A space-saving driving circuit, method, and touch display driver chip

Abstract

This invention provides a space-saving driving circuit, method, and touch display driver chip. The driving circuit includes a touch sensing circuit, a common electrode driving circuit, and several compensation capacitors. During the touch sensing period, the compensation capacitors are used to compensate for parasitic capacitance on the sensing path. The compensation voltage output by the common electrode driving circuit drives the compensation capacitors to cancel out the parasitic capacitance on the sensing path. During the display driving period, the compensation capacitors are reused as storage capacitors to maintain a stable common voltage. This invention reduces the area occupied by the driving circuit on the touch display driver chip by reusing the compensation capacitors and the common electrode driving circuit.

Description

Technical Field

[0001] This invention belongs to the field of driving circuits, and particularly relates to a space-saving driving circuit, method, and touch display driving chip. Prior Technology

[0002] Display panels are widely used in consumer electronics such as mobile phones, watches, and tablets. To reduce costs, touch display driver chips have developed rapidly. They integrate the common electrode driving circuit for display and the touch sensing circuit for touch control into the touch display driver chip, thereby achieving an integrated design of touch and display.

[0003] Specifically, the common electrode within the display panel is driven by the common electrode driving circuit during the display period, and this common electrode driving circuit is connected to an external large storage capacitor to maintain a stable common voltage. The sensing electrode within the display panel is driven by the touch sensing circuit during the touch sensing period. However, due to parasitic capacitance in the signal traces within the display panel and the chip, the sensing signal in the touch sensing circuit is prone to saturation. Therefore, in existing technologies, compensation capacitors are typically used to offset the additional sensing signal introduced by the parasitic capacitance, and corresponding driving circuits are added. It is precisely because of the presence of the external large storage capacitor and the added driving circuit for driving the compensation capacitor that the area occupied by the driving circuit on the touch display driver chip increases. Summary of the Invention

[0004] The purpose of this invention is to provide a space-saving driving circuit, method, and touch display driver chip. By reusing the compensation capacitor and the common electrode driving circuit, the area occupied by the driving circuit on the touch display driver chip is reduced.

[0005] To achieve the above objectives, a first aspect of the present invention provides a method for saving the area of ​​a driving circuit, wherein the driving circuit includes a plurality of compensation capacitors. During the touch sensing period, the compensation capacitors are used to compensate for parasitic capacitances on the sensing path. During the display driving period, the compensation capacitors are reused as storage capacitors to maintain a stable common voltage.

[0006] Optionally, the driving circuit includes a touch sensing circuit and a common electrode driving circuit. During the touch sensing period, the compensation voltage output by the common electrode driving circuit drives the compensation capacitor to cancel the parasitic capacitance on the sensing path.

[0007] Optionally, the first end of the compensation capacitor is connected to the compensation node of the touch sensing circuit, and the first end is also grounded through a first switch; the second end of the compensation capacitor is connected to the voltage output terminal of the common electrode driving circuit.

[0008] Optionally, during the touch sensing period, the first switch disconnects the ground connection of the compensation capacitor, and the common electrode driving circuit outputs a compensation voltage to drive the compensation capacitor so that the compensation capacitor provides capacitance compensation to the sensing path; during the display driving period, the first switch turns on the ground connection of the compensation capacitor so that the compensation capacitor is reused as a storage capacitor to maintain the stability of the common voltage output by the common electrode driving circuit.

[0009] Optionally, the first end of the compensation capacitor is connected to the compensation node of the touch sensing circuit through a second switch. During the display driving period, the second switch disconnects the compensation capacitor from the compensation node of the touch sensing circuit to avoid the compensation capacitor affecting the voltage of the compensation node.

[0010] A second aspect of the present invention provides an area-saving driving circuit comprising: a multiplexer for selecting an output common voltage to drive a common electrode during a display driving period and selecting an output touch voltage to drive a sensing electrode during a touch sensing period; and a plurality of compensation capacitors, wherein during the touch sensing period, the compensation capacitors are used to compensate for parasitic capacitances on the sensing path, and during the display driving period, the compensation capacitors are multiplexed as storage capacitors to maintain a stable common voltage.

