Kazuhiro Umetani

Characteristics analysis and performance evaluation for interleaved boost converter with integrated winding coupled inductor

The integrated magnetic component for interleaved converters has been developed in order to satisfy the demand for high power density of converters. The close-coupled inductor method and the loosely coupled inductor method are well known as techniques that can achieve downsizing of magnetic components. As another approach, the integrated winding coupled inductor has already been proposed. However, the advantages of interleaved converter with the integrated winding coupled inductor have yet to be elucidated fully as compared with the other methods. Therefore, characteristics of inductor ripple current and magnetic flux in the core for the integrated winding coupled inductor are analyzed and evaluated in this paper. As a result of the analysis, integrated winding coupled inductor method provides three attractive features as compared with loosely coupled inductor. The effectiveness of the integrated winding coupled inductor is discussed from theoretical and experimental point of view.

Evaluation of the Lagrangian Method for Deriving Equivalent Circuits of Integrated Magnetic Components: A Case Study Using the Integrated Winding Coupled Inductor

Recently, Lagrangian dynamics have been applied to transforming integrated magnetic components into equivalent circuits of transformers and inductors. This Lagrangian method is expected to yield an equivalent circuit with few components, when applied to an integrated magnetic component with few flux paths that can be magnetized independently. However, properness of this method has not been verified. As a case study, this paper derives the equivalent circuit of the integrated winding coupled inductor using the Lagrangian method to evaluate consistency with the magnetic circuit model and experimental behavior. As a result, the Lagrangian method yielded a simpler equivalent circuit than those by the conventional methods. Additionally, the equivalent circuit of the Lagrangian method is found to be functionally equivalent to the magnetic circuit model and consistent with the experiment. These results support that the Lagrangian method provides proper equivalent circuits and is useful for deriving simple equivalent circuits in some cases.

Analysis of coupled-inductor configuration for an interleaved high step-up converter

High step-up converters are widely used in sustainable energy systems and recently used in automotive applications due to their high voltage gain capability. Nevertheless, with the purpose of obtaining a higher voltage gain, in comparison with conventional boost converters, current high step-up converters often employ additional multiplier cells, which may lead to significant cost-up and low power density. Therefore, a novel two-phase interleaved high step-up converter is proposed in order to minimize additional circuit volume used to achieve large voltage gain. The proposed converter addresses the purpose by a particular coupled inductor where three windings are installed in one or two cores. As a result, the proposed converter can achieve higher voltage gain than the conventional topologies by adding a winding and two diodes to the interleaved two phase boost chopper, besides the coupled-inductor configuration. This paper evaluates two arrangements of the coupled-inductor configuration of the proposed high step-up converter: 1. Three windings integrated in only one core and 2. Two independent inductors with a shared winding. The result revealed that the proposed converter shows higher voltage gain than the normal boost converter and the magnetic integration in the coupled-inductor configuration further increases the voltage gain by 20%.

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.

Evaluation of the Lagrangian method for deriving equivalent circuits of integrated magnetic components: A case study using the integrated winding coupled inductor

Recently Lagrangian dynamics has been applied to transforming integrated magnetic components into equivalent circuits of basic magnetic components such as transformers and inductors. Although the method is beneficial in simple and systematic derivation in many cases, it sometimes leads to different circuits from those by conventional methods. Hence, the Lagrangian method needs equivalence evaluation of transformation. As a case study, this paper derives equivalent circuits of the integrated winding coupled inductor using the Lagrangian method and a conventional method. The equivalent circuits are investigated to verify their consistency with magnetic circuit model and experimental behavior. As a result, the Lagrangian method yields a simpler circuit than that by the conventional method. Nonetheless, both circuits are found functionally equivalent to the magnetic circuit model and consistent with the experiment. The result suggests that the Lagrangian method provides proper transformation and is useful for deriving simple equivalent circuits.

