And what do they mean by "Pure white"? Am happy to assume that warm white is around 2700 and cold white might be 6000-6500. Does that leave pure white at 3500-4000? Or have I taken a step too far in my assumptions/guesses?
LED`s are light emitting sandwiches, with the filling emitting the light.
Means making extra large LEDs dosen`t gain much in output, it would be trapped in the middle.
Cheers Adam
series strings. This avoids the cost and waste heat of a driver.
Presumably there are sharing resistors, arranged so that a single device going open circuit doesn't kill the whole string?
Chris
light (more efficient) and a more pleasant white than the high voltage bulbs
to share the LED driver. Having one driver for lots of low voltage LEDs is probably more efficient than having one driver per LED.
Especially one driver per LED that has to be squeezed into the "bulb".
I don't see how it affects the colour though. Both 12v and 240v are available in a range of colour temperatures, but the same LED ought to give the same white at the same power, regardless of the driver efficiency.
light (more efficient) and a more pleasant white than the high voltage bulbs
ability to share the LED driver. Having one driver for lots of low voltage LEDs is probably more efficient than having one driver per LED.
Yup, I think that is confusing issues that apply to halogen (where LV are "whiter"), but not LED
Heat is the big killer for LEDs and leads to a serious drop in performance or death so I'd be careful in any application where there may be an additional heat source
Most LED failure are down to poor thermal management.
arrays with an overall yellow resin cover are 9 or 16 dice underneath.
series strings. This avoids the cost and waste heat of a driver.
I've got single packages with 24 high power LEDs, I can;t see a need for more than this is a domestic situation - I'm not even sure there would be many applications for this amount of power
Typically you never run more than 6 in a string.
You would never run a large string off the mains if you wanted long life and consistent output.
Good drivers can be around 90% efficient and do not generate a lot of heat. In anything but the simplest low power applications you always run LEDs with a current source not a direct voltage source, certainly not AC .
cheers
David
more light (more efficient) and a more pleasant white than the high voltag= e bulbs
bility to share the LED driver. Having one driver for lots of low voltage L= EDs is probably more efficient than having one driver per LED.
at. The graph of light output versus current is a curve which is steeper at= lower currents. Running several LEDs at low current is more efficient than= running a single LED at high current.
not really...the driver might play a part too but I'm talking of simple com= parison side by side between 2 identical 3 watt bulbs (same manufacturer - = CREE), the only difference being that one is a MR16 low voltage and the oth= er is a GU10 high voltage - the difference in the quality and the quantity = of light emitted by the two is quite noticeable...I have compared other typ= es and makes and the only constant results is that low voltage offer more l= ight and a more pleasant white. Then, we must consider that the low voltage= driver takes a bit away from that efficiency but it is very negligible.
es more light (more efficient) and a more pleasant white than the high volt= age bulbs
s ability to share the LED driver. Having one driver for lots of low voltag= e LEDs is probably more efficient than having one driver per LED.
"but not LED"?! Have you first hand experience or are you just assuming things? Try out by = yourself and tell me.... Then, maybe, the secret is really in the driver or the fact that these 12v = led bulbs runs on low voltage just like the halogen 12v - both are more eff= icient and more pleasant than the high voltage counterparts just because th= ese are low voltage (what about that?).
It seems to me that there is implicit in that the assumption that the voltage that the actual LED receives differs. Do you believe that to be so? Do you have any evidence that is so?
In the case of 12 V halogens you know that they are being supplied with
12 V - through some sort of transformer (whether traditional or electronic) and the filaments are very different to those intened for mains usage.But with LEDs you are most likely not seeing the voltage that the actual Ds receive. Only what you are supplying to the complete device.
Forward voltage on a LED is between IIRC 3v for red and up to 5V for white.
