CN201218943Y

CN201218943Y - A capacitive touch screen

Info

Publication number: CN201218943Y
Application number: CNU200820094221XU
Authority: CN
Inventors: 陆亚军; 纪传瑞; 刘桂云; 杨云; 冯卫
Original assignee: BYD Co Ltd
Current assignee: BYD Co Ltd
Priority date: 2008-05-27
Filing date: 2008-05-27
Publication date: 2009-04-08
Anticipated expiration: 2018-05-27

Abstract

The utility model pertains to the field of touch screen, provides a capacitor type touch screen. The touch screen comprises a plurality of driver electrodes electrically coupled to the voltage source, positioned in the same plane in parallel to each other and having intervals therebetween; a plurality of detection electrodes positioned in a different plane perpendicular to driver electrodes in parallel with each other and having intervals therebetween, wherein coupling capacitors are formed at intersecting points of detection electrodes and driver electrodes; and at least one detection circuit electrically coupled to a detection electrode, detecting electric charge change generated by touching the touch screen, and converting the electric charge change into digital signal to be outputted. By detecting electric charge change when touching the touch screen, the utility model determines whether there is a touch and the touched position. The utility model is capable of improving measurement precision when electric charge is transferred, enhancing precision of positioning when touching. Meanwhile, column by column scanning or parallel column scanning, and row by row outputting or parallel row outputting is capable of being realized.

Description

A kind of capacitive touch screen

Technical field

The utility model belongs to the touch-screen field, relates in particular to a kind of capacitive touch screen.

Background technology

Touch-screen is common input equipment, generally comprises touch panel, controller and software driver.Touch panel has the transparent panel of touch sensitive surface, is mainly used to the touch sensitive incident, and touch signal is sent to controller.Controller is handled touch signal, and the touch signal after will handling exports computer system to.Software driver converts touch event to incident that computer system can be discerned.

Touch-screen mainly comprises resistive touch screen, infrared touch panel, surface acoustic wave touch screen, capacitive touch screen etc.Wherein, in capacitive touch screen, touch panel is coated a kind of material that can stored charge.When panel was touched, a little charge attracted to the touch point, detected this charge variation by charge detection circuit, and this charge variation was sent to controller handles, and determined X, the Y coordinate of touch point, and then judged the position that touches.Because when touch panel was touched, the quantity of electric charge of coupling capacitance changed small, is difficult to accurate detection, therefore be difficult to guarantee the accurate location of touch point.

The utility model content

The purpose of this utility model is to provide a kind of capacitive touch screen, is intended to solve in the existing capacitive touch screen, because it is small to touch the variation of the coupling capacitance that causes, is difficult to the problem that accurately detects.

The utility model is achieved in that a kind of capacitive touch screen, and described touch-screen comprises:

With the voltage source electrical couplings, be positioned at conplane a plurality of being parallel to each other and spaced drive electrode;

Be positioned at Different Plane with drive electrode, and a plurality of be parallel to each other and spaced detecting electrode vertical with drive electrode, the point of crossing of described detecting electrode and drive electrode forms coupling capacitance; And

With described detecting electrode electrical couplings, detect the charge variation that described touch-screen is touched and produces, charge variation is converted at least one testing circuit of digital signal output.

The charge variation that the utility model produces when being touched by the senses touch screen judges whether touch and the position that touches, and can improve the precision of measuring when electric charge shifts, the accuracy of fixed point when strengthening touch.Simultaneously, can realize by column scan or also column scan, and output or also line output line by line, the data based algorithm of generation is handled, and can realize single-point or multiple point touching.

Description of drawings

Fig. 1 is the vertical view of the capacitive touch screen that provides of the utility model;

Fig. 2 is the structural drawing of the capacitive touch screen that provides of the utility model first embodiment;

Fig. 3 is the structural drawing of the capacitive touch screen that provides of the utility model second embodiment;

Fig. 4 is the circuit theory diagrams of the capacitive touch screen that provides of the utility model;

Fig. 5 is that the electric charge of the capacitive touch screen that provides of the utility model shifts the waveform synoptic diagram.

