For electric vehicles (EVs),it is necessary to improve endurance mileage by improving the efficiency.There exists a trend towards increasing the system voltage and switching frequency,contributing to improve charging ...For electric vehicles (EVs),it is necessary to improve endurance mileage by improving the efficiency.There exists a trend towards increasing the system voltage and switching frequency,contributing to improve charging speed and power density.However,this trend poses significant challenges for high-voltage and high-frequency motor controllers,which are plagued by increased switching losses and pronounced switching oscillations as consequences of hard switching.The deployment of soft switching technology presents a viable solution to mitigate these issues.This paper reviews the applications of soft switching technologies for three-phase inverters and classifies them based on distinct characteristics.For each type of inverter,the advantages and disadvantages are evaluated.Then,the paper introduces the research progress and control methods of soft switching inverters (SSIs).Moreover,it presents a comparative analysis among the conventional hard switching inverters (HSIs),an active clamping resonant DC link inverter (ACRDCLI) and an auxiliary resonant commuted pole inverter (ARCPI).Finally,the problems and prospects of soft switching technology applied to motor controllers for EVs are put forward.展开更多
In traction application,speed range of motor is an important index for motor drives.In AC motor control,the maximum speed of the motor is limited by the output voltage capability of the traditional three-phase inverte...In traction application,speed range of motor is an important index for motor drives.In AC motor control,the maximum speed of the motor is limited by the output voltage capability of the traditional three-phase inverter with star connenction of windings.Switching the star connection to delta connection in high-speed range can extend the speed range.In order to extend the speed operation region,star-delta switch proposed by many literatures relies on mechanical relay,which needs a dead zone of tens of milliseconds and seriously affects torque output.Besides,the traditional method will cause current overshoot during the switch transient process,decreasing the device security and reliability.Aiming at the defects existing in the star-delta hard switching,this paper proposes a star-delta soft switching method.Without adding extra power electronics devices,DC-bus capacitor is used to provide the path of zero axis current in the transient process,which helps to achieve the smooth torque output and zero current switch in the transient.Experiments have been done to validate the performance of the proposed method.The switching transient from star to delta connection in the motor drive can be much more stable than hard switching method.展开更多
Based on the existing component models in the Pspice software package, a combined model for Insulat- ed the Bipolar Transistor (IGBT) is established, in which a non - linear is introduced to represent the parasitic ...Based on the existing component models in the Pspice software package, a combined model for Insulat- ed the Bipolar Transistor (IGBT) is established, in which a non - linear is introduced to represent the parasitic capacitance. Using this model, computerized simulation is conducted for the FB - ZVZCS - PWM soft - ewitching converter,the switching and energy-transferring characteristics of the components are analyzed.The simulation results are testified by experiments.It is proved that by abopting appropriate models,computerized simulation becomes an effective tool for investigation of arc welding inverter power source.展开更多
The use of either lossless snubbers or resonant zero voltage switching (ZVS) and zero current switching (ZCS) techniques can increase efficiency and reduce electromagnetic inter ference (EMI) and noise of industrial p...The use of either lossless snubbers or resonant zero voltage switching (ZVS) and zero current switching (ZCS) techniques can increase efficiency and reduce electromagnetic inter ference (EMI) and noise of industrial power equipment at high switching frequencies. This paper presents an adaptive composite soft switching configuration which combines snubber functions and resonant ZCS circuits for switches in inverters using power bridge leg modules. Simulation and experimental results are included.展开更多
