Abstract: A method and apparatus for distributing electrical power is provided. In one embodiment, the apparatus includes: a semiconductor switch adapted to receive input power from a DC power source, adapted to distribute power to a DC/DC module, and adapted to receive a control signal, a charge storage device in operative communication with the semiconductor switch and a return path associated with the DC power source, and a reverse current monitoring logic in operative communication with the semiconductor switch. In this embodiment, the reverse current monitoring logic is adapted to detect reverse current flowing in the semiconductor switch and, in response to detecting the reverse current, is adapted to open the semiconductor switch. Several embodiments of a method of distributing electrical power to a DC load are also provided.

Abstract: A system and method for protecting a reverse battery protected device during loss of battery are disclosed. An embodiment method includes biasing a substrate of a substrate switch of the reverse battery protected device to a lowest potential selected between a battery voltage and ground when the battery voltage is less than a magnitude of a first substrate clamping voltage during reverse battery, clamping the substrate to the first substrate clamping voltage when the battery voltage is greater than the magnitude of the first substrate clamping voltage during reverse battery, and clamping the substrate to a second substrate clamping voltage during loss of battery, where a magnitude of the second substrate clamping voltage is less than the magnitude of the first substrate clamping voltage.

Abstract: A direct current (DC) drive includes a voltage input unit, a comparing unit, a latch unit and a voltage output unit. The voltage input unit has at least one input terminal and at least one output terminal provides a DC voltage. The comparing unit receives the DC voltage and generates a comparison control signal according to a comparison result obtained by comparing a voltage of a positive voltage terminal with a voltage of a negative voltage terminal. The latch unit is connected to the comparing unit and the voltage input unit. The voltage output unit connected to the latch unit receives the DC voltage from the voltage input unit. The latch unit selectively provides the DC voltage to the voltage output unit according to the comparison control signal.

Abstract: Provided is an apparatus and method for preventing reverse power flow of an over current relay. When a neutral line current is greater than a phase current, it is determined that a reverse power flow occurs, and thus a protection relay is prevented from malfunctioning. The apparatus for preventing reverse power flow of an over current relay includes: a detecting unit which detects a phase current and a neutral line current; a reverse power flow determining unit which is electrically connected to the detecting unit and compares the phase current and the neutral line current which are detected by the detecting unit to determine whether or not a reverse power flow occurs; a setting unit which is electrically connected to the reverse power flow determining unit and sets an operation time and the number of operation times of a protection relay; and an operation unit which is electrically connected to the setting unit and operates the protection relay in a manner set by the setting unit.

Abstract: In the case where a battery is reversely connected, unnecessary current-carrying to a glow plug is avoided. Power MOS type field effect transistors 1-1 to 1-n are provided according to a number of glow plugs 5-1 to 5-n to be connected in series between a vehicle battery and the glow plugs 5-1 to 5-n and can be controlled in conduction or non-conduction by a glow-plug control part 51, while a MOS type field effect transistor 2 for protection against reverse connection is provided in series connection between a battery-power joining terminal 3, to which a positive voltage of a vehicle battery is applied, and the ground to cause a reverse current to flow to a fuse 4 through the MOS type field effect transistor 2 at the time of reverse connection of a battery to melt the fuse 4 early whereby current-carrying to the glow plugs 5-1 to 5-n can be avoided.

Abstract: Circuits and methods for protecting polarity-sensitive components, such as light emitting diodes, electrolytic capacitors or integrated circuits, operating from a DC current source including a DC motor, an inductor or relay having a positive terminal and a negative terminal for receiving current from the current source, a protection diode connected parallel with the positive and negative terminals of the motor in a reverse bias configuration, at least one polarity-sensitive component connected in parallel with the protection diode and the DC motor, and a polarity protection transistor connected either between the nominally positive current source terminal and the positive motor terminal, or between the nominally negative current source terminal and the negative motor terminal.

Abstract: A fan system is electrically connected to a power source, and the fan system includes a power reverse protection apparatus, a voltage regulator, a driver, and a fan. The power reverse protection apparatus, electrically connected to the power source, includes a voltage regulator switch and an activating device. The voltage regulator switch receives an input signal and outputs a first output signal according to the input signal. The activating device is electrically connected to the power source and the voltage regulator switch for receiving the input signal and the first output signal, respectively. The activating device outputs a second output signal to the fan according to the first output signal. The voltage regulator is electrically connected to the power source for receiving the input signal from the power source and outputting a regulating signal according to the input signal.