[0011] Optionally, the area-saving driving circuit further includes: a touch sensing circuit; a common electrode driving circuit; during the display driving period, the common electrode driving circuit is allowed by the multiplexer to output a common voltage to drive the common electrode, and during the touch sensing period, the touch sensing circuit is allowed by the multiplexer to output a touch voltage to drive the sensing electrode.

[0012] Optionally, the touch sensing circuit includes: a second sub-driving module for outputting a sensing waveform and converting the sensed capacitance into a current signal; and a third sub-driving module for converting the current signal into a voltage signal.

[0013] Optionally, a compensation node is provided at the input end of the third sub-driving module, and the first end of the compensation capacitor is connected to the touch sensing circuit through the compensation node.

[0014] Optionally, the common electrode driving circuit includes a first sub-driving module, which outputs a common voltage during the display driving period or a compensation voltage during the touch sensing period.

[0015] Optionally, the second end of the compensation capacitor is connected to the output of the common electrode drive circuit.

[0016] Optionally, the first terminal of the compensation capacitor is also connected to ground via a first switch.

[0017] Optionally, the first end of the compensation capacitor is directly connected to the compensation node, or it is connected to the compensation node through a second switch.

[0018] Optionally, the sensing electrode can be reused as the common electrode.

[0019] A third aspect of the present invention provides an area-saving touch display driver chip, including the aforementioned area-saving driver circuit.

[0020] Compared with the prior art, the area-saving driving circuit, method and touch display driving chip provided by the present invention have at least the following beneficial effects: by using the compensation capacitor as a compensation capacitor for parasitic capacitance on the sensing path during the touch sensing period and reusing it as a storage capacitor to maintain the stability of the common voltage during the display driving period, the setting of large off-chip storage capacitors is reduced; at the same time, by reusing the common electrode driving circuit as a driving circuit for driving the compensation capacitor during the touch sensing period, the additional driving circuit dedicated to driving the compensation capacitor is reduced, thereby saving the area occupied by the driving circuit. Simple Explanation of the Diagram

[0021] Figure 1 is a schematic diagram of the driving circuit of a touch display driving chip provided in an embodiment of the present invention;

[0022] Figure 2 is a schematic diagram of the touch sensing circuit and common electrode driving circuit of a touch display driver chip provided in an embodiment of the present invention;

[0023] Figure 3 is a schematic diagram of the touch sensing circuit and common electrode driving circuit of another touch display driver chip provided in an embodiment of the present invention;

[0024] Figure 4 is a schematic diagram of the specific structure of the driving circuit of another touch display driving chip provided in an embodiment of the present invention. Implementation

[0025] The technical solutions, structural features, achieved objectives, and effects of the present invention will be described in detail below with reference to Figures 1 to 4 in the embodiments of the present invention.

[0026] It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions. They are only used to facilitate and clarify the purpose of illustrating the embodiments of the present invention, and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationship, or adjustments to the size should still fall within the scope of the technical content disclosed in the present invention, provided that they do not affect the effects and objectives that the present invention can produce.

[0027] It should be noted that, in this invention, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only the elements expressly listed, but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0028] First, the working principle of existing driving circuits used for touch sensing and display is introduced. During the display driving period, the common electrode is driven by the output of the common electrode driving circuit selected by a multiplexer. Simultaneously, to maintain voltage stability of the common electrode, the common electrode driving circuit is connected to an external large storage capacitor. During the touch sensing period, the sensing electrode is driven by the output of the touch sensing circuit selected by a multiplexer. Due to the presence of parasitic capacitances (e.g., display panel capacitance Csp and chip trace capacitance Csc), the sensing quantity generated by these parasitic capacitances is not only independent of whether a touch is applied, but also saturates the sensing signal within the touch sensing circuit. Therefore, existing technologies use compensation capacitors to offset the sensing signal introduced by parasitic capacitances, and add corresponding additional driving circuitry. Since each touch sensing circuit requires compensation capacitors, the area occupied by existing driving circuits increases, while these compensation capacitors are idle during the display driving period.

