Wide Output Voltage Range Research Articles

Full Soft-Switching Ultra-High Gain DC/DC Converter Using Three-Winding Coupled-Inductor with Modular Scalability for Renewable Energy Applications

This paper proposes a new non-isolated single-switch DC/DC converter with an ultra-high voltage gain, low input current ripple, low voltage stress, soft-switching operation, and modular scalability for renewable sources applications. Here, with the help of a Three-Winding Coupled-Inductor (TWCI) and Voltage Multipliers circuits, ultra-high voltage gains can be achieved without needing a large duty cycle. A regenerative clamp capacitor recycles the energy stored in the leakage inductor; thus, the maximum voltage across the single power switch is restricted. Moreover, at the turn-on instant of the power switch, a Zero Current Switching (ZCS) condition is achieved. By designing a resonant tank, the switched current value of the main switch at the turn-off instant is reduced significantly. Also, the leakage inductor of the TWCI helps all converter diodes to operate under the ZCS condition. Due to full soft-switching performance, the introduced topology can provide a wide output voltage range under a high conversion efficiency. The steady-state analysis and comprehensive comparisons are provided in this paper. A 160 W prototype with 24 V input and 250 V output voltage is developed to validate the theoretical analysis. Due to ZCS operation and low voltage stress (VDS ≈ 40 V), the power loss portion of the MOSFET is low. Moreover, the maximum voltage stresses of the diodes are measured 40 V, 60 V, 90 V, and 110 V that are well below the output voltage. Furthermore, at the full-load condition, the input current ripple is about 20 % and the measured efficiency is about 96.3%.

Interleaved Single-Stage LLC Converter Design Utilizing Half- and Full-Bridge Configurations for Wide Voltage Transfer Ratio Applications

Automotive on-board dc-dc converters are required to operate over a wide input and output voltage range depending on the state of charge of the input and the output battery. Conventionally, the unidirectional power transfer between these batteries is enabled by a two-stage converter concept. A first-stage nonisolated dc-dc converter regulates the input voltage of the galvanically isolated second-stage dc-dc converter such that the second-stage converter operates in its optimum operating point. This article presents a single-stage interleaved LLC resonant converter of 3.6 kW for this purpose. While LLC converters are usually not suitable to cover such a wide voltage range (the input voltage between 240 and 420 V and the output voltage between 8 and 16 V), this LLC converter is operated in a full-bridge mode for large gains and in a half-bridge mode for low gains. For intermediate gains and loads, the LLC employs the phase-shift mode. To operate the interleaved LLCs at equal switching frequencies enabling output current ripple cancellation to reduce the output capacitor, again, the phase-shift mode is utilized to balance the power transfer during the full-bridge mode while the asymmetrical duty-cycle mode is proposed for power balancing during the half-bridge mode. This article analyzes the converter design for these modes of operation and provides a comprehensive design procedure allowing the designer to simultaneously analyze all stress values for various resonant tank designs. A 3.6-kW prototype employing Si superjunction MOSFETs achieves a power density of 2.1 kW/L. The maximum efficiency reaches 96.5%, while for most operating points, it is kept well above 90%. The experimental measurement results validate the analysis and show that phase-shift operation and asymmetrical duty-cycle modulation can be utilized for power balancing for full-bridge and half-bridge configurations, respectively, such that a much smaller output capacitor can be employed.

Implementation of SHE-PWM technique for single-phase inverter based on Arduino

This paper presents design and practical implementation of single-phase inverter based on selective harmonic elimination-pulse width modulation (SHE-PWM) technique. Microcontroller mega type Arduino used as a controller for producing the gate pulses. The optimized switching angles determination results in wide range of output voltage. Depending on number of switching angles, the lower order harmonics (LOHs) can be eliminated to improve the output voltage waveform. A comparison study using MATLAB/Simulink for sinusoidal-PWM and SHE-PWM techniques, which shows for the same LOH in the output voltage waveform, the SHE-PWM has less number of pulses per half cycle than sinusoidal-PWM strategy. The reduction in number of pulses results less switching losses. The simulation done using ten switching angles to drive R-L load. A prototype of SHE-PWM inverter with R-L load is used to validate the simulation results.

