OLED Display Pixel with Dual Off-Voltage Flicker Control
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Solution Overview
Problem
Existing OLED display devices experience image quality degradation due to leakage currents in transistors during low frequency driving, leading to significant flicker.
Innovation Solution
Implementing a dual transistor structure for the third and fourth transistors in the pixel circuit, with adjusted off-voltage levels for the scan and initialization signals in low frequency hold periods to compensate for leakage currents and maintain gate node voltage stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the OLED display device is driven at a relatively low frequency when displaying a still image, then power consumption is reduced, but the stored data signals are distorted by leakage currents of transistors, causing image quality degradation
Solution Approach 1:
The patent applies parameter changes by adjusting the off-voltage levels of scan signals and initialization signals to different values depending on the driving mode (normal or low frequency). In low frequency driving mode, the off-voltage levels are specifically adjusted to compensate for transistor leakage currents, thereby maintaining gate node voltage stability and preventing data signal distortion while enabling power-saving low frequency operation
Solution Approach 2:
The patent implements dynamics by making the pixel circuit adaptable to different driving conditions. The circuit dynamically adjusts its behavior based on the driving mode: in normal mode it operates with standard voltage levels, while in low frequency mode it transitions to adjusted voltage levels that compensate for leakage effects, allowing the same circuit to optimize for both power consumption and image quality under different conditions
2Stability of the object's composition
If the off-voltage levels of scan signals and initialization signals are adjusted in low frequency hold periods, then leakage current effects are compensated and gate node voltage stability is maintained, but the pixel circuit requires more complex voltage control
Solution Approach 1:
The patent applies universality by using the existing scan driver and initialization signal generation circuitry to provide multiple voltage levels. The same hardware components that generate standard voltage levels in normal mode are configured to provide adjusted voltage levels in low frequency mode, eliminating the need for additional dedicated compensation circuitry and reducing overall device complexity
Data Source
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AI summary
A pixel of a display device includes a capacitor; a light emitting diode; and first, second, third, and fourth transistors. The display device has a normal frequency mode and a low frequency mode. Two electrodes of the capacitor are respectively connected to a first voltage source and a gate node. A gate electrode of the first transistor is connected to the gate node. In a hold period in the low frequency mode, both the second and third transistors receive a scan signal, the third transistor diode-connects the first transistor, the fourth transistor receives an initialization signal and transfers an initialization voltage to the gate node, the scan signal is at a first off voltage level, and the initialization signal is at a second off voltage level unequal to the first off voltage level. The cathode of the light emitting diode is connected to a second voltage source.