Soft-switching Circuit Research Articles

A Voltage-Edge-Rate-Limiting Soft-Switching Inverter Based on Auxiliary Resonant Pole

To increase switching frequencies while limiting switching losses in voltage-source inverters, power switches have been made significantly faster with achievable switching times now less than 100 ns. However, faster switches generate larger inverter output voltage edge rates ( ${dv/dt} $ ) and result in deleterious effects in variable-speed drive systems including transient overvoltages at motor terminals, electromagnetic interference, and bearing failures due to microarcs. A common approach for limiting peak ${dv/dt} $ involves using a ${dv/dt} $ filter. However, the ${dv/dt} $ filter introduces extra power losses and increases the overall size and weight of the system. Soft-switching circuits, which were originally developed to reduce switching losses, can help reduce ${dv/dt} $ , but using soft-switching to accurately control ${dv/dt} $ has not been fully explored. In this paper, a new soft-switching circuit, entitled the auxiliary resonant soft-edge pole (ARSEP), is set forth. ARSEP improves the available soft-switching circuits so that ${dv/dt} $ can be accurately controlled through the circuit parameter design. An ARSEP inverter prototype was designed, simulated, and constructed to verify its performance and benefits. Compared to a conventional hard-switched inverter with a ${dv/dt} $ filter, the ARSEP inverter prototype results in a significant reduction in overall power loss, inductor volume, and weight.

COSS Losses in 600 V GaN Power Semiconductors in Soft-Switched, High- and Very-High-Frequency Power Converters

We report losses from charging and discharging the parasitic output capacitor, ${\rm C}_{\rm OSS}$ , in Gallium Nitride (GaN) power devices with voltage ratings over 600 ${\rm V}_{\rm DS}$ . These losses are of particular importance in soft-switched circuits used at MHz switching frequencies, where the output capacitance of the device is charged and discharged once per switching cycle during the device's off-time. This process is assumed lossless. We measure ${\rm C}_{\rm OSS}$ losses from 5–35 MHz sine, square, and Class- $\Phi _{2}$ waveshapes in enhancement-mode and cascode devices, and find that losses are present in all tested devices, equal or greater than conduction losses at MHz frequencies, and exponentially increasing with $\mathbf{dV/dt}$ . The cascode device outperforms the e-mode devices under 300 V, but the e-mode devices are preferred above this operating voltage. Furthermore, we show that, within a device family, losses scale linearly with output energy storage. Packaging appears to have only a minor effect on these losses. Finally, we demonstrate 10 MHz, 200 W dc–dc converters with varying device configurations, showing that, even with constant circulating currents, moving to larger devices with lower ${\rm R}_{\rm DS,ON}$ actually degrades efficiency in certain applications due to ${\rm C}_{\rm OSS}$ losses. In the high-voltage, high-frequency range, these reported losses must be optimized simultaneously with conduction losses on a per-application basis.

Implementation of Resonant and Passive Lossless Snubber Circuits for DC-DC Boost Converter

This paper presents the comparison of resonant and passive lossless snubber circuits implementation for DC-DC boost converter to achieve soft-switching condition. By applying high switching frequency, the volume reduction of passive component can be achieved. However, the required of high switching frequency cause the switching loss during turn-ON and turn-OFF condition. In order to reduce the switching loss, soft-switching technique is required in order to reduce or eliminate the losses at switching devices. There are various of soft-switching techniques can be considered, either to reduce the switching loss during turn-ON only, or turn-OFF only, or both. This paper discusses comparative analyses of resonant and passive lossless snubber circuits which applied in the DC-DC boost converter structure. Based on the simulation results, the switching loss is approximately eliminated by applying soft-switching technique compared to the hard-switching technique implementation. The results show that the efficiency of resonant circuit and passive lossless snubber circuit are 82.99% and 99.24%, respectively. Therefore, by applying passive lossless snubber circuit in the DC-DC boost converter, the efficiency of the converter is greatly increased. Due to the existing of an additional capacitor in soft-switching circuit, it realizes lossless operation of DC-DC boost converter.