Abstract: An IC power protection circuit functions as a surge protection circuit and reverse connection protection circuit. The IC power protection circuit includes an error amplification circuit, positioned and integrated within an integrated circuit and a transistor positioned as a stand-alone element that is separate from the integrated circuit. The integrated circuit includes a sensor signal processing circuit that processes a signal of a sensor. A transistor protects the integrated circuit against a surge voltage from a battery terminal. A resistor is positioned between an output terminal of an error amplifier and a base terminal of the transistor to provide reverse connection protection. Another resistor is connected between a ground and a connection point between the above resistor and the output terminal to provide overvoltage protection for the integrated circuit. A starting resistor is connected between a collector and base of the transistor.

Abstract: The invention relates to integrated electronic circuits in MOS technology that have to be supplied by a cell or a battery that have a relatively high voltage capable of destroying the circuit in the event of a battery connection error, most particularly when a negative voltage is connected to an output of the integrated circuit. The logic output stage connected to this output comprises two pMOS transistors in series operating in push-pull mode under the control of the logic input signal, a first transistor being connected to a high supply terminal of the integrated circuit and the second transistor to a low supply terminal; the output is taken at the junction point of the two transistors. A conduction control circuit, capable of applying a negative voltage relative to the low supply terminal to the gate of the second transistor when the logic input signal passes to a level tending to turn off the first transistor, is interposed between the input and the gate of the second transistor.

Abstract: An apparatus, system, and method are disclosed for preventing reverse current in a switching power supply. An electrical connector receives an input current from an electric source. An input current limiting module substantially prevents the input current from reaching a switching power supply when the input current is flowing in a reverse direction. A voltage reduction module reduces an input voltage of the switching power supply to a switching voltage when the input current is flowing in a forward direction. A switching module closes a switch in response to the voltage reduction module providing the switching voltage. The switch provides the input current a lower impedance path to the switching power supply than does the input current limiting module.

Abstract: An alternative power source provides alternating current (AC) through a proper connector into a first outlet of a pre-existing electrical distribution system which is normally powered by an alternating current electrical power supply through main breakers and a breaker box. At least one of the breakers which controls power from the normal AC electrical power supply on the electrical distribution system is opened prior to connecting the alternative power supply. The alternative power supply provides electricity through the proper connector into the first outlet, or node, to provide alternating current to a selected portion of the electrical distribution system, and possibly to both halves of the pre-existing electrical distribution system if the proper connector is connected to a 240 volt outlet, or if two proper connectors are utilized and connected to first and second outlets with the first and second outlets on each of the two phase (power) wires of the pre-existing electrical distribution system.

Abstract: The object of the present invention is to provide a structure for the electrical protection of photovoltaic facilities in the event a photovoltaic generator (G1-Gp) is connected with its polarity reversed, for what it includes a protection cell that comprises two connection points (1, 2) at which the photovoltaic generator is connected (G1-Gp), at least one device (D) in charge of reducing the voltage of the photovoltaic generator (G1-Gp) in the event of polarity reversion, which is connected in parallel between the aforementioned two connection points, at least one element (M) of breakage and/or protection of the photovoltaic generator (G1-Gp) serially connected to the preceding elements, minimizing the loading on the aforementioned break and/or protection elements.

Abstract: An interface system may be used to connect an electrical device to an electrical bus. The interface system may include a first end and a second end in electrical communication with the first end. Where the interface system is used to connect an electrical device to an electrical bus, the first end may be connected to the electrical bus and the second end may be connected to the electrical device. The interface system may also include a reverse current blocking circuit configured to block current from flowing from the second end to the first end. Additionally, the interface system may include a discharge circuit electrically connected between the first end and the second end for discharging the blocked current.

