Charge distribution compensation circuit and method based on touch sensing channel

Abstract

The invention provides a charge distribution compensation circuit and method based on a touch sensing channel, and the circuit comprises a compensation moving unit which receives and processes a square wave signal, and generates and outputs a compensation charge; the distribution unit is used for receiving and transmitting the compensation charge; the receiving unit is used for generating a reference charge quantity, receiving the compensation charge output by the distribution unit and outputting a net charge quantity; wherein the compensation moving unit comprises a charge moving device, and a multi-stage operational amplifier circuit is arranged in the charge moving device. Through the cascade design of the compensation moving unit, the distribution unit and the receiving unit, a complete charge compensation path is formed, and charge compensation in a touch channel can be effectively achieved. The compensation transfer unit adopts a charge transfer device structure of a multi-stage operational amplifier circuit, so that the accuracy and the stability of charge transfer are improved, and the generation of compensation charges is more accurate.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuits, and in particular 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. In order to prevent the sensor module from taking on too much charge quantization tasks, charge compensation technology is usually required. The existing technology generally adopts a current compensation scheme, that is, the channel is charged and discharged during the t0 time to generate a compensation charge of I0×t0, and it is moved to each touch channel through a current mirror for compensation. However, this solution has obvious shortcomings: first, the current passing through multiple mirrors will cause mismatch problems and affect the compensation accuracy; second, the large current thermal noise will significantly interfere with the normal operation of the sensor. Although the industry continues to propose new solutions, there are often problems such as complex structure and high power consumption. A simple and efficient charge compensation technology is urgently needed. Summary of the invention

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

[0004] A first aspect of the present invention provides a charge distribution compensation circuit based on a touch sensing channel, comprising: a compensation transfer unit, receiving a square wave signal for processing, generating and outputting a 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 comprises a charge transfer device, and a multi-stage operational amplifier circuit is arranged inside the charge transfer device.

[0005] Furthermore, the inverting input terminal of the charge shifter receives a square wave signal, and the non-inverting input terminal is connected to ground via a first resistor in series with a compensation capacitor.

[0006] Furthermore, 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.

[0007] Further, 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.

[0008] Furthermore, the compensation transfer unit includes a first current mirror, and the first current mirror also includes a first MOS tube and a second MOS tube; The gate of the first MOS transistor is connected to the first output terminal of the charge shifter, 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 shifter, 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.

[0009] Further, the distribution unit includes a second current mirror, and the second current mirror includes a third MOS tube and a fourth MOS tube; 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.

[0010] Furthermore, the receiving unit includes 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.

[0011] A second aspect of the present invention provides a charge distribution compensation method based on a touch sensing channel, using the charge distribution compensation circuit based on a touch sensing channel as described in any one of the above items, the method comprising: 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.

[0012] Furthermore, 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 charge shifter 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.

[0013] Furthermore, the net charge on the receiving unit is Vsw×Cs-N×Vsw×Ciom; Where Cs is the reference capacitance value.

[0014] Compared with the prior art, the present invention includes at least 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 a charge transfer structure of a three-stage operational amplifier circuit, which improves the accuracy and stability of charge transfer and makes the generation of compensation charge more accurate. The distribution unit transmits and distributes the compensation charge, which improves the flexibility of the compensation process and makes the compensation more accurate and controllable. The receiving unit generates a reference charge and combines it with the compensation charge to output the net charge, thereby achieving an accurate charge compensation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained such as the provided drawings without paying creative work.

[0016] Figure 1 is a schematic diagram of a charge distribution compensation circuit based on a touch sensing channel in one embodiment of the present invention; Figure 2 FIG. 4 is an internal circuit diagram of a charge shifter in a charge distribution compensation circuit based on a touch sensing channel in an embodiment of the present invention.

[0017] Among them, 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 DESCRIPTION

[0018] The present invention will be described in more detail below in conjunction with the schematic diagram, wherein the preferred embodiment of the present invention is shown, and it should be understood that those skilled in the art can modify the present invention described herein, and still achieve the beneficial 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 of the present invention.

