| 摘要 |
<p>Provided is a motor drive circuit comprising an H-bridge circuit connected with the coil of a motor, a comparator for converting a Hall signal indicating the rotor position of the motor, into a square signal, and a pulse width modulator for generating a pulse signal to regulate the ON time of the coil of the motor. The pulse width modulator is constituted to switch a first mode, in which the duty ratio of the pulse signal is set to 100 %, after the motor was started, and then switched to a predetermined value according to the speed of the motor, a second mode, in which the duty ratio of the pulse signal is continuously set at 100 %, and a third mode, in which the frequency and the duty ratio of the pulse signal are set on the basis of a control signal inputted from the outside. Thus, the pulse width modulator can shorten the starting time period of the motor.</p> |
