Method and apparatus for measuring the voltage of a power source

• US 7,622,893 B2
• Filed: 03/13/2007
• Issued: 11/24/2009
• Est. Priority Date: 03/13/2007
• Status: Active Grant

• Current Assignee: Analog Devices International Unlimited Company (Analog Devices, Inc.)
• Original Assignee: Linear Technology Corporation (Analog Devices, Inc.)
• Inventors: Williams, James Michael
• Primary Examiner(s): TSO, EDWARD H
• Application Number:
  US11/717,126
• Publication Number:
  US 20080231257A1
• Time in Patent Office: 987 Days
• Field of Search: 320/107, 320/112, 320/134, 320/136, 320/141, 320/116, 320/157, 320/162
• US Class Current: 320/112
• CPC Class Codes: G01R 19/2506 Arrangements for conditioning or analysing measured signals, e.g. for indicating peak values G01R19/003 takes precedence; Details concerning sampling, digitizing or waveform capturing displaying waveforms G01R13/00; analog sampling G01R19/0053
• 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
• CPC Class Codes: G01R 31/40 Testing power supplies testing photovoltaic devices H02S50/10

Abstract

Various concepts and techniques are disclosed for measuring the voltage of a power source. An apparatus includes a voltage metering circuit and a transformer having a first winding coupled to the voltage metering circuit and a second winding for coupling to a power source.

Claims

1. A system for determining cell voltage of a power source having multiple cells, the system comprising:

a voltage sensing circuit for determining the cell voltage, and

a transformer having a first winding configured for coupling to the voltage sensing circuit, and a second winding configured for coupling across terminals of a single cell of the power source via a unidirectional current conducting device,

a single transformer being provided for determining voltage of the cell.

2. The system of claim 1, wherein the voltage sensing circuit comprises a sampling voltmeter coupled to the first winding.

3. The system of claim 1, wherein the voltage sensing circuit further comprises a pulse generator coupled to the first winding.

4. The system of claim 1, wherein the voltage sensing circuit comprises a pulse generator configured to excite the transformer, and a sampling voltmeter configured to sample the voltage across the first winding.

5. The system of claim 4, wherein the voltage sensing circuit further comprises a delayed pulse generator configured to enable the sampling voltmeter when the transformer is excited.

6. The system of claim 4, wherein the voltage sensing circuit further comprises a correction circuit configured to correct the sampled voltage for residual error.

7. The system of claim 6, wherein the residual error includes losses introduced by the transformer.

8. The system of claim 6, wherein the residual error includes error introduced by the unidirectional current conducting device.

9. A method of determining voltage of an individual cell of a power source having multiple cells using only a single transformer having first and second windings, the second winding being configured for coupling across terminals of the individual cell via a unidirectional current conducting device, the method comprising the steps of:

exciting the first winding; and

sampling voltage at the first winding when excited.

10. The method of claim 9, wherein the first winding is excited with a pulse.

11. The method of claim 9, further comprising the step of correcting the sampled voltage for residual error.

12. The method of claim 11, wherein the residual error includes losses introduced by transformer.

13. The method of claim 11, wherein the residual error includes error introduced by the unidirectional current conducting device.

14. A system for determining voltages of individual cells of a power source having multiple cells, the system comprising:

a voltage determining circuit,

a first transformer having a first winding configured for coupling to the voltage determining circuit via a first switch, and having a second winding configured for coupling across terminals of a first cell of the power source, and

a second transformer having a first winding configured for coupling to the voltage determining circuit via a second switch, and having a second winding configured for coupling across terminals of a second cell of the power source,

the voltage determining circuit being configured to turn on the first switch and turn off the second switch for determining voltage of the first cell,

the voltage determining circuit being further configured to turn on the second switch and turn off the first switch for determining voltage of the second cell.

15. The system of claim 14, further comprising a first unidirectional current conducting device coupled to the second winding of the first transformer for providing a unidirectional current path between the first cell and the first transformer.

16. The system of claim 15, further comprising a second unidirectional current conducting device coupled to the second winding of the second transformer for providing a unidirectional current path between the second cell and the second transformer.

17. A method of sensing voltages of individual cells of a power source having multiple cells using a voltage sensing circuit, a first transformer having a first winding configured for coupling to the voltage determining circuit via a first switch, and having a second winding configured for coupling across terminals of a first cell of the power source, and a second transformer having a first winding configured for coupling to the voltage determining circuit via a second switch, and having a second winding configured for coupling across terminals of a second cell of the power source, the method comprising the steps of:

sensing voltage of the first cell by turning on the first switch and turning off the second switch, and

sensing voltage of the second cell by turning on the second switch and turning off the first switch.

18. The method of claim 17, wherein the step of sensing voltage of the first cell comprises exciting the first winding of the first transformer and sampling voltage at the first winding of the first transformer.

19. The method of claim 18, wherein the step of sensing voltage of the second cell comprises exciting the first winding of the second transformer and sampling voltage at the first winding of the second transformer.

20. A system for determining voltages of individual cells of a power source having multiple cells, the system comprising:

a processing circuit,

a first transformer having a first winding configured for coupling to the processing circuit, and having a second winding configured for coupling across terminals of a first cell of the power source via a first unidirectional current conducting device,

a second transformer having a first winding configured for coupling to the processing circuit, and having a second winding configured for coupling across terminals of a second cell of the power source via a second unidirectional current conducting device, and

a calibration circuit for providing reference values representing maximum and minimum cell voltages of the power source,

the processing circuit being configured to determine voltages of the first and second cells using the reference values.

21. A computer-readable medium containing instructions executable by a processor, the processor being configured to determine cell voltages of a power source having multiple cells using a plurality of sensing transformers, each of the sensing transformers including a first winding configured for coupling to the processor, and a second winding configured for coupling across terminals of an individual cell of the power source via a unidirectional current conduction device, the instructions comprising:

a program code for determining a reference voltage using a reference transformer; and

a program code for determining the cell voltages based on the reference voltage using the sensing transformers, a single sensing transformer being used for determining voltage of the individual cell.

22. The computer-readable medium of claim 21, wherein the program code for determining the cell voltages includes a code to excite the sensing transformers and a code to sample voltage at the first winding of each of the sensing transformers when excited.

23. The computer-readable medium of claim 22, wherein the reference transformer includes a first winding configured for coupling to the processor and a second winding configured for coupling to a voltage reference, and wherein the program code for determining the reference voltage includes a code to excite the first winding of the reference transformer, and a code to sample the voltage at the first winding of the reference transformer when exited.

24. The computer-readable medium of claim 21, wherein the instructions further comprise a program code to correct the voltage sampled at the first winding of each of the sensing transformers for residual error.