JP5406774B2 - Touch discrimination device and input device - Google Patents

Description

  The present invention relates to a capacitance type touch discrimination device and an input device using the same, and relates to a technique effective when applied to, for example, a touch panel device arranged on a liquid crystal display.

  In recent years, liquid crystal displays are mounted on battery-operated information devices and mobile phones. These displays tend to be equipped with touch panel functions and are increasing year by year. There are several types of touch panels, and typically, a resistance type, a capacitance type, an in-cell type (MOS sensor type), etc. are representative. The touch panel has a mechanism for detecting contact on the display or next to the display pixel of the display. Most of these devices notify the touch panel controller of the state as an electric signal, and are greatly affected by the signal change of the liquid crystal display unit that is also driven by the electric signal. One of the effects is radiation noise emitted from the liquid crystal display, and the operation of the common electrode and drain line in the display causes cross coupling noise in the detection signal of the touch panel. The countermeasures listed in the following patent documents have been taken against these noises.

  Patent Document 1 describes a technique for improving sampling accuracy by sampling the touch panel output signal by removing the change timing of the liquid crystal display drive signal and avoiding noise caused by the liquid crystal display.

  In Patent Document 2, a technique is described in which a noise component is extracted from a touch panel output analog signal including noise by a filter and subtracted from the original analog signal to cancel the noise component.

JP 2001-166882 A JP 2001-125744 A

  In the method of Patent Document 1, when the required sampling period of A / D conversion is equal to the period of the noise generation source, there is a possibility that the change of the sampling timing and the adjustment of the sampling period may fail. In particular, the noise source of the liquid crystal panel can be considered other than the common electrode, and there is a high possibility that a plurality of noise generation cycles occur, and it is considered difficult to adjust so that sufficient noise avoidance is possible.

  In Patent Document 2, the design of a filter that extracts a noise component for canceling depends on the frequency characteristics of noise. If only noise can be separated by a filter, an effect can be expected, but if noise separation is not successful, a side effect of weakening the original signal may occur. Further, the filter largely depends on the structure of the target liquid crystal panel, and it is considered that the filter needs to be optimized or redesigned for each panel. Furthermore, the filter design may be difficult even when the individual differences in noise intensity are large.

  An object of the present invention is to provide a touch discrimination device capable of performing touch discrimination without being affected by noise, and an input device using the touch discrimination device.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  The following is a brief description of an outline of typical inventions disclosed in the present application.

  That is, two electrode lines are sequentially selected from a plurality of electrode lines each having a capacitor electrode in a predetermined order, the charges of the selected two electrode lines are reset, and a voltage is applied to the reference capacitor used for the detection operation. After setting, the reference capacitor is obtained by connecting one capacitor terminal of the reference capacitor to one selected electrode line and connecting the other capacitor terminal of the reference capacitor to the other selected electrode line. A voltage signal is detected as a signal corresponding to the electrode capacity of the selected two electrode lines, and a voltage value for each electrode line is obtained from a number of sequentially detected voltage values.

  Since the electrode capacitance detection operation is performed with two electrode lines as a pair, even if noise occurs in the middle, it can be removed as in-phase noise. Further, when the electrode capacitance detection operation is performed with two electrode lines as a pair, it is not necessary to arrange a reference capacitor for each electrode line, which contributes to a reduction in circuit scale.

  The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.

  That is, even when mounted on a liquid crystal display, touch discrimination can be performed without being affected by noise.

FIG. 1 is a block diagram of an LCD display device to which a touch sensor device according to an embodiment of the present invention is applied. FIG. 2 is a block diagram illustrating the internal configuration of the capacitive touch panel shown in FIG. FIG. 3 is a block diagram illustrating the internal configuration of the data line driving unit with a built-in touch panel driving unit shown in FIG. FIG. 4 is a block diagram illustrating the configuration of a capacitance detection unit and the like that configure the touch panel drive unit of FIG. FIG. 5 is an explanatory diagram of the charge operation for explaining the principle of the detection operation using the configuration of FIG. FIG. 6 is an explanatory diagram of the share operation for explaining the principle. FIG. 7 is an explanatory diagram showing a voltage relationship when the charge operation and the share operation are performed. FIG. 8 is a timing chart illustrating voltage waveforms when the charge operation and the share operation, and the subsequent reset operation and share operation are accumulated. FIG. 9 is a timing chart illustrating the timing of the detection operation. FIG. 10 is an explanatory diagram illustrating a method for calculating the value of the electrode capacitance for each electrode line by the capacitance conversion circuit. FIG. 11 is a block diagram illustrating the configuration of the contact detection circuit. FIG. 12 is a block diagram illustrating the configuration of the coordinate calculation circuit. FIG. 13 is a block diagram illustrating a configuration when the touch panel drive unit of FIG. 3 is formed as a semiconductor integrated circuit. FIG. 14 is a circuit diagram illustrating the configuration of the connection switch. FIG. 15 is a block diagram illustrating another configuration when the touch panel drive unit of FIG. 3 is formed as a semiconductor integrated circuit.

1. First, an outline of a typical embodiment of the invention disclosed in the present application will be described. Reference numerals in the drawings referred to in parentheses in the outline description of the representative embodiments merely exemplify what are included in the concept of the components to which the reference numerals are attached.

  [1] A touch discrimination device (10, 15) according to a typical embodiment of the present invention is selected from a plurality of electrode lines (16, 20 to 35) each having a capacitance electrode and the plurality of electrode lines. A detection unit (48) for detecting a signal corresponding to the capacitance value of the electrode line based on the charge transfer between the electrode line and the presence or absence of contact with the electrode line based on a detection result by the detection unit. And a determination unit (50). The detection unit sequentially selects two electrode lines from a plurality of electrode lines in a predetermined order, resets the charges of the selected two electrode lines, and uses a reference capacitor (105, 901) for detection operation. The reference capacitance is set by connecting one capacitance terminal of the reference capacitance to one selected electrode line and connecting the other capacitance terminal of the reference capacitance to the other selected electrode line. Is detected as a signal corresponding to the electrode capacitances of the two selected electrode lines.

  Since the electrode capacitance detection operation is performed with two electrode lines as a pair, even if noise occurs in the middle, it can be removed as in-phase noise. Further, when the electrode capacitance detection operation is performed with two electrode lines as a pair, it is not necessary to arrange a reference capacitor for each electrode line, which contributes to a reduction in circuit scale.

  [2] In the touch determination device according to item 1, the determination unit determines presence / absence of contact by obtaining a voltage value for each electrode line from a large number of voltage values regarding two electrode lines sequentially selected in a predetermined order. To do.

  By using the voltage value for each electrode line, it is possible to obtain the distribution of the electrode capacity in the plurality of electrode lines, thereby making it possible to determine the contact coordinates.

  [3] In the touch discriminating device according to item 1 or 2, the detection unit detects the voltage value by combining two different electrode lines related to the three electrode lines in the first three times, and then sequentially selects the electrodes. The voltage value is detected by selecting two adjacent electrode lines while shifting the lines one by one (FIG. 10).

