, the R1, R2, and C7 values of the
input portion should be equal to the R3, R4, and C8 values of the
output portion.
8176
<%&
%
%
3
R1 is recommended to be a high-value resistor, in the range from
several hundred kΩ to several MΩ, ±1% tolerance, and of an
anti-electromigration type, such as metal oxide film.
C8, if necessary to reduce high frequency noise, is recommended
to have a capacitance of in the range of 0.1 to 10 nF.
Figure 7. PFC circuit with generic single-phase DCM
16
On-Time, t ON (μs)
15
14
13
12
11
10
9
8
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
VIN terminal voltage, VIN (V)
Figure 8. Typical relationship between VIN and tON
SSC2100-AN
SANKEN ELECTRIC CO., LTD.
9
nal voltage increases to VFB(HSR)enable = 3.4 V (typ) or more, the
control circuit enables the HSR operation. If the VFB terminal
voltage subsequently decreases to VFB(HSR)active = 3.2 V (typ) or
less, whether due to dynamic load change or other conditions, the
control circuit activates the HSR operation.
High Speed Response Function (HSR)
The boost PFC converter is supplied by an AC sinusoidal waveform at the local commercial mains input voltage and frequency.
However, the IC voltage control circuit, described above, characteristically responds at a relatively slow rate. As a result, the
dynamic load response of the IC would be slow, and could cause
the output voltage to drop too quickly.
When HSR is in active operation, the COMP terminal charges
by ICOMP(SOHSR) = −100 μA (typ) and the output power increases
until the COMP terminal voltage increases to 3.2 V (typ).
VFB(HSR)active = 3.2 V (typ) is equivalent to approximately 91.4%
of the rated output voltage, VOUT .
The innovative built-in High Speed Response (HSR) function
reduces variation of the output voltage under dynamic load
change conditions. As shown in Figure 10, when the VFB termi4%
' +0
8#%
L1
&
L2
&
81 76
4
%
4
4
%
3
4
3
4
55%
+5
%1/2
4
%
4
%
8+0
176
8($
)0&
8%%
176
Figure 9. External circuits for VIN and VFB terminals
OUT1,OUT2 Low
HSR OFF
HSR enable
VFB
COMP Sink
3.72 V
3.68 V
HSR active
3.5 V
3.4 V
≈ 3.2 V
3.2 V
SS : Soft start period
CV : Constant voltage operation period
LC : Dynamic load change period
HSR: High speed response operation period
OV : Overvoltage operation period
HSR
0
ICOMP
ICOMP(SK)
0
ICOMP(SO)
Time
SS
CV
LC
CV
OV
CV
100ǴA
㧙30ǴA
Time
ICOMP(SOHSR) 㧙100ǴA
Figure 10. VFB terminal voltage waveforms
SSC2100-AN
SANKEN ELECTRIC CO., LTD.
10
Gate Drive
The OUT1 and OUT2 terminals each directly drive an external
power MOSFET. Currents and voltages are set as follows:
Peak Current
Gate Voltage
Source
Sink
Low
High
–0.5 A (typ)
0.5 A (typ)
0.3 V (max)
10.2 V (typ)
Resistors R7, R8, R9, and R10 in Figure 11 should be selected
for performance in the actual application, because these values
relate to the individual board layout patterns and power MOSFET
capacities. The gate resistors, R7 and R8, are recommended to
be in the range of several ohms to several tens of ohms, and
should be selected to reduce gate voltage ringing and EMI noise.
R9 and R10 help to prevent malfunctions caused by steep dV/dt
during power MOSFET turn-off. The recommended values are
in the 10 to 100 kΩ range. These components should be placed
close to the gate and source terminals of the corresponding power
MOSFET.
Error Amplifier Phase Compensation
The phase compensation circuit is connected between the COMP
and GND terminals, as shown in Figure 12. The COMP terminal
is the output of the internal Error Amplifier. The Error Amplifier circuit, which implements the enhanced response functions,
consists of a transconductance amplifier and switched current
sources. The Error Amplifier response is set below 20 Hz to
maintain power factor correction at standard commercial power
frequencies of 50 or 60 Hz.
The phase compensation components, C4, C5, and R11 (see
Figure 12), have typical recommended values shown below, but
should be selected for performance in the application: to reduce
ripple, or to enhance transient load response at the rated output
voltage.
