PWM waveform generation using microcontrollers

Describes a subharmonic modulator using an 8051 with a customised ULA and an 8049 stored pattern modulator. In this context the PWM waveforms are being produced mainly for the synthesis of variable frequency for AC motor drives. These call for output frequencies up to perhaps 120 Hz for the majority of general purpose drives with special applications up to more than 1 kHz. Carrier frequencies, pulse repetition frequencies or minimum pulse widths also vary not only with speed range, but also with the type of power switching stage