Touch circuit, touch detection method, display panel and display device

The present disclosure generally relates to the field of display technologies and, more particularly, to a touch circuit, a touch detection method, a display panel, and a display device. The touch circuit includes a touch electrode, a touch signal line, and a driving transistor. The driving transistor has a control terminal coupled to the touch electrode, a first terminal receiving a first power signal, and a second terminal coupled to the touch signal line, and is configured to output a current signal to the touch signal line based on a voltage signal of the touch electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present disclosure is based upon International Application No. PCT/CN2019/087985, filed on May 22, 2019, which is based upon and claims priority to Chinese Patent Application No. 201810553991.4, filed on May 31, 2018, titled “TOUCH CIRCUIT, TOUCH DETECTION METHOD, DISPLAY PANEL AND DISPLAY DEVICE”, and the entire contents thereof are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to the field of display technologies, and more particularly, to a touch circuit, a touch detection method, a display panel, and a display device.

BACKGROUND

Touch technology includes self-capacitive touch technology and mutual-capacitive touch technology. Among them, self-capacitive touch technology, due to its simple structure, is widely used in various display technology fields, such as the display technology fields of OLED and AMOLED display devices.

In the related art, a self-capacitive touch circuit generally includes a touch signal line and a touch electrode. When a touch subject (such as a finger) approaches the touch electrode, a voltage on the touch electrode is changed due to capacitive coupling. A position where the touch subject touches may be determined according to a voltage change on the touch electrode sensed by the touch signal line.

However, a voltage signal on the touch electrode may be attenuated when being transmitted through the touch signal line. As the size of a display panel becomes larger, the length of the touch signal line is required to be longer. The longer the touch signal line is, the more serious the effect on the detection of the voltage change of the touch electrode the touch signal line may have, thereby affecting accuracy of touch detection.

It is to be noted that the above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore, it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.

SUMMARY

In an aspect of embodiments of the present disclosure, a touch circuit is provided. The touch circuit includes a touch electrode, a touch signal line, and a driving transistor. The driving transistor has a control terminal coupled to the touch electrode, a first terminal receiving a first power signal, and a second terminal coupled to the touch signal line, and is configured to output a current signal to the touch signal line based on a voltage signal of the touch electrode.

According to an embodiment of the present disclosure, the touch circuit further includes at least one first switching transistor. The first switching transistor has a control terminal receiving a first control signal, a first terminal coupled to the touch electrode, and a second terminal receiving a second power signal, and is configured to charge the touch electrode with the second power signal in response to the first control signal.

According to an embodiment of the present disclosure, the touch circuit further includes a capacitor element. The capacitor element has a first terminal coupled to the control terminal of the driving transistor, and a second terminal receiving a second control signal.

According to an embodiment of the present disclosure, the touch circuit further includes at least one second switching transistor. The second switching transistor has a control terminal receiving a third control signal, a first terminal coupled to the touch electrode, and a second terminal receiving the second power signal, and is configured to charge the touch electrode with the second power signal in response to the third control signal.

According to an embodiment of the present disclosure, the touch circuit is provided on a display panel including a gate driving circuit. The first control signal, the second control signal, and the third control signal share a scan signal provided by the gate driving circuit. A driving timing of the second control signal is earlier than that of the third control signal and later than that of the first control signal.

In another aspect of embodiments of the present disclosure, a display panel is further provided including the touch circuit described above.

According to an embodiment of the present disclosure, the display panel further includes a plurality of driving electrodes extending along a first direction and spaced apart from each other along a second direction. Each of the driving electrodes includes a plurality of first electrode blocks and second electrode blocks arranged alternately and spaced apart from each other. The first electrode block is used as the touch electrode, and the second electrode block is configured to provide a power signal to a driving circuit of the display panel and to further provide the second power signal.

According to an embodiment of the present disclosure, a plurality of touch circuits disposed on a same one of the driving electrodes are coupled to a same touch signal line.

According to an embodiment of the present disclosure, a size of each of the touch electrodes in the first direction varies in the second direction.

In yet another aspect of embodiments of the present disclosure, a touch detection method is further provided for the touch circuit described above, including: charging the touch electrode; converting a voltage signal of the driving electrode into a current signal by using the driving transistor; and determining a touch position according to the current signal.

In yet another aspect of embodiments of the present disclosure, a display device is further provided including the display panel described above.

It is to be understood that the above general description and the detailed description below are merely exemplary and explanatory, and do not limit the present disclosure.

