Pixel Driving Circuit Leakage Current Suppression
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Solution Overview
Problem
Large leakage current in low-temperature polysilicon display panels leads to screen flickering due to poor threshold voltage compensation, resulting in data signal loss and reduced product quality.
Innovation Solution
A pixel driving circuit incorporating low-temperature polysilicon transistors and metal oxide transistors, with a second capacitor Cboost connected between the first node Q and the gate of the second transistor T2, to adjust the potential of node Q and improve data signal range within the gray scale, thereby reducing screen flickering and enhancing brightness uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low-temperature polysilicon transistors are used in the pixel circuit, then manufacturing cost is reduced and ease of manufacture is improved, but leakage current increases causing screen flickering
Solution Approach 1:
The patent combines low-temperature polysilicon transistors (T1, T2, T4) with metal oxide transistors (T3, T5) in a hybrid pixel circuit structure. The metal oxide transistor T3 is specifically used as the switching transistor to provide low leakage current, while low-temperature polysilicon transistors handle other functions, achieving both manufacturing ease and reliability through selective material usage.
Solution Approach 2:
Different transistor types are assigned to different positions within the pixel circuit based on functional requirements. The switching transistor T3 uses metal oxide material for low leakage, while other transistors use low-temperature polysilicon for cost-effectiveness. This local differentiation of material properties optimizes both reliability and ease of manufacture.
2Device complexity
If a 7T1C structure is used in the pixel circuit, then device complexity is reduced, but threshold voltage compensation effect deteriorates causing data signal loss
Solution Approach 1:
The patent merges the 7T1C structure with additional transistors (T5) and capacitors (Cboost) to create an enhanced circuit that maintains simplicity while improving threshold voltage compensation. The added components work together with the existing 7T1C structure to provide better compensation without significantly increasing complexity.
Solution Approach 2:
The patent introduces an intermediary capacitor Cboost connected between the gate of transistor T2 and node Q. This intermediary component helps stabilize the threshold voltage by providing additional compensation, preventing data signal loss while maintaining the overall simplicity of the 7T1C structure.
3Reliability
If metal oxide transistors are used to reduce leakage current, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent merges metal oxide transistors (T3, T5) with low-temperature polysilicon transistors (T1, T2, T4) in a hybrid structure. Only the critical switching transistor T3 uses metal oxide material to provide low leakage current, while other transistors use cheaper low-temperature polysilicon, balancing reliability improvement with manufacturing cost control.
Solution Approach 2:
Metal oxide material is applied locally only where it is most needed - in the switching transistor T3 and potentially T5 - rather than throughout the entire circuit. This localized application of higher-cost material optimizes reliability at critical points while minimizing overall manufacturing cost impact.
Data Source
AI summary
The disclosure provides a pixel driving circuit and a display panel. The pixel driving circuit includes a first transistor, a second transistor, a first capacitor, a second capacitor, and an organic light emitting diode; the second transistor is a low-temperature polysilicon transistor. The disclosure can improve the phenomenon of screen flickering caused by large leakage current of the display panel, thereby being beneficial to improve the brightness uniformity.