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Looking for pulse-rated zener.

Well, some areas of the coutnry have to have basements because of the tornadoes. But here in So. Calif, we seldom have basements, I'm guessing the reasons are:

Because the dwelling is on a sandy soil that has a shallow water table, so the basement would be easily flooded.

Because most of the housing built after WW2 used a poured cement slab for the floor.

Because in a bad earthquake, the rest of the house would fall into the basement.

Because it's cheaper to build a second story out of wood than dig a hole and pour concrete walls, needed for earthquake reasons. Also since it doesn't get cold here, the insulation doesn't have to be that great, so the second story is even cheaper.

Probably a combination of the above.

I think that this place has a cool basement.

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Reply to
Watson A.Name - "Watt Sun, th
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Yes, that's good. One must be careful not to select R too small, because then the FET's current at switch-on might be excessive. And one musn't selecting R too high, because then it'll develop too much voltage from the inductor's current at switch-off, forcing us to use an artificially-high-voltage FET. Selecting R so its maximum voltage drop equals the maximum capacitor voltage sounds promising.

Applying this to Mark Becker's 8uH 15A 1us shutoff requirement, with C = 33nF and R = 7.5 ohms, we get a snappy 0.7us coil-current switch- off, a maximum FET voltage of 190V, and a maximum FET current of only 19A for 0.5us at switch-on. The coil is slow to get up to its 15A current, saving the FET any extra stress.

We need a high-current diode rated for more than 200V. I used both halves of a MUR3040, but despite being a fast-recovery part it still suffers from a reverse-recovery-time delay. This means the inductor rings badly (at 4MHz, 380Vp-p in my model) unless its damped. Adding 0.01uF plus 150 ohms in parallel does the job nicely, and also reduces the FET's Vd-max to 180V and Id-max to 18A.

One big downside to this approach to capturing the inductor's energy is another 15W of power continuously dissipated in the series diode.

--
 Thanks,
    - Win
Reply to
Winfield Hill

Yes thanks thats what i was asking, as both cases have the vds>20v @ high curent. Trying to think of a way of avoiding it yet still using a more deterministic way of setting the peak voltage.

Actualy i was wondering if a cascode mosfet arangement would behave any better, again it might make it less noticable as the bottom device would stay more in control of the current, although i would be worried about this as long ago I had some nasty oscilations when i was trying to make a high voltage power supply with several series mosfets (600v mosfets were very limited at the time), but unfortunatly i never had the time (or the experience back then) to get to the bottom of all the diferent modes of oscilations.

Colin =^.^=

Reply to
colin

Check the rental laws. I understand that in most states (US) that a lease of one year or more, even tho it *states* one year (or more) in reality means "indefinite" which translates to *any* amount of time the renter desires. Some states may require the lease to state one year and one day at minimum for that interpretation. A lease less than one year runs for the specified period. Something to consider and use.

Reply to
Robert Baer

I guess i better use some of my "pocket lint" and get that shack...

Reply to
Robert Baer

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