FAIRCHILD SG6932SZ

Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
FEATURES OVERVIEW
DESCRIPTION
„
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„
„
The highly integrated SG6932 is designed for power
supplies with boost PFC and forward PWM. It requires
very few external components to achieve green-mode
operation and versatile protections / compensation. It is
available in 16-pin DIP and SOP packages.
„
„
„
„
„
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„
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Interleaved PFC / PWM switching
Green-mode PFC and PWM operation
Low operating current
Innovative switching-charge multiplier-divider
Multi-vector control for improved PFC output
transient response
Average-current-mode for input-current shaping
PFC over-voltage and under-voltage protections
PFC and PWM feedback open-loop protection
Cycle-by-cycle current limiting for PFC/PWM
Slope compensation for PWM
Selectable PWM maximum duty cycle 50% and 65%
Brownout protection
Power-on sequence control and soft-start
APPLICATIONS
„
„
„
Switch-mode power supplies with active PFC
Servo system power supplies
PC-ATX power supplies
The patented interleave-switching feature synchronizes
the PFC and PWM stages and reduces switching noise. At
light load, the switching frequency is continuously
decreased to reduce power consumption.
For PFC stage, the proprietary multi-vector control
scheme provides a fast transient response in a
low-bandwidth PFC loop, in which the overshoot and
undershoot of the PFC voltage are clamped. If the
feedback loop is broken, SG6932 shuts off to prevent
extra-high voltage on output.
For the Forward PWM stage, the synchronized slope
compensation ensures the stability of the current loop
under continuous-conduction-mode operation. Hiccup
operation during output overloading is guaranteed. The
soft-start and programmable maximum duty cycle ensure
safe operation.
SG6932 provides complete protection functions, such as
brownout protection and RI open/short latch off.
TYPICAL APPLICATION
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
-1-
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
MARKING DIAGRAMS
SG6932TP
XXXXXXXXYWWV
PIN CONFIGURATION
T: D=DIP, S=SOP
P : Z =Lead Free + ROHS
Compatible
XXXXXXXX: Wafer Lot
Y: Year; WW: Week
V: Assembly Location
VRMS
1
16
IAC
RI
2
15
VEA
IEA
3
14
FBPFC
IPFC
4
13
SS
IMP
5
12
VDD
ISENSE
6
11
OPFC
FBPWM
7
10
GND
IPWM
8
9
OPWM
ORDERING INFORMATION
Part Number
Pb-Free
Package
SG6932DZ
16-pin DIP
SG6932SZ (Preliminary)
16-pin SOP
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
-2-
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
PIN DESCRIPTIONS
Name
Pin No. Type
VRMS
1
Line-Voltage
Detection
Line voltage detection. The pin is used for PFC multiplier and brownout protection.
RI
2
Oscillator Setting
Reference setting. One resistor connected between RI and ground determines the
switching frequency. A resistor with resistance between 12k ~ 47kΩ is recommended. The
switching frequency is equal to [1560 / RI] kHz, where RI is in kΩ. For example, if RI is 24kΩ,
the switching frequency is 65kHz.
IEA
3
Output of PFC Current This is the output of the PFC current amplifier. The signal from this pin is compared with an
Amplifier
internal sawtooth and determines the pulse width for PFC gate drive.
IPFC
4
Inverting Input of PFC The inverting input of the PFC current amplifier. Proper external compensation circuits
Current Amplifier
result in excellent input power factor via average-current-mode control.
IMP
5
Non-inverting Input of
The non-inverting input of the PFC current amplifier and the output of the multiplier. Proper
PFC Current Amplifier
external compensation circuits result in excellent input power factor via average current
and Output of
mode control.
Multiplier
ISENSE
6
Peak Current Limit
Setting for PFC
FBPWM
7
The control input for voltage-loop feedback of PWM stage. It is internally pulled high through
PWM Feedback Input a 6.5kΩ resistance. Usually an external opto-coupler from secondary feedback circuit is
connected to this pin.
IPWM
8
PWM Current Sense
The current sense input for the PWM stage. Via a current sense resistor, this pin provides
the control input for peak-current-mode control and cycle-by-cycle current limiting.
OPWM
9
PWM Gate Drive
The totem pole output drive for PWM MOSFET. This pin is internally clamped under 18V to
protect the MOSFET.
GND
10
Ground
The power ground.
OPFC
11
PFC Gate Drive
The totem pole output drive for the PFC MOSFET. This pin is internally clamped under 18V
to protect the MOSFET.
