Any driver that could step down 7.4V to 3.2-3.8V?

[FNinjaP90]

As the topic suggests. I would like to use two 3.7V PILA 300S batteries end to end to power a 3.2-3.8V 2A laser module, but instead of running them in parallel, it would be easier to run them in series but with a regulated step down circuit. Is there any driver that could do this?

 

[Senses]

I dunno, you may want to check out downbody driver from shoppe

 

[LEDninja]

Micropuck. Look under buck or boost buck wiring.
http://www.leddynamics.com/LuxDrive/content/Page_Micro_App.html#2009 as a Buck/Boost Driver
LEDsupply and Cutter sell them
http://www.ledsupply.com/
http://www.cutter.com.au/proddetail.php?prod=cut201

Also check the Sandwich Shoppe for buck/boost-buck sandwiches
http://home.comcast.net/~theledguy/technical/converter_comparison/index.htm
http://theledguy.chainreactionweb.com/

 

[thehappyman]

As the topic suggests. I would like to use two 3.7V PILA 300S batteries end to end to power a 3.2-3.8V 2A laser module, but instead of running them in parallel, it would be easier to run them in series but with a regulated step down circuit. Is there any driver that could do this?

Fist of all, if use use the batteries in "series" you will limit the availble current, to the laser module, to half of what would be available if the batteries are wired in "parellel".

But if you want the batteries in series, here is an easy, cheapo way to do it.
Measure how much current the array draws, and divide that into the voltage you want to "drop".
In this case you want to drop about 4 volts from the 7.4, leaving 3.4 for the laser module. For example, if the laser module draws 1 amp, Using ohms law (R =E/I) you get 4 volts/1 amp, = 4 ohms. So, putting a 4 ohm resistor in series with the battery and laser module will work for you. And you will need a 5 Watt resistor (P = I x E or 1 x 4 = 4 Watts) to dissapate the heat.

El cheapo yes, will it work, yes, but it isnt super regulated.
But you dont need that.

 

[abvidledUK]

Elementary, my dear Ohms...

 

[2xTrinity]

Are these PILA batteries CR123 sized? If so, you could just buy a 17670, which will give you a bit more energy than 2 CR123 in parallel. However, the advantage of two in series a regulated stepdown is that the brightness won't start to diminish if the battery voltage goes below 3.7 volts on each of your cells (if you have a buck circuit, and input supply voltage drops below output voltage it direct drives -- this will never happen with two cells). Note you lose this advantage if you use the "big 5 ohm resistor" method.

 

[thehappyman]

The Only advantage to the resistor method is that its just one cheap, small component.