GROUND FAULT DETECTION SYSTEM

• US 20120249154A1
• Filed: 03/31/2011
• Published: 10/04/2012
• Est. Priority Date: 03/31/2011
• Status: Active Grant

• Current Assignee: Elite Power Holdings LLC
• Original Assignee: Elite Power Solutions LLC
• Inventors: Dao, Yuan, Schlanger, William
• Granted Patent: US 9,024,639 B2
• Time in Patent Office: Days
• US Class Current: 324/509
• CPC Class Codes: B60L 3/0069 relating to the isolation, e.g. ground fault or leak current
• CPC Class Codes: G01R 31/006 on road vehicles, e.g. automobiles or trucks testing of ignition installations peculiar to internal combustion engines F02P17/00
• CPC Class Codes: G01R 31/385 Arrangements for measuring battery or accumulator variables for monitoring G01R31/382
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults

Abstract

The present application describes, among other things, a ground fault detection system. The system includes an optocoupler, a current sink, and a first voltage source connected in series. The first voltage source can connect to a negative terminal of a battery unit. Upon connection between a positive terminal of the battery unit and a first node at a ground zero reference level, current can flow through the optocoupler and the current sink to cause the optocoupler to output a ground fault detection signal.

Claims

1. A ground fault detection system comprising:

an optocoupler, a current sink, and a first voltage source connected in series, the first voltage source connected to a negative terminal of a battery unit,

wherein upon connection between a terminal of the battery unit and a first node at a ground zero reference level, current flows through the optocoupler and the current sink to cause the optocoupler to output a ground fault detection signal.

2. The ground fault detection system of claim 1, wherein the first node at a ground zero reference level is a chassis of an electric vehicle.

3. The ground fault detection system of claim 1, wherein the ground fault detection signal comprises a logic high signal.

4. The ground fault detection system of claim 1, wherein the optocoupler outputs a logic low signal when the current does not flow through the optocoupler.

5. The ground fault detection system of claim 1, wherein the optocoupler comprises a light emitting diode (LED) and a transistor.

6. The ground fault detection system of claim 5, wherein the connection between the terminal of the battery unit and the first node at the ground zero reference level causes the current to flow through the light emitting diode, the current causes the transistor to conduct, and the transistor causes the optocoupler to output the ground fault detection signal.

7. The ground fault detection system of claim 5, wherein the light emitting diode is connected to first and second terminals of the optocoupler and the transistor is connected to third and fourth terminals of the optocoupler.

8. The ground fault detection system of claim 7, wherein

the first terminal of the optocoupler is connected to a second node at the ground zero reference level,

the second terminal of the optocoupler is connected to the current sink,

the third terminal of the optocoupler is connected to a second voltage source, and

the fourth terminal of the optocoupler is connected to a resistor connected in series with a third node at a ground zero reference level.

9. The ground fault detection system of claim 8, wherein upon connection between the terminal of the battery unit and the first node at the ground zero reference level, the current flows through the light emitting diode from the first terminal of the optocoupler to the second terminal.

10. The ground fault detection system of claim 8, wherein the second voltage source is a 3.3V source.

11. The ground fault detection system of claim 1, wherein

a positive terminal of the first voltage source connects to the negative terminal of the battery unit, and

a negative terminal of the first voltage source connects to the current sink.

12. The ground fault detection system of claim 1, wherein the first voltage source is a 5V source.

13. The ground fault detection system of claim 1, wherein the current sink limits the current flowing through the optocoupler and the current sink to about 2 mA.

14. The ground fault detection system of claim 1, wherein the current sink operates at a voltage exceeding about 5V.

15. The ground fault detection system of claim 1, wherein the current sink comprises a third voltage source, one or more transistors, and one or more resistors.

16. The ground fault detection system of claim 15, wherein the third voltage source, the one or more transistors, and the one or more resistors are configured to form an equilibrium so that the current flowing through the current sink is a substantially constant current.

17. The ground fault detection system of claim 15, wherein any of the transistors comprises a MOSFET or an IGBT.

18. A ground fault detection system comprising:

an optocoupler with a light emitting diode and a transistor;

a current sink connected to the light emitting diode of the optocoupler; and

a first voltage source with a negative terminal connected to the current sink and a positive terminal connected to a negative terminal of a battery unit;

wherein upon connection between a positive terminal of the battery unit and a chassis of an electric vehicle,

i) current flows through the light emitting diode of the optocoupler and the current sink, and

ii) the light emitting diode activates the transistor such that the optocoupler outputs a ground fault detection signal.

19. A method of detecting a ground fault comprising:

connecting a positive terminal of a voltage source to a negative terminal of a battery unit;

connecting a terminal of a battery unit to a node at a ground zero reference level;

flowing a current through a light emitting diode of an optocoupler and a current source; and

activating a transistor of the optocoupler such that the optocoupler outputs a ground fault detection signal.

20. The method of claim 19, further comprising:

deactivating the transistor of the optocoupler when a terminal of the battery unit is not connected to the node at the ground zero reference level; and

connecting a terminal of the optocoupler to the ground zero reference level such that the optocoupler outputs a signal indicating that a ground fault is not detected.