I am working on a zvs driver and most of the parts were sourced from cheap Chinese pc power supplies and the fastest diodes i can find is the 1n4148 signal diode, well the problem is the breakdown voltage is pretty low (75v) and i don't think it will handle more than 24v input ,so what i wanted to do is put two of them in series giving me 150v breakdown voltage, now what I want to know is whether putting them in series will effect thier speed or not

 

It almost certainly won't double the breakdown voltage unless they have closely matched leakage currents. The one with the lowest leakage will have a bigger share of the applied voltage.

 

Why would any sentient being source parts from an existing product? That enterprise is doomed to failure.

 

Welcome to AAC!
Even if two 1N4148s could withstand the voltage, could they handle the current in your application?

 

Can you use a larger diode like the Ulatra Fast series (UF4007 etc.)?

If not, you can try two diodes in series using the commonly accepted method (shown below) of using resistors or resistors and capacitors to swamp out the differences between diodes.
The capacitors are sometimes left out.

Would your circuit still work with the added resistors or added resistors and capacitors?

 

It almost certainly won't double the breakdown voltage unless they have closely matched leakage currents. The one with the lowest leakage will have a bigger share of the applied voltage.

not

Why would any sentient being source parts from an existing product? That enterprise is doomed to failure.

Not everyone abe to buy stuff online
And I cant even find an electronics shop in our town , I live in Algeria

It almost certainly won't double the breakdown voltage unless they have closely matched leakage currents. The one with the lowest leakage will have a bigger share of the applied voltage.

Well It's supposed to discharge the gates of the mosfets so i think it can withstand the current

It almost certainly won't double the breakdown voltage unless they have closely matched leakage currents. The one with the lowest leakage will have a bigger share of the applied voltage.

But they are the exact same diode

 

But they are the exact same diode

Yes, they are the same in theory but are not built exactly the same.
They can differ slightly in their reverse leakage currents, which means they will not share any reverse voltage equally when connected in series, so the one with the lower leakage could reach its breakdown voltage well before the other.

 

not

Not everyone abe to buy stuff online
And I cant even find an electronics shop in our town , I live in Algeria

That might tend erect an obstacle to your activities. I'm not sure why you can't buy things online since that is how almost everyone does it; but even here in the US there have not been local electronics shops where you could buy parts in small quantities for 40 years or more. Since the switch to SMT components in the late '90s and early 2000's it has only gotten worse. Most online places want you to buy a reel of 3000 pieces, assuming you are going to use them in an automated assembly machine.

 

Instead of parts from "cheap Chinese power supplies", I suggest, since new parts can be a BIG CHALLENGE, investigating other scrap electronics, such as older TV sets that were solid state except for the CRTs, also old CRT computer monitors. The horizontal deflection systems contain some rather high voltage higher current components. And the supply of failed CRT devices may be cheap. Here in the US such devices head toward landfills, because there is no demand.
At any rate, it may be worth investigating.

 

On that note (CRT displays) the deflection yokes and degaussing coils are a rich source of expensive magnet wire, provided they aren't all stuck together.