Electroluminescent Display Driving Circuit With Leakage Prevention
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Solution Overview
Problem
Conventional electroluminescent displays face issues with luminance variation due to leakage current during internal compensation of driving transistor characteristics, leading to block dim effects, which are not adequately addressed by existing compensation methods.
Innovation Solution
The proposed solution involves a source-follower type internal compensation method that allocates specific time for threshold voltage compensation in display blocks and electron mobility compensation in a line sequential manner, using a configuration with multiple switching transistors to prevent leakage currents, including a third switching transistor to electrically float the source node and anode of the organic light emitting diode during compensation periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If internal compensation method is used to compensate for driving transistor characteristics, then compensation for threshold voltage and electron mobility is achieved, but leakage current occurs causing block dim effects
Solution Approach 1:
The patent applies preliminary action by performing threshold voltage compensation before data signal writing, and by pre-configuring the pixel circuit with storage capacitors and switching transistors that are activated in specific sequences. The compensation operations are executed in advance during dedicated time periods before the display block is fully activated, preventing leakage current from affecting the final display output.
Solution Approach 2:
The patent implements dynamics by using multiple switching transistors (first switching transistor, second switching transistor, third switching transistor) that dynamically change their conduction states during different time periods. The pixel circuit transitions between different operational modes (compensation mode, data writing mode, display mode) by controlling the switching states of these transistors, allowing the circuit to adapt its configuration to prevent leakage current at different stages.
2Reliability
If compensation operations are performed sequentially for threshold voltage and electron mobility, then accurate compensation is achieved, but display time is reduced
Solution Approach 1:
The patent applies segmentation by dividing the display panel into multiple display blocks that can be compensated and displayed in a sequential manner. Each display block is processed independently through the compensation operations, allowing the system to perform accurate sequential compensation while maintaining overall display continuity. The display panel is also divided into multiple pixel lines that are scanned sequentially.
Solution Approach 2:
The patent implements periodic action by executing compensation operations during specific time periods within each frame cycle. Threshold voltage compensation, electron mobility compensation, data signal writing, and display periods are arranged in a periodic sequence, ensuring that each operation receives adequate time while maintaining a rhythmic operational pattern that optimizes both accuracy and efficiency.
Data Source
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AI summary
An electroluminescent display and a method of driving the same are disclosed. The electroluminescent display includes a driving transistor (DT) configured to generate a driving current depending on a gate-source voltage, a storage capacitor (Cst) configured to store a data voltage (Vdata) and provide the stored data voltage (Vdata) to a gate electrode of the driving transistor (DT), a first switching transistor (ST1) configured to control a gate potential of the driving transistor (DT), a second switching transistor (ST2) configured to control a source potential of the driving transistor (DT), a light emitting diode (OLED) configured to emit light in response to the driving current generated from the driving transistor (DT), and a third switching transistor (ST3) configured to electrically float a source electrode of the driving transistor (DT) and an anode electrode of the light emitting diode (OLED) when one of the first and second switching transistors (ST1, ST2) is turned off.