# State-of-the-Art DC-DC Converters for Satellite Applications: A Comprehensive Review
## 4 Comparative Analysis of Various Topologies  
This section provides a performance analysis and comparison of the various DC-DC converter topologies for satellite applications. The most important consideration for satellite applications is reliability, which must be weighed against other factors like converter cost, efficiency, and power density. Switching devices and their control circuits are considered the parts most prone to failure in a power converter. The lower the component count, the greater the reliability. Capacitors are also prone to failure, especially during high-temperature operations. Although they are troublesome and their reliability is uncertain, they are unavoidable. Space-grade components are used to improve performance, although at an increased cost [128]. Redundancy and modularity are two important means of improving reliability. To improve the converter's power density, the switching frequency can be increased to minimize the size of the passive components while still meeting design specifications. Nevertheless, a larger switching frequency results in increased switching losses and has higher heat dissipation requirements [129]. This also leads to reduced efficiency. Therefore, a trade-off exists between power density, efficiency, and heat dissipation requirements in the converter [130]. Regarding efficiency, high-efficiency operation reduces fuel consumption and extends the satellite's life. Moreover, it results in lower heat dissipation requirements, lower costs, and improved reliability and power density. Semiconductor devices account for most of the losses in power converters, reducing efficiency, especially at high powers. Thus, in high-power satellite applications, parallel connection of several modules is adopted, so that each module carries only a fraction of the total power [104]. This helps improve the efficiency of the converter. Moreover, it also enhances performance by increasing the redundancy, ease of maintenance, scalability, and fault ride-through capabilities of the converter [131]. A schematic demonstration showing the above-mentioned dependencies of various performance parameters for satellite applications is provided in Figure 20. A comparison of isolated, non-isolated, and integrated topologies, as well as the topologies for EP, based on their reliability, redundancy, modularity, power density, and efficiency, is shown in Tables 5-8, respectively. The power density and efficiency values presented in the tables are obtained from the corresponding references, and reliability is classified as \begin{table}
\begin{tabular}{l l l l l l l l l l l} \hline \hline
**Converter** & **References** & \multicolumn{2}{c}{**Switching Frequency (kHz)**} & \multicolumn{2}{c}{\
\begin{tabular}{c} **Component Count** \\ **S** \\ \end{tabular} } & \multicolumn{2}{c}{**Power (W)**} & \multicolumn{2}{c}{**Main Features**} \\  & & & & & & & & & & & \\ Flyback & [116; 117] & - & & 1 & 1 & 1 & 1 & 20 W &
\begin{tabular}{c} Simple circuit, suitable for small satellites. \\ Simple circuit, suitable for small satellites. \\ Simple circuit, would \\ component count. \\ High efficiency, lower \\ weight, high switching \\ frequency, complex \\ control circuitry. \\ High efficiency over wide \\ output range, low \\ component count, parallel \\ or serial switching of \\ multiple output conditions \\ Soft switching, galvanic \\ isolation, simple structure. \\ Decreased EMI, a large \\ output voltage range, high \\ efficiency, and \\ power density. \\ Soft switching, low size of \\ inductor, high power \\ density, and efficiency. \\ \hline \hline \end{tabular} } \\ \end{tabular}
\end{table} 
Table 4: Comparison of various DC-DC converters for EP in satellites. low, medium, or high, based on the component count, redundancy, and modularity of the converter. Additionally, the topologies are classified based on application type and satellite type, as shown in Table 9.