Zero inductor voltage multilevel bus converter

A novel topology to achieve 4:1 voltage step down, aimed at 48 volt to 12 volt conversion, is presented. The primary application for 48 volt to 12 volt conversion is for server power supplies as part of an Intermediate Bus Architecture, as Google and other large companies are pushing to switch from 12 volt to 48 volt server architecture to improve the performance of their data centers. The topology presented in this paper makes use of multi-level switching with flying capacitors to minimize the voltage stress of the switches, allow for significant reduction in the size of the magnetic components by reducing the voltage applied to the inductor, and enable low switching frequencies to be used. The switching scheme used in the topology causes the output inductor to see only the capacitor ripple voltage across its terminals. As this inductor sees almost zero voltage, the ripple current and reliance on magnetics is significantly reduced in this circuit. Through these advantages, the topology can achieve a peak efficiency of 99.5% for 48 volt to 12 volt conversion.