Capacitive touch detection circuit and touch chip

Abstract

The utility model relates to a kind of capacitive touch detection circuit and touch chip, involve detection technical field.The capacitive touch detection circuit includes amplification module, detection module and signal amount control module in it.The signal amount control module is provided in the detection circuit, the charge quantity in the detection circuit is changed, and due to being provided, the input value of operational amplifier can no longer be limited, so as to regulate and control the numerical value of detection signal amount, make it become larger, so that the small change of capacitor is more easily detected, greatly improve the sensitivity and accuracy of detection circuit.Moreover, its detection circuit structure is simple, and faster detection speed can be realized at low cost.

Description

Technical Field

[0001] This application relates to the field of detection technology, and in particular to a capacitive touch detection circuit and a touch chip. Background Technology

[0002] With the widespread application of touch devices in smartphones, tablets, touch screen all-in-one machines, self-service terminals and other devices, the convenience and intuitiveness of human-computer interaction have been greatly improved, and touch sensitivity has become an essential testing process for touch devices.

[0003] Existing touch detection solutions use charge transfer and comparators, employing capacitors to detect changes in voltage or current caused by touch, and then using the comparator's result to determine if a touch action has occurred. However, this detection method has very low accuracy, cannot distinguish between light and heavy touches, and in some scenarios, the signal changes caused by touch actions are usually very small, such as touches while wearing gloves, touches by children, or touches from a distance, sometimes making it impossible to detect whether a touch has occurred. Utility Model Content

[0004] Therefore, it is necessary to provide a capacitive touch detection circuit and touch chip to address the problems of inaccurate and insensitive touch detection.

[0005] To achieve the above objectives, this utility model provides a capacitive touch detection circuit, comprising:

[0006] An amplification module includes an operational amplifier, a first capacitor, and a first switching unit. A first terminal of the first capacitor is connected to a first input terminal of the operational amplifier, and a second terminal of the first capacitor is connected to an output terminal of the operational amplifier. The first switching unit is connected to the first capacitor to control the amount of charge on the first capacitor under different switching states.

[0007] The detection module includes a second capacitor and a second switching unit. The second capacitor is connected between the second switching unit and the ground terminal. The second switching unit is used to connect the second capacitor to voltage V3 or to the first input terminal of the operational amplifier under different switching states, so as to control the amount of charge on the second capacitor.

[0008] The signal control module includes a third capacitor and a third switching unit. The third capacitor is connected between the third switching unit and the first input terminal of the operational amplifier. The third switching unit is used to connect the third capacitor to voltage V1 or voltage V2 in different switching states to control the amount of charge on the third capacitor.

[0009] in, Where C3 is the capacitance of the third capacitor, C2 is the capacitance of the second capacitor, and VCM The voltage value input to the second input terminal of the operational amplifier.

[0010] In one embodiment, the different switching states include a first switching state and a second switching state;

[0011] The amount of charge in the detection circuit in the first switching state is equal to the amount of charge in the detection circuit in the second switching state.

[0012] In one embodiment, the first switching unit is connected to the first capacitor to control the amount of charge on the first capacitor in different switching states based on voltage or not based on voltage.

[0013] In one embodiment, the first switching unit includes a switch S1; the switch S1 is connected in parallel with the first capacitor;

[0014] In the first switch state, switch S1 is closed; in the second switch state, switch S1 is open.

[0015] In one embodiment, the first switching unit includes switch S2, switch S3 and switch S4;

[0016] The switch S2 is connected between the second terminal of the first capacitor and the output terminal of the operational amplifier.

[0017] The switch S3 is connected between the second terminal of the first capacitor and the voltage V4;

[0018] The switch S4 is connected between the first terminal of the first capacitor and the voltage V5;

[0019] Wherein, the voltage value of voltage V5 is the same as the voltage value input to the second input terminal of the operational amplifier, and in the first switching state, switch S2 is open, and switches S3 and S4 are closed; in the second switching state, switch S2 is closed, and switches S3 and S4 are open.

[0020] In one embodiment, the second switching unit includes switch S5 and switch S6;

[0021] The switch S5 is connected between the first terminal of the second capacitor and the voltage V3, and the second terminal of the second capacitor is connected to the ground terminal;

[0022] The switch S6 is connected between the first terminal of the second capacitor and the first input terminal of the operational amplifier.

[0023] In the first switch state, switch S5 is closed and switch S6 is open; in the second switch state, switch S5 is open and switch S6 is closed.

