Patent ID: 8680799
Filing Date: 2014-03-25
Classification: H02P

Abstract:
1. A method for reducing acoustic noise in a brushless direct current (DC) motor, the method comprising: applying a drive signal to a drive circuit; determining a zero-crossing for a back electromotive force (back-EMF) voltage for the brushless DC motor based at least in part on the drive signal; measuring an applied current applied to the brushless DC motor by the driver in response to the drive signal; comparing the zero-crossing for the back-EMF voltage to a zero-crossing for the applied current; and incrementally adjusting the drive signal so as to substantially align the zero-crossing for the back-EMF voltage and the zero-crossing for the applied current, wherein the step of determining further comprises determining a position for the zero-crossing for the back-EMF voltage within a window, wherein the step of comparing further comprises: