Method and apparatus for detecting leakage resistance in an electric vehicle

• US 5,382,946 A
• Filed: 01/08/1993
• Issued: 01/17/1995
• Est. Priority Date: 01/08/1993
• Status: Expired due to Fees

• Current Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Original Assignee: Ford Motor Company
• Inventors: Gale, Allan R.
• Primary Examiner(s): Hofsass, Jeffery A.
• Application Number:
  US08/001,957
• Time in Patent Office: 739 Days
• Field of Search: 340/650, 340/651, 361/42, 361/45, 324/509, 324/510
• US Class Current: 340/650
• 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

Abstract

Provided is a method and circuit for measuring the leakage path resistance in an electric vehicle having an isolated high voltage traction battery and an auxiliary battery grounded to the vehicle. The circuit operates by periodically applying a selected excitation signal and comparing the voltage induced on an energy storage element by the excitation signal to a selected reference voltage during a selected time period. An alternate embodiment of the present invention provides a circuit which operates by applying a periodic excitation signal and comparing the phase shift of the voltage induced on an energy storage element to the phase shift of a signal derived from the excitation signal.

Claims

1. A leakage path detection circuit for detecting leakage current in an electric vehicle having an isolated high voltage traction battery and an auxiliary battery grounded to the vehicle, the circuit comprising:

excitation means for periodically applying an excitation signal to the circuit;

first energy storage means having an input terminal in electrical contact with said excitation means and a grounded output terminal for storing a voltage induced thereon by said excitation means;

second energy storage means having an input terminal in electrical contact with said excitation means and an output terminal in electrical contact with the traction battery for storing a voltage induced thereon by said excitation means;

comparator means in electrical contact with said first and second energy storage means for comparing said induced voltage to a DC reference voltage during a predetermined time period and generating an output signal indicating whether said induced voltage exceeds said reference voltage; and

protect means in electrical contact with said excitation means, comparator means and the respective input terminals of said first and second energy storage means for protecting said comparator means from voltage spikes, wherein said output signal is used to determine the resistance of the leakage path.

2. A circuit as in claim 1, wherein said first energy storage means comprises a capacitor.

3. A circuit as in claim 1, wherein said second energy storage means comprises a capacitor.

4. A circuit as in claim 1, wherein said predetermined time period is 20 ms.

5. A circuit as in claim 1, wherein said selected DC voltage is a reference voltage derived from the level of said excitation signal.

6. A circuit as in claim 1, wherein said excitation means is a switch capable of alternately applying an excitation signal and grounding the circuit.

7. A leakage path detection circuit for detecting leakage current in an electric vehicle having an isolated high voltage traction battery and an auxiliary battery grounded to the vehicle, the circuit comprising:

excitation means for periodically applying a selected signal to the circuit;

first energy storage means having an input terminal in electrical contact with said excitation means and a grounded output terminal for storing a voltage induced thereon by said excitation means;

second energy storage means having an input terminal in electrical contact with said excitation means and an output terminal in electrical contact with the traction battery for storing a voltage induced thereon by said excitation means;

comparator means in electrical contact with said first and second energy storage means for comparing said induced voltage to a signal derived from said excitation signal and generating an output signal indicating the phase shift between said induced voltage and said derived signal during a predetermined time period; and

protect means in electrical contact with said excitation means, comparator means and the respective input terminals of said first and second energy storage means for protecting said comparator means from voltage spikes, wherein said output signal is used to determine the resistance of the leakage path.

8. A circuit as in claim 7, wherein said first energy storage means comprises a capacitor.

9. A circuit as in claim 7, wherein said second energy storage means comprises a capacitor.

10. A circuit as in claim 7, wherein said predetermined time period is 20 ms.

11. A circuit as in claim 7, wherein said excitation means is a switch capable of alternately applying an excitation signal and grounding the circuit.

12. A method of detecting leakage path current in an electric vehicle having an isolated high voltage traction battery and an auxiliary battery grounded to the vehicle, the method comprising the steps of:

providing first energy storage means having an input terminal in electrical contact with said excitation means and a grounded output terminal;

providing second energy storage means having an input terminal in electrical contact with said excitation means and an output terminal in electrical contact with the traction battery;

periodically including a voltage on said first energy storage means by the application of an excitation signal;

comparing the voltage induced on said first energy storage means to a DC reference voltage and generating an output signal indicating whether said induced voltage exceeds said reference voltage during a predetermined time period, wherein said output signal may be used to determine the resistance of the leakage path.

13. A method of detecting leakage path current in an electric vehicle having an isolated high voltage traction battery and an auxiliary battery grounded to the vehicle, the method comprising the steps of:

providing first energy storage means having an input terminal in electrical contact with said excitation means and a grounded output terminal;

providing second energy storage means having an input terminal in electrical contact with said excitation means and an output terminal in electrical contact with the traction battery;

inducing a periodic voltage on said first energy storage means by the application of an excitation signal;

generating an output signal corresponding to the phase shift between the voltage induced on said first energy storage means and a signal derived from said excitation signal during a predetermined time period, wherein said output signal may be used to determine the resistance of the leakage path.