JP2013020479A - Touch panel device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a touch panel device capable of precisely detecting a touch point even on a large sized panel.SOLUTION: The touch panel device controls so that the current of a drive signal applied to transmission electrodes Y0-Y39 gets larger as the length of signal transmission path (Lx+Ly) from a transmission section 9 to a reception section 10 via an electrode intersection point gets larger. The touch panel device also controls so that the frequency of the drive signal gets smaller as the length of signal transmission path gets larger. Particularly, the touch panel device controls the magnitude of the current of the drive signal for each divided region R01-R04, R11-R14; and controls the frequency of the drive signal for each reception group A-D.

Description

  The present invention relates to a capacitive touch panel device in which electrodes are arranged in a grid pattern and detects a touch position based on a change in an output signal of the electrode accompanying a change in capacitance according to a touch operation, in particular, a transmission electrode The present invention relates to a mutual capacitance type touch panel device that detects a touch position by receiving a charge / discharge current signal flowing in a receiving electrode in response to a drive signal applied to the touch panel.

  In a projected capacitive touch panel device, particularly a mutual capacitive touch panel device, it is obtained by receiving a charge / discharge current signal flowing through the receiving electrode in response to a drive signal applied to the transmitting electrode, and performing necessary signal processing on the signal. The touch position is detected from the level signal, but at this time, the touch position is detected based on the amount of change in the level signal according to the touch operation. If there is a large variation, the touch position cannot be detected accurately.

  Such variation in the level signal in the non-touch state is mainly due to the influence of the impedance of the electrode, etc., and the output signal of the reception electrode is output from the transmission unit to the transmission electrode as a drive signal and passes through the electrode intersection. This occurs because the signal propagation path length until the signal is input to the receiver varies depending on the position. That is, as the signal propagation path length increases, the waveform of the received signal is distorted and the level signal decreases, and the level signal change due to this waveform distortion varies depending on the signal propagation path length. Variation occurs in the level signal.

  In response to the problem of deterioration in detection accuracy due to variations in level signals in such a non-touch state, the mutual capacitance type touch panel device controls the amplification factor and integration time of the reception signal output from the reception electrode, and A technique is known in which the detection signal is improved by controlling the voltage of a drive signal applied to a transmission electrode so that level signals in a non-touch state are made uniform (see Patent Document 1).

  In this prior art, by controlling the amplification factor and integration time of the received signal, it is possible to adjust the variation of the level signal detected in the non-touch state with respect to the X direction (the arrangement direction of the receiving electrodes). By controlling the voltage of the drive signal applied to the electrodes, the level signal variation can be adjusted in the Y direction (transmission electrode arrangement direction).

JP 2008-134836 A

  By the way, touch panel devices are widely used in the field of personal computers and personal digital assistants. By combining this touch panel device with a large screen display device, it can be used for presentations and lectures for a large number of people. Can also be used, and convenience can be improved.

  However, when the size of the touch panel device is increased, the electrodes become longer, and a large difference in the signal propagation path length is generated accordingly. Therefore, the variation of the level signal in the non-touch state becomes more remarkable, as described above. In the method of controlling the voltage of the drive signal applied to the transmission electrode, there is a problem that variation in level signals cannot be effectively reduced and sufficient detection accuracy cannot be ensured.

  The present invention has been devised to solve such problems of the prior art, and its main purpose is to be able to accurately detect the touch position even when the size is increased. It is to provide a touch panel device.

  The touch panel device of the present invention includes a panel body in which a plurality of transmission electrodes that are parallel to each other and a plurality of reception electrodes that are parallel to each other are arranged in a grid pattern, and a transmission unit that sequentially selects the transmission electrodes and applies a drive signal A receiving unit that sequentially selects the receiving electrode and receives an output signal of the receiving electrode in response to the driving signal and outputs a level signal for each electrode intersection; and a level signal output from the receiving unit A control unit that detects the touch position and controls the operation of the transmission unit and the reception unit, the transmission unit is configured to be able to change the magnitude of the current of the drive signal, the control unit, Control is performed so that the current of the drive signal increases as the signal propagation path length from the transmission unit through the electrode intersection to the reception unit increases.

  According to the present invention, since the current of the drive signal is controlled to increase as the signal propagation path length increases, the distortion of the received signal waveform that occurs when the signal propagation path length increases is reduced. Since the variation in level signal due to the difference in signal propagation path length can be reduced, the touch position can be detected with high accuracy. When the drive signal current is optimized, that is, when the signal propagation path length is small and the waveform distortion of the received signal is small, the drive signal current is small and unnecessary. Radiation noise can be reduced.

Overall configuration diagram showing a touch panel system to which the touch panel device 1 according to the present embodiment is applied. Schematic configuration diagram of the touch panel device 1 Schematic configuration diagram of the received signal processing unit 32 Schematic configuration diagram of the IV conversion unit 41 Waveform diagram showing a pulse signal applied to the transmission electrode 7 and a voltage signal output from the IV converter 41 The figure explaining the current control of a drive signal Schematic configuration diagram of the drive unit 23 of the transmission unit 9 The figure which shows the specific example of the buffer BF1-BF5 selected by the drive part 23, the electric current value of a drive signal, and the frequency of a drive signal for every division area R01-R04, R11-R14. The figure explaining the frequency control of a drive signal Schematic configuration diagram of the pulse generator 21 of the transmitter 9 Timing diagram showing drive signal output status The figure which shows the change situation of the frequency of the drive signal Timing chart showing the application status of drive signals to the transmission electrodes Y0 to Y39 in the transmission section 9 and the selection status of the reception electrodes X0 to X63 in the reception section 10 for one frame. FIG. 13 is a timing diagram showing in detail the A part shown in FIG. 13 and showing output signals of the IV conversion unit 41, the absolute value detection unit 43, and the integration unit 44 in the reception signal processing unit 32 of the reception unit 10. The figure which shows an example of the frequency characteristic of the unnecessary radiation noise which generate | occur | produces with this touch panel apparatus 1.

