| 摘要 |
PURPOSE:To make an ignition control circuit from a low voltage resistive IC, and improve the accuracy of an operating voltage for high voltage cutoff operation, by providing a high voltage cutoff circuit for deenergizing a switching circuit when a power voltage is abnormal. CONSTITUTION:A Zener diode ZD 10 is provided at a position where a high voltage cutoff circuit is conventionally provided. A cathode of the Zener diode ZD 10 is connected to a circuit power source Vcc, and an anode is grounded. A high voltage cutoff circuit 100 and a voltage divider circuit are provided. The voltage divider circuit is formed in such a manner that a series circuit of resistors 8 and 9 is connected through a resistor 6 to the circuit power source Vcc and the ground. A junction between both the resistors 8 and 9 in the voltage divider circuit is connected through ZD 101 to a base of Tr 102, and a collector of Tr 102 is connected to a collector of Tr 21. In the case of making an ignition control circuit including the high voltage cutoff circuit 100 into a monolithic IC, ZD 10 is set to provide a voltage suitable for a resistance voltage of IC, thus enabling the use of a low voltage-resistance IC.
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