buck converter help needed

[xpitxbullx]

I'm looking to find (or build) a converter to convert 15.2V to 12V. I want to run 'Juice' 3.6V cr123a rechargeable batteries in my ufokillerz mini-HID but they are a little to strong for the max input voltage for the ballast (12V max).

I don't want to build it but if I have to, I can. If someone can give me the ratings for the diode, inducer, capacitor and resistor (I'm think thats what parts are needed). I'm just learning.

I'm just looking for the simplest solution so I can use my rechargeables.

 

[HarryN]

The buck converters usually used in LED lights, which is what I am more familiar with, are usually current limiters, not voltage regulators.

I have seen voltage regulators in the Digikey and maybe Newark electronics. Auto makers commonly use regulators like this, but I think most of them are LDOs, which will dissipate the excess voltage as heat.

Some sites to look at are International Rectifier, On Semiconductor, and perhaps National Semiconductor.

 

[xpitxbullx]

There are different types of buck converters. Which one will meet my needs easiest?

 

[andrewwynn]

go here you can plug in the voltage in and the voltage and current out and it'll show you a part, it will tell you the exact components needed to build it, and even has some pre-fab cktboards depending on the solution it finds.

-awr

 

[Lynx_Arc]

I am guessing you are getting 3.8v from each cell would it be easier to just run it off 3 cells at 11.4v with a dummy cell and when voltage sags down some drop in a 4th cell?

 

[NewBie]

This is a pretty efficient converter:
http://focus.ti.com/docs/prod/folders/print/tps40071.html

A prebuilt eval board is available here for 49.00:
http://focus.ti.com/docs/toolsw/folders/print/tps40071evm-001.html

Software for tweaking the eval module is here, and it will suggest parts to you:
http://focus.ti.com/docs/toolsw/folders/print/tps40k-sw.html

 

[Sway]

This is wonderful information I need one also for my 3x18650 Li-Ion MINI HID.

Here are the spec's for the B10N008 ballast.

Absoulte Max. Instantaneous Voltage...11.8V
Safe Operating voltage 11.0V
Input Voltage for 10W output 10.2V

All this information can be found in the pdf

Later
Kelly

 

[xpitxbullx]

I ordered a free sample of the TPS40070. I'm assuming this is already pre-fabbed. I just need to learn how to adjust the Vin and Vout.

Thanks for the help.

 

[xpitxbullx]

Damn. They just sent me the chip only. It's too small for me to use. I'll need someone to make it for me.

 

[andrewwynn]

xpitx.. no doubt on the size, huh? i was completely shocked when i first got my SOT-23 chips.. however with some patience, a magnifier and believe it or not a crappy RS soldering iron who's tip was as big as the whole chip, i was able to solder up plenty of SMD devices.

in the mood of christmas.. if you mail me the chip i'll put it on a proto board which will make it 100x the size (about the size of my thumbnail) with regular pins you can plug right into a breadboard. It only takes me about 3 minutes to do.. send an SASE with the chip and $5 to cover the proto board.. and I'll put it on and send it back the same day i get it.

-awr

flashlight at rouse dot com is my mail for shipping details.