An H5-Bridge-Based Asymmetric LLC Resonant Converter With an Ultrawide Output Voltage Range


To extend the output voltage range of the conventional LLC topology, a small magnetizing inductance and a large frequency modulation window are required. Both would jeopardize the system performances. To resolve this issue, this article proposes a novel H5-bridge-based asymmetric LLC resonant converter. By configuring the switch pattern of the H5-bridge, two asymmetric LLC resonant tanks could operate in idle, half-bridge, hybrid-bridge, and full-bridge modes. Correspondingly, six operation modes with scaled voltage gains are obtained. Hence, an ultrawide output voltage range is achieved with moderate magnetizing inductance and simplified design of resonant parameters. The switching frequency range is squeezed close to the resonant frequency, which is beneficial for control implementation and circulating current suppression. Furthermore, two resonant tanks facilitate an easier zero-voltage switching (ZVS) of the primary-side MOSFETs and alleviate the current and voltage stresses. The conduction loss is further reduced due to the power-sharing effect between resonant tanks. To achieve a minimized frequency window, the optimized design of two resonant tanks is analyzed. To verify this concept, a 1-kW-rated prototype with 390 V input and 80-450 V output is designed and tested. Primary-side MOSFETs ZVS are achieved over the entire load range. The designed prototype achieves 97.05% peak efficiency and good efficiency performance over the ultrawide output voltage range.

IEEE Transactions on Industrial Electronics