AMOLED Driving Circuit Using LTPS and Oxide TFT Compensation
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Solution Overview
Problem
Conventional P-type driving circuits for active-matrix organic light-emitting diodes (AMOLEDs) using low temperature poly-silicon (LTPS) transistors suffer from threshold voltage deviations due to polycrystalline processes, leading to brightness uniformity issues (mura) and increased current consumption, especially in high-resolution applications.
Innovation Solution
The driving circuit incorporates a current drive unit with LTPS transistors for large current capability and a reset compensation and light emitting control circuit with oxide semiconductor transistors to reduce threshold voltage variations, along with a transistor sharing architecture to minimize the number of transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If P-type driving circuits use LTPS technology to fabricate transistors, then the driving capability and current output are improved, but threshold voltage deviation occurs due to polycrystalline process variations, resulting in brightness uniformity problems
Solution Approach 1:
The patent applies different transistor types in different circuit locations: LTPS transistors are used in the current drive unit where high current capability is needed, while oxide semiconductor transistors are used in the reset compensation and light emitting control circuit where low leakage current is critical. This local differentiation resolves the contradiction by optimizing each location for its specific functional requirement.
2Manufacturing precision
If voltage compensation is performed using multiple transistors, then the threshold voltage deviation is corrected, but the current consumption increases dramatically in high-resolution applications
Solution Approach 1:
The patent extracts the voltage compensation function from the conventional multi-transistor implementation and implements it using oxide semiconductor transistors with ultra-low leakage current. This extraction of the compensation function to a low-power implementation resolves the contradiction between achieving threshold voltage compensation and minimizing current consumption.
3Reliability
If oxide semiconductor transistors are used in reset compensation and light emitting control circuit, then leakage current is reduced and threshold voltage stability is improved, but the device complexity increases due to hybrid transistor fabrication
Solution Approach 1:
The patent changes the material parameter of specific transistors from LTPS to oxide semiconductor to achieve ultra-low leakage current and stable threshold voltage. This parameter change in material selection resolves the contradiction by prioritizing reliability in critical circuit locations where the performance benefit outweighs the fabrication complexity.
Data Source
AI summary
An electronic device includes a substrate, a first silicon transistor, a second silicon transistor and a first oxide semiconductor transistor. The first silicon transistor, the second silicon transistor and the first oxide semiconductor transistor are disposed on the substrate. The first silicon transistor has a first terminal electrically connected to a first voltage level, a second terminal and a control terminal. The second silicon transistor has a first terminal electrically connected to the second terminal of the first silicon transistor, a second terminal electrically connected to a second voltage level, and a control terminal electrically connected to the control terminal of the first silicon transistor. The first oxide semiconductor transistor has a first terminal electrically connected to the first terminal of the second silicon transistor. Wherein, a voltage value of the first voltage level is greater than a voltage value of the second voltage level.