Green Mode PFC/Flyback-PWM Controller
FEATURES OVERVIEW
Interleaved PFC/PWM switching
Green-mode PFC and PWM operation
No switching of PFC at light loads for best power
saving
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
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
Brownout protection
APPLICATIONS
Switching Power Suppliers with Active PFC
High-Power Adaptors
DESCRIPTION
The highly integrated SG6903 is specially designed
for power supplies consist of boost PFC and flyback
PWM. It requires very few external components to
achieve green-mode operation and versatile protections. It
is available in 16-pin SOP packages.
TYPICAL APPLICATION
© System General Corp.
Version 1.0.1 (IAO33.0061.B0)
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 SG6903 will shut off PFC to
prevent extra-high voltage on output. Programmable
two-level output voltage control will reduce 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
output-power limit. Hiccup operation during output
overloading is also guaranteed.
In addition, SG6903 provides complete protection
functions such as brownout protection and RI pin
open/short.
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www.sg.com.tw • www.fairchildsemi.com
SG6903
feature
maintains
constant
September 28, 2007