DETAILED DESCRIPTION

Example embodiments will be described more comprehensively by referring to accompanying drawings now. However, the example embodiments can be embodied in many forms and should not be construed as being limited to embodiments set forth herein; rather, these embodiments are provided so that the present disclosure will be made thorough and complete, and the concept of the example embodiments will be fully conveyed to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures and thus, repeated description thereof will be omitted.

Although relative terms such as “upper” and “lower” are used in this specification to describe relative relationship between one component and another component shown, these terms are used in this specification only for convenience, for example, according to directions of examples shown in the drawings. It can be understood that if a device shown is turned upside down, an “upper” component described will become a “lower” component. Other relative terms, such as “high”, “low”, “top”, “bottom”, “left”, and “right” have similar meanings. When a structure is “on” another structure, it may refer to that the structure is integrally formed on the other structure, or that the structure is “directly” arranged on the other structure, or that the structure is “indirectly” arranged on the other structure through another structure.

The terms “a”, “an”, and “the” are used to indicate the presence of one or more elements/components/etc. The terms “including” and “having” are used in an open-ended manner, and refer to that there may be additional elements/components/etc. in addition to the listed elements/components/etc.

This exemplary embodiment first provides a touch circuit.FIG. 1is a schematic structural diagram of a touch circuit according to an exemplary embodiment of the present disclosure and, as shown inFIG. 1, the touch circuit includes a touch electrode1, a touch signal line2, and a driving transistor3. A control terminal of the driving transistor3is coupled to the touch electrode1, a first terminal of the driving transistor3is configured to receive a first power signal Vin, and a second terminal of the driving transistor is coupled to the touch signal line to output a current signal to the touch signal line according to a voltage signal of the touch electrode.

In this exemplary embodiment, the driving transistor may be either a P-channel thin film transistor or an N-channel thin film transistor. The present exemplary embodiment will be described by taking the P-channel thin film transistor as an example. The first terminal of the driving transistor3is a source electrode, the second terminal is a drain electrode, and the control terminal is a gate electrode. The source electrode of the driving transistor3is configured to receive the first power signal Vin, the drain electrode of the driving transistor3is coupled to the touch signal line2, and the gate electrode of the driving transistor3is coupled to the touch electrode. When the touch circuit is in operation, the driving transistor3operates in a saturation region, and an output current from the drain electrode of the driving transistor3is Iout=k(Vgs−Vth)2=k(Vg−Vs−Vth)2, where Vg is a gate voltage of the driving transistor3, Vs is a source voltage of the driving transistor3, k is a mobility of the driving transistor3, and Vth is a threshold voltage of the driving transistor3. In this exemplary embodiment, Vg is equal to the voltage of the touch electrode, Vs is equal to Vin, and k and Vth are constant values. Therefore, it can be seen that the output current Iout from the drain electrode of the driving transistor3is only related to the voltage of the touch electrode, and a voltage change of the touch electrode can be determined based on the output current Iout from the drain electrode of the driving transistor3. However, when a touch subject (such as a finger) approaches the touch electrode, the voltage of the touch electrode is changed. Therefore, a touch on the touch electrode can be detected by detecting the output current Iout from the drain electrode of the driving transistor3.

In the touch circuit provided by the embodiments of the present disclosure, a voltage signal of a touch electrode is converted into a current signal through a driving transistor. On one hand, it avoids an attenuation of a voltage signal on the touch electrode when being transmitted through a touch line, thereby improving accuracy of touch detection. On the other hand, the touch circuit has a simple structure and low cost.

The exemplary embodiment further discloses a display panel including the touch circuit described above. Specifically,FIG. 2is a schematic structural diagram of a display panel according to an exemplary embodiment of the present disclosure, andFIG. 3is a circuit diagram of a touch circuit in a display panel according to an exemplary embodiment of the present disclosure. As shown inFIGS. 2 and 3, the display panel may include a plurality of driving electrodes5extending along a first direction and spaced apart from each other along a second direction. Each of the driving electrodes5may include a plurality of first electrode blocks51and second electrode blocks52arranged alternately and spaced apart from each other. The first electrode block51may be used as the touch electrode1, and the second electrode block52is configured to provide a power signal to a driving circuit of the display panel. The driving electrode5may be a cathode or an anode. In this exemplary embodiment, it is illustrated by taking that the driving electrode5is used as the cathode. All the second electrode blocks52in the display panel are electrically coupled and have an output voltage VSS.

