OLED AC Driving Circuit Alternating Polarity to Prevent Aging
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Solution Overview
Problem
OLED displays face issues of non-uniformity due to internal resistance and aging, leading to decreased brightness and energy efficiency over time, primarily because of the use of DC driving which results in accumulated carriers forming a built-in electric field.
Innovation Solution
An OLED AC driving circuit with a light-emitting control unit, charging unit, driving unit, storage units, and voltage control units is introduced, which alternates the electrical levels to improve carrier recombination efficiency and reduce internal resistance effects, using transistors and capacitors to maintain constant voltage and prevent voltage drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If DC driving is used to drive OLED, then the circuit structure is simple, but carriers accumulate at interfaces forming built-in electric field causing threshold voltage increase and brightness drop
Solution Approach 1:
The patent applies periodic AC driving instead of continuous DC driving. The driving voltage alternates between positive and negative half-cycles, causing carriers to periodically reverse direction and preventing accumulation at interfaces. This periodic action eliminates the built-in electric field formation while maintaining simple circuit structure.
2Ease of manufacture
If LTPS process is used for manufacturing driving circuit, then the manufacturing process is mature, but transistor threshold voltages show poor uniformity resulting in non-uniform driving currents
Solution Approach 1:
The patent introduces a compensation circuit that detects the actual threshold voltage of each transistor and adjusts the driving current accordingly. The compensation unit stores correction values in memory units and applies them through additional transistors to equalize the driving current across all pixels, compensating for LTPS process variations.
3Power
If lines have internal resistance and OLEDs are current-driven, then voltage drops occur in lines, but power supply voltages at different positions cannot reach required voltage
Solution Approach 1:
The patent divides the power supply system into multiple independent voltage control units, each serving specific regions of the display. Each voltage control unit independently regulates the power supply voltage for its region, compensating for voltage drops caused by line resistance and ensuring uniform power supply across different positions.
Data Source
AI summary
An OLED AC driving circuit, a driving method and a display device are disclosed in the present disclosure. The OLED AC driving circuit includes a light-emitting control unit, a charging unit, a driving unit, a first storage unit, a second storage unit, a first light-emitting unit, a second light-emitting unit, a first voltage control unit and a second voltage control unit. The present disclosure employs the first light-emitting unit and the second light-emitting unit which are connected reversely with each other to make the first light-emitting unit and the second light-emitting unit emit light alternately during two adjacent frames. In one frame, only one light-emitting unit emits light for display while the other one is reversely biased. When the next frame comes, the two units exchange their operating states. The AC driving of the light-emitting units is realized, thus improving the energy utilization efficiency. The cause of the aging of the light-emitting unit is removed completely, and the lifespan of the light-emitting unit is extended largely. The influence of the internal resistance of the lines on the light-emitting current is eliminated, and the display quality of pictures is improved.