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This video was going to be a repair of this Portable USB Charger but as it turns out there wasn’t anything electrically wrong with it. It didn’t work out of the box but I think that must have been caused by some oxidation on the USB contacts. It seems to work like a champ now. The control chip for the DC/DC converter looks to be this DHMF chip. I have never seen the swoop logo before and can’t seem to find any data on this 5 pin device though. It is probably similar to the LT1302 (PDF) that the Adafruit MintyBoost uses. The efficiency of this circuit doesn’t appear to be as efficient as a proper one built using the LT1302 though since when drawing 500mA from the output it can maintain very close to 5 volts out (2.5 watts) but needs an input of 3 volt at 1.3 amps to do it (3.9 watts). This gives us an efficiency of about 64%, the graph from the datasheet of the LT1302 indicates that it could perform at about 86% under these conditions.
The unit does have some build details that I didn’t expect. Most of these commodity items seem to be built with the absolute lowest cost in mind, this might have been what caused the corrosion on the USB jack issue. But there are some other things that are nice to see, the short preventing shields on the flashlight LED leads and a plastic standoff on the red indicator LED. These are not seen by the user and just add assembly time and expense showing that they were trying to make a good product. The PCB looks to be a good quality board and is nicely laid out.
You can view the full size images here.
