LED Lighting Knowledge

Innovative SunLike Natural Spectrum LEDs by Seoul Semiconductor

SunLike LED techology from Seoul Semiconductor and Toshiba

Seoul Semiconductor’s SunLike Series LEDs are the world’s first natural spectrum LEDs, as they produce light that closely matches the spectrum of natural sunlight.

SunLike LED package design


This achievement comes from using a new LED architecture, with a purple emitter in combination with a red, green, and blue (RGB) phosphor mix, unlike conventional white LED that use a blue emitter and yellow phosphor.  By removing the blue LED light source and replacing it with a purple light LED chip, lighting technology is fundamentally transformed. For the first time it is possible to render colors accurately with very low energy use and positive effects on health. Compared with other LED lights, the new SunLike Series does not have a blue energy peak associated with eye discomfort and poor sleep patterns.

Furthermore, an ordinary LED spectrum is very different to sunlight, whereas SunLike’s spectrum is very similar. Thus, the light sources with SunLike Series LEDs will more accurately show the color of objects, as they would appear in natural sunlight. It's natural light spectra has color rendering of CRI-97 – close to CRI-100 of sunlight, and much higher than the CRI-80 of conventional LEDs.

The SunLike packaged LED technology from Seoul is based in part on a Toshiba phosphor technology called TRI-R. By using the TRI-R, the LEDs deliver a uniform and broad spectral power distribution (SPD) that is more like sunlight than are typical phosphor-converted white LEDs.

The applications of this new LED technology, with its diminished blue light peak, similar spectral curve to sunlight, accurate rendering of colors and reduced scattered reflection and glare are many, from Human Centric lighting for our home and office to commercial and art lighting.

Human Centric lighting

‘Human-centric lighting’ describes lighting that is designed to work with the human body’s natural rhythms. It relies on the well-established fact that the human eye detects the presence of a particular wavelength of blue light in the spectrum that makes up sunlight, and uses this to judge what time of day it is. In this way, light helps regulate our sleep–wake cycles and other bodily rhythms, and has a significant impact on our mood and well-being.
Color temperature of sunlight
Human-centric lighting harnesses this effect by adjusting its brightness and colour temperature during the day to mimic natural light. To achieve its purpose, human-centric lighting must have a spectrum that resembles that of real sunlight, with just the right level of the crucial blue wavelength that triggers the body’s response. Most solutions described as human-centric do not have a spectrum that resembles that of real sunlight, so they end up providing too much or too little blue.

Seoul Semiconductor’s SunLike Series LEDs are different, as are the first LEDs to be closely matched to real sunlight, so they have the right level of blue that trigger the desired biological stimulus.

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Home lighting guide with LED strips and fixtures

Home lighting with LEDRISE Lumistrips in covelights

Careful design of the lighting for your home will ensure that the right amount of light is gets where and when it is needed and can be switched on conveniently. Lighting should avoid over-lit areas, and give control and flexibility to create lighting effects for different situations. Well-designed lighting will be inherently easier to use and will function in an energy-efficient way.

The best approach to home lighting design is to use three levels of lighting: general lighting, task lighting and accent lighting. By combining these three levels, the recommended lighting level for each room or activity should be obtained, as below: 

Recommended lighting levels for the Home  in Lux
Living rooms general 50-150
Casual reading 150
Study 150-750
Bedroom general 50-150
Kitchen general 150
Kitchen working areas 400
Bathrooms 150-300
Halls and landings 100-150
Stairs 100-150
Dining rooms 150-450


The three levels of lighting

General lighting should ensure a sufficient minimum level of light in the room. There are plenty of LED light sources that can be used for this purpose: LED modules, strips, luminaries or spotlight. Decide on the desired illuminance level (lux). In living rooms and bedrooms in particular, give a certain degree of flexibility (through control settings/dimmers) so that occupants can raise or lower the general lighting around the set level. Design for the upper end of the Lux ranges in homes with elderly occupants, which generally appreciate a higher level of general lighting. A minimum level of general lighting is required for safe movement in the home, especially on the stairs, but sufficient general LED lighting is considered important for general well-being.

Workplace lighting is needed for certain activities at home, such as reading, preparing food and working from home. LED lamps must be carefully selected, correctly positioned and controlled. Recommended are LED spot lights and high flux LED modules. Lamps or sockets are needed in the right places to ensure flexibility in the availability of work and accent lighting. Depending on the task, LED workplace lighting may be required at different levels. The colour rendering of the light is also very important for some activities and we recommend LED lights with CRI 95 or more.

Accent lighting contributes to the ambiance of a house and is usually done with LED spots and strips. As with workplace lighting, LED luminaires (or sockets) are placed in the right places to emphasise architectural features, furniture and ornaments. Accent lighting is a more personal matter, and depending on the circumstances, spotlighting or floodlighting can be useful.

For each of these levels of lighting, controls can provide a range of lighting options. So in an living room there could be separate controlled circuits for:

  • general lighting 
  • task lighting (typically positioned under the wall units) 
  • accent lighting 

Similar control patterns can be considered in other rooms, with dimmers providing a different lighting atmosphere in salons, dining rooms and bedrooms. Advanced controls, sometimes controlled by a mobile phone or a tablet app, that allow remote adjustment of the amount of light and its color are increasingly popular. Lighting is establishing itself as a lifestyle statement and houses with new and innovative lighting systems are perceived as a marketing advantage.

Lighting of each room in detail:

Living rooms

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Cove lighting with LED strips

A cove luminaire is a light line that can be made via an LED strip that is hidden within a Cove in the wall or ceiling that illuminates an adjacent surface. Light is reflected from this surface into the room to be illuminated. For this reason, light lines are generally referred to as cove or indirect lighting.

Cove lighting is a popular trend in lighting design, focusing on human nature and the behaviour of natural light. It is widely used today, with light lines as the main method of lighting interiors.

The attraction is the similarity with the natural light. With the right light source we could imagine that the bay is actually a hidden window to the outside from which the sunlight streams in.

Let's see how we can achieve the best results with cove lighting.

1. Use of energy-efficient light sources

Choose LED modules or strips with high energy efficiency, at least 100 lm/w, and place them within the coving light so that most of the emitted light uses the reflective surface, wall or ceiling that directs it into the interior. Waste of energy for lighting the interior of the bay should be avoided. LED strips with 120-180° are recommended, which should be placed at an angle if possible:

Surfaces that are more absorptive than reflective, like dark paint or wood should be avoided unless the design is primordial to energy efficiency. White ceilings produce the best results.

2. Select an LED light source with the correct light output.

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Human Centric Lighting

Human Centric Lighting (HCL) is an illumination specially designed to have a positive physiological and/or psychological effect on humans. It consists of adjusting the colour and intensity of the light throughout the day using adjustable white LED lighting solutions.

HCL supports human health, well-being and performance by considering and properly planning the implementation of a lighting system according to the desired visual, emotional and above all biological effects of light. Human Centric Lighting focuses on the needs of people for their living, leisure and working environment. The study is based on the properties and effects of natural light, a dynamic source of changing tone and brightness that changes throughout the day and seasons. 

A combination of white LED light sources, usually warm white (2700K) and cold white (6500K), is used to provide adequate human-centred lighting. This solution is also called Tunable White lighting. By adjusting the intensity of each individual, bright or dull white light with a hue between 2700K and 6500K can be achieved. It is a new way of using and implementing artificial light, corresponding to the changes of natural light and research on the effects on humans.

1. More light, more productivity

Increased lighting intensity allows people to work more concentrated, less tired, make fewer mistakes and more accurately identify mistakes. And what makes life more pleasant for the individual is more lucrative for the company as a whole.

2. More concentration and creativity

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Heat management of LED lamps

The optimal use of a product based on LED technology can be difficult due to an important factor: How the operating temperature can lead to a significant difference between the announced and actual performance of an LED-based product.
Important factors for this effect are LED quality, product design and heat management: how much of the heat generated during operation is dissipated.

If the heat is well managed, an LED-based lighting product will have the announced performance, long life and energy efficiency.

The basics of LED heat management

LEDs use electricity and this process generates heat. This heat must be conducted away as efficiently as possible from the LED in the environment. The design of the LED itself and the luminaire for this purpose is referred to as thermal management. The heat to be dissipated is directly proportional to the luminous flux and power consumption of the LED.

The heat is dissipated via a heat circuit.

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LED operating temperature and lifetime

For LED technology, heat is the biggest enemy. From LED chips to related products such as LED lamps, modules and fittings, high operating temperatures can lead to mechanical failure or a significant drop in performance.

The behaviour of the LED at higher operating temperatures is directly related to the LED quality. High-quality LEDs (such as Nichia or Cree) work within parameters and high temperatures, while low-quality LEDs fail, change color, lose brightness, or form a combination.

