Stepper driver chopper

The impedance in the windings varies with the motor speed, so it plays a role in determining the voltage on-time. At slow motor speeds — and low impedance — the chopper drive provides a short on-time for the voltage, producing a small pulse width.

Alternatively, at high speeds —and high winding impedance — the chopper drive provides a long on-time for the voltage, producing a large pulse width and allowing time for the current to rise sufficiently to produce the rated torque.

A current-sensing resistor placed in series with each winding regulates the current and ensures the shortest time possible for current to build up and decline. As the current increases, voltage develops across the resistor. This voltage is monitored by a comparator , and at a predetermined reference voltage, the output voltage from the drive is turned off chopped until the next pulse occurs.

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Thanks for your help. Reply Cancel Cancel. Hi Kalimuthu, not sure I've correctly understood your schema description. Could you add the schematic? This technique is also referred to as pulse width modulation PWM. Current in a chopper drive is regulated by a current-sensing resistor placed in series with each winding. As current increases, voltage develops across the resistor, and a comparator monitors this voltage level. At a predetermined reference voltage, the output voltage is turned off chopped until the next pulse takes place.

In this way, current builds and declines as the voltage switches off and on, resulting in the proper average current per step cycle. This enables precise control of torque, regardless of variations in the power supply voltage.