CN102043503B - Touch panel reader and multi-channel reader - Google Patents

Abstract

A touch panel reading device and a multi-channel reading device are provided to integrate different types of reading circuits. The reading device set to the first mode uses an integrator to read a touch panel with a small amount of charge. The reading device set to the second mode uses a current-to-voltage conversion unit and an inverting amplifier to read the sensing current of a current-type touch panel to save chip area. The multi-channel reading device set to the third mode uses a plurality of channels to share a set of integrators with a large capacitance value (or area) feedback capacitor (integration capacitor) in turn to read a touch panel with a large amount of charge, thereby significantly reducing the number of large-area feedback capacitors. Therefore, in addition to achieving the purpose of reducing chip area, the embodiments of the present invention can also be applied to various types of touch panels.

Description

Touch panel reader and multi-channel reader

technical field

The present invention relates to a touch device, and in particular to a reading device for a touch panel.

Background technique

With the vigorous development of electronic technology and the popularization of wireless communication and network, various electronic devices have gradually become an indispensable tool in life. However, common input and output (input/output, I/O) interfaces, such as a keyboard or a mouse, are quite difficult to operate. In contrast, a touch panel is an intuitive and simple input and output interface. Therefore, the touch panel is often used as a man-machine interface between people and electronic devices to perform control.

In general, touch panels can be classified into resistive touch panels, optical touch panels, capacitive touch panels, and the like. According to the readout method, it can be divided into current type touch panel (current type touch panel) and charge type touch panel (charge type touch panel). FIG. 1 illustrates a schematic diagram of a photo charge type touch panel and a conventional readout circuit. A plurality of data lines (data lines) and a plurality of scan lines (scan lines) of the optical charge touch panel 110 are respectively driven by a source driver (source driver) 120 and a gate driver (gate driver) 130, and the touch panel A plurality of sensor lines of 110 are coupled to a plurality of readout circuits 140 . FIG. 1 only shows one of the scan lines, one of the data lines and one of the sensing lines.

The storage capacitor Cst1 and the liquid crystal capacitor Clc are respectively coupled to a bias voltage VBIAS1 and a common voltage VCOM. Both the bias voltage VBIAS1 and the common voltage VCOM can be the same voltage or different voltages. When the gate driver 130 turns on the switch SW1 via the scan line, the source driver 120 correspondingly writes pixel data into the storage capacitor Cst1 and the liquid crystal capacitor Clc via the data line. Since the potential difference between the pixel data and the common voltage VCOM correspondingly deflects the liquid crystal molecules of the liquid crystal capacitor Clc, the pixel presents a corresponding gray scale.

According to the bias voltage VBIAS2, the photo transistor PT provides a discharge path between the storage capacitor Cst2 and the bias voltage VBIAS2. If the position where the phototransistor PT is located is not touched by the user, the phototransistor PT will accelerate the discharge of the storage capacitor Cst2 due to external light irradiation. Conversely, if the external light irradiates the phototransistor PT due to the user's touch, the phototransistor PT will slow down the discharge speed of the storage capacitor Cst2. When the gate driver 130 turns on the switch SW2 via the scan line, the reading circuit 140 can read the remaining charge of the storage capacitor Cst2 via the sensing line, and charge the storage capacitor Cst2 to a normal rated voltage level.

The detection method of the reading circuit 140 on the optical charge touch panel 110 is mainly to determine the position touched by the user through the inconsistency of the discharge of the storage capacitor Cst2 or the difference of whether there is a coupling capacitor or not. For the optical charge touch panel 110 , generally an integrator (ie, the operational amplifier 141 and the feedback capacitor Cfb ) is configured in the reading circuit 140 to detect the charge difference of the touch panel 110 . An analog-to-digital converter (analog-to-digital converter, ADC) 143 converts the integration result output by the integrator into a corresponding digital code, and transmits the digital code to an image processing circuit (image processing circuit) 150 for determining the touch position.

FIG. 2 illustrates a schematic diagram of a photo current type touch panel and a conventional reading circuit. The multiple scanning lines of the touch panel 210 are driven by the gate driver 130 , while the multiple sensing lines of the touch panel 210 are coupled to the readout circuit 240 . The pixel layout of a conventional optogalvanic touch panel is shown in FIG. 2 . Each pixel has a switch SW1 and a phototransistor PT. When the bias voltage VBIAS is higher than the voltage of node A, and the gate driver 130 turns on the switch SW1 through the scan line, since the phototransistor PT is in a forward bias state, the sensing current Is will pass through the phototransistor PT and the switch SW1 and flow to the sense line. Wherein, the intensity of the light received by the photosensitive transistor PT will affect the magnitude of the sensing current Is.

By using the reading circuit 240 to detect the magnitude and difference of each online sensing current Is, it can be known whether there is a light-shielding object in the corresponding position of the touch panel 210 (that is, whether there is a foreign object touching the panel 210 ). The reading circuit 240 sends the detection result to the image processing circuit 150 in the form of digital code. The image processing circuit 150 determines the touch position according to the digital codes provided by all the reading circuits 240 . The conventional reading circuit 240 uses an integrator (ie, an operational amplifier 241 and a feedback capacitor Cfb) to convert the sensing current Is into a corresponding voltage, and then an analog-to-digital converter (analog-to-digital converter, ADC) 243 converts the voltage It is converted into a corresponding digital code, and finally the image processing circuit 150 judges the touch position according to the digital code.

