ISOLATION MONITORING SYSTEM AND METHOD UTILIZING A VARIABLE EMULATED INDUCTANCE

• US 20110181306A1
• Filed: 01/24/2011
• Published: 07/28/2011
• Est. Priority Date: 01/26/2010
• Status: Active Grant

• Current Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Original Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Inventors: Nalbant, Mehmet Kadri
• Granted Patent: US 8,598,897 B2
• Time in Patent Office: Days
• US Class Current: 324/713
• CPC Class Codes: G01R 27/18 Measuring resistance to earth , i.e. line to ground

Abstract

A system for measuring leakage resistance between a high voltage (HV) system of a vehicle and a vehicle chassis includes an emulated inductance that is connected between the HV system and the vehicle chassis and that has an inductive reactance that substantially cancels a capacitive reactance between the HV system and the vehicle chassis. A signal source outputs one of an AC current signal and an AC voltage signal between the HV system and the vehicle chassis. A sensor measures one of an AC current response to the AC voltage signal between the HV system and the vehicle chassis and an AC voltage response to the AC current signal between the HV system and the vehicle chassis.

Claims

1. A system for measuring leakage resistance between a high voltage (HV) system of a vehicle and a vehicle chassis, comprising:

an emulated inductance that is connected between the HV system and the vehicle chassis and that has an inductive reactance that substantially cancels a capacitive reactance between the HV system and the vehicle chassis;

a signal source that outputs one of an AC current signal and an AC voltage signal between the HV system and the vehicle chassis; and

a sensor that measures one of;

an AC current response to the AC voltage signal between the HV system and the vehicle chassis; and

an AC voltage response to the AC current signal between the HV system and the vehicle chassis.

2. The system of claim 1, further comprising:

a control module that calculates a leakage resistance based on one of;

the AC current signal and the AC voltage response; and

the AC voltage signal and the AC current response.

3. The system of claim 2, wherein:

the emulated inductance value can be varied; and

the control module adjusts the value of the emulated inductance to N different values, where N is an integer greater than one, to vary the inductive reactance of the emulated inductance.

4. The system of claim 2, wherein:

the emulated inductance includes a variable resistance; and

the control module adjusts the variable resistance of the emulated inductance to N different values, where N is an integer greater than one, to vary the inductive reactance of the emulated inductance.

5. The system of claim 3, wherein the control module selects one of the N values that cancels with capacitive reactance between the HV system and the vehicle chassis.

6. The system of claim 4, wherein the control module calculates the leakage resistance between the HV system and the vehicle chassis by causing the signal source to generate the one of the AC current signal and the AC voltage signal while the one of the N values is selected.

7. The system of claim 4, wherein the emulated inductance further comprises:

an opamp including an inverting input and a non-inverting input; and

a first resistance connected between the HV system and the inverting input of the opamp.

8. The system of claim 7, wherein the emulated inductance further comprises:

a capacitance connected between the HV system and the non-inverting input of the opamp,

wherein the variable resistance is connected to the non-inverting input.

9. The system of claim 2, further comprising:

a first capacitance;

a first resistance;

a second resistance, wherein the first capacitance, the first resistance and the second resistance are connected in series between the HV system and the vehicle chassis; and

an analog to digital converter having a first input connected between the first and second resistance and an output connected to the control module.

10. The system of claim 2, wherein:

the control module generates T values of the leakage resistance, selects S of the T values, where S and T are integers greater than two and S<

T, and calculates a final leakage resistance value as a function of the S values; and

the control module selects the S values based on an enable signal received from one of a HV controller and a vehicle system controller.

11. The system of claim 2, wherein the control module includes:

a sampling module that samples a plurality of half cycles of the one of the AC voltage response and the AC current response; and

a correlation module that generates a plurality of correlation values corresponding to the plurality of half cycles of the one of the AC voltage response and the AC current response.

12. The system of claim 11, further comprising:

a leakage calculating module that calculates the leakage resistance based on selected ones of the plurality of half cycles of the one of the AC voltage response and the AC current response having correlation values that are greater than a predetermined correlation value.

13. The system of claim 11, wherein the correlation module generates the plurality of correlation values by correlating each of the plurality of half cycles of the one of the AC voltage response and the AC current response with one of:

another one of the plurality of half cycles of the one of the AC voltage response and the AC current response; and

a predetermined waverform.

14. A method for measuring leakage resistance between a high voltage (HV) system of a vehicle and a vehicle chassis, comprising:

generating an emulated inductance between the HV system and the vehicle chassis;

substantially cancelling a capacitive reactance between the HV system and the vehicle chassis using inductive reactance of the emulated inductance;

generating one of an AC current signal and an AC voltage signal between the HV system and the vehicle chassis; and

measuring one of;

an AC current response to the AC voltage signal between the HV system and the vehicle chassis; and

an AC voltage response to the AC current signal between the HV system and the vehicle chassis.

15. The method of claim 14, further comprising:

calculating a leakage resistance based on one of;

the AC current signal and the AC voltage response; and

the AC voltage signal and the AC current response.

16. The method of claim 15, further comprising:

adjusting a variable resistance of the emulated inductance to N different values, where N is an integer greater than one, to vary the inductive reactance of the emulated inductance.

17. The method of claim 16, further comprising:

selecting one of the N values that substantially cancels with capacitive reactance between the HV system and the vehicle chassis.

18. The method of claim 17, further comprising:

calculating the leakage resistance between the HV system and the vehicle chassis by generating the one of the AC current signal and the AC voltage signal while the one of the N values is selected.

19. The method of claim 14, further comprising:

generating T values of the leakage resistance;

selecting S of the T values, where S and T are integers greater than two and S<

T; and

calculating a final leakage resistance value as a function of the S values.

selecting the S values based on an enable signal received from one of a HV controller and a vehicle system controller.

20. The method of claim 15, further comprising:

sampling a plurality of half cycles of the one of the AC voltage response and the AC current response; and

generating a plurality of correlation values corresponding to the plurality of half cycles of the one of the AC voltage response and the AC current response.

21. The method of claim 20, further comprising:

calculating the leakage resistance based on selected ones of the plurality of half cycles of the one of the AC voltage response and the AC current response having correlation values that are greater than a predetermined correlation value.

22. The method of claim 20, wherein the plurality of correlation values are generated by correlating each of the plurality of half cycles of the one of the AC voltage response and the AC current response with one of:

another one of the plurality of half cycles of the one of the AC voltage response and the AC current response; and

a predetermined waverform.