KR100312506B1 - Adjusting Method for Brightness and Contrast of Plasma Display Panel Driving with Radio Frequency Signal - Google Patents

Abstract

The present invention relates to a brightness and contrast control method of a high frequency plasma display panel.

In the method of driving a high frequency plasma display panel for generating sustain discharge using a high frequency signal, the method of controlling brightness and contrast of the high frequency plasma display panel according to the present invention comprises the steps of: generating a clock signal of a high frequency band having a predetermined period; A sustain discharge step having a plurality of subfields in which a high frequency signal is switched in accordance with a control pulse based on a count value of a clock signal to maintain a high frequency sustain discharge for a predetermined period; When the luminance or contrast control signal is input from the outside, the method comprises adjusting the switching time of the high frequency signal according to the control pulse to adjust the luminance and contrast by subtracting the sustain discharge period for each of the plurality of subfields.

As a result, the brightness and contrast of the screen can be adjusted to a unit of second (ns), thereby making it possible to precisely adjust analogically.

Description

{Adjusting Method for Brightness and Contrast of Plasma Display Panel Driving with Radio Frequency Signal}

The present invention relates to a high frequency plasma display panel, and more particularly, to a method of adjusting brightness and contrast of a high frequency plasma display panel.

Plasma Display Panel (hereinafter referred to as 'PDP') is a display device using visible light generated from a phosphor when ultraviolet rays generated by gas discharge excite the phosphor. PDP is thinner and lighter than Cathode Ray Tube (CRT), which has been the mainstay of display means, and it has the advantage of being able to realize high-definition large screen and having a wide viewing angle. PDP is composed of a plurality of discharge cells arranged in a matrix form, one discharge cell constitutes a pixel of the screen.

1 is a longitudinal sectional view showing a discharge cell structure of a conventional AC surface discharge PDP. Referring to FIG. 1, the upper plate 20 and the lower plate 22 are provided in parallel with a predetermined distance. The scan electrode 26 and the discharge sustaining electrode 27 are formed side by side with an AC driving signal supplied to the rear surface of the upper substrate 24 constituting the upper plate 20 to form a surface discharge. The dielectric layer 28 formed on the scan electrode 26 and the discharge sustain electrode 27 has a function of accumulating charges during discharge. The protective layer 30 applied over the dielectric layer 28 protects the dielectric layer 28 from sputtering during discharge to extend the life of the pixel cell. On the lower substrate 32 constituting the lower plate 22, a data electrode 34 for address discharge is formed to cross at right angles to the scan electrode 26 and the discharge sustain electrode 27. On the lower substrate 32 and the data electrode 34, a dielectric layer 36 is formed on the entire surface to form wall charges during discharge. In addition, the partition wall 42 is vertically formed between the upper plate 20 and the lower plate 22. The partition wall 42 forms the discharge region 38 of the cell together with the upper plate 20 and the lower plate 22, and distinguishes the discharge cells from each other to block mutual interference between neighboring cells. The phosphor 40 is coated on the dielectric layer 36 and the partition wall 42 of the lower plate 22. The discharge region 38 is filled with a mixed gas of He + Xe or Ne + Xe.

Briefly describing the light emission process, an address discharge occurs between the scan electrode 26 and the data electrode 34 to form wall charges in the upper and lower dielectric layers 28 and 36. The formed wall charges lower the discharge voltage required for surface discharge. In the cells selected by the address discharge, sustain discharge occurs between the two electrodes 26 and 27 by an alternating current signal alternately supplied to the scan electrode 26 and the discharge sustain electrode 27. At this time, ultraviolet rays are generated in the discharge region 38 in the process of transition after the discharge gas is excited. The generated ultraviolet rays excite the phosphor 40 to generate visible light, thereby realizing an image of the PDP.

