A Sensorless Drive Method for Brushless DC Motors Based on Dynamic Compensation of Back EMF Detection

To address the significant errors in traditional back electromotive force (BEMF) zero-crossing detection for brushless DC motor (BLDCM) control systems at low speeds, this paper proposes a dynamic BEMF compensation method. By introducing proportional-integral (PI) control into the comparator, the proposed method dynamically adjusts its reference voltage, thereby effectively compensating for detection errors caused by comparator offset, voltage divider resistor tolerances, and asymmetric three-phase motor parameters. In contrast to existing approaches that rely on prior knowledge of motor parameters (such as equivalent resistance and inductance) or complex neutral-point voltage reconstruction, the proposed scheme automatically corrects commutation errors without requiring specific motor parameters or a complex divider network. Experimental results based on an implemented BLDCM drive system demonstrate that the proposed algorithm not only greatly improves operational smoothness and significantly reduces acoustic noise but also achieves greater error reduction at low speeds, thereby offering a robust solution for optimizing the low-speed performance of sensorless BLDCM drives.