  Accordingly, the voltage value related to the three electrode lines is obtained by solving simultaneous linear equations using the voltage values obtained by combining two different electrode lines related to the three electrode lines in the first three times. For the voltage values of the electrode line pairs thereafter, the voltage values for the respective electrode lines can be easily obtained sequentially by using the previously obtained voltage values of the electrode lines.

  [4] In the touch determination device according to any one of Items 1 to 3, when the detection unit obtains a voltage signal from the reference capacitor, the one capacitor terminal of the reference capacitor is set to a reference voltage (GND), and the other capacitor terminal Let voltage be the voltage signal.

  Thereby, detection of a voltage value becomes easy.

  [5] In the touch discriminating device according to item 4, the electrode capacitance of the electrode line is a ground capacitance, and the voltage is set with respect to the reference capacitance by using one capacitance terminal as a ground voltage (GND). One capacitance terminal of the reference capacitor that is set to the reference voltage when obtaining is a negative voltage.

  Thereby, detection of a voltage value becomes easy.

  [6] In the touch determination device according to item 5, the reference voltage is a ground voltage (GND).

  Thereby, detection of a voltage value becomes easy.

  [7] In the touch discrimination device according to item 6, the detection unit includes a switch made of a MOS transistor for charge transfer, and the substrate potential of the MOS transistor to which a negative voltage is applied is a negative voltage among the MOS transistors. Is done.

  A reliable switching function can be ensured for a negative line pressure signal.

  [8] In the touch determination device according to item 7, the negative substrate potential is a negative potential having the same voltage as a voltage set at one capacitance terminal of the reference capacitor.

  [9] In the touch determination device according to any one of Items 1 to 8, the reference capacitor includes a plurality of capacitors (105, 901) arranged in parallel so as to be selectively separable, and the control unit includes an electrode capacitor of an electrode line. When the value is large, the plurality of capacitors are connected in parallel, and when the value is small, a part of the plurality of capacitors is separated.

  When there is a relatively large capacitance difference between the electrode capacities of the electrode lines in the vertical and horizontal directions as in a touch panel, the size of the reference capacity is optimized according to the size of the electrode capacity of the electrode line to be detected Easy to do.

  [10] In the touch determination device according to any one of Items 1 to 9, the detection unit includes a selection circuit (103, 104) that sequentially selects two electrode lines from a plurality of electrode lines in a predetermined order; A reset switch (108, 109) for resetting the charges of the two selected electrode lines, a reference capacitor (105, 901) used for the detection operation, and a precharge switch (106, 109) for setting a voltage in the reference capacitor 107) and a share for selectively connecting one capacitor terminal of the reference capacitor to the selected one electrode line and selectively connecting the other capacitor terminal of the reference capacitor to the selected other electrode line. Each time the two electrode lines are selected by the ring switch (110, 111) and the selection circuit, the reference capacitor is precharged, the selected electrode line is reset, and the sharing switch is selected. With the on-operation by sequentially controlling the control unit for performing the selected control to obtain the voltage signal from the reference capacitance as a corresponding signal to the electrode capacitance of the two electrode lines and (45).

  [11] In the touch determination device according to item 10, the control unit sequentially controls the resetting of the electrode lines and the ON operation of the sharing switch, and then the selected in a state in which the charge of the reference capacitor is maintained. The operation of accumulating charges on the reference capacitor is controlled by sequentially controlling the resetting of the electrode lines and the ON operation of the sharing switch.

  Detection accuracy can be increased by the stacking operation.

  [12] An input device according to another embodiment of the present invention includes a display control unit (6), a display panel (9) controlled by the display control unit, and a touch panel ( 15) and the touch panel drive unit (10). The touch panel includes a plurality of transparent electrode lines (16, 20 to 35) each having a capacitive electrode, and the drive unit is mounted thereon. The drive unit includes a detection unit (48) that detects a signal corresponding to a capacitance value of the electrode line based on charge transfer between the electrode lines selected from the plurality of electrode lines, and a detection result by the detection unit And a discriminator (50) for discriminating the presence or absence of contact with the electrode wire based on the above. The detection unit sequentially selects two electrode lines from a plurality of electrode lines in a predetermined order, resets the charges of the selected two electrode lines, and uses a reference capacitor (105, 901) for detection operation. The reference capacitance is set by connecting one capacitance terminal of the reference capacitance to one selected electrode line and connecting the other capacitance terminal of the reference capacitance to the other selected electrode line. Is detected as a signal corresponding to the electrode capacitances of the two selected electrode lines.

  Since the electrode capacitance detection operation is performed with two electrode lines as a pair, it can be removed as common-mode noise even in an environment where noise is sequentially generated in synchronization with the display operation of the display panel. Further, when the electrode capacitance detection operation is performed with two electrode lines as a pair, it is not necessary to arrange a reference capacitor for each electrode line, which contributes to a reduction in circuit scale.

  [13] In the input device according to item 12, the determination unit determines presence / absence of contact by obtaining a voltage value for each electrode line from a large number of voltage values related to the electrode lines selected two by two in a predetermined order. .

  By using the voltage value for each electrode line, it is possible to obtain the distribution of the electrode capacity in the plurality of electrode lines, thereby making it possible to determine the contact coordinates.

  [14] In the input device according to item 12 or 13, the detection unit detects the voltage value by combining two different electrode lines related to the three electrode lines in the first three times, and then sequentially selects the electrode lines. The voltage value is detected by selecting two adjacent electrode lines while shifting each of them one by one.

  Accordingly, the voltage value related to the three electrode lines is obtained by solving simultaneous linear equations using the voltage values obtained by combining two different electrode lines related to the three electrode lines in the first three times. For the voltage values of the electrode line pairs thereafter, the voltage values for the respective electrode lines can be easily obtained sequentially by using the previously obtained voltage values of the electrode lines.

  [15] In the input device according to any one of Items 12 to 14, when the detection unit obtains a voltage signal from the reference capacitor, the one capacitor terminal of the reference capacitor is used as a reference voltage, and the voltage of the other capacitor terminal is used as the voltage. Signal.

  Thereby, detection of a voltage value becomes easy.

  [16] In the input device according to item 15, the electrode capacitance of the electrode line is a ground capacitance, and the voltage setting with respect to the reference capacitance is performed using one capacitance terminal as a ground voltage to obtain the voltage signal. One capacitor terminal of the reference capacitor to be set is a negative voltage.

  Thereby, detection of a voltage value becomes easy.

  [17] In the input device of item 16, the reference voltage is a ground voltage.

  Thereby, detection of a voltage value becomes easy.

  [18] In the input device according to item 17, the detection unit includes a switch composed of a MOS transistor for charge transfer, and the substrate potential of the MOS transistor to which a negative voltage is applied is a negative voltage among the MOS transistors. The

  A reliable switching function can be ensured for a negative line pressure signal.

  [19] In the input device of item 18, the negative substrate potential is a negative potential having the same voltage as a voltage set at one capacitance terminal of the reference capacitor.

