DC to DC buck converter

[satiz]

Hi There,

I would like to understand why DC to DC converter inductor has offset or (IMIN in the image) ?

Here is the Image I got from online reference. Can any one pls help me to understand this

 

[Easy peasy]

that's how it works in " continuous mode " or CCM, look up DCM & CCM in buck converters ....

 

[cupoftea]

Attached is a simulation of it in the free download LTspice simulator...
This is the best way to see the operation.

As an exercise, make it go into DCM if you want......or write back here and i will help you.

The inductor in a buck, is just like a high frequency dropper, and helps drop the input voltage without wasting too much power

 

[BradtheRad]

Operating in CCM allows an inductor with lesser saturation rating.

Notice if you reduce frequency, then you have the Ampere waveform traveling a large range between crest and trough. That is, between zero and a high peak (DCM).

However by switching at higher frequency, the AC waveform traverses a smaller distance. It develops greater DC component (Imin in your diagram)(CCM). Nevertheless there's a benefit because peak current is reduced in the inductor. Its saturation rating need not be as great as for a slower switching frequency.

 

[Easy peasy]

@brad - the average DC level in the choke will be the same - for the same power out and Vin.