A low-temperature internal heating strategy without lifetime reduction for large-size automotive lithium-ion battery pack

To overcome the long-standing challenge of poor performance of large-size automotive lithium-ion battery pack at low temperature, an internal self-heating strategy without lifetime reduction is proposed. A new method superimposing the discharge current on alternating current for self-heating is developed to prevent lithium-ion deposition, which not only avoids the measurement difficulty of potential and impedance of anode electrode, but also circumvents inconsistency problem of battery pack. The permissible alternating current and direct current are determined to avoid lithium-ion deposition. An effective yet simple soft-switching circuit is designed for heating of large-size automotive lithium-ion battery pack. The battery pack is warmed up from −20.8 °C to 2.1 °C within 600 s, where the temperature difference among twelve batteries is below 1.6 °C, implying the essentially uniform temperature distribution. Based on the performance analysis for battery pack, no obvious loss of lithium inventory is found and no lifetime reduction is observed after 600 repeated heating tests due to the suitable over-potential of anode electrode and no substantial thermal-induced aging stress. The proposed self-heating strategy, validated for heating uniformly and effectively without lifetime reduction, is of high potential to deliver a practical solution to poor performance of large-size automotive lithium-ion battery pack in cold conditions.

Soft switching circuit to improve efficiency of all solid-state Marx modulator for DBDs

For an all solid-state Marx modulator applied in dielectric barrier discharges (DBDs), hard switching results in a very low efficiency. In this paper, a series resonant soft switching circuit, which series an inductance with DBD capacitor, is proposed to reduce the power loss. The power loss of the all circuit status with hard switching was analyzed, and the maximum power loss occurred during discharging at the rising and falling edges. The power loss of the series resonant soft switching circuit was also presented. A comparative analysis of the two circuits determined that the soft switching circuit greatly reduced power loss. The experimental results also demonstrated that the soft switching circuit improved the power transmission efficiency of an all solid-state Marx modulator for DBDs by up to 3 times.

Soft Switching in Switched Inertance Hydraulic Circuits

Switched inertance hydraulic systems (SIHS) use inductive, capacitive, and switching elements to boost or “buck” (reduce) a pressure from a source to a load in an ideally lossless manner. Real SIHS circuits suffer a variety of energy losses, with throttling of flow during transitions of the high-speed valve resulting in as much as 44% of overall losses. These throttling energy losses can be mitigated by applying the analog of zero-voltage-switching, a soft switching strategy, adopted from power electronics. In the soft switching circuit, the flow that would otherwise be throttled across the transitioning valve is stored in a capacitive element and bypassed through check valves in parallel with the switching valves. To evaluate the effectiveness of soft switching in a boost converter SIHS, a lumped parameter model was constructed. Simulation demonstrates that soft switching improves the efficiency of the modeled circuit by 42% at peak load power and extends the power delivery capabilities by 77%.

A Novel ZVS Step-down Chopper Circuit

In this paper, a new Buck soft-switching topology is proposed to overcome the shortcomings such as large switching losses and strong noise in traditional Buck circuits. The new Buck soft-switching circuit adds auxiliary switches and series resonant circuits. The auxiliary switch is used to control the working state of the series resonant circuit, and then the resonant current generated by the resonant circuit to promote the main switch of the parallel capacitor discharge, the main switch zero voltage conduction and shutdown. Soft-switching technology is a good solution to the traditional Buck circuit defects, improve the efficiency of the circuit. In this paper, the working principle of the new Buck soft-switching circuit is analyzed in detail, and simulation is carried out to ensure the circuit's accuracy.

High-frequency composite pulse generator based on full-bridge inverter and soft switching for biological applications

Applying high-frequency pulses to animals for tissue ablation can reduce the number and intensity of muscle contractions. Hence, developing a composite pulse generator is necessary to investigate the mechanism of tumor ablation under high-frequency composite pulses. In this study, a high-frequency and high-voltage composite pulse generator is proposed for such application. This generator combines the technology of full-bridge soft-switching circuit, MOSFET series, and RCD equalization circuit. This generator has the capability of producing composite pulses, in which the center frequencies of the bursts are up to 2 MHz, the inter-burst delay is 0.1–10 s, the pulse width is from 100 ns to 100 μs, the pulse amplitude is ±3 kV, and the rise time is around 30 ns. The parameters satisfy the requirements of the experiments for studying muscle contraction under high-frequency pulses and tumor ablation. The details of the generator’s production of high-frequency composite pulses are provided. An all-solid-state modular design makes the generator compact and reliable. Initial experiments are then conducted to verify the performances of the proposed generator.

