USB Power Supply/charger Test

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I decided to check a couple of cheap USB power supplies and also a few more expensive ones. Recently there have been some tear downs of USB power supplies on the internet, where people has shown how bad quality and safety they where, I decided to also include a tear down to see how safe they look.
In the test I also included a test with a high voltage ohm meter, to see how much voltage they can handle between mains and low voltage.

Note: Many people call these units USB chargers, but they are not battery chargers, if you connect a battery directly to them they will damage the battery. Most of the time I will call them "ps" for power supply.



USB Power Supply #1

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From: ebay:ecitygo/150660255174
Name: EU USB AC Power Adapter Charger For iPod iPhone 3G S 4G

Official specifications:



Measurements

A small PS that can deliver 1A, lets test it:

USB%20PS%20%231%20load%20sweep

The PS can supply about 0.6A, but the voltage is slightly low.
How does it handle the load over time, in the curves below I test for one hour.

USB%20PS%20%231%200.5A%20load%20test

At 0.5A it is only slightly below minimum voltage.

USB%20PS%20%231%200.6A%20load%20test

but with 0.6A it is significant below.

How does the output look at 0.5A:

Trace%201a

A lot of spikes, this might be fine for running a simple charger, but not for anything electronic.

High voltage test failed.



Tear down

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The electronic can be pulled out of the box with a bit of force.

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The ps has a single rectificer diode, that charges a 2.2uF capacitor. It has two transistors and a opto coupler for feedback. This opto coupler is the reason for the stable voltage during load sweep.

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There is not much space between the mains and the low voltage side.
The (mostly missing) resistors R6, R7, R8 and R9 is used to make it Apple compatible.

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The distance between the two red lines is what it protecting the user from the mains voltage. This distance is way to low (The ruler has 1 mm between tick marks)!



USB Power Supply #2

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From: ebay:365digital/320986478607
Name: USB AC Power Supply Wall Adapter MP3 Charger EU Plug 35DI

Official specifications:



Measurements

According to specifications this ps can deliver 0.5A, how does it measure:

USB%20PS%20%232%20load%20sweep

That load test shows a very interestning looking curve, the ps start at 6 volt, drops to 4.5 volt, goes up to 5.5 volt and drops again. This is not good!

USB%20PS%20%232%200.3A%20load%20test

At a 0.3A load the ps will stabilize at an acceptable voltage after 10 minutes.

USB%20PS%20%232%200.4A%20load%20test

At a 0.4A load the voltage is way to low.

How does the output look at 0.3A

Trace%202a

The output is not very stable and has a lot of noise, this can also be used for a charger, but is not very good for anything with electronic in it.



Tear down

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One screw to remove and it is open.

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The ps has a single rectificer diode, that charges a 2.2uF capacitor, this is very easy to see in the output with the 20 ms periode time. It has one transistors (or IC) and not feed back, i.e. very bad stabilization as can be seen on the load sweep curve.

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Notice the twisting trace at the red wire, it is probably supposed to be a fuse.

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This ps has much better distance from mains to low voltage side.



USB Power Supply #3

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From: ebay:at.store/261030303042
Name: EU USB Wall Home AC Charger Adapter For iPhone 3G 3GS 4 4G 4SAC Adapter EU

Official specifications:



Measurements

Again a 1A ps, how does it live up to that:

USB%20PS%20%233%20load%20sweep

It does deliver 0.5A with a good voltage.

USB%20PS%20%233%200.5A%20load%20test

When it gets hot, the voltage drops a bit, but because it starts well above the minimum limit, there is no problem.

How does the output look at 0.5A:

Trace%203a

The output is not very stable, and has a lot of noise, it is not very good for anything with electronic in it.



Tear down

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The glue used to keep this ps together was very easy to break (Oops).

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The ps has a single rectificer diode, that charges a 2.2uF capacitor. It has two transistors and a opto coupler for feedback. This opto coupler is the reason for the stable voltage during load sweep.

