A New Phase-Delay-Free Commutation Method for BLDC Motors Based on Terminal Voltage

It is well known that there is the commutation interference pulse in zero-crossing points (ZCPs) of back electromotive force (EMF) for brushless direct current (BLdc) motors. Generally, the interference pulse is handled by a low-pass filter (LPF) with a low cutoff frequency. However, the phase delay caused by LPF will deteriorate the performance of BLdc motors. In this letter, a novel phase-delay-free commutation method based on terminal voltage is proposed. The ZCPs and commutation freewheeling signals are obtained according to terminal voltages. Then, the main part of commutation interference pulse is removed through detected freewheeling signals. Finally, the remaining part is eliminated through a fixed delay digital filter (FDF). Comparing with the conventional commutation methods, the faster starting and the phase-delay-free commutation are achieved reliably by the proposed method. The effectiveness of the proposed method is verified through an 80 W BLdc motor.