In AC surface discharge PDP, sustain discharge occurs only once in a very short moment for one spherical pulse. The charged particles generated during surface discharge form wall charges by moving the discharge path formed between the scan electrode 26 and the discharge sustain electrode 27 according to the polarity of the electrodes. The discharge is stopped because the discharge voltage in the discharge region 38 is reduced by the formed wall charge. Accordingly, in the AC surface discharge PDP, most of the discharge time is consumed as a preparation step for the formation of the wall charge and the next discharge, thereby lowering the discharge efficiency. In order to solve this problem, a PDP (hereinafter referred to as an RF PDP) in which discharge is maintained by a radio frequency signal has been proposed. In the RF PDP, electrons vibrating in the discharge area under the force of the high frequency signal supplied to the PDP continuously ionize the discharge gas, thereby causing continuous discharge for most of the discharge time.

2 is a longitudinal sectional view showing a discharge cell structure of the RF PDP. Referring to FIG. 2, the RF PDP includes a data electrode 62 formed on the lower substrate 60, a dielectric layer 64 formed on the lower substrate 60 and the data electrode 62, and a data electrode 62. The scanning electrode 66 formed on the dielectric layer 64 so as to be orthogonal to each other, the partition wall 68 vertically formed on the dielectric layer 64 to distinguish each discharge cell, and the phosphor coated on the inner wall of the partition wall 68 ( 70, the high frequency electrode 74 formed on the rear surface of the upper substrate 72 in a direction parallel to the scan electrode 66 with a predetermined space therebetween, the upper substrate 72, the lower substrate 60 and the partition wall 68 ) Is provided with a discharge region 76 formed to be surrounded by.

Referring to the discharging process of the RF PDP, an AC driving signal is supplied between the data electrode 62 and the scan electrode 66 so that an address discharge occurs between the two electrodes 62 and 66. In this process, electrons and charged particles are generated in the discharge region 76 of the selected discharge cell. Then, as shown in FIG. 2, continuous sustain discharge occurs while the electrons 78 in the discharge region 76 vibrate by the high frequency signal supplied to the high frequency electrode 74. At this time, the scan electrode 66 becomes the ground electrode of the high frequency signal, and sustain discharge is generated between the high frequency electrode 74 and the scan electrode 66. Electrons 78 vibrating between the high frequency electrode 74 and the scan electrode 66 excite the discharge gas in the discharge region 76 and continuously discharge. Ultraviolet rays generated during address discharge and sustain discharge excite the phosphor 70 to generate visible light, thereby realizing an image of the PDP.

In the AC surface discharge PDP and the RF PDP, a gray scale of 256 gray scales representing stepwise brightness required for image display is implemented by an ADS (Addressing Display Separated: ADS) driving method. 3 is a diagram illustrating an ADS driving method for expressing a gray level of one frame in the PDP. One frame for 16.67 ms is time-divided into eight subfields SF1 to SF8 according to the gradation. Each subfield is divided into an addressing period in which address discharge is performed and a sustain discharge period in which sustain discharge is performed. In each subfield, the width of the preset addressing period is the same while the width of the sustain discharge period is different. The sustain discharge period is set in advance so as to increase at a rate of 2 ⁿ (n = 0,1,2,3,4,5,6,7) in each subfield according to the luminance relative ratio.

4 and 5 are waveform diagrams showing driving signals supplied to the electrodes of the PDP for each subfield when the ADS is driven in the AC surface discharge PDP and the RF PDP, respectively. First, in the AC surface discharge PDP of FIG. 4, during the addressing period, a positive pulse is applied to the data electrode 34 and a negative pulse is applied to the scan electrode 26 to generate an address discharge in the selected discharge cell. In the sustain discharge period, alternating current pulses are alternately applied to the scan electrodes 26 and the discharge sustain electrodes 27. As a result, sustain discharge occurs in the addressed discharge cells. As an AC signal that causes sustain discharge, a square pulse having a frequency of 200 Hz to 300 Hz and a pulse width of about 10 to 20 Hz is used. On the other hand, in the case of the RF PDP shown in FIG. 5, a trigger pulse for starting a sustain discharge is supplied to the scan electrode 66 after an address discharge occurs between the data electrode 62 and the scan electrode 66 in the addressing period. The discharge initiated by the trigger pulse leads to continuous sustain discharge by the high frequency signal supplied to the high frequency electrode 74. The frequency of the high frequency signal causing sustain discharge is about several tens of MHz. The period of the corresponding high frequency signal is about several tens of kHz, which is very short compared to the pulse width of the AC pulse used in the AC surface discharge PDP.

