| 摘要 |
PURPOSE:To reduce a loss of a collector of a transistor which drives a proportional valve and to restrain a rise in internal temperature of a device by adopting a switching system for a driving circuit wherein interrupted current is supplied to a smoothing circuit which consists of a choke coil and a capacitor. CONSTITUTION:A comparator 21 which consists of an arithmetic amplifier receives a control voltage VA at the noninverted input terminal and a terminal voltage VB of a resistance 23 which detects a valve current flowing through a solenoid coil 22 of a proportional valve at the inverted input terminal, inverting the output dependently on the comparative relationship between the intensities of both the voltages VA and VB to turn on or off a transistor 24. A transistor 26 is switched on and off in company with the on and off actions of the transistor 24 and supplies a smoothing circuit which consists of a choke coil 27 and a capacitor 28 with a current which is controlled on or off. |
