OLED Pixel Circuit with Voltage Compensation for Luminance Degradation
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Solution Overview
Problem
Organic light emitting display devices face challenges in maintaining desired luminance due to the deterioration of organic light emitting diodes over time, which is exacerbated by voltage drops in the second power supply.
Innovation Solution
A pixel circuit with a driving transistor and a compensator that uses on-voltage and off-voltage to compensate for the deterioration of the organic light emitting diode, including a compensating capacitor and transistors that adjust voltage levels to maintain optimal current flow, regardless of voltage drops in the second power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pixel circuit is used, then device simplicity is maintained, but luminance deteriorates over time due to OLED degradation and voltage drops
Solution Approach 1:
The compensator measures the OLED's on-voltage and off-voltage before the OLED degrades further, calculates the voltage difference, and pre-adjusts the compensation voltage stored in the compensation capacitor. This preliminary action ensures that when the OLED luminance deteriorates, the compensation is already in place to maintain consistent luminance output.
Solution Approach 2:
The compensator continuously monitors the OLED's voltage characteristics (on-voltage when current flows and off-voltage when current does not flow) and uses this feedback information to dynamically adjust the compensation voltage. This closed-loop feedback mechanism ensures that the pixel circuit adapts to OLED degradation and maintains stable luminance over time.
2Reliability
If compensation circuit is added, then luminance consistency is improved, but circuit complexity increases
Solution Approach 1:
The compensator performs multiple functions using a single integrated circuit: it measures both on-voltage and off-voltage, calculates the voltage difference, generates compensation voltage, and stores it in the compensation capacitor. This multi-functional design minimizes the number of additional components needed while achieving effective OLED degradation compensation.
Solution Approach 2:
The compensator automatically measures the OLED's voltage characteristics and generates the appropriate compensation voltage without requiring external intervention or complex control signals. The circuit self-adjusts to maintain luminance consistency, reducing the need for additional control circuitry and simplifying the overall system.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for the maintenance of desired luminance in organic light emitting display devices by compensating for the deterioration of organic light emitting diodes, ensuring consistent image quality despite voltage drops in the second power supply.
Implementation Method 1
The organic light emitting diode produces light by recombining an electron and a hole
Implementation Method 2
a storage capacitor Cst connected between a gate electrode and a first electrode of the second transistor M2
Data Source
AI summary
A pixel to compensate for the deterioration of an organic light emitting diode, the pixel including an organic light emitting diode; a pixel circuit including a driving transistor controlling an amount of current supplied to the organic light emitting diode; and a compensator compensating for the deterioration of the organic light emitting diode by using on-voltage applied when current flows in the organic light emitting diode and off-voltage applied when current does not flow in the organic light emitting diode; wherein the compensator includes: a compensating capacitor having a second terminal connected to a gate electrode of the driving transistor; and a first compensating transistor connected between a first terminal of the compensating capacitor and an anode electrode of the organic light emitting diode.