Series Capacitor Buck Converter Research Articles

A Generalized Current Self-Sharing Strategy in Whole Operating Range for Series Capacitor Buck Converter

A Generalized Current Self-Sharing Strategy in Whole Operating Range for Series Capacitor Buck Converter

Brief Comparison of High-Side Gate Drivers for Series Capacitor Buck Converters

This short article is concerned with the floating high-side gate driver suitable for driving the high side MOSFET/IGBT switch in the series capacitor buck converter family or converters with similar topological features. Biasing the high-side driver in series capacitor buck converters presents an engineering challenge. To alleviate the problem, a modified high-side driver with a voltage lift circuit for driving a high-side switch is proposed. The suggested solution, while being simple and low cost, has several benefits over the earlier propositions. The primary advantage of the proposed circuit is that it relies on a regulated supply to recharge its boot capacitor so to properly bias the high-side driver. Moreover, the proposed driver can operate in a wide range of input voltages while self-adjusting the correct voltage lift according to the operating point of a particular phase of the series buck converter. Thus, any number of phases can be implemented, avoiding cross-coupling effects and providing the high-switch with gating pulses of same amplitude.

Current Sharing Strategy of Three-Phase Series Capacitor Buck Converter for Wide Output Voltage Range Application

Series capacitor buck (SC Buck) converters are widely used in voltage regulator modules (VRMs), electric vehicle, photovoltaic (PV) systems, and so on, for the reason that these converters have the characteristics of high step-down ratio and large output current. However, these characteristics can be realized only when the converter operates in a limited duty-cycle range. In this article, a modified pulsewidth modulation (PWM) scheme based on the principle of ampere-second balance is proposed for the three-phase SC Buck converter to solve the problem. The ampere-second balance of series capacitors is used to balance the phase currents over the entire duty-cycle range. The operating modes, voltage gain and current sharing performance of the converter, control diagram of the proposed converter, and parameter variation analysis are given. Theoretical analysis shows that with the proposed PWM scheme, the converter will have a larger output voltage, unified linear voltage gain expression, and sensorless automatic current sharing over the full duty-cycle range. Moreover, the results show that the parameter variation has nearly influence on the current sharing effect and the excellent balanced current can be achieved under steady state and transient state using the proposed PWM scheme. Finally, a 100-W experimental prototype has been fabricated to verify the performance of the proposed PWM scheme.

Digital Control of Multiphase Series Capacitor Buck Converter Prototype for the Powering of HL-LHC Inner Triplet Magnets

Digital Control of Multiphase Series Capacitor Buck Converter Prototype for the Powering of HL-LHC Inner Triplet Magnets

Steady-State Analysis of Series-Resonator Buck Converter

The series-capacitor buck converter doubles the duty ratio and equalizes the current between two phases. A series-resonator buck (SRB) converter is realized by adding a resonant tank in series with the series-capacitor <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C_s</i> . All switches turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> at zero voltage, and the low-side switches turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> at zero current. This article focuses on modeling the steady-state operation of the SRB converter. The steady-state model calculates voltage gain, component peak voltages, and resonant inductor peak current. The understanding of the relationships between the voltage gain, regulating variable, and state variables help to optimize the power stage design. The expectations were validated by a 2-MHz converter with a peak efficiency of 98.5%, 48 V at the input and 7 V, 20 A at the output.

Series-Resonator Buck Converter—Viability Demonstration

The series-capacitor buck converter doubles the duty ratio, and equalizes the current between two phases. A series-resonator buck converter is realized by adding a resonant tank in series with the series capacitor C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> . All switches turn on at zero voltage, and the low-side switches turn off at zero current. The resonant tank generates additional loss and increases the voltage stress of the low-side switches. A 2-MHz prototype with a peak efficiency of 98.5%, 48 V at the input and 7 V, 20 A at the output was built to demonstrate the viability of the topology.

