Scan inversion symmetric drive

An electroluminescent display system, comprising:

• a thin-film electroluminescent display panel having an electroluminescent phosphor layer and a plurality of row electrodes and column electrodes that define pixel cells on said display panel;
• a plurality of column drivers that apply column voltages to said column electrodes;
• a plurality of row drivers that apply row voltages to said row electrodes;
• a column driver control circuit that controls the application of said column voltages to said column electrodes by said column drivers;
• and
• a row driver control circuit that controls the application of said row voltages to said row electrodes by said row drivers, said row driver control circuit comprising:
• a first circuit that generates a plurality of refresh pulses having a first voltage polarity and spaced apart in time by fixed time intervals, the time interval between a first refresh pulse and a second refresh pulse comprising a first display frame, the time interval between said second refresh pulse and a third refresh pulse comprising a second display frame, said refresh pulses applied to said plurality of row electrodes;
• and
• a second circuit that enables said row drivers to apply write voltage pulses to each of said row electrodes, one at a time, said second circuit enabling said row drivers in a first sequence during said first display frame so that said row electrodes are enabled in a first order during said first display frame and so that said row electrodes are enabled in a second order during said second display frame, said first and second orders selected so that for any one of a plurality of row electrodes, the amount of time between the occurrence of a write pulse on said any one row electrode in said first display frame and the occurrence of said second refresh pulse is substantially equal to the amount of time between the occurrence of said second refresh pulse and the occurrence of a write pulse on said any one electrode in said second display frame;
• wherein said write voltage pulses are applied to said row electrodes in order from the top of the display panel to the bottom of the display panel during said first display frame and said write voltage pulses are applied to said row electrodes in order from the bottom of said display panel to the top of said display panel during said second display frame.

In an electroluminescent display system having a display panel that includes thin, electroluminescent phosphor layer and a plurality of row electrodes and column electrodes defining pixel elements on said display panel, a method of reducing the residual dc voltages across said pixel elements comprising the steps of:

• applying a sequence of refresh pulses having a first voltage polarity to said row electrodes at fixed, spaced-apart intervals;
• between a first of said refresh pulses and a second of said refresh pulses, applying a first sequence to write voltages having a second voltage polarity to said row electrodes in a first order from the top of said display panel to the bottom of said display panel;
• and
• between said second of said refresh pulses and a third of said refresh pulses, applying a second sequence of write voltages to said row electrodes in a second order from the bottom of said display panel to the top of said display panel, said first order and said second order selected so that the sum of the amount of time between said first refresh pulse and the write voltage applied to any one of said row electrodes in said first sequence added to the amount of time between the second refresh pulse and the write voltage applied to said any one of said row electrodes in said second sequence is substantially equal to the amount of time between said first refresh pulse and said second refresh pulse.

A method of reducing the residual dc voltages across the pixel elements of a thin-film electroluminescent display panel, said display including a plurality of row electrodes and a plurality of column electrodes, said row electrodes and said column electrodes crossing to define said pixel elements, said row electrodes driven by a plurality of row drivers, said method comprising the steps of:

• applying a sequence of refresh pulses to said plurality of row electrodes, said refresh pulses each comprising a voltage of a first polarity, each said refresh pulse applied to all of said plurality of row electrodes at substantially the same time, adjacent ones of said refresh pulses spaced apart in time from each other by a fixed amount of time, the fixed amount of time between adjacent refresh pulses defining a display frame;
• applying a plurality of sequences of write pulses, one at a time, to said plurality of row electrodes during each said display frame, said write pulses comprising a voltage of a second polarity different from said first plurality, said plurality of sequences of write pulses repeating after a like plurality of display frames, said plurality of sequences selected so that over said plurality of display frames, for each row electrode the total time from the refresh pulses in the display frames to the next adjacent write pulses is substantially equal to the total time from the write pulses in the display frame to the next adjacent refresh pulses, the number of sequences in said plurality of sequences substantially less than the number of said plurality of row electrodes;
• wherein said number of sequences is equal to two.