The conventional full power converter (FPC) for battery energy storage applications is limited by bulky components and suboptimal efficiency. In response, a series-connected step-up/down partial power converter (SUDPPC) with high power density is proposed in this paper. It consists of an LLC resonant converter operating at a fixed switching frequency cascaded with a full-bridge converter capable of providing bipolar output. By connecting the SUDPPC in series with the load, the voltage stress on the series side and the current stress on the parallel side are markedly reduced. The four-quadrant function provides support for further optimization of the rated power level. Universal series interconnection schemes are elaborated, and design guidelines are formulated based on power distribution characteristics. Furthermore, the topology is evaluated in terms of nonactive power and component stress factor (CSF), and benchmarked against a four-switch buck/boost FPC and a phase-shifted full-bridge step-up partial power converter (SUPPC). Finally, a 1.1kW prototype is developed to experimentally validate the theoretical analysis, demonstrating that only 14.3% of the total active power is processed under full-load conditions, with a peak efficiency of 98.15%.

This paper proposes a fixed frequency pulse width modulation (PWM) for a dual active half-bridge resonant converter. The wide voltage range can be achieved without adding any additional components, and the voltage gain characteristic is independent of the load. Meanwhile, all switches can achieve full range zero voltage switching (ZVS). The driving logic is unified between the primary and secondary sides, allowing for the implementation of both boost and buck modes. Hence, the control logic is simple. In addition, the multiple-order harmonic analysis of the resonant tank is proposed without complex time-domain calculations. Hence, the expression of voltage gain, current characteristics, and soft switching conditions can be conveniently analyzed. Finally, a 500 W experimental prototype was built. The experimental results prove the effectiveness and superiority of the proposed solution.

High-density 380 V–12 V LLC resonant converters typically employ planar transformers with integrated leakage inductance. To achieve Zero-Voltage Switching (ZVS), an air gap is introduced to adjust the magnetizing inductance (Lm). However, this gap alters the internal magnetic field (H) distribution. In Center-Tapped (CT) structures, this alteration leads to asymmetric leakage inductances between the positive and negative half-cycles, causing resonant frequency mismatch and performance degradation, particularly under light-load conditions. In this work, the asymmetrical leakage inductance effect in a CT transformer for a 380 V–12 V LLC resonant converter is systematically investigated. A mathematical model is derived to quantify the leakage inductance distribution, revealing that the relative position between the air gap and the windings significantly affects the symmetry. Based on this modeling analysis, the centralized assembly method is identified as the optimal solution to ensure impedance symmetry. The accuracy of the proposed model and the effectiveness of this structure are validated through Finite Element Analysis (FEA) simulations and a hardware prototype of a 250-W, 600-kHz LLC converter. Results demonstrate that this method eliminates the approximately 11% leakage inductance discrepancy (1.8 μH vs. 1.6 μH), ensuring stable operation across the full load range.

ABSTRACT This paper addresses the demand for electric vehicle DC charging systems compatible with both 400‐ and 800‐V platforms by designing a cascaded AC/DC converter. The front stage employs a Vienna rectifier, characterized by high efficiency and low harmonic distortion. It provides high‐quality DC power while reducing interference to the grid and equipment. The rear stage is reconfigured based on the conventional LLC resonant converter, featuring series‐connected primary windings and series/parallel output terminals. Switching between 400‐ and 800‐V charging modes is achieved by controlling the switching of relays on the secondary side. Based on the operating characteristics of the Vienna rectifier, midpoint potential balancing control and a computationally efficient two‐level Space Vector Pulse Width Modulation (SVPWM) strategy are adopted. The rear stage utilizes dual‐loop constant voltage/constant current control. Combined with hardware parameter optimization, this effectively enhances the current‐sharing performance of the series/parallel structure. A 3.3‐kW experimental prototype was fabricated and subjected to static and dynamic tests. The experimental results demonstrate that the system can stably output the rated voltages of 400 and 800 V. The startup process is free from overshoot, and the system exhibits excellent dynamic response characteristics under rapid load changes.

