DC-DC step-up converter

[sasha]

Hi all,
I am planing to make DC-DC step-up converter. 12V-15V input and
20V-24V output. Current needs to be regulated up to 20A on output.
It will be used for hydrogen generator.
If You have useful schematic or suggestions please post it here.
Thanks!

 

[Sch3mat1c]

If it's doing it by electrolysis, why not just use approx. half as many cells, using wider plates (to carry more current)?

Tim

 

[sasha]

The cell resistance is greatly dependent on electrolyte temperature, and to have constant flow of hydrogen the current need to be constant and voltage variable. That is why higher voltage is a must. The power source is 12V car battery.
Regards.

 

[haldor]

In that case it would be alot cheaper and simpler to just use two car batteries.

 

[sasha]

Unfortunately two battery trick can't help because of changing resistance of the cell. Voltage needed for operating cell is ranging from
7V to 18V depending of electrolyte temp. and to have constant flow of hydrogen current needs to be constant.
Regards.

 

[Sch3mat1c]

Why constant?

 

[haldor]

Unfortunately two battery trick can't help because of changing resistance of the cell. Voltage needed for operating cell is ranging from
7V to 18V depending of electrolyte temp. and to have constant flow of hydrogen current needs to be constant.
Regards.

How much current do you need?

Use two batteries and make a constant current source out of a power transistor, a diode and a couple of resistors.

Here is a set of links to get you started.
http://www.discovercircuits.com/C/constant.htm

Phil

 

[sasha]

Hi guys,
Thanks for link, Haldor. I think I will find something useful on the site.
Have my eye on buck convertor and with some mods should be able to output 20A. Regarding suggestion for linear power supply,
two problems: 1. input voltage is limited to 12V (hydrogen gen. is installed on the truck) and 2. power dissipation is huge (24V in, 7V out
@ 20A = 340W )
Regards.

 

[li_gangyi]

woah wada u want a truck hydrogen gen for?? Could be dangerous u know...20A for a boost converter is also not gonna be easy...super thick cables...super explosive shorts...might wanna go slow here...

 

[sasha]

Dangerous, Yes but I am building only power supply. Somebody else have truck with HG. And I think they now what they doing .

 

[Bakmeel]

For a schematic, surf to the National Semiconductor website, www.national.com and go to the power section. Fill in the design requirements, and click "Create Schematic"

The design generator got a bit stuck on your amperage, but try to fill in some lower current requirements, and then beef it up a bit.

Bouke