A touch button sensitivity adjustment method, circuit and touch switch

Abstract

The present invention proposes a touch key sensitivity adjustment method, circuit and touch switch. The touch key sensitivity adjustment method uses the method of connecting the first end of the first capacitor to the 0 level through the first CMOS switch, connecting the first end of the first capacitor to the first end of the second capacitor through the second CMOS switch, setting the first CMOS switch and the second CMOS switch cycle opposite, connecting the first end of the second capacitor to the output end of the adjustable current source and the first input end of the comparator, and comparing the voltage V REF connected to the second input terminal of the comparator. When the voltage at the second capacitor terminal is less than V REF When the adjustable current source output charging current is adjusted to I, when the voltage at the second capacitor terminal is greater than V REF When the adjustable current source outputs a charging current of λ*I, the comparator output is judged to determine whether the key is pressed, and the sensitivity is adjusted by adjusting the value of λ. The touch key sensitivity adjustment method can flexibly adjust the sensitivity of the touch switch by adjusting the charging current ratio.

Description

Technical Field

[0001] The present invention relates to the field of switch control, and in particular to a touch key sensitivity adjustment method, a circuit and a touch switch. Background Art

[0002] With the development of electrical and electronic technology, household electrical appliances are becoming more and more popular and electronic, radio and television, postal and telecommunications, and computer networks are becoming more and more developed, and the electromagnetic environment is becoming more and more complex and worse. As a result, the electromagnetic compatibility (EMC, electromagnetic interference, EMI, and electromagnetic resistance, EMS) of electrical and electronic products has also received increasing attention from governments and manufacturers. The electromagnetic compatibility (EMC) of electronic and electrical products is a very important quality indicator. It is not only related to the working reliability and safety of the product itself, but also may affect the normal operation of other equipment and systems, and is related to the protection of the electromagnetic environment. The European Community government stipulates that from January 1, 1996, all electrical and electronic products must pass EMC certification and be affixed with the CE mark before they can be sold in the European Community market. This move has caused widespread influence in the world, and governments have taken measures to implement mandatory management of the RMC performance of electrical and electronic products. Internationally, the more influential ones, such as the EU 89 / 336 / EEC Directive (i.e., the EMC Directive) and the US Federal Code CFR 47 / FCC Rules, have put forward clear requirements for electromagnetic compatibility certification.

[0003] EMC includes EMI (electromagnetic interference) and EMS (electromagnetic tolerance). EMI refers to the electromagnetic noise generated by the machine itself when it performs its functions, which is detrimental to other systems; while EMS refers to the ability of the machine to be unaffected by the surrounding electromagnetic environment when performing its functions.

[0004] Because capacitive touch buttons have no mechanical structure, all detections are small changes in electricity, so they are more sensitive to various interferences. In addition, household appliances are directly powered by the mains, and the power grid carries various interference signals, some of which will seriously affect the electrical signals on the circuit board, which can easily cause false detection of touch buttons. For example, there is no button, but the system detects that there is a button; or when the A button is pressed, the system detects that the B button is pressed, etc. If the chip is not handled properly, it will cause safety hazards to the product. From the perspective of EMC certification standards, it is reflected in the immunity to conducted interference induced by radio frequency fields. In actual products, the touch buttons and the human body are usually separated by a panel. Due to the different panel materials and thicknesses of various manufacturers, the chip may not be able to achieve uniform button sensitivity and anti-interference capabilities when making different solutions.

[0005] Capacitive touch buttons are widely used, but the application environment is also complex and changeable. Different PCB traces, different product shapes, different EMC environments, etc. require the chip to have a wider range of applicability and higher anti-EMC performance. Sensitivity is the biggest factor that directly affects product reliability and is also the most difficult part of the algorithm to handle. There are many factors that affect sensitivity, such as: PCB trace length, panel thickness, panel dielectric composition, spacing distance, etc., which are inevitable links in practical applications. Therefore, a reliable sensitivity adjustment method is urgently needed so that the switch can adapt to various complex and changeable environments. Summary of the invention

[0006] In order to solve the deficiencies of the prior art mentioned in the background technology, the present invention proposes a touch button sensitivity adjustment method, circuit and touch switch, which can adjust the sensitivity of the switch according to needs, thereby solving the above technical problems.

