Multimode Control of WPT Systems for Efficiency Improvement in Wide Output Voltage Range Applications

Wide output voltage range applications are challenging for wireless power transfer systems. Under conventional single-mode control [i.e., single full-bridge (FB) or single half-bridge (HB)] based on phase-shift modulation, the system efficiency would be degraded when satisfying wide voltage gain requirement, especially in low gain. The main reason is that wide output voltage regulation requires the conducting angle varying in large operating ranges. When pulsewidths of the square voltage are adjusted to narrow, the switching loss increases and the system efficiency decreases significantly. Therefore, to address the abovementioned issue, in this work, a multimode control is proposed for wide output voltage range applications. Using the multimode control, the inverter can operate in HB mode, HB–HB mode, and FB–HB mode. Compared with an FB inverter, the conducting angle can be effectively maintained larger, and all the switches can realize zero-voltage-switching in a wide range. Thus, the system efficiency can be improved significantly. Furthermore, the online mutual inductance detection unit is not necessary. A 1.7 kW experimental prototype is built to verify the feasibility and effectiveness of the proposed method. The results show that the proposed system can achieve high efficiency from 91.5% to 97.1% under a wide output voltage range.