A new PWM converter based on soft switching is introduced. The converter uses a minimum number of devices, and requires less switching operations than conventional techniques. Switching is realized solely in a ZVS (z...A new PWM converter based on soft switching is introduced. The converter uses a minimum number of devices, and requires less switching operations than conventional techniques. Switching is realized solely in a ZVS (zero voltage switching) mode, therefore the loss is reduced and EMI (electromagnetic interference) is suppressed. The paper analyzes the operation of ZVS, and discusses the methods for maintaining a unit power factor and constant DC voltage. Changing the modulation index M and the phase angle θ keeps the input current in phase with the voltage. It also keeps the current sinusoidal, and ensures a constant output voltage.展开更多
The FB-ZVZCS-PWM converter is realized by the way of subjoiningblock-capacitor into the FB-ZVS-PWM converter. At the freewheeling interval, the primary current isattenuated fast to zero and maintained. And then, power...The FB-ZVZCS-PWM converter is realized by the way of subjoiningblock-capacitor into the FB-ZVS-PWM converter. At the freewheeling interval, the primary current isattenuated fast to zero and maintained. And then, power device of the static leg becomes azero-current-switch (ZCS), power device of the shifted leg becomes a zero-voltage-switch(ZVS). Thus,on one hand IGBT (Insulated gate bipolar transistor) with tail current can be easily used infull-bridge soft-switching converter; on the other hand additional circuiting energy is greatlyreduced. At the same time, less duty cycle loss, lower secondary parasitic resonance, widersoft-switching load range can be achieved. Based on the existing component models in the Pspicesoftware package, a combined model of IGBT is established, in which a non-linear capacitor isintroduced to replace the parasitic capacitor. Using this model, computerized simulation isconducted for the FB-ZVZCS-PWM soft-switching converter, the switching and energy-transferringcharacteristics of the power device are analyzed. Finally, based on the achievement above, a 10 kWarc welding inverter with FB-ZVZCS-PWM converter is developed. The simulation results are testifiedby experiments. It is proved that by adopting appropriate models, computerized simulation is aneffective and useful tool for the development of the arc welding inverter.展开更多
Objective: Dual bronchodilation with long-acting muscarinic antagonist and long-acting β2-agonist combinations are available worldwide in COPD patients. However, the choice of agents remains under debate. We hypothes...Objective: Dual bronchodilation with long-acting muscarinic antagonist and long-acting β2-agonist combinations are available worldwide in COPD patients. However, the choice of agents remains under debate. We hypothesized that switching devices between dry powder and soft mist inhalers without a wash-out period to mimic clinical practice would improve clinical symptoms and lung function. The aim of this study was to examine the effects of switching between once-daily glycopyrronium/indacaterol (GLY/IND) or umeclidinium/vilanterol (UMEC/VI), dry powder inhalers, and tiotropium/olodaterol (TIO/OLO), a soft mist inhaler, in COPD patients. Methods: This was a prospective, open-label, 8-week, observational study with follow-up. Subjects included 57 COPD patients, who attended outpatient clinics at Shizuoka General Hospital for routine check-ups between February and December 2015, receiving GLY/IND (50/110 μg) or UMEC/VI (62.5/25 μg). After an 8-week run-in period, medications were switched to TIO/OLO (5/5 μg). Study outcomes included patient’s global rating (PGR), modified MRC (mMRC), COPD assessment test (CAT), and spirometric and forced oscillatory parameters after 8 weeks. PGR used in this study was a 7-point scale ranging from 1 to 7, with 4 in the middle. Patients who consented to switch from TIO/OLO to GLY/IND or UMEC/VI were followed-up thereafter. Results: In total, 53 patients completed the study (mean age, 75 years;48 males and 5 females;GOLD 1/2/3/4 = 19/27/6/1;mMRC 0/1/2/3/4 = 14/22/12/4/1;UMEC/VI 26, GLY/IND 27). PGR, mMRC, and CAT improved in 20 (38%), 9 (17%), and 15 patients (28%), respectively. Respiratory system resistance at 5 Hz (R5), 20 Hz (R20), and the difference between R5 and R20 (R5 - R20) significantly improved. In a follow-up of 16 patients after switching from TIO/OLO to UMEC/VI (9) or GLY/IND (7), PGR, mMRC, and CAT improved in 5 (31%), 3 (12%), and 4 patients (25%), respectively, and R20 significantly improved (p = 0.011). Conclusions: Switching dual bronchodilators between dry powder and soft mist inhalers improves symptoms and airway narrowing in some COPD patients.展开更多
The design of a general simulation package for AC drive system with soft switching inverter is discussed in this paper. This package is based on the secondary developing of the nonlinear control system simulation lang...The design of a general simulation package for AC drive system with soft switching inverter is discussed in this paper. This package is based on the secondary developing of the nonlinear control system simulation language SIMNON. Being constructed with modularization programming, the package can be used for general purposes conveuieutly and has strong graphic functions. The design principle for this simulation package is discussed in datail in this peper; and an application example (DSC controlled AC drive system with RDCLI) as well as its simulation results are given.展开更多
