Current-Controlled PWM Technique for Brushless DC Motor Drives with a Single Current Sensing Resistor

A current-controlled PWM technique for brushless DC drives with only a single current sensor, particularly a low-cost shunt resistor, is presented. On one hand, the PWM technique offers a unipolar modulation which does not produce current in the floating phase. Therefore the winding currents can be sensed directly with the shunt resistor. On the other hand, the current is controlled with a predictive current control algorithm, which gives fast response and is so simple that it can be executed in every period of the PWM interrupt. In addition, the unipolar PWM modulation features low switching and winding losses. Since the standard three-phase bridge power inverter, without any modification, is maintained, the scheme is therefore suitable for household appliances and HVAC applications in which high robustness, high reliability, and low cost are mainly required.