Diagnosis of electrical failures in capacitive sensors

Patent metadata

Field	Value
Publication number	US-12467816-B2
Application number	US-202217741718-A
Country	US
Kind code	B2
Filing date	May 11, 2022
Priority date	May 11, 2022
Publication date	Nov 11, 2025
Grant date	Nov 11, 2025

Abstract

A capacitive sensor includes a first conductive structure and a second conductive structure that form a first capacitor having a first capacitance that changes in response to an external force acting thereon and includes a MEMS output configured to output a first sense signal representative of the first capacitance; a second capacitor coupled to the MEMS output and configured to output a second sense signal based on the first sense signal; an amplifier comprising an amplifier input and configured to output an amplified signal based on the second sense signal; and a diagnostic circuit configured to receive two measurement signals, generate an offset measurement based on the two measurement signals, and detect a fault on a condition that the offset measurement is outside of a threshold range.

First claim

What is claimed is:

1 . A capacitive sensor, comprising:
a first conductive structure; a second conductive structure that is different from the first conductive structure, wherein at the second conductive structure is movable relative to the first conductive structure in response to an external force acting thereon, wherein the second conductive structure is capacitively coupled to the first conductive structure to form a first capacitor having a first capacitance that changes with a change in a distance between the first conductive structure and second conductive structure, wherein the first capacitance is representative of the external force and the first capacitor comprises a first micro-electromechanical system (MEMS) output configured to output a first sense signal representative of the first capacitance; a second capacitor comprising a first terminal and a second terminal, the first terminal being coupled to the first MEMS output of the first capacitor in order to receive the first sense signal and the second terminal being configured to output a second sense signal based on the first sense signal; an amplifier comprising a first amplifier input coupled to the second terminal of the second capacitor and configured to output a first amplified signal based on the second sense signal; and a diagnostic circuit configured to receive one of the first sense signal, the second sense signal, or the first amplified signal as a first measurement signal, receive one of the first sense signal, the second sense signal, or the first amplified signal as a second measurement signal that is different from the first measurement signal, generate a first offset measurement based on the first measurement signal and the second measurement signal, wherein the first offset measurement is representative of a degree of pattern similarity between the first measurement signal and the second measurement signal, compare the first offset measurement to a first threshold range defined by a first threshold and a second threshold, and detect a first fault on a condition that the first offset measurement is outside of the first threshold range,
wherein the diagnostic circuit comprises:
a comparator circuit configured to compare the first offset measurement to the first threshold range and activate a first fault signal on the condition that the first offset measurement is outside of the first threshold range; and
an error processing circuit configured to receive the first fault signal and generate a second fault signal in response to the first fault signal being activated, uninterrupted, for a predetermined time interval, wherein the second fault signal is indicative of a confirmation of the first fault.

2 . The capacitive sensor of claim 1 , wherein:
the first sense signal is the first measurement signal and the second sense signal is the second measurement signal, and the diagnostic circuit comprises a difference circuit configured to generate the first offset measurement as a difference between the first measurement signal and the second measurement signal.

3 . The capacitive sensor of claim 2 , wherein the first offset measurement is a difference between a direct current (DC) value of the first measurement signal and a DC value of the second measurement signal.

4 . The capacitive sensor of claim 2 , wherein the first sense signal comprises a first alternating current (AC) component and a first direct current (DC) component, the second sense signal comprises a second AC component and a second DC component, wherein the first AC component and the second AC component are in phase with each other.

5 . The capacitive sensor of claim 2 , wherein the diagnostic circuit comprises a first DC shifter configured to shift a first DC component to a mid-supply value and a second direct current (DC) shifter configured to shift a second DC component to the mid-supply value.

6 . The capacitive sensor of claim 2 , wherein the diagnostic circuit comprises:
a first voltage-to-current converter configured to generate the first measurement signal by converting the first sense signal into a first current; and a second voltage-to-current converter configured to generate the second measurement signal by converting the second sense signal into a second current.

7 . The capacitive sensor of claim 1 , wherein:
the first sense signal is the first measurement signal and the first amplified signal is the second measurement signal, and the diagnostic circuit comprises a difference circuit configured to generate the first offset measurement as a difference between the first measurement signal and the second measurement signal.

8 . The capacitive sensor of claim 7 , wherein:
the first sense signal comprises a first alternating current (AC) component and a first direct current (DC) component and the first amplified signal comprises a second AC component and a second DC component, the first AC component and the second AC component are in phase with each other, and the first offset measurement is a difference between the first DC component and the second DC component.

9 . The capacitive sensor of claim 1 , wherein:
the first sense signal is the first measurement signal and the first amplified signal is the second measurement signal, and the diagnostic circuit comprises an averaging circuit configured to generate the first offset measurement as an average of the first measurement signal and the second measurement signal.

10 . The capacitive sensor of claim 9 , wherein:
the first sense signal comprises a first alternating current (AC) component and a first direct current (DC) component and the first amplified signal comprises a second AC component and a second DC component, the first AC component and the second AC component are 180° out of phase with each other, and the first offset measurement is an average of the first DC component of the first measurement signal and the second DC component of the second measurement signal.

11 . The capacitive sensor of claim 1 , wherein:
the second sense signal is the first measurement signal and the first amplified signal is the second measurement signal, and the diagnostic circuit comprises a difference circuit configured to generate the first offset measurement as a difference between the first measurement signal and the second measurement signal.

12 . The capacitive sensor of claim 11 , wherein:
the second sense signal comprises a first alternating current (AC) component and a first direct current (DC) component and the first amplified signal comprises a second AC component and a second DC component, the first AC component and the second AC component are in phase with each other, and the first offset measurement is a difference between the first DC component of the first measurement signal and the second DC component of the second measurement signal.

13 . The capacitive sensor of claim 1 , wherein:
the second sense signal is the first measurement signal and the first amplified signal is the second measurement signal, and the diagnostic circuit comprises an averaging circuit configured to generate the first offset measurement as an average of the first measurement signal and the second measurement signal.

14 . The capacitive sensor of claim 13 , wherein:
the second sense signal comprises a first alternating current (AC) component and a first direct current (DC) component and the first amplified signal comprises a second AC component and a second DC component, the first AC component and the second AC component are 180° out of phase with each other, and the first offset measurement is an averag

Assignees

• Infineon Technologies Ag

Inventors

• Crisu Constantin
• Stoica Dan-Ioan-Dumitru
• Buffa Cesare
• Caspani Alessandro

Classifications

• G01L1/142

  using capacitors · CPC title

• H04R19/04

  Microphones (H04R19/01 takes precedence) · CPC title

• H03F2200/03

  the amplifier being designed for audio applications · CPC title

• H04R2201/003

  Mems transducers or their use · CPC title

• G01R31/52

  Testing for short-circuits, leakage current or ground faults · CPC title