Buck converter calculations
Buck converter calculations
(OP)
Hi. Is there an easy calculation from voltage, & inductance to maximum power transfer ? I had expected to use a 500kHz converter with an 18V supply, but that won't allow the power that I need. I would need either to crank up the voltage, reduce the frequency, or use multiple phases. A lower inductance would allow an increase in peak current, but reduce the energy per cycle.
Thanks-in-advance
Shane
Thanks-in-advance
Shane





RE: Buck converter calculations
Try some of the website calculators from the buck converter manufacturers (TI, Analog Devices, National Semi, etc.). That may get you on the right path.
Z
RE: Buck converter calculations
RE: Buck converter calculations
One guiding equation to determine minimum inductance is:
L(min) = (V(in) - V(hs) - V(out)) * D / (LIR * I(out) * f)
where:
* L(min) - minimum inductance
* V(in), V(hs), V(out) - input voltage, voltage drop across switching device in on state, output voltage
* D - cycle duty (approximately V(out) / V(in) )
* LIR - inductor current ripple ratio, ripple current divided by I(out)
* I(out) - maximum output current
* f - switching frequency
Often V(in), V(hs), V(out) and D are fixed, so all you have to play with is f, LIR and L to maximise your I(out).
See On Semiconductor Application Note AND9135/D for a handy worked example.