| 摘要 |
PURPOSE:To always maintain a predetermined average current by comparing the maximum value of an output current with a voltage obtained by smoothing an input pulse, and controlling ON, OFF a transistor for driving the coil of an actuator based on the compared result. CONSTITUTION:The time of the ON state of a power transistor 2 can be regulated by the time constant of CR of a smoothing unit 14. If the time constant of the CR is large, correction of the time of ON state is increased, and the average value is increased when a power source voltage is low as compared with the case that the power source voltage is high. If the time constant of the CR is suitable, correction of the time of the ON state is suitable, and the average current becomes constant irrespective of the power source voltage. If the time constant of the CR is low, the correction of the time of the ON state is small, and the average current becomes lower when the power source voltage is low as compared with the case that the power source voltage is high. Even if the resistance of the coil 3 of an actuator is varied so that the rise of the current is delayed, similar correction is conducted to hold the average current constant. |
