Soft-switching DC-DC Converter Research Articles

Inverter optimization of soft-switching DC-DC converter*

The paper describes the influence of the magnetizing inductance of the transformer on zero-voltage switching of the primary transistors in a soft-switching full-bridge dc-dc converter with a controlled rectifier and turn-off snubber. The optimized version of the transformer allows for achieving a full zero-voltage and zero-current turn-on of the primary transistors in a full-bridge soft-switching DC-DC converter. The analysis is verified by measurements on a laboratory model of the converter. The influence of undischarged output capacitances on the efficiency is measured as well. Also, the impact of the GaN transistors on the zero-voltage switching is discussed.

Modular high conversion ratio soft-switching DC-DC converters with extended multi-ports structure for multi-energy storage systems interconnection

This paper focus on the advanced multi-energy storage systems interconnection by DC smart grids with high efficiency and high compactness. A non-isolated modular high conversion ratio bidirectional soft switching DC-DC converter and its extended multi-ports structure are proposed in this paper. In each power module of the converter, an auxiliary zero-current transition (ZCT) cell is integrated to achieve the zero-current turn-on and turn-off for all semiconductor devices. Therefore, the switching losses are reduced greatly and the efficiency is improved considerably. The presented converter is suitable for the small and medium power scale interconnection in smart DC grids, and can realize the flexible multi-energy storage system interaction owing to its extended multi-ports structure. Besides, various control schemes are adopted to optimize the control system of this converter, which can improve the performance on energy interaction. The operation principles and design considerations are discussed in details and a 5 kW experimental prototype is constructed to justify the validity of the theoretical analysis.

Soft-Switching Full-Bridge DC-DC Converter with Energy Recovery Capacitor Snubber

This paper describes a high-frequency soft-switching dc-dc converter with a simple energy recovery capacitor snubber on the secondary side. The presented dc-dc full-bridge converter with the energy recovery snubber removes the main drawbacks of the classic Phase Shifted PWM (PS-PWM) dc-dc converter, e.g., the circulating current flowing during the free-wheeling interval and dependency of the soft switching on the load current. The converter utilizes a full-bridge topology with pulse-width modulation and a centre-tapped full-wave controlled rectifier with one active switch. The zero-voltage switching on the primary side is ensured by utilising only the magnetizing current of the high-frequency transformer, and thus is load-independent. The proposed energy recovery snubber is described in detailed time waveforms of the converter and verified by simulation. The control algorithm also removes the circulating current, which is typical for PS-PWM converters. The soft-switching of the secondary side transistor is achieved by a simple capacitor snubber with an energy-recovery circuit connected to the output of the dc-dc converter. The principle of operation is verified by measurements on a 2 kW, 50 kHz laboratory model of the proposed dc-dc converter.

Soft-Switched DC-DC Converter With T-Type Auxiliary Circuit for Vehicular Applications

This article proposed an isolated full-bridge dc&#x2013;dc converter (IFBDC) with T-type auxiliary circuit for vehicular applications. The proposed IFBDC operated with modified pulse width modulation (MPWM) ensured the zero voltage switching turn-<small>on</small> for the active switches of the converter during full-battery charging range. By using MPWM the value of the auxiliary and series inductance of the IFBDC is reduced as compared to phase-shift modulation operated converter. The proposed configuration also pursue the low-temperature rise during the battery charging process. The analysis of the converter is presented in ideal and nonideal parameters. Later, the analysis is verified on MATLAB/ Simulation and PSIM. To validate the results of simulation a 500-W, 80-kHz experimental prototype is developed and gating signals are given by using TMS320F28379D DSP controller.

Soft switched DC-DC converter for hybrid power generation photo voltaic panels using fuzzy logic controller

Maximum Power Point Tracking (MPPT) with a Z source cascaded inverter based on Fuzzy Logic Control (FLC) is proposed in this research for a hybrid photo-voltaic (PV) and wind turbine (WT) system. In the absence of PV or WT power generation, the suggested system offers an uninterrupted power supply to the grid. PV functions as a current source and creates maximum power at maximum power point (MPP), supplying just the deficiency power. This FLC-integrated technique minimises the complexity of typical PID controllers while also improving overall performance. To reduce switching losses, current, and voltage switching stress, a traditional dc/dc boost converter with soft switching has been introduced. To reduce switching stress, a boost converter with zero voltage switching is used. This research focuses on a Zero Voltage Switching (ZVS) technique that uses fuzzy logic control to meet the PV system's MPPT and output voltage regulation requirements. All these PV and wind hybrid systems, a Z-Source network, and a five-level cascaded inverter are part of the proposed topology. The advantages of a Z-source inverter outweigh the disadvantages of a traditional voltage-source inverter. The required stepped output voltage is achieved by boosting the DC link voltage from the PV system using a shoot through state. The suggested system has been simulated with MATLAB/SIMULINK, and the closed loop control technique has been investigated and verified.

