Optimizing Efficiency Driver Comprising Phase-Locked Loop for the Single-Phase Brushless DC Fan Motor

Because the single-phase brushless fan motor presents an inductive load, the winding current will lag the back-electromotive force (EMF) an unequal phase based on the different motor speed. In order to improve the efficiency and torque performance, adjusting the commutation angle to keep the optimizing commutation at different speed is necessary. In this paper, the new structure with low cost to achieve the optimizing commutation is accomplished by the concept of phase-locked loop (PLL) to synchronize the winding current and back EMF. The PLL IC CD4046 is adopted to develop a feedback circuit and performs the function of phase advance. The purpose is to force the winding current to be synchronized with the back-EMF. Finally, the related experimental results are used to confirm the feasibility and effectiveness of the proposed driving method.