Kazuki Iwaya

High efficiency, low harmonic distortion switching type power amplifier using multilevel inverter

This paper proposes a novel ideas of 10 kW 200 kHz power amplifier using the switching technology of Multilevel inverter by compensating dead time. Its amplifier is composed of multiplexing 3 level inverter with interphase reactors. It has 81 switching patterns for 9 level of output voltage and two switching control modes in this proposed multilevel inverter. By employing this control method, the switching frequency can be reduced by about 1/8 of 200 kHz carrier frequency and the circulating current can be reduce within 1 ampere. The efficiency of this system is 95.6% at 4 kW and the THD is under 2% at 5 kHz output frequency with open loop control. Further, by applying the dead time compensation, and the carrier frequency is made to increasing at 400 kHz and realized 200 kHz frequency characteristic. This paper also presents the methods to improve frequency characteristics and distortion for arbitrary output waveforms of the system.

Comparing investigation for a bi-directional isolated DC/DC converter using series voltage compensation

This paper discusses a bi-directional isolated DC/DC converter using series compensation method. The proposed converter consists of a high efficiency resonance full-bridge converter and a series converter. This proposed circuit regulates the output voltage by the series converter, which provides only the differential voltage between the input voltage and the output voltage, which is closed to the nominal voltage. In this paper, four types of the auxiliary circuits are investigated in term of loss. The relationship between the loss element and efficiency characteristics is clarified. The validity of the proposed circuit is confirmed by the loss calculation, with a maximum efficiency of over 94% at 2kW. Moreover, the experimental results confirmed that the proposed circuit, which converts 48-V to 380-V at 1kW, achieves the maximum efficiency of 93.0% at the nominal input voltage region.

Experimental investigation and loss calculation for a bi-directional isolated DC/DC converter using series voltage compensation

This paper discusses for a bi-directional isolated DC/DC converter using series voltage compensation. The proposed converter consists of a high efficiency resonance full-bridge converter and a series converter. The proposed circuit regulates the output voltage by using the series converter, which provides only the differential voltage between the input voltage and the output voltage that is closed to the nominal voltage, since only the resonance converter will operate. In this paper, four types of the auxiliary circuits are investigated using the loss calculation. The relationship between the loss element and efficiency characteristics is clarified. The validity of the proposed circuit was confirmed by experimental results, which converts 48-V to 380-V at 1kW, with a maximum efficiency of 95% at 1 kW at the nominal input voltage region.