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Development of Ultra-High Efficiency, High-Density 4 kW Single Phase AC-DC Converter

Application

The purpose of this project is to develop a 48 V rectifier power supply for telecom and data center applications. With the implementation of WBG devices and optimal topology and advanced control strategies, the proposed rectifier can achieve 98% peak efficiency and high power density. In telecom and data center applications, rectifiers are required to have high efficiency and high power density at the same time. However, currently commercial rectifier products with similar power level usually have difficulty achieving high efficiency and high power density simultaneously. For example, rectifiers featuring high efficiency often have a large size and weight. Besides, none of the 4 kW commercial rectifiers have exhibited a maximum efficiency of over 98%. Therefore, with ultra-high efficiency and small size and weight, the rectifier this project intends to develop is regarded as the next generation medium rectifier for telecom and data center applications.

Research

Ultra-High Efficiency Power Supplies Reduce Cooling and Power Requirements in Data Centers

The project aims to develop a next generation of rectifier power supply with 98% peak efficiency and high density based on new wide band gap devices. To achieve this, approaches in several aspects are conducted:

  1. System architecture: Single-stage architecture consisting of power factor correction (PFC), voltage regulation (VR) and DC-DC converter is designed and implemented.
  2. Power semiconductor devices: New WBG devices like GaN and SiC MOSFETs are implemented as the primary devices. For the secondary side, LV eGaN FET or silicon MOSFETs are considered to be used. Further, advanced packaging and layout techniques are conducted to improve parasitics and associated switching losses.
  3. Passive components: Innovative magnetic devices are designed to fully utilize the superior switching performance of WBG devices. Also, the achieved higher switching frequency enables smaller magnetics. Modern magnetic materials such as nanocrystalline cores are used to minimize passive losses and size
  4. Power quality and EMI filter design: Analyze circuit noise sources and design input filter to meet the conducted EMI, THD and power quality requirements. Also, the filter loss and thermal performance will be measured and optimized.

How WBG Can Help

WBG devices like GaN and SiC MOSFETs and LV eGaN FET are used in the project due to the superior characteristics including lower on-resistance, higher temperature capability, faster switching frequency, etc. First, reduced conduction loss and switching loss can be greatly decreased. For example, the converter can utilize enhancement-mode GaN FETs to reduce switching losses and parallels two FETs in the synchronous rectifier (SR) to reduce conduction loss. Besides, compared with traditional silicon devices, WBG devices help reduce EMI noise, especially operating in high frequencies, so that EMI filter can be designed with smaller size. Also, higher temperature capability enables thermal design to realize higher requirement.

Personnel Involved

Students
  • Jingjing Sun
  • Xingxuan Huang

References

[1] Nils Backman and Roberto Rojas, "Modern Circuit Topology Enables Compact Power Factor Corrected Three-Phase Rectifier Module," in Proceedings of the 24th International Telecommunications Energy Conference (INTELEC), 2002, pp. 107-114.

[2] Cui, Yutian, et al. "High efficiency data center power supply using wide band gap power devices." 2014 IEEE Applied Power Electronics Conference and Exposition-APEC 2014. IEEE, 2014.