LOW COST POWER-SAVING MODE PWM CONTROLLER FOR FLYBACK CONVERTERS

DESCRIPTION

The UTC UCQ3879 provides a CCM/valley switching mixed

mode operation for better efficiency performance. The UTC

UCQ3879 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 UCQ3879 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 UCQ3879 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

* Built in high voltage(680V) startup

* Built in x-cap discharge function

* 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