EP1796065B1 - Apparatus for driving a plasma display panel with APL pre-measurement and corresponding method - Google Patents
Apparatus for driving a plasma display panel with APL pre-measurement and corresponding method Download PDFInfo
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- EP1796065B1 EP1796065B1 EP06125606A EP06125606A EP1796065B1 EP 1796065 B1 EP1796065 B1 EP 1796065B1 EP 06125606 A EP06125606 A EP 06125606A EP 06125606 A EP06125606 A EP 06125606A EP 1796065 B1 EP1796065 B1 EP 1796065B1
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- 238000000034 method Methods 0.000 title claims description 7
- 238000007726 management method Methods 0.000 description 14
- 230000007423 decrease Effects 0.000 description 10
- 238000010586 diagram Methods 0.000 description 5
- 230000003247 decreasing effect Effects 0.000 description 3
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- 101001137935 Aplysia californica Calcium-dependent protein kinase C Proteins 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000013501 data transformation Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 239000004973 liquid crystal related substance Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 230000004304 visual acuity Effects 0.000 description 1
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/28—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using luminous gas-discharge panels, e.g. plasma panels
- G09G3/2803—Display of gradations
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/28—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using luminous gas-discharge panels, e.g. plasma panels
- G09G3/288—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using luminous gas-discharge panels, e.g. plasma panels using AC panels
- G09G3/291—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using luminous gas-discharge panels, e.g. plasma panels using AC panels controlling the gas discharge to control a cell condition, e.g. by means of specific pulse shapes
- G09G3/294—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using luminous gas-discharge panels, e.g. plasma panels using AC panels controlling the gas discharge to control a cell condition, e.g. by means of specific pulse shapes for lighting or sustain discharge
- G09G3/2944—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using luminous gas-discharge panels, e.g. plasma panels using AC panels controlling the gas discharge to control a cell condition, e.g. by means of specific pulse shapes for lighting or sustain discharge by varying the frequency of sustain pulses or the number of sustain pulses proportionally in each subfield of the whole frame
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0271—Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/06—Adjustment of display parameters
- G09G2320/0606—Manual adjustment
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/06—Adjustment of display parameters
- G09G2320/0626—Adjustment of display parameters for control of overall brightness
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/06—Adjustment of display parameters
- G09G2320/066—Adjustment of display parameters for control of contrast
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
- G09G2330/04—Display protection
- G09G2330/045—Protection against panel overheating
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2360/00—Aspects of the architecture of display systems
- G09G2360/16—Calculation or use of calculated indices related to luminance levels in display data
Definitions
- the present invention relates to an apparatus for driving a plasma display panel including brightness/contrast control means for receiving video input data, for modifying the video levels of the video input data in accordance with external adjustments data and for outputting modified video data and power measurement means for measuring a power level of the modified video data. Furthermore, the present invention relates to a corresponding method.
- a PDP plasma display panel
- a PDP controls the gray level by modulating the number of light pulses per frame (sustain pulses). This time-modulation will be integrated by the eye over a period corresponding to the eye time response. Since the video amplitude is portrayed by the number of light pulses, occurring at a given frequency, more amplitude means more light pulses and thus more "ON" time. For this reason, this kind of modulation is also known as PWM, pulse width modulation.
- the number of real gray levels is limited.
- the number of gray levels is more or less equal to 256.
- the problem is that the picture quality is affected when the number of displayed levels is reduced.
- Contrast and brightness controls are usually part of the so called “front-end”, while PDP specific functions (gamma function, Sub-field encoding, etc) are part of the so called “back-end” of the display (see Fig. 3 ).
- APL Average Power Level
- the aim of power management is to keep the power consumption constant (see Fig. 1 ) and to have a peak luminance as high as possible. So for every APL value, the maximal number of sustain pulses to be used is fixed. This number of sustains decreases when the APL increases, and vice versa as shown in Fig. 2 .
- the number of sustain pulses is not limited by the power consumption, but by the available time for sustaining. For this reason, the power consumption of peak-white pictures will be lower than for the other pictures. Consequently, also the power consumption decreases for low APL levels (compare Fig. 1 ).
- the following table shows an allocation of the values of the number of sustain pulses to the average power levels according to Fig. 2 .
