Display Device Initialization Voltage Control for Flexible Substrates
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Solution Overview
Problem
In display devices with flexible substrates, the accumulation of induced charges due to voltage differences between the gate electrode of transistors and voltage lines leads to a shift in the threshold voltage of transistors, increasing leakage current and deteriorating display quality.
Innovation Solution
A display device with a power manager that controls the voltage level of an initialization voltage, changing it from a target level corresponding to image luminance to an initialization level with a lower absolute value, either at specific times or during vertical porch periods, to reduce induced charges and threshold voltage shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high voltage level is applied to the initialization voltage line to ensure proper transistor initialization, then the initialization function is improved, but induced charges accumulate in the substrate causing threshold voltage shifts and increased leakage current
Solution Approach 1:
The patent applies dynamics by making the initialization voltage level variable rather than fixed. The power manager dynamically adjusts the initialization voltage between a first level (lower absolute value) during power-on and a second level (higher absolute value) during normal operation. This dynamic adjustment allows the system to minimize induced charges during critical periods while ensuring proper initialization function when needed.
Solution Approach 2:
The patent changes the voltage parameter of the initialization voltage line based on operational state. The power manager switches between different voltage levels (first level with lower absolute value, second level with higher absolute value) depending on whether the display is in power-on state or normal operation state. This parameter change resolves the contradiction by using lower voltage to minimize harmful induced charges during power-on, while using higher voltage to ensure proper initialization during normal operation.
2Stability of the object's composition
If the initialization voltage is kept at a high level during power-on to maintain transistor threshold voltage, then transistor stability is improved, but display quality deteriorates due to increased leakage current from accumulated induced charges
Solution Approach 1:
The patent applies preliminary action by setting the initialization voltage to a lower absolute value level during the power-on state before normal operation begins. This preliminary voltage level minimizes induced charge accumulation during the critical power-on period. Once the display transitions to normal operation state, the power manager then switches to a higher absolute value voltage level to ensure proper transistor initialization and threshold voltage stability.
Solution Approach 2:
The system dynamically transitions the initialization voltage between different levels based on operational state. During power-on state, the voltage is at a lower absolute value to minimize induced charges and improve display quality. During normal operation state, the voltage switches to a higher absolute value to maintain transistor stability and proper initialization function.
3Object-generated harmful factors
If the initialization voltage level is changed frequently to optimize display quality, then induced charges are reduced, but the complexity of voltage control increases
Solution Approach 1:
The patent applies local quality by implementing different voltage control strategies for different operational states. The power manager uses a first voltage level (lower absolute value) specifically during power-on state to minimize induced charges, and a second voltage level (higher absolute value) specifically during normal operation state to ensure proper initialization. This localized approach to voltage control optimizes display quality during power-on without requiring complex continuous adjustment mechanisms.
Solution Approach 2:
The power manager incorporates feedback by monitoring the operational state of the display device and adjusting the initialization voltage accordingly. When the display transitions from power-on state to normal operation state, the power manager detects this state change and switches the voltage level from the first level to the second level. This feedback mechanism simplifies voltage control by using state-based switching rather than continuous complex adjustment.
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 reduction in induced charges and threshold voltage shifts results in lower leakage currents and improved display quality of images in the display device.
Implementation Method 1
When voltages having mutually different polarities are applied to the gate electrode of the transistor and the voltage line, which are adjacent to each other, respectively, induced charges may be accumulated in a portion of the substrate located under the transistor
Data Source
AI summary
A display device is disclosed that includes a display panel including a plurality of pixels configured to receive an initialization voltage through an initialization voltage line, a controller configured to output a voltage control signal for controlling a voltage level of the initialization voltage, and a power manager configured to provide the initialization voltage to the initialization voltage line, change the voltage level of the initialization voltage to an initialization level at or after a power-on time at which a power starts to be supplied and before a display-on time at which an image starts to be displayed based on the voltage control signal, and change the voltage level of the initialization voltage to a target level corresponding to a luminance of the image at or after the display-on time based on the power control signal.