Dc-Dc Step-up converter with low input voltage dilemma

Reply

  #1  
Old 07-29-11, 08:45 PM
Member
Thread Starter
Join Date: Jul 2011
Location: CA
Posts: 4
Received 0 Votes on 0 Posts
Dc-Dc Step-up converter with low input voltage dilemma

Greetings,

I am looking for a small-size Dc-Dc converter module that is able to handle very low voltage inputs and high amperage inputs. Something with these rough specs:

Vin: 0.8-3V [Although anything above 1.5V would do in a pinch]
Iin Max: 8-9A
Vout: 5-20V [Adjustable]
Iout Max: 2A

I have been searching for such a module for some time, with no avail. I have been able to find suitable Surface-Mount chips, such as MAX863 Chip, but I don't have enough experience/expertise to complete such a module.

Have any of you heard of such a module? Or have any suggestions on how I might accomplish such a step-up? If it helps, I'm using this for a low overall power, ~8W, solar module.

Kind regards,

CptZeus
 
Sponsored Links
  #2  
Old 07-30-11, 06:08 AM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,967
Received 3 Votes on 3 Posts
Welcome to the forums! If you have searched, the identical unit may not be out there. Let us know what your intended purpose is for this. There may be work arounds or alternative means of achieving your goal.
 
  #3  
Old 07-30-11, 04:27 PM
Member
Thread Starter
Join Date: Jul 2011
Location: CA
Posts: 4
Received 0 Votes on 0 Posts
Thank you, well I have a small solar circuit with two 6" cells putting out ~8 Watts in direct sunlight, with a combined voltage of 1V. By desire is to boost this voltage to be able to charge a satellite phone, and some other comm equipment.
 
  #4  
Old 07-30-11, 04:41 PM
GregH's Avatar
Super Moderator
Join Date: Jan 2001
Location: Manitoba
Posts: 10,066
Received 19 Votes on 19 Posts
You need to keep in mind that nothing is ever free!
The percentage increase in voltage you may get from boosting the voltage you will see a corresponding decrease in output current.

To boost 1 volt @ 8 watts would give you 12 volts @ .6 watts, less any circuit losses.
 
  #5  
Old 07-30-11, 05:08 PM
Member
Join Date: Oct 2008
Location: New England
Posts: 10,483
Received 33 Votes on 30 Posts
Greg,
The watts stays about the same, less the circuit losses. It is the current you are referring to, ie 0.6 amps give or take, mostly take.

Cpt, the chip you showed would be one approach, but there should be plenty of inexpensive regulators out there in the range of what you want. Google solar cell regulators and see what you find.

Bud
 
  #6  
Old 07-30-11, 05:45 PM
Justin Smith's Avatar
Member
Join Date: Dec 2010
Location: Cressona, Pa, USA
Posts: 2,546
Received 0 Votes on 0 Posts
You could always get a solar panel that puts out more volts.
 
  #7  
Old 07-30-11, 05:55 PM
Member
Thread Starter
Join Date: Jul 2011
Location: CA
Posts: 4
Received 0 Votes on 0 Posts
Thanks for all the responses guys!
Justin, I'd love to do that, but I'd like to keep the module size minimized as much as possible so that it can be somewhat portable.

Bud, that chip is what I keep jumping back too even though it's slightly over-spec, but I have no idea how to make the board for it with all the resistors, capacitors and fun stuff. Thanks for your suggestion, I'll definitely Google that. BTW, you wouldn't know anything about designing PCB's would you?
 
  #8  
Old 07-30-11, 06:25 PM
Member
Join Date: Apr 2007
Location: Near Buffalo, NY
Posts: 4,239
Received 0 Votes on 0 Posts
You're looking for a "DC Boost Converter". I doubt you'll find what you're looking for as an off-the shelf device rated for those voltage, though. You may have no choice but to build it yourself. Even then it could take a couple of days of bright sunshine to recharge a phone.
 
  #9  
Old 07-30-11, 06:54 PM
Member
Join Date: Oct 2008
Location: New England
Posts: 10,483
Received 33 Votes on 30 Posts
Oh yes, but it has been a very long time, actually back when they actually built everything out of components. Today they configure a chip and compared to what you could build, if you can find a chip you are way ahead.

This is National LM2621 chip and the provide the associated circuit.
LM2621 - Low Input Voltage, Step-Up DC-DC

It's a bit below your description, but just an example.

Keep searching.

If you come up with a circuit you want to try and the components are reasonable, the electronic shops (RS) have a vector board full of tons of holes, and flee clips you push into the holes. Components mount on one side and you wire the other. Actually fun. Soldering iron, volt meter, and some hand tools, but there is nothing wrong with learning about solar panels. They should be around for a few years.

Bud
 
  #10  
Old 07-30-11, 07:29 PM
Member
Thread Starter
Join Date: Jul 2011
Location: CA
Posts: 4
Received 0 Votes on 0 Posts
Thanks Bud, I've seen that one before, but I'll keep hunting for the part/attempt making the board. I'm very much enjoying learning all the new stuff!

Rick, thanks! I think your absolutely right for all the non-phone stuff, but the battery on sat-phone is 2800mAh, so I thought I'd be able to charge it in about 2 hours, here's the math:

Assuming a perfect sunny day,
1V * 8A = 8W = 3.7 * 2.15A
2.15A = 2150 mAh
2800 / 2150 = 1.30 hours
Assuming around 40% inefficiency, (since I'll be using another Dc-Dc step down, after the needed step-up), that would be around two hours.

...Or maybe I am missing something?

As for the other stuff to fully charge it would take almost half a sunny week, since some of it requires much higher voltages (12V/16V/20V), so I was more wishing of extending the battery life by maybe 20%?
 

Last edited by CptZeus; 07-30-11 at 08:01 PM.
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: