LOW COST POWER-SAVING MODE PWM CONTROLLER FOR FLYBACK CONVERTERS
DESCRIPTION
The UTC UC3846 is a high performance current mode PWM controller ideally suited for low standby power and cost effective off-line flyback converter.
Low VDD startup current make the power reliable in 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 burst mode for lower standby power and in decreasing frequency for higher conversion efficiency at light load condition. The PWM switching frequency is programmable
externally at normal operation.
The UTC UC3846 contains protection coverage with
automatic self-recovery including OCP (cycle-by-cycle current limiting), OTP (over temperature 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 internal slope compensation improves system stability at high PWM duty cycle output. Leading-edge blanking on current sense (CS) input removes the signal glitch that offers minimal reqnirement of external component and lower system cost.
Excellent EMI performance is achieved by UTC proprietary frequency hopping technique together with soft driver control.
Audio noise is eliminated because switch frequency is more than 20kHz during operation.
The UTC UC3846 can be used in the applications, such as battery charger, power adaptor, set-top box power supplies, ink jet printers open-frame SMPS |
