Touch detection circuit composed of discrete components

Abstract

The utility model discloses a touch detection circuit composed of discrete components, and relates to the technical field of touch detection circuits, the touch detection circuit comprises a signal input end, a signal enhancement module and a plurality of touch detection modules; the signal input end is connected with the signal enhancement module, and the signal enhancement module is used for enhancing the amplitude of an alternating signal input by the signal input end and outputting the amplitude to each touch detection module; the touch detection module comprises a detection end, a touch sensing piece and rectification assemblies, the output end of the signal enhancement module is connected with the input end of each rectification assembly, the touch sensing piece is connected in the rectification assemblies, and the touch sensing piece is used for changing the amplitude of an alternating current signal when sensing human body touch; the rectifying assembly is used for converting the alternating current signals into direct current signals and outputting the direct current signals, and the detection end judges whether human body touch exists or not by detecting changes of the direct current signals. The touch detection circuit provided by the utility model does not need a special touch chip, and is low in cost, high in sensitivity and good in EMC (Electro Magnetic Compatibility) characteristic.

Description

Technical Field

[0001] This application relates to the field of touch detection circuit technology, and more particularly to a touch detection circuit composed of discrete components. Background Technology

[0002] Currently, touch functionality is usually implemented using dedicated touch chips. However, touch chips are expensive and often suffer from electromagnetic interference. They are very sensitive to power supply voltage ripple. If the power supply voltage ripple is large, it can easily lead to touch malfunction. In addition, touch chips are also prone to electromagnetic radiation, making it difficult to pass space radiation tests. Utility Model Content

[0003] The purpose of this application is to at least solve one of the technical problems existing in the prior art, and to provide a touch detection circuit composed of discrete components, which aims to provide a touch detection circuit that does not require a dedicated touch chip, is low-cost, has adjustable sensitivity, and has good EMC characteristics.

[0004] This application provides a touch detection circuit composed of discrete components, including a signal input terminal, a signal enhancement module, and several touch detection modules;

[0005] The signal input terminal is connected to the signal enhancement module, which is used to enhance the amplitude of the alternating signal input to the signal input terminal and output it to each of the touch detection modules;

[0006] The touch detection module includes a detection end, a touch sensor, and a rectifier assembly. The output end of the signal enhancement module is connected to the input end of each rectifier assembly. The touch sensor is connected in the rectifier assembly and is used to change the amplitude of the alternating signal when a human touch is detected. The rectifier assembly is used to convert the alternating signal into a DC signal and output it. The output end of the rectifier assembly is connected to the detection end for detecting the DC signal. The detection end determines whether a human touch is present by detecting changes in the DC signal.

[0007] According to the technical solution of the embodiments of this application, at least the following beneficial effects are achieved: After an alternating signal is input to the signal input terminal, the signal enhancement module can enhance the amplitude of the alternating signal input to the signal input terminal, thereby increasing the difference in voltage change when there is no touch and improving the detection sensitivity of human touch; The touch detection module includes a detection terminal, a touch sensor, and a rectifier assembly. The touch sensor is used to change the AC signal when a human touch is sensed. That is, the AC signal will not change when there is no human touch, but the amplitude of the AC signal will change when there is a touch. Since the distributed capacitance of each person is different and the amplitude of the AC signal is difficult to detect accurately, the alternating AC signal can be converted into a DC voltage signal by the rectifier assembly, which can be more convenient to detect. The detection terminal can realize touch detection by detecting whether the voltage of the DC signal changes; Based on this, the touch detection module does not need to use a touch chip. Touch detection can be realized by detecting the change of the signal after the touch sensor changes the signal, which reduces the cost of the touch detection circuit and has good EMC characteristics.

[0008] According to some embodiments of this application, the rectifier assembly includes a first capacitor, a first diode, and a second diode. The first diode and the second diode are used to convert the alternating signal into a direct current signal. The output terminal of the signal enhancement module is connected to the first capacitor. One end of the first capacitor is connected to the negative terminal of the first diode and the positive terminal of the second diode, and the other end is connected to the signal enhancement module. The positive terminal of the first diode is grounded.

[0009] When the signal enhancement module enhances the amplitude of the alternating signal input to the signal input terminal, it converts the alternating signal into an alternating voltage signal to improve the detection sensitivity.