  A first invention made to solve the above-mentioned problem is to sequentially select a plurality of transmission electrodes that are parallel to each other and a panel body in which a plurality of reception electrodes that are parallel to each other are arranged in a grid pattern, and the transmission electrodes. A transmission unit that applies a drive signal, a reception unit that sequentially selects the reception electrode, receives an output signal of the reception electrode in response to the drive signal, and outputs a level signal for each electrode intersection; and the reception unit And a control unit that controls the operation of the transmission unit and the reception unit, and the transmission unit can change the magnitude of the current of the drive signal. The control unit is configured to control the current of the drive signal to increase as the signal propagation path length from the transmission unit through the electrode intersection to the reception unit increases.

  According to this, since the current of the drive signal is controlled to increase as the signal propagation path length increases, the waveform distortion of the received signal that occurs when the signal propagation path length increases is reduced. Since the variation in level signal due to the difference in propagation path length can be suppressed, the touch position can be detected with high accuracy. When the drive signal current is optimized, that is, when the signal propagation path length is small and the waveform distortion of the received signal is small, the drive signal current is small and unnecessary. Radiation noise can be reduced.

  According to a second aspect of the invention, the touch detection area is divided into a plurality of divided areas according to the signal propagation path length, and the magnitude of the current of the drive signal is set for each of the divided areas.

  According to this, since the current of the drive signal is changed for each divided region, the control of the drive signal is simplified.

  In this case, since the signal propagation path length depends on the lengths of both the transmission electrode and the reception electrode, the touch detection region may be divided with respect to two directions of the transmission electrode arrangement direction and the reception electrode arrangement direction. Thereby, the variation of the signal propagation path length in each divided region can be reduced, and the current control according to the signal propagation path length can be performed more accurately.

  According to a third aspect of the present invention, the transmission unit is configured to be able to change the frequency of the drive signal, and the control unit decreases the frequency of the drive signal as the signal propagation path length increases. It is set as the structure controlled so that it may become.

  According to this, the distortion of the waveform of the received signal that occurs when the signal propagation path length is increased is reduced, and variation in the level signal due to the difference in the signal propagation path length can be suppressed, so that the touch position can be detected accurately. It can be carried out.

  According to a fourth aspect of the present invention, the receiving electrodes are grouped by a predetermined number along the arrangement direction of the receiving electrodes, and the frequency of the drive signal is set for each group of receiving electrodes.

  According to this, since the frequency of the drive signal is changed for each group of reception electrodes, the drive signal can be easily controlled.

  According to a fifth aspect of the present invention, the control unit has a scan direction in which the reception electrodes are sequentially selected along the arrangement direction of the reception electrodes while applying a drive signal to one transmission electrode. It is set as the structure controlled differently according to it.

  According to this, by changing the scanning direction according to the transmission electrode, the change pattern of the frequency of the drive signal becomes different according to the transmission electrode. Thereby, the frequency spectrum of noise radiated by applying the drive signal to the transmission electrode is dispersed and the noise level is lowered, so that unnecessary radiation noise from the panel surface caused by the drive signal can be reduced.

  In this case, if the scan direction is controlled to change alternately for each transmission electrode, the frequency change pattern of the drive signal changes frequently, so that the frequency spectrum of the radiation noise can be further dispersed. Therefore, unnecessary radiation noise can be further reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall configuration diagram showing a touch panel system to which a touch panel device 1 according to the present embodiment is applied. In this touch panel system, the panel body 3 of the touch panel device 1 is disposed on the front side of the display surface of a plasma display panel (hereinafter referred to as PDP) 2, and the screen of the PDP 2 is displayed through the panel body 3. The PDP 2 is controlled by the PDP control unit 4.

  The panel main body 3 of the touch panel device 1 includes a touch surface 6 on which a touch operation is performed with an indicator (a conductor of a user's fingertip and a stylus, an indicator rod, etc.), and a plurality of transmission electrodes 7 that run in parallel with each other. A plurality of receiving electrodes 8 are arranged in a grid pattern.

  In addition, the touch panel device 1 receives a response signal of the transmission unit 9 that applies a drive signal to the transmission electrode 7 and the reception electrode 8 that responds to the drive signal applied to the transmission electrode 7. A receiving unit 10 that outputs a level signal at each electrode intersection where the receiving electrode 8 intersects, a touch position is detected based on the level signal output from the receiving unit 10, and the operations of the transmitting unit 9 and the receiving unit 10 are performed. And a control unit 11 for controlling.

  The touch position information output from the control unit 11 is input to an external device 12 such as a personal computer, and the display screen data generated here is output to the PDP control unit 4. Thereby, an image corresponding to the touch operation performed by the user with the pointing object on the touch surface 6 of the panel body 3 is displayed on the screen of the PDP 2, and a required image is obtained with the same feeling as when directly drawing with a marker on the touch surface 6. Can be displayed, and buttons displayed on the display screen of the PDP 2 can be operated. Furthermore, an eraser that erases an image drawn by a touch operation can be used.

