Variable Scan Signal Supply for OLED Hysteresis and Power
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Solution Overview
Problem
Organic light emitting diode displays face issues with hysteresis characteristics in driving transistors, leading to inconsistent current flow and luminance due to previous data voltage effects, which are not adequately addressed by existing driving methods.
Innovation Solution
A display device and driving method that vary the number of scan signals based on driving frequencies, with p-type and n-type scan signals being supplied differently during distinct periods to manage hysteresis and reduce power consumption, utilizing p-type and n-type thin film transistors to control current flow effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple scan signals are supplied to improve hysteresis characteristic, then luminance consistency is improved, but power consumption increases
Solution Approach 1:
The patent applies dynamics by making the number of scan signals variable rather than fixed. The driving transistor dynamically adjusts the number of scan signals supplied based on the driving frequency: at high frequencies (first mode), more scan signals are supplied to address hysteresis; at low frequencies (second mode), fewer scan signals are supplied to reduce power consumption. This dynamic adaptation resolves the contradiction between maintaining luminance consistency and minimizing power consumption across different operating conditions.
Solution Approach 2:
The patent changes the parameter of scan signal quantity based on driving frequency. In the first mode (high frequency), i number of scan signals are supplied to compensate for hysteresis effects. In the second mode (low frequency), j number of scan signals (where j < i) are supplied to reduce power consumption while maintaining adequate luminance consistency. This parameter change strategy allows the system to optimize the trade-off between luminance consistency and power consumption for different operating scenarios.
2Use of energy by moving object
If driving frequency is reduced to save power, then power consumption decreases, but hysteresis effect becomes more pronounced
Solution Approach 1:
The patent employs dynamics by adapting the scan signal supply strategy to the driving frequency. When operating in the second mode at reduced driving frequency, the system supplies a reduced number of scan signals (j < i) during specific periods. This dynamic adjustment ensures that even at lower frequencies where hysteresis effects are more pronounced, adequate luminance consistency is maintained through optimized timing and quantity of scan signals, while still achieving power consumption reduction.
3Reliability
If multiple scan signals are supplied during each frame period, then hysteresis characteristic is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the driving operation into distinct modes and periods. The first mode uses i number of scan signals for comprehensive hysteresis compensation, while the second mode uses j number of scan signals for power-efficient operation. Within the second mode, the driving period is segmented into first periods (where scan signals are supplied) and second periods (where scan signals are reduced or omitted). This segmentation allows complex multi-signal driving to be managed through structured, manageable segments rather than continuous complexity.
Solution Approach 2:
The patent implements periodic action by establishing repeating cycles of first periods and second periods within the second mode. The timing controller supplies scan signals in a periodic pattern, alternating between periods with full scan signal supply (first periods) and periods with reduced scan signal supply (second periods). This periodic structure simplifies the control logic compared to continuous complex driving, as the pattern repeats predictably, reducing the overall complexity of the driving method while maintaining hysteresis compensation effectiveness.
Data Source
AI summary
A display device including pixels connected to a p-type scan line, an n-type scan line, and a data line, to display an image in a first mode with a first frequency or a second mode with a second, lower frequency, a first scan driver to supply a p-type signal having a first voltage to the p-type scan line, and a second scan driver to supply an n-type signal having a second, greater voltage to the n-type scan line, the second mode includes a first period corresponding to one frame period and a second period including consecutive frame periods, in which during the first period, the scan drivers supply i number of corresponding signals to the p-type and n-type scan lines, respectively, and during at least one frame of the second period, the first scan driver supplies j number of p-type signals to the p-type scan line.