Mains LED driver for a single LED?

Illum · Nov 28, 2011

There are several places in the house where pictures could use light:shrug: and the current set up of one CREE XPG hi-CRI driven at 1A has satisfied the requirements very well :twothumbs. I am thinking of slowly integrating the POL design to replace other AC fixtures that does not require a huge output of light but I am having trouble finding a suitable mains current source for one single LED. :tired:

Current design is centered at using a 4W PCB mounted AC/DC switcher providing 12V out and a 3021-D-N-1000 buckpuck to provide the current source. This has worked well except for one problem:sick2:. The setup costs on average $50 in materials :ohgeez:

and the minimal project box dimension to accommodate it is 4" x 2" x 1" and I think it could be smaller. :huh:

I'm hoping to locate an equivalent switcher [to cut down on heat

, plain fed up with linear converters melting holes through ABS operating just within a year

] that can provide about 3.5W under a constant current of 1A. :drool:

Anyone has any ideas?:thumbsup:

Kinnza · Nov 29, 2011

For just one LED, I think it would be way easier to use an AC driven LED, running directly from the mains. Way easier, simpler and more efficient.

If the light points are not far one from the other, it would make sense to use a 12VDC PS for some (series wiring) or 3.5-5VDC PS(for parallel wiring, each with its resistor or IC for current regulation). There are cheap transformers with adjustable voltage output and with current output enough for the task (1.5A, for example), usually sized about 2" (cube, give or take), you could use one for each light point (always plus the resistor or IC+resistor for current regulation), no more than 5$ for each (but they tend to be very little efficient, such transformers of good quality often goes near 20$).

purduephotog · Nov 29, 2011

Illum said:
There are several places in the house where pictures could use light:shrug: and the current set up of one CREE XPG hi-CRI driven at 1A has satisfied the requirements very well :twothumbs. I am thinking of slowly integrating the POL design to replace other AC fixtures that does not require a huge output of light but I am having trouble finding a suitable mains current source for one single LED. :tired:

Current design is centered at using a 4W PCB mounted AC/DC switcher providing 12V out and a 3021-D-N-1000 buckpuck to provide the current source. This has worked well except for one problem:sick2:. The setup costs on average $50 in materials and the minimal project box dimension to accommodate it is 4" x 2" x 1" and I think it could be smaller. :huh:

I'm hoping to locate an equivalent switcher [to cut down on heat, plain fed up with linear converters melting holes through ABS operating just within a year ] that can provide about 3.5W under a constant current of 1A.

Anyone has any ideas?:thumbsup:

There are many drivers capable of hitting your specs. The 1A is pretty high, but you should be able to get 700ma drivers for 1 LED (quite small).

In fact, if you look through DX, you'll see a couple designed to be soldered in the base of the lightbulb.

http://www.dealextreme.com/p/700ma-3w-led-constant-current-source-power-supply-driver-90-265v-81780

While I don't have this one (because it appears to be new) I have two or three of the older versions and found them quite solid.

Illum · Nov 29, 2011

Kinnza, well yes, but very few AC driven LEDs exist aside from the one made by SSC, also there's a 60Hz flicker to worry about. But yes, I agree it would be the simplest logistical solution.

yep, there are plenty of single LED drivers at 700ma... this I know for sure. I've stuck with a single LED as opposed to two or three at 700ma due to thermal limitations.
Thanks for the link purduephotog

deadrx7conv · Nov 30, 2011

http://www.acriche.com/en/product/prd/acriche.asp
http://www.acriche.com/en/product/prd/acrich2.asp
http://www.lynklabs.com/index.php?main_page=index&cPath=50
http://www.vollong.com/ProductList.asp?SortID=36&SortPath=0,30,36,
http://ce.citizen.co.jp/lighting_led/en/products/LMC01B.html
http://www.microsolar.com.tw

There are other AC LEDs just can't remember the links, but do believe that they were 'COB' types.

To drive a single 3.3v LED from 120vac is a serious voltage drop. How much power are you losing from that driver/transformer/powersupply....?? Ebay should also have similar to dealextreme. You might be better off making your own driver.

Illum · Nov 30, 2011

deadrx7conv said:
http://www.acriche.com/en/product/prd/acriche.asp

To drive a single 3.3v LED from 120vac is a serious voltage drop. How much power are you losing from that driver/transformer/powersupply....??

lol. no one said it had to be a linear supply. Current setup uses a 87% switcher that puts out 12VDC, then a 90% efficient buckpuck to drive one LED... .87x.9=.78, not bad, very little felt heat

Kinnza · Dec 1, 2011

Say you use a XP-G at 1A, about 3.2-3.3W, with a 78% efficiency. It means a power of 3.25/0.78=4.17W. You reduce the initial efficiency of the bare LED noticeably, from 25% (best case for a 1A driven high CRI XP-G, likely you would get close to 20% on real conditions or if you dont use the top bin) to below 20% (best case, about 16% on average). Really easy to match for AC driven LEDs for cheaper and with far easier installation. There are AC driven LEDs with 100-120Hz frequency and smoothed AC wave so flickering is unnoticeable.

Other interesting possibility is to use high voltage HI CRI XT-E (46V each, 22mA), 3 of each and run them from the rectified 120V mains and a linear current limiting (efficient, cheap and simple for 22mA operation) and a surge protection (MOV varistor and fuse).

Illum · Dec 1, 2011

oo: where can I find this HI CRI XT-E (46V each, 22mA)?

Kinnza · Dec 1, 2011

It is rather new (2011-10-25), so likely is not available on retail yet. Cutter usually has new Cree LEDs the first and XTE and XML hi voltage version are not on sale yet (although on main page there is a report of these new products). It shouldnt last too much. In the meanwhile, you can get some info on them and see if you could use them when available:

http://www.creehighvoltage.com/#home

http://www.cree.com/products/xlamp_HVresources.asp

http://www.cree.com/products/xlamp_xte_hv.asp

http://www.cree.com/products/xlamp_xml_hv.asp

deadrx7conv · Dec 1, 2011

Illum said:
lol. no one said it had to be a linear supply. Current setup uses a 87% switcher that puts out 12VDC, then a 90% efficient buckpuck to drive one LED... .87x.9=.78, not bad, very little felt heat

Not bad? Only if that is exactly what was measured. If you're reading off of paper specs, means little!

Mains LED driver for a single LED?

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