JP2007264317A - Drive unit for display panel and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress complication of an arithmetic processing circuit for a gradation signal and to suppress deviation of display gradation due to distortion of an applied voltage waveform which is caused by various causes. <P>SOLUTION: A drive unit for a display panel including a plurality of pixels performing a gradation display corresponding to the effective value of an applied voltage includes; a signal electrode driving circuit 20 and a scan electrode driving circuit 30 which apply voltages corresponding to gradations to be displayed, to selected pixels while successively selecting the plurality of pixels repeatedly; a voltage monitor circuit 40 which monitors voltages applied to selected pixels; and a voltage correction circuit 50 which corrects the pulse width of an amplitude of the signal voltage applied by the signal voltage driving circuit 20, on the basis of a monitoring result. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a display panel driving device including a plurality of pixels that perform gradation display according to an effective value of an applied voltage, and a display device including the driving device.

  Conventionally, in a simple matrix liquid crystal display device, the occurrence of so-called crosstalk has been a problem, and measures to reduce the influence of crosstalk have been studied.

  One cause of crosstalk is voltage distortion (crosstalk noise) of the scanning signal. This is caused by the influence of the switching of the signal voltage at the signal electrode reaching the scanning voltage at the scanning electrode capacitively coupled via the liquid crystal element.

  In order to suppress the above crosstalk, the technique disclosed in Patent Document 1 employs a configuration in which the gradation value in the gradation signal is counted and the pulse width and pulse height of the applied voltage are corrected based on the counting result. is doing.

  That is, in the above technique, the influence on the scanning signal due to the change of the gradation pulse of all gradations is classified into four levels, and a weighting value is defined for each level. Then, regarding the gradations written to all the pixels related to the selected scan electrode, the total of the weight values corresponding to the levels to which the gradations belong is counted.

Therefore, in the above technique, a decoder for decoding the gradation, a weighting circuit for outputting a weighting value when the gradation is decoded, an OR circuit, and a counter circuit are provided for each gradation. .
JP-A-8-160392 (publication date: June 12, 1996)

  However, the conventional technique has a problem that the circuit configuration for counting the gradation values is complicated. In particular, this problem becomes remarkable when the number of gradations increases.

  Further, in the above conventional technique, the influence of the crosstalk caused by the above-described crosstalk noise, that is, the switching of the signal voltage at the signal electrode reaches the scanning voltage of the scanning electrode capacitively coupled through the liquid crystal element. Even if it is effective against the crosstalk generated by this, it cannot necessarily be said that the display gradation shift due to the distortion of the applied voltage waveform caused by another cause is necessarily effective. As other causes that cause distortion of the applied voltage waveform, various causes are conceivable, for example, the rising or falling of the applied voltage due to the load connected to the signal electrode or the scan electrode.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to suppress the complexity of an arithmetic processing circuit for a gradation signal and to display gradation due to distortion of an applied voltage waveform caused by various causes. This is to suppress the deviation.

  A display panel drive device according to the present invention is a display panel drive device including a plurality of pixels that perform gradation display according to an effective value of an applied voltage. A voltage applying unit that applies a voltage corresponding to a gradation to be displayed to the selected pixel, a voltage monitoring unit that monitors a voltage applied to the selected pixel, and the voltage. And a voltage correction unit that corrects a voltage applied by the voltage application unit based on a result of monitoring by the monitoring unit.

  The drive device having the above configuration performs display by driving a display panel including a plurality of pixels that perform gradation display according to the effective value of the applied voltage, such as a liquid crystal display panel. For this purpose, the voltage application means sequentially selects a plurality of pixels and applies a voltage corresponding to the gradation to be displayed to the selected pixels.

  And in the said structure, while providing the voltage monitoring means which monitors the voltage applied with respect to a selection pixel, the voltage correction means which correct | amends the voltage applied by a voltage application means based on the monitoring result is provided.

  As a result, it is possible to realize a more appropriate display that corrects the deviation of the effective value of the applied voltage caused by the distortion of the applied voltage waveform and suppresses the deviation of the display gradation.

