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1. A Regulated 48V-to-1V/100A 90.9%-Efficient Hybrid Converter for POL Applications in Data Centers and Telecommunication Systems

   Das, Ratul; Le, Hanh-Phuc (March 2019, 2019 IEEE Applied Power Electronics Conference and Exposition (APEC))

   This paper describes the topology, fundamental operations, and key characteristics of a Dual-Phase Multi-Inductor Hybrid (DP-MIH) Converter for Point of Load (POL) telecommunication and data center applications. The circuit topology employs a unique configuration of switched-inductor and capacitor pairs to achieve complete soft charging and native voltage balancing of flying capacitors regardless of mismatches and variations in capacitor and inductor values. The converter topology and its operation are verified by a five-level DP-MIH converter prototype capable of delivering maximum load of 100A at 1V-5V regulated output voltages from a 48V input supply. It achieves 90.9% peak efficiency and 440 w/in3 power density for 48V-to-1V conversion and 95.3% and 2200W/in3 for a 48V-to-5V conversion. 

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2. Multiphase Control for Robust and Complete Soft-charging Operation of Dual Inductor Hybrid Converter

   Xie, Tianshi; Das, Ratul; Seo, Gab-Su; Maksimovic, Dragan; and Le, Hanh-Phuc (March 2019, 2019 IEEE Applied Power Electronics Conference and Exposition (APEC))

   This paper presents a new Multiphase Dual Inductor Hybrid (MP-DIH) Converter for application in data center and telecommunication systems. The converter is based on addition of two output filter inductors to a Dickson switched-capacitor converter. The inductors are operated in multiple phases that are non-overlapped and evenly distributed over one switching cycle, completely soft-charging all flying capacitors even in the presence of practical capacitor mismatches and voltage ripples. In this converter operation, each branch of the switched-capacitor network is activated individually in one charging phase, and two interleaved inductors are employed to softly charge and discharge the capacitors to achieve high efficiency without any complex capacitor sizing or split phase operation. To verify the topology and its soft-charging advantages, a 48V-to-1.8V 20W experimental converter prototype is constructed. The converter achieves 92.4% peak efficiency for 40V-to-1.8V conversion and 92.1% peak efficiency for 48V-to-1.8V conversion at 4A load, and with 20% capacitance variations. 

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3. Demystifying Capacitor Voltages and Inductor Currents in Hybrid Converters

   https://doi.org/10.1109/COMPEL.2019.8769722  

   Das, Ratul; Celikovic, Janko; Abedinpour, Siamak; Mercer, Mark; Maksimovic, Dragan; Le, Hanh-Phuc (June 2019, 2019 20th Workshop on Control and Modeling for Power Electronics (COMPEL))

   This paper presents a modeling method to accurately predict DC and ripple values of flying capacitor voltages and inductor currents in hybrid converters by recognizing a key relationship between median and average values of these state variables. The method is demonstrated for the Dual-Phase Multi-Inductor Hybrid (DP-MIH) converter and 3-Level Buck converter. Analytical details and intuitive explanations are presented for the well-known balancing problem of flying capacitor voltages and inductor current fluctuations in hybrid converters. Simulation results for the converters at different operating conditions are provided to verify the method and analytical results. 

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4. A 95%-Efficient 48V-to-1V/10A VRM Hybrid Converter Using Interleaved Dual Inductors

   https://doi.org/10.1109/ECCE.2018.8557715  

   Seo, Gab-Su; Das, Ratul; Le, Hanh-Phuc (September 2018, 2018 IEEE Energy Conversion Congress and Exposition (ECCE))

   This paper presents a new 48 V-to-1 V hybrid converter. The converter utilizes two interleaved inductors to achieve complete soft-charging of flying capacitors to efficiently support high output currents. This dual inductor hybrid converter (DIHC) features fewer number of switches and more effective switch utilization than a recently reported hybrid Dickson converter, leading to substantially less conduction losses presented by a smaller equivalent output impedance. Experimental results verify the converter's operation principles and advantages in a 300-kHz 20-W prototype achieving 95.02% peak efficiency and 225 W/in3 power density. Its advantages and performance promise a good candidate converter architecture for applications that require large conversion ratios and high output currents, such as data centers and high-performance digital systems. 

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5. An Inductor-First Single-Inductor Multiple-Output Hybrid DC-DC Converter With Integrated Flying Capacitor for SoC Applications

   https://doi.org/10.1109/TCSI.2022.3198389  

   Zhou, Zhiyuan; Tang, Nghia; Nguyen Bai; Hong Wookpyo Hong; Pande, Partha Pratim; Heo, Deukhyoun Heo (December 2022, IEEE transactions on circuits and systems)

   With the increasing complexity of highly integrated system on chips (SoCs), the power management system (PMS) is required to provide several power supplies efficiently for individual blocks. This paper presents a single-inductor multiple outputs (SIMO) an inductor-first hybrid converter that generates three outputs between 0.4V and 1.6V from a 1.8V input. The proposed multiple-output hybrid power stage can improve the conversion efficiency by reducing inductor current while extending the output voltage range compared with the existing hybrid topologies. In addition, the proposed converter employs an on-chip switched-capacitor power stage (SCPS) with a dual switching frequency technique, resulting in a fast response time, low cross-regulation, and reduced number of on-chip pads. Measurement results show that the converter achieves a peak efficiency of 87.5% with a maximum output current of 450mA. The converter is integrated with a fast voltage regulation loop with a 500MHz system clock to achieve less than 0.01mA/mV cross-regulation and a maximum 20mV overshoot at full-load transient response. The design is fabricated in the standard 180nm CMOS technology 

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