Ignition circuit with over-current protection e.g. for IC engine - has current-limiting circuit to separate transistor circuit for each coil monitored via common supply resistor and op. amp. control to limit current to set levels.

摘要

The ignition system has a separate coil for each cylinder, with a transistorised drive for each coil. The supply to the transistors is via a common feed in which a monitoring resistor has its potential drop measured by an op. amp, and compared with a reference signal corresponding to the max. allowable current through the transistors. The supply current is proportionally reduced for the separate transistors to prevent damage. The system provides a simple control circuit to limit the supply current for each transistor. A simple comparator compares the op.amp. output with the reference signal and enables the correction signal to be derived. USE? ADVANTAGE - Simple protection circuit for multi-cylinder engine ignition system; minimum of components required.