VDD
12
Supply
The power supply pin. The threshold voltages for start-up and turn-off are 14V and 10V,
respectively. The operating current is lower than 10mA.
SS
13
PWM Soft-Start
During start-up, the SS pin charges an external capacitor with a 50µA constant current
source. The voltage on FBPWM is clamped by SS during start-up. In the event of a
protection condition occurring and/or PWM being disabled, the SS pin is quickly
discharged. The voltage of SS pin can be used to select 50% or 65% maximum duty cycle.
FBPFC
14
Voltage Feedback
Input for PFC
The feedback input for PFC voltage loop. The inverting input of PFC error amplifier. This pin
is connected to the PFC output through a divider network.
VEA
15
Error Amplifier Output The error amplifier output for PFC voltage feedback loop. A compensation network (usually
for PFC Voltage
a capacitor) is connected between this pin and ground. A large capacitor value results in a
Feedback Loop
narrow bandwidth and improves the power factor.
IAC
16
Input AC Current
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
Function
The peak current limit setting for PFC.
For normal operation, this input is used to provide current reference for the multiplier. The
suggested maximum IAC is 360µA.
-3-
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
BLOCK DIAGRAM
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
-4-
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
VDD
DC Supply Voltage*
25
V
IAC
Input AC Current
2
mA
VHigh
OPWM, OPFC, IAC
-0.5 to 25V
V
VLow
Others
-0.5 to 7V
V
PD
Power Dissipation
0.8
W
TJ
Operating Junction Temperature
-40 to 125
℃
Tstg
Storage Temperature Range
-55 to +150
RθjC
TL
ESD
Test Conditions Value
At TA<50℃
Thermal resistance (Junction-to-Case)
Unit
℃
DIP
33.64
SOP
41.95
℃/W
Lead Temperature (Wave soldering, 10 seconds)
260
℃
Electrostatic Discharge Capability, Human Body Model
4.5
KV
Electrostatic Discharge Capability, Machine Model
250
V
*All voltage values, except differential voltages, are given with respect to the network ground terminal.
RECOMMENDED OPERATING JUNCTION TEMPERATURE: -30°C~ 85°C*
* For proper operation.
ELECTRICAL CHARACTERISTICS
VDD=15V, TA=25°C unless otherwise noted.
VDD Section
Symbol
VDD-OP
Parameter
Continuously Operating Voltage
IDD ST
Start-Up Current
IDD-OP
Operating Current
VTH-ON
Start Threshold Voltage
VDD-min
Min. Operating Voltage
VDD-OVP
VDD OVP1 (turn off PWM with delay)
TVDD-OVP
Delay time of VDD OVP1
Test Conditions
Typ.
Max.
20
Unit
V
VDD -0.16V
10
20
µA
VDD=15V; OPFC OPWM open
6
10
mA
13
14
15
V
9
10
11
V
23.5
24.5
RI=24kΩ
Min.
8
25.5
V
25
µs
Oscillator & Green-Mode Operation
Symbol
Parameter
VRI
RI Voltage
FOSC
PWM Frequency
FOSC-MINFREQ
Minimum Frequency in Green Mode
RI
RIOPEN
RISHORT
Test Conditions
Min.
Typ.
Max.
Unit
1.176
1.200
1.224
V
RI=24kΩ
62
65
68
KHz
RI=24kΩ
18
20
22
KHz
47
kΩ
RI Range
12
RI Pin Open Protection
If RI > RIopen , PWM Turned Off
RI Pin Short Protection
If RI< RIshort , PWM Turned Off
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
-5-
200
kΩ
2
kΩ
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
VRMS for UVP and ON/OFF
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
0.75
0.8
0.85
V
RMS AC Voltage Under-Voltage Threshold
VRMS-UVP-1
to Turn Off PFC (with TUVP Delay) for UVP
Mode1
VRMS-UVP-2
VRMS-UVP-1+ VRMS-UVP-1+ VRMS-UVP-1+
Recovery Level on VRMS for UVP
V
0.17V
0.19V
0.21V
RI=24kΩ
150
195
240
ms
Test Conditions
Min.
Typ.
Max.
