Zero-current Switching Turn-off Research Articles

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.

Split Parallel Semibridge Switching Cells for Full-Power-Range Efficiency Improvement

This article proposes a positively coupled inductor (PCI) based paralleling scheme for basic semibridge switching cells, which are formed by power MOSFETs and diodes. Both the semibridge switching cells and the inductors are split into two parallel parts, and thus, a small differential mode (DM) inductance is formed between the midpoints of the parallel semibridge switching cells. A time-delay-based modulation strategy is applied to generate a controllable circulating current, which enables all active switches to achieve the zero-current switching (ZCS) or zero-voltage switching, and all diodes to achieve ZCS turn-off. Accordingly, the switching loss and the reverse-recovery loss can be significantly reduced. The operating principle of the proposed paralleling scheme is characterized by two complementary operation modes: desynchronized mode with soft-switching (lower switching loss) and synchronized mode with lower conduction loss. Compared with conventional soft-switching schemes, this solution features zero auxiliary switches, constant switching frequency, and improved full-power-range efficiency enabled by the dual operation modes. Furthermore, design guidelines of the PCI are presented where a novel winding arrangement is proposed and verified to obtain a controllable DM inductance. The operation principles and advantages of the proposed paralleling structure are comprehensively validated on both buck and boost dc-dc converters with Si/SiC power MOSFETs and diodes.

Efficient Hybrid-Modulated Single-Stage Wireless Power Receiver With Continuous DC Current

In this article, a single-stage wireless power receiver featuring continuous dc output current, good output regulation, and high conversion efficiency is presented. The topology is achieved via the integration of a diode rectifier circuit into a pair of interleaved buck converters, of which overlapped components are removed. With this, component count (diode's number) reduction is achieved without affecting the combined operation of rectification and voltage regulation. Moreover, its output inductor pair can be conveniently incorporated in integrated-magnetics form to reduce magnetic size. For control, it adopts an ac-input-current-synchronized modulation scheme, which hybridizes phase-shift modulation (PSM) and pulse-width modulation (PWM) control. The PSM enables consistently zero-voltage-switching turn-on of switches and zero-current switching turn-off of diodes for mitigating switching loss, while the PWM modulation performs good regulation of the output voltage of the rectifier. Experimental results of our constructed 100-kHz, 12-V output voltage, 35-W output power prototype show a fairly constant dc output current with 71% current ripple reduction as compared with that of a regular single-phase buck converter, good output regulation with less than 1% regulation error, and efficient ac-dc conversion with a peak efficiency of 96%.

Active Clamp Boost Converter with Blanking Time Tuning Considered

An active clamp boost converter with blanking time auto-tuned is presented herein, and this is implemented by an additional auxiliary switch, an additional resonant inductor, and an additional active clamp capacitor as compared with the conventional boost converter. In this structure, both the main and auxiliary switches have zero voltage switching (ZVS) turn-on as well as the output diode has zero current switching (ZCS) turn-off, causing the overall efficiency of the converter to be upgraded. Moreover, as the active clamp circuit is adopted, the voltage spike on the main switch can be suppressed to some extent whereas, because of this structure, although the input inductor is designed in the continuous conduction mode (CCM), the output diode can operate with ZCS turn-off, leading to the resonant inductor operating in the discontinuous conduction mode (DCM), hence there is no reverse recovery current during the turn-off period of the output diode. Furthermore, unlike the existing soft switching circuits, the auto-tuning technique based on a given look-up table is added to adjust the cut-off time point of the auxiliary switch to reduce the current flowing through the output diode, so that the overall efficiency is upgraded further. In this paper, basic operating principles, mathematic deductions, potential designs, and some experimental results are given. To sum up, the novelty of this paper is ZCS turn-off of the output diode, DCM operation of the resonant inductor, and auto-tuning of cut-off time point of the auxiliary switch. In addition, the efficiency of the proposed converter can be up to 96.9%.

Two-Phase Interleaved Boost Converter with ZVT Turn-On for Main Switches and ZCS Turn-Off for Auxiliary Switches Based on One Resonant Loop

A two-phase interleaved boost converter with soft switching is proposed herein. By means of only one auxiliary circuit with two auxiliary switches having zero-current switching (ZCS) turn-on, two main switches are switched on with zero-voltage transition (ZVT) to enhance the overall efficiency. Moreover, a current-balancing circuit with a no current-balancing bus is utilized to render the load current extracted from the two phases as even as possible, so that the system stability is upgraded. In such a study, this converter, having the input of 24 V ± 10 % and the rated output of 36V/6A, was employed to demonstrate the effectiveness of such a converter by experiment.

