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Power electronics converters operating at elevated temperature usually have degraded performance, such as reduced efficiency, lower noise immunity, and decreased system reliability, compared to those operating at room temperature. Nevertheless, harsh-environment applications, such as deep earth drilling, automotive, avionics, and space exploration, have been utilizing converters in high-temperature environments and are continuously pushing the temperature limits higher and higher with the advances in device technologies and converter design methodologies. This article starts with a literature study to identify the temperature dependence and the temperature limits of individual components. Then, published works about high-temperature converters are examined. Their selection of components is compared. Experimental results are analyzed to reflect on the efficacy of different component selections. Finally, since the latest published high-temperature converter was developed more than five years ago, a 1-kV input, 520-V output, 1-kW, $150$ °C-ambient-temperature-rated dc–dc converter is designed with state-of-the-art devices. Based on the literature review, and the test of the $150$ °C prototype, the main challenges of designing high-temperature power electronics converters are identified and concluded to be time-consuming, difficult, and expensive characterization of components, lack of accurate and computationally efficient models of converters, and optimizing component selection within short development time. [ABSTRACT FROM AUTHOR]

This article presents an analysis of the different loss modes of the switching devices in a class-D series resonant converter operating with either fixed dead time or fixed duty cycle. A feasible operating region where the FETs in the inverter stage only exhibit reverse conduction losses, with no hard-switching, is identified. Furthermore, the impact of using a fixed dead time versus a fixed duty cycle is investigated. We find that using a fixed dead time is superior to using a fixed duty cycle, as a broader operating range can be achieved for the same losses, or the same operating range can be achieved with lower losses. A reduction in the reverse conduction losses of up to 59% or an expansion of the operational frequency range by 33% when using a fixed dead time is found. The modeling approach is validated on a 1-MHz prototype employing GaN switching devices. Lastly, a design example shows how the presented analysis can be used to determine the optimal fixed dead time/duty cycle for use with frequency modulation control such that the losses are minimized. [ABSTRACT FROM AUTHOR]

Boundary conduction mode or critical conduction mode is characterized by an inductor current that operates in the boundary between continuous conduction modes (CCM) and discontinuous conduction modes, making the converter switching frequency dependent on the converter operating conditions. The advantage of this operation mode versus CCM is achieving zero current switching (ZCS) conditions for the converter rectifier, which makes it possible to use silicon diode rectifiers without having a penalty due to reverse recovery issues. Moreover, the main switch turn-on loss is decreased due to ZCS conditions and valley switching operation. However, the penalty is an increased current stress in the circuit and an increased main switch turn-off energy loss. Implementation of the synchronous rectifier in boundary conduction mode (BCM) converters makes it possible to achieve zero voltage switching (ZVS) conditions by extending the synchronous rectifier conduction time after zero current condition in the inductor. High power density and high-efficiency MHz implementations have already been demonstrated in the literature; however, none of the proposed solutions solves the controllability issues of the synchronous rectifier switch. This paper proposes and validates a ZVS self-regulating control method for BCM converters operating in the MHz switching frequency range. [ABSTRACT FROM AUTHOR]

This paper presents a digital control technique to achieve valley switching in a bidirectional flyback converter used to drive a dielectric electroactive polymer-based capacitive incremental actuator. This paper also provides the design of a low input voltage (24 V) and variable high output voltage (0–2.5 kV) bidirectional dc–dc flyback converter for driving a capacitive incremental actuator. The incremental actuator consists of three electrically isolated mechanically connected capacitive actuators. It requires three high-voltage (HV) (2–2.5 kV) bidirectional dc–dc converters to accomplish the incremental motion by charging and discharging the capacitive actuators. The bidirectional flyback converter employs a digital controller to improve the efficiency and charge/discharge speed using the valley switching technique during both charge and discharge processes, without the need to sense signals on the output HV side. Experimental results verifying the bidirectional operation of a HV flyback converter are presented using a 3-kV polypropylene-film capacitor as the load. The energy-loss distributions of the converter are presented when 4- and 4.5-kV HV mosfets are used on HV side. The flyback prototype with a 4 kV mosfet demonstrated 89% charge energy efficiency to charge the capacitive load from 0 V to 2.5 kV, and 84% discharge energy efficiency to discharge it from 2.5 kV to 0 V. [ABSTRACT FROM AUTHOR]

