| 摘要 |
PROBLEM TO BE SOLVED: To efficiently supply safe DC power to the control circuit of a DC-DC converter regardless of the state of a load. SOLUTION: For the DC-DC converter, a constant current circuit 31 is connected between an auxiliary rectifier diode 8 and an auxialiary smoothing capacitor 9 constituting an auxiliary rectifying and smoothing circuit 7, and the output current of the constant current circuit 31 is supplied to the control circuit 12. When a MOS-FET3 is switched off at the time of a heavy load, the charge current flowing to the auxiliary smoothing capacitor 9 of the auxiliary rectifying and smoothing circuit 7 is controlled on a certian level by the constant current circuit 31, so the charge voltage of the auxiliary smoothing capacitor 9 does not rise to the peak value of surge voltage, and the voltage V<SB>O2</SB>of the auxiliary smoothing capacitor 9 is kept at a certain value. Hereby, second safe DC output voltage V<SB>O2</SB>can be supplied to the control circuit 12 via the auxiliary rectifying and smoothing circuit 7 from the auxiliary winding 2c of a transformer 2 regardless of the state of a load. COPYRIGHT: (C)2006,JPO&NCIPI
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