SG6902

Manufacturer Part NumberSG6902
DescriptionGreen-Mode PFC / Flyback-PWM Controller
ManufacturerFairchild Semiconductor
SG6902 datasheet
 
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Green-Mode PFC / Flyback-PWM Controller
www.DataSheet4U.com
FEATURES
Green-mode PFC and PWM operation
No switching of PFC at light loads saves power
Low start-up and operating current
Innovative switching-charge multiplier-divider
Multi-vector control for improved PFC output
transient response
Interleaved PFC/PWM switching
Programmable two-level PFC output voltage
Average-current-mode control for PFC
Cycle-by-cycle current limiting for PFC/PWM
PFC over-voltage and under-voltage protections
PFC and PWM feedback open-loop protection
Brownout protection
Over-temperature protection
APPLICATIONS
Switching Power Supplies with Active PFC
High-Power Adaptors
DESCRIPTION
The highly integrated SG6902 is designed for power
supplies with boost PFC and Flyback PWM. It
requires very few external components to achieve
green-mode operation and versatile protections. It is
available in a 20-pin SOP package.
TYPICAL APPLICATION
© System General Corp.
Version 1.3.1 (IAO33.0022.B3)
Product Specification
The
patented
interleave-switching
synchronizes the PFC and PWM stages and reduces
switching noise. At light loads, the switching
frequency is continuously decreased to reduce power
consumption. If output loading is further reduced, the
PFC stage is turned off to further 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, the SG6902 shuts off PFC to
prevent extra-high voltage on output. Programmable
two-level output voltage control reduces the PFC
output voltage at low line input to increase the
efficiency of the power supply.
For the flyback PWM, the synchronized slope
compensation ensures the stability of the current loop
under
continuous-conduction-mode
Built-in line-voltage compensation maintains a
constant output power limit. Hiccup operation during
output overloading is also guaranteed.
In addition, SG6902 provides protection functions,
such as brownout and RI pin open/short protections.
- 1 -
www.sg.com.tw • www.fairchildsemi.com
SG6902
feature
operation.
September, 2007

SG6902 Summary of contents

  • Page 1

    ... PFC loop, in which the overshoot and undershoot of the PFC voltage are clamped. If the feedback loop is broken, the SG6902 shuts off PFC to prevent extra-high voltage on output. Programmable two-level output voltage control reduces the PFC output voltage at low line input to increase the efficiency of the power supply ...

  • Page 2

    ... XXXXXXXXYWWV ORDERING INFORMATION Part Number Pb-Free SG6902SZ © System General Corp. Version 1.3.1 (IAO33.0022.B3) PIN CONFIGURATION T: S=SOP P : Z=Lead Free + ROHS Compatible Null=regular package XXXXXXXX: Wafer Lot Y: Year; WW: Week V: Assembly Location Package 20-pin SOP - 2 - Product Specification SG6902 www.sg.com.tw • www.fairchildsemi.com September, 2007 ...

  • Page 3

    ... The impedance of the NTC thermistor decreases whenever the temperature increases. Once the voltage of the OTP pin drops below the OTP threshold, the SG6902 is disabled. This is the output of the PFC current error amplifier. The signal from this pin is compared with an internal sawtooth and determines the pulse width for PFC gate drive ...

  • Page 4

    ... Green-Mode PFC / Flyback-PWM Controller www.DataSheet4U.com BLOCK DIAGRAM © System General Corp. Version 1.3.1 (IAO33.0022.B3) Product Specification - 4 - www.sg.com.tw • www.fairchildsemi.com SG6902 September, 2007 ...

  • Page 5

    ... DD-TH-G Green-off Mode © System General Corp. Version 1.3.1 (IAO33.0022.B3) < 50°C A Test Conditions V –0.16V TH-ON OPFC, OPWM Open, R =24kΩ I OVP R =24kΩ Product Specification SG6902 Value Unit -0.3 to +25.0 V -0.3 to +7.0 V SOP 1.15 W -40 to +125 °C -55 to +150 °C SOP 23.64 °C/W 260 ° ...

  • Page 6

    ... PWM Frequency OSC F Minimum Frequency in Green Mode OSC-MINFREQ RI RI Pin Resistance Range RI Pin Open Protection RI OPEN If RI> SG6902 Turns Off open RI Pin Short Protection RI SHORT If RI< SG6902 Turns Off short VRMS for UVP and RANGE Symbol Parameter RMS AC Voltage Under-Voltage Protection Threshold ...

  • Page 7

    ... DD= R =24kΩ 15V; I =100mA DD 13V; I =100mA DD 15V; C 5nF; OPFC= 15V; C 5nF; OPFC= Product Specification SG6902 Min. Typ. Max. Unit 1.5 MHz 70 dB 3 µ 0.25 mA Min. Typ. Max. Unit 90 100 110 µ ...

  • Page 8

    ... Added to Current Sense Test Conditions V 20V DD= V 15V; I =100mA DD 13V; I =100mA DD 15V; C 5nF; OPWM= 15V; C 5nF; OPWM= www.sg.com.tw • www.fairchildsemi.com Product Specification SG6902 Min. Typ. Max. Unit 2.5 3.1 3.5 V KΩ 0.8 1.2 1.5 mA 4.2 4.5 4 +0. ...

  • Page 9

    ... System General Corp. Version 1.3.1 (IAO33.0022.B3) Test Conditions Min. R =24kΩ 1.15 1.35 R =24kΩ Test Conditions Min. R =24kΩ www.sg.com.tw • www.fairchildsemi.com Product Specification SG6902 Typ. Max. Unit 100 11 µA 1.20 1.25 V 1.40 1. µs Typ. Max. Unit 50 56 µA 470 Ω ...

  • Page 10

    ... Product Specification SG6902 Min. Operation Voltge ( Temperature DD-MIN 5℃ 20℃ 35℃ 50℃ 65℃ 80℃ 95℃ 110℃ 125℃ Temperature (℃) Frequency vs. FB Voltage 1.6 1.7 1.8 1.9 2 2.1 2.2 2.3 2.4 2.5 FB Voltage (V) Duty cycle vs. FB Voltage 1 ...

  • Page 11

    ... Product Specification SG6902 ) vs Temperature RMS-H 5℃ 20℃ 35℃ 50℃ 65℃ 80℃ 95℃ 110℃ 125℃ Temperature (℃ Temperature RMS-L 5℃ 20℃ 35℃ 50℃ 65℃ 80℃ ...

  • Page 12

    ... Product Specification SG6902 Maximum Duty Cycle ( Temperature MAX 5℃ 20℃ 35℃ 50℃ 65℃ 80℃ 95℃ 110℃ 125℃ Temperature (℃ Temperature OPEN-LOOP 5℃ 20℃ ...

  • Page 13

    ... Product Specification SG6902 Fall Time ( Temperature F-PWM 5℃ 20℃ 35℃ 50℃ 65℃ 80℃ 95℃ 110℃ 125℃ Temperature (℃) Maximum Duty Cycle ( Temperature MAXPWM 5℃ 20℃ 35℃ ...

  • Page 14

    ... PFC loop, in which the overshoot and undershoot of the PFC voltage are clamped. If the feedback loop is broken, the SG6902 shuts off PFC to prevent extra-high voltage on output. Programmable two-level output voltage control reduces the PFC output voltage at low line input to increase the efficiency of the power supply ...

  • Page 15

    ... PFC and flyback as a second stage, the output voltage of PFC is usually designed around 250V at low line and 390V at high line. This is to improve efficiency at low-line input. In SG6902, the RANGE pin (open-drain structure) is used for the two-level output voltage setting. ...

  • Page 16

    ... Figure 5 shows the total control loop for the average-current-mode control circuit of SG6902. The current source output from the switching charge multiplier-divider can be expressed as: × ...

  • Page 17

    ... I S_peak FIG.7 V Flyback PWM and Slope Compensation As shown in Figure 8, peak-current-mode control is utilized for flyback PWM. The SG6902 inserts a synchronized 0.5V ramp at the beginning of each switching cycle. This built-in slope compensation ensures voltage exceeds the stable operation for continuous-current-mode operation. When the IPWM voltage, across the sense resistor, reaches the threshold voltage, 0 ...

  • Page 18

    ... In the event of a protection condition and/or begins decreasing. PWM being disabled, the SS pin quickly discharges. Gate Drivers SG6902 output stage is a fast totem-pole gate driver. The output driver is clamped by an internal 18V Zener diode to protect the power MOSFET Product Specification SG6902 www.sg.com.tw • ...

  • Page 19

    ... SG6902 has two ground pins. Good high-frequency or RF layout practices should be followed. Avoid long PCB traces and component leads. Locate decoupling capacitors near the SG6902. A resistor (5 ~ 20Ω) is recommended, connected in series from the OPFC and OPWM, to the gate of the MOSFET. Isolating the interference between the PFC and PWM stages is also important ...

  • Page 20

    ... Green-Mode PFC / Flyback-PWM Controller www.DataSheet4U.com REFERENCE CIRCUIT © System General Corp. Version 1.3.1 (IAO33.0022.B3 www.sg.com.tw • www.fairchildsemi.com Product Specification SG6902 September, 2007 ...

  • Page 21

    ... Product Specification SG6902 Detail θ L Detail A Typ. Max. 0.104 0.012 0.092 0.016 0.008 0.508 0.299 0.050 0.419 0.050 ° 0.020X45 0.004 8° ...

  • Page 22

    ... Green-Mode PFC / Flyback-PWM Controller www.DataSheet4U.com © System General Corp. Version 1.3.1 (IAO33.0022.B3 www.sg.com.tw • www.fairchildsemi.com Product Specification SG6902 September, 2007 ...