μ-LED Brightness Control With Dual-Gate PWM Circuit
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Solution Overview
Problem
Current technologies face challenges in efficiently controlling and varying the brightness of micro-light emitting diodes (μ-LEDs) in displays due to limited space and complexity in current control circuits, particularly in achieving high directionality and avoiding the 'fly screen effect' in augmented and virtual reality applications.
Innovation Solution
A control circuit and method that utilize a dual-gate transistor with a backgate for pulse-width modulation, allowing for space-saving and efficient brightness control, and a pulsed voltage signal approach to adjust LED current, enabling operation at multiple brightness levels and temperature stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional control circuits are used for μ-LEDs, then the circuit can control the LED, but the circuit occupies excessive space and increases device complexity
Solution Approach 1:
The patent combines multiple control functions (current regulation, pulse-width modulation, temperature compensation) into a single integrated control circuit that directly interfaces with the μ-LED. This merging of functions reduces the overall circuit area and decreases device complexity while maintaining full control capability over the μ-LED brightness and stability.
Solution Approach 2:
The control circuit is designed with multi-functionality, serving as a universal controller that handles current regulation, PWM dimming control, and temperature compensation simultaneously. This single circuit performs multiple tasks that would traditionally require separate components, thereby reducing space occupation and simplifying the overall device architecture.
2Measurement precision
If continuous voltage signal is used for brightness control, then the control is simple, but the brightness precision and temperature stability are insufficient
Solution Approach 1:
The patent employs pulse-width modulation (PWM) technique where a periodic pulse signal is used instead of a continuous voltage signal. The duty cycle of the periodic pulse varies to control the average brightness, providing precise brightness control. The periodic nature of the signal also enables synchronization with the μ-LED switching, improving control precision while maintaining manageable circuit complexity.
Solution Approach 2:
The control circuit dynamically adjusts the pulse width and frequency based on temperature feedback and desired brightness level. This dynamic adaptation allows the system to maintain precise brightness control under varying temperature conditions, transforming a static control approach into a dynamic one that responds to real-time conditions.
3Illumination intensity
If high current is used to increase brightness, then the brightness is sufficient, but the power consumption increases and temperature stability decreases
Solution Approach 1:
By using pulse-width modulation, the circuit delivers high current only during the pulse duration rather than continuously. The duty cycle determines the average brightness level, allowing the LED to achieve sufficient brightness during the on-period while consuming less power overall. This periodic current delivery reduces heat generation and improves temperature stability compared to continuous high current operation.
Solution Approach 2:
The control circuit preliminarily determines the required brightness level and calculates the appropriate pulse width before applying current to the LED. This preliminary calculation ensures that the minimum necessary current is applied only when needed, optimizing power efficiency while achieving the required illumination intensity, thereby reducing unnecessary power consumption and heat generation.
4Measurement precision
If simple control circuit is used, then the device complexity is low, but the color accuracy and stability are insufficient
Solution Approach 1:
The patent incorporates temperature sensing and compensation mechanisms where the control circuit monitors the μ-LED temperature and adjusts the drive current or PWM parameters accordingly. This feedback loop compensates for temperature-induced color shifts, maintaining color accuracy. The feedback-based approach achieves high color precision without requiring overly complex circuitry, as the compensation is integrated into the existing control structure.
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
The solution enables precise and efficient brightness control of μ-LEDs, reducing the 'fly screen effect' and improving color accuracy and stability, while maintaining temperature stability and reducing power consumption.
Implementation Method 1
A control circuit and method that utilize a dual-gate transistor with a backgate for pulse-width modulation, allowing for space-saving and efficient brightness control
Implementation Method 2
micro-light emitting diodes (μ-LEDs) in displays
Implementation Method 3
a pulsed voltage signal approach to adjust LED current, enabling operation at multiple brightness levels
Implementation Method 4
improving color accuracy and stability, while maintaining temperature stability
Data Source
AI summary
Disclosed are various aspects of a μ-LED or a μ-LED array for augmented reality or lighting applications, in particular in the automotive field. The μ-LED is characterized by particularly small dimensions in the range of a few μm.