- the average power levels are coded on 10 bits.
- APL Total Number of sustains 0 1000 1 1000 2 1000 3 1000 4 1000 5 1000 • • • 50 1000 51 1000 52 1000 53 1000 54 1000 55 1000 56 999 57 998 58 996 59 994 60 991 61 988 62 984 63 979 64 975 65 971 66 966 67 962 68 958 69 954 70 950 71 946 72 942 73 938 74 933 75 929 • • • • 295 449 296 448 297 447 298 446 299 445 300 444 301 442 302 441 303 440 304 439 305 438 • • • • 1005 102 1006 102 1007 102 1008 102 1009 102 1010 102 1011 101 1012 101 1013 101 1014 101 1015 101 1016 101 1017 100 1018 100 1019 100
- the problem of the standard implementation of power management is that when the energy of the input picture of the back-end decreases, the number of sustain pulses increases.
- Fig. 3 shows a principle block diagram of the driving unit of a plasma panel 1.
- the video input signal is first processed in the front end 2.
- the front end includes a scaling unit 4 for adapting the size of the picture to that of the panel.
- the scaled input signal is supplied to a brightness/contrast control block 5.
- This control block 5 receives external signals for tuning or modifying the brightness or the contrast of the picture.
- the video signal is processed respectively and supplied to the back end 3.
- the signal is processed in a usual path including a gamma block 6, a dithering block 7 and an encoding block 8.
- the gamma block 6 performs a data transformation with a look up table in accordance to a nearly quadratic gamma function.
- the output signal of the gamma block 6 is transmitted to the dithering unit 7 which will add for example 4 bit dithering in order to have more discrete video levels at the output.
- the sub field encoding 8 generates sub field data for the video signal.
- the resulting sub field data are sent to the plasma panel 1.
- the output signal of the front end 2 is input into an APL measurement block 10.
- This block supplies an APL level of the brightness/contrast tuned video signal to the power management 9.
- the power management 9 controls the gamma unit 6 and the encoding unit 8. Furthermore, the power management 9 delivers sustain information to the plasma panel 1.
- the APL (measured in the back-end 3) is decreasing; this means that the number of sustains is increasing. This increases partly the contrast.
- the user in fact has to reduce the contrast of the picture by around 4.
- the picture is divided by more than 4, the number of gray levels really used is also divided by around 4. The picture quality is rather low in this case.
- EP-A-1 014 330 discloses a display device including an interface device, which can prevent degradation in resolving power of gray scales for a dark picture signal, wherein the interface device sets a dynamic range of an analog-digital converter according to a peak value of an analog picture signal and EP-A-1 347 434 discloses controlling contrast and brightness of a display panel by means of either a gamma correction unit or a timing and control unit by controlling luminance of the display panel by varying a number of sustain pulses per second. Furthermore, it already has been disclosed a luminance adjusting apparatus for a plasma display panel allowing an adjustment of the luminance of a whole panel in a continuous manner in US-A-5 757 343 .
- an apparatus for driving a plasma display panel including brightness/contrast control means for receiving video input data, for modifying the video levels of the video input data in accordance with external adjustment data and for outputting modified video data, first power measurement means for measuring a power level of said modified video data and for supplying a first video data power level, second power measurement means for measuring a power level of said video input data and for supplying a second video data power level, generator means for generating a third video data power level between said first video data power level and said second video data power level as long as the second power level is higher than the first power level or for generating the third video data power level equal to the larger one of said first and second video data power levels, and data processing means (9) for calculating the maximum number of sustain pulses per frame applicable to said modified video data on the basis of said third video data power level and for controlling the display of said modified video data on said plasma display panel (1) respectively.
- a method for driving a plasma display panel by providing video input data, modifying the video levels of the video input data in accordance with external adjustment data in order to obtain modified video data, measuring a power level of said modified video data and a respective first video data power level, measuring a power level of said video input data and providing a second video data power level, generating a third video data power level between said first video data power level and said second video data power level as long as the second power level is higher than the first power level or generating the third video data power level equal to the larger one of said first and second video data power levels, and processing said modified video data for calculating the maximal number of sustain pulses per frame applicable to said modified video data on the basis of said third video data power level and controlling the display of said modified video data on said plasma display panel respectively.
- the advantage of the present invention is that the APL level of the input video signal can be considered in the back end before the video signal is modified by the brightness/contrast control unit.
- the adjustment of brightness and contrast affects the picture quality on the plasma panel less negative.
- the third power level is the larger one of the first power level and the second power level.
- the power levels measured in the driving apparatus are average power levels related to one picture.
- the data processing means may include power management means for keeping the power consumption of the plasma display panel constant irrespective of the power control information.
- the purpose of the invention presented here is to improve the behavior of power management regarding contrast and brightness control.
- FIG. 3 A comparison between Figures 3 and 4 shows that except for the units 11 and 12 the other elements 1 to 10 of Fig. 4 are also present in the apparatus of Fig. 3 . Therefore, as to the description of these units it is referred to Fig. 3 .
- the content of the front-end 2 and the back-end 3 are only given as examples. It is only mandatory in the front-end 2 to have the APL f measurement unit 11 before the brightness/contrast control 5.
- the APL measured in the front-end is equal to 300.
- the user wants to reduce the contrast by 2. Since the APL in the back-end 3 will decrease, the power management unit 9 will use the APL measured in the front-end 11, this means 300, and so the same number of sustains is used. Therefore in order to reduce the contrast by 2, the video has to be divided by 2.
- the APL measured in the back-end 3 is equal to 150 in this case.
- the power management 9 uses the value 300 as input.
- the invention presented in this document aims at improving the picture quality when the contrast and/or the brightness are reduced. This is achieved by implementing an APL (Average Power Level) function in the front-end and using the measured value in the back-end.
- APL Average Power Level
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Description
- The present invention relates to an apparatus for driving a plasma display panel including brightness/contrast control means for receiving video input data, for modifying the video levels of the video input data in accordance with external adjustments data and for outputting modified video data and power measurement means for measuring a power level of the modified video data. Furthermore, the present invention relates to a corresponding method.
- A PDP (plasma display panel) uses a matrix array of discharge cells, which can only be "ON", or "OFF". Also unlike a CRT (cathode ray tube) or LCD (liquid crystal display) in which gray levels are expressed by analog control of the light emission, a PDP controls the gray level by modulating the number of light pulses per frame (sustain pulses). This time-modulation will be integrated by the eye over a period corresponding to the eye time response. Since the video amplitude is portrayed by the number of light pulses, occurring at a given frequency, more amplitude means more light pulses and thus more "ON" time. For this reason, this kind of modulation is also known as PWM, pulse width modulation.
- For all displays using pulse width modulation, the number of real gray levels is limited. For PDP, in case of standard coding the number of gray levels is more or less equal to 256.
- These various gray levels can only be used when the dynamic of the input picture is at its maximum (in case of 8 bit signal, video values between 0 and 255). In other cases, when the dynamic is reduced (in particular because of contrast or brightness parameters), the number of displayed levels will further decrease.
- The problem is that the picture quality is affected when the number of displayed levels is reduced.
- Unfortunately, when reducing the contrast (by dividing by a certain factor) and/or the brightness (subtracting a certain coefficient from the picture), the maximum value of the picture decreases and so the picture quality is reduced.
- Contrast and brightness controls are usually part of the so called "front-end", while PDP specific functions (gamma function, Sub-field encoding, etc) are part of the so called "back-end" of the display (see
Fig. 3 ). -
- The aim of power management is to keep the power consumption constant (see
Fig. 1 ) and to have a peak luminance as high as possible. So for every APL value, the maximal number of sustain pulses to be used is fixed. This number of sustains decreases when the APL increases, and vice versa as shown inFig. 2 . - In peak-white pictures (low APL at the left side of
Fig. 2 ), the number of sustain pulses is not limited by the power consumption, but by the available time for sustaining. For this reason, the power consumption of peak-white pictures will be lower than for the other pictures. Consequently, also the power consumption decreases for low APL levels (compareFig. 1 ). - The following table shows an allocation of the values of the number of sustain pulses to the average power levels according to
Fig. 2 . The average power levels are coded on 10 bits.APL Total Number of sustains 0 1000 1 1000 2 1000 3 1000 4 1000 5 1000 • • • 50 1000 51 1000 52 1000 53 1000 54 1000 55 1000 56 999 57 998 58 996 59 994 60 991 61 988 62 984 63 979 64 975 65 971 66 966 67 962 68 958 69 954 70 950 71 946 72 942 73 938 74 933 75 929 • • • 295 449 296 448 297 447 298 446 299 445 300 444 301 442 302 441 303 440 304 439 305 438 • • • 1005 102 1006 102 1007 102 1008 102 1009 102 1010 102 1011 101 1012 101 1013 101 1014 101 1015 101 1016 101 1017 100 1018 100 1019 100 1020 100 1021 100 1022 100 1023 100 - As indicated above, the problem of the standard implementation of power management is that when the energy of the input picture of the back-end decreases, the number of sustain pulses increases.
