JP2001067041A - Driving device of plasma display, sub field converting method of plasma display, and plasma display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always provide a linear gradation characteristic without depending on an average image level of an image, by counting the number of lighting pixels in each sub field, determining a luminance correcting amount based on the number of lighting pixels counted in each sub field, and determining the number of retain pulses in each sub field responsive to the luminance correcting amount. SOLUTION: When a digital image signal 1 is fed into a sub field converting circuit 2, a sub field converting portion 3 in the sub field converting circuit 2 divides the fed digital image signal 1 into each sub field, and determines the number of lightings and a lighting period respective to gradation. The sub field converting portion 3 counts the number of lighting pixels in each sub field with update of vertical synchronous period, namely one field update. A luminance correcting portion 4 determines the number of retain pulses in each sub field based on the number of lighting pixels referring to a luminance correcting table, and controls a retain pulse generating circuit 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma display driving device, a plasma display subfield conversion method, and a plasma display device.
In particular, the present invention relates to a plasma display driving device, a plasma display subfield conversion method, and a plasma display device that divide one field period of a video signal into a plurality of subfields and display gray scales by combining the subfields.

[0002]

2. Description of the Related Art Conventionally, when expressing the gradation of an image in a plasma display, one field is divided into a plurality of subfields, and the number of times of lighting and the lighting time of each cell in one subfield period are changed to change the gradation. Has been reproduced.

[0003] In the case of performing 256-level color display,
As shown in FIG. 7, one field is divided into eight subfields SF1, SF2, SF3, SF4, SF5, SF6,
If the light is divided into SF7 and SF8 and light is emitted for the number of times of light emission corresponding to 1, 2, 4, 8, 16, 32, 64, and 128 in each subfield, 256 gradations are obtained by combining the subfields. Color display can be performed. For example, in order to obtain a luminance of 18 gradations, pixels are selected in subfields SF2 and SF5, and no pixels are selected in other subfields.

An example of a plasma display device for performing the above-described gradation display is disclosed in JP-A-11-119729.
Is disclosed in Japanese Patent Application Laid-Open Publication No. HEI 9-203 (1995). This publication describes a configuration in which subfields of various intervals generated at specific times in a frame are generated based on a vertical synchronization signal, and the above-mentioned gradation display is performed based on a timing signal of the subfield.

[0005]

By the way, the plasma display has a problem that the luminance of each cell decreases as the number of lit cells, that is, the lit area increases.

[0006] This is because the discharge current of the entire panel increases due to the increase in the number of cells to be lit, and the voltage of the electrodes decreases due to the impedance of the electrodes in each cell. It is considered to decrease.

Due to this phenomenon, even in the above-described gradation display, the luminance of each subfield changes depending on the number of lighting cells in the subfield, the gradation characteristics become non-linear, and in some cases, the gradation inversion phenomenon. Will occur.

At present, as a countermeasure against this problem, an indirect countermeasure such as processing a video signal to correct characteristics is not taken directly for the drive circuit.

[0009]

A driving apparatus for a plasma display according to the present invention divides one field period of a video signal into a plurality of subfields, and displays gradation by a combination of the subfields. A counting means for counting the number of illuminated pixels in each subfield; a means for determining a luminance correction amount based on the counted number of illuminated pixels in each subfield; and Means for determining the number of sustain pulses.

The driving apparatus for a plasma display according to the present invention divides one field period of a video signal into a plurality of subfields, and displays gradation by a combination of the subfields.
Counting means for counting the number of illuminated pixels in each subfield; means for determining a luminance correction amount based on the counted number of illuminated pixels in each subfield; plasma in each subfield according to the luminance correction amount; Means for determining a voltage value applied to the display panel.

[0011] The subfield conversion method for a plasma display according to the present invention is a subfield conversion method for a plasma display, which divides one field period of a video signal into a plurality of subfields and displays gradation by a combination of the subfields. The video signal is divided for each subfield, the number of lighting in accordance with the gradation, when generating lighting information including at least lighting time, when counting the number of lighting pixels in the subfield, referring to the brightness correction information, The luminance correction amount is determined based on the counted number of lighting pixels in each subfield, and the number of sustain pulses in each subfield is determined according to the luminance correction amount.

