The rise of greenhouse gas levels in the atmosphere is a severe climate change concern. A significant part, such as CO2 emission, comes from internal combustion engine-driven vehicles, incited the automotive sector to focus more on the sustainable electric transportation system. However, electric vehicles face significant charging time, charging methods, and range anxiety challenges. To overcome these challenges, charging technologies for electric vehicle batteries play an essential role. Many types of electric vehicle charging topologies have been discussed in the literature and implemented in many practical applications. This paper presents a state of art criticism of advanced converter topologies and charging methodology for electric vehicle applications. Apart from the conventional topologies, this manuscript has covered the comparative criticism of the recently proposed EV charging technologies regarding charging methods, control strategies, and power levels. Further, this paper discussed the different onboard chargers with their power factor correction topologies, drawbacks, and required corrections. This manuscript provides the research directions for the academic and industrial communities. 

A comprehensive review on advanced charging topologies and methodologies for electric vehicle battery

The phase shift full bridge (PSFB) is a widely known isolated DC-DC converter topology commonly used in medium to high power applications, and one of the best candidates for the front-end DC-DC converter in server power supplies. Since the server power supplies consume an enormous amount of power, the most critical issue is to achieve high efficiency. Several organizations promoting electrical energy efficiency, like the 80 PLUS, keep introducing higher efficiency certifications with growing requirements extending also to light loads. The design of a high efficiency PSFB converter is a complex problem with many degrees of freedom which requires of a sufficiently accurate modeling of the losses and of efficient design criteria. In this work a losses model of the converter is proposed as well as design guidelines for the efficiency optimization of PSFB converter. The model and the criteria are tested with the redesign of an existing reference PSFB converter of 1400 W for server applications, with wide input voltage range, nominal 400 V input and 12 V output; achieving 95.85% of efficiency at 50% of the load. A new optimized prototype of PSFB was built with the same specifications, achieving a peak efficiency of 96.68% at 50% of the load.

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A Practical Approach to the Design of a Highly Efficient PSFB DC-DC Converter for Server Applications

In this article, an interleaved soft-switching bidirectional dc–dc converter (BDC) with high voltage conversion ratio (VCR) and low voltage stress is proposed for battery charging/discharging applications. A built-in transformer (BT) is integrated into conventional half-bridge BDC and three-level structure to achieve high VCR and reduced voltage stresses simultaneously. The feature of BT is that the balanced magnetic flux exists in the magnetic core, which allows for small size of the magnetic core. The current ripple in the battery side is reduced by adopting the interleaved structure. Moreover, the voltage-matching on both sides of the BT is realized by the adjustment of the duty cycle. As a result, even if the battery voltage changes, the BT always operates under the highest efficiency condition. Besides, by employing phase-shift control, power flow can be regulated monotonously. Soft-switching of all the switches within a wide range of battery voltage is obtained by employing the optimal design. The operational principles, characteristics, and design considerations are analyzed in detail. Experimental results from the BT-BDC prototype of 1-kW, 40–60 to 400 V verify the effectiveness.

A Soft-Switching Bidirectional DC–DC Converter With High Voltage Gain and Low Voltage Stress for Energy Storage Systems

Over the past few years, resonant converters have been used extensively in (Digital Switched Mode Power Supply) DSMPS applications such as telecom, server, lighting and onboard chargers. Resonant converters can achieve high efficiency, low level of EMI emissions and allow high frequency operation thanks to the soft switching over the entire operating range. The LLC and LCC resonant DC-DC converter topologies are being used widely in the industry. However, given its complexity, obtaining a reliable model that describes the converters operation is a tedious task. This paper will focus on the analysis of the Half-Bridge (HB) LCC resonant DC-DC converter and its voltage gain computation, derived on the basis of Fundamental Harmonic Approximation (FHA) approach. This method can be applied to any resonant topology and here, in particular, has been applied to the LCC converter.

