| 摘要 |
PROBLEM TO BE SOLVED: To surely protect a control switch at a short circuit fault, etc., on the output side of a power device, by connecting an energy storage means to the control input side of the control switch, performing discharge through this energy storage means causing a switching stage to be in continuity, when a control voltage reaches a specific threshold value, and lowering the control voltage. SOLUTION: A protective circuit monitors a control voltage Ug on a control input side G of a switching transistor T1. During an on-period of the switching transistor T1, a capacitor C1 in the protective circuit is slowly charged via a resistor R1, and during an off-period, the charge of the capacitor C1 is quickly discharged via a diode D1. If the control voltage Ug increases and reaches a specific threshold by the occurrence of a short circuit fault, etc., on the output side of a power device, a transistor T2 and a transistor T3 in a discharging switching stage are turned on via the capacitor C1 to cause a supply voltage VCC to decrease and to lower the control voltage Ug, and the transistor T1 is protected.
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