A Natural Bidirectional Isolated Single-Phase AC/DC Converter With Wide Output Voltage Range for Aging Test Application in Electric Vehicle

To ensure the safety and reliability, the aging test of on-board charger (OBC) and dc/dc auxiliary power module (dc/dc-APM) in electric vehicles are indispensable. However, a wide range of battery voltage levels and fast response to power conversion between forward and backward operations are still challenging aspects of the aging test power system. In this article, an improved ac/dc converter is proposed for the aging test application in electric vehicles. The converter consists of two identical topologies, which is made up of three cascaded converters. The first stage is a single-phase ac/dc rectifier, which realizes unity input power factor and power transmission between the ac grid and dc bus. The second stage is the LLC-dc/dc transformer (LLC-DCX) which provides electrical isolation and fixed voltage transfer ratio. Besides, the natural bidirectional power flow can be achieved by the proposed solution. The third stage is a synchronous buck converter (SBC) which guarantees the high dynamic performance and wide range voltage regulation. Experiments based on an 8-kW prototype are conducted to verify the feasibility and effectiveness of the proposed converter and the related control strategies.

Active pixel sensor readout circuit using indium–tin–zinc-oxide thin-film transistors for image sensor applications

In this study, we describe an active pixel sensor (APS) readout circuit using indium–tin–zinc-oxide (ITZO) thin-film transistors (TFTs). The APS readout circuit with a pixel size of 90 μm was fabricated using ITZO TFTs with a channel length of 2 μm, and its performance was experimentally evaluated. The ITZO TFTs were found to have good low-frequency noise performance with an extracted Hooge’s parameter (α H) of 3.5 × 10−3, and the APS exhibits a high DC voltage gain of ∼0.81 with satisfactory linearity in a wide output voltage range of ∼6.4 V as well as manageable response times of less than 15 μs. The obtained results show the potential of our APS circuits to be applied to TFT-based image sensors with enhanced image quality.

Stability Analysis and Performance Evaluation of a Multifunction Converter

This paper proposes a converter circuit topology that can perform two functions rather than only one function, normally used in the traditional design of Power electronic converters (PEC). Initially the operation of the proposed circuit in boost DC-DC positive or negative mode and inverting mode are outlined. This is followed by the development of a state-space model and extensive frequency-domain and pole-zero stability analyses for the boost mode that give information about the circuit elements requirements and controller design for it . The proposed converter is simulated using Matlab environment and its performance is evaluated using two control strategies to control the load voltage. The results show the good performance of the converter over a wide range of output voltages and converter capability to reverse the output signal performance and follow the reference values via a logic-based control scheme, which is one of the smart grid and micro grid application requirements.

A non‐isolated DC‐DC converter with low voltage stress and high step‐down voltage conversion ratio

This work focuses on a new non-isolated interleaved DC-DC converter with very high step-down voltage conversion ratio. By employing the switched/series capacitor concept, along with the proper component interconnection, the converter features a high step-down voltage conversion ratio where, in the private case of equal duty ratios, it is six times higher than the conventional buck converter. This high step-down voltage conversion ratio is achieved with the lowest number of components compared to other similar topologies of the same conversion ratio. Also, due to the blocking/series capacitors, the voltage stress on the switches is reduced, improving the converter efficiency. One of the key features of the proposed converter is the inherent automatic current sharing between the interleaved phases, which in the case of equal duty ratios, is uniformly distributed. To add on, due to the use of only two interleaved phases, the converter has a wide output voltage range, since the duty cycle can be extended to 0.5. To validate the proposed converter operation, a 250 W wide-input/wide-output experimental prototype was built, achieving a peak efficiency of 94%.

Design of PV MVDC Converter with Wide Output Voltage Range for Series DC System

This paper presents a topology of PV MVDC converter with wide output voltage range for a series DC system and its control strategy. In the series DC system, the PV MVDC converters are input-independent, and their outputs are series-connected. A high-level system voltage is achieved for power collection and transmission. This series boost system is flexible and very suitable for decentralized renewable energy application. A modular topology is present for the MVDC converter to improve its applicability. A reconfigurable topology and its modulation method are proposed for the module of the converter. By regulating of duty cycle of switches, the module can be reconfigured to step-up or step-down mode. The operating principles and theoretical derivations of the reconfigurable topology are discussed in detail in this paper. Multimode control strategy for the converter is designed to adapt to complex operation conditions in a series DC system. With the proposed topology and control strategy, the series-connected PV MVDC converter achieves wide input and output voltage range to adapt to the operating characteristics of the series DC system; 3 kV/80 kW DC–DC module and 20 kV/500 kW PV MVDC converter are developed and operating stably in practice. The operation results are presented in the paper.

