Patent Description:
Touch control panels (also known as touch screens), especially capacitive touch control panels, have been widely used in various user electronic apparatuses. One kind of the capacitive touch control panels relies on a detection circuit to sense a touch action-specifically, a VCOM (reference voltage) electrode on the touch control panel is divided into a plurality of sensor electrodes, i.e., sensor RX (RX is the abbreviated form of receive). As shown in <FIG>, when the sensor RX (VCOM) is touched, an equivalent capacitance of the RX becomes larger, which increases an output voltage Vout of the charge amplifier (CA). In this way, the touch action can be detected based on the change of the output voltage Vout.

However, the sensor electrodes have relatively large parasitic capacitances, including parasitic capacitances of wiring, which are mainly a parasitic capacitance Cbase1 between the sensor electrodes and a source line and between the sensor electrodes and a gate line, and a parasitic capacitance to ground Cbase2. These parasitic capacitances are often relatively large, which will lead to saturation of the output of the charge amplifier and consequently make it impossible to detect the touch action.

<CIT> relates to a capacitive touch input device, wherein a parasitic capacitance is formed due to coupling with other electrodes. In order to eliminate the parasitic capacitance, a guarding signal is applied to said electrode. Said guarding signal is substantially the same as a modulating signal.

<CIT> relates to a touch-sensing method in which control operation timing at which a charge control circuit connected to an input terminal of a pre-amplifier is controlled in consideration of a difference in a location or time constant for each touch electrode.

<CIT> relates to a touch screen controller performing an offset cancellation for cancelling an offset capacitance of a touch screen panel comprising a first channel and a second channel crossing the first channel.

<CIT> relates to a method for operating an input device by applying a charge voltage to a sense element through a first transistor that is between the sense element and a column output line and a first switch that is between the column output line and a drive voltage.

The invention is defined by the independent claim.

The present disclosure provides a detection circuit, a touch control panel and an electronic apparatus so as to eliminate the influence of parasitic capacitances and avoid the defect that the touch action cannot be detected due to the saturation of the output of the charge amplifier.

Based on the implementations of the aspects of the present disclosure, the first excitation signal VSTMH is set to be in-phase with the second excitation signal VSTML, and the amplitude of the first excitation signal VSTMH is larger than that of the second excitation signal VSTML. Therefore, the influence of the parasitic capacitances on the accuracy of touch action detection can be reduced or even avoided, and the area of the detection circuit can be reduced since there is no need to add additional hardware, such that the area of the Touch IC integrated with the detection circuit can be reduced.

Other features and aspects of the present disclosure will become apparent from the following detailed description of exemplary embodiments with reference to the drawings.

The drawings, which are incorporated into and constitute a part of the description, illustrate the exemplary embodiments, features and aspects of the present disclosure together with the description, and serve to explain the principle of the present disclosure.

Various exemplary embodiments, features and aspects of the present disclosure will be described in detail below with reference to the drawings. In the drawings, the same reference signs denote elements with the same or similar functions. Although various aspects of the embodiments are shown in the drawings, unless otherwise specified, the drawings are not necessarily drawn to scale.

The word "exemplary" used here means "serving as an example, embodiment or illustration". Any embodiment described here as "exemplary" is not necessarily to be interpreted as superior to or better than other embodiments.

Furthermore, for a better explanation of the present disclosure, numerous specific details are given in the following detailed description of the embodiments. Those skilled in the art should understand that the present disclosure may also be implemented without certain specific details. In some embodiments, methods, means, elements and circuits that are well known to those skilled in the art are not described in detail in order to highlight the main idea of the present disclosure.

The term "and/or" used herein is only for describing an association relationship between the associated objects, which means that there may be three relationships, for example, A and/or B may denote three situations: A exists alone, both A and B exist, and B exists alone. Furthermore, the character "/' used herein indicates a relationship of "or" between the associated objects before and after the character "/".

The term "a plurality of" in the embodiments of the present disclosure means two or more. The words "first", "second" and the like in the embodiments of the present disclosure are only used to illustrate and distinguish between the described objects, and do not indicate any sequence or any special restriction on the number in the embodiments of the present disclosure, and thus do not constitute any restriction on the embodiments of the present disclosure.