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On this ps the two usb data pins are shorted, this signales that it is a dedicated charger.

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The resistor with brown-black-gold might be working as a fuse.

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There is a good distance between mains and low voltage side.



USB Power Supply #4 Ioncell

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From: intl-outdoor.com
Name: Ioncell 4 USB 2A Power adapter

Official specifications:



Measurements

This is a 2A ps, the total current can be drawn from a single port or from multiple ports. Can it really deliver 2A?

USB%20PS%20%234%20load%20sweep

The answer to that is definitly yes, it has absolutely no problems delivering 2A, it can deliver considerable more.

USB%20PS%20%234%202A%20load%20test

The output is perfectly stable while doing it.

USB%20PS%20%234%203A%20load%20test

The ps does also show a nice output with 3A, at least for the first 30 minutes.

USB%20PS%20%234%203.3A%20load%20test

How much current can it deliver, here I tries 3.3A, sadly that was fatal for the ps. After I removed it from the test bench it could not power up anymore.

How does the output look at 2A:

Trace%204a

Very smooth output, perfect for anything.



Tear down

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I could not open this ps, except with help from a Dremel.

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This ps has a nice construction with input noise filter, bridge rectifier, control IC and opto coupler feedback.

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The four usb outputs are in parallel and there is some resistors to control the voltage on the data pins, probably to make it compatible with Apple.

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It does also have a capacitor between primary and seconday, this is used to reduce noise and due to safety it MUST be a Y capacitor. The capacitor looks like it is.

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This ps uses a real chip for control, it is called THX203H

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There is a good distance between mains and low voltage. At the usb connectors it looks like the distance is short, but when the pcb is in the box, there is a plastic shield between the mains and the low voltage section.



USB Power Supply #5 Skross

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From: www.batteribyen.dk
Name: Euro USB Charger

Official specifications:



Measurements

This ps has two usb output, that can deliver a total of 1.3A according to the specifications, lets check:

USB%20PS%20%235%20load%20sweep

Between 1.2A and 1.3A and then it shuts down, this is very nice doing.

USB%20PS%20%235%201.2A%20load%20test

Running a load test for 1 hour is no problem, it has perfectly stable output.

How does the output look at 1.2A:

Trace%205a

Only a little noise, can be used for anything.



Tear down

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This adapter does not use wires to connect from the plug to the pcb, but some custom clips.

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This ps is designed with a bridge rectifier and a control IC. I cannot see any feedback, but it has a very good regulation anyway (It is probably using a extra winding on the transformer for regulation).

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The distance between mains and output is not that long, part of it is protected by the plastic shield.
Note: There is something that looks like a PCB trace near the wide slot, but it is not.

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Nothing is hidden under the USB connectors.



USB Power Supply #6, KY-738

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The charger was rattling when I got it, that turned out to be some loose plastic pieces inside the charger.

From: ebay:boutique_uno/360542144761
Name: MP3 MP4 Mobile Cell Phone EU Plug USB Power Adapter AC Wall Charger

Official specifications:



Measurements

This ps has one usb output, that can deliver a total of 0.5A according to the specifications, lets check:

USB%20PS%20%236%20load%20sweep

About 0.4A, then the voltage goes below the minimum limit, this is below specifications.
The green led on the power supply turns on at about 90 to 100mA load, the red is on when it has power.

USB%20PS%20%236%200.35A%20load%20test

With a 0.35A load there is no problem running for 1 hour.

USB%20PS%20%236%200.4A%20load%20test

Increasing the load to 0.4A does not look good, the voltage is way to low.

How does the output look at 0.35A:

Trace%206a

It has some noise in the output.



Tear down

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The ps has a single rectificer diode, that charges a 2.2uF capacitor. It has two transistors and a opto coupler for feedback. This opto coupler does keep the output fairly stable, but because the ps cannot deliver much power, the output will drop at around 0.4A.