In the display panel provided in the present exemplary embodiment, the first electrode blocks share the touch electrode. On one hand, such arrangement reduces the number of crossing-nodes of wires, thereby reducing parasitic capacitance between the wires and improving display effect. On the other hand, such arrangement avoids disposing additional touch layers, which reduces the number of wirings, simplifies processes, and saves costs.

In this exemplary embodiment, as shown inFIG. 3, the touch circuit may further include at least one first switching transistor4. A control terminal of the first switching transistor4receives a first control signal S1, a first terminal of the first switching transistor4is coupled to the first electrode block51, and a second terminal of the first switching transistor4receives a second power signal. The first switching transistor4is configured to charge the first electrode block51with the second power signal in response to the first control signal S1.

As shown inFIG. 3, the touch circuit may further include a capacitor element6in order to perform a touch detection in a preset period. A first terminal of the capacitor element6is coupled to the control terminal of the driving transistor3, and a second terminal of the capacitor element6receives a second control signal S2. The first switching transistor4may be disposed on the second electrode block52, and the second power source signal may be provided by the second electrode block52. At this time, a voltage of the second power source signal is VSS, and the first electrode block51is at a voltage VSS when being charged with the second power signal. The first switching transistor4may be a P-channel thin film transistor, the second power signal provided by the second electrode block52may be greater than a threshold voltage of the first switching transistor4, and the second control signal S2may be a pulse signal.

When the second control signal S2is at a high level, a voltage at the control terminal of the driving transistor3is equal to VSS. At this time, the driving transistor is not turned on and the touch circuit does not perform touch detection. When the second control signal S2is at a low level, the first terminal of the capacitor element6has a voltage drop due to a voltage drop at the second terminal, so that the control terminal of the driving transistor3coupled to the first terminal of the capacitor element6also has a voltage drop. At this time, a voltage at the control terminal of the driving transistor3is lower than the threshold voltage of the first switching transistor4, and the driving transistor3is turned on, so that the touch circuit performs touch detection. In the present exemplary embodiment, the touch detection may be controlled according to a time period by disposing the capacitor element6. It should be understood that, in other exemplary embodiments, the driving electrode5may also be an anode, the driving transistor may be an N-channel thin film transistor, the first switching transistor4may be an N-channel thin film transistor, and the second power signal provided by the second electrode block52may be smaller than the threshold voltage of the first switching transistor4, which all belong within the scope of protection of the present disclosure.

In this exemplary embodiment, as shown inFIG. 3, during a touch detection phase of the touch circuit, the first electrode block51will release charges, and the voltage of the first electrode block51will change. Since the first electrode block51and the second electrode block52form a capacitor structure, a voltage change of the first electrode block51will affect the voltage of the second electrode block52, and as a result, the display panel displays abnormally. In this exemplary embodiment, the touch circuit further includes at least one second switching transistor7. A control terminal of the second switching transistor7receives a third control signal S3, a first terminal of the second switching transistor7is coupled to the first electrode block51, and a second terminal of the second switching transistor7can receive the second power signal. The second switching transistor is configured to charge the first electrode block51with the second power signal in response to the third control signal. The first electrode block51is charged with the second power signal in response to the third control signal after the discharging of the first electrode block51is completed, so that the voltages of the first electrode block51and the second electrode block52are the same, and the first electrode block51does not affect normal display.

In this exemplary embodiment, the first control signal S1, the second control signal S2, and the third control signal S3may share a scan signal provided by a gate driving circuit in the display panel. A driving timing of the second control signal S2is earlier than that of the third control signal S3and later than that of the first control signal S1. In the display panel, the gate driving circuit generates scan signals to the pixel driving circuit row by row according to a time sequence. The first control signal S1may share the scan signal of pixels in a previous row, the second control signal S2may share the scan signal of pixels in a middle row, and the third control signal S3may share the scan signal of pixels in a next row. The pixels in the previous row, the pixels in the middle row, and the pixels in the next row refer to three rows of pixels having a relative position in the display panel, and the three rows of pixels may be adjacent or spaced apart from each other. In this exemplary embodiment, the first control signal S1, the second control signal S2, and the third control signal S3of the touch circuit share a scanning signal provided by the gate driving circuit, which can allow touch control to be performed in synchronization with display. Therefore, it is not necessary to set a touch period separately, thereby increasing display time. Such setting avoids a technical problem in the related art that service life of the display panel is short since a normal display is supported by increasing luminance of light emitting elements due to short display time.

