As one who designs electronics at least some of the time, some thoughts.

The electronics cannot be protected against everything, so instead it is intended to fail to safe when it does

In good designs by reputable makes the PCB will often have a link designed to melt, or the inrush resistor is a fusible one. The glued case should be strong enough to contain all the flying parts during the highest energy operation of these mechanisms.

A rigorous failure mode analysis is a large part of the design for a responsible manufacturer, of anything.

(when you do the tests the largest bang is not normally the semiconductor, but it may be a consequence, for example of diode failure, and that is explosive failure of the mains side smoothing capacitor - if that is electrolytic then the good ones have deliberate casing weak spots so they unzip at a defined pressure. If we can we prefer to use ceramic in the smaller high end designs, but only available up to a few uF at a few hundred volts in surface mount.)


I am aware that some designers are not responsible, and the cheaper devices do not met the requirements for double fault or reinforced insulation between primary and secondary, (as generally these are supposed to be class 2, so the output has to float) nor are all cases adequate blast containment, and not all fail safe.

regards Mike.

As one who designs electronics at least some of the time, some thoughts.

The electronics cannot be protected against everything, so instead it is intended to fail to safe when it does

In good designs by reputable makes the PCB will often have a link designed to melt, or the inrush resistor is a fusible one. The glued case should be strong enough to contain all the flying parts during the highest energy operation of these mechanisms.

A rigorous failure mode analysis is a large part of the design for a responsible manufacturer, of anything.

(when you do the tests the largest bang is not normally the semiconductor, but it may be a consequence, for example of diode failure, and that is explosive failure of the mains side smoothing capacitor - if that is electrolytic then the good ones have deliberate casing weak spots so they unzip at a defined pressure. If we can we prefer to use ceramic in the smaller high end designs, but only available up to a few uF at a few hundred volts in surface mount.)


I am aware that some designers are not responsible, and the cheaper devices do not met the requirements for double fault or reinforced insulation between primary and secondary, (as generally these are supposed to be class 2, so the output has to float) nor are all cases adequate blast containment, and not all fail safe.

regards Mike.