###### Abstract  
In this study, a modified design of a two-switch buck-boost (TSBB) converter is proposed to improve power efficiency using fewer conduction components, and the optimal power range is measured. The proposed TSBB converter operates in three topologies: buck, boost, and buck-boost, like the conventional TSBB converter. However, the proposed converter improves the power efficiency in the buck and buck-boost topologies by decreasing conduction loss using the diode in the switch-off section while maintaining the same number of semiconductors as that in the conventional TSBB converter. The power efficiency of the buck topology improves for the power range 10-80 W in the constant voltage (CV) and constant current (CC) modes; it increases on average by 0.75-1.36% and 0.83-2.27% in the CV and CC modes, respectively. The power efficiency of the buck-boost topology step-down improves for the 10-80 W in all modes. This increases the average by 0.73-0.99% and 3.33-4.75% in the CV and CC modes, respectively. The power efficiency of the buck-boost topology step-up increases on average by 1.65-2.00% for 10-80 W in the CV mode. In the CC mode, it increases by 2.17-2.77% on average for 10-50 W.  
c 2022 2022 2022 202  
step-down and step-up cannot be used in applications that require an output voltage of the same polarity as the input voltage because the polarity of the output voltage is opposite to that of the input voltage. Moreover, the power conversion efficiency decreases compared to that of other topologies because the voltage stress of the switch and diode equals the sum of the input voltage \(V_{i}\) and output voltage \(V_{o}\). Therefore, the TSBB converter that can switch to a different topology based on system requirements is used frequently [7; 8; 9; 10]. Figure 2 shows a circuit diagram of a conventional TSBB converter that comprises two switches, two diodes, an inductor, and a capacitor. This TSBB converter operates in the buck, boost, or buck-boost topology based on the operation of the switch [5; 6; 7]. Table 2 summarizes the switching operations of the conventional TSBB converter; it operates in the buck topology by the on/off switching of S\({}_{1}\) while S\({}_{2}\) is always off, and in boost topology by the on/off switching of S\({}_{2}\) while S\({}_{1}\) is always on. Further, the TSBB converter operates in the buck-boost topology by the on/off switching of both S\({}_{1}\) and S\({}_{2}\). It is easy to change the topology despite the increase in parts; the output voltage has the same polarity as the input in the buck-boost topology. Moreover, it is easy to select semiconductors because the voltage stress of the parts does not exceed the input voltage \(V_{i}\) and output voltage \(V_{o}\)[9; 10; 11; 12; 13]. Table 3 presents the switching and conduction semiconductors in each topology of a single switch converter and a TSBB converter. The TSBB converter uses more parts than the single switch converter in each topology owing to the composition and wiring of the semiconductors; this increases the power loss and lowers the power efficiency. The loss of the TSBB converter increases because of the amount of the conduction loss of one diode than the single switch type in the buck topology and the amount of the conduction loss of one switch in the boost topology. Moreover, the power efficiency in the buck-boost topology decreases owing to the switching and conduction losses of one switch and one diode [5; 6; 10]. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Topology**} & \multicolumn{2}{c}{**Current Path**} & \multirow{2}{*}{**Gain (G)**} \\ \cline{2-2} \cline{4-4}  & **Switch ON** & & **Switch OFF** \\ \hline Buck & V\({}_{i}\)-S-L-C\({}_{o}\) & L-C\({}_{o}\)-D & d \\ Boost & V\({}_{i}\)-L-S & V\({}_{i}\)-L-D-C\({}_{o}\) & \(1/(1-\mathrm{d})\) \\ Buck-Boost & V\({}_{i}\)-S-L & L-C\({}_{o}\)-D & d/(\(1-\mathrm{d})\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Current path and gain in topologies.