Circuit arrangement and method for detecting a capacitance and/or a change in a capacitance of a capacitive component

Patent metadata

Field	Value
Publication number	US-9541590-B2
Application number	US-201514614240-A
Country	US
Kind code	B2
Filing date	Feb 4, 2015
Priority date	Feb 6, 2014
Publication date	Jan 10, 2017
Grant date	Jan 10, 2017

Abstract

The present invention relates to a circuit arrangement for detecting a capacitance of a capacitive component and/or a change in the capacitance of a capacitive component, which circuit arrangement comprises, inter alia a monostable flipflop controllable by a control signal and having at least two inputs and one output, wherein a first input of the flipflop is provided for the control signal, and a second input is connected to a capacitive component. The circuit arrangement further comprises a conversion device, which is connected to the output of the monostable flipflop, and an evaluation unit, which is connected to the conversion device in order to evaluate the signal voltage and from this to generate at least one detection value, which indicates the capacitance and/or a change in the capacitance of the capacitive component.

First claim

The invention claimed is:

1. A circuit arrangement for detecting a capacitance of a capacitive component and/or a change in the capacitance of a capacitive component, the circuit arrangement comprising:
a monostable flipflop controllable by a control signal and having at least two inputs and one output, wherein a first input of the flipflop is provided for the control signal,
a capacitive component which is connected to a second input of the monostable flipflop,
a conversion device which is connected to the output of the monostable flipflop and is configured to convert an output signal generated at the output into a signal voltage, and
an evaluation unit which is connected to the conversion device in order to evaluate the signal voltage and to generate at least one detection value based on the signal voltage and which indicates the capacitance and/or a change in the capacitance of the capacitive component,
wherein the monostable flipflop is configured to generate at least one output signal at its output on actuation by the control signal, the duration of said output signal being dependent on the capacitance of the capacitive component, and wherein the conversion device converts the at least one output signal into a signal voltage whose course is proportional to a duration of the output signal,
wherein the conversion device comprises an integrator having an operational amplifier, wherein the integrator is connected between the output of the monostable flipflop and the evaluation unit and configured such that an output signal of the monostable flipflop is present at an amplifier input of the operational amplifier and results in a signal voltage which changes linearly over time, wherein the values which can be assumed by the signal voltage are preset by the output signal and dependent directly from the output signal, and
wherein a magnitude of the signal voltage is controllable and/or a characteristic for the signal voltage is variable via a switchable setting device whose switching state is independent from the output signal, the magnitude of the signal voltage being controllable and/or the characteristic for the signal voltage being variable by setting a gain of the integrator between the output signal generated at the output of the monostable flipflop and the signal voltage generated via the conversion device, wherein a plurality of discrete values for the gain are preset and selectable via the switchable setting device.

2. The circuit arrangement according to claim 1 , wherein the setting device is provided at an output of the operational amplifier and a current fed back to the operational amplifier can be varied by the setting device.

3. The circuit arrangement according to claim 1 , wherein the setting device has at least one field-effect transistor for controlling the magnitude of the signal voltage and/or a change in the signal voltage.

4. The circuit arrangement according to claim 1 , wherein the monostable flipflop is configured such that its output signal can assume two discrete voltage values.

5. The circuit arrangement according to claim 1 , wherein the output signal of the monostable flipflop:
has a minimum value which is less than a voltage value of a reference voltage which is present at the other amplifier input of the operational amplifier, and
has a maximum value which is greater than the voltage value of the reference voltage at the other amplifier input.

6. The circuit arrangement according to claim 1 , wherein, for operation of the operational amplifier, a supply voltage is provided and wherein the circuit arrangement has a voltage divider in order to provide a reference voltage which is present at an amplifier input of the operational amplifier as a partial voltage of the supply voltage.

7. The circuit arrangement according to claim 1 , wherein the integrator is inverting.

8. The circuit arrangement according to claim 1 , wherein a peak value holding element is connected downstream of the integrator in order to store a maximum voltage value of the signal voltage.

9. The circuit arrangement according to claim 8 , wherein the peak value holding element comprises at least one diode and one storage capacitor.

10. The circuit arrangement according to claim 1 , wherein at least one threshold value for the signal voltage is stored in the evaluation unit, and wherein the evaluation unit is configured to generate a tripping signal if this threshold value is exceeded or not reached by the signal voltage.

11. A method for detecting a capacitance of a capacitive component and/or a change in the capacitance of a capacitive component, said method comprising:
controlling a monostable flipflop by applying a control signal to a first input of the monostable flipflop, wherein the monostable flipflop is connected to the capacitive component at a second input,
generating at least one output signal at an output of the monostable flipflop upon application of the control signal, wherein the duration of the output signal generated is dependent on the capacitance of the capacitive component, and
converting the at least one output signal into a signal voltage whose course is proportional to the duration of the output signal,
wherein the output signal is converted by an integrator which has an operational amplifier, the amplifier having the output signal present at an amplifier input thereof and which converts the output signal of the monostable flipflop into a signal voltage which changes linearly over time so that values which can be assumed by the signal voltage are preset by the output signal and dependent directly from the output signal, and
wherein the magnitude of the signal voltage is controllable and/or a characteristic for the signal voltage is variable via a switchable setting device whose switching state is independent from the output signal, the magnitude of the signal voltage being controllable and/or the characteristic for the signal voltage being variable by setting a gain of the integrator between the output signal generated at the output of the monostable flipflop and the signal voltage generated via the conversion device, wherein a plurality of discrete values for the gain are preset and selectable via a switchable setting device.

Assignees

• Brose Fahrzeugteile

Inventors

• Geuther Udo
• Daiminger Ralf
• Russ Detlef

Classifications

• H03K17/955 Primary

  using a capacitive detector · CPC title

• H03K2217/960725

  Charge-transfer · CPC title

• G01M17/00

  Testing of vehicles (testing fluid tightness G01M3/00; testing elastic properties of bodies or chassis, e.g. torsion-testing, G01M5/00; testing alignment of vehicle headlight devices G01M11/06; testing of engines G01M15/00) · CPC title

• G01R27/2605 Primary

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

• H03K2217/96071

  characterised by the detection principle · CPC title