How to Compare LED Products.
(So you don’t get mis-LED)

LED Chips.

There are basically 4 designs of LED chip on the market.

LED Chips 

DIP (Dual Inline Package) this is the 1st generation chip. It is used in the lowest quality lamps generally.
    Advantage. They are cheap! and initially very bright.
    Disadvantage. Poor thermal management properties, overheat and lose light output quickly. (Known as attenuation)

SMD (Surface Mounted Device) 2nd Generation and used in all LED tubes, some spotlights, Corn lights and many others

High Power The options on these tend to be 1 watt, 2 watt, 3 watt etc. Used in spotlights, downlights, floodlights, high bay and many other types of lighting.

COB or Integrated Chip.
These are powerful large chips which are made up of smaller chips and integrated together to form a large single chip.
This type of chip is gaining popularity amongst lighting manufacturers and is used extensively in LED floodlights and High Bay lights. COB is also becoming more popular in spotlights, downlights, track lights etc because there is less labour involved in installing one chip as opposed to many.

Led Chips are made by many different companies and in many countries.

Here is a brief list of the most popular and well known manufacturers.

CREE, Bridgelux (USA)
Samsung, SSC, LG Innotok (Korea)
Nichia, Sharp, Toyoda (Japan)
Osram (Germany)
Philips (Netherlands)
Everlight, Epistar (Taiwan)

All the different styles of chip have a grade. Like a computer chip from entry level to top of the range. So it is not enough just to be told it is a CREE or Epistar chip, you need to know the size and model of the chip, in order to determine the performance.

Packaging or Encapsulating the chip.

The naked LED chips need to be protected from dust and moisture and other environmental hazards and so they go through a process termed ‘Encapsulation’ or packaging. This involves embedding the chips in epoxy resin. The chips can either be purchased ready-encapsulated from the chip original manufacturer or the lighting manufacturer can buy the naked chip and encapsulate them in-house. This is far cheaper but if not done properly, it can have a devastating effect on the performance of the chip,

Below is simplified image of the process.

Schematic depicting steps involved in the active packaging process for LED encapsulation :
(a) a bare LED chip
(b) coating (or immersion) of the bare LED chip with epoxy resin
(c) curing of the resin on the LED chip by emission from the LED itself
(d) the final self-packaged LED after washing away any uncured resin

Lumens
There is a lot of confusing information about the performance or light output of a chip. This usually expressed as lumens per watt, when the sellers advertise their goods.
Claims of 100-125 lumens per watt for certain chips relate to the naked chip, before it is encapsulated and embedded into a fixture. This output will be reduced appreciably by the quality of the encapsulation, lenses and other components. In other words it may well be 125 lum/watt before it goes in, but it certainly won’t be the same when the light comes out of the finished product, the fixture, it will be nearer 80 lum/watt. You need to know the lumen/watt of the whole fixture, including driver.

CRI
The colour rendering index is a measure of the quality of the light and its ability to reproduce a true representation of colour.
The old halogen lamps actually gave a really good CRI, but of course, they were very inefficient,
Chips that offer a higher CRI (say above 75) are more expensive to produce as the phosphors are more expensive and they give less lumens per watt compared to a chip that has lower CRI. Because of this, you need more power to give a high colour rendering from a fixture or lamp. This can be confusing if comparing lumen output of lamps or fixtures. So knowing the CRI of the light source is important to be able to make a fair comparison.

CRI_Comparison  CRI index should not be less than 70 in most applications in order to enable people to differentiate various colours and work more efficiently and correctly

CCT-Colour Temperature

The shade or temperature of White light is measured on the Kelvin Scale.
LED lighting offers a huge range of choice, here is a guide to options and the effect it has on whatever you are illuminating.

    It should be noted that the warmer the colour, the less lumens per watt are achieved and visa versa.

Drive Current

All LED chips are designed to operate under an optimum drive or forward current. This can be 350 mA, 700 mA, 900mA etc. This optimum current balances the amount of light given by the chip, with the ability to dissipate the heat from the base which is vital to ensure that the chip a long and useful (light output) life.
One practice employed by some of the more disreputable manufacturers is to overdrive the chip to achieve more lumens per watt. They do this by pushing a higher current through the chips, via the LED driver. This will make the lamp/Tube/Panel appear bright compared to others, but the higher current will degrade the chip much faster and therefore the light output will diminish a lot sooner than correctly driven chips.

Drivers

LED drivers are without doubt, the ‘Achilles Heel’ of LED lighting and if a lamp fails prematurely, you can be 99.9% sure that it is the driver, not the LED’s. The drivers have electrolyte capacitors inside which can dry out if exposed to a continuous level of high operating temperature. The better quality drivers use larger and higher quality capacitors such as Rubycon from Japan. Also, if the lighting fixture is going to be used more than 12 hours a day, you should consider an external driver.
Remember that HEAT is the main reason that LED lamps and drivers fail or lose brightness too soon.

Warranty

Many manufacturers will offer better quality components in their products if you pay a little extra and based on this, they extend the warranty period. So expect to pay a little more for a product with a 3 year warranty as opposed to 2 years

.