Sep. 23, 2024
Electrical Equipment & Supplies
When choosing lighting types, LEDs are the most popular and reliable option. Besides, within a brief period, it has replaced traditional lighting like- halogen or incandescent bulbs. But how? To find the reason for such popularity, you should know the advantages and disadvantages of LED lighting.
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The advantages of LED lights are numerous. Among these, LEDs&#; energy efficiency, easy maintenance, and durability are the most worth mentioning. Besides, they don&#;t contain harmful gasses or toxic chemicals, which makes them eco-friendly. Yet, these broad advantages are followed by a few drawbacks, i.e., blue LEDs cause pollution and harm eyesight. But still, LED lights are far better options when compared to other conventional lights.
In this article, I&#;ve discussed the benefits and drawbacks of LED lights in detail. Besides, I also suggested LED lighting options that will suit your project the best. So without any further delay, let&#;s jump into the details-
What is LED Lighting?
LED stands for Light-Emitting diodes. A new lighting technology generates visible lighting by passing electricity to semiconductors. Besides, LED lights are energy-efficient and more durable compared to traditional lighting. That is why they have replaced conventional lighting like- incandescent or fluorescent lamps.
How Do LEDs work?
When electricity passes through traditional lighting, like fluorescent bulbs, it heats the filaments to generate visible lighting. But LED lights don&#;t have such a working mechanism. Instead of heating up, they follow the principle of electroluminescence to illuminate.
The semiconductor of LED is composed of two layers- n-type and p-type. The n-type layer contains a surplus of electrons, whereas the p-type creates holes due to electro deficiency.
In this stage, as electricity passes through the diodes, the electron from the n-type jumps toward the holes of the p-type layer using the p-n junction. And this flow of electrons from high electron-concentrated regions to low electron-concentrated areas generates visible light spectrums.
Thus, LED illuminates through the process of electron flow.
Advantages of LED Lighting
At present, LEDs are the most used lighting application worldwide. The popularity of LED lights is due to the benefits they provide that traditional lights lack. These advantages of LED lights are as follows-
Energy Efficient
LED lights consume much less energy than traditional lights. They bring the same intensity of illumination using 5-8 times less energy than incandescent bulbs. Generally, an incandescent bulb&#;s energy is converted to heat rather than light. As a result, significant energy is wasted as system loss. But in LED light, most energy transforms into light with minimal loss. Thus, they are energy-efficient and money-saving.
Optical Delivery Efficiency
The traditional Bulbs emit light in all directions. Due to this, a large portion of the output light is trapped inside reflectors and diffusers. Besides, some light rays escape in unintended directions, causing glaring. In contrast, using compound lenses, LEDs&#; compact form factor and directional nature allow effective light delivery. Thus, the optical efficiency of well-designed LED lighting systems can reach over 90%.
Cost-Effective
The LED lights use less energy and save electricity bills. Moreover, they don&#;t break out easily like glass bulbs. So, no maintenance or frequent changing is required with LEDs. And this is what makes them cost-effective and durable.
Instantaneous Action
LED lights can switch on 140 &#; 220 milliseconds faster than incandescent bulbs. As a result, LED bulbs glow almost instantly. On the other hand, compact fluorescent lamps can take up to 3 minutes to reach their full brightness. In addition, frequent switching doesn&#;t affect the lifespan of LEDs as it shortens the life of incandescent, fluorescent, and HID lamps.
Illumination Uniformity
Non-uniform illumination creates uneven lighting that causes visual fatigue and affects task performance. And to solve these problems, LEDs are great lighting options. They create uniform illumination that contributes to high visual comfort and permits flexibility in task performance.
Spectral Engineering
LED technology offers spectral engineering to engage specific human visual, physiological, or psychological needs. Thus, you can have greater control over the spectral distribution for different lighting. For instance- RGB or RGBW LED strips come with thousands of color mixing options to create aesthetic lighting. Again, tunable white LED strips allow you to control light spectrums by adjusting the color temperature and intensity of the lights.
Dimming Capability
Regular fluorescent lamps are not compatible with dimming control and are expensive too. Meanwhile, LED lights are excellent for dimming capability. Moreover, LED dimming comes with two options: analog dimming (CCR) and digital dimming (PWM).
Analog Dimming Of LED
Analog dimming of LEDs is the most used dimming solution for general lighting. It works through constant current reduction (CCR), controlling the drive&#;s current flow. But the drawback is that analog dimming LEDs don&#;t perform well for current flows below 10%.
Digital Dimming Of LED
Digital dimming of LED works by applying pulse width modulation (PWM) technology. Such a dimming system reduces the power loss of LEDs while dimming them. For instance, LEDs with a PWM dimming system can produce :1 or higher dimming ratios (at 100Hz) without any significant loss of accuracy.
Design Flexibility
LEDs have a wide range of design flexibility. Its small and compact design allows you to use it for various functions. In addition, they offer different lighting design options with versatile categories, i.e., LED bulbs, tube lights, flexible LED strips, or neon lights. And this is why LED lights are the best choice for any lighting solution.
Product Life.
The LED&#;s lifespan is much higher compared to regular incandescent bulbs. Where the average lifespan of incandescent bulbs is thousands of years, LED lights have an average lifespan of 35,000 and 80,000 hours. Plus, it can last 20-25 times longer than a typical halogen and 8-10 times longer than a typical CFL.
Less Bulk
The small structure of the LED lights is one of the plus points, especially regarding LED strips. As a result, they are incredibly lightweight, easy to install, and versatile to use. Besides, LEDs maintain their illuminating performance for their tiny sizing. As a result, these compact lights can glow as bright as traditional fluorescent lights using lesser energy.
Offer Directional Light
Incandescent and CFL bulbs offer directional lights at 360 degrees. Meanwhile, LED lights are directional light sources focusing the lights on 180 degrees. That means it only emits light rays in a particular direction reducing light pollution and unnecessary glaring effects. Thus, LED uses energy and lights more efficiently than traditional fluorescent or incandescent bulbs.
Easy Maintenance
LED lights don&#;t require frequent replacement; as a result, there is no need to keep up with regular maintenance. Thus, it saves your effort, money, and time. Plus, these lights are great for use in remote areas as no maintenance is required.
More Robust
Instead of a glass bulb or tube, like traditional incandescent and halogen lamps, an LED emits light from a block of semiconductors. So, there is no risk of broken glass with LEDs. In addition, LED lights have more extended durability and are incredibly resistant to shock, vibration, and wear.
Attract Fewer Bugs and Insects
Light sources easily attract bugs and insects. Especially in the case of incandescent lighting, the attraction of bugs is more. That is why they are inconvenient to use outdoors. Meanwhile, LED lights are proven to attract fewer bugs and insects. So you can easily use them outdoors.
More information, you can read Do LED Strip Lights Attract Bugs?
