| 摘要 |
PROBLEM TO BE SOLVED: To provide a self-excitation type switching power supply circuit in which generating discharge current is reduced when an oscillation field effect transistor (3) is turned on, and as a result, energy loss in the case of switching is little, and noise is not generated. SOLUTION: The self-excitation type switching power supply circuit sets the time constant of an on-control circuit (12, 23) so that a gate voltage of the oscillation field effect transistor (3) exceeds a threshold voltage V<SB>TH</SB>in the state that the polarity of a feedback winding (2b) voltage is inverted, turns on the oscillation field effect transistor (3) after the primary winding (2a) voltage becomes a power supply voltage or lower, and slowly discharges the charge stored in a stray capacitance between the primary windings (2a) and a parasitic capacity of the oscillation field effect transistor (3). COPYRIGHT: (C)2005,JPO&NCIPI
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