Organic EL Display Current Control via Power Line Voltage Adjustment
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Solution Overview
Problem
Existing organic EL display devices face challenges in preventing the degradation of light emitting elements due to high current flow, which generates heat and reduces the device's lifespan, and existing methods for controlling drive current are complex and affect image luminance, causing discomfort to viewers.
Innovation Solution
An organic EL display device with a matrix arrangement of display pixels and an adjustment unit that adjusts the voltage applied to the power line, using a first and second capacitance element to manage current flow, allowing for independent writing and display of data signal voltage, thereby controlling current and preventing overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a larger current flows into the organic EL panel to increase screen luminance, then the luminance is improved, but the organic EL panel generates heat which leads to shorter life of organic EL elements
Solution Approach 1:
The patent applies preliminary action by calculating the total sum of current for the next frame in advance during the current frame's display period. This allows the system to prepare voltage adjustment decisions before the next frame is displayed, enabling proactive current control to prevent overheating and extend element life without affecting current display quality.
Solution Approach 2:
The patent implements dynamics by dynamically adjusting the voltage of the power line based on calculated current sums. The voltage is changed from an initial voltage to a adjusted voltage when the calculated current sum exceeds a threshold, allowing the system to adaptively control current flow and heat generation in response to varying display requirements.
2Reliability
If gray level of input image data is increased or decreased before displaying the image to control current, then the life of light emitting elements is improved, but the operation becomes complex and it takes time to display the image
Solution Approach 1:
The patent calculates the total sum of current for the next frame during the current frame's display period, performing the analysis work in advance. This preliminary calculation enables rapid voltage adjustment decisions without requiring complex real-time processing that would slow down image display.
Solution Approach 2:
The patent introduces an intermediary mechanism by using a power line voltage adjustment as a mediator between the image data and the light emitting elements. Instead of directly modifying image data gray levels, the system adjusts the power line voltage to control current flow, simplifying the control process while maintaining element protection.
3Reliability
If drive current is controlled in the image being displayed to prevent overheating, then the life of light emitting elements is improved, but the luminance of the image changes which makes the viewer feel uncomfortable
Solution Approach 1:
The patent implements dynamics by adjusting the power line voltage dynamically based on calculated current sums. The voltage remains at its initial value when current levels are acceptable, maintaining normal luminance, and is adjusted only when the calculated current sum for the next frame exceeds a threshold, preventing unnecessary luminance changes.
Solution Approach 2:
The patent performs preliminary calculation of the current sum for the next frame during the current frame's display. This allows voltage adjustments to be made based on predictive analysis rather than reactive changes during display, ensuring luminance stability while preventing overheating.
4Reliability
If a heat dissipation mechanism is added to cool the panel, then the life of organic EL elements is improved, but the panel cannot be made thinner
Solution Approach 1:
The patent converts the harmful effect of high current into a useful control parameter by calculating the total current sum and using it to drive voltage adjustments. This transforms the potential harm of high current operation into a beneficial control mechanism that prevents overheating without requiring additional cooling hardware, maintaining panel thinness.
Solution Approach 2:
The patent implements self-service by having the display device control its own current consumption through voltage adjustment based on calculated current sums. The system monitors and regulates its own power usage without external intervention or additional cooling mechanisms, extending element life through intelligent power management.
Data Source
AI summary
A plurality of display pixels each include: an organic EL element; a capacitance element that holds a first voltage used to cause the organic EL element to emit light; a drive transistor that supplies a current corresponding to the first voltage to the organic EL element; and a capacitance element that holds a second voltage that is a next voltage to be held in the capacitance element. A power line is connected to a drain electrode of the drive transistor or a cathode of the organic EL element. An adjustment unit adjusts the voltage applied to the power line to be lower than the predetermined voltage, when a total current of the plurality of display pixels in the case where a current corresponding to the second voltage is supplied to the organic EL element in each of the plurality of display pixels is greater than or equal to a threshold.