OLED Pixel Circuit Voltage Providing Module for Low Refresh Flicker
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Solution Overview
Problem
At low refresh frequencies, OLED display panels experience brightness differences between writing and holding frames due to threshold voltage drift in thin film transistors, leading to perceptible flicker and brightness decay.
Innovation Solution
A pixel circuit with a voltage providing module, a voltage writing-in module, and a driving module, where the voltage providing module controls the supply of power voltages to the driving module under reset and light-emitting control signals, ensuring all driving transistors are at a consistent reference during switching, mitigating hysteresis effects and threshold voltage drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the refresh frequency of the screen is reduced to meet power consumption demands, then energy efficiency is improved, but brightness uniformity deteriorates due to threshold voltage drift causing perceptible flicker
Solution Approach 1:
The patent applies preliminary action by providing an initial voltage to the driving module before normal operation begins. This initial voltage is specifically designed to counteract threshold voltage drift that occurs during low-frequency operation, thereby preventing brightness decay and flicker before they can manifest. The voltage providing module activates early in the frame cycle to establish stable operating conditions for the driving transistors.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the voltage level provided to the driving module based on the operation mode. When low refresh frequency is detected or anticipated, the system changes the voltage parameter from the normal first power supply voltage to a specially designed initial voltage that compensates for drift effects. This parameter adaptation allows the circuit to maintain brightness uniformity across frames while operating at reduced refresh rates.
2Use of energy by moving object
If low refresh frequency operation is implemented to save power, then energy consumption is reduced, but threshold voltage drift increases causing brightness decay
Solution Approach 1:
The patent implements feedback mechanisms through control circuits that monitor the operating conditions and adjust the initial voltage accordingly. The voltage providing module receives control signals based on the actual performance of the driving module, allowing the system to detect and correct threshold voltage drift in real-time. This closed-loop approach ensures that brightness stability is maintained even during extended low-frequency operation where drift would normally accumulate.
3Use of energy by moving object
If the driving module operates at low refresh frequencies, then power consumption is reduced, but hysteresis effects become more pronounced causing perceptible flicker
Solution Approach 1:
The patent applies preliminary anti-action by introducing an initial voltage that specifically counteracts the hysteresis effects expected during low-frequency operation. This voltage is designed to oppose the directional drift that characterizes hysteresis behavior in thin film transistors. By applying this counter-voltage before the harmful hysteresis effects can fully develop, the system prevents rather than merely corrects the flicker phenomenon.
Data Source
AI summary
A pixel circuit includes a light-emitting element, a voltage providing module, a voltage writing-in module and a driving module. The voltage providing module is respectively connected with a first power supply voltage terminal, an initial voltage terminal, a reset signal terminal, a light-emitting control terminal, a voltage writing-in module and a driving module, and is configured to provide a voltage of the first power supply voltage terminal and a voltage of the initial voltage terminal to the driving module under control of the reset signal terminal to turn on the driving module; and provide the voltage of the first power supply voltage terminal to the driving module under control of the light-emitting control terminal.