| 摘要 |
PROBLEM TO BE SOLVED: To provide a small size and light weight motor driver at a low cost.SOLUTION: The motor driver includes: a rectification circuit that rectifies an AC current to a DC current; a smoothing section that smoothens an output voltage from the rectification circuit; an inverter that inverts a DC output from the smoothing section into a three phase AC current; a brushless DC motor driven by the inverter; a position detection section that detects a rotational position of the brushless DC motor; a speed estimation section that estimates the driving speed of the brushless DC motor based on a signal from the position detection section; and a waveform generation section that generates a waveform of desired voltage and frequency by means of pulse width modulation based on the driving speed of the brushless DC motor estimated by the speed estimation section and the output voltage from the inverter. When the PWM duty is smaller than or equal to a predetermined value, the carrier frequency is changed while ensuring PWM ON-time to a predetermined width. Accordingly, a minimum PWM ON-width can be ensured even in a state that the PWM duty is small. Thus, precise position detection of the brushless DC motor can be constantly obtained. |
