Circuit arrangement for controlling the electromagnetic drive of a switching device

Abstract

A reduction in contact bounce in an electromagnetic switch is accomplished by optimizing armature speed over its travel path with a circuit arrangement for controlling a drive current in the coil of the electromagnetic switch. A superposed speed loop including a speed sensor produces a measured voltage in response to speed of the armature. A converter coupled to the speed sensor converts the measured voltage into a value corresponding to an actual speed of the armature. A first summer receives a constant reference value corresponding to a desired speed for the armature and the value corresponding to the actual speed of the armature, and produces a difference voltage corresponding to a difference between the desired speed and the actual speed of the armature. A proportional element amplifies the difference voltage and produces a desired current value corresponding to the amplified difference voltage. An underlying current control loop including a current sensor produces a measured current value corresponding to a current in the coil. A second summer receiving the measured current value and the desired current value produces an output current corresponding to a difference between the desired current value and the measured current value. A chopper coupled to the output current of the second summer operates with hysteresis for conducting a pulsed control voltage to the coil and is interrupted from doing so when the measured current value is greater than the desired current value plus an hysteresis value.

Dependencies are inferred from the claim text.