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Resonant switched-capacitor converters (SCCs) are being increasingly used in energy conversion systems due to their low cost, low weight, and high efficiency. The zero-current switching (ZCS) feature of an SCC, which can be achieved at a switching frequency below the resonant frequency, not only results in soft switching and, hence, low switching losses, but also reduces the electromagnetic interference caused by the converter. This paper proposes a cascaded step-down SCC (CSD-SCC) with an arbitrary number of converter stages and an exponential output-to-input voltage ratio. This SCC reduces the number of required converter stages for a low voltage conversion ratio and has a low ripple in the output voltage. A mathematical study is proposed to analyze the operating modes of this generalized CSD-SCC under ZCS operation. This study also enables the calculation of the output voltage, the output voltage ripple, and the efficiency for different switching frequencies and loads. The proposed analysis is validated via several simulation and experimental case studies, including a photovoltaic energy conversion system. The experimental CSD-SCC has two converter stages with an efficiency higher than  $\text{95}\%$. [ABSTRACT FROM AUTHOR]

Resonant switched-capacitor converters have widely been used recently to increase conversion power density. The most significant drawback of these converters is voltage regulation problem when their input voltages vary in wide ranges. Here, a basic double voltage-ratio resonant switched-capacitor converter (SCC) is analyzed and simulated below its resonant frequency under the different operation modes to overcome this problem. The converter different parameters are calculated under both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) conditions. The advantages and drawbacks of these operation modes are compared and the closed-loop control of the converter is also investigated based on the extended describing function approach. The given analyses demonstrate that the output voltage can be well-regulated under the CCM1 and DCM2 operation modes even when wide input voltage and load variations are applied. Besides, the DCM1 operation mode must be avoided when output voltage regulation is important. Based on the given analytical and experimental results, switching frequency varies in a reasonable range to regulate the output voltage. Also, faster transient responses, smaller output capacitor, and smaller resonant tank components can be used below the resonant frequency, as compared to the above resonant frequency, but lower efficiency value is achieved. The given approach has been extended to the other resonant SCCs as well. [ABSTRACT FROM PUBLISHER]

LLC resonant converter is one of the most suitable circuit topologies that have been introduced for designing constant output voltage switched-mode power supplies. In this paper, a design procedure is introduced for using this converter as a wide output range voltage source. Unlike constant output voltage applications which need small converter inductance ratio and narrow switching frequency variations, for wide output range applications, large values of these parameters are needed simultaneously and should be optimized. Instead of minimizing the components stresses, leading to a great value of the inductance ratio, proper choice of the converter parameters resulting in a smaller inductance ratio has been done. Maximum value of the capacitor in parallel with the power MOSFETs drain-sources has been derived to realize the zero voltage switching operation in the converter inductive region. Soft switching is achieved for all power devices under all operating conditions. A prototype of the converter has been tested for different regulated output voltages (35-165 Vdc) under different loads (0-3 Adc) and input voltages (320-370 Vdc) for using an ion implanter arc power supply, with maximum efficiency value of 94.7%. Experimental results confirm the high performance of the wide output range LLC resonant converter even under the worst case conditions. [ABSTRACT FROM AUTHOR]

LLC resonant converter with significant resonant inductance is proposed for designing an adjustable wide-range regulated voltage source. Large resonant inductance increases output voltage adjustment range and conversion efficiency, particularly at light loads. Soft switching is achieved for all power devices under all operating conditions by choosing the dead time and maximum switching frequency properly and operating in the converter's inductive region. Using a power-factor-correction (PFC) converter reduces the resonant converter's output voltage dependence to the variations of the main ac input voltage. Thus, the compensation of the load variations and the wide-range adjustment of the regulated output voltage can be achieved by using small switching frequency variations. The proposed method has been used to implement an adjustable wide-range voltage source (35–165 V dc), as an ion implanter arc power supply. An almost flat efficiency curve with maximum value of 94% has been achieved for the converter. Its output current can change from no load to 3 A dc. [ABSTRACT FROM AUTHOR]

LLC resonant converter has been widely used in dc–dc converters. In this paper, optimum dead-time and maximum switching frequency of a wide-adjustable-range LLC resonant converter are investigated for realizing the zero voltage switching (ZVS) operation even under the worst-case conditions. Analyses demonstrate that these parameters depend on the converter inductance ratio and ratio of the converter resonant capacitor and the effective capacitance appeared in parallel with the drain–sources of the power MOSFETs. The necessary dead time for realizing the ZVS operation can be minimized by choosing the normalized maximum switching frequency, properly. Using the dead-time optimum value, soft switching is achieved for all power devices even under the worst-case conditions. Developed prototype of the converter has been tested under different loads (0–3 A dc) and input voltage conditions (320–370 V dc) to achieve a wide-adjustable-range output voltage (40–165 V dc). This dc–dc converter is used as an ion implanter arc power supply. The calculated optimum dead-time and maximum switching frequency are approximately equal to 184 ns and 205.7 kHz, for realizing the ZVS operation at the worst-case conditions. These parameters in the prototype are approximately equal to 195 ns and 203.5 kHz, respectively. [ABSTRACT FROM PUBLISHER]