Based on generalized switching-cell approach, a generalized state-plane analysis for families of soft-switching DC-to-DC converters is presented. It is shown that the analysis of soft-switching DC-to-DC converter families can be analyzed in terms of a simple two-dimensional state-plane diagram. Complete generalized design equations are also given. It is shown that one generalized transformation table is given for the analyzed families. The basic generalized equations are summarized. The concept of generalized state-plane analysis is applied to selected soft-switching families such as ZVS-QRC, ZCS-QRC, QSW-CC, QSW-CV, ZCT-PWM, and ZVT-PWM. Other switching families can also be analyzed using the state-plane method.