Abstract: A switching circuit is provided with a power field effect transistor having a drain terminal, a source terminal and a gate terminal. A gate resistor is connected to the gate terminal. In response to a turn-on signal, a DC gate voltage is produced between the gate resistor and the source terminal. A circuit branch having a normally-on solid state switching device is connected between the gate resistor and the source terminal. The normally-on solid state switching device is turned off in response to the turn-on signal, and enabled in the absence of the turn-on signal to improve the turnoff characteristics of the power field effect transistor.

Abstract: A current limited DC power controller is provided with an output stage having a controllable solid state switching device for conducting current between a pair of output terminals and a drive circuit for controlling the operation of this switching device in response to a control signal. A programmable current source is used to produce a reference current signal in response to a command signal and this reference current signal passes through a resistor to produce a reference voltage signal having a magnitude proportional to the command signal. When the power controller is off, the reference voltage signal is clamped to a preselected value. A second voltage signal proportional to the load current is combined with the referenced voltage signal and used to produce the control signal to which the drive circuit responds.

Abstract: A solid state power controller is provided with an output circuit having a transistor which is connected between a pair of output terminals. Base current to the transistor is provided by a drive circuit which includes a pair of series connected diodes that provide biasing to offset the drive circuit and output transistor base voltage drops. Load current is sensed and a DC bias current is supplied to the diode pair, with the DC bias current being proportional to the load current. For bi-directional operation, a second output transistor is connected in series with the first output transistor and a pair of reverse series connected diode are connected in a circuit branch which parallels the two output transistors. Junction points between the output transistors and the reverse series connected diode circuit branch are connected together to provide for bidirectional load current flow.

Abstract: A bi-directional DC power controller is provided with a bi-directional DC switch connected between a pair of terminals for connection to a pair of line power conductors. A first difference amplifier is connected to receive voltages at these terminals and to produce an output voltage signal which is proportional to the difference in voltages between these terminals when the voltage at one of the terminals is greater than the voltage at the other terminal, and is constant when the voltage at the second terminal is greater than the voltage at the first terminal. A second differential amplifier also receives voltage signals from these terminals and produces an output voltage signal which is proportional to the difference in voltages between the terminals when the voltage at the second terminal is greater than the voltage at the first terminal, and which is constant when the voltage at the first terminal is greater than the voltage at the second terminal.

Abstract: A hybrid electrical power controller is provided with a relay having a coil and a pair of mechanical contacts. A solid state switching device is electrically connected in parallel with the mechanical contacts and the parallel combination of that switching device and the contacts is connected between an input and an output terminal. A relay coil energizing circuit is included and means is provided for producing a signal representative of current flowing in the relay coil following deenergization of the relay coil. A solid state switching device control circuit responds to this signal and turns off the switching device when the signals fall below a predetermined magnitude.

Abstract: A solid state power controller including a switching device which has a first impedance in an ON state and a second, higher impedance in an OFF state is provided with a leakage current shunt circuit. The solid state power controller includes a control circuit for turning the switching device on and off. This control circuit is operatively associated with a shunt circuit operating means which turns the shunt circuit on following a transition of the switching device from an ON state to an OFF state and which renders the shunt circuit inoperative prior to a transition of the switching device from an OFF state to an ON state. The shunt circuit thereby acts to clamp the voltage appearing at a pair of solid state power controller load output terminals.

Abstract: An overcurrent protection system adaptable for use with power controllers the single or multi-phase ac, or dc types includes a load current sensing element in combination with an overcurrent sensing/inverse time delay circuit, a power switch and a crowbar circuit. The system also includes a drive circuit, a drive circuit input current sensor, a trip signal detector and a logic circuit. The overcurrent protection system, according to the present invention, uses the drive circuit to power the overcurrent sensing/inverse time delay circuit, to drive the power switch, and to provide a coupling path for an overcurrent fault signal across electrical isolation interface(s) thereof to the logic circuit. Thus, the need for a separate isolated power supply for powering the overcurrent sensing/inverse time delay circuit and the need for separate optical and/or electromagnetic isolation interfaces for coupling of the overcurrent fault signal are eliminated.

Abstract: A solid-state power controller in combination with a solid-state indication circuit is reminded for exhibiting OFF status using a depletion mode field effect transistor that permits an active signal to appear at its source and drain terminals when its gate, coupled to the power controller, is not energized. Such OFF indication circuitry is also combined with solid state ON indication circuitry using a device such as a bipolar transistor to exhibit an output when its base, coupled to the power controller, is supplied a signal.

Abstract: A solid state circuit breaker is provided with circuitry for permitting off/on/reset operations actuated by mechanical toggle switch for close simulation of magnetic circuit breaker operation in three phase or other multiphase systems. A power continuity feature is provided for load power by locating the control switch so that it opens all of the circuit except the static power switch branch. The control switch is located between two of the supply voltage phases and the power supply for the control circuitry. The correct zero crossover of one phase is utilized to produce turn-on at zero degrees of that one phase while the other two phases are respectively at minus 120.degree. and plus 120.degree. without any significant impairment of overall circuit breaker performance. An overcurrent protection system is included that uses optical isolators with reduced sensing voltages developed directly from terminals of the power switch elements.

Abstract: A solid-state circuit breaker is provided with circuitry for permitting off/on/reset operations actuated by a mechanical toggle control switch for close simulation of magnetic circuit breaker operation. A power continuity feature is provided for load power by locating the control switch so that it opens all of the circuit, except the static power switch branch, between the source and the load, to provide a high degree of fail-safe protection for the apparatus. The power continuity feature includes means for zero crossover synchronization both upon power-up and power-down conditions. A circuit lockout feature is used so that on power-up or turn-on, operation is delayed until the occurrence of an internal power-ready condition. On power-down or turn-off, there is means for circuit retention subsequent to switch opening and internal power removal in order to accomplish load turn-off at a desired zero crossover point of the load power through the power switch.