regular zeners vs tvs

[Howard]

Are there any differences between regular "run of the mill" zeners comapred
to special purpose transient surpressors (TVS) except for the high energy
ratings of the TVS diodes?

If you can limit the transient with a series resistor is there any benefit
in using a TVS diode over a regular zener. For my application I can use a
series 3K ohm with affecting the operation?

Thanks

Howard

 

[Joel Kolstad]

Are there any differences between regular "run of the mill" zeners
comapred to special purpose transient surpressors (TVS) except for the
high energy ratings of the TVS diodes?

TVSes are generally designed to fail short-circuit so that a fuse will blow,
whereas Zener diodes tend to fail open-circuit.

If you can limit the transient with a series resistor is there any benefit
in using a TVS diode over a regular zener. For my application I can use a
series 3K ohm with affecting the operation?

It depends on what input you expect the Zener to handle... if you're
comfortable that the 3K resistor will never be fried (due to long term
application of a high voltage input), I believe you're be fine.

Last time I used a TVS, it was for a 24V input power supply that had a
connector that could -- with EFFORT -- be shoved into another, incorrect
connector with 120V on it. One of the tests we had manufacturing do on
those power supplies was purposely plugging them into 120V AC (this supply
was reverse polarity protected as well) and and making sure that the only
thing that failed was the TVS and/or fuse. (And in actuality, I think it
was always both the TVS and fuse that blew... the TVS would short out long
before the furse otherwise would.)

---Joel Kolstad