This paper proposes a novel implementation strategy for soft switching PFC whose circuit is simple and can achieve low voltage output directly. The main circuit adopts current mode full-bridge converter and all the po...This paper proposes a novel implementation strategy for soft switching PFC whose circuit is simple and can achieve low voltage output directly. The main circuit adopts current mode full-bridge converter and all the power switches can realize ZCS or ZVS in the way of phase-shifted control, using the leakage inductance of the transformer, the junction capacitor of the switches and the stored energy of the output capacitor. The problems such as the function of phase-shifted link in control circuit, the implementation conditions of soft switching and bias restrained are analyzed. The adoption of constant frequency PWM control makes the design of the input and output filter link and the high frequency transformer simple. The transformation ratio regulation so as to achieve low voltage output and electrical insulation can be realized by using high frequency transformer.展开更多
This paper presents a multi-mode control scheme for a soft-switched flyback converter to achieve high efficiency and excellent load regulation over the entire load range. At heavy load, critical conduction mode with v...This paper presents a multi-mode control scheme for a soft-switched flyback converter to achieve high efficiency and excellent load regulation over the entire load range. At heavy load, critical conduction mode with valley switching (CCMVS) is employed to realize soft switching so as to reduce turn-on loss of power switch as well as conducted electromagnetic interference (EMI). At light load, the converter operates in discontinuous conduction mode (DCM) with valley switching and adaptive off-time control (AOT) to limit the switching frequency range and maintain load regulation. At extremely light load or in standby mode, burst mode operation is adopted to provide low power consumption through reducing both switching frequency and static power dissipation of the controller. The multi-mode control is implemented by an oscillator whose pulse duration is adjusted by output feedback. An accurate valley switching control circuit guarantees the minimum turn-on voltage drop of power switch. The pro-totype of the controller IC was fabricated in a 1.5-μm BiCMOS process and applied to a 310 V/20 V, 90 W flyback DC/DC converter circuitry. Experimental results showed that all expected functions were realized successfully. The flyback converter achieved a high efficiency of over 80% from full load down to 2.5 W, with the maximum reaching 88.8%, while the total power consumption in standby mode was about 300 mW.展开更多
The full-bridge zero-voltage and zero-current switching inverter, which can adjust the output power by keeping the duty-cycle of lagging arm constant, changing the duty-cycle of leading arm, is a common circuit topolo...The full-bridge zero-voltage and zero-current switching inverter, which can adjust the output power by keeping the duty-cycle of lagging arm constant, changing the duty-cycle of leading arm, is a common circuit topology of soft-switching inverter arc welding power supplies. However, the output power still remains a certain value when the duty-cycle of leading arm decreases to zero. The working-mode of soft-switching inverter and the waveforms of major parameters with the condition of duty-cycle of leading arm being zero are studied in this paper. U-1 characteristic experiments prove that the minimum output power of soft-switching circuit, which depends on the charged voltage of capacitors in parallel with leading arm, can be decreased by reducing the duty-cycle of lagging arm. By switching working-modes between half-bridge and full-bridge, the output power can swing from zero to the power rating.展开更多
The soft switching are welding inverter reduces switching losses and improves operating environment of devices by using Zero-Voltage-Transition (ZVT) technique. Step-by-step analysis of each timing interval and the as...The soft switching are welding inverter reduces switching losses and improves operating environment of devices by using Zero-Voltage-Transition (ZVT) technique. Step-by-step analysis of each timing interval and the associating voltage and current waveforms are included for the Full-Bridge Zero-Voltage-Switched PWM converter. Numerous design equations supporting the phase-shifted soft switching technique are highlighted.展开更多
Full bridge Zero Voltage Switch PWM converter combines advantages of the PWM control technique and resonant technique. However, Full ZVS is achieved only under large load current because resonant tank of this circu...Full bridge Zero Voltage Switch PWM converter combines advantages of the PWM control technique and resonant technique. However, Full ZVS is achieved only under large load current because resonant tank of this circuit is made up of the parasitic capacitance of the power semiconductors and the leakage inductor of the transformer primary. In this paper two saturable inductors as magnetic switches are added to secondary, so output inductor is always reflected to primary and assists resonant transition. Full ZVS is achieved under lower load current. The above mentioned investigated results are validated by the computerized simulation and hardware circuit experiment.展开更多
The full bridge zero voltage zero current switching ( FB-ZVZCS ) , which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg, was a common circu...The full bridge zero voltage zero current switching ( FB-ZVZCS ) , which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg, was a common circuit of soft switching arc welding inverter power source. However, when the duty ratio of leading leg was reduced to zero, the output power stayed the constant value instead of becoming zero. The working status and waveforms of some major parameters were studied in this paper while the duty ratio of leading leg was zero. It was concluded that the minimum output power of soft switching inverter was related to the charging voltage of paraUel capacitors, and the output power also could be reduced by reducing the duty ratio of lagging leg. A novel two-stage continuous PWM control method that could switch working-mode between full bridge and half bridge was put forward in this paper. This kind of control method could further reduce the output power of soft switching inverter in order to meet the requirement of low heat input of sheet metal welding.展开更多
The systematic mathematical analysis of the high frequency soft-switched AC-AC converter is proposed for variable frequency induction machine load in this paper. Both PWM and square-wave modes of operation have been c...The systematic mathematical analysis of the high frequency soft-switched AC-AC converter is proposed for variable frequency induction machine load in this paper. Both PWM and square-wave modes of operation have been considered. The frequency relation and phase unbalance problem due to discrete time integral half-cycle switching has been discussed in the beginning. Then, generalized Fourier series have been derived for output voltage, output current and supply current in two modes.The analytical results help to understand tbe converter characteristics, design optimally a convertermachine system of arbitrary capacity considering the various trade-off parameters.展开更多
Soft-switching techniques are attractive to unity-power-factor AC/DC converter in the view of the size reduction and EMI suppression. A soft-switched boost PFC converter has been studied based on its topology analysis...Soft-switching techniques are attractive to unity-power-factor AC/DC converter in the view of the size reduction and EMI suppression. A soft-switched boost PFC converter has been studied based on its topology analysis, PSIM simulation and circuit experiment. A special limitation of soft-switching techniques has been found in their AC/DC applications.展开更多
基金funded by Tsinghua University-Weichai Power Intelligent Manufacturing Joint Research Institute (WCDL-GH-2022-0131)。
文摘For electric vehicles (EVs),it is necessary to improve endurance mileage by improving the efficiency.There exists a trend towards increasing the system voltage and switching frequency,contributing to improve charging speed and power density.However,this trend poses significant challenges for high-voltage and high-frequency motor controllers,which are plagued by increased switching losses and pronounced switching oscillations as consequences of hard switching.The deployment of soft switching technology presents a viable solution to mitigate these issues.This paper reviews the applications of soft switching technologies for three-phase inverters and classifies them based on distinct characteristics.For each type of inverter,the advantages and disadvantages are evaluated.Then,the paper introduces the research progress and control methods of soft switching inverters (SSIs).Moreover,it presents a comparative analysis among the conventional hard switching inverters (HSIs),an active clamping resonant DC link inverter (ACRDCLI) and an auxiliary resonant commuted pole inverter (ARCPI).Finally,the problems and prospects of soft switching technology applied to motor controllers for EVs are put forward.
