| 摘要 |
PURPOSE:To gradually rise a current at the starting time by comparing a rotating pulse with a reference time pulse, controlling a counter, and converting by a D/A converter the content into an analog value, and controlling it as a reference voltage. CONSTITUTION:The speed of a spindle motor or the like M of a magnetic disc device is detected by a Hall element 1, inputted to a converter 3, thereby selectively controlling the transistor 5 of a drive circuit 4. On the other hand, the speed signal and the clock of a reference oscillator 8 are inputted to an up/down signal generator 9 to operate a counter 10, the content is converted by a D/A converter 11 to an analog value, which is, in turn, inputted to a comparator 7 together with the detected current value, thereby controlling the converter 3 as a reference voltage. Accordigly, since the reference voltage gradually increases at the starting time, large power consumption does not occur at the transistor 5, and the current can be averaged at the normally rotating time, thereby reducing the variation in the rotation. |
