Application Cases

Experiment Name: Application of Power Amplifiers in Research on Impedance Matching for Dynamic Wireless Power Transfer in Electric Vehicles

Experiment Objective:
To address the system mismatch issue during dynamic wireless charging of electric vehicles, this study focuses on analyzing the causes of mismatch and restoring matching conditions. An impedance matching network with adaptive adjustment capability is embedded in the secondary circuit, enabling the electric vehicle to perform adaptive impedance matching adjustments based on current operating conditions, thereby stabilizing transmission efficiency under varying conditions.

Experimental Equipment: Signal generator, ATA-3040 power amplifier, transmitting coil, receiving coil, rectifier bridge, DC/DC converter, load resistor, oscilloscope, LCR impedance analyzer, Tektronix differential voltage probe, current probe, etc.

Experimental Procedure:
Grid power is rectified and converted into high-frequency alternating current through a high-frequency inverter, generating a high-frequency magnetic field via the transmitting coil. When the receiving coil is placed within this magnetic field, an induced current is generated, transferring electrical energy from the primary side to the secondary side. The energy captured by the secondary side is regulated by a rectifier and a DC/DC converter before being delivered to the load.

Figure: Schematic Diagram of Dynamic Wireless Charging for Electric Vehicles

To verify the feasibility of the impedance matching method, a wireless power transfer (WPT) experimental platform was constructed as shown in the figure.

According to the fundamental working principle of WPT, the primary and secondary coils require energy exchange in a high-frequency electromagnetic field environment. Therefore, standard industrial frequency alternating current is unsuitable, making a high-frequency, high-power power source essential for the WPT system. In this experiment, a signal generator combined with a power amplifier was used to form a high-frequency power source. The signal generator (RIGOL) produces standard waveforms such as square waves and sine waves with a maximum output amplitude. After impedance matching debugging between the signal generator and the power amplifier, the signal generator outputs a high-frequency sinusoidal signal, which is proportionally amplified by the power amplifier to drive the coil, generating a high-frequency magnetic field.

Figure: Wireless Power Transfer Experimental Platform

By detecting the current parameters on the secondary side, the coupling coefficient at different distances was estimated. Based on the coupling coefficient at different distances, the optimal matching parameters were calculated. By switching the series-parallel configuration of the capacitor array, dynamic impedance matching of the DWPT system was achieved, stabilizing the system's transmission efficiency.

Experimental Results:
The experiment estimated the coupling coefficient by detecting the secondary-side current parameters and adjusted the secondary-side impedance matching network in real time based on the current coupling coefficient. This achieved dynamic impedance matching in the WPT system and stabilized transmission efficiency. The experimental results show that compared to the unmatched state, the matched state improved efficiency from 66% to 90% at close range and from 10% to 68% at long range, validating the feasibility of the theoretical method. This approach can provide relevant theoretical guidance for the practical application of dynamic wireless power transfer in electric vehicles.

Figure: Experimental Results

Figure: ATA-3040C Power Amplifier Specifications and Parameters