Pixel Driving Circuit Threshold Voltage Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing 2T1C pixel driving circuit in display technologies faces issues with mura due to varying threshold voltages of thin-film transistors, leading to inconsistent current flow through light-emitting devices and subsequent differences in brightness across pixels.
Innovation Solution
A pixel driving circuit is designed with additional thin film transistors and capacitors to decouple the current flow from the threshold voltage, using a configuration where the current through the light emitting device is determined by the data signal and power voltages, independent of the threshold voltage, thereby stabilizing the brightness across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a 2T1C pixel driving circuit is used, then the device complexity is low, but the brightness uniformity deteriorates due to threshold voltage variations causing mura
Solution Approach 1:
The pixel driving circuit is segmented into multiple functional modules: a first sub-circuit for current mirror operation, a second sub-circuit for threshold voltage compensation, and a third sub-circuit for data signal processing. This segmentation allows each module to perform a specific function, with the current mirror circuit copying a reference current that is independent of threshold voltage variations, thereby achieving brightness uniformity while maintaining reasonable device complexity
Solution Approach 2:
A reference current is introduced as an intermediary element. The reference current serves as a mediator that carries the data signal information without being affected by threshold voltage variations. By using this intermediary reference current in the current mirror configuration, the circuit achieves immunity to threshold voltage mismatches while maintaining structural simplicity
2Device complexity
If the current flow depends on threshold voltage, then the device structure remains simple, but the display quality deteriorates due to mura effects
Solution Approach 1:
The circuit converts the harmful effect of threshold voltage variations into a beneficial outcome by using a current mirror configuration. The mirror transistor copies a reference current that flows through a path independent of the driving transistor's threshold voltage. Thus, even though threshold voltage variations exist due to manufacturing limitations, they are effectively nullified, and the display quality is improved without requiring higher manufacturing precision
3Stability of the object's composition
If additional transistors and capacitors are added to decouple current from threshold voltage, then the brightness uniformity is improved, but the device complexity increases
Solution Approach 1:
The circuit components are designed to perform multiple functions. The capacitor serves both as a storage element for the reference voltage and as part of the compensation mechanism. The additional transistors are configured to perform both current mirroring and threshold voltage compensation simultaneously. This multi-functionality reduces the need for separate dedicated components, thereby limiting the increase in device complexity while achieving current stability independent of threshold voltage
Data Source
AI summary
A pixel driving circuit and a display panel are provided. The pixel driving circuit includes a source of a second thin film transistor electrically connected to a drain of a first thin film transistor, a gate of a sixth thin film transistor configured to receive a third control signal, a source of the sixth thin film transistor electrically connected to a second node, and a drain of the sixth thin film transistor electrically connected to an anode of a light emitting device.