Capacitive Pixel Driving Circuit for μLED Short-Defect Address Detection
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Solution Overview
Problem
In μLED display panels, short defects in μLEDs are difficult to detect, particularly affecting the Y address, and oxide TFTs in display circuits are sensitive to environmental factors leading to brightness non-uniformity (mura).
Innovation Solution
The display device incorporates pixel driving circuits with switches, capacitors, and accommodation spaces to detect short defects by adjusting reference voltage levels and determining electrical relations between nodes, using capacitive coupling to identify defective pixels and compensate for threshold voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If array test is used to detect short defects in μLED, then X address can be detected, but Y address cannot be detected
Solution Approach 1:
The pixel driving circuit is segmented into distinct functional components: a first switch for detecting signals, a capacitor for voltage storage, and an accommodation space for the light-emitting element. This segmentation allows independent testing of electrical connections (X address) and voltage level responses (Y address) to fully detect short defects
Solution Approach 2:
A capacitor is introduced as an intermediary component between the switching element and the light-emitting element. The capacitor stores voltage levels that serve as intermediaries to transmit information about the electrical state, enabling the detection system to infer Y address information through voltage level analysis
2Ease of operation
If oxide TFTs are used as driving TFTs, then pixel current control is achieved, but sensitivity to environmental factors causes brightness non-uniformity
Solution Approach 1:
The capacitor performs preliminary action by pre-storing reference voltage levels before the light-emitting element is activated. By establishing known voltage states in advance, the system creates a baseline for comparison that compensates for subsequent environmental variations, ensuring consistent brightness
Solution Approach 2:
The system utilizes parameter changes in voltage levels stored by the capacitor to detect and compensate for threshold voltage variations in oxide TFTs. By monitoring and adjusting voltage parameters, the system maintains reliable display uniformity despite environmental sensitivity of the oxide TFT materials
3Measurement precision
If detecting operation is performed, then short defects can be identified, but power consumption increases
Solution Approach 1:
The detecting operation is implemented as periodic action rather than continuous operation. The first switch periodically tests the electrical connection and the capacitor periodically stores and releases voltage levels, enabling defect detection only when necessary. This periodic testing significantly reduces overall power consumption compared to continuous monitoring
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 solution effectively identifies both X and Y addresses of defective pixels, reduces sensitivity to environmental factors, and minimizes power consumption and leakage currents, enhancing display uniformity and efficiency.
Implementation Method 1
a capacitor, and an accommodation space. A first terminal of the first switch is coupled with a first node. A first terminal of the capacitor is coupled with the first node. A second terminal of the capacitor is coupled with a second node
Data Source
AI summary
A display device includes multiple pixel driving circuits coupled in series. A first pixel driving circuit of the multiple pixel driving circuits includes a first switch, a capacitor and an accommodation space. A first terminal of the first switch is configured to output the detecting signal. A second terminal of the first switch and a first terminal of the capacitor are coupled to a first node. A second terminal of the capacitor and a first terminal of the accommodation space are coupled to a second node. A second terminal of the accommodation space is configured to receive a reference signal. The accommodating space is configured to accommodate a light-emitting element after a detecting operation. During the detecting operation, an electrical relation between the first terminal of the accommodation space and the second terminal of the accommodation space is determined based on the detecting signal.