Impact of transformer stray capacitance on the conduction loss in a GaN-based LLC resonant converter

Conduction loss, which is greatly affected by transformer stray capacitance, has a huge influence on the efficiency of LLC resonant converters. The reason is that different transformer stray capacitance means different winding charge or discharge during the dead time, and then the magnetizing current and the dead time are changed accordingly. In order to investigate the impact of transformer stray capacitance on device conduction loss in LLC resonant converters, this passage is arranged as follows. Firstly, the transformer stray capacitance model is established and several methods of calculating the transformer stray capacitance are introduced. Next, the relationship between transformer stray capacitance and device conduction loss in LLC resonant converters is derived. Finally, transformers with different stray capacitances are applied in a 1.1MHz 400V-12V 200W GaN-based LLC resonant converter. The loss analysis shows that lower transformer stray capacitance contributes to smaller dead time and higher efficiency.