Product
Specification
Green mode PFC/Forward PWM Controller
SG6931
System General Corp. -
1
- www.sg.com.tw
Version 1.0(IAO33.0024.B0) Dec. 1, 2005
FEATURES OVERVIEW
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
Programmable PWM maximum duty cycle
Power on sequence control and soft-start
Brownout protection
APPLICATIONS
Switch mode Power Suppliers with Active PFC
Servo System Power Supplies
PC-ATX Power Supplies
DESCRIPTION
The highly integrated SG6931 is specially designed for
power supplies consist of boost PFC and Forward PWM.
It requires very few external components to achieve
green-mode operation and versatile
protections/compensation. It is available in 20-pin DIP
and SOP packages.
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, SG6931 will shut 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.
In addition, SG6931 provides complete protection
functions such as brownout protection and RI open/short
protection.
TYPICAL APPLICATION
Product
Specification
Green mode PFC/Forward PWM Controller
SG6931
System General Corp. -
2
- www.sg.com.tw
Version 1.0(IAO33.0024.B0) Dec. 1, 2005
MARKING DIAGRAMS PIN CONFIGURATION
ORDERING INFORMATION
Part Number
Package
SG6931DZ
20-pin PDIP (Lead Free)
SG6931SZ
20-pin SOP (Lead Free)
PIN DESCRIPTIONS
Name Pin
No.
Type
Function
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 having a resistance between 12k ~ 47k is recommended.
The switching frequency is equal to [1560 / RI] kHz, where RI is in k
. For example, if RI is
equal to 24k
, then the switching frequency will be 65 kHz.
OTP
3
Over Temperature
Protection
This pin provides an over temperature protection. A constant current is output from this pin.
If RI is equal to 24k, then the magnitude of the constant current will be 100uA. An external
NTC thermistor must be connected from this pin to ground. The impedance of the NTC
thermistor decreases whenever the temperature increases. Once the voltage of the OTP
pin drops below the OTP threshold, the SG6931 will be shutdown.
IEA 4
Output of PFC Current
Amplifier
This is the output of the PFC current amplifier. The signal from this pin will be compared with
an internal saw-tooth and hence determine the pulse width for PFC gate drive.
IPFC 5
Inverting Input of PFC
Current Amplifier
The inverting input of the PFC current amplifier. Proper external compensation circuits will
result in excellent input power factor via average-current-mode control.
IMP 6
Non-inverting Input of
PFC Current Amplifier
and Output of
Multiplier
The non-inverting input of the PFC current amplifier and also the output of multiplier. Proper
external compensation circuits will result in excellent input power factor via average current
mode control.
SG6931TP
XXXXXXXXYWWV
VRMS
RI
OTP
IEA
IPFC
IMP
ISENSE
FBPWM
IPWM
AGND
IAC
VEA
FBPFC
OVP
SS
VDD
OPFC
GND
OPWM
M_DUTY
T
: D = DIP, S = SOP
P :
Z =Lead Free + ROHS
Compatible
XXXXXXXX
: Wafer Lot
Y
: Year;
WW
: Week
V
: Assembly Location
Product
Specification
Green mode PFC/Forward PWM Controller
SG6931
System General Corp. -
3
- www.sg.com.tw
Version 1.0(IAO33.0024.B0) Dec. 1, 2005
ISENSE 7
Peak Current Limit
Setting for PFC
The peak current limit setting for PFC.
FBPWM
8
PWM Feedback Input
The control input for voltage-loop feedback of PWM stage. It is internally pulled high through
a 6.5 k
resistance. Usually an external opto-coupler from secondary feedback circuit is
connected to this pin.
IPWM
9
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.
AGND
10
Ground
The signal ground.
M_DUTY
11
Maximum duty cycle
of PWM stage
This input is used to determine the maximum duty cycle of the PWM stage. A constant
current source 10uA (RI = 24k
) is output from this pin. Connecting a resistor from this pin
to ground will generate a voltage V
MD
. The maximum duty cycle will be:
M_DUTY (%) =[(V
MD
- 0.2V)
2.9V] x 100. The maximum duty cycle is clamped to 65%.
