In this paper, a nonisolated high step-up soft-switching dc–dc converter is proposed, which is based on a hybrid structure comprising an interleaved boost converter and Dickson switched-capacitor (SC) networks. The high voltage gain can be achieved by the SC networks without an extremely large duty cycle, and the voltage stresses of all the active switches and diodes are kept at levels much lower than the output voltage. Compared with traditional SC converters, the proposed converter can achieve continuous voltage regulation by the PWM technique. The interleaving operation can reduce the input current ripple and improve the power capacity. Resonant inductors with small inductances are inserted into the SC networks to avoid the high current spikes that occur in traditional SC converters. All the active switches can achieve zero voltage switching (ZVS) turn-on. Some of the diodes can achieve zero current switching (ZCS) turn-off, and the other diodes achieve reduced turn-off di/dt rates. The operating principle and essential steady-state characteristics of the converter are analyzed in detail. Finally, a prototype converter with an input voltage of 25–40 V, an output voltage of 400 V, and a rated power of 1 kW is designed and implemented to verify the theoretical analysis.

An optimal dual-phase-shift control strategy of an isolated buck-boost converter is proposed in this paper. The theoretical analysis of dual-phase-shift control strategy is complemented, and the three-dimensional graphs of the output current versus two control variables are given. The optimal operating point is determined by the peak current of a clamped inductor and is shown as control trajectories in the three-dimensional graphs. Moreover, with the optimal dual-phase-shift control strategy, low current value, soft-switching operation, wide input voltage range regulation, whole load range regulation, and high-efficiency performance can be achieved. Furthermore, parameter design method deriving from the minimum peak current of the clamped inductor is given. At the end of this paper, a 1000 W-output prototype is fabricated to verify the effectiveness of the proposed control strategy.

A control strategy with three control variables that containing switching frequency and two duty cycle ratios for isolated buck-boost (IBB) converter is proposed in this paper. The converter only operates in discontinuous current mode (DCM), and boundary current mode (BCM) in the whole voltage range and load range which can achieve excellent soft-switching performance, low energy circulation, and high efficiency. On the basis of operational principle and variables simplification, the optimal operating point that has minimum clamped inductor peak current value is obtained. Under variable frequency control strategy, the converter characteristics are analyzed, such as the direct energy transfer time ratio, peak current value of the clamped inductor and switching frequency. Moreover, the implementation of closed-loop variable frequency control strategy is given with three operational modes: variable frequency BCM mode, constant frequency BCM mode, and variable frequency DCM mode. A 380-V 1-kW output prototype is fabricated, and the experimental results indicate that high efficiency over overall load range has been achieved under variable-frequency control strategy due to the excellent soft-switching performance in the whole range. What’s more, smooth transition between three operational modes is achieved.

In recent years, the LLC resonant converter has been widely used in DC–DC conversion applications. However, the parasitic components of the LLC resonant converter have a significant impact in practical applications, such as influence on the conduction loss and the soft-switching of power devices, the voltage oscillation across rectifier diodes, the unregulated output voltage at light load condition and so on. It is hard to analyze the higher-order circuits by the conventional analysis methods. Focusing on the operational principle of the LLC converter with parasitic components, the differential equation model is presented and solved by the numerical method in this paper. The simulation results verify the correctness of the theoretical analysis. The causes of two different frequency oscillations and the voltage spike are clarified. The design considerations and a specific example of the LLC converter are given. The experimental results are consistent with the simulation results, and the soft-switching of primary-side switches can be achieved in the prototype.

Sequential switching shunt regulator (S3R) has been widely used in satellites for its simple structure and high reliability. Double section functioning, which has two sections operating simultaneously, is the other operating mode of S3R beside the normal mode. It is inevitable and can lead to larger bus voltage ripple, less controllability and higher switching losses. A detailed analysis based on the double section functioning process description is given on the boundary load current, the main bus voltage ripple and the switching frequency. Considering the influence of double section functioning, a new method of control loop design of S3R is proposed based on the small single mathematical model. A 4.5 kW S3R prototype is built to verify the control loop design, and the load region of double section functioning can be limited as designed.

The LLC resonant converter has been widely used in direct current (DC) power supply applications. However, fundamental harmonic approximation or other simplified analyses will introduce inevitable deviations. Therefore, the differential equation model with numerical solution of the LLC converter is proposed in this paper based on the operational principle of the ideal case. In order to solve the differential equation, initial values need to be substituted. The accurate LLC model based on time interval analysis is very complicated and cannot be used. In this paper, solution methods of the initial values corresponding to different switching frequencies are proposed. The initial values can be solved conveniently. Furthermore, the voltage gain curve is modified by the idealized analysis. Lastly, all the above research is verified by PSIM simulation. The work is helpful to understand the operational principle of the LLC resonant converter.