[0019] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0020] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. As described below, the advantages and features of the present invention will become more apparent. It should be noted that the accompanying drawings are in very simplified form and are not in exact proportions, and are only used to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention.

[0021] Embodiment 1 This embodiment provides a charge distribution compensation circuit based on a touch sensing channel. Figure 1 ,include: The compensation transfer unit 1 receives the square wave signal for processing, generates and outputs the compensation charge; A distribution unit 2 receives and transmits the compensation charge; A receiving unit 3 generates a reference charge and receives the compensation charge output by the distribution unit 2, and outputs a net charge; The compensation transfer unit 1 comprises a charge transfer device 11 , and a multi-stage operational amplifier circuit is provided inside the charge transfer device 11 .

[0022] Specifically, the input end of the compensation transfer unit 1 receives the square wave signal provided by the system, and contains a charge shifter 11 provided with a multi-stage operational amplifier circuit. The charge shifter 11 processes the input square wave and outputs the processed compensation charge through the cascade amplification of the multi-stage operational amplifier. The distribution unit 2 is located after the compensation transfer unit 1, and is used to receive the compensation charge output by the compensation transfer unit 1, and transmit the processed compensation charge to the receiving unit 3. The receiving unit 3 generates a reference charge for comparison, and at the same time receives the compensation charge from the distribution unit 2, processes the reference charge and the compensation charge, and finally outputs the net charge as the output signal of the system. A complete signal processing chain is formed by three units: square wave signal → compensation charge → charge distribution → net charge output, thereby realizing the charge compensation function for the touch channel.

[0023] Furthermore, the inverting input terminal of the charge shifter 11 receives a square wave signal, and the non-inverting input terminal is connected to ground via a first resistor in series with a compensation capacitor 14 .

[0024] Specifically, the inverting input receives the signal to be detected, and the input signal can be inverted. The connection between the positive input and the compensation capacitor 14 forms a feedback loop to improve the circuit stability. The design of the dual output port can provide differential signal output and improve the anti-interference ability.

[0025] For details, 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.

[0026] 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 11 further 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.

[0027] Further, 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.

[0028] Specifically, when the first switch is closed, the op amp works in negative feedback mode to complete the sampling of the input signal; when the second switch is closed, the sampled charge is transferred to the output. This inversion control realizes lossless transfer of charge, avoids charge overlap in the sampling and holding stages, and improves the accuracy of charge transfer.

[0029] Furthermore, the compensation moving unit 1 further comprises a first current mirror tube, and the first current mirror tube comprises a first MOS tube 12 and a second MOS tube 13; The gate of the first MOS transistor 12 is connected to the first output terminal of the charge shifter 11, the source is connected to the external power supply terminal, and the drain is connected to the drain of the second MOS transistor 13; the gate of the second MOS transistor 13 is connected to the second output terminal of the charge shifter 11, and the source is grounded; The drain of the first MOS transistor 12 and the drain of the second MOS transistor 13 are also commonly connected to a first resistor.

[0030] Specifically, the first current mirror tube accurately replicates the signal current output by the charge shifter 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.

[0031] Furthermore, 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; The gate of the third MOS tube 21 is connected to the first output end of the charge shifter 11, the source is connected to the external power supply end, 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 end of the charge shifter 11, and the source is grounded.

[0032] Specifically, the second current mirror tube converts the differential signal output by the charge shifter 11 into a single-ended current signal to achieve accurate signal replication and distribution; the differential input structure of the third MOS tube 21 and the fourth MOS tube 22 can improve the common-mode rejection ratio and reduce common-mode interference. At the same time, the linear transmission of the signal is guaranteed through the characteristics of the current mirror, thereby providing a stable and reliable current output for subsequent signal processing, and finally achieving the purpose of signal distribution and processing.