[0024] In one embodiment, the third switching unit includes switch S7 and switch S8;

[0025] The switch S7 is connected between the first terminal of the third capacitor and the voltage V1, the switch S8 is connected between the first terminal of the third capacitor and the voltage V2, and the second terminal of the third capacitor is connected to the first input terminal of the operational amplifier;

[0026] In the first switch state, switch S7 is closed and switch S8 is open; in the second switch state, switch S7 is open and switch S8 is closed.

[0027] In one embodiment, the detection circuit further includes:

[0028] The control module is used to control the closing and opening of the switches in the first switch unit, the second switch unit, and the third switch unit under different switching states, thereby controlling the amount of charge on the capacitor in the detection circuit.

[0029] In one embodiment, the operational amplifier includes a programmable gain amplifier.

[0030] On the other hand, this application also provides a touch chip, including any of the detection circuits described above.

[0031] Compared with existing technologies, the above technical solution has the following advantages:

[0032] This application provides a capacitive touch detection circuit and a touch chip. The capacitive touch detection circuit includes an amplification module, a detection module, and a signal control module. The amplification module includes an operational amplifier, a first capacitor, and a first switching unit. The two ends of the first capacitor are connected to the first input and output terminals of the operational amplifier, respectively. The first switching unit is connected to the first capacitor to control the charge on the first capacitor under different switching states. The detection module includes a second capacitor and a second switching unit. The second switching unit controls the second capacitor to connect to voltage V3 or to the second input terminal of the operational amplifier under different switching states, thereby controlling the charge on the second capacitor. The signal control module includes a third capacitor and a third switching unit. The third capacitor is located between the third switching unit and the first input terminal of the operational amplifier. The third switching unit controls the third capacitor to connect to voltage V1 or voltage V2 under different switching states, thereby controlling the charge on the third capacitor. This detection circuit includes a signal control module, which changes the charge in the detection circuit, and because of the inclusion of the signal control module… Where C3 is the capacitance of the third capacitor, C2 is the capacitance of the second capacitor, and V CM The voltage value input to the second input terminal of the operational amplifier can achieve the following: The larger design allows for greater control over the detection signal, making it easier to detect minute changes in capacitance and significantly improving the sensitivity and accuracy of the detection circuit. Furthermore, its simple detection circuit structure enables faster detection speeds at a lower cost. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the circuit structure of an existing capacitive touch detection circuit.

[0035] Figure 2 This application provides a schematic diagram of the circuit structure of a capacitive touch detection circuit according to an embodiment of the present application.

[0036] Figure 3 A schematic diagram of another capacitive touch detection circuit is provided for embodiments of this application;

[0037] Figure 4 A circuit structure diagram of another capacitive touch detection circuit is provided for the embodiments of this application;

[0038] Figure 5 for Figure 3 The diagram shows the timing control of the switch in the capacitive touch detection circuit.

[0039] Figure 6 for Figure 4 The diagram shows the timing control of the switch in the capacitive touch detection circuit.

[0040] Explanation of reference numerals in the attached diagram: 01-Amplification module; 011-Operational amplifier; 012-First switching unit; C1-First capacitor; 02-Detection module; C2-Second capacitor; 021-Second switching unit; 03-Signal control module; C3-Third capacitor; 031-Third switching unit. Detailed Implementation

[0041] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0043] It should be understood that when a layer is referred to as "on," "adjacent to," or "connected to" other layers, it can be directly on, adjacent to, or connected to other layers, or there can be intervening layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," or "directly connected to" other layers, there are no intervening layers.

[0044] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising,” “including,” or “having,” etc., specify the presence of the stated feature, whole, step, operation, component, part, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof.

[0045] Based on the background information, in related technologies, the charge transfer plus comparator method, due to the use of a comparator, only outputs 0 or 1, resulting in low detection accuracy. Furthermore, it cannot amplify the signal, making it unable to detect minute changes, and the sensitivity of the detection system is also very low. To address the problems of low detection accuracy and sensitivity, related technologies also include detection schemes based on Sigma-Delta Modulators. This method effectively improves detection accuracy, but it also makes the detection circuit more complex, suffers from loop stability issues, and requires many detection cycles to complete a single touch detection, thus slowing down the circuit's detection speed.

