24V to 500-1000V, 20W floating DC-DC converter

Take a look at these maybe:

Someday all the guys who show up every couple of months out of nowhere looking for plans on how to build their own handheld electric zapper-taser will come to terms with the fact that it's one of the more useless "weapons" for just about any purpose there is.

Might as well put it in a heavy enclosure and then bop your enemy on the head with it.

Thanks! That's a good start for a replacement transformer.

ulser. It needs to be a floating or negative converter.

only one I've come across that is isolated is Figure 50 of LT Application N ote 29

-notes/an29f.pdf). It is specified for 1000V, 5W so not beefy enough. The t ransformer is also obsolete, but this comment mentions potential replacemen ts.

es-a-continuous-arc/) that is 1kV, 20W. I just don't know enough about maki ng it adjustable and isolated.

Sigh... it's for a piezo stack. I've seen you comment on other HV PSU threa ds. Do you have any insight for a good isolated design?

I you want to design the whole circuit, take a look at LT3803 and its app notes. It just always seems to work.

Scribble some circuits and we can talk about them. LT Spice includes the 3803 too. It seems to work just like it simulates.

er. It needs to be a floating or negative converter.

y one I've come across that is isolated is Figure 50 of LT Application Note 29

a-continuous-arc/) that is 1kV, 20W. I just don't know enough about making it adjustable and isolated.

has a circuit for a high-voltage output inverter at the bottom of the page, which relies on pulse with modulation to adjust the output voltage.

It's strictly an LTSpice simulation, the output voltage goes higher than yo u need, and the power levels are for biasing a photomultiplier tube and low er than you want.

A bigger transformer, with room for thicker wire would fix most of that - y ou would also need a higher voltage MOSFET switch - 24V into the centre tap of a Baxanadall class oscillator produces a 75.4V peak half-sine across th e MOSFET that is off, and the AP9465GEM is only good for 40V.

The NXP BUK9Y72-80E might do.

Yeah you make it adjustable and isolated more or less the same way you make any other flyback converter adjustable and isolated. You've designed and built a flyback before, right?

If this is a one-off or a few pieces, how about Ultravolt 1C24-N20 ? We used that (actually positive version) to start a product line and later designed a custom one.

In our case, we needed robust short circuit protection and cap charging, which required some knowledge in the flyback control loop - mostly reduced frequency for low end voltage. Other items to take care of were correct snubbering and resistor chains to deal with 1kV on SMD. And discharging on powerdown to avoid accidents!

Transformer is a custom one with 4 HV sections and a 2-turn foil primary around them for down to 14V operation. Each HV section was rectified to a cap and the DC was in series.

I generally like to design or at least modify a current design so I underst and what's going on. This is new territory for me, so I'll look into a star t some simulations. Thanks for the tip on the LTC3803.

illator1.htm

e, which relies on pulse with modulation to adjust the output voltage.

you need, and the power levels are for biasing a photomultiplier tube and l ower than you want.

you would also need a higher voltage MOSFET switch - 24V into the centre t ap of a Baxanadall class oscillator produces a 75.4V peak half-sine across the MOSFET that is off, and the AP9465GEM is only good for 40V.

I'll simulate this one as well and read up on Baxandall oscillators more. I nteresting that this design was never built; I'm sure I would find a way to produce some fireworks.

It will only be a few pieces. The 1C24-N20 does fit the bill (excellent fin d btw), but space constraints may dictate I can't use it. I want to start w ith a custom board and then I can fall back on the Ultravolt if need be. I have ~5uF of HV capacitance and don't actually want fast cap charging, so t he Ultravolt would be overkill in that sense.

The pragmatic way to do this, at least for a one-off, is to buy a dc/dc brick that has a control input, and be done. But as you say, you wouldn't learn much about HV supplies.

LTC/ADI has some starting-point simulations for the 3803.

I'm playing with an isolated flyback right now, probably about 200 volts at very low current, possibly with a voltage regulator on the high side. When my customer gets un-confused about what he actually needs, I'll build him a demo.

Does you piezo move slow or fast? Win Hill has posted some interesting piezo drive ideas here recently.

Oh, Bill doesn't ever build things. He's only here to manufacture insults.

er. It needs to be a floating or negative converter.

y one I've come across that is isolated is Figure 50 of LT Application Note 29

a-continuous-arc/) that is 1kV, 20W. I just don't know enough about making it adjustable and isolated.

If you are going to try building it yourself, then I'd start with the

(2018... thread here

Good luck. Oh buying a ready made HV supply would be a good thing. Gives you something to compare to if/when you have problems putting to whole system together.

George H.

Yep. OP did not like that I disparaged/was skeptical of his plan to build a 20 watt 1000 volt converter out of the gate but it strikes me as a certain kind of madness as a first project if OP has not designed and built a flyback of any type before.

Even if someone here were able to provide a perfect custom design that fit the bill the probability of something not working right on a first prototype is high, and the probability of being able to figure it out without a real working reference design or experience building more modest switchers, is low

Says he's got an implied 1000 volt piezo stack with a capacitance of...5uF? that doesn't sound right. the answer to how fast it moves is "slow" if that's really what it is and you've got 20 watts

That would lift trucks, or buildings.

the answer to how fast it moves is

Yes, the original flyback in the EDN article has as 0.01uF 1500V cap as the main output cap and 0.022u 500Vs as the CW boost caps. this is a 4uF

the EDN circuit isn't in the right ballpark.

Hoping he actually meant 5n or something

ulser. It needs to be a floating or negative converter.

only one I've come across that is isolated is Figure 50 of LT Application N ote 29

-notes/an29f.pdf). It is specified for 1000V, 5W so not beefy enough. The t ransformer is also obsolete, but this comment mentions potential replacemen ts.

es-a-continuous-arc/) that is 1kV, 20W. I just don't know enough about maki ng it adjustable and isolated.

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Since you bring it up, it bothered me when you said that too. I assume people mostly know what they are talking about. Why not be nice?

BTW 5 uF for a piezo stack doesn't strike me as impossible. I used this little multilayer stacks (for motion) that were ~0.1 uf (only 150 V.)

George H.

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The 5uF is the bulk capacitance of the pulser circuit, not the piezo elemen t, to prevent droop during pulses. So the caps are not fully charged and di scharged every cycle that would need to fast cap charge capability of the U ltravolt unit. The bulk capacitance will also be "separated" from the power supply with a resistor to slow charge the caps.

Do the math on how much peak current you'd need to slew a 1000 volt 5uF piezo stack full-range to have a sub-ms response time mah dude! with a