[0029] To address the aforementioned shortcomings, this invention, based on the time-sharing operation characteristic of touch display driver chips, reuses the compensation capacitor in the driver circuit and the common electrode driver circuit to drive the common electrode and compensation capacitor in a time-sharing manner. This reduces the need for setting up large off-chip storage capacitors and additional driver circuits for driving compensation capacitors, thereby saving the footprint of the driver circuit.

[0030] Based on the above-mentioned inventive concept, this invention provides a method for saving the area of ​​a driving circuit. The driving circuit includes several compensation capacitors. The method includes: during the touch sensing period, the compensation capacitors are used to compensate for parasitic capacitance on the sensing path; during the display driving period, the compensation capacitors are reused as storage capacitors to maintain a stable common voltage. By reusing the compensation capacitors as storage capacitors during the display driving period, the driving circuit no longer needs to set up a large off-chip storage capacitor. This saves a large number of large off-chip storage capacitors used in the prior art to maintain a stable common voltage, effectively maintaining the stability of the common voltage, thereby ensuring the stability of the display effect and saving the area occupied by the driving circuit.

[0031] Furthermore, the driving circuit includes a touch sensing circuit and a common electrode driving circuit. During the touch sensing period, the compensation voltage output by the common electrode driving circuit drives the compensation capacitor to cancel the parasitic capacitance on the sensing path. By multiplexing the common electrode driving circuit to output the compensation voltage during the touch sensing period, the additional driving circuit corresponding to each compensation capacitor in the prior art is reduced, thereby saving the area occupied by the driving circuit.

[0032] The compensation capacitor has its first terminal connected to the compensation node of the touch sensing circuit and is also grounded via a first switch. The second terminal of the compensation capacitor is connected to the voltage output terminal of the common electrode driving circuit. Specifically, during the touch sensing period, the first switch disconnects the grounding connection of the compensation capacitor, and the common electrode driving circuit outputs a compensation voltage to drive the compensation capacitor, enabling it to provide capacitance compensation to the sensing path. By disconnecting the first switch, the compensation capacitor is prevented from being grounded, thus avoiding charge release through the ground wire and keeping it at ground potential (0V), preventing it from providing compensation voltage to the touch sensing circuit. During the display driving period, the first switch reconnects the grounding connection of the compensation capacitor, allowing it to be reused as a storage capacitor to maintain the stability of the common voltage output by the common electrode driving circuit. This enables the common electrode driving circuit to provide a more stable voltage hold, thereby ensuring the stability and quality of the displayed image.

[0033] Furthermore, the first end of the compensation capacitor is connected to the compensation node of the touch sensing circuit through the second switch. During the display driving period, the second switch disconnects the compensation capacitor from the compensation node of the touch sensing circuit to avoid the compensation capacitor being grounded and pulling down the voltage of the compensation node, thereby reducing the impact on the preparation state of the touch sensing circuit before sensing. This allows the input and output of the touch sensing circuit to be reset to the corresponding common-mode level before sensing begins, improving the touch sensing efficiency.

[0034] Based on the above-mentioned method for saving driving circuit area, the present invention also provides an area-saving driving circuit, as shown in FIG1. ​​The driving circuit includes: a multiplexer 100, which is connected to a common electrode 101 and a sensing electrode 102, used to select and output a common voltage to drive the common electrode 101 during the display driving period, and to select and output a touch voltage to drive the sensing electrode 102 during the touch sensing period; and several compensation capacitors 200, which are used to compensate for parasitic capacitance on the sensing path during the touch sensing period, and are reused as storage capacitors to maintain the stability of the common voltage during the display driving period. In this embodiment, by reusing the compensation capacitors 200 as storage capacitors during the display driving period, the driving circuit does not need to set up additional large off-chip storage capacitors, saving a large number of large off-chip storage capacitors used in the prior art to maintain the stability of the common voltage, thereby ensuring the stability of the display effect and saving the area occupied by the driving circuit.

[0035] As shown in Figure 1, the area-saving driving circuit further includes a touch sensing circuit 300 and a common electrode driving circuit 400. The first input terminal A1 of the touch sensing circuit 300 is connected to the touch voltage, and the second input terminal A2 of the touch sensing circuit 300 is connected to the compensation capacitor 200. The first input terminal B1 of the common electrode driving circuit 400 is connected to the common voltage, and the first output terminal B2 of the common electrode driving circuit 400 is connected to the compensation capacitor.

