| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a voltage-frequency conversion circuit for highly accurately detecting DC high voltage. <P>SOLUTION: DC output voltage to be detected is applied to a first resistance R1. A first capacitance C1 is connected to an output node of the first resistance R1 directly or via a first inductor L1, and accumulates an electric charge corresponding to an electrical current flowing through the first resistance R1. A photodiode Pd is connected to the output node of the first resistance R1, converts the electrical current into optical pulse signals, and transmits the optical pulse signals to a phototransistor of a frequency-voltage conversion circuit. A first Zener diode ZD1 is connected to the output node of the first resistance R1 in a reverse bias. A switch unit causes the electrical current to flow through the photodiode Pd by turning itself on when the voltage of the output node is equal to or more than Zener voltage of the first Zener diode ZD1, and stops the electrical curent to flow through the photodiode Pd by turning itself off when the electrical current flowing through the first Zener diode ZD1 is less than a predetermined value. <P>COPYRIGHT: (C)2013,JPO&INPIT |
