Shota Kimura

Downsizing Effects of Integrated Magnetic Components in High Power Density DC–DC Converters for EV and HEV Applications

The interleaved DC-DC converters with integrated magnetic components that achieve high power density have recently gained attention in automotive market for eco-friendly cars such as electric vehicles (EV) and hybrid electric vehicles (HEV). Interleaved converters with close-coupled inductors and loose-coupled inductors are well known as the converters capable to achieve high efficiency with low volume and weight. As a new approach, an interleaved converter with integrated winding coupled inductors is proposed. This paper proposes a novel inductor size calculation model. By using this model, the downsizing effects of the integrated magnetic components are discussed at 1 kW output. As a result, interleaved converter with integrated winding coupled inductors is effective for downsizing of the magnetic components with the condition that duty ratio is higher compared to interleaved converters with loose-coupled inductors and close-coupled inductors. In contrast, it is also found that interleaved converter with loose-coupled inductors achieves downsizing of the magnetic component when duty ratio is close to 50 %. The validity of the calculation model is estimated from the experimental viewpoints.

Volume comparison of DC-DC converters for electric vehicles

One of the main problems in autonomous electric vehicles is the volume of the electrical systems, because bulky components carry additional mass and high cost to the total system. Consequently, Interleaving phases and magnetic coupling techniques have been reported as effective methods for increasing the power density of the DC-DC converters that interface the storage unit with the electric motor. However, there are several converter topologies that use these techniques. Therefore, a volume assessment of these topologies is required in order to have a complete understanding when an electric power train is designed. In this paper, a volume modeling methodology is introduced with the purpose of comparing four different DC-DC converter topologies: Single-Phase Boost, Two-Phase Interleaved with non-coupled inductor, Loosely Coupled Inductor (LCI) and Integrated Winding Coupled Inductor (IWCI). This analysis considers the volume of magnetic components, power devices (conventional and next-generation), cooling devices and capacitors. As a result, interleaving phases and magnetic coupling techniques were validated as effective to downsize power converters. In particular, it was found that LCI and IWCI converters offer lower volume in comparison with other topologies.

Potential power analysis and evaluation for interleaved boost converter with close-coupled inductor

Interleaved boost converter with close-coupled inductor is widely employed in drive system for Hybrid Electric Vehicles (HEV) or in renewable energy system, in order to achieve high power density of the converters. For further high power density of magnetic components, this paper presents calculation method for potential power of the magnetic components in interleaved boost chopper circuit with close-coupled inductor. The calculation method for potential power of magnetic components is based on detailed analysis of the characteristic of inductor current and magnetic flux in the core. By applying the method, more easily, design of magnetic components in high power converters. As a result of analysis of potential power, CRM control scheme is effective for miniaturization of the magnetic components in case of interleaved boost converter with close-coupled inductor. Finally, potential power of the interleaved boost converter with close-coupled inductor is discussed from theoretical and experimental results. In this paper, “potential power” means allowable power of inductor.

High power density DC-DC converter for home energy management systems

Environmental issues related to global warming and resources dryness, increase the global concern for reducing the energy consumption using high efficiency and high power density systems. Therefore, home energy management systems (HEMS) deal with these problems by monitoring and controlling the power consumption of home electronics. However, expanding of human living space increases intense requirements to downsize electronic systems. In order to enhance HEMS and optimize the household living space, this paper shows the design and power loss analysis of a high power density DC-DC converter capable to achieve high efficiency with low weight and low volume components. This converter, developed for home electronics and electric vehicles, uses a novel magnetic coupling technique capable to reduce the size of magnetic components and of the converter itself. As a result, a 1 kW interleaved boost converter with integrated winding coupled inductors (IWCI) was designed and experimentally validated obtaining a volumetric power density of 145 cc/kW.

Allowable power analysis for high power density DC-DC converters using integrated magnetic components

The DC-DC converters using integrated magnetic components that may achieve high power density have gained attention in eco-friendly cars such as HEV and PHEV. Interleaved converters with close-coupled inductors and loose-coupled inductors are well known as the converters capable to achieve high efficiency with low volume and weight. As a new approach, an interleaved converter with integrated winding coupled inductors is proposed. This paper presents allowable power calculated method of these circuit topologies in order to realize further high power density. Following the design guidelines of allowable power calculated method for each coupled inductor, the downsizing effects of the magnetic components are compared to conventional interleaved boost converter in the same conditions from the allowable power viewpoints. As a result, CCM operation is effective for downsizing of the magnetic components in case of interleaved boost converter using loose-coupled and integrated winding coupled inductors. On the other hand, interleaved boost converter using close-coupled inductors is effective for downsizing of the magnetic components with CRM operation. This comparative data is discussed from theoretical and experimental viewpoints.

