2 Topology overview

The topology uses two phases operating 180° out of phase with a single DC blocking capacitor, C_b, taking advantage of the ripple current cancellation provided by the two-phase architecture and reducing the root-mean-square (RMS) current stress in C_b. L_b1 and L_b2 are sized to process the high-frequency AC ripple current necessary for TCM operation, removing the DC bias burden required for the inductor used in TCM, as defined in [5]. Using ferrite cores for L_b1 and L_b2 ensures low loss in the presence of the high flux swings necessary for zero voltage switching (ZVS). L_g1 and L_g2 are larger in value than L_b1 and L_b2 (approximately 10 times larger), preventing most of the high-frequency current from flowing into the input source and subsequently improving EMI. In addition, the reduced ripple current in L_g1 and L_g2 enables the possible use of lower-cost core materials. Figure 1 also illustrates the ripple current envelopes for the inductors and switch nodes.