Abstract: A method of operating a relay device, in an electrical circuit comprising first and second main circuit breakers, and a bus tie circuit breaker connecting the first and second main circuit breakers, the method comprising computing a first positive sequence current phasor for the first main circuit breaker and a second positive sequence current phasor for the second main circuit breaker computing a first positive sequence voltage phasor for the first main circuit breaker and a second positive sequence voltage phasor for the second main circuit breaker; computing a correction of the first positive sequence voltage and second positive sequence voltage to a line-to-neutral phase angle reference if there is any rotation in a potential transformer connection; determining a fault has occurred when a magnitude of a current through at least one of the first main circuit breaker or the second main circuit breaker exceeds a predetermined threshold; determining a phase angle difference by comparing the phase angle of the

Abstract: The invention relates to a control circuit which serves for security-critical control of a consumer with an inductive load portion, to be connected to a direct voltage source, and a method for failure control. It is in this case assumed that the control circuit has a power driving assembly, a free-wheeling assembly and a reverse-connection protected assembly. In order to increase the probability of failure recognition, this control circuit is extended by a method for failure control. For this purpose the semiconductor switches of the assemblies, each formed by a MOSFET, are individually driven. The different switching statuses are checked by a diagnostic device which processes voltage values to be read out at outputs of the control circuit. In this way failure-free functionality and also possible causes of failure in the control circuit can be diagnosed.

Abstract: A system for protecting against reverse current flow in an output module of an Industrial Process Control System includes a transistor that is driven by a control signal and a current monitor arranged to monitor a current through the transistor. The system includes a processor that is arranged to receive the monitored current and to generate the control signal in dependence upon the monitored current. The processor is configured to turn off the transistor if a reverse current is detected in the transistor. Extension of the system provides a power feed combiner that is protected against reverse current flow.

Abstract: An electronic device includes an operation circuit, a positive input terminal, a negative input terminal, a resistor, and a field effect transistor. The negative input terminal is used for cooperating with the positive input terminal to receive an input voltage. The field effect transistor includes a source connected to the positive input terminal, a drain connected to the operation circuit, and a gate connected to the positive input terminal and the operation circuit via the resistor.

Abstract: Circuits and methods for protecting polarity-sensitive components, such as light emitting diodes, electrolytic capacitors or integrated circuits, operating from a DC current source including a DC motor, an inductor or relay having a positive terminal and a negative terminal for receiving current from the current source, a protection diode connected parallel with the positive and negative terminals of the motor in a reverse bias configuration, at least one polarity-sensitive component connected in parallel with the protection diode and the DC motor, and a polarity protection transistor connected either between the nominally positive current source terminal and the positive motor terminal, or between the nominally negative current source terminal and the negative motor terminal.

Abstract: A wiring fault correction circuit for determining wiring conditions of an AC supply system includes: input line and neutral conductors connectable to the AC supply system; output line and neutral conductors connectable to a load; first, second, third, and fourth single pole, single throw relays; a first driver circuit for controlling the first and second single pole, single throw relays to respectively connect the input line conductor to the output line conductor and the input neutral conductor to the output neutral conductor in response to a correctly wired AC supply system; and a second driver circuit for controlling the third and fourth single pole, single throw relays to respectively connect the input line conductor to the output neutral conductor and the input neutral conductor to the output line conductor in response to an incorrectly wired AC supply system in which line and neutral conductors are reversed.

Abstract: A load driving device according to an aspect of the present invention may includes an output transistor and a load connected in series between first and second power supply lines, a protection transistor connected between a gate of the output transistor and the second power supply line, the protection transistor turning on the output transistor when a polarity of a power supply connected between the first and second power supply lines is reversed, and a resistor arranged on a line, which supplies a voltage to a back gate of the protection transistor.

Abstract: A power supply control circuit includes a control circuit that controls an output transistor to be rendered conductive by forming a second electrical path between a second power supply line and a control terminal of the output transistor when a power supply voltage is applied in a reverse direction between first and second power supply lines, and that controls a second electrical path to be electrically disconnected when the power supply voltage is applied in a forward direction between the first and second power supply lines.

Abstract: A method of operating a relay device, the method comprising the steps of: providing main circuit-breakers and a bus-tie-breaker connecting the main-circuit-breakers; defining a partial-differential-zone comprising a main circuit breaker and the bus-tie breaker; assigning a first value to the direction of the fault current flowing into the partial differential zone;—assigning a second value to the direction of the fault currents flowing out of the partial-differential-zone, wherein the first value is not equal to the second value;—comparing the values assigned to the fault currents; determining if the fault currents are flowing into the partial differential zone; and determining if at least two of the fault-currents is flowing in a different direction with respect to the partial-differential-zone wherein one of the fault currents is flowing into the partial-differential-zone and one of the fault currents is flowing out of the partial differential zone.

