| 摘要 |
PURPOSE:To obtain a control signal synchronously with a power supply voltage in power feeding by outputting the control signal in response to one of the output signal of 1st and 2nd BPFs connected to an AC power supply, and having frequency around 50 or 60Hz. CONSTITUTION:Suppose that the frequency of an AC power supply 1 is 60Hz, the output of a 2nd absolute value circuit 11 via a 2nd BPF is larger than an input to a 1st absolute value circuit 10 via a 1st BPF 8. A comparator 12 discriminates the quantity and allows a changeover switch 13 to select an output signal from the BPF 9. Thus, a sinusoidal wave signal W2 whose frequency is 60Hz is outputted to a waveform shaping circuit 3, from which a rectangular control signal W3 is obtained. When the frequency of the AC power supply 1 is 50Hz, the output of the 1st absolute value circuit 10 is larger conversely and an output signal from the BPF 8 is selected. |