[0010] The touch sensor is connected to the junction of the first diode and the second diode. The first capacitor converts the input alternating voltage signal into an alternating voltage signal. The touch sensor is used to form a human body distributed capacitance when a human touch is detected. The human body distributed capacitance and the first capacitor form a voltage divider network to change the amplitude of the alternating voltage signal.

[0011] According to some embodiments of this application, the touch detection module further includes a second capacitor, and the second capacitor, the first capacitor, the first diode and the second diode constitute a voltage doubler rectifier circuit, which is used to convert the alternating voltage signal into a DC voltage signal.

[0012] According to some embodiments of this application, after the signal enhancement module enhances the amplitude of the alternating signal input to the signal input terminal, the difference between the DC voltage signal and the absence of human touch changes accordingly, and the touch detection sensitivity of the touch detection circuit also changes synchronously.

[0013] According to some embodiments of this application, the signal enhancement module includes a VDD power supply terminal, a first resistor, a second resistor, and a transistor. The VDD power supply terminal is connected to one end of the second resistor, and the other end of the second resistor is connected to the collector of the transistor. The signal input terminal is connected to one end of the first resistor, and the other end of the first resistor is connected to the base of the transistor. The output terminal of the signal enhancement module is the collector of the transistor.

[0014] According to some embodiments of this application, the alternating signal input at the signal input terminal is used to control the switching on and off of the transistor. When the alternating signal input at the signal input terminal is high, the transistor is turned on and the collector of the transistor is low. When the alternating signal input at the signal input terminal is low, the transistor is turned off and the collector of the transistor is high.

[0015] According to some embodiments of this application, the touch detection module further includes a second capacitor connected between the output terminal of the rectifier component and the detection terminal. The second capacitor is used to filter the DC signal so that the rectified DC signal becomes a stable DC voltage.

[0016] According to some embodiments of this application, the touch detection module further includes a third resistor connected in parallel with the second capacitor, the third resistor being used to discharge the residual voltage of the second capacitor.

[0017] According to some embodiments of this application, the touch sensor is a touch spring.

[0018] According to some embodiments of this application, the signal input terminal is used to input a PWM signal.

[0019] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the description, claims and drawings. Attached Figure Description

[0020] The accompanying drawings are used to provide a further understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0021] The present application will be further described below with reference to the accompanying drawings and embodiments;

[0022] Figure 1This is a schematic block diagram of a touch detection circuit composed of discrete components provided in one embodiment of this application;

[0023] Figure 2 A circuit diagram of a touch detection circuit composed of discrete components provided for one embodiment of this application;

[0024] Figure 3 The voltage waveforms at the microcontroller's AD port of a touch detection circuit composed of discrete components provided in an embodiment of this application are shown when there is a touch and when there is no touch. Detailed Implementation

[0025] This section will describe in detail the specific embodiments of this application. Preferred embodiments of this application are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of this application, but they should not be construed as limiting the scope of protection of this application.

[0026] In the description of this application, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0027] In the description of this application, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. If the terms "first" and "second" are used, they are merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly specifying the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0028] In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0029] The following is in conjunction with the appendix Figure 1-3 This application will be further elaborated upon.

[0030] like Figure 1 As shown, Figure 1 This application provides an embodiment of a touch detection circuit composed of discrete components, including a signal input terminal, a signal enhancement module, and several touch detection modules;

[0031] The signal input terminal is connected to a signal enhancement module, which is used to enhance the amplitude of the alternating signal input to the signal input terminal and output it to each touch detection module;

[0032] The touch detection module includes a detection end, a touch sensor, and a rectifier assembly. The output end of the signal enhancement module is connected to the input end of each rectifier assembly. The touch sensor is connected in the rectifier assembly and is used to change the amplitude of the alternating signal when a human touch is detected. The rectifier assembly is used to convert the alternating signal into a DC signal and output it. The output end of the rectifier assembly is connected to the detection end for detecting the DC signal. The detection end determines whether a human touch is present by detecting changes in the DC signal.

[0033] In this embodiment, the signal input terminal is used to input an alternating signal. The signal input terminal serves as the signal source for driving the touch detection circuit. Therefore, the AC signal input to the signal input terminal can be a square wave signal with a frequency of 300kHz to 400kHz. The signal input terminal can be the PWM port of a microcontroller, and the signal enhancement module can be an operational amplifier or a transistor, among other electrical components.

