im required to design a buck converter that will step down the voltage to supply a piece of equipment.I also require to show the results of simulation of my circuit.

My circuit should meet the following specifications:

Vin=24V

Vout=18V

Max ripple compared to DC input=10%

load resistance=5 Ω

Switching frequency must lie between 50kHz to 200kHz

Assume ideal devices have been used!

ok..so to start of with, I no the circuit im required to design (not sure about the which switching device to choose yet).i have decided to use Pspice Student Version to simulate my circuit.

I have calculated:

Iout=Vout/Rload=18/5=3.6A

ΔI=0.1*3.6=0.36A

D=Vout/Vin=0.75

Now for continuous conduction mode:

we know that L=\(\frac{(Vin-Vout)*(D/Fs)}{Ir}\) whr Ir=ΔI

Now the issue is that i really cannot figure out how to choose Fs!!Once i choose Fs correctly, i can find the value for my filter inductor.

its mentioned in the ques that i can choose between 50kHz to 200kHz, but is there any appropriate logical way to selecting the Switching frequency?

I would also like to know whether its better to use a p/n type MOSFET or IGBT for my circuit and why!

thx