Inductor loss analysis of various materials in interleaved boost converters

High power density DC/DC converters have gained attention in automotive applications for Electric and Hybrid Vehicles. Inductors often appear as the largest component in DC/DC converters. DC/DC converters using a coupled inductor are well-known as one of the topologies which can achieve miniaturization of a magnetic component. Temperature of an inductor tends to be higher in high power density DC/DC converters. Thus, an optimal magnetic property selection is necessary for magnetic designs. In this paper, we have analyzed the relationship between inductor losses that affects the heat and inductor volume as the previous stage of the thermal analysis in the inductor. In addition, this paper presents analytical comparisons of various magnetic materials used in practical designs. This study is focused on interleaved boost converter of integrated winding coupled inductors, loose-coupled inductors and non-coupled inductors. The study is discussed from the view point of inductor losses and inductor volume.

Design method considering magnetic saturation issue of coupled inductor in interleaved CCM boost PFC converter

The demand of high power Continuous Conduction Mode (CCM) Power Factor Correction (PFC) converter installed in charging devices for Electric and Hybrid Vehicles has grown in the recent years. In these converters, the inductor often appears as the largest component, consequently, the CCM boost PFC converter using coupled inductors is well-known as one of the topologies that can achieve miniaturization and weight reduction of the inductors. However, the change of the magnetic flux during a half cycle of the input AC voltage has not yet been analyzed in detail. Therefore, the cause of the difference of the magnetic saturation is not known. In the case of non-coupled inductor, the magnetic saturation occurs at a point of the peak inductor current. In contrast, in the case of the coupled inductor, the magnetic saturation occurs at a different point than the inductor current peak. In this paper, the change of the magnetic flux in a half cycle of the input AC voltage is analyzed. Additionally, the novel design method of the coupled inductor considering the maximum magnetic flux is proposed. Finally, the validity of the novel design method is confirmed by experimental tests.

Feasible evaluations of coupled multilayer chip inductor for POL converter

Point of load (POL) converters are required smaller size and high efficiency performance in IT industrial applications, etc. Interleaved technique, magnetic integration techniques and application of GaNFETs are well known as good approaches to satisfy these demands. Although coupled inductors for POL converters have been proposed in several studies, a coupled multilayer chip inductor has not examined because of the difficulty of its construction. In this paper, a novel coupled multilayer chip inductor for interleaved POL converters is proposed. This novel coupled inductor has a winding pair with inversely coupled in the magnetic core. Further, magnetic material of the coupled inductor is Fe-based metal composite powder (Fe-Si-Cr). In addition, Fe-based powder in the magnetic core has been processed electrical insulation by highly crystallized oxide nano-layer in order to reduce eddy-current losses. Its high efficiency performance is evaluated by interleaved step down chopper circuit prototype using normally off typed GaNFETs with 1MHz switching frequency.

A novel three-phase LLC resonant converter with integrated magnetics for lower turn-off losses and higher power density

The aim of this work is to present a novel topology of a three-phase LLC converter with integrated magnetics. The converter operation and the comprehensive theoretical analysis are presented; this analysis follows the first harmonic approximation (FHA) approach to simplify the system model. Usually, LLC converter achieves zero voltage switching (ZVS) as long as it working in the inductive region. Therefore, the turn off losses are considered as the main source of the switching losses in the converter. In this paper the design in optimized to minimize the switching losses. On the other hand, adapting three discrete transformer cores in this topology will definitely increase the size and volume of the converter. As a result, a novel magnetic integration concept is introduced where all magnetic components of the three-phases are advantageously combined into a single magnetic core to increase the converter power density. Finally, the experimental results are presented to verify the optimized design by showing a reduction in the turn-off losses and the effectiveness of adapting the proposed integrated transformer, in which an increment of 56% in the power density of the converter could be attained.

Analysis and design of passive components for interleaved flyback converter with integrated transformer

Flyback switch mode power supplies have been widely used in low-power applications, such as DC/DC converters, solar micro-inverters and LED drivers. However, flyback converters have several problems related to the volume of the output capacitor as well as high output voltage noise; this is produced by the discontinuous output current. Consequently, interleaved operation with parallel connection on the secondary side can reduce the output current ripple compared with the single-phase flyback converter. Nevertheless, besides the output capacitor, the interleaved operation is unsuitable for transformers if it is desired to obtain light weight and compact performance. To address this problem, the interleaved flyback converter with integrated transformer has been proposed for achieving miniaturization of the output capacitor and transformers. There are mainly two types of the proposed flyback converter with integrated transformer: Parallel and Series types. These two types are categorized based on the connection on the primary side. Nevertheless, quantitative comparison of the volume and power loss has not been analyzed yet. Moreover, the design method of the integrated transformer also has not been conducted with clarity. Hence, in this paper, in order to provide a guide for the design of an interleaved flyback converter for achieving high power density, we analyze the quantitative volume and power losses of the integrated transformer and the input capacitor. Finally, this paper shows some experimental results that validate the appropriateness of the design method for the integrated transformer.