| 摘要 |
PURPOSE:To suppress an overvoltage by connecting a series circuit comprising a Zener diode and a capacitor between a drain and a gate of a FET. CONSTITUTION:A DC power supply 8 and a load 7 are connected in series between the drain and source of a switching MOSFET 1. A gate drive circuit 6 is connected between the gate and source of the FET 1 via a resistor 4. If a drain-gate voltage VDG exceeds a Zener voltage VZD of the Zener diode 2 when the FET 1 is turned off, a current flows to a series circuit comprising the diode 2 and a capacitor 3, the gate-source voltage VGS rises, the OFF operation of the FET is relaxed to suppress the overvoltage. The similar effect is obtained by connecting a series circuit comprising a Zener diode and a capacitor between the collector and base of a switching bipolar transistor. |
