SGP400 Datasheet, PDF (1/15 Pages) Fairchild Semiconductor – Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback

Product Specification
Low-Power Green-Mode PWM Flyback Power Controller without Secondary Feedback
SGP400
FEATURES
„ Linearly decreasing PWM frequency
„ Green-mode under light-load and zero-load
conditions
„ Constant voltage (CV) and constant current (CC)
„ No secondary feedback
„ Low start-up current (8µA)
„ Low operating current (3.6mA)
„ Leading-edge blanking
„ Constant power limit
„ Universal AC input range
„ Synchronized slope compensation
„ 140°C OTP sensor with hysteresis
„ V_DD over-voltage clamping
„ Cycle-by-cycle current limiting
„ Under-voltage lockout (UVLO)
„ Fixed PWM frequency with hopping
„ Gate output maximum voltage clamped at 17V
„ Small SOT-26 package
APPLICATIONS
Low-power flyback power converters, such as:
„ Battery chargers for cellular phones, cordless phones,
PDAs, digital cameras, and power tools
„ Power adapters for ink jet printers, video game
consoles, and portable audio players
„ Open-frame SMPS for TV/DVD standby and other
auxiliary supplies, home appliances, consumer
electronics, and PC 5V standby-power
„ Replacements for linear transformers and
RCC SMPS
TYPICAL APPLICATION
V _IN
DESCRIPTION
This highly integrated PWM controller provides several
features to enhance the performance of low-power
flyback converters. To minimize standby power
consumption, the proprietary green-mode function
provides off-time modulation to linearly decrease the
switching frequency under light-load and zero-load
conditions. This green-mode function enables the power
supply to meet international power conservation
requirements. The supply voltage, V_DD, is also used for
feedback compensation, to regulate the output voltage
without requiring a conventional TL431 and a
photo-coupler. The typical start-up current is only 8µA,
while the typical operating current can be as low as
3.6mA. A large start-up resistance could be used to
achieve even higher power conversion efficiency.
SGP400 integrates a frequency hopping function, which
helps reduce EMI emission of a power supply with
minimum line filters. Built-in synchronized slope
compensation maintains the stability of peak
current-mode control. Proprietary internal compensation
ensures constant output power limiting over a universal
range of AC input voltages, from 90V_AC to 264V_AC.
Pulse-by-pulse current limiting ensures a constant output
current, even if a short-circuit occurs. Also, the internal
protection circuit disables PWM output if V_DD exceeds
22.7V. The gate output is clamped at 16.7V to protect the
power MOS from over-voltage damage. The built-in
over temperature protection (OTP) function shuts down
the controller at 140°C with a 30°C hysteresis. The
SGP400, designed to provide a low-cost total solution for
flyback converters, is available in a small footprint, 6-pin,
SOT-26 package.
R _IN
C _IN
D₁
VDD
Q1
G ATE
W _AUX
SENSE
GND
R_S
D_O
C_O
V_O
© System General Corp.
Version 1.0.1 (IAO33.0084.B0)
-1-
www.sg.com.tw • www.fairchildsemi.com
September 24, 2007