A remote power unit for providing direct current power to a remote power receiver in a direct current power system is provided. A residual current protection circuit comprises a first switch, which opens a positive voltage rail, and a second switch, which open a negative voltage rail. A first current sensor measures a first residual current between the first switch and the remote power receiver, while the first switch is closed and the second switch is opened. A second current sensor measures a second residual current between the second switch and the remote power receiver, while the second switch is closed and the first switch is open. A controller detects a residual current event, if the first residual current and/or the second residual current are above a residual current threshold.

Circuits for providing overcurrent protection are disclosed herein. The circuits feature depletion mode MOSFETs connected to resistive elements, preferably, Positive Temperature Coefficient (PTC) devices, configured in such a way so that the voltage across the PTC device is the same as the gate-to-source voltage of the MOSFET. The circuit may further be configured using a TVS diode, for clamping the drain-to-source voltage of the MOSFET during the overcurrent events. Heat transfer between the MOSFET and the PTC device facilitates overcurrent protection. A two-terminal device including a depletion mode MOSFET, a PTC device, and a TVS diode may provide overcurrent protection to other circuits. A bidirectional circuit c including two MOSFETS disposed on either side of a PTC is also contemplated for AC voltage overcurrent protection.

An electrical receptacle contains a plug outlet that has a pair of contacts for electrical connection to respective hot and neutral power lines. A controlled switch, such as a TRIAC, is connected in series relationship between the outlet contact and the hot power line. Sensors in the receptacle outputs signals to a processor having an output coupled to the control terminal of the controlled switch. The processor outputs an activation signal or a deactivation signal to the controlled switch in response to received sensor signals that are indicative of conditions relative to the first and second contacts.

An electrical receptacle contains a plug outlet that has a pair of contacts for electrical connection to respective hot and neutral power lines. A controlled switch, such as a TRIAC, is connected in series relationship between the outlet contact and the hot power line. Sensors in the receptacle outputs signals to a processor having an output coupled to the control terminal of the controlled switch. The processor outputs an activation signal or a deactivation signal to the controlled switch in response to received sensor signals that are indicative of conditions relative to the first and second contacts.

An electronic control unit (ECU) operates between first and second voltage rails and includes an amplifier circuit and a single current sense circuit coupled to carry a signal to a bus pin and to protect the bus pin from both a short to ground and a short to battery. The single current sense circuit includes a switch circuit that passes the signal to the bus pin and a forward current sensing circuit that provides a second current that is proportional to an output current at the bus pin. The forward current sensing circuit causes the second current to be substantially zero when voltage on the bus pin is above a given value. The single current sense circuit also includes a forward current protection circuit and a reverse current switching circuit that receives the second current and closes a connection to the second voltage when the second current is zero.

An electronic control unit (ECU) operates between first and second voltage rails and includes an amplifier circuit and a single current sense circuit coupled to carry a signal to a bus pin and to protect the bus pin from both a short to ground and a short to battery. The single current sense circuit includes a switch circuit that passes the signal to the bus pin and a forward current sensing circuit that provides a second current that is proportional to an output current at the bus pin. The forward current sensing circuit causes the second current to be substantially zero when voltage on the bus pin is above a given value. The single current sense circuit also includes a forward current protection circuit and a reverse current switching circuit that receives the second current and closes a connection to the second voltage when the second current is zero.

In described examples, a first transistor has: a drain coupled to a source of a depletion-mode transistor; a source coupled to a first voltage node; and a gate coupled to a control node. A second transistor has: a drain coupled to a gate of the depletion-mode transistor; a source coupled to the first voltage node; and a gate coupled through at least one first logic device to an input node. A third transistor has: a drain coupled to the gate of the depletion-mode transistor; a source coupled to a second voltage node; and a gate coupled through at least one second logic device to the input node.

In described examples, a first transistor has: a drain coupled to a source of a depletion-mode transistor; a source coupled to a first voltage node; and a gate coupled to a control node. A second transistor has: a drain coupled to a gate of the depletion-mode transistor; a source coupled to the first voltage node; and a gate coupled through at least one first logic device to an input node. A third transistor has: a drain coupled to the gate of the depletion-mode transistor; a source coupled to a second voltage node; and a gate coupled through at least one second logic device to the input node.

A relay protection device is disclosed for use with a magnetic latching relay, the relay having two stable states. The relay comprises an electromagnetic device which under the effect of a switching impulse current, causes the relay to switch from one of the states to the other. The relay protection device comprises a current detector for connection with electrical control contacts of the relay, which measures a current induced by the switching mechanism, a comparator operable to determine if the current exceeds a predetermined threshold, and a controller for connection with the electrical control contacts and, based on the determination of the comparator, operable to apply a retention voltage across the electrical control contacts so as to cause the electromagnetic device to generate a magnetic field to retain the switching mechanism in its current state.

A bi-directional direct current (DC) solid state power controller (SSPC) architecture and control method. The SSPC protects a DC distribution system by isolating both the positive and negative buses independently in case of short circuit or ground fault. The SSPC architecture includes two self-heal interleaved capacitors and includes a fast, soft-charging control technique that provides line-isolated charging of the DC bulk capacitor to avoid inrush current when powering up the DC distribution system. The soft-charging function alternately charges one of the two interleaved capacitors, while the other capacitor discharges to the DC bulk capacitor. Repetitive switching results in a charging and discharging process that increases the voltage of the DC bulk capacitor prior to powering up the DC distribution system, while keeping the DC power source isolated from the load.