Philips - FAQ

What are LEDs?

LEDs are light emitting diodes. These are electronic components that convert electrical energy directly into light through the movement of electrons within the material of the diode. LEDs are important because owing to their efficiency and low energy, they are beginning to replace most conventional light sources.

Why is LED technology classified as solid state lighting?

The term solid state lighting is used because the electronics produces light directly from solid materials in which the electrons are embedded. It is unlike other technologies, for example fluorescent technology, which requires a gaseous discharge medium to initiate production of light.

What does future-proofing of LED products mean?

LED technology is constantly changing. Rapid innovation continues to improve the performance of LED on an almost daily basis. Future-proofing of LED modules allows luminaire manufacturers to switch from one generation to the next improved generation without major retooling or changes in luminaire design, offering backward compatibility with drivers.

What is binning?

LED chips are mass produced in millions and there are inevitably slight differences in color appearance and light output. Binning is way of sorting the chips so that all the LEDs from one particular bin look the same and have similar light output.

What is a light engine?

A light engine is the LED equivalent of a conventional lamp. It normally consists of a LED chip mounted on a circuit board that has electrical and mechanical fixings, meaning it is ready to be fixed in the luminaire. Note that the light engine may not consist of only one chip; it may be an array of 9 or 16, sometimes with a phosphor coating.

What makes LEDs more robust than other light sources?

LEDs have no gases, filaments, and no moving parts to fatigue. They provide light through a one-step process that takes place within the diode. There is no glass to break or screwed contacts to loosen.

Why do LEDs have a higher initial cost than conventional light sources?

LEDs are made of electronic components that need to be packaged together to offer long-lasting efficient light sources to the end user. Apart from the LED chip itself, which has sapphire and gallium in the semiconductor, the process of packaging with materials like ceramic, rare earth phosphors, silicone, solder, and gold wire add to the overall cost. White LEDs require further tests for calibration and standardization.

What are the economic advantages of using LEDs over conventional light sources?

Although the initial cost of conventional light sources is less than LEDs, the operational and maintenance costs of LEDs are significantly lower. LEDs, having a longer life, reduce maintenance and lamp replacement cost. As LEDs need to be replaced less frequently, the owner spends less on new lamps and the labor needed to change them. LEDs also consume less energy; thus the overall cost of a LED system can be significantly lower than that of a conventional lighting system. Most applications with LEDs offer a payback period as low as three to four years.

What strategies in the development of LED technology help to reduce the cost of LEDs in the future?

Some of the strategies for reducing the cost of LEDs in the future are:

Reduction in the production process.
Simplification and reduction in the number of components.
Introduction of new materials.

What considerations need to be taken into account when integrating LEDs into interior architectural elements or furniture?

Here are some of the aspects that need to be taken into consideration:

Luminaire spacing and layout.
Ways to prevent a view of the light source and minimize glare.
Ventilation/cooling of LEDs.
Wiring access.
Access to LEDs in case of maintenance or replacement.
Location of driver, if not integrated in luminaire.
Switching/dimming capabilities, or control type and location.

What aspects need to be taken in consideration when replacing a light source with LEDs in a retrofit scenario?

The lamp base/holder screw fixing position.
The physical dimension of the LED lamp and how it fits into the existing housing.
The electrical characteristics of LEDs compared to the existing system (mains voltage, low voltage, and control methods).
The location and size of the light emitting surface in relation to the luminaire reflector and in comparison to the original light source.
The light distribution, lumen output, and other photometric properties like color temperature, compared to the original light source.
The heat generated by the LED during operation and maximum operating temperature.

What are the types of LED units available for built-in wardrobes?

Lights built into wardrobes can be of the following types:

Low voltage LED lights with a magnetic switch that comes in two components. One is fixed onto the wardrobe door and the other to the wardrobe itself. When the door is opened, the contact is broken and power is sent to the light.
PIR switches with an infrared motion sensor that activates the light when the wardrobe is opened.

Can I use LEDs in a green house?

LEDs can produce concentrated beams of light at specific light frequencies. While sunlight comprises the entire spectrum of light, LEDs can be designed to emit specific parts of the light spectrum that activate certain photoreceptors in the plant. For example, blue light promotes phototropism and cryptochromes, which contribute to germination and elongation of the plant, while red light stimulates phytochromes, which help the plant to flower at the optimum time. Regulation of the spectrum of light based on the plant’s life cycle promotes faster growth, and a stronger plant than what would be grown under sunlight conditions.
Note that the light output of LEDs lessens at higher temperatures. You should make sure that the luminaire is suitable for the environmental conditions.

Is it true that LED lights do not attract insects?

