# Hybrid Resonant Converter with Three Half-Bridge Legs for Wide Voltage Operation
## 4 Design Procedures and Test Results
The list of equipment that was used to record the results is as follows: Chroma 62012P-600-8 (DC voltage source), Chroma 63112A (DC electronic load), TCP302 and TCP312 (current probe), TDS3014 (digital oscilloscope), and SI-9110 (isolated voltage probe). Figure 7: Voltage curves of the presented circuit: (**a**) low input voltage range; (**b**) medium input voltage range; (**c**) high input voltage range. The experimental waveforms of the developed circuit operated at low input voltage range (\(V_{in}\) = 50-100 V) are shown in Figures 10 and 11. In the low input voltage range, power switches \(S\), \(Q_{5}\), and \(Q_{6}\) were off and only switches \(Q_{1}\)-\(Q_{4}\) were controlled with frequency modulation. Figure 10 illustrates the experimental results at \(V_{in}\) = 50 V input and full load. Figure 10a gives the test waveforms of \(v_{Q1,g}\)-\(v_{Q4,g}\). The switching frequency \(f_{sw}\) under the rated power and \(V_{in}\) = 50 V was about 100 kHz. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Items** & **Symbol** & **Parameter** \\ \hline Input voltage & \(V_{in}\) & 50–400 V \\ Output voltage & \(V_{o}\) & 48 V \\ Rated load current & \(I_{o}\) & 10 A \\ Series resonant frequency & \(f_{r}\) & 150 kHz \\ Output capacitor & \(C_{o}\) & 1080 μ (1080 μF/100 V) \\ Resonant capacitors & \(C_{r1}\), \(C_{r2}\) & 273 μF \\ Power MOSFETs & Q\({}_{1}\)–\(Q_{6}\), \(S\) & Infineon-6R070P6 \\ Resonant inductors & \(L_{r1}\), \(L_{r2}\) & 4.13 μH \\ Rectifier diodes & \(D_{1}\), \(D_{2}\) & PS30M100 SFP \\ Primary and secondary turns of \(T\) & \(n_{p}\), \(n_{8}\) & 8 turns, 4 turns \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Prototype circuit parameters. Figure 8: Control block of the signals \(Q_{1}\)–\(Q_{6}\) and \(S\). Figure 9: Pictures of the proposed converter: (**a**) prototype circuit; (**b**) control board; (**c**) experimental setup. Figure 10b provides the test waveforms of primary-side current \(i_{Lr1}\), capacitor voltage \(v_{Cr1}\), and leg voltage \(v_{ab}\). Due to the switching frequency \(f_{sw}\) = 100 kHz \(<\)\(f_{r}\) = 150 kHz, the resonant current \(i_{Lr1}\) was a quasi-resonant waveform. Figure 10c shows the experimental waveforms of \(V_{o}\), \(I_{o}\), \(i_{D1}\), and \(i_{D2}\). One can observe that the output voltage was regulated at 48 V output, the load current \(I_{o}\) was 10 A, and the diodes \(D_{1}\) and \(D_{2}\) turned off at zero current switching. Figure 11 gives the experimental results at the rated power and \(V_{in}\) = 95 V. The measured gate voltages \(v_{Q1,g}\)-\(v_{Q4,g}\) are given in Figure 11a. The test results of \(v_{ab}\), \(v_{Cr1}\), and \(i_{Lr1}\) are illustrated in Figure 11b. Because the switching frequency \(f_{sw}\) at \(V_{in}\) = 95 V was almost equal to \(f_{r}\), the measured resonant inductor current \(i_{Lr1}\) was a sinusoidal waveform. The experimental waveforms of \(V_{o}\), \(I_{o}\), \(i_{D1}\), and \(i_{D2}\) at the rated power and \(V_{in}\) = 95 V are demonstrated in Figure 11c. \(V_{o}\) was regulated well at 48 V output under \(I_{o}\) = 10 A. Figures 12 and 13 give the test results under the medium input voltage range (\(V_{in}\) = 100-200 V). Under the medium input voltage range, switches \(Q_{3}\) and \(Q_{4}\) were off and \(S\) was on. Figure 12 shows the test results under \(V_{in}\) = 105 V and full load. Figure 12a gives the measured gate voltages \(v_{Q1,g}\), \(v_{Q2,g}\), \(v_{Q5,g}\), and \(v_{Q6,g}\). The measured switching frequency \(f_{sw}\) was about 84 kHz. Figure 12b provides the test results of \(v_{Cr1}\), \(i_{Lr1}\), \(v_{Cr2}\), and \(i_{Lr2}\). Because \(f_{sw}\) = 84 kHz \(<\)\(f_{r}\) = 150 kHz, the resonant currents \(i_{Lr1}\) and \(i_{Lr2}\) were the quasi-sinusoidal waveforms. Figure 12c provides the measured waveforms of \(V_{o}\), \(I_{o}\), \(i_{D1}\), and \(i_{D2}\) at the rated power and \(V_{in}\) = 105 V. The diodes \(D_{1}\) and \(D_{2}\) turned off at zero current switching.