High-Performance Converters for Optimal Utilization of Interconnected Renewable Energy Resources: A Proposed AGORNN Controller

In most of the industrial applications, an interleaved buck converter is used due to its limited requirements of filter and the enhanced converter dynamic. However, it suffers from an extremely small duty ratio when the high voltage ratio is required. To overcome the above drawbacks, a series capacitor buck converter was introduced. Based on the series capacitor converter model, a high-performance buck converter is proposed in this paper. In this paper, a high-performance converter is designed for the optimal utilization of interconnected renewable energy sources with the proposed control technique. The model and design of high-performance converter is revealed with the consideration of enhanced converter efficiency, effective utilization of renewable energy sources and reduced switching loss. The proposed control technique is the organized execution of both the adaptive grasshopper optimization algorithm and recurrent neural network (AGORNN). Here, the searching behavior of the grasshopper is modified by using the search functions like crossover and mutation. In the proposed technique, the adaptive grasshopper optimization algorithm (AGOA) is utilized to generate the optimal gain dataset based on the objective of minimum error function. The accomplished dataset is used to train the recurrent neural network (RNN) and it leads to predict the exact gain parameter for the PI controller. Batteries are used as an energy source, to balance out and allow the renewable power system units to continue running at a steady and stable output power. The proposed model is executed in MATLAB/Simulink working platform, and the execution is assessed with the existing techniques.

Modified step‐down series‐capacitor buck converter with insertion of a Valley‐Fill structure

This study proposes a step-down converter based on the non-synchronous series-capacitor buck converter. Instead of the regular capacitor of the series topology, the Valley-Fill capacitor-diode structure is inserted in order to extend the step-down conversion ratio of the converter from D /2 to D /3, which leads to a gain ranging from 0 to 1/6, since the maximum allowed duty cycle is D = 0.5. The power stage employs only two active switches, five diodes, two capacitors and two inductors. The study investigates the mechanism of the Valley-Fill structure, analyses the pulse width modulation stages during a switching period, theoretically derives the gain considering ideal and non-ideal components, characterises the current distribution for the inductors and the voltage and current stresses among the power semiconductors and capacitors of the power stage. The proposed topology will be qualitatively and quantitatively compared to state-of-the-art step-down converters with similar gain. The study includes simulation and experimental results for a 300 V/12 V prototype up to 100 W of power and operating at 100 kHz switching frequency.

A Modified Series-Capacitor High Conversion Ratio DC–DC Converter Eliminating Start-Up Voltage Stress Problem

In this letter, a modified series-capacitor (SC) high conversion ratio (HCR) dc–dc converter is proposed. The proposed converter inherits most of the advantages of the existing SC HCR dc–dc converter and can eliminate the problem of high switch-voltage stress of the existing converter encountered during start-up using a simple circuit modification. Although an extra capacitor is required in the proposed converter, total series capacitance of the proposed converter is the same as that of the conventional SC converter. In addition, input capacitance of the proposed converter can be reduced by less than half of that of the SC buck converter. A 1-kW prototype converter is built and tested to verify the performance of the proposed converter.

Comparison of a Buck Converter and a Series Capacitor Buck Converter for High Frequency, High Conversion Ratio Voltage Regulators

This paper presents an analytical and experimental comparison of a two-phase buck converter and a two-phase, series capacitor buck converter. The limitations of a conventional buck converter in high-current (10 A or more), and high-frequency (HF, 3–30 MHz) point-of-load voltage regulators with large voltage conversion ratios (10-to-1) are highlighted. The series capacitor buck converter exhibits desirable characteristics at HF, including lower switching loss, less inductor current ripple, automatic phase current balancing, duty ratio extension, and soft charging of the energy transfer capacitor. Analysis of the topologies indicates that switching loss and inductor core loss can dominate at HF. Results from side-by-side 12 V input, 1.2 V output hardware prototypes demonstrate that the series capacitor buck converter has up to 12 percentage points higher efficiency at 3 MHz and reduces power loss by up to 33% at full load (10 A). Some guidelines for inductor selection are provided, and a switch stress comparison reveals that the maximum converter switch stress is reduced by 30%.