Pixel Driving Circuit On-Bias Initialization for OLED Afterimage
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Solution Overview
Problem
Existing OLED products experience short-term afterimages due to the hysteresis effect of driving transistors when switching from a black-and-white picture to a grayscale picture, leading to display quality issues.
Innovation Solution
A pixel driving circuit with a specific configuration including a driving sub-circuit, reset sub-circuit, light-emitting control sub-circuit, and compensation sub-circuits, which are connected to provide controlled power supply voltages to maintain the driving sub-circuit in an on-bias state during initialization, compensating the threshold voltage, and enabling the light-emitting element to emit light effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional pixel circuit is used to drive OLED, then the circuit structure is simple, but short-term afterimage occurs due to hysteresis effect when switching from black-and-white picture to grayscale picture
Solution Approach 1:
The pixel circuit is divided into multiple functional sub-circuits: a driving sub-circuit for threshold voltage compensation, a reset sub-circuit for initializing the light-emitting element, a light-emitting control sub-circuit for controlling the light-emitting phase, and a first compensation sub-circuit for compensating driving transistor threshold voltage. This segmentation allows each sub-circuit to perform its specific function independently, resolving the afterimage issue while maintaining overall circuit manageability
Solution Approach 2:
The reset sub-circuit performs preliminary action by resetting the light-emitting element to a reference voltage before the light-emitting phase begins. This preliminary reset operation eliminates residual charges from previous frames that would otherwise cause short-term afterimages, ensuring clean transition between different display content
2Use of energy by moving object
If the driving sub-circuit is kept in off-state during initialization, then power consumption is reduced, but the data voltage of the next frame is affected by the previous frame's voltage due to hysteresis effect
Solution Approach 1:
The driving sub-circuit dynamically transitions between on-bias and off-states based on the operational phase. During initialization phase, it is set to on-bias state to establish proper voltage levels and eliminate hysteresis effects. During light-emitting phase, it switches to off-state to reduce power consumption. This dynamic state management resolves the contradiction between power consumption and voltage stability
Solution Approach 2:
The circuit changes the bias state parameter of the driving sub-circuit from off-state during normal operation to on-bias state during initialization. This parameter change allows the circuit to overcome hysteresis effects when needed while maintaining low power consumption during display operation, achieving both voltage stability and energy efficiency
Data Source
AI summary
A pixel driving circuit and a driving method thereof, and a display panel are provided. The pixel driving circuit includes a driving sub-circuit, a reset sub-circuit, a light-emitting control sub-circuit, and a first compensation sub-circuit, the reset sub-circuit, the light-emitting control sub-circuit, and the first compensation sub-circuit are configured to, in an initialization phase, under control of a first driving signal and a second driving signal, provide the first power supply voltage provided by the first power supply input terminal to the control terminal of the driving sub-circuit; the first terminal of the driving sub-circuit is connected to the second power supply input terminal to receive the second power supply voltage; and the first power supply voltage and the second power supply voltage are configured to cause the driving sub-circuit to be in an on-bias state in the initialization phase.