| 摘要 |
PURPOSE:To control a valve, by providing a signal converting part in the output side of a pulse width modulating D/A converter and outputting signals of opposite phases of a pulse width duty proportional to a digital control signal of a process and outputting these signal selectively. CONSTITUTION:A pulse width duty cycle signal proportional to a digital control signal is outputted from the output of a digital amplifier 11 to a pulse width modulating D/A converter 13 and is applied to a signal converting part 14. The inputted signal is converted to waveform signals having opposite phases in inverters 141 and 142 connected in series in this converting part 14, and these waveform signals are selected by a selecting switch 143 and are applied to an operational amplifier 144 having the LPF function. Signals having opposite phases which are demodulated in this amplifier 144 are supplied to a voltage- current converting circuit 15 to output a current for controlling a valve 12. Output of inverters 141 and 142 are selected to output an operating signal suitable for the operation of the valve 12. |