Unit
2.95
3.00
3.05
V
Under-Voltage Protection Propagation to
TUVP
Turn Off PFC Delay Time (No Delay for
Start-up)
PFC Stage
Voltage Error Amplifier
Symbol
Parameter
VREF
Reference Voltage
Av
Open-Loop Gain
60
dB
Zo
Output Impedance
110
kΩ
OVPFBPFC
△OVPFBPFC
PFC Over-voltage Protection
PFC Feedback Voltage Protection
Hysteresis
VFBPFC-H
Clamp-High Feedback Voltage
GFBPFC-H
Clamp-High Gain
VFBPFC-L
Clamp-Low Feedback Voltage
GFBPFC-L
Clamp-Low Gain
IFBPFC-L.
Maximum Source Current
3.20
3.25
3.30
V
60
90
120
mV
3.10
3.15
3.20
V
2.90
V
0.5
mA/V
2.75
2.85
6.5
mA/mV
1.5
2.0
mA
IFBPFC-H.
Maximum Sink Current
70
110
UVPVFB
PFC Feedback Under-Voltage Protection
0.35
0.40
0.45
V
VFBHIGH
Output High Voltage on VEA
6
7
8
V
2.6
2.7
2.8
V
40
70
120
µs
Min.
Typ.
Max.
Unit
VRD-FBPFC
TUVP-PFC
Voltage level on FBPFC to Enable OPWM
During Start-up
Debounce Time of PFC UVP
µA
Current Error Amplifier
Symbol
Parameter
VOFFSET
Input Offset Voltage ((-) > (+))
8
AI
Open-loop Gain
60
dB
BW
Unit Gain Bandwidth
1.5
MHz
CMRR
Common-mode Rejection Ratio
70
dB
VOUT-HIGH
Output High Voltage
VOUT-LOW
Output Low Voltage
IMR1, IMR2
Reference Current Source
IL
Maximum Source Current
3
mA
IH
Maximum Sink Current
0.25
mA
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
Test Conditions
VCM=0 ~ 1.5V
mV
3.2
RI=24kΩ (IMR=20+IRI•0.8)
-6-
V
50
0.2
V
70
µA
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
Peak Current Limit
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
IP
Constant Current Output
RI=24kΩ
90
100
110
µA
Peak Current Limit Threshold Voltage
VRMS=1.05V
0.15
0.20
0.25
V
Cycle-by-Cycle Limit (Vsense < Vpk)
VRMS=3V
0.35
0.40
0.45
V
200
ns
Vpk
TpkD
Propagation Delay
Bnkt
Leading-Edge Blanking Time
270
350
450
ns
Typ.
Max.
Unit
360
µA
Multiplier
Symbol
Parameter
Test Conditions
Min.
IAC
Input AC Current
Multiplier Linear Range
0
IMO–max
Maximum Multiplier Current Output;
RI=24kΩ
Multiplier Current Output
VRMS=1.05V; IAC=90µA;
(Low-Line, High-Power)
VEA=7.5V; RI=24kΩ
IMO-1
IMO–2
VIMP
Multiplier Current Output
VRMS=3V; IAC=264µA;
(High-Line, High-Power)
VEA=7.5V; RI=24kΩ
230
Voltage of IMP Open
200
230
65
85
3.4
3.9
µA
280
µA
µA
4.4
V
Typ.
Max.
Unit
16
18
V
PFC Output Driver
Symbol
Parameter
Test Conditions
VZ-PFC
Output Voltage Maximum (Clamp)
VDD=20V
Min.
VOL-PFC
Output Voltage Low
VDD=15V; IO=100mA
VOH-PFC
Output Voltage High
VDD=13V; IO=100mA
TR-PFC
Rising Time
VDD=15V; CL=5nF; O/P=2V to 9V
40
70
120
ns
Tf-PFC
Falling Time
VDD=15V; CL=5nF; O/P=9V to 2V
40
60
110
ns
DC(MAX)
Maximum Duty Cycle
97
%
1.5
8
V
V
93
PWM Stage
FBPWM
Symbol
Parameter
Min.
Typ.
AV
FB to Current Comparator Attenuation
2.2
2.7
3.2
V/V
ZFB
Input Impedance
4
4.2
5
4.5
7
4.8
kΩ
RI=24kΩ
500
600
700
ms
RI=24kΩ
80
95
120
ms
1.9
2.1
2.3
V
60
75
90
Hz/mV
1.35
1.60
1.75
V
FBOPEN-LOOP
TOPEN-PWM-Hiccup
TOPEN-PWM
VN
SG
VG
Test Conditions
PWM Open-Loop Protection Voltage
Interval of PWM Open-Loop Protection
Reset
PWM Open-Loop Protection Delay Time
Frequency Reduction Threshold on
FBPWM
Green-Mode Modulation Slope
Voltage on FBPWM for Minimum
Green-Mode Frequency
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
-7-
Max. Unit
V
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
PWM-Current Sense
Symbol
Parameter
Test Conditions
Min.
