Capacitive sensor device with drift compensation

Patent metadata

Field	Value
Publication number	US-2023349730-A1
Application number	US-202318138985-A
Country	US
Kind code	A1
Filing date	Apr 25, 2023
Priority date	Apr 27, 2022
Publication date	Nov 2, 2023
Grant date	—

Abstract

The present invention relates to a capacitive sensor device comprising a capacitance-measuring circuit, a main sense input and a reference sense input, wherein the capacitive sensor device is configured to measure, using the capacitance-measuring circuit, a current main value of capacitance seen by the main sense input and a current reference value of capacitance seen by the reference sense input, wherein the capacitive sensor device is configured to at least temporarily store at least one previously measured reference value, and wherein the capacitive sensor device is configured to use 1) the current main value, 2) the current reference value and the at least one previously measured reference value, and 3) at least one current correction coefficient, with the capacitive sensor device being configured to adaptively determine the at least one current correction coefficient based on at least the current reference value and the at least one previously measured reference value, for determining a corrected current main value of capacitance. The present invention further relates to a portable electronic device comprising the capacitive sensor device.

First claim

1 . A capacitive sensor device comprising a capacitance-measuring circuit, a main sense input and a reference sense input, wherein the capacitive sensor device is configured to measure, using the capacitance-measuring circuit, a current main value of capacitance seen by the main sense input and a current reference value of capacitance seen by the reference sense input, wherein the capacitive sensor device is configured to at least temporarily store at least one previously measured reference value, and wherein the capacitive sensor device is configured to use
the current main value, the current reference value and the at least one previously measured reference value, and at least one current correction coefficient, with the capacitive sensor device being configured to adaptively determine the at least one current correction coefficient based on at least the current reference value and the at least one previously measured reference value,
for determining a corrected current main value of capacitance.

2 . The capacitive sensor device of claim 1 , wherein the capacitive sensor device is configured to adaptively determine the at least one current correction coefficient by adaptively selecting, based on a selection criterion based on the current reference value and the at least one previously measured reference value, the at least one current correction coefficient from at least two predetermined correction coefficients, and wherein the selection criterion comprises a comparison to at least one threshold.

3 . The capacitive sensor device of claim 2 , wherein the capacitive sensor device is configured to determine a current difference reference value between the current reference value and a comparison reference value from the at least one previously measured reference value, and wherein the comparison comprises comparing the current difference reference value to the at least one threshold.

4 . The capacitive sensor device of claim 3 , wherein the at least two predetermined correction coefficients comprise a first first order correction coefficient and a second first order correction coefficient which differ from one another and wherein a single current correction coefficient is adaptively selected from the first first order correction coefficient and the second first order correction coefficient, wherein the at least one threshold comprises a single threshold, and wherein the capacitive sensor device is configured to determine whether the current difference reference value is larger or smaller than the single threshold, wherein for a larger current difference reference value the first first order correction coefficient is selected as the single current correction coefficient and for a smaller current difference reference value the second first order correction coefficient is selected as the single current correction coefficient, and wherein the capacitive sensor device is configured to determine the corrected current main value by subtracting the product of the single current correction coefficient and a cumulated difference reference value from the current main value.

5 . The capacitive sensor device of claim 3 , wherein the at least two predetermined correction coefficients comprise a first first order correction coefficient and a second first order correction coefficient which differ from one another and wherein a single current correction coefficient is adaptively selected from the first first order correction coefficient and the second first order correction coefficient, wherein the capacitive sensor device is configured to at least temporarily store at least one previously determined difference reference value, and wherein the capacitive sensor device is configured to determine a filtered current difference reference value by applying a filter to the current difference reference value and the at least one stored previously determined difference reference value, wherein the at least one threshold comprises a single threshold, and wherein the capacitive sensor device is configured to determine whether the filtered current difference reference value is larger or smaller than the single threshold, wherein for a larger filtered current difference reference value the first first order correction coefficient is selected as the single current correction coefficient and for a smaller current difference reference value the second first order correction coefficient is selected as the single current correction coefficient, and wherein the capacitive sensor device is configured to determine the corrected current main value by subtracting the product of the single current correction coefficient and a cumulated difference reference value from the current main value.

6 . The capacitive sensor device of claim 3 , wherein the at least two predetermined correction coefficients comprise a first first order correction coefficient, a second first order correction coefficient, a first second order correction coefficient and a second second order correction coefficient, wherein two current correction coefficients are adaptively selected from these four predetermined correction coefficients, wherein the at least one threshold comprises a single threshold, and wherein the capacitive sensor device is configured to determine whether the current difference reference value is larger or smaller than the single threshold, wherein for a larger current difference reference value the first first order correction coefficient is selected as a first current correction coefficient of the two current correction coefficients and the first second order correction coefficient is selected as a second current correction coefficient of the two current correction coefficients, and wherein for a smaller current difference reference value the second first order correction coefficient is selected as a first current correction coefficient of the two current correction coefficients and the second second order correction coefficient is selected as a second current correction coefficient of the two current correction coefficients, and wherein the capacitive sensor device is configured to determine the corrected current main value by subtracting the product of the first current correction coefficient and a cumulated difference reference value and the product of the second current correction coefficient with the square of the cumulated difference reference value from the current main value.

7 . The capacitive sensor device of claim 2 , wherein the at least one threshold comprises a first threshold and a second threshold, wherein the first threshold is smaller than the second threshold, and wherein the at least two predetermined correction coefficients comprise a first correction coefficient, a second correction coefficient and a third correction coefficient, wherein a single current correction coefficient is adaptively selected from these three predetermined correction coefficients, and wherein the capacitive sensor device is configured to select 1) the first correction coefficient as the single current correction coefficient if a cumulated difference reference value is smaller than the first threshold, 2) the second correction coefficient as the single current correction coefficient if the cumulated difference reference value is larger than or equal to the first threshold and smaller than or equal to the second threshold, and 3) the third correction coefficient as the single current correction coefficient if the cumulated difference reference value is larger than the second threshold, and wherein the capacitive sensor device is configured to determine the corrected current main value by subtracting the product of the single current correction coefficient and the cumulated difference reference value from the current main value.

8 . The cap

Assignees

• Semtech Corp

Inventors

• Rouaissia Chaouki
• Grisot Sébastien
• Ott Iii Jerald G

Classifications

• G01D5/24 Primary

  by varying capacitance · CPC title

• G01R27/2605

  Measuring capacitance (capacitive sensors G01D5/24) · CPC title

• H03K17/955

  using a capacitive detector · CPC title

• H03K17/962 Primary

  Capacitive touch switches · CPC title

• H03K2217/94026

  Automatic threshold calibration; e.g. threshold automatically adapts to ambient conditions or follows variation of input · CPC title