| 摘要 |
PURPOSE:To limit the collector voltage of a transistor which turns ON or OFF in response to the position of a rotor in a DC motor to a value lower than the prescribed value by detecting the collector voltage of the transistor and increasing the collector current when the value exceeds the prescribed value. CONSTITUTION:The signal of a rotary phase detector 1 is supplied to a switching signal generator 2 which is controlled by a control signal generator 3, thereby alternately turning ON and OFF transistors 4a, 4b, and driving a DC motor having coils 5, 6. The collector voltages of the transistors 4a, 4b are respectively detected by providing voltage controllers 12a, 12b, the base current is increased when it exceeds the prescribed value, and the increase in the collector voltage due to the increase in the voltage drop of the coils 5, 6 upon increase of the collector current is limited. Accordingly, the abnormal voltage due to counterelectromotive force at the time of interrupting the current can be prevented, and the circuit is extremely reduced in size, thereby enabling to turn it into IC state. |
