Dynamic Charging Time Control for OLED Sub-Pixel Luminance Uniformity
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Solution Overview
Problem
In display panels, particularly in OLEDs, the inconsistent threshold voltage of driving transistors leads to varying emission luminance due to differences in manufacturing processes, temperature, and device aging, resulting in overcharging or undercharging of sub-pixels when using a fixed charging time.
Innovation Solution
A method is implemented to dynamically adjust the charging time of sub-pixels by detecting the voltage difference across the driving transistor's electrodes and comparing it to a target voltage, incrementally increasing the charging time until the desired voltage difference is achieved, ensuring each sub-pixel reaches the self-saturated state consistently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed charging time is used for all sub-pixels, then the control process is simple, but the emission luminance becomes inconsistent due to threshold voltage variations
Solution Approach 1:
The patent implements dynamic charging time adjustment by introducing a feedback mechanism that measures the actual voltage of each sub-pixel and adjusts the charging time accordingly. The charging time is no longer fixed but varies dynamically based on the measured voltage and threshold voltage difference, ensuring consistent emission luminance across all sub-pixels despite manufacturing variations.
Solution Approach 2:
The patent employs a feedback control mechanism where the actual voltage of each sub-pixel is measured during or after charging, and this measurement is used to adjust the charging time for subsequent cycles. The system continuously monitors voltage levels and modifies charging parameters to achieve the desired threshold voltage difference, thereby maintaining luminance consistency.
2Reliability
If the charging time is increased to ensure all sub-pixels are fully charged, then undercharging is prevented, but overcharging occurs in sub-pixels that reach saturation earlier
Solution Approach 1:
The patent uses real-time voltage measurement feedback to determine when each sub-pixel has reached its optimal charging state. By monitoring the actual voltage and comparing it with the target threshold voltage difference, the system can precisely control the charging duration for each sub-pixel, stopping charging when the target is reached to prevent overcharging while ensuring adequate charging for all pixels.
Solution Approach 2:
The patent applies different charging time durations to different sub-pixels based on their individual voltage characteristics. Instead of using a uniform charging time for all sub-pixels, the system tailors the charging duration to each sub-pixel's specific needs, allowing sub-pixels that charge faster to receive shorter charging periods while ensuring that slower-charging sub-pixels receive adequate time, thus preventing both overcharging and undercharging.
3Manufacturing precision
If individual charging times are determined for each sub-pixel to achieve uniform luminance, then emission consistency is improved, but the control process complexity increases
Solution Approach 1:
The patent adjusts the charging time parameter based on measurable voltage characteristics of each sub-pixel. By changing the charging time parameter dynamically according to the measured actual voltage and threshold voltage difference, the system achieves uniform emission luminance without requiring complex control mechanisms, as the adjustment is based on straightforward voltage measurements and calculations.
Solution Approach 2:
The patent enables each sub-pixel to effectively determine its own optimal charging time through the feedback mechanism. The measurement and adjustment process is automated and performed independently for each sub-pixel based on its own voltage characteristics, reducing the need for complex centralized control while achieving individualized charging optimization.
Data Source
AI summary
A method for controlling a charging time of a display panel includes: during t0+kΔt in a (k+1)-th blanking time, writing a data voltage to a gate of a driving transistor, and detecting a voltage Vk_(j,i) of a second electrode of the driving transistor; during a t0+(k+r)Δt in a (k+1+r)-th blanking time, writing the data voltage to the gate of the driving transistor, and detecting a voltage Vk+1_(j,i) of the second electrode of the driving transistor; determining whether ΔVj,i=Vk+1_ji−Vk_ji is less than or equal to a target voltage difference VT; if ΔVj,i≤VT, taking the T=t0+kΔt as an expected charging time of a sub-pixel; if ΔVj,i>VT, cyclically performing the charging step described above to obtain ΔVj,i=Vk+p+1_(j,i)−Vk+p_(j,i), and comparing ΔVj,i with the target voltage difference VT, until ΔVj,i≤VT, taking t0+(k+p+r−1)Δt as the expected charging time of the sub-pixel. p is taken from 1, and increases by 1 for each cycle.