Abstract: A device for protecting a circuit against a polarity reversal of a connection to a D.C. power supply, comprising a controllable switch interposed on said connection between a first terminal of a first voltage of the D.C. power supply and a first terminal of the circuit, and first means for turning-off with a delay the switch in the presence of a reverse polarity.

Abstract: A power supply control circuit is disclosed. The power supply control circuit controls a current which is supplied from a power source to a load. The power supply control circuit includes a reverse current detecting circuit which detects a reverse current flowing from the load to the power source and a reverse current preventing circuit which disconnects a line between the power source and the load when the reverse current is detected by the reverse current detecting circuit.

Abstract: A circuit for protection against reverse circulation of current through the body diode of an FET power switching device switching a load, the power switching device having gate, source and drain terminals, wherein the power switching device is connected in series with the load, the load being connected to the source or drain terminal of the power switching device, the load being capable of providing a voltage across the source and drain terminals sufficient to cause the body diode to conduct, the power switching device being controlled by a driver output stage having a driver output stage body diode, the driver output stage having a substrate set at a substrate voltage level, the reverse circulation protection circuit comprising a circuit for changing the substrate voltage level of the driver output stage so that the voltage across the driver output stage body diode is less than a voltage sufficient to cause the driver output stage body diode to conduct, thereby allowing the power switching device to pass the

Abstract: A load drive device is provided for outputting a control signal to a driving transistor and for driving a load by switching, the driving transistor and the load being connected in series between a direct current power source and ground. The load drive device includes a reverse connection protection unit which is provided in a line leading from a negative side of the direct current power source, and which blocks a current flowing therethrough when the direct current power source is connected in reverse. A failure detection is performed by a failure detection process by monitoring a change of a current flowing via the reverse connection protection unit during the driving transistor is in a conduction state.

Abstract: A protection circuit for a primary battery pack provides the battery pack with reverse charge protection. The protection circuit features a metal oxide semiconductor field effect transistor (MOSFET) with a steady state source to drain voltage. The source to drain voltage is controlled through a feedback loop that includes an operational amplifier. The MOSFET is configured in series with one or more battery cells allowing current to flow from the cells and preventing current from flowing to the cells. The MOSFET provides reverse charge protection with a small forward voltage drop and a small reverse charge leakage current.

Abstract: In one embodiment, a voltage protection circuit uses two back-to-back transistors to receive an unprotected voltage and form a protected voltage.

Abstract: A circuit arrangement for protection against electrostatic discharge for a field-effect transistor is disclosed. The arrangement includes a first and a second controllable path each having a control terminal. The control terminals of the controllable paths are coupled to a source terminal of the field-effect transistor. A first terminal of the first controllable path is connected to a control terminal of the transistor, and a first terminal of the second controllable path is connected to a bulk terminal of the unipolar transistor. Second terminals of the controllable paths are connected to the drain terminal. A voltage regulating device includes the circuit arrangement and a comparator configured to generate a control signal in a manner dependent on a difference between two signals applied thereto. A control output of the comparator is coupled to the control terminal of the transistor.

Abstract: A reverse battery protection circuits that provides an integrated reverse battery condition solution for protection of external NMOS switches during the reverse battery condition is disclosed herein. This reverse battery protection circuit minimizes power consumption during a reverse battery event wherein there is no need for mechanical adjustments such as heat sinking and clamping to extract the heat away from the silicon and not destroy the device. Specifically, the reverse battery protection circuit includes a push-pull gate drive circuit coupled between the first and second power supply rail. A protection subcircuit portion connects between a first output node and the second power supply rail to turn the external FET ‘on’ during the reverse battery condition. In particular, the protection subcircuit portion connects to the external FET device and includes a p-channel device connected between a second output node that biases the external FET device and a first diode.

Abstract: A polarity-reversal protector for power sources, in particular for automobile batteries, which is connected between a power source and at least one consumer and/or at least one generator, is described. The polarity-reversal protector is to prevent the reverse polarity current from flowing through the connected systems, so that the systems may not be damaged in case of polarity reversal. For this purpose, the polarity-reversal protector includes means for recognizing whether the two poles of the power source are connected to the appropriate terminals of the consumer and/or generator, and means for decoupling the power source from the consumer and/or from the generator if the two poles of the power source have been transposed during connection to the consumer and/or generator.