<FIG> shows an equivalent circuit diagram of a general detection circuit. The principle of the circuit shown in <FIG> implementing the touch detection is as follows: the sensor electrode RX (VCOM) is precharged once, and then connected to the input terminal of the charge amplifier through a control switch, so that the charge of the RX will be transferred to the output terminal of the charge amplifier; and because the precharged voltage is constant, when the capacitance of the RX changes, the obtained output voltage Vout of the charge amplifier is different. When a finger touches the panel, the equivalent capacitance of the RX becomes larger, which increases the output voltage Vout of the charge amplifier, that is, a variation of the output voltage of the charge amplifier is obtained by the following formula: <MAT>.

In this way, whether there is a touch can be detected based on the variation ΔV of the output voltage of the charge amplifier.

However, in actual detection, the sensor RX (sensor electrode) has relatively large parasitic capacitances, including parasitic capacitances of wiring, such as a parasitic capacitance Cbase1 generated between the RX and a source line of each transistor in a thin film transistor (TFT) layer of a touch control panel and between the RX and a gate line of each transistor in the TFT layer of the touch control panel, and a parasitic capacitance to ground Cbase2 of the RX. In <FIG>, Cbase1 represents the parasitic capacitance between the sensor and the source line and between the sensor and the gate line, and Cbase2 represents the parasitic capacitance to ground of the RX.

As capacitance values of these parasitic capacitances are large (up to hundreds of pF), the output of the charge amplifier will be saturated. In order to make the charge amplifier work in a linear section, it is necessary to compensate the parasitic capacitances of the RX to eliminate the parasitic capacitances, so that the equivalent input capacitance seen by the charge amplifier is relatively small. In <FIG>, the compensation method adopted is to apply an in-phase excitation signal to the parasitic capacitance Cbase1 and the charge amplifier to eliminate the parasitic capacitance Cbase1. For the elimination of the parasitic capacitance Cbase2, a capacitance compensation circuit (as shown in the dotted box) is used. This capacitance compensation circuit precharges an internal capacitor Ccomp, and then introduces the precharged charge to the RX (VCOM) to eliminate the parasitic capacitance Cbase2. By doing so, the detection circuit needs to occupy a larger chip area, or needs a chip with a larger area.

<FIG> shows a circuit diagram of a detection circuit provided by an embodiment of the present disclosure. Specifically, as shown in <FIG>, the circuit may comprise:.

The touch control panel may be a capacitive touch control panel.

By setting the first excitation signal VSTMH to be in-phase with the second excitation signal VSTML, and setting the amplitude of the first excitation signal VSTMH to be larger than that of the second excitation signal VSTML, the influence of the parasitic capacitances on the touch action detection can be reduced or eliminated. Furthermore, additional hardware is not needed, so the area of the detection circuit can be reduced, thereby reducing the area of the Touch IC where the detection circuit is located.

The difference between the amplitude of the first excitation signal and the amplitude of the second excitation signal can be selected as required, so as to meet the requirement of reducing or eliminating the influence of the parasitic capacitances on the touch action detection. Hence, the difference between the amplitude of the first excitation signal and the amplitude of the second excitation signal is not limited in the present disclosure. <FIG> is an equivalent circuit diagram of the detection circuit shown in <FIG> according to this embodiment. As shown in <FIG>, in one embodiment of the present disclosure, the difference between the amplitude of the first excitation signal and the amplitude of the second excitation signal can be determined by the amplitude of the second excitation signal VSTML, the capacitance value of the first parasitic capacitance Cbase1, the capacitance value of the second parasitic capacitance Cbase2, and the capacitance value of the feedback capacitor Cfb. The first parasitic capacitance Cbase1 is a parasitic capacitance generated between the sensor electrode RX and the source line of the TFT shown in <FIG> and between the sensor electrode RX and the gate line of the TFT shown in <FIG>, and the second parasitic capacitance Cbase2 is a parasitic capacitance to ground of the sensor electrode RX. ΔC represents a variable equivalent capacitance of the sensor electrode RX. Specifically, in response to the sensor electrode being touched, the equivalent capacitance of the sensor electrode becomes larger, resulting in an increase of the voltage Vout at the output terminal.

