DC-DC boost converter

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robert.guttormson

Joined Oct 3, 2009
26
I am designing a boost converter for a motor drive that accepts DC voltage and transforms it to AC. The motor drive accepts 320V DC input. I tried following the principles of a simple boost converter but the output never converges after following all the equations. I added a more than necessary cap to smooth out any ripple. I have simulated a pulse for a particular duty cycle. As usual, I dont know why it doesnt work, read through the other threads on the forum but couldnt figure out. Any or all help is appreciated. TIA
 

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Jony130

Joined Feb 17, 2009
5,487
Well if you will work in CCM then

D = (1 - 140V/320V) = 0.56
So for F = 40KHz
Ton = 14us
L_min = (14us * 140V)/ ( 2 * IL) = 3mH

So if you want to use coil 55uH you need Ton = ( L * 2*IL) /Vin_min = (55uH *0.6A)/140V = 235ns ----> F = 0.56/235ns = 2.3MHz.

So if you change L1 =3.3mH and Ton=14.1us then you will get 320V in LTspice after 250ms

And for DCM change L1= 680uH and Ton = 10.5us
 

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