  In the above configuration, since correction is performed based on the monitoring result, the conventional technique described in the background art section, that is, a technique of determining the correction amount by counting the gradation value of the gradation signal. In contrast, it is possible to simplify the circuit configuration without requiring a complicated calculation using gradation values.

  Further, in the above configuration, since the correction is performed based on the monitoring result, the display gradation shift due to the crosstalk generated by the influence of the switching of the signal voltage at the signal electrode on the scanning voltage at the scanning electrode is caused. The display gradation shift due to distortion of the applied voltage waveform caused by various causes is not limited.

  In the display panel drive device according to the present invention, the voltage correction unit is based on a monitoring result by the voltage monitoring unit in a previous selection period when the same gradation is displayed in an adjacent selection period related to the same pixel. Thus, the voltage applied by the voltage applying means in the subsequent selection period can be corrected.

  In the above configuration, when a still image is displayed or even when a moving image is displayed by writing the same screen more than once, the same floor is used in the adjacent selection period (temporally adjacent selection period) for the same pixel. When the key is displayed, the voltage applied in the subsequent selection period can be corrected based on the monitoring result in the previous selection period.

  In the display panel drive device according to the present invention, the voltage monitoring unit calculates an effective value of the voltage applied to the selected pixel, and at the same time, an ideal effective value preset for the gradation to be displayed. And the calculated effective value can be compared to determine the voltage correction value in the voltage correction means.

  The voltage monitoring means may include storage means for storing an ideal effective value set in advance for each gradation value indicated by the gradation signal.

  In the display panel drive device according to the present invention, the voltage correction means may correct the amplitude of the voltage, the pulse width of the voltage, or both of them.

  A display device according to the present invention can be configured to include any one of the display panel driving devices described above and a display panel driven by simple matrix. The display panel may include a plurality of scanning electrodes and signal electrodes that form pixels at positions intersecting with each other, and the voltage monitoring unit may monitor the voltage applied to each signal electrode. The voltage applied to the scan electrode may be monitored, and the voltage of each signal electrode with respect to the selected scan electrode may be monitored. Which voltage is to be monitored may be determined in consideration of the magnitude of the influence on the display gradation.

  Alternatively, the display device according to the present invention may include any one of the display panel driving devices described above and an active matrix driving display panel. The display panel includes a plurality of scanning electrodes and signal electrodes that form pixels at positions intersecting each other, and the voltage monitoring unit may monitor the voltage applied to each signal electrode.

  The display panel driving apparatus according to the present invention is configured to apply a voltage corresponding to a gradation to be displayed to a selected pixel while sequentially selecting a plurality of pixels and applying the voltage to the selected pixel. Voltage monitoring means for monitoring the voltage to be applied, and voltage correction means for correcting the voltage applied by the voltage application means based on the monitoring result by the voltage monitoring means.

  With the above configuration, it is possible to realize a more appropriate display that corrects the deviation of the effective value of the applied voltage caused by the distortion of the applied voltage waveform and suppresses the deviation of the display gradation.

  In the above configuration, since correction is performed based on the monitoring result, the conventional technique described in the background art section, that is, a technique of determining the correction amount by counting the gradation value of the gradation signal. In contrast, it is possible to simplify the circuit configuration without requiring a complicated calculation using gradation values.

  Further, in the above configuration, since the correction is performed based on the monitoring result, the display gradation shift due to the crosstalk generated by the influence of the switching of the signal voltage at the signal electrode on the scanning voltage at the scanning electrode is caused. The display gradation shift due to distortion of the applied voltage waveform caused by various causes is not limited.

  An embodiment of the present invention will be described with reference to FIGS. 1 to 7 as follows.

  Based on FIG. 1, the structure of the liquid crystal display device 1 of this embodiment is demonstrated. The liquid crystal display device 1 includes a liquid crystal display panel (LCD) 10, a signal electrode drive circuit 20, a scan electrode drive circuit 30, a voltage monitor circuit 40, and a voltage correction circuit 50.