文摘In traction application,speed range of motor is an important index for motor drives.In AC motor control,the maximum speed of the motor is limited by the output voltage capability of the traditional three-phase inverter with star connenction of windings.Switching the star connection to delta connection in high-speed range can extend the speed range.In order to extend the speed operation region,star-delta switch proposed by many literatures relies on mechanical relay,which needs a dead zone of tens of milliseconds and seriously affects torque output.Besides,the traditional method will cause current overshoot during the switch transient process,decreasing the device security and reliability.Aiming at the defects existing in the star-delta hard switching,this paper proposes a star-delta soft switching method.Without adding extra power electronics devices,DC-bus capacitor is used to provide the path of zero axis current in the transient process,which helps to achieve the smooth torque output and zero current switch in the transient.Experiments have been done to validate the performance of the proposed method.The switching transient from star to delta connection in the motor drive can be much more stable than hard switching method.
文摘Based on the existing component models in the Pspice software package, a combined model for Insulat- ed the Bipolar Transistor (IGBT) is established, in which a non - linear is introduced to represent the parasitic capacitance. Using this model, computerized simulation is conducted for the FB - ZVZCS - PWM soft - ewitching converter,the switching and energy-transferring characteristics of the components are analyzed.The simulation results are testified by experiments.It is proved that by abopting appropriate models,computerized simulation becomes an effective tool for investigation of arc welding inverter power source.
基金Supported by the Zhejiang Province Natural Science Foundationthe Royal Society of U.K.
文摘The use of either lossless snubbers or resonant zero voltage switching (ZVS) and zero current switching (ZCS) techniques can increase efficiency and reduce electromagnetic inter ference (EMI) and noise of industrial power equipment at high switching frequencies. This paper presents an adaptive composite soft switching configuration which combines snubber functions and resonant ZCS circuits for switches in inverters using power bridge leg modules. Simulation and experimental results are included.
文摘A new PWM converter based on soft switching is introduced. The converter uses a minimum number of devices, and requires less switching operations than conventional techniques. Switching is realized solely in a ZVS (zero voltage switching) mode, therefore the loss is reduced and EMI (electromagnetic interference) is suppressed. The paper analyzes the operation of ZVS, and discusses the methods for maintaining a unit power factor and constant DC voltage. Changing the modulation index M and the phase angle θ keeps the input current in phase with the voltage. It also keeps the current sinusoidal, and ensures a constant output voltage.
基金This project is supported by National Natural Science Foundation of China(No.50075003)Municipal Natural Science Foundation of Beijing, China(No.3001001).
文摘The FB-ZVZCS-PWM converter is realized by the way of subjoiningblock-capacitor into the FB-ZVS-PWM converter. At the freewheeling interval, the primary current isattenuated fast to zero and maintained. And then, power device of the static leg becomes azero-current-switch (ZCS), power device of the shifted leg becomes a zero-voltage-switch(ZVS). Thus,on one hand IGBT (Insulated gate bipolar transistor) with tail current can be easily used infull-bridge soft-switching converter; on the other hand additional circuiting energy is greatlyreduced. At the same time, less duty cycle loss, lower secondary parasitic resonance, widersoft-switching load range can be achieved. Based on the existing component models in the Pspicesoftware package, a combined model of IGBT is established, in which a non-linear capacitor isintroduced to replace the parasitic capacitor. Using this model, computerized simulation isconducted for the FB-ZVZCS-PWM soft-switching converter, the switching and energy-transferringcharacteristics of the power device are analyzed. Finally, based on the achievement above, a 10 kWarc welding inverter with FB-ZVZCS-PWM converter is developed. The simulation results are testifiedby experiments. It is proved that by adopting appropriate models, computerized simulation is aneffective and useful tool for the development of the arc welding inverter.
