Which Chip is best backbone for single Li-Ion input?

[CampingLED]

Think I should design/build my own driver for a single Li-Ion battery input to get at least 1A output.

Requirements:
- 3.6/3.7 V input (Fully charged and under load/drained 4.5-2.0V input)
- 1A output (up to 1.2A will be fine)
- High efficiency
- Should drive most 3W+ LEDs
- Multi-modes not required
:thinking:
Will appreciate your comments / recommendations.

 

[Drewfus2101]

http://www.candlepowerforums.com/vb/showthread.php?t=192925

The 1050mA output regulator would work. As long as the input voltage is 0.6V over whatever the LED voltage needs to be it will see 1050mA current. Kinda confusing I know.

So for Cree Q5s, this driver isn't the best since they have such a high forward Voltage. For example, they need something like 3.7V to see 1000mA current. So to get a constant 1050mA output you would have to provide this board with 4.3V. A single Lithium Ion battery can't do that very well.

Now if you were using a SSC P4, which has a lower Vf, at something like 3.4V at 1000mA, so this board would only need around 4.0V to see the 1050mA, then you would be alot better off.

So with these boards, your emitter will matter. But read through that thread and it will help you make your decision.

 

[chimo]

If you are doing this for the fun/enjoyment/challenge/experience - great! If not, you can find a bunch of great products that will meet your requirement at the Shoppe.

Looks like you will need a buck-boost.

Other things to consider:
- low battery voltage protection
- open circuit protection

Linear Tech has some nice high-efficiency chips.

You can find lots of info at Newbie/Jarheads site.

 

[CampingLED]

Tks Drewfus2101, I have been watching and participated in your thread. Not quite what I want though.

Tks Chimo, Newby/Jarheads' site is the one that inspired me to try this out. If I remember correctly I also found his site earlier on the day that I first found out about the CPF. The TPS61050 from Texeas Instruments looks like a good option, but I am not sure about the availability in my country.

 

[Supernam]

http://theledguy.chainreactionweb.com/index.php?osCsid=0107616aca9c2f2471a827a254dd8892

Check out GD series. GD1000 is probably what you're looking for.

 

[TorchBoy]

Think I should design/build my own driver for a single Li-Ion battery input to get at least 1A output.

How much weight should we be placing on that "design/build your own driver" bit? Do you want to make something yourself from the ground up or would you be happy buying something off the shelf? If the latter, there are some good suggestions above.

If the former, you could use an LM334 (3 terminal adjustable current source) with a couple of resistors and a capacitor to drive a power transistor (or even better, a low resistance/low voltage drop MOSFET). It's certainly an interesting project - you can get to the point where you're making the set resistor out of a coil of ordinary wire. However, one trouble I found was when the battery went flat the LM334 would try to conduct more current than was really healthy for it, to try to keep the transistor in regulation. If you're using a protected Li-ion cell that might be the ideal solution.