## 6 Conclusions and Future Works  
The present study provided a comprehensive assessment of a Differential-Evolution-assisted optimization of classical compensation topologies for 1 W current-fed IMD wireless charging systems with a biocompatible operating frequency of 13.56 MHz. This innovative approach aimed to indicate that the parallel-series compensation topology fed through a Class-E power amplifier was more stable in the face of coupling factor variation and also tended to reduce the input current despite a frequency oscillation of up to 10%. The system was optimized using a Differential Evolution algorithm in order to select optimal parameters that must provide non-bifurcation criteria, along with higher efficiency. A wide review of the four classical topologies of inductive resonant coupling was made by evaluating their behavior in terms of frequency and coupling factor variations. Once having clarified all the advantages and disadvantages of each, the PS topology was selected. The Differential Evolution algorithm showed rapid convergence to the global maximum of 94.79% for the PS WPT stage efficiency. The values of the primary and secondary inductances obtained for \(L_{2}\) were equal to 430.2 nH; as the efficiency had no dependency on \(L_{1}\), the \(L_{1}\) value remained as previously selected, equal to 610 nH. The main results proved the good stability with an efficiency of around 94% of the PS WPT part. The Class-E PA developed achieved 91% efficiency, with the whole system standing above 86%. The proposed system presents a potential path as a consistent energy supply for implantable medical devices, reducing the number of surgical procedures, also increasing the lifespan of the batteries and allowing operation during recharging. The results highlight the valuable role of the wireless charging systems in medical applications, considering biological factors so as to guarantee operational stability and appropriate efficiency, making the application safe and viable. Future work will rely on evaluating the challenges of transitioning our idealized circuit to practical applications. It is paramount to consider the constraints posed by high-frequency operations. The high-frequency system necessitates sourcing suitable electronic components. GaN field-effect transistors emerge as a viable choice for Switch RDS\({}_{on}\), due to their capability to handle high switching frequencies and compatibility with the project's current requirements. Subsequently, a low-side ultra-fast gate driver optimized for switching GaN FETs in high-speed scenarios is indispensable. A clock oscillator with a frequency of 13.56 MHz will also be required. Designing inductors for  
Figure 20: Delivered active power. (**a**) From the DC power source. (**b**) To the PS circuit. (**c**) To the output load. high-frequency operation presents its unique challenges. The advantage of high-frequency operation is that it necessitates significantly lower inductance values. This makes air-core designs, which eliminate core losses at high frequencies, attractive [29]. Planar inductors on printed circuit boards (PCBs) stand out as they support higher operational frequencies and offer the added benefits of reduced weight and size--factors critical for biomedical applications [30]. High-frequency winding losses in PCB planar inductors are substantially influenced by skin and proximity effects, given the specific geometry of the PCB planar winding conductors [30]. This can lead to increased high-frequency losses. Therefore, an inductor design that holistically considers winding losses, overall performance, and thermal issues becomes crucial [31]. Furthermore, accurate temperature predictions and management of the coupling inductors are vital, not just for the electrical attributes, but also for the overall reliability and performance of the WPT system--integral for any IMD application. Conceptualization and methodology, R.B.G. ; validation, I.M.S.d.J., T.M.T., M.d.C.P., B.d.S.A. and R.L.R.S. ; formal analysis, R.B.G., I.M.S.d.J. and T.M.T.