| 摘要 |
PURPOSE:To prevent a circuit element from expanding the damage of other circuit element and enable normal operation even if the number of parallel circuits decreases, by providing an abnormality detecting circuit for detecting the abnormality of some of plural transistors and by controlling a load current by the output of the abnormality detecting circuit. CONSTITUTION:When a chopper circuit 1 is closed according to an instruction from a control circuit 3, a current flows through a transistor T1 detecting the current. At that time, a voltage appears on an emitter resistor R1 and is feedbacked to the control circuit 3 to regulate the current below a limit. A current flowing through all transistors is their number times more than that through one transistor. If one transistor is damaged, the total current through the transistors becomes (n-1) times. The total current through the transistors decrease automatically according as the number of damaged transistors increases. Therefore, the damage of one transistor does not expand to another. This results in enabling normal operation even if the number of oarallel circuits decreases.
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