mcp1650 inductor calculation DCM mode

mcp1650.py

#!/usr/bin/env python

import time
from math import log10

Vin = 5.0

if Vin < 3.8:
  D = 0.8
else:
  D = 0.56

Vout = 100.0

Lmin = 0.1E-6
Lstart = 1E-6
Lmax = 100E-6

Iout = 20E-3
Pout = Vout * Iout

eff = 0.8

Pin = Pout/eff
print "Pin:", Pin

Fsw = 750E3
Ton = (1./Fsw)*D
print "Ton:", Ton

Llow = Lmin
Lhigh = Lmax

while True:
  L = 10**((log10(Llow) + log10(Lhigh)) / 2)
  Ipk = (Vin/L)*Ton
  Eind = .5*L*Ipk*Ipk
  Pind = Eind*Fsw
  print "L:%e, Ipk:%f, Pind:%f" % (L, Ipk, Pind)
  if Pind < Pin:
    Lhigh = L
  else:
    Llow = L
  time.sleep(1.0)