  The transmission electrodes 7 and the reception electrodes 8 are arranged at the same arrangement pitch (for example, 10 mm), and the number thereof varies depending on the aspect ratio of the panel body 3. For example, 40 transmission electrodes 7 and 64 reception electrodes 8 are provided. Book placed.

  The transmission electrode 7 and the reception electrode 8 intersect with each other in an overlapping manner with an insulating layer interposed therebetween, and a capacitor is formed at an electrode intersection where the transmission electrode 7 and the reception electrode 8 intersect, and the user designates a finger or the like. When a touch operation is performed with an object, when the pointing object approaches or comes into contact with the touch surface 6, the presence or absence of the touch operation can be detected by substantially reducing the capacitance at the electrode intersection point accordingly. .

  Here, the mutual capacitance method is adopted, and when a drive signal is applied to the transmission electrode 7, a charge / discharge current flows through the reception electrode 8 in response thereto, and this charge / discharge current is output from the reception electrode 8 as a response signal. At this time, when the capacitance at the electrode intersection changes according to the user's touch operation, the charge / discharge current of the reception electrode 8, that is, the response signal changes, and the touch position is calculated based on the change amount. In this mutual capacitance method, a level signal obtained by performing signal processing on the response signal in the receiving unit 10 is output for each electrode intersection point between the transmission electrode 7 and the reception electrode 8, and thus a plurality of touch positions are detected simultaneously. So-called multi-touch (multi-point detection) is possible.

  The control unit 11 obtains the touch position (center coordinate of the touch area) from the level signal for each electrode intersection output from the receiving unit 10 by a predetermined calculation process. In the calculation of the touch position, a plurality (for example, 4) adjacent to each other in the X direction (the arrangement direction of the transmission electrodes 7, that is, the width direction of the PDP 2) and the Y direction (the arrangement direction of the reception electrodes 8, that is, the height direction of the PDP 2). The touch position is obtained from the level signal for each electrode intersection of x4) using a required interpolation method (for example, the centroid method). Thereby, the touch position can be detected with a resolution (for example, 1 mm or less) higher than the arrangement pitch (for example, 20 mm) of the transmission electrode 7 and the reception electrode 8.

  In addition, the control unit 11 performs processing for obtaining a touch position every frame period in which reception of the level signal for each electrode intersection is completed over the entire touch surface 6, and the touch position information is frame by frame for the external device 12. Is output. The external device 12 generates display screen data that links the touch positions in time series based on the touch position information of a plurality of temporally continuous frames and outputs the display screen data to the PDP control unit 4. In the case of multi-touch, touch position information including touch positions by a plurality of instructions is output in units of frames.

  FIG. 2 is a schematic configuration diagram of the touch panel device 1. The transmission unit 9 sequentially selects the transmission electrodes 7 and applies a drive signal, and includes a pulse generation unit 21, an electrode selection unit 22, and a drive unit 23. The pulse generation unit 21 generates a pulse that is a source of the drive signal. The electrode selection unit 22 selects the transmission electrodes 7 one by one, and sequentially applies the pulses output from the pulse generation unit 21 to the transmission electrodes 7. The drive unit 23 drives the transmission electrode 7 selected by the electrode selection unit 22 in pulses.

  Further, the transmission unit 9 includes a drive current setting unit 24 and a drive frequency setting unit 25. The drive current setting unit 24 controls the drive unit 23 based on the current selection signal output from the control unit 11, and a drive signal of a current corresponding to the current selection signal is output from the drive unit 23. The drive frequency setting unit 25 holds the set value of the frequency output from the control unit 11, and the pulse generation unit 21 generates a pulse wave based on the frequency held in the drive frequency setting unit 25.

  The reception unit 10 includes an electrode selection unit 31 and a reception signal processing unit 32. In the reception signal processing unit 32, the response signal output from the reception electrode 8 is processed. In the electrode selection unit 31, an analog switch is connected to each reception electrode 8, the reception electrode 8 is selected one by one, and the response signal from the reception electrode 8 is sequentially input to the reception signal processing unit 32.

  The transmission unit 9 and the reception unit 10 operate according to the synchronization signal output from the control unit 11, and while the transmission signal is applied to one transmission electrode 7 in the transmission unit 9, the reception unit 8 receives the reception electrode 8. Are selected one by one and the response signal from the reception electrode 8 is sequentially input to the reception signal processing unit 32 to perform signal processing, and the scanning operation for one line is sequentially repeated for all the transmission electrodes 7. Level signals for all electrode intersections can be acquired.

  The electrode selection unit 31 and the reception signal processing unit 32 are provided for each of the reception groups A to D. In each electrode selection unit 31, analog switches corresponding to each other are turned on / off in parallel, and the charge / discharge current signal of one receiving electrode 8 selected by turning on the analog switch sequentially, Input to the received signal processing unit 32. As described above, since the selection of the reception electrode 8 in the electrode selection unit 31 and the signal processing in the reception signal processing unit 32 are performed in parallel between the reception groups A to D, the signal processing is speeded up and the hardware configuration is large. Can be avoided.

  FIG. 3 is a schematic configuration diagram of the reception signal processing unit 32. The reception signal processing unit 32 performs analog processing on the output signal (charge / discharge current signal) of the reception electrode 8 input via the electrode selection unit 31 and then performs AD conversion to output a level signal. IV A conversion unit 41, a bandpass filter 42, an absolute value detection unit 43, an integration unit 44, a sample hold unit 45, and an AD conversion unit 46 are provided.

