Light-emitting Display Device Scan Driver Timing Control
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Solution Overview
Problem
Conventional light-emitting display devices suffer from flickering issues that degrade image quality, particularly due to luminance differences during variable refresh rate (VRR) driving, where the emission signal is output multiple times in a frame period and anode reset is performed, leading to inconsistent light emission.
Innovation Solution
The proposed light-emitting display device employs a scan driver that outputs emission signals and reset signals with varying delay periods and pulse widths, and uses a combination of p-type low-temperature polycrystalline silicon (LTPS) and n-type oxide transistors to manage subpixel driving, including refresh and skip frame driving modes, to minimize luminance differences and flickering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the emission signal is output multiple times in a frame period during VRR driving, then the refresh rate is improved and power consumption is reduced, but luminance inconsistency and flickering occur
Solution Approach 1:
The patent applies preliminary action by performing anode reset before each emission period. The anode reset signal is output in advance to reset the accumulated charge at the anode of the light-emitting element, ensuring that each emission period starts with consistent initial conditions. This prevents luminance inconsistency caused by varying charge accumulation during multiple emission signals in VRR driving.
Solution Approach 2:
The patent changes the timing parameters of the anode reset signal dynamically. The anode reset signal is output at different time points relative to each emission signal, with the reset timing adjusted based on the emission signal's position in the frame period. This parameter adjustment ensures consistent luminance output across multiple emission periods while maintaining improved refresh rates.
2Loss of energy
If variable refresh rate driving is implemented, then power consumption is reduced, but flickering and image quality degradation occur
Solution Approach 1:
The anode reset is performed as a preliminary action before each emission period during VRR driving. This ensures that the light-emitting element starts each emission period with a consistent charge state, preventing flickering that would otherwise occur due to varying charge accumulation during low-power VRR operation with multiple emission signals.
Solution Approach 2:
The patent maintains continuous anode reset action throughout the VRR driving cycle, ensuring that each emission period receives the necessary charge reset. This continuous reset action eliminates gaps in charge management that would cause flickering, while still allowing the display to operate in low-power VRR mode by controlling the number and timing of emission signals.
3Ease of operation
If multiple emission signals are used in one frame period, then emission control is improved, but inconsistent light emission and image quality occur
Solution Approach 1:
The anode reset signal is output as a preliminary action before each emission signal. This reset operation prepares the anode by removing accumulated charge, ensuring that each emission period starts with identical initial conditions. This preliminary reset action enables precise control of multiple emission signals while maintaining consistent light emission intensity across all emission periods.
Solution Approach 2:
The patent implements a feedback mechanism where the anode reset timing and duration are adjusted based on the emission signal characteristics. The reset signal is synchronized with each emission signal, creating a feedback loop that ensures consistent charge levels at the anode before each emission period, thereby maintaining light emission consistency across multiple emission signals.
Data Source
AI summary
A light-emitting display device includes a display panel including a plurality of subpixels each including a light-emitting element, a data driver configured to supply a data voltage and a reset voltage to each of the subpixels, and a scan driver configured to output an emission signal for controlling a non-emission period and an emission period of the light-emitting element and a reset signal for controlling a reset period of each of the subpixels, wherein the scan driver outputs the emission signal a plurality of times in one frame period and outputs the reset signal a plurality of times in a non-emission period according to the emission signal, and at least one of a plurality of emission signals or a plurality of reset signals has at least one of a different delay period or a different pulse width.