Category Archives: Citizen

Environmentally Friendly LED Lighting Components

Generally, we can say that LEDs are environmentally friendly and recyclable. They have a long lifetime and low power consumption. They don’t contain hazardous substances, for example, mercury as compact fluorescent lamps do. In this blog post, I will present to you four environmentally friendly luminaire component choices.

LED That Don’t Need a Driver

Have you ever looked inside the driver? In the picture above, you can see the inside of the small-sized one. Drivers are made of many different materials and components. That’s why they are hard to recycle. The fewer components product has, the easier it is to recycle. For example, an aluminium heatsink is easy to recycle, because it contains mainly aluminium.

Drivers are the most fragile parts of the luminaire. In general, they can be the first component that breaks from the luminaire.

All traditional LEDs needs a driver to work. Except for AC COB that can be connected straight to the mains power. Because AC COB doesn’t need a driver, luminaire can be a lot smaller than before. This gives more flexibility for the design. At the same time, you can save in logistics and packing. You can read more about AC COB from our blog post.

Same Lumen Output with a Smaller Luminaire

Size is an important feature when designing environmentally friendly luminaires. When you use less material the luminaire gets smaller. And by downsizing the luminaire you can save in logistics and packing.

One great way to make the luminaire smaller is Citizen’s HC COB. It has higher efficacy and lower terminal resistance. This means that you can use a smaller heatsink. Therefor luminaire gets smaller the and you can still get the same lumen output. As a result, it makes HC COB more environmental choice. Read more about HC COB from here.

The Right Amount of Light and Less Light Pollution with Right Optics

When we talk about LEDs, often we come up with light pollution. We can say that almost all outdoor light that doesn’t have a purpose is light pollution. This means that light always needs a target.

When you replace the old light sources (for example HPS-lamps) with same powered LED, you get a lot more light. This is not environmentally friendly. You get a lot of unnecessary light and same time create light pollution.

When we design luminaires with the same lumen output than before, LED saves energy. This is because LED has less than 10% of the incandescent lamp’s power consumption. That’s why it is important to think about lumens, not power when replacing lamps with LEDs.

LEDs light comes from a very small area and from a flat surface, so it is easier to control than a light bulb. In street lights, most of the light pollution comes from light that goes up and away from the road. It is important to choose optics for the luminaire which are designed to minimize the light pollution.

Control the Luminaires with Sensors

There’s a lot of different sensors for different applications. The most familiar ones are the on/off-sensors. They automatically switch the light >on and off  by movement. They save energy, as the light can never be accidentally left on. This type of sensors is already generally used in public spaces.

Another great way to save energy is to use daylight sensors. They react to the light that comes from the outside. This way you can maximize the benefits of the sunlight. For example, during the day, you don’t need as much artificial light as in the evening. Read more about sensors from this blog post.

We have already made big steps in ecology, but still, we have a lot to do. We need to think about the packing of the luminaire and logistics. It’s important to minimize the amount of plastic used in packing. Also, we need to think alternatives for air freight. Small choices really matter.

Below you can download a presentation about Citizen’s AC COB. If you have anything to ask, you can always email to me:

Download Here

Downsize your luminaire with new HC-series

New series of LED, Citizen High Current COB LED is now available. What is High Current COB LED or in other words HC-COB? What new possibilities does it give to us? I’m going to tell you all that in this blog post.

HC-COB is COB that has same LES and package sizes as the previous Citizen generations. Compared to previous generations the HC-COB has higher efficacy and Tc and wider wattage and lumen range.

With new Citizen HC-COB, you can achieve lots of great advantages compared to previous LED-generations. You can downsize luminaire or get more lumens with the same size of the luminaire. So, there’s a possibility to use it in different ways. Let’s get into that.

Downsize your luminaire

Luminaire downsizing has become a trend in the luminaire industry. Nowadays luminaire size must be as small as possible to design luminaires that are cost-effective with less visibility. In public spaces, track lights are in general use. When you downsize those luminaires, you get space that is more spacious and airy.

HC-LED has higher efficacy and maximum Tc. So, you don’t need so large cooling system with it. This means that you can use a smaller heatsink to downsize the luminaire. Same time you can reach same lumens as today.