[0036] Specifically, during the display driving period, the common electrode driving circuit 400 is allowed by the multiplexer 100 to output the common voltage to drive the common electrode 101. During the touch sensing period, the touch sensing circuit 300 is allowed by the multiplexer 100 to output the touch voltage to drive the sensing electrode 102. Furthermore, during the touch sensing period, the common electrode driving circuit 400 is also allowed by the multiplexer 100 to output a compensation voltage to drive the compensation capacitor 200, so that the compensation capacitor 200 can provide capacitance compensation to the sensing path, thereby canceling the sensing signal introduced by parasitic capacitance on the sensing path. In this embodiment, the common voltage is a fixed level to drive the common electrode 101 in a voltage stable state, and during the display driving period, the touch sensing circuit 300 is in a non-operating state.

[0037] As shown in Figure 2, the common electrode driving circuit 400 includes a first sub-driving module 401. The first sub-driving module 401 outputs a common voltage during the display driving period or outputs a compensation voltage during the touch sensing period to realize the time-division multiplexing of the first sub-driving module 401, thereby reducing the additional driving circuit used to drive the compensation capacitor and saving the floor space of the driving circuit.

[0038] As shown in Figure 2, the touch sensing circuit 300 includes a second sub-driving module 301 and a third sub-driving module 302 connected in circuitry. The second sub-driving module 301 is connected to the sensing electrode 101 through the multiplexer 100, and is used to output a sensing waveform and convert the sensed capacitance into a current signal. The third sub-driving module 302 is connected to the output terminal of the second sub-driving module 301, and is used to convert the current signal into a voltage signal, thereby realizing the measurement of the sensed capacitance. Furthermore, a compensation node is set at the input terminal of the third sub-driving module 302 (i.e., the second input terminal A2 of the touch sensing circuit 300), and the first end of the compensation capacitor 200 is directly connected to the compensation node, so that the compensation capacitor 200 is connected to the touch sensing circuit 300, thereby providing a compensation voltage to cancel the parasitic capacitance on the sensing path.

[0039] Further, as shown in Figure 2, the second terminal of the compensation capacitor 200 is connected to the first output terminal B2 of the common electrode driving circuit 400 (i.e., the output terminal of the first sub-driving module 401), so that the common electrode driving circuit 400 can output a compensation voltage during the touch sensing period to drive the compensation capacitor 200 to provide capacitance compensation to the sensing path. In this embodiment, when in the touch sensing period, the touch sensing circuit 300 outputs a sensing waveform, and the compensation voltage output by the common electrode driving circuit 400 has a voltage waveform opposite to the sensing waveform, thereby canceling the parasitic capacitance on the sensing path.

[0040] In this embodiment, as shown in Figure 2, the first end of the compensation capacitor 200 is also connected to ground via a first switch 201. By controlling the opening and closing of the first switch 201, the compensation capacitor 200 is used to compensate for parasitic capacitance on the sensing path and as a storage capacitor to maintain a stable common voltage. Specifically, during the touch sensing period, the first switch 201 is opened, and the common electrode driving circuit 400 outputs a compensation voltage to drive the compensation capacitor 200 to provide capacitance compensation to the sensing path, preventing the compensation capacitor 200 from being grounded and causing charge to be released through the ground wire, thus keeping the compensation capacitor 200 at ground potential (0V) and unable to provide compensation voltage to the touch sensing circuit 300. During the display driving period, the first switch 201 is closed, grounding the compensation capacitor 200. At this time, the compensation capacitor 200 is reused as a storage capacitor to maintain a stable common voltage output by the common electrode driving circuit 400, thereby enabling the common electrode driving circuit 400 to provide a more stable voltage, thus ensuring the stability and quality of the displayed image.