TPD-PWM
Propagation Delay to Output – VLIMIT Loop
VDD=15V, OPWM drops to 9V
60
Typ.
Max.
Unit
120
VLIMIT
Peak Current Limit Threshold Voltage
0.65
0.70
0.75
ns
V
TBNK-PWM
Leading-Edge Blanking Time
270
350
450
ns
△VSLOPE
Slope Compensation
△Vs=△VSLOPE x (Ton/T)
△Vs: Compensation Voltage Added to
Current Sense
0.40
0.45
0.55
V
Unit
Output Driver
Symbol
Parameter
Test Conditions
VZ-PWM
Output Voltage Maximum (Clamp)
VDD=20V
Min.
TPWM
Interval of OPWM Lags Behind OPFC at
Start-up
RI=24kΩ
VOL-PWM
Output Voltage Low
VDD=15V; IO=100mA
VOH-PWM
Output Voltage High
VDD=13V; IO=100mA
8
2
Typ.
Max.
16
18
V
4
6
ms
1.5
V
V
TR-PWM
Rising Time
VDD=15V; CL=5nF; O/P=2V to 9V
30
60
120
ns
TF-PWM
Falling Time
VDD=15V; CL=5nF; O/P=9V to 2V
30
50
110
ns
Typ.
Maximum Duty Cycle
Symbol
Parameter
Test Conditions
Min.
Max.
Unit
DC SS=6V
Maximum Duty Cycle for SS=6V
RI=24kΩ
62
66
%
DC SS=5V
Maximum Duty Cycle for SS=5V
RI=24kΩ
46
50
%
Soft-Start
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
ISS
Constant Current Output for Soft-Start
RT=24kΩ
44
50
56
µA
VDC-MAX-50%
Voltage of SS for 50% Maximum Duty Cycle
5
V
VDC-MAX--65%
Voltage of SS for 65% Maximum Duty Cycle
RD
Discharge Resistance
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
6
V
470
-8-
Ω
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
TYPICAL CHARACTERISTICS
Min. Operation Voltge (VDD-MIN) vs Temperature
20.0
11.0
18.0
10.8
16.0
10.6
14.0
10.4
VTH-MIN(V)
IDD ST (uA)
Start-Up Current (IDD ST) vs Temperature
12.0
10.0
8.0
10.2
10.0
9.8
6.0
9.6
4.0
9.4
2.0
9.2
0.0
9.0
-40℃
-25℃
-10℃
5℃
20℃
35℃
50℃
65℃
80℃
95℃
110℃
125℃
-40℃
-25℃
-10℃
5℃
20℃
35℃
50℃
65℃
Temperature (℃)
Temperature (℃)
Start Threshold Voltage (VTH-ON) vs Temperature
Frequency vs. FB Voltage
80℃
95℃
110℃
125℃
15.0
14.8
70.0
14.6
60.0
Frequency (KHz)
VTH-ON(V)
14.4
14.2
14.0
13.8
13.6
13.4
50.0
40.0
30.0
20.0
10.0
13.2
0.0
13.0
1.3
-40℃
-25℃
-10℃
5℃
20℃
35℃
50℃
65℃
80℃
95℃
110℃
125℃
1.4
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2.2
2.3
2.4
2.5
2.6
FB Voltage (V)
Temperature (℃)
Duty Cycle vs. FB Voltage
Start-up Current vs. VDD Voltage
60.0
50.0
Duty Cycle (%)
Start-up Current (uA)
70.0
10.0
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
40.0
30.0
20.0
10.0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0.0
VDD Voltage (V)
1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2
FB Voltage (V)
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
-9-
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
PFC over Voltage Protection (OVPPFC) vs Temperature
25.5
3.30
25.3
3.29
25.1
3.28
24.9
3.27
OVPPFC (V)
VDD-OVP (V)
VDD OVP Threshold (VDD-OVP) vs Temperature
24.7
24.5
24.3
3.26
3.25
3.24
24.1
3.23
23.9
3.22
23.7
3.21
3.20
23.5
-40℃
-25℃
-10℃
5℃
20℃
35℃
50℃
65℃
80℃
95℃
110℃
-40℃
125℃
-25℃
-10℃
