Memory Based Illumination Device

Abstract

The invention contained herein provides electrical circuits and driving methods to operate a memory cell comprising a capacitance coupled to a breakover conduction switch such as a thyristor, DIAC or one or more complementary transistor pairs. The memory cell comprises a cell capacitance for storing a memory state and for capacitively coupling an applied voltage to the switch. During operation, pulses are applied to write, read or maintain the cell's memory state. An illumination cell comprises an LED, OLED or electroluminescent material in series with each memory cell. Breakover conduction charge passes through the switch and the emissive element to charge the cell capacitance. A memory array of breakover conduction memory cells may be organized into rows and columns for reading and writing an addressable array memory cells. An organic light emitting display memory array may be fabricated using organic light emitting devices and/or materials.

I claim: 
     
         1 . A device, comprising a circuit comprising; an illumination element for conducting opposing first and second currents there-through and a switch having a switching characteristic comprising: opposing first and second conduction voltages; opposing first and second minimum conduction currents; and, opposing conduction regions there-between; wherein said first and second currents flow there-through, respectively. 
     
     
         2 . The device of  claim 1 , said circuit further comprising a capacitance for limiting said first and second currents there-through according to a charging thereof. 
     
     
         3 . The device of  claim 2 , wherein said capacitance, said illumination element, and said switch are disposed in a series arrangement. 
     
     
         4 . The device of  claim 2 , said circuit further comprising at least one of a breakover conduction device, a DIAC, at least one LED, at least one OLED, and a phosphor material. 
     
     
         5 . The device of  claim 1 , said illumination element comprising first and second light emitting portions for conducting and emitting light according to said first and second currents respectively. 
     
     
         6 . The device of  claim 5 , further comprising, first and second electrode portions coupled to said first and second light emitting portions, respectively. 
     
     
         7 . The device of  claim 1 , further comprising a first electrode, disposed on a first surface, coupling said illumination element and a driver for applying opposing first and second time varying pulses and inducing said first and second currents, respectively. 
     
     
         8 . A method comprising:
 a. setting a first voltage across a capacitance;   b. applying a first driving pulse across an illumination cell comprising first and second terminals and, coupled there-between, a series arrangement comprising said capacitance, a light emitting element and a switch; and,   c. wherein said applying a first driving pulse comprises:
 i. applying a second voltage between said first and second terminals in-phase with said first voltage; 
 ii. inducing a first current, according to said first and second voltages and a first conduction characteristic of said switch, through said series arrangement in a first direction; 
 iii. setting a third voltage across said capacitance according to said first voltage and said first current; and, 
 iv. emitting a light pulse according to said first current. 
   
     
     
         9 . The method of  claim 1 , said second voltage is less than said first conduction voltage characteristic. 
     
     
         10 . The method of  claim 1 , further comprising, applying a second driving pulse comprising:
 a. applying a fourth voltage in-phase with said third voltage;   b. inducing a second current, according to said third and fourth voltages and a second conduction characteristic of said switch, through said series arrangement, in a second direction opposite to said first direction;   c. setting a fifth voltage across said capacitance according to said third voltage and said second current; and,   d. emitting a second light pulse according to said second current.   
     
     
         11 . The method of  claim 10 , further comprising; illuminating a device comprising a first electrode and a second electrode coupled to said first and second terminals respectively; said illuminating comprising:
 a. dividing, with time, said illuminating into a plurality of time periods;   b. performing a first setting operation during a first period of said time periods said setting operation comprising; applying a first pulse to said first electrode, applying a second pulse to a second electrode according to display data and, inducing a third current through said illumination cell for setting said first voltage; and,   c. applying a first plurality of said first and second driving pulses during a second period of said time periods according to a predetermined brightness of said second period.   
     
     
         12 . The method of  claim 11 , further comprising, applying a resetting pulse subsequent to said second period for resetting said first voltage. 
     
     
         13 . The method of  claim 12 , said resetting pulse comprising a sixth voltage less than said second voltage. 
     
     
         14 . The method of  claim 13 , said resetting pulse comprising a first transition to said sixth voltage and a second transition to said second voltage. 
     
     
         15 . The method of  claim 12 , said method further comprising; applying a plurality of subfields for rendering a display image wherein a first subfield comprises said first and second time periods and wherein a second subfield comprises a second setting operation and a second plurality of said first and second driving pulses greater in number than said first plurality of driving pulses. 
     
     
         16 . The method of  claim 15 , applying said resetting pulse between said first and second subfields. 
     
     
         17 . The method of  claim 15 , further comprising; applying a writing pulse, between said first and second subfields, comprising applying a seventh voltage greater than said second voltage for setting said first voltage. 
     
     
         18 . An apparatus for emitting light, comprising a circuit comprising:
 a. a first region exhibiting high impedance below predetermined and opposing first and second voltages, and according to respective opposing first and second currents there-through less than predetermined and opposing first and second current levels; and,   b. opposing second and third regions exhibiting respective first and second opposing conductive states according to said first and second voltages and according to said first and second currents there-through greater than said first and second current levels;   c. an element for emitting said light according to said first currents flowing there-through.   
     
     
         19 . The apparatus of  claim 1 , said element comprising opposing first and second light emitting devices wherein said first and second currents flow there-through, respectively. 
     
     
         20 . The apparatus of  claim 1 , said circuit further comprises: a capacitance for applying at least a portion of said first and second voltages and charging according to said first and second currents flowing there-through. 
     
     
         21 . The apparatus of  claim 20 , said circuit comprising a series arrangement of, said capacitance, said element and a switch comprising said first, second and third regions. wherein said first and second currents flow through said series arrangement. 
     
     
         22 . The apparatus of  claim 1 , said circuit comprising at least one of: a breakover conduction device; a DIAC; an LED; an OLED; said element; a light emitting breakover conduction device; a capacitively coupled breakover conduction device; and, a capacitively coupled light emitting breakover conduction device.