[0046] refer to Figure 1 , Figure 1 The diagram shows the circuit structure of a conventional capacitive touch detection circuit. Capacitor Ca1 is connected between the first input and output terminals of a first operational amplifier A. Switch Sa1 is connected in parallel with capacitor Ca1. The first input terminal of the first operational amplifier A is also connected to the first terminal of capacitor Ca2 via switch Sa2. The second terminal of capacitor Ca2 is grounded. Switch Sa3 is connected between the first terminal of capacitor Ca2 and voltage Va1. The second input terminal of the first operational amplifier A receives voltage V. CM-a The output voltage Va at the output terminal of operational amplifier A O In this circuit, capacitor Ca2 is the detection capacitor. When no touch action is performed, the output of the detection circuit will detect the voltage value generated by the absence of touch; when a touch action is performed, the output of the detection circuit will detect the capacitance change caused by capacitor Ca2. This results in a new voltage value. By subtracting the voltage value generated when not touching from the voltage value generated when touching, we can obtain the change in signal quantity caused by the touch.

[0047] For example, in the first state, switches Sa1 and Sa3 are closed, and switch Sa2 is open. At this time, capacitor Ca1 is short-circuited and has no charge. The charge Qa1 in the detection circuit is calculated as follows:

[0048] (Formula 1)

[0049] In the second state, switches Sa1 and Sa3 are open, switch Sa2 is closed, and both capacitors Ca2 and Ca1 are charged. Calculate the charge Qa2 in the detection circuit as follows:

[0050] (Formula 2)

[0051] In both the first and second states, the detection circuit maintains charge conservation, i.e., Qa1 = Qa2, from which we can obtain:

[0052] (Formula 3)

[0053] When no touch action is performed, the output voltage at the output terminal of the first operational amplifier A is calculated according to Qa1=Qa2. for:

[0054] (Formula 4)

[0055] When a touch action is performed, the output voltage at the output terminal of the first operational amplifier A is calculated according to Qa1=Qa2. for:

[0056] (Formula 5)

[0057] in, This represents the change in capacitance of capacitor Ca2.

[0058] At this time, the signal detected by the detection circuit for:

[0059] (Formula 6)

[0060] The calculation yielded:

[0061] (Formula 7)

[0062] The first operational amplifier A can be powered by a single power supply, and the voltage of the single power supply can be... At this time, the output voltage of the first operational amplifier A The maximum range is ; The maximum range is ;at this time Usually very small, in Between. Therefore. The range of the minimum possible value is , If the value is too small, it will be drowned out by the noise, mismatch, gain error and other deviations in the circuit, making it undetectable.

[0063] Based on this, this application provides a capacitive touch detection circuit and a touch chip. The capacitive touch detection circuit includes an amplification module, a detection module, and a signal control module. The following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates this application.

[0064] refer to Figure 2 , Figure 2 This application provides a schematic diagram of the circuit structure of a capacitive touch detection circuit, which includes:

[0065] Amplification module 01 includes operational amplifier 011, first capacitor C1 and first switching unit 012. The first end of the first capacitor C1 is connected to the first input end of operational amplifier 011, the second end of the first capacitor C1 is connected to the output end of operational amplifier 011, and the first switching unit 012 is connected to the first capacitor C1 to control the amount of charge on the first capacitor C1 in different switching states.

[0066] The detection module 02 includes a second capacitor C2 and a second switching unit 021. The second capacitor C2 is connected between the second switching unit 021 and the ground terminal. The second switching unit 021 is used to connect the second capacitor C2 to voltage V3 or to the first input terminal of the operational amplifier 011 under different switching states, so as to control the amount of charge on the second capacitor C2.

[0067] The signal control module 03 includes a third capacitor C3 and a third switch unit 031. The third capacitor C3 is connected between the third switch unit 031 and the first input terminal of the operational amplifier 011. The third switch unit 031 is used to connect the third capacitor C3 to voltage V1 or voltage V2 in different switching states to control the amount of charge on the third capacitor C3.

[0068] in, Where C3 is the capacitance of the third capacitor C3, C2 is the capacitance of the second capacitor C2, and V CM This is the voltage value input to the second input terminal of operational amplifier 011.

[0069] Specifically, in the amplification module 01, the first input terminal of the operational amplifier 011 can be an inverting input terminal, and the second input terminal of the operational amplifier 011 can be a non-inverting input terminal. The first terminal of the first capacitor C1 is connected to the first input terminal of the operational amplifier 011, and the second terminal of the first capacitor C1 is connected to the output terminal of the operational amplifier 011. It should be noted that the connection between the first capacitor C1 and the output terminal of the operational amplifier 011 can be direct or through components; there is no specific limitation, and the connection state can be set according to specific needs. The first switching unit 012 is connected to the first capacitor C1, and the amount of charge on the first capacitor C1 can be controlled by controlling the switching state of the first switching unit 012.

[0070] In detection module 02, the second capacitor C2 serves as the detection capacitor. When there is no touch action, the second capacitor C2 only has its basic capacitance value. When a touch action is performed, the touch action causes a change in the basic capacitance of the second capacitor C2; the amount of change is the touch capacitance generated by the touch. At this time, the second capacitor C2 is equivalent to both the basic capacitance and the touch capacitance. This detection circuit detects whether a touch action has occurred by detecting the change in the second capacitor C2. Specifically, when no touch action is performed, the output terminal of the amplification module 01 will output a voltage value indicating no touch; while when a touch action is performed, the output terminal of the amplification module 01 will detect the capacitance change caused by the second capacitor C2. The resulting new voltage value. By subtracting the voltage value generated when not touching from the voltage value generated when touching, we can obtain the change in signal quantity caused by the touch.

[0071] In this embodiment, different switching states may include a first switching state and a second switching state; the amount of charge in the detection circuit under the first switching state is equal to the amount of charge in the detection circuit under the second switching state. Specifically, the first switching unit 012, the second switching unit 021, and the third switching unit 031 each include two switching states: a first switching state and a second switching state. When adjusting the switching state, the corresponding capacitor undergoes a charging or discharging process. During this process, the charge in the detection circuit is conserved, meaning that the amount of charge in the detection circuit under the first switching state is equal to the amount of charge in the detection circuit under the second switching state.

[0072] In this embodiment, the first switching unit 012 is connected to the first capacitor C1 to control the amount of charge on the first capacitor C1 under different switching states, based on voltage or not. Specifically, the connection method of the first switching unit 012 to the first capacitor C1 is not specifically limited and can be configured according to specific needs. For example, in one embodiment, the first switching unit 012 is connected to a voltage source to control the amount of charge on the first capacitor C1 under different switching states based on voltage; or, in another embodiment, the first switching unit 012 is connected in parallel with the first capacitor C1, in which case the amount of charge on the first capacitor C1 is not controlled based on voltage under different switching states. In this embodiment, the first switching unit 012 controls the amount of charge on the first capacitor C1 under different switching states, and the control method can be based on voltage or not, making the control more flexible.

[0073] Because the input and output of operational amplifier 011 have a certain range, exceeding this range will cause the performance of operational amplifier 011 to degrade or even stop working. Based on formulas 4 and 5, it can be seen that to achieve normal operation of the operational amplifier, its design will lead to V... CM-aThe size limitation leads to a limitation on the signal quantity in Formula 7, which in turn impairs the sensitivity and accuracy of the touch detection solution. However, the capacitive touch detection circuit provided in this embodiment includes a signal quantity control module. Through the design of voltages V1 and V2, the third capacitor C3, and the third switching unit 031, the amount of charge in the detection circuit is altered. Furthermore, due to the inclusion of... This allows the output voltage of operational amplifier 011 to be controlled under conditions of no touch action and touch action. (Quite V) CM-a The proportion affected by the change, such as making the output voltage of operational amplifier 011 completely dependent on the amount of touch when there is no touch action. This control allows for the same input / output range of operational amplifier 011 to... The larger design allows for adjustment of the signal quantity, making it larger and thus easier to detect minute changes in capacitance, significantly improving the sensitivity and accuracy of the detection circuit. Furthermore, its simple detection circuit structure enables faster detection speeds at low cost.

[0074] Further reference Figure 3 , Figure 3 This is a schematic diagram of a capacitive touch detection circuit provided in an embodiment of this application. The first switching unit 012 includes a switch S1. Switch S1 is connected in parallel with a first capacitor C1. In a first switching state, switch S1 is closed; in a second switching state, switch S1 is open. Specifically, switch S1 may include, but is not limited to, a MOSFET. Switch S1 is connected in parallel with the first capacitor C1 to control the amount of charge on the first capacitor C1. When the first switching unit 012 is switch S1, in the first switching state, switch S1 is closed, short-circuiting the first capacitor C1; in the second switching state, switch S1 is open, stopping the short-circuiting of the first capacitor C1.

[0075] The charge conservation in the detection circuit under the first and second switching states is explained below.

[0076] In this embodiment, in the first switching state, switch S1 is closed, short-circuiting the first capacitor C1. The second switching unit 021 is connected to voltage V3 in the first switching state, and the third switching unit 031 is connected to voltage V1 in the first switching state. The input voltage V at the second input terminal of operational amplifier 011 is... CM At this point, according to Q=CU, the amount of charge in the detection circuit under the first switching state can be determined. for:

[0077] (Formula 8)

[0078] Where C3 is the capacitance of the third capacitor C3, and C2 is the capacitance of the second capacitor C2.