Luminaire downsizing means that you can make big savings, for example in aluminum, logistics and packing. As a result, it makes HC-COB more environmental choice.

At the same time when luminaire gets smaller, you can reduce system cost of luminaire. Smaller heatsink is cheaper than the bigger one. And as I said before, we can make big saving in packing materials and logistics when luminaire gets smaller. See the diagram below about how you can save in luminaire system cost.

As a result, you can make lighter and cost-effective luminaires that are more environmentally friendly.

Here’s an example of luminaire downsizing. In this example, we are changing COB version 6 to HC-series. The result is that you can get even more lumens with less LEDs.

Get more lumens from your luminaire

What if you don’t want to downsize your luminaire? Do you want more lumens with the same luminaire? With HC-COB that is possible too.

When you keep the same heatsink or luminaire design and just change the LED to HC-COB, you can get more lumens. This gives you more lumen package options and flexibility in one luminaire design.

Let’s see an example if COB version 6 is replaced by HC-series.

As shown above, you can get even 17,8 % more lumens with HC-COB.

What kind of lumen packages does HC-COB offer?

  • 2700K, 3000K, 3500K, 4000K, 5000K and 6500K
  • Ra70, 80, 90, 97 and Below BBL
  • Lumen range from 500lm up to 77 000lm
  • Same size than previous COB generations

Are you interested in more technical information? Download datasheet below or contact to our specialist. We’ll be ready to help you.

Download Here

Tunable White – Achieve color temperature from 2700K to 6500K with one LED module

Tunable White color changing

The Tunable White is becoming a big trend in residential and office lighting. I introduced one color changing LED product, Dim-to-Warm LED, in the earlier post.  In this post, I will tell you about the Tunable White module. Its color temperature can be changed freely from 2700K to 6500K. This means that you can achieve warm light like incandescent lamp and daylight with only one module. In addition to changing the color temperature, you can also dim the brightness.

Why color changing and Tunable White is a trend? How does it impact humans?  Let me shed light on that.

As we know human mind reacts to brightness and temperature of light. Cool light (e.g., daylight) has a refreshing effect and helps us work at school, office, where ever effective work is needed. Where cool light refreshes, the warm light has a comforting and relaxing effect. Naturally, these lights are presented in daytime during sunrises and sunsets.


Tunable white color chart


How to use Tunable White?

With Tunable White module, you can create better environments for both working and living. You can maximize productivity and improve concentration. Here are just some examples of the usage, but really there are countless ways to use Tunable White. 

One great use for Tunable White is offices. You need a lot of concentration to work effectively. This can be achieved with decent lighting. With this module, as said before, you can control the cool and warm light and dim the brightness. This gives the opportunity to select the right color temperature for office during the daytime.

In residential usage, Tunable White gives a possibility to simulate circadian rhythm. Connect the Tunable White to a control unit, it can change the color temperature automatically by daytime. This way you can enjoy cold refreshing light by midday and get the comforting feeling of warm light by evening.

Now we know some examples, but what kind of luminaires Tunable White is suitable for? Tunable White module is very small sized. This gives options to use it in the wider range of luminaire types.

Here are some examples:

  • Downlight
  • Spotlight
  • Indirect lighting
  • Table light
  • Decorative light

How does it work?

Citizen Tunable White module is made by using “multi-chip” technology. That means it’s made of tiny LED chips that are combined into the same module. Because of its very small size (LCN-C01A is only 15×15 mm), smaller luminaires can be made than before. The small size also gives more even light. The spots between cool and warm dies are almost invisible, which guarantee more smoothly light.

It is made from cool (6500K) and warm (2700K) diodes. The color temperature changes by controlling the output of the two different colored LEDs. LED’s brightness depends on the current; reducing the current the brightness reduces. These features give the option to dim and change the color temperature of LED.

Color curve of Tunable White module.

The Tunable White module has linear color curve because it has two primaries (6500K and 2700K). Advantages of two primaries are greater efficacy and simplicity. As seen in the diagram above, the linear color curve is located under the Black Body Locus (B.B.L.). That affects the color of the light and brings some colors up. You can get white light without greenish tint. This improves contrast in other colors.

