A Cost-Effective Wireless Power Transfer System Utilizing Primary-Side Control with Variable Bus Voltage Regulation

This paper presents a cost-effective, communication free wireless power transfer (WPT) system for grid-powered applications with voltage-defined loads, such as battery chargers and LED drivers. To overcome the trade-offs in conventional two stage systems, which often struggle to maintain zero-voltage switching (ZVS) or require excessive DC-bus voltage variations for wide-range output regulation, the proposed architecture introduces a coordinated primary-side control strategy. The main contribution in achieving a constant-current (CC) to constant voltage (CV) charging profile by regulating the DC-bus voltage of the front-end AC-DC converter within a narrow margin of 10%. This is enabled by a self-oscillating control scheme that automatically tracks the zero-phase-angle frequency, which guarantees a stable, coupling-independent proportional relationship between the primary and output currents while maintaining ZVS. Consequently, the system dynamically regulates the charging current without requiring any real-time secondary-side feedback or bidirectional communication. Furthermore, a rapid frequency-clamping mechanism is introduced to provide inherent primary-side overcurrent protection against sudden receiver displacement. A 13V/36W prototype was constructed and experimentally validated, demonstrating robust CC-CV charging and achieving 90% to 94.5% efficiency across the operating range. This architecture reduces hardware requirements and footprint, while the proposed control remains well suited for single-chip integration owing to its relatively low additional computational burden. © 2026 IEEE.