Convenient To Use
LED lights usually don&#;t blow out abruptly as incandescent bulbs. Instead, it tends to dim over a long period. So, it doesn&#;t require frequent fixture changing as other traditional lighting options.
Environmentally Friendly
Unlike conventional fluorescent bulbs, LED lights don&#;t contain other hazardous substances like- mercury. Additionally, LEDs are highly energy efficient. And this makes them a perfect addition to renewable energy sources like solar power. Thus, LEDs are environmentally friendly in comparison to other lighting options.
Lighting Control
LEDs allow you greater control over lights. For example, you can adjust the brightness of the LEDs to your liking. Besides, you can also control the lighting colors and patterns with smart LEDs like LED strips. In contrast, traditional lighting doesn&#;t offer you such facilities.
Photobiological Safety
Light sources that produce infrared or UV rays cause photobiological hazards. However, LED lights have no infrared (IR) rays which are hazardous to the skin or eyes. On the other hand, fluorescent and incandescent bulbs convert 37% and 73% of the total power consumption into infrared energy, respectively. Besides, the UV ray emission of LED lights is less than 5 uW/lm. In comparison, the UV ray emission by the incandescent lamp and compact fluorescent are 70-80 uW/lm and 30-100 uW/lm. Thus with LEDs, light sources are photo biologically safe and environment friendly.
Radiation Effect
The light source produces radiant energy over the visible range of the light spectrum (IR or UV), causing photobiological hazards. And these rays are responsible for the discoloration of paintings, drying out vegetables and fruits, melting chocolate, etc. But with LEDs, you need not worry about these problems. It only produces radiant energy within the visible wavelength of electromagnetic spectrums (400 nm to 700 nm). And so are suitable for using a museum or confectionery without worrying about product damage.
Fire and Explosion Safety
In traditional light bulbs, the tungsten filament is heated up, or gasses inside the bulb are excited to illuminate the light source. And so, this type of lighting involves a severe risk of exploration and fire breakout. In comparison, LEDs convert electrical energy into electromagnetic radiation inside a semiconductor package. Therefore, unlike traditional bulbs, they don&#;t heat up and are a safer option than conventional light bulbs.
Visible Light Communication (VCL)
Every LED light can be used as an optical access point for wireless data communication (if the LED driver can transform streaming content into digital signals). And utilizing this feature of LEDs, there appeared a new technology, Li-Fi (Light Fidelity). It is a wireless communication system that leverages LEDs&#; &#;ON&#; and &#;OFF&#; sequences to transmit data. Moreover, with Li-Fi, you can get a thousand times wider bandwidth and higher transmission speed than Wi-Fi or Bluetooth.
DC Lighting
LED lights are low-voltage devices that use direct current (DC) distribution grids. This DC lighting feature of LED increases the stability of the installation and reduces the likelihood of lighting failures. In addition, they are more dependable circuits and require less maintenance. And direct lighting-based LEDs are as much as 75% more efficient than incandescent lighting.
No Heat Emission
Traditional incandescent bulbs emit tremendous heat, making them too hot while operating. They turn more than 90% of the electrical energy in an incandescent bulb into heat energy and convert only 10% to light energy. On the other hand, LEDs emit almost no heat during operation. So, they are more efficient and ideal for illuminating artworks that will break down over time with exposure to UV rays.
Cold Temperature Operation
Cold temperature is the biggest challenge for fluorescent bulbs, requiring high voltage to start at cold temperatures. But the start-up of LED lights is independent of temperature. Therefore, they work perfectly at temperatures below -50 degrees Celsius. For this reason, they are ideal for lighting refrigerators, freezers, cold storage, and outdoors.
Customizability
You can customize and play with light colors with LED lights, i.e., LED strips. For instance, an RGB LED strip with an intelligent controller offers you a variety of color combinations with DIY color options. So, you can mix the primary red, green, and blue colors to prepare the desired light color on your own.
Compatible with Smart Home Applications
One of the most outstanding features of LED lights is that they are compatible with smartphones. You can connect them to your through Wi-Fi or Bluetooth and operate them efficiently. Such facilities are far beyond imagination in using traditional light bulbs.
LED Strip LightDisadvantages of LED Lights
Besides numerous advantages, LED lights also have a few disadvantages you should consider before choosing any LED lighting. These are as follows-
Increase the Blue Hazard
The blue light produced by blue and cool white LEDs causes more glare and impairs vision. Studies further show that blue lights affect muscular degeneration and also cause damage to photoreceptor cells. Thus, blue LEDs are harmful to the human eye.
Cause Blue Pollution
The rate of blue light pollution in cool white LEDs is much higher than in other traditional lighting sources. These blue light rays affect the natural circadian rhythms and thus hamper the regular sleeping cycles. Yet, to avoid such situations, you are recommended to avoid using white LEDs with a correlated color temperature above 3,000K. For this, warm-tone LED lighting options like dim to warm LED strips are great choices.
Extremely Voltage-Sensitive
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Related links:LEDs are sensitive to inappropriate voltage inputs. And getting the voltage slightly wrong in an LED-based system is a bigger problem for the LED. So, it is essential to calculate the voltage drop carefully and correctly to avoid any adverse effect on the lifespan of LEDs.
Do Not Allow Spherical Light Distribution
Fluorescent lamps and incandescent sources allow more excellent diverging capability with spherical light distribution. But LEDs&#; directional lighting nature does not allow spherical light distributions. As a result, the diverging light ability of LEDs is also limited.
Expensive
In terms of pricing, halogen is the cheapest category of lighting. But LED lights have advanced technology that makes them more efficient and costly. For instance, you can purchase a halogen bulb for just $3, whereas a regular LED light can cost $10 or more. Yet, as LED lights require low maintenance and less frequent replacement, they are considered more cost-effective.
Incompatibility With Traditional Lighting Controllers
The controllers, i.e., dimmers already installed in homes, are usually designed for incandescent lights. However, an LED light uses a different dimming method that doesn&#;t work with traditional controllers. So, you need to include an additional cost to your LED installation process to get a compatible LED controller.
Types Of LED Bulbs
LED lighting can be classified into two categories based on its formation structures. These are-
In standard LED bulbs, chip remains are lined up in an aluminum circuit board. However, unlike traditional bulbs like halogen or incandescent bulbs, they are not made of glass. Instead, LED bulbs are enclosed by plastic which makes them more robust.
Standard LED BulbsMicroscopic LED chips are combined to form filament wires in filament LED bulbs. And these filaments are coated in a yellow phosphorus coating that gives a warm lighting effect. Besides, these LEDs are enclosed by a glass outlet to provide a traditional bulb outlook. However, filament LEDs are more expensive and mainly used in chandeliers for their classic appearance.
