International Technology Roadmap for Semiconductors 2003の要求清浄度について － シリコンウエハ表面と雰囲気環境に要求される清浄度, 分析方法の現状について －

Achieving high efficiency and high power density features of intermediate bus converter (IBC) in data center application is very critical. This paper proposes a nonisolated switched-tank dc–dc converter (STC) to meet the high requirement of IBC. The proposed STC has fixed voltage conversion ratio. Theoretical analysis provides the guideline for designing resonant tank and nonresonant tank as well as selecting proper deadtime for the proposed circuit. With resonant operation feature of the proposed circuit, zero current switching is realized on all switching devices to help the high-efficiency operation of the proposed converter. Through the proposed design methodology in this paper, power loss on switching devices and planar inductors can be minimized. In addition, detailed power loss analysis and breakdown provide hints for further efficiency improvement. Simulation has been performed to validate the operating principle of the proposed STC. A designed 6x STC (450 W nominal/600 W maximum) based on eGaNFETs is demonstrated. With 54 V typical input voltage, the output of the 6x STC is 9 V. The GaN-based prototype achieves a peak efficiency of 98.55%. Also, it achieves 97.18% efficiency and 750 W/in3 power density at 450 W.

A 98.55% Efficiency Switched-Tank Converter for Data Center Application

A high-efficiency, high-power-density Sigma converter for a 48 V rack architecture in data centers is proposed in this paper. The Sigma converter is a quasi-parallel converter that uses a high-efficiency unregulated converter to deliver the bulk power to the load. A small buck converter is responsible for regulating the output voltage with prescribed dynamic responses. A design guideline for Sigma converter with integrated magnetics is provided in this paper. The unregulated converter is an LLC converter designed with a printed circuit board (PCB) winding matrix transformer, a structure which integrates four elemental transformers into one core. The buck converter is designed with discrete gallium nitride (GaN) devices and a PCB winding inductor. The proposed Sigma converter operates at 48 V input and 1 V-80 A output and can achieve a power density of 420 W/in3 as well as a peak efficiency of 94%.

Single-Stage High-Efficiency 48/1 V Sigma Converter With Integrated Magnetics

Methods are disclosed for routing callers to agents in a contact center, along with an intelligent routing system. One or more agents are graded on achieving an optimal interaction, such as increasing revenue, decreasing cost, or increasing customer satisfaction. Callers are then preferentially routed to a graded agent to obtain an increased chance at obtaining a chosen optimal interaction. In a more advanced embodiment, caller and agent demographic and psychographic characteristics can also be determined and used in a pattern matching algorithm to preferentially route a caller with certain characteristics to an agent with certain characteristics to increase the chance of an optimal interaction.

Systems and methods for routing callers to an agent in a contact center

Resonant switched-capacitor (ReSC) converters have efficient utilization of both active and passive components, and hold the potential to achieve higher efficiency and higher power density than conventional switched-capacitor (SC) and magnetic-based converters. This article presents a new hybrid/resonant SC converter topology, comprising two cascaded 2-to-1 ReSC converters, to address high-conversion-ratio applications. The proposed cascaded resonant converter has a simple structure and operation principle and can achieve one of the best overall metrics among popular ReSC topologies. A 36-60-V input 4:1-fixed-ratio bus converter prototype for data center application is designed and constructed. We present detailed design guidelines and discussions to address practical challenges, such as component variations and interstage decoupling requirements. With 48-V input and operating at the typical zero-current switching mode of ReSC converters, the prototype achieves a peak efficiency of 98.85% (including gate drive loss) and a power density of 2500 W/in
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, both of which are significantly higher than the state of the art. Furthermore, we propose a zero-voltage switching method to improve light-load efficiency. Through this control method, which greatly reduces the output capacitance loss, the prototype can maintain an efficiency above 97% starting from 3% of the rated load, with a peak of 99.0%.

The Cascaded Resonant Converter: A Hybrid Switched-Capacitor Topology With High Power Density and Efficiency

This paper presents a new class of Switched Tank Converters (abbreviated as STCs) for high efficiency high density non-isolated DC-DC application where large voltage step down (up) ratios are required. Distinguished from switched capacitor converters, the STCs uniquely employ LC resonant tanks to partially replace the flying capacitors for energy transfer. Full soft charging, soft switching and minimal device voltage stresses are achieved under all operating conditions. The STCs feature very high efficiency, density and robustness against component non-idealities over a wide range. Furthermore, thanks to the full resonant operation, multiple STCs can operate in parallel with inherent droop current sharing, offering the best scalability and control simplicity. These attributes of STC make it a disruptive and robust technology viable for industry's high volume adoption. A novel equivalent DCX building block principle is introduced to simplify the analysis of STC. A 98.92% efficiency STC product evaluation board (4-to-1, 650W) has been developed and demonstrated for the next-gen 48V bus conversion on data center server boards.

