Search Results (540)

In this research, a step-down converter with a lossless snubber is proposed, and its output is floating; therefore, it can be applied to LED driving applications. Such a structure is a modification of the conventional buck converter by adding a resonant capacitor, a resonant inductor, and two diodes to form this lossless snubber to reduce the switching loss during the switching period. Although the efficiency improvement in this circuit is not as good as the existing soft switching circuits, this circuit has the advantages of simple structure, easy control, and zero voltage switching (ZVS) cutoff. Full article

The LLC resonant converter, as an isolated DC-DC conversion topology, has been widely adopted in industrial applications. However, when operating under wide input/output voltage ranges, a broad switching frequency range is required to achieve the desired voltage gain. This wide frequency variation complicates the design of magnetic components, causes loss of soft-switching characteristics, and deteriorates electromagnetic interference (EMI) performance. To address these challenges, this paper presents a detailed analysis of the L-LCLC resonant converter. By controlling the connection/disconnection of additional inductors and capacitors through switching devices, the topology achieves structural reconfiguration to enhance the voltage gain range. Optimal mode transition points are selected to ensure stable operation during mode transitions, thereby reducing design complexity, minimizing transition losses, and suppressing voltage/current stress. The parameter design methodology for the additional reactive components is systematically developed. The converter’s performance is validated with Simulink, and the experimental prototype is established with 100 W. Both simulation and experimental results confirm that the L-LCLC resonant converter achieves a wide voltage gain range within a narrow frequency band while maintaining stable mode transitions. Full article

Dual Maximum Power Point Tracking (MPPT) inverters are essential in residential and small commercial solar power systems, optimizing power extraction from two independent solar panel arrays to enhance efficiency and energy harvesting. On the other hand, the Three-Level T-Type Voltage Source Inverter (3L T-Type VSI) is known for its reduced switching losses, improved harmonic distortion, and reduced part count in comparison to other three-level topologies. In this paper, a novel architecture is proposed to integrate the dual MPPT structure directly to each DC-side split capacitor of the 3L T-Type VSI, taking advantage of the intrinsic characteristics of the inverter’s topology. Further performance enhancement is achieved by integrating a classical MPPT strategy to the control framework to make it feasible for a real-case grid integration. The combination of these methods ensures faster and stable tracking under dynamic irradiance conditions. Considering that strategies dedicated to balancing the DC-link capacitor’s voltage slightly affect the AC-side current waveform, an enhanced sliding mode control (SMC) strategy tailored for dual MPPT and 3L T-Type VSI is deployed, combining the simplicity of conventional PI controllers used in the independent MPPT-based DC-DC converters with the superior robustness and dynamic performance of SMC. Real-time results obtained using the OPAL-RT Hardware-in-the-Loop platform validated the performance of the proposed control strategy under realistic test scenarios. The current THD was maintained below 4.8% even under highly distorted grid conditions, and the controller achieved a steady state within approximately 15 ms following perturbations in the DC-link voltage, sudden irradiance variations, and voltage sags and swells. Additionally, the power factor remained unitary, enhancing power transfer from the renewable source to the grid. The proposed system was able to achieve efficient power extraction while maintaining high power quality (PQ) standards for the output, positioning it as a practical and flexible solution for advanced solar PV systems. Full article

In order to upgrade the ability of the traditional flyback converter to transfer energy to the load, a dual-flyback converter with two active clamping circuits is added, using the same clamping capacitor to recover the leakage inductance energy. Furthermore, no additional resonant inductor is needed, and both the switches have zero voltage switching (ZVS) to reduce the switching loss. In addition, full-wave rectification is used on the secondary side to decrease the output voltage ripple frequency, which makes it easy to design the output filter. Full article

