Nohon 3C usb charger

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Official specifications:
I got it from a reader

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Measurements


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The charger is rated for 1A and overload trips slightly above that, this looks good.

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I could draw 1A for 1 hour without any problems.
The temperature photos below are taken between 30 minutes and 60 minutes into the one hour test.

Temp3062

M1: 47,0C, M2: 47,7C, HS1: 52,3C
HS1 is the transformer.

Temp3063

M1: 48,4C, M2: 41,9C, HS1: 49,0C

Temp3064

M1: 51,1C, HS1: 56,8C
HS1 is the rectifier diode.

Temp3065

M1: 45,2C, HS1: 55,5C

Temp3067

M1: 50,2C, HS1: 54,7C

10ohm

Noise at 0.5A load is 18mV rms and 534mVpp

5ohm

Noise at 1A load is 23mV rms and 472mVpp



Tear down

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I could not open it with my vice, but instead had to cut it open.

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On the input there is a resistor used as fuse. notice how the transformer has an extension for the output leads (This improves the isolation distance). The white plastic secures good isolation between mains and low volt side.

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The extension of the transformer is very visible here. It is also possible to see the switcher transistor beside the transformer.

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The green part L1 is an inductor.

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On this side of the circuit board there is a bridge rectifier (DB1), a switcher controller IC (U1).
There is also a big rectifier diode just below the usb connector (D3).
Note the zig-zag trace beside D3, it works as a resistor and is placed between the two capacitors, probably to reduce noise slightly.

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The distance between mains and low volt side is nearly 7mm, this is enough.

Testing with 2500 volt and 5000 volt between mains and low volt side, did not show any safety problems.



Conclusion

The adapter has good safety, can deliver the rated current and for a 1A device DCP coding is correct. I could have wished for slightly less peak noise.



Notes

I got the usb power supply from a reader for review.

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