OLED Pixel Scan Timing for Brightness Stability at Low Refresh Rates
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Solution Overview
Problem
Existing organic light-emitting display apparatuses exhibit brightness differences across different driving frequencies due to variations in transistor performance, particularly when using oxide semiconductor transistors.
Innovation Solution
A display apparatus design that includes a pixel structure with specific timing and voltage control signals for scan lines and transistors, utilizing N-channel oxide semiconductor transistors, to maintain consistent brightness across varying driving frequencies by employing a first and one or more second scan periods with defined voltage levels and durations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If oxide semiconductor transistors are used in organic light-emitting display apparatuses, then power consumption is reduced and device reliability is improved, but brightness differences occur across different driving frequencies due to transistor performance variations
Solution Approach 1:
The patent applies dynamics by making the scan period duration variable based on driving frequency. The gate driving circuit dynamically adjusts the time period for providing scan signals to match different driving frequencies, ensuring that oxide semiconductor transistors operate within optimal performance ranges across all frequencies. This dynamic adjustment compensates for transistor performance variations and maintains consistent brightness while preserving low power consumption benefits.
Solution Approach 2:
The patent changes the temporal parameter (scan period duration) to compensate for brightness variations. By adjusting the duration of scan periods based on the driving frequency, the system optimizes transistor switching behavior across different frequencies. This parameter change ensures that oxide semiconductor transistors maintain consistent performance characteristics, eliminating brightness differences while retaining energy efficiency advantages.
2Use of energy by stationary object
If the driving frequency is reduced below maximum driving frequency, then power consumption decreases, but brightness differences and image quality degradation occur
Solution Approach 1:
The gate driving circuit dynamically adapts scan period durations to different driving frequencies. When operating below maximum driving frequency, the circuit extends scan period durations to compensate for reduced switching rates, ensuring oxide semiconductor transistors maintain adequate charge/discharge cycles. This dynamic adaptation prevents brightness degradation while preserving the power consumption benefits of lower driving frequencies.
3Illumination intensity
If scan period duration is extended to improve transistor operation at lower frequencies, then brightness consistency improves, but time efficiency and productivity decrease
Solution Approach 1:
The patent employs periodic action by structuring scan periods with specific durations that repeat at different frequencies. Each scan period is optimized to provide adequate time for oxide semiconductor transistor operation while maintaining a rhythmic, periodic structure. This approach ensures brightness consistency across frequencies without excessive time extension, as the periodic nature allows for efficient packing of operational cycles within each frame period.
Data Source
AI summary
A display apparatus includes a pixel part including a plurality of pixels, and a gate driving circuit. Each of the plurality of pixels is driven in one first scan period and one or more second scan periods during one frame in a driving mode driven at a first driving frequency lower than a maximum driving frequency.