PURPOSE: To provide a miniature AC/DC conversion circuit of low power consumption by connecting one reversed Schottky barrier diode and a plurality of resistors between two digital inverters connected in series, and in parallel thereto.

CONSTITUTION: An AC/DC is inputted from a terminal C1 to a functional block 3. The block 3 is a polarity inversion device, the operation of which is changed with the polarity of the input voltage, and the voltage of a point C is kept to the threshold level of a digital inverter DI1 with the turning on and off of Schottky barrier diodes D1, D2 and the feedback of a resistor D4 even when the input voltage of a point A is either higher or lower than the input threshold voltage of the digital inverter DI1. A functional block 4 is constituted of the block 3 and resistors R1, R3 to act as a full-wave rectification type voltage/ current converter. A functional block 5 is constituted of a digital inverter DI2, a feedback resistor R5 and a capacitor C3 and has the functions of current/ voltage conversion and smoothing to output a direct current to a direct-current voltmeter DCV. Thereby, a linear mean-value type AC/DC converter is formed with low power consumption.