OLED Pixel Scan Timing for Uniform Brightness 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 and control lines, 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
1Ease of manufacture
If oxide semiconductor transistors are used in display apparatus, then device complexity is reduced and ease of manufacture is improved, but brightness differences occur across different driving frequencies
Solution Approach 1:
The patent applies dynamics by making the scan period variable based on driving frequency. The gate driving circuit dynamically adjusts the scan period length - using a first scan period at maximum driving frequency and a second scan period (longer than the first) at lower driving frequencies. This dynamic adjustment compensates for the oxide semiconductor transistor's slower response at lower frequencies, maintaining consistent brightness across different operating conditions while preserving the ease of manufacture benefits of oxide semiconductor technology.
2Use of energy by moving object
If driving frequency is reduced to save power, then energy consumption is decreased, but brightness differences and display uniformity deteriorate
Solution Approach 1:
The patent implements periodic action by structuring the scanning process into distinct periodic phases. At lower driving frequencies, the gate driving circuit inserts a second scan period between frames, creating a periodic pattern of scanning operations. This periodic structure allows the oxide semiconductor transistors sufficient time to respond and stabilize their output, ensuring brightness uniformity is maintained even when the overall driving frequency is reduced for power savings.
3Illumination intensity
If scan period is extended to improve transistor response, then brightness uniformity is improved, but productivity and response speed deteriorate
Solution Approach 1:
The patent applies dynamics by making the scan period variable based on driving frequency. The gate driving circuit dynamically adjusts the scan period length - using a first scan period at maximum driving frequency and a second scan period (longer than the first) at lower driving frequencies. This dynamic adjustment compensates for the oxide semiconductor transistor's slower response at lower frequencies, maintaining consistent brightness across different operating conditions while preserving the ease of manufacture benefits of oxide semiconductor technology.
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.