Satoshi Miyawaki

Optimization design of an isolated DC/DC converter using series compensation on the secondary side

This paper proposes a new circuit topology for a high efficiency isolated buck-boost DC/DC converter. The proposed converter consists of a high efficiency resonance half-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. Therefore, the circuit achieves high efficiency when the input voltage is closed to the nominal voltage, since only the resonance converter will operate. The equivalent circuit of the proposed circuit is mentioned to clarify the circuit operation and circuit design. The experimental results confirmed that the proposed circuit, which converts 48-V input to 12-V output, achieves the maximum efficiency of 94.0% at the nominal input voltage region. Besides, the loss analysis is performed to optimize the circuit parameters.

Loss evaluation of matrix converters using SiC-MOSFETs for flywheel energy storage systems

The paper proposes an energy storage system (ESS) with ultra long lifetime of over 20 years using matrix converters and FWs (Flywheels) to compensate frequency and voltage fluctuation of the power grid. The FWs in the system adopt the pivot bearing, which is one of the levitation bearing to avoid attrition of the FW bearings. The FWs provide maintenance-free for over 20 years. A matrix converter is used for the naturally-cooled to realize ultra long lifetime. Experimental results and loss analysis are given in order to demonstrate advantages of the proposed ESS.

Miniaturization of the boost-up type active buffer circuit in a single-phase inverter

This paper discusses miniaturization of a single-phase grid connected inverter, which has power decoupling function for PV. The power ripple of twice grid frequency is compensated in the proposed circuit with the small capacitor (50 μF) at 200 W. However, the buffer inductor in the proposed circuit becomes large because the buffer inductor current is fluctuated at twice grid frequency by power ripple compensation, and the switching ripple is large at the peak current. In this paper, in order to reduce the size of the buffer inductor, the buffer inductance is optimized in terms of the volume and efficiency according to the switching frequency. As an experimental result, it is confirmed that the input current ripple is reduced by 90 % in the proposed circuit, and the output current THD is 3.5 %. On the other hand, the buffer inductance is reduced by 73 % at 64 kHz of the switching frequency. In addition, the volume of the proposed circuit can be reduced by 37% in compared to the conventional circuit. Finally, from the evaluation of the power density using the Pareto front curve, the proposed circuit can design the high power density in compared to the conventional circuit.

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.

A high efficiency isolated DC/DC converter using series connection on secondary side

This paper proposes a new circuit topology for a high efficiency isolated buck-boost DC/DC converter. The proposed converter consists of a high efficiency resonance half-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. Therefore, the circuit achieves high efficiency when the input voltage is closed to the nominal input voltage, since only the resonance converter will operate. Experimental results are shown in order to demonstrate the advantages of the proposed converters in comparison with a conventional converter. The experimental results confirmed that the proposed circuit, which converts 48 V input to 12 V, achieves 94.0% maximum efficiency point at the nominal input voltage region.