Most insects are primarily attracted to ultraviolet rays, which help them forage, navigate, and select mates. For example, Indian moths are attracted to UV light (365nm) and green light (500nm). LEDs do not have UV content and hence do not attract many insects compared to conventional light sources.

How can LEDs keep food fresher than conventional light sources?

LEDs do not emit ultraviolet light and do not carry heat in the beam, unlike their conventional counterparts. This helps keep food fresher in refrigerators and cold stores.

What are the advantages of LED over neon in signage applications?

LEDs have the following advantages over neon:

Power consumption: LEDs use much less power than neon to deliver the same light output.
Versatility: LEDs offer a far wider range of products and configuration of solutions than neon. Neon lights have limitations due the nature by which they produce light and the way they are fabricated.
Heat dissipation: LEDs produce less heat than neon.
Safety: Neon lights run on high voltage and are unsafe when positioned in places where people can touch them.
Neon lights use fragile glass tubes.
Color range and effects: LEDs offer a wider palette of colors and color changing effects through digital control.
Maintenance: LEDs need virtually no maintenance compared to neon.

What does one need to take into consideration when choosing a light source for art galleries and museums?

It is important to compare the spectral power distribution of the light source (SPD), Color Rendering Index (CRI), Correlated Color Temperature (CCT), and the Color Quality Scale (CQS) of the light source depending on the nature of exhibits/displays to be lit. The illumination level needed within the exhibition and the hours of operation also need to be considered. This is a specialist area, and proper set up of lighting requires the advice of a consultant such as the curator.

How can the color changing ability of LEDs be advantageous in retail and display environments?

In retail and display environments where the range of products changes by the season, the colors can be changed to match the type of product on display. For example, electronic goods may require a cool white light, while a warmer tone may be required for fabrics. When a fashion season has red as a theme, the store can use a color of light with more red in its spectrum to enhance and bring out the vibrancy of the display.

How can flexibility in changing the color temperature offer more comfortable environments?

LEDs offer the capability of changing from warm white to cool white through digital control of the LEDs. This can be used in indoor or partly outdoor environments where the illumination level and color temperature can be adjusted to match the outdoor conditions (e.g. sunny, clear sky, or overcast) depending on the feel required in the space.

What are the benefits of using LEDs in mining areas?

Using LEDs in mining areas has the following benefits:

Better focus on the work area.
Safer environment owing to low glare and LEDs that are cool to the touch.
No start-up time.
LEDs are solid state, so it is easier to make the workplace explosion- and vibration-proof.
LED can be powered with AC or DC and has longer battery backup with option of charging battery with solar panels.
LED lights can be installed with satellite connection and can have integrated motion sensors and GPS, which offers remote access to live information about usage, location, and condition as well as further security features.

Can LEDs help to improve performance in classrooms?

LEDs have the capability to offer “biologically optimised” solutions that simulate the color temperature of the sky. This has been proven to improve concentration and maintain alertness of students in classrooms. It has successfully dealt with a kind of morning tiredness typical to young people. One way of creating the appropriate color temperature is by using a combination of independently controlled blue and white LEDs.

How can LEDs help combat jetlag in air travel between countries?

Use of tunable LEDs in aircrafts can help alter the circadian rhythms of passengers. The time-controlled simulation of daylight, noon, and dusk color temperatures with the LEDs in the aircraft can help passengers to gradually adapt to the time zone of the destination.

How has automobile lighting benefited from LEDs?

p>LED lighting, although more expensive than its incandescent predecessors in automobile lighting, works as a cost-effective solution owing to its digital features that simplify wiring, controls, and the installation process. LEDs offer high-quality light in terms of color rendering and they provide lighting solutions that result in comfort and a more enjoyable driving experience. However, the biggest advantage of LEDs is their long lifecycle and resistance to vibration.

Why LEDs are advantageous in lighting underground caves?

Underground stalactites are damaged by the heat of halogen lamps. Apart from having long lifecycle, LEDs also require much less maintenance than traditional light sources.

How does the wide temperature tolerance expand the application of LEDs?

LEDs work more efficiently in cold temperatures. Better still, the cold air that offers a passive heat absorption extends their lifecycle. This gives LEDs an advantage in various applications like ice-skating rings/tracks, cold storage places, and lighting public places in colder countries.

What is the new development of “Li-fi” that has been recently published?

The recent development of LEDs allows them to not only provide light, but also offer internet connectivity through “Li-fi” technology. By increasing the flicker rate of LEDs, data can be transmitted to specially adapted laptops and electronic devices via the visible spectrum, instead of via the currently used radio and microwaves.

What is Zhaga?

Zhaga is an industry-wide consortium aiming to standardize specifications for interfaces between LED luminaires and light engines. The aim is to permit interchangeability between products made by different manufacturers. Zhaga defines test procedures for luminaires and LED light engines so that the luminaire will accept the LED engine.

What are the LED lighting standards referenced in the Energy Star specification?

ANSI (American National Standard Institute) - Establishes definitions of solid state lighting devices and components. It also provides a common terminology.
IESNA (Illuminating Engineering Society of North America) - Provides procedures for reproducible measurements of photometry, color, and electrical characteristics of solid state lighting products.
UL (Underwriters Laboratories) - Writes safety standards for LED products, including drivers, controllers, arrays, packages, and modules.
NEMA (National Electrical Manufacturers Association) - makes recommendations for mechanical, thermal, and electrical interfaces between luminaires.

What is CELMA?

CELMA is the Federation of National Manufacturers Associations for Luminaires and Electrotechnical components in the European Union. CELMA, along with ELC (European Lamp Companies Federation), provides standards and guides for LED lighting in Europe.

What standards are used to classify LED fittings for harsh, underwater, and outdoor conditions?

IP (Ingress Protection) ratings or UL (Universal Laboratories) ratings are commonly used to determine LED product suitability for various harsh, underwater, or outdoor applications.

How do I know a light fitting is safe?

In Europe, every light fitting must have a CE label, which defines the seller’s claim that the fitting conforms to all relevant European safety standards. The most important of these is EN 60598, which covers electrical, thermal, and mechanical safety.

What is PAS?

PAS is the Publicly Available Standard, an informal rating used in Europe. While it is not a formal EN standard, it is an industry-agreed way of presenting data and procedures.

Why do LEDs require power supply/drivers?

LEDs are low-voltage devices. Therefore, the LEDs require a device/power supply unit/driver or integrated electronics that convert line voltage to low voltage in order to run them. Sometimes, the driver has electronics that can interpret control signals to dim LEDs.

What are there different types of LED power supplies/drivers?

LEDs are driven by constant current (350mA, 700mA, or 1A) drivers or constant voltage (10V, 12V, or 24V) drivers. Constant current drivers fix the current of the system and vary the voltage depending on the load of the LED. Constant voltage drivers require a fixed voltage, and the LED loads are added in parallel across the output of the driver until maximum output currents are reached.

Typically, what sort of applications are constant current drivers used for?

Constant current drivers are typically used in downlights where one or a series of luminaires is used per driver. These are connected in series.

Typically, in what sort of applications are constant voltage drivers used for?

Constant voltage drivers are used in applications where the load is not known and the LED loads are connected in parallel, for example in coves and signage applications. These drivers are sometimes similar to the low voltage electronic and magnetic transformers used in halogen light fixtures (MR16 lamps). The type of LED driver suitable to run a LED product is stated by the LED manufacturer in the product specification.

How do I know what type of driver is required by LED product?

The LED rating of a product is usually noted in milliamps (mA) or volts (V). Products rated in mA can be used with a constant current driver, while those rated in Volts can be run with a constant voltage driver. LEDs designed for constant current drivers cannot run with constant voltage drivers without damaging them.

What is Vf?

Vf is the term used for the LEDs forward voltage. It is the voltage required to activate the LED and produce the output specified, assuming that it is drawing the recommended current.

What is the maximum permissible distance between an LED product and a remote driver?

The maximum permissible distance is dependent on the LED load, conductor size, and the driver used. There is little practical limit on the distance between the driver and LED if you are using a constant current driver because it increases the output voltage to overcome any Volt drop caused by the cable length. The distance between the LED and the driver is more important for constant voltage drivers where there is a voltage drop due to the load and length of cable.

What are the advantages of 24V LEDs over 12V LEDs?

LEDs driven by 24V drivers have longer permissible distances between light source and driver compared to 12V DC LEDs. 12V LEDs are usually suitable for applications where low light outputs are required. 24V LEDs offer products with higher outputs than 12V products.

Is it true that some LEDs can be directly connected to the mains voltage power?

LEDs are inherently low-voltage devices that require drivers. However, many LED products in the market come with built-in drivers and hence can be directly connected to the mains voltage.

What precautions are to be taken when mounting LED drivers?

LED drivers need to be mounted in a ventilated space. Access to the driver needs to be provided for general maintenance purposes. The IP (Ingress Protection) rating of the driver needs to be considered before finalizing the mounting location of the driver (only those drivers designed for outdoor environments can be located outdoors). The distance between the driver and the light source needs to be taken into consideration in order to prevent a voltage drop, which results in reduced output of the LEDs.

How LEDs are dimmed?

