I am counting at least 2 ewcent threads in the Technical Repair forum that are dealing directly with switched mode power supplies from the mains.

Is the no transformerless discussion rule waived for this forum? It got me to thinking that if the rule was strictly enforced for that forum, it would likely mean the near demise of the forum since many consumer devices powered from the mains in the past 10+ years don't use a transformer rather a switched mode supply.

Anyone working on such a piece of equipment should take the precaution of using an isolation transformer during repair. But then again how many hobbyists have one in their list of equipment.

 

SMPS are usually isolated from the mains side?
i.e. not referenced to earth ground.
Max.

 

SMPS are usually isolated from the mains side?
i.e. not referenced to earth ground.
Max.

Don't know but the rules are no transformerless supplies. SMPS is transformerless.

 

They do have an HF isolation transformer usually.
Max.

 

Don't know but the rules are no transformerless supplies. SMPS is transformerless.

SMPS are transformer isolated.

 

theres some only using a coil tough most have the galvanic isolation

Also for reasons, the capacitor approach works for some while then theres a spike and may cause a fire.

I had a General Electric night light once with a tiny tube inside and capacitive doubler and after some while it burned out internally so violently a hole was melted visible on the outside so think this was a commercial and branded appliance

So guess what cobblers and tinkers make out of such design approach statistically we would get certain amount of fires from these supplies

Among other things the capacitor has to be way overrated and of good quality

 

Max is correct: The isolation is the key to acceptability.

The main concern with transformerless power supplies is that they are often used in ways that it could appear isolated which could lead to a dangerous situation. There are other factors, but this is one that I think most understand to be the intent of the prohibition in the User Agreement.

At this time it is preferred to not have material describing these on the forum.

 

SMPS are transformer isolated.

An SMPS can be isolated or not, depending upon whether it has a transformer.

 

Obviously all Wall-Warts are isolated, whether linear or SMPS, the end connector is usually bare and could be dangerous if not isolated.
Max.