Electronic circuitry for pulse-width modulator in motor speed control circuit

摘要

An electronic circuit for limiting the current to an electric motor, thereby controlling its speed, uses a pulse width modulator triggering a semiconducting switch. The modulator has a control unit comprising an oscillator with an analogue switch (6). This is in series with a potentiometer(7) when the modulator is one sort of regulator and in parallel with a condenser, when it is another sort of regulator. Assigned to the analogue switch is a comparator (4) for the current limiting. The switch is an AND gate. The maximum frequency of the oscillator is adjusted by a trimmer (8) in the negative lead of the condenser (10). The electronics are all integrated into a single circuit.