Current derivative sensor

• US 20030034770A1
• Filed: 08/12/2002
• Published: 02/20/2003
• Est. Priority Date: 08/10/2001
• Status: Active Grant

• Current Assignee: Mainstream Scientific, LLC (Innovation Management Sciences, LLC)
• Original Assignee: Shakti Systems Inc.
• Inventors: McShane, Erik A., Shenai, Krishna
• Granted Patent: US 6,791,341 B2
• Time in Patent Office: Days
• US Class Current: 324/117R
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence
• CPC Class Codes: G01R 19/12 Measuring rate of change

Abstract

A system and method for detecting, measuring, and reporting a time derivate of a current signal (di/dt) is provided. A sensing element detects current from a load. The sensing element includes an inductor. The inductor is located in series with the load and includes associated parasitic resistance. A differential potential develops across the inductor and the parasitic resistance. The differential potential is amplified and converted to a single-ended value. The single-ended value is then fed to an analog to digital converter that provides an output representative of di/dt.

Claims

1. A current derivative sensor, comprising in combination:

a sensing element operable to detect current, wherein the current flows through the sensing element, thereby generating a differential potential across the sensing element; and

an analog to digital converter providing an output representative of a time derivative of a current signal (di/dt).

2. The current derivative sensor of claim 1, further comprising a gain circuit operable to amplify and convert the differential potential to a single-ended output.

3. The current derivative sensor of claim 2, wherein the gain circuit is an operational amplifier.

4. The current derivative sensor of claim 3, wherein the gain circuit includes a single-ended gain circuit located at an output of the operational amplifier.

5. The current derivative sensor of claim 3, wherein the gain circuit includes a second differential-input, single-ended gain circuit located at an output of the operational amplifier.

6. The current derivative sensor of claim 1, wherein a load generates the current.

7. The current derivative sensor of claim 6, wherein the load is a conductor operable to generate a transient current signal.

8. The current derivative sensor of claim 6, wherein the load is a conductor selected from the group consisting of integrated circuit interconnect metallization, integrated circuit polysilicon, silicided silicon connectors, printed circuit board traces, insulated wires, and non-insulated wires.

9. The current derivative sensor of claim 1, wherein the sensing element is an inductor located in series with a load.

10. The current derivative sensor of claim 9, wherein parasitic resistance is associated with the inductor.

11. The current derivative sensor of claim 1, wherein the differential potential consists of a DC potential produced as the current flows through parasitic resistance located in the sensing element, a transient potential produced as the current flows through the parasitic resistance, and a transient potential produced as the current flows through an inductor in the sensing element.

12. The current derivative sensor of claim 1, further comprising a calibration circuit operable to determine a parasitic resistance value.

13. The current derivative sensor of claim 12, wherein the calibration circuit determines an inductive value using the parasitic resistance value.

14. The current derivative sensor of claim 12, wherein the calibration circuit includes a plurality of precision matched current sources connected in parallel through independently controlled switches.

15. The current derivative sensor of claim 14, wherein the plurality of precision matched current sources provides substantially identical current magnitudes.

16. The current derivative sensor of claim 14, wherein the independently controlled switches are field-effect transistors.

17. The current derivative sensor of claim 1, wherein the analog to digital converter includes a plurality of Schmitt triggers.

18. The current derivative sensor of claim 17, wherein the plurality of Schmitt triggers are configured with LOW-to-HIGH input transition voltages that are monotonically increasing from substantially a ground potential to a maximum supply voltage.

19. The current derivative sensor of claim 17, wherein the plurality of Schmitt triggers are configured with HIGH-to-LOW input transition voltages that are substantially at maximum supply voltage.

20. The current derivative sensor of claim 17, wherein the plurality of Schmitt triggers stay on until reset.

21. The current derivative sensor of claim 1, wherein the output is displayed on a thermometer-type scale readout.

22. A current derivative sensor, comprising in combination:

an inductor operable to detect current, wherein the current flows through the inductor, thereby generating a differential potential across the inductor;

an operational amplifier operable to amplify and convert the differential potential to a single-ended output; and

a plurality of Schmitt triggers configured to switch from off to on at monotonically increasing transition voltages, wherein the plurality of Schmitt triggers provide an output representative of a time derivative of a current signal (di/dt).

