Question on Nixie Supply

[Ripthorn]

Hi guys, looking at the nixie supply and was wondering if I could use fast recovery diode (150ns) as opposed to ultra fast diodes (50-100 ns).  Regular diodes have about a 2us recovery time, so I wonder if 150 ns is fast enough.  Anyone have any experience or thoughts?

[brett]

Hi
I'm no expert, but I don't see any intrinsic problem with 150ns unless the frequency is very high. 
I'd make sure that the recovery time is much less than half of the cycle time (1% of half the cycle time would be ideal).  Otherwise, efficiency falls as charge and time are wasted turning the diode off.
For 10kHz I would want 100us/2 x 0.01 = 500ns, for 100kHz I figure 50ns would be ideal. At 150ns you are probably very efficient at up to 30kHz, and ok beyond that if you are ok with inefficiency.
cheers 

[earthtonesaudio]

I agree with Brett.  A few dozen ns shouldn't make a huge difference, especially if your switching time is less than 500kHz.  I wouldn't recommend this, but just as an anecdote, I've used slow 1n400x diodes with 500kHz switchers (at LOW currents) and haven't seen any smoke yet.

[German]

Is that hard to get an ultra-fast diode? 

[Mick Bailey]

I use 1N4937 fast recovery diodes with no problem in nixie power supplies..