Continuous conduction mode or discontinuous conduction mode

Hello,

I want to desing a basic dc dc buck converter. But i didn't decide about continuous conduction mode or discontinuous conduction mode. Why i must use CCM ? or DCM ? What will change if i use CCM or DCM ? Which one is more benefit for for me?

Additional question ; What i must use for my swicthing? Nmos ? Pmos? How will i select it ? How will pmos or nmos to effect my circuit?


I have some information about buck and boost converters although i am new in power electronics. Sorry my bad English. Thanks for reading

But i didn't decide about continuous conduction mode or discontinuous conduction mode. Why i must use CCM ? or DCM ? What will change if i use CCM or DCM ? Which one is more benefit for for me?

Click to expand...

DCM is what you might use if you have an inductor which is larger than your load calls for.

Or in case you need to avoid CCM because it would saturate or overheat the inductor.

There's also the idea that using DCM on purpose is preferable to letting the converter go into 'hiccup' (or irregular) mode inadvertently.

Hiccup mode may cause odd noises in the unit. DCM at least is consistent.

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I have created animated simulations of identical buck converters with three different loads. All are running at 50% duty cycle.

Click the link below and the falstad.com website will open. Click Allow to open the connection.

https://tinyurl.com/cg7y2ay

A) The leftmost one has a lighter load. It automatically goes into DCM due to light current flows.

B) The middle one has a medium load. Current flow just reaches zero between cycles.

C) The rightmost one (heavier load) has the coil conducting all the time, and hence it acts more as a filter choke than anything else.

You can adjust values by pressing ctrl (or else alt), and clicking a component. An edit window comes up.

What i must use for my swicthing? Nmos ? Pmos? How will i select it ? How will pmos or nmos to effect my circuit?

Click to expand...

A PNP/Pmos permits you to think in terms of the output stage referenced to ground at its more negative end.

If you want to create bipolar supplies then one can use NPN/Nmos and the other can use PNP/Pmos.

For high power conversion, N-devices traditionally offer better economy and wattage than P-devices. I say traditionally because things have been changing in recent years.

I have some information about buck and boost converters

Click to expand...

For a comparison of buck, boost, and buckboost converters, see my Youtube video showing animated simulations of their inner workings.

It dynamically portrays coil flux fields building and collapsing, and changing emf.

www.youtube.com/watch?v=FT_sLF5Etm4

Thanks for all answers. They will help to me.
I havent been discovered falstad.com before. I watched your simulations and used other tools of falstad. I liked this website. thank you for your sharing with me. and youtube videos are illustrative too

i want to decide the numerical values of my capacitor and inductor.
Is there a few nice sources for calculation of materials? I found some calculation formulas but they are different from each other. I want to use true source.

which values will necessary for my switching mosfet selection? which values are important in mosfet-datasheet for me?
I am an engineering student and i want to handle this subject like an engineer. I know calculation is important for it. And i must know how come out formulas?

It is common to use a frequency above our range of hearing. Say 19 kHz.

A suitable henry value might be 100 uH.

The higher frequency you use, the smaller henry value you can use. Also the smaller the filter capacitor you can use.

How much power you can get from it depends a lot on the minimum On resistance of your switching device.

Here is a tutorial about switched-coil power supplies:

**broken link removed**