  [20] In the input device according to any one of Items 12 to 19, the reference capacitor is composed of a plurality of capacitors arranged in parallel so as to be selectively separable, and the control unit has the plurality of capacitors when the electrode capacitance of the electrode line is large. Are connected in parallel, and when it is small, a part of the plurality of capacitors is separated.

  When there is a relatively large capacitance difference between the electrode capacities of the electrode lines in the vertical and horizontal directions as in a touch panel, the size of the reference capacity is optimized according to the size of the electrode capacity of the electrode line to be detected Easy to do.

  [21] In the input device according to any one of Items 12 to 20, the detection unit includes a selection circuit that sequentially selects two electrode lines from a plurality of electrode lines in a predetermined order; A reset switch for resetting the charge of the electrode line; a reference capacitor used for a detection operation; a precharge switch for setting a voltage in the reference capacitor; and one of the reference capacitors selectively on one of the selected electrode lines. A sharing switch for connecting the capacitor terminal and selectively connecting the other capacitor terminal of the reference capacitor to the other electrode line selected, and the reference capacitor for each selection of the two electrode lines by the selection circuit The precharge, reset of the selected electrode line, and ON operation of the sharing switch are sequentially controlled, and the reference is made as a signal corresponding to the electrode capacity of the two selected electrode lines. And a control unit for controlling to obtain a voltage signal from the amount.

  [22] In the input device according to item 21, the control unit sequentially controls reset of the electrode line and ON operation of the sharing switch, and then the selected electrode in a state in which the charge of the reference capacitor is maintained. A line reset and an ON operation of the sharing switch are sequentially controlled to control an operation of accumulating charges on the reference capacitor.

  Detection accuracy can be increased by the stacking operation.

2. Details of Embodiments Embodiments will be further described in detail.

[Embodiment 1]
FIG. 1 shows an example of an LCD display device to which a touch sensor device according to an embodiment of the present invention is applied. In FIG. 1, 1 is a horizontal synchronizing signal, 2 is a vertical synchronizing signal, 3 is a data enable, 4 is display data, and 5 is a synchronizing clock. The vertical synchronization signal 1 is a signal of one display period (one frame period), the horizontal synchronization signal 2 is a signal of one horizontal period, and the data enable signal 3 is a signal indicating a period during which the display data 4 is valid (display effective period). All signals are input in synchronization with the synchronous clock 5. In this embodiment, these display data are sequentially transferred in a raster scan format from the upper left pixel for one screen, and the information for one pixel is composed of, for example, 6-bit digital data. Reference numeral 6 is a display control unit, 7 is a data line and touch panel control signal, 8 is a scanning line control signal, and the display control unit 6 is a vertical synchronization signal 1, horizontal synchronization signal 2, data enable signal 3, display data 4, and synchronization. From the clock 5, a data line and touch panel control signal 7 for display control and touch panel control and a scanning line control signal 8 for display scanning control are generated.

  9 is an LCD panel, 10 is a touch panel drive unit built-in data line drive unit, 11 is a data line drive signal, 12 is a scan line drive unit, 13 is a scan line selection signal, 14 is a display pixel array, A touch panel drive unit built-in data line drive unit 10, a scan line drive unit 12, and a display pixel array 14 are provided on a single glass substrate. Although not particularly limited, the touch panel drive unit built-in data line drive unit 10 is an LSI (semiconductor integrated circuit), and the scanning line drive unit 12 and the display pixel array 14 are formed of low-temperature polysilicon (LTPS) on a glass substrate. The touch panel drive unit built-in data line drive unit 10 generates a signal voltage to be written to the display pixel array 14 from a signal related to display control among the data line and the touch panel control signal 7, and also on the touch panel from a signal obtained by operating the touch panel. A coordinate signal 17 indicating the coordinates of the position operated in is generated. The scanning line driving unit 12 outputs a scanning line selection signal 13 for selecting a scanning line to which the write signal voltage output as the data line driving signal 11 is written. The display pixel array 14 writes the write signal voltage output as the data line drive signal 11 to the pixels on the line selected by the scanning line selection signal 13, and performs gradation control according to the write voltage. Reference numeral 15 denotes a capacitance type touch panel, 16 denotes a detection electrode line, and the capacitance type touch panel 15 is a substrate including electrode lines made of a plurality of orthogonal transparent conductive films (ITO). Each electrode line is input to the touch panel drive unit built-in data line drive unit 10 as the detection electrode line 16.

  FIG. 2 shows an embodiment of the internal configuration of the capacitive touch panel 15 shown in FIG. Reference numeral 18 denotes an X electrode formed on the X electrode line 20, and reference numeral 19 denotes a Y electrode formed on the Y electrode line, except for the intersection of the X electrode line arranged in the horizontal direction and the Y electrode line arranged in the vertical direction. Many are provided in this area. In this embodiment, a region other than the intersection is filled with a rhombus having the same shape and area. Reference numerals 20 to 25 denote X electrode lines, and 26 to 35 denote Y electrode lines. X and Y are arranged in a non-contact and orthogonal manner, and all electrode lines are output as detection electrode lines 16. Although not particularly limited, in the present embodiment, six X electrode lines and ten Y electrode lines are configured. Therefore, ten electrodes identical to the X electrode 18 and the Y electrode 19 are provided on each X electrode line, and six on each Y electrode line.

  More specifically, the electrodes of the touch panel 15 have a two-layer electrode structure insulated from each other, and the rhombus unit electrodes are connected in the horizontal direction in the first layer and in the vertical direction in the second layer. Yes. Capacitance changes by bringing a finger or the like closer to the upper part of the diamond, and by measuring this change, the approach or contact of the finger or the like to the panel can be detected. Since the first layer is connected in the horizontal direction, it is possible to detect contact with the vicinity of the band extending in the horizontal direction. In other words, by measuring the capacity of the lateral band for all the electrodes, it is possible to detect where in the vertical direction it has come into contact. On the other hand, in the horizontal direction, since the capacitance change is almost the same regardless of the position, the horizontal direction cannot be detected only by the first layer. On the other hand, the second layer has a rhomboid electrode connected in the vertical direction, so it is possible to detect contact with the vicinity of the band extending in the vertical direction, and it is possible to detect where it touched in the horizontal direction. It has become. That is, since the first layer can detect the position in the vertical direction and the second layer in the horizontal direction, the two-dimensional coordinates can be measured by combining both.

  FIG. 3 illustrates the internal configuration of the touch panel drive unit built-in data line drive unit 10 shown in FIG. 36 is a data shift unit, 37 is a data start signal, 38 is a data shift clock, 39 is serial display data, and 40 is parallel display data. The data shift unit 36 takes in the serial display data 39 according to the data shift clock 38 based on the data start signal 37 and sequentially outputs it as parallel display data 40. 41 is a one-line latch unit, 42 is a horizontal latch clock, and 43 is one-line data. The 1-line latch unit 41 outputs the parallel display data 40 that is sequentially output as 1-line data 43 in accordance with a horizontal latch clock 42 that indicates the timing when the output for one line is completed. Reference numeral 44 denotes a D / A converter, which converts 1-line data 43, which is a digital value, into an analog value and outputs it as a data line drive signal 11 that becomes a write signal to a pixel.

