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Correction of Operating Voltage to Prevent Luminance Variation in a Plasma Panel

IP.com Disclosure Number: IPCOM000046659D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Hoffman, HS: AUTHOR [+2]

Abstract

In a plasma panel display device, a current distribution system is used to supply the selection lines. The impedance of this system results in a voltage drop proportional to the number of lighted pels (picture elements) in the line. This means that over the range of panel content, the effective voltage to switch pels will vary with the load, i.e., the number of lighted pels. Such operation produces a deterioration in margins and a variation in brightness which would not occur if the voltage at each pel at the time of switching were held constant. By using a regulated power supply, the voltage can be controlled over a range such that for a full load change, the voltage at the pel can be maintained constant. Analog processing could be used to determine the load, but use of a microprocessor would be preferable.

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Correction of Operating Voltage to Prevent Luminance Variation in a Plasma Panel

In a plasma panel display device, a current distribution system is used to supply the selection lines. The impedance of this system results in a voltage drop proportional to the number of lighted pels (picture elements) in the line. This means that over the range of panel content, the effective voltage to switch pels will vary with the load, i.e., the number of lighted pels. Such operation produces a deterioration in margins and a variation in brightness which would not occur if the voltage at each pel at the time of switching were held constant. By using a regulated power supply, the voltage can be controlled over a range such that for a full load change, the voltage at the pel can be maintained constant. Analog processing could be used to determine the load, but use of a microprocessor would be preferable. An algorithm can be digitally processed to combine the operating repetition rate and the average current to calculate the load. This is done dynamically and used to control the set point of the regulator in the power supply. This is most easily done open loop; however, the voltage at a dummy pel can be measured for comparison to a reference and thus close the loop.

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