-
Fig. 3 shows a principle block diagram of the driving unit of aplasma panel 1. The video input signal is first processed in thefront end 2. The front end includes ascaling unit 4 for adapting the size of the picture to that of the panel. The scaled input signal is supplied to a brightness/contrast control block 5. This control block 5 receives external signals for tuning or modifying the brightness or the contrast of the picture. The video signal is processed respectively and supplied to theback end 3. Within theback end 3 the signal is processed in a usual path including a gamma block 6, a dithering block 7 and anencoding block 8. The gamma block 6 performs a data transformation with a look up table in accordance to a nearly quadratic gamma function. The output signal of the gamma block 6 is transmitted to the dithering unit 7 which will add for example 4 bit dithering in order to have more discrete video levels at the output. Afterwards, thesub field encoding 8 generates sub field data for the video signal. The resulting sub field data are sent to theplasma panel 1. - In a parallel path within the
back end 3 the output signal of thefront end 2 is input into anAPL measurement block 10. This block supplies an APL level of the brightness/contrast tuned video signal to the power management 9. The power management 9 controls the gamma unit 6 and theencoding unit 8. Furthermore, the power management 9 delivers sustain information to theplasma panel 1. - With this arrangement, it is for example interesting to see what happens when the user is decreasing the contrast and/or the brightness.
- When decreasing the contrast and/or the brightness, the APL (measured in the back-end 3) is decreasing; this means that the number of sustains is increasing. This increases partly the contrast.
- For example, the user wants to reduce the contrast by 2 for a picture, which has an APL of 300 (10 bit value). So originally this picture has in average approximately 444*300/1024=130 sustains/cell, and can have a peak luminance of 444 sustains (compare table shown above).
- To obtain in average 130/2=65 sustains/cell, the user in fact has to reduce the contrast of the picture by around 4. For an APL value of 70, according to the table, the average number of sustain is equal to 950*70/1024=65. The peak luminance in this case is also reduced since all brightness levels of the whole picture are divided by more than 4, the maximum value of the picture will not be higher than 255/4.3=60 (this represents 950/4.3=222 sustains). But since, the picture is divided by more than 4, the number of gray levels really used is also divided by around 4. The picture quality is rather low in this case.
- A power controlling circuit for controlling power in a plasma display unit, which adjusts display brightness relative to an input image signal in accordance with an external control signal in the plasma display unit, is already known from
US 2002/140640 A1 .EP-A-1 014 330 discloses a display device including an interface device, which can prevent degradation in resolving power of gray scales for a dark picture signal, wherein the interface device sets a dynamic range of an analog-digital converter according to a peak value of an analog picture signal andEP-A-1 347 434 discloses controlling contrast and brightness of a display panel by means of either a gamma correction unit or a timing and control unit by controlling luminance of the display panel by varying a number of sustain pulses per second. Furthermore, it already has been disclosed a luminance adjusting apparatus for a plasma display panel allowing an adjustment of the luminance of a whole panel in a continuous manner inUS-A-5 757 343 . - In view of that, it is the object of the present invention to provide a driving apparatus for a plasma display panel which improves the picture quality, when the brightness and contrast of the picture are reduced. Furthermore, a respective method shall be provided.
