loading

Introduction:
A voltage step-up is a circuit that increases the voltage. It can be AC/AC, AC/DC, DC/AC or DC/DC.
This voltage step-up is a DC/DC adjustable voltage regulator. Usually a voltage regulator is fed by a higher input than output voltage, for example 9V IN to 5V OUT. This circuit will take a low voltage (down to 0.7V) and step it up to adjustable 2.7-5.5V. Since it is a regulator, the output voltage will stay constant regardless input voltage (0.7-5.5V), as long as output voltage is higher than input. It cannot step-down, only step-up. Are there any ICs that can do both?

I build it for usage in this project:
http://www.instructables.com/id/Battery-Charger-Powered-by-Fire/

Applications:
This is a typical circuit for a battery-powered USB-charger, for example two AA batteries (3V) to power 5V USB. There are tons of DIYs how to create that. They are often hard-specified to 5V output power. This construction can be used in a range of other applications. Many electronic devices work within 3-5 V and often you want to power them by low voltage power sources.

Some input examples:

  • Solar panels
  • Generators
  • Batteries
  • Peltier elements (TEC/TEG modules)

Some output examples:

  • ICs
  • Displays
  • Motors
  • LEDs
  • Battery/USB charger

Costs:
All components cost me about 7€ but it's totally possible to find cheaper components!

If you want to construct this one, then continue reading!

Next Step: Specifications

Step 1: Specifications

I based this project on the Max757 IC. There are other DC-DC step-up modules but this one seems to be the best one for this purpose. It has high efficiency and low input voltage. If you want constant 3.3V or 5V output, then use Max756. Max757 is for adjustable output.
If you want less work and non-adjustable output, then you can buy a complete kit (version 3) with LT1302 IC at Adafruit. It´s also much smaller than my version. I bought it myself because it had higher output power than Max757, but I was not satified, I explain that in last step. If you need more power, then Max1771 seems to be nice (2-16.5V in and adjustable ?-12V out). It has a maximum power of 24W!

You can also buy an "emergency aa battery portable dc charger" on ebay and use the electronics in it. I bought one myself for about 1€ just for fun because it was free shipping from China to Sweden. That uses some kind of joule-thief I think, not very good replacement for this project but quite powerful compared to its size.

Full specification for max757 can be found in this pdf:
http://pdfserv.maximintegrated.com/en/ds/1167.pdf
  • Minimum start-up voltage (@10mA load): 1.1V
  • Minimum start-up voltage (@300mA load): 1.7V
  • Minimum operating voltage (@20mA load): 0.7V
  • Input voltage range: -0.3 to +7V
  • Output voltage range: 2.7 to 5.5V
  • Maximum output load (@input voltage=2V): 200mA@5V, 300mA@3.3V
  • Maximum output load (@input voltage=1V): 50mA@5V, 75mA@3.3V
  • Efficiency: Max 87% (depends on input voltage and output load
  • Quiscent current (@no load, 2V input, 3.3V output): 60µA
  • Operating temperature: 0ºC to +70ºC (Using Max75_C__)
For more info, please see graph images.

Physical size of final board (WxLxH): 32x47x27mm (without inductor, height=17mm) 