[0041] In another embodiment, as shown in FIG3, the first end of the compensation capacitor 200 can also be connected to the compensation node through the second switch 202. The second switch 202 is located between the connection point C of the first switch 201 and the first end of the compensation capacitor 200 and the compensation node. During the display driving period, the second switch 202 is controlled to be disconnected to avoid the compensation capacitor 200 being grounded and pulling down the voltage of the compensation node (i.e., the voltage of the compensation node is 0V), thereby affecting the touch sensing circuit 300 to enter the preparation state before sensing. This allows the input and output of the touch sensing circuit 300 to be reset to the corresponding common-mode level before sensing begins. After the input and output are reset to the common-mode level, the signal baseline used for sensing signal comparison can be stabilized at the common-mode level. The subsequent signal processing unit can more accurately quantify and process the change between the sensing signal and the signal baseline, reduce the error caused by signal baseline fluctuation, improve the processing accuracy of the sensing signal, and improve the touch sensing efficiency.

[0042] It should be noted that the voltage values ​​of the common voltage, sensing voltage, and compensation voltage can be selected according to the actual situation, and this application does not impose any restrictions on this.

[0043] The area-saving drive circuit provided by another embodiment of the present invention will now be described in detail with reference to FIG4.

[0044] Figure 4 is a schematic diagram of a space-saving drive circuit according to another embodiment of the present invention. As shown in Figure 4, with the sensing electrode SX... <k>For example, the sensing electrode SX <k>The first and second sub-driver modules are connected via a multiplexer (MUX). The first sub-driver module includes a common operational amplifier (VCOM_OP), whose non-inverting input is connected to a common voltage reference voltage (VCOM_REF). Different output voltages can be achieved by adjusting the value of the common voltage reference voltage. The non-inverting input of the common operational amplifier (VCOM_OP) is coupled to its output, and the output is connected to the second terminal of a compensation capacitor (Ccomp). The second sub-driver module includes a first operational amplifier (OP1), whose non-inverting input is connected to a sensing reference voltage (Vsx), and whose non-inverting input is coupled to its output. The third sub-driver module includes a second operational amplifier OP2. The non-inverting input of the second operational amplifier OP2 is connected to the first terminal of the compensation capacitor Ccomp and the output of the first operational amplifier OP1 through a mirror circuit. The negative input of the second operational amplifier OP2 is connected to the reference voltage Vref. The output of the second operational amplifier OP2 is connected to the ADC module (analog-to-digital converter, not shown in the figure).

[0045] In a specific implementation, as shown in Figure 4, during the touch sensing period, the first operational amplifier OP1 generates a sensing voltage to drive the capacitors (including the touch capacitor CT, the display panel capacitor Csp, and the chip trace capacitor Csc) to generate current. This current signal Isense is then replicated at a certain ratio and sent to the second operational amplifier OP2. Simultaneously, the first switch S1 disconnects the ground connection, and the second switch S2 is closed. The output of the common operational amplifier VCOM_OP outputs a compensation voltage to drive the compensation capacitor Ccomp to provide a reverse current Icomp to cancel the inductive quantity caused by the parasitic capacitance formed by the display panel capacitor Csp and the chip trace capacitor Csc. Further, the second operational amplifier OP2 converts the canceled current into a voltage and compares it with the reference voltage Vref to obtain two differential voltage signals VOP. <k>and VON <k>The differential voltage signal VOP is then output through the second operational amplifier OP2. <k>and VON <k>The signal is then sent to the ADC module for further signal processing to complete the driving process during the touch sensing period.

[0046] During the display driving period, the first operational amplifier OP1 and the second operational amplifier OP2 are in a non-operating state, and the sensing electrode SX <k>When the common electrode is reused, the first switch S1 is closed and the second switch S2 is open. The common operational amplifier VCOM_OP outputs a common voltage to drive the common electrode. At this time, the compensation capacitor Ccomp is grounded through the first switch S1 and reused as a storage capacitor to maintain the stability of the common voltage, thus ensuring the stability of the display effect.

[0047] The present invention also discloses an area-saving touch display driver chip, wherein the touch display driver chip includes the area-saving driving circuit described in any of the above embodiments.

[0048] In summary, the present invention provides an area-saving driving circuit, method, and touch display driving chip. By using the compensation capacitor 200 as a compensation capacitor for parasitic capacitance on the sensing path during the touch sensing period and multiplexing it as a storage capacitor to maintain a stable common voltage during the display driving period, the requirement for a large off-chip storage capacitor is reduced. At the same time, by multiplexing the common electrode driving circuit 400 as a driving circuit for driving the compensation capacitor 200 during the touch sensing period, the requirement for an additional driving circuit dedicated to driving the compensation capacitor 200 is reduced, thereby saving the area occupied by the driving circuit.

