Power supply device and semiconductor device

摘要

Switching loss is reduced by decreasing the switching frequency of a PFC power supply in light load condition, whereas the switching frequency is maintained high in heavy load operation. Efficiency in light load operation is thus improved without enlarging a boosting inductor and an output smoothing capacitor. A capacitor is provided in a triangular wave generating circuit and the triangular wave generating circuit outputs a triangular wave by charging and discharging this capacitor. Charging and discharging of the capacitor are controlled by an oscillation frequency control circuit output current which is input to a comparator.

主权项

1. A power supply device converting an alternate current voltage to a direct current voltage, comprising:
an output terminal and a ground terminal; a diode bridge to which the alternate current voltage is input; an inductor coupled to an output of the diode bridge; a diode whose anode is electrically coupled to the inductor and whose cathode is electrically coupled to the output terminal; a capacitor electrically coupled between the output terminal and the ground terminal; a switch electrically coupled between the anode of the diode and the ground terminal; a voltage dividing circuit dividing a voltage between the output terminal and the ground terminal; and a PFC controller that includes an error amplifier amplifying a difference between an output voltage of the voltage dividing circuit and a reference voltage, an oscillation frequency control circuit converting an output of the error amplifier to a current, a triangular wave generating circuit outputting a triangular wave from an output current of the oscillation frequency control circuit, and a PWM control circuit opening and closing the switch, based on the triangular wave output by the triangular wave generating, wherein the triangular wave generating circuit comprises another capacitor and outputs the triangular wave by charging and discharging the another capacitor, the triangular wave generating circuit further comprises a first current mirror circuit having two outputs, and a second current mirror circuit having one output, and a current output of the second current mirror circuit is a replica of one current output of the first current mirror circuit.