In the conventional AC surface discharge PDP, the brightness and contrast of the screen are controlled by adjusting the number or duty ratio of the AC pulses applied in the sustain discharge period allocated to each subfield. In contrast, a specific method for adjusting the brightness or contrast of a screen has not been proposed in the RF PDP. In the method of controlling the number of AC pulses, the brightness and contrast are adjusted while increasing or decreasing the AC pulses arranged in each sustain period by the number unit. However, it is difficult to finely adjust in time because the AC pulse is controlled by a unit of a relatively long pulse width of 10 ~ 20㎲. In adjusting the duty ratio of the AC pulse, there is a problem that may affect the discharge effect during sustain discharge. Since the period of the high frequency signal applied for the sustain discharge in the RF PDP is very short, such as several tens of kHz, it is not suitable to apply the brightness control method conventionally used in the AC surface discharge PDP as it is. Accordingly, in order to improve the display quality of the RF PDP, there is a demand for a method of effectively controlling luminance and contrast.

Accordingly, an object of the present invention is to provide a brightness and contrast adjustment method of a high frequency plasma display panel.

1 is a longitudinal cross-sectional view showing a discharge cell structure of a conventional AC surface discharge plasma display panel.

2 is a longitudinal sectional view showing a discharge cell structure of a high frequency plasma display panel;

3 is a diagram illustrating an ADS driving method for expressing a gray level of one frame in a plasma display panel;

4 is a waveform diagram showing a driving waveform for driving an AC surface discharge plasma display panel.

Fig. 5 is a waveform diagram showing driving waveforms for driving a high frequency plasma display panel.

6 and 7 illustrate a method of adjusting luminance of a high frequency plasma display panel according to an exemplary embodiment of the present invention.

8 is a waveform diagram showing a method of adjusting the sustain discharge time.

9A to 9E illustrate a method of adjusting contrast of a high frequency plasma display panel according to an exemplary embodiment of the present invention.

10 is a system block diagram schematically showing a system configuration for adjusting the brightness and contrast of a high frequency plasma display panel.

<Description of Symbols for Main Parts of Drawings>

20: top plate 22: bottom plate

24,72: upper substrate 26,66: scanning electrode

27: discharge sustaining electrode 28,36,64: dielectric layer

30: protective layer 32, 60: lower substrate

34,62: data electrode 38,76: discharge area

40,70 Phosphor 42,68 Bulkhead

74: high frequency electrode 78: electron

100: clock generator 102: system control unit

104: clock counter 106: luminance control unit

108: contrast control unit 110: high frequency generation unit

112: plasma display panel 114: switch

In order to achieve the above object, the brightness and contrast control method of the high frequency plasma display panel of the present invention, in the driving method of the high frequency plasma display panel for generating a sustain discharge using a high frequency signal, a high frequency band clock signal having a certain period Generating; A sustain discharge step having a plurality of subfields in which a high frequency signal is switched in accordance with a control pulse based on a count value of a clock signal to maintain a high frequency sustain discharge for a predetermined period; When the luminance or contrast control signal is input from the outside, the method comprises adjusting the switching time of the high frequency signal according to the control pulse to adjust the luminance and contrast by subtracting the sustain discharge period for each of the plurality of subfields.

Other objects and features of the present invention in addition to the above object will be apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 6 to 10.

