As Tim pointed out, the high frequency SMPS are a *real* shielding issue when used to generate B+ voltages for vintage tube radio battery eliminators. The materials expense may not be worth the few % of efficiency gain over the simple low-freq B+ inverter circuits that have been used for decades.
I built a few for my battery portables many years ago by feeding an H bridge oscillator into a small audio transformer wired backwards. With a simple pi filter on the output to block the ~70hz noise. Regards, Jeff On Apr 12, 7:31 am, Nick <[email protected]> wrote: > On Apr 9, 7:30 am, [email protected] wrote: > > > I can tell you where there would be a fairly big market for high > > efficiency high voltage power supplies (IF THEY CAN BE PROPERLY SHIELDED > > FOR RF LEAKAGE) that is B power supplies.... > > There are many folk who use a derivative of the MAX 1771 design on my > site for tube radios, "stompboxes", headphone & preamps etc. both > amateur & commercial products (though I get no license fees ;-) > > The problem is that the switching frequency varies depending on load > and there are many harmonics which can be large due to the high > switching currents. > > Filtering both input and output of the SMPS & full screening of the > unit itself are pre-requisites. > > Its non-trivial to get right.... -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
