This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2005-287266, filed on Sep. 30, 2005, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a plasma display device and a control method therefor.
2. Description of the Related Art
The plasma display device is a large-sized flat-type display of which market is expanding as a flat television for home use, and power consumption, display quality and a cost of the same order of CRT are required.
The following patent document 1 describes a drive method of the plasma display panel in which a sawtooth-waveform erasing pulse is applied to a main electrode.
Also, the following patent document 2 describes a drive method of the plasma display panel in which a ramp voltage is applied in an initialization period.
[Patent document 1] Japanese Patent Application Laid-open No. Hei 11-352924.
[Patent document 2] Japanese Patent Application Laid-open No. 2000-214823.
It is an object of the present invention to provide a plasma display device and a control method therefor, capable of realizing a high contrast and a wide drive margin by enhancing a reset function in a reset period.
According to the present invention, the plasma display device includes a plurality of sub-frames in one frame, each sub-frame having a reset period, an address period and a sustain discharge period, and in the above address period, a discharge for display selection occurs at least between first and second electrodes, and at the end of the reset period, reset is performed by applying a gradient voltage pulse between the first and second electrodes, and the final gradient voltage pulse in the reset period has an identical polarity to that of a voltage applied between the first and second electrodes when the discharge occurs in the address period, and the plurality of sub-frames is classified into first-type and second-type sub-frames, and in the reset period of the first-type sub-frames, a gradient voltage pulse having the reverse polarity of the final gradient voltage pulse is applied between the first and second electrodes, prior to the final gradient voltage pulse, and in the reset period of the second-type sub-frames, the gradient voltage pulse having the reverse polarity of the final gradient voltage pulse is not applied between the first and second electrodes, and a plurality of first-type sub-frames is existent in one frame, and an attained voltage of the gradient voltage pulse of reverse polarity in at least one first-type sub-frame among the plurality of first-type sub-frames is different from that of the gradient voltage pulse of reverse polarity in other first-type sub-frame.
Further, according to the present invention, the method for controlling the plasma display device includes a plurality of sub-frames in one frame, each sub-frame having a reset period, an address period and a sustain discharge period, and in the address period, a discharge for display selection occurs at least between first and second electrodes, and at the end of the reset period, reset is performed by applying a gradient voltage pulse between the first and second electrodes, and the final gradient voltage pulse in the reset period has an identical polarity to that of a voltage applied between the first and second electrodes when the discharge occurs in the address period, and the plurality of sub-frames is classified into first-type and second-type sub-frames, and in the reset period of the first-type sub-frames, a gradient voltage pulse having the reverse polarity of the final gradient voltage pulse is applied between the first and second electrodes, prior to the final gradient voltage pulse, and in the reset period of the second-type sub-frames, the gradient voltage pulse having the reverse polarity of the final gradient voltage pulse is not applied between the first and second electrodes, and a plurality of first-type sub-frames is existent in one frame, and an attained voltage of the gradient voltage pulse of reverse polarity in at least one first-type sub-frame among the plurality of first-type sub-frames is different from that of the gradient voltage pulse of reverse polarity in other first-type sub-frame.
In the plasma display panel 3, the X-electrode Xi and the Y-electrode Yi form a row extending in parallel in the horizontal direction, while the address electrode Aj forms a column extending in the vertical direction so as to intersect with the X-electrode Xi and the Y-electrode Yi. The Y-electrode Yi and the X-electrode Xi are disposed alternately in the vertical direction. The Y-electrode Yi and the address electrode Aj form a two-dimensional matrix having i rows and j columns. A display cell Cij is formed of a cross point of a Y-electrode Yi and an address electrode Aj and an X-electrode Xi being disposed in an adjacent location correspondingly thereto. The above display cell Cij corresponds to a pixel, by which the plasma display panel 3 can display a two-dimensional image. An HDTV with a full specification has pixels of 1,920 (horizontal direction)×1,080 (vertical direction).
Each sub-frame sf is constituted of a reset period TR, an address period TA and a sustain (hold) discharge period TS. In the reset period TR, a display cell Cij is initialized. To the Y-electrode Yi, a positive obtuse wave (a waveform having a positive gradient) Pr1 and a negative obtuse wave (a waveform having a negative gradient) Pr2 are applied.
