Insulation resistance measuring circuit free from influence of battery voltage

• US 8,779,784 B2
• Filed: 03/23/2010
• Issued: 07/15/2014
• Est. Priority Date: 03/23/2009
• Status: Active Grant

• Current Assignee: SK On Company Limited (SK Innovation Company Limited)
• Original Assignee: SK Innovation Company Limited
• Inventors: Yang, Jeong Hwan, Choi, Ki Seok, Lim, Jae Hwan
• Primary Examiner(s): Assouad, Patrick
• Assistant Examiner(s): BROWN, LAMARR A
• Application Number:
  US13/257,831
• Publication Number:
  US 20120016613A1
• Time in Patent Office: 1,575 Days
• Field of Search: 324426-437, 324/541, 324/544, 324/551, 324/691
• US Class Current: 324/691
• CPC Class Codes: G01R 27/025 Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters
• CPC Class Codes: G01R 27/08 Measuring resistance by measuring both voltage and current
• CPC Class Codes: G01R 27/16 Measuring impedance of element or network through which a current is passing from another source, e.g. cable, power line
• CPC Class Codes: G01R 31/382 Arrangements for monitoring battery or accumulator variables, e.g. SoC
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery

Abstract

Provided is an insulation resistance measuring circuit including: a source resistor unit including a first source resistor connected between a positive terminal of a battery and a second source resistor and the second source resistor connected between a negative terminal of the battery and the first source resistor; a voltage sensing unit sensing a voltage of the first source resistor as a first voltage and sensing a voltage of the second source resistor as a second voltage; and an insulation resistance measuring unit measuring an insulation resistance of the battery through a value obtained by dividing a difference between the first and second voltages by a sum between the first and second voltages.

Claims

1. An insulation resistance measuring circuit comprising:

a source resistor unit including a first source resistor connected between a positive terminal of a battery and a second source resistor and the second source resistor connected between a negative terminal of the battery and the first source resistor;

a voltage sensing unit sensing a voltage of the first source resistor as a first voltage and sensing a voltage of the second source resistor as a second voltage; and

an insulation resistance measuring unit measuring an insulation resistance of the battery through a value obtained by dividing a difference between the first and second voltages by a sum between the first and second voltages.

2. The insulation resistance measuring circuit of claim 1, wherein the voltage sensing unit includes:

a first operational amplifier (OP Amp) connected to the first source resistor through a non-inverting terminal and an inverting terminal thereof, sensing a first source voltage applied to the first source resistor as the first voltage, and outputting the sensed first source voltage through an output terminal thereof; and

a second OP Amp connected to the second source resistor through a non-inverting terminal and an inverting terminal thereof, sensing a second source voltage applied to the second source resistor as the second voltage, and outputting the sensed second source voltage through an output terminal thereof.

3. The insulation resistance measuring circuit of claim 2, wherein the insulation resistance measuring unit includes:

a first subtracter connected to each of output terminals of the first and second OP Amps and outputting a third voltage obtained by subtracting the second voltage output from the second OP Amp from the first voltage output from the first OP Amp;

an adder connected to each of the output terminals of the first and second OP Amps and outputting a fourth voltage obtained by adding the second voltage output from the second OP Amp to the first voltage output from the first OP Amp;

an absolute value circuit connected to an output terminal of the adder and outputting a fifth voltage having an absolute value of the fourth voltage;

a divider connected to each of the subtracter and the absolute value circuit and outputting a sixth voltage obtained by dividing the third voltage output from the subtracter by the fifth voltage output from the absolute value circuit;

a voltage source outputting a seventh voltage having a voltage of 1V; and

a second subtracter connected to each of the divider and the voltage source and outputting an eighth voltage obtained by subtracting the seventh voltage output from the voltage source from the sixth voltage output from the divider.

4. The insulation resistance measuring circuit of claim 3, wherein the insulation resistance measuring unit further includes:

an amplifier connected to the second subtracter and outputting a ninth voltage obtained by amplifying the eighth voltage output from the second subtracter to a predetermined value;

a reference voltage outputter outputting a tenth voltage having a predetermined reference voltage; and

a third subtracter connected to each of the amplifier and the reference voltage outputter and outputting an eleventh voltage obtained by subtracting the tenth voltage output from the reference voltage outputter from the ninth voltage output from the amplifier.

