| 摘要 |
PURPOSE:To obtain an AC output signal having always a desired phase difference from an AC input signal even when its frequency is changed by using an output signal of a phase difference adjusting means so as to change the resistance of the input resistor of an input circuit of a phase shifter or the capacitance of an input capacitor. CONSTITUTION:A phase comparison circuit 24 inputs the AC input signal A and a signal B with a prescribed phase difference to the signal A by a phase shifter 10 via comparators 22, 23 respectively, operates the difference of both the inputs and outputs a signal E corresponding to the phase difference. The output is smoothed by a full wave rectifier circuit 25 and a filter circuit 26. A phase difference adjusting device 28 outputs a control signal G to make zero the deviation between a set value of a phase difference setting device 27 and the output signal of the circuit 26 to a voltage controlled oscillator 29, which oscillates a signal H having a frequency corresponding to the signal G to turn on/off a contact 17 of a phase shifter 10 thereby changing the circuit constitution of the positive side of an operational amplifier 12. The phase shifter is adjusted in a closed loop by using a phase locked loop including the phase difference means and the phase difference adjusting means in such a way. |
