# Hybrid LLC Converter with Wide Range of Zero-Voltage Switching and Wide Input Voltage Operation
## 6 Conclusions  
A new ZVS LLC converter is presented, analysis and realized to have wide load soft switching and wide voltage input operation. In order to accomplish wide load range of ZVS operation, the LLC resonant tank is used to accomplish ZVS turn-on for all active devices. According to the different input voltage ranges (50 V-400 V), the variable voltage gain is used to regulate load voltage constant. To realize the variable voltage gain which is related to the input voltage range (low, medium or high voltage range), two ac power switches are adopted in order to select half bridge or full bridge resonant circuit with the different turns-ratio of transformer. Thus, the wide range of input voltage operation is realized in the proposed circuit. The studied LLC converter can be applied to wide voltage input variation such as switching power converters with long hold-up time requirement, battery systems or solar panel. Compared to the other wide voltage circuit topologies, the proposed converter has no dc voltage level on the resonant converter [17] and less diode conduction loss [18]. However, more power devices are still needed in the proposed converter to realize 8:1 wide voltage operation. Thus, the cost issue is the main drawback of the studied circuit for industry applications. The presented converter \begin{table}
\begin{tabular}{c c} \hline
**Input Voltage V\({}_{\text{in}}\)** & **Efficiency** \\ \hline \(\text{V}_{\text{in}}\) = 50 V \& 50\% load (low voltage range) & 88.1\% \\ \hline \(\text{V}_{\text{in}}\) = 50 V \& 100\% load (low voltage range) & 87.2\% \\ \hline \(\text{V}_{\text{in}}\) = 90 V \& 50\% load (low voltage range) & 89.7\% \\ \hline \(\text{V}_{\text{in}}\) = 90 V \& 100\% load (low voltage range) & 88.1\% \\ \hline \(\text{V}_{\text{in}}\) = 110 V \& 50\% load (medium voltage range) & 89.5\% \\ \hline \(\text{V}_{\text{in}}\) = 110 V \& 100\% load (medium voltage range) & 88.2\% \\ \hline \(\text{V}_{\text{in}}\) = 190 V \& 50\% load (medium voltage range) & 91.3\% \\ \hline \(\text{V}_{\text{in}}\) = 190 V \& 100\% load (medium voltage range) & 90.1\% \\ \hline \(\text{V}_{\text{in}}\) = 210 V \& 50\% load (high voltage range) & 90.3\% \\ \hline \(\text{V}_{\text{in}}\) = 210 V \& 100\% load (high voltage range) & 89.6\% \\ \hline \(\text{V}_{\text{in}}\) = 400 V \& 50\% load (high voltage range) & 92.5\% \\ \hline \(\text{V}_{\text{in}}\) = 400 V \& 100\% load (high voltage range) & 91.8\% \\ \hline \end{tabular}
\end{table} 
Table 2: Measured efficiencies under input voltage and load conditions. \begin{table}
\begin{tabular}{c c} \hline
**Input Voltage V\({}_{\text{in}}\)** & **Switching Frequency f\({}_{\text{sw}}\) (kHz)** \\ \hline \(\text{V}_{\text{in}}\) = 50 V \& 50\% load (low voltage range) & 61 \\ \hline \(\text{V}_{\text{in}}\) = 50 V \& 100\% load (low voltage range) & 52 \\ \hline \(\text{V}_{\text{in}}\) = 90 V \& 50\% load (low voltage range) & 85 \\ \hline \(\text{V}_{\text{in}}\) = 90 V \& 100\% load (low voltage range) & 81 \\ \hline \(\text{V}_{\text{in}}\) = 110 V \& 50\% load (medium voltage range) & 57 \\ \hline \(\text{V}_{\text{in}}\) = 110 V \& 100\% load (medium voltage range) & 55 \\ \hline \(\text{V}_{\text{in}}\) = 190 V \& 50\% load (medium voltage range) & 101 \\ \hline \(\text{V}_{\text{in}}\) = 190 V \& 100\% load (medium voltage range) & 98 \\ \hline \(\text{V}_{\text{in}}\) = 210 V \& 50\% load (high voltage range) & 57 \\ \hline \(\text{V}_{\text{in}}\) = 210 V \& 100\% load (high voltage range) & 54 \\ \hline \(\text{V}_{\text{in}}\) = 400 V \& 50\% load (high voltage range) & 104 \\ \hline \(\text{V}_{\text{in}}\) = 400 V \& 100\% load (high voltage range) & 97 \\ \hline \end{tabular}
\end{table} 
Table 3: Measured switching frequencies under input voltage and load conditions. has been developed in the laboratory and its effectiveness was validated through experiments by a laboratory prototype circuit. [PERSON] designed and evaluated this project and was also responsible for writing this paper [PERSON] measured the experimental waveforms.