| 摘要 |
PROBLEM TO BE SOLVED: To prevent malfunction at short-circuit of capacitor which rectifies an AC voltage inducted to a transformer auxiliary coil of a switching power supply.SOLUTION: Power 11 is converted into a DC voltage, by using a rectification smoothing section 12 and fed to a primary-side coil L1 of a transformer TR; an AC voltage corresponding to a winding ratio with the primary-side coil is induced in a secondary-side coil L2 on the basis of the operation of a switching element Q1; and the DC voltage is converted by a diode D1 and the capacitor C2. The power supply device includes the function for determining a soft start time, at a value of a capacitor Cs connected to a start terminal 15a from the rectification smoothing section 12 via a resistor R2, and feeds the power as power at the start of a control section 15, which feeds a switching pulse Ps to the switching element Q1. The AC voltage induced to an auxiliary coil L3 of the transformer TR is rectified by an auxiliary coil rectification smoothing section 16, and fed as the power of the control section 15. A compensation circuit 17 is connected between the start terminal 15a and a DC power supply Vc, in order to prevent the heat generation of a diode D2 and a resistor R3 owing to the short-circuit of the capacitor C4. |
