AYK, there are many events that bring about the dreaded reverse recovery in the LLC......so thats overload, short cct output....undervoltage input.....startup, re-start-up, heavy load transients, and some more. Also, since even one single instance of the reverse recovery in an LLC can kill or seriously weaken the converter, the detection needs to detect the disaster before it happens, and then stop switching the fets so it doesnt happen..........to detect this (imminent_reverse_recovery) in that timescale is extremely challenging.......as discussed, infineon claims to have LLC circuitry and software that can do that ( i think they do?)...........but if it works, then it is truly amazing........without that software based proteciton, it needs the series diode to be sure of not getting reverse recovery based destruction.
But yes, and its literally amazing that the App Notes and semico's dont talk of this.......touting LLC controllers without mentioning it isn't a great idea...some of the LLC App Notes work through Ohms Law calcs with you......but then dont bother to tell you about the reverse recovery issue.
And if infineon really do have that avoid_reverse_recovery software....then the Nobel Prize wouldnt be enough for them!
This approach to solving the dv/dt issue in mosfets has been around since power mosfets were first used in aggressive switching -
Thanks yes...
..AYK, its an old technique, but i believe needs re-introduction and re-birthing, due to the rising popularity of the "current sloshing" converters like the LLC....AYK, "current sloshers" slosh the primary current about so that the fet diode comes on just before the fet switchs on........others in the same category, AYK, are Phase shift full bridge and the "Half_bridge_with_big_leakage_inductance_but_no_output_inductor"...aswell as one variety of the forward converter if the leakage L in the txfmr is big enough. (Active clamp forward).
AYK, the problem with "current sloshing", is that it can get "out of phase", and the diode can get sloshed on just as the opposite fet is turned ON....literally one single instance of this can kill or seriously weaken the converter....thats why its so difficult to avoid if you dont use the series diode.
...and its literally amazing that the App Notes and semico's dont talk of this.......touting LLC controllers without mentioning it isn't a great idea...some of the LLC App Notes work through Ohms Law calcs with you......but then dont bother to tell you about the reverse recovery issue.
And if infineon really do have that avoid_reverse_recovery software....then the
Nobel Prize wouldnt be enough for them!
...or even a mention on BBC's "click" program!!