Active LED Module with Integrated Drive Transistor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing LED technologies face challenges in creating compact, cost-effective, and efficient LED modules for color displays and lighting applications due to the need for separate current sources and driver circuits for each color LED, which increases space and cost, and results in reduced light-to-dark contrast and inefficiencies in addressing and interconnection.
Innovation Solution
The integration of a vertical LED with a vertical drive transistor in a single die, allowing for active impedance control through a control terminal, enabling LEDs of different colors to be connected in parallel and addressed with a common voltage, reducing sensitivity to forward voltage and parasitic voltage drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If separate current sources and driver circuits are used for each color LED, then each LED can be controlled independently, but the device size and complexity increase
Solution Approach 1:
The patent combines multiple LED elements (red, green, blue) and their driver circuits into a single integrated LED module. The module includes a first LED element, second LED element, third LED element, first drive transistor, second drive transistor, and third drive transistor all integrated together. This merging eliminates the need for separate external driver circuits for each LED, reducing overall device complexity while maintaining independent control capability through the integrated transistor structures.
Solution Approach 2:
The LED module is designed as a universal building block that can be used in various display configurations. The integrated structure with multiple LED elements and drive transistors in a single module serves multiple functions: it provides independent control of different color LEDs, eliminates external driver requirements, and can be arranged in passive matrix or active matrix configurations. This multi-functionality resolves the contradiction by providing independent control without requiring separate external drivers for each LED.
2Area of stationary object
If LEDs of different colors are connected in parallel, then space is reduced, but forward voltage variations cause control problems
Solution Approach 1:
The patent merges multiple LED elements of different colors (red, green, blue) with their respective drive transistors into a single integrated module. This allows parallel connection of different color LEDs while maintaining reliable control because each LED has its own integrated drive transistor that compensates for forward voltage variations. The integration ensures that space is reduced while forward voltage matching problems are solved through the dedicated transistor for each LED.
Solution Approach 2:
The patent applies local quality by providing each LED element with its own dedicated drive transistor within the integrated module. The first drive transistor controls the first LED element, the second drive transistor controls the second LED element, and the third drive transistor controls the third LED element. This localized control structure addresses forward voltage variations at the source by tailoring the drive characteristics to each specific LED element, enabling reliable parallel operation of different color LEDs with reduced area.
3Device complexity
If passive matrix addressing is used, then device complexity is reduced, but light-to-dark contrast decreases due to inadvertent forward bias
Solution Approach 1:
The patent integrates drive transistors directly with each LED element in the module, which maintains the simplicity of passive matrix addressing while solving the contrast problem. The integrated transistor structure ensures that when a row or column is not selected, the LED remains properly biased through the transistor's inherent characteristics, preventing inadvertent forward bias. This merging approach preserves low addressing complexity while achieving high light-to-dark contrast.
4Reliability
If downward facing LEDs are added for reverse bias protection, then reliability is improved, but they cause light emission in non-addressed rows reducing contrast
Solution Approach 1:
The patent integrates the reverse bias protection function directly into the LED module structure with the upward facing LEDs and drive transistors. The downward facing LEDs are incorporated into the same integrated module, and their operation is controlled by the same drive transistors that control the upward facing LEDs. This integrated approach ensures that reverse bias protection is provided while preventing unwanted light emission, as the transistor control prevents the downward LEDs from conducting in non-addressed rows, thus maintaining high contrast.
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 solution allows for compact, efficient, and cost-effective LED modules that can be easily integrated into displays and lighting systems, providing improved light-to-dark contrast and flexibility in color mixing and brightness control, while minimizing the need for external driver circuits.
Implementation Method 1
An LED die is typically mounted on a larger substrate for heat dissipation and packaging
Implementation Method 2
LEDs may be controlled by a current source to achieve a desired brightness
Data Source
AI summary
LED modules are disclosed having a control MOSFET, or other transistor, in series with an LED. In one embodiment, a MOSFET wafer is bonded to an LED wafer and singulated to form thousands of active 3-terminal LED modules with the same footprint as a single LED. Despite the different forward voltages of red, green, and blue LEDs, RGB modules may be connected in parallel and their control voltages staggered at 60 Hz or greater to generate a single perceived color, such as white. The RGB modules may be connected in a panel for general illumination or for a color display. A single dielectric layer in a panel may encapsulate all the RGB modules to form a compact and inexpensive panel. Various addressing techniques are described for both a color display and a lighting panel. Various circuits are described for reducing the sensitivity of the LED to variations in input voltage.