文摘Objective: Dual bronchodilation with long-acting muscarinic antagonist and long-acting β2-agonist combinations are available worldwide in COPD patients. However, the choice of agents remains under debate. We hypothesized that switching devices between dry powder and soft mist inhalers without a wash-out period to mimic clinical practice would improve clinical symptoms and lung function. The aim of this study was to examine the effects of switching between once-daily glycopyrronium/indacaterol (GLY/IND) or umeclidinium/vilanterol (UMEC/VI), dry powder inhalers, and tiotropium/olodaterol (TIO/OLO), a soft mist inhaler, in COPD patients. Methods: This was a prospective, open-label, 8-week, observational study with follow-up. Subjects included 57 COPD patients, who attended outpatient clinics at Shizuoka General Hospital for routine check-ups between February and December 2015, receiving GLY/IND (50/110 μg) or UMEC/VI (62.5/25 μg). After an 8-week run-in period, medications were switched to TIO/OLO (5/5 μg). Study outcomes included patient’s global rating (PGR), modified MRC (mMRC), COPD assessment test (CAT), and spirometric and forced oscillatory parameters after 8 weeks. PGR used in this study was a 7-point scale ranging from 1 to 7, with 4 in the middle. Patients who consented to switch from TIO/OLO to GLY/IND or UMEC/VI were followed-up thereafter. Results: In total, 53 patients completed the study (mean age, 75 years;48 males and 5 females;GOLD 1/2/3/4 = 19/27/6/1;mMRC 0/1/2/3/4 = 14/22/12/4/1;UMEC/VI 26, GLY/IND 27). PGR, mMRC, and CAT improved in 20 (38%), 9 (17%), and 15 patients (28%), respectively. Respiratory system resistance at 5 Hz (R5), 20 Hz (R20), and the difference between R5 and R20 (R5 - R20) significantly improved. In a follow-up of 16 patients after switching from TIO/OLO to UMEC/VI (9) or GLY/IND (7), PGR, mMRC, and CAT improved in 5 (31%), 3 (12%), and 4 patients (25%), respectively, and R20 significantly improved (p = 0.011). Conclusions: Switching dual bronchodilators between dry powder and soft mist inhalers improves symptoms and airway narrowing in some COPD patients.
文摘The design of a general simulation package for AC drive system with soft switching inverter is discussed in this paper. This package is based on the secondary developing of the nonlinear control system simulation language SIMNON. Being constructed with modularization programming, the package can be used for general purposes conveuieutly and has strong graphic functions. The design principle for this simulation package is discussed in datail in this peper; and an application example (DSC controlled AC drive system with RDCLI) as well as its simulation results are given.
基金Sponsored by the Power Electronics Science and Education Development Program of Delta Environmental & Educational Foundation ( Grant No.DREO2006010).
文摘This paper proposes a novel implementation strategy for soft switching PFC whose circuit is simple and can achieve low voltage output directly. The main circuit adopts current mode full-bridge converter and all the power switches can realize ZCS or ZVS in the way of phase-shifted control, using the leakage inductance of the transformer, the junction capacitor of the switches and the stored energy of the output capacitor. The problems such as the function of phase-shifted link in control circuit, the implementation conditions of soft switching and bias restrained are analyzed. The adoption of constant frequency PWM control makes the design of the input and output filter link and the high frequency transformer simple. The transformation ratio regulation so as to achieve low voltage output and electrical insulation can be realized by using high frequency transformer.
基金the National Natural Science Foundation of China (No. 90707002)the Natural Science Foundation of Zheji-ang Province, China (No. Z104441)
文摘This paper presents a multi-mode control scheme for a soft-switched flyback converter to achieve high efficiency and excellent load regulation over the entire load range. At heavy load, critical conduction mode with valley switching (CCMVS) is employed to realize soft switching so as to reduce turn-on loss of power switch as well as conducted electromagnetic interference (EMI). At light load, the converter operates in discontinuous conduction mode (DCM) with valley switching and adaptive off-time control (AOT) to limit the switching frequency range and maintain load regulation. At extremely light load or in standby mode, burst mode operation is adopted to provide low power consumption through reducing both switching frequency and static power dissipation of the controller. The multi-mode control is implemented by an oscillator whose pulse duration is adjusted by output feedback. An accurate valley switching control circuit guarantees the minimum turn-on voltage drop of power switch. The pro-totype of the controller IC was fabricated in a 1.5-μm BiCMOS process and applied to a 310 V/20 V, 90 W flyback DC/DC converter circuitry. Experimental results showed that all expected functions were realized successfully. The flyback converter achieved a high efficiency of over 80% from full load down to 2.5 W, with the maximum reaching 88.8%, while the total power consumption in standby mode was about 300 mW.