Next step: Materials
<p>Can any pre-made kits be used? Such as this one? <br><br>http://www.miniinthebox.com/1pcs-usb-dc-0-9v-to-5v-voltage-step-up-boost-module-blue_p1654669.html?currency=CAD&amp;litb_from=paid_adwords_shopping&amp;utm_source=google_shopping&amp;utm_medium=cpc&amp;adword_mt=&amp;adword_ct=104789748001&amp;adword_kw=&amp;adword_pos=1o1&amp;adword_pl=&amp;adword_net=g&amp;adword_tar=&amp;adw_src_id=1364803665_328601761_24197849641_pla-163015348374&amp;gclid=CNGM2827hMwCFVdahgodCSoKPA</p>
<p>That one is all over eBay but its problem is it is hardwired to 5v output.</p>
<p>I am getting the output voltage same as that of input.Why??</p>
<p>where I could get such inductors ?</p><p>can you help me ?</p>
<p>When I'm looking at the specifications for it, the temperature limit is 70 degrees celsius. Isn't that quite low to use in context with teg's? Atleast if you'd have it within one unit.</p>
<p>great project</p><p>can i place your project on my website.</p><p>i'm working on a website which is related to electrical projects.</p><p>i also mention your name, link and other info.</p><p>plz reply</p>
<p>Wouldn't this be a way more efficient Joule Thief like circuit? Even at 86% efficiency that is far superior to a JTs. </p>
<p>Bro can i ask, is this really working below 0.7v input supply? because im having trouble with my module, it only generates 0.2v :/</p>
According to the paper it should but it depends on the output load. Try measure voltage with no load or find an adjustable voltage source and start at higher input voltage. Then lower it and see where it drops. If that doesn't work then the circuit is either damaged or wrong.
Hello! Thanks for this instructables :) <br>I've a question: Why on the scheme on pin 6-2 there's a P1 and R1 but on the &quot;shopping list&quot; and the board scheme there's also P1R1 and a P1R2? <br>Thanks!
Hi,<br>I had to think a bit and now I remember! It&acute;s actually in the description in some way. In the layout i have simplified P1 to make the drawing easier to understand. But P1 in the drawing consists of P1+P1R1+P1R2 in serie. P1R1+P1R2=57Kohm and P1=100Kohm. That create the correct interval of 57-157k&Omega; instead of 0-100Kohm if you just use P1.<br><br>That make sense?
I want to make this circuit but it is confusing in p1 + p1 r1 + p1 r2 in series and how to join in series in drawing and values of p1 + p1 r1 + p1 r2 plzz give me reply
<p>Hi,</p><p>I am new here.</p><p>Can i use this with multiple 18650 batteries in parallel ?</p><p>If changes, would you please share ?</p>
<p>thanks for giving such a beautiful and knowledgeable details............</p>
I need a item like this to detect .7v-5v no more load then 20ma and trigger a 5v relay
Is there a way to make this detect 0.7v and less then 20ma and output 5v
<p>sir i am thinking to make this project, to make a portable 5v charger for my android phone with my 6v lead acid battery may i ask if i can change the IC maybe LM2623 by T.I. or LM2621 by T.I because it can go input from 0.8v to 14v? please reply thanks</p>
<p>are there any replacements for the IC</p><p>because there arent any in my electronics store ..</p>
<p>did you connect anything to LB1</p>
<p>need some help i built the above schematic but it didtn work was wondering if you had any advice</p>
<p>HI Joohansson,,,I'm doing this as my miniproject. But my faculty is asking me to simulate this circuit first. So can you please suggest me any simulation softwares which has MAX757 IC and IN5817 diode.I tried with ORCAD PSPICE I could not get the schottky diode library there.</p>
Sorry, I have no experience with simulation software.
Oh ok ok,,,,,thanks for your immediate response..
<p>HI Joohansson,,,I'm doing this as my miniproject. But my faculty is asking me to simulate this circuit first. So can you please suggest me any simulation softwares which has MAX757 IC and IN5817 diode.I tried with ORCAD PSPICE I could not get the schottky diode library there.</p>
<p>I don't know if someone already told you that LT1073 does Step-Up and Step-Down. Just telling because you asked if there is an IC that can.</p><p>Greetz and thank you for writing this. :)</p>
<p>i want to get all the accessories of this project ,from wher I can ourchase in Pakistan</p>
<p>i want to get all the accessories of this project ,from wher I can ourchase in Pakistan</p>
<p>i want to get all the accessories of this project ,from wher I can ourchase in Pakistan</p>