  45 is a detection control unit, 46 is a detection switch drive signal, 47 is a coordinate conversion timing signal, 48 is a capacitance detection unit, 49 is a capacitance difference value, and 50 is a coordinate conversion unit. The detection control unit 45 generates a detection switch drive signal 46 for controlling the detection operation in the capacitance detection unit 48 and a coordinate conversion control signal 47 for controlling the operation in the coordinate conversion unit 50. In this embodiment, the detection operation and the coordinate conversion operation are performed on the basis of one horizontal period in synchronization with the horizontal latch clock 42. The capacitance detection unit 48 performs a detection operation by charge redistribution using the electrode capacitances of the two electrode lines of the detection electrode lines 16 and outputs a capacitance detection signal 49. The coordinate conversion unit 50 calculates the capacitance of each electrode line using the capacitance detection signal 49, calculates the coordinates of the touched position from the capacitance distribution state, and outputs the coordinate signal 17 indicating the calculated coordinates. .

  FIG. 4 illustrates the configuration of the capacitance detection unit 48 and the like constituting the touch panel drive unit of FIG. In the figure, 101 is a touch panel electrode, 102 is a touch panel electrode signal line, 103 is a positive selector, 104 is a negative selector, 105 is a reference capacity, 106 is a reference capacity voltage positive set switch, 107 is a reference capacity voltage negative set switch, and 108 is positive. Electrode reset switch, 109 is a negative electrode reset switch, 110 is a positive polarity share switch, 111 is a negative polarity share switch, 112 is an A / D conversion circuit, 113 is a capacitance conversion circuit, 114 is a contact detection circuit, 115 is a coordinate detection circuit, 116 Is touch panel timing control unit, 117 is coordinate information, 118 is contact information, 119 is positive electrode select signal, 120 is negative electrode select signal, 121 is positive electrode reset signal, 122 is negative electrode reset signal, 123 is positive electrode share signal, 124 is Negative share signal, 125 is the first reference capacity Voltage set signal, 126 reference capacitance ground signal, 127 is an AD conversion start signal.

  The electrode line 16 of the touch panel is connected to the inputs of the positive selector 103 and the negative selector 104. The positive selector 103 selects any one of the plurality of electrode lines 16 and connects it to the output. The positive selector 103 is composed of an analog switch, and connects one electrode line 16 selected thereby and the positive share switch 110. When selected, the potential at both ends of the switch 110 propagates in both directions. The negative selector 104 is different from the positive share switch 103 in that the output connection destination is the negative share switch 111. Reference numeral 105 denotes a reference capacitor (detection capacitor), and the capacitance detection result of the electrode line of the touch panel remains as a voltage in this capacitor, and this voltage is supplied to the AD conversion circuit 112 to obtain a digital value of the measurement result.

  A reference capacitance voltage positive set switch 106 and a reference capacitance voltage negative set switch 107 are switches for applying a constant voltage to the reference capacitance 105. The reference capacitance initial voltage set signal 125 and the reference capacitance ground signal 126 are used as a constant voltage source 128, respectively. And ground voltage GND. When setting an initial voltage to the reference capacitor 105 at the start of contact detection, both switches 106 and 107 are turned on by signals 125 and 126, whereby the reference capacitor 105 is charged by the voltage of the constant voltage source 128.

  The positive electrode reset switch 108 and the negative electrode reset switch 109 are switches for resetting the voltage of the electrode selected by the selectors 103 and 104 to the ground voltage GND. When two of the electrode lines 16 of the touch panel 15 are selected by the selectors 103 and 104, the switches 110 and 111 are turned on so that the two selected electrode lines are connected to the ground voltage GND. Reset to. After reset, these switches 108 and 109 are turned off. The switch 108 is switch-controlled by a positive electrode reset signal 121, and the switch 109 is switch-controlled by a negative electrode reset signal 122. The positive polarity share switch 110 and the negative polarity share switch 111 are switches that connect the electrode line selected by the selectors 103 and 104 to both ends of the reference capacitor 105. The electrode lines are initially set to the ground voltage GND by the switches 108 and 109. And then turned on, whereby charge sharing occurs between the reference capacitor 105 and the electrode capacitor of the touch panel 15, and the electrode selected by both the positive selector 103 and the negative selector 104. The charge on the reference capacitor 105 is reduced by an amount proportional to the electrode capacitance of the line. The A / D conversion circuit 112 converts the voltage generated in the reference capacitor 105 into a digital value, and the converted digital value is supplied to the capacitance conversion circuit 113.

  The capacitance conversion circuit 113 calculates a value proportional to the electrode capacitance of each electrode line of the touch panel 15 based on the input digital value as a capacitance value, and gives the calculated value to the contact detection circuit 114. The contact detection circuit 114 determines the presence / absence of contact based on the capacitance value calculated by the capacitance conversion circuit 113, outputs the determination result as contact information 118, and simultaneously calculates the capacitance change intensity of each electrode line, The capacitance change intensity is given to the coordinate detection circuit 115. The coordinate detection circuit 115 calculates the touch coordinates of the touch panel by calculating the center of gravity using the capacitance change intensity of each electrode line, and outputs this as coordinate information 117.

  The detection control unit 45 performs overall timing control for the above-described detection operation. The selection control signals 119 and 120 of the selectors 103 and 104, the switch control signals 121 to 126 of the switches 106 to 111, and the A / D conversion circuit 112 A conversion start signal 127 is generated. Some circuits such as the detection control unit 45 may be realized by a CPU and its operation program.

  Here, the principle of the detection operation using the configuration of FIG. 4 will be described. In the following description, Ca is the combined electrode capacity of the electrode line selected by the positive selector 103 (including human finger capacity in the case of touch), and Cb is the combined electrode capacity of the electrode line selected by the negative selector 104 (touch In some cases, including human finger capacity), Cc means reference capacity 105. In one detection operation cycle for a pair of electrode lines, a charge operation and a share operation are first performed, and subsequently, a reset operation and a share operation are repeated a required number of times.

  As illustrated in FIG. 5, the charge operation is an operation in which Ca and Cb are reset to the ground level by the reset switches 108 and 19, and the voltage Vc is set to Cc by the charge switches 106 and 107. As illustrated in FIG. 6, the share operation is an operation in which Ca, Cb, and Cc are connected in series by the share switches 110 and 111 to perform charge redistribution, and accordingly, the Cc according to the capacitance values of Ca and Cb. Stored charge (voltage between terminals of Cc) decreases. Although not shown, the reset operation is an operation in which Cc is maintained as it is, and Ca and Cb are reset to the ground level by the reset switches 108 and 109.

  FIG. 7 shows the voltage relationship when the charge operation and the share operation are performed. Assuming that the voltage between the terminals of Ca is Va, the voltage between the terminals of Cb is Vb, and the voltage between the terminals of Cc is Vc, Vc = Va + Vb from the series connection relationship of Ca, Cb, and Cc. When the reset operation and the share operation are subsequently performed, the accumulated charge of Cc (inter-terminal voltage of Cc) further decreases while maintaining the relationship of Vc = Va + Vb.

