Flush-mounted electrical socket with USB - interior, minitest, thermal imaging (overheating test)

The LC-13-A is a flush-mounted, single electrical socket with earthing and two additional USB ports for powering/charging mobile devices. Its dimensions (width 8.4x8.4 cm, depth 4 cm) allow it to be easily installed in most fi 60 mm boxes. In this topic, I will test how it is built and investigate how hot it will get when operating under full load. I'll show the results in the form of thermal imaging camera images, so we'll also see which components heat up the most.

Indeed, this product is slightly deeper than typical sockets, it is worth checking the box before buying.

Unscrew the screw to remove the front panel:

There are vents in the case, but I don't think they provide much - after all, it's sealed in a box anyway. The back of the case is on hooks, let's take a look inside.

The whole thing is cleverly built with two boards and deep USB ports. The manufacturer has made an effort to pack this efficiently into the available space.

Inside is a small power supply in flyback topology. The PCB is signed LB1223-BDUSB, but you can't see the chip markings. This will need to be unsoldered.

After unsoldering you can see an interesting design. Here we have on one side a path instead of a fuse and a rectifier bridge, and on the other side USB ports and a capacitor for 6.3 V, this is connected by a CY capacitor. The distance between the 'hot' and 'cold' side is a little worrying, it's only a few mm.

On the other side of the PCB we have two ICs - a PL3368 inverter controller and a 45R25P synchronous rectifier.


After visual inspection I soldered the whole thing back together:


Time for a load test. Up to 2.3 A at 5.1 V can be drawn:

The thermal imaging shows nicely how even the warm air from the LD35 artificial load warms the table top:


Now the most interesting thing - the transformer heats up quite a bit, up to 70 °C, the inverter controller tops it, reaching 80 °C.


In summary , the socket does its job, although the USB does not offer the QC standard support required by most modern devices and in addition it gets quite hot, potentially even hotter than my tests showed, as I tested with the case removed and outside the box. The construction inside is quite economical, I was a little concerned by the small distance between the mains voltage side and the low-voltage secondary. It was also interesting to see how the transformer is built, but I didn't want to dismantle it.
Do you use this type of socket with extra USB?