MSC-PoL: An Ultra-Thin 220-A/48-to-1-V Hybrid GaN-Si CPU VRM with Multistack Switched Capacitor Architecture and Coupled Magnetics

Wang, Ping; Giuliano, David; Allen, Stephen; Chen, Minjie

doi:10.1109/apec43580.2023.10131617

Cited by 13 publications

(5 citation statements)

References 24 publications

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“…Recent advances in 48-to-1 V conversion include, for example, hybrid switched capacitor [1-4], switched resonant tank [3], transformer-isolated [5], and composite "sigma" converters [6]. A different, "direct power conversion" principle was introduced in [7] and demonstrated for 48 V-to-12 V and 12 V-to-1 V applications.…”

Section: Fixed Ratio Conversionmentioning

confidence: 99%

48V to 1V Active-Clamp Stacked Direct Forward Converter

Sinha,

Majmunović,

Maksimović

2023

2023 IEEE 24th Workshop on Control and Modeling for Power Electronics (COMPEL)

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This thesis presents a 48 V-to-1 V stacked direct forward (SDF) dc-dc converter consisting of four 12 V-to-1 V direct forward (DF) modules connected in input-series outputparallel (ISOP) configuration. In each DF module, there is no secondary-side inductance, and a single-ended forward transformer is driven at a high duty cycle to reduce the switch root-mean-square currents. An active clamp is employed on the primary side to reset the transformer, limit the switch voltage stress, and facilitate zero voltage switching. The approach is verified by simulation results on a 12 V-to-1 V, 50 A, 200 kHz prototype module using GaN devices and a planar transformer, and having a peak efficiency of 93.9% and the full-load efficiency of 91.8%. In this thesis, experimental results are presented for a 12 V-to-1 V DF prototype. I would like to thank my thesis advisor, Dr. Dragan Maksimovic, for giving me the opportunity to do my master's thesis under his guidance. Thanks to his guidance and encouragement, I was able to gain a lot of valuable knowledge in the field of power electronics and keep myself motivated throughout the completion of my thesis. Additionally, I would like to thank Dr. Luca Corradini and Dr. Robert W. Erickson, who have helped me learn and better understand analysis, modeling, design and control techniques in power electronics. I would like to thank my peers who supported and encouraged me during the completion of my thesis. Finally, I would like to thank my parents for their support as well as inspiration throughout my graduate studies. v Contents Chapter

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Section: Fixed Ratio Conversionmentioning

confidence: 99%

48V to 1V Active-Clamp Stacked Direct Forward Converter

Sinha,

Majmunović,

Maksimović

2023

2023 IEEE 24th Workshop on Control and Modeling for Power Electronics (COMPEL)

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“…Furthermore, high light load efficiency and fast response ability under high load transients (>1000A/μs) are another two major concerns. The existing 48‐V VRM solutions 4–31 can be classified into two categories: single‐stage and two‐stage approaches.…”

Section: Introductionmentioning

confidence: 99%

“…In general, the single‐stage scheme is considered to exhibit higher efficiency than the two‐stage scheme since the electrical energy is converted only once in the former. To achieve a high conversion ratio, the single‐stage 48‐V VRM approaches usually integrate a transformer with a large turn ratio 4–10 or use a switched‐capacitor divider circuit integrated by multi‐phase buck converters 11–14 . The transformer‐based full bridge (FB) structure with a current doubler rectifier was the first approach to directly convert 48 to 1 V 4 .…”

Section: Introductionmentioning

confidence: 99%

“…The switched capacitor integrated multiphase buck converters, 11–14 as another type of single‐stage approach with a high conversion ratio, are considered to achieve higher power density at the expense of more switches. The significant two advantages of these topologies are the low operating voltages of switches and the elimination of transformers.…”

Section: Introductionmentioning

confidence: 99%

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A novel two‐stage solution for low‐power 48‐V voltage regulator module (VRM) using high step‐down hybrid LLC with integrated planar transformer