A suitable driver needs to have two channel outputs to control CCT and intensity of the light. So, you need 1-10V, DALI or another two-channel driver to control the Tunable White luminaire.

Our high-quality Moons S Series Intelligent Drivers have great compatibility with the Tunable White module. They also have deep dimming from 100 % even to 0,1 %. You can program correct tuning and dimming curves for your luminaire. With Moon’s drivers, you can get everything out of this LED module.

If you have anything to ask, please don’t hesitate to contact us. For more information please download the presentation and the datasheets link down below.

Download Here

Dim-to-Warm – COB LED that dims like halogen


Dim-to-Warm is COB LED which works like halogen lamp when dimmed. Its specialty is that when you dim it the color temperature gets warmer. Usually dimming does not affect the color temperature of the LED. Dim-to-Warm LED imitates the effect of the halogen lamp which gets warmer by dimming. With full power you can get color temperature 3100K and at lowest 1850K.

Dim-to-Warm LED suits especially highly for decorative luminaries, for example used in restaurants, hotels, cruise cabins and home interiors. It’s perfect for space where you want to have dimmed and warm toned atmospheric lighting.

LED has great advantage compared to an incandescent lamp. Its power consumption is less than 10% of the incandescent lamp’s power consumption.

The color temperature of candlelight, incandescent and halogen lamp.

The color temperature of candlelight, incandescent and halogen lamp.


There are seven different packages from 900 to 3000 lumens. You can download more information about the product here.

Where and how to use?

Dim-to-Warm LED is great for places where you want the light that dims like halogen or incandescent lamp. You can use it for example for restaurants, hotels, cruise cabins and decorative luminaires where you have been using halogens before.

It’s easy to use. You can use Dim-to-Warm LED for all the luminaires where you have been using COB LED or you can use it to replace led modules. All optics, lenses and reflectors that are compatible with COB LED, suit also for Dim-to-Warm LED. LES area is CLC20-series for 9,8 mm and at CLC30-series for 15,2 mm.

How Dim-to-Warm works?

As we know, usually LEDs don’t change the color when you dim them. They always retain approximately the same color temperature when the brightness is reduced. LED’s brightness depends on the current; reducing the current the brightness reduces.

Dim-to-Warm LED is made from cold and warm LED areas. It has an internal control circuit which dims the cooler area first and later starts to control current of the warm one.  The color temperature gets warmer when dimmed.  This way the dimming works similarly in incandescent or halogen lamp.

The diagram below shows how the color temperature gets warmer when led is dimmed down and the current and brightness reduces (black color). You can also compare it to halogen lamp (grey color).


Dim-to-Warm is a COB LED, so you don’t need any complicated special features from the driver, like two-channeling or programming features. Ordinary triac dimmable driver is enough. We have tested ELT’s DLC-drivers with it, and they have good compatibility.

Click the button below to download the datasheets and material. You can find more information and our product codes from the presentation. If you have any questions about Dim-to-Warm, please don’t hesitate to contact us.

Download Here

Thank You for Everyone at Elfack 2017

I would like to thank everyone who we met at the Elfack Exhibition in Gothenburg, Sweden.

We had some good conversations with our existing customers as well as new people. This year we tested the color quality of Citizen’s LEDs at our stand. We got many answers through our questionnaire and found out that many visitors were excited about this new way of lighting.

If you took part in the test, you will receive the test results soon. We will also share these results with the public a little later.

We had a chance to show you our new products and the feedback we got from you was very encouraging.  I went through all the products in my last blog post, and if you wish to download more information about them, you are most welcome to do so here.

The products displayed at Elfack include:

  • aLED Engine
  • Citizen Gen 6
  • AC COB
  • Citizen Vivid Series
  • Furukawa Heatpipe
  • Merrytek sensors
  • Letaron & aLED Drivers

Our personnel will contact you as agreed, if they haven’t already. In case you have anything to ask, you can contact us directly.


What We Are Presenting in Elfack?

Elfack exhibition will be held in Gothenburg, Sweden from 9th to 12th of May. As it has been with previous exhibitions, we will be releasing new products and presenting the latest technology at our stand.

This year we will introduce and present the following products at our stand F04:70.

aLED Engine

aLED Engine

aLED Light Engine

We designed aLED Engine for applications that require a lot of light. aLED Engine consists of Furukawa heat pipe and Citizen COB LED.

In addition you can also choose a suitable optics and LED driver for the light engine from our selection. Suitable drivers are available as on/off, 1-10V dimming and DALI dimming.

aLED Engine is also compatible with Merrytek sensors, which allow you to control the lighting as you wish.

The 300W engine produces 36.000 lm at 4.000K and weighs only 3,6 kg with a driver installed.

aLED Engine will be at our stand in Elfack. There you can see the engine in action and try it with a daylight sensor.

Download More Information

Furukawa HYC Series

Furukawa HYC Series uses heat pipe technology to transfer the heat and makes heat sinks more efficient in cooling the LED.

how heat pipe works

How Heat Pipe Works

Heat Pipe’s thermal conductivity is almost 200 times better compared to copper. This allows the heat sink to be a lot smaller than we are used to.

Smaller heat sink reduces the weight of the luminaire dramatically.

The heat pipes effectively transfer heat from the heat source throughout the whole heat sink cooling the heat source faster than ever.

Heat Pipe vs. No Heat Pipe

Heat Pipe vs. No Heat Pipe

Furukawa heat pipes are compatible with Citizen COBs.

Furukawa heat pipes will be at our stand so you can see and try how light they are.

Read more about Furukawa heatpipe from here.

aLED & Letaron Drivers

aLED Driver

aLED Driver

aLED and Letaron offer a versatile range of both constant current and constant voltage drivers from low to high power (from 1 W up to 600 W).

Ouw own aLED drivers are best suited for high power applications. They are all available in IP68 and can be ordered as on/off, 1-10V dimming or DALI dimming.

Letaron drivers are best suited for low power applications, although they are available up to 52W.

Letaron offers a variety of designs to suit your needs including round, rectangular and slim models.

The Letaron low power drivers are also compatible with OLED light sources.

aLED and Letaron drivers will be on at our stand so you can see and try them yourself.


Merrytek sensors

Merrytek offers a wide range of different sensors. Some sensors come with LED driver and some are independent and can be connected to LED driver.

Merreytek has products particularly designed for eg. homes, schools, stairways, warehouses, offices, parking garages and outdoor use.

Merrytek’s intelligent lighting control products include:

  • Microwave motion and daylight sensors
  • Dimmable LED drivers
  • LED drivers with intergrated sensors

There will be Merrytek products on display at our stand. We will have an aLED engine wiht Merrytek’s daylight sensor on our stand, so you can see how it functions.

Citizen Gen 6, AC COB &Vivid Series

Citizen released Gen 6 COB and AC COB earlier this year with improvements compared to the previous versions.

Thermal Resistance

Thanks to better heat resistance, you can use much smaller heat sink. Gen 4 on the left, Gen 5 on the middle and Gen 6 on the right.

For the new Vivid series we’ve prepared a demo wall at Elfack for you to examine the possibilities of color quality control in LED lighting.

Seminar about color quality

We will organize a seminar about color quality on the first day of the exhibition.

Color comparison Vivid COBColor Comparison Regular COB 3000K Ra80 vs. Vivid Brilliant

The seminar will take place on Tuesday 9th of May.
Time: 16:00-19:00
Place: Hotel Gothia Towers, Tower 1, meeting room R22-23

The program:

  • Doors open at 16:00
  • Coffee
  • Welcome / Arrant Light Oy by Janne Mäkinen, Managing Director / Arrant-Light Oy
  • Color Quality with CITIZEN by Kosuke Tsuchiya, Field Application Engineer / Citizen Electronics Co.
  • Demonstration and open discussion
  • Refreshments and snacks
  • Close at 19:00

Please sign up for the seminar as soon as possible or latest by April 30th. We have limited seats and there is room for the first 20 persons only.

Sign Up for Our Seminar

Welcome to visit our stand F04.70 at Elfack.

All datasheets and other material will be available from our website soon. If you wish to download material about these new products before the exhibition. You can do that here.

Citizen COB lineup

Citizen COB LEDs generation 6 – What is new?

Citizen have released generation 6 from their successful series of Citizen COB LEDs. In this post I’ll go briefly through, what is new and what advantages these COBs have compared to previous generations.

There are five main points at generation 6 from Citizen:

1. Performance increase

Performance will up to 7% depending on CRI of LEDs. There will be also slight decrease on forward voltage, which increases lm/W efficacy on LEDs.

2. MacAdam 2-step option

MacAdam 2-step binning will be an option in new generation. Although we have had very tight 3-step binning already, there is now option to order also 2-step versions of COBs. So if you desire to have 2-step SDCM COBs in your products, we have now solution for that.

3.Thermal resistance decrease

Thermal resistance is further decreased from generation 5. Decrease from generation 5 is 5% and from generation 4 even 38,5%. This allows you to minimize your need for heat dissipation. Another option is that you can create new, bigger lumen categories with your existing products.

Thermal Resistance

On the left a heat sink needed for COB Gen 4 LED. On the middle heat sink needed for gen 5 LED. On the right, heat sink needed for COB gen 6 LED. The power of the LED is same in every case.

4. Increase of maximum Tc

Maximum Tc-temperature has been set to 120 degC. Allowable Tc-temperature will rise from 105 degC to 120 degC. This will help you to maximize light output from your design, so you can use smaller heat sinks to get more light.

5. Increase of maximum Tj

You will be allowed to have higher Tj-temperature than in previous generations, so maximum Tj-temperature will be now 150 degC. This will give you wider LED driving options especially with bigger COB packages.

Citizen COB LEDs continue to increase their performance and offer amazing coverage for lumen packages. Packages range from under 100 lumens up to 60 000 lumens from single light source. If you haven’t yet tried Citizen COB LEDs, now it is good time to learn why Citizen has been top player in the industry for so long time.

You can download the whole catalogue, datasheets and simulator tool for Generation 6 COBs from our website.

Download Catalogue, Gen 6 Datasheets and Simulator Now

Vivid LEDs: Special Color Rendering With Spectrum Tuning

When we talk about color rendering, traditionally that conversation has been filled with CRIs and Ra-indexes. These traditional ways of telling how well certain light source represents sunlight have been criticised because they may not tell the whole truth.

In recent years, LED manufacturers have been trying to answer this criticism by creating different products. Terms like “premium white”, “crispy white”, “pearl white” and “vivid white” have come to LED markets.

Despite the different terms, they are all meant for the same purpose: To represent certain colors and make the lighting look better. I will be using term “Vivid” as it is the term Citizen Electronics uses. And to be honest, it describes the purpose of these LEDs quite well.

Color rendering

Color rendering means simply how well a white light source can show, or render, the true colors of different physical objects compared to sunlight. You know the effect when you buy a jacket in the clothes shop and it looks completely different in sunlight.

Colors are divided into 15 indexes (R1-R15). A general color rendering index (CRI or Ra-index) is defined as an average of the sum of first eight indexes (R1..R8). However, these first 8 indexes are rather less saturated colors, while indexes R9-R12 represent highly saturated colors (red, yellow, green, blue).

CRI 100 = Sunlight

For example, in grocery stores, a shopkeeper may want to highlight red color of meat or colors of vegetables. This means that the general color rendering index doesn’t really tell anything about the rendering capabilites of the light. In this case, high rendering index of some of R9-R12 indexes is necessary. It doesn’t matter how high the CRI is, R9-R12 can be anything.

CRI 83 (look at R9)

CRI 83 (look at R9)

The above image shows the index values of R1-R15. The CRI is 83, but look at the R9 value. Not very good.

So basically, the LED itself can have the CRI of 97 and you still have no idea how does it render red or green for example.

Vivid via Spectrum tuning

Vivid LEDs are made using spectrum tuning. In short, this means that the phosphorus of the LED has been modified. How it is modified, depends on the LED and the intended application. Note that spectrum tuning can be made also by using RGB-LEDs.

For example, Vivid White LED’s spectrum has been tuned so that it represents white and bright colors as well as possible. The colors are more saturated than under typical normal LED light.

