In LLC the switching frequency will be in the right of the resonance frequency or above the resonance frequency, so we will be in the inductive region, if we let the LLC operate in the left of the resonance frequency , it will be in capacitive region and this will cause problem and may be the 2 switch conduct in the same time, can some one please explain why this happen

 

What are you on about?

 

What are you on about?

I am asking why in LLC converter ,we have to operate in the inductive region

 

Try read this
http://www.infineon.com/dgdl/Applic...n.pdf?fileId=db3a30433a047ba0013a4a60e3be64a1

never fall into the capacitive region operation.Such requirement is due to that Zero Voltage Switching (ZVS) is only achieved in the
inductive region, in addition to that capacitive operation means that current leads the voltage, so the current in the MOSFET will reverse direction before the MOSFET turns off, then after the MOSFET turns off the reverse current will flow in the MOSFET’s body diode, which will cause a body diode hard commutation once the other MOSFET in the bridge turns on, which in turn will cause reverse recovery losses and noise, and might cause high current spikes and device failure