Sorry, this is a resonant royer, without the second winding for driving the= transistors.=20 Similar to the first schematic here: https://www.eevblog.com/forum/projects/efficient-magnetics-design-for-offli= ne-resonant-push-pull-(royer)-converter/ Just add a bridge rectifier on the output and a feedback path to a comparat= or that drives the power control fet (Q3) in this circuit. I'm nowhere near regulation, but if I alter the circuit to regulate at 40V = instead of 400V it actually works in spice, turning "Q3" on and off appropr= iately. -----Original Message----- From: piclist-bounces@mit.edu On Behalf Of Jason = White Sent: Thursday, July 5, 2018 12:31 PM To: Microcontroller discussion list - Public. Subject: Re: [EE] 3V - 400V royer converter Before I read Sean's email: Post the LTSPICE file, I recall facing a simila= r issue recently in a power supply design class I took. I think the issue w= as something simple like a 1milliohm series resistance in the default LTSPI= CE inductor & switch models. Changing it to 1 nanoohm fixed that. After I read Sean's email: if you need to model saturation you can do it bu= t I think you'll have to define your own model/subcircuit. On Thu, Jul 5, 2018 at 1:12 PM, Van Horn, David < david.vanhorn@backcountry= access.com> wrote: > I'm having some trouble with an exercise in LTSpice, for a DC-DC=20 > converter from 3V (Lithium cell nominal) to 400V Basically, no matter=20 > how I set up the transformer I don't seem to get past 40V. > It's been a while since I built a Royer converter, and I think I'm=20 > missing something in the transformer design. > > Taking a WAG at the inductor design, I have a center tapped primary of=20 > two 10uH inductors. > I defined the relationship as Pin =3D Pout =3D (Vin * Iin) =3D (Vout *=20 > Iout), more or less. > Vout / Vin =3D turns ratio 400/3 =3D 133/1 turns ratio > > Since inductance is kN^2, I defined the output inductor to be the=20 > inductance of one half of the primary winding (10uH) multiplied by=20 > (133^2) Coupling between all inductors in the transformer is 0.95, anothe= r WAG. > > I added 1uH leakage inductance (not coupled ) to both legs of the=20 > primary, but not to the centertap leg. > > Ancillary problem, whenever I define the output inductor with a param=20 > statement like .param L2=3DL1*(133^2) I get the dreaded "Time step too sm= all" > message pointing to my mosfets. > I have to work it outside of spice, and then use something like .param=20 > L2 =3D 178mH. > > > > -- > David VanHorn > Lead Hardware Engineer > > Backcountry Access, Inc. > 2820 Wilderness Pl, Unit H > Boulder, CO 80301 USA > phone: 303-417-1345 x110 > email: david.vanhorn@backcountryaccess.com backcountryaccess.com> > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive=20 > View/change your membership options at=20 > http://mailman.mit.edu/mailman/listinfo/piclist > -- Jason White -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/chang= e your membership options at http://mailman.mit.edu/mailman/listinfo/piclis= t --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .