Vehicle starter protective system

Claim 1

A vehicle starter protective system operative in combination with an AC generator in a vehicle comprising: a starter, a battery positioned in said vehicle, a key switch connected to said battery, a starter relay having a relay coil and relay contacts positioned between said starter and said key switch, a digital-to-analog converter means connected to said AC voltage generator for receiving the AC voltage generated by said AC generator for converting said AC voltage to a variable DC voltage, switching means including a first and second transistor connected in a Schmidt trigger configuration for operating said starter relay in accordance with the output of said digital-toanalog converter, wherein said digital-to-analog converter includes a capacitor charged in response to the voltage generated by said AC generator, said voltage having a frequency corresponding to the rotational rate of the rotor of said AC generator, and a resistor connected between said capacitor and the base terminal of said first transistor of said switching means, said capacitor and said resistor forming a delay means for maintaining the on-state of said first transistor for a fixed period of time after the rotational rate of said rotor falls below a predetermined level, and a pulse generator connected between said digital-to-analog converter and the neutral point of said AC generator, said pulse generator including a smoothing circuit for filtering the signal of said neutral point to derive the average value thereof, a tHird transistor coupled to the output of said smoothing circuit and controlled by the filtered voltage of said smoothing circuit, and a fourth transistor connected to said third transistor, said fourth transistor being connected to said delay circuit.