FIG. 3 illustrates a schematic diagram of a capacitive touch panel and a conventional reading circuit. Generally, the Y-axis direction and the X-axis direction of the capacitive touch panel 310 each have a plurality of sensing lines. A coupling capacitor Cp is formed between a sensing line in the Y-axis direction and a sensing line in the X-axis direction. Each sensing line is configured with an integrator 320 , and each integrator 320 is configured with an operational amplifier 322 and a feedback capacitor Cfb. Initially, the positive inputs of all operational amplifiers 322 receive a reference voltage Vref of 0V, and all switches 323 are turned on, so all sensing lines are charged to 0V. Next, each integrator 320 will turn off the switch 323 to perform a read operation. During the off period of the switch 323, assuming that there is no conductive object (such as a finger) close to the touch panel 310, when the reference voltage Vref changes from 0V to 5V, the integrator 320 in the direction of the Y axis and the direction of the X axis will make the coupling capacitor Cp twice The terminal voltage is 5V. Since there is no need to charge and discharge the coupling capacitor Cp, when the reference voltage Vref changes to 5V, this change will be reflected on the output of the integrator 320 . After each integrator 320 completes the read operation, all the switches 323 are turned on again, and so on.

When a conductor (such as a finger) approaches the touch panel 310 , an additional capacitance Cf (as shown in FIG. 3 ) will be formed at the corresponding position. When the switch 323 is off, when the reference voltage Vref changes from 0V to 5V, the corresponding integrator 320 needs to charge and discharge the extra capacitor Cf via the sensing line. Therefore, when the reference voltage Vref changes to 5V, the output OUT of the integrator 320 corresponding to the additional capacitor Cf will change, and the formula is OUT=5+[(5V−0V)×Cf]/Cfb. The integrator 320 sends the reading result to a subsequent circuit (including an analog-to-digital converter and an image processing circuit, not shown here) to determine the position coordinates. The touched position can be located by the difference between the signal read by the sensing line forming the extra capacitance Cf and the signal read by the sensing line without the extra capacitance Cf. It can be seen from the above formula that if the additional capacitor Cf is larger, the feedback capacitor Cfb will be larger, otherwise it is easy to make the output of the integrator 320 reach saturation and the touch position cannot be determined.

However, in order to prevent the output of the integrator from reaching saturation, the feedback capacitor Cfb in the integrator must also increase its capacitance accordingly (that is, increase its area). Since each sensing line requires an integrator, the chip area occupied by the integrator will be considerable. Furthermore, different types of touch panels require readout circuits with different functions to read out their signals and convert them into digital signals that can be operated by subsequent image processing circuits. If a reading circuit with different functions is used for each type of touch panel, the flexibility of the touch panel reading device will be relatively narrow.

Contents of the invention

The invention provides a reading device and a multi-channel reading device for a touch panel, which are applicable to various types of touch panels.

The present invention proposes a reading device for a touch panel, including a first selector, a second selector, a third selector, a fourth selector, a current-to-voltage conversion unit, a first resistor, a second resistor, a first operational amplifier, feedback capacitor, and feedback switch. The common end of each of the selectors is selectively electrically connected to the first selection end or the second selection end. The input end of the current-to-voltage conversion unit is coupled to the first selection end of the first selector. The first end of the first resistor is coupled to the output end of the current-to-voltage conversion unit. The first selection terminal of the second selector is coupled to the second terminal of the first resistor, and the second selection terminal of the second selector is coupled to the second selection terminal of the first selector. The first input terminal of the first operational amplifier is coupled to the common terminal of the second selector, and the second input terminal of the first operational amplifier receives a reference voltage. The common terminal of the third selector is coupled to the first input terminal of the first operational amplifier. The common terminal of the fourth selector is coupled to the output terminal of the first operational amplifier. The first terminal of the second resistor is coupled to the first selection terminal of the third selector, and the second terminal of the second resistor is coupled to the first selection terminal of the fourth selector. The first end of the feedback capacitor is coupled to the second selection end of the third selector, and the second end of the feedback capacitor is coupled to the second selection end of the fourth selector. The first terminal and the second terminal of the feedback switch are respectively coupled to the first terminal and the second terminal of the feedback capacitor.

The invention provides a multi-channel reading device for a touch panel. The multi-channel reader includes an integrator and multiple channels. Each channel individually includes an input selector, a first selector, a second selector, a third selector, a fourth selector, a current-to-voltage conversion unit, a first resistor, a second resistor, a first operational amplifier, a feedback capacitor , feedback switch, and output selector. The common end of each of the selectors is selectively electrically connected to the first selection end or the second selection end. The first selection terminal of the input selector is coupled to the input terminal of the integrator. The common terminal of the first selector is coupled to the second selection terminal of the input selector. The input end of the current-to-voltage conversion unit is coupled to the first selection end of the first selector. The first end of the first resistor is coupled to the output end of the current-to-voltage conversion unit. The first selection terminal of the second selector is coupled to the second terminal of the first resistor, and the second selection terminal of the second selector is coupled to the second selection terminal of the first selector. The first input terminal of the first operational amplifier is coupled to the common terminal of the second selector, and the second input terminal of the first operational amplifier receives a reference voltage. The common terminal of the third selector is coupled to the first input terminal of the first operational amplifier. The common terminal of the fourth selector is coupled to the output terminal of the first operational amplifier. The first terminal of the second resistor is coupled to the first selection terminal of the third selector, and the second terminal of the second resistor is coupled to the first selection terminal of the fourth selector. The first end of the feedback capacitor is coupled to the second selection end of the third selector, and the second end of the feedback capacitor is coupled to the second selection end of the fourth selector. The first terminal and the second terminal of the feedback switch are respectively coupled to the first terminal and the second terminal of the feedback capacitor. The first selection terminal of the output selector is coupled to the output terminal of the integrator, and the second selection terminal of the output selector is coupled to the output terminal of the first operational amplifier.

