Analogue=to=digital converter for electric motor speed control - counts clock pulses produced during period of PWM signal obtd. from error comparison with triangular wave

摘要

A speed error voltage (7) in analogue form is low-pass filtered (1) to remove noise and higher harmonics, and compared (2) with a triangular wave (8) of constant amplitude and frequency (800 Hz). A pulse-width modulated signal (9) is forwarded to a microprocessor (3) with a clock signal generator (31) which gives a digital output for control of the inverter (4) supplying current to the motor (5). An encoder (6) coupled to the motor gives feedback to the microprocessor so that the speed error is reduced to zero. ADVANTAGE - Does not use integrated circuit. Stable and precise digitisation is achieved independently of the triangular-wave frequency and temp. Resolution is improved by use of earlier measurements.