| 摘要 |
PROBLEM TO BE SOLVED: To surely perform signal transmission even when the current transmission efficiency of a photoelectric converting circuit is lowered. SOLUTION: A photocoupler PC2 for current detection is provided while having the equal current transmission efficiency with a photocoupler PC1 for signal transmission when performing the signal transmission through the photocoupler PC1 for signal transmission, and light emitting parts Pd1 and Pd2 of these photocouplers PC1 and PC2 are serially connected. Since a detection current Im on the side of a light receiving part Pt2 of the photocoupler PC2 for current detection can be regarded equal with a secondary current I2 on the side of a light receiving part Pt1 of the photocoupler PC1 for signal transmission, the state of the secondary current I2 can be estimated from the detection current Im. Therefore, when the detection current Im is lower than a preset reference value, by reducing the resistance value of a primary current control part 20, a primary current I1 is increased so that the secondary current I2 is increased as well according to this reduction and an output signal VOUT becomes a prescribed voltage value. Thus, even when current transmission efficiency is lowered, the output signal VOUT of the prescribed value can be surely transmitted. |
