LOW COST POWER-SAVING MODE PWM CONTROLLER FOR FLYBACK CONVERTERS
DESCRIPTION
The UC3973 is a high performance current mode PWM
controller ideally suited for low standby power. Low VDD startup
current make the power reliable on startup design and a large
value resistor could be used in the startup circuit to minimize the
standby power. At no load condition, the IC operates in
power-saving mode for lower standby power, decreasing frequency
for Higher conversion efficiency at light load condition.
The UC3973 contains protection with automatic recovery
including OLP (over load protection), programming OTP (over temperature protection), OVP (over voltage protection), UVLO (VDD over voltage clamp and under voltage
lockout).To protect the power MOSFET, Gate-drive output is fixed up to 16V max. The UC3973 contains protection
OCP (cycle-by-cycle current limiting).
The internal slope compensation improves system stability at high PWM duty cycle output. Leading-edge
blanking on current sense input removes the signal glitch, which offering minimal external component count in the
design. Excellent EMI performance is achieved with UTC proprietary frequency hopping technique
(ZL201020615247.1) together with soft driver control. Audio noise is eliminated due to switch frequency more than
20kHz during operation.
The UC3973 has such applications as: battery charger, power adaptor, set-top box power supplies, ink jet
printers, open-frame SMPS.
FEATURES
* UTC proprietary frequency hopping technology for Improved EMI performance.
* Power-saving mode for high light-load and standby efficiency
* Soft Start
* Dynamic peak current limiting for constant output power
* Built-in synchronized slope compensation
* OLP,OVP and VDD clamp for higher security
* Programming OTP for higher security
* Fixed switch frequency 65kHz
* Gate output voltage clamped at 15V
* Low start-up current
* Cycle-by-cycle Current Limiting
* Under voltage lockout (UVLO)
* Few external components required |