  In the IV converter 41, the current signal output from the receiving electrode 8 is converted into a voltage signal. In the band pass filter 42, a process for removing a signal having a frequency component other than the frequency of the drive signal applied to the transmission electrode 7 is performed on the output signal of the IV conversion unit 41. The absolute value detector (rectifier) 43 performs full-wave rectification on the output signal of the bandpass filter 42. The integration unit 44 performs processing for integrating the output signal of the absolute value detection unit 43 in the time axis direction. In the sample hold unit 45, a process of sampling the output signal of the integration unit 44 at a predetermined timing is performed. The AD converter 46 AD-converts the output signal of the sample hold unit 45 and outputs a level signal for each electrode intersection.

  FIG. 4 is a schematic configuration diagram of the IV conversion unit 41. The IV conversion unit 41 includes an operational amplifier OPA, a resistance component R, a first capacitance component C1, and a second capacitance component C2. The resistance component R and the first capacitance component C1 are included in the operational amplifier OPA. One input side and the output side are connected in parallel. The second capacitance component C2 is provided on the other input side of the operational amplifier OPA and is GND-connected.

  FIG. 5 is a waveform diagram showing a pulse signal applied to the transmission electrode 7 and a voltage signal output from the IV converter 41. FIG. 5 (A) shows a case according to the prior art, and FIG. Each case according to the invention is shown. The voltage signal shown in the figure is a waveform after the band-pass filter 42 cuts a signal having a frequency component other than the frequency of the drive signal applied to the transmission electrode 7.

  Normally, when a pulse signal (drive signal) is applied to the transmission electrode 7, as shown in FIG. 5A, waveforms A1 and A3 due to charging of the capacitor at the electrode intersection are observed at the rise of the pulse wave, and then As the transient response, waveforms A2 and A4 due to the discharge from the capacitor at the electrode intersection are observed, and thereafter a small waveform that gradually attenuates is observed. Further, at the fall of the pulse wave, a waveform B1 due to discharge from the capacitor at the electrode intersection is observed, and as a transient response, a waveform B2 due to charging of the capacitor at the electrode intersection is observed, and thereafter a small waveform that gradually attenuates. Is observed.

  Here, when there is a touch operation, the capacitance of the capacitor at the electrode intersection is reduced, so that the amplitude of the voltage signal output from the IV conversion unit 41 is reduced. For this reason, the presence or absence of a touch operation can be determined by the change in the peak value, but since the touch panel device 1 is used in combination with the PDP 2 having a large screen, between the transmission electrode 7 and the reception electrode 8 as the size increases. The overall electrostatic capacity increases, and the change in electrostatic capacity due to the touch operation on the entire electrostatic capacity becomes extremely small, so that the detection accuracy of the touch position decreases.

  Therefore, here, the IV conversion unit 41 outputs the voltage signal output from the IV conversion unit 41 corresponding to the rising and falling of one pulse wave in the pulse signal applied from the transmission unit 9 to the transmission electrode 7. The conversion characteristics of the IV converter 41 are set so that the amplitude phases are substantially matched and the amplitude phases of the voltage signals corresponding to the falling edge of one pulse wave and the rising edge of the next pulse wave are substantially matched. .

  That is, a waveform B1 due to discharge at the fall of the same pulse wave is superimposed on a waveform A2 due to discharge (transient response) at the rise of one pulse wave, and charging (transient at the fall of one pulse wave) The waveform A3 due to charging at the rise of the next pulse wave is superimposed on the waveform B2 due to (response).

  In this way, a substantially amplified waveform can be obtained as shown in FIG. This is due to the cumulative addition of pulses after the main pulse in the impulse response, and the signal output from the IV converter 41 exhibits a sine wave and the same frequency as the pulse signal applied to the transmission electrode 7. Become an ingredient.

  Such conversion characteristics can be obtained by adjusting the time constant of the conversion circuit of the IV conversion unit 41. In the IV conversion unit 41, a time constant is determined according to the resistance value of the resistance component R and the capacitance values of the first and second capacitance components C1 and C2. By adjusting the time constant, the time constant shown in FIG. As shown, it is possible to obtain a conversion characteristic that realizes amplification by matching the amplitude phase. A configuration in which the resistance value and the capacitance value of each component is 0, for example, the capacitance of the second capacitance component C2 is 0 is also possible.

  In order to realize such signal amplification, it is desirable to set the time constant of the IV conversion unit 41 to a value suitable for the frequency of the pulse signal applied to the transmission electrode 7. Since the frequency is changed, the relationship between the time constant and the frequency cannot be strictly optimized. However, since the adjustment range when changing the frequency of the pulse signal is small, even if the time constant is not changed according to the change of the frequency, the signal amplification is not greatly affected.

  Now, in the touch panel device 1, as shown in FIG. 2, the signal propagation path length from the transmission unit 9 through the electrode intersection to the reception unit 10, specifically, the distance from the transmission unit 9 to the electrode intersection. Lx + Ly obtained by adding Lx and the distance Ly from the electrode intersection to the receiving unit 10 varies depending on the position, but when the signal propagation path length increases, the signal waveform is distorted from a sine wave as shown in FIG. The distortion of the signal waveform increases as the signal propagation path length increases. When the signal waveform is distorted, the level signal becomes small. Therefore, when the drive signal is applied to all the transmission electrodes 7 under the same conditions (current and frequency), the level signal in the non-touch state varies. In particular, since the touch panel device 1 is used in combination with the PDP 2 having a large screen, the signal propagation path length increases as the size of the touch panel device 1 increases. Therefore, the variation in the level signal in the non-touch state becomes more remarkable.