When connecting a renewable energy source to a medium-voltage grid, it has to fulfil grid codes and be able to work in a medium-voltage range (>10 kV). Multilevel converters (MLCs) are recognized for their low total harmonic distortion (THD) and ability to work at high voltage compared to other converter types, making them ideal for applications connected to medium-voltage grids whilst being compliant with grid codes and voltage ratings. Cascaded H-bridge multilevel converters (CHBs-MLC) are a type of MLC topology, and they does not need any capacitors or diodes for clamping like other MLC topologies. One of the problems in these types of converters involves the double-frequency harmonics in the DC linking voltage and power, which can increase the size of the capacitors and converters. The use of line frequency transformers for isolation is another factor that increases the system’s size. This paper proposes an isolated CHBs-MLC topology that effectively overcomes double-line frequency harmonics and offers isolation. In the proposed topology, each DC source (renewable energy source) supplies a three-phase load rather than a single-phase load that is seen in conventional MLCs. This is achieved by employing a multi-winding high-frequency transformer (HFT). The primary winding consists of a winding connected to the DC sources. The secondary windings consist of three windings, each supplying one phase of the load. This configuration reduces the DC voltage link ripples, thus improving the power quality. Photovoltaic (PV) renewable energy sources are considered as the DC sources. A case study of a 1.0 MW and 13.8 kV photovoltaic (PV) system is presented, considering two scenarios: variations in solar irradiation and 25% partial panel shedding. The simulations and design results show the benefits of the proposed topology, including a seven-fold reduction in capacitor volume, a 2.7-fold reduction in transformer core volume, a 50% decrease in the current THD, and a 30% reduction in the voltage THD compared to conventional MLCs. The main challenge of the proposed topology is the use of more switches compared to conventional MLCs. However, with advancing technology, the cost is expected to decrease over time. Full article

This paper introduces a non-isolated ultra-high voltage gain topology using the combination of the coupled-inductor-based inverting buck-boost converter (IBB) and voltage multiplier (VM) structure. In the proposed converter, an ultra-high step-up voltage gain can be achieved with a small duty cycle thanks to a coupled inductor and VMs. The voltage stress and the losses of the switches in the proposed converter are even less than other conventional topologies. Unlike other coupled-inductor topologies, a large voltage spike caused by the leakage inductance of the coupled inductor is smoothed by the capacitor in the voltage multiplier. In addition, zero-voltage switching (ZVS) turn-on for the switches and zero-current switching (ZCS) turn-off for the diodes can be achieved with the energy stored in the leakage inductance. A 360 W (40 V/380 V) prototype converter is implemented to prove the advantages of the proposed converter, with a maximum efficiency of 98.4%. Full article

This paper introduces a high-conversion ratio multiphase nonisolated converter built from generic LC cells. The unique architecture that hinges on a generic capacitor inductor switching module enables the high modularity of the topology, providing a quick extension of the converter design in an interleaved configuration for lower ripple and higher current output. The generic module comprises the basic power components of a nonisolated DC–DC converter, where the unique interaction between the capacitor and the inductor results in a soft charging operation, which curbs the losses of the converter, and contributes to a higher efficiency. Additional features of the new converter include a significantly extended effective duty ratio, and a lower voltage stress on the switches, a very high output current, and architecture-inherent output current sharing that balances the loading between the phases. In addition, a power extension using a paralleling and interleaving approach is presented to provide higher output current capabilities. Simulation and experimental results of a modular interleaved three-phase prototype demonstrate an excellent proof of concept and agree well with the theoretical analyzes developed in this study. Full article

In order to achieve a long-pulse-width output, a new long-pulse-width modulator based on the charging power supply of LCC-type high-frequency resonant converters and the pulse-generating unit in series IGBT switching technology has been designed. The relationship between the resonant cavity gain and the switching frequency has been derived. In the charging phase, the critical intermittent control mode is used to increase the charging speed, and in the voltage stabilization phase, the hysteresis burst control strategy is used to improve voltage accuracy. The simulation results show that the output pulse amplitude is 10 kV, the pulse width can reach 650 μs, and the top-drop is about 12%. Thus, a long pulse width modulator is developed. The output pulse voltage can reach 4 kV, and the output pulse width is 650 μs. The power supply reduces the capacity of the energy storage capacitor, which has industrial application value. Full article

