Display Black Voltage Control for Variable Refresh Luminance Stability
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Solution Overview
Problem
In display devices supporting variable frequency driving, the increased time without data voltage writing in a frame leads to increased current leakage through sub-pixel switching transistors, causing luminance differences.
Innovation Solution
The display device adjusts the black data voltage based on driving frequency, dimming level, and temperature, using a driving controller to determine offset voltages for various components like black data voltage, anode initialization voltage, and gate high voltage, to minimize luminance differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable frequency driving is supported, then adaptability is improved, but current leakage increases causing luminance differences
Solution Approach 1:
The patent implements dynamic adjustment of the black data voltage based on the actual driving frequency of the display device. The driving controller continuously monitors the driving frequency and dynamically modifies the black data voltage parameter accordingly, allowing the system to adapt to different operating conditions while maintaining consistent luminance performance across variable frequencies
Solution Approach 2:
The patent changes the electrical parameter (black data voltage) in response to changes in driving frequency. By establishing a relationship between driving frequency and optimal black data voltage values, the system adjusts this critical parameter to compensate for frequency-induced variations in transistor leakage characteristics, thereby maintaining luminance consistency
2Productivity
If the time without data voltage writing increases, then productivity is improved, but current leakage increases
Solution Approach 1:
The patent applies preliminary action by pre-determining the appropriate black data voltage value based on the expected or measured driving frequency before the actual display operation begins. This proactive adjustment ensures that the transistor leakage is compensated in advance, preventing luminance differences before they occur during extended periods without data writing
3Reliability
If black data voltage is adjusted, then luminance consistency is improved, but device complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the driving controller monitors the actual driving frequency of the display device and uses this information to adjust the black data voltage. This closed-loop control ensures that the system automatically compensates for frequency variations without requiring manual intervention or complex external calibration equipment
Solution Approach 2:
The driving controller performs multiple functions: it manages the overall display operation, monitors driving frequency, determines appropriate black data voltage values, and outputs control signals to the data driver. By consolidating these functions in a single controller, the patent avoids adding separate dedicated circuits for each function, thereby limiting the increase in device complexity
Data Source
AI summary
A display device includes a display panel including a sub-pixel, a gate driver which provides a gate signal to the sub-pixel, a data driver which provides a data voltage to the sub-pixel, a driving voltage generator which provides a gamma reference voltage including a black data voltage to the data driver, and a driving controller which determines an offset voltage of the black data voltage based on at least one selected from a driving frequency, a dimming level, and a temperature.