| 摘要 |
PURPOSE:To prevent a power transistor from being damaged, by providing a low voltage detection circuit at the output of a power source for a driving circuit. CONSTITUTION:The titled circuit is designed so that the drop of the output voltage of a power source transformer 10 is detected at the low voltage detection circuit A-12, and after around 20ms, an alarm signal is issued, and the output voltages of a control power source circuit 11 and a base power source circuit 13 issue the normal values for 20ms to stop a base circuit 5 by an OR circuit 6. However, when the output of the control power source circuit 11 drops even within 20ms due to the abnormality of the power source circuit or overload, alarm is issued from the low voltage detection circuit B-14, thereby, stops the base circuit. Also, when the output voltage of the base power source circuit 13 drops, the base circuit 5 is stopped by the low voltage detection circuit C-15. In such a way, the power transistor can be protected, and the driving circuit with high reliability can be obtained.
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