[0034] It is understandable that a touch detection circuit composed of discrete components includes a signal input terminal, a signal enhancement module, and several touch detection modules. The signal input terminal is connected to the signal enhancement module, which is used to enhance the amplitude of the alternating signal input to the signal input terminal and output it to each touch detection module. That is, the signal input terminal and the signal enhancement module can be regarded as a signal source for outputting a high amplitude signal. The touch detection circuit composed of discrete components includes a signal source and several touch detection modules. The signal input of each touch detection module is the same, ensuring that the detection results of each touch detection module are the same.

[0035] It should be noted that the signal enhancement module is used to enhance the amplitude of the alternating signal input to the signal input terminal, but it does not change the frequency, duty cycle, or other characteristics of the alternating signal input to the signal input terminal.

[0036] The output of the signal enhancement module is connected to the input of each rectifier component, and the output of the rectifier component is connected to the detection terminal for detecting DC signals. That is, the rectifier component is the part of the touch detection module that receives signals. The signal output by the signal enhancement module is transmitted to the rectifier component of each touch detection module. After the rectifier component processes the signal, it is transmitted to the detection terminal. Therefore, the signal transmission path is signal input terminal - signal enhancement module - rectifier component - detection terminal.

[0037] The touch sensor is connected to the rectifier assembly, meaning it functions as part of the rectifier assembly. The touch sensor and rectifier assembly together form a touch rectifier unit. The signal output from the signal enhancement module is transmitted to the touch rectifier unit, processed, and then transmitted to the detection end. The touch sensor changes the alternating signal when it detects human touch, and the rectifier assembly converts the alternating signal into a direct current signal before outputting it. In other words, if there is no human touch after the alternating signal from the signal enhancement module is transmitted to the rectifier assembly, the rectifier assembly will rectify the alternating signal from the signal enhancement module into a direct current signal. After the signal is received, it is transmitted to the detection end. If there is human touch, before the rectifier component rectifies the alternating signal output by the signal enhancement module, the amplitude of the alternating signal is changed by the touch sensor, and then the rectifier component rectifies the changed alternating signal into a DC signal before transmitting it to the detection end. At this time, the DC signal will be different from the DC signal when there is no human touch. The detection end can determine whether there is human touch by detecting the voltage change of the DC signal. For example, if the DC signal voltage remains unchanged, it can be determined that there is no human touch. When the DC signal voltage changes, it can be determined that there is human touch.

[0038] The rectifier assembly can be a voltage doubler rectifier circuit composed of diodes and capacitors. The rectifier assembly needs to have a port for the touch sensor to connect to; the touch sensor can be a capacitive touch detection sensor; the detection terminal can be the AD port of a microcontroller. For example, in one embodiment, the rectifier assembly is a voltage doubler rectifier circuit composed of diodes and capacitors, the touch sensor is a capacitive touch detection sensor, and the touch sensor is connected in series with the capacitor in the voltage doubler rectifier circuit.

[0039] It should be noted that the signal enhancement module and rectifier components do not include inductors, because inductors emit electromagnetic radiation, so removing inductors can effectively reduce EMC electromagnetic radiation.

[0040] In some embodiments of this application, the touch detection circuit composed of discrete components, such as Figure 2 As shown, the rectifier assembly includes a first capacitor, a first diode, and a second diode. The first and second diodes are used to convert the alternating signal into a direct current signal. The output terminal of the signal enhancement module is connected to the first capacitor. One end of the first capacitor is connected to the negative terminal of the first diode and the positive terminal of the second diode, and the other end is connected to the signal enhancement module. The positive terminal of the first diode is grounded.

[0041] When the signal enhancement module amplifies the amplitude of the alternating signal input to the signal input terminal, it converts the alternating signal into... amplitude Larger Alternating voltage signals are used to improve detection sensitivity;

[0042] The touch sensor is connected to the junction of the first diode and the second diode. The first capacitor converts the input alternating voltage signal into an alternating voltage signal. The touch sensor is used to form a human body distributed capacitance when it senses a human touch. The human body distributed capacitance and the first capacitor form a voltage divider network to change the amplitude of the alternating voltage signal.

