Have you ever seen such a DC power supply as in the attachment?

 

Yes, it is aversion of the transformerless power supply where the 0.68uF capacitor limits the current. There is no isolation so the output is live and inclined to kill you.

Discussion of this type of supply is not allowed on here.

 

Yes, it is aversion of the transformerless power supply where the 0.68uF capacitor limits the current. There is no isolation so the output is live and inclined to kill you.

Discussion of this type of supply is not allowed on here.

I think there was a policy change after the takeover. Your impression might be outdated.

 

What is missing from the drawing is that the other side of the mains connection is connected to one side of the load. The ground symbol, which is used incorrectly, tries to hide that fact.
Stating the hazards of such a supply scheme should be required. "Yes, it can work, but absolutely it poses a serious shock hazard."

 

What is missing from the drawing is that the other side of the mains connection is connected to one side of the load

No. It is confusing because it is drawn upside down compared to the normal presentation. The two wires on the right of the drawing are the load connections. The diode at the right hand side should be a zener whose rating will define the output voltage.

 

I think there was a policy change after the takeover. Your impression might be outdated.

Yes, there was. Far better to give guidance for the safety of members.

 

Killing hot circuit. Literary meaning.

 

A more precise copy from the U.S patent:


Yes, they are most common. In this case the earth ground symbol is misapplied - that is probably "circuit common" rather than actual earth. The circuit and things connected to them are dangerous because they are not isolated from the AC mains.

The principle of operation is described in this Microchip application note.