Is this charger safe?

[oldway]

Then by that logic 99% of crap no name brand (or fake) consumer grade power supplies aren't safe. Throw away your phone charger now!....yes, indeed, it is a very serious problem of safety.

The tests must be carried out at factory....there is no way to control if these tests are really carried out or not.
If some accident happen, there is also no recourse to justice against the firm established in PRC.
So the only way to guarantee safety is to buy a product from a reputable and known firm.

The example given by Wraper is interesting because 2 well-known companies are responsible for the safety of the power supply:
1) Delta which is a known firm.
2) the manufacturer of the monitor.
In case of an accident, these two known firms can be prosecuted as well as their legal representatives in Europe.
In the case of a no-name brand, it is impossible to locate it, these types of firms open and close in one hour and the owners disappear into nature

[oldway]

There is also another reason why one can not trust unknown brand products made in China.

It is the safety concern that is totally different in China from that in Europe.

Here is an extract from an answer that Blueskull had posted on this subject.

https://www.eevblog.com/forum/chat/incredible-lack-of-safety/
Reply #14 on: July 16, 2017, 04:41:52 PM

"....BTW, in China it's allowed to put a price on human lives unless the possibility of death is very high (which makes it murder). If the expectancy of life loss cost is lower than the cost to prevent this, then no bosses will install extra safety systems. In fact, workers don't essentially hate this practice since should something happens, the settlement can be well higher than his or her lifetime income, which can change their family's fate. I've read news that Chinese workers intentionally pinch their fingers into machines to get thousands, tens of thousands or even hundreds of thousands of CNY worth of settlement."

[wraper]

BTW, the design shown in Wrapper's picture is almost illegal to sell in EU due to the lack of PFC. I think power supplies above 75W (input) are required to have PFC, and the self oscillation topology with diode rectification

BTW it's not illegal to sell because that PSU is certainly below 75W. What self oscillation topology? It has proper PWM controller. Self oscillation topology is long gone in the past or used in the most cheap and crappy Chinese chargers of low power. And nobody uses synchronous rectifier at such PSUs.

doesn't look like it will achieve 88% efficiency at full load either. I think it's a repair part, not for a new product design.

88% efficiency at full load, are you gone mad? It's a requirement for 80 Plus Gold certified PSU. And yes that board is old.

[wraper]

It's used in 22" TV, should be around 40W max power consumption. I measured power consumption of my 30" CCFL backlit DELLs in the past (long gone now). IIRC it was around 130w at max brightness.

[madires]

We will never agree because your point of view is that of an amateur who knows nothing about quality control and who treats safety with lightness and unconsciousness, whereas I has been quality control manager (actually retired).
Sorry, but in a quality control department, a person like you has no place. More or less does not exist in quality control...It pass or it fails.....

Oh dear, you're one of those people who's so indoctrinated with procedure, they blindly follow it, without actually understanding its limitations or applying any critical thinking whatsoever: monkey see, monkey do. Clearly there's no point in attempting to have a rational discussion.

Tunnel vision with a green "Pass" and a red "Fail". A green "Pass" only states that the device passed the test and we assume the device is safe to use. But that's only an assumption tagged with some probability. If your mains got spikes up to 5kV your "safe" wall wart, hi pot tested with 4kV, isn't safe anymore despite the fancy certification label and proper QA. I doubt anyone is checking for the worst case of a direct hit by a lightning strike.

[Zero999]

We will never agree because your point of view is that of an amateur who knows nothing about quality control and who treats safety with lightness and unconsciousness, whereas I has been quality control manager (actually retired).
Sorry, but in a quality control department, a person like you has no place. More or less does not exist in quality control...It pass or it fails.....

Oh dear, you're one of those people who's so indoctrinated with procedure, they blindly follow it, without actually understanding its limitations or applying any critical thinking whatsoever: monkey see, monkey do. Clearly there's no point in attempting to have a rational discussion.

Tunnel vision with a green "Pass" and a red "Fail". A green "Pass" only states that the device passed the test and we assume the device is safe to use.

Yes, also note that the test just demonstrates that it can withstand that voltage under laboratory conditions. It doesn't prove that the design is safe, i.e. mechanical construction, the creapage and clearances are sufficient for the pollution degree rating. The manufacturing facility might be considerably cleaner and less polluted, than the conditions in the field. That's something which needs to be verified by design.