5℃
20℃
80℃
95℃
110℃
125℃
95℃
110℃
125℃
95℃
110℃
125℃
95℃
110℃
125℃
90.0
80.0
TR(nS)
FOSC (KHz)
65℃
100.0
68.0
67.5
67.0
66.5
66.0
65.5
65.0
64.5
64.0
63.5
63.0
62.5
62.0
70.0
60.0
50.0
40.0
30.0
-40℃ -25℃ -10℃
5℃
20℃
35℃
50℃
65℃
80℃
95℃ 110℃ 125℃
-40℃
-25℃
-10℃
5℃
20℃
Temperature (℃)
35℃
50℃
65℃
80℃
Temperature (℃)
PWM Frequency (FOSC-GREEN) vs Temperature
Falling Time (TF-PFC) vs Temperature
22.0
100.0
21.5
90.0
21.0
80.0
20.5
TF (nS)
FOSC-MINFREQ (KHz)
50℃
Rising Time (TR-PFC) vs Temperature
PWM Frequency (FOSC) vs Temperature
20.0
19.5
70.0
60.0
50.0
19.0
40.0
18.5
18.0
30.0
-40℃
-25℃
-10℃
5℃
20℃
35℃
50℃
65℃
80℃
95℃
110℃
125℃
-40℃
-25℃
-10℃
5℃
20℃
Temperature (℃)
35℃
50℃
65℃
80℃
Temperature (℃)
Reference Voltage (VREF) vs Temperature
Maximum Duty Cycle (SS=5V) vs Temperature
3.05
50.0
3.04
49.5
3.03
49.0
DCMAX (%)
3.02
VREF (V)
35℃
Temperature (℃)
Temperature (℃)
3.01
3.00
2.99
2.98
48.5
48.0
47.5
47.0
2.97
46.5
2.96
2.95
46.0
-40℃
-25℃
-10℃
5℃
20℃
35℃
50℃
65℃
80℃
95℃
110℃
125℃
Temperature (℃)
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
-40℃
-25℃
-10℃
5℃
20℃
35℃
50℃
65℃
80℃
Temperature (℃)
- 10 -
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
Rising Time (TR-PWM) vs Temperature
Maximum Duty Cycle (SS=6V) vs Temperature
66.0
120.0
65.5
110.0
100.0
TR-PWM (nS)
DCMAX (%)
65.0
64.5
64.0
63.5
90.0
80.0
70.0
60.0
63.0
50.0
62.5
40.0
62.0
30.0
-40℃
-25℃
-10℃
5℃
20℃
35℃
50℃
65℃
80℃
95℃
110℃
125℃
-40℃
-25℃
-10℃
5℃
20℃
Temperature (℃)
50℃
65℃
80℃
95℃
110℃
125℃
95℃
110℃
125℃
110℃
125℃
Fall Time (TF-PWM) vs Temperature
4.80
4.75
4.70
4.65
4.60
4.55
4.50
4.45
4.40
4.35
4.30
4.25
4.20
110.0
100.0
90.0
TF-PWM (nS)
FBOPEN-LOOP (V)
PWM Open Loop Protection voltage (FBOPEN-LOOP) vs Temperature
80.0
70.0
60.0
50.0
40.0
30.0
-40℃
-25℃
-10℃
5℃
20℃
35℃
50℃
65℃
80℃
95℃
110℃
125℃
-40℃
-25℃
-10℃
5℃
20℃
Temperature (℃)
35℃
50℃
65℃
80℃
Temperature (℃)
Constant Current Output for Soft Start (ISS) vs Temperature
PWM Open Loop Protection Delay Time (TOPEN-PWM) vs Temperature
120
55
115
54
53
110
52
105
ISS (uA)
TOPEN-PWM (mS)
35℃
Temperature (℃)
100
95
51
50
49
48
90
47
85
46
80
45
-40℃
-25℃
-10℃
5℃
20℃
35℃
50℃
65℃
80℃
95℃
110℃
125℃
Temperature (℃)
-40℃
-25℃
-10℃
5℃
20℃
35℃
50℃
65℃
80℃
95℃
Temperature (℃)
Peak Current Limit Threshold Voltge (VLIMIT) vs Temperature
0.75
0.74
0.73
VLIMIT (V)
0.72
0.71
0.70
0.69
0.68
0.67
0.66
0.65
-40℃
-25℃
-10℃
5℃
20℃
35℃
50℃
65℃
80℃
95℃
110℃
125℃
Temperature (℃)
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
- 11 -
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
OPERATION DESCRIPTION
The highly integrated SG6932 is designed for power
supplies with boost PFC and forward PWM. It requires
very few external components to achieve green-mode
operation and versatile protections / compensation.
