| 摘要 |
PURPOSE:To smoothly distribute a current at the starting and accelerating times by detecting the operating voltage of a transistor which drives polyphase coils and operating current correcting means when the voltage is lower than the prescribed value, thereby preventing the oversaturation of the transistor. CONSTITUTION:A DC motor which has a field magnet 11 and 3-phase coils 12- 14 is controlled by an instruction signal generator 18 by respectively applying signals from a rotor position detecting Hall elements 15-17 to differential amplifiers 43-45. In this case, transistors 51-53 which detect the operating voltages of coil driving transistors 48-50 are provided therein, the collector currents are supplied to a current mirror circuit B in response to the degree of the saturation, and a transistor 24 is controlled, thereby reducing the currents of the transistors 48-50. Accordingly, the oversaturation of the transistors 48-50 can be prevented, thereby smoothly distributing the current at the starting and accelerating times and reducing ripples at the time of switching the coils. |