6 and 7 illustrate a method of adjusting luminance of an RF PDP according to an embodiment of the present invention. In the luminance control method according to the present invention, the luminance of the entire screen is controlled by decreasing or increasing the time at which the actual sustain discharge occurs at a predetermined rate for each sustain discharge period pre-assigned for each subfield. To this end, the control signal for turning on / off the high frequency signal supplied to the high frequency electrode is synchronized with a clock pulse having a very short pulse width in units of 같이 as shown in FIG. FIG. 6 shows a case where the high frequency signal is applied in all periods for each sustain discharge period set for each subfield, and thus the sustain discharge occurs to show the maximum luminance. On the other hand, in order to lower the brightness of the screen as compared with the case of FIG. 6, the time at which the actual sustain discharge occurs in each sustain discharge period set for each subfield is reduced by a certain ratio as shown in FIG. In the case of FIG. 7, the time at which the actual sustain discharge occurs is adjusted to half of the preset sustain discharge period for each subfield. This indicates a state in which the luminance is adjusted to 50% of the maximum luminance shown in FIG. 6. In the conventional AC surface discharge PDP, since the width of the AC pulse causing the sustain discharge is relatively long, the sustain discharge cannot be finely controlled in time. However, in the method of adjusting the luminance of the RF PDP according to the present invention, since the period of the high frequency signal causing the sustain discharge is very short in several tens of milliseconds, the sustain discharge can be turned off at any time using a clock pulse having a pulse width in milliseconds. Accordingly, by finely adjusting the time of sustain discharge, the luminance can be precisely controlled analogously.

9A to 9E illustrate a method of adjusting contrast of an RF PDP according to an embodiment of the present invention. As in the case of adjusting the luminance, the contrast is controlled by decreasing or increasing the time at which the actual sustain discharge occurs at a different rate for each sustain discharge period preset in each subfield. 9A illustrates a frame timing diagram of a basic screen in which contrast is not adjusted. 9B and 9D show frame timing diagrams when contrast is adjusted, respectively. 9C and 9E show waveform diagrams of a high frequency signal corresponding to the cases of FIGS. 9B and 9D, respectively. In order to adjust the contrast of the screen higher than in the case of FIG. 9A, as shown in FIGS. 9B to 9C, the time at which the actual sustain discharge occurs for each subfield is adjusted. That is, the actual sustain discharge time in the sustain discharge period allocated to the eighth subfield SF8 is set to be the same as in the case of FIG. 9A, and is gradually allocated from the seventh subfield SF7 to the first subfield SF1. The ratio of the time when the actual maintenance discharge occurs in the sustained discharge period is adjusted gradually. Then, the bright portion of the screen in charge of the eighth subfield SF8 maintains the basic screen state of FIG. 9A, and the screen portion in charge of the seventh to first subfields SF7 to SF1 gradually darkens. As a result, the luminance difference between the bright and dark portions of the screen is increased, resulting in a higher contrast than the case of FIG. 9A. In order to adjust the contrast of the screen lower than in the case of FIG. 9A, as shown in FIGS. 9D to 9E, the time at which the actual sustain discharge occurs in each subfield is adjusted. That is, the actual sustain discharge time in the sustain discharge period allocated to the first subfield SF1 is set to be the same as in the case of FIG. 9A, and is gradually allocated from the second subfield SF8 to the eighth subfield SF8. The ratio of the time when the actual maintenance discharge occurs in the sustained discharge period is adjusted gradually. Then, the dark portion of the screen that is in charge of the first subfield SF1 maintains the basic screen state of FIG. 9A, and the screen portion that is in charge of the second to eighth subfields is gradually darkened. As a result, the luminance difference between the dark part and the bright part of the screen is reduced, resulting in a lower contrast than the case of FIG. 9A. Meanwhile, when adjusting the sustain discharge time in the second subfield SF2 to the seventh subfield SF7, as shown in FIGS. 9B to 9E, the sustain discharge time and the eighth discharge time in the first subfield SF1 are shown. The time is adjusted to linearly decrease or increase in consideration of the linearity between the sustain discharge times in the subfield SF8.

10 is a system block diagram schematically illustrating a system configuration for adjusting the brightness and contrast of an RF PDP. Referring to FIG. 10, a luminance and contrast adjustment system according to the present invention includes a clock generator 100 for generating a clock pulse, a clock counter for counting clock pulses, and supplying a synchronization signal to the system controller 102. 104, a luminance adjusting unit 106 and a contrast adjusting unit 108 for supplying a luminance and contrast adjusting signal to the system control unit 102, a high frequency generating unit 110 for generating a high frequency signal, and a high frequency generating unit The switch 114 connected between the 110 and the high frequency electrode 74 of the PDP 112 and the switch 114 are controlled in accordance with the luminance and contrast adjustment signals in synchronization with the synchronization signal input from the clock counter 104. The system control unit 102 is provided.

