Zero-current Switching Condition Research Articles

Design of class-E power amplifier for zero-current switching operation with MOSFET nonlinear output parasitic capacitance

The subnominal condition is defined as only the zero-current switching (ZCS) condition is satisfied. On the other hand, as the operating switching frequency increases, the effect of the MOSFET nonlinear output parasitic capacitance increases. This article introduced the design expressions with the analytical approaches for the design of the class-E power amplifier with a shunt inductor at the subnominal condition, taking into account the MOSFET nonlinear drain-to-source capacitance. The element's values for achieving the subnominal condition are expressed as a function of the phase shift between the input and output voltage. Moreover, the MOSFET nonlinear drain-to-source capacitance affects the switch-current waveform. Therefore, the switch-current waveform does not satisfy the class-E ZCS conditions if the nonlinear effect of the MOSFET output parasitic capacitance ignored. Using the class-E subnominal operation, the degree of the design freedom of the class-E power amplifier is increased by one. The maximum output power along with the increment of the operating frequency at the subnominal condition is obtained. A circuit design example using the proposed design procedure of the class-E power amplifier with ZCS condition is given. The waveforms obtained from the laboratory measurements showed the quantitative agreements with PSpice simulations that proved the usefulness and effectiveness of our proposed design expressions. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:801–808, 2014

Soft-Switching Current-Fed Push–Pull Converter for 250-W AC Module Applications

In this paper, a soft-switching single-inductor push-pull converter is proposed. A push-pull converter is suitable for low-voltage photovoltaic ac module systems, because the step-up ratio of the high-frequency transformer is high, and the number of primary-side switches is relatively small. However, the conventional push-pull converter does not have high efficiency because of high-switching losses due to hard switching and transformer losses (copper and iron losses) as a result of the high turn ratio of the transformer. In the proposed converter, primary-side switches are turned ON at the zero-voltage switching condition and turned OFF at the zero-current switching condition through parallel resonance between the secondary leakage inductance of the transformer and a resonant capacitor. The proposed push-pull converter decreases the switching loss using soft switching of the primary switches. In addition, the turn ratio of the transformer can be reduced by half using a voltage-doubler of secondary side. The theoretical analysis of the proposed converter is verified by simulation and experimental results.

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.

Single-Stage Resonant Battery Charger With Inherent Power Factor Correction for Electric Vehicles

This paper presents the study of a single-stage onboard battery charger for electric vehicle (EV) and plug-in hybrid EV (PHEV) applications. The topology had never been seen in any literature or patents but is employed in the NLG5 charger made by Brusa Elektronik AG. We thoroughly analyzed the topology and thought it would be beneficial to publish it so that advanced work can be done based on the existing structure. The charger directly transfers power from the alternating current (ac) to the battery side; thus, the bulky electrolytic capacitor in a traditional two-stage charger is eliminated. Power factor correction (PFC) is inherently achieved; thus, the control becomes very simple. In addition, all the power switches work at a zero-current switching (ZCS) condition to reduce the switching loss. The charger charges the battery with a sinusoidal-like charging current instead of a constant direct current. However, this current waveform has minimal impact on the battery life and efficiency, as demonstrated by other studies. Hence, having the advantages of high efficiency, compact size, easy control, and no need of an electrolytic capacitor, the topology is suitable for the PHEV and the pure EV onboard charging applications.

Performance Study of Class-E Power Amplifier With a Shunt Inductor at Subnominal Condition

This paper presents analytical expressions for the class-E power amplifier with a shunt inductor for satisfying the subnominal condition and 50% duty ratio. The subnominal condition means that only the zero-current switching condition (ZCS) is achieved, though the nominal conditions mean that both the ZCS and zero-current derivative switching (ZCDS) are satisfied. The design values for achieving the subnominal condition are expressed as a function of the phase shift between the input and output voltages. The class-E amplifier with subnominal condition increases one design degree of freedom compared with that with the nominal conditions. Because of the increase in the design degree of freedom, one more relationship can be specified as a design specification. It is shown analytically that the dc-supply voltage and the current are always proportional to the amplitude of the output voltage and the current as a function of the phase shift. Additionally, the output power capability is affected by the phase shift, and the peak switch voltage has influence on the phase shift as well. This paper gives a circuit design example based on our proposed design expression by specifying the peak switch voltage instead of the ZCDS condition. The measurement and PSpice simulation results agree with the analytical expressions quantitatively, which show the validity of our analytical expressions.

