| 摘要 |
PURPOSE:To eliminate the need to use more than one transformer by controlling the power voltage of an output amplifier by connecting a switch element in series to a DC power source, by comparing its output with an input signal to an output amplifier through a low-pass filter, and by turning on and off the switch element on the basis of the comparison output. CONSTITUTION:A fixed DC voltage obtained through a commercial transformer 46 and insulated from an AC power source side is brought under the chopper control of switches 38 and 43, and an amplifier power voltage (e) is varied following up an input signal (ei). When the power voltage of an output terminal 10 drops below the reference voltage of a voltage comparator 41, an FET50 as a main switch is turned on and a voltage passed through a smoothing circuit 39, i.e. the voltage of the output 10 rises gradually. When it reaches a potential exceeding the reference voltage of the voltage comparator 41, the output voltage of the voltage comparator 41 is made negative and an FET51 turns off to turn of the FET50. |