[0007] In a first aspect, a touch key sensitivity adjustment method is provided, wherein the first end of a first capacitor is connected to a 0 level through a first CMOS switch; the first end of the first capacitor is connected to the first end of a second capacitor through a second CMOS switch; the first CMOS switch is set to have opposite switching cycles to the second CMOS switch; the first end of the second capacitor is also connected to the output end of the adjustable current source and the first input end of the comparator; the comparison voltage V REF connected to the second input terminal of the comparator; when the voltage at the second capacitor terminal is less than V REF When the adjustable current source output charging current is adjusted to I, when the voltage at the second capacitor terminal is greater than V REF When the charging current output by the adjustable current source is adjusted to λ*I; by judging the output of the comparator, it is determined whether the key is pressed, and the sensitivity adjustment is achieved by adjusting the size of λ.

[0008] Further, where 0≤λ≤1.

[0009] Furthermore, the switch sensitivity can be adjusted by the following formula:

[0010]

[0011] Where T is the second CMOS switch period, CI is the built-in capacitor, CT is the touch switch capacitance when no key is pressed, C′ T is the capacitance of the touch switch when the key is pressed, t is the time for the output terminal voltage change to increase due to touch, the sensitivity of the switch is determined by the ratio of t to T, and the sensitivity of the switch is adjusted by λ.

[0012] The present invention also discloses a touch key detection circuit with adjustable sensitivity, comprising a first capacitor, a second capacitor, a first CMOS switch, a second CMOS switch, an adjustable current source, and a comparator; the first capacitor is a touch switch capacitor, and the second capacitor is a built-in capacitor; the first end of the first capacitor is connected to the 0 level through the first CMOS switch; the first end of the first capacitor is connected to the first end of the second capacitor through the second CMOS switch; the first CMOS switch and the second CMOS switch have opposite cycles; the first end of the second capacitor is also connected to the output end of the adjustable current source and the first input end of the comparator; the comparison voltage V REF connected to the second input terminal of the comparator; when the voltage at the second capacitor terminal is less than V REF When the adjustable current source outputs a charging current of I, when the voltage at the second capacitor terminal is greater than V REF When the charging current output by the adjustable current source is λ*I; by judging the output of the comparator, it is determined whether the key is pressed, and the sensitivity adjustment is achieved by adjusting the size of λ.

[0013] Further, where 0≤λ≤1.

[0014] Furthermore, the switch sensitivity is adjusted by the following formula:

[0015]

[0016] Where T is the second CMOS switch period, CI is the built-in capacitor, CT is the touch switch capacitance when no key is pressed, C′ T is the capacitance of the touch switch when the key is pressed, t is the time for the output terminal voltage change to increase due to touch, the sensitivity of the switch is determined by the ratio of t to T, and the sensitivity of the switch is adjusted by λ.

[0017] The invention also discloses a touch switch which uses the circuit to adjust sensitivity.

[0018] The present invention adopts a scenario-based signal adaptive processing method to analyze various signal scenarios and switch signal scenarios, so that the touch electronic device can perform comprehensive analysis and processing of the signal, realize adaptive processing of the signal within the current signal scenario and adaptive switching and processing between signal scenarios, thereby ensuring the adaptability of key touch judgment information in various signal scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 Touch detection circuit;

[0021] Figure 2 Internal signal schematic diagram;

[0022] Figure 3 Schematic diagram of no button output;

[0023] Figure 4 There is a schematic diagram of key output;

[0024] Figure 5 Schematic diagram of built-in capacitor voltage without buttons;

[0025] Figure 6 There is a schematic diagram of the built-in capacitor voltage of the button. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the described embodiments are part of the embodiments of the present invention, not all of the embodiments, and all other embodiments obtained by ordinary technicians in the field without creative work based on the embodiments of the present invention are within the scope of protection of the present invention.

