TW201533635A - Detection circuit for capacitive touch screen and capacitive touch device - Google Patents

Abstract

The present invention is applicable to the field of touch technology and provides of a detection circuit for a capacitive touch screen to be disposed in a capacitive touch device, which comprises a core detection module and a data processing and communication module, the core detection module communicates with the data processing and communication module via a communication interface, the data processing and communication module and the communication interface are electrically connected to the system circuit; the core detection module includes an internal power supply and an internal grounding. The capacitive touch device has a system power supply and a system grounding, therefore, the internal power supply is connected to the system power supply via a first switch, the internal grounding is connected to the system grounding via a second switch; the first and the second switches are opened during a detection process, and are closed after the detection. As a result of the power grounding isolation, the touch screen will not encounter inaccurate detection and misreport when subjected to a hard press, and also avoid systematic power interference; because the data processing and communication module and the system circuit are in the same power domain, risks of interface error or damage are eliminated, thereby improving the reliability of the detection circuit.

Description

Capacitive touch screen detection circuit and capacitive touch device

The invention belongs to the field of touch technology, and particularly relates to a capacitive touch screen detection circuit and a capacitive touch device.

A capacitive touch device is an electronic device with a capacitive touch screen, which at least includes a capacitive touch screen and a display device, and more commonly an LCD. As shown in Figure 1, when there is an LCD device near the capacitive touch screen, parasitic capacitance will be generated between the LCD screen and the capacitive touch screen. The Clm and Cln in the figure will generate the electric field distribution of the capacitive touch screen. The effect is that the electric induction lines emitted from the detecting electrode M and the detecting electrode N can be sucked away. As shown in Figure 2, when the touch is light, the capacitive touch screen hardly deforms, and the parasitic capacitance becomes Clm' and Cln', and the amount of change is small, Clm' Clm, Cln' Cln, so this effect is almost unchanged when there is no touch, and has no effect on the touch screen detection and calculation coordinates. Referring to FIG. 3 further, when the touch screen is deformed by heavy pressure, the variation of the parasitic capacitance is large. At this time, the parasitic capacitances Clm" and Cln" change a lot when there is no touch, thereby affecting the touch screen detection. Results and coordinate accuracy, even false positives can occur.

In response to the above problems, the prior art proposes the following solutions:

The first one is to improve the structure, enhance the hardness of the touch screen, or fill other solid materials between the touch screen and the LCD to reduce the shape of the touch screen during heavy pressure. Change the amplitude, or increase the distance between the touch screen and the LCD to reduce the electric field change caused by the deformation. This solution is not achievable in many machine applications where the structure has been determined. The method of increasing the hardness of the cover plate also increases the cost and cannot solve the problem fundamentally.

Secondly, through data processing, the characteristics, trends and amplitudes of the influence of touch screen deformation on data are analyzed, and repaired and compensated on the software. The solution can only be improved to a certain extent, and the deformation is still serious, and the complexity of the software debugging is increased, and the detection accuracy may be adversely affected.

Third, the grounding isolation method is adopted, and the method has the following two types:

1. As in Chinese patent application 201310253774.0, and referring to FIG. 4, the detection circuit 401 and the whole system 402 adopt different power sources and grounding, the grounding of the detecting circuit 401 and the grounding of the whole system 402 are isolated from each other, and the detecting circuit 401 adopts GND1, the whole machine The other components in the system 402 adopt GND2. At this time, the LCD will become an unrelated conductor for the touch screen, that is, a suspended conductor, and the conventional technology (Chinese Patent Application 201210212641.4) can completely avoid the defect caused by the LCD. influences. At the same time, in order to solve the problem that the detection circuit and the system cannot communicate, a magnetic coupling or an optocoupler device can be set to realize communication.

2. As in Chinese patent application 201310253774.0, and referring to FIG. 5, the detecting circuit 501 and the whole system 502 adopt different power sources and groundings, and a switch K1 is added between the detecting circuit grounding and the whole system grounding, and the switch is switched during the detecting period. K1 is disconnected, and switch K1 is closed after the end of the test to replenish the charge and complete communication with the system.