- According to the present invention this object is solved by an apparatus for driving a plasma display panel including brightness/contrast control means for receiving video input data, for modifying the video levels of the video input data in accordance with external adjustment data and for outputting modified video data, first power measurement means for measuring a power level of said modified video data and for supplying a first video data power level, second power measurement means for measuring a power level of said video input data and for supplying a second video data power level, generator means for generating a third video data power level between said first video data power level and said second video data power level as long as the second power level is higher than the first power level or for generating the third video data power level equal to the larger one of said first and second video data power levels, and data processing means (9) for calculating the maximum number of sustain pulses per frame applicable to said modified video data on the basis of said third video data power level and for controlling the display of said modified video data on said plasma display panel (1) respectively.
- Furthermore, there is provided a method for driving a plasma display panel by providing video input data, modifying the video levels of the video input data in accordance with external adjustment data in order to obtain modified video data, measuring a power level of said modified video data and a respective first video data power level, measuring a power level of said video input data and providing a second video data power level, generating a third video data power level between said first video data power level and said second video data power level as long as the second power level is higher than the first power level or generating the third video data power level equal to the larger one of said first and second video data power levels, and processing said modified video data for calculating the maximal number of sustain pulses per frame applicable to said modified video data on the basis of said third video data power level and controlling the display of said modified video data on said plasma display panel respectively.
- The advantage of the present invention is that the APL level of the input video signal can be considered in the back end before the video signal is modified by the brightness/contrast control unit. Thus, the adjustment of brightness and contrast affects the picture quality on the plasma panel less negative.
- According to a preferred embodiment of the present invention the third power level is the larger one of the first power level and the second power level. With this feature it is possible that the total power of the picture remains unchanged even if the brightness or contrast of the picture is varied.
- Preferably, the power levels measured in the driving apparatus are average power levels related to one picture.
- Furthermore, the data processing means may include power management means for keeping the power consumption of the plasma display panel constant irrespective of the power control information.
- The present invention will now be explained in more detail along with the attached figures, showing in:
- Fig. 1
- a diagram of the power consumption over the average power level;
- Fig. 2
- a diagram of the number of sustain pulses over the average power level;
- Fig. 3
- a block diagram of a driving unit of a plasma panel according to the prior art;
- Fig. 4
- a block diagram of a driving unit of a plasma panel according to the present invention.
- The purpose of the invention presented here is to improve the behavior of power management regarding contrast and brightness control.
- The idea is that when contrast and/or brightness decrease, the power management should not increase the number of sustains. Otherwise the user needs to further decrease the contrast and/or the brightness. Then, the picture quality would further decrease, too.
- This can be done by using for power management 9 the same APL value than the one before the contrast/brightness decrease. This value can be measured with the help of an additional
APL measurement unit 11 placed in the front-end 2 before the contrast/brightness control unit 5 as shown inFig. 4 . - However, this value cannot be used directly. Otherwise when the energy is increased by the front-end 2 (by increasing the contrast and/or the brightness for example) the power on the
display 1 could be higher than the maximum value allowed. Therefore in this case the power has to be reduced by the power management block 9. - A comparison between
Figures 3 and4 shows that except for theunits other elements 1 to 10 ofFig. 4 are also present in the apparatus ofFig. 3 . Therefore, as to the description of these units it is referred toFig. 3 . - As already mentioned, there are two APL measurements: one in the front-
end 2, and the other one in the back-end 3. The power management unit 9 will use the maximum of these two values to determine the number of sustains to be displayed. This maximum is provided by acomparator unit 12. So the implementation is very simple. - The content of the front-
end 2 and the back-end 3 are only given as examples. It is only mandatory in the front-end 2 to have the APLf measurement unit 11 before the brightness/contrast control 5. - Since this solution can only lead the power management unit 9 to use a higher value of APL, the number of sustains to be displayed can only be reduced. This means that the power consumption will be reduced in this case. This is a real advantage as to the tuning of contrast or brightness.
