Backplane Current Mirror Circuit for Micro LED Heating
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Solution Overview
Problem
Existing backplane designs for emissive displays face challenges in efficiently driving high current to micro emissive pixel elements, particularly in maintaining low resistance configurations to prevent excessive heating and ensuring matching performance characteristics across multiple devices.
Innovation Solution
The use of multiple parallel current sources with similar threshold voltages, along with a complex current mirror circuit and additional reference/current source circuits that can be switched in or out, to facilitate current averaging and reduce heating, while ensuring consistent performance across emissive elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single current source is used to drive micro emissive pixel elements, then the circuit design is simple, but excessive heating occurs due to high current concentration
Solution Approach 1:
The patent divides a single current source into multiple parallel current sources (e.g., four current sources labeled 414a, 414b, 414c, 414d). Each current source delivers a portion of the total current to the micro LED, distributing the current load and reducing heating in any single path while maintaining the ability to drive high current overall.
2Adaptability or versatility
If current sources with different threshold voltages are used, then device variability is accommodated, but inconsistent brightness performance occurs across emissive elements
Solution Approach 1:
The patent employs current mirror circuits that replicate and scale reference currents to multiple output current sources. By using matched transistors in the current mirrors and carefully designed reference current circuits, the system ensures that all current sources produce identical current magnitudes despite potential variations in device parameters, thereby achieving consistent brightness across all micro LEDs.
3Temperature
If multiple parallel current sources are used, then heating is reduced through current distribution, but device complexity increases
Solution Approach 1:
The patent merges multiple current sources into a unified structure using current mirror circuits. The current sources share common reference current circuits and control mechanisms, allowing them to operate as an integrated system rather than independent units. This merging approach distributes current to reduce heating while maintaining manageable circuit complexity through shared components and symmetric design.
4Illumination intensity
If high current is delivered to micro emissive elements, then brightness is sufficient for applications, but excessive heating and reliability issues occur
Solution Approach 1:
The patent segments the high current delivery into multiple parallel paths, each handling a fraction of the total current. This segmentation reduces the current density and thermal load on any single micro LED and its driving circuitry, thereby improving reliability and reducing failure risk while maintaining sufficient total brightness for automotive headlamp and display applications.
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 enables the delivery of modulated high current to emissive elements, minimizing heating and ensuring consistent brightness across the array, thereby improving the performance and reliability of emissive display systems, such as in automotive headlamps and additive manufacturing devices.
Implementation Method 1
the pixel drive circuits comprises a current mirror circuit and multiple parallel current sources with similar threshold voltages
Implementation Method 2
facilitate current averaging and reduce heating
Implementation Method 3
use of a suitable voltage to drive the LED will cause electrons within the LED to combine with electron holes, resulting in the release of energy in the form of photons, a feature referred to as electroluminescence
Data Source
AI summary
A backplane operative to drive an array of emissive pixel elements is disclosed. A plurality of pixel drive circuits form part of an array of emissive elements. The plurality of pixel drive circuits are disposed to form a plurality of rows and a plurality of columns. The plurality of pixel drive circuits are organized into sets of pixel drive circuits, and each set comprises at least one pixel drive circuit.