  FIG. 8 illustrates voltage waveforms when the charge operation and the share operation, and the subsequent reset operation and the share operation are accumulated. By the first sharing operation, the positive side electrode of Cc is lowered in level, and accordingly, the negative side electrode of Cc becomes lower than the ground level GND. Ca and Cb are set to voltages Va and Vb that satisfy the relationship of Vc = Va + Vb. Naturally, Vb is a negative voltage with respect to the ground level GND, and Va is a raw voltage with respect to the ground level GND. In the subsequent share operation, the positive side electrode level of Cc further decreases, and accordingly, the negative side electrode of Cc approaches the ground level GND. Ca and Cb are set to voltages Va and Vb that satisfy the relationship of Vc = Va + Vb, and the voltage across Cc decreases as the reset operation and the share operation are repeated. Even if external noise is received during the share operation period, it is canceled as common-mode noise and does not affect the operation result. By connecting the negative side of Cc to the ground level GND at the end of the stacking operation, a voltage signal Vc corresponding to the sum of the electrode capacities of the two electrode lines to be measured can be obtained. The voltage accumulation is performed by performing the reset operation and the share operation following the initial charge operation and the share operation in order to increase the measurement accuracy, and the accumulation is not necessarily required.

  To obtain the electrode capacity of each of the electrode lines (L1, L2, L3, L4, L5,...) Based on the detection signal corresponding to the sum of the holding voltages of the electrode capacities of two different electrode lines in accordance with the principle described above. First, the detection voltage V1 + V3 related to the electrode capacity of the electrode lines L1 and L3 is obtained, the detection voltage V1 + V2 related to the electrode capacity of the electrode lines L1 and L2 is obtained for the second time, and the electrode capacity of the electrode lines L2 and L3 is obtained for the third time. The detection voltages V2 + V3 are obtained, and thereafter, the detection voltages V3 + V4 and V4 + V5 relating to the adjacent electrode lines such as L3 and L4 and L4 and L5 are obtained. V1, V2, and V3 can be obtained by solving the simultaneous equations for the first detection result and the third detection result, substituting V3 into the fourth result, V4, and the fifth result. By substituting V4, it is possible to obtain the voltage related to the electrode capacitance of the subsequent electrode lines such as V5, and thereby, the capacitance distribution in the X and Y directions of the touch sensor can be obtained. It is possible to calculate the coordinates of the selected position.

  In the configuration of FIG. 4, the detection operation according to the above principle is performed as follows. First, the detection control unit 45 outputs a positive electrode select signal 119 and a negative electrode select signal 120 so that the positive electrode selector 103 and the negative electrode selector 104 select one electrode line from the touch panel 15 one by one. At this time, the selection electrodes are controlled so as not to be the same. Next, the reference capacitance voltage positive set switch 106 and the reference capacitance voltage negative set switch 107 are turned on by the reference capacitance initial voltage set signal 125 and the reference capacitance ground signal 126, a constant voltage is set in the reference capacitance 105, and the switch after the setting is completed. By turning off 106 and 107, the voltage of the reference capacitor 105 is held.

  Next, by operating the positive electrode reset signal 121 and the negative electrode reset signal 122, the positive electrode reset switch 108 and the negative electrode reset switch 109 are turned on, and the selectors 103 and 104 select the positive electrode and the negative electrode. Reset the line voltage to ground level GND. After resetting, the switches 108 and 109 are turned off, whereby the ground level is held in the selected pair of electrode lines.

  Next, by using the positive share signal 123 and the negative share signal 124 to turn on the positive share switch 110 and the negative share switch 111, the reference capacitance 105 and the electrode line selected by each of the selectors 103 and 104 are selected. As a result, an amount of charge is transferred from the reference capacitor 105 to the electrode line in proportion to the electrode capacity of the electrode line. The charge transfer is completed by turning off the switches 110 and 111 after a certain time after the charge transfer converges, and the charge from the reference capacitor 105 is reduced in proportion to the total capacity of the electrode lines connected to the positive electrode and the negative electrode, As a result, the holding voltage of the reference capacitor 105 also decreases. By measuring the decrease in the holding voltage of the reference capacitor 105 generated by repeating the electrode reset operation and the reference capacitor share connection operation a plurality of times, the electrode capacitance value corresponding to the presence or absence of the touch state of the touch panel 15 is measured. When the holding voltage of the reference capacitor 105 is measured, the positive electrode potential of the reference capacitor 105 becomes a holding voltage by turning on the switch 107 and setting the negative electrode side to the ground level GND. This holding voltage is supplied to the A / D conversion circuit 112 and converted into a digital value.

FIG. 9 illustrates the operation timing of the detection operation. Here, one measurement cycle is shown when the positive electrode select signal 119 selects the Nth electrode line of the touch panel 15 and the negative electrode select signal 120 selects the N + 1th electrode line. The selection mode of the electrode lines will be described later, but is controlled so as not to be at least the same. At the first timing 0 of the measurement cycle, the reference capacitor initial voltage set signal 125 and the reference capacitor ground signal 126 are set to the high level, and the reference capacitor 105 A constant voltage is set. At timing 1, the signals 125 and 126 are both set to the low level, and the reference capacitor 105 is disconnected from the power supply 128 and the ground potential GND to hold the set voltage. At timing 1, the positive electrode reset signal 121 and the negative electrode reset signal 122 are set to the high level, and the voltages of the electrode lines selected by the selectors 103 and 104 as the positive electrode and the negative electrode are reset to the ground level GND. These signals 121 and 122 are set to low level at timing 2, and the electrode lines selected as the positive electrode and the negative electrode are disconnected from the ground level GND.

  At timing 2, the positive share signal 123 and the negative share signal 124 are set to the high level, the reference capacitor 105 is connected to the electrode lines selected by the selectors 103 and 104 as the positive electrode and the negative electrode, and the reference capacitor is connected to the pair of electrode lines. Charge transfer occurs from 105.

  At timing 3, the positive share signal 123 and the negative share signal 124 are set to a low level, the reference capacitor 105 and the electrode line are disconnected, and the influence of the next electrode reset is not given to the reference 105.

  In timings 3 to 12, timings 1 and 2 are repeated a plurality of times. In this example, it is repeated 6 times including the timings 1 and 2, but the number can be increased or decreased by adjustment.

  Finally, at timing 13, only the reference capacitor ground signal 126 is set to the high level, and at the same time, the AD conversion start signal 127 is also set to the high level, and the holding voltage of the reference capacitor 105 is measured.

