# DC-DC Buck Converters with Quasi-Online Estimation of Filter Capacitor Equivalent Parameters
## 4 Discussion
From the perspective of the conditions in Appendix A, the scheme used in the experiments was characterized by \(\rho_{R}=26.92\) and \(\rho_{2,1}=0.10419\) for the 470 uF capacitor C21 and \(\rho_{2,2}=0.2626\) for the 220 uF capacitor C22. In this case also, the scheme lends itself to determining with a good approximation the value of the equivalent capacities. For a purely resistive load of the converter, the impact of the higher values of \(\rho_{2,1}\) and \(\rho_{2,2}\), in relation to the diagram in Figure 9 is visible: the dispersion of \(\hat{R}_{se,1}\) values are \(1.31531\%\), and that of \(\hat{R}_{se,2}\) only \(0.307099\%\). As a result, the values of the equivalent parameters of the filter capacitors, obtained in the mentioned experimental conditions, confirm the validity of the proposed scheme. Theoretically, the proposed converter scheme can be applied regardless of the type of load: resistive or resistive-inductive. Experimentally, it was found that in the presence of the resistive-inductive load, the dispersion ranges of the values of \(\hat{R}_{se\_1}\) and \(\hat{R}_{se\_2}\) increased by approx. 5 times. The experiments carried out in this context failed to identify a cause that could explain this effect. Finally, it should be noted that the method underlying the scheme in Figure 12 can also be used when the output filter of the converter is a battery of at least two capacitors connected in parallel. 4. Both schemes estimate equivalent parameters \(C_{e}\), \(R_{se}\) and measure operating temperatures \(\theta\) or \(\theta_{1}\) and \(\theta_{2}\) of the filter capacitors and send them out. The operating temperature is necessary to take into account its influence on the estimated values of the equivalent parameters [2]. Since the estimating process of the capacitor parameters with POs takes less than one second, the temperature of the investigated capacitor can be considered constant during the estimation. 5. The proposed DC-DC buck converter schemes are designed by completing the basic scheme of the converter (represented in black in Figures 9 and 12) with new components, including a microcontroller (represented in red in the two figures). This means additional costs for the converter. However, they offer the benefit of enabling predictive maintenance for the converter, leading to reduced operational costs in applications where increased reliability is required. 6. Each of the DC-DC buck converter schemes proposed in this paper is suitable for integration into a specialized integrated circuit. For example, in Figure 12, the integration can be based on the segmentation in Figure 15. The components within the boxed part of Figure 15 have been selected both for their technological integration feasibility and because they do not require parameterization in the application design process. Outside the integrable part are connected components that cannot be integrated (Load and coil L\({}_{1}\)) and components whose parameters depend on the application (capacitors \(C21\), \(C22\), external resistors \(R_{ext1}\), \(R_{ext2}\) and temperature sensors \(S_{\theta 1}\) and \(S_{\theta 2}\)).