Patent ID: 7768226

Claim:
A motor drive device operable to start an N-phase motor having N phase (where N is an integer of two or more) motor windings by supplying a search current and a starting current in a search and start mode, and to drive the N-phase motor by supplying drive current in a back electromotive force (back-EMF) voltage mode, the motor drive device comprising: a drive signal generator operable to produce a search drive signal, a starting drive signal, and a normal drive signal; a driver operable to produce the search current, starting current, and drive current, respectively, based on the search drive signal, the starting drive signal, and the normal drive signal; a pseudo-neutral-point voltage generator operable to generate a pseudo-neutral-point voltage representing the average voltage of the N-phase motor terminals; and a terminal difference voltage detector operable to detect a terminal difference voltage denoting the difference between the N-phase motor terminal voltage and the pseudo-neutral-point voltage, and to output a detection result signal; wherein said drive signal generator controls the starting drive signal based on the search drive signal and the detection result signal in the search and start mode.