| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply device capable of improving a power factor in a period when an input voltage is less than an output voltage.SOLUTION: A power supply device 10 comprises a rectifier circuit 12, an input capacitor C1, a step-down converter circuit 14, an output capacitor C2 and a current conduction circuit 15. The rectifier circuit 12 rectifies an alternating current. The input capacitor C1 smooths an input voltage after rectification. The step-down converter circuit 14 inputs the input voltage after smoothing and has field-effect transistor Q1 stopping operation in a period when the input voltage is less than an output voltage while operating in a period when the input voltage exceeds the output voltage. The output capacitor C2 is provided at an output side of the step-down converter circuit 14 and has a capacity greater than a capacity of the input capacitor C1. The current conduction circuit 15 is provided between the rectifier circuit 12 and the input capacitor C1 and causes an input current to flow in the period when the input voltage is less than the output voltage.SELECTED DRAWING: Figure 1 |
