Michael A. Powers wrote:
>
> Hi All,
>
> I am currently using a PIC to control a frequency modulated buck converter power supply.  I'm not quite sure what values I should use for the output inductor and capacitor.  I've found some formulas for PWM controlled devices, but nothing for FM.  Does anyone have advice / formulas they could share?


Hi Mike, sorry I don't have formulae you can use,
but I have worked on some FM type SMPS units when
they were popular in some old computer systems.
Normally they are a "packet" operation, the packet
of energy is transferred to the load with each
switching, ie fixed "on" time if you like, and
when the load increases you send the packet more
often, ie freq increases. It's not a great system
compared to PWM as you need much better output
filtering and expect a second (pi) filter as a
minimum and much larger caps etc. Any reason you
can't just get the PIC to give increased "on" time
ie PWM, instead of FM?? Curious!
-Roman

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