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USB Power Supply #7

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From: ebay:lotsgoods88/110740713894
Name: USB AC Power Supply Plug Adapter for MP4 MP3 Charger EU

Official specifications:



Measurements

This ps has one usb output, that can deliver a total of 1 according to the specifications, lets check:

USB%20PS%20%237%20load%20sweep

About 0.6A, then the voltage goes below the minimum limit.

USB%20PS%20%237%200.55A%20load%20test

The output at 0.55A looks nice.

USB%20PS%20%237%200.6A%20load%20test

At 0.6A the voltage varies a bit, probably due to temperature changes

USB%20PS%20%237%200.65A%20load%20test

Increasing the current a bit more and the voltage is far below specifications and not very stable.

How does the output look at 0.55A:

Trace%207a

There is a lot of noise in the output.



Tear down

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The ps has a four rectificer diode (i.e. a bridge), that charges a 2.2uF capacitor. It has two transistors (one of them a power transistor) and a opto coupler for feedback. This opto coupler does keep the output fairly stable.
It does also have a capacitor between primary and seconday, this is used to reduce noise and due to safety it MUST be a Y capacitor, but the used capacitor is not.

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The distance between mains and low voltage is way to short on this ps.



USB Power Supply #8

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From: ebay:sinedy/180653247293
Name: BlackBerry Power AC Charger Mini Micro USB Adapter EU

Official specifications:



Measurements

This ps has one usb output, that can deliver a total of 0.75A according to the specifications, lets check:

USB%20PS%20%238%20load%20sweep

About 0.65A, then the voltage goes below the minimum limit.

USB%20PS%20%238%200.65A%20load%20test

The output at 0.65A looks acceptable.

USB%20PS%20%238%200.7A%20load%20test

At 0.7A the voltage is way to low.

How does the output look at 0.65A:

Trace%208a

There is a lot of noise in the output.



Tear down

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The ps has a single rectificer diode, that charges a 4.7uF capacitor. It has two transistors (On smd and one power) and a opto coupler for feedback. This opto coupler is the reason for the stable voltage during load sweep.

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The main capacitor is mounted very close to the usb connector, this is not very safe.

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It looks like there is a white line between mains and low volt on the pcb, but this does not help with the distance, that is very short.



USB Power Supply #9

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From: av-cables.dk/44004
Name: 230V til 1 x USB lader - 1000 mA

Official specifications:



Measurements

This ps has one usb output, that can deliver a total of 0.75A according to the specifications, lets check:

USB%20PS%20%239%20load%20sweep

Looking at this curve, the ps can deliver 1.4A, this looks very good.

USB%20PS%20%239%201A%20load%20test

The first test at 1A does not work as expected, after 23 minutes the ps begins doing funny stuff.

USB%20PS%20%239%200.9A%20load%20test

Doing a test at 0.9A works much better.

USB%20PS%20%239%201.4A%20load%20test

I was curious about 1.4A load, as can be seen above it can do that for about 5 minute.

How does the output look at 0.9A:

Trace%209a

It has some noise in the output.



Tear down

No tear down for this charger (It requires a Dremel to open).



USB Power Supply #10

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From: av-cables.dk
Name: 230V til 2 x USB lader - 2000 mA.

Official specifications:



Measurements

This ps has two usb output, that can deliver a total of 2A according to the specifications, lets check:

USB%20PS%20%2310%20load%20sweep

Looking at this curve, the ps can deliver more than 3A, this looks very good.

USB%20PS%20%2310%202A%20load%20test

A test at 2A looks very good.

USB%20PS%20%2310%202.5A%20load%20test

A 2.5 test does also look very good. I am not going to test at higher current, I do not want to risk damaging this ps.

How does the output look at 2A:

Trace%2010a

The ps has a very nice output voltage with low noise.



Tear down

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The ps has input noise filter, a rectificer diode, that charges three 6.8uF capacitor. It has an IC and a power transistors. There is no opto coupler, but it has a fairly stable output anyway.
It does also have a capacitor between primary and seconday, this is used to reduce noise and due to safety it MUST be a Y capacitor and it is.

