A bipolar-starting and unipolar-running method to drive a hard disk drive spindle motor at high speed with large starting torque

This paper presents a method to drive a hard disk drive (HDD) spindle motor at high speed with large starting torque by utilizing a bipolar-starting and unipolar- running algorithm. It proposes a novel inverter circuit to switch from bipolar to unipolar drive, or vice versa. It also develops a digital signal processor (DSP)-based brushless dc (BLDC) motor controller not only to drive the BLDC motor with the bipolar or unipolar method, but also to switch from one method to the other at any speed. Torque-speed-current curves of a BLDC motor driven by bipolar or unipolar method are investigated experimentally, and the effectiveness of the proposed method is also verified by using the developed controller experimentally. This research shows that the proposed method starts the BLDC motor with large starting torque that can be obtained by a bipolar drive, and it runs the BLDC motor at high speed that can be driven by unipolar drive.