A Family of Dual Resonant Switched-Capacitor Converter With Passive Regenerative Snubber

In this article, a step-down switched-capacitor converter (SCC) and a step-up SCC with an integrated passive regenerative snubber (PRS) are proposed based on the Cuk dual resonance core (DRC). The members of the DRC converter family overcome the barrier for SCCs to achieve continuous output voltage regulation. One remaining challenge is the turn-off spikes and oscillations during the switch turn-off transient that cause voltage stress and power loss to the transistor and diode. The proposed integrated PRS eliminates voltage spikes and oscillations across the transistor and diode during the turn-off process. Moreover, zero voltage switching (ZVS) turn-on for the clamped mosfet, zero current switching (ZCS) turn-on for the other mosfet and ZCS turn-off for all diodes are achieved. A comprehensive analysis of the operation principle, conversion ratio curves, component stress, and regenerative power of the proposed converters with regenerative snubbers is given. Furthermore, a performance comparison between the proposed snubber configuration and two conventional methods is given. A 50 V/99.25 V step-up converter prototype of 125 W has demonstrated a peak efficiency of 98.4%. The analysis is verified by both simulation and experiments.

High Step-Up Interleaved dc–dc Converter With Asymmetric Voltage Multiplier Cell and Coupled Inductor

In this article, a novel high step-up interleaved dc-dc converter is presented, which is composed of an interleaved structure, an asymmetric voltage multiplier cell (AVMC), and a passive lossless clamped circuit. Compared to the classical interleaved boost converter, the proposed converter has a higher voltage gain owing to the employment of the AVMC and the coupled inductor. In addition, the input current ripple is limited to low values with the help of the interleaved structure, which gives more lifetime to the input power source. The voltage stresses of main switches are substantially low so that the MOSFETs with low voltage rate and ON-resistance (RDS(ON)) can be used. In addition, the voltage stresses and the reverse recovery problems of diodes are improved dramatically. Moreover, the zero current switching (ZCS) turn-on of switches and the ZCS turn-off of the clamp diodes are realized to reduce the switching losses. The leakage inductor energy is recycled and the voltage spikes are improved greatly by the passive lossless clamped circuit so that the efficiency can be upgraded further. Finally, a 400-W, 40-V-input, 400-V-output prototype is established to demonstrate the performance of this converter. The highest efficiency is about 97.3% and the full-load efficiency is approximately 97%.

Single-Switch Single Power-Conversion PFC Converter Using Regenerative Snubber

This paper presents a single-switch single power-conversion (S $^\text{3}$ PC) power factor correction (PFC) converter. Using the series-resonant circuit, the S $^\text{3}$ PC converter provides bidirectional core excitation for the transformer and obtains higher power capability compared with the conventional single-switch PFC converters. Also, the series-resonant circuit provides zero-current switching turn-off for the output diodes, so that the reverse-recovery loss is alleviated. The regenerative snubber not only avoids the voltage spike of the switch but also recycles the absorbed energy. Because these features are obtained with only a single switch and through single power-conversion, the S $^\text{3}$ PC converter has high efficiency and simple structure. The control algorithm derived from feedback linearization enables the S $^\text{3}$ PC converter to obtain good controllability. Also, by using this control algorithm, the proposed converter performs both PFC control and output power control through single power-conversion. With these advantages, the S $^\text{3}$ PC converter provides maximum efficiency of 96.4% and high power factor in excess of 0.994. The proposed converter is theoretically analyzed in detail, and experimental results are applied to a 1-kW prototype to show its validity.

Naturally Adaptive, Low-Loss Zero-Voltage-Transition Circuit for High-Frequency Full-Bridge Inverters With Hybrid PWM

This paper proposes a low-loss, auxiliary zero-voltage-transition (ZVT) circuit to realize zero-voltage-switching (ZVS) for all the main switches of a full-bridge inverter, and inherent zero-current-switching (ZCS) turn-on and ZCS turn-off for the auxiliary switches. Two configurations consisting of discrete inductor and coupled inductor structures are proposed. The advantages of the proposed strategy include the provision to implement zero-state modulation schemes such as unipolar and hybrid pulse width modulation schemes in the full-bridge inverter to achieve low THD, naturally adaptive auxiliary inductor current and the elimination of capacitor voltage balancing issues seen in other similar ZVT approaches. The modulation scheme and the commutation stages are analyzed in detail. The complete inverter including the auxiliary ZVT branch is modeled in detail. Finally, a 1 kW, 400 kHz switching frequency inverter of the proposed topology using SiC MOSFETs has been built to validate the theoretical analysis. The ZVT with hybrid modulation technique is implemented in DSP TMS320F28335 resulting in full ZVS for the main switches in the full-bridge inverter. Compared to conventional hard switching full-bridge inverter, the proposed scheme improves the California Energy Commission efficiency from 95.58% to 97.63% and the peak efficiency from 96.29% to 97.91%.