Filament LED BulbsDifferent LED Lighting Technologies
LED lights have a wide range of variations in lighting types and technologies. And these lighting technologies are of the following four types-
DIP (Dual In-Line Package) LEDs are the traditional form of LED lights. They have a plastic-coated chip structure with two straight and parallel connecting pins. And compared to modern LEDs, DIP LEDs have less efficiency and can only emit a limited amount of brightness (around 4 lumens/LED).
Advantages Disadvantages long feet of DIP enable the led bulbs to perform better on heat dissipationSupports long lifetime for LED displaysCan deliver &#;focused&#; screenConsumes less energy Can&#;t go smaller than 10mm pixel pitchSmaller viewing angle Higher production and manufacturing costSMD LEDs are surface-mounted diodes placed directly onto the surface of printed circuit boards (PCBs). Compared to DIP LEDs, SMD LEDs are more efficient and brighter, making them a better lighting option. In addition, where a DIP LED uses three independent bulbs for RGB, SMD can put three diodes in the same chip. Thus, SMD LEDs are more compact and offer versatile lighting options.
Advantages Disadvantages Small in size ( 2mm indoors and 5mm outdoors)Higher lighting resolutionBetter viewing angles Better color accuracy and slightly improved reliabilitySupports versatile light-controlling options It uses more energy in comparison to DIP LEDsHarder to Service May create dots; (can be avoided using high-density SMD LEDs)COB (Chip on board) LED is a high-powered LED lighting technology where chips are directly encapsulated on a substrate ( PCB or silicon) to produce LED arrays. As a result, they can have brighter illumination compared to DIP and SMD. Moreover, COB LEDs are energy efficient and carry multiple diodes (9 or more) in a single chip.
Advantages Disadvantages Condensed dimension supports spotless lighting High efficiency; (produces greater brightness using less energy) Great uniformityStrong intensityLess heat emission Supports large focusing areas Lower repairabilityLimited color selectionMore expensive than SMD chipsChip scale package LEDs or CSP is the latest LED technology that emits the highest illumination at the smallest size available in the market. These LED packages are equivalent to the size of LED chips or at most 20%. One of the main benefits of such LEDs is that they do not require a soldered wire connection. That is how they reduce thermal resistance and possible light failure points.
Advantages Disadvantages Better heat dissipationHigher lumen densityNo holder and alloy wiring requirements Fewer production processesMore flexible & reliablePoor light transmittanceHigh priceGhosting phenomenon of backlight penetration.Why Choose LED Strips For Lighting?
LED strips are the most flexible and versatile lighting category of LED lighting. They are ideal for both indoor and outdoor uses. Besides, LED strips offer you a wide range of light-controlling facilities that opens numerous reasons to choose them for lighting. Yet, I have highlighted a few strong reasons why you should go for LED strips instead of other LED lighting-
Flexibility
LED strips are super flexible and have a rope-like structure that supports bending for easy installation. As a result, these strips are very lightweight and convenient to use. Besides, they also offer you resizing/cutting facilities. Thus, you can use these flexible LED strips anywhere with ease.
Versatility
When it comes to versatile lighting, nothing can beat LED strips. Indoor lighting or outdoor, they are suitable for ant lighting tasks. Besides, they have advanced technology that offers intensity adjustment, dimming, color temperature control, and many other options. And so you can use them in the bedroom, kitchen, bathroom, facade lighting, office lighting, etc. Apart from all these, you can also make signage with these flexible strips and use it for commercial purposes or indoor decor.
Light Control Options
LED strips like &#;RGBX, Tunable White, dim to warm, or addressable LED strips offer you adequate control over light color and intensity. For instance, with RGB LED strips, you can get 16.7 million hues mixing the primary red, green, and blue! Again, tunable white LED strips color temperature adjusting facilities. You can control the light&#;s temperature from K to K to bring warm to cool shades of white. Besides, there is another category of LED strips known as dim-to-warm. These strips provide dimming facilities for warm white shades (K to K) that give a relaxing and candle-like effect.
Yet, addressable LEDs stand out regarding color-controlling options. With these LED strips, you can control the color of every strip segment. Thus, you can have multi-coloring that gives a rainbow-like effect.
Customizable
LED strips offer various customization facilities unavailable on other LED lighting types. For instance, LEDYi has customizable options where you can choose the strip&#;s length, width, dimension, IP ratings, voltage, or even power consumption requirements for your LED strips. Besides, we also offer you the facility to include your labels and company information in our LED strips. So, LED strips by LEDYi are the best lighting solutions for personal, commercial, or business purposes.
Easy Install
LED strips are very easy to install and require lower maintenance. You don&#;t need any professional assistance installing LED strips. As they are flexible and resizable, you can install them on your own using connectors and LED drivers. Besides, these accessible installation features of LED strips offer you personalizing options where you can customize LED lighting using these flexible strips.
Check out How to Cut, Connect, and Power LED Strip Lights for a complete guide to LED strip installation.
Waterproof
Water-resistant features are crucial for any lighting type, especially outdoors. But no worries, LEDYi offers you the best waterproof lighting solution with IP67 and IP68-rated LED strips. So you can use them in the bathroom, poolside, or outdoor lighting. Yet, to choose the ideal waterproof LED strips, you must know about IP ratings. In this case- IP Rating: The Definitive Guide will help you to pick the best LED strips for your lighting project.
Color Accuracy
Light color accuracy is measured with Color Rendering Index (CRI). The higher the CRI rating, the better color quality a light can provide. For instance, single LED strips by LEDYi offers high CRI, Ra>90 / Ra>95, that gives accurate color as the natural lighting. Thus, the high CRI ratings of LED strips make them suitable for domestic and commercial purposes. For example, you can use them in shopping malls or outlets to showcase your product without worrying about color degradation.
Cost Effective & Durable
LED strips are more durable and energy-effective than other traditional light forms. It uses the least energy to bring out the maximum brightness. Thus, it saves your electricity bills minimizing power usage. And, regarding durability, LED strips can last much longer than classic lighting. Besides, LEDYi offers a five years warranty on its LED strips, ensuring their quality and performance.
Components of LED Strip LightHow To Choose LED Strips?
In choosing the ideal LED strips, you should consider some primary factors. These are as follows-
Length
Usually, the standard length of LED strip lights is 5 meters per reel. So, you must first calculate your length requirements and purchase reels accordingly. Yet, LEDYi offers customized options for strip lengths to meet your project requirements.
Dimension
The dimension of the LED chip is an essential factor to consider as it affects the lighting outlook. And the greater the dimension of the chip, the more prominent the lighting effect it creates. For instance, an SMD LED strip with a chip dimension of 5.6mm * 3.0mm glows brighter than SMD with a chip dimension of 2.2mm * 1.6mm.
Color
LED strips have a wide range of coloring options like- single color, RGB, RGBW, tunable white, dim-to-warm, addressable LED strips, etc. All of these lighting options offer you versatile light coloring options.