Analysis and Implementation of a Half Bridge Class-DE Rectifier for Front-End ZVS Push-Pull Resonant Converters

An analysis of the junction capacitance in resonant rectifiers which has a significant impact on the operating point of resonance circuits is studied in this paper, where the junction capacitance of the rectifier diode is to decrease the resonant current and output voltage in the circuit when compared with that in an ideal rectifier diode. This can be represented by a simplified series resonant equivalent circuit and a voltage transfer function versus the normalized operating frequency at varied values of the resonant capacitor. A low voltage to high voltage push-pull DC/DC resonant converter was used as a design example. The design procedure is based on the principle of the half bridge class-DE resonant rectifier, which ensures more accurate results. The proposed scheme provides a more systematic and feasible solution than the conventional resonant push-pull DC/DC converter analysis methodology. To increase circuit efficiency, the main switches and the rectifier diodes can be operated under the zero-voltage and zero-current switching conditions, respectively. In order to achieve this objective, the parameters of the DC/DC converter need to be designed properly. The details of the analysis and design of this DC/DC converter’s components are described. A prototype was constructed with a 62–88 kHz variable switching frequency, a 12 VDC input voltage, a 380 VDC output voltage, and a rated output power of 150 W. The validity of this approach was confirmed by simulation and experimental results.

Analysis and Design of a High Step-up Current-Fed Multiresonant DC–DC Converter With Low Circulating Energy and Zero-Current Switching for All Active Switches

A high-efficiency high step-up current-fed multiresonant converter (CFMRC) is proposed for interfacing the sustainable power sources, such as PV panels and fuel cells, which are characterized by low-voltage high-current output and have strict current ripple requirement. The proposed converter has the features of low input current ripple, low circulating energy, achieving zero-current switching (ZCS) for all active switches, and common ground driving. In order to further improve the efficiency and the power density of the CFMRC, coupled inductor and voltage doubler are applied to the two input inductors and the output rectifier, respectively. The operation principle of the CFMRC is introduced. Its dc voltage gain and the ZCS conditions of both the primary switches and the secondary rectifier are also derived based on the steady-state analysis. Finally, a design guideline is given. The theoretical analysis of the CFMRC was verified on a 150-W prototype. An average efficiency of 95.9% was achieved over the entire maximum power point tracking range (23-38 V), with a 350-V output at full load.

Feed-Forward Compensator of Operating Frequency for APWM HB Flyback Converter

A feed-forward frequency compensator for an asymmetrical pulsewidth modulated (APWM) half-bridge (HB) flyback converter is proposed to increase its power conversion efficiency. Under a variable input voltage, the APWM HB flyback converter cannot be satisfied with the zero-current switching (ZCS) condition of output rectifiers because the variation of the turn-ON duration of main switches, which regulate the output voltage, induces their improper turn-OFF duration. This means that the resonance of a primary current during the turn-OFF of the switches is out of the ZCS operation of the output rectifiers. To avoid this improper operation, the resonant network should be designed with a marginal turn-OFF duration that guarantees the ZCS. However, this makes the converter operate with poor efficiency because of increasing conduction losses. The proposed feed-forward frequency compensator can properly change the converter's operating frequency to reduce the conduction losses according to the variation of the input voltage satisfying the ZCS condition of the output rectifiers. Operation principles, steady-state analysis, and soft-switching conditions are analyzed to derive the frequency compensation algorithm of the APWM HB flyback converter. Experimental results using a 240-W prototype converter show that the proposed compensation algorithm can improve the power conversion efficiency of the APWM HB flyback converter under the input-voltage variation.

Contactless power interface for plug-in electric vehicles in V2G systems

Contactless power interface for plug-in electric vehicles in V2G systems In the paper a bi-directional power electronic interface based on an inductive coupled contactless energy transfer system for plug-in vehicles with Vehicle-to-Grid (V2G) capability is presented. To minimize the total losses of the system, a series resonant compensation circuit is applied assuring Near to Zero-Current Switching (N2ZCS) condition for insulated-gate bipolar transistors. The analytical expression of the dc voltage and current gains as well as energy transfer efficiency is given and discussed. The system uses modified FPGA based integral control method adjusting resonant frequency and guarantees very fast and stable operation. Simulation and experimental results illustrating properties of the developed 40-60kHz switching frequency operated 15kW laboratory prototype are presented.