• C4: 0.047 to 0.47 μF
• C5: 0.47 to 10 μF
• R11: 10 to 100 kΩ
Thermal Shutdown Protection (TSD)
When the temperature of the IC increases to TJTSDH =
150°C (min) or more, the control circuit stops switching operation. Conversely, when temperature decreases to TJTSDL = 140°C
or less, the control circuit restarts switching operation. The hysteresis of the detection temperature, TJTSDHYS, is 10°C (typ).
8176
55%
%1/2
+5
8+0
176
8($
)0&
8%%
176
L1
&
L2
&
%
55%
+5
%1/2
4
3
%
4
4
3
4
Figure 11. External circuits for OUTx terminals
SSC2100-AN
4
8176
4
%
%
4
%
8+0
176
8($
)0&
8%%
176
Figure 12. Phase compensation circuit (external COMP terminal circuit)
SANKEN ELECTRIC CO., LTD.
11
Overcurrent Protection (OCP)
The inductor current of both inductors is monitored by the detection resistor, R5, and is input to the IS terminal, as shown in
Figure 13.
The overcurrent protection function has two stages, IS Lower
OCP, and IS Upper OCP, described below.
IS Lower Overcurrent Protection, VIS(OCPL) When the
inductor current is increasing and if the IS terminal voltage
decreases to VIS(OCPL) = −0.42 V (typ), the control circuit limits the output power by turning off either one or both power
MOSFETs, according to the output states of both OUT1 and
OUT2, as follows:
• If either one of OUT1 or OUT2 is high when the fault occurs,
that output is now set low (so both outputs are off). Figure 14 is
RC1
EIN
L1
D2
L2
D3
• If both OUT1 and OUT2 are high when the fault occurs, the
output that went high earlier than the other output (considering
the current pulses only) is now set low (the other output remains
high). Figure 15 is an example where both OUT1 and OUT2 are
high (Q1 and Q2 are on), and the IS terminal detects VIS(OCPL) or
lower. Under this condition, because OUT1 was set high before
OUT2 was, OUT1 is now set low (and OUT2 remains high).
R5 (see Figure 13) should be selected for performance in the
actual application, such that IS terminal voltage reaches VIS(OCPL)
or lower under the conditions of minimum input voltage and peak
load.
VOUT
MOSFET(Q1)
Drain current
%
Q1
Q1:OFF
C2
Q2
MOSFET(Q2)
Drain current
R10
Inductor current IL
an example. Where the IS terminal voltage falls to VIS(OCPL) or
lower while OUT1 is high (Q1 is ON) and OUT2 is low, under
this condition, OUT1 is set to low.
R9
OUT1
terminal
R5
R8
R7
R6
SSC2100
%1/2
+5
8+0
176
8($
)0&
8%%
176
OUT2
terminal
IS
terminal
When both OUT1and OUT2 are set to high,
OUT1 which is set to high ahead is set to low
C3
VIS(OCPL)
㧙0.42V(TYP)
Figure 15. VIS(OCPL) operation waveform after both OUT1 and OUT2 are
set to high
Figure 13. External circuits for IS and OUTx terminals
MOSFET(Q1)
Drain current
Q1= OFF
MOSFET(Q2)
Drain current
OUT1
terminal
MOSFET(Q1)
Drain current
MOSFET(Q2)
Drain current
OUT1 is set to low
after detecting VIS(OCPL)
OUT1
terminal
OUT2
terminal
OUT2
terminal
IS
terminal
IS
terminal
VIS(OCPL)
㧙0.42V(TYP)
Figure 14. VIS(OCPL) operation waveform after OUT1 is set to high
and OUT2 is set to low
SSC2100-AN
Abnormal state, such as
inductor is shorted
or is saturated
Both OUT1 and OUT2
are set to low after
detecting V IS(OCPH)
VIS(OCPH)
㧙0.55V(TYP)
Figure 16. Phase compensation circuit (external COMP terminal circuit)
SANKEN ELECTRIC CO., LTD.
12
R6 is a damping resistor, which buffers IS terminal current
against surge currents, such as inrush currents. It is recommended
to have a value of 100 Ω.
C3, if necessary to reduce high frequency noise, is recommended
to have a capacitance of in the range of 0.1 to 10 nF.