Tunable White LED Strips:
Tunable white LED strips offer you to change the color temperature of white lights to create warm to cool shades. These strips are connected to a tunable white controller with which you can adjust the color temperature from K to K. So if you are looking for adjustable white lighting, tunable white LED strips are your best option.
Dim-To-Warm LED Strips:
Dim-to-warm LED strips are great for warm and cozy lighting effects (K to K). With these strips, you can create candle-like natural effects for your indoor lighting. Besides, dim-to-warm LED strips are the best option for bedroom lighting as warm lighting creates a relaxing vibe and improves sleeping cycles.
Single-Color LED Strips:
Single-color LED strips are the most basic category of LED strips. They are available in different colors like- red, green, blue, yellow, pink, etc. You can choose any of these colors that suits you best. Besides, these LED strips are available in different power consumption and IP ratings, making them suitable for versatile uses.
RGBX LED Strips:
RGBX LED strips offer millions of color variations, mixing the primary colors- red, green, blue, and white. The most popular category of RGBX LED strips includes RGB, RGBW, and RGBWW. They are suitable for both indoors and outdoors and so widely used in the house, automobile, marine, commercial lighting, etc. Yet, before purchasing RGBX LED strips, check out &#;RGB vs. RGBW vs. RGBIC vs. RGBWW vs. RGBCCT LED Strip Lights&#; to find the best RGB variants for your lighting project.
Addressable LED Strips:
Addressable LED strips are the most versatile LED lighting options. They allow you to control the lighting in segments. That is, you can get multiple colors at a time running through the strips. In addition, they are visually attractive and come with many advanced technologies for which they are also known as dream color or magic LED strips.
LED Density
The density of LEDs indicates the number of LED chips per meter. The higher the density, the more even lighting it produces. Besides, LEDs with lower density create dots. So, it is always better to go with higher-density LEDs. Yet, LEDYi offers you LED density from 30LEDs/m to 720LEDs/m. And for dotless lighting, you can also go for our COB LED strips.
CRI Rating
CRI rating indicates the color accuracy of lighting. That is, with higher CRI grades, you get better color perceptions. So, always go for a LED strip with a higher color rendering index, CRI> 90 or above.
IP Rating
Ingress progress or IP rating denotes a fixture&#;s protection level against liquid and solid ingress. The IP rating allows us to find whether an LED strip is ideal for any particular use. For example- LED strips with IP65 are dust-protected but are not waterproof. So, though you can use them in areas where they may face dust issues, they are not suitable for wet environments. For water-resistant options, you need to go with IP67 or IP68.
Power Consumption
LED strips are available in various power consumption options from 2.4w/m to 30w/m. Besides, LEDYi offers customized options to get the ideal power consumption rate for your lighting tasks.
Therefore, these are the things that you must keep in mind before choosing any LED strips for your lighting project. Yet, if you need to inquire, contact the LEDYi service team, and we will help you to get the most suitable strips for your task.
DMX512 Addressable LED Strip RGBWAre LED Lights Better Than Regular Lights?
Let&#;s compare LED lights and regular lights to find the better one between them-
Therefore, from the above discussion, undoubtedly, LED lights are a better option than regular lights.
Can You Use LED Strips For Outdoor Lighting?
Of course! LED strips are great for outdoor lighting. You can use them as signage, facade lighting, architectural lighting, outdoor event lighting, pool lighting, street lighting, etc. But for outdoor lighting, you must consider the dustproof and water-resistant capability of the strips. So, it would be best to look for LED strips with higher IP ratings, as outdoor lighting faces adverse weather conditions like- dust, rain, and storms.
FAQs
Conclusion
LED lights have many worth-mentioning advantages that I have already described above. They are energy-efficient, eco-friendly, and more durable. Besides, unlike traditional lighting, they can perform in adverse weather conditions. Apart from these, they also come with a few disadvantages, like- blue hazards and pollution caused by blue LEDs. But you can cut these issues by implementing the appropriate LED lighting options.
However, LED strips are the most convenient and versatile among the wide range of LED lighting options. You can use them for any illuminating task, from the bedroom to marine lighting. So, without any further delay, contact LEDYi soon to get the best LED strip for your lighting project!
The global lighting market has been undergoing a radical transformation driven by the massively growing adoption of light emitting diode (LED) technology. This solid state lighting (SSL) revolution fundamentally altered the underlying economics of the market and dynamics of the industry. Not only different forms of productivity were enabled by SSL technology, the transition from conventional technologies towards LED lighting is profoundly changing the way people think about lighting as well. Conventional lighting technologies were designed primarily for addressing the visual needs. With LED lighting, the positive stimulation of biological effects of light on people's health and well-being is drawing increasing attention. The advent of LED technology also paved the way for the convergence between lighting and the Internet of Things (IoT) , which opens up a whole new world of possibilities. Early on, there has been a great deal of confusion about LED lighting. High market growth and huge consumer interest create a pressing need to clear the doubts surrounding the technology and to inform the public of its advantages and disadvantages.An LED is a semiconductor package comprising an LED die (chip) and other components that provide mechanical support, electrical connection, thermal conduction, optical regulation, and wavelength conversion. The LED chip is basically a p-n junction device formed by oppositely doped compound semiconductor layers. The compound semiconductor in common use is gallium nitride (GaN) which has a direct band gap allowing for a higher probability of radiative recombination than semiconductors with an indirect band gap. When the p-n junction is biased in the forward direction, electrons from the conduction band of the n-type semiconductor layer move across the boundary layer into the p-junction and recombine with holes from the valence band of the p-type semiconductor layer in the active region of the diode. The electron-hole recombination causes the electrons to drop into a state of lower energy and release the excess energy in the form of photons (packets of light). This effect is called electroluminescence. The photon can transport electromagnetic radiation of all wavelengths. The exact wavelengths of light emitted from the diode is determined by the energy band gap of the semiconductor.The light generated through electroluminescence in the LED chip has a narrow wavelength distribution with a typical bandwidth of a few tens of nanometers. Narrow-band emissions result in light having a single color such as red, blue or green. In order to provide a broad spectrum white light source, the width of the spectral power distribution (SPD) of the LED chip must be broadened. The electroluminescence from the LED chip is partially or completely converted through photoluminescence in phosphors. Most white LEDs combine short wavelength emission from InGaN blue chips and the re-emitted longer wavelength light from phosphors. The phosphor powder is dispersed in a silicon, epoxy matrix or other resin matrixes. The phosphor containing matrix is coated onto the LED chip. White light can also be produced by pumping red, green and blue phosphors using an ultraviolet (UV) or violet LED chip. In this case, the resulting white can achieve superior color rendering . But this approach suffers from a low efficiency because the large wavelength shift involved in the down-conversion of UV or violet light is accompanied with a high Stokes energy loss.The invention of incandescent lamps well over a century ago revolutionized artificial lighting. At present, we are witnessing the digital lighting revolution enabled by SSL. Semiconductor-based lighting not only delivers unprecedented design, performance and economic benefits, but also enables a plethora of new applications and value propositions previously thought impractical. The return from harvesting these advantages will strongly outweigh the relatively high upfront cost of installing an LED system, over which there is still some hesitation in the marketplace.One of the main justifications for migrating to LED lighting is energy efficiency. Over the past decade, luminous efficacies of phosphor-converted white LED packages have increased from 85 lm/W to over 200 lm/W, which represents an electrical to optical power conversion efficiency (PCE) of over 60%, at a standard operating current density of 35 A/cm2. Despite the improvements in the efficiency of InGaN blue LEDs, phosphors (efficiency and wavelength match to the human eye response) and package (optical scattering/absorption), the U.S. Department of Energy (DOE) says that there remains more headroom for PC-LED efficacy improvements and luminous efficacies of approximately 255 lm/W should be practically possible for blue pump LEDs . High luminous efficacies are unquestionably an overwhelming advantage of LEDs over traditional light sources&#;incandescent (up to 20 lm/W), halogen (up to 22 lm/W), linear fluorescent (65-104 lm/W), compact fluorescent (46-87 lm/W), induction fluorescent (70-90 lm/W), mercury vapor (60-60 lm/W), high pressure sodium (70-140 lm/W), quartz metal halide (64-110 lm/W), and ceramic metal halide (80-120 lm/W).Beyond significant improvements in light source efficacy, the ability to achieve high luminaire optical efficiency with LED lighting is less well-known to general consumers but highly desired by lighting designers. The effective delivery of the light emitted by light sources to the target has been a major design challenge in the industry. Traditional bulb-shaped lamps emit light in all directions. This causes much of the luminous flux produced by the lamp to be trapped within the luminaire (e.g. by the reflectors, diffusers), or to escape from the luminaire in a direction that is not useful for the intended application or simply offensive to the eye. HID luminaires such as metal halide and high pressure sodium generally are about 60% to 85% efficient at directing light produced by the lamp out of the luminaire. It is not uncommon for recessed downlights and troffers that use fluorescent or halogen light sources to experience 40-50% optical losses. The directional nature of LED lighting allows effective delivery of the light, and the compact form factor of LEDs allows efficient regulation of luminous flux using compound lenses. Well-designed LED lighting systems can deliver an optical efficiency greater than 90%.Uniform illumination is one of the top priorities in indoor ambient and outdoor area/ roadway lighting designs. Uniformity is a measure of relationships of the illuminance over an area. Good lighting should ensure uniform distribution of lumens incident over a task surface or area. Extreme luminance differences resulted from non-uniform illumination can lead to visual fatigue, affect task performance and even present a safety concern as the eye needs to adapt between surfaces of difference luminance. Transitions from brightly illuminated area to one of very different luminance will cause a transitional loss of visual acuity, which has large safety implications in outdoor applications where a vehicle traffic is involved. In large indoor facilities, uniform illumination contribute to high visual comfort, permits flexibility of task locations and eliminates the need of relocating luminaires. This can be particularly beneficial in high bay industrial and commercial facilities where substantial cost and inconvenience are involved in moving luminaires. Luminaires using HID lamps have a much higher illuminance directly below the luminaire than areas farther away from the luminaire. This results in a poor uniformity (typical max/min ratio 6:1). Lighting designers have to increase fixture density to ensure the illuminance uniformity meets the minimum design requirement. In contrast, a large light emitting surface (LES) created from an array of small-sized LEDs produces light distribution with a uniformity of less than 3:1 max/min ratio, which translates to greater visual conditions as well as a significantly reduced number of installations over the task area.Because of their directional emission pattern and high flux density, LEDs are inherently suited to directional illumination. A directional luminaire concentrates light emitted by the light source into a directed beam that travels uninterrupted from the luminaire to the target area. Narrowly focused beams of light are used to create a hierarchy of importance through the use of contrast, to make select features to pop out from the background, and to add interest and emotional appeal to an object. Directional luminaires, including spotlights and floodlights, are widely used in accent lighting applications to enhance the prominence or highlight a design element. Directional lighting is also employed in applications where an intense beam is needed to help accomplish demanding visual tasks or to provide long range illumination. Products that serve this purpose include flashlights , searchlights, followspots stadium floodlights , etc. An LED luminaire can pack enough of a punch in its light output, whether to create a very well defined "hard" beam for high drama with COB LEDs or to throw a long beam far out in the distance with high power LEDs LED technology offers the new capability to control the light source's spectral power distribution (SPD), which means the composition of light can be tailored for various applications. Spectral controllability allows the spectrum from lighting products to be engineered to engage specific human visual, physiological, psychological, plant photoreceptor, or even semiconductor detector (i.e., HD camera) responses, or a combination of such responses. High spectral efficiency can be achieved through maximization of desired wavelengths and removal or reduction of damaging or unnecessary portions of the spectrum for a given application. In white light applications, the SPD of LEDs can be optimized for prescribed color fidelity and correlated color temperature (CCT) . With a multi-channel, multi-emitter design, the color produced by LED luminaire can be actively and precisely controllable. RGB , RGBA or RGBW color mixing systems which are capable of producing a full spectrum of light create infinite aesthetic possibilities for designers and architects. Dynamic white systems utilize multi-CCT LEDs to provide warm dimming that mimics the color characteristics of incandescent lamps when dimmed, or to provide tunable white lighting that allows independent control of both color temperature and light intensity. Human centric lighting based on tunable white LED technology is one of the momentums behind much of the latest lighting technology developments.LEDs come on at full brightness almost instantly (in single-digit to tens of nanoseconds) and have a turn-off time in the tens of nanoseconds. In contrast, the warm up time, or the time which the bulb takes to reach its full light output, of compact fluorescent lamps can last up to 3 minutes. HID lamps require a warm-up period of several minutes before providing usable light. Hot restrike is of much greater concern than initial start-up for metal halide lamps which were once the principal technology employed for high bay lighting and high power floodlighting in industrial facilities, stadiums and arenas. A power outage for a facility with metal halide lighting can compromise safety and security because the hot restrike process of metal halide lamps takes up to 20 minutes. Instant start-up and hot restrike lend LEDs in a unique position to effectively carry out many tasks. Not only general lighting applications benefit greatly from the short response time of LEDs, a wide range of specialty applications are also reaping this capability. For example, LED lights may work in synchronization with traffic cameras to provide intermittent lighting for capturing moving vehicle. LEDs switch on 140 to 200 milliseconds faster than incandescent lamps. The reaction-time advantage suggests that LED brake lights are more effective than incandescent lamps at preventing rear-impact collisions. Another advantage of LEDs in switching operation is the switching cycle. The lifespan of LEDs is not affected by frequent switching. Typical LED drivers for general lighting applications are rated for 50,000 switching cycles, and it's uncommon for high performance LED drivers to endure 100,000, 200,000, or even 1 million switching cycles. LED life is not affected by rapid cycling (high frequency switching). This feature makes LED lights well suited to dynamic lighting and for use with lighting controls such as occupancy or daylight sensors . On the other hand, frequent on/off switching may shorten the life of incandescent, HID, and fluorescent lamps. These light sources generally have only a few thousands of switching cycles over their rated life.The ability to produce light output in a very dynamic way lends LEDs perfectly to dimming control, whereas fluorescent and HID lamps do not respond well to dimming. Dimming fluorescent lamps necessitates the use of expensive, large and complex circuitry in order to maintain the gas excitation and voltage conditions. Dimming HID lamps will lead to a shorter life and premature lamp failure. Metal halide and high pressure sodium lamps cannot be dimmed below 50% of the rated power. They also respond to dimming signals substantially slower than LEDs. LED dimming can be made either through constant current reduction (CCR), which is better known as analog dimming, or by applying pulse width modulation (PWM) to the LED, AKA digital dimming. Analog dimming controls the drive current flowing through to the LEDs. This is the most widely used dimming solution for general lighting applications, although LEDs may not perform well at very low currents (below 10%). PWM dimming varies the duty cycle of the pulse width modulation to create an average value at its output over a full range from 100% to 0%. Dimming control of LEDs allows to align lighting with human needs, maximize energy savings, enable color mixing and CCT tuning, and extend LED life.The digital nature of LEDs facilitates seamless integration of sensors, processors, controller, and network interfaces into lighting systems for implementing various intelligent lighting strategies, from dynamic lighting and adaptive lighting to whatever IoT brings next. The dynamic aspect of LED lighting ranges from simple color changing to intricate light shows across hundreds or thousands of individually controllable lighting nodes and complex translation of video content for display on LED matrix systems. SSL technology is at the heart of large ecosystem of connected lighting solutions which can leverage daylight harvesting, occupancy sensing, time control, embedded programmability, and network-connected devices to control, automate and optimize various aspects of lighting. Migrating lighting control to IP-based networks allows intelligent, sensor-laden lighting systems to interoperate with other devices within IoT networks . This opens possibilities for creating a wide array of new services, benefits, functionalities, and revenue streams that enhance the value of LED lighting systems. The control of LED lighting systems can be implemented using a variety of wired and wireless communication protocols, including lighting control protocols such as 0-10V, DALI, DMX512 and DMX -RDM, building automation protocols such as BACnet, LON, KNX and EnOcean, and protocols deployed on the increasingly popular mesh architecture (e.g. ZigBee , Z-Wave, Bluetooth Mesh , Thread).The small size of LEDs allows fixture designers to make light sources into shapes and sizes suited for many applications. This physical characteristic empowers the designers with more freedom to express their design philosophy or to compose brand identities. The flexibility resulted from direct integration of light sources offers possibilities to create lighting products that carry a perfect fusion between form and function. LED light fixtures can be crafted to blur the boundaries between design and art for applications where a decorative focal point is commanded. They can also be designed to support a high level of architectural integration and blend in any design composition. Solid state lighting drives new design trends in other sectors as well. Unique styling possibilities allow vehicle manufacturers to design distinctive headlights and taillights that give cars an appealing look.An LED emits light from a block of semiconductor&#;rather than from a glass bulb or tube, as is the case in legacy incandescent, halogen, fluorescent, and HID lamps which utilize filaments or gases to generate light. The solid state devices are generally mounted on a metal core printed circuit board (MCPCB), with connection typically provided by soldered leads. No fragile glass, no moving parts, and no filament breakage, LED lighting systems are therefore extremely resistant to shock, vibration, and wear. The solid state durability of LED lighting systems has evident values in a variety of applications. Within an industrial facility, there are locations where lights suffer from excessive vibration from large machinery. Luminaires installed alongside roadways and tunnels must endure repeated vibration caused by heavy vehicles passing by at a high rate of speed. Vibration makes up the typical working day of work lights mounted on construction, mining and agricultural vehicles, machinery and equipment. Portable luminaires such as flashlights and camping lanterns are often subject to impact of drops. There are also many applications where broken lamps present a hazard to occupants. All these challenges demand a rugged lighting solution, which is exactly what solid state lighting can offer.Long lifetime stands out as one of the top advantages of LED lighting, but claims of long life based purely on the lifetime metric for the LED package (light source) can be misleading. The useful life of an LED package, an LED lamp, or an LED luminaire (light fixtures) is often cited as the point in time where the luminous flux output has declined to 70% of its initial output, or L70. Typically, LEDs (LED packages) have L70 lifetimes between 30,000 and 100,000 hours (at Ta = 85 °C). However, LM-80 measurements that are used for predicting the L70 life of LED packages using the TM-21 method are taken with the LED packages operating continuously under well controlled operating conditions (e.g. in a temperature-controlled environment and supplied with a constant DC drive current). By contrast, LED systems in real world applications are often challenged with higher electrical overstress, higher junction temperatures, and harsher environmental conditions. LED systems may experience accelerated lumen maintenance or outright premature failure. In general, LED lamps (bulbs, tubes) have L70 lifetimes between 10,000 and 25,000 hours, integrated LED luminaires (e.g. high bay lights, street lights , downlights) have lifetimes between 30,000 hours and 60,000 hours. Compared with traditional lighting products&#;incandescent (750-2,000 hours), halogen (3,000-4,000 hours), compact fluorescent (8,000-10,000 hours), and metal halide (7,500-25,000 hours), LED systems, in particular the integrated luminaires, provide a substantially longer service life. Since LED lights require virtually no maintenance, reduced maintenance costs in conjunction with high energy savings from the use of LED lights over their extended lifetime provide a foundation for a high return on investment (ROI).LEDs are photobiologically safe light sources. They produce no infrared (IR) emission and emit a negligible amount of ultraviolet (UV) light (less than 5 uW/lm). Incandescent, fluorescent, and metal halide lamps convert 73%, 37%, and 17% of consumed power into infrared energy, respectively. They also emit in the UV region of the electromagnetic spectrum&#;incandescent (70-80 uW/lm), compact fluorescent (30-100 uW/lm), and metal halide (160-700 uW/lm). At a high enough intensity, light sources that emit UV or IR light may pose photobiological hazards to the skin and eyes. Exposure to UV radiation may cause cataract (clouding of the normally clear lens) or photokeratitis (inflammation of the cornea). Short duration exposure to high levels of IR radiation can cause thermal injury to the retina of the eye. Long-term exposure to high doses of infrared radiation can induce glassblower's cataract. Thermal discomfort caused by incandescent lighting system has long been an annoyance in the healthcare industry as conventional surgical task lights and dental operatory lights use incandescent light sources to produce light with high color fidelity. The high intensity beam produced by these luminaires delivers a large amount of thermal energy that can make patients very uncomfortable.Inevitably, the discussion of photobiological safety often focuses the blue light hazard, which refers to a photochemical damage of the retina resulting from radiation exposure at wavelengths primarily between 400 nm and 500 nm. A common misconception is that LEDs may be more likely to cause blue light hazard because most phosphor converted white LEDs utilize a blue LED pump. DOE and IES have made it clear that LED products are