5. The insulation resistance measuring circuit of claim 3, wherein when a voltage of the battery is V, the insulation resistance of the battery is R_iso, each of resistance values of the first and second source resistors is R_s, the first voltage is V₁, the second voltage is V₂, the third voltage is V₃, and the fourth voltage is V₄, the first to fourth voltages measured at the time of insulation breakdown of a cathode of the battery are as follows:

6. The insulation resistance measuring circuit of claim 3, wherein when a voltage of the battery is V, the insulation resistance of the battery is R_iso, each of resistance values of the first and second source resistors is R_s, the first voltage is V₁, the second voltage is V₂, the third voltage is V₃, and the fourth voltage is V₄, the first to fourth voltages measured at the time of insulation breakdown of an anode of the battery are as follows:

7. The insulation resistance measuring circuit of claim 4, wherein when a voltage of the battery is V, the insulation resistance of the battery is R_iso, each of resistance values of the first and second source resistors is R_s, the first voltage is V₁, the second voltage is V₂, the third voltage is V₃, and the fourth voltage is V₄, the fifth voltage is V₅, the sixth voltage is V₆, the seventh voltage is V₇, the eighth voltage is V₈, the ninth voltage is V₉, the tenth voltage is V₁₀, and the eleventh voltage is V₁₁, the fifth to eleventh voltages measured at the time of insulation breakdown of a cathode of the battery or insulation breakdown of an anode thereof are as follows:

8. The insulation resistance measuring circuit of claim 1, wherein the source resistor unit, the voltage sensing unit, and the insulation resistance measuring unit are implemented as one-chip.

15. The insulation resistance measuring circuit of claim 1, wherein the battery is a high voltage battery for a hybrid vehicle.

9. An insulation resistance measuring circuit comprising:

a source resistor unit including a first source resistor connected between a positive terminal of a battery and a second source resistor and the second source resistor connected between a negative terminal of the battery and the first source resistor;

a first operational amplifier (OP Amp) connected to the first source resistor through a non-inverting terminal and an inverting terminal thereof, sensing a first source voltage applied to the first source resistor as the first voltage, and outputting the sensed first source voltage through an output terminal thereof;

a second OP Amp connected to the second source resistor through a non-inverting terminal and an inverting terminal thereof, sensing a second source voltage applied to the second source resistor as the second voltage, and outputting the sensed second source voltage through an output terminal thereof;

an analog to digital converter connected to each of output terminals of the first and second OP Amps, converting each of the first and second voltages into digital signals, and outputting first and second voltage signals; and

a microcontroller measuring an insulation resistance of the battery through a value obtained by dividing a difference between the first voltage of the first voltage signal and the second voltage of the second voltage signal by a sum between the first voltage of the first voltage signal and the second voltage of the second voltage signal.

10. The insulation resistance measuring circuit of claim 9, wherein the microcontroller receives each of the first voltage of the first voltage signal and the second voltage of the second voltage signal from the analog to digital converter, calculates a third voltage obtained by subtracting the second voltage of the second voltage signal from the first voltage of the first voltage signal, a fourth voltage obtained by adding the second voltage to the first voltage, a fifth voltage having an absolute value of the fourth voltage, a sixth voltage obtained by dividing the third voltage by the fifth voltage, a seventh voltage having a voltage of 1V, and an eighth voltage obtained by subtracting the seventh voltage from the sixth voltage, and measures the insulation resistance of the battery through the eighth voltage.

11. The insulation resistance measuring circuit of claim 10, wherein the microcontroller calculates a ninth voltage obtained by amplifying the eighth voltage to a predetermined value, a tenth voltage having a predetermined reference voltage value, and an eleventh voltage obtained by subtracting the tenth voltage from the ninth voltage, and measures the insulation resistance of the battery through the eleventh voltage.

12. The insulation resistance measuring circuit of claim 10, wherein when a voltage of the battery is V, the insulation resistance of the battery is R_iso, each of resistance values of the first and second source resistors is R_s, the first voltage is V₁, the second voltage is V₂, the third voltage is V₃, and the fourth voltage is V₄, the first to fourth voltages measured at the time of insulation breakdown of a cathode of the battery are as follows:

13. The insulation resistance measuring circuit of claim 10, wherein when a voltage of the battery is V, the insulation resistance of the battery is R_iso, each of resistance values of the first and second source resistors is R_s, the first voltage is V₁, the second voltage is V₂, the third voltage is V₃, and the fourth voltage is V₄, the first to fourth voltages measured at the time of insulation breakdown of an anode of the battery are as follows:

14. The insulation resistance measuring circuit of claim 11, wherein when a voltage of the battery is V, the insulation resistance of the battery is R_iso, each of resistance values of the first and second source resistors is R_s, the first voltage is V₁, the second voltage is V₂, the third voltage is V₃, and the fourth voltage is V₄, the fifth voltage is V₅, the sixth voltage is V₆, the seventh voltage is V₇, the eighth voltage is V₈, the ninth voltage is V₉, the tenth voltage is V₁₀, and the eleventh voltage is V₁₁, the fifth to eleventh voltages measured at the time of insulation breakdown of a cathode of the battery or insulation breakdown of an anode thereof are as follows:

16. The insulation resistance measuring circuit of claim 9, wherein the source resistor unit, the first OP Amp, the second OP Amp, the analog to digital converter, and the microcontroller are implemented as one-chip.