100/120 Hz light flicker regulations  and being "green"? - Page 1
Forum section: electronics / general

author: ocset
author_rank: Super Contributor
timestamp: June 17, 2020, 09:34:39 pm
content: With Greta Thunberg getting stronger politically, do you believe there will be a relaxation on 100Hz/120Hz light flicker laws? (EN12464)For example, the most efficient way to power LEDs (at 200W) off the EU/UK mains, is with a BCM Boost PFC feeding a long series LED bank. However, like that, in order to get light flicker down to low enough levels, one needs at least 100uF of (450V+) capacitance across the LED bank. This is bound to be electrolytic capacitance, since at 100uF, films are just too expensive.Electrolytics have life time issues, and so this is not a “green” solution, unless of course the light flicker laws can be softened, and then just a small film capacitor can suffice instead of the large electrolytic bank.At 200W, off the mains, one can of course achieve low light flicker and use low amounts of capacitance…however, this needs two power stages….a PFC stage, followed by eg a Buck LED driver stage……..the Buck LED driver stage can then reject the high output ripple of the “lowly output capacitanced” PFC stage…however, two power stages in cascade means less efficiency…..so again Greta Thunberg “laws” are violated. So will Light flicker level regulations be softened?

author: themadhippy
author_rank: Super Contributor
timestamp: June 17, 2020, 10:09:11 pm
content: when has sense ever come into the equation if its deemed to be "green". Take the uk ban on incandescent lamps,cfl's were the new saviour,but don't mention there sunday name , low pressure mercury vapor , the lousy power factor,crap colour temperature or the flicker because well there green

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 17, 2020, 11:00:27 pm
content: Quote from: treez on June 17, 2020, 09:34:39 pmDon't need to cascade them, have a buck/boost stage in parallel with the output to handle the capacitor charging/discharging. It only needs to handle enough power to null out the ripple.Or just accept that good quality electrolytic capacitors will last a very long time if used within ratings.

author: bdunham7
author_rank: Super Contributor
timestamp: June 18, 2020, 01:02:21 am
content: I hope not--flicker is awful. Add a ceiling fan if you like seizures.I think the biggest reliability issue with LED lighting is that they try so hard to conform to old incandescent formats so as to not need new fixtures. The ones I have that are new fixtures entirely with sealed LED assemblies (and filter caps, no flicker) are wonderful--they don't get hot, no flicker, they dim nicely, etc. I have a bunch of fairly nice 2700K A19 bulbs that were subsidized by the power company, a dollar each. One failed, so I sawed it apart. It has a surprisingly robust setup for a cheap bulb--30 led chips on 5 boards arranged on a heat sink with an internal fin structure, but smooth on the outside. Lower down, there's a power supply that responds to dimming and has an electrolytic capacitor, all sort of potted or coated on a small, cheap board.These get hot. I measured the base of another one at 205F after an hour of operation. So what failed? 3 of the LEDs burned out! I bypassed that board and gave it power, the power supply worked, the remaining LEDs lit, the el-cap appears to be fine.Stop with the electrolytic capacitor FUD. I repair a fair amount of stuff and I've only had three 'failures' of capacitors in the past year--one was a mylar film cap in a megger (blew out at 1000V), one was an SMD tantalum and the third, a 35-year old el-cap was destroyed by a failed diode that gave it a big jolt of AC.For your 200W LED application, if you can manage to keep the temp below 70C, these will last you 24 years or so of continuous use, give or take, for $2 or so a pop.https://www.mouser.com/ProductDetail/Lelon/RUA101M2WBK-2235?qs=wd5RIQLrsJjTcuU6xe71Gg%3D%3D

author: trobbins
author_rank: Frequent Contributor
timestamp: June 18, 2020, 01:27:51 am
content: Quote from: treez on June 17, 2020, 09:34:39 pmPerhaps you can provide a lifetime estimate comparison, so as not to provide a seemingly biased presumption for this thread, and statement that this 'is not' a green solution. Also a quick summary of population trends for '200W' assemblies and the total population of mains powered LEDs would be useful to clarify if circa 200W assemblies are a significant energy consumption segment, or just quite niche.

author: ocset
author_rank: Super Contributor
timestamp: June 18, 2020, 09:38:15 am
content: QuoteThanks yes, that is good valueThough in some Apps, say if it was 90degC, and the lamp was on all the time, then thats 3.65 years for that RUA El cap.90degc isnt unusual in some apps. As you know, keeping things cool means bigger heatsinks and fans..and fans have limited lifetimes, unless they are pricey.Cheapest, for some apps, is just to avoid electrolytics and tolerate 100/120Hz flicker.

author: bdunham7
author_rank: Super Contributor
timestamp: June 18, 2020, 01:38:37 pm
content: Quote from: treez on June 18, 2020, 09:38:15 amThe whole point of my story was that my A19 application DID run at 90C and it still wasn't the (much cheaper) el-cap that ended up failing.

