Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1998-11-03
2001-04-17
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S063000, C345S067000, C345S068000
Reexamination Certificate
active
06219012
ABSTRACT:
The invention relates to a flat panel display apparatus, and a method and apparatus for minimizing EMI radiations from the flat panel display.
Prior art U.S. Pat No. 5,541,618 discloses sub field driven flat panel displays. An embodiment describes a surface discharge type plasma display panel (further referred to as PDP). A plurality of X-electrodes each arranged parallel and close to a plurality of Y-electrodes, and address electrodes orthogonal to the X and Y electrodes are arranged on a surface of a panel. Electrodes crossing each other are insulated with an insulating layer. An address cell is formed at each crossing of the Y-electrodes and the address electrodes. Display cells are formed between the Y-electrode and the adjacent X-electrode, close to the corresponding address cells, respectively. An address period is performed concurrently on all the Y-electrodes. In address periods, a write pulse is applied to all the X-electrodes while a first sustain pulse that is opposite to the write pulse is applied to all the Y-electrodes, and the address electrodes are kept at zero volts. Accordingly, all the display cells are discharged. Next, immediately subsequent to the write pulse a second sustain pulse opposite to the write pulse is applied to all the X-electrodes, so that a wall charge is generated in each display cell and a part of the associated address cell. Next, an erase pulse is applied sequentially to each of the Y-electrodes. Concurrently to the application of the erase pulse, an address pulse is selectively applied to an address electrode of a display cell not to be lit later during the subsequent display period by erasing a wall charge. At a cell to which no address pulse is applied, the wall charge is maintained and the cell will lit during the subsequent display period.
In a first display period subsequent to the first address period, sustain pulses are applied to all the cells by applying first sustain pulses to all the Y-electrodes and second sustain pulses alternately to all X-electrodes. The cells with a wall charge are lit by the sustain pulses.
If the flat panel display is driven in a sub field mode, the above mentioned operations are repeated in the subsequent sub fields.
It is a drawback of the flat panel display apparatus of the prior art that it generates a high amount of electro-magnetic interference (further referred to as EMI).
It is an object of the invention to provide a flat panel display apparatus and a method for driving such an apparatus generating less EMI.
To this end, the invention provides a method and apparatus for driving a flat panel display that drives two complementary sets of pairs of electrodes in the flat panel display with opposing currents.
A pair of scan and sustain electrodes (in the prior art referred to as X and Y electrodes, in the claims referred to as first and second electrodes) is associated with each display cell (also referred to as display element). A display cell may be a portion of a plasma channel at the intersection of the a pair of scan and sustain electrodes and an address electrode (further referred to as data electrode). The plasma channel may be aligned with the data electrodes or with the scan and sustain electrodes. The scan and sustain electrodes each are divided in at least two groups such that the pairs of scan and sustain electrodes are divided in at least two groups. Drive signals are supplied to the groups of scan and sustain electrodes such that the currents in the pairs of scan and sustain electrodes belonging to different groups flow in opposite direction. The EMI generated due to the currents in a certain pair of scan and sustain electrodes is almost canceled by the EMI generated due to the currents flowing in the opposite direction in a nearby situated pair of scan and sustain electrodes belonging to a different group. Consequently, the total amount of EMI decreases.
In the prior art all pairs of scan and sustain electrodes are driven in a same way. Consequently, all currents in the scan and sustain electrodes have a same direction. This causes a high amount of EMI, especially during the display period (also referred to as sustain period) during which all scan and sustain electrodes are driven at the same time.
In first embodiment of the invention, the drive circuit for driving the sustain electrodes is very simple as it consists of conductors interconnecting the sustain electrodes in groups.
In a another embodiment of the invention, pairs of scan and sustain electrodes belonging to different groups alternate. In this way, a maximum compensation of the EMI generated by the two consecutive pairs is obtained, because a minimal area between successive pairs with opposite currents adds to the EMI, and a maximum correlation between the signals on the rows exist.
REFERENCES:
patent: 5420602 (1995-05-01), Kanazawa
patent: 5436634 (1995-07-01), Kanazawa
patent: 5541618 (1996-07-01), Shinoda
patent: 5654728 (1997-08-01), Kanazawa
patent: 5835072 (1998-10-01), Kanazawa
patent: 5841413 (1998-10-01), Zhu et al.
patent: 5874932 (1999-02-01), Nagaoka et al.
patent: 5943030 (1999-08-01), Minamibayashi
patent: 0549275B1 (1997-05-01), None
Dinh Duc
Hjerpe Richard
U.S. Philips Corporation
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