[0043] In this embodiment, the rectifier assembly includes a first capacitor C1, a first diode D1, and a second diode D2. The cathode of the first diode D1 is connected to the anode of the second diode D2, thereby forming a rectifier circuit. The first capacitor C1 is used to convert the alternating voltage signal input from the signal enhancement module into an alternating voltage signal, that is, the first capacitor C1 acts as an isolation capacitor. The subsequent rectifier circuit is used to rectify the alternating signal into a direct current signal. The output terminal of the signal enhancement module is connected to the first capacitor C1. Point A in the figure is the connection point between the signal enhancement module and the first capacitor C1. Therefore, point A is the output terminal of the signal enhancement module and also the alternating signal input terminal of the rectifier assembly. One end of the first capacitor C1 is connected to the signal enhancement module, and the other end is connected to the cathode of the first diode D1 and the anode of the second diode D2. The anode of the first diode D1 is grounded.

[0044] Based on this, the alternating signal output by the signal enhancement module is input from point A and converted into an AC voltage signal by the first capacitor C1. Then it is rectified by the first diode D1 and the second diode D2, and then output from the negative terminal of the second diode D2 for detection by the detection terminal.

[0045] When a signal enhancement module amplifies the amplitude of an alternating signal input to the signal input terminal, it converts the alternating signal into an alternating voltage signal with a larger amplitude. In other words, the alternating signal input to the signal input terminal may be a PWM signal, and the signal enhancement module may also be a transistor. The transistor has a load resistor and a DC power supply voltage source VDD at its collector, and the collector of the transistor is the output terminal of the signal enhancement module. By applying a PWM signal to the base of the transistor to control the transistor's on / off state, the alternating signal output by the signal enhancement module becomes an alternating voltage signal with a larger amplitude. The signal frequency is the same as the PWM signal frequency, and the signal amplitude is the same as the power supply voltage VDD, which is equivalent to enhancing the amplitude of the PWM signal input to the signal input terminal.

[0046] The touch sensor is connected to the junction of the first diode D1 and the second diode D2, that is, the junction of the negative terminal of the first diode D1 and the positive terminal of the second diode D2. The touch sensor is used to form a distributed capacitance of the human body when it senses a human touch. Since the human body is equivalent to a metal plate storing induced charge, when the human body approaches the touch sensor, the human body and the touch sensor form a parallel distributed capacitance. One end of this distributed capacitance is grounded, and the other end is connected in series with the first capacitor C1. The distributed capacitance of the human body and the first capacitor C1 form a voltage divider network. After the alternating voltage signal is input from point A, it is coupled through the first capacitor C1 and converted into a voltage. Due to the presence of a voltage divider network, the potential at the connection point between the negative terminal of the first diode D1 and the positive terminal of the second diode D2 changes, thus altering the amplitude of the AC signal. When no human body is near the touch sensor, the AC signal enters directly from point A and passes directly through the first diode D1. At this time, the potential at the connection point between the negative terminal of the first diode D1 and the positive terminal of the second diode D2 will be different from the potential when a human body is near the touch sensor. This results in a difference in the DC voltage output at the negative terminal of the second diode D2. The detection end can determine whether a human body has touched the sensor by detecting whether the DC voltage changes.

[0047] It is understandable that when the signal enhancement module has a DC power supply voltage source VDD, the first capacitor C1 can also be used as an isolation capacitor. The alternating voltage signal output by the signal enhancement module is isolated by the first capacitor C1 after being input from point A, and then rectified by the first diode D1 and the second diode D2. The first capacitor C1 is used to isolate the DC power supply voltage source and the DC channel of the microcontroller and forms a voltage divider with the distributed capacitance of the human body to prevent the voltage sent to the detection end after rectification from being too high and potentially damaging the microcontroller.

[0048] It should be noted that this embodiment uses Figure 2 The components C1, TK1, D1, D2, R3, C2, and the AD1 port of the microcontroller are described as examples. Figure 2 The circuit formed by C3, TK2, D3, D4, R4, C4 and the AD2 port of the microcontroller is the same as the circuit formed by C1, TK1, D1, D2, R3, C2 and the AD1 port of the microcontroller, and will not be described in detail here.

[0049] In some embodiments of this application, the touch detection circuit composed of discrete components includes a second capacitor C2. The second capacitor C2, the first capacitor C1, the first diode D1, and the second diode D2 constitute a voltage doubler rectifier circuit, which is used to convert AC voltage signals into DC voltage signals.

[0050] In the touch detection circuit composed of discrete components provided in some embodiments of this application, after the amplitude of the alternating signal input to the signal input terminal of the signal enhancement module changes, the difference between the DC voltage signal and the absence of human touch changes accordingly, and the touch detection sensitivity of the touch detection circuit also changes synchronously.

