Organic EL Display Power Control Circuit Merging Lines
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Solution Overview
Problem
Existing organic EL display devices face challenges in reducing the scale and power consumption of the power control circuit while maintaining a high aperture ratio and ensuring sufficient time for threshold detection with a simplified configuration.
Innovation Solution
The implementation of a display device with a scanning signal line driver circuit that collectively drives scanning and control lines, including a write control transistor and an emission control transistor, allows for initialization and threshold detection periods separate from the frame period, reducing the need for initialization potential lines and minimizing power control circuit complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the constant-current control mode is used to control the current applied to organic EL elements, then compensation for threshold voltage variations and element deterioration is achieved, but the number of drive transistors and lines increases, reducing the aperture ratio
Solution Approach 1:
The patent combines the control line and power line into a single shared line. The control line serves dual purposes: controlling the emission control transistor and providing power to the pixel circuit during different time periods. This merging reduces the total number of lines required, thereby increasing the aperture ratio while maintaining the constant-current control mode's compensation capabilities
Solution Approach 2:
The patent employs periodic switching of the shared line between control signal mode and power supply mode. During the emission period, the line provides control signals; during other periods, it provides power. This time-division multiplexing allows a single line to fulfill multiple functions, reducing circuit complexity while maintaining reliable operation
2Measurement precision
If separate initialization and threshold detection periods are implemented outside the frame period, then reliable threshold detection is ensured, but the circuit configuration and timing complexity increase
Solution Approach 1:
The patent performs initialization and threshold detection as preliminary actions before the main frame period begins. By completing these preparatory operations in advance using the shared line, the system ensures accurate threshold detection without interfering with the normal display operation during the frame period. This preliminary action approach maintains precision while simplifying the overall timing structure
Solution Approach 2:
The shared line serves multiple functions: it acts as a control line during emission periods, provides power during initialization and threshold detection periods, and enables both compensation and initialization operations. This multi-functionality reduces the need for separate dedicated lines for each operation, simplifying the circuit configuration while maintaining detection accuracy
Data Source
AI summary
A display device (100) includes a plurality of pixel circuits (10), a gate driver circuit (2) coupled to a plurality of scanning signal lines Gi and a plurality of control lines Ei, and a power control circuit (4) coupled to a plurality of power lines VPi via a common power line. The pixel circuits (10) each include an organic EL element, a plurality of TFTs, and a capacitor, and are controlled to collectively receive initialization potentials at the beginning of a frame through the power lines VPi, collectively perform threshold detection immediately thereafter, and then perform writing and light-emission operations. Thus, the aperture ratio of the pixel circuits (10) can be kept high, the power control circuit (4) typically has only one output buffer so that the circuit scale thereof is small, drive by potential is performed only once, so that power consumption is low, and threshold detection is performed only once, so that a sufficient amount of time can be ensured for a detection period.