[0079] In the second switching state, switch S1 is open, stopping the short circuit of the first capacitor C1. The second switching unit 021 is connected to the first input terminal of operational amplifier 011 in the second switching state, disconnecting the applied voltage V3. The third switching unit 031 is connected to voltage V2 in the second switching state, disconnecting the applied voltage V1. The input voltage V at the second input terminal of operational amplifier 011... CM At this point, according to Q=CU, the amount of charge in the detection circuit under the second switching state can be determined. for:

[0080] (Formula 9)

[0081] Where C3 is the capacitance of the third capacitor C3, C2 is the capacitance of the second capacitor C2, and C1 is the capacitance of the first capacitor C1. This is the output voltage at the output terminal of operational amplifier 011.

[0082] According to the law of charge conservation: Q1 = Q2, we get:

[0083] (Formula 10)

[0084] When no touch action is performed, the output voltage at the output terminal of operational amplifier 011 is calculated according to Q1=Q2. for:

[0085] (Formula 11)

[0086] When a touch action is performed, the output voltage at the output terminal of operational amplifier 011 is calculated based on Q1=Q2. for:

[0087] (Formula 12)

[0088] in, This represents the change in capacitance of the second capacitor C2.

[0089] At this time, the signal detected by the detection circuit for:

[0090] (Formula 13)

[0091] The calculation yielded:

[0092] (Formula 14)

[0093] Because the input and output of operational amplifier 011 have a certain range, exceeding this range will cause the performance of operational amplifier 011 to degrade or even stop working. This is based on the output formula of operational amplifier 011. It can be seen that in order to achieve the normal operation of operational amplifier 011, its design will lead to... Size limitations, which in turn lead to semaphores Size is limited by This can impair the sensitivity and accuracy of touch detection solutions.

[0094] Based on this, this application sets ,get Furthermore, substituting into formula 11, we get... Compared to existing output formulas, this improves... Output formula The proportion in, or in other words, under the same input and output range of operational amplifier 011, compared with existing technologies The designable value is larger, which in turn makes the semaphore... The increased size improves detection sensitivity and accuracy.

[0095] For example, the output formula of operational amplifier 011 when not touched is formula 11: If with =10 is the upper limit of the output value for the operational amplifier 011 to operate normally, assuming , , The proportions are basically the same, that is , Both are 33.33%, then The maximum value is set to around 3 or 4. And if... , Each accounts for 10%. With a proportion of 80%, the maximum value is 8. At this point, the semaphore... The improvement is limited. However, based on this application, by setting... , can make Further obtained ,Right now The maximum value can be set to 10, at which point a relatively large value can be obtained. ,and The signal quantity can be controlled without exceeding the output voltage range of the operational amplifier. Increase in size. Semaphore When the signal is enlarged for a touch action, This makes it easier to detect, thus greatly improving the sensitivity of the detection circuit. Furthermore, its detection circuit structure is simple, allowing for faster detection speeds at low cost.

[0096] Further reference Figure 4 , Figure 4 A schematic diagram of the circuit structure of another capacitive touch detection circuit provided in the embodiment of this application; the first switching unit 012 includes switch S2, switch S3 and switch S4;

[0097] Switch S2 is connected between the second terminal of the first capacitor C1 and the output terminal of operational amplifier 011; switch S3 is connected between the second terminal of the first capacitor C1 and voltage V4; switch S4 is connected between the first terminal of the first capacitor C1 and voltage V5; wherein, the voltage value of voltage V5 is the same as the voltage value V input to the second input terminal of operational amplifier 011. CM Similarly, in the first switch state, switch S2 is open, and switches S3 and S4 are closed; in the second switch state, switch S2 is closed, and switches S3 and S4 are open.

[0098] Specifically, switches S2, S3, and S4 may include, but are not limited to, MOSFETs. In the first switching state, switch S2 is open, and switches S3 and S4 are closed. At this time, the charge on the first capacitor C1 changes based on voltages V4 and V5. In the second switching state, switch S2 is closed, and switches S3 and S4 are open. At this time, the charge on the first capacitor C1 does not change based on voltage. The charge conservation in the detection circuit under the first and second switching states will be explained below.

[0099] In this embodiment, in the first switching state, switch S2 is open, and switches S3 and S4 are closed, connecting the first terminal of the first capacitor C1 to voltage V5. The voltage value of voltage V5 is the same as the voltage value V input to the second input terminal of operational amplifier 011. CM Same, that is, V5 equals V CM The second terminal of the first capacitor C1 is connected to voltage V4. The second switching unit 021 is connected to voltage V3 in the first switching state, and the third switching unit 031 is connected to voltage V1 in the first switching state. At this time, according to Q=CU, the charge Q1 in the detection circuit in the first switching state is:

[0100] (Formula 15)

[0101] Where C3 is the capacitance of the third capacitor C3, C2 is the capacitance of the second capacitor C2, and V CM C1 is the input voltage at the second input terminal of operational amplifier 011, and C1 is the capacitance of the first capacitor C1.

