LED Pixel Circuit With Current Sensing for Low-Leakage Routing
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Solution Overview
Problem
Designing displays with light-emitting diodes is challenging due to issues such as high transistor leakage currents, slow transistor switching speeds, routing complexity, and voltage drops from ohmic losses, which adversely affect performance.
Innovation Solution
The display incorporates an array of pixels with light-emitting diodes, each equipped with drive and emission transistors, data storage capacitors, and switching transistors, utilizing semiconducting-oxide and silicon transistors to optimize performance. Control signals are provided by display driver circuitry, and current sensing circuitry measures transistor performance to compensate for aging effects, allowing efficient operation at low refresh rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional transistor designs are used in display pixels, then routing and control can be simplified, but transistor leakage current increases and switching speed decreases
Solution Approach 1:
The transistor gate is divided into two independent gates (first gate and second gate), allowing separate control of channel formation and current modulation. This segmentation enables precise control of leakage current while maintaining simple routing architecture.
Solution Approach 2:
The invention changes the electrical parameters by applying different voltages to the first and second gates independently. By varying gate voltages dynamically, the transistor can operate in different modes (high current drive vs. low leakage) without changing the physical structure or routing complexity.
2Device complexity
If conventional transistor designs are used in display pixels, then device structure can be simplified, but transistor switching speed becomes slow
Solution Approach 1:
The gate is segmented into two independent gates that can be controlled separately. The first gate establishes the basic channel while the second gate provides rapid switching control, achieving fast switching speeds without complicating the overall device structure.
Solution Approach 2:
The first gate is used to pre-establish the conductive channel in advance, so that when switching is needed, only the second gate needs to act, significantly reducing the switching time while keeping the device structure simple.
3Speed
If higher drive currents are used to improve switching speed, then switching speed increases, but voltage drops due to ohmic losses increase
Solution Approach 1:
Instead of increasing drive current to improve switching speed, the invention changes the control parameter by applying optimized voltage combinations to the two gates. This achieves fast switching through enhanced electric field control rather than brute-force current increase, minimizing ohmic losses.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces transistor leakage current and optimizes display performance by minimizing routing resources and compensating for aging, enabling efficient operation at variable refresh rates while maintaining display uniformity.
Implementation Method 1
Each of the pixels may have a light-emitting diode such as an organic light-emitting diode that emits light in response to application of a drive current
Data Source
AI summary
A display may have an array of pixels each of which has a light-emitting diode such as an organic light-emitting diode. A drive transistor and an emission transistor may be coupled in series with the light-emitting diode of each pixel between a positive power supply and a ground power supply. The pixels may include first and second switching transistors. A data storage capacitor may be coupled between a gate and source of the drive transistor in each pixel. Signal lines may be provided in columns of pixels to route signals such as data signals, sensed drive currents from the drive transistors, and predetermined voltages between display driver circuitry and the pixels. The switching transistors, emission transistors, and drive transistors may include semiconducting-oxide transistors and silicon transistors and may be n-channel transistors or p-channel transistors.