| 摘要 |
PURPOSE:To miniaturize a circuit outputting a sinusoidal bell ring signal and to facilitate the ringing by using the sinusoidal wave voltage of a bell ringing frequency as the reference voltage of a control circuit. CONSTITUTION:A sinusoidal wave superimposed on a DC reference voltage is used for the reference voltage inputted to one input of an error amplifier circuit 21 in a control circuit 16 and in inputting an output voltage Vout changing in a high frequency filter circuit 14 to the other input, the pulse width of a pulse signal Ps outputted from a pulse width control circuit 22 changes according to the error and the result is inputted to a high frequency interruption circuit 11 via a waveform shaping circuit 24 and a drive circuit 25. Since the control circuit 16 is operated to correct the output voltage Vout with respect to a reference voltage Vref, the output voltage Vout changes in response to the change in the reference voltage Vref.
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