DC-DC converter control loop doubt

[amriths04]

design of control loop for a dc dc converter

could anyone tell me,,why in voltage mode feedback, the loop crossover (UGF) frequency must be atleast 1/5th to 1/6th less than that of switching frequency?

i want to know the exact reason for the above. what will happen if UGF=fs/3?

 

[eem2am]

analog loop converter dc-dc

voltage mode is slower than current mode...............and often used with smps's with lc filters in output.............

you wont manage to get good phase margin and gain margin if you go to high in freq for your UGXF.

also, having ugxf for any converter means you are more susceptible to noise.

if your ugxf is near F(sw)/2 then you'll be too responding to your switching frequency ripple.

so to be honest..........keep it less than f(sw)/5 sounds good...........

lower means poorer transient response.