But that's only an assumption tagged with some probability. If your mains got spikes up to 5kV your "safe" wall wart, hi pot tested with 4kV, isn't safe anymore despite the fancy certification label and proper QA. I doubt anyone is checking for the worst case of a direct hit by a lightning strike.

I agree, if you're struck by lightning, there are far more serious things to worry about, than getting a shock off a dodgy wall wart!

[oldway]

Standards set reasonable limits that ensure a high level of safety.
These limits are sufficiently high to leave a good margin of error and to compensate for problems due to the aging of the insulation.

But the High Pot tests do not protect users against falling meteorites or bullshit like taking your charger with you in your bath or in the shower .

[IanMacdonald]

As regards safety of small SMPS wall warts, Big Clive has done some teardowns on YT. While you can see easily enough if there are adequate clearances on the PCB, the thing that's not so easy to determine is if there is adequate insulation on the transformer leads where they go into the windings.

Since the inner winding much cross the outer one to reach its terminals, if all it has as this point is varnish then it's not very safe. Most do have a sleeve though. It's the ones that don't which are potential death traps.

A split bobbin is of course much better, but rare on budget items.

Bear in mind the switching input may have 400v or more on it, so potentially more dangerous from a shock hazard POV than straight mains.

Since finding out typically means breaking the transformer apart, only feasible to examine sacrificially on a one-per-batch basis.

[Gyro]

Unfortunately split bobbin transformers don't work well in an smps due to the high leakage inductance at their switching frequency.

The closest approach was a side by side interleaved winding transformer used by Pace in their Set Top Boxes. They did have good physical barrier but the interconnections involved looked like a spider's web. I always felt they were far too susceptible to physical damage compared to the standard SMPS style. They were cheap to manufacture (in the UK) however.

Photo attached.

P.S. I always felt far more comfortable with closely specified transformers from the far-east with triple insulated wire, regular sample teardown inspection and 100% hipot testing.

[wraper]

A split bobbin is of course much better, but rare on budget items.

Split bobbin takes additional size and is horrible for efficiency and load regulation.

[fourtytwo42]

It is really good this subject is still going strong, perhaps I feel a little sorry for the OP who must be totally confused by now BUT it's great to see people actually seriously thinking about the safety of stuff many peeps take for granted. I do feel that equipment intended for a testbench scenario as the OP indicated should have extra safety levels, after all it's bad enough risking bangs and smoke from ones prototypes under test but you don't want the test gear doing it and even more so you want the test gear to behave properly irrespective of what your prototype does!

I noticed the comments here about split bobbin, an excellent way of achieving the creepage requirement and used in many smallish 50hZ transformers BUT it is also becoming used in smps to deliberately increase the leakage inductance for resonant designs, yes I agree the voltage regulation of the transformer is worse as a result of the high leakage but the feedback loop takes care of that. You will see many consumer items using split bobbin now as resonant smps designs increases efficiency (reduce cost).

Hopefully the more this discussion continues the more people will become aware of real safety issues and why they should distrust lots of mass produced products! There is no serious regulation anymore, look at Grenfell tower!! Where were the building regulations and inspectors, ineffectual and none.

[oldway]

It seems to me that this subject has had a very important influence on many forum members concerning the safety of these crap chargers and cheap wall wart.

It was amazing that everyone was very concerned about the safety of multimeters, whereas a switching power supply or a charger can be much more dangerous than a multimeter.

Those who have read this topic have realized that there is a serious safety problem when using a device with no name or an unknown name.

Indeed, safety is guaranteed by factory tests, especially the hipot, but what guarantee are there that these tests are actually performed or not?
When it comes to renowned firms, there are third-party controls that check the compliance of the tests.

But this is not the case for small Chinese firms that try to manufacture these devices at the lowest price, with unskilled labor and without means or technical skills.

A rented location, a few dozen tables, chairs and soldering irons are enough to open an charger and wall warts industry ....

And you entrust your lives to them?

Never trust these cheap chargers and SMPS ....
A good quality device is indeed a little more expensive, but it's worth it

[madires]

Please tell that all the vendors who package their devices together with a cheap crappy wall warts. I can't remember any consumer electronics with a SMPSU from Delta/Mean Well/etc. in the box. Only unknown Chinese SMPSU vendors.

