High-Frequency and Precision Three-Phase Sine/PWM Controller With Near-Zero Frequency of MPU Intervention—Novel Design Supporting Distributed AC Drive Systems

Abstract

Conventional pulsewidth-modulation (PWM) schemes fully depend on a microprocessor (MPU) for extensive real-time computation, intervention, and housekeeping, and are limited to applications at low fundamental frequencies and low precision. At 20-kHz switching, the overhead of a modern 16-bit CPU increases up to 90%, making virtually no time available for regular control tasks. It also has poor cycle-to-cycle accuracy of /spl plusmn/5-10 /spl mu/s. A novel self-managed high-frequency and precision PWM architecture and integrated circuit are developed for distributed drive control systems. This architecture permits near-zero interfacing rate with the coprocessor, thus eliminating the overhead of the MPU's intervention and housekeeping, while being capable of both asynchronous and synchronous PWM at a range of 0-1000 Hz of fundamental frequencies, expandable to several kilohertz. A cycle-to-cycle accuracy of 50 ns is achievable in precision open-loop control. Experimental results verify our new design. This effectively supports distributed ac drive systems with highly coordinated controls.