Masanori Ishigaki

A new isolated multi-port converter using interleaving and magnetic coupling inductor technologies

This paper proposes a new multi-port converter with interleaved magnetic coupling technologies. With the focus on the impedance behavior of coupled magnetic components and the control parameters, this multi-port converter integrates one isolated dc-dc converter and two multi-phase boost converters, and controls these topologies independently. The proposed converter has the capability to connect four dc applications or sources in total, and so brings significant cost reduction and improves the total loss consumption of power systems. In addition, magnetic isolation brings high reliability of complex power systems such as electric vehicles or grid-connected industries. In this paper, the basic circuit behavior is verified by theoretical considerations and experiments. An example of the proposed circuit as a multifunctional dc power system is demonstrated with the simulation results. Such an approach could bring about variable application fields to dc electric power systems.

Analysis and Design of a Multiport Converter Using a Magnetic Coupling Inductor Technique

A novel multiport dc-dc converter with a coupling magnetic inductor is analyzed and designed. The proposed circuit integrates two multiphase converters and one isolated dc-dc converter. These converters can be controlled independently in one circuit by adjusting the duty ratio and phase angle difference. There are four dc ports in the circuit, and the dc power can be delivered multidirectionally among the four dc ports. In this paper, a 1.5-kW prototype of the multiport converter was constructed and successfully operated under full power. The experimental results confirm the theoretical analysis, and the conversion efficiency is above 90% over a wide range of output power. In addition, an example of a multifunctional power conversion system using the multiport converter is demonstrated.

Analysis and design of a multi-port converter using a magnetic coupling inductor technique

In the present paper, a novel multi-port converter with coupled magnetic components is analyzed and designed. The proposed circuit integrates two multi-phase converters and one isolated dc-dc converter. These converters can be controlled independently and simultaneously by duty cycle and phase-shift modulation, because the impedance behavior of magnetic components is different for each converter. A 1.5-kW prototype of the multi-port converter has been constructed and successfully operated under full power at a switching frequency of 40 kHz. The experimental waveforms confirm the theoretical analysis, and the conversion efficiency is above 90% over a wide range of output power. In addition, loss analysis is carried out in order to define the critical parts of the proposed converter.

Performance impact of luminescent coupling on monolithic 12-junction phototransducers for 12 V photonic power systems

A twelve-junction monolithically-integrated GaAs phototransducer device with >60% power conversion efficiency and >14 V open-circuit voltage under monochromatic illumination is presented. Drift-diffusion based simulations including a luminescent coupled generation term are used to study photon recycling and luminescent coupling between each junction. We find that luminescent coupling effectively redistributes any excess generated photocurrent between all junctions leading to reduced wavelength sensitivity. This broadened response is consistent with experimental measurements of devices with high-quality materials exhibiting long carrier lifetimes. Photon recycling is also found to significantly improve the voltage of all junctions, in contrast to multi-junction solar cells which utilize junctions of differing bandgaps and where high-bandgap junctions benefit less from photon recycling.

Loss estimation of an isolated three-port DC-DC converter for automotive applications

A three-port DC/DC converter (TPC) having DC48V and DC12V ports, and an isolated DC port is designed and analyzed. The newly designed TPC integrates a non-isolated bi-directional DC-DC (NBC) converter and an isolated dual-active-bridge (DAB) converter using a coupling inductor technique, and DC power can be delivered multi-directionally among three DC ports. In the present study, a loss estimation method for the TPC is developed in order to analyze losses in all load conditions. A 750 W, 125 kHz prototype using a Si MOSFET is constructed in order to confirm the accuracy of the newly developed estimation method. The measured efficiency is over 90% for a wide range of load conditions, and the calculated efficiency curves correspond well with the measured efficiencies. In addition, the improvement in efficiency provided by using a GaN FET is also discussed. The efficiency is expected to increase 2% by replacing the Si MOSFET with a GaN FET. Finally, a prototype using a GaN FET is constructed in order to verify the above estimation.