A Self-Protected Single-Stage LLC Resonant Rectifier

This article develops an advanced self-protected single-stage ac-dc LLC resonant converter, in which one diode is introduced to realize overvoltage prevention to achieve self-protection, lower costs, and smaller size. Besides, the proposed converter can also realize power factor correction (PFC), soft switching, and a wide output voltage range, which meets the needs of many applications, such as liquid crystal display (LCD) TV power supply. Detailed analyses are presented to well demonstrate the features of the proposed converter, including the PFC and zero voltage switching turn-on functions. Thereafter, closed-loop control and parameter matching design are conducted in this study. Lastly, prototype experimentation of 220-V ac, 200 W verifies the effectiveness of the proposed converter design.

Concept design of the control method for the NBI acceleration grid power supply-conversion system of CFETR

The China Fusion Engineering Test Reactor (CFETR) uses a negative-ion neutral beam injection (N-NBI) system that requires a powerful acceleration grid power supply (AGPS). The AGPS is rated at -1000 kV/80 A and feeds one injector. AGPS-conversion system, which uses a three-level neutral-point-clamped active front-end rectifier as well as a five-level neutral-point-clamped / cascaded H-bridge inverter, was investigated in the reference design. Because the control problem of the conversion system is crucial for the AGPS, a well-designed control method can improve the steady-state performance during operation substantially. To achieve the full potential of the proposed design and meet the challenging demands of the CFETR N-NBI system, a new control method is proposed and investigated in this paper. Considering the requirement to provide a wide range output voltage, the new control method provides an adjustable DC-link voltage for the rectifier with unity power factor and a suitable modulation factor for the inverter, while maintaining a low ripple voltage of output voltage. The steady performance of the AGPS is successfully improved using phase-shifted carrier-pulse-width modulation. Simulation results are performed that validate the new control method.

Operation and design analysis of an interleaved high step‐up DC–DC converter with improved harnessing of magnetic energy

SummaryIn this paper, a new interleaved DC–DC converter based on a coupled and a single input inductor is proposed. The suggested high step‐up converter utilizes various inductive and capacitive methods to transfer magnetic energy more efficiently. The output voltage is regulated with the switches' duty cycle and the coupled inductor (CI) turns ratio, which provide a wide output voltage range. Interleaving improves the converter reliability, employs both the first and third areas of CI's B‐H plane, cancels DC component of the CI, and reduces the input current ripple of the proposed converter with twice switching frequency. Utilization of two output ports for voltage stress and ripple reduction in each port, recycling the stored energy of inductances in both forward and flyback mechanisms, alleviation of switch voltage spikes, operation without circulating current, high power density, independency of switch voltage stress to the CI turns ratio, and continuous input current can be mentioned as other features. In this paper, continuous and discontinuous conduction modes' steady‐state analytics, power loss calculations, and design procedure of the proposed converter are followed with comprehensive comparisons to evaluate the capabilities. Eventually, experimental results are presented to validate theoretical calculations.

A 2×3 Reconfigurable Modes Wide Input Wide Output Range DC-DC Power Converter

There is an increasing demand for efficient and low-profile power converters in almost all industrial applications. Some require stable performance over a wide range of input voltages, whereas others require converters with a stable performance over a wide range of output voltages. In this regard, little work has been done to combine both requirements into one solution. This work suggests a unique solution that addresses both requirements at once. A power converter with 2×3 reconfigurable modes has been presented, able to operate with DC gains of 1, 2 and 4, which can be further extended to 8. The converter shows stable performance for the extended range of both input and output voltage. The flexible reconfigurable feature of the proposal can be applied in a variety of applications. Two reconfigurable modes on the input side can be configured following the variation in the line voltage to maintain a stable performance, and three reconfigurable modes for the output voltage, which raises the output voltage from 24V to 48V and 96V. The proposal is applied in an example application of a phase shifted full bridge converter. The converter is characterized for \textV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in</sub> =100-400V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> , \textP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> = 1kW.