no different from other light sources that have the same color temperature with respect to the blue light hazard. Phosphor converted LEDs do not pose such a risk even under strict evaluation criteria.LEDs produce radiant energy only within the visible portion of the electromagnetic spectrum from approximately 400 nm to 700 nm. This spectral characteristic gives LED lights a valuable application advantage over light sources that produce radiant energy outside the visible light spectrum. UV and IR radiation from traditional light sources not only poses photobiological hazards, but also leads to material degradation. UV radiation is extremely damaging to organic materials as photon energy of radiation in the UV spectral band is high enough to produce direct bond scission and photooxidation pathways. The resulting disruption or destruction of the chromophor can lead to material deterioration and discoloration. Museum applications require all light sources that generate UV in excess of 75 uW/lm to be filtered in order to minimize irreversible damage to artwork. IR does not induce the same type of photochemical damage caused by UV radiation but can still contributes to damage. Increasing the surface temperature of an object may result in accelerated chemical activity and physical changes. IR radiation at high intensities can trigger surface hardening, discoloration and cracking of paintings, deterioration of cosmetic products, drying out of vegetables and fruits, melting of chocolate and confectionery, etc.Fire and exposition hazards are not a characteristic of LED lighting systems as an LED converts electrical power to electromagnetic radiation through electroluminescence within a semiconductor package. This is in contrast to legacy technologies which produce light by heating tungsten filaments or by exciting a gaseous medium. A failure or improper operation may result in a fire or an explosion. Metal halide lamps are especially prone to risk of explosion because the quartz arc tube operates at high pressure (520 to 3,100 kPa) and very high temperature (900 to 1,100 °C). Non-passive arc tube failures caused by end of life conditions of the lamp, by ballast failures or by the use of an improper lamp-ballast combination may cause the breakage of the outer bulb of the metal halide lamp. The hot quartz fragments may ignite flammable materials, combustible dusts or explosive gases/vapors.LEDs can be switched on and off at a frequency faster than the human eye can detect. This invisible on/off switching ability opens up a new application for lighting products. LiFi (Light Fidelity) technology has received considerable attention in the wireless communication industry. It leverages the "ON" and "OFF" sequences of LEDs to transmits data. Compared current wireless communication technologies using radio waves (e.g., Wi-Fi, IrDA, and Bluetooth), LiFi promises a thousand times wider bandwidth and a significantly higher transmission speed. LiFi is considered as an appealing IoT application due to the ubiquitousness of lighting. Every LED light can be used as an optical access point for wireless data communication, as long as its driver is capable of transforming streaming content into digital signals.LEDs are low voltage, current-driven devices. This nature allows LED lighting to take advantage of low voltage direct current (DC) distribution grids. There is an accelerating interest in DC microgrid systems which can operate either independently or in conjunction with a standard utility grid. These small-scale power grids provide improved interfaces with renewable energy generators (solar, wind, fuel cell, etc.). Locally available DC power eliminates the need for equipment-level AC-DC power conversion which involves a substantial energy loss and is a common point of failure in AC powered LED systems. High efficiency LED lighting in turn improves the autonomy of rechargeable batteries or energy storage systems. As IP-based network communication gains momentum, Power over Ethernet (PoE) emerged as a low-power microgrid option to deliver low voltage DC power over the same cable that delivers the Ethernet data. LED lighting has clear advantages to leverage the strengths of a PoE installation.LED lighting excels in cold temperature environments. An LED converts electrical power into optical power through injection electroluminescence which is activated when the semiconductor diode is electrically biased. This start-up process is not temperature-dependent. Low ambient temperature facilitates dissipation of the waste heat generated from LEDs and thus exempts them from thermal droop (reduction in optical power at elevated temperatures). In contrast, cold temperature operation is a big challenge for fluorescent lamps. To get the fluorescent lamp started in a cold environment a high voltage is needed to start the electric arc. Fluorescent lamps also lose a substantial amount of its rated light output at below-freezing temperatures, whereas LED lights performs at their best in cold environments&#;even down to -50°C. LED lights therefore are ideally suited for use in freezers, refrigerators, cold storage facilities, and outdoor applications LED lights produces notably less environmental impacts than traditional lighting sources. Low energy consumption translates to low carbon emissions. LEDs contain no mercury and thus create less environmental complications at end-of-life. In comparison, the disposal of mercury-containing fluorescent and HID lamps involves the use of strict waste disposal protocols.Don't get excited over the wealth of benefits offered by LED lighting. While this technology is definitely a landmark achievement in the history of electric lighting, it raises problems of its own. The lighting industry is facing a challenge in a magnitude it has never had to deal with before. Solid state lighting altered the philosophy of design and engineering. Lighting systems are no longer dumb illuminants, they have evolved into power electronics. In other words, the design of lighting systems is unprecedentedly complex. LEDs are self-heating, current-sensitive and luminously intensive semiconductor light sources. This gives rise to the largest concern of LED Lighting&#;the performance and reliability of an LED system heavily rely on a multidimensional work. The LED package metrics are just one aspect of the holistic design and systems engineering of an LED lighting system. Many other interdependent factors come into play, including thermal management , drive current regulation, and optical control.Armchair experts often compile a long list of disadvantages for LED lighting. And to make the story sensational they would never forget to mention that LED lighting can induce blue light hazards. White light is basically a mixture of wavelengths from different color bands. All whites with the same color appearance, regardless of the light sources from which the light is emitted, have roughly the same proportion of blue wavelengths across the visible spectrum. The color appearance of white light may be characterized as having a correlated color temperature (CCT). The blue content of a light source generally corresponds to its CCT. The higher the CCT the higher the proportion of blue wavelengths. Under the same luminance and illuminance conditions, blue radiation from a K LED product is as low as that from a K incandescent lamp, and blue radiation from a K LED product is as high as that from a K fluorescent lamp. As with other light sources, the blue light hazard is rarely a concern for white LEDs. The ability to engineer the spectral composition of white light is a huge advantage of LED technology. With LED lighting, any spectral composition of light that positively contributes to human health and well-being can be produced. Human centric lighting , a major technology trend that is driving the growth of the lighting industry, harvests the CCT tuning capability of LED systems to adjust the amount of blue radiation for a healthy spectrum of white light.In fact, LED lighting has only a few intrinsic disadvantages.The most well-known weakness of LED lighting is that LEDs produce a byproduct&#;heat. LEDs are called sell-heating devices because they generate heat within the device package&#;rather than radiating heat in the form of infrared energy. Around half of the electrical energy fed to an LED is converted into heat, which must be conducted and convected through a physical thermal path. Failure to maintain the device junction temperature below a set limit may accelerate the kinetics of failure mechanisms such as atomic defect generation and growth in the active region of the diode, carbonization and yellowing of the encapsulant, and