文摘The full-bridge zero-voltage and zero-current switching inverter, which can adjust the output power by keeping the duty-cycle of lagging arm constant, changing the duty-cycle of leading arm, is a common circuit topology of soft-switching inverter arc welding power supplies. However, the output power still remains a certain value when the duty-cycle of leading arm decreases to zero. The working-mode of soft-switching inverter and the waveforms of major parameters with the condition of duty-cycle of leading arm being zero are studied in this paper. U-1 characteristic experiments prove that the minimum output power of soft-switching circuit, which depends on the charged voltage of capacitors in parallel with leading arm, can be decreased by reducing the duty-cycle of lagging arm. By switching working-modes between half-bridge and full-bridge, the output power can swing from zero to the power rating.
文摘The soft switching are welding inverter reduces switching losses and improves operating environment of devices by using Zero-Voltage-Transition (ZVT) technique. Step-by-step analysis of each timing interval and the associating voltage and current waveforms are included for the Full-Bridge Zero-Voltage-Switched PWM converter. Numerous design equations supporting the phase-shifted soft switching technique are highlighted.
文摘Full bridge Zero Voltage Switch PWM converter combines advantages of the PWM control technique and resonant technique. However, Full ZVS is achieved only under large load current because resonant tank of this circuit is made up of the parasitic capacitance of the power semiconductors and the leakage inductor of the transformer primary. In this paper two saturable inductors as magnetic switches are added to secondary, so output inductor is always reflected to primary and assists resonant transition. Full ZVS is achieved under lower load current. The above mentioned investigated results are validated by the computerized simulation and hardware circuit experiment.
文摘The full bridge zero voltage zero current switching ( FB-ZVZCS ) , which could adjust the output power by keeping the duty ratio of lagging leg constant and changing the duty ratio of leading leg, was a common circuit of soft switching arc welding inverter power source. However, when the duty ratio of leading leg was reduced to zero, the output power stayed the constant value instead of becoming zero. The working status and waveforms of some major parameters were studied in this paper while the duty ratio of leading leg was zero. It was concluded that the minimum output power of soft switching inverter was related to the charging voltage of paraUel capacitors, and the output power also could be reduced by reducing the duty ratio of lagging leg. A novel two-stage continuous PWM control method that could switch working-mode between full bridge and half bridge was put forward in this paper. This kind of control method could further reduce the output power of soft switching inverter in order to meet the requirement of low heat input of sheet metal welding.
文摘The systematic mathematical analysis of the high frequency soft-switched AC-AC converter is proposed for variable frequency induction machine load in this paper. Both PWM and square-wave modes of operation have been considered. The frequency relation and phase unbalance problem due to discrete time integral half-cycle switching has been discussed in the beginning. Then, generalized Fourier series have been derived for output voltage, output current and supply current in two modes.The analytical results help to understand tbe converter characteristics, design optimally a convertermachine system of arbitrary capacity considering the various trade-off parameters.
基金Sponsored by the Scientific Research Foundaltion fbr the Returned Overseas Chinese Scholars,Ministry of Education
文摘Soft-switching techniques are attractive to unity-power-factor AC/DC converter in the view of the size reduction and EMI suppression. A soft-switched boost PFC converter has been studied based on its topology analysis, PSIM simulation and circuit experiment. A special limitation of soft-switching techniques has been found in their AC/DC applications.