IS Upper Overcurrent Protection, VIS(OCPH) If the IS terminal voltage decreases to VIS(OCPH) = −0.55 V (typ) or lower, the
control circuit limits the output power on a pulse-by-pulse basis
by setting both OUT1 and OUT2 low, which turns off both power
MOSFETs. This is shown in Figure 16. This protection function
operates under abnormal conditions such as when an inductor is
shorted or is saturated.
Overvoltage Protection (OVP)
The overvoltage protection function has two stages, Soft OVP,
and OVP, illustrated in Figure 17 and described below.
VFB Output Soft Overvoltage Protection, VFB(SOVP) When
VFB terminal voltage increases to VFB(SOVP) = 3.68 V (typ), Soft
Overvoltage Protection is activated. This discharges the COMP
terminal by ICOMP(SK) = 100 μA (typ) and the output voltage is
decreased. VFB(SOVP) = 3.68 V (typ) is equivalent to about 105%
of the rated output voltage, VOUT .
The output voltage threshold that initiates Soft Overvoltage Protection, is calculated approximately as follows:
VOUT(norm)
(2)
VOUT(SOVP) ≈
× VFB(SOVP)
VFB(REF)
where VOUT(norm) is VOUT under normal operating conditions, and
VFB(REF) is the Error Amplifier reference voltage, 3.5V (typ).
VFB terminal
voltage
3.72 V(typ)
VFB Output Overvoltage Protection, VFB(OVP) When the
VFB terminal voltage increases to VFB(OVP) = 3.72 V (typ), both
OUT1 and OUT2 are set low on a pulse-by-pulse basis, which
stops the output supply by turning off the power MOSFETS.
When VFB terminal voltage decreases to VFB(SOVP) , the control
circuit stops discharging from the COMP terminal and restores
switching operation.
The output voltage threshold that initiates Overvoltage Protection, is calculated approximately as follows:
VOUT(norm)
(3)
VOUT(OVP) ≈
× VFB(OVP)
VFB(REF)
where VOUT(norm) is VOUT under normal operating conditions, and
VFB(REF) is the Error Amplifier reference voltage, 3.5V (typ).
R3 is recommended to be a high-value resistor, in the range from
several hundred kΩ to several MΩ, ±1% tolerance, and of an
anti-electromigration type, such as metal oxide film.
C8 is recommended if necessary to reduce high frequency noise,
and should have a rating of 0.1 to 10 nF.
Open Loop Detection (OLD)
In the event that the output voltage detection resistor, R3 (see
Figure 18), opens and VFB terminal voltage decreases to
VFB(OLDL) = 0.5 V (typ) or less, the control circuit stops the
switching operation and enters standby mode. VFB(OLDL) =
0.5 V (typ) is equivalent to about 14.3% of the rated output voltage, VOUT .
When the VFB terminal voltage subsequently increases to
VFB(OLDH) = 0.7 V (typ) or more, the control circuit restores
switching operation. VFB(OLDH) = 0.7 V (typ) is equivalent to
about 20% of the rated output voltage, VOUT .
OUT1,OUT2 is set to low
≈ 106% of V OUT
3.68 V(typ)
8176
VFB(OVP)
≈ 105% of V OUT
VFB(SOVP)
3.50 V(typ)
%
VFB(REF)
4
VOUT =100%
0
CV
OV
55%
%1/2
+5
Time
CV
Ǵ#
4
COMP terminal
current
100ǴA(typ )
ICOMP(SK)
%
%
4
%
8+0
176
8($
)0&
8%%
176
Time
CV : Constant voltage operation period
OV : Overvoltage operation period
Figure 17. Overvoltage operation waveform and external circuit
SSC2100-AN
SANKEN ELECTRIC CO., LTD.
13
Open Terminal Protection (OTP)
The specifications of this design example are:
The VFB, IS, and VIN terminals each have dedicated internal
Open Terminal Protection functions.
• AC input voltage: 85 to 264 VAC
• Total output power of two-phase interleaved PFC: 400 W
(PO = 200 W for each phase)
VFB Open Protection The VFB terminal is internally connected with a pull-up current source. In the event that the VFB
terminal is open, VFB terminal voltage is pulled-up to the internal supply voltage, the IC overvoltage protection is activated, and
both OUT1 and OUT2 are set low, decreasing the output voltage.
