Achieving High Power Density In A Regulated IBC For Data Center Applications

The Current Approach And Infineon's Novel Regulated DR-HSC Topology

- ROBERTO RIZZOLATTI

Introduction

Approximately half of the energy consumed in a typical data center is wasted, either during power conversion or through cooling. Given the increasingly urgent requirement to reduce CO2 emissions, this undesirable situation required addressing at both system and converter levels. Research indicates that using 48 V power distribution at the rack level would help to reduce power losses, and this approach is now widely adopted. 48 V distribution enables a more efficient way to transfer power to the payload (i.e., ASIC/CPU/GPU), where a twostage approach is commonly adopted. The first stage is the intermediate bus conversion from 48 V to 12 V and the second from 12 V to lower voltage levels.

However, there is a significant gap between the full-load efficiencies attainable using unregulated and regulated converters. This limits the use of higher power density solutions when stepping down from 48 V to 12 V. This article presents Infineon's novel regulated topology for implementing a regulated intermediate bus converter (IBC) that allows much greater power density in data-center applications.

48 V architecture at server motherboard level: the current two-step approach

The first stage (48 V to 12 V) commonly employs either a resonant converter, such as an LLC, or a switched tank converter (STC). In contrast, the second stage typically uses a multi-phase buck topology. It has been shown that switched capacitor converters can be used to achieve high power density with a 4:1 ratio. In contrast, LLC resonant converters are widely used for IBC because they allow zero voltage switching (ZVS) operation on the primary side and zero current switching (ZCS) operation on the secondary. However, in situations where regulation is required, LLCs start to drift away from resonant operation, leading to a decrease in conversion efficiency.