Non‐resonant soft‐switching technique with linear current on switching cycle time‐scale for switched‐capacitor DC‐DC converters

The switched-capacitor DC-DC converters have been widely applied to convert energy from low voltage to DC bus for the power generation systems with fuel cells, photovoltaic array, and so on. However, the large capacitance is generally selected to eliminate the high current spike of switched-capacitors in the hard-switching switched-capacitor (SC) DC-DC converters, which will lead to the large volume and weight of capacitors and of converters. To solve this problem, a non-resonant soft-switching (NRSS) technique with linear current on switching cycle time-scale for switched-capacitor DC-DC converters is first proposed in this paper, which achieves zero-current-switching (ZCS) turn-on of switches and ZCS turn-off of diodes with linear current on switching cycle time-scale. In detail, the NRSS technique is proposed based on the idea that the current of an auxiliary inductor on switching cycle time-scale is considered as the linear parts for the resonant current of the auxiliary inductor on resonant cycle time-scale. The proposed NRSS technique is utilized into SC DC-DC converter and the current spikes of switches can be reduced to two third by using the same capacitance compared with the hard-switching SC DC-DC converters and be reduced to a third compared with the resonant soft-switching SC DC-DC converters. Further, nine new soft-switching SC DC-DC converters, with single switch and double switches, are built based on the proposed non-resonant soft-switching technique. Finally, the non-resonant soft-switching technique is verified theoretically and experimentally by three of the nine proposed SC DC-DC converters. This paper provides a new way to realize soft-switching during the non-resonant interval on switching cycle time-scale and a new method to significantly reduce the required capacitance in SC DC-DC converters.

A soft-switching high gain DC–DC converter for renewable energy systems

ABSTRACT In order to improve the efficiency of high gain DC-DC converter using MOSFET as switching device, a novel zero-voltage soft-switching high gain DC-DC converter is presented. A main switch tube is used to replace the output diode in the conventional boost converter, and an auxiliary network is added to make the two switches realise true ZVS soft turn-on and all diodes realise true ZCS soft turn-off, which improves the efficiency and effectively suppresses the negative effect of diode reverse recovery. Furthermore, the output end of the converter is composed of three output capacitors in series, which avoids the converter working at the limit duty cycle, increases the voltage gain and reduces the switch voltage stress. Therefore, MOSFET with low voltage level and low on resistance can be selected as switching devices. The resonant capacitor and leakage inductance are used to reduce the current at the turn-off time of the switch. The operating principle and steady-state characteristics of the converter are analysed in detail. The design idea of the main parameters is given, and the efficiency and loss of the converter are evaluated. Finally, the experimental results on a 100 W prototype show that the efficiency reaches 95.79% at rated power.

Soft Switching Interleaved High Step-Up Converter With Multifunction Coupled Inductors

This article presents an efficient interleaved soft switching dc-dc converter for high step-up applications. In the proposed converter, two multifunction coupled inductors are employed to increase the voltage gain, accomplish soft switching operation for all semiconductors in a wide range of load variations, and smooth the input current. Besides, the leakage inductance energy is recovered to enhance the voltage gain and efficiency while assisting soft switching condition for the switches and diodes. In addition, no auxiliary switch or extra magnetic element is employed in the proposed converter while the voltage stress of switches and diodes is rather low. These have led to simple structure, high density, low cost, and improved efficiency. Theoretical analysis and design considerations for the proposed converter are presented. Moreover, the experimental results of a 48 to 500 V laboratory prototype approve the effectiveness of the proposed topology.

A Review of High Efficiency Non-Isolated DC-DC Power Converters for Electric Vehicle Charging Application

The electric vehicle (EV) charging systems employ dc-dc power converters as EV chargers. Currently, the expected high penetration of electric vehicle (EV) demands for the integration of the renewable energy sources (RES) into the electric vehicle charging system as a promising solution to cut down the load on the electrical grid. These systems interface with RES by implementing dc-dc power converters. Moreover, with the advent of high-power dc charging, the charging efficiency is largely dependent on the performance of the power converters. Hence, to improve the charging, the soft switching dc-dc converters are implemented to maintain low switching losses and to achieve high-efficiency operation. This paper reviews the non-isolated, soft switching dc-dc power converters for EV charging application. For this purpose, different types of soft switching topologies, namely the snubber, the series resonant, the shunt resonant and the pulse frequency modulated converters are investigated. The advantages and the disadvantages associated with these converters are highlighted. Furthermore, to perform a comparative evaluation, the topologies are simulated in a standard simulation platform. Consequently, the relative standing of the converters depending on several parameters, i.e. the component count, the output voltage and current ripple, the soft switching range, and the power losses are established. Finally, based on these results, the optimum applicability of the converters in the EV charging application is determined.&#x0D; GUB JOURNAL OF SCIENCE AND ENGINEERING, Vol 6(1), Dec 2019 P 60-74

