| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply unit wherein a recovery current is reduced. SOLUTION: The power supply unit comprises a switch element connected with one of the terminals of a power supply portion; a diode one end of which is connected with the switch element and the other end of which is connected with the other terminals of the power supply; a smoothing capacitor connected between the switch element and the other terminal of the power supply portion; and a magnetic element connected between the switch element and the smoothing capacitor. A second magnetic element is placed in the path of a recovery current which flows from the switch to the diode when the switch is closed, and a second capacitor which is connected with the second magnetic element in parallel with the switch is provided. Thus, when the switch is open, the second capacitor is charged with a current to the second magnetic element, and when the switch is closed, a resonance circuit which passes a discharge current from the second capacitor is formed among the power supply, the second magnetic element, and the diode so that the resonance circuit go through the second magnetic element, the switch, and the second capacitor.
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