Digital Implementation of PWM Techniques for Two-phase Eight-switch Inverter fed Brushless DC Motor Drives

Abstract

This paper reports an investigation of pulse width modulation (PWM) techniques fo r two-phase brushless DC (BLDC) motors fed by a two-phase eight-switch inverter in a fan a pplication. The three-phase BLDC motor is widely applied in industry; however, a lower-cost t wo-phase BLDC motor and drive circuit has been greatly in demand in recent years. In this p aper, we introduce a mathematical model of the two-phase BLDC motor with sinusoidal back electromotive forces (EMFs) based on traditional three-phase BLDC motors. To simplify the dr ive algorithm and speed up its application, we analyze the principle of block commutation for a two-phase BLDC motor drive in the 180-electrical-degree conduction mode, and we further propose five PWM schemes to improve the commutation performance of the two-phase BLDC drive. The effectiveness of the proposed PWM methods is verified through experiments.