In one embodiment of the present disclosure, the amplitude of the first excitation signal and the amplitude of the second excitation signal satisfy a preset numerical relationship, which is expressed by the following formula: <MAT>.

The amplitude of the first excitation signal may refer to a difference between the high level value and the low level value of the first excitation signal, and the amplitude of the second excitation signal may refer to a difference between the high level value and the low level value of the second excitation signal.

In one embodiment of the present disclosure, a second switch S2 is connected in series between the sensor electrode RX and the first input terminal-. The second switch S2 can be used to reset the charge of the electrode RX, and when one touch action detection is completed, the second switch S2 can be turned off to charge the electrode RX for the next touch action detection.

In one embodiment of the present disclosure, the first excitation signal and the second excitation signal are in-phase square signals with the same period. The first excitation signal and the second excitation signal can also be in other forms, which is not limited by the present disclosure.

In one embodiment of the present disclosure, the first input terminal is an inverting input terminal and the second input terminal is a non-inverting input terminal.

With reference to the equivalent circuit diagram of the detection circuit shown in <FIG>, the working principle by which the detection circuit eliminates the parasitic capacitances Cbase1 and Cbase2 is explained below:.

The above four steps can complete one touch action detection, and complete sampling and quantization of one complete excitation signal period.

The following explanation is made by taking the VSTIM (excitation signal) jumping from the low level to the high level (that is, from the above Step <NUM> to the above Step <NUM>) as an example:.

In addition, while effectively eliminating the parasitic capacitances, compared with the parasitic capacitance elimination method shown in <FIG>, the method shown in <FIG> and <FIG> can also effectively reduce the chip area occupied by the detection circuit, thus reducing the area of the chip. The detection circuit shown in <FIG> serves as a touch section in an integrated-touch-driver (ITD) chip, and the area of the compensation capacitor and the compensation circuit accounts for about <NUM>% of the area of the chip. According to the embodiments of <FIG> and <FIG>, the area of the chip can be reduced by <NUM>%.

According to the implementation of the detection circuit provided by the above embodiment, the first parasitic capacitance Cbase1 and the second parasitic capacitance Cbase2 can be eliminated by applying the first excitation signal and the second excitation signal and making the two excitation signals satisfy the above preset numerical relationship, thereby avoiding the influence of the parasitic capacitances on the accuracy of the touch action detection. While avoiding the influence of the parasitic capacitances on the accuracy of the touch action detection, the above detection circuit does not need additional hardware, which can effectively reduce the area of the detection circuit, and further save the area of the Touch IC integrated with the detection circuit.

Based on a detection circuit described in the above embodiments, the present disclosure also provides a touch panel, which comprises a capacitive touch panel including the detection circuit.

In an embodiment of the present disclosure, a common electrode VCOM of the touch control panel can be divided into one or more of the sensor electrodes RX.

<FIG> shows a block diagram of an electronic apparatus <NUM> comprising the above touch control panel according to an exemplary embodiment. The electronic apparatus <NUM> may comprise the above touch control panel. The electronic apparatus <NUM> may be a mobile phone, a computer, a digital broadcast electronic apparatus, a message transceiver, a game console, a tablet device, medical equipment, fitness equipment, a Personal Digital Assistant (PDA), or the like.

Referring to <FIG>, the electronic apparatus <NUM> may comprise one or more of the following components: a processing component <NUM>, a memory <NUM>, a power supply component <NUM>, a multimedia component <NUM>, an audio component <NUM>, an input/output (I/O) interface <NUM>, a sensor component <NUM>, and a communication component <NUM>.

The processing component <NUM> generally controls the overall operation of the electronic apparatus <NUM>, such as operations related to display, phone call, data communication, camera operation, and record operation. The processing component <NUM> may comprise one or more processors <NUM> to execute instructions. Furthermore, the processing component <NUM> may comprise one or more modules for facilitating interaction between the processing component <NUM> and other components. For example, the processing component <NUM> may comprise a multimedia module to facilitate the interaction between the multimedia component <NUM> and the processing component <NUM>.

