LOW COST POWER-SAVING MODE PWM CONTROLLER FOR FLYBACK CONVERTERS
DESCRIPTION
The UTC UC3875A is a high performance current mode PWM controller ideally suited for low standby power. The PWM switching frequency is programmable externally at normal operation. 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 UTC UC3875A contains protection with automatic recovery including OLP (over load protection), 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 UTC UC3875A contains protection OCP (cycle-by-cycle current limiting). The internal slope FBensation improves system stability at high PWM duty cycle output. Leading-edge blanking on current sense input removes the signal glitch, which offering minimal external FBonent 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 UTC UC3875A 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
* Dynamic peak current limiting for constant output power
* Built-in synchronized slope FBensation
* OTP,OLP,OVP and VDD clamp for higher security
* Programmable PWM Frequency
* Gate output voltage clamped at 16V
* Low start-up current * Cycle-by-cycle Current Limiting
* Under voltage lockout (UVLO)
* Few external FBonents required