Design of Anisotropic Thermal Conductivity in Multilayer Printed Circuit Boards

The design of anisotropic thermal conductivity in multilayer printed circuit boards (PCB) is studied, where the flow of heat is manipulated through the informed layout of circuit board electrothermal traces. Three representative circuit board configurations are considered to illustrate the basic method. A baseline circuit board (Configuration 1) comprising a heat-generating device in thermal communication with a heat sensitive device by the way of a standard electrical trace connection is studied first to characterize heat flow due to conduction and convection. Building off of this baseline structure, the thermal management advantages and disadvantages of a closed heat shield for anisotropic PCB thermal conductivity are explored using the second circuit board (Configuration 2). The design of the third multilayer circuit board (Configuration 3) with optimized anisotropic PCB thermal conductivity for enhanced heat flow control is simultaneously explored. It is experimentally shown that, for PCBs subject to free convection and power densities on the order of 1-10 W/cm2, the design technique allows for noticeable (-10 °C) reduction in the temperature of the heat sensitive device without a significant (<;3 °C) increase in the heat-generating device temperature. The experimental heat transfer results are verified through simulations that further confirm and explain the functionality and limitations of the heat flow control concept. The effect of Joule heating is also investigated numerically. A conceptual framework for electrothermal codesign of multilayer PCBs with integrated heat flow control and more device-dense packaging is proposed.

Mobility Analysis of Electric Autonomous Vehicle Networks Driven by Energy-Efficient Rerouting

Increasing demand for urban mobility has contributed to heavy traffic in metro areas, rising transportation costs and travel times. The concept of driverless centrally-controlled electric vehicles has been attracting attention for its potential of minimizing traffic congestion. This study is introducing the tools and methods needed for evaluating the benefits of the concept. An intelligent route planning algorithm, along with a traffic simulation environment, which is coupled to a vehicle performance model have been developed. An interactive graphical tool has been created to showcase the resulting benefits of the concept and to support the conceptual design of energy efficient electric vehicles for centralized large scale operations. The study has identified correlations between a driving environments traffic density and the potential of relieving the effects of congestion, with considerable travel time, energy and vehicle wear savings attainable.

A new optically-isolated power converter for 12 V gate drive power supplies applied to high voltage and high speed switching devices

We present a new design for an isolated power converter using optical power transducer (OPT) technology. The converter transmits optical power from a laser diode (LD) to a phototransducer (PT) across an air gap. The PT device consists of 12 GaAs pn junctions, each current-matched to achieve a record optical-to-electrical power conversion efficiency of ≥ 66% with an open-circuit voltage of 14.5 V. Using a LD with 840 nm wavelength, the OPT can output more than 3.2 W of electrical power with 25% electrical-to-optical-to-electrical conversion efficiency, a value twice as efficient as a similar OPT built using previous generation PT technology. This new prototype successfully provides the driving power to the gate driver for 75 kV/μs fast switching of a SiC-MOSFET, made possible by a low stray input-to-output capacitance of ≤ 1 pF. We measure a 70% reduction in conducted electromagnetic interference (EMI) compared to a conventional transformer-based isolated power supply.

Electrothermal Circuit Design With Heat Flow Control—Synchronous Buck Converter Case Study

Electrothermal design of a synchronous buck converter with heat flow control is presented. A commercial reference circuit design for a synchronous buck converter is selected for the study. A functional printed circuit board (PCB) of the converter is fabricated and tested to establish baseline performance. The baseline PCB layout is modified by incorporating a design of electrothermal traces from a heat flow control optimization study. Electrical plus thermal characteristics of each design are experimentally evaluated. It is found that the modified design manipulates the heat flow across the PCB. At low output current (<5 A) and under free convection, the circuit with electrothermal traces produces slightly lower switch and inductor temperatures, 1 °C–3 °C, and higher circuit efficiency (up to 7.4%). At higher power levels with free convection, the modified circuit exhibits slightly higher device temperatures and the same circuit efficiency as the baseline circuit. Adding a thermoelectric cooler to the system for active temperature control in combination with the electrothermal traces yields a 3 °C–5 °C device temperature reduction at 20-A output current. The unpopulated PCB inductance and populated board electrical impedance are measured separately for the modified circuit design. Higher inductance, modified electrical impedance, and reduced input current amplitude is observed due to a low-pass filter effect from the electrothermal traces. A discussion is provided regarding a range of future electrical and thermal research directions for circuit applications. The need for further integration of multiphysics codesign methodologies with the state-of-the-art analysis tools is explained.

28 W/cm 3 high power density three-port DC/DC converter cell for dual-voltage 12-V/48-V HEV subsystem

Realizing both of compact and low energy consumption is technical issue on development of electricity-rich automotive subsystems. In the present work, a 12-V/48-V dual-voltage subsystem using three-port DC/DC converter cells is proposed, and the high power density cell design is studied to achieve ultra-compact subsystem in hybrid-electric-vehicle. A 500 W, 400 kHz prototype is developed with GaN FETs, and its efficiencies are evaluated. The prototype achieves power density of 28 W/cm at rated power, and its efficiency is measured more than 91% over a wide output power range, with a maximum efficiency of 93.7%.