Apr 16, 2009 #1 A amriths04 Full Member level 5 Joined Jul 15, 2006 Messages 263 Helped 23 Reputation 46 Reaction score 9 Trophy points 1,298 Activity points 2,819 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?
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?
Apr 16, 2009 #2 E eem2am Banned Joined Jun 22, 2008 Messages 1,179 Helped 37 Reputation 74 Reaction score 24 Trophy points 1,318 Activity points 0 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.
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.