The above method 1 requires an additional magnetic coupling or optical coupling device, which increases the cost; when the switch is disconnected, the communication interface and the system are in different power domains, which may bring additional risks such as interface errors or damage, and need Special handling of the interface also increases costs. At the same time, the above two methods can not cover some additional interference related to the system power supply, which has a certain impact on the detection accuracy.

The object of the present invention is to provide a capacitive touch screen detection circuit, which aims to effectively avoid the influence of heavy pressure on touch detection, and eliminate interference related to system power supply, thereby improving detection accuracy.

The present invention is implemented in such a manner that a capacitive touch screen detection circuit is disposed in a capacitive touch device, including: a core detection module and a data processing and communication module, and the core detection module communicates with the data through a communication interface The processing and communication module performs communication, and the data processing and communication module and the communication interface are electrically connected to the system circuit of the capacitive touch device; the core detection module has an internal power supply and an internal ground, and the capacitive touch device The system has a system power supply and a system ground. The internal power supply is connected to the system power supply through a first switch. The internal ground is connected to the system ground through a second switch, and the first switch and the second switch are simultaneously disconnected during the touch detection process. Close at the same time after the end of the test. Another object of the present invention is to provide a capacitive touch device, including a stacked display screen and a capacitive touch screen, and a capacitive touch screen detecting circuit.

The detection circuit provided by the invention has a switch between the power source and the ground of the core detection module and the power source and the ground of the system, and the power ground isolation is performed during the detection process, so that the display screen of the touch device is opposite to the capacitive touch The screen is only an unrelated conductor, so that the capacitive touch screen will not detect inaccurate or misreported when it is under heavy pressure. At the same time, due to the power isolation, the system power supply is avoided, further Improved detection accuracy; in addition, The solution is only to isolate the core detection module from the power supply ground, and the other parts of the detection circuit are not isolated from the system power supply and ground. The data processing and communication module is still connected to the system power supply and ground, that is, data processing. And the communication module and the system circuit are in the same power domain, thus eliminating the risk of interface error or damage, and no special processing on the interface, thereby improving the reliability of the detection circuit and reducing the cost.

1‧‧‧ core detection module

11‧‧‧Internal power supply

12‧‧‧Internal grounding

2‧‧‧Data Processing and Communication Module

3‧‧‧Communication interface

4‧‧‧Capacitive touch devices

41‧‧‧System Power Supply

42‧‧‧System grounding

5‧‧‧First switch

51‧‧‧First system control switch

52‧‧‧First detection circuit control switch

6‧‧‧Second switch

61‧‧‧Second system control switch

62‧‧‧Second detection circuit control switch

7‧‧‧ Third switch

401‧‧‧Detection circuit

402‧‧‧The whole machine system

501‧‧‧Detection circuit

502‧‧‧The whole machine system

1 is a partial structural diagram of a capacitive touch device in the prior art; FIG. 2 is a schematic diagram of a lightly pressed state of a capacitive touch screen in the prior art; FIG. 3 is a heavy pressure state of a capacitive touch screen in the prior art; FIG. 4 is a schematic diagram of a capacitive touch screen isolation detection scheme 1 in the prior art; FIG. 5 is a schematic diagram of a capacitive touch screen isolation detection scheme 2 in the prior art; FIG. 6 is a capacitor provided by an embodiment of the present invention; FIG. 7 is a partial circuit diagram of a capacitive touch screen detection circuit according to an embodiment of the present invention; FIG. 8 is a partial circuit diagram of a capacitive touch screen detection circuit according to an embodiment of the present invention; (two).

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the description here The specific embodiments described are merely illustrative of the invention and are not intended to limit the invention.

FIG. 6 is a schematic diagram of a capacitive touch screen detection circuit according to an embodiment of the present invention. For convenience of description, only parts related to the embodiment are shown.