In an embodiment of the present invention, when in the first mode, the input selector, the first selector, the second selector, the third selector, the fourth selector, and the output selector all select to connect their common terminals to Connect to its second select terminal.

In an embodiment of the present invention, when in the second mode, the input selector, the first selector, the second selector, the third selector, the fourth selector, and the output selector all select to connect their common terminals to Connect to its first selection terminal.

In an embodiment of the present invention, when in the third mode, the first selector, the second selector, the third selector, and the fourth selector all choose to electrically connect their common terminals to their second selection terminals, And the feedback switch is turned on. In the third mode, the input selector and output selector of one of the channels choose to connect its common terminal to its first selection terminal electrically, while the input selectors and output selectors of other channels choose to connect their The common end is electrically connected to the second selection end thereof.

Based on the above, the embodiments of the present invention integrate different types of readout circuits. The current-to-voltage conversion unit and the inverting amplifier are used to read the sensing current of the current-mode touch panel, thereby avoiding the use of an integral capacitor and reducing the chip area occupied by the feedback capacitor. In some embodiments, a group of integrators are shared among multiple channels in turn to read the sense charges of the capacitive touch panel, so the area of the feedback capacitor (integrating capacitor) can be greatly reduced. Therefore, in addition to achieving the purpose of reducing chip area, the embodiments of the present invention are more applicable to various types of touch panels.

In order to make the above-mentioned features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail with reference to the accompanying drawings.

Description of drawings

FIG. 1 illustrates a schematic diagram of an optical charge touch panel and a conventional reading circuit;

FIG. 2 illustrates a schematic diagram of an optogalvanic touch panel and a conventional reading circuit;

3 illustrates a schematic diagram of a capacitive touch panel and a conventional reading circuit;

4 is a schematic circuit diagram illustrating a reading device for a touch panel according to an embodiment of the present invention;

5 is a schematic diagram illustrating an equivalent circuit of the reading device set in the first mode in FIG. 4 according to an embodiment of the present invention;

FIG. 6 is a schematic diagram illustrating an equivalent circuit of the reading device set in the second mode in FIG. 4 according to an embodiment of the present invention;

FIG. 7 is another schematic circuit diagram illustrating the current-to-voltage conversion unit in FIG. 4 according to an embodiment of the present invention;

FIG. 8 is another schematic circuit diagram illustrating the current-to-voltage conversion unit in FIG. 4 according to an embodiment of the present invention;

9 is a schematic circuit diagram illustrating a multi-channel reading device for a touch panel according to another embodiment of the present invention;

FIG. 10 is a schematic diagram illustrating an equivalent circuit of the reading device set in the third mode in FIG. 9 according to an embodiment of the present invention;

FIG. 11 is a waveform diagram illustrating a reset signal and a reference voltage according to an embodiment of the present invention.

Detailed ways

The following embodiments will take the optical charge touch panel 110 and the optical current touch panel 210 as examples to illustrate the application examples of the reading device of the present invention. However, the scope of application of the present invention should not be limited thereto.

FIG. 4 is a schematic circuit diagram illustrating a reading device 400 for a touch panel according to an embodiment of the present invention. The input end of the reading device 400 is coupled to the sensing line of the touch panel 401, and the output end of the reading device 400 sends the reading result to the subsequent circuit (including the analog-to-digital converter and the image processing circuit, not shown here. Shown) to determine the coordinates of the touch position. The touch panel 401 can be a charge touch panel (such as the optical charge touch panel 110 shown in FIG. 1 ), or a current touch panel (such as the optical current touch panel 210 shown in FIG. ).

The reading device 400 includes a first selector 411, a second selector 412, a third selector 413, a fourth selector 414, a current-to-voltage conversion unit 420, a first resistor R1, a second resistor R2, a first operational amplifier OP1, a feedback capacitor Cfb and a feedback switch SWfb. The common end of each of the selectors 411 - 414 is selectively electrically connected to the first selection end or the second selection end. For example, the selector 411 may electrically connect its common terminal to its first selection terminal, or electrically connect its common terminal to its second selection terminal. In this embodiment, the selector 411 and the selector 413 are demultiplexers, and the selector 412 and the selector 414 are multiplexers.

A common end of the selector 411 is coupled to a corresponding sensing line of the touch panel 401 . The input end of the current-to-voltage conversion unit 420 is coupled to the first selection end of the selector 411 . A first terminal of the resistor R1 is coupled to the output terminal of the current-to-voltage conversion unit 420 , and a second terminal of the resistor R1 is coupled to the first selection terminal of the selector 412 . The second selection terminal of the selector 412 is coupled to the second selection terminal of the selector 411 . A first input terminal of the operational amplifier OP1 is coupled to the common terminal of the selector 412 , and a second input terminal of the operational amplifier OP1 receives the first reference voltage Vref. In this embodiment, the first input terminal of the operational amplifier OP2 is an inverting input terminal (inverting input), and the second input terminal of the operational amplifier OP2 is a non-inverting input terminal (non-inverting input). The output terminal of the operational amplifier OP1 sends the reading result to a subsequent circuit (not shown) to determine the coordinates of the touch position.