[0051] Understandably, the detection end determines whether there is human touch by detecting whether the DC voltage changes. In addition, when a human body is close to the touch sensor, the human body and the touch sensor form a parallel human body distributed capacitance. The human body distributed capacitance and the first capacitor C1 form a voltage divider network to change the amplitude of the AC voltage signal. The size of the human body distributed capacitance affects the size of the change in the amplitude of the AC voltage signal. The size of the human body distributed capacitance formed when different human bodies touch may be different, and the size of the human body distributed capacitance formed may also be different depending on the distance between the human body and the touch sensor. If the human body distributed capacitance is too small, the change in the amplitude of the AC voltage signal will be too small, so that the DC voltage output by the rectifier component does not change much when there is human touch. If the detection accuracy of the detection end is low, it may not be able to detect the change in DC voltage when there is human touch.

[0052] Based on this, since the magnitude of the human body's distributed capacitance cannot be changed, if it is necessary to improve the detection sensitivity of the touch detection circuit without increasing the detection accuracy of the detection end, the amplitude of the alternating signal input to the signal input terminal can be increased by enhancing the signal enhancement module. This results in a larger amplitude of the AC voltage signal input from the signal enhancement module to the rectifier component. In this way, even if the human body's distributed capacitance and the first capacitor C1 form a voltage divider network that reduces the amplitude of the AC voltage signal when the human body is close to the touch sensor, the DC voltage signal output by the rectifier component will still be relatively increased. That is, the difference between the DC voltage signal with and without human touch will increase synchronously, thereby synchronously increasing the touch detection sensitivity of the touch detection circuit. Similarly, if it is necessary to reduce the detection sensitivity of the touch detection circuit, the amplitude of the AC signal input to the signal input terminal of the signal enhancement module can be reduced.

[0053] In some embodiments of this application, the touch detection circuit composed of discrete components, such as Figure 2 As shown, the signal enhancement module includes a VDD power supply terminal, a first resistor R1, a second resistor R2, and a transistor Q1. The VDD power supply terminal is connected to one end of the second resistor R2, and the other end of the second resistor R2 is connected to the collector of the transistor Q1. The signal input terminal is connected to one end of the first resistor R1, and the other end of the first resistor R1 is connected to the base of the transistor Q1. The output terminal of the signal enhancement module is the collector of the transistor Q1.

[0054] In this embodiment, the second resistor R2 is connected between the VDD power supply terminal and the collector of the transistor Q1. The second resistor R2 can limit the maximum current flowing through the collector of the transistor Q1, prevent the transistor Q1 from being damaged by excessive current, and enable the collector output of the transistor Q1 to be close to 0V when it is turned on.

[0055] The first resistor R1 is connected between the signal input terminal and the base of the transistor Q1. The first resistor R1 can also limit the maximum current flowing through the base of the transistor Q1.

[0056] It is understandable that the alternating signal input at the signal input terminal serves as a driving signal, which can drive the transistor Q1 to repeatedly turn on and off. The frequency of the alternating signal input at the signal input terminal is transmitted to the collector of the transistor Q1. The alternating signal output from the collector of the transistor Q1 is a square wave with an amplitude equal to the voltage at the VDD power supply terminal and a frequency equal to the frequency of the alternating signal input at the signal input terminal. This is equivalent to increasing the amplitude of the alternating signal input at the signal input terminal to the amplitude of the voltage at the VDD power supply terminal.

[0057] It is understandable that the greater the distance between the human body and the touch sensor, the smaller the DC voltage difference between the presence and absence of touch at the detection end. If the difference is too small, it will be difficult to detect whether there is a touch. Therefore, the signal enhancement module can amplify the amplitude of the alternating signal input to the signal input terminal to increase the DC voltage difference between the presence and absence of touch at the detection end, thereby improving the detection sensitivity of touch detection. Thus, by selecting different voltages input to the VDD power supply terminal, different DC voltage differences can be obtained when there is a touch and when there is no touch at the detection end, thereby adjusting the touch detection sensitivity. In addition, by further increasing the voltage input to the VDD power supply terminal, the DC voltage difference between the presence and absence of touch at the detection end can be further increased. Even when the distance between the human body and the touch sensor is far, forming an air-touch, a certain DC voltage difference can still be formed at the detection end, which can be detected by the detection end. Therefore, in one embodiment, the touch detection circuit composed of discrete components provided in this application can support air-touch.