At highish powers
more light (more efficient) and a more pleasant white than the high voltage= bulbs=20
"cool white" (3w cool white is brighter than 4w warm white) - if in need o= f a warmer hue then I'd just use the "cool white" and a shade/filter over i= t.
iciency too!=20
evident where less leds are involved.
ite LEDs which are binned to specific colour temperatures, where the bins a= re also different sizes (i.e., the closer you want your LED to be to a part= icular colour temperature, the more you pay). I have EasyWhite MCEs in my k= itchen (3500K) and there is no noticeable difference in colour or light out= put between them.
"The colour temperature is unrelated to the driver voltage." try by yourself if you can and tell me...
Sticking a filter over a cool white bulb reduces efficiency - true...but at= least you got a choice! and a way to choose how much light you need and yo= ur degree of white or other hues (your choice). Instead with a warm white you stuck with what the manufacturer gave you...
Precisely. So what difference inherent to the mains vs low voltage distinction would make efficiency or colour differ - if you look at the individual LED elements - rather than the entire package? I can't see any. Because the LEDs would be getting the approx. 5V you quote regardless.
I've no idea how led bulbs are built nor concerned about the inner workings= of transformers etc. etc. I've just bought different types of led bulbs an= d compared them side by side (as simple and empirical as that). All the high voltage led bulbs I've had so far (different type of design an= d power and white) are inferior to the 12v leds I'm using in my bathrooom -= even those produced by the same manufacturer and same wattage lose the bat= tle - my first choice from now on is going to be 12v cool white...then, for= practical reasons I would use high voltage leds too (second choice).
we are going in circles here... I've bought some batches of bulbs from China - all from the same manufactur= er: Cree (3watts bulbs cool white high voltage and 12v also 4watta warm whi= te 12v) and compared on my kitchen table before deciding which type to go f= or...see, I got no doubts...the numbers provided by wiki or any techy sourc= e means nothing until you see by yourself - let's say that maybe, the batch= of the 3watts low voltage was the better of the lot? (as all them 4 perfor= med better than the rest).
more light (more efficient) and a more pleasant white than the high voltage bulbs
ability to share the LED driver. Having one driver for lots of low voltage LEDs is probably more efficient than having one driver per LED.
yourself and tell me....
bulbs runs on low voltage just like the halogen 12v - both are more efficient and more pleasant than the high voltage counterparts just because these are low voltage (what about that?).
Just sounds like a lot of bollocks
A well designed 240V led has a switched mode convertor that takes in
240VAC and spits out a constant current probably with something like 12-24V compliance voltage. This should 80-90% efficientA 12V Led driver, istill a switched mode constant current source with
80-90% efficiency, but the 240VAC to 12VDC switcher supplying this will also be in the 80-90% efficiency range. so the overall efficiency wrt 240VAC, will be lower for this configuration. - 60-80%
Fine. I entirely believe what you say as an observation/description. But am deeply sceptical that it is due to the low voltage supplied to the device in and of itself. The differences within and between batches are well known to vary considerably.
Well its one of those language things. Whiter LEDS need higher voltages.
But LEDs don't change colour with voltage apart from going brown and smokey..theres always some way of limiting the current and voltage to them.
.
I have first hand experience of both mains / LV halogen, and also LEDs.
Have tried, and have told you.
Complete twaddle with no technical foundation.
The diode junctions will be run at (roughly) the same forward voltage by the LED driver regardless of the external power supply voltage.
Granted, there is a huge difference in performance of different LEDs, also a big difference in how well they are heatsinked etc. Designs also vary dramatically. So its quite possible that one designed for mains use to look very different to one designed for 12V use. However its equally possible for them to look exactly the same.
For certain values of "we"...
So you bought completely different bulbs that are advertised as being different powers, and with different colour temperatures, and concluded they look different?
That must have been a shock.
Now you think its the supply voltage to the SMPSU built into the bulb that made them look different and not the fact that they were designed to look different in the first place?
Your point being what exactly?
(you do know that LED performance falls off with lower colour temperatures I take it - so 2700K lamps of the same power as 3500K lamps will emit significantly less light)
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.