DC motor PWM speed control method e.g. for motor vehicle

摘要

The electronic speed control of a DC motor uses PWM triggering of a transistor switch (1) for the motor voltage supply. There are condensers (4,5,8) acting as filters against interference voltages. The PWM frequency is 100 kHz. The condensers are foil ones. The transistor is a FET. Between this and the voltage source (2) there is a pi-filter comprising a series inductance and two of the condensers, whose non-live sides are earthed. At the output of the FET is a freewheel diode (6) between this and earth, followed by a second series inductance (7), then the other condenser.