Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Help on simple DC/DC convertor(step up)~

Status
Not open for further replies.

him27hk

New Member
Hello everybody, i am a newbaby to electronics~ soory for my poor english:p

I need help on a DC/DC converter, 3v in and 12v out convertor, i hope no IC is required, as simple as possible(may be using wire-wound core). The load is around 750ma, 1a max, and no need to regulate.

Thx everyone~
 
Hey, I'm just a novice too, but I looked into somthing like that a few weeks ago and came up with no simple solution except to buy an expensive, premade converter. There are ICs avalible that will supply upto 500ma, but I couldn't find any that would go over that current. I did find an artical on building a DC/DC converter that was interesting, but way over my head as a beginner project. I have the page saved on my home computer, i'll try and remember to post it tonight.
 
that's a pretty big conversion ... 12 watts is 4a at 3v, plus another 30% for overhead, so you're lookin at 5 amps from your voltage source, it'll take some good batteries!

check out linear.com as well as national.com ... you'll need an IC; an smps controller, as well as a handful of other components ... since regulation isn't a big deal for you, the components need not be critcal in value, "close enough" will work fine.
 
Here is an artical on building a SMPS that I thought was kinda interesting. It deals with higher voltage then what you need, but I would think if one knows what he's doing you could modify it.

**broken link removed**
 
You can get modules for this but they're expensive and I've never seen one that can convert 3V to 12V.

The next logical choice would be an IC but I've not seen any that will work as low as 3V.

I've used this switcher before to set up 12V to 24V, it should work down to 3V with 12V output but it will need some modifications.

Try the following:
R1 = 100R
R2 = 4.7k
D1 = 12V
L1:
Try two times 8 turns of 22SWG wound bifilar style (two coils in parallel) on the driver and 6 of 35SWG on the feedback. You might (probably) need a secondary add another coil consisting of 18 turns of 18SWG and wind it the in the oposite direction to the other coils.

I can't promise this will work but it's worth a go.
 

Attachments

  • Switch.pdf
    73.7 KB · Views: 1,579
  • stepup.PNG
    stepup.PNG
    18.2 KB · Views: 7,174
Help on simple DC/DC convertor(step up)

Hi all
Please consider this IC MC34063A . the datashhet can be downloaded from STonline.com

the application is simple and low component count with regulation possible .

sarma
 
that chip is also availble from TI ... the only thing I don't like about it is the peak current limit programming resistor (Rsc).

it takes fractional ohmage to set, which either requires some expensive resistors or a PCB with a deliberately small long trace
 
I know it's a pain but five one ohm resistors don't take up that much space, not the smt types anyway.
 
hi,

I've used this before: **broken link removed**

Although it requires a minimum of 5v on the input and can only provide 90mA out...its a start. I'd suggest using CMOS 4069 for the chip, and adding a MOSFET driver. As long as the Inductor can cope with 5A+ continuous, it sohuld work fine, and its a pretty small circuit that doesn't require any wound components...as well as providing some regulation. I know you said you didn't need regulation...but otherwise it'll swing between 8 and 15v (thats what mine did). Its also surprisingly efficient for what it is, and small.

Well I tihnk I'm done selling that idea, gotta love EDN's design idea's. An alternative would be to use a 555 timer, and a cockroft -walton multiplier...althoughagain it'll need a MOSFET to drive it, and is probably a waste of time regarding efficiency. I didn't want to repeat what others have said, they're pretty good idea's, especially for the quick and dirty approach.

I must say though, its gonna be tricky working at 3v 5A...I didn't know 3v bats could kick out that sort of current...internal resistance...

Blueteeth.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top