Achieve Zero-voltage Switching Research Articles

Three-Legged High-Gain Phase-Modulated DC–AC Converter for Mitigation of Device Capacitance Induced Ringing Voltage

In this paper, a method is proposed to eliminate the voltage ringing problem in a phase-modulated dc–ac converter, also known as a micro-inverter. The basic idea is to apply a time-critical two-stepped voltage waveform to the input of the converter bridge connected to the filter inductor. This method is implemented by a new topology that has one more switching leg added to the full bridge voltage fed converter. It produces a second voltage level and adds it to the first by using a transformer. The advantages of the proposed method are as follows. It almost eliminates the requirement of a voltage clamp, there is no circulating current in the freewheeling state, and the secondary side devices have less voltage and current stress compared to a conventional phase-modulated converter. The overall benefit is an improvement in converter efficiency even for a high-voltage conversion ratio application. The proposed topology operates with a secondary side modulation scheme that achieves zero-voltage switching of four devices on the primary side and either zero-voltage switching or zero-current switching of all the devices on the secondary side, over the entire line cycle of the ac output. Finally, the experimental results verify the proposed method.

Analysis and Comparison of Push–Pull Class-E Inverters With Magnetic Integration for Megahertz Wireless Power Transfer

This paper presents the circuit design and magnetic integration of push–pull class-E inverters for wireless power transfer (WPT) up to megahertz. The design criterion for achieving zero-voltage switching (ZVS) of a class-E inverter with coupled windings is derived mathematically. The approaches of magnetic integration for push–pull class-E inverters are analyzed and compared. Then, a new magnetic structure with hybrid magnetic materials is proposed to build the integrated inductors with either coupled windings or uncoupled windings. A 3-MHz WPT system is built to verify the analysis. The detailed comparison of the class-E inverters with magnetic integration is presented in terms of switch voltage, efficiency, harmonic currents, and thermal distribution. In the optimized design example, the switches keep ZVS over the entire load range without using any closed-loop control. The system efficiency reaches 87.1% at 350-W output power.

An Interleaved Flyback-Typed LED Driver With ZVS and Energy Recovery of Leakage Inductance

Flyback converter has advantages of simple circuit configuration and easy control. However, it suffers two problems. One is the active switch is hard switching. The other is a very high voltage spike when the active switch is turned off . In order to solve these problems, this paper presents a novel dc-to-dc converter that mainly consists of two interleaved flyback converters. Both active switches can achieve zero-voltage switching on without the use of any active clamp circuit or snubber circuit. In addition, the leakage flux energy can be delivered to the output by using two added diodes. It helps to reduce the voltage spikes on the active switches and improve circuit efficiency. The steady-state analyses at different operation modes and the mathematical equations for parameters design are provided. Finally, a 200-W prototype circuit for driving high-brightness light-emitting diodes (LEDs) is built and tested to verify the feasibility of the proposed circuit. The LEDs are dimmed from 100% to 10% full power. Satisfactory performances are obtained from the experimental results.

High-Efficiency Bidirectional Buck–Boost Converter for Photovoltaic and Energy Storage Systems in a Smart Grid

This paper proposes a new bidirectional buck–boost converter, which is a key component in a photovoltaic and energy storage system (ESS). Conventional bidirectional buck–boost converters for ESSs operate in discontinuous conduction mode (DCM) to achieve zero-voltage switching turn- on for switches. However, operation in DCM causes high ripples in the output voltage and current, as well as low power-conversion efficiency. To improve the performance of the conventional converter, the proposed converter has a new combined structure of a cascaded buck–boost converter and an auxiliary capacitor. The combined structure of the proposed converter reduces the output current ripple by providing a current path and the efficiency is increased. A prototype was built and tested to verify the effectiveness of the converter. The proposed converter has a maximum efficiency of 98%, less than ${\text{5.14}}{ \text{V}}_{{\text{p.p}}}$ of output voltage ripple, and less than ${\text{7.12}}{ \text{A}}_{{\text{p.p}}}$ of output current ripple. These results were obtained at an input voltage of 160 V, switching frequency of 45 kHz, output voltage of 80–320 V, and output power of 16–160 W. The experimental results show that the proposed converter has improved performance compared to the conventional converter.

