Fault detection circuit

Details Fault detection circuit Fault detection circuit

1986-11-14

1988-04-05

Pellinen, A. D.

Electricity: electrical systems and devices

Safety and protection of systems and devices

With specific current responsive fault sensor

361 93, 123490, 323285, H02H 3093

Patent

active

047362677

ABSTRACT:
In a solenoid fuel injection system, an output transistor (16) receives switching signals to control through current therein which is provided to a solenoid fuel injection coil (11) in series with a current sensing resistor (17). A current control circuit (12) provides pulse width modulation control of solenoid current by monitoring the voltage across the sensing resistor. The fault detection circuit provides separate fault signals for short circuits at either the first or second end terminals (E, H) of the solenoid coil. Separate voltage comparators (18, 23) monitor voltages at the first and second end terminals, and separate delay timers (20, 25) effectively gate the comparator outputs to indicate actual detected short circuits. Each of the fault detection signals sets a fault latch (22) which then acts to reduce current through the output transistor and coil. The fault latch is periodically reset. For a fault detection, the output transistor is protected from excessive current resulting from a short circuit at one end terminal (H). The transistor and coil are also protected from a short circuit at the other end terminal (E) which results in the lack of a current sense signal causing the controller (12) to attempt to maintain the output transistor constantly on.

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"Injector Fault Testing Methods" in Motorola Technical Developments, vol. 3, Mar. 1983 by Robert W. Deutsch;

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