# Analysis and Implementation of a Hybrid DC Converter with Wide Voltage Variation
## 5 Experimental Results  
Figure 7 shows the measured input voltage \(V_{in}\) and the switch signals \(S_{ac1}\) and \(S_{ac2}\). It is clear that \(S_{ac1}\) is off and \(S_{ac2}\) is on when 60 V \(\leq V_{in}\) < 120 V. The converter is operated at a low voltage range input, shown in Figure 1b. If 120 V \(\leq V_{in}\) < 240 V, then \(S_{ac1}\) and \(S_{ac2}\) are both on, and the converter is operated at the medium voltage range input conditions, shown in Figure 1c. If 240 V \(\leq V_{in}\)\(\leq\) 480 V, then \(S_{ac1}\) is on and \(S_{ac2}\) is off and the converter is operated at the high voltage range input conditions, shown in Figure 1d. For forward power flow operation (battery charge), the constant current control (\(I_{o}\) = 7.8 A) is selected to charge the battery (or load) from \(V_{o}\) = 40 V to 52 V. When the battery voltage reaches 52 V, then the constant voltage control (\(V_{o}\) = 52 V) is selected to charge battery. Figure 8a gives the measured load current, load voltage, and input voltage under \(V_{in}\) = 60 V and the forward power flow operation. When \(V_{o}\) is increased from 40 V and \(V_{o}\)\(\leq\) 52 V, the load current \(I_{o}\) is controlled at 7.8 A. If the load voltage is reached at 52 V, then the load voltage \(V_{o}\) is controlled at 52 V and the load current is redecreased from 7.8 A. Therefore, the maximum load power is at \(V_{o}\) = 52 V and \(I_{o}\) = 7.8 A. Figure 8b-e show the measured results of the converter under \(V_{in}\) = 60 V, \(I_{o}\) = 7.8 A, and \(V_{o}\) = 40 V conditions. The gate signals of \(S_{1}\)-\(S_{4}\) are provided in Figure 8b. The switching frequency is about 55 kHz. The measured voltage and current of switch \(S_{1}\) are provided in Figure 8c. It is clear that \(S_{1}\) is turned on at zero-voltage switching. The experimental waveforms on the primary-side of the converter are given in Figure 8d. The leg voltage \(v_{ab}\) = \(\pm V_{in}\) = \(\pm\)60 V. Figure 8e shows the measured results of the resonant current and voltage on the secondary-side of the converter. When \(i_{L,2}\) is positive (or negative), the voltage \(v_{C,2}\) is increased (or negative). If \(i_{L,2}\) = 0, then \(v_{C,2}\) is kept at a constant value. Similarly, the measured results of the converter under \(V_{in}\) = 60 V, \(I_{o}\) = 7.8 A, and \(V_{o}\) = 52 V (maximum power) conditions are given in Figure 8f-i. \begin{table}
\begin{tabular}{c c} \hline
**Items** & **Parameter** \\ \hline \(C_{1}\), \(C_{2}\) & 560 \(\mu\)F/400 V \\ \(C_{3}\), \(C_{4}\) & 220 \(\mu\)F/100 V \\ \(C_{r,1}\) & 192 nF \\ \(C_{r,2}\) & 5.8 \(\mu\)F \\ \(L_{r,1}\) & 13 \(\mu\)H \\ \(L_{r,2}\) & 0.43 \(\mu\)H \\ \(L_{m,1}\) & 65 \(\mu\)H \\ \(S_{1}\)–\(S_{4}\), \(S_{ac1}\) & FGH60N60 (600 V/60 A) \\ \(S_{5}\)–\(S_{8}\), \(S_{ac2}\) & P80 NF12 (120 V/80 A) \\ \(C_{o}\) & 660 \(\mu\)H/100 V \\ Transformer \(n_{p}\):\(n_{8}\) & 22:4 \\ \hline \end{tabular}
\end{table} 
Table 1: Circuit parameters used in the prototype circuit. Figure 8: \(Cont.\)  
The measured results of the converter operated at \(V_{in}\) = 118 V and the maximum power (\(I_{o}\) = 7.8 A and \(V_{o}\) = 52 V) condition are provided in Figure 9. From Figures 8 and 9, one can observe that the converter has less voltage gain at \(V_{in}\) = 118 V so that the switching frequency of the converter at the \(V_{in}\) = 118 V condition is higher than the switching frequency at the \(V_{in}\) = 60 V condition. According to Figure 8c,g and Figure 9b, power switch \(S_{1}\) is turned on at zero-voltage switching for both the \(V_{in}\) = 60 V and 118 V cases.