PGND
12
Ground
The power ground
OPWM
13
PWM Gate Drive
The totem pole output drive for PWM MOSFET. This pin is internally clamped under 18V to
protect the MOSFET.
OPFC
14
PFC Gate Drive
The totem pole output drive for PFC MOSFET. This pin is internally clamped under 18V to
protect the MOSFET.
VDD 15 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
16
PWM Soft Start
During startup, the SS pin will charge an external capacitor with a 50uA constant current
source. The voltage on FBPWM will be clamped by SS during startup. In the event of a
protection condition occurring and/or PWM being disabled, the SS pin will be quickly
discharged.
OVPPFC 17
PFC over-voltage
input
The over-voltage input of the PFC stage. The comparator will disable the PFC output driver
if this input exceeds 3.25V. This pin can be connected to the FBPFC pin or it can be
connected to the PFC boost output through a divider network. This pin provides an extra
input for PFC over-voltage protection.
FBPFC 18
Voltage Feedback
Input for PFC
The feedback input for PFC voltage loop. The inverting input of PFC error amp. This pin is
connected to the PFC output through a divider network.
VEA 19
Error-Amp Output for
PFC voltage feedback
loop
The error-amp output for PFC voltage feedback loop. A compensation network (usually a
capacitor) is connected between this pin and ground. A large capacitor value will result in a
narrow bandwidth and hence improve the power factor.
IAC
20
Input AC Current
For normal operation, this input is used to provide current reference for the multiplier. The
suggested maximum IAC is 360 uA.
Product
Specification
Green mode PFC/Forward PWM Controller
SG6931
System General Corp. -
4
- www.sg.com.tw
Version 1.0(IAO33.0024.B0) Dec. 1, 2005
BLOCK DIAGRAM
Product
Specification
Green mode PFC/Forward PWM Controller
SG6931
System General Corp. -
5
- www.sg.com.tw
Version 1.0(IAO33.0024.B0) Dec. 1, 2005
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
Test
Conditions Value Unit
V
DD
DC Supply Voltage*
25
V
I
AC
Input AC Current
2
mA
V
High
OPWM, OPFC, IAC
-0.5 to 25V
V
V
Low
Others
-0.5 to 7V
V
P
D
Power Dissipation
At T
A
<50 0.8
W
T
J
Operating Junction Temperature
-40 to +125
T
stg
Storage Temperature Range
-55 to +150
DIP 34.64
R
j-C
Thermal resistance (Junction to Case)
SOP 35.44
/W
DIP 260
T
L
Lead Temperature (soldering 10sec)
SOP 230
ESD capability, HBM model
4.5
KV
ESD
ESD capability, Machine model
250
V
*All voltage values, except differential voltages, are given with respect to the network ground terminal
RECOMMENDED OPERATING JUNCTOIN TEMPERATURE: -30C~ 85C*
* For proper operation
ELECTRICAL CHARACTERISTICS (V
DD
=15V, T
A
=25C UNLESS NOTED)
VDD section
Symbol Parameter
Test
Conditions
Min.
Typ.
Max.
Unit
V
DD-OP
Continuously Operating Voltage
20
V
I
DD ST
Start-Up
Current
V
TH(ON)
0.16V
10
20
uA
I
DD OP
Operating
Current
V
DD
= 15V; OPFC, OPWM open
6
10
mA
V
TH-ON
Start
Threshold
Voltage
13 14 15 V
V
DD-min
Min. Operating Voltage
9
10
11
V
V
DD-OVP
VDD OVP1 (turn off PWM with delay)
23.5
24.5
25.5
V
TV
DD-OVP
Delay time of VDD OVP1
RI= 24k
8
25
uS
Oscillator & Green-Mode Operation
Symbol Parameter
Test
Conditions
Min.
Typ.
Max.
Unit
V
RI
RI Voltage
1.176
1.2
1.224
V
F
OSC
PWM frequency
RI= 24k
62 65 68 KHz
F
OSC-MINFREQ
Minimum frequency in green mode
RI= 24k
18 20 22 KHz
RI
RI range
12
47
k
RI
OPEN
RI Pin Open Protection
If RI> RI
open
, PWM will be turned off
200
k
RI
SHORT
RI Pin Short Protection
If RI< RI
short
, PWM will be turned off
2
k
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