| 摘要 |
PURPOSE:To keep the current of the coil of a step motor almost constant and stably drive the motor, by providing a battery voltage detection circuit and by changing the turn-on resistances of transistors for supplying the current to the coil of the step motor, depending on the output of the detection circuit. CONSTITUTION:When the terminal voltage of a battery is high, the output of a battery voltage detection circuit 1 is at ''H'' and the output of an inverter 2 is at ''L''. Clocked inverters 3, 4 supplied with these outputs do not function. Inverters 5, 6 supplied with outputs from the output terminals 7a, 7b of a driving wave form generation circuit 7 act to limit the current of a coil 8 by the turn-on resistances of the channels of the inverters 5, 6. When the terminal voltage of the battery is low, the output inverters 5, 6. When the terminal voltage of the battery is low, the output of the battery voltage detection circuit 1 is at ''L'' and the output of the inverter 2 is at ''H''. At that time, the clocked inverters 3, 4 function and the current of the coil 8 is limited by the parallel-coupled value of the turn-on resistances of the channels of the inverters 5, 6. |
