Self-oscillating contactless resonant converter with phase detection contactless current transformer

Owing to the simplicity and rapidly response, self-oscillating control strategy is of great potential in contactless power transmission. Considering the characteristics of a fully compensated contactless resonant converter (CRC), the conception of transfer impedance was introduced, and a self-oscillating control strategy was proposed for serial/serial (S/S) compensated CRC. To provide passive current phase detection solution for self-oscillating contactless resonant converter (SOCRC), a secondary winding shorted current transformer, called phase detection contactless current transformer (PDCCT) was proposed. Moreover, the time delay in both PDCCT and control circuitry were studied and compensated. Finally, a 60 W SOCRC with PDCCT was fabricated. The experimental results verify that the proposed PDCCT can detect the secondary current and feedback to the primary side accurately. And with self-oscillating control strategy, which offers the driver signals for the inverter by detecting secondary current phase, constant voltage gain can be achieved. A dynamic test circuit is also designed and the experimental results show that SOCRC can response to parameter changes in a switching period.