[0027] like Figure 1 The circuit includes two capacitors, two CMOS switches, an adjustable current source and a comparator.

[0028] If the current I remains unchanged, the output will be as follows through the periodic adjustment of the COMS switch: Figure 2 As shown in the waveform, SO represents the COMS switching cycle and COMP_0 is the output signal.

[0029] When initializing the switch, adjust the power supply current so that the COMP_0 output is close to a 50% duty cycle. The waveform is as follows: Figure 3 shown.

[0030] When the button is touched, the capacitance at the switch changes due to the touch, and the duty cycle of the comparator output changes. Within a fixed detection time, such as 1ms, another counter is used to count the time when COMP_0 is low. By comparing the length of time when COMP_0 is low, it can be determined whether the button is pressed. Figure 4As shown, COMP_0 is low for a period longer than Figure 3 The time when COMP_0 is low, at which time it is determined that the button is pressed.

[0031] Will Figure 1 The power supply in the circuit is modified into an adjustable power supply to adjust the current in different periods of time. When the voltage on the built-in capacitor is less than the comparator comparison voltage V REF When the charging current is I, when the voltage is greater than V REF When , the charging current is adjusted to λ*I, where 0≤λ≤1.

[0032] like Figure 5 As shown in the figure, it is a schematic diagram of the voltage change on the built-in capacitor when no key is pressed. Figure 6 As shown in Figure 1, when a key is pressed, the time that the voltage on the built-in capacitor is lower than VREF increases due to the change in key capacitance.

[0033] The following will derive the theoretical value of the regulation circuit. In the formula, C I is the built-in capacitor, C T C' is the capacitance of the button port when no button is pressed. T is the capacitance of the key port when a key is pressed, and λ is the voltage exceeding V REF The charging current series after that, T is the CMOS switching cycle.

[0034] When initialization is complete, it is known that V REF Calculate the value of I by using T

[0035] v1*C I =V2*(C I +C T )---------------------------------------①

[0036]

[0037]

[0038] From ② From ③ Substituting into ①, we get the following formula

[0039]

[0040] When a key is pressed, the basic formula is as follows:

[0041] V′1*C I =V′2*(C I +C′ T )-------------------------------------⑤

[0042]

[0043] (V REF -V3)*C I =I*t----------------------------------------⑦

[0044]

[0045] For the convenience of calculation, let From ⑤~⑧, we can get

[0046]

[0047] at the same time, Substituting into the above formula, we get

[0048]

[0049] From ⑥⑦⑨, we get

[0050]

[0051] Substituting ④ into the above formula, we can get:

[0052]

[0053] It is the ratio of the touch value change, which represents the sensitivity of the switch. It can be seen from the formula that the size of the ratio value can be adjusted by λ, thus realizing the adjustment of the switch sensitivity.

[0054] The following is a theoretical verification of the adjustment degree.

[0055] Consider two extreme cases. When λ=0, the formula is

[0056] Take C I =200pF, C T =10pF, C′ T =11pF, calculate

[0057] When λ=1, the formula is

[0058] Take C I =200pF, C T =10pF, C′ T =11pF, calculate

[0059] Fixed capacitance, the influence on sensitivity when changing λ value. In the table, delateCT represents the percentage change of touch button capacitance, and deltaT represents the percentage change of detected touch value, the same below.

[0060] λ= 0 λ= 0.5 λ= 1 CI 2.0OE-10 CI 2.00E-10 CI 2.00E-10 CT 1.00E-11 CT 1.00E-11 CT 1.00E-11 CT′ 1.10E-11 CT′ 1.10E-11 CT′ 1.10E-11 delatCT 10％ delatCT 10％ delatCT 10％ deltaT= 9.479％ deltaT= 27.027％ deltaT= 363.636％

[0061] When the λ value is small, the influence of different built-in capacitance values ​​on sensitivity