Isolated soft‐switched boost DC–DC converter with low‐voltage stress and high step‐up ratio

This study presents a novel soft-switched isolated boost converter which can provide a high-step-up ratio and high efficiency with low-voltage stress for portable application as well as a photovoltaic-assisted converter system. A lossless active clamp snubber circuit helps in achieving zero-voltage-switching turn-off and zero-current-switching (ZCS) turn-on of the main switch and ZCS turn-off of diodes that reduce switching losses. An auxiliary switch with an energy recovery circuit helps to increase power conversion efficiency and reduces switching stress across the main switch. The proposed idea is simulation through computer-assisted software PSIM 9.1.1 and validated experimentally through a designed prototype 250 W direct current (DC)–DC converter.

New Parallel Loaded Resonant Converter With Wide Output Voltage Range

This paper proposes a new parallel loaded resonant converter operating in a narrow switching frequency under wide output voltage range. The proposed converter is capable of operating under zero-voltage switching turn-on of switches and zero-current switching turn-off of diodes. Also, the resonant capacitor with feasible capacitance and current rating can be selected by adjusting the turn ratio of the transformer, making the proposed converter more realizable in high power application. Further, the proposed converter has zero voltage gain at notch resonant frequency, and therefore there are no current and voltage stress in the resonant tank during start-up. Experimental results from a 3-kW prototype are provided to validate the proposed concept.

Soft-Switched High Voltage Gain Boost-Integrated Flyback Converter Interfaced Single-Phase Grid-Tied Inverter for SPV Integration

A two-stage grid-tied efficient solar photovoltaic (SPV) system with zero voltage switching (ZVS) and zero current switching (ZCS) at the dc–dc converter stage and adaptive synchronization at the inverter stage is proposed. In the first stage, an improved high step-up boost-integrated flyback converter with quasi resonant voltage multiplier cell is proposed. ZVS turn-on of all mosfet s and ZCS turn-off of all diodes of resonant voltage multiplier cell results in high efficient power conversion compared with the conventional boost-integrated flyback converters. Small-sized coupled inductor enhances magnetic utilization in this converter. Second stage consists of a single-phase H-bridge grid interfaced inverter with variable band hysteresis current control technique. Amplitude adaptive notch filter is used to extract fundamental unit voltage vector of grid voltage required for estimation of synchronized reference current for hysteresis controller. A 250 W laboratory prototype is developed and experimentally evaluated. Experimental results demonstrate efficient renewable energy conversion at dc–dc converter stage and quality power injection at dc–ac inverter stage of the proposed grid-tied SPV system under changing solar insulation levels.

Quasi‐resonant DC‐link H5 PV inverter

By removing transformer from PV inverters, they become more attractive for distributed power generation systems. Regardless of their some extra leakage currents, transformer-less inverters would be more advantageous regarding their higher efficiency. However, using traditionally hard-switching converters still causes to drastic switching losses, high di/dt and electromagnetic interference. Quasi-resonant DC-link techniques have promising features to provide zero-voltage switching (ZVS) condition for full bridge inverters, but they are not suitable for transformer-less PV inverters due to consequent high leakage current. In this study, a transformer-less PV inverter is proposed by adapting a proper quasi-resonant DC-link technique to the H5 topology. Using only two auxiliary switches, ZVS turn on and turn off for high-frequency bus switch and ZCS turn on and ZVS turn off for high-frequency switches of the bridge as well as ZVS turn on and turn off of the antiparallel diodes of main switches are realised. Zero current switching (ZCS) turn on and ZVS turn off for auxiliary switches and ZVS turn on and ZCS turn off for antiparallel diodes are also provided. To verify the proposed circuit operation, a 20 kHz 1 kW quasi-resonant DC-link H5 PV inverter prototype is implemented and operation characteristics, soft switching conditions and design rules are confirmed.

Improved single‐phase transformerless inverter with high power density and high efficiency for grid‐connected photovoltaic systems

This study proposes an improved single-phase transformerless inverter with high power density and high efficiency for grid-connected photovoltaic systems. The proposed inverter is comprised of the dual-paralleled-buck inverter and two auxiliary circuits for the zero-current switching turn-off of the diodes. The dual-paralleled-buck inverter and auxiliary circuits are joined by two coupled inductors. To achieve high power density, the proposed inverter operates at high switching frequency of 40 kHz. This leads to lower filter inductors and lower conduction losses of the filter inductors than conventional full-bridge inverters. Moreover, two auxiliary circuits reduce the switching losses caused by high switching frequency operation. Furthermore, the proposed inverter provides the low common-mode leakage current, which satisfies the criteria given by VDE-0126-1-1. Thus, the proposed inverter achieves the maximum efficiency of 99%. The operation principle of the proposed inverter is analysed and verified. Experimental results for a 1 kW prototype are obtained to show the performance of the proposed inverter.

