Current Generator for OLED Brightness Uniformity
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Solution Overview
Problem
Conventional organic light emitting displays face issues with non-uniform brightness due to OLED deterioration and variations in threshold voltage/mobility of driving transistors, leading to inconsistent image quality.
Innovation Solution
A current generator with a variable power source, amplifiers, and an analog-to-digital converter is integrated into the display to supply or sink current, allowing for compensation of OLED deterioration and transistor characteristics, thereby ensuring uniform brightness through data correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional pixel circuits are used to control OLED current, then the display can operate with simple circuitry, but brightness uniformity deteriorates due to OLED deterioration and transistor parameter variations
Solution Approach 1:
The patent applies preliminary action by measuring the actual current flowing through the OLED during a non-display period before the display period. This preliminary measurement allows the system to detect OLED deterioration and transistor parameter variations in advance, enabling compensation before the actual display operation, thus maintaining brightness uniformity without requiring complex real-time control circuits during display.
Solution Approach 2:
The patent implements feedback by using the measured current information from the non-display period to adjust or compensate for OLED performance degradation. The measured current serves as feedback about the OLED's actual state, allowing the system to compensate for brightness variations and maintain uniform display quality across different pixels and over time.
2Device complexity
If OLED deterioration is not compensated, then the circuit remains simple, but image brightness becomes non-uniform over time
Solution Approach 1:
The system performs preliminary current measurement during non-display periods before the display period begins. This advance measurement captures OLED deterioration state early, allowing compensation to be applied before the display period, thereby extending the effective uniform brightness duration throughout the OLED's operational life.
Solution Approach 2:
The patent applies self-service by having the OLED pixel itself participate in the measurement process during non-display periods. The pixel circuit measures its own current flow state, and this self-measured information is then used to compensate for the pixel's aging effects, allowing the display to maintain uniformity without requiring external intervention or complex additional circuitry.
3Device complexity
If transistor parameter variations are not addressed, then the circuit design remains simple, but brightness consistency across pixels deteriorates
Solution Approach 1:
The system performs preliminary current measurement during non-display periods to detect transistor parameter variations before the display period. By measuring the actual current flow and comparing it with expected values, the system can identify pixels with abnormal transistor characteristics in advance, enabling compensation to maintain brightness consistency across all pixels.
Solution Approach 2:
The patent implements feedback by using the measured current information to identify and compensate for transistor parameter variations. The measured current serves as feedback about the transistor's actual performance state, allowing the system to adjust or compensate for brightness variations caused by transistor parameter spread, thereby achieving consistent brightness across pixels.
Data Source
AI summary
A current generator for supplying or sinking current to/from pixels. The current generator includes a variable power source, a first amplifier having a first input terminal coupled to the variable power source, a sensing resistor coupled between an output terminal of the first amplifier and an external terminal of the current generator, and a second amplifier having a first input terminal and a second input terminal coupled to respective ends of the sensing resistor and an output terminal coupled to a second input terminal of the first amplifier.