Power supply device and semiconductor device
AssigneeRenesas Electronics Corporation
InventorsKazuhito Ayukawa, Nobutoshi Kasai, Daisuke Iijima
Life of this patent
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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.
Claims3
A method of controlling a power supply device configured to supply DC power to a load circuit,
- the power supply device including:
- an output terminal and a ground terminal;
- a diode bridge to which an alternating 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 first capacitor electrically coupled between the output terminal and the ground terminal;
- a switch transistor electrically coupled between the anode of the diode and the ground terminal,
- a voltage dividing circuit coupled with the output terminal and the ground terminal;
- and
- an error amplifier coupled with the voltage dividing circuit and a reference voltage;
- an oscillation frequency control circuit coupled with the error amplifier;
- a triangular wave generating circuit coupled with the oscillation frequency control circuit, and which includes a second capacitor, a first current mirror circuit having two current outputs, and a second current mirror circuit having one current output that is a replica of a first of the two current outputs of the first current mirror circuit;
- and
- a PWM control circuit coupled with the triangular wave generating circuit, and the method comprising the steps of:
- (a) generating a voltage information signal in the voltage dividing circuit by dividing a voltage between the output terminal and the ground terminal;
- (b) generating a first voltage signal in the error amplifier by amplifying a difference between the voltage information signal and the reference voltage;
- (c) converting the first voltage signal to a first current signal in the oscillation frequency control circuit;
- (d) generating a triangular wave signal by charging and discharging the second capacitor based on the first current signal;
- (e) generating a PWM signal based on the triangular wave signal in the PWM control circuit;
- and
- (f) controlling the switch transistor with the PWM signal.
Dependencies are inferred from the claim text.