| 摘要 |
PURPOSE:To increase the driving speed without creating excessive heat from a motor by switching a current supplied to the motor for two kinds, high and low. CONSTITUTION:When a PD signal input to a base terminal of a transistor Tr1 is set to 'Hi' level, a reference voltage Vr of an operational amplifier 12 is lowered. Since a current value flowing to a coil 11 of a stepping motor is restricted by a transistor Tr2 having a base voltage created by the output of said operational amplifier 12, the reference voltage Vr is lowered and thus a current flowing through the coil 11 is also decreased. Thus, by setting the PD signal to 'Lo' level during the start of the stepping motor and by setting the PD signal to 'Hi' level when the stepping motor has rotated to a predetermined value, the current flowing to the coil 11 increases only during acceleration when a large drive torque is required. |
