Am I asking the impossible? 12v (input) LED drivers

[kerris]

Hi people.
I am looking for an LED driver which can operate from a 12v dc supply to run LED panel lights (12w) which are normally run from 220v ac. The supplied driver information shows: input 85-265v 60/60Hz; output 24-42v 300mA (multimeter actually shows approx. 38-41v output when powered from 220v ac)
I'm afraid I really know nothing about this and have sent countless emails to suppliers without success. I am beginning to think I am asking the impossible. Without the appropriate knowledge I am lost.
Can anyone please advise whether such a device is a) possible, b) to their knowledge available?
I really would be most grateful - I have tried to find out with absolutely no success.

 

[KrisBlueNZ]

Hi and welcome to Electronics Point

Your LED panel lights are specified for an input voltage range of 85~265V AC. This strongly implies that they have a switching power supply inside. Can you see inside? Look for a circuit board that looks a bit like this one:


The distinctive features are the transformer in the middle, and the big cylindrical electrolytic capacitor to the right of it. If it has a switching power supply that operates down to 85V AC you should be able to power it from a DC-to-DC boost converter that produces a DC output in the range 120V to 350V DC from your 12V DC source.

DC-to-DC boost converters are available from eBay but I haven't seen one with an output voltage of more than 80V and you need at least 120V. You can't connect two of them in series unless at least one of them is isolated, and they normally aren't.

You would also need to ensure that your boost converter can supply the required amount of power. If your panel lights are rated for 12W I would use a boost converter rated for at least 20W, which corresponds to an output current of 170 mA (0.17 amps) at 120V DC.

Something like this would work: http://www.axiomatic.com/step-up-converter.html but it's rated for 2A output current, which is 240W - twelve times what you need.

So you need a DC-to-DC boost converter with 12V DC input and an output somewhere from 120V DC to 350V DC at 20 watts. It will be driving a switching power supply that supplies power to a LED panel. That's what to ask for. I've looked on Digi-Key and Mouser and they don't have anything suitable. It's a bit of a niche requirement. Good luck!

 

[kerris]

Hi and welcome to Electronics Point

Your LED panel lights are specified for an input voltage range of 85~265V AC. This strongly implies that they have a switching power supply inside. Can you see inside? Look for a circuit board that looks a bit like this one:

View attachment 14881
The distinctive features are the transformer in the middle, and the big cylindrical electrolytic capacitor to the right of it. If it has a switching power supply that operates down to 85V AC you should be able to power it from a DC-to-DC boost converter that produces a DC output in the range 120V to 350V DC from your 12V DC source.

DC-to-DC boost converters are available from eBay but I haven't seen one with an output voltage of more than 80V and you need at least 120V. You can't connect two of them in series unless at least one of them is isolated, and they normally aren't.

You would also need to ensure that your boost converter can supply the required amount of power. If your panel lights are rated for 12W I would use a boost converter rated for at least 20W, which corresponds to an output current of 170 mA (0.17 amps) at 120V DC.

Something like this would work: http://www.axiomatic.com/step-up-converter.html but it's rated for 2A output current, which is 240W - twelve times what you need.

So you need a DC-to-DC boost converter with 12V DC input and an output somewhere from 120V DC to 350V DC at 20 watts. It will be driving a switching power supply that supplies power to a LED panel. That's what to ask for. I've looked on Digi-Key and Mouser and they don't have anything suitable. It's a bit of a niche requirement. Good luck!

Hi KrisBlue
Many thanks for taking trouble to reply.
I have opened the driver which has a similar circuit board to the one shown. As I said the driver outputs about 38 - 41v when measured on a multimeter -it puzzles me why I would not be looking for something which produces similar voltage??? (but from a 12v supply rather than mains 220v) The light itself works on this voltage . . . . so why 120v-350v? (I wish I had listened more in physics lessons!)
Thanks again.

 

[KJ6EAD]

It may be easier, cheaper and/or more efficient to get lights that fit your form factor and output requirements that are designed to operate from 12VDC…unless you're committed to the 220VAC panels for some reason.

 

[KrisBlueNZ]

Yes, if you're prepared to replace the driver power supply with one that's powered directly from 12V, instead of converting 12V to 120~350V and feeding that into the existing driver power supply, that's tidier and more efficient. But that driver power supply is set up specifically to provide the current (300 mA) and voltage range (up to 42V) that the LED panel needs. If you want to replace it, the replacement needs to match.

That existing power supply is a universal AC mains-powered supply. It converts the high-voltage input down to around 40V as used by the panel. Why 120~350V? Because that's the worldwide AC mains supply voltage range that the power supply is designed to operate from.

You could also do what KJ6EAD suggests - replace the whole unit with one that can be powered from 12V. This may be the most economical solution.

A quick search on eBay turned up this unit which looks suitable. I can't vouch for the quality or reliability though.

http://www.ebay.com/itm/wdm-1x-powe...876?pt=LH_DefaultDomain_0&hash=item2a1d96ed6c

 

[kerris]

Thanks to both KJ6EAD & KrisBlueNZ - yes I understand. I have really searched for something suitable (& available) specifically for 12v and cannot say I have found anything we would be happy with.
Personal aesthetic preference interferes here with practicalities I'm afraid. (eg I found a number of 12v 'ceiling lights' - but many are very plastic looking and the more robust ones are rather old fashioned. The mains powered LED is white (many are brass coloured or nickel/stainless etc) and flat and very thin. Despite being designed to be recessed it is only about 15mm deep.( again something I have had difficulty finding in 12v).
I have spent some hours looking for 12v drivers and have emailed around 15 suppliers so I apologise if it seems I have not tried. Your 'quick search' has brought up something I did not find in hours of searching (including eBay). Many thanks. I accept the question re. reliability. I guess that the fact it suggests up to 12 x 1w means that powering one 12w light will leave no margin for safety. Still worth trying though. Thanks again.