[0102] In the second switching state, the first switching unit 012 has switch S2 closed and switches S3 and S4 open, meaning the first capacitor C1 is connected in parallel with operational amplifier 011. The second switching unit 021 is connected to the first input terminal of operational amplifier 011 in the second switching state. The third switching unit 031 is connected to voltage V2 in the second switching state. At this time, according to Q=CU, the charge Q2 in the detection circuit in the second switching state is:

[0103] (Formula 16)

[0104] Where C3 is the capacitance of the third capacitor C3, C2 is the capacitance of the second capacitor C2, C1 is the capacitance of the first capacitor C1, and V CM This refers to the input voltage at the second input terminal of operational amplifier 011. This is the output voltage at the output terminal of operational amplifier 011.

[0105] According to the law of charge conservation: Q1 = Q2, we get:

[0106] (Formula 17)

[0107] When no touch action is performed, the output voltage at the output terminal of operational amplifier 011 is calculated according to Q1=Q2. for:

[0108] (Formula 18)

[0109] When a touch action is performed, the output voltage at the output terminal of operational amplifier 011 is calculated based on Q1=Q2. for:

[0110] (Formula 19)

[0111] in, This represents the change in capacitance of the second capacitor C2.

[0112] At this time, the signal detected by the detection circuit for:

[0113] (Formula 20)

[0114] The calculation yielded:

[0115] (Formula 21)

[0116] Similarly, because the input and output of operational amplifier 011 have a certain range, exceeding this range will cause the performance of operational amplifier 011 to degrade or even stop working. This is based on the output formula of operational amplifier 011. It can be seen that in order to achieve the normal operation of operational amplifier 011, its design will lead to... Size limitations, which in turn lead to semaphores Size is limited by This can impair the sensitivity and accuracy of the touch detection solution. For example, when operational amplifier 011 is powered by a single power supply, the single power supply voltage can be... ,at this time Often restricted to ,Right now .

[0117] Based on this, this application sets ,get Furthermore, substituting into formula 18, we can obtain... Compared to the existing output formula, the existing... Output formula The percentage in was replaced with At this time, due to It is an additional input voltage, so a suitable design can be freely created. This allows for further setting of relatively large [sizes / sizes]. ,and It will not exceed the normal output voltage range of operational amplifier 011, further improving the flexibility of the detection circuit.

[0118] For example, the output formula of operational amplifier 011 when not touched is formula 18: At this time, with The relevant value is It can be set , making Further obtained = Design a suitable It can make It will not exceed the output voltage range of operational amplifier 011. At this time, No longer affecting , We can freely design larger values ​​and further achieve greater results. This allows the semaphore Increase in size. Semaphore When the signal is enlarged for a touch action, This makes it easier to detect, thus greatly improving the sensitivity of the detection circuit. Furthermore, its detection circuit structure is simple, allowing for faster detection speeds at a low cost. This detection circuit significantly improves detection sensitivity, and its simple structure allows for faster detection speeds at a low cost.

[0119] Further reference Figure 3 or Figure 4 As shown, the second switching unit 021 may include switch S5 and switch S6; switch S5 is connected between the first terminal of the second capacitor C2 and the voltage V3, and the second terminal of the second capacitor C2 is connected to the ground terminal; switch S6 is connected between the first terminal of the second capacitor C2 and the first input terminal of the operational amplifier 011; wherein, in the first switching state, switch S5 is closed and switch S6 is open; in the second switching state, switch S5 is open and switch S6 is closed.

[0120] Switches S5 and S6 may include, but are not limited to, MOSFETs. It should be noted that the above is merely one example of the second switching unit 021. The second switching unit 021 only needs to be able to receive voltage V3 in the first switching state and connect to the first input terminal of operational amplifier 011 in the second switching state; no specific limitations are imposed.

[0121] In this embodiment, the second switching unit 021 is implemented by switches S5 and S6. The detection module 02 circuit is simple and can achieve faster detection speed at low cost.