A Novel High-Power-Factor AC/DC LED Driver With Dual Flyback Converters

This paper proposes a novel ac/dc light-emitting diode driver. The circuit configuration consists of a low-pass filter, a diode rectifier, and two flyback converters which are interleaved operated with 180° phase shift. Although both flyback converters lose the capability of galvanic isolation in this proposed circuit, the active switch of each converter can achieve zero-voltage switching without needing to use the additional active clamping circuit or snubber circuit. Also, the energy stored in the leakage inductance of the coupled inductor can be either recycled or supplied to the output load, resulting in high circuit efficiency and low product cost. Besides, high power factor and low total current harmonic distortion are obtained by operating the flyback converters in discontinuous current mode. The steady-state analyses of different operation modes and the design criteria for circuit parameters are provided. Finally, a 200-W prototype circuit was implemented. Satisfactory performances are obtained from the experimental results.

7.2-kV Single-Stage Solid-State Transformer Based on the Current-Fed Series Resonant Converter and 15-kV SiC <sc>mosfet</sc>s

This paper proposes a novel two-level single-stage direct ac–ac converter for realizing a 7.2-kV medium-voltage (MV) solid-state transformer (SST) based on 15-kV SiC mosfet s. A new current-fed series resonant converter (CFSRC) topology is proposed to address major challenges in MV ac–ac converters such as achieving zero-voltage switching (ZVS) for the MV mosfet s across wide voltage and load ranges and minimizing system capacitance. The topology is analyzed with both time-domain analysis and first harmonic approximation to provide useful equations for circuit design. Constant deadtime strategy is adopted, allowing partial ZVS to occur at low-voltage (LV) levels. ZVS behavior over wide voltage range is investigated, and calculation of the associated loss from partial ZVS is presented. System parameters are optimized based on the tradeoff between conduction loss and switching loss. The 15-kV mosfet has been tested continuously at a park voltage of 10 kV and 37 kHz, indicating stable device operation and an extremely high voltage × frequency figure of merit. Moreover, inherent cycle-by-cycle current limiting in the proposed CFSRC under output short-circuit circumstance is realized by paralleling diodes to the LV resonant capacitors. Without employing any additional current sensors, the input and circulating currents are limited to a safe range automatically when the short-circuit occurs. This paper presents detailed short-circuit protection operating principles and peak resonant current equation to aid the design of the resonant tank. A full-scale and compact SST that converts 7.2 kV ac to 240 V ac is developed to verify the theoretical analysis. This is the highest reported voltage rating for two-level-based power converters without device series connection. ZVS is verified and achieved over wide voltage and load ranges with a peak efficiency of 97.8%. A short-circuit experiment is conducted at 3-kV peak voltage to verify the analysis. Experimental results closely match the theoretical analysis.

Class-DEM Tuned Power Amplifier

This paper proposes a Class-DEM tuned power amplifier. The proposed amplifier achieves zero-voltage switching (ZVS), zero-voltage derivative switching (ZVDS), and zero-current switching (ZCS) at turning- on , and ZVS, ZVDS, ZCS, and zero-current derivative switching at turning- off . Therefore, the switching losses are extremely low, which is suitable for high-frequency operation. Moreover, the switch voltage stress is low, which is no more than its input voltage. A proposed amplifier was designed, built, and tested. The measured power conversion efficiency was 93.2% under the condition of the main input voltage of 46.8 V, the operating frequency of 1 MHz, and the output power of 4.87 W.

An Interleaved Soft Switching High Step-Up Converter With Low Input Current Ripple and High Efficiency

This paper proposes a high step-up low-ripple dc-dc converter for sustainable energy conversion. A high step-up voltage gain is obtained with an input-current doubler and a switched-capacitor circuit rather than having to use a transformer with a high turn ratio. A low input current ripple is achieved since the current ripples of two input inductors cancel each other out when the primary-side branches work in an interleaving way. A low output voltage ripple is got by charging and discharging complementarily with each other of two output capacitors. In addition, the proposed converter achieves zero-voltage switching (ZVS) for all power switches and zero-current switching (ZCS) for all rectifier diodes, which reduces the switching loss significantly. Moreover, an active-clamp capacitor is installed on the input-current doubler to suppress the voltage spike across the switches. A 400-W prototype converter was realized to demonstrate the above-mentioned performance.

