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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. An 80-W 94.6%-Efficient Multi-Phase Multi-Inductor Hybrid Converter

   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 Multi-Phase Multi-Inductor Hybrid (MP-MIH) converter that features high efficiency at large conversion ratios, while operating the switches with duty cycles larger than state-of-the-art hybrid topologies. In this converter, the capacitors are soft-charged and soft- discharged through three inductors operated in three interleaving phases. An experimental six-level three-phase converter prototype achieves 94.6% peak efficiency and 425 W/in3 power density for conversions from 48V to 1V-2V at loads of up to 40A. This multi-phase multi-inductor hybrid converter architecture can be extended to any number of switched-capacitor network levels to support wide range of input and output voltages and load currents in data centers, telecommunication and other high- performance digital systems. 

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3. A 120V-to-1.8V 91.5%-Efficient 36-W Dual-Inductor Hybrid Converter with Natural Soft-charging Operations for Direct Extreme Conversion Ratios

   https://doi.org/10.1109/ECCE.2018.8557854  

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

   This paper presents a new dual inductor hybrid converter (DIHC) that is capable of efficient direct non-isolated DC-DC conversions with extremely large voltage conversion ratios. The converter employs two interleaved inductors and a switched-capacitor (SC) network to bring several significant topological benefits. Capacitance of the flying capacitors of this new topology can be optimally sized to achieve natural, complete soft-charging for all capacitors. This novel capacitor soft-charging feature is a key contribution of this work and can be exploited to overcome the limitations of conventional SC converters suffering from capacitor hard charging losses. The converter topology and its operation are verified in an 36-W converter prototype for 40-120V input to 0.9V-1.8V output up to 20A of current load that achieves peak efficiencies of 91.5% for 120V-to-1.8V and 87.3% for 120V-to-0.9V conversion. Its advantages and performance at extreme conversion ratios push the limit of point-of-load converters, reducing complexity and cost for bus voltage distributions, as well as enabling fewer conversion stages and thus higher efficiency for data centers and high-performance digital systems. 

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4. 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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5. A Two-Stage Cascaded Hybrid Switched-Capacitor DC-DC Converter with 96.9% Peak Efficiency Tolerating 0.6V/μs Input Slew Rate During Startup

   https://doi.org/10.1109/ISSCC42613.2021.9365763  

   Xia, Ziyu ; Stauth, Jason T. ( February 2021 , IEEE International Solid- State Circuits Conference (ISSCC))

   null (Ed.)

   Efficient high-conversion-ratio power delivery is needed for many portable computing applications which require sub-volt supply rails but operate from batteries or USB power sources. In such applications, the power management unit should have a small volume, area, and height while providing fast transient response. Past work has shown favorable performance of hybrid switched-capacitor (SC) converters to reduce the size of needed inductor(s), which can soft-charge high-density SC networks while supporting efficient voltage regulation [1-5]. However, the hybrid approach has its own challenges including balancing the voltage of the flying capacitor and achieving safe but fast startup. Rapid supply transients, including startup, can cause voltage stress on power switches if flying capacitors are not quickly regulated. Past approaches such as precharge networks [3] or fast balancing control [5] have startup times that are on the order of milliseconds. This paper presents a two-stage cascaded hybrid SC converter that features a fast transient response with automatic flying capacitor balancing for low-voltage applications (i.e., 5V:0.4 to 1.2V from a USB interface). The converter is nearly standalone and all gate drive supplies are generated internally. Measured results show a peak efficiency of 96.9%, <; 36mV under/overshoot for 1A/μs load transients, and self-startup time on the order of 10μs (over 100× faster than previous works). 

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