LEDs are dimmed either by Pulse Width Modulation PWM or Constant Current Reduction CCR. PWM dimming involves switching current at a high frequency from zero to the rated output current. As for CCR dimming, the lighting level required is proportional to the current flowing through the LED. Current flows through the LED continuously and is reduced or increased based on whether the LED is to be dimmed further or made brighter.

What are the relative advantages of PWM dimming?

The following are the advantages of PWM dimming:

Smooth dimming capability
More precise output levels
Better consistency in color over various levels

What are the disadvantages of PWM (Pulse Width Modulation) dimming?

The following are the disadvantages of PWM dimming:

Relatively higher cost.
The flicker perceived in peripheral vision in case the driver is run below 100Hz frequency.
The stroboscopic effect evident in fast-moving environments when the driver frequency is low.
The Electromagnetic Interference (EMI) issues owing to rise and fall of the current in PWM dimming.
Performance issues that arise when the driver is mounted remotely from the light source.

In which applications is CCR (Constant Current Reduction) dimming is most suited?

CCR dimming is good in:

Outdoor applications and damp locations.
Places that have strict EMI requirements like medical suites.
Places where there is a lot of motion and rotary machinery.
Applications where the drivers are to be placed at long distances from the light source.

Can mains voltage LED products be dimmed with traditional incandescent dimmers?

Although LED products are marked as compatible with traditional dimmers, there are various degrees to which LED products are compatible with incandescent dimmers. Compatibility needs to be checked and tested on a product-by-product basis for the following most common undesirable behaviors:

Reduced dimming range
Flickering of the lamp
Inconsistent performance based on the number and different types of LEDs connected to a single incandescent dimmer

What is the difference between analogue and digital dimming?

Analogue dimming is usually referred to as 1 - 10V dimming. In this case, a DC voltage is sent to the driver, which dims the LEDs in response to the voltage. With digital dimming, the driver receives a digital signal which tells it how to respond. The advantage of digital dimming is that fixtures are addressable. You can also have many more different levels of light output when using digital dimming.

What lighting protocol is appropriate for an application?

For applications where single colors and white LEDs are used, analogue or PWM dimming protocols can be used to switch or dim LEDs. For intelligent controls like creating dynamic effects, tuning of white light, and more, DMX or Ethernet protocols can be used. Digital dimming works better with large numbers of luminaires.

Why do some LEDs flicker when dimmed or turned off?

This is usually due to incompatibility between the driver and the control system. When purchasing an LED product, it is important to use the correct driver type as specified by the manufacturer. It is also important to check that the LED is dimmable. Some retrofits are not.

Why is the heat sink design critical for the performance of an LED fitting?

Heat management is critical for the performance of LEDs. Increasing heat in LEDs has the following effects on performance characters:

Reduction in luminous flux.
Color shift (change in color appearance).
Reduction of LED life.

What is the two-phase heat exchange technique of cooling LEDs?

The two-phase heat exchange technique is a cooling technique that uses the advantages of both active and passive cooling methods.
It works on the principles of evaporation and condensation. The process requires disposable heat to initiate the process that happens in a hermetically sealed tube that is filled with a minute quantity of liquid. The system has cooling fins around the tube to dissipate heat. This system offers high reliability and zero operation costs. Plus, it is not orientation dependent.

What is junction temperature?

Junction temperature is the LED’s active region; the point at which the diode connects to the base. This is where the electrons jump between the two semiconductors to produce photons. A low junction temperature helps LEDs to produce more light, while also reducing lumen depreciation. Junction temperature is affected by the driver current, the thermal path, and the ambient temperature.

What are the different types of optical systems for LEDs?

The following are the types of optical systems for LEDs:

Primary systems with integrated lenses - specific beam angles.
Secondary optical systems in the form of lenses, reflectors, or diffusers.
Combinations of primary and secondary optics for specific applications.

Why are lenses preferred over reflectors for many LED luminaires?

LEDs are directional sources of light as opposed to traditional luminaires, which are omni-directional. When LEDs are fitted with reflectors, much of the light at the center of the beam passes out of the system without even touching the reflector. This reduces the scope of modulation of the light beam and can be the cause of glare. Lenses, however, help guide virtually every ray of light emitted by the LED.

What are the different ways in which luminaire design can help reduce glare from LEDs?

Here are the few ways in which glare can be reduced from LEDs:

Use of microprismatic technology to develop special diffusers that disperse light from individual LEDs. This system gives out homogeneous light with optimum levels of contrast avoiding any direct or reflected glare.
Design of secondary reflectors systems; where the primary reflector, which will hide the view of the LED and direct the light into the secondary reflector that will distribute the light in the intended way.
Use of a combination of TIR (Total Internal Reflection) lenses/collimator lens, which produce a parallel beam of light, and a facetted lens. This combination will distribute the light beam as intended.

