Critical conduction mode (CRM) is widely used in totem-pole Boost power factor correction converters due to its compatibility with soft-switching and high switching frequency. Conventionally, a current sensor or zero-current detector is required to realize CRM operation. The system performances highly rely on the behaviors of peripheral circuits. Additional power loss and delay are also introduced. Moreover, the inductor current contains obvious differential mode noise, which brings interferences to the sensing signals. To address this issue, a novel CRM realization method is proposed. It utilizes an inductor current estimator model to estimate the averaged current and to predict the current zero-crossings. The noisy sensing signal is replaced by estimated values. Therefore, the zero-current detection circuit is removed, which simplifies the peripheral circuit design. Valley-switching and zero-voltage switching can also be achieved. Operation principles, digital implementation, and error suppression of the proposed control are analyzed. The proposed concepts are validated on a 550 W, 150kHz−1.6MHz, GaN-based prototype. Experimental results record 98.96% peak efficiency with a 0.9972 power factor.

Plug-in electric vehicles’ charger is preferred to cover an ultrawide battery voltage range with the vehicle-to-grid capability. Conventional bidirectional resonant dc–dc converters suffer from the contradiction among wide voltage gain range, squeezed dc-link voltage span, and narrow switching frequency band. To solve the issue, this article proposes a novel H5-bridge-based bidirectional CLLC converter. By configuring the switch pattern, the H5-bridge can form the modes of single half-bridge, dual half-bridge, half full-bridge, and dual full-bridge, respectively. Correspondingly, six gain curves can be derived. Combined with the variable dc-link framework, the converter constrains the switching frequency in the vicinity of the resonant frequency with optimal efficiency. The converter achieves an ultrawide battery voltage range with a squeezed dc-link span. A bidirectionally synchronous rectification method is proposed to improve the efficiency further. To verify the proposed concept, a 1-kW rated prototype with a 320–420 V dc link is built and tested. It validates the battery voltage 55–420 V for charging and 230–420 V for discharging. Zero-voltage turn- on and zero-current turn- off are achieved in the rectifying mosfet s. The prototype exhibits 98.04% peak efficiency and good overall efficiency performance.

High power density with low hardware cost is one of the driving forces in the evolvement of plug-in electric vehicles (PEVs) onboard chargers. To achieve this target, this paper proposes a highly integrated ac/dc converter for PEV charging applications. In the proposed structure, a single-phase bidirectional totem-pole power-factor-correction (PFC) converter is implemented mainly using the existing components in the driving system. The motor drive and windings are reused as switches and inductors, respectively. Therefore, the hardware cost of the onboard charger is significantly reduced. SiC semiconductors are employed to resolve the reverse recovery issues. The proposed converter is featured with reduced components count, reduced input current ripples, and bidirectional power flow. Circuit analysis and design considerations are detailed. A 500 W bidirectional ac/dc converter prototype is designed and tested to verify the concept.

In LLC converters, the transformer’s lumped winding parasitic capacitance degrades the zero-voltage-switching performance as well as power delivery capability. However, the literature survey indicates that there is still a lack of a systematic methodology to guide the optimal winding of the transformer. In this paper, a method to reduce the parasitic capacitance is proposed. The mechanism of the parasitic lumped winding capacitance in spiral winding transformer is detailed. A performance comparison between the conventional winding and proposed winding is conducted experimentally. The experimental results show that using the proposed design, the lumped winding capacitance is reduced from 14.40pF/turn to 1.76pF/turn.

The dilemma between wide input range and narrow frequency band is a classic problem for the frequency modulated LLC converters. Using reconfiguring bridge can mitigate this issue effectively. However, there is a lack of systematic consideration in converter design and optimization. To address this challenge, this work introduces a six-mode LLC converter based on a reconfigurable H5 bridge, and systematically presents its optimal design methodology in ultra-wide input range applications. The dual LLC resonant tanks are driven by identical switching frequency, and provide a normalized gain range from 1 to 5. Synchronized rectification is employed on the secondary side to improve the gain and efficiency. The load distributions between dual tanks are analyzed in detail. It indicates that the equivalent output capacitance of the primary-side MOSFETs is reduced. This enhances the ZVS performance and reduces the circulating loss. The optimal design of transformer ensures a continuous voltage gain over adjacent modes. A 48V, 500W laboratory prototype is designed to validate the concept. The designed prototype is adapted to an 80V∼400V input range. The maximum efficiency is 96.95%.