OLED Pixel Driving Circuit With Source Follower for Luminance Uniformity
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Solution Overview
Problem
Existing OLED driving circuits face issues such as threshold voltage variations in transistors leading to luminance non-uniformity, IR drop affecting power supply voltage, and leakage currents causing brightness fluctuations within frames.
Innovation Solution
A pixel driving circuit utilizing a source follower configuration decouples current flow from power supply voltage, correlating it with a reference signal to mitigate luminance non-uniformity, employing a source follower, driving, data writing, compensation, and reset sub-circuits to stabilize current flow across multiple frame cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional OLED driving circuit is used, then the circuit structure is simple, but the luminance uniformity deteriorates due to threshold voltage variations and power supply voltage fluctuations
Solution Approach 1:
The patent introduces a source follower circuit as an intermediary between the power supply voltage line and the driving transistor. This source follower acts as a buffer that isolates the driving transistor from power supply voltage fluctuations, thereby improving luminance uniformity without requiring fundamental changes to the overall circuit architecture
Solution Approach 2:
The patent segments the driving circuit into distinct functional modules: a first reset sub-circuit, a source follower sub-circuit, a driving sub-circuit, a data writing sub-circuit, a compensation sub-circuit, and a second reset sub-circuit. This modular segmentation allows each sub-circuit to perform its specific function optimally, contributing to improved luminance uniformity while keeping the overall design organized and manageable
2Reliability
If threshold compensation is completed within 1H time, then the operating speed is fast, but the threshold compensation is insufficient
Solution Approach 1:
The patent employs periodic action by dividing the compensation process into two distinct phases occurring at different time periods: first reset phase (first H time) and second reset phase (second H time). This periodic approach allows sufficient time for accurate threshold compensation while maintaining the overall frame timing structure, thereby improving compensation accuracy without excessive time loss
3Reliability
If data writing and threshold compensation share the same time slot, then the operating efficiency is high, but the threshold compensation accuracy deteriorates
Solution Approach 1:
The patent segments the operation timeline into distinct time slots: the first reset phase is dedicated exclusively to threshold compensation, while the second reset phase is dedicated to data writing. This temporal segmentation ensures that threshold compensation receives sufficient time and attention for accurate execution, while data writing occurs in a separate phase, thereby maintaining both compensation accuracy and overall operating efficiency
4Manufacturing precision
If power supply voltage line is used directly, then the circuit is simple, but IR drop causes luminance non-uniformity
Solution Approach 1:
The patent introduces a source follower circuit as an intermediary between the power supply voltage line and the driving transistor. This source follower acts as a buffer that isolates the driving transistor from power supply voltage fluctuations, thereby improving luminance uniformity without requiring fundamental changes to the overall circuit architecture
Data Source
AI summary
A pixel driving circuit, a control method for the pixel driving circuit and a display device. The pixel driving circuit is configured to drive a light-emitting element to emit light cross multiple frame cycles, and each frame cycle includes at least a first frame in a timing sequence. The pixel driving circuit includes: a source follower sub-circuit, a driving sub-circuit, a data writing sub-circuit, a compensation sub-circuit, a first reset sub-circuit and a second reset sub-circuit, and a light-emitting control sub-circuit. The pixel driving circuit of the present application utilizes a source follower configuration, which decouples the magnitude of the current flowing through the pixel driving circuit from a power supply voltage and instead correlates the magnitude of the current flowing through the pixel driving circuit with a reference signal on the reference signal line.