Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: The present invention is directed to largely improve the efficiency at the time of light load of a power supply apparatus using a power factor correction (PFC) controller. A PFC controller is provided with a voltage-current converter. The voltage-current converter converts voltage of a signal output from an error amplifier for detecting voltage level of output voltage to an arbitrary current value and outputs the current value as a correction current. The voltage-current converter outputs a correction current of a large current value when the error amplifier detects that the load is light, and the PFC controller performs control to decrease the output voltage.

Abstract: 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.

Abstract: The present invention provides a method of improving efficiency in a full load region in a PFC power source of an active filter method by controlling a switch circuit of the PFC power source in association with an output power of the PFC power source. A pair of two switches controlling charging/discharging an inductor is provided. A MOSFET switch having a small current capacity is used as one of the switches, and an IGBT switch of a large current capacity is used as the other switch. When an output of a voltage dividing circuit for dividing voltage of an output terminal of the PFC power source is smaller than a threshold voltage, only the MOSFET switch is operated. When the output exceeds a threshold voltage, the IGBT switch is also operated.

Abstract: The present invention is directed to largely improve the efficiency at the time of light load of a power supply apparatus using a PFC controller. A PFC controller is provided with a voltage-current converter. The voltage-current converter converts voltage of a signal output from an error amplifier for detecting voltage level of output voltage to an arbitrary current value and outputs the current value as a correction current. The voltage-current converter outputs a correction current of a large current value when the error amplifier detects that the load is light, and the PFC controller performs control to decrease the output voltage.