A Current-Fed Multiresonant Converter with Low Circulating Energy and Zero-Current Switching for High Step-Up Power Conversion

A high-efficiency high step-up dc-dc converter is proposed for renewable energy harvesting, where the sustainable power sources, such as PV panels and fuel cells, are characterized by low-voltage high-current output. The proposed converter employs the current-fed half-bridge structure to generate a square-wave current source. Then, a multiresonant tank is used to provide high voltage gain, absorb the parasitic parameters of the transformer, and create zero-current switching (ZCS) condition for all primary switches. By applying a single capacitor instead of LC for the output filter, the maximum voltage of the resonant capacitor is clamped to the output voltage, which reduces the circulating energy within the circuit and offers ZCS to the rectifying diodes. The operation principle is introduced and the steady-state analysis is also carried out for the derivation of the dc voltage gain and the ZCS conditions of the primary switches. The performance of the proposed converter was verified by a 150-W prototype. A peak efficiency of 95.2% was achieved by running the prototype at 255 kHz with 23-V input and 350-V output.

Improving the Efficiency of IGBT Series-Resonant Inverters Using Pulse Density Modulation

This paper analyzes a high-power (50 kW) high-frequency (150 kHz) voltage-fed inverter with a series-resonant load circuit for industrial induction heating applications, which is characterized by a full bridge inverter made of insulated-gate bipolar transistor and a power control based on pulse density modulation (PDM). This power control strategy allows the inverter to work close to the resonance frequency for all output-power levels. In this situation, zero-voltage switching and zero-current switching conditions are performed, and the switching losses are minimized. An additional improvement of inverter efficiency is achieved by choosing appropriate values of the modulation index. Results are verified experimentally using a prototype for induction hardening applications. A comparative study between the PDM and the classical power control by frequency variation will be made.

Contactless Energy Transfer System With FPGA-Controlled Resonant Converter

Power supply based on an inductive coupled contactless energy transfer system is presented in this paper. The energy is transferred using a rotatable transformer and a power electronic converter. To minimize total losses of the system, a series resonant compensation circuit is applied assuring zero-current switching condition for insulated-gate bipolar transistors. The analytical expression of the transfer dc voltage gain is presented and discussed. The novelty of the system lies in the application of a fully digital field-programmable-gate-array-based controller and a protection system. The resonant frequency is adjusted by a primary peak current regulator. Some simulation and experimental results illustrating the operation of the developed 3-kW 60-kHz laboratory prototype are given. Although the presented power supply with a rotatable transformer is constructed mainly for robotics and manipulators, the described design and control methodology has general validity and can be applied for a wide class of contactless power supply with core or coreless transformers.

A ZERO-CURRENT SWITCHING PWM FLYBACK CONVERTER WITH LOW CURRENT STRESS

An actively current clamped zero-current switching (ZCS) flyback converter is proposed in this paper. ZCS condition is obtained for all transistors for reducing switching loss and electromagnetic interference. With the current clamping technique, current stress of the converter is low. Output voltage of this converter can be controlled with fixed frequency. Electrical isolation is provided. Operation principles are discussed in the paper. Mathematical descriptions and computer simulation verification are provided.

Family of Zero-Current Transition PWM Converters

In this paper, a new auxiliary circuit is introduced for applying to buck, buck-boost, zeta, forward, and flyback converters. This auxiliary circuit provides a zero-current switching condition for all switching elements. The proposed zero-current transition (ZCT) pulsewidth-modulated buck converter is briefly described. Also, a ZCT flyback converter is analyzed, and its different operating modes are presented. Design considerations are explained, and a design example along with the experimental results of the ZCT flyback converter is presented.