This letter presents a new zero-voltage-switching (ZVS) isolated dc–dc converter which combines a boost half-bridge (BHB) cell and a full-bridge (FB) cell, so that two different type of power sources, i.e., both current fed and voltage fed, can be coupled effectively by the proposed converter for various applications, such as fuel cell and supercapacitor hybrid energy system. By fully using two high- frequency transformers and a shared leg of switches, number of the power devices and associated gate driver circuits can be reduced. With phase-shift control, the converter can achieve ZVS turn-on of active switches and zero-current switching (ZCS) turn-off of diodes. In this letter, derivation, analysis, and design of the proposed converter are presented. Finally, a 25–50 V input, 300–400 V output prototype with a 600 W nominal power rating is built up and tested to demonstrate the effectiveness of the proposed converter topology. [ABSTRACT FROM AUTHOR]

This paper presents a low-cost bidirectional isolated dc–dc converte, derived from dual-active-bridge converter for the power sources with variable output voltage like supercapacitors. The proposed converter consists of push-pull-forward circuit half-bridge circuit (PPFHB) and a high-frequency transformer; this structure minimizes the number of the switching transistors and their associate gate driver components. With phase-shift control strategy, all the switches are operated under zero-voltage switching (ZVS) condition. Furthermore, in order to optimize the converter performance and increase efficiency, optimal design methods and criteria are investigated, including coupled inductors design, bidirectional power flow analysis, harmonics analysis, and ZVS range extension. Based on all the optimal parameters, higher efficiency can be achieved. Finally, prototypes are built in laboratory controlled by digital signal processor for comparison purpose. Detailed test results verify the theoretical analysis and demonstrate the validity of optimization design method. [ABSTRACT FROM PUBLISHER]

The trend toward high power density, high operating frequency, and low profile in power converters has exposed a number of limitations in the use of conventional wire-wound magnetic component structures. A planar magnetic is a low-profile transformer or inductor utilizing planar windings, instead of the traditional windings made of Cu wires. In this paper, the most important factors for planar transformer (PT) design including winding loss, core loss, leakage inductance, and stray capacitance have individually been investigated. The tradeoffs among these factors have to be analyzed in order to achieve optimal parameters. Combined with an application, four typical winding arrangements have been compared to illustrate their advantages and disadvantages. An improved interleaving structure with optimal behaviors is proposed, which constructs the top layer paralleling with the bottom layer and then in series with the other turns of the primary, so that a lower magnetomotive force ratio m can be obtained, as well as minimized ac resistance, leakage inductance, and even stray capacitance. A 1.2-kW full-bridge dc–dc converter prototype employing the improved PT structure has been constructed, over 96% efficiency is achieved, and a 2.7% improvement, compared with the noninterleaving structure, is obtained. [ABSTRACT FROM PUBLISHER]

Most switched mode power supplies provide a regulated voltage at their output. However, there are applications requiring a controlled current. Among others are battery chargers, test equipment for converters driven by solar cells, and LED drivers. This paper describes a dc–dc power converter realizing such a current source. The converter is based on a boost converter, supplied by a voltage source and acting as a current source. The boost converter can increase the output voltage above the input voltage. The converter provides a high control bandwidth based on a self-oscillating current loop. As additional practical features, soft start and output overvoltage limitation are included and described in this paper. The modulator, the control, and the power stage are described in detail and verified by the experiment. [ABSTRACT FROM AUTHOR]

This paper presents an isolated bidirectional dc/dc converter based on primary parallel isolated boost converter (PPIBC). This topology is an efficient solution in low voltage high power applications due to its ability to handle high currents in the low voltage side. In this paper, the converter has been modeled using non-ideal components and operated without any additional circuitry for startup using a digital soft-start procedure. Simulated and measured loop gains have been compared for the validity of the model. On-the-fly current direction change has been achieved with a prototype interconnecting two battery banks. A second prototype has been constructed and tested for supercapacitor operation in constant power charge mode. [ABSTRACT FROM AUTHOR]