In this paper, a structure-reconfigurable LLC (SR-LLC) resonant converter is proposed for wide output voltage applications. The converter can operate in half-bridge mode or full-bridge mode by modulating the driving signal of the switches. Four operation modes with scaled voltage gains are obtained by the independent or combined operation of resonant tanks. Compared with the conventional full-bridge LLC converter, the voltage gain range is greatly extended without extra switches. The consistent resonance parameters of two tanks allow four operating modes to have the same resonant frequency, which facilitates the design of magnetic components. Moreover, zero-voltage switching (ZVS) of the primary-side MOSFETs can be achieved in all modes. A 3.3-kW prototype with 75 V-450 V output voltage is built to verify the feasibility and effectiveness of the proposed converter. The peak efficiency of the prototype is 97.3%, and the efficiency curve is smooth in the ultra-wide output voltage range.

This article proposes a multimode hybrid LLC resonant converter with wide output voltage range. Without auxiliary switches, the converter can operate in three different modes by controlling the drive signals of the primary switches: low-gain mode, medium-gain mode, and high-gain mode. Variable frequency modulation is adopted in each operation mode, and an ultra-wide output voltage range can be achieved with smooth mode transition in the proposed converter. The characteristic circuit structure allows the converter to maintain a wide voltage gain range even though magnetizing inductance is designed to be larger. In addition, zero-voltage switching of the primary side mosfet s can be realized due to the operation region above resonant frequency and justified parameter design in whole voltage range. Finally, a 3.3-kW prototype with 60–420 V output voltage is built to verify the effectiveness of the proposed converter. The prototype achieves 97.5% peak efficiency and demonstrates good efficiency performance over an ultra-wide output voltage range.

A reconfigurable half-bridge compensation topology is proposed in this brief for automatic guided vehicles (AGV) wireless charging system. Considering the cost and reliability, a simple and reconfigurable structure without extra passive element and additional relay is developed, the reconfigurable topology could realize the shift from inductor-capacitor-capacitor-inductor-capacitor-capacitor (LCC-LCC) topology to series-inductor-capacitor-capacitor (S-LCC) topology, and further achieve load-independent constant current (CC) and constant voltage (CV) outputs, full design freedom for current and voltage gain. Accompanying with a special switching strategy of mode transition, the proposed reconfigurable circuit could realize smooth cutting off of inductor current without spike across switch. Moreover, module of zero-current could be saved in the proposed topology. The proposed circuit has less switches and could achieve zero phase angle (ZPA) operating and zero voltage switching (ZVS) in the whole charging process, which allows the lower cost and power losses. An experimental prototype is established to validate the feasibility of the reconfigurable half-bridge compensation topology and switching strategy.

A bidirectional hybrid dc–dc resonant converter with a wide voltage gain range and three operating modes for both forward and backward operations is proposed. The converter features a symmetrical structure on both sides and can be configured as three variable structures: a full-bridge converter, a dual-phase half-bridge CLLC converter, and a single-phase half-bridge CLLC converter, to enhance efficiency under low-voltage and light-load conditions. No extra device is required, and the operating mode of the proposed converter can be switched through various modulation strategies. Additionally, integrating the resonant inductance into the transformer reduces the number of components, thereby increasing power density. During three distinct operational modes, zero-voltage switching can be achieved for all active switches, significantly reducing switching losses and enhancing the overall system efficiency. A 3.3-kW experimental prototype has been constructed. In forward operation, the primary side dc bus voltage is maintained at 400V, while the secondary side battery voltage can be adjusted within a range of 250–450 V, achieving wide-range voltage output regulation. In backward operation, the voltage across the battery terminals ranges from 250 to 450 V, enabling wide-range voltage input regulation. Based on the battery voltage level, the converter employs a traditional dual-active-bridge mode for lower voltages and a bidirectional CLLC resonant mode for higher voltages.

A compact magnetic coupler of inductive power transferring (IPT) system for automated guided vehicles (AGVs) is proposed in this paper, which consists of a double-D (DD) transmitter (Tx) and a compact dual-coil receiver (Rx). By overlapping between one coupling peak point and another coupling null point of two Rx coils, the Rx of magnetic coupler achieves relatively small output voltage fluctuations, as well as minimizes its size. In addition, to eliminate cross-coupling of the dual-coil Rx, a mutual decoupling device composed of two lumped inductors is adopted, which possesses the same mutual inductance as the dual-coil Rx. Finally, based on the proposed magnetic coupler and its special way of decoupling, a 3kW IPT system is constructed with 180mm×390mm Tx, 150mm×210mm Rx, 40mm airgap magnetic coupler and inductor/capacitor/capacitor-series (LCC-S) based decoupling compensation network. The experimental results show that output voltage varies in proportion to the mutual inductance of Tx and Rx. The measured efficiency is 89.5% to 94.5% under the voltage range of 155V to 220V during the 90mm misalignment.

In this article, an optional series/parallel LLC resonant converter with inherent load-independent output characteristics is introduced in the electric vehicles (EVs) on-board chargers. The converter operates at two different fixed resonant frequency points: the parallel-resonant frequency or series-resonant frequency as needed and performs as output current source or voltage source, respectively. A simplified open-loop modulation strategy is proposed during the whole charging process. It not only removes the need for feedback control to limit charging current to desired levels in the constant current (CC) charging mode but the batteries can also operate safely in the constant voltage (CV) charging mode. The converter operates at a fixed switching frequency during CC and CV charging thanks to this frequency-selective network characteristic and the dual-fixed-frequency point operation strategy. Moreover, a smooth transition between the two modes is achieved by employing a pulse-frequency modulation. In addition, an active branch for current-injection is needed to help the switches realize zero-voltage switching (ZVS) in the CC charging mode. Finally, a 2kW 250~430V output experimental prototype is built. The experimental results show that the soft switch is realized and the high efficiency is maintained in the whole load range, and the maximum efficiency is 97.5%.