Voltage Oriented Controller Based Vienna Rectifier for Electric Vehicle Charging Stations

Vienna rectifiers have gained popularity in recent years for AC to DC power conversion for many industrial applications such as welding power supplies, data centers, telecommunication power sources, aircraft systems, and electric vehicle charging stations. The advantages of this converter are low total harmonic distortion (THD), high power density, and high efficiency. Due to the inherent current control loop in the voltage-oriented control strategy proposed in this paper, good steady-state performance and fast transient response can be ensured. The proposed voltage-oriented control of the Vienna rectifier with a PI controller (VOC-VR) has been simulated using MATLAB/Simulink. The simulations indicate that the input current THD of the proposed VOC-VR system was below 3.27% for 650V and 90A output, which is less than 5% to satisfy the IEEE-519 standard. Experimental results from a scaled-down prototype showed that the THD remains below 5% for a wide range of input voltage, output voltage, and loading conditions (up to 2 kW). The results prove that the proposed rectifier system can be applied for high power applications such as DC fast-charging stations and welding power sources.

A Method of Reconfiguring Flying Capacitor Multilevel Input Stage for Wide Input Voltage Range Converter Design

Wide input or output voltage range converters are required in various applications, including railway, industrial, military, aerospace, and many more. However, it has been challenging to achieve and maintain high efficiency under a wide range of input or output voltages of operation because of shifting operating conditions and compromised component selections required to cover a wide voltage range of operation. In this article, a method of reconfiguring the flying capacitor multilevel power conversion input stage is revealed for a wide voltage range of operation. A pulse voltage is produced by the input stage. With proper configuration under different input voltage levels, the voltage across key components, namely power switches, inductors, and capacitors, can be maintained relatively constant. In this way, components can be selected and optimized for very confined operating conditions. Also, the amplitude and frequency of the pulse voltage produced by the input stage are also maintained relatively constant. Therefore, a followed filter stage, a resonant tank, or an isolation + rectifier stage can be designed and operated with optimization. High and maintained overall efficiency are achieved over a wide change of the input voltage.

Small signal modelling and stability analysis of internal ramp compensated constant on‐time controller with improved output voltage accuracy for point of load application

This paper investigates a constant on-time controller (COT) with internal ramp compensation and improved output voltage accuracy for point of load applications. The pulse width modulation (PWM) output is generated based on internal ramp: by sensing the regulated output voltage and comparing it to an internal reference target, an error signal is generated. This error signal is used to generate a reference for an added ramp signal, which is compared against an error voltage to generate a PWM trigger signal. An adaptive constant on-time scheme ensures a fairly constant switching frequency over a wide range of input and output voltages. This COT control algorithm is able to achieve high accuracy regulation (±0.5% of target) and fast transient response during load step change. A frequency domain small signal model is proposed, and an open loop gain transfer function is developed for this COT control system. The proposed small signal model and design analyses are verified with SIMPLIS simulations and experimental results.

High-Efficiency LLC Resonant Converter With Reconfigurable Voltage Multiplying Rectifier for Wide Output Voltage Applications

This article presents a reconfigurable voltage multiplying rectifier (RVMR) to improve the performance of an LLC resonant converter for wide output voltage applications. The RVMR can operate as voltage-doubler mode or voltage-quadrupler mode according to the primary switching strategy. Two operation modes split a wide output voltage range into two narrow ranges. Therefore, the RVMR enables the LLC resonant tank to be designed in a narrow output voltage range, which results in a narrow switching frequency range, high efficiency, and high power density. A smooth mode transition can be achieved by adopting a phase-shift control to general pulse frequency modulation control without any additional switch. The proposed RVMR LLC converter can improve its efficiency by 2.9% and reduce component volume by 26% compared to the conventional full-bridge LLC resonant converter. A 750-W prototype with 400 V input, 100-300 V output voltage, and 2.5 A max output current has been built and tested to verify the effectiveness of the proposed converter.