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There is a very good isolation distance between mains and low voltage on this charger.



USB Power Supply #11

This ps is the same as #3, but from another dealer.

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From: e.beautyshop24 / 180973732363
Name: EU PLUG USB POWER ADAPTER TRAVEL HOME WALL CHARGER FOR IPHONE 4G 4 4S IPOD

Official specifications:



Measurements

This ps has two usb output, that can deliver a total of 1A according to the specifications, lets check:

USB%20PS%20%2311%20load%20sweep

Looking at this curve, the ps can deliver about 0.5A.

USB%20PS%20%2311%200.5A%20load%20test

Doing a actual load at this current, shows that 0.5A is a bit too much for this ps.

USB%20PS%20%2311%200.45A%20load%20test

Reducing the current to 0.45A looks much better.

How does the output look at 0.45A:

Trace%2011a

There is a lot of noise in the output.



Tear down

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The ps has a single rectificer diode, that charges a 2.2uF capacitor. It has two transistors and a opto coupler for feedback. This opto coupler is the reason for the stable voltage during load sweep.

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There is a good distance between mains and low voltage side.



USB Power Supply #12

This ps looks the same as #2, but when looking at the tear down it is easy to see that the construction is different.

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From: zyy123087/400308826772
Name: USB AC Power Supply Plug Adapter for MP4 MP3 Charger EU

Official specifications:



Measurements

This ps has two usb output, that can deliver a total of 1A according to the specifications, lets check:

USB%20PS%20%2312%20load%20sweep

Looking at this curve, the ps can deliver about 0.35A.

USB%20PS%20%2312%200.35A%20load%20test

Doing a actual load this, shows that 0.35A is a tiny bit too much for this ps (the voltage goes below 4.75 volt).

How does the output look at 0.35A:

Trace%2012a

There is a lot of noise in the output.



Tear down

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The ps has a single rectificer diode, that charges a 2.2uF capacitor. It has two transistors and a opto coupler for feedback. This opto coupler is supposed to stabilize the output voltage, but does not really work.

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There is some isolation distance.



USB Power Supply #13

This ps is nearly the same as #1, but from a different dealer.

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From: wwwdot999/390512458592
Name: EU Plug USB Wall Charger AC Power Adapter For iPhone 3GS ...

Official specifications:



Measurements

This ps has one output, that can deliver a 1A according to the specifications, lets check:

USB%20PS%20%2313%20load%20sweep

Looking at this curve, the ps can deliver about 0.6A.

USB%20PS%20%2313%200.6A%20load%20test

Doing a actual load this, shows that 0.35A is a tiny bit too much for this ps (the voltage goes below 4.75 volt).

USB%20PS%20%2313%200.65A%20load%20test

Trying to draw slight more current does not work.

How does the output look at 0.6A:

Trace%2013a

There is a lot of noise in the output.

High voltage test failed.



Tear down

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The ps has a single rectificer diode, that charges a 2.2uF capacitor. It has two transistors and a opto coupler for feedback. This opto coupler is the reason for the stable voltage during load sweep.

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I have marked the mains connected parts with red and the low volt parts with blue. There is less than 0.5 mm between them.
This is extremely unsafe.



Conclusion

With the cheap chargers I had not expected much and the result proved that. The isolation distance is seldom large enough and many of the chargers has a lot of noise in the output. There is also a problem with the output current, it is often considerable lower than rated.

comparison

Looking at the result, the only ones I will be using are 4, 5, 9 and 10.
Number 1 and 13 is way to dangerous to use



Notes

5, 9 and 10 are bought in Denmark, this means higher price (Denmark is very expensive) and probably better safety due to EU regulations.
Efficiency and noise is measured at the "Measured current"

In the tear down section for each ps, it is possible to click on some of the pictures to get larger versions.

One important aspect of safety is the transformator, in the above I have not disassembled it to see if it is safe, but anything that can handle 5kV will be mostly safe.

Read more about how I test USB power supplies/charger

Index to all tested USB power supplies/charges