| 摘要 |
PURPOSE: An ignition power transistor protection circuit is provided to prevent breakdown of the transistor by forcibly turning off the transistor when the transistor is continuously turned on during a predetermined time period. CONSTITUTION: A circuit comprises an ECU(11), a driving transistor(Q1), an ignition power transistor(Q2) and a comparator(20). The ECU outputs an engine ignition time control signal so as to cut off or supply the driving current flowing at an ignition coil. The ECU outputs a high state power transistor off signal so as to forcibly turn off the ignition power transistor when a high state interrupt signal is continuously input to an interrupt terminal(INT) during a predetermined time period. The driving transistor is turned on when the ECU outputs a high state engine ignition time control signal and applies the output signal to a base, and turned off when the ECU outputs a low state engine ignition timing control signal and applies the output signal to the base. The driving transistor is connected to a power supply terminal(Vbat) via a resistance(R1). The ignition power transistor is turned on when a high state bias voltage is applied to a base and supplies driving current to the ignition coil connected to a collector. The comparator has a non-inverting terminal(+) connected between the collector of the driving transistor and the base of the ignition power transistor, and an inverting terminal(-) connected with voltage distribution resistances(R2,R3).
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