A Charge Distribution Compensation Circuit and Method Based on Touch Sensing Channels

Abstract

The present invention provides a charge distribution compensation circuit and method based on a touch sensing channel. The circuit includes: a compensation transfer unit that receives a square wave signal, processes it, generates and outputs compensation charges; a distribution unit that receives the compensation charges and transmits them; a receiving unit that generates a reference charge amount and simultaneously receives the compensation charges output by the distribution unit, and outputs a net charge amount. Among them, the compensation transfer unit includes a charge transfer device, and a multi-stage operational amplifier circuit is provided inside the charge transfer device. Through the cascaded design of the compensation transfer unit, the distribution unit and the receiving unit, a complete charge compensation path is formed, which can effectively achieve charge compensation in the touch channel. The compensation transfer unit adopts the structure of a charge transfer device with a multi-stage operational amplifier circuit, which improves the accuracy and stability of charge transfer, and makes the generation of compensation charges more accurate.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuits, and particularly to a charge distribution compensation circuit and method based on a touch sensing channel. Background Art

[0002] In touch screen sensing technology, whether it is mutual capacitance or self-capacitance sensing mode, a large amount of charge will enter the sensor module. To avoid the sensor module from undertaking an excessive charge quantization task, charge compensation technology is usually required. The existing technology generally adopts a current compensation scheme, that is, the channel is charged and discharged within time t0 to generate a compensation charge amount of I0×t0, and it is transferred to each touch channel for compensation through a current mirror. However, this scheme has obvious deficiencies: First, the current passing through multiple levels of mirrors will cause mismatch problems, affecting the compensation accuracy; second, the large current thermal noise will significantly interfere with the normal operation of the sensor. Although the industry constantly proposes new solutions, they often have problems such as complex structure and high power consumption. There is an urgent need for a simple and efficient charge compensation technology. Summary of the Invention

[0003] The purpose of the present invention is to solve the problem of current mismatch in charge compensation of the existing technology.

[0004] In a first aspect of the present invention, there is provided a charge distribution compensation circuit based on a touch sensing channel, including: a compensation transfer unit, which receives a square wave signal for processing, generates and outputs compensation charge;

[0005] a distribution unit, which receives the compensation charge and transmits it;

[0006] a receiving unit, which generates a reference charge amount and simultaneously receives the compensation charge output by the distribution unit, and outputs a net charge amount;

[0007] Wherein, the compensation transfer unit includes a charge transfer device, and a multi-stage operational amplifier circuit is provided inside the charge transfer device.

[0008] Further, the inverting input terminal of the charge transfer device receives the square wave signal, and the non-inverting input terminal is grounded through a first resistor in series with a compensation capacitor.

[0009] Further, the multi-stage operational amplifier circuit is a three-stage operational amplifier circuit, and the three-stage operational amplifier circuit includes a differential input stage, an intermediate stage and an output stage.

[0010] The input terminals of the differential input stage are connected to the input terminal of the three-stage operational amplifier circuit, the output terminals are respectively connected to the first input node and the second input node of the intermediate stage, the output terminal of the intermediate stage is connected to the output stage, and the output terminal of the output stage is connected to the output terminal of the three-stage operational amplifier circuit;

[0011] The charge transfer device further includes a first switch pair and a second switch pair. The first switch pair is connected between the input terminal and the output terminal of the three-stage operational amplifier circuit; the second switch pair is connected between the output terminal of the three-stage operational amplifier circuit and the ground.

[0012] Further, the first switch and the second switch are controlled by a clock signal;

[0013] When the first switch is closed, the second switch is open; when the first switch is open, the second switch is closed.

[0014] Further, the compensation transfer unit includes a first current mirror, and the first current mirror further includes a first MOS transistor and a second MOS transistor;

[0015] The gate of the first MOS transistor is connected to the first output terminal of the charge transfer device, the source is connected to the external power supply terminal, and the drain is connected to the drain of the second MOS transistor; the gate of the second MOS transistor is connected to the second output terminal of the charge transfer device, and the source is grounded;

[0016] The drain of the first MOS transistor and the drain of the second MOS transistor are also commonly connected to a first resistor.

