| 摘要 |
PURPOSE:To perform proper tap selecting operation at the on time of the power supply detecting a brush position by comparing brush voltage obtained from several tap selecting operations at the on time of the power supply with a specified voltage. CONSTITUTION:In the periphery of an annular resistor 1, taps 2-1-2-4 are provided which are connected to a grounding terminal or a positive potential terminal through analog switches S1-S4. A brush 3 slides on the resistor 1 and the voltage of the brush 3 is applied to a differential amplifier 6 through buffer amplifier 4. For other input of the differential amplifier 6, the analog voltage of a D/A convertor 5 that is decided by position assigning signals D0-Dn is applied. The output of the differential amplifier 6 is compared with the zero level by a comparator 7, and this compared result is discriminated by a discriminator 8 and the position of a brush is detected. |
