OLED Pixel-Driving Circuit with Emission Control for Grayscale Uniformity
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Solution Overview
Problem
OLED display panels face issues with grayscale nonuniformity due to dependence on threshold voltage and power supply voltage, leading to variations in driving current and luminance across pixels, resulting in afterimages and IR drop-related voltage fluctuations.
Innovation Solution
A pixel-driving circuit with an emission-control sub-circuit using two transistors and capacitors, where the driving current is independent of the threshold voltage and power supply voltage, achieved by controlling the gate-to-source voltage through a reference-voltage signal and data signal, ensuring consistent luminance across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional pixel-driving circuits use driving current dependent on threshold voltage and power supply voltage, then the circuit structure is simple, but grayscale nonuniformity occurs and luminance varies across pixels
Solution Approach 1:
The patent changes the voltage parameters by introducing a reference voltage signal and adjusting gate-to-source voltage to make the driving current independent of threshold voltage and power supply voltage variations, thereby achieving grayscale uniformity across pixels
Solution Approach 2:
The emission-control sub-circuit implements feedback control by using the reference voltage signal to regulate the gate-to-source voltage of the driving transistor, compensating for threshold voltage drift and power supply voltage drops to maintain consistent driving current
2Ease of operation
If driving current depends on threshold voltage, then the circuit operation is straightforward, but threshold voltage drift causes luminance variations and afterimages
Solution Approach 1:
The emission-control sub-circuit provides continuous feedback control by comparing the reference voltage with the actual driving conditions and adjusting the gate-to-source voltage accordingly, compensating for threshold voltage drift to maintain stable luminance
Solution Approach 2:
The circuit performs preliminary voltage adjustment by pre-establishing the gate-to-source voltage through the reference voltage signal before the driving transistor operates, ensuring the driving current remains independent of subsequent threshold voltage changes
3Device complexity
If power supply voltage fluctuates, then the power supply is simple, but voltage drops cause driving current variations and grayscale nonuniformity
Solution Approach 1:
The emission-control sub-circuit implements feedback by continuously monitoring the power supply voltage through the reference voltage signal and adjusting the gate-to-source voltage to compensate for voltage drops, maintaining constant driving current despite power supply fluctuations
Solution Approach 2:
The patent changes the gate-to-source voltage parameter dynamically based on the reference voltage signal to offset power supply voltage drops, ensuring the driving current remains independent of power supply voltage variations
Data Source
AI summary
A pixel-driving circuit includes a driving sub-circuit with at least one transistor and one capacitor coupled to a light-emitting device. The pixel-driving circuit further includes an initialization sub-circuit coupled to the light-emitting device and configured to initialize the light-emitting device with a initialization signal under control of a scan signal. Additionally, the pixel-driving circuit includes a data-input sub-circuit coupled to the driving sub-circuit and configured to write the data signal to the driving sub-circuit under control off scan signal. Furthermore, the pixel-driving circuit includes an emission-control sub-circuit having two transistors of different types and one capacitor coupled to the driving sub-circuit and the light-emitting device and configured to control the driving sub-circuit to output a driving current based on the data signal under control of a control signal and a reference-voltage signal.