[Milsurplus] EMI from LED lighting

[J. Forster]

Apparently, dilution is the solution to pollution, in electronics too. Do
you know how much they vary the frequency/period?

-John

==============



> My company makes IC's for electronic ballasts so I can provide a little
> insight.  Be forewarned that the story isn't a comforting one.
>
> First of all the LED itself is as benign as an incandescent lamp.  The
> problem lies with the switching power supplies that feed a constant
> current
> from a high voltage to the low voltage of the LEDs.   All these products
> must pass FCC Part 15.  They are not cut any slack with regard to meeting
> the spectral mask just because they are "green" and represent a
> multi-billlion dollar industry.  Unfortunately, the FCC's spectral mask in
> the HF spectrum is insufficient to protect a sensitive receiver from
> noise.
>  Lights are everywhere so unless your antenna is far removed from your
> home
> and fed with well-shielded coax, you will likely experience some noise
> proportional to that proximity.  Most of the noise will emanate from the
> AC
> line feed not the small circuit board.  So choking off the currents on the
> AC line will help more than extra shielding around the lamp.  The IC
> makers
> are under pressure to make the chips cheap and to require minimal external
> components for meeting EMI.  This translates into various PWM schemes that
> smear out the noise spectrum so as to avoid high amplitude fixed frequency
> spikes.  So instead of getting a few strong raspy tones in our radios we
> get a general raising of the noise floor.  The total noise energy is the
> same, just spread out.  The more consumer PWM stuff near your antennas,
> the
> higher the noise floor becomes.
>
> I wish I had a happier story to tell.  Unfortunately, PWM devices are
> appearing everywhere in the home while the FCC is all about "let the
> market
> decide" and opening up spectrum (including your home power line) for
> various digital data formats.  The FCC doesn't really care about AM radio
> and the next generation of consumers doesn't either. The BCB is so
> "yesterday."  Hams are just kind of caught up in the tide.
>
> Dennis AE6C
>
>
> *A friend asks:*
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> *My biggest question about LED lighting is how much radio interference
> itgenerates at frequencies up to about 30 MHz (HF).  Other users of
> theradio spectrum are more concerned by interference at higher
> frequencies,through VHF and UHF.AFAIK, an LED by itself does not generate
> radio interference; it is theelectronics between the LEDs and the AC power
> line that concerns me.Fluorescent lights (both CFLs and long straight
> tubes) with electronicballasts are bad because an electronic ballast
> switches AC line power withvery short rise & fall times, so the ballast
> strongly excites the linewith radio-frequency power at whole-number
> multiples of the switchingfrequency up to 30 MHz and beyond.It is possible
> to reduce this radio ?noise? or interference to a tolerablelevel by means
> of shields, L-C filters, and ferrite chokes; but very fewmanufacturers of
> fluorescent lighting products do.  If they do anything,it is nowhere near
> enough.I?m waiting for the prices of LED-lighting products to drop further
> beforeI buy some for evaluation.  Meanwhile, can anyone direct us to
> published,quantitative information about the radio noise generated by LED
> lightingproducts?Best,-John*
> ______________________________________________________________
> Milsurplus mailing list
> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Milsurplus at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>