UNISONIC TECHNOLOGIES CO., LTD
UC3879A
Preliminary
CMOS IC
LOW COST POWER-SAVING
MODE PWM CONTROLLER
FOR FLYBACK CONVERTERS
DESCRIPTION
The UTC UC3879A provides a CCM/valley switching mixed
mode operation for better efficiency performance. The UTC
UC3879A 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.
SOP-8
The UTC UC3879A 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 UC3879A 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 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
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