However, most people are not aware of this fact. They usually give heat and warmth a positive connotation. The misunderstanding that heat is good also comes from the fact that the sun and classic incandescent or halogen lamps have a warm ray. The heat comes from the considerable amount of infrared radiation in its spectrum, which can be high enough to keep food in fast food restaurants warm with light bulbs.

 

The spectrum of the LED (blue line), the fluorescent tube (green line) compared to the sun (orange line) and the incandescent/halogen lamps (violet line).

Heat and LED technology

Such a setup is necessary because high temperature operation must be avoided at all costs with LED technology. If you do not do this while doing so, lead to at least one of the following points:

  1. Complete failure of the LED
  2. The light output is permanently reduced (lumen degradation), even if the problem with the high temperature is solved.
  3. The light output is reduced in time, while the LED operates at a high temperature.
  4. The color temperature of the white LED changes

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Macadam Ellipses color sorting (3 step, 5 step, 7 step)

To understand what Macadam Elipse color sorting is, we must first know the consistency of the LED colors.

The color consistency of the LEDs has a simple explanation. Anyone can see when the color consistency is poor, especially in white light. The picture below clearly shows this, the white LED light has different shades.

 

Thus, a high color consistency means that all white LEDs have the same hue, while a poor color consistency looks like in the image above. This is the most extreme case where LEDs or lights have mixed all the white tones: Warm white, pure white and cold white in one installation. However, the same phenomenon also exists for products marketed as warm white, pure (natural) white or cold white.

White light has different shades

Although there is no consensus, warm white light for LEDs has a value of 2500K-4000K on the colour temperature scale, pure white 4000K-5000K and cold white 5000K-10,000K.

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LED luminous efficacy

The luminous efficacy of LEDs measures how effectively a light source produces visible light. With LEDs it is the ratio of luminous flux to electrical power.

The highest luminous efficacy today is 220 lumens per watt from Nichia 757G LEDs, while many other manufacturers offer LEDs in the 120-180 lumens per watt range. Cheap LEDs have an efficiency of only 50 lumens per watt.

Top performance LED High Performance LED Good Performance LED Poor Performance LED
220 lm/W 150-200 lm/W 100-149 lm/W 50-99 lm/W

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TM-30 Color Fidelity Index

CRI is a monovalent quantification of how good (or bad) an artificial source is in color rendering compared to a reference standard illuminant modeled after daylight.

It was introduced in 1974 by the International Commission on Illumination (CIE) because the possibilities of coloring with the white light of the many types of gas lamps that were then on the market are very different. Today, with over 40 years of use, the CRI index is firmly rooted in the lighting industry and among professionals.

However, it did not meet with much approval from the general public, since shortly after its introduction it no longer really became relevant to the decision to purchase lighting.

The reason for this was that most lamps were built for specific applications that required a minimum CRI value, so the choice of lamp could not be wrong.

For example, for office or any other linear lighting, almost everyone used the Tri-Phospor linear fluorescent tubes that have been on the market since the 1970s, all with CRI over 80. For the home, you had the choice between incandescent lamps and halogen with both CRI100 and retail and other high-intensity spot lighting, where the metal halide lamps with CRI min 85. The street lighting was reserved for high-intensity and very efficient sodium vapor lamps, which despite poor CRI very few interested.

LED technology changed this in 2000. It is the first light source that can be used for any application and offers the full range of performance and quality, including the ability to accurately reproduce colors. This is because LEDs are installed directly in luminaires, lamps and strips, as shown in the example below:

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

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Color Rendering Index (CRI)

The Color Rendering Index, commonly referred to as CRI, is a method by which we can measure how color looks to the human eye, depending on the light source compared to the sun. The CRI offers a scale of values up to 100, where 100 is the best color rendering light quality and a value below zero is very poor color rendering. The higher the CRI value (also called CIE Ra), the more accurate the colors are.

If a luminaire has a CRI of 100, this means that there is no difference in colour rendering between the light and the reference light (the sun). Likewise, a CRI of 75 means that the light bulb reproduces a 75% replica of the visible colors shown by the sun, since both lights have the same color temperature. This means that if the reference light is the light of the sun during sunset, the light source to be measured must also have the same color temperature to allow the most accurate comparison with the CRI measurement.

To obtain white light from an artificial source, a combination of different emitted wavelengths is required, something that was discovered at the beginning of the 20th century.  From then on many "recipes" to produce white light and combine the  different wavelengths were invented and still are.

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