The patented interleave-switching feature synchronizes
the PFC and PWM stages and reduces switching noise. At
light load, the switching frequency is linearly decreased to
reduce power consumption.
The PFC function is implemented by averagecurrent-mode control. The patented switching charge
multiplier-divider provides high-degree noise immunity
for the PFC circuit. This also enables the PFC circuit to
operate over a much wider region. The proprietary
multi-vector output voltage control scheme provides a fast
transient response in a low-bandwidth PFC loop, in which
the overshoot and undershoot of the PFC voltage are
clamped. If the feedback loop is broken, the SG6932 shuts
off PFC to prevent extra-high voltage on output.
For the forward PWM, the synchronized slope
compensation ensures the stability of the current loop
under continuous-mode operation. Hiccup operation
during output overloading is also guaranteed. To prevent
the power supply from drawing large current during
start-up, the start-up for PWM stage is delayed 4ms after
the PFC output voltage reaches its setting value.
In addition, SG6932 provides complete protection
functions such as brownout protection and built-in latch
for over-voltage and RI open/short.
Figure 1. Input Voltage Detection
Switching Frequency / Current Sources
The switching frequency of SG6932 can be programmed
by the resistor RI connected between RI pin and GND.
The relationship is:
fPWM =
1560
(kHz ) ------------RI (kΩ)
(1)
For example, a 24kΩ resistor RI results in a 65kHz
switching frequency. Accordingly, constant current IT
flows through RI.
I
T
=
1.2V
RI (kΩ )
(mA) ----------------
(2)
IT is used to generate internal current reference.
IAC signal
Line Voltage Detection (VRMS)
Figure 1 shows the IAC pin connected to input voltage by
a resistance and the current, IAC, is the input for PFC
multiplier. For the linear range of IAC 0~360µA, the range
input voltage should be connected a resistance over 1.2M.
Figure 2 shows a resistive divider with low-pass filtering
for line-voltage detection on VRMS pin. The VRMS
voltage is used for the PFC multiplier and brownout
protection. For brownout protection, when the VRMS
voltage drops below 0.8V, OPFC turns off.
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
- 12 -
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
Figure 4. Control Loop of PFC Stage
Figure 2. Line-Voltage Detection on VRMS Pin
The current source output from the switching charge
multiplier-divider can be expressed as:
Interleave Switching / Green-Mode
The SG6932 uses interleaved switching to synchronize
the PFC and PWM stages. This reduces switching noise
and spreads the EMI emissions. Figure 3 shows off-time
(TOFF) inserted between the turn-off of the PFC gate
drives and the turn-on of the PWM.
The off-time (TOFF) is increased in response to the
decreasing of the voltage level of FBPWM; therefore, the
PWM switching frequency is linearly decreased to reduce
switching losses.
IMO = K ×
IAC × VEA
(µA )
VRMS 2
(3)
IMP, the current output from IMP pin, is the summation of
IMO and IMR1. IMR1 and IMR2 are identical fixed-current
sources. R2 and R3 are also identical. They are used to pull
high the operating point of the IMP and IPFC pins when
the voltage across RS goes negative with respect to
ground.
Through the differential amplification of the signal across
RS, better noise immunity is achieved. The output of IEA
is compared with an internal sawtooth and the pulse width
for PFC is determined. Through the average current-mode
control loop, the input current IS is proportional to IMO:
OPFC
OPWM
TOFF
IMO × R 2 = IS × RS
(4)
Figure 3. Interleaved Switching
According to Equation 4, the minimum value of R2 and
maximum of RS can be determined since IMO should not
exceed the specified maximum value.
PFC Operation
The purpose of a boost active power factor corrector (PFC)
is to shape the input current of a power supply. The input
current waveform and phase follow that of the input
voltage. Using SG6932, average-current-mode control is
utilized for continuous-current-mode operation for the
PFC booster. With the innovative multi-vector control for
voltage loop and switching-charge multiplier-divider for
current reference, excellent input power factor is achieved
with good noise immunity and transient response. Figure
4 shows the total control loop for the
average-current-mode control circuit of SG6932.
