LED Package Multi-Current PWM for Wide Dynamic Range
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Solution Overview
Problem
Conventional LED displays face challenges in achieving high resolution and dynamic range with small pixel pitches due to complexity and cost scaling, limited by current driving techniques that require high frequencies and shared drivers, leading to parasitic resistance and brightness discontinuities.
Innovation Solution
Implementing multiple current sources at different levels within an LED package to provide varying current pulse width modulation (PWM) signals, allowing for increased dynamic range without increasing frequency, by selectively turning on and off different current sources during a PWM period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current driving techniques are used with high frequencies and shared drivers, then LED displays can achieve basic brightness control, but parasitic resistance and brightness discontinuities increase, limiting dynamic range
Solution Approach 1:
The current driving function is segmented into multiple independent current sources (first current source, second current source, third current source) with different current levels. Each current source can be independently controlled by separate PWM signals, eliminating the need for shared drivers and reducing parasitic resistance effects. This segmentation enables continuous brightness adjustment across a wide dynamic range without brightness discontinuities.
Solution Approach 2:
The system dynamically selects and combines different current sources based on the required brightness level. By varying the combination of current sources activated and their respective PWM duty cycles, the system achieves continuous brightness control across a dynamic range of 1,000,000:1 or 16,000,000:1 without requiring high clock frequencies, thereby maintaining brightness continuity while reducing driver complexity.
2Reliability
If high clock frequencies are used to increase dynamic range, then brightness control resolution improves, but power consumption and parasitic effects increase
Solution Approach 1:
The dynamic range is achieved through segmentation of current sources with different current levels (first current source with first current level, second current source with second current level, third current source with third current level) rather than relying on high clock frequencies. Each current source is controlled by its own PWM signal, allowing the system to achieve 1,000,000:1 or 16,000,000:1 dynamic range at lower frequencies, thereby reducing power consumption and parasitic effects.
Solution Approach 2:
The system changes the parameter of current level by activating different combinations of current sources with different current levels rather than changing frequency. By adjusting which current sources are active and their PWM duty cycles, the system achieves high dynamic range resolution without increasing clock frequency, thus avoiding the associated power consumption and parasitic effects.
3Measurement precision
If multiple current sources are used to increase dynamic range, then brightness control precision improves, but device complexity increases
Solution Approach 1:
The brightness control function is segmented across multiple current sources with different current levels, where each source is controlled by its own PWM signal. This segmentation enables precise brightness control by selectively combining current sources, achieving 1,000,000:1 or 16,000,000:1 dynamic range. The modular architecture of independent current sources actually simplifies the overall control logic compared to single high-frequency PWM approaches.
Solution Approach 2:
Each current source serves multiple functions: it can be independently controlled, combined with other current sources, and adjusted via PWM duty cycle. This multi-functionality allows the system to achieve high brightness control precision across the full dynamic range using the same set of current sources, reducing the need for additional specialized components and thereby managing device complexity.
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
Enhances the dynamic range of LED displays to 1,000,000:1 or 16,000,000:1 without high clock frequencies, ensuring monotonic brightness transitions and reducing power consumption and parasitic effects.
Implementation Method 1
Light-emitting diodes (LEDs) are solid-state devices that convert electrical energy to light and generally include one or more active layers of semiconductor material (or an active region) arranged between oppositely doped n-type and p-type layers. When a bias is applied across the doped layers, holes and electrons are injected into the one or more active layers where they recombine to generate emissions such as visible light or ultraviolet emissions.
Implementation Method 2
an LED driver configured to drive the LED chip by pulse width modulation (PWM), the LED driver comprising a plurality of current sources configured to provide varying current levels to the LED chip
Data Source
AI summary
Light-emitting diode (LED) packages and, more particularly, LED packages with varying current pulse width modulation (PWM) signals and related methods are disclosed. Varying current PWM is provided by having multiple current sources at different current levels for each LED chip in an LED package. An output PWM signal for each LED chip is routed to selectively turn on and off different combinations of current sources to provide varying current levels associated with varying brightness levels for each LED chip. By providing multiple current sources for each LED chip, the dynamic range of current levels and corresponding brightness levels may be increased for a same PWM clock frequency.