Ignition system with overvoltage and excess current protection

Details Ignition system with overvoltage and excess current protection Ignition system with overvoltage and excess current protection

1979-05-17

1981-01-13

Lall, P. S.

Internal-combustion engines

High tension ignition system

Power supply, ignition coil primary, and interrupter element...

123644, 315209T, F02P 100, H05B 4136

Patent

active

042443440

ABSTRACT:
In a known ignition system, the emitter-collector circuit of the ignition transistor is connected in series with the primary winding of the ignition coil and with a precision resistor. When the voltage across the latter exceeds a predetermined value, an auxiliary transistor is switched to a conductive state. The emitter-collector circuit of the auxiliary transistor is connected to the base of the ignition transistor and, when conductive, prevents further increases of current through the primary winding of the ignition coil. To protect this circuit, a series circuit including two Zener diodes is connected between the base and collector of the ignition transistor. Further, a voltage divider is connected in parallel with the emitter-collector circuit of the ignition transistor and an additional resistor is connected between the base and the emitter thereof. When overvoltages across the primary winding cause breakdown of the Zener diodes, the current through the Zener diodes is blocked from the emitter-collector circuit of the auxiliary transistor either by a diode or by a blocking transistor having an emitter-collector circuit connected in parallel with the base-emitter circuit of the auxiliary transistor. The blocking transistor is maintained in the conductive state blocking the auxiliary transistor throughout the application time of an externally applied blocking signal which is adapted to maintain the ignition transistor in the blocked state.

REFERENCES:
patent: 3605713 (1971-09-01), Masters et al.
patent: 4020816 (1977-05-01), Chateau
patent: 4088107 (1978-05-01), Chateau
patent: 4122814 (1978-10-01), Ford
patent: 4128091 (1978-12-01), Balan et al.
patent: 4130101 (1978-12-01), Jundt et al.

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