# Inductor and capacitor in DC-DC converters

#### f123

Oct 26, 2018
9
Here is what I know about the inductors and capacitors in the buck converter starting from transient.

Inductor and capacitor : during the switch is on, the inductor current will increase from zero with a constant slope that is Vg-0/L, (Vo = 0 at first) during DTs. Then this will charge the capacitor to some point. During the switch is off, the inductor current will decrease with a constant slope of -Vo/L with Vo being close to zero, meaning a small decrease in current during Ts. during many period Ts, we will reach steady state, which the increase in current in the inductor is the same a the decrease during Ts. This also the same for the capacitor voltage.

Since the net change in inductor voltage is zero during Ts and how net change in the capacitor current is zero?

How this can explain the energy transfer?

Based on that, how do know the steady state given this circuit? do we have to get it from observing this second order LC filter?

I got things mixed and got confused a lot. Would any please refer me to a link that explain all this or can anyone explain this to me please?

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#### kellys_eye

Jun 25, 2010
5,146
Many of the major semiconductor manufacturers that deal in SMPS components have design sheets and application notes that describe operation and construction of such circuits right from basics.

Here's one example - look from page 35 for the basic topology explanations.

https://www.onsemi.com/pub/Collateral/SMPSRM-D.PDF

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