Output Voltage, VOUT Selection
The DC input voltage must always be lower than output voltage
in a boost converter. Hence, the rated output voltage, VOUT , is set
to be at least 10 V higher than the peak voltage of the commercial
AC mains input voltage:
IS Open Protection The IS terminal is internally connected
with a pull-up current source. In the event that the IS terminal is
open, the IS terminal voltage is pulled-up to the internal supply voltage, the IC overcurrent protection is activated, and both
OUT1 and OUT2 are set low, decreasing the output voltage.
VOUT ≥ √2 × VINRMS + 10 (V)
(4)
For example:
VIN Open Protection The VIN terminal is internally connected
with a pull-up current source. In the event that the VIN terminal
is open, the VIN terminal voltage is pulled-up to the internal supply voltage, and the control circuit limits IC operation or stops it.
VOUT ≥ √2 × 264 (VAC) + 10 (V) ≈ 383 (V)
Hence, VOUT is set to 390 VDC.
Inductor Current
Parameters Design
The waveform of the inductor current is triangular. The maximum peak current, ILPEAK (MAX), running through each inductor is
calculated in two stages.
Symbols in this section are defined as follows:
• PO: PFC output power per phase (W)
First, calculate the maximum input power, PIN(MAX). Defining the
output power margin as KOM and the inductor saturation margin
as KLM, PIN(MAX) can be calculated as follows:
• η: PFC efficiency (%)
• tON: On-time (sec.)
• VINRMS: Input rms voltage (V)
KOM × KLM × PO
(5)
(W)
η
where η is the efficiency, which depends on the on-resistance,
PIN(MAX) =
• VOUT: PFC output voltage (V)
• IINRMS: Input rms current (A)
4%
'+0
L1
&
L2
&
8176
%
4
4
4
3
%
4
3
4
55%
+5
%1/2
8+0
4
%
4
%
176
8($
)0&
8%%
176
Figure 18. External VFB terminal circuit
SSC2100-AN
SANKEN ELECTRIC CO., LTD.
14
RDS(on) , of the power MOSFET and the forward voltage, Vf , of
the rectifier diode. η is generally in the range of 0.90 to 0.97.
KOM and KLM depend on the design margins. Generally, as reference, KOM and KLM are in the range of 1.2 to 1.3.
For example:
1.2 × 1.2 × 200 (W)
PIN(MAX) =
≈ 313 (W)
0.92
Finally, calculate the single-phase maximum inductor peak current, ILPEAK(MAX) . Defining the minimum input rms voltage as
VINRMS(MIN) , ILPEAK(MAX) is calculated as follows:
ILPEAK(MAX) =
For example:
ILPEAK(MAX) =
2√2 × PIN(MAX)
(6)
VINRMS(MIN)
Inductance Value
The inductance for a single phase, L, is calculated as follows:
(H)
(7)
where tON(MAX) can be determined from the VIN terminal voltage,
using the chart in Figure 8.
To calculate the VIN terminal voltage, VIN , recall that the values
of R1 and R2 (see Figure 18) for VIN terminal voltage detection
should be equal to the values of R3 and R4 for VOUT detection.
Defining the rectified AC input voltage as EIN , the VIN terminal
voltage, VIN , is calculated as follows:
R
V
Given: 1 + 3 = V OUT , then
R4
FB(REF)
EIN
VIN =
VOUT ⁄ VFB(REF)
where VFB(REF) is as defined for Equation 3.
(8)
For example, to calculate the inductance value, L, given an input
of 85 VAC, first determine VIN by applying Equation 8:
VIN
√2 × 85 (VAC)
≈ 390 (V) ⁄ 3.5 (V) ≈ 1.08 (V)
Substituting into Equation 7:
N=
√2 × 85 (VAC) × 12.4 (μs)
102 (mm2) × 250 (mT)
(9)
× 10 9 ≈ 58 (turns)
Overcurrent Detection Resistance
First, the maximum duty cycle, DON(MAX) , can be calculated as
follows:
DON(MAX) =
VOUT – √2 × VINRMS(MIN)
(%)
VOUT
(10)
For example:
DON(MAX) ≈
390 (V) – √2 × 85 (VAC)
≈ 69%
390 (V)
KR is calculated differently for DON(MAX) greater than or equal to
50%, than for DON(MAX) less than 50%, as follows:
Given: DON(MAX) ≥ 50% , then
KR = 1 +
DON(MAX) – 0.5
DON(MAX)
DON(MAX) < 50% , then
0.5 – DON(MAX)
KR = 1 +
1 – DON(MAX)
or,
(11)
For example, with a duty cycle of 69% :
0.69 – 0.5
≈ 1.28
0.69
The composite inductor current, ILCMP(MAX) , is calculated as
follows:
ILCMP(MAX) = KR × I 'LCMP(MAX)
√2 × 85 (VAC) × 12.4 (μs)
≈ 143 (μH)
10.4 (A)
SSC2100-AN
√2 × VINRMS(MIN) × tON(MAX)
× 10 9 (turns)
Ae × ∆BMAX
For example:
N=
KR ≈ 1 +
Then determine tON(MAX) from Figure 8. Given a VIN of 1.08 V,
tON(MAX) is approximately 12.4 μs.
