| 摘要 |
PROBLEM TO BE SOLVED: To provide the semiconductor relay where thermal destruction is prevented when an overcurrent is supplied to a semiconductor switch element connected between relay output terminals. SOLUTION: A light emitting element 1 and a photovoltaic element 2 are placed opposite to each other. A MOSFET 3 being a semiconductor switch element is conductive when a photoelectromotive force of the photovoltaic element 2 is applied between a gate and a source of the MOSFET 3. A MOSFET 8 is connected between relay input terminals 6a, 6b. A temperature sensing element 5 is connected to a gate of the MOSFET 8. The MOSFET 8 is closed when a control input is given between the relay input terminals 6a, 6b. When a voltage drop of a diode 10 is decreased by a generated heat by the MOSFET 3, a MOSFET 11 is conductive, a gate voltage of the MOSFET 8 is decreased less than the threshold voltage and the MOSFET 8 is nonconductive. A resistance of a resistor 9 is selected so that a current flowing to the light emitting element 1 via the resistor 9 is in the order ofμA.
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