An ASIC-based PWM waveform generator for AC motor control applications

An application-specific integrated circuit (ASIC) is presented which acts in conjunction with a standard microcontroller (the 8051 family) to produce a compact and effective AC motor control system. The system is based on synchronous pulsewidth modulation (PWM) and is capable of implementing both natural and regular sampling PWM as well as the optimum harmonic elimination and distortion minimization techniques. Lookup table size is minimized using information stored over one 30 degrees segment of the three-phase switching patterns. Disturbance-free carrier ratio changes are implemented under microprocessor control giving a wide speed range and a smooth efficient transition to six-step operation. The necessary dead-time circuitry to ensure that a delay exists between commutation of the devices in the power converter is also implemented on the ASIC, as well as an output inhibit control for power converter protection.<>