UNISONIC TECHNOLOGIES CO., LTD

UC3837L

CMOS IC

www.unisonic.com.tw

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Copyright © 2016 Unisonic Technologies Co., Ltd

QW-R103-145.A

LOW COST POWER-SAVING

MODE PWM CONTROLLER

FOR FLYBACK

CONVEBNOERS

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DESCRIPTION

The UTC UC3837L is a high performance current mode PWM

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 UC3837L contains protection with automatic recovery

including OLP (over load protection), OCP (cycle-by-cycle current

lockout). It also provides the protections including OTP (over

temperature protection), OVP (over voltage protection) in UTC

UC3837L

with latched shut down. 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 UC3837L has such applications as: battery charger,

power adaptor, set-top box power supplies, ink jet printers,

open-frame SMPS.

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FEATURES

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* 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 ( in UTC UC3837L with latch shut down)

* Programming BNO/Line OVP 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