23. The current derivative sensor of claim 22, wherein a single-ended gain circuit is located at an output of the operational amplifier.

24. The current derivative sensor of claim 22, wherein a differential-input, single-ended gain circuit is located at an output of the operational amplifier.

25. The current derivative sensor of claim 22, wherein a load generates the current.

26. The current derivative sensor of claim 25, wherein the load is a conductor operable to generate a transient current signal.

27. The current derivative sensor of claim 25, wherein the load is a conductor selected from the group consisting of integrated circuit interconnect metallization, integrated circuit polysilicon, silicided silicon connectors, printed circuit board traces, insulated wires, and non-insulated wires.

28. The current derivative sensor of claim 22, wherein the inductor is located in series with a load.

29. The current derivative sensor of claim 22, wherein parasitic resistance is associated with the inductor.

30. The current derivative sensor of claim 22, wherein the differential potential consists of a DC potential produced as the current flows through parasitic resistance located in the sensing element, a transient potential produced as the current flows through the parasitic resistance, and a transient potential produced as the current flows through an inductor in the sensing element.

31. The current derivative sensor of claim 22, further comprising a calibration circuit operable to determine a parasitic resistance value.

32. The current derivative sensor of claim 31, wherein the calibration circuit determines an inductive value using the parasitic resistance value.

33. The current derivative sensor of claim 31, wherein the calibration circuit includes a plurality of precision matched current sources connected in parallel through independently controlled switches.

34. The current derivative sensor of claim 33, wherein the plurality of precision matched current sources provide substantially identical current magnitudes.

35. The current derivative sensor of claim 33, wherein the independently controlled switches are field-effect transistors.

36. The current derivative sensor of claim 22, wherein the plurality of Schmitt triggers are configured with LOW-to-HIGH input transition voltages that are monotonically increasing from substantially a ground potential to a maximum supply voltage.

37. The current derivative sensor of claim 22, wherein the plurality of Schmitt triggers are configured with HIGH-to-LOW input transition voltages that are substantially at maximum supply voltage.

38. The current derivative sensor of claim 22, wherein the plurality of Schmitt triggers stay on until reset.

39. The current derivative sensor of claim 22, wherein the output is displayed on a thermometer-type scale readout.

40. A method of measuring a time derivative of a current signal (di/dt), comprising in combination:

sensing current from a load, thereby generating a differential potential;

amplifying the differential potential;

converting the differential potential to a single-ended output; and

triggering an analog to digital converter based on the differential potential, thereby providing an output representative of a time derivative of a current signal (di/dt).

41. The method of claim 40, wherein the step of sensing current from a load, the differential potential is generated across a sensing element.

42. The method of claim 41, wherein the sensing element is an inductor located in series with the load.

43. The method claim 42, wherein parasitic resistance is associated with the inductor.

44. The method of claim 40, wherein the differential potential consists of a DC potential produced as the current flows through parasitic resistance located in the sensing element, a transient potential produced as the current flows through the parasitic resistance, and a transient potential produced as the current flows through an inductor in the sensing element.

45. The method of claim 40, wherein the load is a conductor operable to generate a transient current signal.

46. The method of claim 40, wherein the load is a conductor selected from the group consisting of integrated circuit interconnect metallization, integrated circuit polysilicon, silicided silicon connectors, printed circuit board traces, insulated wires, and non-insulated wires.

47. The method of claim 40, wherein a differential-input, single-ended output gain circuit is operable to amplify and convert the differential potential.

48. The method of claim 40, wherein the analog to digital converter includes a plurality of Schmitt triggers.

49. The method of claim 40, further comprising displaying an output of the analog to digital converter on a thermometer-type scale readout.