LOW COST POWER-SAVING MODE PWM CONTROLLER FOR FLYBACK CONVERTERS

DESCRIPTION
The UTC UC3873H 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 UTC UC3873H contains protection with automatic recovery including OLP (over load protection), OCP (cycle-by-cycle current limiting), and UVLO (VDD over voltage clamp and under voltage lockout). It also provides the protections including OTP (over temperature protection), OVP (over voltage protection) in UTC UC3873H with automatic recovery. To protect the power MOSFET, Gate-drive output is fixed up to 16V max. 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 UTC UC3873H 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 with automatic recovery
* OTP and OVP( automatic recovery)
* VDD clamp for higher security
* Programming OTP for higher security
* Fixed switch frequency 100kHz
* Gate output voltage clamped at 16V
* Low start-up current
* Cycle-by-cycle current limiting
* Under voltage lockout (UVLO)
* Few external components required