Calculating inductance for boost converter - units

• Calculating inductance for boost converter - units
  Posted by newtekuser on 04 Mar, 2024 05:15
• Watching Phil's Lab video on calculating the value for the inductor and want to know what units he used to get the 23uH value for the inductor.
  
  
  Vout = 16V
  Vin = 5V
  Eff = 0.8
  Fsw = 1.5MHz
  
  First he uses the estimation formula for the inductor ripple current =  0.3 * Iout (max) * Vout/Vin = 96mA
  
  Then he feeds the inductor ripple current into the inductance formula (Vin(Vout - Vin) ) / Vout * f * IL = 23uH
  
  Does he express the 1.5MHz frequency as 1.5 and ripple current as 0.096
  
  OR
  
  1.5MHz frequency as 1.5 and ripple current as 96, then multiplies everything by 1000 ?
• #1 Reply
  Posted by newtekuser on 04 Mar, 2024 05:40
• Answering my own question: the frequency value is in MHz and the current ripple is in Amps
  
  so (5 * (16-5)) / 16 * 1.5 * 0.096 = 23uH
• #2 Reply
  Posted by Berni on 04 Mar, 2024 06:15
• You are supposed to put everything into equations as base units. so the 1.5MHz should be 1500000 Hz and the result should be 0.000023 H
  
  Just that since Mega is x1000000 and is on the bottom of the fraction so becomes /1000000 and Micro is /1000000 the units just happen to work out in a nice way, letting you work with numbers without a bunch of zeroes.
• #3 Reply
  Posted by Terry Bites on 04 Mar, 2024 14:07
• I've used this handy tool. https://www.coilcraft.com/en-us/tools/dc-dc-optimizer/#/search
  Give up on inches and farenheit.