# An Active-Clamp Forward Inverter Featuring Soft Switching and Electrical Isolation
## 5 Experimental Results
\begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**Component Parameters**} \\ \hline Bus filter, \(C_{k}\) & 2000 \(\mu\)F \\ Main switch, \(S_{m1}\) & 6R045 \\ Auxiliary switch, \(S_{a1}\) & 47N60C3 \\ MOSFETs, \(S_{1}\)–\(S_{4}\) & 47N60C3 \\ Diodes, \(D_{1}\), \(D_{2}\) & C3D10060A \\ Transformer turn ratio, \(n\) & 10 \\ Magnetizing inductor, & 835 \(\mu\)H \\ \(L_{m1}\) & 4 \(\mu\)H \\ Leakage inductor, \(L_{r1}\) & 4 \(\mu\)H \\ Clamping capacitor, \(C_{c1}\) & 4 \(\mu\)F \\ Inductor, \(L_{1}\) & 3 mH \\ Capacitor, \(C_{f}\) & 4.7 \(\mu\)F \\ Output inductor, \(L_{0}\) & 1 mH \\ Output capacitor, \(C_{o}\) & 4.7 \(\mu\)F \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Component parameters of the proposed inverter. The proposed active-clamp forward inverter is driven by SPWM signals. Figure 9a,b are the simulation and measured waveforms of the output voltage \(v_{\rm o}\) and output current \(i_{\rm o}\) when the inverter is operated at 48 V input voltage, and Figure 9c,d are the simulation and measured waveforms of the output voltage \(v_{\rm o}\) and output inductor current \(i_{L1}\). It can be seen from the figures that the output voltage and current are in the form of a sine wave with low distortion, which proves that this isolated inverter can effectively convert the DC voltage into an AC output. Furthermore, Figure 10 shows the measured waveforms of the output voltage \(v_{\rm o}\) and output current \(i_{\rm o}\) when the inverter operates with the step load change between 320 W and 160 W. As can be seen, the output voltage can be quickly and stably regulated to a sine wave of 110 Vrms, proving that the proposed inverter has good dynamic voltage regulation capability. In addition, the line regulation is 1.26%, and the load regulation is 0.78%, which meets the general specifications of \(\pm\)3%. Figure 11 shows the simulation and measured waveforms of the main-switch voltage \(v_{ds1}\), the main-switch current \(i_{sm1}\), and the clamp-capacitor voltage \(v_{cc1}\), when the inverter is operated at 48 V  
Figure 10: Measured waveforms of output voltage \(v_{\rm o}\) and output current \(i_{\rm o}\) when the inverter is operated with a step-load change of (**a**) from 320 W to 160 W; (**b**) from 160 W to 320 W.  
Figure 9: **(a)** Simulation waveforms of \(v_{\rm o}\) and \(i_{\rm o}\), (**b**) measured waveforms of \(v_{\rm o}\) and \(i_{\rm o}\), (**c**) simulation waveforms of \(v_{\rm o}\) and \(i_{L1}\), and (**d**) measured waveforms of \(v_{\rm o}\) and \(i_{L1}\), at 48 V input voltage and a full load of 400 W.  
input voltage and the full load of 400 W. Since the resonant current flows through the anti-parallel diode \(D_{m1}\) before the main switch \(S_{m1}\) is turned on, it can be seen from Figure 11a,b that the main switch \(S_{m1}\) can achieve the characteristics of ZVS turn-on, which can effectively reduce switching loss. In addition, it can be seen from Figure 11c,d that the maximum value of the clamp-capacitor voltage \(v_{cc1}\) is about 95 V, which can effectively limit the voltage stress of the main power switch \(S_{m1}\). Therefore, the power MOSFET with lower voltage rating and lower on-resistance can be selected to reduce conduction loss. Table 3 shows the total harmonic distortion (THD) and odd-order harmonics of the output voltage \(v_{\text{o}}\) when the inverter is operated at 48 V and 72 V input voltages. The results meet the requirements of electrical standards and verify the correctness of the theoretical analysis again. Figure 12 shows the measured efficiency curve of the active-clamp forward inverter. The highest efficiency is 90.2% at 48 V input and 91.5% at 72 V input, respectively. Furthermore, Figure 13 shows the measured waveforms of the load current \(i_{L}\), the inverter output current \(i_{o}\), the utility-line current \(i_{s}\) and the utility-line voltage \(v_{s}\), under the operation of grid-connection mode.