The memory <NUM> is configured to store various types of data to support the operations of the electronic apparatus <NUM>. Examples of these data include instructions for any application or method operated on the electronic apparatus <NUM>, contact data, telephone directory data, messages, pictures, videos, etc. The memory <NUM> may be implemented by any type of volatile or non-volatile storage apparatuses or a combination thereof, such as a Static Random Access Memory (SRAM), an Electrically Erasable Programmable Read-Only Memory (EEPROM), an Erasable Programmable Read-Only Memory (EPROM), a Programmable Read-Only Memory (PROM), a Read-Only Memory (ROM), a magnetic memory, a flash memory, a magnetic disk, or a compact disk.

The power supply component <NUM> supplies electric power to various components of the electronic apparatus <NUM>. The power supply component <NUM> may comprise a power supply management system, one or more power supplies, and other components related to the generation, management, and allocation of power for the electronic apparatus800.

The multimedia component <NUM> comprises a screen providing an output interface between the electronic apparatus <NUM> and a user. In some embodiments, the screen may comprise a Liquid Crystal Display (LCD) and a Touch Panel (TP). If the screen comprises the touch panel, the screen may be implemented as a touch control panel to receive an input signal from the user. The touch panel comprises one or more touch sensors to sense the touch, sliding and gestures on the touch panel. The touch sensor may not only sense a boundary of the touch or sliding operation, but also detect the duration and pressure related to the touch or sliding operation. In some embodiments, the multimedia component <NUM> comprises a front camera and/or a rear camera. When the electronic apparatus <NUM> is in an operating mode such as a shooting mode or a video mode, the front camera and/or the rear camera may receive external multimedia data. Each front camera and rear camera may be a fixed optical lens system or have a focal length and optical zooming capacity.

The audio component <NUM> is configured to output and/or input an audio signal. For example, the audio component <NUM> comprises a microphone (MIC). When the electronic apparatus <NUM> is in the operating mode such as a call mode, a record mode and a voice identifying mode, the microphone is configured to receive an external audio signal. The received audio signal may be further stored in the memory <NUM> or sent by the communication component <NUM>. In some embodiments, the audio component <NUM> also comprises a loudspeaker which is configured to output the audio signal.

The I/O interface <NUM> provides an interface between the processing component <NUM> and a peripheral interface module. The peripheral interface module may be a keyboard, a click wheel, buttons, etc. These buttons may include, but are not limited to: a home button, a volume button, a start button, and a lock button.

The sensor component <NUM> comprises one or more sensors which are configured to provide state evaluation in various aspects for the electronic apparatus <NUM>. For example, the sensor component <NUM> may detect an on/off state of the electronic apparatus <NUM> and relative positions of the components such as a display and a keypad of the electronic apparatus <NUM>. The sensor component <NUM> may also detect the position change of the electronic apparatus <NUM> or a component of the electronic apparatus <NUM>, presence or absence of a user contact with the electronic apparatus <NUM>, directions or acceleration/deceleration of the electronic apparatus <NUM> and the temperature change of the electronic apparatus <NUM>. The sensor component <NUM> may include a proximity sensor configured to detect the presence of nearby objects without physical contact. The sensor component <NUM> may further comprise an optical sensor, such as a Complementary Metal Oxide Semiconductor (CMOS) or Charge Coupled Device (CCD) image sensor, for use in the imaging application. In some embodiments, the sensor component <NUM> may further comprise an acceleration sensor, a gyroscope sensor, a magnetic sensor, a pressure sensor or a temperature sensor.

The communication component <NUM> is configured to facilitate the communication in a wired or wireless mode between the electronic apparatus <NUM> and other apparatuses. The electronic apparatus <NUM> may access a wireless network based on communication standards, such as wireless fidelity (Wi-Fi), a <NUM>nd generation mobile communication technology (<NUM>), a <NUM>rd generation mobile communication technology (<NUM>), or a combination thereof. In an exemplary embodiment, the communication component <NUM> receives a broadcast signal or broadcast related information from an external broadcast management system via a broadcast channel. In an exemplary embodiment, the communication component <NUM> further comprises a Near Field Communication (NFC) module to promote the short range communication. For example, the NFC module may be implemented on the basis of a Radio Frequency Identification (RFID) technology, an Infrared Data Association (IrDA) technology, an Ultra Wide Band (UWB) technology, a Bluetooth (BT) technology and other technologies.