A subfield conversion method for a plasma display according to the present invention is a subfield conversion method for a plasma display that divides one field period of a video signal into a plurality of subfields and displays gradation by a combination of the subfields. When the video signal is divided for each subfield and the lighting information including at least the lighting frequency and the lighting time is generated according to the gradation, the number of lighting pixels in the subfield is counted, and the luminance correction information is referred to. Determining a luminance correction amount based on the counted number of lighting pixels in each subfield, and determining a voltage value applied to the plasma display panel in each subfield according to the luminance correction amount. Is what you do.

A plasma display device according to the present invention uses the driving device or the subfield conversion method according to the present invention.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a driving apparatus for a plasma display according to the present invention. When the digital video signal 1 is input to the subfield conversion circuit 2, the input digital video signal is divided for each subfield in the subfield conversion unit 3 of the subfield conversion circuit 2, and the number of lightings is adjusted according to the gradation. The lighting time is determined.
Further, the subfield conversion unit 3 counts the number of illuminated pixels in each subfield by updating the vertical synchronization period, that is, updating one field, and based on the count, the brightness correction unit 4 refers to the brightness correction table to check the brightness of each subfield. The number of sustain pulses is determined, and sustain pulse generating circuit 7 is controlled.
Note that the subfield conversion unit 3 also serves as a lighting information generating unit that generates lighting information such as the number of times of lighting and a lighting time according to the gradation, and a unit that counts the number of lit pixels in the subfield. The brightness correction unit 4 also serves as a means for determining a brightness correction amount based on the counted number of lighting pixels in each subfield, and a means for determining the number of sustain pulses in each subfield according to the brightness correction amount. I have. The panel drive circuit 5 is a drive circuit for lighting the cells from lighting information, sustain pulses, and the like for each subfield, and an image is displayed on the panel display unit 6.

Therefore, a decrease in the discharge current due to an increase in the number of cells to be lit can be suppressed by controlling the number of sustain pulses, a variation in luminance can be prevented, and finally the gradation characteristics can be improved. The control of the number of sustain pulses corrects a decrease in luminance due to a decrease in discharge current by controlling the number of discharges.

The discharge current may be reduced by controlling the voltage value of the sustain pulse. By increasing the voltage, the rounding of the pulse waveform can be improved, and the discharge current value can be increased. Of course, the number of pulses to be maintained and the control of the voltage may be appropriately combined.

As a technique related to the present invention, Japanese Patent Laid-Open Publication No.
Japanese Patent No. 35205 discloses that the number of illuminated pixels in a certain scanning period is counted, and the number of sustain pulses applied to the scanning side electrode is changed according to the number of illuminated pixels.

Since the plasma display performs rewriting display for each pixel in a unit called a subfield, the subfield conversion circuit holds data for one field. In the present invention, in order to determine the number of illuminated cells in one screen, the data during the subfield conversion is counted simultaneously, and the result is passed to the luminance correction unit in the form of the number of illuminated cells in a certain subfield. The luminance correction unit corrects the number of sustain pulses with emphasis on the subfield having the largest number of lightings. On the other hand, Japanese Unexamined Patent Publication No.
In Japanese Patent Application Laid-Open No. 5 (1999) -1995, the number of illuminated pixels is counted for each scanning line. In the present invention, since the luminance correction is performed for each field, the uniformity of luminance is further improved.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 2 shows a circuit diagram of an embodiment of a driving apparatus for a plasma display according to the present invention.

As shown in FIG. 2, the digitized video signal 1 is input to the subfield converter 3. The subfield conversion unit 3 includes a subfield conversion configuration unit 31,
It comprises a counter 32 and a latch 33.

The subfield conversion unit 31 converts the digital video signal 1 into the number of lighting times and the lighting time according to the gradation for each subfield. Then, the subfield conversion unit 31 outputs the lighting information for each subfield that has been subjected to the subfield conversion to the panel drive circuit 5, and sends the data being subjected to the subfield conversion to the counter 32 to the counter 32. The counter 32 counts the number of illuminated pixels in each subfield by one field update, and the latch 12 updates the count for each field. In addition, if necessary, the counter 32 and the latch 33 are processed in the subfield conversion component 31.
A field memory is provided for delaying the lighting information which is subjected to the subfield conversion and output to the panel drive circuit 5 by one field.

