## 5 Conclusions and Future Works  
In this article, we focused on a CCM flyback converter. Aiming to solve the problem of the output voltage of a flyback converter being easily affected by the input voltage and load fluctuations and the perturbation of the internal inductor and capacitor parameters, the control of the CCM flyback converter was studied and designed. A second-order  
\begin{table}
\begin{tabular}{c c c c} \hline
**Control Methods** & **Degrees of Freedom** & **Percentage Undershoot** & **Percentage Overshoot** \\ \hline PID & 1 & 12.5\% & 28.33\% \\ Second-order LADRC & 2 & 9.17\% & 23.33\% \\ \hline \end{tabular}
\end{table}
Table 2: Comparison between PID and second-order LADRC of the flyback converter.  
Figure 11: Output voltage experimental waveform when input voltage dips. (**a**) PID control; (**b**) second-order LADRC.  
\begin{table}
\begin{tabular}{c c c c c} \hline
**Control Methods** & **[34]** & **[35]** & **[36]** & **This Paper** \\ \hline Converter type & Flyback & Buck & Buck-boost & Flyback \\ Control approach & PID compensation & BP neural network PID & LMI-Fuzzy & LADRC \\ Controller parameter adjustment method & Online & Online & Online & Offline \\ Number of sensors & 1 & 1 & 2 & 1 \\ Algorithm calculation amount & More & More & More & less \\ Simplicity in implementation & Complicated & Complicated & Complicated & Simple \\ \hline \end{tabular}
\end{table}
Table 3: Comparison of various control techniques with proposed control methods.  
LADRC system, equivalent to a second-order degree-of-freedom system, was developed, and the Bode diagram of the controller was analyzed and observed for parameter design, which can avoid a large number of parameter trials. The controller parameters of the two control modes were varied; when the adjustment time and overshoot of the output voltage response of the system were roughly the same, the flyback converter system was subjected to internal disturbances, such as input voltage, load hopping external interference, and transformer excitation inductance transition inside the converter, and the simulation and experimental results verify that the proposed second-order LADRC strategy is superior to PID control in terms of anti-disturbance performance and robustness. This study has enriched the research on the anti-interference performance of the output voltage of this type of converter.  
The second-order LADRC method constructed does not require an accurate object model, only requires sampling of output voltage information, and has the advantages of simple control, strong robustness, and anti-interference. It has broad application prospects in the field of nonlinear systems of DC-DC power electronic converters such as Forward, Push-Pull, and Full/Half Bridge.  
Conceptualization, Y.Y. and J.Y.; methodology, Y.Y. and M.K.; software, Y.Y. and M.K.; validation, Y.Y., M.K. and Y.L.; formal analysis, J.Y.; investigation, J.Y.; resources, J.Y. and M.K.; data curation, Y.Y.; writing--original draft preparation, Y.Y. and J.Y.; writing--review and editing, Y.Y. and M.K.; visualization, M.K. and Y.L.; supervision, M.K.; project administration, Y.Y.; funding acquisition, J.Y. and Y.L. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Natural Science Foundation of Guangxi Province of China, grant number: 2020 GXNSFBA297124 and 2022 Guilin Innovation Platform and Talent Plan, Contract No.: 20220124-2.  
Not applicable.  
Data Availability Statement: Data are contained within the article.  
The authors would like to acknowledge the financial support provided by the Opening Project of Key Laboratory of Advanced Manufacturing and Automation Technology, Guilin University of Technology.  
The authors declare no conflict of interest.