# Resonant Asymmetrical Half-Bridge Flyback Converter
## 4 Experimental Results  
Figure 7 shows the experimental setup blocks of the system test. Figure 8a shows the measured result of the conversion efficiency. The prototype can achieve better efficiency at lower input voltages and more load currents. This prototype circuit is based on COT control, so the controller increases \(T_{on}\) and reduces \(f_{sw}\) as the load increases. When the input voltage decreases, \(T_{on}\) also increases. Figure 8b shows the frequency curve with variation of load current and input voltage. Since the previous calculation does not take the parasitic effect of individual components into consideration, the actual switching frequency is lower than the theoretical calculation result. The results of \(f_{sw}\) at high input voltage and low input voltage at light load are 148 kHz and 129 kHz, respectively. Finally, the variation range \(\Delta f_{sw}\) of \(f_{sw}\) can be calculated as \(\pm\)16.7%, which is much less than the results of \(\pm\)95.4% in [1] and \(\pm\)100% in [2], respectively. \[\Delta f_{sw}=\pm\frac{f_{\text{max}}-f_{\text{min}}}{2\cdot f_{\text{min}}}= \pm\frac{148\text{ kHz}-110\text{ kHz}}{2\cdot 110\text{ kHz}}=\pm 16.7\%, \tag{98}\] \begin{table}
\begin{tabular}{c c} \hline \hline
**Part Number** & **Component Information** \\ \hline \(Q_{1},Q_{2}\) & AON7246, 60 V, 15 m\(\Omega\) (Alpha \& Omega Semiconductor, \\ Sunnyvale, CA, USA) \\ \hline \(Q_{3}\) & AON6500, 30 V, 0.95 m\(\Omega\) (Alpha \& Omega Semiconductor, \\ Sunnyvale, CA, USA) \\ \hline \(C_{r}\) & 4.7 μF/50 V/1206(Murata) \\ \hline \(L_{m}\) of \(L\) & C055200A2 (Magnetics Inc., Pittsburgh, PA, USA) \\  & 18.25 μH@100 kHz \\  & 18.15 μH@150 kHz \\ \hline \(L_{r}\) of \(L\) & 1.854 μH@100 kHz \\  & 1.954 μH@150 kHz \\ \hline Half bridge driver & HIP2101(Renesas, Tokyo, Japan) \\ \hline \(C_{O}\) & 470 μF/16 V FPCAP(Nichicon, Kyoto, Japan) \\ \hline \(C_{in}\) & 390 μF/63 V(Chemicon, Tokyo, Japan) \\ \hline SR driver & MP6905(Monolithic Power Systems, Kirkland, WA, USA) \\ \hline Controller & EP3C5 FPGA (Intel/Altera, Santa Clara, CA, USA) \\ \hline DAC & TLV5637 (Texas Instruments, Dallas, TX, USA) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Key components information of the prototype circuit. Figure 7: Measurement setup of the system test. Figures 9 and 10 show the measured waveforms of \(v_{gs1}\), \(v_{gs2}\), \(v_{Cr}\), and \(v_{gs2}\) for different input voltages of 24 V and 48 V at 10%, 50%, and 100% load, respectively. They show that higher input voltage induces more parasitic capacitance energy of the switch and lower \(i_{Lr}\) under the same load, so it is not easy to achieve the complete ZVS turn-on. However, the switches turned-on at the lowest \(v_{ds}\) still reduce the switching loss. As the load increases, \(i_{Lr}\) rises to expand the voltage range of ZVS turn-on. When the output load is more than 40% of the rated load, ZVS turn-on is also achieved at the high voltage input. Figures 11 and 12 show the measured waveforms of \(v_{gs1}\), \(v_{gs2}\), \(v_{Cr}\), and \(i_{Lr}\) for different input voltages of 24 V and 48 V at 10%, 20%, 50%, and 100% load, respectively. The variation of \(i_{Lr}\) and \(v_{Cr}\) at different input voltages is not significant. However, \(i_{Lr}\) and \(v_{Cr}\) increase significantly with the rising load. Figures 13 and 14 show the waveforms of \(v_{gs1}\), \(v_{gs2}\), \(v_{ds3}\), and \(i_{N2}\) for different input voltages of 24 V and 48 V at 10%, 20%, 50%, and 100% load, respectively. The more \(i_{N2}\) is, the higher \(v_{ds3}\) becomes. This is the driving mechanism of MP6905 SR IC, which controls the conduction resistance of MOSFET \(Q_{3}\) at a fixed interval, so that \(v_{ds3}\) remains at \(-32\) mV. Figure 15 shows the measurement results of the phase margin (PM) and gain margin (GM) under different load and different input voltage conditions, and the effect of increasing load on PM and GM is not significant under the same input voltage. Under the same load, the change of input voltage can cause the PM and GM to deteriorate.