The count output from the latch 33 of the subfield converter 3 is input to the luminance corrector 4. The brightness correction unit 4 includes a comparator 41, a brightness correction amount detection unit 42, and a sustain pulse number adjustment unit 43.

The comparator 41 determines the number of light emitting cells with respect to the total number of cells from the count number of each subfield output from the latch 33, and the luminance correction amount detecting section 42 performs luminance correction together with external control from a microcomputer or the like. Determine the amount and output the sustain pulse correction number. The luminance correction amount is obtained from the luminance correction coefficient α. The brightness correction coefficient α sets the sustain pulse increment when the number of lighting dots is 0 to 0, and increases the sustain pulse when the number of lighting dots is large. The sustain pulse number adjusting section 43 adds the sustain pulse correction number to the sustain pulse initial value and outputs the sustain pulse number to the sustain pulse generating circuit 7.

FIG. 3 is a diagram showing an ideal relationship between the number of lighting dots, the luminance, and the number of sustain pulses. At the lighting dot number Nmax without correction, the luminance is Lm due to the decrease in the discharge current.
It will go down to in. At this time, the number of sustain pulses is increased from the normal number of sustain pulses Pbase, and the number of sustain pulses is set to Pmax at Nmax, so as to compensate for a decrease in luminance.

The sustain pulse generating circuit 7 comprises a selector 71 and a counter 72. The selector 71 selects a predetermined subfield based on the subfield switching timing pulse, and outputs the number of sustain pulses to the counter 72. The sustain pulse generation clock is input to the counter 72, and a sustain pulse corresponding to the number of sustain pulses is output to the counter 72.
Is output to the panel drive circuit 5.

The panel drive circuit 5 is a drive circuit for driving the panel display unit 6 to light the cells from the lighting information for each subfield from the subfield conversion unit 3, the sustain pulse from the sustain pulse generation circuit 7, and the like. , And the data control gate array 51 of FIG. The panel display unit 6 includes the data-side drivers 61 and 62, the scanning-side drivers 63 and 64, and the plasma display panel 65 in FIG.
Consists of

The configuration and driving method of the panel drive circuit and the panel display section are described in the above-mentioned Japanese Patent Application Laid-Open No. 5-35205. FIG.
FIG. 5 is a block diagram showing a plasma display device including a panel display unit disclosed in Japanese Patent Laid-Open No. H10-207, FIG. 5 is a timing chart showing driving pulses applied to the plasma display panel, and FIG. 6 is a timing chart showing a drive pulse applied to the drive signal.

First, an example of a driving method of a plasma display will be described with reference to FIGS. As shown in FIGS. 4 and 5, low-frequency address pulses and high-frequency sustain pulses are applied to the scanning electrodes of the plasma display panel 65 connected to the scanning drivers 63 and 64. Is the discharge starting voltage Vf
Set near. When a certain dot (XL, YM) on the plasma display panel 65 is turned on, a pulse having a phase opposite to the address pulse is applied to the data side driver 61,
The voltage is applied to the data side electrode XL of the plasma display panel 65 connected to 62 and a voltage higher than the discharge starting voltage Vf is applied as a composite waveform to cause discharge. Once the discharge has occurred, the discharge is likely to occur due to the influence of the generated charged particles. Even if the pulse applied to the data side electrode is removed, the discharge continues only with the sustain pulse.

When a certain dot (XL, YM + 1) on the plasma display panel 65 is turned off, the scanning side electrode YM +
A pulse having the same phase as the address pulse applied to 1 is applied to the data side electrode XL, and a voltage smaller than Vf is applied as a composite waveform to suppress the occurrence of discharge.

In this embodiment, as shown in FIG.
The lighting information for each subfield from the subfield conversion unit 3 is output to the data drivers 61 and 62 via the data control gate array 51, and the data drivers 61 and 62 output the data electrodes X1 to Xend based on the lighting information.
Is applied with a sustain pulse driving waveform of a predetermined applied voltage.
The adjusted sustain pulse (sustain pulse obtained by adding the sustain pulse correction amount to the initial value of the sustain pulse) from the sustain pulse generating circuit 7 is output to the scanning drivers 63 and 64 via the data control gate array 51. The scanning drivers 63 and 64 scan the scanning electrodes Y1 to Ye based on the sustain pulse.
A sustain pulse driving waveform of a predetermined applied voltage is applied to nd.