  In order to eliminate such variations in the level signal in the non-touch state, the drive signal current may be set large so that the signal waveform is not distorted even at the position where the signal propagation path length becomes the largest. When a large current is passed through all the transmission electrodes 7 in accordance with the position where the path length becomes the longest, the panel surface on which the transmission electrodes 7 and the reception electrodes 8 are disposed, and the circuit board constituting the transmission unit 9 and the reception unit 10 Unnecessary radiation noise radiated from the sound source increases, and the S / N ratio decreases accordingly, so that the detection accuracy cannot be increased.

  Therefore, in the present embodiment, as will be described in detail below, current control for changing and controlling the magnitude of the current of the drive signal applied to the transmission electrode 7 according to the signal propagation path length, and drive applied to the transmission electrode Frequency control for changing and controlling the frequency of the signal is performed.

  First, drive signal current control will be described. FIG. 6 is a diagram for explaining current control of a drive signal. In FIG. 6, 40 transmitting electrodes 7 are indicated as Y0, Y1,... Y39 from the end, and 64 receiving electrodes 8 are indicated as X0, X1,.

  In the present embodiment, current control is performed so that the current of the drive signal increases as the signal propagation path length increases. In particular, in the present embodiment, the touch detection area 15 is divided into a plurality of divided areas R01 to R04 and R11 to R14 according to the signal propagation path length, and the current of the drive signal is divided for each of the divided areas R01 to R04 and R11 to R14. Current control is performed so as to change the magnitude, and the magnitude of the current of the drive signal is set for each of the divided regions R01 to R04 and R11 to R14.

  Further, in the present embodiment, the reception electrodes X0 to X63 are grouped for each predetermined number, and the transmission electrodes Y0 to Y39 are also grouped for each predetermined number, and the reception electrodes X0 to X63 and the transmission electrodes Y0 to Y39 are grouped. Thus, the touch detection region 15 is divided with respect to two directions of the arrangement direction of the transmission electrodes Y0 to Y39 (Y direction) and the arrangement direction of the reception electrodes X0 to X63 (X direction).

  Specifically, 64 reception electrodes X0 to X63 are provided every 16 reception groups A (X0 to X15), reception groups B (X16 to X31), reception groups C (X32 to X47), and reception groups D. They are grouped into four groups (X48 to X63). In addition, 40 transmission electrodes Y0 to Y39 are grouped into two transmission groups E (Y0 to Y19) and transmission groups F (Y20 to Y39) every 20 lines. By the grouping of the reception electrodes X0 to X63 and the transmission electrodes Y0 to Y39, the touch detection area 15 is divided into eight division areas R01 to R04 and R11 to R14.

  Comparing the signal propagation path length for each of the divided areas R01 to R04 and R11 to R14, the signal propagation path length is the smallest in the divided area R11, the largest in the divided area R04, and equal in the divided areas R01 and R12. The divided region R02 is equal to the divided region R13, the divided region R03 is equal to the divided region R14, the divided region R11, the divided regions R01, R12, the divided regions R02, R13, the divided regions R03, R14, and the divided region R04. It becomes large in order.

  Thus, the signal propagation path length changes in five stages in the order of divided region R11, divided regions R01 and R12, divided regions R02 and R13, divided regions R03 and R14, and divided region R04. The currents i1 to i5 in the scan periods of R01, R12, the divided regions R02, R13, the divided regions R03, R14, and the divided region R04 have a relationship of i1 <i2 <i3 <i4 <i5.

  The change of the current of the drive signal is performed by the drive unit 23 of the transmission unit 9 shown in FIG. FIG. 7 is a schematic configuration diagram of the drive unit 23 of the transmission unit 9. FIG. 8 is a diagram illustrating specific examples of the buffers BF1 to BF5 selected by the driving unit 23, the current value of the driving signal, and the frequency of the driving signal for each of the divided regions R01 to R04 and R11 to R14. The frequency of the drive signal shown in FIG. 8 will be described in detail later.

  As shown in FIG. 7, the driving unit 23 includes an electrode driving unit 51 for each transmission electrode 7. In each electrode driving unit 51, five buffers BF1 to BF5 are connected in parallel, and by selecting any one of the buffers BF1 to BF5, the driving signal applied to the transmission electrode 7 has five levels of currents i1 to i5. Can be adjusted.

  In the control unit 11, in synchronization with the horizontal synchronization signal output to the electrode selection unit 22, the currents i1 to i5 set for each of the divided regions R01 to R14 at the start of each scan period of the divided regions R01 to R14. A current selection signal to be selected is output to the drive current setting unit 24, and the drive current setting unit 24 selects one of the buffers BF1 to BF5 based on the current selection signal from the control unit 11. Thereby, in the electrode drive part 51, the drive signal of the electric currents i1-i5 set for every division area R01-R14 is output for every scanning period of division area R01-R14.

  As described above, the signal propagation path length changes in five stages in the order of the divided region R11, the divided regions R01 and R12, the divided regions R02 and R13, the divided regions R03 and R14, and the divided region R04. Buffers BF1 to BF5 are selected in each scan period of divided regions R01 and R12, divided regions R02 and R13, divided regions R03 and R14, and divided region R04, and currents i1 to i5 defined by the buffers BF1 to BF5 are selected. Is set to 4 mA, 8 mA, 16 mA, 24 mA, and 32 mA, respectively, as shown in FIG. 8, for example.

