Continuation of Transformerless Power Supply design

[danadakk]

There was a question about a zener failing and turnon transients possibly damaging
zener in circuit from BradtheRad and Klaus. Some one shut off thread before this was
addressed.

Here is a trans sim, the switch was activated at 300V on the positive 1/2 cycle of
220 line V.

As you can see lots of transient current and power into zener :

Regards, Dana.

 

[KlausST]

Hi,

Thanks Dana for your effort.

We see (expectable) a rather high peak of current. Short, but really stressful for the diode. I can´t imagine the temperature stress on a very tiny zener die.
In one datasheet I saw a surge current rating (I_P) of 810mA for this diode. Surely we see more than 180mA.


Klaus

 

[FvM]

Your simulation illustrates why I characterized 1 ohm series resistor as built-in self destruction. Unfortunately original poster of the previous thread https://www.edaboard.com/threads/transformerless-power-supply-issue.410247/ isn't willing to discuss circuit failure referring to actual component values.

 

[danadakk]

Small change in 1 ohm to 10 ohms makes big difference :

Regards, Dana.