LOW COST POWER-SAVING MODE PWM CONTROLLER
FOR FLYBACK CONVERTERS
DESCRIPTION
The UTC UC3856 is a high performance current mode PWM
controller ideally suited for low standby power. An externally
JFET’s gate pin is connected the ST pin, It can achieve HV start,
and when start was overed, it is no long consume current to
depress the power off. 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 UC3856 contains protection with automatic recovery
including OLP (over load protection), OTP (over temperature
protection), OVP (over voltage protection), UVLO (VDD over voltage
clamp and under voltage lockout).To protect
the power MOSFET, Gate-drive output is fixed up to 15V max. The UTC
UC3856 contains protection OCP (cycle-by-cycle current limiting).
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 UC3856 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
* OTP,OLP,OVP and VDD clamp for higher security
* High efficiency HV start
* Gate output voltage clamped at 15V
* Low start-up current
* Cycle-by-cycle current limiting
* Under voltage lockout (UVLO)
* Few external components required |