Lu,

Ma,

et al. 2023

Circuit Theory & Apps

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SummaryIn this paper, a novel two‐stage solution based on a 1‐MHz high step‐down hybrid LLC converter is proposed for low‐power 48 V voltage regulator modules (VRM). Since the hybrid LLC DCX converter with high step‐down ability is employed as the first‐stage, lower bus voltage can be obtained with the same transformer turns, which contributes to enhancing the duty cycle and efficiency of the second‐stage multi‐phase buck converter. Thus, an overall efficiency improvement can be achieved in the proposed two‐stage system, especially in low‐power applications. To further improve efficiency and power density, a novel integrated planar transformer is adopted for the double resonant tanks of the hybrid LLC converter. To validate the analysis, a 150‐W hardware prototype of the hybrid LLC converter is constructed in the laboratory. To ensure a fair comparison with existing LLC DCX designs, the output voltage is set at 6 V. The measured efficiency results of the first‐stage demonstrate an efficiency advantage at low power output levels compared to the similar full bridge LLC designs, especially at an output of around 100 W. Under the nominal 48‐V input, the first‐stage achieves a peak efficiency of 98.5% and a full load efficiency of 94.62%. Furthermore, a 4‐phase buck converter with nominal 6‐V input and 1.6‐V output is constructed to evaluate the efficiency performance of the overall system. When the second stage operates at 500 kHz, the proposed two‐stage system achieves a peak efficiency of 93.2% at 40A load, while maintaining an efficiency of 91.2% at 65A output. The calculated efficiency of the proposed two‐stage solution exhibits higher performance compared to the majority of single‐stage schemes.

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“…The series-capacitor-buck (SCB) converter [3]- [6] shown in Fig. 1 is one such hybrid SC converter that has recently been adopted in data center applications, both as a stand-alone high step-down solution [7], and embedded within 48:1 hybrid switched-capacitor converters [8]- [12]. Relative to the multi-phase interleaved buck converter, the SCB converter offers decreased switch voltage rating, which enables use of lower-voltage switches with higher figure-ofmerit [13]; extended duty cycle, which enables a large conversion ratio with sufficient duty cycle resolution; and decreased total inductor volt-seconds, which allows for decreased inductive energy storage volume.…”

Section: Introductionmentioning

confidence: 99%

Steady-State Analysis of Series-Capacitor Buck Converters in Discontinuous Capacitor Voltage Mode

Biesterfeld,

Zhu,

Iyer

et al. 2023

2023 IEEE 24th Workshop on Control and Modeling for Power Electronics (COMPEL)

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The series-capacitor buck (SCB) converter is a compact and highly-efficient alternative to the multi-phase buck converter and has recently been demonstrated in data center applications. To achieve high power density, it is desirable to reduce the total flying capacitance in this topology. However, for sufficiently small flying capacitances, a discontinuous capacitor voltage mode (DCVM) manifests, leading to an imbalance in inductor currents. This work provides a detailed derivation of the relationship between the critical capacitance describing the onset of DCVM and converter operating parameters. Moreover, the inductor current imbalance is characterized through the development of a clamped steady-state model. To recover balancing when flying capacitance below the critical value is used, a technique to drive the branches with modified duty cycles in a constant power regime is proposed. Experimental validation of the steadystate model and recovery of inductor current balancing are demonstrated on a 4-branch SCB prototype.

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MSC-PoL: An Ultra-Thin 220-A/48-to-1-V Hybrid GaN-Si CPU VRM with Multistack Switched Capacitor Architecture and Coupled Magnetics

Cited by 13 publications

References 24 publications

48V to 1V Active-Clamp Stacked Direct Forward Converter

48V to 1V Active-Clamp Stacked Direct Forward Converter

A novel two‐stage solution for low‐power 48‐V voltage regulator module (VRM) using high step‐down hybrid LLC with integrated planar transformer

Steady-State Analysis of Series-Capacitor Buck Converters in Discontinuous Capacitor Voltage Mode

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