A contactless charger with LLC tank and microcontroller

This article presents a contactless charger based on LLC resonant tank and 8-bit microcontrollers. A separated transformer couples the fixed and mobile parts of the contactless charger with two separate windings. The fixed part is composed of a half-bridge circuit and an LLC resonant tank, and the mobile part is just a diode rectifying and filtering circuit. For the purpose of control, each part has an 8-bit microcontroller, encoding and decoding ICs accompanying infrared transmitter and receiver are used to close the feedback control loop. Overall, the designed charger is fully digitalized and no other analog circuits are required. Therefore, the charging function is programmable. Since the coupling of two separated windings is loose, the ratio of leakage to magnetizing inductance is the key parameter of the contactless transformer. By means of fundamental approximation, the resonant LLC tank is analyzed and a prototype charger is built to demonstrate the designed charging function.