Nonlinear voltage controlled current source with feedback circuit

• US 20040095297A1
• Filed: 11/20/2002
• Published: 05/20/2004
• Est. Priority Date: 11/20/2002
• Status: Abandoned Application

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Sanford, James L., Libsch, Frank R.
• Application Number:
  US10/300,640
• Publication Number:
  US 20040095297A1
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0408 Integration of the drivers onto the display substrate
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• CPC Class Codes: G09G 2320/0219 Reducing feedthrough effects in active matrix panels, i.e. voltage changes on the scan electrode influencing the pixel voltage due to capacitive coupling
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0252 Improving the response speed
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2360/147 the originated light output being determined for each pixel
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/325 the data current flowing through the driving transistor during a setting phase, e.g. by using a switch for connecting the driving transistor to the data driver
• CPC Class Codes: G09G 3/3283 in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements

Abstract

A light emitting pixel circuit comprising a light emitting diode having a parasitic capacitance and coupled to a current source; nonlinear feedback means for rapidly charging the parasitic capacitance and for enabling immediately following such charging, illumination of the diode, responsive to a predefined constant current level from the current source.

Claims

1. A light emitting pixel circuit comprising a light emitting diode having a parasitic capacitance and coupled to a current source;

nonlinear feedback means for rapidly charging the parasitic capacitance and for enabling, immediately following such charging, illumination of the diode responsive to a predefined constant current level from the current source.

2. A light emitting pixel circuit wherein said current source is voltage controlled by operation of the feedback means.

3. A light emitting pixel circuit including means for controlling the charging time.

4. A light emitting pixel circuit, wherein the feedback means include current sense means.

5. A light emitting pixel circuit as defined in claim 4, wherein the current sense means includes two interconnected operational amplifiers.

6. A light emitting pixel circuit as defined in claim 5, wherein the current source includes two interconnected operational amplifiers.