Embodiment

In order to make the purpose of this utility model, technical scheme and advantage clearer,, the utility model is further elaborated below in conjunction with drawings and Examples.Should be appreciated that specific embodiment described herein only in order to explanation the utility model, and be not used in qualification the utility model.

In the utility model, the electric charge on the coupling capacitance is transferred to testing circuit, when touch-screen is touched, detect charge variation by testing circuit, can accurately judge the position that no touch and touch are arranged.

Fig. 1 shows the vertical view of the capacitive touch screen that the utility model provides, and for convenience of explanation, only shows the part relevant with the utility model.

This capacitive touch screen is made up of the two conductive layers of the separated by spaces that comprises a glass.The material of conductive layer generally is ITO (indium oxide).Strip shaped electric poles on each plane is parallel to each other and has at interval, and the electrode on the Different Plane is vertical mutually, and the point of crossing of two layer planes forms coupling capacitance 11.For example point as object, near coupling capacitance 11, the electric charge on the coupling capacitance 11 is siphoned away by the person, and the quantity of electric charge changes.

The electrode 10A (not shown) that links to each other with voltage source plays driving action, the electrode 10B (not shown) that links to each other with testing circuit, a detection effect.When driving voltage,

electrode

10A and 10B produce coupling capacitance 11, simultaneously, testing circuit line by line or parallel detection 10B go up change in charge.When a certain row were connected with driving voltage, other was listed as ground connection.After all provisional capitals are scanned, represent that these row drive end, then carry out the scanning of next column.When all row all are scanned one time, represent a loop ends, then carry out next one circulation again.

Testing circuit can be measured the coupling capacitance on each electrode 10B, its effect is intensity and a change amount of determining coupling capacitance 11, simulating signal is become numerical data, pass to the controller of back and handle (not shown), determine the position that the coordinate of touch area promptly touches, thereby realize the function of single-point touches or multiple point touching.

In the utility model, the quantity of testing circuit is arbitrarily, can also can a testing circuit all be arranged each electrode 10B only with one.

Fig. 2 shows the structure of the capacitive touch screen that the utility model first embodiment provides, its electrode 10A and electrode 10B by the apart of transparent conductive medium structure forms, the electrode 10A of this apart is over-molded on two different layers with electrode 10B, forms two conductive layers.Be parallel to each other and have at interval at the strip shaped electric poles of same conductive layer, the electrode of different conductive layers is vertical mutually, and the point of crossing of the electrode on the two conductive layers forms coupling capacitance 11.Wherein, different coordinate of the common expression of each electrode 10A and electrode 10B, coordinate can be cartesian coordinate system (x and y), polar coordinate system (r, θ) or other coordinate systems.Electrode 10A electrical couplings plays driving action to voltage source (scheming not shown).Every strip electrode 10B all connects a testing circuit 30 that plays detection effect.When driving voltage, electrode 10A and electrode 10B produce coupling capacitance 11, and the testing circuit 30 parallel detection electrode 10B that are connected with every strip electrode 10B go up change in charge, and this charge variation is converted to digital signal, export controller (scheming not shown) to.Controller is handled this digital signal, and judge touch point position according to the coordinate (as x, y coordinate or r, θ coordinate etc.) of touch point, convert this touch event to incident that computing machine can be discerned by software driver (scheming not shown) again, handle according to algorithm, can realize the function of single-point or multiple point touching.

In the present embodiment,, thereby can go up change in charge by parallel detection 10B because every strip electrode 10B all connects a testing circuit 30, and can and the line output testing result, can reduce sweep time to greatest extent, improve sweep frequency.

