Bridge sensor biasing and readout

Patent metadata

Field	Value
Publication number	US-11255696-B2
Application number	US-201815962266-A
Country	US
Kind code	B2
Filing date	Apr 25, 2018
Priority date	Apr 28, 2017
Publication date	Feb 22, 2022
Grant date	Feb 22, 2022

Abstract

A circuit for biasing and reading out a bridge sensor structure comprises at least two pairs of connection terminals. The circuit comprises an excitation signal generator for generating an excitation signal for biasing and/or exciting the bridge, in which the excitation signal is provided as a non-constant periodic continuous function of time, and a detection circuit for obtaining the sensor signal from the bridge sensor structure by electrically connecting the detection circuit to any pair of connection terminals while applying the excitation signal to another pair. The circuit comprises a switch unit for switching the electrical excitation signal and for switching the detection circuit. A controller controls the switch unit to switch the first pair from being connected to the excitation signal generator at a time when the generated excitation signal is in a predetermined signal range where the excitation signal value is substantially equal to zero.

First claim

The invention claimed is:

1. A circuit for biasing a bridge sensor structure and for reading out a sensor signal from said bridge sensor structure, the circuit comprising:
at least two pairs of connection terminals including a first pair of connection terminals and a second pair of connection terminals, each pair of said at least two pairs of connection terminals being adapted for connecting to complementary terminals of said bridge sensor structure;
an excitation signal generator for generating an electrical excitation signal for biasing and/or exciting the bridge sensor structure, wherein said excitation signal is provided as a non-constant periodic continuous function of time, wherein the function is defined in a range comprising a zero reference value of the excitation signal;
a detection circuit electrically connected to one of the first pair or second pair of said at least two pairs of connection terminals, said detection circuit being configured to obtain said sensor signal from said bridge sensor structure while said excitation signal is applied to at least a different one of the first pair or the second pair of said at least two pairs of connection terminals;
a switch unit that
switches the electrical excitation signal generated by the excitation signal generator from being supplied to the first pair of said at least two pairs of connection terminals to the second pair of said at least two pairs of connection terminals and switches the detection circuit from being connected to the second pair of said at least two pairs of connection terminals to the first pair of said at least two pairs of connection terminals and
switches the electrical excitation signal generated by the excitation signal generator from being supplied to the second pair of said at least two pairs of connection terminals to the first pair of said at least two pairs of connection terminals and switches the detection circuit from being connected to first pair of said at least two pairs of connection terminals to the second pair of said at least two pairs of connection terminals; and

a controller that controls said switch unit to switch the electrical excitation signal and the detection circuit at an instant in time when said excitation signal generator generates the excitation signal substantially equal to a zero reference value at a distance to an extremum in a range of 0% to 10% relative to the full range of the function,
wherein the controller is adapted to detect the value of the excitation signal being substantially equal to the zero reference value,
wherein the controller further includes a comparator that detects when the excitation signal is substantially equal to the zero reference value in said range of 0% to 10%, and
wherein the controller controls said switch unit to switch the electrical excitation signal and the detection circuit when the comparator detects said signal in said range.

2. The circuit of claim 1 , wherein said excitation signal generator is adapted for generating a sinusoidal electrical current waveform and/or a sinusoidal voltage waveform as said electrical excitation signal.

3. The circuit of claim 1 , wherein said excitation signal generator is adapted for generating said electrical excitation signal in the form of two complementary voltages and wherein said controller is adapted for detecting each zero-crossing of a differential voltage signal calculated as an absolute value of the difference between said two complementary voltages, at which zero-crossing the absolute value of the difference between said two complementary voltages is zero or, alternatively, less than a predetermined tolerance threshold.

4. The circuit of claim 3 , wherein said switch unit and said controller are adapted for applying said two complementary voltages to the first pair of the at least two pairs of connection terminals, where said switch unit and said controller are adapted for switching the excitation signal from being supplied to the first pair of said at least two pairs of connection terminals to the second pair of said at least two pairs of connection terminals at a predetermined zero-crossing of said detected zero-crossings, thus iterating over a plurality of spinning phases delimited in time by said detected zero-crossings or a subset of said detected zero-crossings.

5. The circuit of claim 1 , wherein said at least two pairs of connection terminals consists of the first pair and the second pair of connection terminals for connecting respectively to a first node pair and a second node pair of the bridge sensor structure, said switch unit and said controller being adapted for exchanging connections of the first pair and second pair of connection terminals to the excitation signal generator and the detection circuit such that said excitation signal is alternatingly applied to one of the first node pair and second node pair while obtaining said sensor signal via another of the first node pair and the second node pair.

6. The circuit of claim 1 , wherein said detection circuit is adapted for obtaining said sensor signal in the form of a Hall plate readout signal from said bridge sensor structure being a resistive bridge structure in the form of a Hall element.

7. The circuit of claim 1 , wherein, when said excitation signal generator generates the excitation signal substantially equal to a zero reference value, an electrical current as said excitation signal supplied to said first pair of connection terminals is substantially equal to a zero current at a distance to an extremum in a range of 0% to 10% relative to the full range of the function.

8. The circuit of claim 1 , wherein said detection circuit comprises a low noise amplifier for amplifying said sensor signal.

9. The circuit of claim 1 , wherein said detection circuit comprises a continuous-time integrator or averager for integrating or averaging said sensor signal, wherein the sensor signal is an electrical quantity acquired via the first pair or second pair of connection terminals connected to the pair of sensing nodes, and wherein said continuous time integrator or averager is adapted for integrating or averaging said electrical quantity.

10. The circuit of claim 1 , wherein said circuit comprises an excitation integrator and/or excitation averager for determining an average current and/or a total charge flowing through the pair of connection terminals connected to the excitation signal generator during a predetermined time interval, said excitation integrator and/or excitation averager comprising a capacitor receiving during said predetermined time interval a current representative for a biasing current corresponding to said excitation signal.

11. The circuit of claim 10 , wherein said controller is adapted for determining a sensor readout value based on said integrated or averaged readout signal and on a value indicative of a change of the amount of charge stored in the capacitor during said time interval;
wherein said detection circuit comprises a continuous-time integrator or averager for integrating or averaging said sensor signal.

12. The circuit of claim 1 , wherein said controller is adapted for controlling the detection circuit to obtain the sensor signal from the bridge sensor structure only in a predetermined time interval during each spinning phase wherein the spinning phase refers to the time in between two consecutive switchings of the switch unit, and for ignoring or zeroing the sensor signal during the spinning phase when outside said predetermined time interval.

13. The circuit of claim 12 , wherein said predetermined time interval excludes a time frame immediately after said two consecutive switchin

Assignees

• Melexis Tech Sa

Inventors

• Raman Johan
• Rombouts Pieter

Classifications

• G01L9/06

  of piezo-resistive devices · CPC title

• G01D3/02 Primary

  with provision for altering or correcting the law of variation · CPC title

• G01R33/075

  Hall devices configured for spinning current measurements · CPC title

• G01L1/2262

  involving simple electrical bridges · CPC title

• G01L9/12

  by making use of variations in capacitance {, i.e. electric circuits therefor} · CPC title