Yasuto Watanabe

High power density DC/DC converter using the close-coupled inductors

Among the specifications of eco-friendly electric vehicles, some will incorporate voltage converters in their systems to make full use of their power sources. The DC-DC converter using coupled inductors is known as one of converter types that may achieve higher power density. This paper focused on this circuit type especially using close-coupled inductors. Following, the elucidation of design guidelines for the close-coupled inductors theoretically, the superiority of the circuit in terms of reducing the size and losses in the magnetic components was demonstrated clearly through comparison with coupled inductors with looser coupling used in interleaved boost circuits and an inductor of boost chopper circuits. Finally, test results for a prototype of the proposed converter achieved a maximum power density of 24.7 kW/liter and a maximum efficiency of 98.4 % on an output of 42 kW (a maximum input current of 233 A) for a time rating of a few minutes.

High power DC/DC converter using extreme close-coupled inductors aimed for electric vehicles

The DC-DC converter using coupled inductors is known as one of the topologies that achieve higher power density. This paper focused on this topology especially using extreme close-coupled inductors (ECCI). Following the elucidation of design guidelines for the coupled inductor theoretically, the superiority of the interleaved converter using ECCI in terms of reducing the size and losses in the magnetic components is demonstrated clearly through comparison with an interleaved converter using a set of looser-coupled inductors and a conventional single inductor converter. The effect of increasing a magnetic coupling factor of a set of coupled inductors from 0.980 to 0.999 is investigated by comparing it with other inductors of interleaved converters. The high power prototype converter with the coupling factor of 0.999 provides excellent performance with a time rating power density of 25.6 kW/liter.

High power density interleaved DC/DC converter using a 3-phase integrated close-coupled inductor set aimed for electric vehicles

Among eco-friendly electric vehicles, some incorporate DC/DC converters in their electrical drive systems to make full use of their power sources. For increasing the power density of the converters, a 3-phase interleaved converter using an inductor set of inductors and close-coupled inductors is investigated. The inductor set of a 3-phase topology is shown to be smaller in size and lose less power in comparison to that of a 2-phase topology while meeting the required specifications for high powered electric vehicles having a 200∼400 volt battery. The 3-phase converter using the inductor set was designed on the condition of using IGBT with a switching frequency of 15 kHz. It achieved a high power density of 21.4 kW/liter at 120 kW output on a boost ratio of 1.38 with 98.0% efficiency and it achieved an efficiency of more than 97% in a frequent usage zone with low temperature rise.

High power density 3-level converter with switched capacitors aimed for HEV

The 3-level circuit topology is a suitable option for increasing power density of DC/DC converters. The advantage is theoretically investigated in comparison with an interleaved topology using a set of coupled inductors. The prototype achieved a high power density of 26.8 kW/liter at 60 kW output with 97.5% efficiency.