mukesh said:
hi sir,
i am working in the UPS field .. i wanted to know that what is the max
freq we can choose for flyback converter ..... i am using the ferrite
core transformer . is there any limitation for freq ? what is the
max working freq for ferrite core transformer??????????
Look in the catalogs. You can get ferrite cores for much higher
frequencies than the ones you're using. The usual limitations on power
supply efficiency vs. frequency is parasitic capacitance and diode lag
effects, which don't come from the core. This capacitance makes it
harder to drive the FETs quickly, and the recovery times of the diodes
(should you use them) causes some lost energy each cycle. Dealing with
gate capacitance increases circuit complexity, as does eliminating the
diodes by using synchronous rectification.
Driving the frequency up is attractive because the core size goes up
roughly with the amount of energy it has to store, and the amount of
energy stored is roughly proportional to the power supply's power output
times one cycle time. This means that a higher switching frequency
means smaller cores.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Posting from Google? See
http://cfaj.freeshell.org/google/
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at
http://www.wescottdesign.com/actfes/actfes.html