I. Introduction
The growing popularity of electric vehicles (EVs) due to concerns about greenhouse gas emissions, and the threat of fossil fuel depletion [1]. Most EVs are equipped with on-board chargers (OBCs) as an important device for supplementing electrical energy [2]. Fig 1 shows the power architecture of the typical two-stage OBCs system, with power factor correction (PFC) stage, followed by DC/DC conversion stage [3],[4]. The APFC have been adopted in converter to meet the harmonic regulations and IEEE standards. Among them, the APFC with boost converter topology gained significant attention due to its simplicity in design and control, which different configurations in the boost PFC topology are discussed [5]. As the output voltage in the battery packs of these vehicles is typically in the range of 200-450V, an additional DC-DC converter is required to meet the requirement. The safety requirement of on-board vehicle charging call for isolation between the grid and vehicle [6]. However, The current products of OBCs are mainly silicon (Si)-based design and operate typically at less than 100 kHz switching frequency, which results in large profile of the passive components unable to meet the demands of automobile manufacturer for lightweight, efficient, and reliability [7]–[9]. In order to improve the power density of OBCs, it an effective solution to increasing the switching frequency to shrink the passive components size significantly by apply wide band-gap (WBG) power semiconductor devices [10]. Compared with Si power devices, WBG devices can operate at higher switching frequencies, have smaller on-resistance, and have no reverse recovery current. Furthermore, WBG devices have the potential for lower cost and better manufacturability [11]. But even WBG devices require a soft-switching technique owing to the relatively large turn-on loss in high-frequency operations. In, a two-stage on-board charger structure based on WBG devices is proposed. Its totem PFC operation in critical conduction mode (CRM) to realize soft switching. Due to the large swing in input current under CRM mode, the PFC rectifiers require large differential mode (DM) input filter with multi-phase interleaving and poses large high frequency related conduction and core losses in the magnetics. For isolated dc/dc stage, the CLLC resonant converter featuring the same soft-switching technique as the LLC resonant converter is selected. However, the resonant converter requires the introduction of a resonant capacitor (large current), the transformer power density is relatively low, and the efficiency decreases at high frequencies. proposes a multi-phase-shift (MPS) control method to extend the soft switching area and reduced current stress of dc/dc stage. However, there are many operating modes controlled by MPS. Multi-mode switching increases the complexity and uncertainty of the control system.