What are common challenges or problems when using LED fixtures in harsh environments?

The LED drivers can fail early due to ingress of moisture or condensation. The driver enclosure needs to be properly sealed to prevent this.
LEDs are less resistant to damp than other light sources. This means that particular attention needs to be given to the light fixture seal and cable glands.

What are the various causes of condensation within LED luminaires?

Heat build-up occurs as the luminaire is turned on, and it cools down when it is switched off.
Pressure changes caused by a change in altitude and environmental conditions during transportation in cargo holds or planes.
Thermal shock due to rain, snow, or washing cycles.

What are the product features to look for in LEDs used in harsh environments?

More rugged O-rings and gaskets for more robust seals.
Thicker enclosures to prevent movement around seals to prevent breakage of seals.
Additional bolting around gaskets and seals to prevent snapping of seals.
A vent made of two-way permeable membrane. This allows water vapor and gas (except for liquid water) to pass through.

Is it true that LEDs do not produce heat?

No. It is true that there is no heat, IR, in the beam. However, the LED fixture itself, does produce heat. However it may become warm or hot, to the touch.

The LED luminaire is hot to touch. Why is this?

The LED chip or light engine produces heat. This needs to be dissipated as quickly as possible. This is normally done with a heat sink, which often has fins. Cool LEDs are more efficient than hot ones. They also have a longer life. Of course, higher power LEDs generally run hotter than low power ones because of the extra heat to remove.

What does a life of 50,000 hours mean in the case of LEDs?

50,000 hours would imply 5.7 years if the light is operated for 24 hours a day, 7.6 years if the lights are on 18 hours per day, and 11.4 years if the light functions for 12 hours a day.

Why is the life of LEDs is measured as lumen depreciation?

Unlike conventional light sources that reduce in output and eventually fail, LED products do not normally suddenly fail. Instead, the light output reduces over time.
The normal convention is to measure the life from when the output has reduced by 30%, i.e. when there is 70% light output remaining. This is often quoted as the L70 life and is measured in hours.

What are the factors that affect the lifespan of the LEDs?

The thermal management of LEDs. If LEDs come on a standalone chip, appropriate heat sinks have to be designed to prevent premature failure of LEDs.
The electrical stress: Running LEDs at currents higher than specified make the LED run hot. This can happen with wrongly matched drivers. For example, if the driver produces 700mA, but the LED needs 350mA, this will put stress on the LED and reduce its lifespan.
Higher ambient temperatures than the ones that the LED is rated for will reduce its expected life.

Is lifespan reduced if the LEDs are frequently turned on and off?

Unlike discharge lamps, LEDs are semiconductors and their lifespan is not affected by the number of times they are turned on and off.

How much longer does an LED last than a conventional light source?

Typically, an LED will last four times longer than a CFL and 25 times longer than an incandescent source that puts out the same amount of light.

What is the best way to compare the output of LEDs with other light sources?

Sometimes simply comparing the lumen output of LEDs and conventional light sources may not be adequate. The amount of light falling on a specific task area (the lux) gives a more realistic comparison. You should also consider the amount of illumination visible on walls. This helps identify applications where LEDs offer better solutions than other light sources.

Does increasing the wattage of LEDs increase their output?

This may occur if you are using the same product from the same brand, with the same optics and hardware. However, in general, the nature of the components (like the optical system, heat sink, LED chip, and the driver) affects the output more than the wattage does. A 3Watt LED luminaire from one manufacturer will have a different output compared to a 3Watt LED luminaire from another manufacturer, even if the same LED chip is used. Hence, using a high-quality chip alone does not guarantee better performance. Note that as the wattage increases, the efficiency drops slightly. An LED driven at 3W will emit slightly less than three times the output of the one driven at 1W.

Why are LEDs considered more efficient than conventional light sources?

When comparing the lumen output between LEDs and conventional light sources, LEDs may have lower lumen value in many cases. However LEDs are directional light sources, all the lumens emitted from an LED are directed towards the task area. Conversely, conventional sources emit light in all directions. The light is then modulated in a given direction with optical systems like reflectors and lenses. The amount of lumens that falls in the intended task area from an LED light source is greater than that of a conventional light source.

What is the difference between absolute photometry and relative photometry?

Absolute photometry measures very precisely the lumens emitted by a specific luminaire, while relative photometry can be adjusted to measure light distribution by various lamps with different lumen outputs. Most LEDs are permanently fixed in the luminaire along with its optics. Replacement in case of premature failure means replacing the whole luminaire and not just the light source. The lumen performance of LEDs is best evaluated by considering the various accessories the light passes through (lenses, reflectors, etc.) before it falls on the surface to be lit. As a result, absolute photometry is the method usually used to measure LED performance. Note that some luminaires have replaceable LED modules, but the same arguments apply.

