GROUND FAULT CIRCUIT INTERRUPTER AND METHOD

• US 20110080177A1
• Filed: 10/02/2009
• Published: 04/07/2011
• Est. Priority Date: 10/02/2009
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: Layton, Kent D., Beck, Riley D., Grange, Scott R., Tyler, Matthew A.
• Granted Patent: US 8,390,297 B2
• Time in Patent Office: Days
• US Class Current: 324/509
• CPC Class Codes: G01R 15/18 using inductive devices, e.g. transformers
• CPC Class Codes: G01R 27/16 Measuring impedance of element or network through which a current is passing from another source, e.g. cable, power line
• CPC Class Codes: G01R 27/18 Measuring resistance to earth , i.e. line to ground
• CPC Class Codes: H02H 1/0092 concerning the data processing means, e.g. expert systems, neural networks
• CPC Class Codes: H02H 1/04 Arrangements for preventing response to transient abnormal conditions, e.g. to lightning or to short duration over voltage or oscillations; Damping the influence of dc component by short circuits in ac networks
• CPC Class Codes: H02H 3/33 using summation current transformers H02H3/347 takes precedence

Abstract

A method and circuit for determining a circuit element parameter in a ground fault circuit interrupter circuit. An electrical signal provided to a first node is used to generate another electrical signal at a second node. The electrical signal at the second node is multiplexed with a modulation signal to generate a modulated signal that is then filtered and converted into a digital representation of a portion of the circuit element parameter. The electrical signal at the second node is multiplexed with the modulation signal after it has been phase shifted to produce a modulated signal that is filter and converted into a digital representation of another portion of the circuit element parameter. In another aspect, a slope based solenoid self-test method is used for self-testing in a GFCI circuit. Alternatively, a method for determining a wiring fault is provided using a digital filter.

Claims

1. A method for determining a circuit element parameter, comprising:

providing a first electrical signal at a first node;

using the first electrical signal to generate a second electrical signal at a second node;

generating a third electrical signal from the second electrical signal; and

using the third electrical signal to generate a fourth electrical signal.

2. The method of claim 1, further including inputting the fourth electrical signal into a first modulator.

3. The method of claim 2, further including inputting the fourth electrical signal into a second modulator.

4. The method of claim 2 wherein the second and third electrical signals are current signals.

5. The method of claim 2, wherein the first and fourth electrical signals are voltage signals.

6. The method of claim 5, wherein the second and third electrical signals are current signals.

7. The method of claim 2, further including multiplying the fourth electrical signal with a fifth electrical signal to generate a sixth electrical signal.

8. The method of claim 7, further including multiplying the fourth electrical signal with a seventh electrical signal to generate an eighth electrical signal.

9. The method of claim 8, further including inputting the sixth and the eighth electrical signals into first and second low pass filters to generate first and second filtered electrical signals, respectively.

10. The method of claim 9, further including converting the first and the second filtered electrical signals into first and second digital filtered electrical signals, respectively.

11. The method of claim 1, further including generating a fifth electrical signal from the fourth electrical signal.

12. The method of claim 11, wherein the fourth and fifth electrical signals are differential signals.

13. The method of claim 11, further including combining the fourth and the fifth electrical signals together to form a first modulation signal, wherein the fourth and the fifth electrical signals are out of phase with each other.

14. The method of claim 13, further including combining the fourth and the fifth electrical signals together to form a second modulation signal, wherein the fourth and the fifth electrical signals are out of phase with each other.

15. The method of claim 1, wherein determining the circuit element parameter comprises determining the impedance of a single wound single current transformer.

16. A circuit for determining a circuit element parameter, comprising:

a transconductance amplifier having first and second input terminals and first and second output terminals;

a first multiplier having first and second input terminals and an output terminal, the first input terminal coupled to the second output terminal of the transconductance amplifier and the second input terminal coupled for receiving a first electrical signal; and

a second multiplier having first and second input terminals and an output terminal, the first input terminal coupled to the second output terminal of the transconductance amplifier.

17. The circuit of claim 16, further including a phase shifting element having an input terminal and an output terminal, the input terminal coupled for receiving the first electrical signal and the output terminal coupled to the second input terminal of the multiplier.

18. The circuit of claim 16, wherein the circuit is a single wound single current transformer impedance measurement circuit.

19. A method for determining an operating condition of a sub-module within a ground fault circuit indicator module, comprising:

generating a current in a device;

measuring a rate at which a mains voltage level decreases in response to the current generated in the device; and

generating an operating condition signal in accordance with the rate at which the mains voltage level decreases.

20. The method of claim 19, wherein measuring the rate at which the mains voltage level decreases comprises measuring the rate at which the mains voltage level decreases from its steady state level.

21. A method for determining an occurrence of a wiring fault, comprising dynamically changing signal filtering depending on filtering conditions.

22. The method of claim 21, further including setting a first fault threshold, wherein if a fault exceeds the first fault threshold for a first period of time, the wiring fault has occurred.