[0058] In the touch detection circuit composed of discrete components provided in some embodiments of this application, the alternating signal input at the signal input terminal is used to control the on / off state of transistor Q1. When the alternating signal input at the signal input terminal is high level, transistor Q1 is turned on and the collector of transistor Q1 is low level. When the alternating signal input at the signal input terminal is low level, transistor Q1 is turned off and the collector of transistor Q1 is high level.

[0059] In this embodiment, the alternating signal input at the signal input terminal serves as a driving signal to control the switching on and off of transistor Q1, ensuring that the switching frequency of transistor Q1 is the same as the frequency of the alternating signal input at the signal input terminal. Specifically, when the AC signal input at the signal input terminal is high, transistor Q1 is turned on, and the collector of transistor Q1 is at a low level. When the AC signal input at the signal input terminal is low, transistor Q1 is turned off, and the collector of transistor Q1 is at a high level. That is, the level of the AC signal input at the signal input terminal is opposite to the level of the collector of transistor Q1. Therefore, the VDD power supply terminal, the first resistor R1, the second resistor R2, and transistor Q1 can be a level conversion circuit used to convert the level of the alternating signal input at the signal input terminal.

[0060] In some embodiments of this application, the touch detection circuit composed of discrete components, such as Figure 2 As shown, one end of the second capacitor C2 is connected between the output terminal and the detection terminal of the rectifier component, and the other end of the second capacitor C2 is grounded. The second capacitor C2 is used to filter the DC signal so that the rectified DC signal becomes a stable DC voltage.

[0061] In some embodiments of this application, the touch detection circuit composed of discrete components, such as Figure 2 As shown, the touch detection module also includes a third resistor R3, which is connected in parallel with the second capacitor C2. The third resistor R3 is used to discharge the residual voltage of the second capacitor C2.

[0062] In this embodiment, the third resistor R3 is connected in parallel with the second capacitor C2. That is, the output terminal of the rectifier component, the third resistor R3, the second capacitor C2, and the detection terminal are connected in sequence. The third resistor R3 serves as a discharge resistor to discharge the residual voltage of the second capacitor C2.

[0063] In some embodiments of this application, the touch detection circuit composed of discrete components, such as Figure 2 As shown, the touch sensor is a touch spring TK1.

[0064] In this embodiment, the touch spring TK1 serves as a touch sensor, used to sense human touch or air-based touch.

[0065] In some embodiments of this application, the touch detection circuit composed of discrete components, such as Figure 2 As shown, the signal input terminal is used to input PWM signals.

[0066] It is understandable that the signal input terminal is used to input PWM signals. The signal input terminal can be the PWM output terminal of the microcontroller, and correspondingly, the detection terminal can be the AD port of the microcontroller.

[0067] In one embodiment, the signal input terminal is used to input the PWM signal, the detection terminal is the AD port of the microcontroller, the signal enhancement module includes a VDD power supply terminal, a first resistor R1, a second resistor R2, and a transistor Q1, the rectifier assembly includes a first capacitor, a first diode, and a second diode, the touch sensor is connected to the connection point of the first diode and the second diode, and the touch spring TK1 serves as the touch sensor; in terms of specific component selection, the first resistor R1 can be selected from 2K to 3.3K, the second resistor R2 can be selected from 1K to 4.7K, the third resistor R3 can be selected from 1M, the first capacitor C1 can be selected from 10pF, the second capacitor C2 can be selected from 100nF, the first diode D1 and the second diode D2 can be diodes of the 1N4148 type, and the transistor Q1 is selected from 80 For NPN transistors of models 50, 9013, and 9014, the microcontroller can be selected with an ADC detection port and a PWM port, a maximum operating voltage of 5.5V, and built-in diode clamping protection for the I / O port. The waveform output of the microcontroller's PWM port requires a frequency of 300KHz to 400KHz and a duty cycle of 1:1. For microcontrollers with a power supply voltage of 5V, the power supply VDD can be selected from 5.6V to 6.8V. For microcontrollers with a power supply voltage of 3V or 3.3V, the power supply VDD can be selected from 4V to 5.5V. This is to prevent the voltage sent to the microcontroller's AD port after rectification by the rectifier component from being too high when there is no touch, which would exceed the microcontroller's operating voltage. The VDD power supply can be controlled by a Zener diode or Zener chip with the corresponding voltage regulation specification.

