Highly Efficient Dual-Side Wireless Power Transfer:

Implementation of Synchronization and Wireless Communication

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Abstract

This thesis presents a practical topology for achieving highly efficient dual-side wireless power transfer (WPT). Traditional WPT systems with a diode rectifier on the secondary side lack flexibility in load matching, requiring the integration of an additional dc/dc converter at the back end. However, this approach leads to increased power losses and costs. In contrast, this thesis proposes the use of an active rectifier comprising MOSFETs, replacing the diode rectifier.

By employing a dual active bridge topology with dual-side control, optimal load tracking is achieved by tuning one side and communicating the desired duty cycle or phase angle to the other side. To address practical challenges, two key aspects are considered.

Firstly, synchronization is established between the generated current on the
secondary side and the new active rectifier, enabling efficient load tracking and the potential for zero voltage switching (ZVS). This is accomplished using a printed circuit board (PCB) equipped with zero current crossing detection (ZCCD), validated with an 85kHz test signal. The PCB triggers the PWM output of the secondary side microcontroller with a latency of less than < 50ns, utilizing the trip-zone digital compare sub-block integrated into the TMS320F28379D.

Secondly, seamless wireless communication between the primary and secondary sides is essential. While the secondary side can measure
the current and voltage across the load to adjust its duty cycle for optimal conditions, the primary side lacks this information. Therefore, the secondary side transmits the new duty cycle to the primary side to
ensure consistent power flow. The nRF24L01+ wifi module is utilized as a dual-purpose transmitter and receiver for achieving wireless communication. Validation of this wireless communication is performed
by remotely controlling an external LED, connected to the receiver side, from a distance of approximately 5m.accurately to the transmitted values. Additionally, a mathematical modeling approach is used to optimize power delivery and mitigate high-frequency noise by incorporating two parallel MLCC capacitors on a custom PCB near the nRF24L01+ module.