A Current-Fed Dual-Active-Bridge DC–DC Converter Using Extended Duty Cycle Control and Magnetic-Integrated Inductors With Optimized Voltage Mismatching Control

For a current-fed dual-active-bridge bidirectional dc–dc converter, an extended duty cycle control is proposed. The low-voltage-side (LVS) bottom switch duty cycle can operate lower than 50%. The conduction loss of switches can be reduced by using low-voltage-rating mosfet s for the LVS. Meanwhile, a voltage mismatching control with adaptive clamp voltage regulation is proposed to achieve zero-voltage switching for all switches throughout full load range. Besides, for LVS dc inductors, a magnetic-integrated technique is used to reduce core loss, and power density can be improved by the use of only one core. The effectiveness of the proposed control is verified by the experimental results of a 1-kW laboratory prototype.

A Structure-Reconfigurable Series Resonant DC–DC Converter With Wide-Input and Configurable-Output Voltages

This paper proposes a new series resonant dc-dc converter with four configurable operation states depending on the input-voltage and output-voltage levels. It suits well for the dc-dc stage of grid-connected photovoltaic systems with a wide-input voltage range and different grid voltage levels, i.e., 110/120 V and 220/230/240 V. The proposed converter consists of a dual-bridge structure on the primary side and a configurable half- or full-bridge rectifier on the secondary side. The root-mean-square (RMS) currents are kept low over a fourfold voltage-gain range; the primary-side mosfets and secondary-side diodes can achieve zero-voltage switching on and zero-current switching off, respectively. Therefore, the converter can maintain high efficiencies over a wide voltage gain range. A fixed-frequency pulsewidth-modulated control scheme is applied to the proposed converter, which makes the gain characteristics independent of the magnetizing inductance and thereby simplifies the design optimization of the resonant tank. The converter topology and operation principle are first described. Then, the characteristics, i.e., the dc voltage gain, soft switching, and RMS currents, are detailed before a performance comparison with conventional resonant topologies is carried out. Furthermore, the design guidelines of the proposed converter are also presented. Finally, the experimental results from a 500-W converter prototype verify the feasibility of the proposed converter.

Modeling, Analysis, and Implementation of High Voltage Low Power Flyback Converter Feeding Resistive Loads

In High Voltage flyback converters, the dominant factor that influences a converter operation is the parasitic capacitance. A significant portion of input energy is utilized in charging the parasitic capacitances of the circuit, which is circulated back to the source at the end of every switching cycle. The circulating energy is a function of output voltage, load power, and parasitic capacitances and remains significant in High Voltage Low Power (HVLP) applications. This energy transfer phenomenon involving parasitic capacitances results in a reduced fraction of input energy reaching the load in every cycle, thereby resulting in an apparent deviation in the converter operating point compared to ideal flyback in case of resistive loads. An analytical energy-based model is derived, which includes the effect of parasitic capacitances, and is valid for steady state and dynamics of HVLP flyback converters feeding resistive loads. The influence of parasitic capacitances on the switch voltage of the converter is exploited to achieve Zero Voltage Switching (ZVS), thereby minimizing the turn- on loss. The proposed analytical model is verified through simulation and experimental results on 1.5 kV/ 5 W and 1.5 kV/ 200 mW resistive loads.

A Single-Stage High-Power Factor Converter with Synchronized Self-Excited Technique for LED Lighting

This paper proposes a single-stage, high power-factor light-emitting diode (LED) driver with a self-excited control scheme for the power switches. The self-excited mechanism is accomplished by fetching the driving voltages from a center-tapped transformer. The frequency of the driving voltages is exactly the same as the resonant frequency of the resonant converter, thus synchronizing the resonant frequency with the switching frequency and achieving zero-voltage switching (ZVS) and zero-current switching (ZCS) of power switches. The circuit topology is mainly composed of a half-bridge LC resonant converter, along with a boost-type power-factor corrector (PFC) to fulfill the single-stage structure, meaning that the presented LED driver possesses high power-factor features and low switching loss. Finally, a 40 W prototype circuit is implemented and tested, and the experimental results exhibit a satisfactory performance.

A 500-kHz, 3.3-kW Power Factor Correction Circuit With Low-Loss Auxiliary ZVT Circuit

A new, low-loss, auxiliary zero-voltage-transition (ZVT) circuit for a boost-based power factor correction (PFC) circuit is proposed for a battery charger application in an electric vehicle. The auxiliary circuit comprises of a resonant inductor, an auxiliary mosfet, and a diode. This inductor resonates with the capacitances of the main mosfet and main diode during the turn-on transition to achieve zero-voltage switching, whereas the auxiliary mosfet itself turns off with zero-current switching. The conduction time of the auxiliary circuit is very small compared to the switching period of the main boost converter, and hence it processes only a small fraction of the output power. This allows efficient operation of the boost converter even while using Silicon mosfet s at relatively high switching frequencies. A discharge mechanism comprising of a capacitor and low-frequency diode helps transfer the energy processed in the auxiliary circuit to the output. The proposed ZVT circuit has no effect on the control scheme of the main PFC, and is easy to implement with a digital processor. The operating principles, waveforms in different intervals, and the design of the auxiliary ZVT circuit are presented in detail. Some extensions of the proposed concept in terms of different discharge mechanisms and coupled-inductor implementations are also discussed. The analysis and performance of PFC with ZVT circuit and its benefits are validated through extensive simulation and experimental results from a 3.3-kW/500-kHz hardware prototype.

Integrated Half-Bridge CLLC Bidirectional Converter for Energy Storage Systems

This paper proposes an integrated half-bridge CLLC (IHBCLLC) resonant bidirectional dc–dc converter suitable as an interface between two dc voltage buses in various applications including energy storage systems. This converter is an integration of a half-bridge CLLC resonant circuit and a buck/boost circuit. Compared with the traditional pulse frequency modulation and phase-shift controlled CLLC resonant converter, for the proposed convertor, the high voltage gain can be obtained from pulse width modulation. Synchronous pulse width modulation is adopted for the converter, and the switching frequency is equal to the resonant frequency. The CLLC resonant circuit can help MOSFETs to achieve soft switching and high voltage gain. The simulation analysis of the modulation schedule and operating principle of the proposed converter prove that the converter is able to achieve zero-voltage switching or zero-current switching. Experimental results obtained from a 1-kW converter prototype confirm the theoretical analysis and the simulation results.

A Dual Half-Bridge Phase-Shifted Converter With Wide ZVZCS Switching Range

This paper presents a phase-shifted dual-half-bridge converter, which achieves zero-voltage switching (ZVS) for the leading-leg switches and zero-current switching (ZCS) for the lagging-leg switches. The proposed converter contains two paralleled half-bridge inverters in the primary side. The rectifier stage is composed of six diodes connected with the form of full-bridge rectification. The ZVS condition is created by the output filter inductor and leakage inductor, while the ZCS condition is created by the blocking capacitors. A wide range of soft-switching operation can be achieved with small leakage inductors. Compared with the traditional phase-shifted full-bridge converter, the proposed converter can obtain a three-level output rectified voltage, and the power is transferred from the primary side to the secondary side during the whole period, which can significantly reduce the current ripple of the output filter inductor. In this paper, the operation principle and relevant analysis are presented. A laboratory prototype is built to verify the performance of the proposed converter.

Isolated Single-Phase Matrix Converter Using Center-Tapped Transformer for Power Decoupling Capability

This paper proposes a bidirectional isolated single-phase matrix converter with a center-tapped transformer, which is used in a battery storage system connecting to a single-phase ac load. The proposed converter consists of a full-bridge inverter, a high-frequency center-tapped transformer, and a matrix converter. The matrix converter is employed with a pulse density modulation in order to achieve zero-voltage switching (ZVS). On the other hand, a common-mode voltage of the center-tapped transformer and a small capacitor are utilized in order to absorb the power ripple of the single-phase ac load without additional switches. Furthermore, the switches in the full-bridge inverter partially achieve ZVS in order to reduce the switching loss. These characteristics result in a high-power-density converter. As the experimental results with a 1 kW-prototype, the proposed converter reduces the dc current ripple generated by a single-phase ac load by 80.2% in the discharging mode and 76.8% in the charge mode. Besides, the low ac-side voltage total harmonic distortion in the discharge are below 3.0% over the entire ac power range.

