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USB Travel Charger

USB Travel Charger


Lot's of little appliances can be charged straight from a USB port these days. However carrying a PC with you all the time isn't very practical, and laptops need to be plugged in to mains if they're to last long enough to charge anything. That's where the travel charger comes in! A small pocket sized device which runs from 2 - 4V, in other words two 1.5V batteries. Easy to take with you anywhere no matter how desolate the location, just remember to bring batteries. ;-)

Schematic

Similar to the Minty Boost, except it uses a  more common PWM chip (at least in my neck of the woods), the LM3578.  It's just a boost converter which boosts the battery voltage up to a regulated 5V. The support components were more less just taken from the datasheet. They take care of feedback compensation, oscillation frequency and voltage regulation. The load regulation is good, IIRC it only dropped from 5.05V to 4.95V when sourcing 250mA. Even when the battery voltage dropped to 1.80V (the LM3578 is rated for 2V minimum) the output was still 4.45V while charging my ipod. The chip did get warm however, so use fresh batteries. According the Minty Boost site by selecting either pull up or down resistors the charging current can be changed between 100mA and 250mA. See the bottom of the page. Don't forget to check the USB port pin-out. Next summer I'll have to make some kind of mini-generator for hard-core survivalists.

Opened container  Full view of charger  charging Ipod nano



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This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License.

Disclaimer: I do not take responsibility for any injury, death, hurt ego, or other forms of personal damage which may result from recreating these experiments. Projects are merely presented as a source of inspiration, and should only be conducted by responsible individuals, or under the supervision of responsible individuals. It is your own life, so proceed at your own risk! All projects are for noncommercial use only.