  The liquid crystal display panel 10 is a simple matrix drive (passive matrix drive) liquid crystal display panel. As is conventionally known, the liquid crystal display panel 10 sandwiches a liquid crystal layer between substrates facing each other, and each substrate has a plurality of signal electrodes (SEG electrodes) 12 and scanning electrodes (scan electrodes) formed in a stripe shape. COM electrodes) 13 are provided. Each signal electrode 12 and each scanning electrode 13 are arranged so as to cross each other through a liquid crystal layer, and a pixel is formed in each crossing region.

  The signal electrode drive circuit 20 drives the signal electrode 12 by a pulse width modulation method. That is, a signal voltage having a pulse width corresponding to the gradation indicated by the gradation signal is generated based on the gradation signal input from the outside, and is output to each signal electrode 12.

  The scan electrode drive circuit 30 applies a scan voltage to the selected scan electrode 13 while sequentially selecting each scan electrode 13.

  The relationship between the signal voltage and the scanning voltage and the voltage applied to the pixel, which is the difference between them, is shown in the timing chart of FIG. In FIG. 2, the pulse width of the signal voltage is illustrated as being constant, but the pulse width actually changes based on the grayscale signal. As a result, the lengths of the on period and the off period in FIG. 2 change. Each pixel performs gradation display according to the effective value of the applied voltage (corresponding to the area of the hatched area in FIG. 2).

  The voltage monitor circuit 40 is for determining a correction value for correcting the signal voltage by measuring the signal voltage applied to each signal electrode 12. A specific configuration of the voltage monitor circuit 40 is shown in FIG.

  The voltage monitor circuit 40 includes a memory 41, an A / D conversion circuit 42, an integration circuit 43, and a comparison operation circuit 44. Among these, one set of the A / D conversion circuit 42, the integration circuit 43, and the comparison operation circuit 44 is provided corresponding to each signal electrode 12.

  In this voltage monitor circuit 40, the A / D conversion circuit 42 converts the signal voltage of each signal electrode 12 into digital data while sampling, and the integration circuit 43 integrates the digital data for each selection period. Thereby, the effective value of the signal voltage in each selection period is calculated. The sampling interval is set to be sufficiently fine for each selection period.

  Then, the comparison operation circuit 44 compares the effective value of the signal voltage in each selection period with the ideal effective value set in advance for the gradation to be displayed by the signal voltage in the selection period. A correction value for correcting the voltage is determined.

  The ideal effective value is determined in advance for each gradation to be displayed and stored in the memory 41. When a signal voltage corresponding to a certain gradation is applied to the signal electrode 12, an ideal effective value corresponding to the gradation is output to the comparison operation circuit 44.

  For this purpose, for example, an ideal effective value corresponding to each gradation may be stored in an address corresponding to a digital value of the gradation signal (a 6-bit digital value in the case of 64 gradation display). . That is, the ideal effective value of 0 gradation can be stored in address “000000”, the ideal effective value of 1 gradation can be stored in address “000001”, and the ideal effective value of 64 gradations can be stored in address “111111”. That's fine.

  The correction value determined by the comparison operation circuit 44 is a pulse width adjustment value Δt for adjusting the pulse width of the signal voltage or an amplitude adjustment value ΔV for adjusting the amplitude of the signal voltage.

  Here, the pulse width adjustment value Δt and the amplitude adjustment value ΔV will be described with reference to FIGS. 4 (a) to 4 (d).

  The ideal waveform of the signal voltage is a rectangular waveform having an amplitude V as shown in FIG. 4A, and the voltage value V is in the selection period (one horizontal period) H during the period H ′ corresponding to the gradation to be displayed. By being applied, an effective voltage Ve = V × H ′ / H is obtained.

  On the other hand, as shown in FIG. 4B, the actual signal voltage waveform is a waveform whose rise and fall are dull due to the influence of a load connected to the signal electrode 12 and the like. Therefore, the actual effective voltage deviates from the ideal effective voltage corresponding to the area of the shaded area A in FIG. This shift causes a shift in display gradation.

  Therefore, the area corresponding to the area of the shaded portion A is compensated by the shaded portion B in FIG. For this purpose, the rising timing of the signal voltage is accelerated from α to α ′. The pulse width adjustment value Δt indicates the time width to be advanced.