A New Measurement Circuit to Evaluate Current Collapse Effect of GaN HEMTs Under Practical Conditions

The gallium nitride transistors suffer from current collapse effect in operation regions, which leads the dynamic ON-resistance to increase when high voltage is applied to the transistor. Dynamic ON-resistance under practical application conditions is also an important factor for the reliability and conduction efficiency of transistors. To measure the dynamic ON-resistance and evaluate the current collapse effect, a softswitching circuit based on synchronous buck topology is proposed in this paper. To apply high-voltage and high-current stresses to the device without additional spikes and oscillation, resonance technique has been employed. As a result, the proposed circuit could produce sufficient power stresses to the devices with general equipment. To achieve accurate measurement of ON-resistance under switching operations and eliminate the saturation of oscilloscope probes, an active voltage clamp circuit is developed. Operation principles and design analysis of the circuit are described in this paper. The dynamic ON-resistance measurement method is illustrated in detail. Furthermore, a prototype circuit has been built. A simulation and experiments were carried out to verify the performance of the system. A comparison of the active clamp circuit with common voltage probes is presented through the measurement results. The experimental results confirm that dynamic ON-resistance can be accurately measured using the proposed circuit and the current collapse effect can be evaluated under practical operation conditions with high precision.

Passive Lossless Snubbers Using the Coupled Inductor Method for the Soft Switching Capability of Boost PFC Rectifiers

In order to minimize switching losses for high power applications, a boost PFC rectifier with a novel passive lossless snubber circuit is proposed. The proposed lossless snubber is composed of coupled inductors merged into a boost inductor. This method compared with conventional methods does not need additional inductor cores and it reduces extra costs to implement a soft switching circuit. Especially, the proposed circuit can reduce the reverse recovery current of output diode rectifiers due to the coupling effect of the inductor. During turn-on and turn-off operating modes, the proposed PFC converter operates under soft switching conditions with high power conversion efficiency. In addition, the performance improvement and analysis of the operating effects of the coupled inductors were also presented and verified with a 3.3 kW prototype rectifier.

Structure of 15-Level Sub-Module Cascaded H-Bridge Inverter for Speed Control of AC Drive Applications

This paper deals with the implementation of a single phase 15-level Sub-Multilevel Cascaded H-Bridge Inverter (SMCHBI) for variable speed industrial drive applications. It consists of sub-multilevel modules and H-bridge inverter configuration. Sub-multilevel switches synthesize stepped DC link voltage and current from the DC sources. H-bridge inverter switches renovate stepped DC link voltage and current into sinusoidal waveform. Compared with conventional Cascaded Multilevel Inverter (CMLI), the proposed system employs the reduced number of power switches, DC sources and gate driver requirements. The proposed system not only reduces the overall system cost but also reduces the voltage stress across the inverter switches. The proposed system does not required additional resonant soft switching circuits for Zero Voltage Switching (ZVS) of inverter. In the proposed method, variable frequency method is adopted for the speed control of industrial induction motor drives. A prototype model of 15-level SMCHB is developed and the performance of the systems is validated experimentally.

Analysis, Design, and Experimental Results of the Semidual-Active-Bridge Converter

A new soft-switching circuit topology derived from the popular dual-active-bridge converter (DAB) topology is proposed for applications requiring only unidirectional power flow such as the dc-dc stage of a photovoltaic power converter, and battery charger for electric vehicles. The topology named as the semidual active bridge (S-DAB) is obtained by replacing the fully active (four switches) bridge on the load side of a DAB by a semiactive (two switches and two diodes) bridge. In addition to the reduced number of active switches, the topology offers several other advantages including extended zero-voltage switching (ZVS), and smaller output filter requirement. The operating principles, waveforms in different intervals and expression for power transfer, which differ significantly from the basic DAB topology, are presented in detail. The ZVS characteristics and requirements are analyzed in detail and compared to those of DAB. A small-signal model of the new configuration is also derived. The analysis and performance of S-DAB are validated through extensive simulation and experimental results from a 1-kW hardware prototype.

Research on Active Equalization of Lithium Battery via SOC

This paper presents an active equalization method for lithium battery via SOC. The high accuracy of SOC is promised by extended Kalman filter algorithm (EKF) based on the adaptive parameters equivalent-circuit model at all SOC region. Then a small size, low loss resonant soft-switching active equalization circuit is presented. That circuit combined with SOC do precisely balance the battery pack during charge and discharge processes, which can effectively improve the battery pack’s using life.

