How can an offline LED driver last 20 years?

[c_mitra]

If the lightning strike is close by, all bets are off, but at least yours (if 1200V) has the greatest chance of surviving...

Lightning rarely strikes directly the 220V/110V line; it hits the major transmission lines which are stretched across vast open area at significant altitudes. Although the topmost conductor is a ground wire, the voltage is induced on the high tension lines and significant energy is passed onto the lines.

This energy finally passes through several distribution transformers and they will simply stretch the pulse- reducing the peak height and increasing the duration. Also a number of transformers will share the same high tension line thereby decreasing the overall impact. Transmission line capacitance can be large (I have no idea about the value/km) but the overall energy many not be very large.

However, if the lightning strikes the low voltage line (220V/110V) near your place, then... (but the phone lines are rarely affected)

 

[treez]

Respectfully the above is a novice answer, as, at 1200V, all other items on the same line blow up first, protecting your equipment

Thanks, of course, as you know, lighting circuits are usually separate, so there won't be much else on it to quench any overvoltage transient. But i get the picture that 1200V ratings is pretty 'cast iron' in terms of general longevity.

 

[Easy peasy]

In a standard house, everything is fed off a single phase (for 230Vac anyhow) so all connected equipment including lights will see the same P-N transient and PN to earth transient...

 

[D.A.(Tony)Stewart]

Areas with aerial ac power distribution and frequent lightning strikes such as southern US ( FLorida) impose high failure rates to electronic equipment , even some with MOV protection. The advertised warnings are disconnect your computer during a lightning storm. Even some line filters and MOVs are inadequate in some areas. In the 80's "We" developed methods to survive 3kV, 6kV and 15kV transients and compared the costs for our SMPS in high-rel environments with high-volume, low-cost methods. It is a blend of methods using CM chokes (2), Pi filter, TVS, MOV's and fail-safe plastic caps.

Dysan marketting have no credible evidence to support well-reasoned Dysan engineering concepts, some of which are original for lighting such as the electrical connections used for linear position rods. The heatsinks are old concepts and nothing in their design supports their wild MTBF claims.
Distributed lighting with focal lenses will always be cheaper than centralized LEDs with Cu heat distribution. LED strips are easily fabricated with distributed dissipation with < $0.1/W costs in volume. Microlenses and proper luminaire design do offer putting the light down without the glare of a 10W LED.

The claims that all fluorescent lights are not efficient are blatent lies or ignorance.

I use tri-phosphor tubes with 88 lumens per watt which as good as the majority of LED luminaires and can drive one to four (4) 32W tubes independantly The tri-phosphor gives a better CRI than most single phosphor LEDs with a blue substrate. CRI is the index to render colour accurate on a pallette of pastel test patterns. Although LED's can give better colour saturation on tests, wide spectrum lights render higher CRI for coloured prints but does not mean best contrast for reading, which is the intent of Dysan's luminaires.


Large array LED's with higher power density than a XEON core ( W/mm^2) but can be kept cool better with patented vertical microtubes and another design uses spiral vortex convection fins, better than planar copper vapor phase tubing but effective in tight space like all Laptops for GPU's and some CPU's.

Power meters have a 100kA arc gap set at 6kV built in. After this the best attenuation is by filtering with high insulation rating of 15kV. After that the current is limited to the clipping suppression methods available such as TVS and the rise time is now slow enough for MOV's and has tubes are negative resistance devices which can also fail from follow-on current. The PU and PE caps can absorb the high dv/dt spikes and attenuate further with low ESR ratio from series L*dI/dt, but resonance must still be designed to control maximum Q and resonant frequencies.

The best approach for surge protection is a blend of CM choke rejection in 2 stages, LC Diff mode filtering, thus significantly attenuating a 6kV worst case pulse by filtering, attenuation, clipping, and isolation in the SMPS transformer. Most TV's are only rated to 3kV transients but may survive 5kV or more depending on pulse width.

