| 摘要 |
A transistor is brought into conduction when, for example, a voltage between both ends of a second clamp capacitor exceeds a predetermined reference voltage. A resistance value of a discharge resistor is smaller than a value obtained by dividing the reference voltage by the maximum value of a current flowing through the discharge resistor. When the transistor is brought into conduction as a result of a voltage between both ends of the second clamp capacitor exceeding the predetermined reference voltage, a voltage applied to the discharge resistor, which results from a regenerative current, is larger one of the voltage between both ends of the second clamp capacitor and a voltage drop of the discharge resistor due to the regenerative current. The voltage drop and the voltage between both ends are smaller than a voltage between DC power supply lines, whereby it is possible to reduce an electrostatic capacitance of the discharge resistor.
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