discoloration of plastic package housing. Beyond the maximum rated junction temperature, the service life of an LED will be reduced by 30% to 50% for every 10 ° C rise in junction temperature.The most unknown, and also the biggest weakness of LED lighting is that LEDs are delicate power electronics. They are extremely picky about their food&#;drive current. For LEDs, their high sensitivity to forward current is a double-edged sword. It gives lighting systems superior controllability but also makes drive current regulation enormously challenging. A very small change in drive current will cause the light output to fluctuate. LEDs are DC-driven devices, however they often have to be fed with an AC power source. Incomplete suppression of the alternating waveform after rectification may result in a residual ripple (residual periodic variation) in the current output from the driver to the LEDs. This ripple causes the LEDs to flicker at twice the frequency of the incoming line voltage, i.e. 100Hz or 120Hz. The electrical and thermal interdependence of LEDs also adds complexity to load regulation. As junction temperature rises, forward voltage decreases, the electrical power delivered to the LED is also reduced. On the other hand, the higher the drive current the greater the waste heat generated at the semiconductor die. Overdriving what an LED is rated for may lead to early failure of the LED due to thermal runaway. Nevertheless, the most damaging threat to LEDs comes from electrical overstresses (EOS). An EOS occurs when the drive current or voltage exceeds the component maximum rated values. There are many possible sources of electrical overstresses, which include electrostatic discharge (ESD), inrush current, or other types of transient power surges. The vulnerability of LEDs to various types of electrical stresses therefore necessitates tight regulation of the drive current.A third disadvantage is that LEDs have a high flux density. The concentrated light sources of directional light can potentially create glare. High luminances in the field of view interfere with seeing (disability glare) or cause a sensation of irritation or pain (discomfort glare). Additional optics to mitigate glare can be incorporated into the luminaires design, but they often result in high optical loss.The last but not least, increased complexity of system design leads to a higher first cost of LED products when compared with legacy lighting products. This makes cost optimization an important part of the luminaire design process. When the cost pressure outweighs performance and reliability of the products, a stream of problems will arise.With cost being the ever-present concern, no LED lighting solution today is without compromise. The fact that LED products are built on a holistic framework heightens the trickiness in the lighting market. The design and engineering of LED systems, in a way, are about coping with trade-offs between different aspects of lighting (e.g. cost, efficiency, lighting quality, lifespan). While ethical lighting manufacturers address or reduce these trade-offs through innovative design and advanced engineering, there are a number of unethical players that cut corners and game the technology.When thermal management is effectively applied, the system efficiency of an LED lighting product is the cumulative efficiency of its LEDs, driver and optics. The efficacy of LED packages should not be equated with the efficacy of an LED luminaire. There can be cases where LEDs have a luminous efficacy of 200 lm/W but the luminaire has a luminous efficacy of 100 lm/W only. Such a high efficacy discrepancy between the light source and lighting system can be attributed to inefficient power conversion, ineffective light delivery, or a combination of both. Increasing power conversion efficiency of the AC-DC driver and optical delivery efficiency is, therefore, another way to improve lighting efficiency. The use of low cost driver circuits is the primary cause of abnormally low system efficiency. Linear power supplies , for example, have been tremendously favored by manufacturers of entry-level products. These driver circuits have significantly less circuit parts count and thus a considerably lower cost in comparison with switching power supplies . One of the problems with a linear regulator, however, is its low power conversion efficiency because it operates by dissipating excess power as heat.The efficacy of an LED lighting system can undergo a rapid drop due to the use of low-performing LEDs, inadequate thermal management, overdriving, or a combination of them. Rapid lumen depreciation often occurs in lighting systems that uses mid-power plastic LED packages. These light sources have a high initial efficacy thanks to their high reflectivity plastic cavities and leadframe plating. But the plastic housing made of synthetic resins such as PPA and PCT will discolor when exposed to high temperatures. Operating these LEDs at elevated junction temperatures due to overdriving and/or inefficient heat dissipation will accelerate thermal degradation in packaging materials and lead to a permanent reduction in light output.The reliability of an LED system will be determined by all its constitutive parts and their ability to survive environmental or operational stresses. While the majority of parametric failures of LEDs such as lumen depreciation and color shifts of are temperature-dependent, the majority of catastrophic failures of LEDs are driver-dependent. An LED system is only as good as its weakest link, and the driver is usually this link. The driver is the heartbeat of an LED system as it undertakes to execute many sub-tasks sequentially or in parallel. Among these sub-tasks protecting LEDs from power surges and poor incoming power quality is especially important since the catastrophic failures of LEDs are often caused by EOS events. LED drivers typically make use of electrolytic capacitors to absorb the surge energy, smooth out the large output current ripple, and filter EMI. The lifespan of electrolytic capacitors is heavily dependent on the operating temperature and the ripple current flowing through it. This makes the driver itself to be frequently the first component of an LED system to fail because low cost drivers rarely use high operating temperature capable capacitors. Linear power supplies operate without using electrolytic capacitors and hence have a higher circuit reliability. However, the LEDs operated by these circuits are subject to electrical overstresses.Among the variables that contribute to the quality of lighting, flicker control and color quality are often traded for lower cost system designs. As previously discussed flicker occurs when there are large ripples in the DC current. Low cost driver solutions such as single-stage SMPS circuits or linear regulators generally do not perform well in ripple suppression. The lighting industry also indulges in offering lighting products that have a low color rendering index (CRI) and high color temperature. This is due to the presence of the trade-off between luminous efficacy and spectral quality. To deliver high color rendering lighting, the light source must spread radiant power uniformly across the visible spectrum. This involves down-conversion of a large amount of short wavelength photons (e.g. blue photons). The larger the amount of short wavelength photons is converted the higher the Stokes energy loss. This results in a lower efficacy for LEDs with a higher color rendering performance.Despite suffering from additional energy loss associated with wavelength conversion, the efficacy of LEDs with a high CRI is already sufficiently high to strike a balance between energy efficiency and color rendering. Most LED products designed for interior lighting are still being offered with an underperforming color quality. The light produced by these products is good at rendering medium-saturated colors but deficient in wavelengths for reproducing saturated colors.Similarly, for an LED to produce warm white light a considerable amount of short wavelength light emitted by the LED chip needs to be down-converted into longer wavelength light. This causes phosphor converted LEDs with a cool white appearance to deliver a higher efficacy than those with a warm white appearance. Lighting products with a high color temperature (e.g. 6,000 K - 6,500 K) are heavily pushed in markets where consumers are less aware of the biological effect of blue-enriched cool white light. Nocturnal melatonin suppression due to exposure to high CCT light can disrupt circadian rhythms and results in negative health consequences.
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