In the address period TA, emission or non-emission of each display cell Cij can be selected by means of a discharge between the address electrode Aj and the Y-electrode Yi, and an accompanying discharge between the X-electrode Xi and the Y-electrode Yi. More specifically, scanning pulses Py are successively applied to the Y-electrodes Y1, Y2, Y3, Y4, . . . . By applying an address pulse Pa to the address electrode Aj corresponding to the above each scanning pulse Py, a discharge occurs between the address electrode Aj and the Y-electrode Yi. With the above discharge, functioning as a pilot burner, a discharge between the X-electrode Xi and the Y-electrode Yi occurs. As a result of the above discharge, wall charges are produced on the X-electrode Xi and the Y-electrode Yi, and thus, emission or non-emission of a desired cell Cij can be selected.
In the sustain period TS, a sustain discharge is performed between the X-electrode Xi and the Y-electrode Yi of the selected display cell Cij, and thereby emission is performed. In each sub-frame sf, the number of times of emission caused by sustain discharge pulses Ps between the X-electrode Xi and the Y-electrode Yi (namely, the length of the sustain period TS) differs. This can fix a gradation value. Each sustain discharge pulse Ps is a pulse having either 0 V or a voltage Vs.
Next, the structure of one frame according to the present embodiment is described more specifically. Each frame fk or the like includes, for example, 10 sub-frames sf1-sf10. A first sub-frame sf1 is a first-type sub-frame shown in
In the reset period TR, initialization of the display cell Cij is performed. First, a positive gradient voltage pulse 401 having a gradually increasing voltage is applied to the Y-electrode Yi, while −140 V is applied to the X-electrode Xi. In case of the first sub-frame sf1, the attained voltage of the positive gradient voltage pulse 401 is 259 V, while in case of the sixth sub-frame sf6 to the tenth sub-frame sf10, the attained voltage of the positive gradient voltage pulse 401 is 166 V. In the case of the first sub-frame sf1, a positive gradient voltage pulse is applied between the Y-electrode Yi and the X-electrode Xi, of which attained voltage becomes 259+140=399 V. Also, in each case of the sixth sub-frame sf6 to the tenth sub-frame sf10, a positive gradient voltage pulse is applied between the Y-electrode Yi and the X-electrode Xi. The attained voltage becomes 166+140=306 V, which is lower than the attained voltage 399 V of the first sub-frame sf1.
Next, a negative gradient pulse 402 having a gradually decreasing voltage is applied to the Y-electrode Yi, while 60 V is applied to the X-electrode Xi. The attained voltage of the negative gradient voltage pulse is −149 V. At this time, a negative gradient voltage pulse is applied between the Y-electrode Yi and the X-electrode Xi.
In the address period TA, emission or non-emission of each display cell Cij can be selected by the discharge between the address electrode Aj and the Y-electrode Yi and the accompanying discharge between the X-electrode Xi and the Y-electrode Yi. Specifically, negative scanning pulses (−153 V) are successively applied to the Y-electrodes Y1, Y2, Y3, Y4 . . . , and by applying an address pulse (70 V) to the address electrode Aj corresponding to the above each scanning pulse, a discharge occurs between the address electrode Aj and the Y-electrode Yi. With the above discharge functioning as a pilot burner, a discharge between the X-electrode Xi and the Y-electrode Yi occurs. At this time, 60 V is applied to the X-electrode Xi. As a result of the above discharge, wall charges are produced on the X-electrode Xi and the Y-electrode Yi, and thus, emission or non-emission of a desired display cell Cij can be selected.
In the sustain period TS, a sustain discharge is performed between the X-electrode Xi and the Y-electrode Yi of the selected display cell Cij, so as to perform emission. To the X-electrode Xi, first, a sustain discharge pulse of −120 V is applied, and thereafter, sustain discharge pulses of 94 V and sustain discharge pulse of −94 V are applied alternately. To the Y-electrode Yi, sustain discharge pulses of 94 V and sustain discharge pulse of −94 V are applied alternately. A discharge occurs between the X-electrode Xi and the Y-electrode Yi, each time a voltage of 94+94=188 V is applied.
As shown in
The scanning circuit 8 shown in
As described above, one frame fk, etc. are constituted of the plurality of sub-frames sf1-sf10. Each sub-frame sf1-sf10 includes the reset period TR, the address period TA and the sustain discharge period TS. In the address period TA, a discharge for display selection occurs at least between the X-electrode Xi and the Y-electrode Yi. At the end of the reset period TR, the gradient voltage pulse 402 or 501 is applied to the Y-electrode Yi and the gradient voltage pulse corresponding thereto is applied between the X-electrode Xi and the Y-electrode Yi. Thus, resetting is performed. The gradient voltage pulse applied at the end of the reset period TR has the identical polarity (for example, negative polarity) to the voltage applied between the X-electrode Xi and the Y-electrode Yi when the discharge occurs in the address period TA. Namely, in the reset period TR, a negative gradient voltage pulse 402 or 501 is applied to the Y-electrode Yi, while in the address period TA, a negative scanning pulse (−153 V) is applied to the Y-electrode Yi.
