Current measurement circuit

• US 5,845,275 A
• Filed: 01/07/1997
• Issued: 12/01/1998
• Est. Priority Date: 01/11/1996
• Status: Expired due to Term

• Current Assignee: SGS-Thomson Microelectronics (STMicroelectronics NV)
• Original Assignee: SGS-Thomson Microelectronics (STMicroelectronics NV)
• Inventors: Le Van Suu, Maurice
• Primary Examiner(s): MacDonald, Allen R.
• Assistant Examiner(s): Rhodes, Jason W.
• Application Number:
  US08/780,430
• Time in Patent Office: 693 Days
• Field of Search: 395/3, 395/61, 395/900, 323/313, 323/312, 706/1, 706/52, 706/900, 324/132, 324/76.11
• US Class Current: 706/1
• CPC Class Codes: G01R 19/25 using digital measurement techniques
• CPC Class Codes: Y10S 706/90 Fuzzy logic

Abstract

A circuit for the measurement of current in a load includes a non-linear element for transforming a current into a voltage and includes a fuzzy logic processor to process a measurement of the voltage and provide an information element representing the current. The device permits the precise use of semi-conductor or other components for the measurement of current in making a linear approximation of the current-voltage characteristics of the semi-conductors used by using triangular type membership functions. The linear approximation may also be combined with a Gaussian interpolation.

Claims

1. A circuit for measuring current in a load, the circuit comprising:

a non-linear circuit element; and

a fuzzy logic processor electrically coupled to the non-linear circuit element, the fuzzy logic processor receiving a voltage value from the non-linear circuit element;

wherein the fuzzy logic processor converts the voltage value to an information element representing the current in the load using membership functions and decision rules that represent a characteristic curve of the non-linear circuit element.

2. A circuit according to claim 1, wherein the non-linear circuit element is a MOSFET type measurement transistor having a source connected to a ground and a drain connected to an input of the fuzzy logic processor and to a terminal of the load.

3. A circuit according to claim 2, wherein the transistor connected to the load has its drain connected to its gate.

4. A circuit according to claim 2, wherein the transistor connected to the load has its gate connected to a control circuit and wherein said transistor is used as a switch.

5. A circuit according to claim 1, wherein the non-linear circuit element is a MOSFET type measurement transistor having its source connected to the ground and its drain connected to an input of the fuzzy logic processor and to a bias circuit, and wherein an intermediate transistor has its drain connected to the terminal of the load, its source connected to the ground and its gate connected to the gate of the measurement transistor.

6. A circuit according to claim 5 wherein the intermediate transistor is parallel-connected with a plurality of transistors whose dimensions are identical to those of the intermediate transistor.

7. A circuit according to claim 5, wherein the measurement transistor has its dimensions identical to the dimensions of the intermediate transistor.

8. A circuit according to one of claims 2 to 4, wherein:

the MOSFET transistors are replaced by bipolar transistors;

the gates are replaced by bases;

the sources are replaced by emitters; and

the drains are replaced by collectors.

9. A circuit according to claim 1, wherein the non-linear circuit element is a diode.

10. A circuit according to claim 1, wherein the non-linear circuit element is constituted by two diodes, parallel-connected in reverse to each other.

11. A circuit according to claim 1, wherein the non-linear circuit element is a measurement thyristor whose trigger is connected to a control signal.

12. A circuit according to claim 11, wherein the measurement thyristor is parallel-connected with a plurality of thyristors having identical dimensions.

13. A circuit according to claim 1, wherein the non-linear circuit element is a measurement triac whose trigger is connected to a control signal.

14. A circuit according to claim 13, wherein the measurement triac is parallel-connected with a plurality of triacs having identical dimensions.

15. A circuit according to claim 1, wherein the fuzzy logic processor comprises a non-volatile memory zone and wherein membership functions and decision rules pertaining to the information representing the current are stored in the non-volatile memory.

16. A circuit according to claim 15, wherein the membership functions are of a triangular type.

17. A circuit according to claim 16, wherein the fuzzy logic processor carries out a linear approximation of a current-voltage transfer characteristic of the non-linear element.

18. A circuit according to claim 15, wherein the membership functions are of a Gaussian type.

19. A circuit according to claim 15 wherein the triangular type membership functions are used simultaneously with Gaussian type membership functions.

20. A circuit according to claim 15, wherein voltage thresholds demarcating the membership functions are stored in the non-volatile memory during a calibration of the measurement circuit.

21. A circuit according to claim 15, wherein the decision rules determine an information element representing the current in the load.

22. A circuit according to claim 15, wherein the fuzzy logic processor has several information inputs and wherein the decision rules determine a control signal.

23. A circuit according to claim 1, wherein the non-linear circuit element is a semiconductor.

24. A circuit according to claim 1, wherein the information element represents the instantaneous current.

25. A circuit according to claim 1, wherein the characteristic curve is a current/voltage transfer curve of the non-linear circuit element.