High power led boost converter

[upsidedownorangejuice]

I'm looking for a appropriate boost converter to supple a 39 volt LED @82.7W using 2100ma the battery i have concidered has 39 Wh at 4.6volts
Bit of a tough one here if not practical im also considering getting a higher voltage battery (portible drill battery @ 18volts or 24)
was wondering if any one could suggest how i get this done keeping in mind small would be nice but i dont mind having to carry

[dannyf]

I would consider a fly back converter, possibly push pull.

[georges80]

To boost to ~40V at 2A I'd suggest you look at using the 18V pack. Even at 82W output and about 87W input (assuming reasonable efficiency in the driver) you have about 87W/15V (discharge pack) = 5.8A.

Unless you have experience designing boost drivers at that output level, it's a reasonable challenge, especially the PCB layout and thermal path.

cheers,
george.

[Alex Eisenhut]

4.6V? That's an odd voltage, what kind of battery is this?

[upsidedownorangejuice]

It is a custom battery a high performance cave light manufacture uses
Think your right an 18volt would be the way to go if not in parrell

[ovnr]

Hmm... That doesn't by any chance happen to be a Bridgelux Vero 29 LED?


As has been said, try to start out with as high a battery voltage as possible. There are some LED drivers from Linear that should be up to the task - I'll have a look around later, in a bit of a hurry right now.

Edit: Here's some you can look at. I'd probably go with the LT3755 or LT3795.

[Seekonk]

I was just doing the same thing at my camp, a little less power.  At a wharehouse store I found  18W flush mount lamps for $14 after power company instant rebate.  The LED took about 41V and the camp is 12V.  I'm fond of these 150W boost converters on ebay that are less than $5 shipped.  They boost up to 35V, limited mostly by the 35V cap.  I could have removed the cap, I've been soldering for 40 years but these cheap thru hole boards with no lead solder make that risky.  I would prefer just to bend the cap and break it off.

Anyway, I didn't do any of that.  The toroid has enough space under it, if not it can be soldered and lifted.  I added  a separate seven more turns of wire with a high speed diode and filter cap.  This was added in series with the output of the 150W boost converter.  I added a 1K pot in series with the 10K pot on the board.  This allows me to vary the brightness from 1/4W to 10W.  That is almost too bright for the bathroom.  Since I am no where near over current on the LED, voltage control is only on the boost converter.  It does not sense the total voltage on the LED.  I could have done that or sensed the returning current for constant  current control.  This is a quick cheap solution for some of those odd voltage LED.  I have some 91V MR16 spots that i will be tryint that with next.

When I get some time I will try rewiring the factory converter that came with the lamp.  I should be able to use the output winding as the boost inductor.

[mazurov]

For this power level it is easier to change supply voltage to be as close to Vf as practical. This will increase efficiency and help with dimensions (you want it portable, correct?). Take 2 LEDs instead of one and drive them separately at 1A each (the Vf will be lower too). Meanwell LDD H-series drivers are available up to 1A (LDD-1000H), Vin up to 55V and 2-ish volts input-output delta minimum if you want good regulation. Design your battery accordingly - the LDD is a buck driver so you'd need ~Vf+3V. Ryobi 40V lawnmower LiPo is 110W, weighs about a kilo and can be carried in one hand.

[upsidedownorangejuice]

It's like n350 dollars for a 40v rioby battery i wish i was made from money 
but yeas the benfits of been close to voltage wood be verry good

[Richard Head]

I would consider a fly back converter, possibly push pull.

Flyback and push-pull are completely different topologies.

Flyback is boost derived and push-pull is buck derived.

[mzzj]

I would consider a fly back converter, possibly push pull.

Flyback and push-pull are completely different topologies.

Flyback is boost derived and push-pull is buck derived.

So what? Both are perfectly workable alternatives.

[Richard Head]

I just re-read the post. I misunderstood Danny's comment. Apologies.
I see he is suggesting one or the other.

[mazurov]

It's like n350 dollars for a 40v rioby battery

Depends on the dollar. IIRC they want ~120 US dollars for it here in the states. I can buy a leaf blower with battery included for about US$200.