Current-Fed Parallel-Resonant DC–AC Inverter for Cold-CathodeFluorescent Lamps With Zero-Current Switching

This letter proposes a novel current-fed parallel-resonant dc-ac inverter with zero-current switching (ZCS) for cold-cathode fluorescent lamps (CCFLs). The leakage inductance of the transformer is integrated within the resonant tank in order to reduce the voltage spikes across the switches. A laboratory prototype is implemented to drive a 617 mm/7W CCFL. Experimental results indicate that the switches of the proposed resonant inverter are operated under the ZCS condition, and the efficiency is approximately 86.8%. The lamp voltage is about 977 V and the lamp current is 7 mA.

An Efficient Power-Factor Correction Scheme for Plasma Display Panels

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper presents an efficient power-factor correction (PFC) scheme for plasma display panels (PDPs) to reduce harmonic currents and power consumption. A high-efficiency interleaved boost converter is proposed, which can reduce the conduction losses and diode reverse-recovery problems in the continuous-conduction-mode operation. A zero-current switching (ZCS) condition is obtained to solve the reverse-recovery problems of the output diodes. In addition, a control strategy is suggested for the use of the proposed converter in a practical design. A high power factor can be achieved without sensing the input voltage. The analysis of the proposed converter and its design considerations are presented in detail. The experimental results based on a 600-W prototype are discussed to evaluate the proposed converter for a PFC circuit in a 50-in PDP power supply unit. </para>

Family of isolated zero-voltage transition PWM converters

A new family of zero-voltage transition (ZVT) PWM converters is introduced. In this family of converters, zero-voltage switching condition is achieved for main switch and zero-current switching condition is attained for auxiliary switch. A ZVT flyback converter from the proposed family of converters is analysed and various operating intervals are presented. The introduced ZVT flyback converter characteristics are compared with other ZVT converters. A laboratory prototype of this converter is realised and experimental results are shown.

High efficiency battery charger with a buck zero-current-switching pulse-width-modulated converter

A resonant converter has low switching losses, a small circuit volume and high power density and is also light. High-frequency switching converters have replaced conventional hard-switching converters. This study utilises a buck zero-current-switching (ZCS) pulse-width-modulated converter for battery chargers to manage resonant converters flexibly. An auxiliary switch is inserted into the resonant loop to control the resonant time. The operating modes of the circuit and the equivalent circuits are identified by analysing the operating principles of the charger circuit, based on the turn-on conditions of the active switches. The equations that are used to determine the circuit parameters are obtained from the equivalent circuits. The developed charger provides the advantages of hard-switching and resonant converters with constant-frequency control, reduced resonant time and the operability of all switching components in the charger under a ZCS condition, markedly reducing switching losses. Experimental results reveal the theoretical effectiveness of the developed novel battery charger circuit. The developed battery charger has a practical mean charging efficiency of over 90% and is highly suited to high-frequency operations with high charging efficiency.

Three-Phase Sinusoidal Rectifier Consisting of Three Thyristors and a Resonant Switch

Three-phase sinusoidal rectifier consisting of three thyristors and a resonant switch is presented. The switching transition of resonant switch is mainly governed by a series resonance and this allows the thyristors to turn on and off under the zero-current switching condition. Also, the currents flowing through power devices are always limited to the dc current. The experimental prototype employing three inverter-grade thyristors and two insulated-gate bipolar transistors is implemented to investigate the operation. The results confirm that the sinusoidal input currents with a near-unity power factor can be obtained under the pulse-width modulation.

Experimental Study of a Soft-Switched Isolated Bidirectional AC DC Converter Without Auxiliary Circuit

An isolated ac-dc converter topology includes a capacitively snubbered voltage source converter (VSC) and a cycloconverter, coupled by a medium frequency transformer. The topology offers the possibility of bilateral power flow as well as three-level pulse width modulation on the ac side. It is shown that by alternately commutating the VSC and the cycloconverter it is possible to achieve either zero-voltage or zero-current switching conditions for all semiconductor devices in all points of operation. This is the case without any need for auxiliary semiconductor devices. At low load the transformer current may be insufficient for recharging the VSC snubber capacitors. In this case, however, it is possible to utilize the cycloconverter for providing a current path by which a quasi-resonant commutation can be made. The design and operation of a 40-kVA prototype converter system is described. It is shown how the rather complex switching logic required for implementing the chosen algorithm for commutation and modulation can be realized by using modern programmable logic devices [field programmable gate array (FPGA)]. Measurement results from the prototype converter are presented and analyzed. The measurements indicate that the studied commutation algorithm works well in practice