A power conversion device includes a power switching circuit that supplies AC voltages generated between switching elements operating as upper arms and switching elements operating as lower arms, and a control circuit that generates and supplies to the driver circuit signals for controlling the switching operation of the switching elements by a PWM method in a first operational region in which frequency of an AC power to be outputted is low, and that generates and supplies to the driver circuit signals for controlling the switching operation of the switching elements at timings based upon the phase of the AC power to be outputted in an operational region in which the frequency of the AC power to be outputted is higher than in the first operational region.

Power Conversion Device

EMI filters are widely used in power electronics converters to meet EMI standards. Since the common-mode inductor is often the largest single magnetic component, it must be optimized for size and cost. This paper investigates and presents datasheet and experimental comparisons of the magnetic materials aimed for a common-mode choke design. Several magnetic materials are considered: amorphous iron, nanocrystalline, ferrite and iron-nickel alloys. The material analysis compares and contrasts various effects, such as dimensional resonance, eddy current and core geometry. Finite element analysis is validated with experimental investigation of selected magnetic materials: ferrite and nanocrystalline.

Magnetic material selection for EMI filters

This article proposes a high-power density 1.8 kW auxiliary power module (APM) for electric vehicles (EVs) based on gallium nitride devices. A design procedure for the high-frequency phase-shift full-bridge with current-doubler rectifier using printed circuit board (PCB)-based planar magnetics is proposed. Leakage inductance analysis of the high-frequency pulsewidth-modulation converter is given to achieve both regulation and zero-voltage-switching turn- on . Then, the magnetics optimization procedure for the customized planar core is proposed with a magnetic figure-of-merit concept to meet the high-power density target. Technical considerations are detailed to meet the extreme temperature constraint imposed on the EVs components. Finally, the proposed APM is demonstrated with a switching frequency of 700 kHz and a power density of 8.1 kW/L (132.8 W/in3).

Power Density Optimization of 700 kHz GaN-Based Auxiliary Power Module for Electric Vehicles

PROBLEM TO BE SOLVED: To provide a power conversion device capable of continuing an operation of a load when power transmission between conversion circuits magnetically coupled with each other becomes difficult.SOLUTION: A power conversion device comprises: a first conversion circuit having a first input-output port to which a load is connected, and a second input-output port to which a first battery is connected; a second conversion circuit magnetically coupled with the first conversion circuit, and having a third input-output port to which a second battery different from the first battery is connected; and a controller performing first control of stepping down or stepping up a voltage of the third input-output port to a target voltage to supply a power from the second battery to the load and the first battery. The power conversion device has voltage determination means determining whether or not a voltage of the first input-output port is lower than a predetermined value of the target voltage or less. In a case where the voltage determination means determines that the voltage of the first input-output port is lower than the predetermined value during execution of the first control, the controller performs second control of supplying a power from the first battery to the load, in stead of the first control.

Power conversion device

A new partly isolated three-port converter is introduced in this study for hybrid energy applications. Two boost circuits form the main input port and a bidirectional battery port of the converter. Therefore, both of them are of a current-fed type, making the converter more suitable for renewable energy applications. In addition, the boost circuits are benefited from a mutual active clamp circuit. The circuit in cooperation with the leakage inductance of transformers provides soft switching, while employing a few number of semiconductors. Furthermore, on the secondary side, two voltage-doubler rectifiers are merged. As a result, the converter employs less number of components, which participate in all power conversion modes. Since most of the renewable energy sources have a relatively low voltage level, the converter retains high voltage gain. These features have resulted in an efficient and inexpensive converter. A thorough analysis has been made and justified by simulation and experimental results.

A New Soft-Switched Three-Port DC/DC Converter With High Voltage Gain and Reduced Number of Semiconductors for Hybrid Energy Applications

A highly accurate filter simulation requires a high precision SPICE model for the common mode choke. Conventional SPICE models for chokes consist of parallel RLC circuits and show a substantial difference between the measured and simulated impedance characteristics due to the lack of frequency-dependent complex permeability considerations. Here, we propose a novel SPICE model for a common mode choke that includes the frequency-dependent complex permeability. This model uses a transfer function in the s-domain to describe frequency-dependent elements. Moreover, two model parameter estimation methods are proposed; a measurement based method and a datasheet based method. High accuracy is achieved with the measurement based model by extracting the model parameter using the measured impedance characteristics of the actual coil. In the datasheet based method, the model parameter is estimated from the datasheet and the shape of the coil without the actual coil. Finally, we show that not only the impedance characteristics of a choke can be expressed, but also the insertion loss of a T-type filter can be predicted much more accurately than presently possible using a conventional model. This SPICE model is the first to express the frequency-dependent inductance and resistance of the choke with high accuracy; therefore, it is expected to be useful for filter design.

Novel SPICE model for common mode choke including complex permeability

The present invention provides a power conversion circuit system in which a circulating current can be reduced by accurately detecting the circulating current, to thereby improve efficiency in power conversion. The power conversion circuit system includes a power conversion circuit composed of a primary conversion circuit having left and right arms and a secondary conversion circuit having left and right arms, and a control circuit for controlling switching of switching transistors in the primary and secondary conversion circuits. The control circuit detects the circulating current at at least one of timings lagged by π/2+φ/2 from at least either a peak timing or a valley timing in a carrier counter where φ represents a difference in phase between the primary and secondary conversion circuits, and performs feedback control for reducing the detected circulating current to zero.

Power conversion circuit system

This article aims to realize an isolated dc–dc converter with high power density, high power efficiency, and low noise performance. Although a dual-active-half-bridge (DAHB) converter can achieve high efficiency, it requires input and output low-pass filters to suppress the operational ripple current and switching noise. Owing to the volume of the filters, a DAHB converter cannot be implemented with high power density. This article presents a design theory for a novel isolated bidirectional dc–dc converter with built-in filters. The proposed converter is derived from a DAHB converter and can eliminate the input and output filters via split windings and tank capacitors; the principle of elimination is based on $LC$ low-pass filter function and zero-ripple-current operation. As the number of transistors, capacitors, and magnetic cores of the proposed converter are equal to those of the DAHB converter, the application of the proposed converter allows volume reduction by eliminating the filter components at the input and output ports. Theoretical equations are derived to design a power flow control function and a filter function simultaneously. Finally, prototypes of a DAHB converter and the proposed converter are constructed for comparison. The results demonstrate that the input port noise of the proposed prototype is lower than that of the DAHB prototype by 10 dB (peak) over 1 MHz, and the proposed approach can achieve a significant improvement in efficiency.

Design of an Isolated Bidirectional DC–DC Converter With Built-in Filters for High Power Density

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.

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

An electric power conversion circuit system for reducing core loss in a transformer particularly during light loading and improving conversion efficiency during light loading comprising an electric power conversion circuit composed of a primary side conversion circuit having a left arm and a right arm and a secondary side conversion circuit having a left arm and a right arm, and a control circuit for controlling switching of switching transistors of the first side conversion circuit and the secondary side conversion circuit. When the output voltage is at a relatively light load, the control circuit controls to change the duty of the transmitting side among the primary side conversion circuit and the secondary side conversion circuit and controls to change the half-bridge phase differences of the left arm and the right arm of the primary side conversion circuit and the secondary side conversion circuit, respectively.

Shuntaro Inoue

Papers

Novel SPICE model for common mode choke including complex permeability

Power conversion circuit system

Design of an Isolated Bidirectional DC–DC Converter With Built-in Filters for High Power Density

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

Electric power conversion circuit system