LOW COST POWER-SAVING MODE PWM CONTROLLER FOR FLYBACK CONVERTERS

DESCRIPTION

The UTC UC3873C 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 UC3873C 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

UC3873C 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 UC3873C 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 65kHz

* Gate output voltage clamped at 16V

* Low start-up current

* Cycle-by-cycle current limiting

* Under voltage lockout (UVLO)

* Few external components required