Abstract: The invention is a dual stage power supply with a protection circuit for preventing reverse conduction through the lower voltage driver of the dual stage power supply and excess power dissipation when the higher voltage driver is on. In one embodiment of the invention, the protection scheme comprises a comparator that detects when the voltage on the output pad exceeds a predetermined voltage and a protection transistor which is controlled by the comparator to block reverse conduction through the lower voltage driver when the higher voltage driver is operating.

Abstract: A circuit for protecting a battery includes an n-well formed within a p substrate. A p-type resistor is formed with in the n well and has a connection to the battery. An n+ ring is also formed in the n well and substantially surrounds the p-type resistor.

Abstract: A field effect transistor (FET) is used as the protection circuit. The gate is grounded through an electrical element. The voltage source is connected to the drain of the FET. The load is connected to the source of the FET. At low input voltages, the FET conducts in body diode mode. At higher input voltages, the FET turns “on” and conducts more efficiently.

Abstract: An apparatus includes a blocking N-channel MOS (LDMOS) transistor that prevents current flow when the supply connection is reversed. When connected properly, the body diode conducts to provide a start-up function. A bias generator is employed to enable the low drop-out voltage function, allowing the output voltage to be very close to supply.

Abstract: The present invention relates to a hard disk drive system having overvoltage protection circuits for various types of overvoltage conditions. For example, the system includes one or more hard disk drive integrated circuit chips residing on a board and a hard disk drive power plug receptacle residing on the board having two different value power supply ports associated therewith. The receptacle is operable to receive a power plug therein, wherein when the power plug is inserted therein in a proper orientation the two different value voltages are properly supplied to the one or more hard disk drive integrated circuit chips, and wherein when the power plug is inserted therein in an improper orientation the two different value voltages are switched with respect to their intended values.

Abstract: An electrical circuit is provided for detecting direction of a current flowing on a line, in particular of a bus of a test equipment. The circuit comprises a sense resistor coupled within the line. A first comparator is connected with its positive input to the line on one of the two sides of the sense resistor and with its negative input connected to the line on the other one of the two sides of the sense resistor. A second comparator with one of its inputs is connected to the line on one of the two sides of the sense resistor and with the other one of its inputs is provided with a voltage divider. Said first comparator provides an output signal depending on the direction of the current flowing on the line, and said second comparator provides a second output signal defining whether the first output signal is valid or not.

Abstract: The invention relates to a control circuit for a direct current motor with a reverse pole protection device, which is connected to the electric circuit of the electrolytic capacitor and the free-wheeling diode in order to reduce losses in the reverse pole protection device.

Abstract: The present invention is a method and system for preventing voltage spike feedback with switched inductive loads connected to isolated redundant power supplies. A voltage clamp circuit of the present invention may clamp the voltage spikes caused by inductive loads within a power supply system to a safe voltage level. When the common output voltage of the redundant power supplies becomes too large, the voltage clamp circuit of the present invention may clamp the common output voltage to a safe voltage level at or slightly above the higher voltage of the parallel connected power supplies.

Abstract: A protecting apparatus includes a back-flow preventing Zener diode having a cathode connected directly to a control terminal of a main transistor formed on a semiconductor substrate. A protecting transistor has an output terminal connected to an anode of the back-flow preventing Zener diode and an input terminal connected to an input terminal of the main transistor. A protecting capacitor or Zener diode circuit is connected between a control terminal of the protecting transistor and the input terminal of the main transistor for allowing initial surge current, when caused based on a rapid surge, to flow into the control terminal of the protecting transistor. The protecting transistor, when turning on in response to the initial surge current, allows next surge current succeeding the initial surge current to flow into the control terminal of the main transistor via the back-flow preventing Zener diode.

Abstract: An integrated overvoltage and reverse voltage protection circuit. The protection circuit includes a field-effect transistor having a source terminal coupled to an input terminal of the protection circuit, and a drain terminal coupled to an output terminal of the protection circuit. A resistor is coupled between the source terminal and the body terminal of the field-effect transistor to inhibit reverse current flow during a reverse voltage condition. A voltage-current dependent circuit is coupled between the gate terminal and the source terminal of the field-effect transistor, and is configured to apply a voltage between the gate terminal and the source terminal that is dependent on the current passing through the voltage-current dependent circuit. A current application circuit is coupled to the voltage-current dependent circuit and is configured to apply a current that limits or even altogether stops an applied overvoltage condition from reaching a load circuit.

