| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply unit wherein stable direct-current output voltage free from ripple voltage or the like is obtained, the circuitry is simplified, and the cost can be reduced. SOLUTION: The switching power supply unit is so constituted that the following operation is performed: Input voltage is charged into a smoothing capacitor through a reactor; the charging voltage is alternately chopped by a transformer and two switching elements at a predetermined frequency; and alternating voltage of a predetermined frequency is produced on the output side of the transformer, and is rectified and outputted. More specifically, a current is passed through the reactor via one in the on state of the two switching elements. When the state of the switching element in the on state changes to the off state, the energy stored in the reactor is applied in a superposing manner to the capacitor to boost the charging voltage. The boosted charging voltage is input to the input side of the transformer through the other switching element whose state changes from the off state to the on state. Thus, alternating voltage of the predetermined frequency is produced on the output side of the transformer. The alternating voltage is rectified and outputted. COPYRIGHT: (C)2005,JPO&NCIPI
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