A Fully Soft-Switched Single Switch Isolated DC–DC Converter

This paper proposes a soft-switched single switch isolated converter. The proposed converter is able to offer low cost and high power density in step-up application due to the following features: zero-current switching (ZCS) turn-on and zero-voltage switching (ZVS) turn-off of switch and ZCS turn-off of diodes regardless of voltage and load variation; low rated lossless snubber; reduced transformer volume compared to flyback-based converters due to low magnetizing current. Experimental results on a 100 kHz, 250 W prototype are provided to validate the proposed concept.

English

A new dual active-clamping dc-dc converter is proposed to obtain high efficiency. The proposed converter employs a dual active-clamping technique, while a resonant voltage doubler rectifier scheme controls the output voltage with the pulse width modulation technique. The dual active-clamping circuit serves to recycle the energy stored in the leakage inductor or the magnetizing inductor and provides zero-current turn-off switching. The voltage stresses of the main switches are clamped. The voltage transient spikes across the dual active-clamping circuit and the current stress of the current-fed side switches are limited by auxiliary dual active-clamping circuits on both sides, and zero-current switching is achieved. Also, to reduce the output voltage variation, a modified PI controller is suggested.

Zero voltage switching DC converter for high‐input voltage and high‐load current applications

A new DC/DC pulse-width modulation (PWM) converter with the functions of zero voltage switching (ZVS) for power switches and zero current switching (ZCS) for rectifier diodes is presented for high-input voltage and high-load current applications. Three-level PWM circuit with two clamped diodes and one flying capacitor is adopted to achieve ZVS turn-on for all power switches, to balance two input capacitor voltages and to limit the voltage rating of each switch at one-half of input voltage. Two three-level PWM circuits with the same power switches are used to share the load current for medium power applications. Series–parallel resonant converter or LLC (L r, L m and C r) converter is adopted to achieve ZCS turn-off for rectifier diodes. Thus, the switching losses of power switches are reduced and the reverse recovery losses of rectifier diodes are eliminated. In order to high load current application, four centre-tapped rectifiers are connected in parallel to reduce the current rating of rectifier diodes and transformer windings. Experiments are provided to verify the effectiveness of the proposed converter.

A New Soft switching Fly Back DC-DC Converter with Minimal Auxiliary Circuit Elements

A new soft switching pulse-width-modulated (PWM) fly back dc/dc converter with a simple auxiliary circuit is proposed. By adding this auxiliary circuit to the conventional pulse width modulation isolated fly back converter, all power semiconductor devices are soft switched. Therefore switches turn-on under ZCS condition and turn off under zero current zero voltage switching (ZCZVS) condition and diode operates at zero current switching (ZCS) turn-on and turn-off. In addition, the proposed converter frequency is constant and has no additional current stress in the main switch in comparison with conventional ones. Simulation and experimental results justify the theoretical analysis.

Implementation of a soft switching DC/DC converter without reverse recovery loss for rectifier diodes

This study presents an interleaved soft switching converter to achieve ripple current reduction, zero-voltage switching (ZVS) turn-on for MOSFETs and zero-current switching (ZCS) turn-off for fast recovery diodes. Active snubber circuit is used in the proposed circuit to absorb the energy stored in the leakage inductor and to achieve ZVS turn-on for power switches. The resonant tank composed of the leakage inductor and the resonant capacitor at the secondary side is used to achieve ZCS turn-off for all rectifier diodes. The reverse recovery loss on rectifier diodes can be eliminated. Thus, the low-cost fast recovery diodes can be used at the secondary side. The interleaved pulse-width modulation scheme is used to control two converter cells in order to achieve load sharing and input ripple current reduction. Experiments with a 400 W prototype, verifying the effectiveness of the proposed converter, are described.

직접전력변환 방식을 이용한 능동 클램프 AC-DC 컨버터

This paper proposes an active-clamp ac-dc converter with direct power conversion that has a simple structure and achieves high efficiency. The proposed converter is derived by integrating the step-down ac chopper and the output-voltage doubler. The proposed converter provides direct ac-dc conversion and dc output voltage without using any full-bridge diode rectifier. The step-down ac chopper using an active-clamp mechanism serves to clamp the voltage spike across the main switches and provides zero-voltage turn-on switching. The resonant-current path formed by the leakage inductance of the transformer and the resonant capacitor of the output-voltage doubler achieves the zero-current turn-off switching of the output diodes. The operation principle of the converter is analyzed and verified. A 500W prototype is implemented to show the performance of the proposed converter. The prototype provides maximum efficiency of 95.1% at the full load.