| 摘要 |
A balanced amplifier delivers a detection voltage in order to carry out power supply control. A level shift circuit shifts the level of the detection voltage to a level shift voltage for a +5 Volts system, namely, a low withstand voltage system. An adder adds a reference voltage VREF2 to the level shift voltage as a D.C bias voltage and produces an added voltage. A variable attenuator attenuates the added voltage and produces an attenuated voltage. A subtracter subtracts the reference voltage VREF2 from the attenuated voltage and produces a subtracted voltage. The subtracted voltage is converted into a current by a voltage-current converting circuit and turns back to the balanced amplifier as a signal for a high withstand voltage system. Thus, a signal process can be carried out by a circuit of a low withstand voltage.
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