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 method of controlling a power supply device configured to supply DC power to a load circuit (Ld),
the power supply device having an inductor (L1) configured to receive AC rectified power; and a switch transistor (Q100) coupled with the inductor and switching current through the inductor on and off, the method comprising the steps of:
(a) generating a voltage information signal (VFB) based on an output voltage (Vout) applied to the load circuit;(b) generating a first voltage signal (V1) based on the voltage information signal (VFB); and(c) generating a PWM signal (Vgd) based on the first signal (V1), the PWM signal (Vgd) controlling the switch transistor, wherein a frequency of the PWM signal (Vgd) continuously increases as the output voltage (Vout) increases.