Those who apply this embodiment can determine the level of the reference voltage Vref according to their design requirements and the type of the touch panel 401 . For example, the reference voltage Vref is set to half of the system voltage VDDA level (VDDA/2), or set to the band-gap voltage (band-gap voltage), or set to +5V, or set Set to other fixed voltage. In some embodiments, the reference voltage Vref may be set as a time-varying voltage in response to the reset signal RESET. FIG. 11 is a waveform diagram illustrating a reset signal and a reference voltage according to an embodiment of the present invention. When the reset signal RESET is logic low level, the reference voltage Vref is the ground voltage (ie 0V). After the reset signal RESET turns to a logic high level, the reference voltage Vref turns to half of the system voltage VDDA (ie VDDA/2, eg +5V) in response to the reset signal RESET.

The common terminal of the selector 413 is coupled to the first input terminal of the operational amplifier OP1. The common terminal of the selector 414 is coupled to the output terminal of the operational amplifier OP1. A first terminal of the resistor R2 is coupled to a first selection terminal of the selector 413 , and a second terminal of the resistor R2 is coupled to a first selection terminal of the selector 414 . A first end of the feedback capacitor Cfb is coupled to the second selection end of the selector 413 , and a second end of the feedback capacitor Cfb is coupled to the second selection end of the selector 414 . The first terminal and the second terminal of the feedback switch SWfb are respectively coupled to the first terminal and the second terminal of the feedback capacitor Cfb. The feedback switch SWfb is controlled by the signal RESETB, wherein the signal RESETB is an inverted signal of the reset signal RESET.

When in the first mode, each of the selectors 411 - 414 selects to electrically connect their common end to the second selection end. In the first mode, when the feedback switch SWfb is turned off, the operational amplifier OP1 and the feedback capacitor Cfb form an integrator. The reading device 400 set in the first mode can read the sensing signal of the optical charge touch panel 110 .

FIG. 5 is a schematic diagram illustrating an equivalent circuit of the reading device 400 set in the first mode in FIG. 4 according to an embodiment of the present invention. Here, it is assumed that the touch panel 401 is the optical charge touch panel 110 as shown in FIG. 1 . When the system is powered on or reset, the system will set the reset signal RESET to an enable state (for example, a logic low level). When the reset signal RESET is at a logic low level (that is, the signal RESETB is at a logic high level), the feedback switch SWfb is turned on to reset the feedback capacitor Cfb. When the reset signal RESET is in a disabled state (such as a logic high level, that is, the signal RESETB is a logic low level), and the switch SW2 is turned on, the integrator can control the touch panel 110 (ie, the touch panel 110 The sensing line of the panel 401) performs an integral operation, and then the operational amplifier OP1 sends the reading result to a subsequent circuit (not shown) to determine the coordinates of the touch position.

Referring to FIG. 4 , when in the second mode, the selectors 411 to 414 each select to electrically connect their common terminals to the first selection terminal. In the second mode, the reading device 400 can be regarded as a reading circuit composed of a current-to-voltage conversion unit 420 and an inverting amplifier 610 . The reading device 400 set in the second mode can read the sensing signal of the optogalvanic touch panel 210 .

FIG. 6 is a schematic diagram illustrating an equivalent circuit of the reading device 400 set in the second mode in FIG. 4 according to an embodiment of the present invention. Here, it is assumed that the touch panel 401 is the optogalvanic touch panel 210 as shown in FIG. 2 . The current-to-voltage conversion unit 420 converts the sensing current Is of the current mode touch panel 210 into a sensing voltage Vs. The input terminal of the inverting amplifier 610 composed of the resistor R1 , the resistor R2 and the operational amplifier OP1 is coupled to the output terminal of the current-to-voltage conversion unit 420 to receive the sensing voltage Vs. After the inverting amplifier 610 gains the sensing voltage Vs, the reading result can be sent to a subsequent circuit (not shown) to determine the coordinates of the touch position.

In this embodiment, the current-to-voltage conversion unit 420 includes a third resistor 421 and a unity gain amplifier. Here, the operational amplifier 422 is implemented as a unity gain amplifier. A first end of the resistor 421 is used as an input end of the current-to-voltage conversion unit 420 , and a second end of the resistor 421 is coupled to a second reference voltage (eg, ground voltage). The first terminal of the operational amplifier 422 (ie, the input terminal of the unity gain amplifier) is coupled to the first terminal of the resistor 421, and the second terminal of the operational amplifier 422 is coupled to the output terminal of the operational amplifier (ie, the output terminal of the unity gain amplifier) , and the output terminal of the operational amplifier 422 is used as the output terminal of the current-to-voltage conversion unit 420 . In order to cope with the different characteristics of different touch panels, the person applying this embodiment can use "variable resistors" to realize the resistors 421, R1 and/or R2 according to their design requirements.

FIG. 7 is a schematic diagram illustrating another circuit of the current-to-voltage conversion unit 420 in FIG. 4 according to an embodiment of the present invention. The current-to-voltage conversion unit 420 includes a resistor 710 and a current mirror 720 . A first end of the resistor 710 receives a third reference voltage (such as the system voltage VDDA), and a second end of the resistor 710 is coupled to the resistor R1. Here, the resistor 710 is implemented with a P-channel metal-oxide-semiconductor (PMOS) transistor 711 to reduce the chip area occupied by the resistor 710 . A first terminal (eg, source) of the transistor 711 receives the system voltage VDDA, and a second terminal (eg, drain) and a control terminal (eg, gate) of the transistor 711 are coupled to the resistor R1 .

The primary current terminal of the current mirror 720 receives the sensing current Is, and the secondary current terminal of the current mirror 720 is coupled to the second terminal of the resistor 710 . By setting the current multiplier of both the master current terminal and the slave current terminal of the current mirror 720, the current mirror 720 can amplify the weak sensing current Is. The amplified sensing current is converted into a sensing voltage Vs via the resistor 710 . In this way, under the condition that the phototransistor PT is irradiated by strong light or weak light, the variation range of the obtained sensing voltage Vs can be increased, so the recognition degree of the sensing voltage Vs can be increased. The sensing voltage Vs is amplified again by the inverting amplifier 610 to facilitate processing by subsequent circuits.

