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Need help to design buck circuit

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asiregar

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Hello,

Can someone help me to design a buck circuit with this spesification:
Vin = 48V - 60V
Vout = 48V
Imax out = 15A

how to select the very best frequency to apply to this circuit?

please..
 

Hi,

I recommend to do some research on your own.
Even in this forum there are a lot of similar threads.

To many of them I recommended to to go to a SMPS_IC_manufacturer internet site and use their interactive selection guide.
This I have to repeat here.

****
BTW: your specifications can be fulfilled: You can´t have 48V output with a buck converter and 48V input. There always is a voltage drop.

Thus you need to modify your specifications:
* change input voltage range
* or change output voltage
* or change topology (maybe buck-boost)

Klaus
 

Vout = 48V
Imax out = 15A
Click to expand...
It will be low frequency for such a power... mainly limited by the semiconductor used.. unless you switch it very fast with e.g. GaN.
 

CataM said:
It will be low frequency for such a power... mainly limited by the semiconductor used.. unless you switch it very fast with e.g. GaN.
Click to expand...

Hi,

Can I ask why that is? Thanks. Related to realistic power dissipation limitations? It also needs a lot of on-time to charge appropriate inductors and/or capacitors?
 

Related to realistic power dissipation limitations?
Click to expand...
Yes. A buck converter is a hard-switched topology, so only the switching losses are major part of the total losses.
The higher the frequency, higher the switching losses, so frequency must be reduced. Doing so, increases the size of the magnetics and hence price.

A way to still keep a reasonably high frequency, the losses must be counteracted via switching faster (lower turn on/off times), moving from Si MOSFET to GaN.
 
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    d123

    d123

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If you have no size and weight restrictions, you can design for 50-70 kHz and make life easier for your self

If you have a buck circuit with 100% high side drive then you can have 48Vin & 48Vout but there will be a slight IR drop in the fet.

there are plenty of driver chips for this, with and without level shifting for the high side series pass buck switch

also consider a P channel fet on the high side - easier to drive/level shift in some respects...

good luck...
 

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