| 摘要 |
PURPOSE: An over current protecting circuit of an automatic voltage adjusting device is provided to protect a switch element by interrupting current applied to a base of the switch element when an over voltage is generated at a primary inductor. CONSTITUTION: An over current protecting circuit of an automatic voltage adjusting device comprises a primary inductor(Np) which has one end connected to a power and the other end connected to a collector of a switching transistor(Tr1). A driven resistor(Rg) has a first terminal connected to a positive terminal of a dc line stage and a second terminal connected to a first node. The base and the collector of the switching transistor are connected to first and second nodes. A capacitor(C1) whose one end is connected to the second node, has the other end connected to an anode of a zener diode(ZD), which has a cathode connected to the first node. A first resistor(Rb) whose one end is connected to the first node, has the other end connected to a cathode of a first diode(D1) through a third node. A second resistor(R1) whose one side is connected to the third node, has the other side connected to one sides of third and fourth resistors(R2,R3), respectively. The other side of the third resistor(R2) is connected to the second node. A transistor(Tr2) whose collector is connected to the second node, has an emitter connected to the first node. The base of the transistor(Tr2) is connected to the other side of the fourth resistor(R3).
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