Here, the current mirror 720 includes a first transistor 721 and a second transistor 722 . In this embodiment, the transistors 721 and 722 are realized by N-channel metal oxide semiconductor (NMOS) transistors. The first terminal (such as the drain) of the transistor 721 is used as the main current terminal of the current mirror 720, the second terminal (such as the source) of the transistor 721 receives the fourth reference voltage (such as the ground voltage), and the control terminal of the transistor 721 (such as Gate) is coupled to the first end of the transistor 721. The first terminal of the transistor 722 serves as the slave current terminal of the current mirror 720 , the second terminal of the transistor 722 receives the fourth reference voltage (ground voltage), and the control terminal of the transistor 722 is coupled to the control terminal of the transistor 721 . By determining the aspect ratio of the transistors 721 and 722 , the current multiplier of both the master current terminal and the slave current terminal of the current mirror 720 can be set.

FIG. 8 is another schematic circuit diagram illustrating the current-to-voltage conversion unit 420 in FIG. 4 according to an embodiment of the present invention. This embodiment is similar to FIG. 7 , so part of the content will not be repeated. The difference between the two is that in FIG. 8 , the current mirror 730 is used to replace the aforementioned current mirror 720 . The current mirror 730 includes a first transistor 731 , a second transistor 732 , a third transistor 733 and a fourth transistor 734 . A first terminal (such as a drain) of the transistor 731 serves as a main current terminal of the current mirror 730 , and a control terminal (such as a gate) of the transistor 731 is coupled to the first terminal of the transistor 731 . A first terminal (such as a drain) of the transistor 732 serves as a slave current terminal of the current mirror 730 , and a control terminal (such as a gate) of the transistor 732 is coupled to a control terminal of the transistor 731 . The first end (eg drain) of the transistor 733 is coupled to the second end (eg source) of the transistor 731, the second end (eg source) of the transistor 733 receives a reference voltage (eg ground voltage), and the transistor 733 The control terminal (eg gate) is coupled to the first terminal of the transistor 733 . The first terminal (such as the drain) of the transistor 734 is coupled to the second terminal (such as the source) of the transistor 732, the second terminal (such as the source) of the transistor 734 receives a reference voltage (ground voltage), and the control of the transistor 734 A terminal (eg gate) is coupled to the control terminal of the transistor 733 .

FIG. 9 is a schematic circuit diagram illustrating a multi-channel reading device 900 for a touch panel according to another embodiment of the present invention. The reading device 900 has a plurality of channels, the input end of each channel is coupled to the corresponding sensing line of the touch panel 901, and the output end of each channel sends the reading result to the subsequent circuit (including analog-to-digital converter and The image processing circuit (not shown here) determines the coordinates of the touch position. The touch panel 901 can be an optical charge touch panel 110 , an optogalvanic touch panel 210 , a capacitive touch panel 310 or other types of touch panels.

The multi-channel reader 900 includes an integrator 910 and a plurality of channels, each of which includes an input selector, a single-channel reader (such as the reader 400 shown in FIG. 4 ) and an output selector. For example, a first channel includes an input selector 920-1, a single-channel reader 400-1, and an output selector 930-1, and a second channel includes an input selector 920-2, a single-channel reader 400-2 and an output selector 930-2. By analogy, the nth channel includes an input selector 920-n, a single-channel reader 400-n, and an output selector 930-n. A common end of each of the selectors 920-1-920-n and 930-1-930-n is selectively electrically connected to the first selection end or the second selection end. For example, the common terminal of the input selector 920-1 may be electrically connected to its first selection terminal, or its common terminal may be electrically connected to its second selection terminal. In this embodiment, the input selectors 920-1~920-n are demultiplexers, and the output selectors 930-1~930-n are multiplexers.

The integrator 910 includes an operational amplifier OP3 , a feedback capacitor 912 and a feedback switch 911 . The first input terminals of the operational amplifier OP3 are coupled to the first selection terminals of the input selectors 920-1˜920-n in all channels. The first terminal and the second terminal of the feedback capacitor 912 are respectively coupled to the inverting input terminal and the output terminal of the operational amplifier OP3. The first terminal and the second terminal of the feedback switch 911 are also respectively coupled to the inverting input terminal and the output terminal of the operational amplifier OP3. The non-inverting input terminal of the operational amplifier OP3 receives the reference voltage Vref. Here, the capacitance value (or area) of the feedback capacitor 912 is much larger than the capacitance value (or area) of the feedback capacitor Cfb of each channel.

In this embodiment, the implementations of the single-channel reading devices 400 - 1 - 400 - n are the same as the reading device 400 shown in FIG. 4 , so details thereof will not be repeated here. In addition, the first channel will be described in detail below, and other channels can be deduced by referring to the description of the first channel.

In the first channel, the common end of the input selector 920 - 1 is coupled to the corresponding sensing line (for example, the first sensing line) of the touch panel 901 . The first selection terminal of the input selector 920-1 is coupled to the input terminal of the integrator 910, and the second selection terminal of the input selector 920-1 is coupled to the common of the selector 411 in the single-channel reading device 400-1. end. The first selection terminal of the output selector 930-1 is coupled to the output terminal of the integrator 910, and the second selection terminal of the output selector 930-1 is coupled to the first operational amplifier OP1 in the single-channel reading device 400-1 output terminal.

