We repeatedly use the term “good quality LED” when talking about the benefits of LED lighting & fixtures. This is to emphasise how vital it is to select high quality products and designs and to avoid the pitfalls of lower quality still readily available on the market.
So how do we determine good quality LED? The key factors are:
Thermal management is key
This relates to the temperature at the junction of the LED and PCB it is mounted on. The cooler this temperature, the higher the performance will be (lumen per watt output) and the higher the reliability.
The junction temperature is determined by the drive current and the heat dissipation. The drive current is what puts the heat there, and in terms of how you can determine good quality, this is the first thing to look for. It should be stated on the product data sheet and on the driver.
Our fixtures are run at 100mA whilst drive currents of up to around 350mA should be fine for good quality LED. I would have concerns at ) 0.5A & above. We have seen low bay office type fittings at 1.5A!
The drive current will determine the lumen output from the fitting, so over-driving them to achieve the lumen output needed suggests the light engine (driver +LEDs) is not an efficient one. Over-driving them will have the LEDs running hot, so both lifetime and reliability will reduce – again, at O.5A and above, significantly so.
Efficacy relates to the combined efficiency of the light engine and efficiency of the fixture. This is the overall / net Lumen Output of the fitting referred to as Absolute Photometry.
Always check that it is Absolute Photometry that is quoted, and not “relative photometry”. Relative is purely the lumen per watt output from the light- engine only, so falsely will quote a higher number; when placed in its fitting, some light will be trapped/ lost.
Some companies misleadingly quote in relative – whether by error or intention.
Good lighting design is crucial to high quality lighting solutions. No matter how good the product is, the installation needs to appropriately uniform, the right CCT, CRI and UGR to be of high quality