I have built a circuit that can drive a 3.3v AC output at a few hundred mA. The wave has a frequency of 150Khz. I want to step this up to 60-90v at ~0.5 Watts to drive an ultrasonic piezo. However, I am having difficulty finding a transformer. From what I understand, I am looking for one with a coil ratio between 1:20 and 1:30, and a relatively small VA. I would also like the transformer to be as small as possible (low height is more important than small footprint). I have looked on common electrical supply house websites like Digikey, but their filters aren't all that helpful. Coil ratio is never a filter option, and anytime I find one that I think might work, it is made to operate at 60Hz. Also, when I search "1:30," I get results for current transformers, and I don't believe that these are suitable for my application. I would greatly appreciate some guidance on how to search for a transformer and possibly some suggested devices.

Secondly, I am not positive that I am on the right track for this project. The circuit that I created is a class E amplifier. Should I be feeding Vcc 60-90v DC (by using a flyback converter, for instance) rather than throwing a transformer on the output? The idea is to prioritize making the circuit small with some consideration for efficiency. Thanks for the help!

  • \$\begingroup\$ There is a good chance you could just use something like a Triad Magnetics FS20-120-C2 and run it 'backwards'. Being made for 60 Hz is likely not a problem at these levels...a bit more resistive/lossy is all I would expect. \$\endgroup\$ – evildemonic Oct 30 '19 at 21:29
  • \$\begingroup\$ @evildemonic 60 Hz to 150kHz? It may be more than a bit more lossy. But it's probably worth a try. \$\endgroup\$ – TimWescott Oct 31 '19 at 0:00
  • \$\begingroup\$ There's a lot of difference between a transformer designed for 50 / 60Hz and one for use at 150kHz. The Triad product appears to have a laminated iron core which is fine for mains frequencies but will almost certainly be very lossy at 150kHz. I would think you need to look at high frequency ferrite cores and a custom design. \$\endgroup\$ – Peter Jennings Oct 31 '19 at 0:01
  • \$\begingroup\$ With the stipulation that I may be completely off base -- you may want to wind one. DigiKey should be able to sell you E-cores, bobbins and clips. It would be up to you to do the designing, though. \$\endgroup\$ – TimWescott Oct 31 '19 at 0:02
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    \$\begingroup\$ @BenWatson, this might be exactly what I'm looking for. I'll try it out an let you know! \$\endgroup\$ – user3286192 Oct 31 '19 at 7:33

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