I want to thank Tomas Hudson for an excellent technical article [Understanding LLC Operation (Part I): Power Switches and Resonant Tank | Article | MPS], but I think there may be some typographical errors at the very end of it. If I understand the four Operating Modes (which is not a given), some of the waveforms shown in Figure 8 may be mislabeled.
At the beginning of Mode 1, switch S1 has just been turned on (enhanced), so Vgs1 should transition from low to high. Figure 8 shows Vgs2 transitioning from low to high. I would expect Vds1 to rapidly drop to zero and Is1 to ramp up to a higher level as Lr and Lm “charge”. Figure 8 shows Is1 remaining near zero for the duration of Mode 1.
If my understanding is correct, then Figure 8 is incorrect. Or, is my thinking completely misaligned with reality for the LLC converter? 