There is an increasing need for more efficient power conversion from 48 V dc to point-of-load (PoL) applications in datacenters. This work presents a new hybrid converter with Multi-Level Binary (MLB) voltages on the flying capacitors that is well-suited for PoL applications with very high conversion ratios. The proposed MLB-PoL converter can be viewed as an 8-to-1 multi-phase doubler switched-capacitor (SC) converter merged with a two-phase interleaved buck converter. Compared to other two-phase hybrid SC topologies, multi-phase operation can help achieve higher conversion ratio in the SC stage with an equal or fewer number of components, and thus reduce the switch and inductor stress of the following buck stage. In addition, the output inductors in the proposed topology benefit from a frequency multiplication effect similar to that of the flying capacitor multilevel (FCML) converter. This can help further reduce the inductor size without increasing the switching frequency. A 48 V to 2.5-1.0 V converter prototype with 65 A output current was built and tested. At 48 V to 2 V, the prototype achieved 95.1% peak efficiency (94.3% including gate drive loss) and 395 W/in 3 power density.
In this study, a light emitting diode (LED) driver containing an integrated transformer with adjustable leakage inductance in a high-frequency isolated LLC resonant converter was proposed as an LED lighting power converter. The primary- and secondary-side topological structures were analyzed from the perspectives of component loss and component stress, and a full-bridge structure was selected for both the primary- and secondary-side circuit architecture of the LLC resonant converter. Additionally, to achieve high power density and high efficiency, adjustable leakage inductance was achieved through an additional reluctance length, and the added resonant inductor was replaced with the transformer leakage inductance without increasing the amount of loss caused by the proximity effect. To optimize the transformer, the number of primary- and secondary-side windings that resulted in the lowest core loss and copper loss was selected, and the feasibility of the new core design was verified using ANSYS Maxwell software. Finally, this paper proposes an integrated transformer without any additional resonant inductor in the LLC resonant converter. Transformer loss is optimized by adjusting parameters of the core structure and the winding arrangement. An LLC resonant converter with a 400 V input voltage, 300 V output voltage, 1 kW output power, and 500 kHz switching frequency was created, and a maximum efficiency of 97.03% was achieved. The component with the highest temperature was the transformer winding, which reached 78.6 °C at full load.
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