Cathode Potential Controller for Organic EL Display
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Solution Overview
Problem
Organic EL display panels experience fluctuations in driving current due to temperature changes, affecting emission luminance, as current vs. voltage characteristics of organic EL elements are temperature-dependent, and existing techniques fail to adequately correct these fluctuations during bootstrap operations of drive transistors.
Innovation Solution
A cathode potential controller system that includes a self-light emitting element for voltage measurement, a constant current source, an electrode-to-electrode voltage measuring portion, a cathode potential determining portion, and a cathode potential applying portion, which measures and adjusts the cathode potential to maintain a consistent driving voltage state akin to room temperature, thereby stabilizing the driving current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a drive transistor is driven with the same voltage, then the circuit operation is simple, but the driving current fluctuates depending on temperature
Solution Approach 1:
The patent implements a feedback mechanism where the measured anode electrode potential is fed back to adjust the cathode potential. The cathode potential controller continuously monitors the anode potential through the monitoring element and dynamically adjusts the cathode potential to compensate for temperature-induced variations, thereby stabilizing the driving current without complicating the overall circuit operation.
Solution Approach 2:
The system uses a monitoring element (which can be the same type as the display elements) that automatically responds to temperature changes by changing its own characteristics. This self-service approach allows the monitoring element to provide real-time temperature compensation data without requiring external sensors or complex control circuits, maintaining operational simplicity while improving current stability.
2Reliability
If the anode electrode potential is measured using a monitoring element, then the driving current fluctuation can be corrected, but the circuit configuration becomes more complex
Solution Approach 1:
The monitoring element serves multiple functions: it acts as both a display element (emitting light) and a sensing element (providing temperature compensation data). This multi-functionality eliminates the need for separate sensing circuits or additional components, as the same element used for display purposes also provides the necessary feedback information for correcting driving current fluctuations.
Solution Approach 2:
The patent combines the monitoring function with the display function by using the same self-light emitting element for both purposes. The anode electrode potential measurement is integrated into the existing display circuitry, merging the sensing and display operations into a unified system that reduces overall circuit complexity while achieving accurate temperature compensation.
3Reliability
If existing correction techniques are used, then the high potential side power source can be controlled, but the influence of bootstrap operation fluctuations is not corrected
Solution Approach 1:
The system performs preliminary measurement of the anode electrode potential before the bootstrap operation completes. By measuring the potential early in the operation cycle and using this information to adjust the cathode potential, the system proactively compensates for expected fluctuations rather than reacting to them after they occur, thereby maintaining luminance stability throughout the entire operation cycle.
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
The system effectively corrects the temperature-induced fluctuations in driving current, maintaining consistent luminance and power consumption, while simplifying the circuit configuration and reducing panel temperature, thus enhancing the performance and cost-effectiveness of organic EL display devices.
Implementation Method 1
an organic EL element for voltage measurement disposed outside an effective display region; or a self light emitting element for display and measurement constituting a specific pixel
Data Source
AI summary
A cathode potential controller for controlling a common cathode potential applied to a self light emission type display panel in which an emission state of each of pixels is driven and controlled in accordance with an active matrix drive system, the cathode potential controller including: a self light emitting element; a constant current source; an electrode-to-electrode voltage measuring portion; a cathode potential determining portion; and a cathode potential applying portion.