Been keeping an eye out and playing with simple discrete circuits for quite a while now, without much success.
Has anyone come across a low power / low noise / high efficiency SMPS method to convert 8-40VDC to 2-8V at 100mW, say for a bunch of codecs and DSP stuff? All specs somewhat optimistic - all compromises entertained. The 40V max would be plenty for me, as 100mW would load down a standard 48V/6k8 phantom power source to below 40V anyway (after the obligatory output buffer transistors).
I first assumed that for the high ratio I'd need a transformer or tapped choke, but now I'm leaning more towards larger magnetics, lower PWM frequency (eg 96kHz nominal, to reduce any residual beats with audio codecs to near-DC), wider range and more efficient drive. Maybe use cheap ISDN or LAN magnetics?
All thoughts appreciated.