Soft Start and Overload Protection of a 2MHz Wireless Power Transfer System without Communication between Transmitter and Receiver

Industrial applications necessitate wireless power transfer (WPT) systems featuring small transmitter and receiver coils, along with compact receiver-side circuits. These requirements pose challenges in achieving high switching frequencies for sufficient power density.This paper shows a resonant wireless power transfer system incorporating current control. The system delivers up to 590W while operating at a switching frequency of 2MHz, an input voltage of 400V, and an output voltage of 48V. The current control enables a soft start without requiring knowledge of the receiver side status such as the output voltage and prevents overcurrent during overload conditions. Additionally, the control facilitates a receiver detection function by monitoring the magnitude of the resonant current and input current. The system is straightforward to implement and solely controlled on the primary side of a wireless power system. Such systems are appealing when aiming for a compact and simple receiver design without requiring communication between the transmitter and receiver for control purposes.