Mode 2 [t1, t2]: At some time through the switching
cycle, SBYF is switched off, and its counterpart in the
opposite phase leg, SAYF, is turned on under zero-current
condition, because the built-in diode of SAYR has been
reversed-biased by the positive voltage drop on CAY. The
load current will therefore charge up CBY and discharge
CAY, making the output voltage decrease to zero at t = t2