Controlling dynamic range

Abstract

A device (601) for controlling the dynamic range of a force sensing device includes a plurality of drive lines (606) and a plurality of sense lines (607) arranged to form a plurality of intersection points to define a plurality of keys. Each key includes a sensing element (602) exhibiting a variable resistance. A controller (603) is configured to convert an analog output from each sensing element into a digital output, and an input amplifier is configured to provide a signal gain to adjust a range of the controller by the signal gain. The input amplifier includes a transimpedance amplifier (604) connected to a gain resistor (605).

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to UK patent application No. 22 09 719.0 filed on July 1, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a device for controlling the dynamic range of a force sensing device and a method for controlling the dynamic range of a force sensing device. Background Art

[0004] Many modern electronic devices use keyboards as input devices for the electronic devices. A conventional keyboard may use a switch-type mechanism, wherein the keys on the keyboard operate in a conventional on / off mode. Another type of keyboard includes a membrane having a matrix structure in the membrane including a plurality of keys, the keys being located at each intersection of the matrix.

[0005] In use, when several keys on a matrix keyboard are pressed at the same time, the current in the matrix will cause the unpressed keys to be activated. This phenomenon is called the "ghost key phenomenon", and the activated unpressed keys are called "ghost keys". In addition, another problem faced by matrix keyboards is crosstalk, that is, when a key is pressed, several keys in the same row or column of the matrix will be activated.

[0006] Another problem with these keyboards is that they typically contain a large number of sensing elements for measuring force. Typically, there are as many keys on a keyboard as there are sensing elements. During production and manufacturing, the sensing elements may experience manufacturing variations, resulting in the output response varying from key to key when the sensing element corresponding to a particular key is activated. Therefore, it is difficult to achieve consistent characteristics and signal range for each sensing element. In addition, force sensors with low sensitivity or small resistance changes can only utilize a small portion of the dynamic range, resulting in low sensitivity.

[0007] Traditional systems use a voltage divider input combined with a force sensing resistor. However, this approach does not provide a suitable method or architecture to optimize low and high force inputs. Summary of the invention

[0008] According to one aspect of the present invention, there is provided a device for controlling the dynamic range of a force sensing device, comprising: a plurality of drive lines and a plurality of sense lines, arranged to form a plurality of intersections to define a plurality of keys; each of the keys comprising a sensing element exhibiting a variable resistance, the device further comprising: a controller configured to convert an analog output from each of the sensing elements into a digital output; an input amplifier configured to provide a signal gain so that the range of the controller is adjusted by the signal gain, the input amplifier comprising a transimpedance amplifier connected to a gain resistor.

[0009] The apparatus may be arranged to form an electronic keyboard or integrated in an electronic device.

[0010] According to a second aspect of the present invention, there is provided a method for controlling the dynamic range of a force sensing device, comprising the following steps: providing a device comprising a plurality of drive lines and a plurality of sense lines arranged to form a plurality of intersections to define a plurality of keys, each of the keys comprising a sensing element exhibiting a variable resistance; activating the sensing element in response to a mechanical interaction; providing a current to an input amplifier in response to the mechanical interaction from the sensing element, the input amplifier comprising a transimpedance amplifier connected to a gain resistor; receiving a signal gain from a response to the input amplifier; and adjusting the range of a controller configured to convert an analog output from each of the sensing elements into a digital output by means of the signal gain.

[0011] The embodiments of the present invention are described by way of example only and are illustrated with reference to the accompanying drawings. The detailed embodiments illustrate the best implementation known to the inventors and provide support for the claimed invention. However, the embodiments are exemplary only and should not be used to interpret or limit the scope of the claimed invention. The purpose of the embodiments is to provide guidance to those skilled in the art. Components and processes distinguished by ordinal numbers such as "first" and "second" do not necessarily define any order or priority. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 An electronic device including a keyboard having a plurality of keys is shown;

[0013] Figure 2 A schematic diagram showing an exemplary sensing array suitable for a membrane keyboard is shown;

[0014] Figure 3 A simplified circuit diagram of an apparatus for detecting mechanical interactions is shown, the apparatus including a keyboard membrane having force sensing capabilities;

[0015] Figure 4 Shows Figure 5 A simplified circuit diagram of a circuit with multiple keys pressed.

[0016] Figure 5 a graph showing typical characteristics of a plurality of sensing elements;

[0017] Figure 6 A schematic diagram of an inverting transimpedance amplifier with an integrated force sensing resistor element is shown;

[0018] Figure 7 An exemplary embodiment of an analog-to-digital converter with a range of applications and an optimized dynamic range is shown.

[0019] Figure 8 A circuit schematic for optimizing dynamic range using bias resistors is shown;

[0020] Fig. 9 An exemplary embodiment with a calibrated sensing element to optimize dynamic range is shown;

[0021] Fig.10 A schematic diagram showing another circuit using a bias resistor;

[0022] Fig.11 A circuit schematic diagram showing another exemplary embodiment using a gain resistor; and

[0023] Fig.12 A schematic diagram of another embodiment of a circuit including a dynamic switch is shown. DETAILED DESCRIPTION

[0024] Figure 1

[0025] Figure 1 A typical scenario of an electronic device including a keyboard is shown. The electronic device 101 includes a personal computer, which includes a display 102 and a keyboard 103. In this embodiment, the keyboard 103 includes a plurality of keys 104 arranged in the form of a keyboard membrane. When pressure is applied to each key, each key provides input to the electronic device 101 to control an application running on the electronic device 101.

[0026] In one embodiment, any one of the plurality of keys 104 may be used to control a gaming application, which in one embodiment, for example, may include controlling a character or the like, requiring simultaneous pressing of the plurality of keys 104 to activate the plurality of keys simultaneously. In this manner, the electronic device 101 is configured to allow simultaneous pressing of the plurality of keys, which may occur on the keyboard membrane where the keys 104 are located.

[0027] Figure 2

[0028] Figure 2The keyboard film (eg, the front Figure 1 Schematic diagram of an exemplary sensing array of a keyboard membrane described herein.

[0029] The sensing array 201 includes a plurality of conductive rows 202 and a plurality of conductive columns 203. In this embodiment, the driving control unit 204 is configured to sequentially provide voltages to the plurality of conductive columns 203 or driving lines to make current flow through the driving lines.

[0030] The sensing array 201 also includes a sensing control unit 205 configured to receive outputs from the plurality of conductive rows 202 or sensing lines. In this embodiment, the outputs are received in analog form and converted to digital outputs by an analog-to-digital converter or similar device as required.

[0031] In this embodiment, the sensing array 201 includes a plurality of sensing elements arranged at each intersection between the drive line 202 and the sensing line 203. Each sensing element includes a material that exhibits a variable resistance in response to an applied force. Since each sensing element corresponds one-to-one to a plurality of keys of the keyboard 103, when a force is applied to a key (or sensing element), the resistance of the sensing element decreases, and current flows through the sensing element and the intersection.

[0032] In one embodiment, the sensing element comprises a quantum tunneling material (e.g. manufactured by the applicant Peratech Holdco Limited under the trademark materials for sale).

[0033] In one embodiment, multiple rows and multiple columns are arranged on the upper conductive layer and the lower conductive layer, and the sensing layer defining the sensing element is applied to the column or row. When pressure is applied, the sensing layer contacts the opposite conductive layer and is compressed to reduce the resistance of the sensing layer. In this way, the resistance of each sensing element depends on the applied force or area, such as the magnitude of the force applied to a key on the keyboard 103.

[0034] In another embodiment, the sensing element includes a conductive finger electrode including a first plurality of interdigitated fingers and a second plurality of interdigitated fingers on a single conductive layer, and a second layer including a variable resistance material. In this way, the sensing array can provide a pressure output across two layers. It should be understood that in other embodiments, other arrangements can be used.

[0035] Thus, in use, such as in the present embodiment, the drive line 206 is driven by the drive control unit 204 , and when the sensing element 207 is activated due to the applied force, current flows through the sensing line 208 to the sensing control unit 205 .

[0036] Although the described examples use a keyboard with a keyboard membrane, it should be understood that the present invention is also applicable to other keyboard arrangements using multiple sensing elements (such as Figure 2 described in ).

[0037] Figure 3

[0038] Figure 3 A simplified circuit diagram of a keyboard membrane for a keyboard using force sensing resistors is shown in the form of a circuit schematic.

[0039] In this embodiment, the device 301 includes a keyboard membrane 302 , an input amplifier unit 303 and a controller 304 .

[0040] The keyboard film 302 includes a plurality of drive lines arranged as a plurality of columns 304 and a plurality of sensing lines arranged as a plurality of rows 305. There are keys at each intersection between the plurality of columns 304 and the plurality of rows 305, such as keys 306, 307, 308 and 309. In the present embodiment, each key includes a sensing element with a variable resistor and is represented by a variable resistor. Therefore, when each key is subjected to an applied force or pressure, the resistance through the key is reduced. The measurement of such force can be carried out in an analog manner by the structure described herein, which can represent the pressure magnitude applied to a given key.

[0041] In the present embodiment, the input amplifier unit 307 is shown as a plurality of input amplifiers corresponding to each sensing line or row. Each input amplifier is configured to provide a voltage potential to any inactive drive line or inactive sensing line. The input amplifier unit 307 provides an output voltage to the controller 304, which is determined by the state of each key pressed. In the present embodiment, each input amplifier includes a transimpedance amplifier that provides a low impedance.

[0042] The controller 304 includes means for converting analog outputs into digital signals for further processing. In the present embodiment, this includes an analog-to-digital converter 310, which converts the analog output of each key or sensing element into a digital output for further processing when force is applied to the relevant key. In another embodiment, the analog-to-digital converter may be replaced by an alternative means such as a Schmitt Trigger to convert the output of the input amplifier unit 303 from an analog output to a digital output.

[0043] In the illustrated embodiment, the keyboard membrane 302 includes three rows and three columns. It should be understood that, in practice, many keyboard membranes are much larger, but the operating principles are basically similar.

[0044] Figure 4

[0045] Figure 4 Again, a schematic diagram of the device 301 is shown, in which force is simultaneously applied to keys 306, 307, 308 and 309. In this embodiment, as force is applied to each key, the resistance on each key decreases. In this way, current can flow more freely from the input provided on the drive line to the output of the controller 304 via the input amplifier 303.

[0046] In this embodiment, a voltage is applied to drive line 304B, and when key 309 is read, current is transmitted along 304B and across line 305B through amplifier 403 to analog-to-digital converter 310. Although each of keys 306, 307, and 308 has been pressed, they are blocked due to the high voltage of 401. Although key 307 is activated on the same column as key 309, the conduction path through key 307 is not read, and the voltage in the circuit can be controlled by amplifier 403 to prevent interference.

[0047] In another embodiment, the voltage amplifier may include a voltage buffer amplifier configured to drive the voltage potential of each of the inactive drive lines and inactive sense lines, and a multiplexer configured to sequentially activate each drive line. This provides an alternative to providing a transimpedance amplifier on each sense line. This is particularly advantageous for large sense array matrices because it can reduce the number of components required for the key.

[0048] In examples that include a sensing element, it is advantageous to obtain readings in an analog format because this provides the entire force spectrum for a given applied pressure. During scanning, each key that includes a sensing element can be modeled as a variable resistor to show how resistance changes with applied force.

[0049] Each transimpedance amplifier provides a controlled input voltage through a virtual ground, thereby sinking current at the input node. Therefore, the voltage can be controlled at the input node and current can be blocked from flowing through the transimpedance amplifier when sinking current.

[0050] In this way, the present invention allows any number of keys to be pressed at a given time without any restrictions on the size of the matrix array. In this way, in gaming applications, multiple keys can be pressed simultaneously, and this can be controlled by a larger keyboard and a larger matrix.

[0051] Figure 5

[0052] Figure 5 Graph showing typical force sensing characteristics of a sense element used in a typical sense array according to the present application.

[0053] Figure 5A plurality of force resistance curves 501, 502 and 503 are shown, each curve representing a separate sensing element. Curve 502 represents the average force resistance response of a typical sensing element according to the present invention. However, it should be understood that for a plurality of sensing elements, such as those constituting an electronic keyboard (e.g. Figure 1 For sensing elements of an electronic keyboard 103 in FIG. 1 , each sensing element may have a difference 504 in force resistance response, as shown by curves 501 and 503. The difference 504 may be large and may affect the output from multiple keys 104. Therefore, this factor must be taken into account when optimizing the response of any key 104.

[0054] In this embodiment, the force resistance response represents the dynamic range 505 of the force sensing device. In conventional systems, the corresponding dynamic range 506 of the analog-to-digital converter (ADC) matches the dynamic range of the sensing element 505 without further calibration.

[0055] Therefore, in this manner, any force sensing device with low sensitivity or small resistance change may only be able to utilize a small portion of the dynamic range 506. This will result in poor sensitivity, poor signal-to-noise ratio (SNR), poor resolution, and potentially low yield.

[0056] Therefore, while in some applications it may be sufficient to use the same dynamic range 505 of the force sensing element as the dynamic range 506 of the ADC, the circuit may still need to be adjusted to accommodate the dynamic range 506 of the analog-to-digital converter.

[0057] Figure 6

[0058] Figure 6 A schematic diagram of a circuit that can be used to control the dynamic range of an analog-to-digital converter (ADC) is shown.

[0059] The circuit schematic is shown as an inverting amplifier mode. However, it will be appreciated that the examples described therein may also be provided as non-inverting versions by following substantially similar principles as described herein. However, for simplicity, the present application focuses on the entire inverting amplifier mode and a single sensing element, which may further form part of a sensing array and electronic keyboard as previously described.

[0060] In this embodiment, the device 601 includes a sensing element 602, which provides a force sensing resistor with a variable resistance. The sensing element 602 is represented as a variable resistor with a variable resistance value. The controller 603 includes an analog-to-digital converter configured to convert the analog output of the force sensing resistor 602 into a digital output.

[0061] The sensing element 602 is electrically connected to the controller 603 via a transimpedance amplifier 604 arranged with a gain resistor 605 . The transimpedance amplifier is configured to convert the signal from the sensing element 602 into a voltage for sampling by the controller 603 .

[0062] Typically, the transimpedance amplifier 604 provides signal gain through the resistor 605 to adjust the lowest measurable resistance from the sensing element 602 to the lower range of the controller 603. Figure 6 In the inverting amplifier mode shown, the sense element 602 is configured with a lower resistance value and measures at the low end of the ADC dynamic range. In embodiments where the amplifier is provided in a non-inverting amplifier mode, the high end of the ADC dynamic range is configured by corresponding circuitry.

[0063] In this embodiment, voltage V+ is provided along drive line 606 to drive sense element 602. When activated, the voltage across sense element 602 passes through sense line 607, resistor 605 and transimpedance amplifier 604 to provide a voltage output V OUT In this mode, the controller 603 is configured in single-ended mode, measuring the voltage from zero to the reference voltage V REF The output voltage between V OUT Thus, the output voltage can be calculated from the resistance values ​​of the force sensing element 602 , the gain resistor 605 , and the transimpedance amplifier 604 .

[0064] Therefore, the dynamic range of the ADC can be calculated to lie between infinity and a value determined by the reference voltage (V REF ) multiplied by the gain resistor and divided by the reference voltage (T REF ) calculated.

[0065] In conventional systems, parameters are usually set so that the dynamic range of the ADC 603 covers the entire dynamic range of the sensing element 602. In some cases, as mentioned previously, it may be difficult to achieve a good signal-to-noise ratio, especially when the sensing element has large variations. Therefore, in some applications, it is preferred to allow a narrower resistance range, which means limiting not only the lowest resistance, but also the highest resistance that can be measured. Therefore, Figure 6 The example can be adapted to use different reference voltage combinations to achieve customization of the dynamic range.

[0066] For example, if the reference voltage (V REF ) is reduced to a value lower than the transimpedance amplifier voltage (T REF ), a compensation effect similar to that of adding a bias resistor can be produced. According to the present invention, this method can produce a more suitable dynamic range.

[0067] Figure 7

[0068] Therefore, the embodiments described herein can provide Figure 7 Another method consistent with the example shown. Figure 7 shows another force resistance diagram, replicating the Figure 5 501, 502 and 503 are shown in FIG. Each of the curves 501, 502 and 503 is related to a sensing element that may be present in the electronic keyboard example.

[0069] In this embodiment, an application range 701 is shown within which the preferred sensitivity is associated with the sensing element used in a particular application. Thus, in this embodiment, the dynamic range 702 of the analog-to-digital converter can be calculated as Figure 7 Thus, the circuits described herein can adjust the performance of the sensing element to a more ideal application range 701 while accommodating variations between each sensing element 504 .

[0070] This optimization range can be obtained by Figure 6 The device shown in FIG. 1 is implemented, but it can also be further implemented by Figure 8 The embodiment shown in is implemented.

[0071] Figure 8

[0072] Figure 8 Shown according to Figure 7 The diagram shown is a schematic diagram of a circuit for optimizing the dynamic range of an analog-to-digital converter.

[0073] Figure 8 Examples and Figure 6 The embodiment of is substantially similar, only a bias resistor 801 is added, which further controls and converts the response from the sensing element 802 by limiting the highest measurable resistance. Therefore, in this embodiment, the device also includes a transimpedance amplifier 803 and a gain resistor 804, which are also electrically connected between the sensing element 802 and the controller including the analog-to-digital converter 805.

[0074] In a similar manner, voltage V+ is applied along drive line 806 and is transmitted along sense line 807 after sense element 802 is activated.

[0075] In this embodiment, the combination of resistors 801 and 804 can control the upper and lower limits of the resistance range so that the dynamic range of the analog-to-digital converter is fully optimized to match the range of the force sensing element used in a specific application.

[0076] Fig. 9

[0077] Another embodiment provides a further reconfiguration of the device, incorporating dynamic switching to provide greater flexibility in terms of throughput and signal-to-noise ratio output. In this embodiment, force-resistance curves 501, 502, and 503 corresponding to multiple sensing elements have a variation 504 and an application range 701. However, in addition, calibration of each sensing element may produce three independent dynamic ranges 901, 902, and 903 for the analog-to-digital controller. Dynamic ranges 901, 902, and 903 correspond to force-resistance curves 501, 502, and 503, respectively.

[0078] In this way, the device can be configured to select from dynamic ranges 901, 902 and 903 according to the requirements of the relevant application.

[0079] In special cases where the force-resistance response includes lower gradients, these narrower ranges can be exploited to improve signal-to-noise quality. Wider ranges can allow sensing elements with more significant resistance changes to operate within the measurable range of the analog-to-digital converter to further improve yield.

[0080] An example circuit that provides this functionality is Fig.10 shown.

[0081] Fig.10

[0082] In this embodiment, the sensing element 1001 is electrically connected to the analog-to-digital converter 1002 through a transimpedance amplifier 1003 and a gain resistor 1004. In addition, a bias resistor 1005 is included, and an electrical switch 1006 is provided, which can activate or deactivate the bias resistor 1005 as needed. Therefore, in this embodiment, the range can be further controlled by activating or deactivating the switch 1006 as needed. This is conducive to achieving the control of the upper and lower limits.

[0083] This provides a relatively low cost solution as only a single switch control and a number of fixed resistors need to be provided in addition to the existing circuitry.

[0084] Fig.11

[0085] Fig.11 A circuit diagram in another exemplary embodiment of the present invention is shown.

[0086] In this embodiment, Fig.11 The circuit in the previous Figure 8 The circuit shown in is basically similar, and includes a sensing element 1101 and an analog-to-digital converter 1102, which are electrically connected via a transimpedance amplifier 1103 and a resistor 1104. A bias resistor 1105 is also included in this embodiment.