With reference to FIG. 6, the capacitive touch screen detection circuit provided by the embodiment of the present invention is disposed in a capacitive touch device for detecting a touch event. The capacitive touch screen detection circuit comprises: a core detection module 1 and a data processing and communication module 2, and the core detection module 1 performs information interaction with the data processing and communication module 2 through the communication interface 3 according to a preset protocol. Both the processing and communication module 2 and the communication interface 3 are electrically connected to the system circuit of the capacitive touch device 4. Further, the core detecting module 1 has an internal power source 11 and an internal grounding 12. The capacitive touch device 4 has a system power source 41 and a system ground 42. The system power source 41 and the internal power source 11 are two independent power sources. Ground 42 and internal ground 12 are also independent of one another. The internal power source 11 is connected to the system power source 41 through the first switch 5, and the internal ground 12 is connected to the system ground 42 through the second switch 6. During the touch event detection process, the first switch 5 and the second switch 6 are simultaneously disconnected, and the detection ends. After that, the first switch 5 and the second switch 6 are simultaneously closed to ensure normal communication between the detecting circuit and the system. In this embodiment, the entire detection circuit is divided into a plurality of modules, and only a part of the detection circuit, the internal power source 11 and the internal ground 12 of the core detection module 1 are connected to the system power supply 41 and the system ground 42 of the whole machine, and the detection circuit The other parts of the data processing and communication module 2 are still connected to the system circuit of the whole machine. At the same time, the core detection module 1 communicates with the data processing and communication module 2 through the newly added communication interface 3 according to the newly-defined protocol. At the same time, the data processing and communication module 2 communicates with the whole system normally, thereby ensuring normal communication with the system when the power supply ground of the core detection module 1 is isolated.

The working principle of the capacitive touch screen detection circuit is: during the detection process, The first switch 5 and the second switch 6 are simultaneously disconnected, so that the internal power source 11 of the core detecting module 1 and the system power source 41 of the capacitive touch device 4 are isolated, so that the ground of the core detecting module 1 and the grounding of the whole system are grounded. In isolation, the core detection module 1 is powered by the internal power source 11. The core detection module 1 outputs the detection data to the data processing and communication module 2 through the newly defined communication interface 3 according to the newly defined protocol, and the data processing and communication module 2 outputs the information to the system circuit of the whole machine through the interface component. . After the detection is completed, the first switch 5 and the second switch 6 are simultaneously closed, and the communication between the core detecting module 1 and the system circuit is resumed, and the internal power source 11 of the core detecting module 1 can be charged by the system power source 41. The detection circuit provided by the embodiment of the present invention has a power supply and ground isolation during the detection process, so that the display screen of the touch device (such as LCD) is only an unrelated conductor relative to the capacitive touch screen, so that the capacitor The touch screen does not detect inaccurate or misreported when it is under heavy pressure. At the same time, due to power isolation, the system power supply is avoided, and the detection accuracy is further improved. In addition, the solution is only for core detection. The module is isolated from the power supply ground, and the other parts of the detection circuit are not isolated from the system power supply and grounding. The data processing and communication module is still connected to the system power supply and ground, that is, the data processing and communication module and system. The circuit is in the same power domain, thus eliminating the risk of interface errors or damage, and does not require special handling of the interface, thereby improving the reliability of the detection circuit and reducing the cost.