Straightforward Measurement Method of Common Source Inductance for Fast Switching Semiconductor Devices Mounted on Board

Recent progress of widebandgap semiconductor switching devices enabled extremely high-frequency operation of power converters owing to their ultrafast switching capability. Fast switching may cause large switching noise at the common source inductance, which may increase the switching loss and lead to false triggering. Therefore, measurement of the common source inductance is often intensely required in practical design of fast switching power converters. However, measurement of the common source inductance is difficult, because 1) the wiring path hidden beneath the molded package significantly contributes to this inductance, 2) the mutual inductance between the gating circuit and the power circuit also contributes to this inductance, and 3) this inductance cannot be defined as the stray inductance of a loop wiring path. These difficulties are addressed in this paper by proposing a novel measurement method of the common source inductance. The proposed method is applicable to already-mounted power circuits. In addition, the proposed method offers a straightforward measurement procedure with common instruments, such as a signal generator, an oscilloscope, and voltage and current probes. Along with the measurement principle, this paper also presents an experiment to evaluate the proposed method.

High Step-Up Interleaved Converter for Renewable Energy and Automotive Applications

High step-up DC-DC converters are widely used in many industrial appliances and recently introduced in renewable energy systems and automotive applications due to their high voltage gain capability. Nevertheless, current high step-up converters often employ additional circuitry with the purpose of increasing the voltage gain. Consequently, the converter will be bulky, heavy and expensive, because the use of these additional passive and active components influences the power density and the cost of the whole application. Therefore, the well-known techniques of interleaving phases and magnetic coupling are applied in a novel high step-up converter with the purpose of helping tackle these problems. Using these techniques, high voltage gain and reduction of circuit elements can be achieved. In this paper, the operating principle of this converter is summarized and the voltage gain is analyzed. Moreover, the analyzed topology is compared with several outstanding high step-up converters recently proposed that use the concept of interleaving phases and magnetic coupling. Finally, the analyzed converter was experimentally tested and the effectiveness in terms of higher voltage gain and number of components than the current topologies is validated.

A novel high step-down interleaved converter with coupled inductor

Nowadays, high power density has become essential in networking, telecommunications and computing applications. Additionally, the electronic equipment used in these applications requires a very-low voltage feeding even when its power supply has a much higher voltage rating. Therefore, high step-down converters with high power density performance are required for these applications. Consequently, a novel two-phase interleaved high step-down converter is proposed in order to fulfill the requirements of high power density and high step-down conversion ratio of these applications. The proposed converter addresses the objective by a particular coupled inductor where three windings are only installed in one core. As a result, the proposed converter can achieve higher step-down ratio than the conventional topologies by adding a winding and two switches to the interleaved two phase buck converter, besides the coupled-inductor configuration. In this paper, the novel topology is introduced and analyzed in order to find its conversion ratio operation. Then, the proposed topology is compared to conventional topologies and some improved high step-down converters recently proposed. Finally, the proposed converter is experimentally validated and the results revealed that the proposed converter shows higher step-down conversion ratio than the conventional buck converter with a further increment of 40% in the conversion ratio when the converter is operating at a duty cycle of 30% and ratio of turns of 2.

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.

Novel magnetic structure of integrated differential-mode and common-mode inductors to suppress DC saturation

Integrating differential-mode (DM) and common-mode (CM) inductors onto a single core has been expected to miniaturize EMI filters. However, the previously-reported magnetic structure often suffers from saturation by DC current, hindering miniaturization by integration. This problem seems exacerbated by the fact that this conventional structure tends to induce large DC flux because its equivalent number of turns for the DM inductance is restricted to only half of the total number of turns. This paper addresses the problem by proposing a novel structure that assigns more turns to the DM inductance to suppress the DC flux more effectively. This paper confirmed theoretically and experimentally that the proposed structure is equivalent to series-connected DM and CM inductors. Additionally, analytical estimation revealed that the proposed structure reduced core volume by 41% compared to the conventional structure under the same amount of copper. These results suggest effectiveness of the proposed structure for miniaturizing EMI filters.