Patent ID: 7982420
Filing Date: 2011-07-19
Classification: H02P

Abstract:
1. An energization timing determination circuit comprising a position detecting means for outputting a position signal corresponding to the rotational position of a rotor to determine energization timing used to drive a brushless DC motor; a detected shift length computing means for carrying out computation based on position signal switching intervals obtained from position signals outputted from the position detecting means in a previous at least one cycle of electrical angle and thereby determining a detected shift length of the position signals; and a correcting means for correcting energization timing based on the position signals according to the detected shift length, wherein the detected shift length computing means measures a high-level time and a low-level time within the previous at least one cycle with respect to each position signal outputted from the position detecting means, and computes a duty shift length of the position signal based on the difference value obtained by subtracting the low-level time from the high-level time.