how can I select zener diode in this circuit

[zhengchao201105]

for example:how can I select the zener in this circuit ?which parameter should I focus on？dose anyone can share me some good idea
you can find in this ciucuit the pulsed current is about 5A,so 1n5352 is right?

 

[In2Dusk]

You should choose a zener diode with sufficient wattage rating so it wont burn out. Voltage over zener diode times current that flow through it should be less than it's wattage rating. For example: you have 5V 1W rated diode, so the current through it shouldnt be more then 1/5 A.

 

[BradtheRad]

1N5352 is a 15V zener rated 5W.

My simulation shows it carries bursts of over 4 amps. That is 70 watts.

It's for a small portion of the cycle, but it is still a big demand on a component rated for 5W.

By the way, the capacitive drop method wastes several amps during 1/2 of the cycle.
However if you use a full-wave diode bridge, you can have put this to use. You can still use a capacitor to achieve AC drop, and it can be a lower microfarad value.

Per schematic:

 

[FvM]

Assuming sufficient thermal capacity of the Z-diode, it must me at least rated for the average power, which is about Vz*Iavg. Obviously it's not achieved with the said diode. In a real circuit other than in simulation, 1N4148 would "fuse" long before.

Another points to consider, most electrolytic capacitors from the market won't stand the large AC current for long.

A reasonable purpose of the circuit doesn't seem in reach.

 

[sina.parsnejad]

dude you can improve the circuit without punting such strain on the ziner
for example put a cap in serial with D1