LCC Resonant Converter Design and Transfer Function Computation Using FHA Analysis

Phase-Shifted Full Bridge (PSFB) topology in its four-diode variant is the choice with the lowest part count in applications that demand high power, high voltage, and galvanic isolation, such as in Electric Vehicle (EV) chargers. Even though the topology is prevalent in power electronics applications, no single, unified analytical model has been proposed for the design process of four-diode PSFB converters. As a result, engineers must rely on simulations and empirical results obtained from previously built converters when selecting components to properly match the DC source voltage level with the DC load voltage requirements. In this work, the authors provide a design-oriented analysis approach for obtaining the output voltage and semiconductor current values, ready for implementation in a spreadsheet- or MATLAB-type software to automate design optimization. The proposed formulas account for all the first-order nonlinear dependencies by considering the impact of each of the following eight design parameters: DC-link voltage, load resistance, phase-shift ratio, switching frequency, transformer turns ratio, magnetizing inductance, series inductance, and output inductance. The results are verified through experiments at the power level of 10 kW and the DC-link voltage level of 800 V by using a grid simulator and a SiC-based two-level Active Front End (AFE) with a DC–DC stage based on the PSFB topology. The accuracy of the output voltage formula is determined to be around 99.6% in experiments and 100.0% in simulations. Based on this exact model, an automated design procedure for high-power high-voltage SiC-based PSFB converters is developed. By providing the desired DC-link voltage, output voltage, output power, output current ripple factor, maximum temperatures, and semiconductor and heatsink databases, the algorithm calculates a set of feasible designs and points to the one with the lowest semiconductor losses, dimensions, or cost.

Closed-Form Formulas for Automated Design of SiC-Based Phase-Shifted Full Bridge Converters in Charger Applications

This paper proposes a novel modulation technique for the bidirectional operation of the phase-shift full-bridge (PSFB) dc/dc power converter. The forward or buck operation of this topology is well known and widely used in medium-to-high-power dc-to-dc converters. In contrast, backward or boost operation is less typical since it exhibits large drain voltage overshoot in devices located at the secondary or current-fed side—a known problem in isolated boost converters. For that reason, other topologies of symmetric configuration are preferred in bidirectional applications. In this work, we propose a modulation technique overcoming the drain voltage overshoot of the isolated boost converter, without additional components other than the ones in a standard PSFB and still achieving full or nearly full ZVS in the primary or voltage-fed side devices along all the load range. The proposed modulation has been tested in a bidirectional 3.3 kW PSFB achieving a 98% of peak efficiency in buck mode (380 V input, 54.5 V output), and a 97.5% in boost mode (51 V input, 400 V output). This demonstrates that the PSFB converter may become a relatively simple and efficient topology for bidirectional dc-to-dc converter applications.

Modulation Scheme for the Bidirectional Operation of the Phase-Shift Full-Bridge Power Converter

The requirements for the blocking voltage of the rectification devices on the secondary side of phase shift full bridge (PSFB) dc–dc converter topology are, by nature, higher than for other quasiresonant or fully resonant topologies (DAB, LLC). This is especially aggravated in wide range operation converters and further increased by the rectifiers’ drain voltage overshoot. Unlike other resonant topologies, the inductor at the output of the PSFB effectively decouples the capacitor bank from the rectification stage, which otherwise acts as a strong lossless snubber. Higher blocking voltage requirements for the rectification devices worsen their Figure of Merit, increasing their related losses and decreasing the overall efficiency of the converter. In this article, the main causes of the rectifiers drain voltage overshoots in PSFB are analyzed. Design guidelines for the mitigation of the different causes are introduced, as well as a novel modulation scheme for the overshoot reduction, while the output filter operates in discontinuous conduction mode, without penalties in performance, complexity, or cost. A prototype of PSFB DC-DC converter of 3300 W, with 400-V input to 54.5-V output nominal voltages, was designed and built to test the proposed solutions achieving a peak efficiency of 98.12% at 50% of load.

David Meneses

Papers

Modulation Scheme for the Bidirectional Operation of the Phase-Shift Full-Bridge Power Converter

A Practical Approach to the Design of a Highly Efficient PSFB DC-DC Converter for Server Applications

Synchronous Rectifiers Drain Voltage Overshoot Reduction in PSFB Converters