  In the figure, reference numerals 301 and 302 denote voltage waveforms of the bipolar electrodes of the reference capacitor 105 that holds a voltage as a result of the capacitance measurement. At timing 0, the positive electrode is at a constant voltage and the negative electrode is at the ground level GND. At timing 1, a voltage is not applied from the outside and is in a high impedance state, and the voltage at timing 0 is held. At timing 2, charge transfer to the electrode line occurs, and at the same time, the negative electrode side changes to a level lower than the ground level. This is because the capacitance of the electrode line of the touch panel 15 is a ground capacitance (anti-ground capacitance), and is a voltage change due to the touch panel 15 electrode being connected to both electrodes of the reference capacitor 105. By making the negative voltage lower than the ground level GND, it is possible to measure the electrode capacities of two electrode lines at a time by one reference capacitor 105, and the electrode capacities of the two electrode lines are not the same electrode but the positive electrode, By connecting to each of the negative electrodes, it is possible to cancel the common-mode noise superimposed on the two electrodes on the reference capacitor 105. Reference numerals 303 and 304 exemplify a state where positive pulse noise having the same phase is superimposed on the positive terminal and the negative terminal of the reference capacitor 105. Since the pulse noise is superimposed on the positive electrode terminal and the negative electrode in the same direction by the same amount, the potential moves in the same direction on both poles of the reference capacitor 105 and the noise is canceled.

  FIG. 10 illustrates an electrode capacitance value calculation method for each electrode line by the capacitance conversion circuit 113. In the figure, the column 401 shows the electrode capacity pair of the electrode line selected by the detection operation, the column 402 shows the calculation formula of the capacitance value obtained by the detection operation for the selected electrode capacitance pair, and the column 403 shows A This means the detection value 49 output from the / D conversion circuit 112.

  In this example, only the first set is the electrode capacity of the electrode lines separated as C1 and C3, but the other detections are the electrode capacity of the adjacent electrode lines as the detection object. Detection is performed such that all electrodes are selected by shifting. As a result, the same number of detection operations as the number of electrodes are performed as a whole, and the output value of 403 is obtained by the same number as the number of electrodes. These values are the values of the capacity calculation formula shown in the column 403. When the number of electrodes is N, N-element linear equations are formed. That is, by solving this N-element linear equation, the value (correlation value) of the electrode capacity of each electrode line can be calculated from the 403 output value. In this example, it is assumed that there are seven electrode wires, and the capacitance values V1 to V7 are obtained based on the seven output values Vx1 to Vx7. The first three measurements are all combinations in which two electrodes are selected from the three electrodes C1, C2, and C3, and the values of V1, V2, and V3 are obtained from these three values according to the expressions 404, 405, and 406. Is calculated. By determining these three values, V4 to V7 are sequentially determined thereafter. The capacitance value calculated in this way is supplied to the subsequent contact detection circuit 114.

  FIG. 11 illustrates the configuration of the contact detection circuit 114. In the figure, reference numeral 501 denotes a current capacitance value, that is, a capacitance value for each electrode line output from the capacitance conversion circuit 113. Reference numeral 502 denotes a capacitance value before contact, for example, a moving average value (baseline value) of imposed capacitance values for each electrode line in the case of non-touch. 503 is a subtracter, 504 is a touch detection threshold value for identifying touch / non-touch, 505 is a comparator, 506 is a touch capacitance value, and 507 is touch information.

  In this configuration, the past capacitance value of each electrode line is held as the pre-contact capacitance value 502. An example of a method for generating this value is a moving average value of past capacity values. The difference between the current capacitance value 501 and the capacitance value 502 before contact of the corresponding electrode line is calculated by the subtractor 503, and the result is output as the contact capacitance value 506. Further, the contact capacitance value 506 is compared with the contact detection threshold value 504 by the comparator 505, and when the contact capacitance value 506 is a value equal to or greater than the contact detection threshold value 504, it is determined that there is a contact with the capacitive electrode of the touch panel 15; The contact information 507 having a logical value corresponding to the presence or absence of contact is output from the comparator 505.

  FIG. 12 shows the configuration of the coordinate calculation circuit 115. 602 is a cumulative adder that inputs a contact capacitance value 506, 603 is a weighting counter, 604 is a multiplier, 605 is a cumulative adder that inputs the output of the multiplier 604, 606 is a divider, and 607 is a contact coordinate value 117. It is a resolution converter that outputs. Reference numeral 608 denotes a horizontal resolution, and reference numeral 609 denotes a vertical resolution.

  First, the contact capacitance value 506 that is an input from the outside is sequentially input by the same number as the number of electrode lines, and is first cumulatively added by the cumulative adder 602. At the same time, the contact capacitance value 506 is input to the multiplier 604 and multiplied by the weighting value generated from the weighting counter 603. The weighting counter 603 is updated in synchronization with the input of the contact capacitance value 506 to the coordinate calculation circuit 115. The output of the multiplier 604 is input to the cumulative adder 605 and cumulatively added to obtain a weighted cumulative value. After the contact capacitance value 506 is input by the number of electrode lines, the outputs of the cumulative adder 602 and the cumulative adder 605 are input to the divider 606, and the cumulative adder 601 accumulates the cumulative addition result of the cumulative adder 605. Find the quotient from the result of the addition. This value becomes the center of gravity of the capacitance values of all electrodes, that is, the contact center of gravity value. Thereafter, the contact centroid value is input to the resolution converter 607, and a contact coordinate value 610 corresponding to the resolution is calculated using one of the horizontal resolution 608 and the vertical resolution 609.

  As described above, in the first embodiment, the touch line difference device cancels the radiation noise from the liquid crystal panel, and enables highly accurate contact detection regardless of the display operation state of the liquid crystal panel.

[Embodiment 2]
FIG. 13 illustrates a configuration when the touch panel drive unit of FIG. 3 is formed as a semiconductor integrated circuit. An example in which the touch panel drive unit is mounted on an LSI (semiconductor integrated circuit) such as an LCD driver as in the first embodiment will be described. Components having the same functions as those described in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.

  701 is a detection circuit LSI in which the touch panel drive unit is formed as a semiconductor integrated circuit, 702 is a touch panel electrode signal pin, 703 is an external reference capacitance positive pin, 704 is an external reference capacitance negative pin, 705 is a contact information output pin, and 706 is a coordinate Information output pin.

  Since the reference capacitor 105 becomes an external peripheral component of the detection circuit LSI 701, the size of the external reference capacitor 105 can be selected according to the characteristics of the touch panel 15 to be attached. This facilitates adjustment of detection sensitivity. The same detection LSI 701 can be used for various touch panels. Further, by forming a semiconductor integrated circuit, the connection switches 106 to 111 can be configured by on-chip MOS transistors.

  FIG. 14 illustrates the configuration of the connection switch. In the figure, 801 is an N-channel MOS transistor (NMOS transistor), 802 is a P-channel MOS transistor (PMOS transistor), 803 and 804 are switch terminals, 805 is a control terminal, 806 and 807 are inverters, and 808 is an NMOS substrate potential. , 809 are negative power supplies.

  The NMOS transistor 801 operates as a positive switch and connects the switch terminal 803 and the switch terminal 804 when the output of the inverter 807 is at a high level, thereby enabling signal input / output. When the level is low, the connection between the switch terminals 803 and 804 is cut off, and a high impedance state is established.

