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I am currently working on a motor driver that should operate on 100V or higher voltages. I need to implement logic there with 3.3V. I could provide additional, low voltage source but that would give more connections. I Was wondering what is the best and cost/ size efficient way of going from 100V dc to 3.3V dc? I havent found any IC's allowing to do that, most of the dc-dc converters work from a maximum 40V dc input voltage. I would apreciate all help!

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  • \$\begingroup\$ Misspell, "cost".Edited. \$\endgroup\$ – Bremen Jul 20 '15 at 8:38
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100VDC is in the domain of Switch Mode power supplies, which, for example, phone chargers are. You can get a ringing-core SMPS down to a cubic centimetre or two, especially if the system doesn't require high degrees of isolation between high and low voltage sides.

I would look into buying or building a small ringing-core SMPS, or using those cheap crappy fake Apple mini cubes from China for 5V and then going to 3.3V if you are lazy. Those things are dangerous and should not be used in the mains, but if you open them up and make sure no shorts can happen by unfolding the innards or at least glueing some stuff up, you have a tiny 5V supply from 80V to 300V DC.

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  • \$\begingroup\$ Do you have any experience in any particular circuit/ IC? \$\endgroup\$ – Bremen Jul 20 '15 at 6:48
  • \$\begingroup\$ @ŁukaszPrzeniosło Not in the eensy weensy domain, no. But if you google Ringing Core there's a couple of good tutorials. They don't use a chip, but rather a MOSFET (usually) that gets driven by the transformer itself with a capacitor to get it into resonance. ST had a great app note on it, but I can't find it on the Googlies and I'm at the office now, so it's a huge hassle to find the PDF on my home network from here. \$\endgroup\$ – Asmyldof Jul 20 '15 at 7:30
  • \$\begingroup\$ I see, thank you. The problem is though that to my circuit, a DC voltage of value 100V will be supplied. As far as I can think of a power supply, they would have to use a transformer, which requires AC voltage. This kind of complicates whings for me. \$\endgroup\$ – Bremen Jul 20 '15 at 7:32
  • \$\begingroup\$ @ŁukaszPrzeniosło A switching power supply works perfectly well with DC. A SMPS (Switch Mode Power Supply) usually first rectifies the AC to then switch it at 25kHz to 250kHz, self driven. \$\endgroup\$ – Asmyldof Jul 20 '15 at 7:33
  • \$\begingroup\$ ill try to find something more, thank you for help. \$\endgroup\$ – Bremen Jul 20 '15 at 7:34

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