Dysan's MTBF claims are wild to say the least and based on poor assumptions not engineering evidence. Nowhere do they report the junction rise or actual FIT's, confidence levels used or environmental stress of their life test. It is probably a theoretical comparison to 2.5x 50K theoretical marketing values based on other lamps wild claims of 50khrs but with a 15'C cooler junction temp thus Arhenius improvement of a little more than double the MTBF.

All of this assumes defect free which never exists in a manufacturing process that is not mature.
It must be calculated and must be demonstrated.

For Aerospace, it's a whole different game. They MUST use old technology with big lithography because the gamma rays can significantly reduce breakdown voltage which might start at 10kV/mm or 10V/um and 1um lithography is too small for Aerospace. ( XEON's are 25nm now and pushing 15)

 

[D.A.(Tony)Stewart]

typo Correction..
"wide spectrum lights render higher CRI for coloured prints but does not mean best contrast for reading, which is the intent of Dysan's luminaires."
I meant wide spectrum (e.g. halogen CRI=100) means better reading contrast of blueprints, pastel text, or in dimly lit rooms.

Next time you have a chance compare reading an old book in front of an RGB TV, a White LED , a 2-phospor (cool or warm tube and a tri-phosphor tube and a dull gray sky and see which will be worst. ( RGB-TV on whitescreen, then ...) It is due to the missing spectrum that gives poor reflection contrast but gives a perfect "apparent " white for direct incident light.

 

[treez]

Thanks SunnySkyguy, so white LEDs just havent got it when it comes to office lighting then?, -compared to fluorescents?...i mean office lighting is very often for reading off bits of paper.
We cant buy any LEDs that have that important bit of the spectrum?...maybe a mixture of white leds, blue leds and red leds would be better than a fluorescent for the contrast purpose?

 

[c_mitra]

I meant wide spectrum (e.g. halogen CRI=100) means better reading contrast of blueprints, pastel text, or in dimly lit rooms.

I do have plenty of old books (>40y and more) and printed on poor paper (it crumbles when folded) and I hate to read (and type) from the monitor but indirect daylight (inside room) is the most comfortable for me for reading. I still prefer the tungsten lamp more than the LED and CFL (both cool and warm but warm is slightly more pleasant to me).

But I am sufficiently old to be non representative.

 

[treez]

Sorry, but I am convinced that the Dyson “Cu-Beam” LED light is the world’s greatest in terms of keeping the LEDs cool, and thus prolonging their lifetime, and thus prolonging the quality of the luminaire for the longest time…you only have to look at the detail of the heat pipes etc…no other lamp does it like that..

Cu-Beam led light:
https://www.dyson.co.uk/lighting/cu-beam-suspended-lights.aspx

 

[c_mitra]

and thus prolonging the quality of the luminaire for the longest time…

1. Harsh shadows; good for strong impressionist photographs but not for doing any useful work.

2. Too little, too less; The light is not uniform even on the table seen in the advt.

3. The cooling does increase the efficiency (electricity to visible light conversion) but by how much?

4. The cooling does increase the life (MTBF) but by how much?

5. How efficient is the cooling? E.g., compared to a Al cooling block (like one used for the CPU in many desktop PC)?

6. Which particular quality of the luminaire is being prolonged? It will go out of fashion in 5 years.

Will the company replace the luminaire if it fails after 19 years? I bet they won't.

 

[treez]

3. The cooling does increase the efficiency (electricity to visible light conversion) but by how much?

4. The cooling does increase the life (MTBF) but by how much?

5. How efficient is the cooling? E.g., compared to a Al cooling block (like one used for the CPU in many desktop PC)?

This is the competitor to the Dyson Cu-Beam lamp….though in my humble opinion its not quite as sleek as the Dyson Cu-Beam….