This paper presents a novel design optimization strategy for LLC resonant converters that enhances full-load efficiency while operating across wide input and output voltage ranges. Achieving regulation over a wide output voltage range imposes more stringent design constraints on the converter, demanding higher inductance ratio and wider switching frequency range compared to constant output voltage applications. While numerical optimization techniques are effective for determining the optimal parameters of the converter; however, this effectiveness comes at a substantial computational cost. This work establishes a set of closed-form analytical equations that not only constitute a complete, step-by-step procedure for optimal design without reliance on numerical solvers, but also provide a framework for analyzing design trade-offs. The proposed methodology distinguishes itself from conventional approaches by offering a systematic and non-iterative procedure that is computationally efficient for determining an optimal design. The proposed procedure is validated through the simulation of a 495 W LLC converter specified for a wide operational range with a 320–370 V input and a 35–165 V output. The converter achieved the full output voltage range at the worst-case conditions and attained peak efficiency near the full load, while maintaining soft switching across the entire operating range.

Fixed-Frequency-Based Continuous Topology-Morphing Control for CLLLC Resonant Converters

Reduced Order Equivalent Circuit Model of Series Resonant Converter Considering the Interaction between Resonant Elements

Design of a 330 W 700 kHz half-bridge LLC resonant converter

A Frequency Independent Closed-Loop Frequency Dithering Technique to Attenuate Conducted EMI for Dual-Active Bridge Series Resonant Converter

A Multi-population genetic programming algorithm to model estimation for LLC resonant converter

As is customary in general automatic control theory, the open-loop system includes all components of resonant DC-DC converters, including the error amplifier and the power stage, except for the summing junction. The paper is devoted to the analysis of the circuitry and operating principles of the control-system components of DC converters, which, unlike the power stage and the error amplifier, have not been comprehensively addressed in the literature. The purpose of study is to analysis of the circuit topology and functional operation of open-loop control system components for resonant DC-DC converters based on commercial integrated circuits implementing frequency and phase control. Materials and methods. The analysis of the circuit design and operation of the resonant converter control system was performed using the circuit diagrams, timing diagrams, and formulas provided in the technical documentation for commercial ICs produced by leading manufacturers. Results. The structural diagrams of open-loop frequency and phase control systems for resonant DC-DC converters are presented and described, along with piecewise time-domain descriptions of their functional blocks. It has been established that all timing generators are based on the charge-discharge principle of a timing capacitor. Frequency control involves varying the switching frequency, while phase control implies shifting the phase of the control pulses of one leg of the half-bridge relative to the other at a fixed switching frequency, which simplifies the control system. Examples of circuit implementations using the UC3865, L6599, and UC3871 integrated circuits are provided, along with a discussion of pulse shaping circuits and the specific features of feedback implementation. Conclusions. The generation of clock pulses in the master oscillators for both frequency and phase control systems of DC-DC converters is performed by cyclic charging and discharging of a timing capacitor, whose parameters determine the output frequency of the system. The phase control scheme contains fewer functional units compared to the frequency control scheme, simplifying its practical implementation. As semiconductor manufacturing technology has advanced, the control ICs have also evolved – from using n-p-n bipolar transistors to hybrid circuits incorporating p-n-p and MOS transistors – which has significantly influenced the circuit design and operation of control ICs for resonant converters.

ABSTRACT In this paper, we propose a novel single‐stage LLC converter with power factor correction (PFC) for efficient and cost‐effective on‐board charging (OBC) for electric vehicles (EVs). This OBC circuit retains the advantages of zero‐voltage switching (ZVS) and zero‐current switching (ZCS) of LLC resonant converters while realizing high power factor performance. Detailed mathematical derivations and circuit design are presented, followed by experimental verification with a 200 W prototype circuit showing its efficacy. Furthermore, a comparison between the commercially available two‐stage OBC converter and the proposed single‐stage LLC converter is conducted. While the performance of these two converters is similar, the new single‐stage LLC resonant converter shows significant advantages with 24.97% reduction in size and 15.92% in bill‐of‐materials cost. This solution creates a compact and cost‐effective alternative for EV‐OBC.

