Realizing compact power converters requires operation at high switching frequencies. However, this introduces challenges in maintaining soft switching over wide operating conditions and enabling scalable high-power operation without compromising efficiency. This thesis develops circuit architectures, control strategies, and design methodologies to address these challenges in high-frequency power converters, with applications in multi-MHz wireless power transfer (WPT) and wide-operating-range wired chargers. First, an auxiliary zero-voltage-switching (ZVS) inductor-based approach is developed for multi-MHz capacitive WPT systems. It achieves ZVS without requiring large inductive phase shifts from the resonant matching network, significantly reducing circulating currents. Experimental validation using a 6.78-MHz, 12-cm air-gap prototype demonstrates 5% higher efficiency and 32% higher power transfer compared to the conventional ZVS approach. Next, a low-loss multi-MHz magnetic-core toroidal inductor is developed to replace bulky air-core matching network inductors in capacitive WPT systems. Using NiZn ferrite, quasi-distributed air gaps, and interleaved foil windings, a 13.56-MHz, 5-μH prototype inductor operating at 20 A peak achieves a quality factor of ~1190 with a 4× reduction in volume compared to air-core counterparts. To address power scaling limitations in multi-MHz capacitive WPT systems, scalable power architectures are developed using passive power combining networks, along with device-level paralleling enabled by a highly symmetric PCB layout. These techniques are experimentally validated through multi-kilowatt prototypes, culminating in the highest-power capacitive WPT system demonstrated to date at 44.3 kW, achieving 85.2% peak dc-to-dc efficiency and 132.9 kW/m² power transfer density. For wired charging applications, a fully soft-switched impedance control network (ICN)-based single-stage ac–dc converter is developed. An auxiliary ZVS approach combined with phase-shift control enables soft-switching of all high-frequency transistors while achieving power factor correction (PFC) and output regulation. A reconfigurable active-bridge architecture further improves the ICN converter performance over wide operating ranges. A 2-kW universal-input ICN-based ac–dc prototype with a 200 V to 500 V output range is built and tested, achieving a power density of 104 W/in³ and a peak efficiency of 94.4%. The ICN architecture is further extended to multi-output single-stage ac–dc converters using a multi-winding transformer and a generalized phase-shift control strategy, enabling simultaneous regulation of multiple isolated outputs while maintaining soft-switching and PFC operation. A 3.3-kW universal-input dual-output prototype, with each output port supporting 24 V to 96 V and up to 1.65 kW, is built and tested, achieving a power density of 162 W/in³ and a peak efficiency of 94.8%. Finally, a modeling framework is developed to analyze soft-switching behavior in resonant converters operating under beat-frequency modulation, where multiple switching frequencies are simultaneously present.