[0033] Furthermore, the receiving unit 3 includes an operational amplifier 31, a positive phase input terminal of the operational amplifier 31 is connected to a positive phase input terminal of the charge shifter 11, and a negative phase input terminal and an output terminal of the operational amplifier 31 are connected to an output terminal of the distribution unit 2; The output end of the operational amplifier 31 is connected in series with a second resistor, and the second resistor is connected in series with a reference capacitor 32 and grounded; A signal receiving terminal is also provided between the second resistor and the capacitor.

[0034] Specifically, in this receiving unit 3, the operational amplifier 31 generates a voltage difference by receiving the output of the charge shifter 11, which is equivalent to generating a reference charge on the reference capacitor 32. At the same time, the input end of the operational amplifier 31 also receives the output of the charge shifter 11, that is, the in-phase square wave signal, and outputs a net charge due to the action of the charge shifter 11.

[0035] Embodiment 2 This embodiment provides a charge distribution compensation method based on a touch sensing channel, using the charge distribution compensation circuit based on the touch sensing channel as described in Embodiment 1, and the method includes: Apply a square wave signal to the signal receiving end of the compensation transfer unit 1; 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 3 .

[0036] Furthermore, the amount of compensation charge generated by the compensation transfer unit 1 is N×Vsw×Ciom; Wherein, N is the ratio of the first current mirror tube in the charge shifter 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.

[0037] Furthermore, the net charge on the receiving unit 3 is Vsw×Cs-N×Vsw×Ciom; Where Cs is the reference capacitance value.

[0038] In this embodiment, in the capacitance detection mode of the channel, a square wave signal with a voltage difference of Vsw is inputted into the signal receiving end of the receiving unit 3 ; meanwhile, a square wave signal with the same phase is also inputted into the input end of the charge shifter 11 .

[0039] The receiving unit 3 generates a voltage difference of Vsw, which is equivalent to the reference capacitor 32, generating a charge Vsw×Cs. At the same time, the input end of the charge shifter 11 inputs a square wave signal of the Vsw swing amplitude. Due to the unit negative feedback, the output end is also a voltage difference signal of Vsw; the charge equivalent to the compensation capacitor 14 is Vsw×Ciom.

[0040] After the charge shifter 11 generates charges, the charges will be shifted by the distribution unit 2. The amount of charges shifted depends on the ratio N between the current mirror tube of the charge shifter 11 and the compensation current mirror tube in the distribution unit 2. The compensation charge is N×Vsw×Ciom. Due to the action of the charge shifter 11, the remaining amount of charges is (Vsw×Cs-N×Vsw×Ciom), and it is only necessary to shift these charges to the subsequent circuit for quantization detection.

[0041] The above specific examples are used to illustrate 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 art, according to the concept of the present invention, some simple deductions, modifications or substitutions can 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 comprises a charge transfer device, and a multi-stage operational amplifier circuit is arranged inside the charge transfer device.

2. The charge distribution compensation circuit based on the touch sensing channel according to claim 1, characterized in that: The inverting input terminal of the charge shifter receives a square wave signal, and the non-inverting input terminal is connected to ground via a first resistor in series with a compensation capacitor.

3. 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.

4. The charge distribution compensation circuit based on the touch sensing channel according to claim 3, 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.

5. The charge distribution compensation circuit based on the touch sensing channel according to claim 1, characterized in that: The compensation moving unit further includes a first current mirror tube, and the first current mirror tube includes a first MOS tube and a second MOS tube; The gate of the first MOS transistor is connected to the first output terminal of the charge shifter, 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 shifter, 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.

6. The charge distribution compensation circuit based on the touch sensing channel according to claim 1, characterized in that: 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 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.

7. 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.

8. 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 7, 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.

9. The charge distribution compensation method based on the touch sensing channel according to claim 8, characterized in that: 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 charge shifter to the second current mirror tube in the current mirror circuit, Vsw is the voltage difference of the square wave signal, and Ciom is the compensation capacitance value.

10. The charge distribution compensation method based on the touch sensing channel according to claim 8, 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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