  Alternatively, the area corresponding to the area of the shaded portion A is compensated by the shaded portion B ′ in FIG. For this purpose, the amplitude of the signal voltage is increased from V to V ′. The amplitude adjustment value ΔV indicates the voltage width to be increased.

  Here, the waveform of the signal voltage is adjusted by one of the pulse width and amplitude of the signal voltage, but the waveform of the signal voltage may be adjusted by both of the above.

  In order to calculate the pulse width adjustment value Δt or the amplitude adjustment value ΔV in the comparison arithmetic circuit 44, the pulse width adjustment value Δt using the effective value of the signal voltage from the integration circuit 43 and the ideal effective value from the memory 41 as variables. Alternatively, a function calculation for calculating the amplitude adjustment value ΔV may be set in advance. Alternatively, a look-up table that outputs the pulse width adjustment value Δt or the amplitude adjustment value ΔV using the effective value of the signal voltage from the integration circuit 43 and the ideal effective value from the memory 41 as inputs may be used.

  Next, the voltage correction circuit 50 shown in FIG. 1 will be described. The voltage correction circuit 50 controls the signal electrode drive circuit 20 on the basis of the pulse width adjustment value Δt or the amplitude adjustment value ΔV sent from the voltage monitor circuit 40, so that FIG. 4C or FIG. The waveform of the signal voltage explained based on (1) is adjusted. In FIG. 1, the voltage correction circuit 50 is illustrated as a block different from the signal electrode drive circuit 20, but the voltage correction circuit 50 may be incorporated in the signal electrode drive circuit 20.

  Here, the adjustment of the waveform of the signal voltage is effective adjustment when displaying the same gradation. Therefore, the voltage correction circuit 50 determines whether or not the same gradation is displayed in a selection period that is temporally adjacent to the same pixel, and the voltage in the previous selection period is displayed only when the same gradation is displayed. Based on the monitoring result (Δt or ΔV) by the monitor circuit 40, the signal voltage applied by the signal electrode drive circuit 20 in the subsequent selection period is corrected.

  As for the case where the same gradation is displayed in the selection period that is temporally adjacent to the same pixel, the frame constituting the moving image is displayed in addition to the case where the still image is displayed or the moving image is displayed. It can be considered that the frame frequency (refresh rate) of the liquid crystal display panel 10 is larger than the rate.

  Generally, the refresh rate is about 75 Hz (75 times written per second) or higher, and the frame rate constituting the moving image is about 30 fps (30 frames per second), so at least the same screen is written twice. It will be. Therefore, the monitoring result by the voltage monitoring circuit 40 can be obtained by the first writing, and the waveform of the signal voltage in the second writing can be adjusted based on the monitoring result.

  Note that the above correction can be performed even when the same gradation is not displayed in a selection period that is temporally adjacent to the same pixel. For this purpose, the voltage correction circuit 50 stores the monitor result (Δt or ΔV) obtained by each gradation display, and uses the monitor result stored when the gradation display is performed next time to use the signal voltage. The waveform may be adjusted.

  As described above, in the liquid crystal display device 1, only the signal voltage of the signal electrode 12 is monitored by the voltage monitor circuit 40. The reason is that since the pulse width of the signal voltage changes depending on the display gradation, the pulse width becomes small depending on the display gradation, so that the influence of the dullness of the waveform tends to increase.

  On the other hand, in order to more accurately monitor the voltage applied to the selected pixel, the voltage between the selected scan electrode 13 and each signal electrode 12 may be monitored.

  For this purpose, as shown in FIG. 5, a switching circuit 60 for connecting the selected scan electrode 13 to the voltage monitor circuit 40 is added to the liquid crystal display device 1. What is necessary is just to add the difference circuit (not shown) which calculates | requires the difference of the voltage of each signal electrode 12, and the voltage of the selected scanning electrode 13, and supplies to each A / D conversion circuit 42.

  Alternatively, in the case where the signal voltage hardly causes the waveform to become dull, but rather the waveform distortion in the scanning voltage causes a shift in display gradation, only the scanning voltage of the scanning electrode 13 is applied as shown in FIG. You may make it monitor.

