International Business Machines Corporation

James B Trushell

William J Martin

William R Lamoureux

Tony N Criscimagna

John Robert Cielo

Terry W Barclay

In large size high resolution plasma panels, a smaller discharge gap between the electrodes reduces the operating margin of the panel, i.e., the difference between the maximum and minimum sustain voltage (V.sub.s max and V.sub.s min). Rather than preset these values which vary with each panel at the time of fabrication, the invention provides a control system for determining the V.sub.s max and V.sub.s min and the optimum operating point between these values for each panel. An associated microprocessor determines the V.sub.s min for each panel through a testing algorithm, and the V.sub.s max is provided by either adding a predetermined increment to the V.sub.s min or by a testing sequence. The operating point is designated as a predetermined increment below V.sub.s max. The invention operates each time the panel is turned on, thereby compensating for voltage drift or other panel parameter variations. By using a high speed microprocessor, the entire sequence is accomplished in a short time, while exercising the cells through the test sequence eliminates some of the 'start-up' problems sometimes associated with such displays.

Plasma display margin control

A plasma discharge display device is operated at a high frequency above the response range of the inherent wall charge storage phenomenon and utilizes a refresh buffer. The vertical drive selection includes a pair of shift registers operated in parallel into which data from the host or associated controller is loaded, with an individual driver associated with each register stage. The horizontal lines are addressed through associated shift registers in an even-odd interlace sequence to generate a display on a horizontal scan basis. The horizontal drivers are referenced at the level and frequency of the high frequency energizing signals, while the vertical drivers are selectively set to ground or a positive a.c. voltage according to the state of associated register cells. By using the high frequency signal in the horizontal axis as a floating reference and unique selection techniques, the display is operated by low voltage signals. The normal sustain and erase operations associated with conventional plasma discharge devices are eliminated, while the write operation does not require either the precise timing or logical considerations associated with the selective operation of conventional plasma discharge display devices. The low voltage drive requirements permits use of low voltage driver circuitry which is susceptible to low cost monolithic fabrication techniques.

Buffered high frequency plasma display system

In driving gas panel or plasma display devices, characters are generated on the panel display as a sequence of dots by applying appropriate drive signals to selected orthogonal conductors, each conductor requiring an associated driver. In a low character count small plasma display such as a single row display utilizing a 5.times.7 dot character matrix, a significant load is presented to the horizontal drivers, while a substantial number of drivers are required to drive the vertical axis. To improve the load distribution and increase the drive efficiency of such a system, the horizontal conductors are divided into four distinct groups, with associated drivers, while a single set of vertical conductors is used to drive the vertical conductors, which are positioned to intersect each of the groups of horizontal conductors. The individual load requirements as well as the number of vertical drivers are reduced by a factor of four at a nominal increase in the number of horizontal drivers, thereby providing a significant cost reduction. The specific wiring pattern used to achieve this result on a plasma display device is disclosed herein.

Reduced connection for 22 character gas panel

A system for addressing and controlling a gaseous discharge display or memory device is adapted for intercommunication between a processor or controller and a gaseous discharge display device. Signals of write amplitude are selectively applied to ionize individual cells or a plurality of cells in the form of character slices or lines to form the elements of a display. To facilitate communication between low level control logic signals and high level write and sustain signals, one of the axes or sets of conductors is maintained at ground potential, while signals of full write or sustain amplitude are applied to the orthogonal conductors. Writing is generally accomplished by adding a write pulse to the trailing edge of the selected conductor. By maintaining the busier axis at ground potential direct communication between the control logic and drive circuitry is provided, the isolation circuits required to communicate between the busy axis and the controller or processor are eliminated, the separate sustain drivers normally required to sustain the busy axis are eliminated and only a single set of drivers and isolation circuitry is required to interconnect the control logic to the drive selection circuitry. By operating in this mode, the sustain signal is not interrupted during a write operation thereby permitting use of the inherent margin in the panel and providing a display of uniform intensity.

Gas panel single ended drive systems

To compensate for the relatively wide variation in the electrical operating parameters of a gaseous discharge device resulting from varied physical characteristics, the amplitude of the signal used to sustain a discharge is determined, generated and controlled as a function of the physical characteristics of the panel. In operation, a plurality of sample cells are used for control purposes, and the sustain signal applied to the sample cells is incremented from zero during each sustain cycle until the sample cells are discharged, to determine the minimum sustain signal V.sub.S min. required to sustain the discharge. An offset circuit is used to increase the sustain signal by a predetermined amount above the V.sub.S min. level for panel operation, and a voltage regulator is connected in a closed loop arrangement with the sustain generator to automatically adjust the sustain signal to compensate for variation in the physical parameters of the device due to aging.

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Saugerties, NY, United States of America

James B Trushell