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300A Single-Stage 48V Voltage Regulator with Multiphase Current Doubler Rectifier and Integrated Transformer

Circuit topology
Fig. 1. Schematic of the proposed converter with inte-grated multiphase current doubler rectifier.
  High-current, high-power-density 48 V voltage regulator modules (VRMs) are critical for 48 V data center power architecture. In the paper, a single-stage 48 V converter with multiphase current doubler rectifiers is proposed for CPUs in data center applications, as shown in Fig. 1. The magnetizing inductors of the matrix transformer are used as the output inductors of the multiphase current doubler rectifier. A magnetic integration structure for the matrix transformer is proposed and optimized, which creates negative coupling between multiphase current doubler rectifiers. With GaN devices as primary side devices and low voltage silicon devices as secondary synchronous rectifiers (SRs), the proposed converter can achieve high efficiency and high power density. A 48/1.8 V 300 A converter is designed, which can reach a peak efficiency of 92.7% and a full-load efficiency of 90.0%.
  The prototype of the multiphase current doubler rectifier is shown in Fig. 2. With the pro-posed integrated multiphase current doubler rectifier, the footprint is 21 mm × 50 mm and the thickness is 4.45 mm. The compact prototype means the power density can reach 1.9 kW/in3 and 332 W/in2 under 300 A output current and 1.8 V output voltage. Even if the 160 A continuous current is considered, the power density can still be larger than 1 kW/in3.
  The footprint of the 48/1.8 V prototype is compared with the state-of-art 12/1.8 V multiphase buck converter with the same output current ability. Furthermore, in Fig. 2, it can be observed that the secondary side gate drivers, which are highlighted with red boxes, take a lot of foot-prints. If the gate drivers are integrated into the secondary SRs, which is a common practice for commercial products, the footprint can be further reduced to 21 mm × 42 mm. It means a smaller footprint than the state-of-art 12/1.8 V multiphase buck converter. The proposed 48/1.8 V converter sets a new record of power density for single-stage 48V solutions.
Hardware prototypes
Fig. 2. Comparison between the proposed 48/1V converter and 12/1V multiphase buck converter.

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