[0017] Further, the distribution unit includes a second current mirror, and the second current mirror includes a third MOS transistor and a fourth MOS transistor;

[0018] The gate of the third MOS transistor is connected to the first output terminal of the charge transfer device, the source is connected to the external power supply terminal, and the drain is connected to the drain of the fourth MOS transistor; the gate of the fourth MOS transistor is connected to the second output terminal of the charge transfer device, and the source is grounded.

[0019] Further, the receiving unit includes an operational amplifier. The non-inverting input terminal of the operational amplifier is connected to the non-inverting input terminal of the charge transfer device, and the inverting input terminal and the output terminal of the operational amplifier are connected to the output terminal of the distribution unit;

[0020] The output terminal of the operational amplifier is also connected in series with a second resistor, and the second resistor is connected in series with a reference capacitor and grounded;

[0021] A signal receiving terminal is also provided between the second resistor and the reference capacitor.

[0022] In a second aspect of the present invention, a charge distribution compensation method based on a touch sensing channel is provided. Using the charge distribution compensation circuit based on a touch sensing channel as described in any one of the above, the method includes:

[0023] Applying a square wave signal to the signal receiving terminal of the compensation transfer unit;

[0024] Meanwhile, a square wave signal in phase with the signal receiving end is applied to the input end of the receiving unit.

[0025] Furthermore, the compensation charge quantity generated by the compensation transfer unit is N×Vsw×Ciom;

[0026] Wherein, N is the ratio of the first current mirror tube in the charge transfer device to the second current mirror tube in the distribution unit, Vsw is the voltage difference of the square wave signal, and Ciom is the compensation capacitance value.

[0027] Furthermore, the net charge quantity on the receiving unit is Vsw×Cs - N×Vsw×Ciom;

[0028] Wherein, Cs is the reference capacitance value.

[0029] Compared with the prior art, the present invention at least includes the following beneficial effects: Through the cascade design of the compensation transfer unit, the distribution unit and the receiving unit, a complete charge compensation path is formed, which can effectively realize the charge compensation in the touch channel. The compensation transfer unit adopts the charge transfer device structure of a three-stage operational amplifier circuit, which improves the accuracy and stability of charge transfer and makes the generation of compensation charges more accurate. The distribution unit transmits and distributes the compensation charges, improves the flexibility of the compensation process, and makes the compensation more precisely controllable. The receiving unit generates reference charges and combines them with the compensation charges to output the net charge quantity, achieving an accurate charge compensation effect. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained as provided without creative efforts.

[0031] Figure 1 It is a schematic diagram of a charge distribution compensation circuit based on a touch sensing channel in an embodiment of the present invention;

[0032] Figure 2 It is the internal circuit diagram of the charge transfer device in the charge distribution compensation circuit based on the touch sensing channel in an embodiment of the present invention.

[0033] Wherein, 1 - compensation transfer unit; 11 - charge transfer device; 12 - first MOS tube; 13 - second MOS tube; 14 - compensation capacitor; 2 - distribution unit; 21 - third MOS tube; 22 - fourth MOS tube; 3 - receiving unit; 31 - operational amplifier; 32 - reference capacitor. Detailed Embodiments

[0034] The present invention will be described in more detail below with reference to the schematic diagrams, in which the preferred embodiments of the present invention are shown. It should be understood that those skilled in the art can modify the present invention described herein while still achieving the advantageous effects of the present invention. Therefore, the following description should be understood as being widely known to those skilled in the art and not as a limitation on the present invention.

[0035] It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variation thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device.

[0036] The present invention will be described more specifically by way of example in the following paragraphs with reference to the accompanying drawings. As will be described below, the advantages and features of the present invention will become clearer. It should be noted that the accompanying drawings are in a very simplified form and are drawn using non-precise scales, and are only used to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention.

