Patent ID: 9685894
Date: 2017-06-20
CPC Classifications: H02P

Claim:
1. A brushless motor controller for switching, based on a detected value of a pulse induced voltage induced in a non-energized phase, between energization modes for causing switching elements bridge-connected to a three-phase brushless motor to apply, to two phases, a pulse voltage according to a pulse width modulation signal, the brushless motor controller comprising: limiting means for, when a set duty of the pulse width modulation signal is less than a first predetermined value, limiting, to the first predetermined value, a duty during a predetermined period among a plurality of contiguous periods of the pulse width modulation signal to be applied to the switching elements connected to one of the two phases so as to set the predetermined period as a period for detecting the pulse induced voltage; adjusting means for adjusting a duty during a period other than the predetermined period among the plurality of contiguous periods in the pulse width modulation signal on the basis of the set duty and the duty during the predetermined period which is limited to the first predetermined value, the duty during the period other than the predetermined period being applied to the switching elements connected to the one of the two phases when the set duty is not less than a second predetermined value that is less than the first predetermined value, but applied to the switching elements connected to the other of the two phases when the set duty is less than the second predetermined value; and correcting means for correcting and increasing the duty during the predetermined period when the set duty is less than the second predetermined value.