VRR Display Pixel Circuits with Variable Anode Reset Frequency
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Solution Overview
Problem
Existing organic light-emitting display devices face challenges in maintaining response characteristics and image quality at low grayscale levels when operating in Variable Refresh Rate (VRR) mode, with issues such as anode charge delay leading to increased stain amounts and degraded visibility during frequency changes.
Innovation Solution
The display device incorporates a pixel circuit with a driving transistor, storage capacitor, and reset transistor, where the operating frequency of the scan signal is varied for anode reset frames in VRR mode, dividing refresh frames into multiple sub-frames with specific frequency settings to improve visibility and reduce anode charge delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the operating frequency of the scan signal is set to a specific frequency for the anode reset frame, then visibility in frequency change is improved, but response characteristics deteriorate and stain amount increases due to anode charge delay at low grayscale
Solution Approach 1:
The patent applies dynamics by making the operating frequency of the scan signal variable rather than fixed. Specifically, the frequency is adjusted based on the grayscale level: at low grayscale levels, a lower frequency is used to reduce anode charge delay and staining, while at higher grayscale levels, a higher frequency maintains visibility. This dynamic frequency adjustment resolves the contradiction between visibility and response characteristics.
Solution Approach 2:
The patent changes the operating frequency parameter of the scan signal based on grayscale conditions. By setting different frequency values for different grayscale ranges, the system optimizes both visibility and response characteristics. The frequency parameter is modified to match the charge characteristics of the anode at different luminance levels, thereby resolving the technical contradiction.
2Illumination intensity
If the operating frequency of the scan signal is set to a specific frequency for the anode reset frame, then visibility in frequency change is improved, but stain amount increases at low grayscale
Solution Approach 1:
The patent uses dynamic frequency adjustment where the scan signal frequency varies with grayscale level. At low grayscale levels where staining occurs, the frequency is reduced to allow complete discharge of the anode, preventing charge accumulation and staining. At higher grayscale levels, the frequency is increased to maintain visibility, thus dynamically resolving the contradiction between visibility and stain prevention.
Solution Approach 2:
The operating frequency parameter is changed based on grayscale conditions to control stain formation. By lowering the frequency at low grayscale levels, the system allows sufficient time for anode charge discharge, preventing staining. The parameter change adapts the frequency to match the charge characteristics at different luminance levels, resolving the contradiction.
3Use of energy by moving object
If VRR mode is implemented for power consumption reduction, then energy efficiency improves, but image quality characteristics deteriorate at low grayscale
Solution Approach 1:
The patent maintains VRR mode for power savings while dynamically adjusting the scan signal frequency based on grayscale level. This dynamic adjustment ensures that at low grayscale levels, the frequency is lowered to prevent staining and maintain image quality, while at higher grayscale levels, the frequency can be higher to maintain visibility. This resolves the contradiction between energy efficiency and image quality.
Solution Approach 2:
The patent changes the frequency parameter of the scan signal according to grayscale conditions within the VRR framework. This parameter modification allows the system to maintain low power consumption through VRR while preventing image quality degradation at low grayscale by using appropriate frequency values, thus resolving the technical contradiction.
Data Source
AI summary
The display device includes a pixel circuit, wherein the pixel circuit includes: a light-emitting element configured to emit light based on a driving current; a driving transistor configured to control the driving current, and including a gate electrode, a source electrode, and a drain electrode, wherein a data voltage is applied to the source electrode; a storage capacitor connected to and disposed between the gate electrode of the driving transistor and a power voltage; and a reset transistor configured to apply an initialization voltage to an anode electrode of the light-emitting element in response to a scan signal, wherein when the display device operates in a Variable Refresh Rate mode for a refresh frame, an operating frequency of the scan signal varies for an anode reset frame of the refresh frame. Thus, response and image quality characteristics at a low gray level are simultaneously improved.