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
- 13 -
There are different concerns in determining the value of
the sense resistor, RS. The value of RS should be small
enough to reduce power consumption, but large enough to
maintain the resolution. A current transformer (CT) may
be used to improve the efficiency of high power
converters.
To achieve good power factor, the voltage for VRMS and
VEA should be kept as DC as possible, according to
Equation 3. Good RC filtering for VRMS and narrow
bandwidth (lower than the line frequency) for voltage
loop are suggested for better input current shaping. The
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
transconductance error amplifier has output impedance
RO (>90kΩ) and a capacitor CEA (1µF ~ 10µF) connected
to ground (as shown in Figure 5). This establishes a
dominant pole f1 for the voltage loop:
f1 =
1
2π × R0 × CEA
3.15V
+
2.85V
(5)
RA
The average total input power can be expressed as:
FBPFC
-
RB
3V
Pin = Vin( rms ) × Iin( rms )
∝ VRMS × I MO
∝ VRMS ×
I AC × VEA
2
VRMS
+
K
IACxVEA
2
V RMS
VEA
C EA
(6)
Vin
× VEA
RAC
∝ VRMS ×
∝ VEA
2
VRMS
Figure 5. Multi-Vector Error Amplifier
From Equation 6, VEA, the output of the voltage error
amplifier, actually controls the total input power and the
power delivered to the load.
Multi-Vector Error Amplifier
The voltage-loop error amplifier is transconductance,
which has high output impedance (> 90kΩ). A capacitor
CEA (1µF ~ 10µF) connected from VEA to ground
provides a dominant pole for the voltage loop. Although
the PFC stage has a low bandwidth voltage loop for better
input power factor, the innovative multi-vector error
amplifier provides a fast transient response to clamp the
overshoot and undershoot of the PFC output voltage.
Figure 5 shows the block diagram of the multi-vector
error amplifier. When the variation of the feedback
voltage exceeds ± 5% of the reference voltage, the
transconductance error amplifier adjusts its output
impedance to increase the loop response. If RA is opened,
SG6932 shuts off immediately to prevent extra-high
voltage on the output capacitor.
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
SG69XX
-
- 14 -
Cycle-by-Cycle Current Limiting
SG6932 provides cycle-by-cycle current limiting for both
PFC and PWM stages. Figure 6 shows the peak current
limit for the PFC stage. The PFC gate drive is terminated
once the voltage on the ISENSE pin goes below VPK.
The voltage of VRMS determines the voltage of VPK. The
relationship between VPK and VRMS is shown in Figure 6.
The amplitude of the constant current, IP, is determined by
the internal current reference, IT, according to the
equation:
Ip = 2 × I
T
= 2×
1.2V
R
I
(7)
Therefore, the peak current of the IS is given by
(VRMS<1.05V):
IS_peak =
(Ip × RP) - 0.2V
RS
(8)
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
0.55V
FBPWM
+
+
IPWM
0.7V
SG69XX
Figure 6. Current Limit
Figure 8. Slope Compensation
Power-On Sequence / Soft-Start
The SG6932 is enabled whenever the line voltage is higher
than the brownout threshold. Once the SG6932 is active,
the PFC stage is enabled first. The PWM stage is enabled
following a 4ms delay after FBPFC voltage exceeds 2.7V.
During start-up of PWM stage, the SS pin charges an
external capacitor with a constant-current source. The
voltage on FBPWM is clamped by SS during start-up. In
the event of a protection condition occurring and/or PWM
being disabled, the SS pin is quickly discharged.
Limited Power Control
Every time the output of power supply is shorted or over
loaded, the FBPWM voltage increases. If the FB voltage
is higher than a designed threshold, 4.2V, for longer than
95ms, the PWM output is turned off.
Gate Drivers
SG6932 output stages are fast totem-pole gate drivers.
The output driver is clamped by an internal 18V Zener
diode to protect the power MOSFET.
3V
2.7V
FBPFC
Protections
The SG6932 provides full protection functions to prevent
the power supply and the load from being damaged. The
protection features include:
OPFC
4mS
PFC Feedback Over-Voltage Protection. When the PFC
feedback voltage exceeds the over-voltage threshold, the
SG6932 inhibits the PFC switching signal. This
protection also prevents the PFC power converter from
operating abnormally while the FBPFC pin is open.
OPWM
Figure 7. Power-On Sequence
Forward PWM and Slope Compensation
The PWM stage is designed for forward power converters.
