Drive unit and motor system for brushless dc motors

A motor system comprising:

• a brushless DC motor that includes a rotor, n-phase (n is a natural number of two or more) windings that rotate the rotor, and an element that detects a rotation position of a rotation reference provided on the rotor at a predetermined interval;
• and
• a drive unit for the brushless DC motor comprising:
• a rotation position acquisition unit that acquires a signal from the element;
• a waveform control unit that acquires a signal from each of a host device and the rotation position acquisition unit;
• and
• a waveform output unit that applies voltage to the n-phase windings based on the signal from the waveform control unit, wherein
• the waveform control unit
• outputs a signal for driving the brushless DC motor by intermediate value energization to the waveform output unit after a rotation start signal is acquired from the host device until a signal in which the rotation position of the rotation reference is detected is first acquired from the element, and
• outputs a signal for driving the brushless DC motor by sine wave energization to the waveform output unit when the signal in which the rotation position of the rotation reference is detected is acquired from the element, and
• the waveform control unit applies voltage corresponding to a sine value of an angle θM of a winding of one phase of the n-phase windings (the angle θM is a predetermined angle included in a rotation range having the rotation reference positioned when the rotor is stopped among a plurality of rotation ranges that are divided in accordance with the rotation position detected by the element) when the brushless DC motor is to be driven by intermediate value energization, and outputs a signal for applying voltage corresponding to a sine value of an angle having similar phase difference as the sine wave energization drive with respect to the angle θM to the rest of the windings.