LED 101: Understanding the Fundamentals of LED Lighting

In this blog post, we celebrate the 30th anniversary of the high brightness blue LED, a pivotal innovation in lighting technology by Nichia Corporation. This remarkable journey began with a modest announcement in November 1993 by Nichia, a then-obscure chemical company based in rural Tokushima, Japan. Eschewing grandiose launch events, Nichia chose a simple interview with a local newspaper to introduce their groundbreaking blue LED, the NLPB500. The post explores the early applications of blue LEDs in traffic signals, displays, and scanners, and the subsequent development of the 3-in-1 LED for high-resolution indoor displays.

This led to the revolutionary creation of white LEDs, combining blue LED technology with YAG phosphor. The impact of this innovation extends far beyond lighting, influencing industries and contributing to environmental conservation. The post also discusses the future prospects of LED technology, including ongoing research in areas like Li-Fi and the potential of emerging technologies like OLEDs and quantum dots. To learn more about this fascinating journey of innovation and its far-reaching implications, we invite you to read the full article and join us in celebrating this significant milestone.

Luminous efficacy measures how effectively a light source produces visible light. With LEDs and other light sources, luminous efficacy is the ratio of luminous flux to electrical power, known as lumens per watt (lm/w). For example, the light output (luminous flux) of a 1 Watt LED can be very bright for high efficacy or barely visible for low.

The luminous efficacy is one of the defining factors of LED performance. Top performance LEDs, with the highest luminous efficacy, have 220 lumens per watt (lm/w), such as the Nichia 757G LEDs. High performance LEDs, like those from many other manufacturers, have 150-200 lm/w. At the far end, we have the low cost, poor performance LEDs with an efficiency of less than 99 lumens per watt.

Introduction to the Color Rendering Index (CRI)

In 1974, the International Commission on Illumination (CIE) introduced the Color Rendering Index (CRI) to compare the color rendering of artificial light sources to a reference standard illuminant modeled after daylight. The CRI aimed to express the quality of white light produced by various types of gas lamps available in the market at that time.

Over the past 40 years, the CRI index has become deeply ingrained in the lighting industry and among professionals. However, it remained relatively unknown to most consumers since it wasn't particularly relevant to their decision-making when purchasing lighting. Manufacturers produced most lamps based on their CRI value for specific applications, ensuring that the choice of lamp could not be wrong. For instance, office or linear lighting typically used Tri-Phosphor linear fluorescent tubes with a CRI over 80. Homes relied on incandescent lamps and halogens with a CRI of 100, while retail spaces utilized metal halide lamps with a minimum CRI of 85.

The makeup of some fixture types for common applications, such as down-lighting, spot-lighting, office-lighting and street-lighting. All can use LEDs.

LED strip lighting systems, also known as LED tapes or LED ribbon lights, have become increasingly popular due to their versatility and energy efficiency. These lighting solutions come in various forms, including flexible LED strips, rigid LED strips, Zhaga LED strips, backlight LED strips, flexible backlight LED strips, and power LED strips. In this article, we will delve into the different types of LED strip lighting systems, discussing their unique features, advantages, and potential applications.

The New EU Energy Label: Key Changes and Implications

The new energy labels apply to four product categories: fridges and freezers, dishwashers, washing machines, and television sets (and other external monitors). From September, they also apply to light bulbs and lamps with fixed light sources, including LED bulbs, LED strips, and LED fixtures.

The primary change in the new EU energy label is the return to a simpler A-G scale, replacing the previous A+, A++, and A+++ ratings, which had become increasingly common, particularly for LED lights. This change was implemented to ensure clarity for consumers and motivate businesses to innovate and develop more energy-efficient products, contributing to a reduction in greenhouse gas emissions.

The new A-G scale is stricter, with only a few products initially able to achieve the "A" rating. This approach leaves room for future advancements in energy efficiency. Consequently, the most energy-efficient products from the past will now typically receive "B", "C", or "D" ratings. The updated EU energy label for LED lights, compared to the old one, can be seen below:

White light is a combination of different wavelengths

To understand the CRI color rendering index, we need a brief explanation of how sunlight is perceived as white.

Glass prisms are an easy experiment to visualize the composition of sunlight. It shows white light is a combination of different wavelengths in the electromagnetic spectrum.

To have white light from an artificial source, a mix of different emitted wavelengths is required. However, a close analysis of the white light of artificial lighting shows that not all white light is the same.

The ABCs of energy efficiency

A lighting installation can be energy efficient in three ways:

A) The light is emitted with the lowest possible energy consumption.

B) The total light output of the installation is at an optimum, as defined by its purpose or the activities it needs to support.

C) The composition of the white light is on tune with the sensitivity of our eyes.

Read more below...

LED strips and modules used for lighting fixture use, in general, multiple LEDs.

As operating a single LED generates heat, more is generated when multiple LEDs are mounted on a PCB, due to the mutual effect. As such, in the case of LED strips or modules, the junction temperature (TJ) of each LED gets higher, compared to a single light source. This leads to the decrease in the LEDs lifetime and luminous flux.

For LED strips and modules, a better thermal management is required to minimize TJ and allow a longer lifetime of the installed products. For this purpose, the LED pitch, the PCB base material and the use of aluminum profile must be taken in consideration.

Linear LED light fixtures and LED tubes also feature a cover that protects the LEDs and diffuses the light. This cover is usually made of polycarbonate (a resin) and sometimes of glass. 

The cover has a certain light transmission rate that impacts the light's luminous flux and glare. If a cover has a high transmission rate, it will minimize the depreciation rate of the lamp’s luminous flux by reducing the light diffusion. However, the light of individual LED’s can be visible, increasing the glare effect.

Below, we present an evaluation of four covers to showcase light transmission and glare.