<p>DC-DC converters are key topologies in many industries and perform an increasingly important role in the power electronics. Over the past decade, many advanced techniques have been used to solve the optimized modulation strategy for the DC-DC converters, in order to promote the operation efficiency. As one of the most classic DC-DC converter, the dual active bridge (DAB) converter has attracted more and more attention in the utilization of the isolated DC-DC power conversion systems, due to its good performance. Aiming to provide a comprehensive analysis of different optimizing techniques for the DC-DC converters, this paper provides an overview and comparison of the advanced optimization modulation strategies with a case study on the DAB converter. Firstly, typical phase-shift modulation strategies and variable frequency modulation strategies are analyzed. Then, the application of four categories of optimization techniques is introduced, which including numerical optimization methods, metaheuristic methods, reinforcement learning (RL) methods and deep reinforcement learning (DRL) methods. The experimental results suggest that the TPS modulation method has the potential to achieve the highest efficiency and best performance, compared with SPS, EPS and DPS. Moreover, the DRL methods is best suited to solve the modulation optimization problem of the DAB converter. Finally, this paper provides corresponding enlightenment and suggestions for further improving the operation efficiency of the DAB converter.</p>