so look up interactive power loss calculators at the inductor manufacturer websites, they'll give you core loss (and total AC loss) with your buck parameters.
Well said Siwastaja, i totally agree.
With those coilcraft parts , you can definetely get your core loss and windings resistance loss.
You really should deffo do this.
Indeed, if there is no online calculator, then pick an inductor that has a calculator for your core and windings loss.
Coilcraft and vishay and others have core loss calculators, deffo.
I trust also that you have a schottky across your low side fet...for those little intervals when the fet turns off.
What is your vout/vin?
Make sure you dont have shoot though due to eg spurious on turning of the lower fet when the high side fet turns on...you can solve this by suitably slowing down the on turning of the high side fet, and by having a low impedance off drive for the low side fet.
Bear in mind that if you are using a controller with on_board slope compensation, then you may find that if your duty cycle is greater than 0.5, you will have to choose a higher inductance inductor in order to avoid subharmonic oscillation......often, the supplied slope compensation isnt much, and you need to have say just 12% or so ripple in the inductor current....dont make the current ramp too low in gradient though, as otherwise your current sense may trip prematurely every now and then and cause noisy operation.
I assume its a current mode buck.?
Is it one of those linear.com bucks? (now analog.com)
Which controller do you use?
Are you isng the little QFN FETs, and how have you provided thermal situation for them....thermal vias to bottom layer copper? Beware, the source of the top fet is a switching node, and the drain of the bottom fet is a switching node...you need to minimise their area so as to pass EMC.....But not so little that you fail thermal.
Good idea with the thermal cam....get one with a "highest temperature fix" feature, then you can find the hottest bit even if your hands cant hold the cam totally still.
Seriously, i reckon without "highest temperature fix"...then a thermal cam is rubbish for use with electronics.
If your duty cycle is low, then the rds of the top fet is not so important......
If your controller only gives low voltage gate drive, then ensure your fets can be fully driven on by that low voltage
By using larger inductor, ripple current is smaller, hence given same output capacitors, ripple voltage is also smaller, and also the converter runs in CCM at lower loads. With a suitable load, this would mean lower noise, which could be important. But efficiency could be lower.
I woudlnt be sure that a ccm buck is "always" less noisy than a DCM buck.....after all, in CCM, the low side parallel diode gets slammed off by the sudden oncoming of the top fet, so this is quite an EMC_noisy event....with DCM, the top fet turns on after the low side diode has no current flowing in it...
..Which brings up another point...in deep DCM, the buck shoudl have a way of knowing to turn off the low side fet just after the current in it has finished flowing...otherwise, there is a chance of getting high backflow of current in the inductor in terms of light load....and this could possibly saturate the inductor, but its likely that your controller deals with this.
...having said that, there are actually synch bucks which always have current flowing in the inductor (except at zero crossings)..and when you are on no load, the current flows
(sloshes) backwards and forwards in the inductor.