The plurality of sub-frames sf1-sf10 is classified into the first-type sub-frames and the second-type sub-frames. The first sub-frame sf1 is the first-type sub-frame shown in
In the reset period TR of the first-type sub-frame shown in
In the reset period TR of the second-type sub-frame shown in
There is a plurality of first-type sub-frames existent in one frame. In at least one first-type sub-frame (for example, the sub-frame sf1) among the plurality of first-type sub-frames, the attained voltage (for example, 259 V of the Y-electrode, and 399 V between the Y-electrode Yi and the X-electrode Xi) of the gradient voltage pulse 401 having reverse polarity is different from the attained voltages (for example, 166 V as to the Y-electrode Yi, and 306 V between the Y-electrode Yi and the X-electrode Xi) of the gradient voltage pulses 401 of reverse polarity in other first-type sub-frames (for example, the sub-frames sf6-sf10).
Among the plurality of first-type sub-frames in one frame, the absolute voltage value of the gradient voltage pulse 401 having reverse polarity (for example, 259 V of the Y-electrode Yi, and 399 V between the Y-electrode Yi and the X-electrode Xi) in the top first-type sub-frame (for example, the sub-frame sf1) is greater than the absolute values of the attained voltages (for example, 166 V as to the Y-electrode Yi, and 306 V between the Y-electrode Yi and the X-electrode Xi) of the gradient voltage pulses 401 of reverse polarity in the second or later first-type sub-frame (for example, the sub-frames sf6-sf10).
Among the plurality of first-type sub-frames in one frame, the absolute value of the attained voltage of the gradient voltage pulse 401 having reverse polarity in the top first-type sub-frame (for example, the sub-frame sf1) has the greatest value among the absolute values of the applied voltages between the X-electrode Xi and the Y-electrode Yi in the above one frame.
Normally, the number of the first-type sub-frames having a high attained voltage (259 V) of the positive gradient voltage pulse 401 is set to one. However, a plurality may be accepted. In case of the plurality, although the probability of missing address in the address period TA is decreased, background emission increases.
The second-type sub-frames enable restraint of background emission, producing a higher contrast.
The sub-frames sf6-sf10 are first-type sub-frames having low voltage (166 V) of the attained voltage of the positive gradient voltage pulse 401. The above sub-frames play the role of restoring wall charge when the temperature of the plasma display panel 3 becomes high and the wall charge is attenuated. Accordingly, by detecting the temperature of the plasma display panel 3, as the temperature of the plasma display panel 3 is higher, it is desirable to increase the number of the first-type sub-frames having a low voltage (166 V) of the attained voltage of the positive gradient voltage pulse 401, or to increase the attained voltage of the positive gradient voltage pulse 401 thereof. Also, generally the temperature becomes up and down in the overall plasma display device. Therefore, instead of really detecting the temperature of the plasma display panel 3, it may be possible to detect the temperature of other different places in the device having a similar structure to the plasma display panel, such as the chassis.
Thus, in response to the temperature of the plasma display panel 3 or the chassis detected by the temperature sensor 22, the drive control circuit 7 shown in
Also, the drive control circuit 7 controls to set to a higher value the absolute value of the attained voltage of the gradient voltage pulse 401 having reverse polarity in at least one first-type sub-frame [in particular, the first-type sub-frames of a low voltage (166 V) of the attained voltage of the positive gradient voltage pulse 401], as the temperature of the plasma display panel or the chassis becomes higher.
As described above, according to the present embodiment, it becomes possible to enhance a reset function in the reset period. As a result, the background emission can be restrained, and the drive margin can be expanded particularly at the time of high temperature. This makes it possible to realize a plasma display device having a high contrast and a wide drive margin.
In the aforementioned embodiments, typical examples for embodying the present invention have merely been described, and it is not to be understood the technical scope of the present invention restrictively. The present invention may be implemented in various forms without deviating from the technical idea or the major features of the present invention.
According to the present invention, it becomes possible to enhance a reset function in the reset period. As a result, the background emission can be restrained, and the drive margin can be expanded particularly at the time of high temperature. This makes it possible to realize a plasma display device having a high contrast and a wide drive margin.
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