[0122] Further reference Figure 3 or Figure 4 As shown, the third switching unit 031 may include switch S7 and switch S8; switch S7 is connected between the first terminal of the third capacitor C3 and voltage V1, switch S8 is connected between the first terminal of the third capacitor C3 and voltage V2, and the second terminal of the third capacitor C3 is connected to the first input terminal of operational amplifier 011; wherein, in the first switching state, switch S7 is closed and switch S8 is open; in the second switching state, switch S7 is open and switch S8 is closed.

[0123] Specifically, switches S7 and S8 may include, but are not limited to, MOSFETs. Switch S7 is connected between the first terminal of the third capacitor C3 and voltage V1, and switch S8 is connected between the first terminal of the third capacitor C3 and voltage V2. In the first switching state, switch S7 is closed, switch S8 is open, and voltage V1 is applied to the third capacitor C3. In the second switching state, switch S7 is open, switch S8 is closed, and voltage V2 is applied to the third capacitor C3. The third switching unit 031 can control the amount of charge on the third capacitor C3 by applying different voltages in different switching states. It should be noted that the above is only one example of the third switching unit 031; the third switching unit 031 only needs to be able to apply voltage V1 in the first switching state and voltage V2 in the second switching state, and is not specifically limited.

[0124] In this embodiment, the third switch unit 031 is implemented by switches S7 and S8. The signal control module 03 has a simple circuit and can achieve faster detection speed at low cost.

[0125] In another embodiment of this application, the detection circuit may further include a control module, which is used to control the closing and opening of the switches in the first switch unit 012, the second switch unit 021 and the third switch unit 031 under different switching states, thereby controlling the amount of charge on the capacitor in the detection circuit (not shown).

[0126] Specifically, the control module controls the detection circuit to be in either the first or second switching state by controlling the closing and opening of the switches in the first switching unit 012, the second switching unit 021, and the third switching unit 031, thereby controlling the amount of charge on the capacitor. According to the law of conservation of charge, the amount of charge is the same in the first and second switching states, allowing the signal quantity to be calculated.

[0127] It should be noted that the control module can be electrically connected or communicatively connected to the switches in the first switch unit 012, the second switch unit 021, and the third switch unit 031, without any specific limitations.

[0128] It should also be noted that the timing of the closing or opening of the first switching unit, the second switching unit, and the third switching unit as defined in various embodiments of this application may have a slight delay. By adding some delay to the timing, the control module allows each switch to conduct sequentially, which can reduce the uncertainty of charge distribution when multiple switches are turned off simultaneously, making the error more predictable and compensable, and reducing the error rate. Furthermore, the control module can also strictly separate the operation of each stage, for example, separating the sampling stage from the holding stage, to ensure that the charge flows only along the designed path.

[0129] For example, corresponding Figure 3 The timing diagram for the closing and opening of each switch in the structure shown is provided for reference. Figure 5 In the first switching state P1, switches S1, S5, and S7 are closed, while switches S8 and S6 are open. In the second switching state P2, switches S1, S5, and S7 are open, while switches S8 and S6 are closed. It should be noted that during the transition from the first switching state P1 to the second switching state P2, switch S1 can be opened first, then switches S5 and S7 can be opened simultaneously, and switch S8 can be closed. Finally, switch S6 can be closed. By controlling the timing of different switches, the switches can be turned on or off sequentially, reducing the uncertainty of charge distribution when multiple switches are simultaneously turned off, making errors more predictable and compensable, and reducing the error rate.

[0130] For example, corresponding Figure 4 The timing diagram for the closing and opening of each switch in the structure shown is provided for reference. Figure 6 In the first switching state P1, switches S3, S4, S5, and S7 are closed, while switches S2, S8, and S6 are open. In the second switching state P2, switches S3, S4, S5, and S7 are open, while switches S2, S8, and S6 are closed. It should be noted that during the transition from the first switching state P1 to the second switching state P2, switch S4 can be opened first, then switches S3, S5, and S7 can be opened simultaneously, and switches S2 and S8 can be closed. Finally, switch S6 can be closed. By controlling the timing of different switches, the switches can be turned on or closed sequentially, reducing the uncertainty of charge distribution when multiple switches are turned off simultaneously, making errors more predictable and compensable, and reducing the error rate.

[0131] In this embodiment, the control module can reduce errors during the detection process and improve the detection progress.

[0132] In another embodiment of this application, the operational amplifier 011 can be implemented using a programmable gain amplifier. Specifically, a programmable gain amplifier can be flexibly adjusted according to specific application requirements, thereby providing better signal processing performance. It can provide appropriate gain within different input signal strength ranges to avoid problems of signals being too strong or too weak. In addition, the programmable gain amplifier can also provide lower power consumption and higher dynamic range to adapt to different application environments.

