Electrode device, circuit arrangement and method for the approach and touch detection

1. Method for the approach and touch detection with a sensor device, which comprises at least one first electrode, one second electrode and one third electrode, wherein the sensor device can be operated in a first operation mode or in a second operation mode, the method comprising the steps of:

in each operating mode, supplying the first electrode with a first alternating electrical signal, so that a first alternating electric field is emitted at the first electrode,

in the first operation mode, evaluating a first electric signal which is received from the second electrode which detects said first alternating electric field, and

in the second operation mode, supplying the second electrode with a second alternating electrical signal, so that a second alternating electric field is emitted at the second electrode in addition to the first alternating electric field generated by the first electrode, which is coupled to the third electrode, wherein a second electric signal received from the third electrode is detected when an object approaches the sensor device thereby coupling the first alternating electric field and the second alternating electric field produce into the third electrode, and

in the second operation mode, evaluating the second electric signal which is received from the third electrode detecting said first and second alternating electric fields.

2. Method according to claim 1 , wherein a first predetermined threshold value, which is indicative for a touch of the sensor device by an object, is assigned to the first operation mode, wherein the sensor device changes from the first operation mode to the second operation mode, as soon as the first electric signal exceeds or falls below the first predetermined threshold value.

3. Method according to claim 1 , wherein a variable second threshold value, which is indicative for an approach of the object to the sensor device, is determined and assigned to the second operation mode, wherein determination of the second threshold value depends on a level of the first electric signal.

4. The method according to claim 1 , wherein when switching to the second operation mode, a frequency and/or amplitude of the first alternating electrical signal is adjusted.

5. The method according to claim 4 , wherein when operating in the first operation mode, changing from the first operation mode to the second operation mode, as soon as the first electric signal exceeds or falls below a first predetermined threshold value.

6. The method according to claim 4 , wherein when operating in the second operation mode, determining a second variable threshold value which depends on a level of the first electric signal.

7. The method according to claim 6 , further comprising the steps of:

generating a first detection signal as soon as the first electric signal exceeds or falls below the first predetermined threshold value, and

generating a second detection signal as soon as the second electric signal exceeds or falls below the second variable threshold value.

8. The method according to claim 7 , wherein the sensor device comprising at least the one first electrode, the one second electrode and the one third electrode is arranged within a mobile phone and wherein the method is performed within a mobile phone having a display and wherein the second detection signal causes said display to be turned off.

9. The method according to claim 4 , when operating in the first operation mode, using a first predetermined threshold value and when operating in the second operation mode, using a second variable threshold value which is determined after switching from the first to the second operating mode.

10. The method according to claim 1 , further comprising at least one fourth electrode.

11. The method according to claim 10 , wherein

in the second operation mode, generating a third alternating electric field through the fourth electrode and receiving, in addition to the first alternating electric field emitted at the first electrode and the second alternating electric field emitted at the second electrode, a third alternating electric field emitted at the fourth electrode by the third electrode.

12. The method according to claim 10 , wherein a third alternating electrical signal is fed to the fourth electrode and is selected in such a way, that, in the first operation mode, without interference by an object an alternating electric field emitted at the fourth electrode is substantially coupled only to the second electrode.

13. The method according to claim 10 , wherein the fourth electrode, the second electrode and the third electrode are arranged relative to each other, in such a way that without interference by an object an alternating electric field emitted at the fourth electrode is substantially coupled only into the second electrode.

14. The method according to claim 10 , wherein a third alternating electrical signal fed to the fourth electrode is dephased with respect to the first alternating electrical signal and/or has a lower amplitude with respect to the first alternating electrical signal.

15. The method according to claim 10 , wherein a third alternating electrical signal fed to the fourth electrode is in phase with the first alternating electrical signal.

16. The method according to claim 10 , further comprising: in the second operation mode, feeding a fourth alternating electrical signal to the fourth electrode thereby generating a fourth alternating electric field.

17. The method according to claim 10 , further comprising: in the second operation mode, feeding the first alternating electrical signal to the first electrode, wherein the second electric alternating signal is substantially in phase with the first alternating electrical signal.

18. The method according to claim 10 , wherein the sensor device comprising at least the one first electrode, the one second electrode and the one third electrode is arranged within a mobile device having a ground or mass and wherein the fourth electrode is coupled with the ground or mass of the mobile device in the first operation mode and/or in the second operation mode.