IGNITION APPARATUS HAVING A CURRENT LIMITING FUNCTION FOR AN INTERNAL COMBUSTION ENGINE

摘要

An ignition apparatus for an internal combustion engine includes a current limiter for limiting a current supplied from a power source to an ignition coil to a predetermined maximum value irrespective of temperature variations. A current sensing resistor is connected between the power transistor and ground for sensing the magnitude of a primary winding current. A first constant current supply is connected at one end thereof to the base of the power transistor and at the other end to one end of the current sensing resistor through a first transistor. A second constant current supply is connected at one end thereof to the base of the power transistor and at the other end to the other end of the current sensing resistor through a second transistor. A differential amplifier has a first input terminal connected to a junction between the first constant current supply and the first transistor, a second input terminal connected to a junction between the second constant current supply and the second transistor, and an output terminal connected to the base of the power transistor. A temperature coefficient compensator is connected to one of the first and second input terminal of the differential amplifier for compensating for a change in the resistance of the current sensing resistor due to a variation in temperature so that a temperature dependent change in the reference voltage at the first input terminal of the differential amplifier matches a temperature dependent change in the voltage at the second input terminal thereof.