| 摘要 |
PURPOSE:To control the current of a solenoid valve, by comparing a value, which is obtained by comparing and integrating a voltage corresponding to the current supplied to an electromagnetic working equipment and a control input voltage which controls the opening of the solenoid valve, and a triangular wave oscillation output with each other to output a turn-on/off signal. CONSTITUTION:When a signal Vd of an output terminal (d) of a comparator 222 is high-level, a transistor TR226 becomes conductive, and a current is supplied to a coil 213 of a solenoid valve, and a voltage Ve between both terminals of a current detecting resistance 211 becomes as shown in figure. The voltage Ve is amplified by an operational amplifier 228 and becomes a voltage Vf in figure at an output terminal (f). When a voltage Va of a control input terminal (a) is changed as shown by the dotted line in figure 3, an integrator 227 integrates the voltage Va in a proportion in accordance with the deviation of the voltage Va from the voltage Vf to output a voltage signal Vb shown in figure to an output terminal (b). A triangular wave oscillator 230 outputs a triangular wave Vc to an output terminal (c). The comparator 222 compares the output Vb with the output Vc to switch the TR226, thus controlling the current of the coil 213. |
