OLED Driving Transistor Mobility Compensation Circuit
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Solution Overview
Problem
Existing organic light-emitting diode (OLED) devices face challenges in maintaining consistent emission luminance due to mobility variance among driving transistors, which is tone-dependent and restricts achieving higher luminance levels, as current compensation techniques are ineffective across various emission tones and potentials.
Innovation Solution
A light-emitting device with a control unit that supplies a first data potential to set the gate-source voltage of driving transistors to a compensated voltage, followed by a second data potential to address mobility variance, allowing for consistent luminance across different tones and increasing drain-source current for higher luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mobility compensation is performed using conventional techniques, then luminance variance is suppressed for specific emission tones, but luminance variance cannot be suppressed for other tones
Solution Approach 1:
The patent implements dynamic mobility compensation by adjusting the compensation period based on the emission tone. The control unit determines the compensation period according to the gray level of the image signal, making the compensation process adaptive to different emission conditions. This resolves the contradiction by enabling luminance consistency across all tones while maintaining the effectiveness of mobility compensation.
Solution Approach 2:
The patent changes the compensation period parameter dynamically based on the emission tone and gray level. By adjusting this temporal parameter according to the specific emission conditions, the system achieves effective mobility compensation across different tones, resolving the tone-dependent limitation of conventional fixed-period compensation techniques.
2Reliability
If current is restricted during mobility compensation operations, then mobility variance is corrected, but desired emission luminance and higher luminance levels cannot be achieved
Solution Approach 1:
The patent segments the driving waveform into distinct phases: a mobility compensation period with restricted current for correcting mobility variance, and a subsequent emission period with full current for achieving desired luminance levels. This temporal segmentation allows both mobility correction and high luminance output to be achieved without mutual interference.
Solution Approach 2:
The patent performs mobility compensation as a preliminary action before the actual emission phase. By completing the mobility correction in advance during the compensation period, the system ensures that the subsequent emission phase can operate at full current capacity to achieve the desired high luminance levels without being constrained by mobility variance.
3Device complexity
If a single compensation period is used for all gray levels, then the compensation process is simple, but compensation effectiveness varies across different gray levels
Solution Approach 1:
The patent implements a dynamic compensation period determination mechanism that adjusts the compensation duration based on the gray level of the image signal. The control unit calculates the appropriate compensation period for each gray level, ensuring optimal compensation effectiveness across the full range of emission tones while maintaining manageable system complexity through automated determination.
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 approach effectively suppresses luminance variance and enables higher emission luminance by determining the second data potential based on the first, ensuring consistent performance regardless of emission tone, and increasing the drain-source current.
Implementation Method 1
When an electric current flows between the pixel electrode and the counter electrode, electrons and electron holes recombine in the organic thin film, causing the organic thin film and organic EL element to emit light
Data Source
AI summary
A light-emitting device includes a light-emitting element that emits light of an amount based on the size of a driving current; a driving transistor, the gate thereof being electrically connected to a first node, that outputs a current flowing between the drain-source as the driving current; and a control unit that supplies a first data potential to the first node and supplies a current to the driving transistor so as to set the voltage between the gate and source of the driving transistor to a compensated voltage based on the mobility of the driving transistor, and then supplies a second data potential determined in accordance with the first data potential to the first node.