Ground fault circuit interrupter and method

• US 9,331,469 B2
• Filed: 03/14/2013
• Issued: 05/03/2016
• 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: Beck, Riley D., Layton, Kent D.
• Primary Examiner(s): Valone, Thomas F
• Application Number:
  US13/829,366
• Publication Number:
  US 20130215537A1
• Time in Patent Office: 1,146 Days
• Field of Search: 324/509
• US Class Current: 1/1
• CPC Class Codes: G01R 27/18 Measuring resistance to earth , i.e. line to ground
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• 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 3/162 for ac systems
• CPC Class Codes: H02H 3/33 using summation current transformers H02H3/347 takes precedence
• CPC Class Codes: H03F 1/303 using a switching device H03F1/305, H03F3/005, H03F3/38 take precedence
• CPC Class Codes: H03F 2203/45152 Balancing means being added at the input of a dif amp to reduce the offset of the dif amp
• CPC Class Codes: H03F 2203/45228 A transformer being added at the output or the load circuit of the dif amp
• CPC Class Codes: H03F 2203/45288 Differential amplifier with circuit arrangements to enhance the transconductance
• CPC Class Codes: H03F 3/45 Differential amplifiers differential sense amplifiers G11C7/062

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 ground fault circuit interrupter module, comprising:

an offset correction circuit having first and second inputs and at least one output, the offset correction circuit including at least one of a chopper amplifier or an auto-zeroing circuit;

a switch having first, second, and third conduction terminals and a control terminal, the first conduction terminal coupled to the first input of the offset correction circuit;

a biasing module having an input and an output, the output of the biasing module coupled to the second conduction terminal of the switch; and

a signal generator having an output coupled to the third conduction terminal of the switch.

2. The ground fault circuit interrupter module of claim 1, wherein the offset correction circuit comprises the chopper amplifier.

3. The ground fault circuit interrupter module of claim 2, wherein the chopper amplifier comprises:

a first differential pair of transistors, wherein each transistor of the first differential pair of transistors has a control electrode and first and second current carrying electrodes;

a first switching network having first, second, and third conduction terminals, and first and second control terminals, the first conduction terminal coupled to the control electrode of a first transistor of the differential pair of transistors, the second conduction terminal of the first switching network serving as the first input of the offset correction circuit, and the third conduction terminal of the first switching network serving as the second input of the offset correction circuit; and

a second switching network having first, second, and third conduction terminals, and first and second control terminals, the first conduction terminal of the second switching network coupled to the control electrode of a second transistor of the differential pair of transistors, the second conduction terminal of the second switching network coupled to the third conduction terminal of the first switching network, and the third conduction terminal of the second switching network coupled to the second conduction terminal of the first switching network.

4. The ground fault circuit interrupter module of claim 3, wherein the chopper amplifier further includes:

a second differential pair of transistors, each transistor of the second differential pair of transistors having a control electrode and first and second current carrying electrodes;

a third switching network having first, second, and third conduction terminals and first and second control terminals, the first conduction terminal coupled to the first current carrying electrode of a first transistor of the differential pair of transistors and the second conduction terminal coupled to the first current carrying electrode of a second transistor of the second differential pair of transistors;

a first switch having a control terminal and first and second conduction terminals, the first conduction terminal coupled to the control electrodes of the first and second transistors of the second differential pair of transistors and the second conduction terminal coupled to the first current carrying electrode of the first transistor of the second differential pair of transistors; and

a second switch having a control terminal and first and second conduction terminals, the first conduction terminal coupled to the control electrodes of the first and second transistors of the second differential pair of transistors and to the first conduction terminal of the first switch and the second conduction terminal coupled to the first current carrying electrode of the second transistor of the second differential pair of transistors.

5. The ground fault circuit interrupter module of claim 4, further comprising first and second biasing transistors, the first biasing transistor having a control electrode, a first current carrying electrode coupled to the first current carrying electrode of the first transistor of the second pair of differential transistors and the second current carrying electrode coupled to the first current carrying electrode of the first transistor of the first pair of differential transistors, the second biasing transistor having a control electrode, a first current carrying electrode coupled to the first current carrying electrode of the second transistor of the second pair of differential transistors and the second current carrying electrode coupled to the first current carrying electrode of the second transistor of the first pair of differential transistors.

6. The ground fault circuit interrupter module of claim 1, wherein the offset correction circuit comprises the auto-zeroing circuit.

7. The ground fault circuit interrupter module of claim 6, further comprising an amplifier having at least one input and an output, the at least one input coupled to the at least one output of the offset correction circuit.

8. The ground fault circuit interrupter module of claim 7, wherein the offset correction circuit comprises an auto-zeroing circuit having first and second inputs and an output, the first input coupled to the output of the biasing module, the second input coupled to the output of the signal generator, and the output coupled to the at least one input of the amplifier.