**broken link removed**

…it does have Heat pipe cooling aswell though, but unfortunately has the led driver suspended on top of it, so its not going to run that cool, and cannot be big enough to contain the nice 1200V caps that Easy Peasy was talking about, or the transient filtration components that SunnySkyGuy spoke of.

Also, the Dyson Cu-Beam has multiple heat pipes which correctly take heat away from the LEDs, and distribute it into a clever multi-finned heatsink design. Keeping cool as possible is what long life LED is all about, so for me, just comparing these two LED lights tells me the Dyson one will run a lot cooler.

 

[D.A.(Tony)Stewart]

Thanks SunnySkyguy, so white LEDs just havent got it when it comes to office lighting then?, -compared to fluorescents?...i mean office lighting is very often for reading off bits of paper.
We cant buy any LEDs that have that important bit of the spectrum?...maybe a mixture of white leds, blue leds and red leds would be better than a fluorescent for the contrast purpose?

LEDs with 80 CRI are comparable to std 2 phosphor FL tubes, but in my opinion not as good as tri-phospor tubes, but then they cost 4x more than std tubes. but have comparable MTBF 30~50kh+

 

[treez]

Rather than MOV's etc, just design the front end with 1200V parts. This gives good immunity on 230Vac line, no mov's needed....

So do people agree that the cost of spending money on surge protectors with Varistors with thermal disconnect technology is a waste of time?
(ie like the Littelfuse ones linked in the first post)
….Because what is best (for offline power supply life-time) is simply using 1200V capacitors in the front-end of the power supply?

 

[treez]

Rather than MOV's etc, just design the front end with 1200V parts. This gives good immunity on 230Vac line, no mov's needed....

Thanks, but i thought MOVs were actually a regulatory requirement on any offline SMPS?

 

[Easy peasy]

it's amazing what people think without reading any standards...

 

[dick_freebird]

To some extent this involves luck and environment,
but I have many chip designs that are still in service
past 20 years active life (overdesigned "HiRel" parts,
subjected to well less than their rated temperature,
but still).

None of them exposed to the whims and misfortunes
of the local power line. I'd be unsurprised to see a bit
of extremely fine print about that somewhere at the
back of the product insert.

At any rate, "can" or "will", in the case of a product
that has not been around for a significant portion of
its rated life, must definitely be considered with some
skepticism. It's certainly not impossible. But the actual
odds do figure into value and yet are not likely given,
leading the consumer to imagine 100.0% since no
asterisk appears to a casual inspection.

 

[treez]

The thing is, even if we are using 1200v parts, what if along comes a transient bigger than that?...at some point, that transient protector/fuse "crowbar" action is going to be needed..surely?

 

[Easy peasy]

well, a 320V MOV (ac) starts to clamp real current at about 800V-900V so 1200V parts allow this to happen, but also, as mentioned previously, other equip on the line will have blown up and clipped the transient by then, let them fail first...

 

[treez]

well that sounds a good idea, but regarding the MOV being a regulatory requirement, i believe it is otherwise the super cheap Far Eastern import power supplies wouldnt use them, and they all do. (I appreciate theres a transient test the PSU must pass to get regulatory approval,but i cant afford the spec to see what it is.)

 

[Easy peasy]

to meet the standard, the easiest way is to have something to absorb the peak energy, hence a mov, but 1200V parts and the right sort of filtering will also pass the required standards....

 

[D.A.(Tony)Stewart]

So do people agree that the cost of spending money on surge protectors with Varistors with thermal disconnect technology is a waste of time?
(ie like the Littelfuse ones linked in the first post)
….Because what is best (for offline power supply life-time) is simply using 1200V capacitors in the front-end of the power supply?

MOV's are so inexpensive the cost of using them is far better than the cost of risk of not using them, when properly selected for appropriate markets.
But if your product is used in area that gets 10 surges on a storm day like Florida or a lot of above ground power distribution, you may want to include more effective ways of reducing the current surge without significant ageing such as filtering to raise impedance at more cost.