The touch panel 901 corresponding to the first mode may be the optical charge touch panel 110 shown in FIG. 1 . When in the first mode, the input selectors 920-1~920-n, the selectors 411~414 and the output selectors 930-1~930-n of all the channels respectively select and electrically connect their common terminals to the second selection terminal . In the first mode, when the feedback switch SWfb is turned off, the operational amplifier OP1 and the feedback capacitor Cfb form an integrator. Each channel of the multi-channel reading device 900 set in the first mode can be equivalent to an integrator as shown in FIG. 5 (ie, the reading device 400 in FIG. 5 ). Therefore, the multi-channel reading device 900 set in the first mode can read the sensing signal of the optical charge touch panel 110, and then deliver the reading result to the subsequent circuit ( not shown) to determine the coordinates of the touch position.

Referring to FIG. 9 , the touch panel 901 corresponding to the second mode may be the optogalvanic touch panel 210 shown in FIG. 2 . When in the second mode, the input selectors 920-1~920-n and the output selectors 930-1~930-n of all the channels respectively select and electrically connect their common terminals to the second selection terminal, while the selectors 411～ 414 each choose to electrically connect their common end to the first selection end. In the second mode, each channel of the multi-channel reading device 900 can be regarded as a reading circuit composed of a current-to-voltage conversion unit 420 and an inverting amplifier 610 , as shown in FIG. 6 . Therefore, the current-to-voltage conversion unit 420 can convert the sensing current Is of the current mode touch panel 210 into the sensing voltage Vs. After gaining the sensing voltage Vs, the inverting amplifier 610 composed of the resistor R1, the resistor R2 and the operational amplifier OP1 can pass the reading result to the subsequent circuit ( not shown) to determine the coordinates of the touch position.

Referring to FIG. 9 , the touch panel 901 corresponding to the third mode may be the capacitive touch panel 310 shown in FIG. 3 . When in the third mode, the selectors 411 - 414 of each channel select to electrically connect their common terminals to their second selection terminals, and the feedback switches SWfb of each channel are turned on. Therefore, the reading devices 400-1˜400-n of each channel form a unit-gain amplifier, as shown in FIG. 10 .

FIG. 10 is a schematic diagram illustrating an equivalent circuit of the reading device 900 set in the third mode in FIG. 9 according to an embodiment of the present invention. It is assumed here that the touch panel 901 is the capacitive touch panel 310 as shown in FIG. 3 . Referring to FIG. 10 , when the system is in the initial power-on period, or the system is in the reset period, the system will set the reset signal RESET to an enabled state (for example, a logic low level), and the input selectors 920- 1 to 920-n and the output selectors 930-1 to 930-n respectively select and electrically connect their common terminals to the second selection terminal. When the reset signal RESET is at a logic low level (that is, the signal RESETB is at a logic high level), the feedback switch 911 is turned on to reset the feedback capacitor 912 .

Referring to FIG. 10 and FIG. 11, when entering the first channel period T1, the system will set the reset signal RESET to a logic high level (that is, the signal RESETB is a logic low level), and the input selector 920- 1 and the output selector 930-1 select to electrically connect their common end to its first selection end, while the input selectors (such as input selector 920-n) and output selectors (such as input selector 930-n) of the remaining channels ) is selected to electrically connect its common terminal to its second selection terminal. Thus, during the first pass, T1, the first pass may use the integrator 910 . When the reset signal RESET is a logic high level and the switch 911 is turned off, the integrator 910 can integrate the sensing line of the touch panel 310 (that is, the touch panel 901), and then the operational amplifier OP3 will read The result is delivered to a subsequent circuit (not shown) through the output selector 930-1 to determine the coordinates of the touch position. During the period T1 of the first channel, except for the first channel, the input terminals of the other channels are coupled to the corresponding sensors of the touch panel 310 through the input terminals of their internal unity gain amplifiers (ie, the reading devices 400-2˜400-n). survey line.

When the current channel period (such as the first channel period T1) ends but has not yet entered the next channel period (such as the second channel period T2) (equivalent to the reset period), the system will set the reset signal RESET to a logic low level (As shown in FIG. 11 ), the feedback switch 911 is turned on to reset the feedback capacitor 912 . During this period, the input selectors 920-1 to 920-n and the output selectors 930-1 to 930-n of all channels select to electrically connect the common terminal to the second selection terminal, so that the unity gain amplifier (ie read The devices 400 - 1 - 400 - n ) are coupled to the sensing lines of the touch panel 110 .

Then enter the second channel period T2. During the period T2 of the second channel, the second channel (not shown in FIG. 10 , which can be analogized to the relevant description of the first channel) can use the integrator 910, while the remaining channels use the input terminals of their internal unity gain amplifiers It is coupled to the corresponding sensing line of the touch panel 310 so as to replace the input end of the integrator. By analogy, when entering the nth channel period Tn, the nth channel can use the integrator 220 , while the other channels are coupled to the corresponding sensing lines of the touch panel 110 through the input terminals of their internal unity gain amplifiers. For the detailed operations of the second channel period T2 , .

To sum up, the above embodiments integrate different types of readout circuits. When the multi-channel reading device 900 operates in the second mode, the multi-channel reading device 900 utilizes the current-to-voltage conversion unit 420 and the inverting amplifier to read the sensing current of the current-mode touch panel, thus avoiding the use of integrating capacitors. Reduce the chip area occupied by the feedback capacitor. In the third mode, the multi-channel reading device 900 reads the sense charges of the capacitive touch panel by sharing a group of integrators among multiple channels in turn, so the area of the feedback capacitor (integrating capacitor) can be greatly reduced . Therefore, the multi-channel reading device 900 of this embodiment can not only reduce the chip area, but also be applicable to various types of touch panels.

