MicroLED Voltage Modulation for High-Vf Outlier Pixel Driving
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Solution Overview
Problem
Existing linear driving schemes for micro LED arrays face challenges in efficiently managing outlier pixels with excessively high forward voltage, leading to heat loss and visible dark spots due to undriven or underdriven LEDs.
Innovation Solution
A dynamic voltage modulation and PWM phase control scheme that identifies and synchronizes the power supply with outlier pixels, ensuring their compliance voltage is met during specific periods, minimizing heat loss and maintaining efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If microLEDs are operated at high current densities to achieve sufficient brightness, then illumination intensity is improved, but defective LEDs with excess current fail prematurely
Solution Approach 1:
The patent applies local quality by assigning different current densities to different LEDs within the same display panel. Specifically, outlier LEDs that produce insufficient light are operated at higher current densities than standard LEDs, allowing each LED to be driven according to its individual performance characteristics rather than using a uniform current density for all LEDs.
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the operating current density for each LED based on its measured light output performance. LEDs are categorized into different groups (standard, outlier low, outlier high) and each group is assigned a specific current density parameter, enabling flexible adaptation of operational parameters to individual LED characteristics.
2Device complexity
If uniform current density is applied to all LEDs, then device complexity is reduced, but display uniformity deteriorates due to outlier LEDs
Solution Approach 1:
The patent applies local quality by assigning different current densities to different LEDs within the same display panel. Specifically, outlier LEDs that produce insufficient light are operated at higher current densities than standard LEDs, allowing each LED to be driven according to its individual performance characteristics rather than using a uniform current density for all LEDs.
Solution Approach 2:
The system performs self-characterization by having each LED effectively 'introduce itself' through initial testing measurements. The controller characterizes each LED's light output and automatically assigns appropriate current density parameters without requiring manual intervention or complex external calibration equipment.
3Illumination intensity
If outlier LEDs are operated at higher current densities to compensate for low output, then illumination intensity is improved, but power consumption increases
Solution Approach 1:
The patent applies partial or excessive action by operating only the necessary subset of outlier LEDs at higher current densities rather than all LEDs. By identifying and targeting only the specific outlier LEDs that require compensation, the system achieves the needed illumination improvement while minimizing the overall power consumption increase that would result from uniformly driving all LEDs at high current density.
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 approach enhances electrical efficiency to above 80% by optimizing the driving of outlier pixels, reducing visible dark spots, and minimizing heat loss in micro LED arrays.
Implementation Method 1
Each pixel element of the display includes a plurality of individually addressable microLEDs
Data Source
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AI summary
A micro light emitting diode (LED) die can include a matrix of micro LEDs with a variety of forward voltages. A method of reducing a number of undriven or under driven uLEDs can include providing, by a power supply, an alternating current voltage (VLED) with a minimum voltage (VMIN) and a maximum voltage (VMAX), VMIN being sufficient to drive a plurality of micro light emitting diodes (uLEDs) of a uLED die using a plurality of uLED drivers, identifying, by a controller coupled to the uLED drivers, a uLED of the plurality of uLEDs with a forward voltage (Vf) greater than VMIN, and altering, by the controller, a time of a rising edge of a pulse width modulation (PWM)-on time of the uLED such that Vf of the uLED is less than VLED for the PWM-on time.