  The buffer BF1 is selected during the scan period of the divided region R11, and the drive signal is output at a current i1 = 4 mA. The buffer BF2 is selected in the scan period of the divided regions R01 and R12, and the drive signal is output at a current i2 = 8 mA. The buffer BF3 is selected in the scan period of the divided regions R02 and R13, and the drive signal is output at a current i3 = 16 mA. The buffer BF4 is selected in the scan period of the divided regions R03 and R14, and the drive signal is output at a current i4 = 24 mA. The buffer BF5 is selected in the scan period of the divided region R04, and the drive signal is output at a current i5 = 32 mA.

  As described above, by controlling the drive signal current to increase as the signal propagation path length increases, the waveform distortion of the received signal that occurs when the signal propagation path length increases is reduced. Since variations in level signals due to differences in signal propagation path length can be suppressed, the touch position can be detected with high accuracy. When the drive signal current is optimized according to the signal propagation path length, that is, when the signal propagation path length is small and the waveform distortion of the received signal is small, the drive signal current becomes small and unnecessary. Since no current is passed, unnecessary radiation noise can be reduced.

  In addition, since the drive signal current is controlled to change for each of the divided regions R01 to R04 and R11 to R14, the current of the drive signal is set in each scan period of each of the divided regions R01 to R04 and R11 to R14. The size of the signal does not change, and the control of the drive signal is simplified. In particular, in this embodiment, since it is divided with respect to the two directions of the arrangement direction of the transmission electrode 7 (Y direction) and the arrangement direction of the reception electrode 8 (X direction), it is divided in each of the divided regions R01 to R04, R11 to R14. Variations in the signal propagation path length can be reduced, and current control according to the signal propagation path length can be performed more accurately.

  Next, frequency control of the drive signal will be described. FIG. 9 is a diagram for explaining the frequency control of the drive signal. In FIG. 9, 40 transmitting electrodes 7 are indicated as Y0, Y1,... Y39 from the end, and 64 receiving electrodes 8 are indicated as X0, X1,.

  In the present embodiment, frequency control is performed so that the frequency of the drive signal decreases as the signal propagation path length increases. In particular, in the present embodiment, frequency control is performed so as to change the frequency of the drive signal for each of the reception groups A to D, and the frequency of the drive signal is set for each of the reception groups A to D.

  The signal propagation path length increases in the order of reception group A, reception group B, reception group C, and reception group D. The frequencies f1 to f4 of the reception groups A to D are f1> f2> f3> f4. For example, as shown in FIG. 8, they are set to 3.02 MHz, 2.96 MHz, 2.91 MHz, and 2.85 MHz, respectively.

  The frequency of the drive signal is changed by the pulse generator 21 of the transmitter 9 shown in FIG. FIG. 10 is a schematic configuration diagram of the pulse generation unit 21 of the transmission unit 9.

  The pulse generation unit 21 includes a clock oscillator 55, a PLL synthesizer 56, and a timing control unit 57. The clock oscillator 55 generates a reference clock. The PLL synthesizer 56 converts the reference clock output from the clock oscillator 55 into a frequency based on the set frequency value held in the drive frequency setting unit 25. The timing control unit 57 outputs the clock pulse output from the PLL synthesizer 56 at a predetermined timing.

  In the control unit 11, in synchronization with the horizontal synchronization signal output to the electrode selection unit 22, the frequency set value set for each reception group A to D is set at the start of the scan period of each reception group A to D. Output to the drive frequency setting unit 25. Thereby, in the PLL synthesizer 56, based on the setting value of the drive frequency setting unit 25, a pulse having a frequency set for each reception group A to D is output for each scan period of each reception group A to D. .

  Here, the PLL synthesizer 56 is used for frequency conversion, but other frequency conversion means using a frequency divider or the like may be employed.

  In the present embodiment, as shown in FIG. 9, the receiving electrodes X0 to X63 are sequentially selected along the arrangement direction of the receiving electrodes X0 to X63 while the drive signal is applied to one of the transmitting electrodes Y0 to Y39. The scanning direction to be controlled is controlled to be different depending on the transmission electrodes Y0 to Y39. In particular, in this embodiment, control is performed so that the scan direction changes alternately for each of the transmission electrodes Y0 to Y39. That is, the scanning direction is reversed between the even lines and the odd lines of the transmission electrodes Y0 to Y39.

  That is, in the even-line transmission electrodes Y0, Y2, Y4,..., As indicated by the arrow A, the reception electrodes X0 to X63 are selected from one end side close to the transmission unit 9 toward the other end side. On the other hand, as shown by arrow B, the reception electrodes X0 to X63 are selected from the other end side far from the transmission unit 9 toward the one end side in the transmission electrodes Y1, Y3, Y5.

  FIG. 11 is a timing chart showing the output state of the drive signal. FIG. 11A shows the case of even-numbered transmission electrodes Y0, Y2, Y4..., And FIG. The cases of Y3, Y5. FIG. 12 is a diagram illustrating a change state of the frequency of the drive signal.

  As shown in FIG. 11, a drive signal is applied to the transmission electrodes Y0 to Y39 corresponding to each scan period of the reception groups A to D according to the horizontal synchronization signal (HSYNC). ), In the case of the transmission electrodes Y0, Y2, Y4... Of even lines, the order is reception group A, reception group B, reception group C, and reception group D, and the frequency of the drive signal is f1, f2. , F3, and f4. On the other hand, as shown in FIG. 11B, in the case of the odd-numbered transmission electrodes Y1, Y3, Y5,..., The receiving group D, the receiving group C, the receiving group B, and the receiving group A are in this order. The frequency of f1 changes gradually to f4, f3, f2, and f1.