[oldway]

Please tell that all the vendors who package their devices together with a cheap crappy wall warts. I can't remember any consumer electronics with a SMPSU from Delta/Mean Well/etc. in the box. Only unknown Chinese SMPSU vendors.

They will reply that they know nothing about electricity or electronics and that you can buy a better wall wart if you want.

On the other hand, you who have enough knowledge and information in the field of electricity or electronics, you are responsible because you know that it is dangerous.

[Mr. Scram]

It seems to me that this subject has had a very important influence on many forum members concerning the safety of these crap chargers and cheap wall wart.

It was amazing that everyone was very concerned about the safety of multimeters, whereas a switching power supply or a charger can be much more dangerous than a multimeter.

Those who have read this topic have realized that there is a serious safety problem when using a device with no name or an unknown name.

Indeed, safety is guaranteed by factory tests, especially the hipot, but what guarantee are there that these tests are actually performed or not?
When it comes to renowned firms, there are third-party controls that check the compliance of the tests.

But this is not the case for small Chinese firms that try to manufacture these devices at the lowest price, with unskilled labor and without means or technical skills.

A rented location, a few dozen tables, chairs and soldering irons are enough to open an charger and wall warts industry ....

And you entrust your lives to them?

Never trust these cheap chargers and SMPS ....
A good quality device is indeed a little more expensive, but it's worth it

Before, it has been discussed that you trust your life to what you apparently consider unproven devices every day, no matter how stringent or paranoid you actually are. I don't see how repeating the same point of view over and over is going to change much, other than simply wearing people with other views down.

Yes, it is good to be aware of safety. Yes, it is good to be aware that very cheap products might yield very real dangers. But no, you're in no way capable of checking everything you use and depend on in such a way that you're not entrusting your life to total strangers with, quite likely, very different opinions about safety and danger. Even aircraft have crashed due to mechanics being complacent and doing stupid things, like using the wrong bolts. Those aircraft more often than not have all the appropriate stamps, ticks and signatures when they take off. Buying a more expensive ticket isn't going to save you.

[IanMacdonald]

Well, I agree that these cheap SMPS are a concern, particularly as the collector/drain voltage on a flyback converter can easily be double the mains voltage, so you are talking about something that's potentially more dangerous than touching a live mains supply.

With multimeters, I think it's the usual issue with safety certifications: We start with an uncontrolled situation that is downright hazardous, we go through the stage where that has effectively been fixed but don't stop there. Instead, the certification requirements continue to ramp-up into the realm of micromanagement where insane levels of protection are required, levels which would only have any relevance to a tiny proportion of uses for the instrument.

It's this inability to find a sensible balance that's the real problem with all kinds of bureaucracy and red tape.

[oldway]

Those aircraft more often than not have all the appropriate stamps, ticks and signatures when they take off. Buying a more expensive ticket isn't going to save you.

Incorrect comparison: if you pay more, the risk is the same as you are traveling on the same plane.
With a charger or a wall wart, if you pay more, you have a safer and better quality device tested according to standards.

[Mr. Scram]

Incorrect comparison: if you pay more, the risk is the same as you are traveling on the same plane.
With a charger or a wall wart, if you pay more, you have a safer and better quality device tested according to standards.

It's a correct comparison, I'm afraid, as there is more than one aircraft operated by more than one operator or crew. Not that it matters, because even the most well regarded airlines, flying the aircraft models with near perfect safety records and all the requisite stamps, ticks and signatures have come hurtling down due to dumb luck, human stupidity, a basic oversight or a combination of the three.

You will need to trust your life to strangers and some of them, if not most, have different standards from yours. I understand that when your life was spent being a safety inspector, you'd like to believe otherwise, but there's no such thing as being sure in life. There's sure enough and that's about it.

[oldway]

An accident is seldom the consequence of a single defect, it is, in most cases, the consequence of a series of errors or faults, both material and human.

To minimize the risks, all possible faults must be remedied.

For chargers and wall warts, it is essential to ensure that the conditions of double insulation standards are guaranteed by a hipot test.

It is clear that there is no guarantee that this test is actually performed, except by the seriousness and reputation of the manufacturer.

Most insulation faults go unnoticed because they do not result in a fatal accident.

Indeed, mostly that's the accumulation of several factors which lead to a fatal outcome.

But we have to act on each of these factors and not neglect anything to reduce the risks, it is the principle of safety