USB Desktop Charger 12A

DSC_8924

Official specifications:
I got this charger from ebay dealer: flashman852

DSC_8920 DSC_8922 DSC_8923

I got this charger in a retail package.

DSC_8926
DSC_8927
DSC_8928
DSC_8929 DSC_8925



Measurements


USB%20Desktop%20Charger%2012A%20%236%20load%20sweep

First test is on a single connector, it does not look like it has any individual protection.

USB%20Desktop%20Charger%2012A%20load%20sweep

Doing all connectors at once I can increase the current, but not up to the promised 12A, protection kicks in at 10A. It is less than specified, but more than I believe anybody will be using.

USB%20Desktop%20Charger%2012A%208A%20load%20test

To be reasonable with the output loads I decided to test at 8A, if it stays cool I can always do another at a higher current.
The 8A load was handled fine, except it did not stay cool (See photos below).
The temperature photos below are taken between 30 minutes and 60 minutes into the one hour test.

Temp1732

M1: 84,0C, M2: 77,4C, HS1: 110,5C
It looks like it can be used to keep coffe warm. It is the transformator that is really hot.

Temp1733

M1: 57,4C, M2: 47,5C, HS1: 84,3C

Temp1734

M1: 69,9C, M2: 69,7C, HS1: 72,9C

Temp1735

M1: 78,0C, M2: 41,9C, HS1: 80,0C

0.6ohm

With a 8A load the noise is 70mVrms and 2300mVpp.
The rms noise is acceptable, but the peak-peak noise is way to high.

2.5ohm

Reducing the load to 2A the noise is 60mV rms and 3200mVpp, i.e. lower rms noise, but higher peak noise.

10ohm

With 0.5A load the peak noise increases even more: 48mV rms and 3500mVpp



Tear down

DSC_9321

This unit was fairly easy to open, I just had to remove 6 small screws.

DSC_9322

It contains a big transformer for the many amps, the mains capacitor is also fairly large.
The input is protected with a fuse and a NTC.
Both the switcher transistor and two diodes on the low volt side have a heatsink.

DSC_9323

DSC_9324

DSC_9325 DSC_9326

The capacitors besides the transformer is marked 105C, but when the transformer heats the outside of the box to 110C, they are not going to last long.

DSC_9327

On the bottom of the circuit board is the mains switcher IC.

DSC_9328

DSC_9329

Nice, it is a safety capacitor.

DSC_9330

There is a fairly good distance between low volt side and mains, it looks like the shortest distance is between 4 and 5 mm, this is not enough, but fairly good.

DSC_9331

But it is not enough to have a lot of distance on the circuit board, there must be distance between parts with mains voltage and parts on the low volt side everywhere. In air the distance must be 4mm, the two heat sinks are a bit too close and there is no protection agains hard bumps (They do go down to the circuit board and for that reason they need >6 mm distance).
The 5000 volt test did not fail due to this, but because voltage jumped from the mains heatsink to the transformer and then from the transformer to the low voltage diodes.


The charger passed 2500 volt test, but failed a isolation test with 5000 volt, this makes it doubtful to use with 230VAC mains.



Conclusion

This usb power supply can deliver a lot of current, but the power quality is very bad and it gets to hot. Missing individual protection on the outputs is also a problem, 10A in a single usb connector is not very good. It looks like the designer has learned something about isolation distances, but obvious not enough.

Due to the power quality and the safety I will not recommend it.



Notes

Index of all tested USB power supplies/chargers
Read more about how I test USB power supplies/charger