In the embodiment described above, the decrease in luminance due to the decrease in the discharge current is suppressed by controlling the number of sustain pulses. However, it may be performed by controlling the voltage value of the sustain pulses. The configuration of the driving device that controls the sustain pulse voltage value is the same as the configuration in FIG. Of course, the number of pulses to be maintained and the control of the voltage may be appropriately combined.

[0034]

As described above, according to the present invention,
The number of lit cells in each subfield is counted, and the luminance level of each cell is kept constant by dynamically controlling the number of sustain pulses and / or the voltage value applied to the plasma display, thereby preventing a relative decrease in luminance. Thus, a linear gradation characteristic can always be obtained without depending on the APL (average image level) of the image.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a driving device of a plasma display of the present invention.

FIG. 2 is a block diagram of a specific embodiment of a plasma display driving device according to the present invention.

FIG. 3 is a diagram showing an ideal relationship between the number of lighting dots, the luminance, and the number of sustain pulses.

FIG. 4 is a block diagram showing a plasma display device.

FIG. 5 is a timing chart showing driving pulses applied to the plasma display panel.

FIG. 6 is a timing chart showing a driving pulse applied to the plasma display panel on which the sustain pulse correction has been performed.

FIG. 7 is a diagram showing a gradation display method of an image in a plasma display.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Video signal 2 Subfield conversion circuit 3 Subfield conversion part 4 Brightness correction part 5 Panel drive circuit 6 Panel display part 7 Sustain pulse generation circuit

Claims (9)

[Claims] 1. A plasma display driving apparatus which divides one field period of a video signal into a plurality of subfields and displays gradation by a combination of the subfields, counts the number of illuminated pixels in each subfield. Means, a means for determining a luminance correction amount based on the counted number of lighting pixels in each subfield, and means for determining the number of sustain pulses in each subfield according to the luminance correction amount. Driving device for a plasma display. 2. A plasma display driving apparatus which divides one field period of a video signal into a plurality of sub-fields and displays gradation by a combination of the sub-fields, counts the number of illuminated pixels in each sub-field. Means for determining a luminance correction amount based on the counted number of lighting pixels in each subfield, and means for determining a voltage value applied to the plasma display panel in each subfield according to the luminance correction amount And a driving device for a plasma display. 3. The plasma display driving device according to claim 2, wherein the voltage value is a voltage value of a sustain pulse applied between a scan electrode and a data electrode. 4. The driving device for a plasma display according to claim 1, wherein the video signal is divided into subfields, and the number of times of lighting and the lighting time are adjusted in accordance with a gradation. It has lighting information generating means for generating at least lighting information including, and the counting processing by the means for counting the number of lighting pixels in the subfield is performed together with the lighting information generating processing by the lighting information generating means. Drive device for plasma display. 5. A subfield conversion method for a plasma display, which divides one field period of a video signal into a plurality of subfields and displays gradation by a combination of the subfields, wherein the video signal is divided for each subfield. When generating lighting information including at least the number of times of lighting and lighting time according to the gradation, count the number of lighting pixels in the subfield, refer to the luminance correction information, and count the number of lighting pixels in each subfield. A subfield conversion method for a plasma display, wherein a luminance correction amount is determined based on the number of pixels, and the number of sustain pulses in each subfield is determined according to the luminance correction amount. 6. A subfield conversion method for a plasma display, which divides one field period of a video signal into a plurality of subfields and displays gradation by a combination of the subfields, wherein the video signal is divided into subfields, When generating lighting information including at least the number of times of lighting and lighting time in accordance with the gradation, the number of lighting pixels in the subfield is counted, and the lighting in each of the counted subfields is counted by referring to the luminance correction information. A subfield conversion method for a plasma display, wherein a luminance correction amount is determined based on the number of pixels, and a voltage value applied to a plasma display panel is determined in each subfield according to the luminance correction amount. 7. The method according to claim 6, wherein the voltage value is a voltage value of a sustain pulse applied between a scan electrode and a data electrode. Method. 8. A plasma display device using the plasma display drive device according to claim 1. Description: 9. A plasma display apparatus using the method for converting a subfield of a plasma display according to claim 5. Description: