FAIRCHILD FL7732

FL7732
Single-Stage PFC Primary-Side-Regulation Offline
LED Driver
Features
Description

Cost-Effective Solution: No Input Bulk Capacitor or
Feedback Circuitry

Power Factor Correction
This highly integrated PWM controller provides several
features to enhance the performance of low-power
flyback converters. The proprietary topology enables
simplified circuit design for LED lighting applications.

Accurate Constant-Current (CC) Control,
Independent Online Voltage, Output Voltage,
and Magnetizing Inductance Variation

Linear Frequency Control Improves Efficiency and
Simplifies Design

Open-LED Protection

Short-LED Protection

Cycle-by-Cycle Current Limiting

Over-Temperature Protection with Auto Restart

Low Startup Current: 20μA

Low Operating Current: 5mA

Frequency Hopping for Better EMI Performance

VDD Under-Voltage Lockout (UVLO)

Gate Output Maximum Voltage Clamped at 18V

SOP-8 Package

Application voltage range: 80VAC ~ 308VAC
By using single-stage topology with primary-side
regulation, a LED lighting board can be implemented
with few external components and minimized cost. No
input bulk capacitor or feedback circuitry is required. To
implement good power factor and low THD, constant
on-time control is utilized with an external capacitor
connected to the COMI pin.
Precise constant-current control regulates accurate
output current versus changes in input voltage and
output voltage. The operating frequency is proportionally
adjusted by the output voltage to guarantee DCM
operation with higher efficiency and simpler design.
FL7732 provides open-LED, short-LED, and overtemperature protection features. The current limit level
is automatically reduced to minimize output current and
protect external components in a short-LED condition.
FL7732 also has a frequency-hopping function in the
oscillator for better EMI performance. The FL7732
controller is available in an 8-pin SOP package.
Applications

LED Lighting System
Ordering Information
Part Number
Operating
Temperature Range
Package
Packing
Method
FL7732M
-40°C to +125°C
8-Lead, Small Outline Integrated Circuit Package (SOIC)
Tape & Reel
© 2011 Fairchild Semiconductor Corporation
FL7732 • Rev. 1.0.2
www.fairchildsemi.com
FL7732 — Single-Stage PFC Primary-Side-Regulation Offline LED Driver
February 2012
FL7732 — Single-Stage PFC Primary-Side-Regulation Offline LED Driver
Application Diagram
BRIDGE DIODE
TRANS
Line
Input
FUSE
FL7732
4
5
7
3
VDD
GATE
GND
N.C
COMI
VS
GND
CS
2
8
6
1
Figure 1. Typical Application
Internal Block Diagram
Shutdown
Internal
Bias
S
VDD Good
VDD 4
VOVP
+
-
OSC
Gate
Driver
Q
R
-
+
OCP Level
Controller
+
-
GND 3
Q
+
S
TSD
VS
LEB
1 CS
VOCP
Sawtooth
Generator
-
VDD Good
2 GATE
R
7 COMI
NC
Error
Amp.
5
Freq.
+
DCM Frequency
Controller
tdis
Detector
VREF
TrueCurrent™
Calculation
6 VS
GND 8
Sample & Hold
VS
Figure 2. Functional Block Diagram
© 2011 Fairchild Semiconductor Corporation
FL7732 • Rev. 1.0.2
www.fairchildsemi.com
2
F: Fairchild Logo
Z: Plant Code
X: 1-Digit Year Code
Y: 1-Digit Week Code
TT: 2-Digit Die Run Code
T: Package Type (M=SOP)
M: Manufacture Flow Code
ZXYTT
7732
TM
Figure 3. Top Mark
Pin Configuration
CS 1
8 GND
GATE 2
7 COMI
GND 3
6 VS
VDD 4
5 NC
Figure 4. Pin Configuration
Pin Definitions
Pin #
Name
Description
1
CS
2
GATE
PWM Signal Output. This pin uses the internal totem-pole output driver to drive the power
MOSFET.
3
GND
Ground
4
VDD
Power Supply. IC operating current and MOSFET driving current are supplied using this pin.
5
N.C
No Connect
6
VS
Voltage Sense. This pin detects the output voltage information and discharge time for
maximum frequency control and constant current regulation. This pin is connected to an
auxiliary winding of the transformer via resistors of the divider.
7
COMI
Constant Current Loop Compensation. This pin is connected to a capacitor between the
COMI and GND pin for compensation current loop gain.
8
GND
Ground
Current Sense. This pin connects a current-sense resistor to detect the MOSFET current for
the output-current regulation in constant-current regulation.
© 2011 Fairchild Semiconductor Corporation
FL7732 • Rev. 1.0.2
FL7732 — Single-Stage PFC Primary-Side-Regulation Offline LED Driver
Marking Information
www.fairchildsemi.com
3
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.
(1,2)
Max.
Unit
30
V
VVDD
DC Supply Voltage
VVS
VS Pin Voltage
-0.3
7
V
VCS
CS Pin Input Voltage
-0.3
7
V
VCOMI
COMI Pin Input Voltage
-0.3
7
V
VGATE
GATE Pin Input Voltage
-0.3
30
V
PD
Power Dissipation (TA<50°C)
633
mW
JA
Thermal Resistance (Junction to Air)
158
°C /W
JC
Thermal Resistance (Junction to Case)
39
°C /W
Maximum Junction Temperature
150
°C
150
°C
260
°C
TJ
TSTG
Storage Temperature Range
TL
Lead Temperature (Soldering 10s)
ESD
Electrostatic Discharge Capability
-55
Charged Device Model, JESD22-C101
5
KV
Human Body Model, JESD22-A114
2
KV
Notes:
1. Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device.
2. All voltage values, except differential voltages, are given with respect to the GND pin.
© 2011 Fairchild Semiconductor Corporation
FL7732 • Rev. 1.0.2
FL7732 — Single-Stage PFC Primary-Side-Regulation Offline LED Driver
Absolute Maximum Ratings
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4
VDD=15V and TA=25°C, unless otherwise specified.
Symbol
Parameter
Condition
Min.
Typ.
Max.
Unit
VDD Section
VDD-ON
Turn-On Threshold Voltage
14.5
16.0
17.5
V
VDD-OFF
Turn-Off Threshold Voltage
6.75
7.75
8.75
V
3
4
5
mA
2
20
μA
23.5
25.0
V
1.5
V
IDD-OP
Operating Current
IDD-ST
Startup Current
VOVP
VDD Over-Voltage-Protection Level
At Maximum Frequency
CL=1nF
VDD=VDD-ON – 0.16V
22.0
Gate Section
VOL
Output Voltage Low
VDD=20V, IGATE=-1mA
VOH
Output Voltage High
VDD=10V, IGATE=+1mA
5
V
Peak Sourcing Current
VDD=10 ~ 20V
60
mA
Peak Sinking Current
VDD=10 ~ 20V
180
mA
tr
Rising Time
CL=1nF
tf
Falling Time
CL=1nF
Isource
Isink
VCLAMP
Output Clamp Voltage
100
150
200
ns
20
60
100
ns
12
15
18
V
60
65
70
kHz
Oscillator Section
fMAX-CC
fMIN-CC
Maximum Frequency in CC
VDD=10V, 20V
Minimum Frequency in CC
VDD=10V, 20V
21.0
23.5
26.0
kHz
VSMAX-CC
VS for Maximum Frequency in CC
f=fMAX-2kHz
2.25
2.35
2.45
V
VSMIN-CC
VS for Minimum Frequency in CC
f=fMIN +2kHz
0.55
0.85
1.15
V
fHOPPING
Frequency Hopping Range
±1.8
±2.9
±4.0
kHz
tHOPPING
Frequency Hopping Period
tON(MAX)
Maximum Turn-On Time
2
ms
s
12
14
16
2.475
2.500
2.525
V
2.38
2.43
2.48
V
Current-Sense Section
VRV
Reference Voltage
VCCR
EAI Voltage for CC Regulation
tLEB
Leading-Edge Blanking Time
tMIN
Minimum On Time in CC
tPD
VCS=0.44V
VCOMI=0V
Propagation Delay to GATE
50
300
ns
600
ns
100
150
FL7732 — Single-Stage PFC Primary-Side-Regulation Offline LED Driver
Electrical Characteristics
ns
tDIS-BNK
tDIS Blanking Time of VS
1.5
s
IVS-BNK
VS Current for VS Blanking
100
A
85
mho
Current-Error-Amplifier Section
Gm
Transconductance
ICOMI-SINK
COMI Sink Current
VEAI=3V, VCOMI=5V
COMI Source Current
25
38
A
38
A
VEAI=2V, VCOMI=0V
25
VCOMI-HGH
COMI High Voltage
VEAI=2V
4.9
VCOMI-LOW
COMI Low Voltage
VEAI=3V
ICOMI-SOURCE
V
0.1
V
Continued on the following page…
© 2011 Fairchild Semiconductor Corporation
FL7732 • Rev. 1.0.2
www.fairchildsemi.com
5
VDD=15V and TA=25°C, unless otherwise specified.
Symbol
Parameter
Condition
Min.
Typ.
Max.
Unit
VCS Threshold Voltage for OCP
0.60
0.67
0.74
V
VLowOCP
VCS Threshold Voltage for Low OCP
0.13
0.18
0.23
V
VLowOCP-EN
VS Threshold Voltage to Enable Low
OCP Level
0.4
V
VLowOCP-DIS
VS Threshold Voltage to Disable Low
OCP Level
0.6
V
Over-Current Protection Section
VOCP
Over-Temperature Protection Section
TOTP
TOTP-HYS
Threshold Temperature for OTP(3)
140
Restart Junction Temperature
Hysteresis
150
10
160
o
C
o
C
Note:
3. If over-temperature protection is activated, the power system enters Auto-Recovery Mode and output is disabled.
Device operation above the maximum junction temperature is NOT guaranteed. OTP is guaranteed by design.
© 2011 Fairchild Semiconductor Corporation
FL7732 • Rev. 1.0.2
FL7732 — Single-Stage PFC Primary-Side-Regulation Offline LED Driver
Electrical Characteristics (Continued)
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6
Voltage-Mode control. With Fairchild’s innovative
TRUECURRENT™ technique, constant-current output
can be precisely controlled.
FL7732 is AC-DC dimmable PWM controller for LED
lighting applications. TRUECURRENT™ technique and
internal line compensation regulate accurate LED
current independent or input voltage, output voltage,
and magnetizing inductance variations. The TRIAC
dimming function block provides smooth brightness
control compatible with a conventional TRIAC dimmer.
The linear frequency control in the oscillator reduces
conduction loss and maintains DCM operation in the
wide range of output voltage, which implements high
power factor correction in a single-stage flyback
topology. A variety of protections, such as short/openLED protection, over-temperature protection, and cycleby-cycle current limitation stabilize system operation
and protect external components.
PFC and THD
In a conventional boost converter, Boundary Conduction
Mode (BCM) is generally used to keep input current inphase with input voltage for PF and THD. In
flyback/buck boost topology, constant turn-on time and
constant frequency in Discontinuous Conduction Mode
(DCM) can implement high PF and low THD, as shown
in Figure 6. Constant turn-on time is maintained by the
internal error amplifier and a large external capacitor
(typically over 1µF) at the COMI pin. Constant
frequency and DCM operation are managed by linear
frequency control.
Startup
Powering at startup is slow due to the low feedback loop
bandwidth in PFC converter. To boost powering during
startup, an internal oscillator counts 12ms to define
Startup Mode. During Startup Mode, turn-on time is
determined by Current-Mode control with a 0.2VCS
voltage limit and transconductance becomes 14 times
larger, as shown in Figure 5. After startup, turn-on time
is controlled by Voltage Mode using COMI voltage and
error amplifier transconductance is reduced to 85Mho.
IIN
IIN_AVG
VDD = VDD_ON
VIN
GATE
Constant Frequency
VCS
Figure 6. Input Current and Switching
0.2V
VCOMI
Linear Frequency Control