[0062] λ= 0.5 λ= 0.5 λ= 0.5 CI 2.00E-10 Cl 2.00E-09 CI 2.00E-08 CT 1.00E-11 CT 1.00E-11 CT 1.00E-11 CT′ 1.10E-11 CT′ 1.10E-11 CT′ 1.10E-11 delatCT 10％ delatCT 10％ delatCT 10％ deltaT= 27.027％ deltaT= 29.674％ deltaT= 29.967％

[0063] Effect of different built-in capacitance values ​​on sensitivity when λ is large

[0064] λ= 0.95 λ= 0.95 λ= 0.95 Cl 2.00E-10 Cl 2.00E-09 CI 2.00E-08 CT 1.00E-11 CT 1.00E-11 CT 1.00E-11 CT′ 1.10E-11 CT′ 1.10E-11 CT′ 1.10E-11 delatCT 10％ delatCT 10％ delatCT 10％ deltaT= 185.714％ deltaT= 351.351％ deltaT= 385.757％

[0065] It can be seen that λ plays the role of an amplification factor. When the value of λ is small, the size of the built-in capacitor has little effect on the sensitivity. When the value of λ is large, the size of the built-in capacitor has an effect on the sensitivity. Therefore, the sensitivity can be adjusted by λ.

[0066] Finally, it should be noted that the above is only a preferred embodiment of the present invention, which is only used to illustrate the technical solution of the present invention, and is not used to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A touch key sensitivity adjustment method, characterized in that: Connecting a first end of a first capacitor to a 0 level through a first CMOS switch, wherein the first capacitor is a touch switch capacitor; Connecting the first end of the first capacitor to the first end of the second capacitor through a second CMOS switch, wherein the second capacitor is a built-in capacitor; Setting the first CMOS switch to have an opposite cycle to the second CMOS switch; The first terminal of the second capacitor is also connected to the output terminal of the adjustable current source and the first input terminal of the comparator; The comparison voltage V REF connected to the second input terminal of the comparator; When the voltage at the second capacitor terminal is less than V REF When the charging current of the adjustable current source is adjusted to I, when the voltage at the second capacitor terminal is greater than V REF When the charging current of the adjustable current source is adjusted to λ*I; Determine whether the key is pressed by judging the comparator output, and adjust the sensitivity by adjusting the value of λ; Where 0≤λ≤1; The switch sensitivity is adjusted by the following formula: Where T is the second CMOS switching period, C I is the built-in capacitor, C T is the touch switch capacitance when no key is pressed, C ′ T is the capacitance of the touch switch when the key is pressed, t is the time for the output terminal voltage change to increase due to touch, the sensitivity of the switch is determined by the ratio of t to T, and the sensitivity of the switch is adjusted by λ.

2. A touch key detection circuit with adjustable sensitivity, characterized in that It includes a first capacitor, a second capacitor, a first CMOS switch, a second CMOS switch, an adjustable current source, and a comparator; The first capacitor is a touch switch capacitor, and the second capacitor is a built-in capacitor; The first end of the first capacitor is connected to the 0 level through the first CMOS switch; The first end of the first capacitor is connected to the first end of the second capacitor through the second CMOS switch; The first CMOS switch has an opposite cycle to the second CMOS switch; The first terminal of the second capacitor is also connected to the output terminal of the adjustable current source and the first input terminal of the comparator; the comparison voltage V REF connected to the second input terminal of the comparator; When the voltage at the second capacitor terminal is less than V REF When the charging current of the adjustable current source is I, when the voltage at the second capacitor terminal is greater than V REF When the charging current of the adjustable current source is λ*I; Determine whether the key is pressed by judging the comparator output, and adjust the sensitivity by adjusting the value of λ; Where 0≤λ≤1; The switch sensitivity is adjusted by the following formula: Where T is the second CMOS switching period, C I is the built-in capacitor, C T is the touch switch capacitance when no key is pressed, C ′ T is the capacitance of the touch switch when the key is pressed, t is the time for the output terminal voltage change to increase due to touch, the sensitivity of the switch is determined by the ratio of t to T, and the sensitivity of the switch is adjusted by λ.

3. A touch switch, characterized in that The touch switch comprises the circuit as claimed in claim 2.

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