PFC / Flyback PWM Controller
Interleaved PFC/PWM switching
Low start-up and operating current
Innovative switching charge multiplier-divider
Multi-vector control for improved PFC output
Average-current-mode control for PFC
Programmable two-level PFC output voltage
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
Constant power limit for PWM
Over-temperature protection (OTP)
Switching Power Supplies with Active PFC and
The highly integrated SG6901A is designed for power
supplies with boost PFC and flyback PWM. It requires
very few external components to achieve versatile
protections. It is available in a 20-pin SOP package.
The patented interleave-switching feature synchronizes
the PFC and PWM stages and reduces switching noise.
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 SG6901A 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
For the flyback PWM, the synchronized slope
compensation ensures the stability of the current loop
under continuous-conduction-mode operation. Built-in
line-voltage compensation maintains constant
output-power limit. Hiccup operation during output
overloading is also guaranteed.
In addition, SG6901A provides protection functions, such
as brownout and RI pin open/short protection.
© System General Corp.
Version 1.0.1 (IAO33.0062.B0)
- 1 - www.sg.com.tw • www.fairchildsemi.com
September 26, 2007