A Soft-Switched Bi-directional DC-DC Converter for a BLDC motor based Electric Vehicle

A Soft-Switched Bi-directional DC-DC Converter for a BLDC motor based Electric Vehicle

Single-switch boost DC-DC converter with zero-current-switching, high power density and low electromagnetic interference

Soft switching DC-DC converters with high power density are highly demanded for compact and high-reliability applications. It is beneficial to provide soft switching conditions without an extra switch and a large number of passive components. In this paper, a zero current switching resonant boost converter is introduced which has only one switch and a simple auxiliary circuit including an inductor and a capacitor. The size of the boost inductor is considerably reduced because it acts as a resonant inductor. Due to the simple structure and small inductors, the power density is increased and measured about 106.4 W/in3. There is no extra voltage stress on the switch and the diode. Theoretical analysis of the proposed converter in DCM and CCM operations are presented and verified by the experimental results. Also, conducted EMI of the proposed converter is measured and compared to the regular boost converter, which shows the compliance with CISPR 11 standard.

Nonisolated High Step-Up Soft-Switching DC–DC Converter With Interleaving and Dickson Switched-Capacitor Techniques

In this article, a nonisolated high step-up soft-switching dc-dc converter is proposed, which is based on a hybrid structure comprising an interleaved boost converter and Dickson switched-capacitor (SC) networks. The high voltage gain can be achieved by the SC networks without an extremely large duty cycle, and the voltage stresses of all the active switches and diodes are kept at levels much lower than the output voltage. Compared with the traditional SC converters, the proposed converter can achieve continuous voltage regulation by the pulsewidth modulation (PWM) technique. The interleaving operation can reduce the input current ripple and improve the power capacity. Resonant inductors with small inductances are inserted into the SC networks to avoid the high current spikes that occur in the traditional SC converters. All the active switches can achieve zero-voltage switching (ZVS) turn-on. Some of the diodes can achieve zero-current switching (ZCS) turn-off, and the other diodes achieve reduced turn-off ${di/dt}$ rates. The operating principle and essential steady-state characteristics of the converter are analyzed in detail. Finally, a prototype converter with an input voltage of 25–40 V, an output voltage of 400 V, and a rated power of 1 kW is designed and implemented to verify the theoretical analysis.

Design of Soft-Switching Hybrid DC-DC Converter with 2-Phase Switched Capacitor and 0.8nH Inductor for Standard CMOS Process

A soft-switching hybrid DC-DC converter with a 2-phase switched capacitor is proposed for the implementation of a fully-integrated voltage regulator in a 65 nm standard CMOS process. The soft-switching operation is implemented to minimize power loss due to the parasitic capacitance of the flying capacitor. The 2-phase switched capacitor topology keeps the same resonance value for every soft-switching operation, resulting in minimizing the voltage imbalance of the flying capacitor. The proposed adaptive timing generator digitally calibrates the turn-on delay of switches to achieve a complete soft-switching operation. The simulation results show that the proposed soft-switching hybrid DC-DC converter with a 2-phase 2:1 switched capacitor improves the efficiency by 5.1% and achieves 79.5% peak efficiency at a maximum load current of 250 mA.

Bidirectional Resonant DC-DC Converter for Microgrid applications

This paper presents a non-isolated bidirectional soft-switching dc-dc converter for DC microgrid energy storage synchronization. To assist the soft switching of switches and diodes, the LCL resonant circuit is applied and an input end half-bridge boost converter is enforced. Using the voltage doubler circuit introduced on the output side, a voltage gain of 2X is achieved. Through the non-isolated circuit, the total voltage gain is obtained. The capacitive divider halves the voltage on the greater hand. The circuit performs a high frequency ripple of low output voltage. Diodes guarantee zero voltage Turn ON for switches and zero current turn ON and turn OFF during buck / boost operation Although no internal snubber circuits are available, the circuit ensures low voltage stress across semiconductor systems.

Multi‐input high step‐up inverter with soft‐switching capability, applicable in photovoltaic systems

In this study, a new multi-input high step-up inverter, based on isolated soft-switching DC-DC converter blocks is proposed. Each of these blocks can provide zero-voltage and zero-current switching for its semiconductors, which improve power efficiency. The interesting feature of this DC-DC converter is using bidirectional switches to generate both positive and negative output voltage levels in each DC-DC block with an appropriate control scheme. Each DC-DC converter operates by simple pulse width modulation control through fixed frequency and has two degrees of freedom, which provide the capability of output voltage regulation or maximum power point tracking. The proposed inverter consists of the cascaded connection of these DC-DC converters at their output terminal. This inverter can operate with high voltage gain, where the output voltage of each DC-DC converter is regulated. Furthermore, it can generate more output voltage levels with less number of DC-DC blocks. All these advantages make the proposed inverter suitable for photovoltaic power conditioning systems. In this study, the theoretical analysis with steady-state waveforms, design constraints, resonant tank analysis and comparison study are given. Then, experimental results of both the proposed inverter and its DC-DC blocks are presented.

