What is the multi-pixel-droop of LED-arrays?5 answersThe multi-pixel droop of LED arrays refers to the reduction in efficiency observed in high-power GaN-based LEDs when multiple pixels are utilized. Efficiency droop in LEDs is primarily caused by a decrease in internal quantum efficiency (IQE) with increasing current density. This phenomenon impacts visible light communication systems using LEDs, affecting dimmable VLC systems based on pulse-amplitude modulation (PAM). High-power LEDs with interdigitated multipixel array (IMPA) chip designs show advantages such as improved current spreading and higher emission efficiency at high currents, attributed to lower series resistance and reduced local active region overheating. Additionally, a multi-pixel photoconductive emitter has been developed to generate THz beams with different polarization states, showcasing optimization capabilities through bias adjustments on specific pixels.
Is there an article about a led-array with fully seperated leds?5 answersYes, there is an article discussing a LED array with fully separated LEDs. The article by Hisashi Masui, Shimizu Ken, and Dohner Emmapresents methods for creating pixelated array light emitters with closely-spaced pixels having ultra-smooth sidewalls. The process involves using a converter layer of phosphor particles dispersed in a binder on a rigid carrier, which is then singulated to form an array of phosphor pixels with smooth side walls. These phosphor pixels are later attached to a corresponding array of LEDs. This innovative approach ensures that the LEDs in the array are fully separated and have controlled morphology, allowing for precise and efficient light emission.
How long can a piezoelectric charged battery power a led light?5 answersA piezoelectric charged battery can power a LED light for varying durations based on the specific setup and charging method. Research has shown that a piezoelectric energy generator can store energy in a lithium battery package for street lighting, powering a 12W LED light for 12 hours. Additionally, experiments with piezoelectric materials have demonstrated the ability to charge a lead-acid battery through foot beats, with the voltage increasing until the battery is fully charged. Furthermore, a piezoelectric-driven self-charging supercapacitor power cell was able to charge to 110 mV in 300 seconds under palm impact, successfully lighting a green LED. These findings collectively suggest that a piezoelectric charged battery can power a LED light for several hours to potentially days, depending on the specific system design and energy conversion efficiency.
What's the most efficient way to power an led from a battery?4 answersThe most efficient way to power an LED from a battery is by using a buck-boost converter. This topology is commonly adopted because it can handle battery voltages that are either higher or lower than the forward voltage of the LED. However, traditional buck-boost converters have drawbacks such as switching and conduction losses and the need for off-chip components. To improve efficiency, hybrid buck-boost converters have been introduced, which reduce effective resistance but require extra off-chip flying capacitors. Additionally, for color mixing, extra power is needed to regulate and balance the current, especially when the forward voltages of the LEDs are unequal. Another approach is to use a PV-Battery system with a power management algorithm and maximum power point tracking, which offers a dependable and sustainable solution for LED lighting. Soft switching techniques can also be employed to achieve greater efficiency at higher frequencies.
What is the purpose of the array of LEDs?5 answersThe purpose of the array of LEDs is to provide precise and controlled illumination in various applications. The Opto-Array developed by Azadi et al. is specifically designed for perturbing neuronal activity in large brains, such as non-human primates, with high spatial and temporal resolution. Huska et al. describe an apparatus with an array of LEDs arranged in a predetermined pattern on a substrate, which can be used for various purposes. AL-Forati and Rashid propose a positioning system for multi-robot localization that utilizes an array of LEDs distributed uniformly in the environment to collect information for localization. Kim presents an LED illumination device with an array of LEDs that can control the shape of the light distribution pattern and prevent reduction of illuminance. Staloff describes an apparatus with an array of LEDs, each having an asymmetric optical characteristic, which can be used in an illumination system.
Who made cathode ray?8 answers