[0087] In this embodiment, Figure 8 and Fig.10 The fixed resistors in the DAC have been replaced by high resolution digitally controlled resistor arrays (RDACs). This provides a more complex solution that incorporates variable resistors. However, it should be understood that its use may be driven by cost.

[0088] Fig.12

[0089] Fig.12 A circuit schematic of another embodiment is shown, which includes dynamic switching.

[0090] In this embodiment, the sensing element 1201 is again connected to the analog-to-digital converter 1202 through a transimpedance amplifier 1203 and a gain resistor 1204 .

[0091] In this embodiment, the reference voltage V of the analog-to-digital converter 1202 REF and the reference voltage T of the transimpedance amplifier 1203 REF Digital control is performed via a voltage digital-to-analog converter (DAC).

[0092] Therefore, in Fig.12 In the embodiment of the present invention, an n-bit digital-to-analog converter 1205 is connected to the analog-to-digital converter 1202, and another n-bit digital-to-analog converter 1206 is electrically connected to the transimpedance amplifier 1203. Correspondingly, the reference voltage V REF and T REF For further digital control and dynamic switching.

[0093] This combination of reference voltages provides a substantially similar optimization range for the analog-to-digital converter using the corresponding resistors in the previous example. Fig.11 This particular approach may be more cost effective than the example shown, especially if one or more voltage DACs are already built into the system.

Claims

1. A device for controlling the dynamic range of a force sensing device, comprising: A plurality of driving lines and a plurality of sensing lines are arranged to form a plurality of intersections to define a plurality of keys; Each of the keys includes a sensing element exhibiting a variable resistance, and the apparatus further includes: a controller configured to convert an analog output from each of the sensing elements into a digital output; An input amplifier is configured to provide signal gain such that the range of the controller is adjusted by the signal gain, the input amplifier comprising a transimpedance amplifier connected to a gain resistor.

2. The device according to claim 1, wherein: The signal gain is provided by the gain resistor.

3. The device according to claim 1 or 2, wherein: The gain resistors include a high resolution digitally controlled resistor array. 4 . The device according to claim 1 , further comprising a bias resistor configured to limit an upper limit of a measured resistance of the sensing element. 5 . The apparatus of claim 4 , further comprising an electrical switch configured to activate and deactivate the bias resistor.

6. The device according to claim 4 or 5, wherein: The bias resistors include a high-resolution digitally controlled resistor array.

7. A device according to any one of the preceding claims, wherein: The input amplifier is further configured to provide a voltage potential to each of the inactivated drive lines and each of the inactivated sense lines.

8. A device according to any one of the preceding claims, wherein: The plurality of driving lines are arranged into a plurality of columns, and the plurality of sensing lines are arranged into a plurality of rows, so as to form a sensing array.

9. The device according to any one of the preceding claims, wherein: Each of the sensing elements includes a quantum tunneling material.

10. The apparatus of any preceding claim, further comprising a voltage digital-to-analog converter configured to control a reference voltage.

11. The device according to claim 10, wherein: The reference voltage is a reference voltage from the controller.

12. The device according to claim 10, wherein: The reference voltage is a reference voltage from the input amplifier.

13. A device according to any one of the preceding claims, wherein: The device forms part of an electronic keyboard.

14. An electronic device comprising the device according to any one of the above claims.

15. A method for controlling the dynamic range of a force sensing device, comprising the steps of: Providing an apparatus comprising a plurality of drive lines and a plurality of sense lines arranged to form a plurality of intersections to define a plurality of keys, each of the keys comprising a sense element exhibiting a variable resistance; activating the sensing element in response to a mechanical interaction; providing a current to an input amplifier in response to the mechanical interaction from the sensing element, the input amplifier comprising a transimpedance amplifier connected to a gain resistor; receiving a signal gain from a response to said input amplifier; as well as A range of a controller configured to convert an analog output from each of the sensing elements to a digital output by the signal gain is adjusted.

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