AUTONOMOUSLY CALIBRATED MAGNETIC FIELD SENSOR

• US 20130093412A1
• Filed: 06/27/2011
• Published: 04/18/2013
• Est. Priority Date: 06/30/2010
• Status: Active Grant

• Current Assignee: LEM International SA (LEM Holding SA)
• Original Assignee: Lem Intellectual Property SA (LEM Holding SA)
• Inventors: Kayal, Maher, Pastre, Marc, Anelli, Giovanni Maria, Ajbl, Andrea
• Granted Patent: US 9,404,991 B2
• Time in Patent Office: Days
• US Class Current: 324/202
• CPC Class Codes: G01R 33/0017 Means for compensating offset magnetic fields or the magnetic flux to be measured; Means for generating calibration magnetic fields
• CPC Class Codes: G01R 33/0029 Treating the measured signals, e.g. removing offset or noise
• CPC Class Codes: G01R 33/0035 Calibration of single magnetic sensors, e.g. integrated calibration
• CPC Class Codes: G01R 33/07 Hall effect devices
• CPC Class Codes: G01R 35/005 Calibrating; Standards or reference devices, e.g. voltage or resistance standards, "golden" references G01R33/0035, G01R35/002 take precedence

Abstract

Magnetic field sensor including a magnetic field sensing circuit (2) comprising a reference magnetic field generator (8) and a magnetic field sensing cell (6), and a signal processing circuit (4) connected to the output of the magnetic field sensing cell and comprising a demodulator circuit and a gain correction feedback circuit (30, 28, 47) for correcting error fluctuations in the transfer characteristic of the magnetic field sensor. The sensor further comprises a reference current generator (3) configured to generate a reference current I ref, the reference current generator connected to the magnetic field sensing circuit (2) configured for generating the reference magnetic field B ref and to the gain correction feedback circuit configured for providing a reference signal (y_ref) to which an output signal of the demodulator circuit may be compared.

Claims

1-12. -12. (canceled)

13. Magnetic field sensor including a magnetic field sensing circuit comprising a reference magnetic field generator and a magnetic field sensing cell, and a signal processing circuit connected to the output of the magnetic field sensing cell and comprising a gain correction feedback circuit for correcting fluctuations in the transfer characteristic of the magnetic field sensor, characterized in that the sensor further comprises a reference current generator configured to generate a reference current I_ref, the reference current generator connected to the magnetic field sensing circuit configured for generating the reference magnetic field B_ref and to the gain correction feedback circuit configured for providing a reference signal y_ref to which an output signal of the demodulator circuit may be compared.

14. Sensor according to claim 13, wherein the reference current generator is connected to a reference coil of the reference magnetic field generator via a current mirror circuit configured to copy the reference current I_ref and to generate a second reference current I_ref,coil that drives the coil to generate the reference magnetic field B_ref.

15. Sensor according to claim 13, wherein the gain correction feedback circuit is connected to the reference current generator via a current mirror circuit configured to copy the reference current I_ref and to generate a further reference current (I_ref,r) that is fed into the gain correction feedback circuit.

16. Sensor according to claim 13, wherein the current mirror circuit is connected to a demodulator of the gain correction feedback circuit.

17. Sensor according to claim 13, wherein the reference current generator comprises an integrated circuit element generating a bandgap voltage reference V_BG applied across an internal resistor R_BG to generate the reference current I_ref.

18. Sensor according to claim 13, wherein the signal processing circuit includes a voltage-current (V/I) conversion circuit connected to outputs of a measurement signal demodulator of the signal processing circuit.

19. Sensor according to claim 18, wherein the voltage-current (V/I) conversion circuit comprises a circuit configured to integrate and sample and hold a measurement signal.

20. Sensor according to claim 13, wherein the signal processing circuit includes a demodulator circuit comprising at least two demodulators in parallel configured to separate the measurement signal and the reference signal simultaneously.

21. Sensor according to claim 13, wherein the signal processing circuit includes a demodulator circuit comprising a demodulator operable in at least two successive demodulation modes configured to process the measurement and reference signals separately.

22. Electrical current sensor for measuring an electrical current flowing in a conductor by measuring an external magnetic field generated by the current to be measured, the electrical current sensor comprising a magnetic field sensor according to claim 13.

23. Electrical current sensor according to claim 22, comprising a magnetic core made of a material with high magnetic permeability and having an air-gap in which the magnetic field sensing cell is positioned.