Abstract: A controller for a pulse width modulating (PWM) power converter. The controller monitors an output voltage and a current through a magnetic element for modulating a duty cycle of a main power switch. The controller is an eight-pin integrated circuit which controls either a forward converter or a post regulator without internal modifications. The monitored current of the forward converter forms a positive sensing signal. The monitored current of the post regulator forms a negative sensing signal. A current sense circuit of the controller forms an absolute value of either sensing signal. A soft-start circuit of the controller forms a start-up voltage ramp which is proportional to the level of a Vcc supply without requiring an external capacitor. A duty cycle of the main switch is gradually increased by comparing the start-up voltage ramp to the absolute value of the sensing signal. A pulse skipping circuit of the controller disables switching of the main switch under light load conditions.

Abstract: A controller for a pulse width modulating (PWM) power converter. The controller monitors an output voltage and a current through a magnetic element for modulating a duty cycle of a main power switch. The controller is an eight-pin integrated circuit which controls either a forward converter or a post regulator without internal modifications. The monitored current of the forward converter forms a positive sensing signal. The monitored current of the post regulator forms a negative sensing signal. A current sense circuit of the controller forms an absolute value of either sensing signal. A soft-start circuit of the controller forms a start-up voltage ramp which is proportional to the level of a VCC supply without requiring an external capacitor. A duty cycle of the main switch is gradually increased by comparing the start-up voltage ramp to the absolute value of the sensing signal. A pulse skipping circuit of the controller disables switching of the main switch under light load conditions.

Abstract: A combination PFC-PWM integrated circuit converter controller having a power factor correction stage and a pulse-width modulation stage. The power factor correction stage provides unity power factor and a regulated intermediate output voltage by sensing a current in the power factor correction circuit and by sensing the regulated intermediate output voltage in a voltage control loop. The regulated intermediate output voltage is sensed by an error amplifier that includes a current mirror. A dc supply voltage for powering the integrated circuit is generated that is representative of the regulated intermediate output voltage. The dc supply voltage is sensed for an overvoltage protection function. By sensing the intermediate regulated output voltage in the voltage control loop and by sensing the dc supply voltage for overvoltage protection, a component failure is less likely to affect both functions than if a single voltage was sensed for both functions.