THD In Light Bulbs

If you are not using a dimmer, then I would not get too worried. It's just another small switching power supply on your AC line, and odds are you already have quite a few (all those USB chargers, and they can be worse).

If you have a dimmer, then yes, things could be noisier as the power supply in the bulb will have capacitors on the front end which will result in higher peak currents when the dimmer turns on (120 times a second, 100 in some parts of the world).

There are some bulbs/lights that do not have switch mode power supplies in them, but simple linear regulators. They are common in low cost flush mount ceiling lights, but not very common in bulbs. I would avoid most as they can have lots of invisible flicker.

twoleftears,

That is a link to a highly technical article, that is itself really only applicable to one IC / control architecture. Most EEs would not understand the subtleties of it, let alone most people here. It is really not applicable to the ops question.

Basically a switching power supply, akin to a USB charger, and about the same power level as well.

I don't see anything about EnergyStar for these bulbs. If they were EnergyStar, they would have to meet some minimum power factor requirements that would normally mean less harmonics on the AC line. Since they don't appear to be, they could be poor (akin to those USB chargers).

b_limo1,065 posts01-04-2020 12:01pmCan someone elaborate on smart light bulbs?  I recently added 8, color changing, dimmable, smart led bulbs from sengled...

It would be within the realm of an EE if they had the experience and knowledge on the topic. EE is a big area and most EE's would not have the specific knowledge in the area for this article to be of much use without some extensive studying. Heck many EEs who work in this area do not understand what's discussed very well.   I am very qualified to make that statement. You are not. It's not really appropriate to the ops question as it only deals with one particular implementation that could be one of numerous used in a bulb and says little about PF and THD of actual LED bulbs. 


Again, if you are going to troll me, which you are obviously doing as you respond almost every post I make in new threads, then you need to step up your technical game.

Summary:

• If you have no dimmer on the line, then the incandescent bulb will inject less noise.
• If you have a dimmer on the line, but the dimmer is on full, the LED will likely inject more noise. It will depend on the dimmer and LED bulb.
  
• If you have a dimmer on the line, but the dimmer is not on full, the LED bulb will inject more high frequency noise, but the incandescent bulb will inject more low frequency noise (as it will be drawing 5-6x the power). I can't comment on how your specific equipment will behave.

Unfortunately there are no absolutes, but this is about as good a guideline as can be given.

If it wasn't LEDs it would be compact fluorescents or vacuum tubes. They would use more power and there would be even more noise. LEDs are not noisy, just the power supplies used to drive them.

No, that is not what it means. A power factor <1 simply means that current and power are out of phase. This does not mean that there is "wasted power". Power factor does not give any definitive indication of wasted power.

That means that half of the power going in is wasted and the unused "power" is dumped into the neutral leg.

Power factor can give an indication of the potential for noise (in the form of THD), but only if you know the circuit. The THD of up to 35% is the important figure of merit in this case. It is unlikely to be << 35% or they would have just used a lower number in their marketing.  At this low power level, power factor will not have any appreciable impact on other equipment but the noise from high THD may.