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Summary: Resonant converters have been widely applied in many fields, such as electric vehicles, renewable energy sources, and switch‐mode power supply. Conventional resonant converters generally adopt pulse frequency modulation (PFM), which would cause an extremely wide frequency variation range under wide output applications. However, it would lead to high electromagnetic interference (EMI), low utilization of magnetic components, and loss of soft switching features. For catering to wide output range applications, this paper proposes a self‐adaptive narrow frequency range PFM and asymmetrical voltage‐cancelation hybrid modulation strategy to solve the above problem. The advantages of the proposed strategy include (1) narrow frequency variation range; (2) self‐adaptive shift frequency; and (3) full process achievement of zero voltage switch. The modulation strategy and operational principle and performance analysis of the proposed method are given. Eventually, a series resonant converters–based experimental platform was implemented to verify the proposed strategy. [ABSTRACT FROM AUTHOR]

Dual active converter (DAB) can achieve high efficiency when the voltage ratio (the ratio of the input voltage to the output voltage equivalent to the primary side) is one, but when the voltage ratio is not one, the light-load efficiency drops sharply. Based on the realization logic of DAB light-load, this article proposes a modulation method with asymmetric compression duty cycle, which only increases one degree of freedom and does not need additional components to significantly improve the light-load efficiency. First, this article introduces the existing problems and solutions of the traditional scheme and puts forward a new modulation strategy. Then, the operating modes and power characteristics are analyzed. Then, the influence of duty cycle compression on reflux power and current stress is analyzed. Finally, a prototype with an input voltage of 100–200V, an output voltage of 50 V, and a full load power of 300–600 W is built to verify the analysis. [ABSTRACT FROM AUTHOR]

In the application of bipolar DC bus configuration in the DC nanogrid, the unbalanced voltage of two outputs in bipolar DC bus, due to the unbalanced conditions of loads and/or energy sources, will cause deterioration of the power quality of the bus and may damage the switch, affecting the stability and safety of the system. In order to solve the problem of unbalanced voltage of two outputs, interleaved series capacitor based dual‐output converter with a high conversion ratio is presented in this paper. By applying negative current mode (NCM) to the main inductor, the character of two‐output self‐balancing and zero voltage switching (ZVS) of all switches for such this topology configuration is achieved. In the NCM mode, the parallel diodes of main switches are not conducted during dead time and guarantee the flowing path to load side. Thus, based on this condition, volt‐second balance of main inductor is obtained to get the character of two‐output self‐balancing. Furthermore, by adopting series capacitor in the proposed topology and based on the charge‐balance of the intermediate block capacitor, inductor current existed in the two phase could be auto‐sharing. Comprehensive operational principle analysis, loss analysis, and efficiency of the proposed converter under different load conditions have been given, and the comparison analysis of three operation modes and selection of negative current mode is clarified. Small signal model of the proposed converter is described to convenient for the controller design. Finally, simulation results and a 20–220 V prototype are built to verify the character analysis of the proposed converter. [ABSTRACT FROM AUTHOR]

In this study, a wide load range zero‐voltage zero‐current switching (ZVZCS) dual‐active‐bridge DC–DC converter using auxiliary parallel networks is proposed. The outstanding feature of the proposed converter is that all of the switches are allowed to operate with zero‐voltage switching while four of the switches are allowed to operate with zero‐current switching, due to the use of two auxiliary parallel networks, which were paralleled to two active bridges, respectively. Furthermore, the circulating current losses can be reduced significantly by using unified boundary trapezoidal modulation method. Based on these merits, the proposed converter has some advantages for the wide range load variation applications with less circulating current losses. The operation principles, soft‐switching conditions and loss analyses comparison are given in this study. These benefits and characteristics mentioned above are verified from the experimental results by using a 1 kW prototype. [ABSTRACT FROM AUTHOR]

High voltage step-down converters are very popular in distributed power systems, voltage regular modules, automatic vehicles, etc. To avoid extreme duty cycles, a series capacitor-based buck converter with a coupled inductor is proposed in this paper. In this converter, the voltage stresses of the power switches are clamped to half of the input voltage. Thus, low voltage rating MOSFETs with a low Rds,on could be utilized to improve the performance of the proposed converter. Moreover, synchronous MOSFETs are also used to reduce the conduction losses of the switches. Zero voltage switching (ZVS) for the main power switches is achieved using the coupled-inductor technique. In addition, through adding a bypass flowing path, a negative current is established to guarantee the ZVS condition of the power switches. The operating principle of the proposed converter is described in this paper, and the DC voltage gain ratio, automatic current sharing, soft switching condition and design guideline of the critical parameters are also given. Finally, experimental results obtained from a 60 V/200 W prototype are presented to verify the analysis of the proposed converter. [ABSTRACT FROM AUTHOR]