SG6905 Datasheet, PDF (1/21 Pages) Fairchild Semiconductor – Green mode PFC/Flyback-PWM Controller

Green mode PFC/Flyback-PWM Controller
FEATURES
Interleaved PFC/PWM switching
Green mode PWM operation
Low start-up and operating current
Innovative switching charge multiplier-divider
Multi-vector control for improved PFC output
transient response
Average-current-mode control for PFC
PFC over-voltage and under-voltage protections
PFC remote on/off Control
PFC and PWM feedback open-loop protection
Cycle-by-cycle current limiting for PFC/PWM
Slope compensation for PWM
Constant power limit for PWM
Power-on sequence control
Brownout protection
Over temperature protection
APPLICATIONS
Switching Power Suppliers with Active PFC
High-Power Adaptors
DESCRIPTION
The highly integrated SG6905 is specially designed for
power supplies with boost PFC and flyback PWM. It
requires very few external components to
Product Specification
SG6905
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 SG6905 will shut off PFC to
prevent extra-high voltage on output.
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.
During start-up, the RDY pin will be pulled low until the
PFC output voltage reaches to the setting level. This
signal can be used to control the second power stage for
proper power on sequence.
SG6905 provides complete protection functions such as
brownout protection and RI pin open/short.
TYPICAL APPLICATION
© System General Corp.
Version 1.1.1 (IAO33.0060.B1)
-1-
www.sg.com.t w • www.fairchildsemi.com
September 27, 2007