inductor Lr
resonates back to the same level as the magnetizing current, Lr
and Cr
stop resonating.
Lm now participates in the resonant operation and the second time interval begins. During this time
interval, dominate resonant components change to Cr
and Lm in series with Lr
. The ZVS operation in
region ○2 is guarantees by operating the converter to the right side of the load gain curve. For a
switching frequency below resonant Fr1, it could falls in either region ○2 or region ○3 depends on the
load condition.