Pixel Compensation Circuit for Low-Frequency Display Flicker
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Solution Overview
Problem
Display devices driven at low frequencies experience increased leakage current and luminance differences between frames, leading to flicker phenomena due to kick-back voltage increases in pixel circuits.
Innovation Solution
Incorporating dual transistors with compensation capacitors and voltage lines to manage gate voltages, reducing kick-back voltage by providing compensation voltages that change in a manner that suppresses leakage current, and using larger overlapping areas for capacitors to enhance capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the display device is driven at a relatively low frequency to reduce power consumption, then power consumption is reduced, but leakage current in the pixel circuit increases causing luminance differences and flicker phenomena
Solution Approach 1:
The compensation capacitor is pre-charged to a compensation voltage during a programming period before the display period. This preliminary action stores the necessary charge to counteract the kick-back voltage that will occur during low-frequency operation, allowing the device to maintain stable luminance even when driven at reduced frequencies for lower power consumption
Solution Approach 2:
The compensation capacitor acts as an intermediary element between the pixel circuit components. It mediates the voltage fluctuations by absorbing and releasing charge as needed, isolating the light emitting element from the kick-back voltage effects and enabling stable display operation at low frequencies
2Use of energy by stationary object
If the period of one frame is extended to reduce refresh rate and power consumption, then power consumption is reduced, but leakage current increases causing voltage changes at common nodes
Solution Approach 1:
The compensation capacitor is pre-charged to a compensation voltage during a programming period before the display period. This preliminary action stores the necessary charge to counteract the kick-back voltage that will occur during low-frequency operation, allowing the device to maintain stable luminance even when driven at reduced frequencies for lower power consumption
Solution Approach 2:
The compensation voltage is determined based on the threshold voltage of the driving transistor, creating a feedback mechanism that automatically adjusts the compensation level. This feedback ensures that the compensation capacitor is charged to the appropriate voltage to counteract leakage effects, maintaining voltage stability during extended frame periods
3Reliability
If compensation capacitors and compensation voltage lines are added to suppress kick-back voltage increases, then display stability is improved, but device complexity increases
Solution Approach 1:
The compensation capacitor is integrated within the pixel circuit structure, sharing space and components with other pixel elements. The compensation voltage line is merged with existing voltage lines in the circuit, reducing the need for separate dedicated lines and minimizing the increase in device complexity while still providing effective kick-back voltage suppression
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces leakage current and improves low-frequency characteristics of display devices by maintaining constant voltages and minimizing flicker phenomena.
Implementation Method 1
a first compensation electrode overlapping at least a portion of the first common area to define the first compensation capacitor
Data Source
AI summary
A display device includes: a light emitting element; a driving transistor configured to transmit a driving current to the light emitting element; a first dual transistor comprising a first sub transistor connected to a gate electrode of the driving transistor, and a second sub transistor configured to connect an input electrode of the first sub transistor and an output electrode of the driving transistor; an active layer comprising a first common area defining the input electrode of the first sub transistor and an output electrode of the second sub transistor; a first compensation electrode overlapping at least a portion of the first common area to define the first compensation capacitor; and a first compensation voltage line configured to provide a first compensation voltage to the first compensation electrode.