[0133] It is understood that the first switching unit 012, the second switching unit 021, and the third switching unit 031 in the above detection circuit can also take other forms, and are not limited to the forms already mentioned in the above embodiments, as long as they can achieve the function of increasing the signal amount and improving the detection accuracy and speed.

[0134] In another embodiment of this application, a touch chip is also provided, including any of the detection circuits described above. Specifically, this touch chip can be an MCU chip, integrating touch detection technology into the MCU, which significantly reduces product costs and allows more products to utilize touch detection technology.

[0135] Specifically, the touch chip uses the aforementioned detection circuit. It should be noted that the touch chip can also achieve the same effects as the aforementioned detection circuit. It not only has high detection sensitivity, but also has a simple implementation structure and can achieve faster detection speed at low cost.

[0136] In the description of this specification, references to terms such as "some embodiments," "another embodiment," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0137] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features of the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0138] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A capacitive touch detection circuit, characterized in that, include: An amplification module includes an operational amplifier, a first capacitor, and a first switching unit. A first terminal of the first capacitor is connected to a first input terminal of the operational amplifier, and a second terminal of the first capacitor is connected to an output terminal of the operational amplifier. The first switching unit is connected to the first capacitor to control the amount of charge on the first capacitor under different switching states. The detection module includes a second capacitor and a second switching unit. The second capacitor is connected between the second switching unit and the ground terminal. The second switching unit is used to connect the second capacitor to voltage V3 or to the first input terminal of the operational amplifier under different switching states, so as to control the amount of charge on the second capacitor. The signal control module includes a third capacitor and a third switching unit. The third capacitor is connected between the third switching unit and the first input terminal of the operational amplifier. The third switching unit is used to connect the third capacitor to voltage V1 or voltage V2 in different switching states to control the amount of charge on the third capacitor. in, Where C3 is the capacitance of the third capacitor, C2 is the capacitance of the second capacitor, and V CM The voltage value input to the second input terminal of the operational amplifier.

2. The detection circuit according to claim 1, characterized in that, The different switch states include a first switch state and a second switch state; The amount of charge in the detection circuit in the first switching state is equal to the amount of charge in the detection circuit in the second switching state.

3. The detection circuit according to claim 2, characterized in that, The first switching unit is connected to the first capacitor to control the amount of charge on the first capacitor in different switching states based on voltage or not.

4. The detection circuit according to claim 3, characterized in that, The first switching unit includes a switch S1; the switch S1 is connected in parallel with the first capacitor; In the first switch state, switch S1 is closed; in the second switch state, switch S1 is open.

5. The detection circuit according to claim 3, characterized in that, The first switching unit includes switch S2, switch S3 and switch S4; The switch S2 is connected between the second terminal of the first capacitor and the output terminal of the operational amplifier. The switch S3 is connected between the second terminal of the first capacitor and the voltage V4; The switch S4 is connected between the first terminal of the first capacitor and the voltage V5; Wherein, the voltage value of voltage V5 is the same as the voltage value input to the second input terminal of the operational amplifier, and in the first switching state, switch S2 is open, and switches S3 and S4 are closed; in the second switching state, switch S2 is closed, and switches S3 and S4 are open.

6. The detection circuit according to any one of claims 2-5, characterized in that, The second switching unit includes switch S5 and switch S6; The switch S5 is connected between the first terminal of the second capacitor and the voltage V3, and the second terminal of the second capacitor is connected to the ground terminal; The switch S6 is connected between the first terminal of the second capacitor and the first input terminal of the operational amplifier. In the first switch state, switch S5 is closed and switch S6 is open; in the second switch state, switch S5 is open and switch S6 is closed.

7. The detection circuit according to any one of claims 2-5, characterized in that, The third switching unit includes switch S7 and switch S8; The switch S7 is connected between the first terminal of the third capacitor and the voltage V1, the switch S8 is connected between the first terminal of the third capacitor and the voltage V2, and the second terminal of the third capacitor is connected to the first input terminal of the operational amplifier; In the first switch state, switch S7 is closed and switch S8 is open; in the second switch state, switch S7 is open and switch S8 is closed.

8. The detection circuit according to claim 1 or 2, characterized in that, The detection circuit further includes: The control module is used to control the closing and opening of the switches in the first switch unit, the second switch unit, and the third switch unit under different switching states, thereby controlling the amount of charge on the capacitor in the detection circuit.

9. The detection circuit according to claim 1, characterized in that, The operational amplifier includes a programmable gain amplifier.

10. A touch chip, characterized in that, Includes the detection circuit described in any one of claims 1-9.

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