[0049] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above. Therefore, the scope of protection of the present invention should be defined by the appended claims.

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Claims

1. A method for saving driving circuit area, characterized in that the driving circuit includes a plurality of compensation capacitors, wherein during the touch sensing period, the compensation capacitors are used to compensate for parasitic capacitance on the sensing path, and during the display driving period, the compensation capacitors are reused as storage capacitors to maintain a stable common voltage.

2. The method as described in claim 1, wherein the driving circuit includes a touch sensing circuit and a common electrode driving circuit, and during the touch sensing period, the compensation voltage output by the common electrode driving circuit drives the compensation capacitor to cancel the parasitic capacitance on the sensing path.

3. The method as described in claim 2, wherein the first end of the compensation capacitor is connected to the compensation node of the touch sensing circuit, and the first end is also grounded through a first switch; the second end of the compensation capacitor is connected to the voltage output terminal of the common electrode driving circuit.

4. The method as described in claim 3, characterized in that, during the touch sensing period, the first switch disconnects the ground connection of the compensation capacitor, and the common electrode driving circuit outputs a compensation voltage to drive the compensation capacitor so that the compensation capacitor provides capacitance compensation to the sensing path; during the display driving period, the first switch turns on the ground connection of the compensation capacitor so that the compensation capacitor is reused as a storage capacitor to maintain the stability of the common voltage output by the common electrode driving circuit.

5. The method according to any one of claims 2 to 4, characterized in that the first end of the compensation capacitor is connected to the compensation node of the touch sensing circuit through a second switch, and during the display driving period, the second switch disconnects the compensation capacitor from the compensation node of the touch sensing circuit to avoid the compensation capacitor affecting the voltage of the compensation node.

6. A space-saving drive circuit, characterized in that it comprises: A multiplexer is used to select an output common voltage to drive a common electrode during the display driving period and to select an output touch voltage to drive a sensing electrode during the touch sensing period; a plurality of compensation capacitors are used to compensate for parasitic capacitance on the sensing path during the touch sensing period and are reused as storage capacitors to maintain the stability of the common voltage during the display driving period.

7. The area-saving driving circuit as claimed in claim 6, characterized in that it further comprises: a touch sensing circuit; a common electrode driving circuit; during the display driving period, the common electrode driving circuit is allowed by the multiplexer to output a common voltage to drive the common electrode, and during the touch sensing period, the touch sensing circuit is allowed by the multiplexer to output a touch voltage to drive the sensing electrode.

8. The area-saving driving circuit as claimed in claim 7, characterized in that the touch sensing circuit includes: a second sub-driving module for outputting a sensing waveform and converting the sensed capacitance into a current signal; and a third sub-driving module for converting the current signal into a voltage signal.

9. The area-saving drive circuit as described in claim 8, characterized in that a compensation node is provided at the input terminal of the third sub-drive module, and the first terminal of the compensation capacitor is connected to the touch sensing circuit through the compensation node.

10. The area-saving driving circuit as claimed in any one of claims 7 to 9, characterized in that the common electrode driving circuit includes a first sub-driving module, the first sub-driving module outputting a common voltage during the display driving period or outputting a compensation voltage during the touch sensing period.

11. The area-saving drive circuit as claimed in claim 10, characterized in that the second terminal of the compensation capacitor is connected to the output terminal of the common electrode drive circuit.

12. The area-saving drive circuit as claimed in claim 9, characterized in that the first terminal of the compensation capacitor is also connected to ground via a first switch.

13. The area-saving drive circuit as claimed in claim 9, characterized in that the first end of the compensation capacitor is directly connected to the compensation node, or is connected to the compensation node through a second switch.

14. The area-saving drive circuit as claimed in claim 6, characterized in that the sensing electrode is reused as the common electrode.

15. An area-saving touch display driver chip, comprising the area-saving driver circuit described in any one of claims 6 to 14.

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