Ignition apparatus for an internal combustion engine having a current limiting function

摘要

An ignition apparatus for an internal combustion engine having a current limiting function is simple in construction and can avoid variations In the current limiting values for respective power transistors 103. A current limiting circuit 109 includes a common resistor 105 connected at one end thereof to a power supply 101 and at the other end thereof to a plurality of ignition voltage generating circuits 104. an operational amplifier 107 making a comparison between a voltage V105 across the resistor 105 and a reference voltage Vr which corresponds to a predetermined upper limit current for each power transistor 103 and generating an output signal A of a magnitude proportional to a difference (V105-Vr) therebetween, and a plurality of transistors 108 provided one for each power transistor 103 and connected to receive the output signal A from the operational amplifier 107 for limiting a current through a corresponding power transistor 103 in response to the output signal A. The current limiting circuit 107 serves to sense a current flowing through each power transistor 103 and limit it to a predetermined upper limit value to thereby protect each power transistor from damage due to an overcurrent therethrough.