When the switch 114 is turned on at the end of the addressing period of each subfield, the high frequency signal generated from the high frequency generator 110 is supplied to the high frequency electrode of the PDP 112 to maintain the discharge. Begins. In the present invention, the brightness and the contrast are adjusted by adjusting the time when the switch 114 is turned off, that is, the time when the sustain discharge stops for each subfield. The system control unit 102 controls the on / off operation of the switch 114. The system controller 102 generates a control signal for turning off the switch 114 in synchronization with the synchronization signal generated from the clock counter 104. Since the high frequency signal has a short period of several tens of kHz, a pulse having a short pulse width in ㎱ can be used as the clock pulse counted by the clock counter 104. Accordingly, the switch 114 can be turned on / off in units of 되어 so that brightness and contrast can be finely adjusted analogously. The system control unit 102 generates a control signal for turning on the switch 114 at the end of the addressing period in each subfield. On the other hand, the timing of generating the control signal for turning off the switch 114 in the system control unit 102 depends on the control signal input from the brightness control unit 106 and the contrast control unit 108. When the user adjusts the brightness of the screen to high through the input device, the brightness controller 106 supplies a corresponding control signal to the system controller 102. The timing at which the system control unit 102 outputs a control signal for turning off the switch 114 in synchronization with the synchronization signal of the clock counter 104 by the input control signal is delayed by a predetermined ratio for each subfield. . As a result, the time during which the actual sustain discharge takes place in each subfield is lengthened by a certain ratio, thereby increasing the brightness of the entire screen. On the other hand, if the user adjusts the brightness low, the time point at which the control signal is output so that the switch 114 is turned off by the system controller 102 is advanced by a predetermined ratio for each subfield. As a result, the time during which the actual sustain discharge occurs in each subfield is shortened by a certain ratio, thereby lowering the brightness of the entire screen. In the method of adjusting the contrast of the screen, the contrast adjusting unit 108 is a point in time when the system control unit 102 generates a control signal such that the switch 114 is turned off for each subfield similarly to the case of adjusting the brightness. The contrast is adjusted by adjusting by the control signal generated from the.

As described above, in the brightness and contrast adjustment method of the high frequency plasma display panel according to the present invention, when the brightness and contrast are adjusted by the user, the off-time point of the high frequency signal is adjusted in the sustain discharge period pre-assigned for each subfield. Adjust the time when actual maintenance discharge occurs. As a result, the brightness and contrast of the screen can be adjusted in units of watts compared with the conventional AC surface discharge plasma display panel which controls the number of discharge pulses during sustain discharge.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (5)

In a driving method of a high frequency plasma display panel for generating sustain discharge using a high frequency signal, Generating a clock signal of a high frequency band having a predetermined period; A sustain discharge step having a plurality of subfields in which the high frequency signal is switched and the high frequency sustain discharge is maintained for a predetermined period in accordance with a control pulse based on a count value of the clock signal; And adjusting the switching time of the high frequency signal according to the control pulse when the luminance or contrast control signal is input from the outside to adjust the luminance and contrast by adding or subtracting the sustain discharge period for each of the plurality of subfields. A brightness and contrast adjustment method of a high frequency plasma display panel. The method of claim 1, When the luminance control signal is input, the brightness and contrast control method of the high frequency plasma display panel, characterized in that the sustain discharge period is added or subtracted at a constant rate for each of the plurality of subfields for which the sustain discharge period is set differently. The method of claim 1, When the contrast control signal is input, the luminance and contrast control of the high frequency plasma display panel is characterized by relatively adding or subtracting the sustain discharge periods of at least two or more subfields among a plurality of subfields having different sustain discharge periods. Way. The method of claim 1, And a period of the clock signal is in nanosecond units. delete