Why is it necessary to use absolute photometry for LEDs?

The lumen output of an LED is dependent on the thermal management/heat sink design, electrical characteristics such as the junction and rated ambient temperature, driver currents, and the optical system. This means that the light output is very much dependent on the design of the actual luminaire. This is unlike other light sources like HID where the photometrics of a luminaire are fairly independent of the lamp used.

What are “cold” and “hot” lumens?

These terms do not have any photometric or engineering meaning. However, "cold lumens" is the light output of the LED chip alone when it is first switched on. "Hot lumens", refers to the light output of the LED when it is fully warmed up in the luminaire. The hot lumen value may be 30% - 50% lower than the cold lumen value.

Why are LEDs considered green technology?

LEDs are more efficient than most other light sources, so they usually consume less energy for a given task or at a specific light output. Also, they do not contain hazardous materials such as toxic mercury. Moreover, LEDs have a longer lifespan and hence reduce the frequency of disposal of lamps.

How can LED lighting help reduce CO2 emission?

LEDs normally use less power for a given application compared to traditional halogen and fluorescent sources. As such, the overall kW/hr consumption per year is less, which helps reduce the overall CO2 emissions.

How are LEDs disposed/recycled?

LEDs are primarily made of electronic components like PCBs, diodes, semiconductors, etc. Therefore, they must be treated in the same way the traditional electronics are. They are collected separately from household wastes and must be treated the same as standard electronic equipment.

Are all retrofits powered by main voltage?

Most retrofits have the appearance of a conventional lamp and are used as a direct replacement for the existing one, i.e. they have a screw or bayonet cap base. With downlights and spotlights, it's common to have a 50mm dia reflector lamp. The mains voltage ones are usually called GU10, which refers to the flattened pins on the base. However, some are available for 12V supply fed from a transformer, e.g. direct replacements for 50mm dichroic LV downlights. These will have thinner pins and are often called MR16 or GU5.3 lamps.

Will the light output be the same?

As with complete LED luminaires, it is important to ask the supplier for the lumen output and to compare this with the unit you are replacing. If it is a spotlight, compare the two lamps side by side. Poor quality sales literature often states the output from the LED chip and not the complete lamp.

Some retrofits appear a bit cool, why is this?

Retrofit lamps are offered with various white light outputs, ranging from warm to cool. This is often indicated on the packaging. Typically, it might say “2700K Warm White” or “4000K Cool White.” The bigger the number, the cooler is the appearance.

Can I put a retrofit in an enclosed or sealed luminaire?

The general answer is no. The electronics in the retrofit will overheat and lead to a short lifecycle. A better solution is to use an LED module with a remote driver.

Can linear LEDs be used as a substitute for T8 or T5 fluorescent lamps?

Most LED tubes, although they have the same size, lamp base as a linear fluorescent, and possibly a similar lumen output, do not have the same omni-directional light distribution. Many luminaires emit 20%-30% less light output with narrower beam spreads when fitted with LEDs. This is especially true of troffers with reflectors that offer batwing (widespread) light distribution with fluorescents. This needs to be taken into account when considering the overall 30-50% less power usage by LEDs with increased system efficiencies. It is likely that the luminaire will need some rewiring and this should be done in conformance with the local electrical installation standards.

How is light produced in an LED?

Light emitting diodes produce light by the movement of electrons between the two terminals of diode, which occur by a process called electroluminescence. When a light emitting diode is electrically connected, electrons start moving at the junction of N-type and P-type semiconductors within the diode. When there is a jump over electrons at the p-n junction, the electron loses a portion of its energy. In regular diodes this energy loss is in the form of heat. However, in LEDs the specific type of N and P conductors produce photons (light) instead of heat. The amount of energy lost defines the color of light produced.

Core components of LED soldered to a printed circuit board

A typical LED is made with a chip, which is the semiconductor that produces the light when electrically connected. The chip is connected by a very thin bond wire to provide electrical contact that acts as the cathode. The chip is bonded with a thermal heat sink and a ceramic base. The chip is enclosed by a lens that not only protects the chip, but also modulates the light beam to the desired angle, depending on the nature of the lens. For production of white light, the chips are coated with phosphor.

How are LEDs different from other light sources in the way they produce light?

LEDs produce light by direct conversion of electrical energy to light energy. On the other hand, incandescent light sources produce light by heating a filament until it grows red hot. Linear and compact fluorescent lamps use a UV discharge plus a phosphor to produce the light. HID lamps use the ionization of gases in a discharge tube which produce photons.

