Leakage current detection device with self-testing function

Patent metadata

Field	Value
Publication number	US-9547047-B2
Application number	US-201514614334-A
Country	US
Kind code	B2
Filing date	Feb 4, 2015
Priority date	Dec 15, 2014
Publication date	Jan 17, 2017
Grant date	Jan 17, 2017

Abstract

A leakage current detection device coupled to AC power supply wires carrying an AC signal, which includes: a leakage current detection circuit including a leakage current detector, the leakage current detection circuit operating during first half-cycles among positive and negative half-cycles of the AC signal to detect a leakage current of the power supply wires and to disconnect the power supply wires from an output side when a leakage current exceeding a first threshold value is detected; and a self-detecting circuit coupled to the leakage current detection circuit, operating during second half-cycles among the positive and negative half-cycles of the AC signal to test whether the leakage current detection circuit is functioning normally.

First claim

What is claimed is:

1. A leakage current detection device coupled to AC power supply wires carrying an AC signal, comprising:
a leakage current detection circuit including a leakage current detector, the leakage current detection circuit operating during first half-cycles among positive and negative half-cycles of the AC signal to detect a leakage current of the power supply wires and to disconnect the power supply wires from an output side when a leakage current exceeding a first threshold value is detected; and
a self-detecting circuit coupled to the leakage current detection circuit, operating during second half-cycles among the positive and negative half-cycles of the AC signal to test whether the leakage current detection circuit is functioning normally,
wherein the self-testing circuit includes: a simulated leakage current generator circuit, for generating a first leakage current exceeding the first threshold value on at least one of the power supply wires, and a comparator circuit coupled to the simulated leakage current generator circuit, for outputting a first drive signal to drive the simulated leakage current generator circuit to generate the first leakage current.

2. The leakage current detection device of claim 1 , wherein the self-testing circuit further includes:
a switching element; and
a period-setting circuit including a first resistor and a first capacitor coupled in series, the period-setting circuit being coupled to the switching element and a first input terminal of the comparator circuit, wherein the switching element provides a discharge path for the first capacitor.

3. The leakage current detection device of claim 2 ,
wherein the self-testing circuit further includes a reference voltage generator circuit;
wherein the comparator circuit includes:
a first input coupled between the first resistor and the first capacitor of the period-setting circuit for receiving a voltage signal on the first capacitor; and
a second input coupled to the reference voltage generator circuit for receiving a reference voltage signal; and
wherein the period-setting circuit and the reference voltage generator circuit receive a common voltage signal from one of the power supply wires.

4. The leakage current detection device of claim 2 , wherein the leakage current detection circuit further includes:
a processor unit coupled to the leakage current detector and the switching element for driving the switching element based on signals from the leakage current detector.

5. The leakage current detection device of claim 3 , wherein an output of the comparator circuit is coupled to the switching element, wherein when the first input of the comparator has a higher voltage than the second input of the comparator, the comparator outputs a signal to trigger the switching element to become conductive.

6. The leakage current detection device of claim 2 , further comprising a power output end and a reset switch connected between the power supply wires and the power output end;
wherein the leakage current detection circuit further includes a solenoid coupled to the switching element, wherein when the switching element becomes conductive during the first half-cycles, the solenoid operates to open the reset switch.

7. The leakage current detection device of claim 6 , wherein the leakage current detection circuit further includes:
a branch auxiliary switch coupled between the solenoid and the power supply wires, the branch auxiliary switch and the reset switch RESET being mechanically linked to open and close at the same time.

8. The leakage current detection device of claim 6 , wherein the leakage current detection circuit further includes:
a first fault indicator unit coupled to the solenoid for indicating whether the reset switch is closed.

9. The leakage current detection device of claim 1 , wherein the self-testing circuit further includes:
a second fault indicator unit coupled to an output of the comparator circuit, for emitting a fault indication signal when the comparator continues to output a high voltage signal.

10. The leakage current detection device of claim 2 , further comprising:
a neutral-leakage indicator circuit coupled between a ground wire and a neutral wire of the power supply wires, for emitting a signal based on the voltage variation on the neutral wire to indicate that the neutral wire is charged.

11. The leakage current detection device of claim 2 , wherein the self-testing circuit further includes:
a drive circuit having its first input coupled to an output of comparator circuit and its output coupled to a control electrode of the switching element, for driving the switching element based on the output signal of the comparator circuit.

12. The leakage current detection device of claim 2 , wherein the switching element is a silicon controlled rectifier.

Assignees

• Li Chengli

Inventors

• Li Chengli
• Yue Guolan

Classifications

• G01R35/00

  Testing or calibrating of apparatus covered by the other groups of this subclass · CPC title

• G01R31/42 Primary

  AC power supplies · CPC title

• H02H3/335

  the main function being self testing of the device · CPC title

• G01R31/52

  Testing for short-circuits, leakage current or ground faults · CPC title