Current control circuit with particular application in bipolar and unipolar constant current control of stepmotors

摘要

The present invention is a switch mode current control circuit which is particularly useful with step motors. The circuit has a first transistor, a coil and a first resistor connected in a series with a first voltage source. An opto coupler having a light emitting diode and a second transistor therein has the light emitting diode connected across the first resistor and the second transistor is connected across the base emitter junction of the first transistor. A second resistor is connected to the base of the first transistor and to the second voltage source. A diode is connected across the coil.