[0037] Embodiment 1

[0038] This embodiment provides a charge distribution compensation circuit based on a touch sensing channel. Please refer to Figure 1 , which includes:

[0039] A compensation transfer unit 1 that receives a square wave signal, processes it, and generates and outputs compensation charges;

[0040] A distribution unit 2 that receives the compensation charges and transmits them;

[0041] A receiving unit 3 that generates a reference charge amount and simultaneously receives the compensation charges output by the distribution unit 2, and outputs a net charge amount;

[0042] Among them, the compensation transfer unit 1 includes a charge transfer device 11, and a multi-stage operational amplifier circuit is provided inside the charge transfer device 11.

[0043] Specifically, the input end of the compensation transfer unit 1 receives the square wave signal provided by the system. Inside it, there is a charge transfer device 11 equipped with a multi-stage operational amplifier circuit. Through the cascading amplification of the multi-stage operational amplifiers, the charge transfer device 11 processes the input square wave and outputs the compensated charge after processing. The distribution unit 2 is located behind the compensation transfer unit 1, used to receive the compensated charge output by the compensation transfer unit 1, and transmit the processed compensated charge to the receiving unit 3. The receiving unit 3 generates a reference charge quantity for comparison, and at the same time receives the compensated charge from the distribution unit 2, processes the reference charge and the compensated charge, and finally outputs the net charge quantity as the output signal of the system. A complete signal processing link is formed by the three units: square wave signal → compensated charge → charge distribution → net charge output, realizing the charge compensation function for the touch channel.

[0044] Further, the inverting input end of the charge transfer device 11 receives the square wave signal, and the non-inverting input end is grounded through a first resistor in series with a compensation capacitor 14.

[0045] Specifically, receiving the signal to be detected through the inverting input can perform inverting processing on the input signal. The connection between the non-inverting input and the compensation capacitor 14 forms a feedback loop, improving the circuit stability. The design of the dual output ports can provide differential signal output, improving the anti-interference ability.

[0046] Specifically, please refer to Figure 2 , in this embodiment, preferably, the multi-stage operational amplifier circuit is a three-stage operational amplifier circuit, and the three-stage operational amplifier circuit includes a differential input stage, an intermediate stage, and an output stage.

[0047] The input end of the differential input stage is connected to the input end of the three-stage operational amplifier circuit, and the output ends are respectively connected to the first input node and the second input node of the intermediate stage. The output end of the intermediate stage is connected to the output stage, and the output end of the output stage is connected to the output end of the three-stage operational amplifier circuit;

[0048] Inside the charge transfer device 11, there are also a first switch pair and a second switch pair. The first switch pair is connected between the input end and the output end of the three-stage operational amplifier circuit; the second switch pair is connected between the output end of the three-stage operational amplifier circuit and the ground.

[0049] Further, the first switch and the second switch are controlled by a clock signal;

[0050] When the first switch is closed, the second switch is open, and when the first switch is open, the second switch is closed.

[0051] Specifically, when the first switch is closed, the operational amplifier operates in a negative feedback mode to sample the input signal; when the second switch is closed, the sampled charge is transferred to the output. Through this inverting control, lossless charge transfer is achieved, avoiding charge overlap during the sampling and holding phases and improving the accuracy of charge transfer.

[0052] Further, the compensation transfer unit 1 further includes a first current mirror tube, and the first current mirror tube includes a first MOS tube 12 and a second MOS tube 13;

[0053] The gate of the first MOS tube 12 is connected to the first output terminal of the charge transfer device 11, the source is connected to the external power supply terminal, and the drain is connected to the drain of the second MOS tube 13; the gate of the second MOS tube 13 is connected to the second output terminal of the charge transfer device 11, and the source is grounded;

[0054] The drain of the first MOS tube 12 and the drain of the second MOS tube 13 are also commonly connected to a first resistor.

[0055] Specifically, the first current mirror tube accurately replicates the signal current output by the charge transfer device 11, maintains the current magnitude relationship, realizes the mirror transmission of the current, and ensures the stability and consistency of the signal. The compensation capacitor 14 stores the charge converted by the current mirror, realizes the timed sampling and holding of the charge, and ensures the continuity and stability of the charge transfer.

