Displacement detection device for a portable apparatus

• US 20060213267A1
• Filed: 11/30/2005
• Published: 09/28/2006
• Est. Priority Date: 12/01/2004
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Tronconi, Michele, Pasolini, Fabio, Chiesa, Enrico
• Granted Patent: US 7,672,806 B2
• Time in Patent Office: Days
• US Class Current: 73/510
• CPC Class Codes: G01P 15/0891 with indication of predetermined acceleration values G01P15/135 takes precedence
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G11B 19/04 Arrangements for preventing, inhibiting, or warning against double recording on the same blank or against other recording or reproducing malfunctions

Abstract

In a displacement detection device, an acceleration sensor generates at least a first acceleration signal relating to an axis of detection, and a displacement detection circuit is connected to the acceleration sensor has a comparator stage for comparing the acceleration signal with a programmable acceleration threshold and generates a displacement-detection signal. A high-pass filter is arranged between the acceleration sensor and the comparator stage so as to reduce a DC component of the acceleration signal. The cut-off frequency of the high-pass filter is modified according to the type of displacements that are to be detected.

Claims

1. A displacement detection device, comprising:

an acceleration sensor generating a first acceleration signal relating to a first axis of detection; and

a displacement detection circuit connected to said acceleration sensor and comprising a first comparator stage for comparing said first acceleration signal with a first acceleration threshold and generating a first displacement detection signal, said displacement detection circuit further comprises first filtering means arranged between said acceleration sensor and said first comparator stage and configured to reduce a DC component of said first acceleration signal.

2. The device of claim 1 wherein said first filtering means comprise a high-pass filter.

3. The device of claim 1 wherein said first filtering means comprise a proportional-integral controller or a band-pass filter.

4. The device of claim 1, further comprising cut-off frequency modifying means connected to said first filtering means for modifying the cut-off frequency of said first filtering means.

5. The device of claim 1 wherein said acceleration sensor and said displacement detection circuit are integrated in a single chip.

6. The device of claim 1 wherein said displacement detection circuit comprises a second comparator stage for comparing said first acceleration signal with a second acceleration threshold lower than said first acceleration threshold.

7. The device of claim 6 wherein said first and second acceleration thresholds are settable, and said displacement detection circuit comprises a first memory element storing said first acceleration threshold and a second memory element storing said second acceleration threshold.

8. The device of claim 6 wherein said displacement detection circuit further comprises a hysteresis memory element having a first input and a second input;

said first comparator stage having an output connected to said first input, and said second comparator stage having an output connected to said second input.

9. The device of claim 8 wherein said hysteresis memory element comprises a set/reset register.

10. The device of claim 1 wherein said displacement detection circuit further comprises an enabling stage connected to said first comparator stage and receiving an enabling signal, said enabling stage configured to supply at an output said first displacement-detection signal when said enabling signal satisfies a given condition.

11. The device of claim 7 wherein said displacement detection circuit further comprises a third memory element cascaded to said first comparator stage and configured to store said first displacement-detection signal.

12. The device of claim 1 wherein said acceleration sensor comprises a linear accelerometer with three axes of detection further generating a second acceleration signal and a third acceleration signal, said first, second, and third acceleration signals relating to a component of the acceleration along a respective axis of detection;

and wherein said displacement detection circuit further comprises a second comparator stage and a third comparator stage for comparing, respectively, said second and third acceleration signals with said first acceleration threshold and generating a second displacement-detection signal and a third displacement-detection signal; and

second and third filtering means arranged, respectively, between said acceleration sensor and said second and third comparator stages and configured to reduce a DC component, respectively, of said second acceleration signal and of said third acceleration signal.

13. The device of claim 1, further comprising a microprocessor connected to said displacement detection circuit;

and wherein said acceleration sensor, said displacement detection circuit and said microprocessor are integrated in a single chip.

18. A portable apparatus, comprising a displacement detection device according to claim 1, said portable apparatus chosen from the group comprising laptops, PDAs, audio players, cellphones, and video cameras.

