| 摘要 |
PURPOSE:To provide a solid state relay capable of preventing destruction by an overcurrent with simple constitution. CONSTITUTION:A photodiode array 2 optically coupled with a light emitting diode 1 and a critesistror 4 thermally coupled with a MOSFET 3 are parallelly connected between the source and the gate of the MOSFET 3. The critesistor 4 is a semiconductor element provided with negative resistance/ temperature characteristics. When an abnormal overcurrent by load short-circuit or the like is made to flow, heat by the heat generation of the MOSFET 3 is conducted to the critesistor 4. Thus, when the temperature of the critesistor 4 becomes nearly 100 deg.C, the resistance value drastically drops and a bias voltage between the gate and the source of the MOSFET 3 becomes approximately OV. As a result, the MOSFET 3 is turned off, the abnormal overcurrent is not made to flow and the destruction of this solid state relay is prevented. |
