OLED Pixel Driving Circuit AC Power Control
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Solution Overview
Problem
OLED display panels face issues with non-uniform brightness due to threshold voltage drift and voltage drops in driving transistors, leading to uneven brightness and accelerated aging from DC power supply.
Innovation Solution
A display panel with pixel driving circuits connected to multiple power lines, including a first and second power line, where the second power line provides AC power to the light emitting device, allowing it to be forward-biased during display and reversed-biased in other stages, along with a sampling compensation assembly and switch assemblies to manage voltage and current, independent of threshold voltage and supply voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If DC power supply is used to drive OLED, then the light emitting device can be continuously powered, but the aging of the light emitting device is accelerated
Solution Approach 1:
The patent applies periodic action by switching the power supply between positive and negative polarity in alternating cycles. The light emitting device is driven by AC power signal that alternates between forward bias (light emitting stage) and reverse bias (non-light emitting stage), preventing continuous operation in one state that causes aging. This periodic polarity switching extends device lifespan while maintaining operational stability.
2Device complexity
If simple pixel driving circuit is used, then device complexity is reduced, but brightness uniformity deteriorates due to threshold voltage drift and voltage drops
Solution Approach 1:
The patent applies preliminary action by performing compensation operations before the actual light emitting stage. The sampling compensation assembly measures and compensates for threshold voltage drift and voltage drops in advance during initialization and sampling stages, storing compensation values in capacitors. This preliminary compensation ensures brightness uniformity is maintained throughout operation without requiring complex real-time correction circuits.
3Device complexity
If threshold voltage drift and voltage drops are not compensated, then device complexity is reduced, but brightness uniformity deteriorates
Solution Approach 1:
The patent implements feedback through the sampling compensation assembly that continuously monitors and compensates for threshold voltage drift and voltage drops. During the sampling stage, the circuit measures the actual voltage conditions and stores compensation values. During the light emitting stage, these compensation values are applied to correct the driving current, ensuring brightness uniformity. This feedback mechanism maintains performance without requiring overly complex circuit architecture.
Data Source
AI summary
A display panel includes a plurality of pixel driving circuits arranged in an array along a row direction and a column direction. The display panel further comprises a plurality of first control lines, a plurality of second control lines, a plurality of data lines, and a plurality of power lines. Each of the pixel driving circuits is correspondingly connected to the first control line, the second control line, the data line, and two power lines, and the two power lines comprises a first power line and a second power line. The pixel driving circuit includes: a driving transistor, a storage capacitor, a sampling compensation assembly, a first switch assembly, a second switch assembly and a light emitting device.