The Simulation Study of Soft Switching Power Factor Correction Circuit Based on MATLAB

This paper discusses the soft switching circuit—Boost-ZVT converter, and studies the role of Boost-ZVT converter in the factor correction circuit(PFC). Distinguished from the past Boost converter, the Boost-ZVT converter implements the main switch of the soft turn-off, reducing switching losses and improving the system efficiency. At last, Matlab software is carried out the main circuit simulation. The simulation results show that Boost-ZVT circuit has a good effect in PFC circuit design, and has a wide application in practical circuit design.

A Novel Design of Soft Switching Based on Three-Phase Current Source Inverter

This paper presents a novel soft switching topology and its control method applied on three-phase current source inverter. The main switch transistors of the inverter can be achieved in soft switching on the current pass-through step, which can reduce switch stress and improve efficiency. The soft switching circuit consists of two auxiliary switch transistors and some passive devices, such as inductor, capacitor and diode. It has many advantages as follows, simple control, fewer devices, high reliability, and so on. This paper analyzes the principle of soft switching circuit, and simulate by using the current space vector control method with MATLAB. The simulation results demonstrate the feasibility of the method.

A Charger Design for Aircraft Batteries Based on ZVS Phase-Shifted Full-Bridge Soft-Switching Circuit

A design idea of power supply for aircraft battery charger is proposed, which is based on the thought of aircraft batteries characters such as small capacity and same working voltage range. The crucial parameters of the power supply are set depended on analyzing the capacity and voltage range of aircraft batteries. After analyzing the features of power converters, the ZVS phase shifted full-bridge soft-switching circuit is chose and then crucial components are designed. The experiment results show that the design scheme of the power supply can meet using-requirements. The design scheme of general-purpose power supply solve the problem that aircraft battery charger has bad general-using ability.

Research on a Novel Soft-Switching Buck Converter

Based on classical zero voltage transition buck pwm converter, an ideal buck converter with pwm-controlled soft-switching circuit is proposed. The proposed auxiliary circuit allows the main switch to operate with zero-voltage switching. Besides, all of the semiconductor devices operate under soft-switching conditions. Thus, losses were reduced. It was analyzed in detail to demonstrate the operating principle of the novel circuit. Finally, simulation results are given analysis and the simulation results are provided to verify the performance of the proposed buck Converter.

Analysis, Design, and Implementation of a Soft-Switching Converter With Two Three-Level PWM Circuits

This paper proposes a new soft-switching circuit for high-input-voltage applications to achieve zero voltage switching (ZVS), implement load current sharing, reduce the voltage stress of switches at <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$V_{\rm in}$</tex></formula> /2, and decrease current rating of the rectifier diodes and the output inductors. Two three-level pulse-width modulation (PWM) circuits with the same active switches are operated with the phase-shift PWM scheme. Two center-tapped rectifiers are adopted at the secondary side such that the current rating of the transformer windings, rectifier diodes, and output filter inductors are reduced and have only one diode conduction loss in the forward current path. Based on the resonant behavior by the output capacitance of active switches and the leakage inductance (or external inductance), all power switches are turned ON at ZVS. The operation principle, circuit analysis, and design example are discussed in detail. Finally, experiments with 1-kW prototype are provided to verify the effectiveness of the proposed converter.

New Soft Switching Circuit using Lossless Snubber Circuit for Zero-Voltage-Transition Converter

A new soft switching circuit system with a lossless snubber circuit as an auxiliary circuit in the soft switching circuit is proposed in this letter. Soft switching operation is achieved for the main switch and the auxiliary switch. Moreover, zero current switching operation in the turn-off of the main switch is also realizable in the proposed circuit by using the charging voltage of the auxiliary capacitor in the lossless snubber circuit.

Practical Evaluations of a ZVS-PWM DC–DC Converter With Secondary-Side Phase-Shifting Active Rectifier

This paper presents a feasibility investigation of a zero-voltage switching (ZVS) pulsewidth modulation (PWM) dc-dc converter with secondary-side phase-shifting power control scheme. The ZVS-PWM dc-dc converter treated here can achieve soft commutation in all the power devices under the wide range of output power variation. By the phase-shifting control that is based on the secondary-side rectifier linked with a high-frequency planar transformer, the effective reduction of idling power in the primary-side inverter as well as snubber-less rectifications in the secondary-side rectifier can be actually attained. The essential experimental data obtained from a 100-kHz/2.5-kW prototype are described herein to validate the soft-switching circuit and control scheme, and then the effectiveness of the dc-dc converter is discussed and evaluated from a practical point of view.