Switched tank converters

This paper presents a new class of switched tank converters (abbreviated as STCs) for high-efficiency high-density nonisolated dc–dc applications where large voltage step down (up) ratios are required Distinguished from switched capacitor converters, the STCs uniquely employ LC resonant tanks to partially replace the flying capacitors for energy transfer Full soft charging, soft switching, and minimal device voltage stresses are achieved under all operating conditions The STCs feature very high efficiency, power density, and robustness against component nonidealities over a wide range of operating conditions Furthermore, thanks to the full resonant operation, multiple STCs can operate in parallel with inherent droop current sharing, offering the best scalability and control simplicity These attributes make STC a disruptive and robust technology viable for industry's high volume adoption A novel equivalent DCX building block principle is introduced to simplify the analysis of STC A 989% efficiency STC product evaluation board (4-to-1, 650 W) has been developed and demonstrated for the next-generation of 48-V bus conversion for data center servers

Switched Tank Converters

High-performance cloud computing enables many key future technologies such as artificial intelligence (AI), self-driving vehicle, big data analysis, and the Internet of things (IoT), using clustered CPU and GPU servers in the datacenter. To improve the power efficiency and the infrastructure flexibility, the computing industry is adopting 54 VDC to power the servers in the open compute racks. In this paper, a new modeling technique for a soft-switched dc–dc converter is presented and suitable to guide optimal design in different applications, for example, 54 V to point of load (PoL) for the new open compute rack. To improve the model accuracy and reduce the complexity, this paper proposes a reduced-order linear differential equation (LDE) based modeling technique to discover the following: 1) the tank resonance involving the output inductor; 2) the output current ripple and its impact on power efficiency; 3) the proper on-time control for soft switching; 4) the unique bleeding mode under the heavy load; 5) the output power capability of the converter; and 6) component tolerance analysis and impact on the performance of the converter. With the power loss estimation, design guidelines are provided for a reference design and design improvement based on this new modeling technique. Using the proposed method, great accuracy can be expected in the efficiency estimation. Simulation and experimental results are provided to verify the modeling technique in a 54–1.2 V 25 A dc–dc converter prototype.

New Modeling Method and Design Optimization for a Soft-Switched DC–DC Converter

Integrated voltage regulators (IVRs) support an increasing number of voltage domains while enhancing the transient response and enabling fine-grained dynamic voltage frequency scaling. A voltage regulator (VR)-on-package is a promising IVR topology, which supports high-voltage transmission within a printed circuit board and package, leading to lower distribution loss. A power delivery network within a VR-on-package environment is presented in this paper. This paper also presents a study of VR top- and bottom-placement topologies within a system-in-package environment in terms of electromagnetic interference (EMI) and power integrity. This comparative analysis targets a specific server package application, and the power integrity evaluation is focused on the power delivery network between the VR and IC. The VR top-placement topology exhibits more than $3\times $ less EMI and 15.3% lower worse case IR drop as compared with the VR bottom-placement topology. The tradeoffs are, however, a greater package power loss and higher package cost due to the larger number of package layers in the VR top-placement topology. The VR top-placement topology exhibits a 52.6% higher power loss through the package than the VR bottom-placement topology.

Power Noise and Near-Field EMI of High-Current System-in-Package With VR Top and Bottom Placements

For an interleaved flyback micro-inverter, the efficiency at heavy load is mainly determined by the conduction loss and switching loss of the semiconductor switches and magnetic components, whereas the efficiency at light load is primarily determined by the frequency-dependent losses such as the MOSFET driving loss, the turn-off loss and the transformer core loss. To shield one phase is an effective method to reduce the frequency-dependent loss and to minimize the overall loss during wide range. In this paper, both Boundary Conduction Mode (BCM) and Discontinuous Conduction Mode (DCM) control strategies are investigated for the flyback micro-inverters. Then 2Ф DCM and 1Ф DCM control methods are investigated and a hybrid control method is proposed to minimize the overall loss depending on different load current to achieve high efficiency in wide load range. The experimental results verified the benefits of the proposed hybrid control method.

Xin Li

Papers

Switched tank converters

Switched Tank Converters

New Modeling Method and Design Optimization for a Soft-Switched DC–DC Converter

Power Noise and Near-Field EMI of High-Current System-in-Package With VR Top and Bottom Placements

An optimal control method for photovoltaic grid-connected interleaved flyback micro-inverters to achieve high efficiency in wide load range