L≈
Defining the turns number of the inductor as N, the effective area
of inductor core as Ae (mm2), and the maximum magnetic flux
density as ∆BMAX (mT), N is calculated as follows:
The overcurrent detection resistor, R5 (Figure 18), sets the level
for monitoring the composite inductor current of both boost
converters, ILCMP . Because the composite inductor current (see
Figure 2) varies according to the duty cycle, DON , a coefficient
KR is calculated from DON , and used in the calculation of R5 by
determining ILCMP(MAX) .
2√2 × 313 (W)
≈ 10.4 (A)
85 (VAC)
√2 × VINRMS(MIN) × tON(MAX)
L≥
ILPEAK(MAX)
Inductor Turns
(12)
where I ′LPEAK(MAX) is calculated as follows:
SANKEN ELECTRIC CO., LTD.
15
I 'PEAK(MAX) ≈ 2√2 × KOM × PO
η × VINRMS(MIN)
(A)
(13)
Design Notes
External Components
For example:
Take care to use properly rated, including derated as necessary,
and proper types of components. The part identifier codes in the
following refer to Figure 19.
I 'PEAK(MAX) ≈ 2√2 × 1.2 × 200 (W) ≈ 8.7 (A)
0.92 × 85 (VAC)
Substituting into Equation 12:
ILCMP(MAX) ≈ 1.28 × 8.7 (A) ≈ 11.1 (A)
Finally, R5 is calculated from the peak current of the composite
inductor current and the threshold voltage, as follows:
R5 ≤ |VIS(OCPL)| (Ω)
ILCMP(MAX)
(14)
For example:
R5 ≈
|–0.42 (V, typ)|
≈ 0.038 (Ω)
11.1 (A)
RC1
VAC
• Electrolytic capacitor C2. Apply proper derating for ripple current, voltage, and temperature rise. Use of high ripple current and
low impedance types, designed for switch mode power supplies
(SMPS), is recommended.
• Inductors L1 and L2. Apply proper derating against temperature
rise due to core and copper losses.
• Current detection resistor R5. A high frequency switching current flows through R5, and may cause poor operation if a high
inductance resistor is used. Choose a low inductance and surgeproof type.
• Higher-rated resistors for high applied voltage. Choose a
resistor type, such as metal oxide film, that is not susceptible to
EIN
L1
D2
L2
D3
VOUT
Q1
Q2
C1
C2
R10
R1
R9
R3
R5
R6
R8
SSC2100
1 COMP
IS 8
2 VIN
R11
External power
supply
C6
R2
R4
C5 C4
C7
R7
Main circuit
Signal ground
OUT1 7
3 VFB
GND 8
4 VCC
OUT2 5
C8 Cf
C3
Figure 19. External circuits for SSC2100 connection
SSC2100-AN
SANKEN ELECTRIC CO., LTD.
16
degradation by electromigration, or by electrolytic corrosion or
oxidation of the resistive material.
frequency and high voltage, and the PCB trace design and component layouts should comply with all safety guidelines.
• Bypass diode D1. Choose a surge-current–proof type diode for
D1, which is a bypass diode to protect D2 and D3 against excessive currents, such as inrush current.
Furthermore, in the case where MOSFETs are being used as the
switching devices, take into account the positive thermal coefficient of RDS(on) when preparing a thermal design.
• Rectifiers D2 and D3. Choose an ultra–high-speed type diode
with short trr (reverse recovery time) to reduce noise and power
loss.
