METHOD AND CIRCUIT FOR DETECTING THE PRESENCE, POSITION AND/OR APPROACH OF AN OBJECT IN RELATIVE TO AT LEAST ONE ELECTRODE

• US 20090219039A1
• Filed: 10/30/2006
• Published: 09/03/2009
• Est. Priority Date: 10/28/2005
• Status: Active Grant

• Current Assignee: Microchip Technology Germany GmbH (Microchip Technology Incorporated)
• Original Assignee: IDENT Technology AG (Microchip Technology Incorporated)
• Inventors: Fasshauer, Peter
• Granted Patent: US 7,969,166 B2
• Time in Patent Office: Days
• US Class Current: 324/682
• CPC Class Codes: G01V 3/088 operating with electric fields G01V3/082 takes precedence
• CPC Class Codes: H03K 17/955 using a capacitive detector

Abstract

A circuit for detecting the presence, position or the approach of an object in an observation area, the circuit has a sensor electrode assembly with an electrode that forms part of a capacitor system whose capacitance relative to a reference potential (e.g. ground) is dependent on the presence, position or approach of objects in the observation area. An evaluation circuit coupled to the sensor electrode detects a phase shift of the capacitance of the condenser system. An LC network is coupled to the capacitor system, and an oscillator connected to the electrode applies a frequency to the system formed by including the electrode and the LC network at a frequency within the range of a parallel resonance frequency of the LC network.

Claims

1. A circuit for detecting the presence, position or the approach of an object in an observation area, the circuit comprising:

a sensor electrode assembly comprising an electrode that forms part of a capacitor system whose capacitance relative to a reference potential is dependent on the presence, position or approach of objects in the observation area,

an evaluation circuit coupled to the sensor electrode for detecting a phase shift of the capacitance of the condenser system,

an LC network coupled to the capacitor system, and

a generator including an oscillator connected to the electrode for applying a frequency to the system formed by including the electrode and the LC network at a frequency within the range of a parallel resonance frequency of the LC network.

3. The circuit according to claims 1, wherein the phase shift is detected by comparing the actual phase of the capacitance of the generator with a comparison signal from the generator.

4. The circuit according to claim 1 wherein the signal from the generator is a generator trigger signal.

5. The circuit according to claim 1 wherein the signal from the generator is the generator potential.

6. The circuit according to claim 1 wherein the LC network comprises an inductor and at least one capacitor for forming a parallel resonant circuit.

9. The circuit according to at claim 1 wherein the evaluation circuit can also detect a change in capacitance of the capacitor system based on an amplitude change.

10. The circuit according to claim 9 wherein the evaluation circuit is embodied such that it considers both a phase shift and an amplitude change together.

11. The circuit according to claim 1 wherein in order to detect the phase shift, an exciter signal and a current, or a potential signal of the LC network are correlated.

12. A motor-vehicle door-locking system having a circuit according to claim 1.

13. A security system, having a circuit comprising a circuit according to claim 1.

14. A position-detection system, having a circuit according to claim 1.

15. The position-detection system according to claim 14 wherein the electrode includes at least one X-electrode for detecting a presence or approach in a first X-detection direction.

16. The position-detection system according to claim 15 wherein multiple X-electrodes are distributed at a spacing from one another across the observation area.

17. The position-detection system according to claim 14 wherein the electrode includes at least one Y electrode for detecting a presence or approach state in a second Y-detection direction.

18. The position-detection system according to claim 17 wherein multiple Y-electrodes are distributed across the observation area.

19. The position-detection system according to claim 14 wherein the electrode includes at least one Z-electrode for detecting a presence or approach state in a third detection direction.

2. (canceled)

7-8. -8. (canceled)

20. A method for detecting the presence of an object in an observation area, using a capacitor system including a sensor electrode whose capacitance is dependent on the presence of the object in an observation area, the method comprising the steps of:

operating a parallel resonant circuit formed by the capacitor system and an inductor to apply a generator potential at a frequency in the range of parallel resonance frequency of the resonant circuit, and

detecting a change of the phase of the exciter and not a resonance in the parallel resonant circuit to evaluate whether an object is present in the observation area.

21. The method according to claim 20 wherein the exciter frequency is varied.

22. The method according to claim 20, wherein the change of the exciter frequency occurs in dependence on the phase position.

23. The method according to claim 20 wherein a change of the exciter frequency is evaluated as a presence signal.

24. The method according to claim 20 wherein the resonance frequency of the circuit is changed by changing the capacitance or the inductance, of circuit elements of the resonant circuit.

25. A circuit for detecting the position or presence of an object in an observation area, the circuit comprising:

a sensor electrode assembly comprising a first electrode forming part of a capacitor system whose capacitance to a reference potential is dependent on the presence or position of objects in an observation area bordered by the first electrode,

an LC network coupled to the capacitor system and having a parallel resonance frequency,

a generator for applying a frequency to the electrode and the LC network at a frequency within the range of the parallel resonance frequency of the LC network, and

evaluating means coupled to the sensor electrode for tracking resonance behavior of the LC network in capacitance changes of the detection capacitor system including the sensor electrode.

26. The circuit according to claim 25 wherein the LC network includes a parallel-connected resonant circuit formed by an inductor and a capacitor and the potential created at the resonant circuit is fed back via an operational amplifier.

27. The circuit according to claim 25, further comprising

a varactor diode circuit or a gyrator near the LC network.

29. The circuit according to claim 27 wherein the tracking requirement at the gyrator or at the varactor diode circuit is used to detect an approach.

30. The circuit according to claim 25, further comprising the step of

retuning the system such that it runs at a defined phase shift between an exciter event and the resonance in the range of the parallel resonance frequency.

28. (canceled)