| 摘要 |
PURPOSE:To enable voltage detection which is stable in the primary-side input quantity of a power source input to the performed on the secondary side by constituting a power source for feeding electricity to the hardware circuit and its peripheral circuit on the power source secondary side and a power source utilized for a voltage detecting means so that they have the opposite polarities. CONSTITUTION:A power circuit S1 has a rectifying circuit composed of a diode D1 and capacitors C2 and C3 and DC-converted electric power is inputted to a three-terminal regulator Q2 to generate +5V, which is applied to a microcomputer Q1 and its peripheral circuit. The circuit consisting of a diode D2, a capacitor C5, a Zener diode ZD1, respective resistances R1, R2, R3 and R4, and a capacitor C6 is a primary-side voltage detecting circuit S2. In this circuit, +5V is rectified by the diode D2 and capacitor C5 into a negative voltage, which is shifted in level by the Zener diode ZD1 and the resistances R1, R2, and R3 in a trailing stage and inputted to the analog input terminal ADCO of the compute Q1. An input voltage is judged from this input voltage and a primary-side load is controlled according to the input voltage. |