[0068] Taking the scenario of touching the TK1 touch spring with a 3mm thick glass barrier as an example, and referring to the relevant references... Figure 3 , Figure 3 The diagrams show the voltage waveforms at the microcontroller's AD port when there is touch and when there is no touch. With VDD=5V, the voltage V2 at the AD port is 2.2V when there is touch, and V1 is 2.36V when there is no touch, a difference of approximately 0.16V. With VDD=6V, the voltage V2 at the AD port is 3.9V when there is touch, and V1 is 4.16V when there is no touch, a difference of approximately 0.26V. It is evident that the higher the VDD, the greater the voltage difference at the AD port when there is touch, and the higher the touch sensitivity.

[0069] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application.

Claims

1. A touch detection circuit composed of discrete components, characterized in that, It includes a signal input terminal, a signal enhancement module, and several touch detection modules; The signal input terminal is connected to the signal enhancement module, which is used to enhance the amplitude of the alternating signal input to the signal input terminal and output it to each of the touch detection modules; The touch detection module includes a detection end, a touch sensor, and a rectifier assembly. The output end of the signal enhancement module is connected to the input end of each rectifier assembly. The touch sensor is connected in the rectifier assembly and is used to change the amplitude of the alternating signal when a human touch is detected. The rectifier assembly is used to convert the alternating signal into a DC signal and output it. The output end of the rectifier assembly is connected to the detection end for detecting the DC signal. The detection end determines whether a human touch is present by detecting changes in the DC signal.

2. The touch detection circuit composed of discrete components according to claim 1, characterized in that, The rectifier assembly includes a first capacitor, a first diode, and a second diode. The first diode and the second diode are used to convert the alternating signal into a direct current signal. The output terminal of the signal enhancement module is connected to the first capacitor. One end of the first capacitor is connected to the negative terminal of the first diode and the positive terminal of the second diode, and the other end is connected to the signal enhancement module. The positive terminal of the first diode is grounded. When the signal enhancement module enhances the amplitude of the alternating signal input to the signal input terminal, it converts the alternating signal into an alternating voltage signal to improve the detection sensitivity. The touch sensor is connected to the junction of the first diode and the second diode. The first capacitor converts the input alternating voltage signal into an alternating voltage signal. The touch sensor is used to form a human body distributed capacitance when a human touch is detected. The human body distributed capacitance and the first capacitor form a voltage divider network to change the amplitude of the alternating voltage signal.

3. The touch detection circuit composed of discrete components according to claim 2, characterized in that, The touch detection module further includes a second capacitor. The second capacitor, the first capacitor, the first diode, and the second diode constitute a voltage doubler rectifier circuit, which is used to convert the alternating voltage signal into a DC voltage signal.

4. The touch detection circuit composed of discrete components according to claim 3, characterized in that, After the signal enhancement module enhances the amplitude of the alternating signal input to the signal input terminal, the difference between the DC voltage signal and the absence of human touch changes accordingly, and the touch detection sensitivity of the touch detection circuit also changes synchronously.

5. The touch detection circuit composed of discrete components according to claim 1, characterized in that, The signal enhancement module includes a VDD power supply terminal, a first resistor, a second resistor, and a transistor. The VDD power supply terminal is connected to one end of the second resistor, and the other end of the second resistor is connected to the collector of the transistor. The signal input terminal is connected to one end of the first resistor, and the other end of the first resistor is connected to the base of the transistor. The output terminal of the signal enhancement module is the collector of the transistor.

6. The touch detection circuit composed of discrete components according to claim 5, characterized in that, The alternating signal input at the signal input terminal is used to control the switching on and off of the transistor. When the alternating signal input at the signal input terminal is high, the transistor is turned on and the collector of the transistor is low. When the alternating signal input at the signal input terminal is low, the transistor is turned off and the collector of the transistor is high.

7. The touch detection circuit composed of discrete components according to claim 3, characterized in that, The second capacitor is connected between the output terminal of the rectifier assembly and the detection terminal. The second capacitor is used to filter the DC signal so that the rectified DC signal becomes a stable DC voltage.

8. The touch detection circuit composed of discrete components according to claim 7, characterized in that, The touch detection module also includes a third resistor, which is connected in parallel with the second capacitor and is used to discharge the residual voltage of the second capacitor.

9. The touch detection circuit composed of discrete components according to claim 1, characterized in that, The touch sensor is a touch spring.

10. The touch detection circuit composed of discrete components according to claim 1, characterized in that, The signal input terminal is used to input PWM signals.

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