Further, the detecting circuit realizes connection and disconnection of the power supply ground of the core detecting module 1 and the capacitive touch device 4 through the parallel switch. Referring specifically to FIG. 7, the first switch 5 includes a first system control switch 51 and a first detection circuit control switch 52 connected in parallel between the system power source 41 and the internal power source 11 of the core detection module 1, and the second The switch 6 includes a second system control switch 61 and a second detection circuit control switch 62 connected in parallel between the system ground 42 and the internal ground 12 of the core detection module 1. Among them, the system controls the first system control The switch 51 and the second system control switch 61 are closed to realize the connection between the system power source 41 and the system ground 42 and the internal power source 11 and the internal ground 12 of the core detecting module 1, for powering up the detecting circuit, after the power is completed, in the touch detection In the stage, the system disconnects the first system control switch 51 and the second system control switch 61, and the detection circuit controls the disconnection and connection of the first detection circuit control switch 52 and the second detection circuit control switch 62 according to the touch condition. That is, the system is powered by the detection circuit, and the disconnection and connection of the first switch and the second switch are controlled by the detection circuit. The parallel switch can make the detection circuit complete the power-on and enter the normal working state quickly and effectively. The circuit structure is simple, the reliability is good, and the implementation is easy.

With reference to FIG. 7, the system ground 42 can also be connected to the output end of a driving circuit through the third switch 7. The output potential of the driving circuit is equal to the potential of the output end of the capacitive charging circuit in the capacitive touch screen detecting circuit. The third switch 7 is closed when the first switch 5 and the second switch 6 are simultaneously turned off. Further referring to FIG. 8, when the power source and the ground are isolated, the system ground GND_S of the touch screen system is connected to the output of the capacitor Ctm charging circuit in the capacitive touch screen detection circuit by closing the third switch 7. The output of the output terminal is Vch relative to the internal ground, that is, the voltage of the capacitor Ctm is Vch, and the system is grounded to connect a parasitic capacitor Clm and a plate of the detection circuit capacitor Ctm, when the system ground is connected to the output end of the Ctm charging circuit. When the voltage signal Vch of the detection circuit drives the system ground, the voltage of the upper and lower plates of the parasitic capacitance Clm is also Vch, which is equivalent to making the voltages of the detection electrodes M and LCD in FIG. 1 equal, ΔV=0, which is equivalent to shielding. Covering the influence of Clm further improves the detection accuracy.

The capacitive touch screen detection circuit provided by the invention is suitable for use in various capacitive touch devices, and therefore the capacitive touch device provided with the detection circuit is also within the protection scope of the present invention.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. Within the scope.

1‧‧‧ core detection module

11‧‧‧Internal power supply

12‧‧‧Internal grounding

2‧‧‧Data Processing and Communication Module

3‧‧‧Communication interface

4‧‧‧Capacitive touch devices

41‧‧‧System Power Supply

42‧‧‧System grounding

5‧‧‧First switch

6‧‧‧Second switch

Claims (6)

A capacitive touch screen detection circuit is disposed in a capacitive touch device, and comprises: a core detection module and a data processing and communication module, wherein the core detection module processes and communicates with the data through a communication interface The module performs communication, and the data processing and communication module and the communication interface are electrically connected to the system circuit of the capacitive touch device; the core detection module has an internal power supply and an internal ground, and the capacitive touch device has a system power supply And the system is grounded, the internal power source is connected to the system power source through the first switch, the internal ground is connected to the system ground through the second switch, and the first switch and the second switch are simultaneously disconnected during the touch detection process, and simultaneously after the detection ends closure. The capacitive touch screen detecting circuit of claim 1, wherein the ground of the system is further connected to an output end of a driving circuit through a third switch, the output potential of the driving circuit and the capacitive touch screen detecting circuit The output terminals of the capacitor charging circuit have the same potential, and the third switch is closed when the first switch and the second switch are simultaneously turned off. The capacitive touch screen detecting circuit of claim 1, wherein the internal power source is a capacitive energy storage device. The capacitive touch screen detecting circuit of claim 1, 2 or 3, wherein the first switch comprises a first system control switch and a first detection circuit control switch connected in parallel with each other; the second switch comprises parallel to each other The second system control switch and the second detection circuit control the switch. A capacitive touch device comprising a stacked display screen and a capacitive touch screen, further comprising the capacitive touch screen detecting circuit according to any one of claims 1 to 4. The capacitive touch device of claim 5, wherein the display screen is a liquid crystal display.