OVERVOLTAGE PROTECTING CIRCUIT OF TRANSISTOR

摘要

PURPOSE:To protect a transistor from overvoltage and to attain a free wheel function in a simple way by connecting a high-speed Zener diode between the collector and the emitter of the transistor. CONSTITUTION:A Zener diode 4 is connected between a collector 2 and an emitter 3 of a transistor TR1 which constitutes a high frequency inverter. The working speed of the diode 4 is accelerated by a rough time killer, and the diode 4 has the reverse recovery time of <=3musec. The Zener voltage is set higher than the power supply voltage which is supplied to the TR1 and at the same time lower than the breakdown strength level of the collector. The diode 4 having a high-speed operation functions as a free wheel diode. In case the overvoltage is applied, the diode 4 conducts to protect the TR1 from the overvoltage.