Abstract: The invention relates to a polarity protection circuit, which is used in a power supply arrangement where a power supply is connected via supply voltage lines to a load. The polarity protection circuit further contains a first protective semiconductor switch, which is a metal oxide semiconductor field effect transistor, and which gets its control voltage via a certain connection from said supply voltage lines. The second semiconductor switch is a transistor, which also gets its control voltage via a certain connection from said supply voltage lines. If the supply voltage has the wrong polarity the first protective semiconductor switch is kept in the non-conducting state. If for instance in the supply voltage lines during normal operation there occurs a short circuit, which tends to change the direction of the current, then the transistor rapidly discharges the gate charge of the first protective semiconductor switch, and the current flow in the wrong direction is prevented.

Abstract: A power semiconductor device which makes a heat come hard to arise in a particular element and is able to control an increase of the amount of a power loss caused by a tail current, even in case that plural power semiconductor elements are connected in parallel is provided.

Abstract: A circuit for protecting a power switch in the event of a reverse battery connection, wherein the power switch comprises a MOSFET having a body diode and the MOSFET is connected in series with a load, the circuit comprising terminals connected to the circuit and normally connectable to respective positive and negative power potentials of the battery, and the circuit comprising a switching circuit coupled to the terminals such that the switching circuit turns on the power switch in the event that the terminals are connected with a reverse battery connection.

Abstract: The present invention is directed to a circuit for reversing the polarity of a high voltage power supply. Circuits according to embodiments of the invention may include four switches, one or more of which may be solid-state switches. The solid-state switches may include a transistor stack that is supplied a biasing voltage in response to the receipt or removal of a control signal. When the biasing voltage is supplied to one transistor in the stack to change it to the closed or “ON” state, the other transistors in the stack may also be changed to the closed state in a cascading process. The control signal may be a low voltage signal and may be isolated from the solid-state switch by a control switch, which may be an optocoupler.

Abstract: The invention relates to a protective circuit for electronic modules, especially driver modules, for protecting against polarity reversal and against rupturing of the neutral conductor. A first protective diode (D1) is arranged, with the cathode thereof, in the supply lead (3) such that it leads to the t supply potential (GND). Said supply lead is supplied by the lower-lying supply potential (GND) and is provided for the circuit parts (A1) connected in incoming circuit from the module (B1). A second protective diode (D2) is arranged, with the diode thereof, in the supply terminal (4) of the module (B1) such that it leads to the supply potential (GND), said supply terminal being supplied by the lower-lying supply potential (GND).

Abstract: A circuit device for solar energy application includes a solar panel as power supply and a rechargeable cell pack for receiving the power transferred from the solar panel. The circuit device uses a MOSFET as a current blocking device. The Drain and the Source of the MOSFET are conductively connected directly with the solar panel and the cell pack respectively so that the body diode of the MOSFET is forward interposed between the solar panel and the cell pack for prevention of a reverse current when charging is stopped.

Abstract: An LED illumination module for a flashlight has a housing, electronic control circuitry, and one or more LEDs connected in series and to the circuitry. The module is characterized in that the module is shaped to modularly replace an incandescent-bulb in an existing flashlight. In one aspect the control circuitry operates in a dual mode to extend life of the unit, and to warn when battery replacement is warranted.

Abstract: A circuit breaker that functions like a double pole double throw (DPDT) switch is used to isolate the commercial power grid from an external power source. When in the “on” position the circuit breaker serves as a main power input circuit breaker allowing power from the commercial power grid to feed into existing wiring. In the “off” position the commercial power grid is disconnected and isolated from the existing wiring. Instead, the switch mechanism is connected to an external power source such as a generator. The generator can be safely operated without risking power backfeed into the commercial power grid.

Abstract: A power filter circuit for protecting electronic equipment from electromagnetic interference introduced by a supply system circuit includes a fault/condition sensing circuit capable of detecting whether the supply system circuit is properly wired. The sensing circuit controls switching circuits in accordance with the determination of whether the supply system is properly wired. The sensing circuit activates a first switching circuit to form a short circuit between the neutral and ground conductors of the power filter circuit when it is determined that the supply system circuit is properly wired. If any wiring fault conditions, including a reverse polarity wiring, is detected by the sensing circuit, the first switch is not activated and the short circuit is not formed between the neutral and ground conductors.