  The PMOS transistor 802 operates as a negative switch, and when the output of the inverter 806 is at a low level, the switches 803 and 804 are connected to each other so that signals can be input and output. At the high level, the connection between the switches 803 and 804 is cut off, and a high impedance state is established. Further, since the output of the inverter 806 becomes the input of the inverter 807, the relationship between the output of the inverter 806 and the output of the inverter 807 is always inverted, and as a result, the NMOS transistor 801 and the PMOS transistor 802 are switch-controlled in the same phase. Therefore, a switch in which the NMOS transistor 801 and the PMOS transistor 802 are combined is connected when the control terminal 805 is at a high level, and has a high impedance when the control terminal 805 is at a low level. Further, by using the substrate potential 808 of the NMOS transistor as a negative power source, the voltage can be correctly transmitted even when the switch terminals 803 and 804 are below the ground level. In the figure, for convenience, one 810 negative power source is connected to one switch, but it goes without saying that the negative power source of all the switches can be shared. In addition, LCD noise has a characteristic that the noise that appears in the high direction and the noise that emerges in the low direction are symmetrical, and the magnitude is almost the same, and the probability of charge leakage due to noise generation exceeding the power supply voltage is positive voltage, negative voltage For the reason that both are equal, it is desirable that the negative power supply voltage 810 is an absolute value equal to the power supply voltage 128.

[Embodiment 3]
FIG. 15 illustrates another configuration when the touch panel drive unit of FIG. 3 is formed as a semiconductor integrated circuit. The difference from the second embodiment is that the reference variation capacitor 901 can be selectively used together with the reference capacitor 105. Components having the same functions as those described in FIGS. 4 and 13 have the same reference numerals. The detailed description is omitted.

  Reference numeral 901 is a reference variable capacity, 902 is a reference variable capacity positive connection switch, 903 is a reference variable capacity negative connection switch, and 904 is a reference variable capacity connection signal. The difference from FIG. 13 is that the external connection of the reference capacitor 105 is changed to on-chip, and another reference variable capacitor 901 is arranged in parallel with the reference 105 and can be selectively connected in parallel with the switches 901, 03. This is the point.

  Since the touch panel 15 electrode line is mounted on the LCD panel, depending on the shape of the LCD panel, the electrode capacity of the horizontal electrode line and the vertical electrode line may be twice as large. There is a possibility that the optimal adjustment value of does not match. As shown in the present embodiment, two reference capacitors 105 and 901 are provided inside, for example, during the detection of the capacitor electrode of the vertical electrode line in FIG. Operates the reference capacitor as the sum of 105 and 901 by setting the signal 904 to the high level and turning on the switches 902 and 903. Also, during the detection of the 202 lateral electrodes, the signal 904 is set to the low level. The switches 902 and 903 are turned off, and the reference capacitor is operated only as 105. Accordingly, it is possible to configure a detection circuit that does not deteriorate in performance even for an elongated touch panel in which the capacity difference between the vertical direction and the horizontal direction is large.

  According to the embodiment described above, the electrode lines are selected two by two, and the selected electrode lines are connected to the positive electrode and the negative electrode of the reference capacitor, so that the radiation noise from the liquid crystal panel is in phase with both electrodes of the reference capacitor. As a result, the influence of noise can be eliminated from the voltage value of the reference capacitance to be finally measured.

  When the touch panel drive unit is mounted on-chip in a semiconductor integrated circuit, the reference capacity is configured externally, so that the detection sensitivity can be adjusted by selecting the external reference capacity according to the characteristics of the touch panel to be attached. The same semiconductor integrated circuit on-chip the unit can be used for various touch panels.

  By making the substrate potential of the MOS switch used to transfer the charge between the reference capacitor and the electrode line when the touch panel drive unit is on-chip into a semiconductor integrated circuit, the negative potential of the reference capacitor is reduced. Capacitance detection can be performed without error even when the level is lower than the ground level.

  In the case of an electrode having a large capacitance value in a state where there is no contact, two electrodes are arranged in parallel so that the reference capacitor provided on the semiconductor integrated circuit can be separated by on-chip the touch panel drive unit. By using a capacitive element and detecting with one capacitive element when it is small, it is possible to easily realize a detection circuit that does not deteriorate the performance even for a long and narrow touch panel in which the capacitive difference between the vertical and horizontal directions increases. is there.

  Although the invention made by the present inventor has been specifically described based on the embodiments, it is needless to say that the present invention is not limited thereto and can be variously modified without departing from the gist thereof.

  For example, the polarity of the precharge voltage with respect to the reference capacitor, the reset charge state with respect to the electrode capacitor of the electrode line, the voltage applied to the other capacitor electrode when taking out the signal voltage from one capacitor electrode of the reference capacitor, and the like are as described above. Without being limited, it is possible to reverse the polarity or to adopt another voltage relationship.

  The present invention can be widely applied not only to a mobile terminal device such as a mobile phone but also to a PC having a touch input mechanism integrated with a display, an operation panel of an electronic device, and the like.

101 Touch Panel Electrode 102 Touch Panel Electrode Signal Line 103 Positive Selector 104 Negative Selector 105 Reference Capacitance 106 Reference Capacitance Voltage Positive Set Switch 107 Reference Capacitance Voltage Negative Set Switch 108 Positive Electrode Reset Switch 109 Negative Electrode Reset Switch 110 Positive Share Switch 111 Negative Share Switch 112 A / D conversion circuit 113 Capacitance conversion circuit 114 Contact detection circuit 115 Coordinate detection circuit 116 Touch panel timing control unit 117 Coordinate information 118 Contact information 119 Positive electrode select signal 120 Negative electrode select signal 121 Positive electrode reset signal 122 Negative electrode reset signal 123 Positive electrode share signal 123 124 Negative share signal 125 Reference capacitor initial voltage set signal 126 Reference capacitor ground signal 127 AD conversion start signal 20 Rhombic unit electrodes 19 1-layer electrode (lateral direction)
18 Second layer electrode (longitudinal direction)
301 Reference Capacitance Positive Voltage Waveform 302 Reference Capacitance Negative Voltage Waveform 303 Reference Capacitance Positive Electrode Noise Waveform 304 Reference Capacitance Negative Electrode Noise Waveform 401 Selection Electrode Set 402 Capacitance Calculation Formula Shown by Selection Electrode Set 403 Output Value of A / D Conversion Circuit 501 Present Capacitance value 502 Capacitance value before contact 503 Subtractor 504 Contact detection threshold 505 Comparator 506 Contact capacitance value 507 Contact information 601 Contact capacitance value 602, 605 Cumulative adder 603 Weighted counter 604 Multiplier 606 Divider 607 Resolution converter 608 Horizontal Resolution 609 Vertical resolution 610 Contact coordinate value 701 Detection circuit LSI
901 Reference variable capacity 902 Reference variable capacity positive connection switch 903 Reference variable capacity negative connection switch 904 Reference variable capacity connection signal

Claims (22)