Figure 19 shows an example of external circuit connections. The
following should be taken into consideration when designing the
circuit layouts:
• Bypass diodes and rectifier diodes for power factor correction
(PFC). Sanken Electric has many product line-ups for bypass
diodes and rectifiers for PFC applications. Please contact the
Sanken Electric Sales Department to inquire about them.
• Avoid placing traces parallel and adjacent to control system or
main circuit traces, to avoid interference due to crosstalk noise.
• Connect the GND terminal directly to R5 with a short, dedicated trace. The goal is to reduce common mode impedance by
separating the IC control system ground from the main circuit
ground. Also, connect R6 directly to R5 with a dedicated trace.
Circuit Layout Design
PCB circuit trace design and component layout affect proper
functioning during operation, EMI noise, and power dissipation.
Therefore, where high frequency current traces form a loop, as in
Figure 20, wide, short traces and small circuit loops are important
to reduce line impedance. In addition, local ground and earth
ground traces affect radiated EMI noise, and the same measures
should be taken into account.
• Connect external components to the IC with the shortest traces
practicable.
Switch mode power supplies consist of current traces with high
• Place R10 between the gate and source terminals of Q2.
• If the distance between C6 and the IC is lengthy, place Cf (a
film capacitor in the 0.1 to 1 μF /50 V range) between the VCC
and GND terminals.
• Place R9 between the gate and source terminals of Q1.
D1
RC1
L1
D2
L2
D3
VAC
C1
Q1
VOUT
C2
Q2
GND
R5
Figure 20. High frequency current loop
SSC2100-AN
SANKEN ELECTRIC CO., LTD.
17
All performance characteristics given are typical values for
circuit or system baseline design only and are at the nominal
operating voltage and an ambient temperature of 25°C, unless otherwise stated.
• The contents in this document are subject to changes, for improvement and other purposes, without notice. Make sure that this is the
latest revision of the document before use.
• Application and operation examples described in this document are quoted for the sole purpose of reference for the use of the products herein and Sanken can assume no responsibility for any infringement of industrial property rights, intellectual property rights or
any other rights of Sanken or any third party which may result from its use.
• Although Sanken undertakes to enhance the quality and reliability of its products, the occurrence of failure and defect of semiconductor products at a certain rate is inevitable. Users of Sanken products are requested to take, at their own risk, preventative measures
including safety design of the equipment or systems against any possible injury, death, fires or damages to the society due to device
failure or malfunction.
• Sanken products listed in this document are designed and intended for the use as components in general purpose electronic equipment or apparatus (home appliances, office equipment, telecommunication equipment, measuring equipment, etc.).
When considering the use of Sanken products in the applications where higher reliability is required (transportation equipment and
its control systems, traffic signal control systems or equipment, fire/crime alarm systems, various safety devices, etc.), and whenever
long life expectancy is required even in general purpose electronic equipment or apparatus, please contact your nearest Sanken sales
representative to discuss, prior to the use of the products herein.
The use of Sanken products without the written consent of Sanken in the applications where extremely high reliability is required
(aerospace equipment, nuclear power control systems, life support systems, etc.) is strictly prohibited.
• In the case that you use Sanken products or design your products by using Sanken products, the reliability largely depends on the
degree of derating to be made to the rated values. Derating may be interpreted as a case that an operation range is set by derating the
load from each rated value or surge voltage or noise is considered for derating in order to assure or improve the reliability. In general,
derating factors include electric stresses such as electric voltage, electric current, electric power etc., environmental stresses such
as ambient temperature, humidity etc. and thermal stress caused due to self-heating of semiconductor products. For these stresses,
instantaneous values, maximum values and minimum values must be taken into consideration.
In addition, it should be noted that since power devices or IC's including power devices have large self-heating value, the degree of
derating of junction temperature affects the reliability significantly.
• When using the products specified herein by either (i) combining other products or materials therewith or (ii) physically, chemically
or otherwise processing or treating the products, please duly consider all possible risks that may result from all such uses in advance
and proceed therewith at your own responsibility.
• Anti radioactive ray design is not considered for the products listed herein.
• Sanken assumes no responsibility for any troubles, such as dropping products caused during transportation out of Sanken's distribution network.
• The contents in this document must not be transcribed or copied without Sanken's written consent.
SSC2100-AN
SANKEN ELECTRIC CO., LTD.
18
Similar pages