Fig. 3 shows the structure of the capacitive touch screen that the utility model second embodiment provides, and it only is that with the difference of capacitive touch screen shown in Figure 2 all electrode 10B all are connected with testing circuit 30 by an on-off controller 12.Under the control of on-off controller 12, testing circuit 30 serial detecting electrode 10B go up change in charge, and electrode 10B is gone up change in charge are converted to digital signal, serial export controller (scheming not shown) to.In the utility model, because only need be for capacitive touch screen is provided with a testing circuit, thereby reduced the use of practical devices, simplified the structure of capacitive touch screen, reduced the capacitive touch screen cost.

Fig. 4 shows the circuit structure of the capacitive touch screen that the utility model provides, and for convenience of explanation, only shows the part relevant with the utility model.

Drive electrode 21 forms coupling capacitances 23 with detecting electrode 22, and drive electrode 21 is corresponding with electrode 10A among Fig. 1, and detecting electrode 22 is corresponding with electrode 10B among Fig. 1, and coupling capacitance 23 is corresponding with the coupling capacitance 11 among Fig. 1.Drive electrode 21 electrical couplings are to the voltage source (not shown).Detecting electrode 22 electrical couplings are to testing circuit 30.Drive electrode 21 is connected with voltage source through switch 24, and through switch 25 ground connection.Detecting electrode 22 is connected with testing circuit 30 through switch 26, and through switch 27 ground connection.

Testing circuit 30 comprises operational amplifier 33, be connected across the normal phase input end of operational amplifier 33 and the sampling capacitor 31 and the switch 32 of output terminal, the comparer 34 that is connected with the output terminal of operational amplifier 33, and be connected the counter 35 of the system's pulse number when being used for recording voltage from 0V to threshold voltage with comparer 34.Wherein, the normal phase input end of operational amplifier 33 is connected with detecting electrode 22 by switch 26, the inverting input cross-over connection ground of operational amplifier 33, and sampling capacitor 31 is in parallel with switch 32, another input termination threshold voltage V of comparer 34 _Th

The principle of work of testing circuit 30 is that the electric charge on the coupling capacitance 23 is transferred on the sampling capacitor 31, system's pulse number that the voltage on the counter 35 record sampling capacitors 31 passes through when 0V reaches threshold voltage.When touch panel is touched, cause the variation of coupling capacitance 23, thereby the change in voltage on the sampling capacitor 31 is transferred in influence, finally cause the difference of the pulse number of record, the difference of counter 35 register system pulse numbers, and the difference of pulse number transferred to controller (scheming not shown), in order to judge that touch-screen has or not the position that is touched and touches.

At first,

Closing Switch

24 and 25, the charge circuit of formation coupling capacitance 23, to coupling capacitance 23 chargings, the capacitance of establishing coupling capacitance 23 is Cx.Cut-

off switch

24 and 25 again, Closing

Switch

24 and 26 simultaneously forms the charge circuit of sampling capacitor 31, and the electric charge on the coupling capacitance 23 is transferred on the sampling capacitor 31, and the capacitance of establishing coupling capacitance 23 is Cs.Obtain the value of U2 according to Q=Cx*U1=Cs*U2, comparer 34 compares voltage on the sampling capacitor 31 and threshold voltage, and the voltage on sampling capacitor 31 does not reach threshold voltage V _ThThe time, the circulation said process is transferred to the electric charge of coupling capacitance 23 on the sampling capacitor 31, up to comparer 34 with magnitude of voltage on the sampling capacitor 31 and threshold voltage V _ThWhen comparing, the magnitude of voltage on the sampling capacitor 31 has reached threshold voltage V _ThTill, its oscillogram is as shown in Figure 5.Voltage on sampling capacitor 31 has reached threshold voltage V _ThThe time, Closing Switch 32 is discharged to sampling capacitor 31, makes the magnitude of voltage zero clearing on the sampling capacitor 31.Through said process, the quantity of electric charge of coupling capacitance 23 can be transferred to sampling capacitor 31.Voltage on the counter 35 record sampling capacitors 31 reaches threshold voltage V from 0V _ThThe time system's pulse number.

