AC Power Supply Question

Hi all. I'm looking to drive 4 XP-G's from 110 VAC with dimming capabilities for an under cabinet lighting project. Leds are XPGWHT-U1-0000-00AE7 from Cutter. I was looking through the 1000's of AC drivers on Mouser and got a bit stuck. Please help me understand a couple of basics:
1. With a CC driver, do I care about the rated output voltage, or will the unit adjust the voltage as needed to drive the leds at the rated current? Most of the units are rated for higher voltage than I need.
2. What is the best way to incorporate dimming? If it matters, I don't need the dimming control to be at the wall switch; a little pot next to the power supply would be fine too.

Thank you!

SnowplowTortoise said:

1. With a CC driver, do I care about the rated output voltage, or will the unit adjust the voltage as needed to drive the leds at the rated current?

Click to expand...

A LED driver will adjust the output voltage to whatever is needed to output its set current. And will be able to do so within a certain voltage range. Bottom of that range should be > than what the LEDs need. Top of that range should preferably be something that's still safe to touch.

Or in other words: if those 4 XP-G's go in series, then 10-14V (or so) should fall within that LED drivers' output range.

Most of the units are rated for higher voltage than I need.

Click to expand...

Well then, that's an easy criterium to separate [what you want] from the many available ones.

2. What is the best way to incorporate dimming?

Click to expand...

There's 2 basic methods: 'analog' current control, and PWM.

Afaik PWM has the advantage that LED tint isn't affected, but the disadvantage that it may cause (visible?) flicker. Current control doesn't have this flicker issue but may affect LED tint, in particular at very low drive levels.

Some drivers even allow those 2 methods to be combined. How it's done exactly, depends on the driver (and that might be another selection criterium: how much / what external circuitry is needed to control dimming).

At what current you intend to drive these XP-G's when "full on" ?

Thanks very much for the info. I don't think I would need to drive these very hard - 1A would be plenty, but I'm not finding anything even close. My criteria are:
- PWM dimming - TRIAC compatible would be nice but would accept any manner of control
- 120 VAC input
- 10-14V output at 700-1200 mA

Maybe I need to cobble together something with a MaxFlex-type driver and simple DC power supply? Seems impossible that there isn't something available off-the-shelf.

SnowplowTortoise said:

Thanks very much for the info. I don't think I would need to drive these very hard - 1A would be plenty, but I'm not finding anything even close. My criteria are:
- PWM dimming - TRIAC compatible would be nice but would accept any manner of control
- 120 VAC input
- 10-14V output at 700-1200 mA

Maybe I need to cobble together something with a MaxFlex-type driver and simple DC power supply? Seems impossible that there isn't something available off-the-shelf.

Click to expand...

those are pretty modest requirements .. most any 1amp 12v adapter should work

Power Supply Adapter LINKSYS MT12-4120100-A1 AC / DC 12v 1.0amp $4
http://www.ebay.com/itm/Power-Supply-Adapter-LINKSYS-MT12-4120100-A1-AC-DC-12v-1-0amp-/151291465609

Thanks cy. Yeah, I don't think I would have trouble coming up with a DC power supply. I tend to hoard those things. So you're suggesting I go the Maxflex route to achieve the dimming?

I think I found something. Had to search Digikey instead of Mouser.

http://www.digikey.com/product-detail/en/VLED15-120-1000/102-2234-ND/2583051

ELV/TRIAC, 90-135 VAC input, 10-16 VDC output at 1A.

$38? Yikes!

How about this:

http://www.amazon.com/dp/B00AH2OX5E/?tag=cpf0b6-20

Thanks. Jim. Unfortunately I had already ordered the other one but that might have been a good option. I don't see a output voltage range listed in the specs - just "12V". If that is the max, it is probably only enough to get to 500-600mA.

brickbat said:

$38? Yikes!

How about this:

http://www.amazon.com/dp/B00AH2OX5E/?tag=cpf0b6-20

Click to expand...

that sure looks like a low cost, $18 solution that designed to do exactly as described ..

==========
12V 12W Dimmable CV DC LED Driver ETL (UL) approved
Price: $14.99 + $3.50 shipping

Input range from 100~120V AC, 50-60Hz, Pf> 0.95
Magnetic Dimmable DC Output: 12V, 1000mA (12W)
Dimmable, Suitable for Leading Edge or Trailing Edge TRIAC dimmers
Protection: Short-Circuit / Over Current / Over Voltage and Auto-recovery Mode

cy said:

that sure looks like a low cost, $18 solution that designed to do exactly as described ..

==========
12V 12W Dimmable CV DC LED Driver ETL (UL) approved
Price: $14.99 + $3.50 shipping

Input range from 100~120V AC, 50-60Hz, Pf> 0.95
Magnetic Dimmable DC Output: 12V, 1000mA (12W)
Dimmable, Suitable for Leading Edge or Trailing Edge TRIAC dimmers
Protection: Short-Circuit / Over Current / Over Voltage and Auto-recovery Mode

Click to expand...

Yup,

It's easy to make cheap product (not that this really is), when you apply FAKE ETL markings to your product.

That is not what a real marking would look like. A real marking does NOT have INTERTEK at the bottom, it would have the Control Number that you would be able to look up to see if it is real.

Feel free to search for eversale, ever sale, etc. on http://etlwhidirectory.etlsemko.com/WebClients/ITS/DLP/products.nsf/$$Search?OpenForm

I have submitted a notification to Intertek .... will likely do the same with UL since they seem to fake their labels as well.


Semiman

what about the Recom one: http://www.digikey.com/product-detail/en/RACT20-1050/945-1778-ND/3776070 It offers Triac dimming. I have used many of their RACD versions whcih are non-dimmable and they work great

1050mA output, 12-18V so it would drive 5-6 LED's

Thanks again for the suggestions. The problem I had with the Recom unit is the input voltage is too high and I don't see a US version available.

I received the VLED15 unit. Seems to work fine. I'm just a bit disappointed with amount of light I'm getting from 5 LEDs at 1A, so I may increase to 8 or 10 LEDs and drive them a bit harder. In such case, I will have to pick up a new driver. I've narrowed it down to the following:
http://www.digikey.com/product-detail/en/RACD45-1250A/945-2136-ND/4504505
http://www.digikey.com/product-detail/en/PLED75W-054-C1400-D/1121-1222-ND/4271599
http://www.digikey.com/product-detail/en/LED50W-36-C1400-D/1121-1088-ND/2786586