What are O-LEDs?

O-LEDs are organic light emitting diodes. They are made of carbon based films sandwiched between two electrodes; one is a metallic cathode and one is a transparent anode, which is usually transparent glass.

What are the characteristics of O-LEDs that make it different from other light sources?

O-LEDs are two thin, flat dimensional surfaces, offering a soft, glare-free luminous surface. Some versions of O-LEDs are flexible. They can be transparent, mirrored, or diffused when not electrically connected.

How is white light produced by LEDs?

LEDs do not directly produce white light. There are two ways in which white light is produced by LEDs as below:

Using a blue LED with a phosphor coating to convert blue light to white light by a process called fluorescence.
Combining red, blue, and green LEDs to produce white light. White light is produced by varying the intensities of the individual red, blue, and green chips.

What are tuneable white LEDs?

Tunable white LEDs are light engines that combine individual chips to produce a range of CCT from warm white and cool white.

How is colored the light produced by LEDs?

The light color is dependent on the inorganic material used in the P-type and N-type semiconductors (organic material in the case of O-LED). Different inorganic materials in the semiconductor release different amounts of energy when the LED is connected to a power supply. The amount of energy released defines the color of the light produced. For example, red is low-energy light and blue is high-energy light.

Why do LEDs produce more vibrant and saturated colors than conventional lamps?

LEDs emit a very narrow spectrum of light. The type of material used in the semiconductor permits only a specific wavelength of light (one color) to be emitted when electrons cross the junction.

What does the RGB LED mean?

The RGB LED means red, blue, and green LEDs. RGB LED products combine these three colors to produce over 16 million hues of light. Note that not all colors are possible. Some colors are “outside” the triangle formed by the RGB LEDs. Also, pigment colors such as brown or pink are difficult or impossible to achieve.

What are the different types of RGB LEDs?

The following are the different types of RGB LEDs:

R/G/B/W - Has an additional white LED. It is often used where you need a pure white as well other combined colors.
RGB/3 in 1 LED - Uses a red, blue, and a green LED chip mounted within a common light engine and focused through a lens to produce a more uniform hue across the beam of light.
RGBW/4 in 1 LED - similar to the RGB LED, but with a warm white LED integrated in the light engine to offer more color tones.
RGBA - Has an additional amber LED chip.

How is Amber light produced?

This is a phosphor - converted Amber LED. Amber uses special phosphors in combination with royal blue LED chips.

What are AlGaAs, AlInGap and InGaN?

These are chemical symbols used for materials used in the manufacturing process of LEDs to generate specific colors.

AlGaAs - Aluminium Gallium Arsenide used to generate red and amber portions of the visible spectrum.
AlInGap - preferred chip technology using Aluminium, Indium, Gallium, and phosphorous to produce red, orange, and amber colors.
InGaN - Indium, Gallium, and Nitrogen used to produce green, blue, and white colors.

What does correlated colour temperature, CCT, mean?

Color temperature defines the color appearance of a white LED. CCT is defined in degrees Kelvin; a warm light is around 2700K, moving to neutral white at around 4000K, and to cool white, at 5000K or more. Note that CCT does not tell you anything about the color rendering ability of the LED.

What defines the color temperature of a white LED?

The thickness of the phosphor layer and the wavelength of the blue chip influence the color temperature of the LED.

What are the standard comparisons used to evaluate the color quality of light sources?

Color Rendering Index - CRI indicates the accuracy with which a light source such as an LED can reveal the various colors of an object. The standard CRI system is based on eight colors across the spectrum.
Additional R-values of CRI are used to represent certain colors. The appropriate R-values are application specific. For example, R9 represents red and is good for lighting flesh. It also tends to make the light warmer.
Color Quality Scale CQS is a new system that uses a wider palette of 15 reference colors against the smaller palette of 8 reference colors used for the CRI system.

In what contexts do R-9 values of CRI of LED lamps become important?

The CR-9 represents red tones, which are prevalent in skin tones, clothes, vegetable, and meat. For make-up rooms, supermarket, and grocery meat and vegetable counters, if the same visual freshness as seen with halogens and incandescent lights sources is required, looking into R-9 values of LEDs is a must. Usually, gallery owners and artists will easily note the difference in effect when red tones are prevalent in the art work.

What is the SPD of a light source?

SPD is the Spectral Power Distribution of a light source. The visible white light that we see is made up of a spectrum of various colors of light, ranging from wavelengths of 380nm (violet) to 760nm (red). The SPD is a graph that shows the power (strength) of each wavelength of light produced by a particular light source.

What is a MacAdam Ellipse?

