Dual USB Charger With Switching Regulator

This is a portable USB Charger. It uses a high efficiency switching regulator that runs at 85 - 94% efficiency depending on input voltage and load.
It takes an input voltage from 8 to 16 volts and can run from anything from a 9 volt battery to a car battery.
It has 2 USB ports and easily charges 2 power hungry devices at once.

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Step 1: Parts & Tools

Parts

LM2678 - 5V Switching Regulator
STPS10L25D Schottky Diode
22µH 5A 15mΩ Inductor
470µF 16V Electrolytic Capacitor
120µF 16V Electrolytic Capacitor
100nF Film Capacitor
10nF Ceramic Capacitor
Dual Type A USB Jack
5.5 x 2.5 mm Barrel Jack
5.5 x 2.5 mm Barrel Plug
3x2x1" Project Enclousure
Slide Switch
Protoboard or PCB
LED & Resistor (Optional)

Tools

Soldering Iron
Dremel
Wire Cutters
Needle Nose Pliers
X-Acto Knife
Screw Driver

monkizzle says: Aug 20, 2012. 5:45 AM

the link for the 10nF Ceramic Capacitor point to the same thing ask the 100nF Film Capacitor. Does anyone know the right digikey product number for the 10nF Ceramic Capacitor?

rocketman221 (author) in reply to monkizzleAug 20, 2012. 11:26 AM

The link is fixed now.
478-4862-ND or any 10nf ceramic cap will work.

luketanti says: Jan 18, 2011. 6:35 AM

Hi Nice instructable!! I am planing to make a power supply for and old computer (Intel celeron 553Mhz) and wish to use this as the main 5v supply. I will connect this to a car battery. To use the full 5amp usage do I have to adjust the circuit please??

rocketman221 (author) in reply to luketantiJan 18, 2011. 3:15 PM

For a full 5 amps you need a different inductor.
Use a 10uH inductor with a current rating of 10A or more.
Digikey # 732-1418-ND would work.

It also needs a larger output capacitor 330uF would work.
The diode will need a small heat sink, the regulator might need one too.

If you are running it from a car battery be sure to put a fuse on the battery.

rocketman221 (author) in reply to rocketman221Jan 18, 2011. 3:18 PM

Edit:
That's Digikey part number M1400-ND Not 732-1418-ND

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=M1400-ND

luketanti in reply to rocketman221Jan 19, 2011. 3:05 AM

Thanks Very Much. I'll try with those changes.

luketanti in reply to luketantiJan 24, 2011. 8:24 AM

Hi. I tried with those specs you said and my voltage output is 8.5v to 9v. I am sure I have the 5 volt version. What could be wrong. I tried it with a pc power supply from the 12v rail. I think the output voltage should be nearly 5 volts right? Can some on help please.

luketanti in reply to luketantiJan 24, 2011. 10:41 AM

Another thing is I found another circuit similar to this bu instead uses 22uh inductor and 4 extra capcitors. It says that it is good to give 5 amp.
here it is.

luketanti in reply to luketantiJan 24, 2011. 12:00 PM

I am sorry to replay again but I want to tell you that I tried a different inductor. Instead of 10uh I used a 22uh and now the voltage with no load is 6.5 volts. When I connect a small fan the voltage goes down to a steady 5 volts just as I want and I thought it was ok but when I tried to connect a wireless bridge rated at 5 volts 1 amp the voltage went down to 2.5 volts. What is the matter it. Can you help me please. Could the diode be the cause. I am using a 1N5818 diode because I can not find to buy it in my country. Thanks.

rocketman221 (author) in reply to luketantiJan 24, 2011. 3:05 PM

The 1N5818 diode you used is only rated for 1 amp, and has a drop of 550mV to 875mV.
The diode I listed is rated 10 amps and has a 460mV drop.
Try to find one with similar ratings. The lower the voltage drop the better.

The schematic you used it fine. The inductor should be toroidal otherwise it creates interference, in that case the feedback line should be kept away from the inductor.

Switching power supplies need a load, mine seems fine with just 10mA from the LED. With a load the power supply should be 4.9V - 5.1V

luketanti in reply to rocketman221Jan 25, 2011. 7:25 AM

I replaced the diode with F5KQ60 and added an LED with the output and not the volatge with no load is between 5 volts to 5.5 volts. That is acceptable. But now the new problem is when I apply a load of more than 120mAh the voltage drops instantly to 3.4 volts. I can not find the cause may be you can help me?
Thank you very much. You have help me alot.

rocketman221 (author) in reply to luketantiJan 25, 2011. 11:32 AM

The diode should be OK.
What is the current rating on your inductor. For a 5A output it should be rated at least 10A.

luketanti in reply to rocketman221Jan 25, 2011. 1:08 PM

The inductor is from coilcraft Part number is DO5040h-223MLB. This is the specs
Inductance 22uH
DCR max (mOhms) 24
SRF typ (mHz) 13
Isat (A) 11.8
Irms (A) 5.7

And I am noticing that the output capacitor 330uf 16v is getting bloated. I do not know why. This is the second one I changed and the same results.

rocketman221 (author) in reply to luketantiJan 25, 2011. 3:05 PM

Make sure the output capacitor is connected the right way. They will bulge out if the are put in backwards or are run at too high of voltage.
The inductor should be fine although it might get warm.

How is the circuit layout? Some of the lines should be kept short. (refer to the diagram)

luketanti in reply to rocketman221Jan 27, 2011. 3:54 AM

Thanks very Much!! I had connected the out capacitor with pin 6 instead. That is why it got bulged. Now it works perfect. Exactly 5V output and can supply 5 amp.
Thanks again!!

alfredhenriksen says: Aug 28, 2010. 6:21 AM

i liked it! The cool thing is that if you've only got a 16V/1A supplier, the output amperage can be higher than 1A. I have played a little with LM2576, and became surprised when I got 4.16A out of it. PS: Why does it get 3.09 in rating when I rated it as 5.0, and I am the first one to rate it? "3.09 (1 ratings) Your rating: 5.0"