Fluxgate magnetic sensor readout apparatus

Patent metadata

Field	Value
Publication number	US-9684039-B2
Application number	US-201615043924-A
Country	US
Kind code	B2
Filing date	Feb 15, 2016
Priority date	Aug 15, 2013
Publication date	Jun 20, 2017
Grant date	Jun 20, 2017

Abstract

Compact, low power fluxgate magnetic sensor readout circuits and apparatus are presented in which demodulator or rectifier circuit to modulates a sense signal from the fluxgate sense coil, and the demodulated signal is provided to an amplifier circuit with a transconductance or other amplifier and one or more feedback capacitors connected between the amplifier input and amplifier output to integrate the amplifier output current and provide a voltage output signal indicating the magnetic field sensed by the fluxgate sensor.

First claim

What is claimed is:

1. A sensor readout apparatus for providing an output signal from a fluxgate magnetic sensor, comprising:
a rectifier circuit having an input coupled to an end of a sense coil of the fluxgate magnetic sensor, and an output;
an amplifier having a differential input coupled to the output of the rectifier circuit, and a differential output; and
a capacitor coupled between the differential input of the amplifier and the differential output of the amplifier,
wherein the differential input of the amplifier has a first amplifier input and a second amplifier input, wherein the differential output of the amplifier has a first amplifier output and a second amplifier output, wherein the capacitor is a first feedback capacitor connected between the first amplifier output and the first amplifier input, and wherein the apparatus further includes a second feedback capacitor connected between the second amplifier output and the second amplifier input.

2. The sensor readout apparatus of claim 1 , further comprising a reset circuit operative to selectively discharge the first and second feedback capacitors.

3. The sensor readout apparatus of claim 2 , further comprising a control circuit configured to provide a switching control signal to operate the rectifier circuit sequentially in first and second states in each of a plurality of sensing cycles, wherein the control circuit is configured to selectively discharge the first and second feedback capacitors every integer number N sensing cycles, wherein N is greater than or equal to 1.

4. The sensor readout apparatus of claim 3 , wherein the integer number N is configurable according to a gain input signal provided to the control circuit.

5. The sensor readout apparatus of claim 1 , wherein the input of the rectifier circuit is a first rectifier input, wherein the rectifier circuit includes a second rectifier input, and wherein the apparatus further comprises a disable circuit operative to selectively connect the first and second rectifier inputs together to disable the sensor readout apparatus.

6. The sensor readout apparatus of claim 1 , wherein the amplifier is a transconductance amplifier.

7. A sensor readout apparatus for providing an output signal from a fluxgate magnetic sensor, comprising:
a rectifier circuit having an input coupled to an end of a sense coil of the fluxgate magnetic sensor, and an output;
an amplifier having an input coupled to the output of the rectifier circuit, and an output;
a capacitor coupled between the input of the amplifier and the output of the amplifier;
a reset circuit operative to selectively discharge the capacitor; and
a control circuit configured to provide a switching control signal to operate the rectifier circuit sequentially in first and second states in each of a plurality of sensing cycles, wherein the control circuit is configured to selectively discharge the capacitor every integer number N sensing cycles, wherein N is greater than or equal to 1.

8. The sensor readout apparatus of claim 7 , wherein the integer number N is configurable according to a gain input signal provided to the control circuit.

9. A sensor readout apparatus for providing an output signal from a fluxgate magnetic sensor, comprising:
a rectifier circuit having a first rectifier input coupled to an end of a sense coil of the fluxgate magnetic sensor, a second rectifier input, and an output;
an amplifier having an input coupled to the output of the rectifier circuit, and an output;
a capacitor coupled between the input of the amplifier and the output of the amplifier; and
a disable circuit operative to selectively connect the first and second rectifier inputs together to disable the sensor readout apparatus.

10. The sensor readout apparatus of claim 9 , further comprising a reset circuit operative to selectively discharge the capacitor.

11. The sensor readout apparatus of claim 9 , wherein the amplifier is a transconductance amplifier.

12. A magnetic sensing apparatus, comprising:
a fluxgate sensor structure, including a core structure, at least one excitation coil wound around at least a portion of the core structure, and a sense coil;
an excitation circuit configured to provide a periodic bidirectional excitation current waveform to the excitation coil;
a control circuit configured to control timing of the periodic bidirectional excitation current waveform; and
a sensor readout circuit, comprising:
a rectifier circuit having an input coupled to an end of the sense coil of the fluxgate magnetic sensor, and an output;
an amplifier having an input coupled to the output of the rectifier circuit, and an output; and
a capacitor coupled between the input of the amplifier and the output of the amplifier.

13. The magnetic sensing apparatus of claim 12 ,
wherein the input of the rectifier circuit is a first rectifier input, the end of the sense coil is a first end of the sense coil, and the output of the rectifier circuit is a first rectifier output,
wherein the rectifier circuit includes:
a second rectifier input coupled to a second end of the sense coil;
a second rectifier output; and
a switching circuit operative in a first state to electrically couple the first rectifier input to the first rectifier output and to electrically couple the second rectifier input to the second rectifier output, and in a second state to electrically couple the first rectifier input to the second rectifier output and to electrically couple the second rectifier input to the first rectifier output, and

wherein the control circuit is configured to provide at least one switching control signal to alternate operation of the switching circuit between the first and second states.

14. The magnetic sensing apparatus of claim 13 , wherein the input of the amplifier is a differential input having a first amplifier input and a second amplifier input, wherein the output of the amplifier is a differential output having a first amplifier output and a second amplifier output, wherein the capacitor is a first feedback capacitor connected between the first amplifier output and the first amplifier input, and wherein the apparatus further includes a second feedback capacitor connected between the second amplifier output and the second amplifier input.

15. The magnetic sensing apparatus of claim 12 , further comprising
a reset circuit operative to selectively discharge the capacitor,
wherein the control circuit is configured to operate the excitation circuit and the rectifier circuit in each of a plurality of sensing cycles individually corresponding to one period of the periodic bidirectional excitation signal, and
wherein the control circuit is configured to selectively discharge the capacitor every integer number N sensing cycles, wherein N is greater than or equal to 1.

16. The magnetic sensing apparatus of claim 12 , further comprising a disable circuit operative to selectively disable the sensor readout circuit.

17. The magnetic sensing apparatus of claim 12 , wherein the amplifier is a transconductance amplifier.

18. A sensor interface circuit for interfacing a fluxgate magnetic sensor, comprising:
an excitation circuit configured to provide a periodic bidirectional excitation current waveform to an excitation coil of the fluxgate sensor according to at least one excitation timing control signal;
a sensor readout circuit, comprising:
a rectifier circuit having an input coupled to an end of a sense coil of the fluxgate magnetic sensor, and an output;
an amplifier having an input coupled to the

Assignees

• Texas Instruments Deutschland
• Texas Instruments Inc

Inventors

• Schaffer Viola
• Ivanov Mikhail Valeryevich

Classifications

• G01R33/0023

  Electronic aspects, e.g. circuits for stimulation, evaluation, control; Treating the measured signals; calibration (G01R33/0017 takes precedence) · CPC title

• G01R33/0041 Primary

  using feed-back or modulation techniques · CPC title

• G01R33/04 Primary

  using the flux-gate principle · CPC title