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Flicker

NVC's ARCATEC drivers take the lead in delivering low-flicker performance

Almost all LEDs flicker to some extent and this is often increased during dimming. Flicker is caused by Ripple Current - a regular fluctuation of the output of the driver. The best drivers have current ripple of less than 10%, but on others the ripple can be several times this. Our Phoenix LED battens, for example, all use low-flicker driver with <8% ripple.

The frequency of flicker varies greatly from product to product, but with LEDs it is generally in the range of 100 – 1,000Hz. By comparison, mains flicker (as with switch-start products) is 50Hz and fluorescent Hf products are operating typically at 40,000-60,000Hz.

The extent of flicker is measured in two ways, Percent Flicker and Flicker Index. In both cases a low figure indicates better performance. A poor LED fitting might have a percent flicker of 50 and a flicker index of 0.3. A better fitting might have a percent flicker of 17.5 and a flicker index of 0.05.

Frequency effects our perception of flicker; a flicker index of 0.2 might be deemed unacceptable at 100Hz, but acceptable at 300Hz. It is therefore not helpful for a manufacturer to claim “My flicker index is better than yours.” The extent to which flicker matters (or not) is a function of the extent of the flicker and the frequency.

Can we see flicker? Generally we cannot see flicker, but some people are sensitive to it and for them it can cause headaches, as was the case with people working under some old fluorescent fittings operating at 50Hz.

A digital camera is not the best way to judge flicker. What you see through a digital camera is a function of LED flicker and the camera’s frequency of operation.

Standards

The drivers used on all our products comply with EN61003, the relevant driver standard, but this does not set a maximum allowed level of flicker. A new standard, IEEE1789, sets maximum allowed flicker percentages for different frequencies of operation, but this is not a European standard, there is no European equivalent at present and IEEE1789 has been criticised for setting very low levels of permissible flicker. Nevertheless, we have adopted IEEE1789, as have some other leading manufacturers, and this standard is implemented in the ARCATEC range of drivers. This is your assurance that with ARCATEC drivers you receive levels of flicker that are amongst the lowest in our industry.