Test report on Vivid White aLED Module

Test report on Vivid White aLED Module. Click the image to open it in new tab for better view.

These LEDs work very well for example, in clothing stores, where you have a lot of different colors that need to look good.

Here are two good principals when choosing LED:

  1. Think about your application, what colors do you want to highlight?
  2. Don’t stare at the CRI (unless you get a full report), it might not tell everything


Traditional way of thinking color rendering solely through the CRI should be updated. More importantly, you should know what you want to highlight and ask for a LED suited for your application.

Download More Information About Vivid


How to use Citizen LED simulator

Datasheets are essential part when you compare how different light sources work in your solution. Usually it can be time taking and exhausting to glance at datasheet and find values you are looking for. This gets even harder if you have multiple LEDs or different LED packages, which would mean that you have look at multiple datasheets to get different values.

This is the reason why Citizen has created a Citizen LED simulator. The simulator is very easy to use and makes comparing different LED packages a lot easier. If you haven’t yet tried it or you don’t have the simulator, you can download it for free from our website.

Citizen LED simulator basic view

Citizen LED simulator basic view.

The steps

Follow these steps to use the simulator.

You can choose desired CCT and Ra and selection simulator shows packages and product codes of existing products.

You can choose desired CCT and Ra and selection simulator shows packages and product codes of existing products.

  1. Select the CCT and Ra

First you need to select desired CCT and Ra from condition input field.

You can choose desired CCT and Ra and the selection simulator shows packages and product codes of existing products.

  1. Choose whether you want to search based on the desired lumen amount or driving current

After you have selected color temperature and CRI value, you can choose between driving current (forward current in simulator) or desired luminous flux.

  1. Input the Tc-temperature

Then you can input Tc-temperature. If you have no idea how much Tc is or would be in your solution, values around 60 degrees are realistic to use as many light sources reach temperatures close to that while being used.


In this example, I have chosen that I want my LED to be 4000K, Ra80 Min. And I want to see what options we have to get around 3000 lumens out from luminaire. Luminaire optics etc. will drain around 300-400 lumens in my solution. So I have determined that I need 3400 warm lumens from LED and estimated that Tc-temperature is 60 degrees.


I can see that I have ten different LED packages I can get the 3400 lumens from. In first column after product code you can see what current you should use to get these values. If you don’t have LED driver, in which you can choose output current, it is recommended to then select current value you have LED drivers available in. In this case, 700mA seems to be a good choice as many of the LED’s have driving current close to that.

So I change “forward current” instead of “luminous flux” from the condition input and insert 700mA.

LED packages which give you desired lumens with 700mA. We still have six options to choose from.

LED packages which give you desired lumens with 700mA. We still have six options to choose from.

This will give me a list of LEDs I can use with 700mA driver. And more importantly give me a good overview of LED packages that can give me my desired lumen amount. If you have problem that you can’t find driver with suitable current, you can contact me for help.

In this case, CLU028-1204 would suit my lumen need quite nicely and CLU048-1212, would probably be an overkill for this application. All the other options, might suit my solution although they give roughly 10% more lumens. Whether this is ok, depends really on my application and desired efficacy.

Other applications

Citizen LED simulator is also powerful tool to use when you want to see easily how much lumens you get when driving LED with different currents. Good example is that if you have LED driver which has different current options and flexible LED package, you can use only two components to realize many different lumen packages.

As an example I did this exercise with ELT 42W multicurrent LED-driver and Citizen CLU038-1205 LED package. This driver has option to select different driving currents with dipswitch. If we take Esko’s advice and look from driver datasheet, we can see that output voltage area is suitable from 500mA to 1000 mA.

Below you can see LED characteristics with different current. I have also added forward current column to make this table easier to read. Tc temperature is 60 degrees in all cases.

Table with CLU038-1205 4000K Ra80 LED from 500mA to 1000mA.

Table with CLU038-1205 4000K Ra80 LED from 500mA to 1000mA.

You can also use the LED simulator to estimate the amount of lumens lost due to your luminaire (optics etc.). If you measure LED Tc-point and input the driving current you use to simulator, you should have pretty good estimation that how much lumens you should get out from your luminaire.