<p>Found Step-up/Step-down IC's while looking around for 757's :D<br><br>The MAX167x series! </p><p>http://www.alldatasheet.com/view.jsp?Searchword=MAX167</p>
Nice! Only 300mA output current but still quite useful for some applications like LED driver.
My mistake, it support even higher current. 500mA at 3V, seems to be better than the 757.
<p>Yeah :D Seems they discontinued the 757 in favour of it. <br>It was a fortuitous find :3</p>
<p>P.s. Love the campfire TEG btw! I'll be adapting it into something similar for a college project/infinite music from my phone while camping :3</p>
Cool!
<p>You mentioned - </p><p>Since it is a regulator, the output voltage will stay constant regardless input voltage (0.7-5.5V), as long as output voltage is higher than input.</p><p>Shouldn't it be that &quot;as long as the input voltage is higher than output&quot;?</p><p>By going what you mentioned, so if I have a 2.4V battery cell, I can power a 5V load, even if the cell drops to 1.8V after sometime? It will still output 5V and have the load running.</p><p>Thanks.</p>
<p>You mentioned - </p><p>Since it is a regulator, the output voltage will stay constant regardless input voltage (0.7-5.5V), as long as output voltage is higher than input.</p><p>Shouldn't it be that &quot;as long as the input voltage is higher than output&quot;?</p><p>By going what you mentioned, so if I have a 2.4V battery cell, I can power a 5V load, even if the cell drops to 1.8V after sometime? It will still output 5V and have the load running.</p><p>Thanks.</p>
A better description is &quot;as long as input is lower than output&quot;. 1.8V should be fine as long as the output current is not too high. I think I have a graph you can look at or it was in one of my other instructables.
<p>If I needed to supply up to 1A output at 5.5V and a supply (battery) of 3V minimum, would this circuit be able to handle it? the Efficiency graph only goes up to 500mA, so I think I would need another regulator to do the job. Do you know of a variable output regulator that would work?</p>
<p>i constructed the circuit on a breadboard, but on testing, it only produces 0.8V output for an input range of 1-6V. Please how do I know if the issue is with the connection or if the ic is damaged. Thank you. </p>
Hard to tell. I will have to do a verification of the circuit. I will write here again when/if I have time to do that.
Ok. Thank you.
<p>Hi, I am trying out this project. I was able to find all the parts except the Max757C. Please help me as to what to do? I was able to find 756C. What should be the circuit changes and is there any equivalent IC. Please help me. I really need more information. Thank you in advance. </p>
You might have already found a converter that can boost, and buck. In case you haven't, you should take a look at this: http://en.wikipedia.org/wiki/Single-ended_primary-inductor_converter . It's called a SEPIC converter, it can even go from buck to boost, or vica versa, without an interuption in the output power, you won't even notice when it crosses the input voltage. <br> <br>Thom
Thanks, I might try that circuit some day =) Looks easy to build.
Joo where did you happen to find theses maxim 757 ICs I cannot find them anywhere
https://www.elfa.se/elfa3~se_sv/elfa/init.do?item=73-076-31&amp;toc=0&amp;q=max757
Thank you very much for the link! ( is it in German?)also would the product ship from Germany or where ever it comes from ?
It was Swedish. You can choose other countries:<br>https://www.elfa.se/elfa3~se_sv/StartPage.do?ignorecookie=true
Hello, I appreciate your contributions but my question is, it possible to build a DC-DC step-up with input voltage of 6V/ 2Amh to out-put of 12V/7Amh if your answer is yes, email me kingjoejoe29@yahoo
You're exceeding the maximum rating on the boost switch output (pin 8, LX). Somewhere between 5 and 10,000 volts, it will fry. At 5.5V out, you're probably OK but if somebody wanted higher voltage, it would be cool to put an extra stage in there to take the extra voltage so you could get more out.

About This Instructable

177,317views

780favorites

License:

Bio: I like to design, construct and experiment with both old and new technology, especially when it includes mechatronics. I'm also devoted to photography, computers ... More »
More by Joohansson:Fan Powered by any Heat Source Super Light Quadcopter Thermoelectric Rotational Ornament 
Add instructable to: