This diploma thesis deals with the design, implementation and subsequent measurement of self-oscillating resonant DC/DC converters with an air-core planar transformer.
The first part of the thesis is devoted to the theoretical analysis of the given topic. It describes the basic principles of wireless power transfer, the properties of planar coils, the air-core transformer and coupled resonant circuits.
The second part focuses on the design of specific variants of air-core transformers and converters. First, a 2.5 W converter with a planar air-core transformer with a diameter of 15 mm was designed. For the same converter, two additional transformer variants were designed, in which the primary and secondary coils are placed opposite each other on a double-sided printed circuit board. Furthermore, a higher-power variant with a target output power of 10 W was designed.
The third part is focused on the simulation of the individual converters in the LTspice program. The simulations were used to verify the functionality of the circuit, the voltage waveforms on the transistors and the operating frequency of the converters.
The final part deals with the experimental measurement of the realized converters. The measured results are then compared.