# A Novel Bidirectional Wireless Power Transfer System for Mobile Power Application
## 3 Simulation and Experimental Results  
To verify the feasibility of the proposed bidirectional wireless power transfer system, the well-known software Power SIM Version 9.0 (Powersim Inc, Rockville, M.D, USA, 2010) is adopted to perform the simulation process. In the simulation, the switches, capacitors and inductors are assumed to be ideal. A transformer with a loosely coupled inductor and relatively larger magnetizing inductor is adopted to simulate the transmitter and receiver.  
Meanwhile, a prototype is constructed using a coreless plane transformer to verify the theoretical results. The simulation and experimental parameters for the proposed bidirectional wireless power transfer system are listed in Table 1. Where the LED load is adopted to emulate the portable device, the mobile power supply is used to provide 5V voltage source. The transmitter and receiver coils are the same type and the photo is shown in Table 1 with a detailed description. The instantaneous current and voltage in experiment are measured by the oscilloscope YOKOGAWA DLM2024.  
The simulation and experimental results of resonant capacitor voltage \(V_{c1}\) and current \(i_{c1}\) with the corresponding control switching signal are shown in Figure 9a,b, respectively. As can be observed from Figure 9, the capacitor voltage \(V_{c1}\) and current \(i_{c1}\) are resonated following the switching frequency. One can see that both the simulation and experimental results are in very close agreement. Figure 10a shows the inductor voltage \(V_{L2}\) and current \(i_{L2}\) simulation results with the corresponding control switching signal. The corresponding experimental results are shown in Figure 10b. As can be seen from Figure 10, the inductor \(L_{2}\) stabilizes the output current. Although the simulation and experimental waveforms of \(V_{L2}\) and \(i_{L2}\) have something different due to the parasitic effects, the simulation and experimental behavior are very similar. The inductor voltage \(V_{L1}\) and current \(i_{L1}\) simulation and experimental results with the corresponding control switching signal are shown in Figure 11a,b. From Figure 11, one can find that both the simulation and experimental results are in very close agreement.  
Figure 8: Equivalent circuit of proposed bidirectional power transfer system operated in the State 4.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **Primary Side Circuit** & **Secondary Side Circuit** \\ \hline Inductor & \(L_{1}=1\) mH & \(L_{2}=1\) mH \\ \hline Resonant tank & \(C_{1}=660\) nF, \(L_{1}=15.3\) uH & \(C_{2}=660\) nF, \(L_{2}=15.3\) uH \\ \hline Transmitter/Receiver & 20 turns, width of winding = 2.7 mm, with two layers & 20 turns, width of winding = 2.7 mm, with two layers \\ \hline LED Load to Emulate portable device & Forward voltage 3.5 V \\ \hline Switching frequency & Approximately 50 kHz \\ \hline MOSFET & IRF 540 \\ \hline Transistor & 2222A NPN, 2907A PNP \\ \hline PWM IC & Low Voltage PWM Controller (LT1619 or MAX1967) \\ \hline Coil of Transmitter/Receiver & & \\ Length 50 mm & & \\ width 50 mm & & \\ High 5.4 mm & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Parameters of the proposed bidirectional wireless power transfer system for simulation and experimentation.  
Figure 10: The (**a**) simulated waveforms and (**b**) measured waveforms of (Top) control signal of switch 1, (Middle) inductor voltage \(V_{1,2}\), and (Bottom) inductor current \(i_{L2}\).  
Figure 9: The (**a**) simulated waveforms and (**b**) measured waveforms of (Top) control signal of switch 1, (Middle) capacitor voltage \(V_{c1}\), and (Bottom) capacitor current \(i_{c1}\).