14gm gm
FL7732 — Single-Stage PFC Primary-Side-Regulation Offline LED Driver
Functional Description
As mentioned above, DCM should be guaranteed for
high power factor in flyback topology. To maintain DCM
across the wide range of output voltage, frequency is
linearly adjusted by output voltage in linear frequency
control. Output voltage is detected by the auxiliary
winding and the resistive divider connected to the VS
pin, as shown in Figure 7.
Startup Mode: 12ms
ILED
Time
OSC
Figure 5. Startup Sequence
VOUT
Linear Frequency
Controller
Constant-Current Regulation
The output current can be estimated using the peak
drain current and inductor current discharge time since
output current is same as the average of the diode
current in steady state. The peak value of the drain
current is determined by the CS pin and the inductor
discharge time (tdis) is sensed by tdis detector. By using
three points of information (peak drain current, inductor
discharging time, and operating switching period);
TRUECURRENT™ calculation block estimates output
current. The output of the calculation is compared with
an internal precise reference to generate an error
voltage (VCOMI), which determines turn-on time in
© 2011 Fairchild Semiconductor Corporation
FL7732 • Rev. 1.0.2
f
6
VS
VS
Figure 7. Linear Frequency Control
www.fairchildsemi.com
7
Primary
Current
Figure 10 shows operational waveforms in short-LED
condition. Output voltage is quickly lowered to 0V right
after a short-LED event. Then the reflected auxiliary
voltage is also 0V, making VS less than 0.4V. 0.2V OCP
level limits primary-side current and VDD hiccups up and
down between UVLO hysteresis.
LED Short !
Secondary
Current
nV O
Lm
VO =
VO.NOM
VIN
t
t DIS
n
VO =
75% VO.NOM
3
V
4 O
Lm
VCS
0.2V
4
t
3
4
t DIS
3
n
VO =
60% VO.NOM
3
V
5
Lm
VDD
VDD_ON
O
5
t DIS
3
VDD_OFF
5
t
3
Figure 10. Waveforms in Short-LED Condition
Figure 8. Primary and Secondary Current
BCM Control
Open-LED Protection
The end of secondary diode conduction time is possibly
over a switching period set by linear frequency control.
In this case, FL7732 doesn’t allow CCM and the
operation mode changes from DCM to BCM. Therefore,
FL7732 eliminates sub-harmonic distortion in CCM.
FL7732 protects external components, such as diode
and capacitor, at secondary side in open-LED condition.
During switch-off, the VDD capacitor is charged up to the
auxiliary winding voltage, which is applied as the
reflected output voltage. Because the VDD voltage has
output voltage information, the internal voltage
comparator on the VDD pin can trigger output OverVoltage Protection (OVP), as shown in Figure 11. When
at least one LED is open-circuited, output load
impedance becomes very high and output capacitor is
quickly charged up to VOVP x NS / NA Then switching is
shut down and the VDD block goes into Hiccup Mode
until the open-LED condition is removed, as shown in
Figure 12.
Short-LED Protection
In case of a short-LED condition, the switching
MOSFET and secondary diode are stressed by the high
powering current. However, FL7732 changes the OCP
level in a short-LED condition. When VS voltage is lower
than 0.4V, OCP level becomes 0.2V from 0.7V, as
shown in Figure 10, so powering is limited and external
components current stress is reduced.
LEB
FL7732 — Single-Stage PFC Primary-Side-Regulation Offline LED Driver
When output voltage decreases, secondary diode
conduction time is increased and the linear frequency
control lengthens the switching period, which retains
DCM operation in the wide output voltage range, as
shown in Figure 8. The frequency control lowers the
primary rms current with better power efficiency in the
full-load condition.
Internal
Bias
1 CS
VDD Good
VOCP
+
-
+
-
VDD 4
At VS < 0.4V,
VOCP = 0.2V
VOVP
6 VS
At VS > 0.6V,
VOCP = 0.7V
S
Figure 9. Internal OCP Block
VDD Good
Q
Shutdown Gate Driver
R
Figure 11. Internal OVP Block
© 2011 Fairchild Semiconductor Corporation
FL7732 • Rev. 1.0.2
www.fairchildsemi.com
8
Over-Temperature Protection (OTP)
The FL7732 has a built-in temperature-sensing circuit to
shut down PWM output if the junction temperature