Dynamic Improvement with a Feedforward Control Strategy of Bidirectional DC-DC Converter for Battery Charging and Discharging

With the increasing importance of power accumulator batteries in electric vehicles, the accurate characteristics of power accumulator batteries have an important role. In order to evaluate the power accumulator battery, battery charging and discharging is indispensable. In this article, a H-bridge bidirectional DC-DC converter is presented which can charge and discharge the battery with different voltage levels and one of the merits of this topology is that a wide output voltage range can be easily achieved. In the control part, a proportional-integral (PI) control strategy is adopted to ensure a stable and reliable operation of the converter. Furthermore, compared with the PI control strategy, a duty ratio feedforward control is utilized to obtain the rapid current dynamic response. In this article, firstly, the system configuration for battery charging and discharging is introduced, then the operating principles and mathematical model of the DC-DC converter are analyzed and derived. Secondly, for bidirectional DC-DC converters, the PI control method and duty ratio feedforward control method are put forward and designed. Finally, the simulation model is established based on PSIM software and the experiment platform is also built in lab. The results of the simulation and experiment research show that the H-bridge bidirectional DC-DC converter can operate reliably and stably during the charging, discharging and power flow reverse modes. In addition, the dynamic response of the charging and discharging current can also be further improved by introducing the duty ratio feedforward control method.

A Soft-Charging-Based SC DC–DC Boost Converter With Conversion-Ratio-Insensitive High Efficiency for Energy Harvesting in Miniature Sensor Systems

This paper introduces a fully integrated switched-capacitor (SC) DC-DC boost converter suitable for energy harvesting in miniature sensor systems with varying harvesting source and battery voltages. Unlike the conventional SC DC-DC boost converters, where efficiency is optimized only for a few topology-dependent voltage conversion ratios (VCRs), the proposed soft-charging-based SC converter achieved VCR-insensitive evenly high efficiency for a wide range of input and output voltages. A test chip was fabricated in 180nm process, and the measured peak efficiency and average efficiency are 85.3% and 83.6%, respectively, for 1.8V regulated output voltage and a wide range of input voltages (0.95–1.8 V). Also, a peak efficiency of 88.9% and average efficiency of 87.6% are achieved for a wide range of battery output voltages (3.0–4.2 V) and a 1.2V harvesting source input voltage.

High-Performance Megahertz-Frequency Resonant DC–DC Converter for Automotive LED Driver Applications

This paper introduces a megahertz-frequency resonant dc–dc converter that inherently achieves a load-independent output current while maintaining high efficiency across a wide output voltage range. These properties make the proposed converter well-suited for automotive light-emitting diode (LED) driver applications, where a varying number of LEDs need to be driven with a constant current. The proposed converter achieves load-independent output current by utilizing an LCL -T resonant network, and achieves high efficiency using a comprehensive design optimization methodology. This LCL -T resonant converter is also capable of regulating its output current at any desired value by utilizing phase-shift control. The performance of the LCL -T resonant converter is theoretically and experimentally compared with an LC 3 L and an LCLC resonant converter. For the experimental comparison, prototypes LCL -T, LC 3 L , and LCLC resonant converters are designed to operate at 2 MHz and across an output voltage range of 3.3–49.5 V while supplying a constant 0.5 A output current to the LEDs. The LCL -T resonant converter prototype achieves a peak efficiency of 91.1%, which is 0.6% and 1.8% higher than the peak efficiency of the LC 3 L and the LCLC converter prototypes, respectively. Furthermore, the LCL -T converter prototype maintains 0.8% and 1.6% higher average efficiency over its 15:1 output voltage range relative to the LC 3 L and the LCLC converter prototypes, respectively.

High-Efficiency SiC-Based Isolated Three-Port DC/DC Converters for Hybrid Charging Stations

This article proposes a novel isolated three-port dc/dc converter based on a series resonant converter and a dual active bridge (DAB) converter for electric-vehicle charging stations with fast and slow charging functions. With this three-port structure, the proposed converter has fewer components, which results in lower system cost and volume compared with separate charger systems. A simple control method using phase-shift and frequency modulations was developed to control the output power of the fast and slow charging ports simultaneously. An optimal phase-shift angle was also derived to minimize the transformer current for when only the DAB converter is operated for slow charging. To verify the converter operation, a 5-kW SiC-based prototype with a power density of 2.74 kW/dm3 was built and tested with an input voltage of 600 V. A high-efficiency performance over a wide output voltage range has been achieved, and the peak efficiency is 98.2% at the rated conditions.