  In this way, the scanning direction is reversed between the transmission electrodes Y0, Y2, Y4... Of the even lines and the transmission electrodes Y1, Y3, Y5. The pattern and the change pattern in which the frequency gradually increases are repeated alternately.

  As described above, by controlling so that the frequency of the drive signal decreases as the signal propagation path length increases, the distortion of the waveform of the received signal that occurs when the signal propagation path length increases is reduced. Since variations in level signals due to differences in signal propagation path length can be suppressed, the touch position can be detected with high accuracy.

  Further, by controlling so that the frequency of the drive signal decreases as the signal propagation path length increases, the frequency of the drive signal changes while the drive signal is applied to one of the transmission electrodes Y0 to Y39. By changing the scanning direction for sequentially selecting the reception electrodes X0 to X63 according to the transmission electrodes Y0 to Y39, the change pattern of the frequency of the drive signal becomes different according to the transmission electrodes Y0 to Y39. For this reason, since the frequency spectrum of the noise radiated by applying the drive signal to the transmission electrodes Y0 to Y39 is dispersed and the noise level is lowered, the unnecessary radiation noise from the panel surface caused by the drive signal is reduced. Can do.

  Also, by controlling the frequency of the drive signal for each reception group A to D, the frequency of the drive signal does not change during each scan period of each reception group A to D, and the drive signal is controlled. It will be easy.

  Next, the operations of the transmission unit 9 and the reception unit 10 will be described in general with reference to timing diagrams. FIG. 13 is a timing diagram showing one frame of the application state of the drive signal to the transmission electrodes Y0 to Y39 in the transmission unit 9 and the selection state of the reception electrodes X0 to X63 in the reception unit 10. FIG. 14 is a timing diagram showing in detail the A part shown in FIG. 13 and the respective output signals of the IV conversion unit 41, the absolute value detection unit 43, and the integration unit 44 in the reception signal processing unit 32 of the reception unit 10. is there. Note that these signals are detected in a non-touch state in which no touch operation is performed.

  As shown in FIG. 13, first, a vertical synchronization signal (VSYNC) that defines the start timing of one frame is output from the control unit 11 to the transmission unit 9. Thereafter, a horizontal synchronization signal (HSYNC) that defines the timing of applying the drive signal to each of the transmission electrodes Y0 to Y39 is output from the control unit 11 to the transmission unit 9, and the transmission electrodes are transmitted in accordance with the horizontal synchronization signal (HSYNC). Y0 to Y39 are sequentially selected, and a drive signal is applied to the transmission electrodes Y0 to Y39.

  At this time, as shown in FIG. 14, pulse waves P1 to P16, each of which includes a predetermined number of pulses corresponding to one of the reception electrodes X0 to X15, are received by the transmission electrode Y0 as a drive signal. It is repeatedly applied 16 times corresponding to the number of electrodes X0 to X15 (16). In the receiving unit 10, the receiving electrodes X <b> 0 to X <b> 15 are sequentially selected by the electrode selecting unit 31 in synchronization with the application timing of the pulse waves P <b> 1 to P <b> 16, and output signals from the receiving electrodes X <b> 0 to X <b> 15 are received from the electrode selecting unit 31. The signals are sequentially input to the signal processing unit 32.

  The IV conversion unit 41 outputs sine waves S1 to S16 corresponding to the pulse waves P1 to P16. The sine waves S1 to S16 are full-wave rectified by the absolute value detection unit 43 and then integrated by the integration unit 44. It is processed. The output signal of the integration unit 44 is sampled by the sample hold unit 45 at a timing (sampling point) after a predetermined integration period, and a sampling voltage is output. The sampling voltage is AD converted by the AD conversion unit 46 and then output to the control unit 11 as a level signal.

  FIG. 14 shows the case where the reception electrodes X0 to X15 of the reception group A are selected in the transmission electrode Y0, but the same applies to other cases.

  Further, as shown in FIG. 13, the pulse waves P1 to P16 (drive signals) are large in current for each scan period of the divided areas R01 to R14 determined by the combination of the reception groups A to D and the transmission groups E and F. The frequency changes at the same time for each scanning period of the reception groups A to D.

  Specifically, in the transmission electrodes Y0 to Y19 of the transmission group E, in the selection period of the reception electrodes X0 to X15 of the reception group A, that is, the scan period of the divided region R01, the drive signal of the frequency f1 is output as the current i2. In the selection period of the reception electrodes X16 to X31 of the reception group B, that is, the scan period of the divided region R02, the drive signal of the frequency f2 is output as the current i3, and the reception electrodes X32 to X47 of the reception group C, that is, the scan of the divided region R03 In the period, the drive signal having the frequency f3 is output as the current i4, and in the scan period of the reception electrodes X48 to X63 of the reception group D, that is, the divided region R04, the drive signal having the frequency f4 is output as the current i5.

