Quote:
Originally Posted by Radio Wrangler
Quote:
Originally Posted by Electronpusher0
so the switching frequency must be between 50 and a few hundred hertz.
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That's not a bad choice for the job. Most modern switcher designs with ferrite transformers would likely be switching within the long/medium wave bands, or have fat harmonics in them, creating hell. |
I can vouch for that - the interference is the hardest nut to crack!
I made a converter this year providing HT, LT, and GB- operating from a 12V SLA battery. Overall efficiency is around 80% (it's based on a flyback converter running at 25kHz), but I needed 3-stage LC filtering on the HT output, the LT output, and the 12V input (and 3-stage RC filtering on the GB output) to keep it quiet.
Working at low frequencies does offer the opportunity to use slow switching devices, keeping RFI right down, while not hurting efficiency by much because there are fewer switching events per second. The down side is that the size of the transformer increases. But, it's still not going to be massive, at a few watts only if power, and I can see the attraction of using an off-the-shelf transformer.