Modular multilevel converter (MMC)-based power electronic transformers (PETs) present a promising solution for connecting AC/DC microgrids to facilitate renewable energy access. However, the capacitor ripple voltage in MMC-based PET submodules hinders volume optimization and power density enhancement, significantly limiting their application in distribution networks. To address this issue, this study introduces an optimized method for suppressing the submodule capacitor ripple voltage in MMC-based PET systems under normal and grid fault conditions. First, an MMC–PET topology featuring upper and lower arm coupling is proposed. Subsequently, a double-frequency circulating current injection strategy is incorporated on the MMC side to eliminate the double-frequency ripple voltage of the submodule capacitor. Furthermore, a phase-shifting control strategy is applied in the isolation stage of the dual-active bridge (DAB) to transfer the submodule capacitor selective ripple voltages to the isolation stage coupling link, effectively eliminating the fundamental frequency ripple voltage. The optimized approach successfully suppresses capacitor ripples without increasing current stress on the isolated-stage DAB switches, even under grid fault conditions, which are not addressed by existing ripple suppression methods, thereby reducing device size and cost while ensuring reliable operation. Specifically, the peak-to-peak submodule capacitor ripple voltage is reduced from 232 V to 10 V, and the peak current of the isolation-stage secondary-side switch is limited to ±90 A. The second harmonic ripple voltage on the LVDC bus can be decreased from ±5 V to ±1 V with the proposed method under the asymmetric grid voltage condition. Subsequently, a system simulation model is developed in MATLAB/Simulink. The simulation results validated the accuracy of the theoretical analysis and demonstrated the effectiveness of the proposed method. Full article

Inductor parameter variations often affect the control performance of digital current mode (CM)-controlled buck converters as their high performance relies on accurate converter modeling. However, recent studies have shown that reliably monitoring inductance with current sensors and high-frequency sampling greatly increases the overall cost of this process. To address this issue, an online inductance monitoring method without a current sensor is proposed in this study. First, an inductance calculation model is derived by applying the dynamic characteristics of a buck converter with inductor volt-second and capacitor charge balance principles. The model’s accuracy is guaranteed by considering inductor current switching ripple characteristics. Nevertheless, output capacitor equivalent series resistance (ESR) can degrade the accuracy of the proposed calculation model. Thus, to enhance the tolerance of the inductance calculation model to capacitor ESR, the ESR effect on inductance monitoring is investigated. With the proposed capacitor ESR estimation method, inductance monitoring achieves reliable accuracy, even for a buck converter with high capacitor ESR. The effectiveness of the proposed method is verified by simulations and experiments on a buck converter with digital sensorless current mode (SCM) control. Full article

The high switching speed of SiC MOSFETs can induce resonance between parasitic inductors and capacitors, owing to rapid changes in current and voltage, leading to excessive crosstalk parasitic oscillation. This can increase SiC MOSFETs’ gate oxide voltage stress, reducing their service life and even directly leading to gate overvoltage failure. However, there is still a lack of investigations of active control of gate driving in systematic converters because crosstalk parasitic oscillation, indicated by high frequencies in MHz, is challenging to control in a power converter with gate voltage stability and high switching speed. This paper investigates an active gate drive based on negative feedback to fully drive SiC MOSFETs with high efficiency and stable gate voltage to exploit the advantages of high dv/dt over 20 V/ns in SiC MOSFETs and further realize the miniaturization of power conversion systems. It first investigates a dynamic model of SiC MOSFET gate-interfered oscillation in parallel application derived from a circuit with equivalent junction capacitance in power devices. Then, the operating principle of the Negative Feedback Active Gate Drive (NFAGD) application strategy for parallel SiC MOSFETs is demonstrated. Finally, the experiment verifies the proposed strategy’s effectiveness in suppressing crosstalk parasitic oscillation in parallel SiC MOSFETs, and an 8 kW synchronous buck converter prototype is built to verify the NFAGD’s performance in systematic converter applications. Full article

This article proposes a high-efficiency isolated three-port resonant converter for DC microgrids, combining a dual active bridge (DAB)–LLC topology with hybrid Pulse Width Modulat-Pulse Frequency Modulation (PWM-PFM) phase shift control. Specifically, the integration of a dual active bridge and LLC resonant structure with interleaved buck/boost stages eliminates cascaded conversion losses. Energy flows bidirectionally between ports via zero-voltage switching, achieving a 97.2% efficiency across 150–300 V input ranges, which is a 15% improvement over conventional cascaded designs. Also, an improved PWM-PFM shift control scheme dynamically allocates power between ports without altering switching frequency. By decoupling power regulation and leveraging resonant tank optimization, this strategy reduces control complexity while maintaining a ±2.5% voltage ripple under 20% load transients. Additionally, a switch-controlled capacitor network and frequency tuning enable resonant parameter adjustment, achieving a 1:2 voltage gain range without auxiliary circuits. It reduces cost penalties compared to dual-transformer solutions, making the topology viable for heterogeneous DC microgrids. Based on a detailed theoretical analysis, simulation and experimental results verify the effectiveness of the proposed concept. Full article

This paper presents a successive approximation register (SAR) and incremental sigma-delta modulator (ISDM) hybrid analog-to-digital converter (ADC) that operated at a minimum voltage supply of 0.575 V. A thorough analysis of the non-linearities caused by PVT variations and common-mode voltage (VCM) shifts in the ISDM stage is presented. The ADC employs an improved high-precision double-bootstrapped switch, and the synchronous clock is also double-bootstrapped to work under the low supply voltage. A modified merged capacitor switching (MCS) approach is presented to maintain a stable VCM at the differential input. The chip was fabricated using a 0.18 µm CMOS process, with a core area of 0.21 mm². It consumed only 0.42 µW at a 0.6 V supply and a sampling rate of 10 kS/s, which achieved an effective number of bits (ENOB) of 11.03. The resulting figure of merit (FOM_W) was 20.05 fJ/conversion-step, which is the lowest reported for ADCs of this architecture in a 0.18 µm process. Full article

This article presents an efficient non-isolated DC-DC hybrid converter for direct large-ratio step-down applications such as data centers. The converter topology employs a three-level-assisted Dickson switched capacitor network and interleaved dual inductors, significantly mitigating voltage swings at the switching nodes. As a result, the conduction duration of rectifying switches is substantially extended. This configuration is suitable for both odd- and even-order converters, achieving self-balancing of the flying capacitor voltages and inductor currents. To address uneven interleaved inductor currents, a duty-cycle-matching-based current distribution method is proposed to ensure equal current sharing and facilitate loss transfer between inductors. Additionally, an intrinsic charge-ratio-based method for capacitance optimization is introduced to achieve quasi-complete soft charging of the flying capacitors. This method eliminates surge currents during reconfiguration of the capacitor network, reduces losses, and enhances the capacitor utilization. Operating at 300 kHz, the prototype achieves high-ratio voltage conversion from 48 V to 0.5–2.0 V, with a maximum output current of 30 A. It attains a peak efficiency of 91.96% and a power density of 944.88 W/in³. Quasi-complete soft charging of the flying capacitors results in an approximate 2.94% improvement in the conversion efficiency. Full article

A grid-connected converter is the interface between renewable energy power generation systems, such as solar power generation, wind power, hydropower, etc., and the power grid, responsible for the stable and efficient transmission of electric energy generated by renewable energy power generation systems to the grid. In order to realize local access for distributed photovoltaic power generation devices and energy storage devices, a composite three-port converter has the advantages of small size, low cost and high power density compared with a combined three-port converter. In view of the current problems of the existing compound three-port (AC/DC/DC) converters, such as DC and AC circulating current in current composite three-port converters and the harmonic control problem, the proposed compound three-port topology consists of a full-bridge inverter with six switching tubes, a zigzag transformer, two sets of filter inductors and two filter capacitors. Among them, the power frequency transformer adopts the zigzag connection method, which can effectively restrain the AC circulation and eliminate the DC magnetic flux of the iron core while introducing the third port. Firstly, the principle of AC/DC and DC/DC power conversion in the composite three-port topology is analyzed, which has higher efficiency than other topologies. Secondly, the topology control strategy is analyzed, and a two-loop hybrid current control method with improved current loop is proposed. When the DC-side voltage fluctuates, the DC offset of the battery can effectively improve the stability of the network side. Through the MATLAB/Simulink simulation experiment platform, the high efficiency of energy conversion and stable grid-connected operation characteristics are verified. Finally, the experiment of integrating into the power grid was carried out. Experiments were used to verify the effectiveness and feasibility of the proposed topology and strategy. The experimental results show that Total Harmonic Distortion (THD) can be controlled below 3%. Full article