author: f4eru
author_rank: Super Contributor
timestamp: June 18, 2020, 05:33:15 pm
content: 200W LED ? that is an industrial light, equivalent to over a kW of incandescent.What is the application for that ?Also, there are clever ways around that, for example :- a second DCDC converter, reducing caps a lot, because of increased voltage swing, perhaps even allowing ceramics- combining the two DCDC into a single one, with clever switching and a single inductor ? -> better efficiency, less cost than the 2DCDC solution- switching a few of the load LEDs on and off, or paralell/series, in order to increase voltage swing on the cap, reducing the cap, even allowing ceramics -> there are clever linear (!) chips doing the linreg + switching trick- using in paralell a DCDC with a capdropper, providing some 90° phase shift, reducing the necessary buffer a lot- using 3-phase with alternating segments (quite common for industrial lighting at those power levels)....I agree with bdunham7, that too many LED "bulbs" are sold, it is absolutely the wrong format for LED, a sphere is designed to get and stay hot, and to fail, EL-caps or not.If you have an application staying ON all the time, NEVER EVER use a bulb form factor (and ask yourself why so much ON time anyway is needed in the first place ?)

author: Siwastaja
author_rank: Super Contributor
timestamp: June 18, 2020, 06:14:33 pm
content: As explained to you repeatedly, it's almost trivial to design in 20000-30000h lifetime with electrolytic capacitors. This can be optimized to be close to that of the LED emitters; in optimal case, multiple components lose their effectiveness approximately at the same time. The environmental impact of replacing such low weight of electronics every 15 years is negligible. Likely, better LED emitters are available then; this also reduces the stress to the elcaps because higher efficiency means less heat.If anything, manufacturers could be sanctioned if their products fail to meet the promised lifetime figures. This would force them to do proper design without cutting corners, such as using an underspecified elcap.Feel free to ignore this as always.

author: Siwastaja
author_rank: Super Contributor
timestamp: June 19, 2020, 07:05:33 am
content: Also note that poor power factor has some environmental issues with it. The only way to improve the PF of LED lights, without causingmassiveflicker, is to store energy. This practically can only mean electrolytic capacitors.About flicker, whether it's somewhat acceptable, or totally unacceptable, depends on the temporal utilization of the input voltage. It's not a frequency thing; a light which illuminates at 10000 lumen for 0.1ms and 0 lumen for 9.9ms is totally unbearable to anyone, including yourself, but something that outputs 133 lumens for 7.5ms, then 0 lumens for 2.5ms, looks just fine to most, excluding the most sensitive. Both "flicker at 100Hz", and both output 100lm average.For example, 230Vrms 50Hz AC, after rectification, varies between 0V and 320V so that 0V dips and 320V peaks happen every 1/100Hz = 10ms. Thereispower available almost all the time, but it's available at varying voltages. Now if you just add a LED string, say a model where the LEDs start emitting at 250V, you are only utilizing the input power whenever input voltage is between 250V and 320V. In time-domain, this is a small portion of the period. Hence you have a light that stays off most of the time, and blinks strongly at 100Hz. This is unacceptable flicker.OTOH, let's say you just power one LED, Vf=3.0V, from said rectified 0V to 320V power input, say you use a constant-current limiter in series with it. Now the LED lights up between 3V and 320V, it's basically on 99% of the time.Technicallyit's still "flickering" at 100Hz, but obviously appears completely flicker-free. Still no caps! Obviously the efficiency is almost zero for such linear regulator.One way to reduce flicker withsmallamount of capacitance, not requiring elcaps, is to use active DC/DC that extracts power from the input regardless of the input voltage, to power the LED continuously. Say, accepting a bit of flicker, it would need to work between say 50V to 320V. Boost to 400V, or buck to 50V would be obvious choices. Now this converter needs to drawmorecurrent from the input during low input voltage to give constant power, constant light output to the LED. This would be anopposite active PFC, a device which actively tries to destroy power factor to near zero. And such a converter is still somewhat expensive.Adding energy storage simply solves the problems. And because electrolytic capacitors are low-cost, reliable, well-known, industry-proven components that are fairly easy to design in by any competent designer, proper LED lights will continue using electrolytic capacitors.And some crappy lights will continue to flicker.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 19, 2020, 10:48:43 pm
content: Quote from: Siwastaja on June 19, 2020, 07:05:33 amSome video displays have the backlight on for a short time every period, albeit on a slightly higher frequency of 8.3ms for a 120Hz display. That avoids motion blur by effectively making the pixel transitions invisible. Now if you use 3D glasses, that halves the frequency to 16.7ms, which indeed makes for an awful experience. Hence the introduction of 240Hz displays.It's possible to make a flicker free light with no energy storage and a high power factor by making them 3 phase. Problem is that only specialty applications will have any chance of 3 phase for lights.Now I wonder if the cabin lighting in aircraft flicker at 800Hz. One could say that at such a high frequency, flicker is not a problem, while another could say that since it takes so little capacitance to smooth it out and aerospace hardware is held to a very high standard, that it only makes sense to smooth it out.