Patent ID: 7245475

Claim:
A relay drive circuit for driving a relay having a coil with a rated coil voltage from an input voltage that exceeds the rated coil voltage, comprising: a transformer-rectifier for generating a bulk voltage from the input voltage to drive the coil; an electronically controlled switching device operatively coupled to energize the coil with the bulk voltage when in a conducting state; a Zener diode coupled across the coil; a power dissipating electronic switching device coupled across the Zener diode; and a controller operatively coupled to the switching device and the power dissipating electronic switching device, the controller monitoring the bulk voltage; and wherein the controller enables the switching device to energize the coil for a first period sufficient to ensure actuation of the relay and to prevent damage to the coil based on the bulk voltage; and wherein the controller thereafter modulates the switching device to maintain energization of the coil and to prevent damage thereto when the bulk voltage is greater than the rated coil voltage.