High amp USB supply

Discussion in 'General Electronics Chat' started by Dr.killjoy, Apr 5, 2015.

  1. Dr.killjoy

    Thread Starter Well-Known Member

    Apr 28, 2013
    I am looking to make a 12v dc to 5v dc for a usb charger with about 5amps.. My problem is that I use a dc usb charger to charge my work tablet and phone .. But my poor charger gets very hot from pulling so much juice and I am looking to upgrade into mounting 4 usb sockets to a pcb and use a switch mode voltage regulator.. I have not picked out a voltage regulator yet but will have to roam mouser catalog later for some part ideas..But do you guys have suggestions or ideas ???

    Jay Sr
  2. Ramussons

    Active Member

    May 3, 2013
    From what I understand, your present charger is not able to charge both your devices simultaneously.
    You intend to expand the charging outlets to 4 using a 12 volt to 5 volt regulator.

    If a single device is to draw 5 amps, then the USB plug/socket will not last long. It's not designed for such heavy currents.

    If you intend to use a single regulator for the 12 V to 5 V conversion, you will need to use Isolation Diodes for each USB socket. Your convertor will need to take care of this Diode Voltage Drop.

    Price wise, cost of a single convertor with 4 diodes will be far less than the cost of 4 convertors.
    Reloadron likes this.
  3. Papabravo


    Feb 24, 2006
    Building a switching regulator is not a project I would recommend for the novice builder. There are significant challenges in component selection, PCB layout, testing, debugging. Did I mention PCB layout? They tend to misbehave when constructed as a breadboard. In short, I think the better solution is to find chargers that meet your requirements and be done with it. You could also hire someone to design this for you and you could observe the way he works and learn something.
  4. ScottWang


    Aug 23, 2012
    LM2679-5, 5V/5A output.
  5. Reloadron

    Well-Known Member

    Jan 15, 2015
    Nothing wrong with getting a SMPS power supply and making your own USB type charger but there are a few caveats. First the pins in a USB connector are only rated for so much current before things get warm and start to melt as was mentioned. My laptop charger runs warm but gets the job done. Your work tablet and phone will only draw so much charge current. Really matters not if the source can provide 1 amp, 5 amps or 100 amps. Having a 5 volt, 5 amp SMPS may allow charging more devices at once but each device will only draw its rated charge current.
    Using these connectors as an example the maximum current in the data sheet is shown as 1.0 amp. So even if I use them with a source capable of 5 amps or greater I should not allow more than one amp to flow through them. Combine that with each device will only draw its rated charge current and you need to ask yourself if having a 5 amp SMPS is really practical?

  6. JWHassler


    Sep 25, 2013
    Each device contains a lithium-battery charging circuit that has no need/use for more than 1 amp, so the connectors' ratings are not an issue.
    Building an SMPS with the capacity run several is not trivial, but is completely doable.
  7. Dr.killjoy

    Thread Starter Well-Known Member

    Apr 28, 2013
    Is it better to buy a ebay one or just build a nice one on perf board ???

    I will have to check out Isolation diodes and will post up schematics for help.. You pretty much nail what I am trying to do..

    I have done some reading on smps and I know it's somewhat above my head but Afrotechmods did a nice build of one .. My plan was to pick one from mouser and use the datasheet schematic for my build instead of trying of building my own..

    Will have to check it out

    I don't want more power to charge faster but more power so I can charge everything and not have a problem ..I am using a Samsung Tablet for working and when I charge my phone and tablet at the same time the charger gets really hot and I have smoke a couple cheapo chargers before .. The charger I using has a 2.1amp port and 1amp port .. When I plug tablet into the 2.1amp port and 1amp goes to my phone it starts to get hot and then I have to unplug my phone ...

    Ok Thanks
  8. Reloadron

    Well-Known Member

    Jan 15, 2015
    All things considered, if I were you, I would just buy a 5 volt 5 Amp SMPS and build a nice charging station. If you want to get downright fancy put the power supply in a small project box and get a handful of panel mount USB connectors. Heck find a scrap motherboard and hack the connectors. Then if you want to get really fancy and ultra cool you could add a current meter/volt meter to the box. Ebay is loaded with little current/voltmeters for literally a few bucks. :)