OLED Repair Circuit Maintains Luminance Without Blind Spots
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Solution Overview
Problem
Organic light emitting diode (OLED) displays face defects in the pixel circuit, leading to reduced yield and luminance issues, as existing repair methods either fail to correct the defect or result in a blind spot, rather than maintaining desired luminance.
Innovation Solution
Incorporating a repair circuit with transistors connected between repair lines and power lines, and a switching unit that selectively connects the OLED to either the data or repair lines, allowing the repair circuit to supply driving current and maintain light emission even when a defect occurs in the pixel circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a repair circuit is added to correct pixel defects, then the yield and reliability are improved, but the device complexity increases
Solution Approach 1:
The repair circuit is nested within the existing pixel circuit structure. The repair transistor is integrated into the pixel circuit, sharing the same layout space and utilizing existing circuit nodes. This allows the repair functionality to be embedded without significantly increasing the overall device area or structural complexity.
Solution Approach 2:
A switching unit is introduced as an intermediary component that selectively connects the pixel circuit to either the data line or the repair line. This mediator enables the system to switch between normal operation mode and repair mode, allowing defect correction without permanently altering the circuit structure or requiring complex reconfiguration.
2Illumination intensity
If the switching unit is used to connect OLED to repair lines, then the luminance is maintained, but the device complexity increases
Solution Approach 1:
The switching unit operates periodically, switching between connecting to the data line and connecting to the repair line based on the timing of the driving signals. During normal operation, the switch connects to the data line; when a defect is detected, it switches to connect to the repair line. This periodic switching is controlled by timing signals that synchronize with the pixel driving cycle.
Solution Approach 2:
The repair line is pre-charged to the appropriate voltage level before the switching occurs. The switching unit is configured in advance to connect to the repair line at the appropriate moment in the driving cycle, ensuring that the OLED receives the correct driving voltage immediately when the switch transitions, without requiring complex real-time voltage adjustment.
3Reliability
If repair circuits are added to each pixel, then the defect correction capability is improved, but the manufacturing cost increases
Solution Approach 1:
The repair circuit components, particularly the repair transistor and repair line, serve multiple functions. The repair transistor can operate in different modes (cut-off mode for isolation, linear mode for current control) depending on the defect type and timing. The same repair circuit structure can correct various types of pixel defects including stuck pixels, dim pixels, and lines with multiple defects, reducing the need for different repair mechanisms for different failure modes.
Data Source
AI summary
An organic light emitting display including a repair circuit is disclosed. In one aspect the organic light emitting diode (OLED) display includes a pixel unit having a plurality of pixels positioned at the intersection of scanning lines, data lines, and power lines, The OLED display further includes an organic light emitting diode OLED connected to the pixel circuit, and repair lines disposed in parallel with data lines and repair circuits connected to the repair lines and the power lines. The OLED display further includes a switching unit for selectively connecting output lines of the data driving unit to the repair lines or the data lines.