| 摘要 |
PURPOSE:To remove the affect of an offset of the output voltage and the irregularity of the sensitivity of a magnetic field detector in a DC motor control circuit by limiting the amplifed output voltages of the magnetic field detector within the upper and lower reference voltages wherein two reference voltages vary interlockingly with the neutral potential as a center. CONSTITUTION:The output voltage of the Hall element 30 is amplified by the differential amplifier 48 around the neutral potential VE of the reference voltages VC and VD as a center, is limited at the upper and the lower amplitudes by the diodes 51, 54 to the voltages VC and VD, and applied through power transistors 57, 58 to a stator coil 63. The voltages VC and VD are determined by the base potential vs of a transistor 21. The amplitude of the drive voltage may be altered from the value near the power supply voltage VCC to zero. Further since the neutral potential VE does not alter, the electric powers consumed in the power transistors 57, 59, 61 and 58, 60, 62 are equal. |