[0056] Further, the distribution unit 2 includes a second current mirror tube, and the second current mirror tube includes a third MOS tube 21 and a fourth MOS tube 22;

[0057] The gate of the third MOS tube 21 is connected to the first output terminal of the charge transfer device 11, the source is connected to the external power supply terminal, and the drain is connected to the drain of the fourth MOS tube 22; the gate of the fourth MOS tube 22 is connected to the second output terminal of the charge transfer device 11, and the source is grounded.

[0058] Specifically, the second current mirror tube converts the differential signal output by the charge transfer device 11 into a single-ended current signal to achieve accurate replication and distribution of the signal; the differential input structure of the third MOS tube 21 and the fourth MOS tube 22 can improve the common-mode rejection ratio, reduce common-mode interference, and at the same time ensure the linear transmission of the signal through the characteristics of the current mirror, thereby providing a stable and reliable current output for subsequent signal processing and ultimately achieving the purpose of signal distribution and processing.

[0059] Further, the receiving unit 3 includes an operational amplifier 31, the non-inverting input terminal of the operational amplifier 31 is connected to the non-inverting input terminal of the charge transfer device 11, and the inverting input terminal and the output terminal of the operational amplifier 31 are connected to the output terminal of the distribution unit 2;

[0060] The output terminal of the operational amplifier 31 is also connected in series with a second resistor, and the second resistor is connected in series with a reference capacitor 32 and grounded;

[0061] A signal receiving end is also provided between the second resistor and the capacitor.

[0062] Specifically, in this receiving unit 3, the operational amplifier 31 generates a voltage difference by receiving the output of the charge transfer device 11, which is equivalent to generating a reference charge on the reference capacitor 32. At the same time, the input terminal of the operational amplifier 31 also receives the output of the charge transfer device 11, that is, a co-phase square wave signal, and a net charge is output due to the action of the charge transfer device 11.

[0063] Embodiment 2

[0064] This embodiment provides a charge distribution compensation method based on a touch sensing channel, and uses the charge distribution compensation circuit based on the touch sensing channel as described in Embodiment 1. The method includes:

[0065] Applying a square wave signal to the signal receiving end of the compensation transfer unit 1;

[0066] At the same time, applying a square wave signal in phase with the signal receiving end to the input terminal of the receiving unit 3.

[0067] Further, the compensation charge quantity generated by the compensation transfer unit 1 is N×Vsw×Ciom;

[0068] Wherein, N is the ratio of the first current mirror tube in the charge transfer device 11 to the second current mirror tube in the distribution unit 2, Vsw is the voltage difference of the square wave signal, and Ciom is the compensation capacitance value.

[0069] Further, the net charge quantity on the receiving unit 3 is Vsw×Cs - N×Vsw×Ciom;

[0070] Wherein, Cs is the reference capacitance value.

[0071] In this embodiment, in the capacitance detection mode of the channel, a square wave signal with a voltage difference of Vsw is injected into the signal receiving end of the receiving unit 3; at the same time, a co-phase square wave signal is also injected into the input terminal of the charge transfer device 11.

[0072] The receiving unit 3 generates a voltage difference of Vsw, which is equivalent to generating a charge Vsw×Cs on the reference capacitor 32. At the same time, a square wave signal with a Vsw swing is injected into the input terminal of the charge transfer device 11. Due to the relationship of unit negative feedback, the output terminal is also a pressure difference signal of Vsw; the charge equivalent to the compensation capacitor 14 is Vsw×Ciom.

[0073] After the charge transporter 11 generates charges, the charges will be transported by the distribution unit 2. The transported charge quantity depends on the ratio N of the current mirror tube of the charge transporter 11 to the compensation current mirror tube in the distribution unit 2. Then the compensation charge is N×Vsw×Ciom. Due to the effect of the charge transporter 11, the remaining charge quantity is (Vsw×Cs - N×Vsw×Ciom), and only these charges need to be transported to the subsequent circuit for quantization detection.

