Patent ID: 7915843

Claim:
A motor drive apparatus comprising: a Hall element which outputs a first and a second sinusoidal signal of mutually opposite phases, in accordance with rotor position; a first comparator which compares the first sinusoidal signal and the second sinusoidal signal outputted from the Hall element and outputs a rectangular wave signal; a pulse width modulation signal generation circuit which detects timing of phase switching, based on the first sinusoidal signal and the second sinusoidal signal outputted from the Hall element, and outputs a pulse width modulation signal whose duty ratio gradually changes, in a predetermined time-period in which phase switches; and a drive circuit which combines the rectangular wave signal and the pulse width modulation signal, by a logical operation, to drive a motor that is to be driven, wherein the pulse width modulation signal generation circuit comprises: an amplifier which amplifies difference between the first sinusoidal signal and the second sinusoidal signal outputted from the Hall element, and outputs the difference as an absolute value signal; and a pulse width modulation comparator which compares the absolute value signal outputted from the amplifier with a cyclic voltage, and outputs a pulse width modulation signal; wherein the duty ratio reaches a minimum level at a time of phase switching.