SG6902 Datasheet, PDF (1/22 Pages) Fairchild Semiconductor – Green-Mode PFC / Flyback-PWM Controller

Green-Mode PFC / Flyback-PWM Controller
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.
Product Specification
SG6902
The patented interleave-switching feature
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 operation.
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.
TYPICAL APPLICATION
© System General Corp.
Version 1.3.1 (IAO33.0022.B3)
-1-
www.sg.com.tw • www.fairchildsemi.com
September, 2007