Load-Independent Push–Pull Class-$\Phi _{2}$ Inverter With Single Compact Three-Winding Inductor

This article proposes a push–pull class-
$\Phi _{2}$
inverter with a single three-winding integrated inductor. A design methodology is presented to achieve load-independent operation of the proposed class
$\Phi _{2}$
inverter, ensuring consistent soft-switching operation and constant voltage gain under varying load conditions. A compact magnetic structure is proposed to implement the three-winding integrated inductor, which distinctly reduces the number and size of magnetic components compared with conventional class
$\Phi _{2}$
inverters. By flux cancellation and core sharing, the magnetic integration not only reduces the inductor's overall volume and losses but also maintains the inverter's high efficiency. A 6.78-MHz
LCC
-S resonant wireless power transfer prototype is built to validate the proposed methodology and the magnetic structure. Furthermore, an active push–pull class-
$\Phi _{2}$
rectifier is implemented and demonstrates the load-independent resistive input. The experimental results indicate that the prototype performs robust soft switching over the entire load range, from no load to 320 W output. The voltage gain remains nearly constant, varying within +1%/-3.5%. Moreover, the measured dc–dc peak efficiency of the system reaches 91% at 170 W output, whereas the estimated peak efficiency of the class-
$\Phi _{2}$
inverter attains 96.6%. The proposed magnetic structure offers compact dimensions and low loss characteristics for the megahertz inverter.