  That is, instead of the voltage monitor circuit 40, a voltage monitor circuit 40 ′ for monitoring the scan voltage of the scan electrode 13 is provided, and the amplitude adjustment value ΔV from the voltage monitor circuit 40 ′ is used instead of the voltage correction circuit 50. A voltage correction circuit 50 ′ that adjusts the waveform of the scanning voltage by controlling the scanning electrode driving circuit 30 based on the above may be provided.

  In this case, since the ideal waveform of the scanning voltage is constant regardless of the display gradation, it is not necessary to store an ideal effective value for each display gradation.

  Further, the liquid crystal display device 1 may include an active matrix driving liquid crystal display panel 10 ′ instead of the simple matrix driving liquid crystal display panel 10.

  As is well known in the art, the liquid crystal display panel 10 ′ has a liquid crystal layer sandwiched between substrates facing each other, and a plurality of signal electrodes 12 ′ and scanning electrodes 13 each formed in a stripe shape on one substrate. Is equipped with. Each signal electrode 12 and each scanning electrode 13 are arranged so as to cross each other, and a switching element (not shown) and a pixel electrode 14 are formed corresponding to each crossing portion. Further, a common electrode (not shown) is formed on almost the entire surface of the other substrate.

  In this case, since the display gradation is determined by the signal voltage applied to the signal electrode 12 ′, the voltage monitor circuit 40 monitors the signal voltage applied to each signal electrode 12 ′ as in the case of FIG. become.

  As described above, the display panel driving apparatus of the present invention drives the display panels 10 and 10 ′ including a plurality of pixels that perform gradation display according to the effective value of the applied voltage, and the voltage applying unit. The signal electrode drive circuit 20 and the scan electrode drive circuit 30 functioning as the voltage monitor circuits 40 and 40 ′ functioning as voltage monitoring means, and the voltage correction circuits 50 and 50 ′ functioning as voltage correction means.

  The signal electrode drive circuit 20 and the scan electrode drive circuit 30 apply a voltage corresponding to the gradation to be displayed to the selected pixel while sequentially selecting the plurality of pixels sequentially. The voltage monitor circuits 40 and 40 'monitor the voltage applied to the selected pixel. The voltage correction circuits 50 and 50 ′ correct the voltage applied by the signal electrode drive circuit 20 or the scan electrode drive circuit 30 based on the monitoring result by the voltage monitor circuits 40 and 40 ′.

  Thereby, in the liquid crystal display device 1, it is possible to realize a more appropriate display by correcting the deviation of the effective value of the applied voltage caused by the distortion of the applied voltage waveform and suppressing the deviation of the display gradation.

  Further, since the liquid crystal display device 1 performs the correction based on the monitoring result, the conventional technique described in the background art column, that is, the correction value is determined by counting the gradation value of the gradation signal. Unlike the technique, the above correction can be realized by a relatively simple circuit configuration as shown in FIG. 3 without requiring a complicated calculation using the gradation value.

  Further, since the liquid crystal display device 1 performs the correction based on the monitoring result, the display gradation of the display tone due to the crosstalk generated when the influence of the switching of the signal voltage at the signal electrode reaches the scanning voltage at the scanning electrode. Not only the deviation but also the display gradation deviation due to the distortion of the applied voltage waveform caused by various causes can be suppressed.

  1 and 5 to 7, the voltage monitor circuits 40 and 40 ′ are arranged on the opposite side of the signal electrode drive circuit 20 or the scan electrode drive circuit 30 with the liquid crystal display panels 10 and 10 ′ interposed therebetween. However, it may be arranged on the same side as the signal electrode drive circuit 20 or the scan electrode drive circuit 30. However, in this case, since the arrangement of the wiring is somewhat complicated, a configuration in which the wiring is arranged on the opposite side is desirable.

  Further, the voltage monitor circuits 40 and 40 ′ may be incorporated in the signal electrode drive circuit 20 or the scan electrode drive circuit 30 (for example, incorporated in one IC).

  The present invention is not limited to a liquid crystal display panel, but is another display panel including a plurality of pixels that perform gradation display according to the effective value of an applied voltage, such as a PDP (plasma display panel) or an EL (electroluminescence) display panel. Etc.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention can be suitably used to improve display quality in displays such as personal computers, PDAs, mobile phones, and digital cameras.

It is a block diagram which shows the structure of the liquid crystal display device which concerns on one Embodiment of this invention. 2 is a timing chart showing a relationship between a signal voltage, a scanning voltage, and a voltage applied to a pixel in the liquid crystal display device of FIG. FIG. 2 is a block diagram illustrating a configuration of a voltage monitor circuit in the liquid crystal display device of FIG. 1. (A) is a waveform diagram showing an ideal waveform of the signal voltage, (b) is a waveform diagram showing an actual waveform of the signal voltage, and (c) is a pulse width for correcting the waveform of (b). It is a waveform diagram which shows the state to adjust, (d) is a waveform diagram which shows the state which adjusts an amplitude in order to correct | amend the waveform of (b). It is a block diagram which shows the modification of the liquid crystal display device of FIG. It is a block diagram which shows the other modification of the liquid crystal display device of FIG. It is a block diagram which shows the further another modification of the liquid crystal display device of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 10 Liquid crystal display panel (display panel)
10 'liquid crystal display panel (display panel)
20 Signal electrode drive circuit (voltage application means)
30 Scan electrode drive circuit (voltage application means)
40 Voltage monitor circuit (voltage monitor means)
40 'voltage monitoring circuit (voltage monitoring means)
50 Voltage correction circuit (voltage correction means)
50 'voltage correction circuit (voltage correction means)
60 Switching circuit

Claims (12)

In a driving device for a display panel including a plurality of pixels that perform gradation display according to an effective value of an applied voltage,
Voltage application means for applying a voltage corresponding to the gradation to be displayed on the selected pixel while sequentially selecting the plurality of pixels;
Voltage monitoring means for monitoring the voltage applied to the selected pixel;
A display panel drive device comprising: voltage correction means for correcting a voltage applied by the voltage application means based on a monitoring result by the voltage monitoring means.   When the same gradation is displayed in the adjacent selection period related to the same pixel, the voltage correction means is based on the monitoring result by the voltage monitoring means in the previous selection period, and the voltage application means in the subsequent selection period. The display panel drive device according to claim 1, wherein a voltage to be applied is corrected.   The voltage monitoring means calculates an effective value of the voltage applied to the selected pixel, and compares the ideal effective value preset for the gradation to be displayed with the calculated effective value. 3. The display panel drive device according to claim 2, wherein a correction value of a voltage in the voltage correction means is determined.   4. The display panel drive device according to claim 3, wherein the voltage monitor means includes storage means for storing an ideal effective value preset for each gradation value indicated by the gradation signal.   5. The display panel drive device according to claim 1, wherein the voltage correction unit corrects the amplitude of the voltage. 6.   6. The display panel drive device according to claim 1, wherein the voltage correction unit corrects a pulse width of the voltage. A display panel drive device according to any one of claims 1 to 6,
A display device comprising a display panel driven by a simple matrix. The display panel includes a plurality of scanning electrodes and signal electrodes that form pixels at positions intersecting each other,
The display device according to claim 7, wherein the voltage monitoring unit monitors a voltage applied to each signal electrode. The display panel includes a plurality of scanning electrodes and signal electrodes that form pixels at positions intersecting each other,
The display device according to claim 7, wherein the voltage monitoring unit monitors a voltage applied to each scanning electrode. The display panel includes a plurality of scanning electrodes and signal electrodes that form pixels at positions intersecting each other,
The display device according to claim 7, wherein the voltage monitoring unit monitors a voltage of each signal electrode with respect to a selected scanning electrode. A display panel drive device according to any one of claims 1 to 6,
A display device comprising an active matrix drive display panel. The display panel includes a plurality of scanning electrodes and signal electrodes that form pixels at positions intersecting each other,
The display device according to claim 11, wherein the voltage monitoring unit monitors a voltage applied to each signal electrode.

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