  On the other hand, in the transmission electrodes Y20 to Y39 of the transmission group F, during the selection period of the reception electrodes X0 to X15 of the reception group A, that is, the scan period of the divided region R11, the drive signal of the frequency f1 is output as the current i1. In the selection period of the receiving electrodes X16 to X31, that is, the scanning period of the divided region R12, the drive signal of the frequency f2 is output as the current i2, and in the receiving electrodes X32 to X47 of the receiving group C, that is, the scanning period of the divided region R13, A drive signal having a frequency f3 is output as a current i3, and a drive signal having a frequency f4 is output as a current i4 during the scan period of the reception electrodes X48 to X63 of the reception group D, that is, the divided region R14.

  The receiving electrodes X0 to X63 are selected in the arrangement order of the receiving electrodes X0 to X63. In the case of the transmitting electrodes Y0, Y2, Y4... Of the even lines and the transmitting electrodes Y1, Y3, Y5. The scanning direction, that is, the selection order of the receiving electrodes X0 to X63 is opposite to each other. Specifically, in the case of even-line transmission electrodes Y0, Y2, Y4..., It is selected from the reception electrode X0, and in the case of odd-line transmission electrodes Y1, Y3, Y5. The

  Next, the reduction of the unnecessary radiation noise level due to the frequency control of the drive signal described above will be described with a specific example. FIG. 15 is a diagram illustrating an example of frequency characteristics of unnecessary radiation noise generated in the touch panel device 1. FIG. 15A illustrates a case where the frequency of the drive signal is fixed to a constant frequency (3.02 MHz). FIG. 15B shows a case where the drive signal is changed within a predetermined change range (2.85 MHz to 3.02 MHz).

  As shown in FIG. 15A, when the frequency of the drive signal is fixed at 3.02 MHz, unwanted radiation noise is observed mainly at an integer multiple of 3.02 MHz. On the other hand, as shown in FIG. 15B, when the frequency of the drive signal is changed in the range of 2.85 MHz to 3.02 MHz, the spectrum distribution of unwanted radiation noise is dispersed and the noise level is several dB to It is 10 dB lower and it can be seen that unnecessary radiation noise can be reduced.

  As described above, in the present embodiment, the current control for changing the magnitude of the drive signal current for each of the divided regions R01 to R14 set according to the signal propagation path length, and the drive signal for each reception group A to D. By performing frequency control for changing the frequency of the signal, variation in the level signal due to the difference in signal propagation path length can be suppressed, the touch position can be detected accurately, and unnecessary radiation noise can be reduced.

  In the present embodiment, as shown in FIG. 6, the current control is performed to change the magnitude of the current of the drive signal for each of the divided regions R01 to R04, R11 to R14. It is also possible to change the magnitude of the current of the drive signal for each of these or for each of the reception groups A to D. Further, in the present embodiment, the frequency control for changing the frequency of the drive signal for each of the reception groups A to D is performed. However, for each of the divided regions R01 to R04, R11 to R14, or one of the reception electrodes X0 to X63. It is also possible to change the frequency of the drive signal for each book.

  In the present embodiment, as shown in FIG. 9, the scan direction is alternately changed for each of the transmission electrodes Y0 to Y39, that is, the scan direction is changed between the even lines and the odd lines of the transmission electrodes Y0 to Y39. The scanning directions of the even lines and the odd lines may be reversed from the illustrated example. Furthermore, a configuration in which the scan direction is changed for each of the plurality of transmission electrodes Y0 to Y39, for example, the scan direction is changed by three each. Furthermore, a configuration in which the scan direction is randomly changed is also possible.

  INDUSTRIAL APPLICABILITY The touch panel device according to the present invention has an effect of accurately detecting the touch position even when the size is increased, and is useful as a capacitive touch panel device, particularly a mutual capacitive touch panel device. .

1 Touch Panel Device 2 PDP (Plasma Display Panel)
3 Panel body 4 PDP control unit 6 Touch surface 7, Y0 to Y39 Transmission electrode 8, X0 to X63 Reception electrode 9 Transmission unit 10 Reception unit 11 Control unit 15 Touch detection area BF1 to BF5 Buffer A to D Reception group E, F Transmission Group R01-R04, R11-R14 Divided area

Claims (5)

A panel body in which a plurality of transmitting electrodes that run parallel to each other and a plurality of receiving electrodes that run parallel to each other are arranged in a lattice pattern,
A transmitter for sequentially selecting the transmission electrodes and applying a drive signal;
A receiving unit that sequentially selects the receiving electrodes and receives an output signal of the receiving electrodes in response to the drive signal and outputs a level signal for each electrode intersection;
A control unit that detects a touch position based on a level signal output from the reception unit and controls operations of the transmission unit and the reception unit;
The transmission unit is configured to be able to change the magnitude of the current of the drive signal,
The control unit controls the current of the driving signal to increase as the signal propagation path length from the transmitting unit to the receiving unit through the electrode intersection increases. apparatus.   The touch panel device according to claim 1, wherein the touch detection area is divided into a plurality of divided areas according to the signal propagation path length, and the magnitude of the current of the drive signal is set for each of the divided areas. . The transmission unit is configured to be able to change the frequency of the drive signal,
The touch panel device according to claim 1, wherein the control unit controls the frequency of the drive signal to be lowered as the signal propagation path length is increased.   4. The touch panel device according to claim 3, wherein the receiving electrodes are grouped into a predetermined number along the arrangement direction of the receiving electrodes, and the frequency of the drive signal is set for each group of the receiving electrodes. 5. .   The control unit performs control so that a scan direction for sequentially selecting the reception electrodes along the arrangement direction of the reception electrodes varies depending on the transmission electrodes while a drive signal is applied to one transmission electrode. The touch panel device according to claim 3 or 4, characterized in that:

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