Efficiency Improving Strategies on GaN-based LLC Converter with Non-uniform Air Gap Transformer

Strict efficiency requirements for power supply unit (PSU) are certified by EPA, ErP/EuP, ENERGY STAR, etc. The manufacturers pay strong attention to these requirements and adopt new circuit topologies or control strategies for PSU design to meet high efficiency. In this paper, the adaptive driving strategies(ADS) on efficiency improvement are presented with the topologies of Gallium Nitride (GaN) based LLC converter utilizing non-uniform air gap transformer. The dynamic gate voltage control is effective for power saving at light load and for low switching losses at rated load. Furthermore, the LLC converter utilizing non-uniform air gap transformer is conducted through variation of magnetizing inductance to reduce power loss to perform light load efficiency improving. The experimental results are demonstrated on the LLC converter of 400V input voltage, 300kHz, 300W and 12V output voltage. The efficiency of the LLC converter can achieve 98.3 % at rated output power and 92.3% at 10W output power.