ABSTRACT Electric vehicles (EVs) typically rely on two independent systems for wireless power transfer (WPT) and conductive charging. This paper introduces a fully integrated charging architecture that unifies both charging functionalities into a single hardware platform. The core of the proposed system is a single‐layer parallel‐wound dual‐coil structure, which replaces the conventional transformer in the CLLC resonant converter and enables full resonant capacitor sharing between the onboard charger (OBC) and WPT receiver. Unlike prior dual‐layer coil designs, the proposed structure not only supports high‐frequency OBC operation but also maintains strong magnetic coupling essential for WPT. By incorporating a compensating inductor for circuit symmetry and a DC‐side series connection in WPT mode, the system achieves complete hardware integration without additional AC‐side switching. Experimental results demonstrate that the DC–DC stage maintains efficiency above 96% across the operating range, validating the feasibility of a compact, cost‐effective, and compatibility‐assured dual‐mode charging solution.

Mathematical model and parameter analysis of high-power LC series resonant converters for electromagnetic launchers

In view of the new energy vehicles on the market superfast charging system and for the subsequent automotive components to provide reliable voltage conversion function, puts forward a high stability, high density, high power based on matrix transformer three-phase LLC resonance converter, due to the parallel resonance parameters (resonance inductance, capacitor, excitation inductance), the transformation of each phase resonance cavity different, leading to the phase resonance current and rectifier current imbalance. Therefore, on the basis of the three-phase LLC resonance converter, the method of original edge series and auxiliary edge parallel to add multiple groups of transformers to each phase. On the basis of not adding any additional circuit, the automatic flow sharing capacity of the resonance converter is improved, and the anti-interference ability and stability of the resonance converter are enhanced. Compared with the traditional LLC resonant converter, the converter can effectively reduce the ripple of output voltage, reduce the damage to subsequent components, and realize the ZVS of the original primary side switch tube and the secondary side diode, reducing the loss of the converter. The topological structure and driving waveform and the working principle are introduced first, and then the gain characteristics and soft switches of the converter are analyzed. Finally, the feasibility of this scheme is verified through experiments.

ABSTRACT To address the challenge of wide‐range output regulation in LLC resonant converters, this paper proposes a novel hybrid control strategy. By replacing only two diodes on the secondary side with MOSFETs, without increasing the number of resonant elements, the converter achieves a wide voltage output range of 175 to 450 V. The hybrid control strategy primarily employs the secondary side semi‐active (SSSA) control method, combined with variable bus voltage (VBV) control and primary side phase shift (PSPS) control method, ensuring that the converter always operates at the resonant frequency. This approach enables high conversion efficiency and soft switching of all MOSFETs. Additionally, the area equivalence principle is utilized to derive exact expressions for the resonant current and converter gain in the SSSA mode, simplifying the converter design process. An experimental prototype was designed and tested, demonstrating the feasibility of the proposed control strategy with an input voltage range of 300 to 400 V, an output voltage range of 175 to 450 V, and a rated power of 6.6 kW. The prototype achieved a maximum conversion efficiency of 97.8%.

This paper proposes a single-phase AC-AC solid-state transformer (SST) that eliminates bulky energy storage components. The proposed matrix-type structure comprises a line-frequency (LF) rectifier, a half-bridge (HB) LLC resonant converter, a buck–boost converter, and an LF inverter. The HB LLC resonant converter not only achieves high efficiency at unity voltage gain but also provides high-frequency (HF) isolation as a DC transformer (DCX). Meanwhile, the buck–boost converter ensures precise voltage regulation. The replacement of traditional DC-link electrolytic capacitors with small film capacitors effectively suppresses the second-harmonic power ripple, leading to a significant improvement in both power density and operational reliability. Experimental results from a 1 kW prototype demonstrate high-quality sinusoidal input and output, a wide range of zero-voltage switching (ZVS) operations, and stable output voltage control.

Voltage generation for Sawyer-Tower Coss loss measurement based on resonant converters

Super twisting sliding mode control for high-efficiency and fast charging of electric vehicles using current-fed resonant converter: 400 V and 800 V validation

Optimization approach of LLC resonant converter parameters for electric vehicles based on interior-point algorithm