19. The portable apparatus of claim 18, further comprising a microprocessor, said microprocessor connected to an output of said displacement detection device for determining the direction of displacement of said portable apparatus.

14. A method for detection of the displacements of a portable apparatus, comprising:

detecting at least a first acceleration signal correlated with the acceleration of said portable apparatus along a first axis of detection;

comparing said first acceleration signal with a first acceleration threshold;

generating a first displacement-detection signal based on the comparison between said first acceleration signal and said first acceleration threshold; and

attenuating by filtering a DC component of said first acceleration signal before comparing said first acceleration signal with said first acceleration threshold.

15. The method of claim 14, further comprising modifying a cut-off frequency associated with said attenuating by filtering, said modifying the cut-off frequency carried out before said attenuating by filtering.

16. The method of claim 15 wherein modifying comprises selecting a mode of operation chosen between at least a first mode associated with fast movements of said portable apparatus, and a second mode associated with slow movements of said portable apparatus, said modifying step further comprising increasing said cut-off frequency in said first mode and decreasing said cut-off frequency in said second mode.

17. The method of claim 14, further comprising:

detecting a second acceleration signal and a third acceleration signal correlated with the acceleration of said portable apparatus along a second axis of detection and a third axis of detection, respectively;

attenuating by filtering a DC component of said second acceleration signal and of said third acceleration signal; and

after attenuating by filtering, comparing said second acceleration signal and said third acceleration signal with said first acceleration threshold for generating, respectively, a second displacement-detection signal and a third displacement-detection signal.

20. A circuit, comprising:

an input circuit receiving an external acceleration signal and generating therefrom a filtered acceleration signal having a reduced DC component;

a detection circuit receiving the filtered acceleration signal and further receiving a threshold signal and generating in response thereto a detection signal; and

a microprocessor receiving the detection signal and generating in response thereto an actuation signal.

21. The circuit of claim 20 wherein the microprocessor is configured to determine a direction of movement in response to the detection signal.

22. The circuit of claim 20, further comprising a threshold circuit configured to provide the threshold signal.

23. The circuit of claim 22 wherein the threshold circuit is configured to provide adjustment to the threshold signal.

24. The circuit of claim 22 wherein the input circuit comprises a filtering circuit configured to filter the external acceleration signal and to generate the filtered acceleration signal.

25. The circuit of claim 24 wherein the filtering circuit is adapted to provide adjustment in the filtering of the acceleration signal.

26. A circuit for processing an acceleration signal, comprising:

an input circuit configured to receive an external acceleration signal and to generate a filtered acceleration signal;

a first threshold signal circuit configured to store and output a first threshold signal;

a comparator circuit configured to receive the first acceleration signal and the first threshold signal and to output a detection signal; and

an enabling circuit configured to receive the detection signal and an external enabling signal and to generate a logic signal in response thereto.

27. The circuit of claim 26, further comprising a second comparator circuit and a second threshold circuit storing a second threshold signal, the second comparator circuit configured to receive the second threshold signal and the filtered acceleration signal and to output a further detection signal, and further comprising a latch circuit configured to receive the detection signal and the further detection signal and to output a displacement detection signal to the enabling circuit.

28. The circuit of claim 27, further comprising a displacement register to receive an output of the enabling circuit.

29. The circuit of claim 26, further comprising a modification circuit configured to generate a modification signal that is received by the filter circuit to modify the filtered acceleration signal generated by the filter circuit.

30. The circuit of claim 26, further comprising a plurality of input circuits, each configured to receive an external acceleration signal corresponding to a different direction of acceleration, and a plurality of comparator circuits each receiving as input the first threshold signal and a respective acceleration signal from a respective input circuit;

and a plurality of enable circuits, each enable circuit configured to receive a detection signal from a respective comparator circuit and to receive a respective external enabling signal and to output a logic signal.

31. The circuit of claim 30, further comprising a plurality of modification circuits, each coupled to a respective input circuit to modify filtering of the acceleration signal to generate the filtered acceleration signal.