Class E/F$_3$ Tuned Power Oscillator

This paper proposes a Class E/F $_3$ tuned power oscillator based on the Class E/F $_3$ amplifier. The oscillator has a feedback-loop circuit and starts the oscillation in automatic. In addition, the oscillator achieves zero-voltage switching and zero-voltage derivative switching; therefore, the switching losses are reduced under high oscillation frequency. Moreover, the third harmonic tuned by providing a third harmonic series resonant circuit reduces the switch voltage stress of the mosfet sufficiently. The oscillator was designed, built and tested using an IRFR120Z power mosfet . Under the condition of the input voltage 6.003 V, following results were shown: the measured oscillation frequency was 801.6 kHz, the output power was 0.9075 W, and the power conversion efficiency was 86.24%.

Studies on a Hybrid Full-Bridge/Half-Bridge Bidirectional CLTC Multi-Resonant DC-DC Converter with a Digital Synchronous Rectification Strategy

This study presents a new bidirectional multi-resonant DC-DC converter, which is named CLTC. The converter adds an auxiliary transformer and an extra resonant capacitor based on a LLC resonant DC-DC converter, achieving zero-voltage switching (ZVS) for the input inverting switches and zero-current switching (ZCS) for the output rectifiers in all load range. The converter also has a wide gain range in two directions. When the load is light, a half-bridge configuration is adopted instead of a full-bridge configuration to solve the problem of voltage regulation. By this method, the voltage gain becomes monotonous and controllable. Besides, the digital synchronous rectification strategy is proposed in forward mode without adding any auxiliary circuit. The conduction time of synchronous rectifiers equals the estimation value of body diodes’ conduction time with the lightest load. Power loss analysis is also conducted in different situations. Finally, the theoretical analysis is validated by a 5 kW prototype.

An Improved Current-Doubler Rectifier for the Marine Controlled Source Electromagnetic Transmitter

High power marine controlled source electromagnetic transmitters have gained interest with applications in marine geological survey and mineral resources exploration. The direct current to direct current (DC-DC) converter that is typically used in marine transmitters has some issues, as the insulated-gate bipolar transistor (IGBT) tube cannot achieve zero-voltage switching (ZVS). In particular, lagging-leg switching cannot easily achieve ZVS. The conversion efficiency of the heat converter requires improvement. This paper proposes an improved current-doubler rectifier for the marine controlled source electromagnetic transmitter (ICDR-MCSET). Resonant inductance is increased and a blocking capacitor is added to the converter (DC-DC) circuit, where the converter can achieve ZVS in a wide load range. This results in the effective decrease of the heating temperature and the improvement of transformation efficiency. Saber software simulation and a 20 KW electromagnetic transmitter are used to verify the results, which show that the method is feasible and effective.

A 2-MHz Wide-Input Hybrid Resonant Converter With Ultracompact Planar Coupled Inductor for Low-Power Integrated On-Chip Applications

A trend for low-power conversion system is to integrate every component to a single chip. Magnetic component has been the key to determine the power density of the integrated switching power converter. In this paper, a hybrid resonant buck-type converter with an ultracompact custom-designed coupled inductor is presented for low-power integrated on-chip applications. This converter achieves zero-voltage switching for the high-side switch and near zero-voltage zero-current switching for low-side and auxiliary switches. The soft-switching condition allows the circuit operating at high switching frequencies. An ultracompact planar coupled inductor with a dimension of 5.25 mm × 1.95 mm × 3.86 mm is designed and customized for future integrated on-chip applications. The high-power density of this magnetics component is achieved by high switching frequency and optimized printed circuit board (PCB) windings design. A hardware prototype with 24 to 60-V input and 3.3 to 5-V, 3-A output operating at 2–3 MHz is presented to verify the circuit operation. The prototype achieves a peak efficiency of 90.7% using silicon devices at 2-MHz switching frequency.