This is an elliptical region on the CIE chromaticity diagram that contains all the colors that are indistinguishable to the average human eye, from the color at the center of the ellipse. Adjacent ellipses are “just distinguishable” in terms of color. This system is used to refine the binning process of LED colors. Slight color differences in the appearance of LED light are measured in MacAdam ellipses or steps.

What quality process guarantees the consistency of the color appearance of LEDs?

LEDs are standardized for consistency in color and performance through a process called binning, and they are classified further in the MacAdam steps. During the manufacturing process LEDs are allocated to specific 'bin' numbers based on tests conducted to determine their color, lumen output, and forward voltage. LEDs from each bin are further classified in a 7-step MacAdam ellipse.

What other parameters can be used to evaluate the color quality of light?

Apart from CRI, R-values, and CQS, color consistency is also a measure of the quality of light. The color consistency can be evaluated at several levels as follows:

Consistency over time: Color shifts over the lifetime of LEDs.
Consistency between different products and batches: Color tone variations from batch to batch.
Consistency across the beam of light: Color shift across the beam of the LEDs.
Consistency between color specification in the datasheet and the one seen when the LED is used.

Why do some white LEDs start emitting an almost bluish tone over time?

The white LEDs are made of a phosphor coated blue LED chip. The degradation of the phosphor layer over time causes the bluish tone of the light emitted. This degradation is most likely to be caused by the chip running too hot. Remote phosphor technology overcomes this issue.

Why does the color appearance of the LEDs change after some period of use?

There are several possible reasons why this happens:

The LEDs are being overrun by the use of an inappropriate driver.
The application temperature is different from the operating temperature noted in the LED datasheet.
A heat build-up may occur due to improper thermal management.
The phosphor may have degraded due to overheating or other reasons.

What are the advantages of remote phosphor process as compared to the phosphor coated LEDs?

The remote phosphor process offers:

Longer lifespan, as it reduces temperatures and slows down the rate at which the phosphor layer degenerates.
Increased system efficiency with reduced operating temperature of the system.
Better color stability with longer life of phosphors.
Less glaring than phosphor coated LEDs.
More consistent flux output and correlated color temperature for the products, since LEDs from various bins can be used to produce light with consistent characteristics using the remote phosphor process.

What terms describe the different forms of LEDs from basic electronics to fully functional light fixtures that are available on the market?

Here are the various terminologies for developmental stages of LED in chronological order:

LED Die - A small block of light-emitting semi-conducting material on which functional LED circuitry is fabricated.
LED Package - This includes an LED die or more than one LED die with an optical element and mechanical, thermal and electrical interface.
LED Module - This includes an LED package or an LED die, possibly with an optical element connected to a circuit board, and with thermal, mechanical, and electrical interface that are intended to be connected to the load side of the driver.
LED Engine - This is an LED module or array of packages with the associated control gear/LED driver. It is the nearest equivalent to the lamp in a conventional luminaire.

What does SMD mean?

SMD means surface mounted diode. This is a better technology than the first generation DIP LEDs. The SMD type LEDs are mounted on an aluminum substrate and enveloped in an epoxy resin.

What are the advantages of SMD over DIP LEDs?

The advantages of SMD over DIP LEDs are:

Smaller size
More lumen output
Better heat dissipation
Lower lumen depreciation
Longer life

What are the various types of LED chip packages available on the market?

The basic types of chip LEDs are:

SMD (Surface Mounted Diode) is a standalone chip on a ceramic base that can be integrated into various packages for linear LED strips or downlights.
COB (Chip On Board) LED, which comes as a high-powered chip in direct contact with a printed circuit board optimal thermal management.
MCOB (Multiple Chips On Board) LEDs, which are multiple COB LEDs integrated to form a single chip. This technology is used in LED bulbs and tubes.
MCCOB (Multiple Chips and Cups on Board) packages, which are used for high-bay fixtures and floodlights.

What are the typical types of LED modules available on the market?

LED modules may be available in the following forms:

Prefabricated chip on the board, which can be used for specific applications by luminaire manufacturers who design the heat sink and mounting conditions.
Chip on the board with an optical lens or diffuser as a prefabricated piece with or without integrated heatsink. That can be used by luminaire manufacturers to integrate into luminaire.
Retrofit lamps to replace older (halogen) technology. This comes with an integrated heat sink and standard lamp base that can be fitted directly into existing luminaires with a standard lamp holder.
Prefabricated luminaires with an integrated LED light source and heat sink complete with luminaire housing that is available as a sealed piece. The driver may be integral with the housing or may be remote.

What is ZigBee?

Zigbee is a technology developed by a global alliance of companies to create wireless solutions for energy management. These solutions include a new open standard for LED lighting controls.

FAQ

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How do LEDs produce light?

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