Although the present invention has been disclosed as above with the embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims (25)

1. the reading device of a contact panel comprises:

First selector, its common ends optionally are electrically connected to first selecting side or second selecting side;

Electric current is to voltage conversion unit, and its input end is coupled to first selecting side of said first selector;

First resistance, its first end is coupled to the output terminal of said electric current to voltage conversion unit;

Second selector; Its common ends optionally is electrically connected to first selecting side or second selecting side; First selecting side of wherein said second selector is coupled to second end of said first resistance, and second selecting side of said second selector is coupled to second selecting side of said first selector;

First operational amplifier, its first input end is coupled to the common ends of said second selector, and second input end of said first operational amplifier receives first reference voltage;

Third selector, its common ends optionally are electrically connected to first selecting side or second selecting side, and the common ends of wherein said third selector is coupled to the first input end of said first operational amplifier;

The 4th selector switch, its common ends optionally are electrically connected to first selecting side or second selecting side, and the common ends of wherein said the 4th selector switch is coupled to the output terminal of said first operational amplifier;

Second resistance, its first end is coupled to first selecting side of said third selector, and second end of said second resistance is coupled to first selecting side of said the 4th selector switch;

Feedback capacity, its first end is coupled to second selecting side of said third selector, and second end of said feedback capacity is coupled to second selecting side of said the 4th selector switch; And

Feedback switch, its first end and second end are coupled to first end and second end of said feedback capacity respectively.

2. the reading device of contact panel as claimed in claim 1, wherein said electric current to voltage conversion unit comprises:

The 3rd resistance, its first end is as the input end of said electric current to voltage conversion unit, and second end of said the 3rd resistance is coupled to second reference voltage; And

Unity gain amplifier, its input end are coupled to first end of said the 3rd resistance, and the output terminal of said unity gain amplifier is as the output terminal of said electric current to voltage conversion unit.

3. the reading device of contact panel as claimed in claim 2; Wherein said unity gain amplifier comprises second operational amplifier; First end of said second operational amplifier is as the input end of said unity gain amplifier; Second end of said second operational amplifier is coupled to the output terminal of said second operational amplifier, and the output terminal of said second operational amplifier is as the output terminal of said unity gain amplifier.

4. the reading device of contact panel as claimed in claim 1, wherein said electric current to voltage conversion unit comprises:

The 3rd resistance, its first termination is received the 3rd reference voltage, and second end of said the 3rd resistance is as the output terminal of said electric current to voltage conversion unit; And

Current mirror, its principal current end be as the input end of said electric current to voltage conversion unit, and said current mirror be coupled to second end of said the 3rd resistance from current terminal.

5. the reading device of contact panel as claimed in claim 4, wherein said the 3rd resistance is transistor, said transistorized first termination is received said the 3rd reference voltage, said transistorized second end and control end be coupled to said current mirror from current terminal.

6. the reading device of contact panel as claimed in claim 4, wherein said current mirror comprises:

The first transistor, its first end are as the principal current end of said current mirror, and second termination of said the first transistor is received the 4th reference voltage, and the control end of said the first transistor is coupled to first end of said the first transistor; And

Transistor seconds, its first end as said current mirror from current terminal, second termination of said transistor seconds is received said the 4th reference voltage, and the control end of said transistor seconds is coupled to the control end of said the first transistor.

7. the reading device of contact panel as claimed in claim 6, wherein said the 3rd reference voltage is a system voltage, and said the 4th reference voltage is a ground voltage.

8. the reading device of contact panel as claimed in claim 4, wherein said current mirror comprises:

The first transistor, its first end is as the principal current end of said current mirror, and the control end of said the first transistor is coupled to first end of said the first transistor;

Transistor seconds, its first end as said current mirror from current terminal, and the control end of said transistor seconds is coupled to the control end of said the first transistor;

The 3rd transistor, its first end is coupled to second end of said the first transistor, and the said the 3rd transistorized second termination is received the 4th reference voltage, and the said the 3rd transistorized control end is coupled to the said the 3rd transistorized first end; And

The 4th transistor, its first end is coupled to second end of said transistor seconds, and the said the 4th transistorized second termination is received said the 4th reference voltage, and the said the 4th transistorized control end is coupled to the said the 3rd transistorized control end.

9. the reading device of contact panel as claimed in claim 1, wherein when in first pattern, said first, second, third, fourth selector switch is all selected its common ends is electrically connected to its second selecting side.

10. the reading device of contact panel as claimed in claim 1, wherein when in second pattern, said first, second, third, fourth selector switch is all selected its common ends is electrically connected to its first selecting side.

11. the reading device of contact panel as claimed in claim 1, the common ends of wherein said first selector are electrically connected to corresponding sense wire in the said contact panel.