A plurality of electrode wires each having a capacitance electrode;
A detection unit for detecting a signal corresponding to a capacitance value of the electrode line based on charge transfer between the electrode lines selected from the plurality of electrode lines;
A determination unit that determines presence or absence of contact with the electrode line based on a detection result by the detection unit;
The detection unit sequentially selects two electrode lines from a plurality of electrode lines in a predetermined order, resets the charges of the selected two electrode lines, and sets a voltage to a reference capacitor used for a detection operation. Thereafter, a voltage signal obtained in the reference capacitor by connecting one capacitor terminal of the reference capacitor to the selected one electrode line and connecting the other capacitor terminal of the reference capacitor to the selected other electrode line. Is detected as a signal corresponding to the electrode capacity of the two selected electrode lines.   The touch determination apparatus according to claim 1, wherein the determination unit determines presence / absence of contact by obtaining a voltage value for each electrode line from a large number of voltage values regarding two electrode lines sequentially selected in a predetermined order.   The detection unit detects the voltage value by combining two different electrode lines for the three electrode lines in the first three times, and then moves the adjacent two electrode lines while sequentially shifting the electrode lines to be selected one by one. The touch determination apparatus according to claim 1, wherein a voltage value is detected by selecting an electrode line.   The touch determination device according to claim 1, wherein when the detection unit obtains a voltage signal from the reference capacitor, one capacitor terminal of the reference capacitor is used as a reference voltage, and the voltage of the other capacitor terminal is used as the voltage signal. The electrode capacity of the electrode line is a ground capacity,
The setting of the voltage with respect to the reference capacitor is performed using one capacitor terminal as a ground voltage,
The touch determination device according to claim 4, wherein one of the capacitance terminals of the reference capacitance that is used as a reference voltage when obtaining the voltage signal is a negative voltage.   The touch determination apparatus according to claim 5, wherein the reference voltage is a ground voltage.   The touch determination device according to claim 6, wherein the detection unit includes a switch composed of a MOS transistor for charge transfer, and the substrate potential of the MOS transistor to which a negative voltage is applied is a negative voltage among the MOS transistors. .   The touch determination apparatus according to claim 7, wherein the negative substrate potential is a negative potential having the same voltage as a voltage set at one capacitance terminal of the reference capacitor. The reference capacitor comprises a plurality of capacitors arranged in parallel so as to be selectively separable,
The touch determination device according to claim 1, wherein the control unit connects the plurality of capacitors in parallel when the electrode capacity of the electrode line is large, and separates a part of the plurality of capacitors when the electrode line is small. The detection unit includes a selection circuit that sequentially selects two electrode lines from a plurality of electrode lines in a predetermined order;
A reset switch for resetting the charges of the two selected electrode lines;
A reference capacity used for the detection operation;
A precharge switch for setting a voltage in the reference capacitor;
A sharing switch that selectively connects one capacitor terminal of the reference capacitor to the selected one electrode line and selectively connects the other capacitor terminal of the reference capacitor to the other electrode line selected;
Each time two electrode lines are selected by the selection circuit, the selected two electrodes are sequentially controlled by precharging the reference capacitor, resetting the selected electrode line, and turning on the sharing switch. The touch determination apparatus according to claim 1, further comprising: a control unit that performs control for obtaining a voltage signal from the reference capacitor as a signal corresponding to the electrode capacitance of the line.   The controller sequentially controls reset of the electrode line and ON operation of the sharing switch, and then resets the selected electrode line while maintaining the charge of the reference capacitor, and the sharing switch The touch determination apparatus according to claim 10, wherein the ON operation is sequentially controlled to control the operation of accumulating charges on the reference capacitor. An input device having a display control unit, a display panel controlled by the display control unit, a touch panel overlaid on the display panel, and a drive unit for the touch panel,
The touch panel includes a plurality of transparent electrode lines each having a capacitance electrode, and the drive unit is mounted.
The drive unit is configured to detect a signal corresponding to a capacitance value of the electrode line based on charge transfer between the electrode lines selected from the plurality of electrode lines;
A determination unit that determines presence or absence of contact with the electrode line based on a detection result by the detection unit;
The detection unit sequentially selects two electrode lines from a plurality of electrode lines in a predetermined order, resets the charges of the selected two electrode lines, and sets a voltage to a reference capacitor used for a detection operation. Thereafter, a voltage signal obtained in the reference capacitor by connecting one capacitor terminal of the reference capacitor to the selected one electrode line and connecting the other capacitor terminal of the reference capacitor to the selected other electrode line. Is detected as a signal corresponding to the electrode capacity of the two selected electrode lines.   The input device according to claim 12, wherein the determination unit determines presence / absence of contact by obtaining a voltage value for each electrode line from a large number of voltage values related to two electrode lines sequentially selected in a predetermined order.   The detection unit detects the voltage value by combining two different electrode lines for the three electrode lines in the first three times, and then moves the adjacent two electrode lines while sequentially shifting the electrode lines to be selected one by one. The input device according to claim 12, wherein a voltage value is detected by selecting an electrode line.   The input device according to claim 12, wherein when the detection unit obtains a voltage signal from the reference capacitor, one capacitor terminal of the reference capacitor is used as a reference voltage, and the voltage of the other capacitor terminal is used as the voltage signal. The electrode capacity of the electrode line is a ground capacity,
The setting of the voltage with respect to the reference capacitor is performed using one capacitor terminal as a ground voltage,
The input device according to claim 15, wherein one capacitance terminal of a reference capacitor that is set as a reference voltage when obtaining the voltage signal is a negative voltage.   The input device according to claim 16, wherein the reference voltage is a ground voltage.   The input device according to claim 17, wherein the detection unit includes a switch made of a MOS transistor for charge transfer, and the substrate potential of the MOS transistor to which a negative voltage is applied is a negative voltage among the MOS transistors.   The input device according to claim 18, wherein the negative substrate potential is a negative potential having the same voltage as a voltage set at one capacitor terminal of the reference capacitor. The reference capacitor comprises a plurality of capacitors arranged in parallel so as to be selectively separable,
13. The input device according to claim 12, wherein the control unit connects the plurality of capacitors in parallel when the electrode capacity of the electrode line is large, and separates a part of the plurality of capacitors when the electrode line is small. The detection unit includes a selection circuit that sequentially selects two electrode lines from a plurality of electrode lines in a predetermined order;
A reset switch for resetting the charges of the two selected electrode lines;
A reference capacity used for the detection operation;
A precharge switch for setting a voltage in the reference capacitor;
A sharing switch that selectively connects one capacitor terminal of the reference capacitor to the selected one electrode line and selectively connects the other capacitor terminal of the reference capacitor to the other electrode line selected;
Each time two electrode lines are selected by the selection circuit, the selected two electrodes are sequentially controlled by precharging the reference capacitor, resetting the selected electrode line, and turning on the sharing switch. The input device according to claim 12, further comprising: a control unit that performs control for obtaining a voltage signal from the reference capacitor as a signal corresponding to an electrode capacitance of a line.   The controller sequentially controls reset of the electrode line and ON operation of the sharing switch, and then resets the selected electrode line while maintaining the charge of the reference capacitor, and the sharing switch The input device according to claim 21, wherein the ON operation is sequentially controlled to control the operation of accumulating charges in the reference capacitor.

Images