In an exemplary embodiment, the electronic apparatus <NUM> can be implemented by one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), controllers, microcontrollers, microprocessors, or other electronic components.

Aspects of the present disclosure have been described herein with reference to the flowchart and/or the block diagrams of the method and device (systems) according to the embodiments of the present disclosure. It will be appreciated that each block in the flowchart and/or the block diagram, and combinations of blocks in the flowchart and/or block diagram, can be implemented by the computer-readable program instructions.

These computer-readable program instructions may be provided to a processor of a general purpose computer, a dedicated computer, or other programmable data processing devices, to form a machine, such that when the instructions are executed by the processor of the computer or other programmable data processing devices, a device which implements the functions/actions specified in one or more blocks in the flowchart and/or block diagram is generated. These computer-readable program instructions may also be stored in a computer-readable storage medium, and the instructions cause the computer, programmable data processing device and/or other devices to function in a particular manner, such that the computer-readable storage medium having instructions stored thereon comprises a product that includes instructions implementing aspects of the functions/actions specified in one or more blocks in the flowchart and/or block diagram.

The computer-readable program instructions may also be loaded into a computer, other programmable data processing devices, or other devices to cause a series of operational operations to be executed on the computer, other programmable devices or other devices, so as to produce a computer implemented process, such that the instructions executed on the computer, other programmable devices or other devices implement the functions/actions specified in one or more blocks in the flowchart and/or block diagram.

Claim 1:
A detection circuit, comprising:
a charge amplifier (CA) comprising a first input terminal, a second input terminal, and an output terminal;
a feedback capacitor (Cfb), both ends of which are electrically connected to the first input terminal and the output terminal respectively:
a sensor electrode (RX) electrically connected to the first input terminal;
wherein a first excitation signal (VSTIMH) is applied to a thin film transistor (TFT) in a touch control panel where the detection circuit is located, a second excitation signal (VSTIML) is applied to the second input terminal;
characterized in that
the feedback capacitor (Cfb) being in parallel connection with a first switch (S1); and
an amplitude of the first excitation signal (VSTIMH) being larger than an amplitude of the second excitation signal (VSTIML), wherein
a difference between the amplitude of the first excitation signal (VSTIMH) and the amplitude of the second excitation signal (VSTIML) is determined by the amplitude of the second excitation signal (VSTIML), a capacitance value of a first parasitic capacitance (Cbase1), a capacitance value of a second parasitic capacitance (Cbase2), and a capacitance value of the feedback capacitor (Cfb), wherein the first parasitic capacitance (Cbase1) is a parasitic capacitance generated between the sensor electrode (RX) and a source line and a gate line of the thin film transistor (TFT), and the second parasitic capacitance (Cbase2) is a parasitic capacitance to ground of the sensor electrode (RX),
the first excitation signal (VSTIMH) and the second excitation signal (VSTIML) are in-phase square signals with a same period,
the amplitude of the first excitation signal (VSTIMH) and the amplitude of the second excitation signal (VSTIML) satisfy a preset numerical relationship, which is expressed by the following formula: <MAT>
where ΔVSTIM_HL represents the difference between the amplitude of the first excitation signal (VSTIMH) and the amplitude of the second excitation signal (VSTIML);
VSTIML_H represents a high level value of the second excitation signal (VSTIML);
VSTIML_L represents a low level value of the second excitation signal (VSTIML);
Cbase<NUM> represents the capacitance value of the first parasitic capacitance (Cbase1);
Cbase<NUM> represents the capacitance value of the second parasitic capacitance (Cbase2);
Cfb represents the capacitance value of the feedback capacitor (Cfb); and
VOUT represents (VSTIML_L + VSTIML_H)/<NUM>.