Inside a Poundland mains (240v) USB power supply.

I bought one of these cheap power supplies from Poundland purely to take to bits, thinking it was going to be a hideous electrical deathtrap. I was pleasantly surprised to see that the internal build quality actually seemed to be quite good. There was modest filtering, good electrical separation, proper opto-isolated feedback and the transformer had a heavily insulated secondary winding. The only thing that is a bit odd is the choice of 5.5V for the output. Off load it actually measured about 5.7V and it withstood a couple of short circuits as I probed the awkward connector.
Given how many of the cheap ebay USB power supplies from China are potential deathtraps, it was quite nice to see one that made an effort to be compliant with safety standards.