| 摘要 |
PROBLEM TO BE SOLVED: To improve the utilization efficiency of a power supply voltage by operation either a first or a second output transistor for supplying power supply voltage or ground potential to a coil at a pseudo-saturation or saturation region and at the same time using the voltage between a collector and an emitter as the drive current detection signal of a motor for controlling rotary speed. SOLUTION: The collector current of a transistor Q14 of output circuits DV1, DV2, and DV3 is set larger than that of the emitter current of a transistor Q15, and the transistor Q14 is operated at either a saturation or pseudo- saturation region. As a result, the voltage at the low-level side of the voltage waveform of phases U, V, and W becomes proportional to a coil current. In this case, the voltage at the low-level side of terminals T1, T2, and T3 is detected, compared with a control voltage Vcont of a control system with an amplifying circuit AMP, fed back to a current source transistor Q16 provided at the emitter of the differential circuit of the output circuits DV1, DV2, and DV3, so as to control the rotary speed of the motor. |
