LOW COST POWER-SAVING MODE PWM CONTROLLER FOR FLYBACK CONVERTERS

DESCRIPTION

The UTC UC3916A provides a CCM/valley switching mixed

mode operation for better efficiency performance. The operation

mode stays at CCM at heavy load, and switch to valley switching at

light load.

The UTC UC3916A is a highly integrated current mode PWM

control IC with high voltage start up, optimized for high

performance, low standby power consumption and cost effective

offline flyback converter applications. 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 UC3916A 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), BNO(AC Brown Out protection) , LNO(AC

Over voltage protection), OVP (VCC or DC output over voltage

protection) 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 minima

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.

UTC UC3916A is packaged by using tiny SOP-8 package. It

has such applications as: battery charger, power adaptor, set-top

box power supplies, ink jet printers, open-frame SMPS.

FEATURES

* Proprietary frequency hopping for Improved EMI performance

* Cycle-by-cycle current limiting

* CCM/Valley Switching Operation

* Fixed switch frequency 60~70kHz

* Dynamic peak current limiting for constant output power

* Built-in synchronized slope compensation

* Gate output voltage clamped at 16V

* Adjustable DC output OVP

* OLP/VCC OVP/OTP/BNO/LNO (automatic recovery)

* Internal Soft Start