- In a variant implementation, the
comparator unit 12 can be replaced by agenerator unit 12 that generates an APL level that is comprised between the two measured APL levels. This APL value should be greater than APLb and, if APLf > APLb, said APL value can be any value comprised between APLb and APLf. - Now, the example of the introductory part of the description shall be regarded again. The APL measured in the front-end is equal to 300. The user wants to reduce the contrast by 2. Since the APL in the back-
end 3 will decrease, the power management unit 9 will use the APL measured in the front-end 11, this means 300, and so the same number of sustains is used. Therefore in order to reduce the contrast by 2, the video has to be divided by 2. The APL measured in the back-end 3 is equal to 150 in this case. - The power management 9 uses the value 300 as input. The average number of sustains is equal to 444*150/1024=65, but the maximum value of the picture will be 255/2=127. So the number of gray levels really used will be divided by around 2. This means that the number of gray levels really used is twice as big as in the standard implementation. So finally the picture quality is significantly improved.
- In summary, the invention presented in this document aims at improving the picture quality when the contrast and/or the brightness are reduced. This is achieved by implementing an APL (Average Power Level) function in the front-end and using the measured value in the back-end.
Claims (6)
- Apparatus for driving a plasma display panel (1) including- brightness/contrast control means (5) for receiving video input data, for modifying the video levels of the video input data in accordance with external adjustment data and for outputting modified video data,- first power measurement means (10) for measuring a video data power level of said modified video data and for supplying a first video data power level, characterized by- second power measurement means (11) for measuring a video data power level of said video input data and for supplying a second video data power level and- generator means (12) for generating a third video data power level between said first video data power level and said second video data power level as long as the second video data power level is higher than the first video data power level or for generating the third video data power level equal to the larger one of said first and second video data power levels, and- data processing means (9) for calculating the maximum number of sustain pulses per frame applicable to said modified video data on the basis of said third video data power level and for controlling the display of said modified video data on said plasma display panel (1) respectively.
- Apparatus according to claim 1, wherein said third video data power level is the larger one of said first video data power level and said second video data power level.
- Apparatus according to claim 1 or 2, wherein said video data power levels are average power levels related to one picture.
- Method for driving a plasma display panel (1) by- providing video input data,- modifying the video levels of the video input data in accordance with external adjustment data in order to obtain modified video data,- measuring a video data power level of said modified video data and providing a first video data power level,characterized by- measuring a video data power level of said video input data and providing a second video data power level and- generating a third video data power level between said first video data power level and said second video data power level as long as the second video data power level is higher than the first video data power level or generating the third video data power level equal to the larger one of said first and second video data power levels, and- processing said modified video data for calculating the maximal number of sustain pulses per frame applicable to said modified video data on the basis of said third video data power level and controlling the display of said modified video data on said plasma display panel respectively.
- Method according to claim 4, wherein said third video data power level is the larger one of said first video data power level and said second video data power level.
- Method according to claim 4 or 5, wherein said video data power levels are average power levels related to one picture.
Priority Applications (1)
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EP06125606A EP1796065B1 (en) | 2005-12-12 | 2006-12-07 | Apparatus for driving a plasma display panel with APL pre-measurement and corresponding method |
Applications Claiming Priority (2)
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EP05292660A EP1796064A1 (en) | 2005-12-12 | 2005-12-12 | Apparatus for driving a plasma display panel with APL pre-measurement and corresponding method |
EP06125606A EP1796065B1 (en) | 2005-12-12 | 2006-12-07 | Apparatus for driving a plasma display panel with APL pre-measurement and corresponding method |
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EP1796065A1 EP1796065A1 (en) | 2007-06-13 |
EP1796065B1 true EP1796065B1 (en) | 2011-09-28 |
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JP3891499B2 (en) * | 1995-04-14 | 2007-03-14 | パイオニア株式会社 | Brightness adjustment device for plasma display panel |
JP3556138B2 (en) * | 1998-12-24 | 2004-08-18 | 富士通株式会社 | Display device |
JP4616495B2 (en) * | 2001-03-29 | 2011-01-19 | パナソニック株式会社 | Power limit circuit for plasma display |
JP2002351392A (en) * | 2001-05-28 | 2002-12-06 | Matsushita Electric Ind Co Ltd | Plasma display |
EP1347434A1 (en) * | 2002-03-18 | 2003-09-24 | Koninklijke Philips Electronics N.V. | Contrast and brightness control of a display |
JP3720813B2 (en) * | 2003-02-26 | 2005-11-30 | キヤノン株式会社 | Video display device |
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