12. the hyperchannel reading device of a contact panel comprises:

Integrator; And

A plurality of passages, wherein each passage comprises:

Input selector, its common ends optionally are electrically connected to first selecting side or second selecting side, and first selecting side of wherein said input selector is coupled to the input end of said integrator;

First selector, its common ends optionally are electrically connected to first selecting side or second selecting side, and the common ends of wherein said first selector is coupled to second selecting side of said input selector;

Electric current is to voltage conversion unit, and its input end is coupled to first selecting side of said first selector;

First resistance, its first end is coupled to the output terminal of said electric current to voltage conversion unit;

Second selector; Its common ends optionally is electrically connected to first selecting side or second selecting side; First selecting side of wherein said second selector is coupled to second end of said first resistance, and second selecting side of said second selector is coupled to second selecting side of said first selector;

First operational amplifier, its first input end is coupled to the common ends of said second selector, and second input end of said first operational amplifier receives first reference voltage;

Third selector, its common ends optionally are electrically connected to first selecting side or second selecting side, and the common ends of wherein said third selector is coupled to the first input end of said first operational amplifier;

The 4th selector switch, its common ends optionally are electrically connected to first selecting side or second selecting side, and the common ends of wherein said the 4th selector switch is coupled to the output terminal of said first operational amplifier;

Second resistance, its first end is coupled to first selecting side of said third selector, and second end of said second resistance is coupled to first selecting side of said the 4th selector switch;

Feedback capacity, its first end is coupled to second selecting side of said third selector, and second end of said feedback capacity is coupled to second selecting side of said the 4th selector switch;

Feedback switch, its first end and second end are coupled to first end and second end of said feedback capacity respectively; And

Outlet selector; Its common ends optionally is electrically connected to first selecting side or second selecting side; First selecting side of wherein said outlet selector is coupled to the output terminal of said integrator, and second selecting side of said outlet selector is coupled to the output terminal of said first operational amplifier.

13. the hyperchannel reading device of contact panel as claimed in claim 12, wherein said electric current to voltage conversion unit comprises:

The 3rd resistance, its first end is as the input end of said electric current to voltage conversion unit, and second end of said the 3rd resistance is coupled to second reference voltage; And

Unity gain amplifier, its input end are coupled to first end of said the 3rd resistance, and the output terminal of said unity gain amplifier is as the output terminal of said electric current to voltage conversion unit.

14. the hyperchannel reading device of contact panel as claimed in claim 13; Wherein said unity gain amplifier comprises second operational amplifier; First end of said second operational amplifier is as the input end of said unity gain amplifier; Second end of said second operational amplifier is coupled to the output terminal of said second operational amplifier, and the output terminal of said second operational amplifier is as the output terminal of said unity gain amplifier.

15. the hyperchannel reading device of contact panel as claimed in claim 12, wherein said electric current to voltage conversion unit comprises:

The 3rd resistance, its first termination is received the 3rd reference voltage, and second end of said the 3rd resistance is as the output terminal of said electric current to voltage conversion unit; And

Current mirror, its principal current end be as the input end of said electric current to voltage conversion unit, and said current mirror be coupled to second end of said the 3rd resistance from current terminal.

16. the hyperchannel reading device of contact panel as claimed in claim 15; Wherein said the 3rd resistance is transistor; Said transistorized first termination is received said the 3rd reference voltage, said transistorized second end and control end be coupled to said current mirror from current terminal.

17. the hyperchannel reading device of contact panel as claimed in claim 15, wherein said current mirror comprises:

The first transistor, its first end are as the principal current end of said current mirror, and second termination of said the first transistor is received the 4th reference voltage, and the control end of said the first transistor is coupled to first end of said the first transistor; And

Transistor seconds, its first end as said current mirror from current terminal, second termination of said transistor seconds is received said the 4th reference voltage, and the control end of said transistor seconds is coupled to the control end of said the first transistor.

18. the hyperchannel reading device of contact panel as claimed in claim 17, wherein said the 3rd reference voltage is a system voltage, and said the 4th reference voltage is a ground voltage.

19. the hyperchannel reading device of contact panel as claimed in claim 15, wherein said current mirror comprises:

The first transistor, its first end is as the principal current end of said current mirror, and the control end of said the first transistor is coupled to first end of said the first transistor;

Transistor seconds, its first end as said current mirror from current terminal, and the control end of said transistor seconds is coupled to the control end of said the first transistor;

The 3rd transistor, its first end is coupled to second end of said the first transistor, and the said the 3rd transistorized second termination is received the 4th reference voltage, and the said the 3rd transistorized control end is coupled to the said the 3rd transistorized first end; And

The 4th transistor, its first end is coupled to second end of said transistor seconds, and the said the 4th transistorized second termination is received said the 4th reference voltage, and the said the 4th transistorized control end is coupled to the said the 3rd transistorized control end.

20. the hyperchannel reading device of contact panel as claimed in claim 12, wherein when in first pattern, said input, first, second, third, fourth, outlet selector are all selected its common ends is electrically connected to its second selecting side.

21. the hyperchannel reading device of contact panel as claimed in claim 12; Wherein when the time in second pattern; Said input selector and said outlet selector are all selected its common ends is electrically connected to its second selecting side, and said first, second, third, fourth selector switch is all selected its common ends is electrically connected to its first selecting side.

22. the hyperchannel reading device of contact panel as claimed in claim 12, wherein when at three-mode, said first, second, third, fourth selector switch is all selected its common ends is electrically connected to its second selecting side, and said feedback switch is conducting.

23. the hyperchannel reading device of contact panel as claimed in claim 22; Wherein at said three-mode; Said input, the outlet selector of a passage are all selected its common ends is electrically connected to its first selecting side in the middle of the said passage, and said input, the outlet selector of rest channels are all selected its common ends is electrically connected to its second selecting side in the middle of the said passage.

24. the hyperchannel reading device of contact panel as claimed in claim 22; In the time of wherein when finishing during the present passage but during not getting into next passage as yet, the said input of said passage, outlet selector are all selected its common ends is electrically connected to its second selecting side.

25. the hyperchannel reading device of contact panel as claimed in claim 12, the common ends of the said input selector of wherein said passage are coupled to the corresponding sense wire of said contact panel.

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