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1. A New High Step-Up DC-DC Topology with Zero DC Magnetizing Inductance Current and Continuous Input Current

   https://doi.org/10.1109/APEC39645.2020.9124151  

   Mahmoudi, Mohsen; Ajami, Ali; Babaei, Ebrahim; Abdolmaleki, Nima; Wang, Caisheng (March 2020, 2020 IEEE Applied Power Electronics Conference and Exposition (APEC))

   null (Ed.)

   A new high-voltage-gain non-isolated dc-dc topology for applications in renewable energies is proposed. A coupled inductor with three windings is used to increase the proposed topology voltage gain. In addition to increasing the voltage gain, the proposed topology also has other prominent features including continuous input current and zero dc magnetizing inductance current, which reduces the losses and size of coupled inductor core. Furthermore, the continuous input current guarantees a low-volume input filter, which is essential for renewable energy applications. The leakage inductor stored energy is recycled via the diode and capacitor and transferred to the converter output for increasing the efficiency and reducing voltage stresses on the converter components. 

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2. A Matrix Autotransformer Switched-Capacitor Converter for Data Center Application

   https://doi.org/10.1109/TPEL.2023.3308888  

   Qiu, Maohang; Wei, Mengxuan; Liu, Xiaoyan; Meng, Haoran; Cao, Dong (December 2023, IEEE Transactions on Power Electronics)

   This article proposes a matrix auto-transformer switched-capacitor dc–dc converter to achieve a high voltage conversion ratio, high efficiency, and high power density for 48-V data-center applications. On the high-voltage side, the proposed converter can fully leverage the benefits of high-performance low voltage stress devices similar to the multilevel modular switched-capacitor converter. Compared with the traditional isolated LLC converter with a matrix transformer, the proposed solution utilized a matrix autotransformer concept with merged primary and secondary side windings, thus leading to reduced transformer winding loss. The resonant inductor could be integrated into the transformer similar to the LLC converter. Because of the matrix autotransformer design, it can achieve a current doubler rectifier on the low voltage side. For less than 8-V low output voltage application, the current doubler rectifier design can fully utilize the best figure-of-merit 25-V device, which is more efficient than the full-bridge rectifier solution using two 25-V devices during the operation. All the devices can achieve zero voltage switching or zero current switching and can be naturally clamped without additional clamping circuits. A 500-W 48-V to 6-V dc–dc converter hardware prototype has been developed with optimized device selection and integrated matrix autotransformer design. Both simulation and experiment results have been provided to validate the features and benefits of the proposed converter. The maximum efficiency of the proposed converter can reach 98.33%. 

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3. Highly Efficient Rectifier and DC-DC Converter Designed in 180 nm CMOS Process for Ultra-Low Frequency Energy Harvesting Applications

   https://doi.org/10.1109/DCAS51144.2020.9330671  

   Gunti, Avinash; Biswas, Dipon K.; Mahbub, Ifana; Adhikari, Pashupati R.; Reid, Russell C. (November 2020, 2020 IEEE 14th Dallas Circuits and Systems Conference (DCAS))

   null (Ed.)

   This paper presents the integration of an AC-DC rectifier and a DC-DC boost converter circuit designed in 180 nm CMOS process for ultra-low frequency (<; 10 Hz) energy harvesting applications. The proposed rectifier is a very low voltage CMOS rectifier circuit that rectifies the low-frequency signal of 100-250 mV amplitude and 1-10 Hz frequency into DC voltage. In this work, the energy is harvested from the REWOD (reverse electrowetting-on-dielectric) generator, which is a reverse electrowetting technique that converts mechanical vibrations to electrical energy. The objective is to develop a REWOD-based self-powered motion (such as walking, running, jogging, etc.) tracking sensors that can be worn, thus harvesting energy from regular activities. To this end, the proposed circuits are designed in such a way that the output from the REWOD is rectified and regulated using a DC-DC converter which is a 5-stage cross-coupled switching circuit. Simulation results show a voltage range of 1.1 V-2.1 V, i.e., 850-1200% voltage conversion efficiency (VCE) and 30% power conversion efficiency (PCE) for low input signal in the range 100-250 mV in the low-frequency range. This performance verifies the integration of the rectifier and DC-DC boost converter which makes it highly suitable for various motion-based energy harvesting applications. 

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4. Accurate ZVS Analysis of a Full-Bridge T-Type Resonant Converter for a 20-kW Unfolding-Based AC-DC Topology

   https://doi.org/10.1109/OJPEL.2024.3400256  

   GURUDIWAN, SHUBHANGI; Zade, Aditya; Wang, Hongjie; Zane, Regan (January 2024, IEEE Open Journal of Power Electronics)

   Unfolding-based single-stage ac-dc converters offer benefits in terms of efficiency and power density due to the low-frequency operation of the Unfolder, resulting in negligible switching losses. However, the operation of the Unfolder results in time-varying dc voltages at the input of the subsequent dc-dc converter, complicating its soft-switching analysis. The complication is further enhanced due to the nonlinear nature of the output capacitance ( Coss ) of MOSFETs employed in the dc-dc converter. Furthermore, unlike two-stage topologies with a constant dc-link voltage, as seen in high-frequency grid-tied converters, grid voltage fluctuations also impact the dc input voltages of the dc-dc converter in unfolding-based systems. This work comprehensively analyzes the soft-switching phenomenon in the T-type primary bridge-based dc-dc converter used in unfolding-based topologies, considering all the aforementioned challenges. An energy-based methodology is proposed to determine the minimum zero-voltage switching (ZVS) current and ZVS time during various switching transitions of the T-type bridge. It is shown that the existing literature on the ZVS analysis of the T-type bridge-based resonant dc-dc converter, relying solely on capacitive energy considerations, substantially underestimates the required ZVS current values, with errors reaching up to 50%. The proposed analysis is verified through both simulation and hardware testing. The hardware testing is conducted on a 20-kW 3- ϕ unfolding-based ac-dc converter designed for high-power electric vehicle battery charging applications. The ZVS analysis is verified at various grid angles with the proposed analysis ensuring a complete ZVS operation of the ac-dc system throughout the grid cycle. 

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5. An efficient DC‐DC converter for inductive power transfer in low‐power sensor applications

   https://doi.org/10.1002/cta.3285  

   Lu, Ruikuan; Hossain, Md. Kamal; Alexander, J. Iwan; Massoud, Yehia; Haider, Mohammad R. (April 2022, International Journal of Circuit Theory and Applications)

   Summary Inductive power transfer has become an emerging technology for its significant benefits in many applications, including mobile phones, laptops, electric vehicles, implanted bio‐sensors, and internet of things (IoT) devices. In modern applications, a direct current–direct current (DC–DC) converter is one of the essential components to regulate the output supply voltage for achieving the desired characteristics, that is, steady voltage with lower peak ripples. This paper presents a switched‐capacitor (SC) DC–DC converter using complementary architecture to provide a regulated DC voltage with an increased dynamic response. The proposed topology enhances the converter efficiency by decreasing the equivalent output resistance to half by connecting two symmetric SC single ladder converters. The proposed converter is designed using the standard 130‐nm BiCMOS process. The results show that the proposed architecture produces 327‐mV DC output with a rise time of 60.1 ns and consumes 3.449‐nW power for 1.0‐V DC supply. The output settling time is 43.6% lower than the single‐stage SC DC–DC converter with an input frequency of 200 MHz. The comparison results show that the proposed converter has a higher power conversion efficiency of 93.87%and a lower power density of 0.57 mW/mm²compared to the existing works. 

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