# Hybrid Resonant Converter with Three Half-Bridge Legs for Wide Voltage Operation
## 4 Design Procedures and Test Results
Similarly, the measured waveforms of the proposed converter under \(V_{in}\) = 195 V and full load are provided in Figure 13. The measured switching frequency \(f_{sw}\) = 163 kHz at \(V_{in}\) = 195 V and full load so that \(i_{Lr1}\) and \(i_{Lr2}\) were the sinusoidal waveforms, as shown in Figure 13b. Under the high input voltage range (\(V_{in}\) = 200-400 V), power switches \(Q_{3}\), \(Q_{4}\), and \(Q_{5}\) were off, and \(S\) and \(Q_{6}\) were on. Figure 14 shows the experimental waveforms under \(V_{in}\) = 205 V, \(V_{o}\) = 48 V, and \(P_{o}\) = 480 W. Figure 14a shows the measured gate voltages \(v_{Q1,g}\), \(v_{Q2,g}\), \(v_{S,g}\), and \(v_{Q6,g}\). The measured switching frequency \(f_{sw}\) = 82 kHz at \(V_{in}\) = 205 V. Figure 14b provides the measured waveforms \(i_{Lr1}\), \(i_{Lr2}\), \(v_{Cr1}\), and \(v_{Cr2}\). Due to \(f_{sw}\) (82 kHz) \(<\)\(f_{r}\) (150 kHz), the measured currents \(i_{Lr1}\) and \(i_{Lr2}\) were the quasi-sinusoidal waveforms. Figure 14c gives the measured waveforms \(V_{o}\), \(I_{o}\), \(i_{D1}\), and \(i_{D2}\). The diodes \(D_{1}\) and \(D_{2}\) turned off at zero current with soft switching operation. Figure 15 provides the experimental waveforms at the rated power and \(V_{in}\) = 400 V. The switching frequency \(f_{sw}\) = 160 kHz. The measured switch waveforms of \(Q_{1}\) at \(V_{in}\) = 50, 95, 195, and 400 V cases are measured in Figure 16. One can observe that \(Q_{1}\) all turned on at zero voltage switching. It can be predicted that \(Q_{2}\)-\(Q_{6}\) were also turned on under zero voltage due to the _LLC_ (inductor-inductor-capacitor) series resonant behavior. Figure 17 provides the measured circuit efficiencies for different load power (20%, 50%, and 100% loads) and input voltages (\(V_{in}\) = 50-400 V). For the same output power, the primary-side current at low input voltage range such as \(V_{in}\) = 50 V was greater than high input voltage range such as \(V_{in}\) = 205 V. This will introduce more conduction losses on the primary-side components under low input voltage range. Therefore, the presented circuit had better circuit efficiency at the high input voltage range. Figure 11: Experimental results at \(V_{in}\) = 95 V and full load: (**a**) \(v_{Q1,g}\)–\(v_{Q4,g}\); (**b**) \(v_{ab},v_{C1,1},i_{L1}\); (**c**) \(V_{o},I_{o}\), \(i_{D1},i_{D2}\). Figure 12: Experimental results at \(V_{in}=105\) V and full load: (a) \(v_{Q1,\delta},v_{Q2,\delta},v_{Q5,\delta},v_{Q6,\delta}\); (b) \(v_{C71},i_{Lr1}\), \(v_{C72},i_{Lr2}\); (c) \(V_{o},I_{o},i_{D1},i_{D2}\). Figure 14: Experimental results at \(V_{in}\) = 205 V and full load: (**a**) \(v_{Q1,g}\), \(v_{Q2,g}\), \(v_{S,g}\), \(v_{Q6,g}\); (**b**) \(v_{Cr1}\), \(i_{Ir1}\), \(v_{Cr2}\), \(i_{Ir2}\); (**c**) \(V_{o}\), \(I_{o}\), \(i_{D1}\), \(i_{D2}\). Figure 16: Experimental results at switch \(Q_{1}\) under (**a**) \(V_{in}\) = 50 V and 50% load; (**b**) \(V_{in}\) = 50 V and 100% load; (**c**) \(V_{in}\) = 95 V and 50% load; (**d**) \(V_{in}\) = 95 V and 100% load; (**e**) \(V_{in}\) = 195 V and 50% load; (**f**) \(V_{in}\) = 195 V and 100% load; (**g**) \(V_{in}\) = 400 V and 50% load; (**h**) \(V_{in}\) = 400 V and 100% load.