A protection and attenuation circuit for sensitive AC loads is described. The circuit provides AC power protection and attenuation utilizing high-efficiency switch-mode techniques to attenuate an AC power signal by incorporating a bidirectional, transistorized switch driven from a pulse width modulation signal, PWM. The circuit monitors characteristics of the AC power signal driving a known load and characteristics of the load or other elements and determines the duty cycle of the pulse width modulated signal, PWM, based upon the duration and amplitude of the over-voltage, over-current, over-limit or other event.

This device for actively discharging an electrical energy storage device has a branch having first and second ends connected respectively to positive and negative terminals of the electrical energy storage device, and between the two ends, a thermistor having a resistance that increases with a temperature of the thermistor and a switch designed to receive a control signal (v.sub.GS) to change from an open state to a closed state, the thermistor and the switch being connected to one another so that, when the switch is closed, a discharge current (i.sub.D) enters through the first end, flows through the thermistor (210) and the switch one after the other, and emerges through the second end; and a device for controlling the switch. The control device is connected to the switch so as to provide the control signal (v.sub.GS) independently of the resistance of the thermistor.

Disclosed are electrical relay assemblies including a positive temperature coefficient thermistor (PTC) for reverse connection protection. In some embodiments, a relay assembly includes a relay socket receiving a relay, a power source connected to the relay socket, and a positive temperature coefficient thermistor (PTC) connected between the relay socket and the power source.

A radial-leaded over-current protection device comprises a PTC element, a first electrode lead, a second electrode lead and an electrically insulating encapsulation layer. The PTC element comprises a first conductive layer, a second conductive layer and a PTC material layer laminated therebetween. The PTC material layer comprises crystalline polymer and conductive filler dispersed therein. The first electrode lead has an end connecting to the first conductive layer, whereas the second electrode lead has an end connecting to the second conductive layer. The electrically insulating encapsulation layer includes a fluorine-containing polymer, and wraps around an entire outer surface of the PTC element and the ends of the first and second electrodes connecting to the PTC element. The electrically insulating encapsulation layer has a thickness of 10.sup.2˜10.sup.5 nm, and the radial-leaded over-current protection device has an initial resistance R.sub.bf of 0.0017˜0.0027Ω.

A surge protection apparatus may include an input terminal; an output terminal, the output terminal electrically coupled to the input terminal; a ground terminal, the ground terminal electrically coupled to the input terminal and output terminal; a positive temperature coefficient (PTC) fuse, the PTC fuse connected in electrical series between the input terminal and output terminal; a crowbar device, the crowbar device electrically connected to the ground terminal and output terminal, wherein the crowbar device is in electrical series with the PTC fuse between the input terminal and ground terminal; and a central frame portion, the central frame portion electrically coupled to the input terminal, output terminal and ground terminal, wherein the crowbar device is disposed on a first side of the central frame portion and the PTC fuse is disposed on a second side of the central frame portion, opposite the first side.

A radial-leaded over-current protection device comprises a PTC element, a first electrode lead, a second electrode lead and an electrically insulating encapsulation layer. The PTC element comprises a first conductive layer, a second conductive layer and a PTC material layer laminated therebetween. The PTC material layer comprises crystalline polymer and conductive filler dispersed therein. The first electrode lead has an end connecting to the first conductive layer, whereas the second electrode lead has an end connecting to the second conductive layer. The electrically insulating encapsulation layer includes a fluorine-containing polymer, and wraps around an entire outer surface of the PTC element and the ends of the first and second electrodes connecting to the PTC element. The electrically insulating encapsulation layer has a thickness of 10.sup.2˜10.sup.5 nm, and the radial-leaded over-current protection device has an initial resistance R.sub.bf of 0.0017˜0.0027Ω.

An over-current protection device comprises first and second electrode layers and a PTC material layer laminated therebetween. The PTC material layer comprises a polymer matrix and carbon black. The polymer matrix comprises a fluoropolymer having a melting point higher than 150° C. The carbon black is dispersed in the polymer matrix. A resistance jump R.sub.jump_1000@16V/50A of the over-current protection device at 16V/50 A by 1000 cycles is 0.80-1.20. A resistance jump R.sub.1000@16V/50A of the over-current protection device at 25V/50 A by 1000 cycles is 0.90-1.30.

An over-current protection device comprises first and second electrode layers and a PTC material layer laminated therebetween. The PTC material layer comprises a polymer matrix and carbon black. The polymer matrix comprises a fluoropolymer having a melting point higher than 150° C. The carbon black is dispersed in the polymer matrix. A resistance jump R.sub.jump_1000@16V/50A of the over-current protection device at 16V/50 A by 1000 cycles is 0.80-1.20. A resistance jump R.sub.jump_1000@25V/50A of the over-current protection device at 25V/50 A by 1000 cycles is 0.90-1.30.

The present disclosure includes: a power generator; and a power line through which power generated by the power generator is transmitted to a load. The power line between the power generator and the load is provided with: a current limitation device configured to, when detecting occurrence of a fault current, limit the fault current; and a current interruption device configured to interrupt current heading for the load, in conjunction with the limitation of the fault current performed by the current limitation device.

A power supply control device controls power supply from a DC power source to a load, by turning on or off a MOSFET. A current regulation circuit regulates a current flowing through a device resistor to a current proportional to a voltage between the drain and the source of the MOSFET. A drive circuit turns off the MOSFET when a voltage across a resistor circuit exceeds a predetermined voltage. The on-resistance of the MOSFET varies according to an ambient temperature of the MOSFET. The resistance of the resistor circuit varies in a direction different from a direction in which the on-resistance of the MOSFET varies, according to the ambient temperature of the MOSFET.