## 2 Operation Principle  
Figure 3 shows the circuit diagram of the proposed TSBB converter. Like the conventional TSBB converter, the proposed TSBB converter is composed of two switches, two diodes, an inductor, and a capacitor; further, it operates in three topologies based on the switching of S\({}_{1}\) and S\({}_{2}\), and it operates in the buck topology by the on/off switching of S\({}_{1}\), in the boost topology by the switching of S\({}_{2}\), and in the buck-boost topology by the simultaneous on/off switching of S\({}_{1}\) and S\({}_{2}\). Table 4 summarizes the switching operations of the proposed TSBB converter. Table 4 indicates that the switching operations of S\({}_{1}\), S\({}_{2}\), and D\({}_{1}\) are the same as those of the conventional TSBB converter. However, D\({}_{2}\) performs on/off switching in the buck topology and is always off in the buck-boost topology. Figure 4 presents the operation principle of the proposed TSBB converter in each topology. The switch-on/off sections are divided by the operation of the switch that transfers the energy to the inductor. The semiconductors located in the current path in each section are conduction semiconductors; the semiconductor that only operates in one of the switch-on/off sections is the switching semiconductor. Table 5 compares the switching and conduction semiconductors between the conventional and proposed TSBB converters. In comparison with the conventional TSBB converter, the proposed TSBB converter undergoes an increase in the switching loss of D\({}_{2}\) in the switch-on section and a decrease in the conduction loss of D\({}_{2}\) in the switch-off section. In the buck-boost topology, the switching and conduction losses of D\({}_{2}\) in the switch-off section decrease. Table 6 compares the stress between the conventional and proposed TSBB converters; they have the almost same voltage stress in buck and boost topologies, but in the buck-boost topology, the stress of D\({}_{1}\) increases to \(V_{i}+V_{o}\). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Topology**} & \multirow{2}{*}{**Period**} & \multicolumn{4}{c}{**Component**} \\ \cline{3-6}  & & \(\mathbf{S_{1}}\) & \(\mathbf{S_{2}}\) & \(\mathbf{D_{1}}\) & \(\mathbf{D_{2}}\) \\ \hline \multirow{2}{*}{Buck} & Switch ON & ON & Always & OFF & ON \\  & Switch OFF & OFF & OFF & ON & OFF \\ \hline \multirow{2}{*}{Boost} & Switch ON & Always & ON & Always & OFF \\  & Switch OFF & ON & OFF & OFF & ON \\ \hline \multirow{2}{*}{Buck-Boost} & Switch ON & ON & ON & OFF & Always \\  & Switch OFF & OFF & OFF & ON & OFF \\ \hline \end{tabular}
\end{table} 
Table 4: Switch operation of the proposed TSBB converter. Figure 3: Circuit diagram of the proposed TSBB converter. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Topology**} & \multicolumn{5}{c}{**Conventional**} \\ \cline{2-7}  & \multicolumn{2}{c}{\(\mathbf{S_{1}}\)} & \(\mathbf{S_{2}}\) & \(\mathbf{D_{1}}\) & \(\mathbf{D_{2}}\) \\ \hline Buck & \(V_{i}\) & - & \(V_{i}\) & - \\ \hline Boost & - & \(V_{o}\) & - & \(V_{o}\) \\ \hline Buck-Boost & \(V_{i}\) & \(V_{o}\) & \(V_{i}\) & \(V_{o}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Comparison of stress in each TSBB converter: (a) Voltage stress; (b) Current stress. Figure 4: Operation principle of the proposed TSBB converter: (a) Buck; (b) Boost; (c) Buck-boost. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Topology**} & \multirow{2}{*}{**Gain**} & \multicolumn{2}{c}{**Conventional**} & \multicolumn{2}{c}{**Ref.