LOW COST POWER-SAVING MODE PWM CONTROLLER FOR FLYBACK CONVERTERS

DESCRIPTION

The UC3863A is a high performance current mode PWM
controller ideally suited for low standby power. The PWM switching
frequency is programmable externally at normal operation. 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 UC3863A 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) 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 UC3863A 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
* Dynamic peak current limiting for constant output power
* Built-in synchronized slope compensation
* OLP with automatic recovery
* OTP and OVP with automatic recovery
* VDD clamp for higher security
* Programmable PWM Frequency
* Gate output voltage clamped at 16V
* Low start-up current
* Cycle-by-cycle Current Limiting
* Under voltage lockout (UVLO)
* Few external components required