OLED Pixel Driving Circuit Threshold Compensation
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Solution Overview
Problem
The current OLED array substrates experience brightness unevenness due to differences in threshold voltages of drive transistors, leading to voltage drops along power supply lines, resulting in inconsistent display brightness across adjacent pixel circuits despite identical input luminance data.
Innovation Solution
A pixel driving circuit is introduced, comprising a reset circuit, compensation and data-in circuit, and light-emitting control circuit, which includes transistors and capacitors to compensate for threshold voltage differences and voltage drops, ensuring consistent current flow through drive transistors and thus uniform brightness across the display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If threshold voltage differences among drive transistors are ignored, then device complexity is reduced, but display brightness uniformity deteriorates
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the gate voltage of the drive transistor based on measured threshold voltage differences. The compensation circuit modifies the control signal according to the actual Vth variations, transforming fixed voltage driving into adaptive voltage control to maintain uniform brightness across pixels with different transistor characteristics
Solution Approach 2:
The patent implements feedback through a measurement and compensation mechanism. The threshold voltage difference is measured between adjacent pixels, and this information is fed back to the compensation circuit which adjusts the gate voltage accordingly. This closed-loop approach ensures that brightness uniformity is maintained by continuously compensating for Vth variations
2Illumination intensity
If voltage drops along power supply lines are compensated, then display brightness uniformity is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by measuring and compensating for voltage drops before they affect the light-emitting device. The compensation circuit anticipates the voltage loss along the power supply line and pre-adjusts the gate voltage to account for the expected voltage drop, ensuring uniform brightness across all pixels including those at the end of long power supply lines
Solution Approach 2:
The patent uses parameter changes to counteract voltage drops by dynamically adjusting the gate voltage based on the position and voltage loss characteristics of each pixel circuit. The compensation mechanism modifies the control parameter (gate voltage) to offset the voltage drop effect, maintaining consistent driving conditions across the display
3Illumination intensity
If compensation circuits are added to address threshold voltage differences, then display brightness uniformity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies merging by integrating the compensation functionality into the existing pixel circuit structure. The compensation circuit shares common components such as capacitors and transistors with the standard pixel circuit, combining multiple functions into a unified design. This reduces the incremental manufacturing complexity compared to adding completely separate compensation systems
Data Source
AI summary
Embodiments of the present disclosure provide a pixel driving circuit. The pixel driving circuit includes a reset circuit, a compensation and data-in circuit, a drive transistor, and a light-emitting control circuit. The reset circuit is configured to reset a voltage of a control electrode of the drive transistor according to a first and third control signals. The compensation and data-in circuit is configured to receive a reference signal from the data line according to the first control signal, receive a data signal from the data line according to a second control signal, and apply a compensation voltage to the control electrode of the drive transistor based on the reference signal, the data signal, and a voltage of the first voltage terminal. The light-emitting control circuit is configured to control the light-emitting device to emit light according to a third control signal.