The power factor correction techniques have received great attention. A discontinuous conduction mode (DCM) converter eliminates the complicated circuit control requirement, reduces the number of components, and reduces the filter reactive components size. The disadvantage of the DCM converter is to increase the voltage and current stresses of the switching devices because the device must be switched off at a maximum inductor current.
The buck-type PFC-DCM converter has several advantages such as a restriction of rush current, easy protection of short circuit and low rating voltage of devices. In general, the output do voltage of the buck-type PFC-DCM converter is limited up to one tenth of the input ac voltage because of a distortion of the input current waveform at higher output do voltage.
A new soft-switching buck-type PFC-DCM converter is proposed. The proposed circuit is able to achieve the zero voltage switching (ZVS) at the maximum current. Therefore, the new soft-switching buck-type PFC-DCM converter decreases the voltage and current stresses of the switching devices. In this circuit, resonant capacitor, which is used for soft-switching operation, is utilized for the improvement of an input current waveform.

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In recent years, the harmonics and EMI noise sent out from an electric power conversion system are getting a great deal of attention in electromagnetic environment problems. The considerations of this problem have been getting important by recent significant improvement of auto-arc-suppressing device and switching speed. Therefore, there is need to do a detail frequency analysis such as transient phenomena. So, we have proposed the analytic technique using Wavelet-transform which is possible to catch a phenomenoni from the both sides of the time and the frequency. In this paper, we analysed the actual measured data in the switching interval by using Wavelet-transform. Then, based on obtained result, we describe the validity of Wavelet-transform and the application to the power electronics field.

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This paper shows a result which evaluated a half-bridge converter for the purpose of the improvement in power factor and efficiency about an X-ray high-voltage generator. By making the inverter input voltage higher by the boosting function of the converter, the current flowing through the IGBTs of the inverter can be reduced. Thereby, the current rating of the device can be reduced. Moreover, boosting inverter input voltage can make the turn ratio of the high-voltage transformer smaller, which leads to reduction in stray load loss originated from leakage magnetic flux and in copper loss.

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This paper proposes a novel high performance vector control system of a synchronous motor using a low switching frequency PWM inverter with an output L-C filter. An excellent high speed response characteristics of the L-C filter output voltage has been realized using a novel Deadbeat control algorithm.

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In a Non-Contact Energy Transfer System which supplies continuous energy to movers by electromagnetic induction, the efficiency is low owing to low excitation impedance because of the wide air gap of the magnetic core in the pick-up coil. The excitation impedance can be increased by the resonance with a capacitor connected parallel to the pick-up coil. The resonant pick-up coil works as a high frequency constant current source for the load.
In this paper, are measured efficiencies of the experimental system and calculated ones of the equivalent circuit are described.

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In this paper, practical design considerations for the novel prototype of the high frequency transformer link full-bridge type soft-switching phase-shift PWM controlled DC-DC power converter with ZVS and ZCS bridge legs using tapped inductor filter are presented. The proposed tapped inductor filter assisted phase-shift PWM DC-DC converter can achieve constant frequency soft-switching operation under conditions of the wide load range and input voltage variations and to minimize circulating current, which occurs due to presence of the leakage inductance of the high frequency transformer. The optimum practical design of the tapped inductor turns ratio is significant to effectively reduce circulating current and achieve high efficiency of the DC-DC power conversion under 100kHz high frequency operation. The 1kW-100kHz with 36V input DC source and 100V output side breadboard circuit using the power MOSFETS is built and tested. The actual efficiency 97% is obtained at maximum.

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This paper presents a novel system topology of high efficiency single-phase sinewave inverter, which is composed of partial sinewave boost chopper circuit in the first power processing stage and partial sinewave full-bridge inverter in the second power processing stage operated by sinewave modulated time-sharing control scheme. Its unique operating principle of two stage power processing stage with dual mode time-sharing sinewave modulation scheme is basically described and evaluated on the basis of the computer simulation and experimental considerations.

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We have considered a voltage-source type series-resonant ZCS-PFM DC-DC Converter in order to drive an industrial-use magnetron for generating high power microwave in advance. This DC-DC converter can achieve a complete zero current soft switching by assist of the transformer parasitic parameter and a lossless inductive snubber. And the output power is regulated over all power ranges without audible frequency range due to the magnetizing current of the high-frequency transformer. However, this DC-DC converter has a weak point that it is easy to oscillate by the parasitic capacitance of the switching device and the lossless inductive snubber. Therefore in this paper, the new topology that can solve that weak point without hurting good characteristics of that converter is proposed and evaluated on the basis of simulation and experimental results.

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This paper presents two novel prototypes of the utility AC power source connected sinewave inverter using the high-frequency two-switch flyback transformer which is more suitable and acceptable for the small-scale solar photovoltaic and fuel cell generator interfaced power conditioners. The proposed sinewave soft-switching PWM power conditioner with a high-frequency AC link has a function of electrical isolation including sinewave hard-switching PWM power conditioner with a high frequency link, which is considered for solar photovoltaic power conditioner and fuel cell generator related power conditioner from the viewpoints of safety and reliability in total system. The discontinuous conduction mode (DCM) operation of the flyback transformer in this circuit system is also introduced to feature a simple, low-cost and high-efficiency topology of the sinewave inverter circuit and digital control implementation. The operating principle of the proposed sinewave soft-switching PWM inverter circuit as compared with sinewave hard-switching PWM inverter are described for the designing of circuit parameters. Moreover, the digitally controlled sinewave PWM control processing scheme is presented herein. Finally, the sinewave soft-switching PWM inverter prototype is actually built and tested to verify the validity of the proposed power conditioner for new energy generation systems.

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Recently, the generating electricity used clean energy source attracts attention and various research have been investigated. Electric power is taken out effectively in the photovoltaic power generator, and it is research on the control of inverter to use it as an a. c power source. The inverter is controlled by MPPT control when it applied to the resistance as the load. The voltage amplification circuit is necessary in order to compose this system and the experiment result, is presented in this paper.

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[in Japanese]

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