Provided are a protection circuit and a photovoltaic system capable of irreversibly interrupting a current path of photovoltaic units such as solar cells by a signal in an emergency such as a fire. The protection circuit includes: a photovoltaic units 26, a protection element 2 provided on a current path of the photovoltaic units 26, and a switch 3 for activating the protection element 2, wherein the protection element 2 irreversibly interrupts the current path of the photovoltaic units 26.

An explosion-proof device includes a frame having a hollow shape, the frame housing an electrical component and a battery capable of supplying the electrical component with electric power. A protection device is configured to stop electric supply to the electrical component from the battery, if there is a risk of an explosive atmosphere entering the frame. The battery is housed in an explosion-proof container, within the frame, and thus it is possible to suppress damage to surroundings effectively even in case of ignition of an explosive atmosphere flowing into the frame by the battery.

An explosion-proof device includes a frame having a hollow shape, the frame housing an electrical component and a battery capable of supplying the electrical component with electric power. A protection device is configured to stop electric supply to the electrical component from the battery, if there is a risk of an explosive atmosphere entering the frame. The battery is housed in an explosion-proof container, within the frame, and thus it is possible to suppress damage to surroundings effectively even in case of ignition of an explosive atmosphere flowing into the frame by the battery.

A circuit for measuring temperature of an external switch is disclosed. The circuit includes a variable resistor, a switch coupled to the variable resistor in series, a fixed value resistor coupled to the variable resistor and a comparator coupled between the variable resistor and the fixed value resistor. The circuit is configured to compare voltage drop between a drain and a source of the external switch when the external switch is in ON state with voltage drop at the variable resistor and output a signal to indicate an overtemperature based on the comparing.

A temperature abnormality detection system of the present invention includes a first temperature sensor that measures a first temperature indicated by a target device and a second temperature sensor that measures a second temperature indicated by ambient air around the target device. A temperature difference between the first temperature and the second temperature is calculated, and when this temperature difference becomes a predetermined threshold value or more, it is determined that a temperature abnormality of the target device has occurred.

The carbon monoxide detector and shutoff system is an electrical switching device. The carbon monoxide detector and shutoff system inserts into an electrical connection between the national electric grid and an electrical load. The carbon monoxide detector and shutoff system senses the carbon monoxide concentration within the atmosphere. Should the detected concentration of carbon monoxide exceed a threshold level, the carbon monoxide detector and shutoff system interrupts the circuit between the national electric grid and the electrical load. The carbon monoxide detector and shutoff system comprises a pass-through circuit, a control circuit, and a housing. The housing contains the pass-through circuit and the control circuit. The pass-through circuit inserts a relay between the national electric grid and the electrical load. The control circuit is an electrical circuit that opens and closes the relay in response to the detected concentration of carbon monoxide.

The carbon monoxide detector and shutoff system is an electrical switching device. The carbon monoxide detector and shutoff system inserts into an electrical connection between the national electric grid and an electrical load. The carbon monoxide detector and shutoff system senses the carbon monoxide concentration within the atmosphere. Should the detected concentration of carbon monoxide exceed a threshold level, the carbon monoxide detector and shutoff system interrupts the circuit between the national electric grid and the electrical load. The carbon monoxide detector and shutoff system comprises a pass-through circuit, a control circuit, and a housing. The housing contains the pass-through circuit and the control circuit. The pass-through circuit inserts a relay between the national electric grid and the electrical load. The control circuit is an electrical circuit that opens and closes the relay in response to the detected concentration of carbon monoxide.

An electric wire protection device includes a voltage adjusting unit that adjusts voltage of a power source side and supplies the resulting voltage to a load, and a controller that includes a calculation unit configured to compute temperature information of an electric wire connecting the power source and the load from a value of an electric current flowing through the voltage adjusting unit, and that is configured to make the voltage adjusting unit into a shutoff state of shutting off the power source and the load on the basis of the temperature information.

An electrical shut-off device (10) is provided and includes a housing (11), first and second inputs (12, 13) and an output disposed on the housing, a transmission/reception (T/R) module (14) coupled to the first input, an input device (15) coupled to the second input, an electrical device coupled to the output and a processor (20). The processor is in signal communication with the T/R module, the input device and the electrical device via the first and second inputs and the output, respectively. The processor is configured to issue an instruction via the T/R module and to take an action relative to the electrical device responsive to a signal being received by the T/R module and to take an additional action in accordance with an actuation state of the input device.

Systems, methods, techniques and apparatuses of power switch control are disclosed. One exemplary embodiment is a power switch comprising a thyristor-based branch including a thyristor device; a FET-based branch coupled in parallel with the thyristor-based branch and including a FET device; and a controller. The controller is structured to turn on the FET device, turn on the thyristor device after turning on the FET device based on a thyristor voltage threshold, and update the thyristor voltage threshold based on a voltage measurement corresponding to the thyristor-based branch measured while the thyristor device is turned on.