"Rod Speed" wrote in message
...


"alan_m" wrote in message
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On 13/03/2019 20:32, Fredxx wrote:
On 13/03/2019 19:13, alan_m wrote:
On 13/03/2019 18:44, Brian Gaff wrote:
So for the old BC light holders what are the best value that do not
chuck
out more RF than light?
Brian



Why should a LED and the power conditioning circuits in most LED bulbs
push out any RF?

Because they tend to use switching power supplies using small high
frequency components.



Really? That may have been true for compact CFL low energy bulbs but many
of the LEDs seem to have a bridge rectifier, a current limiting series
capacitor and perhaps an addition smoothing capacitor, all operating at
a maximum of 50Hz. There is no voltage conversion necessary as the LED
arrays, connected in series operate at high (mains) voltages.

But the better LED bulbs dont do it that way because
then a single led failure see the entire bulb or half of it
fail. Doesnt cost anymore to use a proper switch mode
power supply and avoid that failure mode. You just use
a different regulator chip that costs the same and save
the relative high cost of the dropper cap, particularly
with the higher quality bulbs that have to use the
relatively expensive dropper caps.

And its easy to see which approach is used with a particular
bulb, just wag your finger quickly between your eye and the
bulb and you will see a fixed black image of your finger with
the bulbs that use a high frequency switch mode supply.