| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply device reducible in the power consumption of a start-up circuit while being switching-operated by a separate excitation system and suppressing the lowering of a start-up speed. SOLUTION: At the start-up of power supply, self-oscillation is generated by power fed from a starting resistor R3, and an operation as a self-oscillation type switching power supply is started. By the start of the self-oscillation, when a charging voltage of a capacitor C4 is raised and reaches a prescribed level, a npn transistor Q2 is driven by a self-oscillation stop part 30, and the self-oscillation is stopped. On the other hand, when a separate excitation control part 40 operates by receiving the charging voltage of the capacitor C4, a drive signal is fed to the npn transistor Q1 from the separate excitation control part 40 after the self-oscillation is stopped by the self-oscillation stop part 30, whereby an operation as a separate excitation type switching power supply is started. COPYRIGHT: (C)2005,JPO&NCIPI
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