Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2003-05-23
2004-09-21
Tran, Thuy Vinh (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C345S063000, C345S211000
Reexamination Certificate
active
06794824
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. § 119 from two applications for AUTOMATIC POWER CONTROL (APC) METHOD AND DEVICE OF PLASMA DISPLAY PANEL (PDP) AND PDP DEVICE HAVING THE APC DEVICE earlier filed in the Korean Intellectual Property Office on May 24, 2002 and there duly assigned Serial No. 2002-28963, and for AUTOMATIC POWER CONTROL (APC) METHOD AND DEVICE OF PLASMA DISPLAY PANEL (PDP) AND PDP DEVICE HAVING THE APC DEVICE earlier filed in the Korean Intellectual Property Office on Jul. 30, 2002 and there duly assigned Serial No. 2002-44801.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma display panel (PDP) device. More specifically, the present invention relates to an automatic power control (APC) method and device of a PDP, and a PDP device including the APC device.
2. Description of the Related Art
In general, a PDP requires a device for controlling power consumption according to load ratios, since it has high power consumption depending on its driving features. To control the power consumption, an automatic power control (APC) method is employed.
FIG. 1
shows a conventional APC method. As shown, the load ratio axis L has n load ratios 0~L
1
, L
1
~L
2
, . . . , L
n−1
~L
n
, and the sustain number axis has predetermined numbers N
n
, N
n−1
, . . . , N
1
matched with the respective n load ratios. For example, the maximum sustain number N
n
is applied to the frame that belongs to the minimum load ratio range 0~L
1
, and the minimum sustain number N
1
is applied to the frame that belongs to the maximum load ratio range L
n−1
~L
n
.
According to the above-noted conventional power control method, if a video screen is instantly switched, its brightness is severely changed which causes video deterioration.
The APC method includes a fast APC and a slow APC. In the fast APC, power consumption is directly applied to a predetermined APC table stage according to input data to thereby reduce power consumption. In the slow APC, data are applied to a desired APC stage, and the data are slowly lowered to a predetermined APC stage by a predetermined time unit to thereby control the power consumption.
However, since the fast APC forcibly darkens the data from the original brightness so as to reduce the power consumption, a user becomes aware of brightness changes, and the slow APC allows generation of a very large integrated power to the video while greatly changing brightness which cannot be detected by a person, and it also allows an increase in the current stress of a power supply or a PDP driver so as to correspond to peak power consumption. Accordingly, it becomes difficult to design the PDP driver, and prevent heat generation, thereby worsening reliability of components.
FIG. 2
shows a graph for showing conventional slow and fast APC algorithms.
A PDP device controls brightness according to a number of sustain pulses. In the case of a full white screen having high brightness, since the power consumption becomes very high because of a display width and a number of sustain pulses, it is difficult to realize the PDP device. To prevent this problem, input video data are mapped into a predetermined APC table to reduce the number of sustain pulses in advance, and they are displayed to reduce the power consumption.
Referring to
FIG. 2
, the fast APC processes video data in real-time to reduce the number of sustain pulses and display the video data, and the slow APC displays data with many sustain pulses so as to display the available maximum brightness at the time of initially inputting data, and controls predetermined linear time intervals to a predetermined table value by gradually reducing the number of sustain pulses and reducing the brightness, thereby adjusting the final brightness.
FIG. 3
shows a conventional brightness graph with respect to time.
Referring to
FIG. 3
, the brightness is steeply changed by abruptly reducing the number of sustain pulses in the desired brightness in the case of the fast APC. A person can sense this abrupt brightness change, which looks like a screen flashing phenomenon.
Differing from this, since the slow APC displays slow brightness changes, the person cannot easily sense the changes. The slow APC improves sensed video quality, but if screens that have great differences of brightness are repeated, a large amount of integrated power is generated as shown in
FIG. 2
, and hence, the lifetime of the PDP is shortened, it is difficult to design a power supply and a driving board, and many stresses are provided to components, and accordingly, the life span of the corresponding product is decreased.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to shorten a brightness control speed in the case of high gray with low recognition rate of a person depending on the brightness changes, and lengthen the brightness control speed in the case of low gray with high recognition rate of a person depending on the brightness changes through a predetermined number of inflection points to thereby reduce integrated power and eliminate screen flashing.
It is another object of the present invention to prevent sudden changes of brightness on a PDP screen in a method for controlling a PDP driving power.
In one aspect of the present invention, an automatic power control method for a plasma display panel including a plurality of address electrodes and a plurality of scan electrodes and sustain electrodes alternately arranged in pairs, includes: calculating a load ratio change between current input data and previous input data; comparing the calculated load ratio change with a predetermined number of threshold values to determine to which area it belongs; determining a brightness control speed which is a time for applying a new brightness value matched with the determined area; and outputting sustain pulse information corresponding to a load ratio of current data at the determined brightness control speed.
In another aspect of the present invention, an APC device for a PDP including a plurality of address electrodes and a plurality of scan electrodes and sustain electrodes alternately arranged in pairs, includes: an ASL sensor for measuring a load ratio of external input video signals; a first memory for storing the load ratio of the input video signal data; a second memory for storing information of a number of sustain pulses depending on the load ratio; a power controller for calculating a load ratio change between the current input data and the previous input data stored in the first memory, comparing the calculated load ratio change with a predetermined number of threshold values to determine a brightness control speed which is a time for applying a new brightness value, and outputting sustain information matched with the load ratio at the determined brightness control speed; and a video data processor for correcting and outputting the video signals.
In still another aspect of the present invention, A PDP device includes: a PDP including a plurality of address electrodes and a plurality of scan electrodes and sustain electrodes alternately arranged in pairs; a controller for correcting and outputting external video signals, comparing a load ratio of current input signals with a previous load ratio to calculate a load ratio change, comparing the calculated load ratio change with a predetermined number of threshold values to determine a brightness control speed which is a time for applying a new brightness value, and outputting sustain pulse information matched with the load ratio of the current input video signals at the determined brightness control speed; an address data generator for generating address data corresponding to the correction data output by the controller, and applying them to the address electrodes of the PDP; and a sustain scan pulse generator for respectively generating sustain and scan pulses matched with sustain information, and applying them to the sustain elect
Lee Joo-Young
Song Yoo-Jin
Bushnell , Esq. Robert E.
Samsung SDI & Co., Ltd.
Tran Thuy Vinh
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