When touch panel is touched, promptly when object (as finger) during near coupling capacitance 23, electric charge on the coupling capacitance is siphoned away by object, the quantity of electric charge of coupling capacitance 23 is changed, according to Q=Cx*U1=Cs*, learn that the voltage U 2 on the sampling capacitor 31 also changes, the voltage on sampling capacitor 31 reaches threshold voltage V _ThThe time, the voltage on the sampling capacitor 31 of counter 35 records reaches threshold voltage V from 0V _ThThe time system that passes through pulse number also change, thereby judge that capacitive touch screen is touched.When 30 pairs of drive electrodes 21 of testing circuit and detecting electrode 22 scan, can obtain the coordinate of touch point, by the coordinate of touch point is analyzed and is handled, can learn touch point position, can realize the function of single-point or multiple point touching as required.

Because the electrode in the capacitive touch screen in the two conductive layers is orthogonal, be parallel to each other and the interval with the electrode in one deck conductive layer, be subjected to of the influence of mutually vertical or parallel electrode with respect to the earth potential of the big surf zone of other circuit and capacitive touch screen, may produce stray capacitance 28, stray capacitance 28 may exert an influence to testing circuit 30.In the utility model, by

switch

24 and 25 can 28 pairs of testing circuits 30 of shield parasitic capacitance influence, thereby improve the degree of accuracy that detects.

The charge variation that the utility model produces when being touched by the senses touch screen judges whether touch and the position that touches, and can improve the precision of measuring when electric charge shifts, the accuracy of fixed point when strengthening touch.Simultaneously, can realize by column scan or and column scan, corresponding can realize exporting line by line or and line output, and four kinds of combined methods all are feasible.In addition, adopt testing circuit of the present utility model, can save the A/D conversion, directly convert analog quantity to digital processing, reach the purpose of simplifying circuit.

The above only is preferred embodiment of the present utility model; not in order to restriction the utility model; all any modifications of within spirit of the present utility model and principle, being done, be equal to and replace and improvement etc., all should be included within the protection domain of the present utility model.

Claims

1. A capacitive touch screen, characterized in that the touch screen comprises:

Electrically coupled with a voltage source, a plurality of parallel and spaced driving electrodes located on the same plane;

A plurality of parallel and spaced detection electrodes located on different planes from the drive electrodes and perpendicular to the drive electrodes, where the intersections of the detection electrodes and the drive electrodes form coupling capacitances; and

At least one detection circuit is electrically coupled with the detection electrode, detects the charge change generated by the touch screen being touched, and converts the charge change into a digital signal for output.

2. The capacitive touch screen according to claim 1, wherein there are a plurality of detection circuits, each detection circuit is correspondingly connected to a detection electrode, and detects changes of charges on the plurality of detection electrodes in parallel.

3. The capacitive touch screen according to claim 1, wherein the capacitive touch screen further comprises:

A switch controller, one end of the switch controller is connected to all detection electrodes, and the other end is connected to the detection circuit;

Under the control of the switch controller, the detection circuit detects the change of the charge on the plurality of detection electrodes in series.

4. The capacitive touch screen according to claim 1, 2 or 3, wherein the detection circuit comprises:

An operational amplifier connected to the detection electrode corresponding to the detection electrode at the positive phase input end;

A sampling capacitor and a switch connected across the non-inverting input terminal and the output terminal of the operational amplifier, the switch is connected in parallel with the sampling capacitor;

a comparator connected to the output of the operational amplifier, and the threshold voltage; and

It is connected with the output terminal of the comparator to record the difference in the number of system pulses and output the counter.

5. The capacitive touch screen according to claim 1, wherein the touch screen further comprises:

one end is connected to a voltage source, and the other end is connected to the first switch of the driving electrode; and

A second switch with one end connected to the driving electrode and one end grounded.

6. The capacitive touch screen according to claim 1, wherein the touch screen further comprises:

One end is connected to the detection electrode, and the other end is connected to the third switch of the detection circuit; and

A fourth switch with one end connected to the detection electrode and one end grounded.