| 摘要 |
PURPOSE:To prevent the excessively large of a load current by setting the load current at the specified maximum load current during the time, when the reading of the load current by a load-current reading means is not performed, by a duty-ratio determining means. CONSTITUTION:The load current flowing through a driving coil 12a of a stepping motor, which is controlled by switching elements 14a1-4, is detected as the voltage, which is generated across both ends of a shunt resistor 13a1. The voltage is inputted into a microcomputer 11. The inputted load current and a specified current-preset value are compared, and the duty ratio is determined. The determination sets the load current stored in the microcomputer 11 as the maximum load current. Thus, the phenomenon that the load current actually flowing through the driving coil 12a becomes excessively large, can be prevented. |