DC-DC converter with a wide range of providing a natural switching mode at ZVS mode

This paper introduced an isolated soft switching DC-DC converter with an active rectifier. The converter has two bidirectional and two reverse conducting devices at the inverter side and utilizes phase-shift control with one variable and constant switching frequency. Instead of relying on the magnetizing or circulating current, the soft-switching operation of the proposed converter using novel modulation method is provided by relatively short additional switching state, which minimizes the energy circulation. This interval is introduced by taking advantage of the reverse blocking capability of the devices in the rectifier side and ensures the recharge of snubber capacitance at the inverter side. The soft switching operation of the converter is load-independent and does not require introduction of multi-mode control strategies. Thanks to the novel modulation algorithm, the converter features ZVS and ZCS over a wide operating range, even at no-load condition. The solution is aimed to reduce the problem of high circulating energy in the existing PWM topologies at light load. For the proposed solution, the amount of circulating energy is load adaptive, which results in good weighted performance over a range of possible operating points. Operation and design aspects of the converter were presented and verified experimentally.

High‐efficiency soft‐switching step‐up DC–DC converter derived from a synchronous boost converter

This study presents a high-efficiency soft-switching step-up DC-DC converter. The proposed converter achieves zero-voltage switching of power switches and zero-current switching of the output diode. Also, it has improved the voltage conversion ratio. Moreover, the switch voltage stress can be lowered than the output voltage. Hence, improved efficiency, especially at full load, is achieved. The operational principle and detailed analysis of the proposed converter are given. The performance of the proposed converter is verified by testing a prototype converter implemented in the laboratory on an output 200 V-200 W.

Design and Evaluation of a Reconfigurable Stacked Active Bridge DC–DC Converter for Efficient Wide Load Range Operation

This paper presents the design and implementation of a large-step-down soft-switched dc-dc converter based on the active bridge technique which overcomes some of the limitations of the conventional Dual Active Bridge (DAB) converter. The topology comprises a double stacked-bridge inverter coupled to a reconfigurable rectifier through a special three-winding leakage transformer. This particular combination of stages enable the converter to run in an additional low-power mode that greatly increases light-load efficiency by reducing core loss and extending the zero-voltage switching (ZVS) range. The converter is implemented with a single compact magnetic component, providing power combining, voltage transformation, isolation, and energy transfer inductance. A 175 kHz, 300 W, 380 V to 12 V GaN-based prototype converter achieves 95.9% efficiency at full load, a peak efficiency of 97.0%, an efficiency above 92.7% down to 10% load and an efficiency above 79.8% down to 3.3% load.

Soft-switched non-isolated high step-up multi-port DC-DC converter for hybrid energy system with minimum number of switches

This paper proposes a non-isolated high step-up multi-input DC-DC converter for utilizing in hybrid applications. This converter provides the interfaces between input power sources, energy storage devices and load. The resonant auxiliary circuit used in the proposed converter provides soft switching condition for the main switches as well as charging the storage device which has caused considerable improvement in the converter efficiency. This converter uses only three switches to control the power absorbed from a unidirectional input, the power absorbed or stored in the bidirectional port and also the power transmitted to load while provides soft switching condition of all semiconductor devices. Thus, the number of switches applied is same as conventional hard switched converters for this purpose. This converter shares only one inductor between all inputs, so the volume is reduced. Various converter operating modes are discussed and design considerations are presented. Finally, to validate the theoretical analysis, a prototype of the proposed converter is implemented for a 400 V output voltage at 200 W.

Modeling, control, and implementation of the soft switching dc-dc converter for battery charging/discharging applications

This paper presents a soft switching bidirectional buck-boost converter for battery charging and discharging systems. The proposed method comprises of Inductance Capacitance Diode combination of the bidirectional dc-dc converter with one more electric switch is presented to accomplish high efficiency, high conversion ratio and maximum output power compared to the other bidirectional converters. It works in both steps up and steps down conversions. The proposed converter has alleviated the switching stress problems in the conventional bidirectional dc-dc converter. It suppresses the switching losses by zero voltage and zeroes current turn ON and OFF all switches. The complete steady-state analysis of the proposed bi-directional converter has described with its operating modes. Design consideration of parameters also presented to realize the converter characteristics. The switching stress on the power semiconductor devices is given, and the comparisons between the proposed technique and other bidirectional converters are illustrated with some results. Finally, the experimental prototype of 20 kHz, 315 W output power converter developed, and its feasibility verified through computer simulation results.