Akihiko Kanouda

Thin type DC/DC converter using a coreless wire transformer

A 10 W class thin type DC/DC power converter is developed which uses a new type of coreless wire transformer. The power converter is intended for portable equipment use. The coupling factor of the wire transformer is more than 95% at frequencies higher than 100 kHz. When applied in a 3 output DC/DC power converter, the power converter is only 5.5 mm thick and has 70% efficiency.<<ETX>>

Stable startup of seamless controlled parallel bidirectional DC-DC converter

A smart control method for Bidirectional DC-DC Converter has been developed. Both charge and discharge with buck / boost mode transition are achieved by common control structure without mode judgment. This simple structure is also extended to a parallel system, and controls multiple output power for both directions. The function has some exceptional case at the period of start-up and stop, because introduced complementary switching flows unexpected reverse current. To avoid the unexpected reverse current, we introduced the selective disable function of complementary switching and achieved stable start and stop control. This improvement also equipped the system additional charge only operation. Improved control structure was evaluated at the four-parallel converter system.

A novel bridgeless PFC boost rectifier with a simple ZVS circuit

A power-factor-correction (PFC) rectifier using a novel circuit topology and its control method was developed and tested. To reduce both conduction and switching losses, the proposed circuit is based on a bridgeless PFC boost rectifier with a zero-voltage-switching (ZVS) function. To achieve ZVS, the proposed circuit topology employs a simple auxiliary circuit consisting of one MOSFET, one inductor, and one capacitor. The auxiliary MOSFET is simply driven alternately with the main MOSFETs. The results of testing demonstrated that all three switching devices can be switched under ZVS. A 1-kW prototype rectifier attained an input power factor of 99%. Moreover, at switching frequency of 100 kHz, the proposed prototype reduced loss by 16% compared to a conventional-bridgeless prototype.

Seamless controlled parallel bi-directional DC-DC converter for energy storage system

A scalable parallel bidirectional DC-DC converter system, which enables efficient seamless control using an H-bridge topology, was developed and evaluated. Although the unified control structure is simple, four drive-mode, both charge and discharge with buck/boost, can be handled. The proposed system was extended for use in simple parallel converter management. This scheme achieves high efficiency over a wide load range, especially for light loads. The only hardware required is a power line and communication cable connection. All other functions are provided by software and operate autonomously. A 5-kW prototype converter was constructed and evaluated, and a four-unit parallel converter system was tested and confirmed to work well, changing load between 20-kW discharge and 20-kW charge.

Development of Direct Methanol Fuel Cell Charger Using Electric Double Layer Capacitor

A pulse charge control system is presented in this paper for use as a new charger system. It is a hybrid system of the Direct Methanol Fuel Cell (DMFC) and Electric Double Layer Capacitor (EDLC). It is smaller than the maximum output design. A jump up voltage protection method and an energy increase control method are presented for the advanced pulse charge control. The experimental results when using the energy increase control method are presented to prove the performance of the output power.

Expectations of next-generation power devices for home and consumer appliances

This paper describes expected effects and characteristics required for next-generation power devices to be used in home appliances and consumer electronics. This paper focuses on the challenges presented by the IH cooking heater, energy storage systems, and solar power generation system and presents the circuits that will solve these challenges. Also, requirements for power devices used for the circuits are specified. The authors also show the effect of reducing the recovery loss when a SiC diode is applied to the boost converter. Moreover, the efficiency characteristics are compared for using the SJ-MOSFET and IGBT in the boost converter. The experimental results revealed that SJ-MOSFET improves the efficiency by 0.3 percentage point more than the IGBT. By using the SiC diode and SJ-MOSFET, efficiency of the boost converter is 98.7 % at rating 5.7 kW and output DC 380 V.