Self testing ground fault circuit interrupter (GFCI) with end of life (EOL) indicator, secondary power supply for EOL and self test circuitry, and device for opening line hot when EOL occurs
A self test (ST) ground fault circuit interrupter (GFCI) provides a half wave rectifier for powering circuitry for determining and annunciating end of life (EOL) of the GFCI regardless of a shorted diode bridge or opening of a printed circuit board (PCB) trace. A fuse resistor is provided to open before an open PCB trace can occur. A microprocessor-controlled heat-conducting circuit is provided adjacent to a thermal fuse to controllably open the thermal fuse and remove power from face receptacle contacts and load terminals when EOL occurs.
1. A fault detector comprising:
line side terminals for receiving an input power signal;
load side terminals for connecting to a load;
hot and neutral conductors for connecting respective line side terminals to corresponding load side terminals;
a ground fault circuit interrupter circuit for detecting faults and controllably operating at least one switching device to open at least one of the hot and neutral conductors upon detection of a fault;
a processing device connected to the ground fault circuit interrupter circuit for performing self-test operations to determine if the ground fault circuit interrupter circuit is malfunctioning;
an end of life (EOL) indicator controllably operated by the processing device to indicate end of life of the fault detector;
a full wave rectifier diode bridge connected across the hot and neutral conductors for supplying a rectified power signal to the ground fault circuit interrupter circuit; and
a secondary power supply circuit connected to the hot and neutral conductors for providing power to the processing device and the EOL indicator;
wherein the secondary power supply circuit is a half wave rectified power supply; and
wherein the fault detector comprises a voltage regulator having an output connected to the processing device, and wherein the half wave rectified power supply comprises a conductive path extending from the hot conductor to an input of the voltage regulator, and a diode serially connected to the conductive path.
2. A fault detector as claimed in claim 1 , wherein the half wave rectified power supply diode is connected to the conductive path proximally to where the hot conductor receives power from an AC power source connected to the line terminals.
3. A fault detector as claimed in claim 1 , wherein the EOL indicator is connected to the conductive path of the half wave rectified power supply.
4. A fault detector as claimed in claim 1 , wherein the secondary power supply circuit comprises a diode connected to the neutral conductor to provide a path separate from the neutral conductor for the processing device to return current to neutral when at least one of the ground fault circuit interrupter circuit and the full wave rectifier diode bridge malfunctions.
5. A fault detector as claimed in claim 1 , further comprising a fuse resistor connected between the hot conductor and a line input of the full wave rectified diode bridge.
6. A fault detector as claimed in claim 1 , further comprising a thermal fuse connected in series with the hot conductor, and a heat-conducting device connected to the processing device to receive an output therefrom and disposed proximally to the thermal fuse, the processing device being operable to apply a voltage across the heat-conducting device to cause its surface temperature to increase and thereby increase the surface temperature of the thermal fuse to a temperature at which the thermal fuse opens when the processing device determines end of life of the fault detector.
7. A fault detector as claimed in claim 6 , wherein the heat-conducting device comprises at least one of a resistive element, a solenoid, a printed circuit board trace, and a semiconductor part, and is characterized by reaching a selected temperature at EOL.
8. A fault detector as claimed in claim 6 , wherein the heat-conducting device is connected to the processing device via at least one of a silicon controlled rectifier (SCR), a transistor circuit and an electronic gating device.
9. A fault detector comprising:
line side terminals for receiving an input power signal;
load side terminals for connecting to a load;
hot and neutral conductors for connecting respective line side terminals to corresponding load side terminals;
a ground fault circuit interrupter circuit for detecting faults and controllably operating at least one switching device to open at least one of the hot and neutral conductors upon detection of a fault;
a processing device connected to the ground fault circuit interrupter circuit for performing self-test operations to determine if the ground fault circuit interrupter circuit is malfunctioning;
an end of life (EOL) indicator controllably operated by the processing device to indicate end of life of the fault detector;
a full wave rectifier diode bridge connected across the hot and neutral conductors for supplying a rectified power signal to the ground fault circuit interrupter circuit;
a secondary power supply circuit connected to the hot and neutral conductors for providing power to the processing device and the EOL indicator; and
a regulator having an output connected to the processing device, wherein the secondary power supply circuit comprises a conductive path extending from a hot conductor node to an input of the voltage regulator, the hot conductor node also being connected to the hot conductor and a line input of the full wave rectified diode bridge.
10. A fault detector as claimed in claim 9 , wherein the secondary power supply circuit comprises a half wave rectified power supply diode serially connected to the conductive path.
11. A fault detector as claimed in claim 9 , wherein the half wave rectified power supply diode is connected to the conductive path proximally to where the hot conductor receives power from an AC power source connected to the line terminals.
12. A fault detector as claimed in claim 9 , wherein the secondary power supply circuit comprises a diode connected to the neutral conductor to provide a path separate from the neutral conductor for the processing device to return current to neutral when at least one of the ground fault circuit interrupter circuit and the full wave rectifier diode bridge malfunctions.
13. A fault detector as claimed in claim 9 , further comprising a fuse resistor connected between the hot conductor and the line input of the full wave rectified diode bridge.
14. A fault detector as claimed in claim 9 , further comprising a thermal fuse connected in series with the hot conductor, and a heat-conducting device connected to the processing device to receive an output therefrom and disposed proximally to the thermal fuse, the processing device being operable to apply a voltage across the heat-conducting device to cause its surface temperature to increase and thereby increase the surface temperature of the thermal fuse to a temperature at which the thermal fuse opens when the processing device determines end of life of the fault detector.
15. A fault detector as claimed in claim 14 , wherein the heat-conducting device comprises at least one of a resistive element, a solenoid, a printed circuit board trace, and a semiconductor part, and is characterized by reaching a selected temperature at EOL.
16. A fault detector as claimed in claim 14 , wherein the heat-conducting device is connected to the processing device via at least one of a silicon controlled rectifier (SCR), a transistor circuit and an electronic gating device.