| 摘要 |
PURPOSE:To suppress increase of the number of parts and the loss by providing a capacitor for absorbing the flywheel current flowing through a load upon turn OFF of a main switching circuit and subjecting main switching element to negative current feedback thereby establishing constant current characteristics. CONSTITUTION:Upon turn ON of a main switching element TR1 within positive half cycle of a power supply 10, a load current flows through a diode D1, the main switching element TR1, a resistor r1 and a diode D2 into a load 12 thus charging a capacitor C1 with a polarity shown on the drawing. Upon turn OFF of the main switching element TR1, the capacitor C1 is discharged through the load 12. Since the voltage Vo of a switching signal G from a gate control circuit 30 is applied between the gate and the counter-source side of the resistor r1, voltage drop (r1.ID) across the resistor r1 due to a surge current increases upon turn ON of the main switching element TR1 and the gate-source voltage VGS of a FET decreases. Consequently, rising of the drain current ID is limited by the FET. |
