| 摘要 |
A step-up switching power supply device small in switching loss, comprising a coil portion (3a) and a first diode (4) series-connected between one end of a dc power supply (2) and one end of a smoothing first capacitor (5), a first switching element (8) connected between a node (A) between the coil portion (3a) and the first diode (4) and the other end of the dc power supply (2), a second magnetic element (7) and a second switching element (9) series-connected between the node (A) and the other end of the dc power supply (2), and a second diode (10) and a second capacitor (11) series-connected between a node between the second magnetic element (7) and the second switching element (9) and the above node (A). When the second switching element (9) is turned on, an increase in current flowing through the second switching element (9) is restricted by the second magnetic element (7), while, when the second switching element (9) is turned off, an increase in voltage between the opposite ends of the second switching element (9) is restricted by charging of the second capacitor (11), thereby significantly reducing the switching loss of the second switching element (9).
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