As for how to design a buck converter, I referred to Kevin’s documentation on bucker converter IC Buck Converters

Synchronous Buck Converter

For maximum efficiency the buck converter we selected will be synchronous, with a little bit of research, I discovered that the main difference is that the diode is replaced/connected in parallel with another FET. The turning on and turning off of the switch is controlled by the on/off of the two FETs.

The benefit for that is the increased efficiency and reduced diode loss (R_dson*I_d<Vf*I)

Power losses

Inductors: has DC Resistance (DCR) loss, P_L=I_0^2*R_ESR

Diode: forward voltage drop (note that it is only conducting for (1-D)*T seconds) P_D=I_0*V_f*(1-D)

MOSFET: 1. Conduction loss, P_Cond=I_0^2*R_ds*D

2. Switching loss, P_sw=[V_ds*I_0*(t_on+t_off)]/2T_s

Component selection

Buck Converter IC

This is the most important part, once we have selected the IC we can select other components (inductors, capacitors, resistors) based off the specs of the IC.

Since we are converting from 24V to 5V, we need to consider a buck converter IC with: maximum input voltage larger than 24V; output voltage adjustable/fixed at 5V; rated output voltage should be larger than 5A; if possible the switching frequency should be a wide range; step-down, buck converter only (no buck-boost).

After applying all of the above constraints to DigiKey search query, my options came down to around 30 ICs, at first I was only considering TI’s IC, and the main IC are the LMR and TPS series. After I enlarge my options to other manufacturers, I found other good chips. Applying more close constraints and looking at the Datasheets more carefully, it comes down to 2 options:

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With this chip, the footprint configuration looks really complicated, other than that there is no critical weakness of this IC

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The only problem with this chip, is that the switching frequency is fixed, that may cause some problems when selecting Inductors, luckily, after calculation I can source pretty good inductors based on the fixed frequency, so in the end I chose the MP2491CGQB-Z chip

Image AddedImage Added

Inductor

From the data sheet the design requirements of the inductors is that:

DC current rating 25% larger than output current (5A)
DC Resistance should be smaller thatn 15mOhms
I_sat (Saturation current) should be larger or equal to high side switch current

The current ripple can be calculated in the following equation

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And the value of inductor can be calculated using the following equation, substitute in all the values.

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I chose standardize inductor values, and calculate the K backwards (4.7uH, 5.1uH, 5.6uH, 6.2uH)

Inductance	4.7uH	5.1uH	5.6uH	6.2uH
K value	0.343	0.316	0.288	0.26

Based on that, I started looking on Digikey for the different inductors. The constraints are that inductors should be shielded, and with current rating and saturation current around 7-10A.

5.6uH:

https://www.digikey.ca/en/products/detail/sumida-america-inc/177CDMCCDS-470MC/9490436 *if set K=0.35, but still bigggg

https://www.digikey.ca/en/products/detail/vishay-dale/IHLP6767GZER560M11/2139396

https://www.digikey.ca/en/products/detail/pulse-electronics/PA4344-563NLT/5641842

https://www.digikey.ca/en/products/detail/codaca/VSAB1770-560M/16731527

https://www.digikey.ca/en/products/detail/coilcraft/XGL1010-563MED/21381839 *Seems to be the best one but not available on DigiKey

https://www.digikey.ca/en/products/detail/shenzhen-sunlord-electronics-co-ltd/MWSA1206S-470MT/14120328 *set at 0.35, relatively smaller

https://www.digikey.ca/en/products/detail/bourns-inc/SRP1265A-470M/4876628 *0.35, smaller (the above one is the smallest available)

4.7uH:

https://www.digikey.ca/en/products/detail/bourns-inc/SRP6060FA-4R7M/9351055

*The rated current and isat are a little bit high, small size (6mmx6mm) (1.86)

https://www.digikey.ca/en/products/detail/abracon-llc/ASPIAIG-F6060-4R7M-T/20096290