Asymmetric muti⁃mode LLC resonant converter with limited FM range for wide output voltage range application

Traditional LLC resonant converters with frequency control are often limited by the effective adjustment range of switching frequency, making it difficult to achieve a wide output voltage range. To solve this problem, an asymmetric multi-mode wide output LLC resonant converter with limited frequency modulation range was studied. The converter adopts a dual resonant cavity and an asymmetric structure corresponding to different transformer ratios. Based on the different combinations of primary side switches, the dual resonant cavities can operate in three different modes: single half bridge, double half bridge, and half bridge pluse full bridge, thereby obtaining three different voltage gains and ensuring that the normalized gain adjustment range between each mode does not exceed 1. 5. It is possible to achieve a wide output voltage range within a narrow switching frequency range. A 300 W experimental prototype was established to verify that the proposed converter can achieve a wide output voltage range of 1 - 3 times, and achieved zero voltage swtich of the primary side switching transistor and zero current switch of the secondary side diode. It has good soft switching performance and was verified the feasibility of the converter. © 2024 Editorial Department of Electric Machines and Control. All rights reserved.