High Efficiency High Density 1 MHz 380V-12V DCX With Low FoM Devices

With the rapid development of informationization of society,the scale of Internet data centers is increasing day by day,which results in rapid growth of data center energy consumption.Compared with the traditional AC power supply system,the high-voltage DC power supply architecture has the advantages of high energy efficiency,simple structure and high reliability,which is the future trend.In the high-voltage DC power supply architecture,an isolated step-down bus converter module is required which should be integrated on the server motherboard.The on-board integration requires high efficiency and high power density.The series resonant converter can achieve the zero voltage turn-on of the switch in primary side and the zero current turn-off of the secondary rectifier,which provides high efficiency and high power density at a high frequency for SRC almost eliminates the switching loss.However,DC/DC modules based on high-voltage Si devices at high frequency can’t meet the requirements of on-board integration for its low efficiency and power density.In order to improve the efficiency and power density of converters based on Si devices,the following research has been done.In the design of a SRC DCX procedure,in order to reduce the conduction loss of the primary switch,the device with a lower on-resistance is preferred.However,the analysis of the operation of SRC especially the ZVS of primary switch in the dead time,pointed out that the device with lower on-resistance would increase the rms value of the primary side current in the resonant tank.The compromise between the on-resistance and the rms current of the primary side should be designed carefully.In addition,the analysis also pointed out that conduction loss is related to the device’s NFoM and dead time.Furthermore,the design of the dead time should take both the conduction loss of the primary switches and secondary SRs in to account.However,the dead time is limited by the high-voltage Si device due to its high NFoM.Therefore,the using of series-connected low NFoM Si device which take the place of high-voltage Si devices is proposed in this paper.The core loss and copper loss of the transformer usually occupy a large part of the total loss in high frequency converters especially that with low-voltage high-current output.Based on the mathematical model of the total loss of the transformer,the design of multiple separate matrix transformers is adopted with the balance of size and loss of transformer.An input-series output-parallel multiphase interleaved SRC DCX is proposed.A prototype with an input voltage of 380V,an output voltage of 12V,and an output current of 150A is built up to verify the design.