Peak current mode control is used to optimize system
performance. Slope compensation is added to stabilize the
current loop. The SG6932 inserts a synchronized
positively sloped ramp at each switching cycle. The
positively sloped ramp is represented by the voltage
signal Vs-comp. In the example in Figure 8, the ramp signal
voltage is 0.55V.
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
- 15 -
Second PFC Over-Voltage Protection (OVP_PFC). The
PFC stage over-voltage input. The comparator disables
the PFC output driver if this input exceeds 3.25V. This pin
can be connected to the FBPFC pin or the PFC boost
output through a divider network. This pin provides an
extra input for PFC over-voltage protection.
PFC Feedback Under-Voltage Protection. The SG6932
stops the PFC switching signal whenever the PFC
feedback voltage drops below the under-voltage threshold.
This protection feature is designed to prevent the PFC
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
power converter from experiencing abnormal conditions
while the FBPFC pin is shorted to ground.
VDD Over-Voltage Protection. The PFC and PWM stages
are disabled whenever the VDD voltage exceeds the
over-voltage threshold.
RI Pin Open / Short Protection. The RI pin is used to set
the switching frequency and internal current reference.
The PFC and PWM stages of SG6932 are disabled
whenever the RI pin is short or open.
PCB Layout
independently tied from the decoupling capacitor to the
PFC output capacitor CO. The ground in the output
capacitor CO is the major ground reference for power
switching. To provide a good ground reference and reduce
the switching noise of both the PFC and PWM stages, the
ground traces 6 and 7 should be located very near and be
low impedance.
The IPFC pin is connected directly to RS through R3 to
improve noise immunity. Do not incorrectly connect to
the ground trace 2. The IMP and ISENSE pins should be
connected directly via the resistors R2 and RP to another
terminal of RS.
SG6932 has a single ground pin, which prevents high sink
currents in the output being returned separately. Good
high-frequency or RF layout practices should be followed.
Avoid long PCB traces and component leads. Locate
decoupling capacitors near the SG6932. A resistor of 5 ~
20Ω is recommended, connected in series from the output
to the gate of the MOSFET.
Isolating the interference between the PFC and PWM
stages is also important. Figure 9 shows an example of the
PCB layout. The ground trace 1 is connected from the
ground pin of SG6932 to the decoupling capacitor, which
should be low impedance and as short as possible. The
ground trace 2 provides a signal ground. It should be
connected directly to the decoupling capacitor CDD and/or
to the ground pin of the SG6932. The ground trace 3 is
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
- 16 -
Figure 9. PCB Layout
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
REFERENCE CIRCUIT
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
- 17 -
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
PACKAGE INFORMATION
16 PINS – PLASTIC DIP (D)
θ
D
9
16
E1
eB
E
8
1
A2
L
A
e
b1
A1
DIMENSION
Symbol
A
A1
A2
b
b1
D
E
E1
e
L
eB
Millimeter
Min.
0.381
3.175
18.669
θ°
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
6.121
2.921
8.509
0°
Typ.
Max.
5.334
3.302
1.524
0.457
19.177
7.620
6.299
2.540
3.302
9.017
7°
Inch
Min.
Typ.
3.429
0.015
0.125
19.685
0.735
6.477
0.241
3.810
9.525
0.115
0.335
15°
- 18 -
0°
Max.
0.210
0.130
0.060
0.018
0.755
0.300
0.248
0.100
0.130
0.355
7°
0.135
0.775
0.255
0.150
0.375
15°
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
16 PINS – PLASTIC SOP (S)
16
9
E
1
H
Detail A
F
8
b
c
e
θ
D
A2
A
L
y
Detail A
A1
DIMENSION
Symbol
A
A1
A2
b
c
D
E
e
H
L
F
y
θ°
Millimeter
Min.
1.346
0.101
1.244
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
Typ.
Max.
1.753
0.254
1.499
Inch
Min.
0.053
0.004
0.049
0.406
0.203
9.804
3.810
10.008
3.988
0.386
0.150
6.198
1.270
0.228
0.016
0.394
0.157
0.050
0.381X45°
0°
Max.
0.069
0.010
0.059
0.016
0.008
1.270
5.791
0.406
Typ.
0.244
0.050
0.015X45°
0.101
8°
- 19 -
0°
0.004
8°
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007
Product Specification
SG6932
Green-Mode PFC / Forward PWM Controller
© System General Corp.
Version 1.1.1 (IAO33.0011.B2)
- 20 -
www.sg.com.tw • www.fairchildsemi.com
September 19, 2007