If you find out that the loss is too big, the you can either change the LED to a different package or improve the optics of your luminaire.As you can see, you can use this driver & LED combo for a luminaire from ~2500lm to ~5000lm.

Please feel free to contact me if you have any questions.

You can download the latest simulator below.

Download COB Selection Simulator


What is COB LED

COB LEDs are very popular nowadays in LED lighting business. We talk and write about COBs, and our customers use COBs in their luminaires, but what exactly is COB? First of all, the abbreviation COB comes from words Chip-on-Board.

Citizen COB frontside, The yellow substance is phosphor, which turns the blue light of the chip white

Citizen Electronics’ COB frontside, The yellow substance is phosphor, which turns the blue light of the chip white

In COB packages many LED chips are usually attached to substrate with non-conductive adhesive. LED chips are wire bonded together to make different LED setups. The amount of single LED chips, inside a one COB LED package, can vary from few pieces up to several hundred pieces. Substrate is located on base material. Base material of COB LED is usually MCPCB or ceramic PCB. COBs often have blue diodes and use yellow phosphor layer to convert light to desired color temperature.


General drawing of a COB LED.

General drawing of a COB LED.

In early years of 21st century there were few SMD LED packages, which could be considered almost as COB packages due to their construction. Generally COB LEDs became available and popular in LED lighting market around year 2007. At first there were first quite a lot doubts towards COB LEDs in the market . Mainly because this package construction enabled LED manufacturers to put high powers in small package. Over then, this “high power” meant over 10W,

Also there was very little experience of COB LEDs, so these LEDs had a lot to prove.  Although now several lifetime tests have shown that COB packages are very reliable, if heat management is done properly.

When thinking about heat management, one important feature is thermal resistance. But it is worth noticing, that you can’t define which COB LED is better to conduct heat just from thermal resistance value. You should actually test LEDs in your own application.

Today COB LEDs are available from few hundred lumens up to 30,000 lumens. This means that

Citizen COB backside, aluminium PCB, which will conduct the heat to the heat sink effectivily. However it won't be enough to cool the LED

Citizen Electronics’ COB backside, aluminium PCB, which will conduct the heat to the heat sink effectively. However it won’t be enough to cool the LED

almost every light source can be replaced with COB LED. So available powers go from few watts up to almost 200 watts. The most powerful COBs require exessive heat sinks because they generate a lot of heat.

COBs offer great variety due to possibility to have many different LED setups even inside one COB package. Usually LED manufacturers have different lumens packages available in same size COB, so lighting manufacturers is able to use e.g. same connectors and optics in different solutions. Also it is good to remember that usually you can underdrive or overdrive COB LEDs and those might have quite wide driving range. This allows you to drive LEDs with very high efficacy, you can make balanced solution or you can make economical lumens.

COB LEDs are generally used in luminaires where lamp or single spot light sources have been used. So basically COB LEDs are used in almost every kind of luminaire. Although COB LEDs are used less often in linear lights or  panel lights, some solutions of that kind have been made with COBs. Luminaires which have really high luminous flux are usually made with more than one COB LED to distribute heat flux and to ease design of heat sink.

Sochi Olympic cauldron, Lights made using Citizen COB

Sochi Olympic cauldron, Lights made using Citizen Electronics’ COB (Copyright: Zers Pride LLC)

COBs offer very high luminous fluxes from small size packages and thus allow flexible design of luminaire. This gives you more freedom, when designing a luminaire. COB packages usually have excellent uniformity of light from light emitting surface, this is important e.g. if you want to avoid multiple shadow effect, which might occur with SMD based solution. It is also very easy to test COB LEDs. You only need COB LED, constant current driver and e.g. piece of aluminium, which can be used as heat sink.

LED Shadows: On the left, a shadow from a COB. On the right, a shadow from a LED with multiple light sources

LED Shadows: On the left, a shadow from a COB. On the right, a shadow from a LED with multiple light sources

We can see that COB LEDs have been very important development step in LED lighting business. This great package design has allowed to increase powers used inside one LED package tremendously. Also one good indicator of success of COBs is that today every major LED manufacturer and package maker has COB LEDs in their selection.

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