The inductance DOES matter here, although the actual value isn't critical. The inductor in a switching power supply "balances" the inductor by maintaining a specific amount of voltage across that inductor for a certain amount of time for a given peak inductor current. What this looks like formulaically (new word!) is L = (V*S)/I where L is your inductor, V is the output voltage, S is in seconds and I is the peak current seen by the inductor. What this tells you is that for a certain frequency, you have to maintain a certain voltage across the inductor for a certain amount of time for a given current. If you end up losing this balance, be it increasing the current output, changing the on-time or changing the input voltage, it's the controller IC's job to sense that an imbalance has occurred and either increase or decrease the on-time of the switch accordingly. When the switch controller cannot maintain this balance, the inductor saturates and draws too much current so that either the switch will blow or the inductor will burn out (if the IC doesn't blow first).
I think that in your case, you haven't calculated or measured the peak currents seen by the inductor. For the supply I've finally finished designing (I'll post on it soon after more testing), the peak inductor current is MUCH higher than the rated output current - we're talking 2.85A peak inductor current vs. a 50mA output current. The peak currents in your circuit could be much higher than this still! The peak current is dictated by the inductor size where a smaller inductor draws more current. You're going to either need a higher current inductor or a larger value, but remember that a larger value inductor will increase switch stress.
I'm not sure which schematics you're basing your design off of either, I'm just going off of general knowledge. I will say that my new HV supply design is superior to the other designs I've seen so far in that it has pulse-by-pulse monitoring of the output voltage and would shut off (hopefully) before anything blows up. I have no grudge against 555 timer based designs or anything, I just don't know who designed the things or how good of a job they've done on their supplies. I usually don't trust something that I found on the internet until I've done at least some preliminary calculations to ensure that the design is a good/safe one.
I'm hoping to have my supply posted by this weekend, so maybe you can play around with it and give me some feedback. I have a little 1W tube amp already planned out for this supply, so I'm really stoked to get the supply finished finally and tested out in a real application. I'm also going to do a layout for the supply with a huge focus on making everything as small as possible. I'm hoping to find a FET that doesn't need to be heatsinked which would save a LOT of room, or perhaps I can use a DPAK or D2Pak part and mount it directly to the board. Either way, look for my post coming up soon.