[0074] The above uses specific examples to elaborate on the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the technical field to which the present invention pertains, based on the idea of the present invention, several simple deductions, deformations or substitutions can also be made.

Claims

1. A charge distribution compensation circuit based on a touch sensing channel, characterized in that: include: The compensation transfer unit receives the square wave signal for processing, generates and outputs the compensation charge; A distribution unit, receiving and transmitting the compensation charge; A receiving unit, generating a reference charge amount, receiving the compensation charge output by the distribution unit, and outputting a net charge amount; The compensation transfer unit includes a charge transfer device, and a multi-stage operational amplifier circuit is provided inside the charge transfer device; the inverting input terminal of the charge transfer device receives a square wave signal, and the non-inverting input terminal is connected to the ground after being connected in series with a compensation capacitor via a first resistor; The compensation transfer unit further includes a first current mirror tube, which includes a first MOS tube and a second MOS tube; the gate of the first MOS tube is connected to the first output end of the charge transfer device, the source is connected to the external power supply end, and the drain is connected to the drain of the second MOS tube; the gate of the second MOS tube is connected to the second output end of the charge transfer device, and the source is grounded; the drain of the first MOS tube and the drain of the second MOS tube are also commonly connected to a first resistor; The distribution unit includes a second current mirror tube, and the second current mirror tube includes a third MOS tube and a fourth MOS tube; The amount of compensation charge generated by the compensation transfer unit is N×Vsw×Ciom, wherein N is the ratio of the first current mirror tube in the compensation transfer unit to the second current mirror tube in the distribution unit, Vsw is the voltage difference of the square wave signal, and Ciom is the compensation capacitance value.

2. The charge distribution compensation circuit based on the touch sensing channel according to claim 1, characterized in that: The multi-stage operational amplifier circuit is a three-stage operational amplifier circuit, and the three-stage operational amplifier circuit includes a differential input stage, an intermediate stage and an output stage. The input end of the differential input stage is connected to the input end of the three-stage operational amplifier circuit, the output end is respectively connected to the first input node and the second input node of the intermediate stage, the output end of the intermediate stage is connected to the output stage, and the output end of the output stage is connected to the output end of the three-stage operational amplifier circuit; The charge shifter also includes a first switch pair and a second switch pair. The first switch pair is connected between the input and output ends of the three-stage operational amplifier circuit; the second switch pair is connected between the output end of the three-stage operational amplifier circuit and ground.

3. The charge distribution compensation circuit based on the touch sensing channel according to claim 2, characterized in that: The first switch and the second switch are controlled by a clock signal; When the first switch is closed, the second switch is open, and when the first switch is open, the second switch is closed.

4. The charge distribution compensation circuit based on the touch sensing channel according to claim 1, characterized in that: The gate of the third MOS tube is connected to the first output end of the charge mover, the source is connected to the external power supply end, and the drain is connected to the drain of the fourth MOS tube; the gate of the fourth MOS tube is connected to the second output end of the charge mover, and the source is grounded.

5. The charge distribution compensation circuit based on the touch sensing channel according to claim 1, characterized in that: The receiving unit comprises an operational amplifier, a positive phase input terminal of the operational amplifier is connected to a positive phase input terminal of the charge shifter, and a negative phase input terminal and an output terminal of the operational amplifier are connected to an output terminal of the distribution unit; The output end of the operational amplifier is connected in series with a second resistor, and the second resistor is connected in series with a reference capacitor and is grounded; A signal receiving terminal is also provided between the second resistor and the reference capacitor.

6. A charge distribution compensation method based on a touch sensing channel, using the charge distribution compensation circuit based on a touch sensing channel according to any one of claims 1 to 5, characterized in that: The method comprises: Applying a square wave signal to the signal receiving end of the compensation moving unit; At the same time, a square wave signal having the same phase as that of the signal receiving end is applied to the input end of the receiving unit.

7. The charge distribution compensation method based on the touch sensing channel according to claim 6, characterized in that: The net charge on the receiving unit is Vsw×Cs-N×Vsw×Ciom; Where Cs is the reference capacitance value.

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