exceeds 150°C. While PWM output is shut down, the
VDD voltage gradually drops to the UVLO voltage. Some
of the FL7732’s internal circuits are shut down and VDD
gradually starts increasing again. When VDD reaches
16V, all the internal circuits start operating. If the
junction temperature is still higher than 140°C, the PWM
controller is shut down immediately.
Frequency Hopping
EMI reduction is accomplished by frequency hopping,
which spreads the energy over a wider frequency range
than the bandwidth measured by EMI test equipment.
FL7732 has an internal frequency-hopping circuit that
changes the switching frequency ±2.9kHz.
Figure 12. Waveforms in Open-LED Condition
Under-Voltage Lockout (UVLO)
The turn-on and turn-off thresholds are fixed internally at
16V and7.5V, respectively. During startup, the VDD
capacitor must be charged to 16V through the startup
resistor to enable the FL7732. The VDD capacitor
continues to supply VDD until power can be delivered
© 2011 Fairchild Semiconductor Corporation
FL7732 • Rev. 1.0.2
FL7732 — Single-Stage PFC Primary-Side-Regulation Offline LED Driver
from the auxiliary winding of the main transformer. VDD
must not drop below 7.5V during this startup process.
This UVLO hysteresis window ensures that the VDD
capacitor is adequate to supply VDD during startup.
www.fairchildsemi.com
9
8.00
16.2
7.90
15.9
7.80
VDD_OFF
VDD_ON
16.5
15.6
7.70
7.60
15.3
7.50
15.0
-40
-30
-15
0
25 50 75
Temperature[ºC]
85
-40
100 125
4.20
23.5
4.10
23.4
4.00
23.3
3.90
0
25 50 75
Temperature[ºC]
85
100 125
23.2
23.1
3.80
23.0
3.70
-40
-30
-15
0
25 50 75
Temperature[ºC]
85
-40
100 125
Figure 15. IDD-OP vs. Temperature
-30
-15
0
25 50 75
Temperature[ºC]
85
100 125
Figure 16. VOVP vs. Temperature
75.0
26.0
72.0
24.8
69.0
23.6
FMIN-CC [kHz]
FMAX-CC [kHz]
-15
Figure 14. VDD-OFF vs. Temperature
VOVP
IDD_OP
Figure 13. VDD-ON vs. Temperature
-30
66.0
63.0
60.0
FL7732 — Single-Stage PFC Primary-Side-Regulation Offline LED Driver
Typical Performance Characteristics
22.4
21.2
20.0
-40
-30
-15
0
25 50 75
Temperature[ºC]
85
100 125
-40
Figure 17. fMAX_CC vs. Temperature
© 2011 Fairchild Semiconductor Corporation
FL7732 • Rev. 1.0.2
-30
-15
0
25 50 75
Temperature[ºC]
85
100 125
Figure 18. fMIN_CC vs. Temperature
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10
2.55
2.51
2.53
2.47
2.51
VVVR
VCCR
2.55
2.43
2.49
2.47
2.39
2.45
2.35
-40
-30
-15
0
25 50 75
Temperature[ºC]
85
-40
100 125
Figure 19. VCCR vs. Temperature
-15
0
25 50 75
Temperature[ºC]
85
100 125
Figure 20. VVVR vs. Temperature
0.190
0.72
0.187
0.71
0.184
VOCP-Low
VOCP-High
-30
0.70
0.181
0.69
0.178
0.68
0.175
-40
-30
-15
0
25 50 75
Temperature[ºC]
85
-40
100 125
Figure 21. VOCP-HIGH vs. Temperature
© 2011 Fairchild Semiconductor Corporation
FL7732 Rev.1.0.1
-30
-15
0
25 50 75
Temperature[ºC]
85
100 125
Figure 22. VOCP-LOW vs. Temperature
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12
FL7732 — Single-Stage PFC Primary-Side-Regulation Offline LED Driver
Typical Performance Characteristics (Continued)
5.00
4.80
A
0.65
3.81
5
8
B
1.75
6.20
5.80
PIN ONE
INDICATOR
4.00
3.80
1
5.60
4
1.27
(0.33)
1.27
0.25
C B A
LAND PATTERN RECOMMENDATION
SEE DETAIL A
0.25
0.10
1.75 MAX
0.25
0.19
C
0.51
0.33
0.10 C
OPTION A - BEVEL EDGE
0.50 x 45°
0.25
R0.10
GAGE PLANE
R0.10
FL7732 — Single-Stage PFC Primary-Side-Regulation Offline LED Driver
Physical Dimensions
OPTION B - NO BEVEL EDGE
0.36
NOTES: UNLESS OTHERWISE SPECIFIED
8°
0°
0.90
0.40
A) THIS PACKAGE CONFORMS TO JEDEC
MS-012, VARIATION AA, ISSUE C,
B) ALL DIMENSIONS ARE IN MILLIMETERS.
C) DIMENSIONS DO NOT INCLUDE MOLD
FLASH OR BURRS.
D) LANDPATTERN STANDARD: SOIC127P600X175-8M.
E) DRAWING FILENAME: M08AREV13
SEATING PLANE
(1.04)
DETAIL A
SCALE: 2:1
Figure 23. 8-Lead, Small Outline Integrated Circuit Package (SOIC)
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/
© 2011 Fairchild Semiconductor Corporation
FL7732 Rev.1.0.1
www.fairchildsemi.com
12
FL7732 — Single-Stage PFC Primary-Side-Regulation Offline LED Driver
© 2011 Fairchild Semiconductor Corporation
FL7732 Rev.1.0.1
www.fairchildsemi.com
13