FIG. 4is a timing diagram of control signals in a touch circuit according to an exemplary embodiment of the present disclosure. As shown inFIG. 4, in period t1, S1is at a low level, S2is at a high level, and S3is at a high level. During this period, the first switching transistor is turned on, the second switching transistor is turned off, and the first electrode block51is charged to be at VSS with the second power signal. Since VSS is greater than the threshold voltage of the first switching transistor4, the driving transistor is turned off, and the output current from the driving transistor is Iout=0. During period t2, S1is at a high level, S2is at a low level, and S3is at a high Level. During this period, the first switching transistor is turned off, the second switching transistor is turned off, and the first terminal of the capacitor element6has a voltage drop due to the voltage drop of the second terminal, so that the voltage Vgate of the control terminal of the driving transistor3coupled to the first terminal of the capacitor element6is dropped to VSS+ΔV, where ΔV is a voltage variation of the second control signal. At this time, the voltage at the control terminal of the driving transistor is less than the threshold voltage of the first switching transistor4, and the driving transistor3is turned on. When no touch control occurs, the driving transistor3outputs a current I=I1, and when a touch control occurs, the driving transistor3outputs a current I=I2. During period t3, S1is at a high level, S2is at a high level, and S3is at a low level. The first switching transistor4is turned off, the second switching transistor7is turned on, and the touch electrode1is charged to be at VSS with the second power signal.

FIG. 5is a schematic structural diagram of a touch circuit of a display panel in the related art. Each touch electrode500is coupled to one detection line501. In this exemplary embodiment, as shown inFIG. 2, a plurality of touch circuits provided on a same driving electrode5may be coupled to a same touch signal line2. Such arrangement can reduce the number of pins of a detection unit coupled to the touch signal line, and reduce the cost of the detection unit.

In this exemplary embodiment, if the size of a driving electrode of the display panel in the second direction is relatively large and a touch area is smaller than the size of the driving electrode in the second direction, it is difficult to determine a specific location of the touch area over the driving electrode along the second direction. In this exemplary embodiment, as shown inFIG. 6, which is a schematic structural diagram of a touch electrode in a display panel according to an exemplary embodiment of the present disclosure, the size of each of the touch electrodes (i.e., the first electrode block51) in the first direction changes along the second direction. InFIG. 6, there are two touch points A and B on the first electrode block51. The area around a touch point A is larger than the area around a touch point B. When the two points A and B are touched, different capacitance changes occur on the first electrode block51. Specific touch positions can be obtained through the different capacitance changes. InFIG. 6, there are two touch points C and D on the second electrode block52. The touch point C is closer to the first electrode block51, and the touch point D is farther from the first electrode block51. When the points C and D are touched, different capacitance changes occur on the first electrode block51, and specific touch positions can be obtained through the different capacitance changes. Therefore, such arrangement can improve touch accuracy. InFIG. 6, the size of the first electrode block51in the first direction changes stepwise along the second direction. It should be understood that there are more ways to change the size, in the first direction, of the first electrode block51along the second direction, which all belong within the scope of protection of the present disclosure.

This exemplary embodiment also provides a touch detection method, which is applied to the above touch circuit.FIG. 7is a flowchart of a touch detection method according to an exemplary embodiment of the present disclosure. As shown inFIG. 7, the method includes the following steps.

At S1, the touch electrode is charged.

At S2, a voltage signal of the touch electrode is converted into a current signal by using the driving transistor.

At S3, a touch position is determined according to the current signal.

The touch detection method provided in this exemplary embodiment has the same technical features and working principles as the touch circuit described above, and the above content has been described in detail, and is not repeated herein.

The present disclosure also provides a display device including the above display panel.

In this exemplary embodiment, the specific type of the display device is not particularly limited, and may be any type of display device commonly used in the art, such as an OLED display. The display device provided in this exemplary embodiment has the same technical features and working principles as the display panel described above, and the above content has been described in detail, and is not repeated here.

Those skilled in the art will readily contemplate other embodiments of the present disclosure after considering the specification and practicing the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that conform to the general principles of this disclosure and include the common knowledge or conventional technical means in the technical art which are not disclosed in this disclosure. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

It should be understood that the present disclosure is not limited to the precise structure that has been described above and illustrated in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the disclosure is limited only by the following claims.