Conventional Buck Converter Research Articles

Nonisolated High-Step-Down DC–DC Converters With Low Component Count and Voltage Stress

This paper proposes two new non-isolated high step-down DC/DC converters. The converters' voltage conversion ratio and their semiconductor components' voltage stress are improved compared to the conventional buck converter. By coupling the inductors of the first proposed converter, its volume and price is reduced. By employing a clamp circuit with low elements to the first proposed converter, the second proposed converter is introduced, in which its voltage conversion ratio and the voltage stress of components are improved significantly; thus, in high input voltage applications, high-quality components (switches with low on-resistance and diodes with low forward voltage) can be used. In these converters, the leakage inductances of the coupled inductor are clamping, and their energy is recovered. The proposed converters have fewer elements than related high step-down counterparts' converters leading to lower volume and losses due to lower elements, increasing efficiency. The switches of the proposed converters are switches simultaneously, reducing the converters' control circuit complexity. This paper discusses the theoretical analysis and operational principle of both proposed converters. Besides, to verify their performances, experimental results of the converters with 155-24 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> input and output voltage are presented.

An interleaved high step‐down coupled inductor based quadratic DC‐DC converter

AbstractA high step‐down direct current‐direct current (DC‐DC) buck converter with a coupled‐inductor in its topology is presented in this study. The switching pattern of the proposed converter is interleaved; therefore, the voltage stress on the semiconductors and the components is low since the primary high voltage will be divided between the blocking capacitors on the primary side. Thus, the voltage stress on semiconductor elements will be low. As a result, the preselected elements can be chosen with low voltage ratings. In addition, there are cells with coupled inductors utilized in the structure that helps the converter to provide improved voltage gain in its output terminal. Typically, narrow duty cycles are needed to achieve high gain in conventional buck converters, but the proposed converter has obtained a high conversion ratio even with wider duty ratios. Besides, the proposed converter has a constant equation for the voltage gain for the whole range of duty cycles. Theoretical analysis and comparison with other recent converters of similar types have been conducted to demonstrate the proposed converter performance. Furthermore, to verify the theoretical analysis, a 600 W prototype of the proposed converter with 820 V/30 V is implemented, and experimental results are presented.

GaN-based step-down power converter and control strategy for hydrogen energy systems

The conventional Si-based semiconductors suffer from low switching frequency, high conduction loss and low efficiency. These shortcomings hinder the improvement of power electronic power converter performance. An attractive solution is to replace Si-based semiconductor devices with the wide-bandgap semiconductors based on gallium-nitride material. In terms of the step-down converters which are used for hydrogen energy systems, it is difficult for the traditional buck circuit to eliminate the output current ripple and achieve fault-tolerant operation. Therefore, topologies of the step-down power converter also need improvement. In this paper, a GaN-based step-down power converter and control strategy for hydrogen energy systems is presented. Firstly, the mathematical analysis of the conventional buck converter is done to clarify why it has limitations regarding the reliability and current ripple. Another alternative solution is discussed but still suffers from ripples. In order to eliminate the current ripple and enhance the fault-tolerant ability, a novel GaN-based solution is given and both analysis and design are provided. The current ripple can be perfectly cancelled and fault-tolerant operation can be fully achieved. The comparison is carried out with the existing solutions. The time-domain simulation tests are carried out. And the experimental prototype is established based on the enhancement mode GaN transistor. The experimental results verify the effectiveness of proposed design regarding the current ripple cancellation and dynamic performance.

An Ultrahigh Step-Down DC–DC Converter Based on Switched-Capacitor and Coupled Inductor Techniques

In this article, high step-down dc–dc converters are widely employed in data center applications. Due to the higher step-down conversion ratio in the new generation 48 V voltage regulator module, a conventional buck converter is not suitable for such applications. To conquer this problem, a novel dc–dc converter is proposed in this article to achieve an ultrahigh step-down voltage conversion ratio for data centers. The nonisolated topology can be optimally designed to integrate both the switched-capacitor and coupled inductor techniques, which allows zero-voltage-switching (ZVS) of all active switches to be achieved and improves high efficiency. In addition, the converter presents the advantages of lower voltage stress, ultrahigh voltage gain, common ground, and simple control strategy. A comprehensive analysis of the steady-state analysis, derivation of voltage gain, voltage stress, and ZVS condition is presented in detail. Finally, a 30 W, 48-to-1 V experimental prototype is built and tested, which validates the ultrahigh step-down voltage gain and soft-switching characteristic of the proposed converter. The maximum efficiency of the prototype is 89.1% and the efficiency is 81.4% in full-load condition.

Analysis and small-signal modeling of simplified cascade multiphase DC-DC buck converter

One of the power converters that are often implemented in renewable energy applications is a DC-DC power converter. One of such converters is a step-down converter or buck converter whose output voltage is lower than its input. A novel DC-DC buck converter for low output-voltage and high output current applications is presented in this paper. When compared to the conventional buck converter, the voltage ratio of the proposed topology is higher. The output of this converter also has lower ripple. Thus, the proposed topology is appropriate for renewable applications. The operating principle and small-signal model analysis are discussed in detailed. Finally, a simulation studies is carried out by PSIM to verify performances of the offered topology

Non-Isolated Power Factor Corrected AC/DC Converter with High Step-Down Voltage Ratio for Low-Power Applications

This paper proposes a high step-down ratio AC-DC converter employing a quadratic buck converter with power factor correction. Conventional active power factor correction topologies employ boost-based correction schemes for unity power factor operation. This will require a steeper step-down ratio and higher switch voltage stress apart from complexity in the control scheme with sensors. The structure of the proposed topology is developed by combining the power factor correction stage with a high step-down stage. The passive input filter is split up into two for the purpose of reducing the thermal heating apart from offering a higher power factor. A single switch operation reduces the complexity of the control scheme. In addition, the number of conducting devices during the current path is also the same as the conventional buck converter due to cascading and hence offers lower conduction losses. The need for the converter to operate at an extremely low duty cycle is reduced due to the quadratic stage structure. The proposed converter operates at a moderate duty cycle, offering higher step-down voltage apart from reducing filtering requirements. MATLAB R2020b is used for carrying out simulation studies. Xilinx FPGA-based controller using system generator is implemented for the generation of pulses of appropriate duty cycle. Simulation and experimental results for a 150 W prototype are presented. An investigation and comparative evaluation of the conventional bridgeless buck system with the quadratic buck converter are carried out. The proposed structure offers the benefit of a higher step-down voltage ratio incorporating an inherent power factor correction stage along with the AC/DC stage.

A Novel Nonisolated GaN-Based Bidirectional DC–DC Converter With High Voltage Gain

A nonisolated bidirectional dc–dc converter is proposed for energy storage systems in this article. The proposed converter is composed of three active switches, two synchronous rectifiers, two clamping capacitors, and two inductors. The proposed converter has advantages of being a simple structure, a fewer number of components, a common ground, lower voltage stress, and wide voltage gain range. Compared with the conventional buck converters, the novel converter triples the effective duty cycle and lowers voltage stresses across the active switches. A 300-W/500-kHz GaN-based experimental prototype is built and tested to verify the correctness and validity, demonstrating a peak efficiency of 94.54% in step-down mode and a peak efficiency of 94.88% in step-up mode.

Integrated Quadruple Output Synchronous Buck Converter for E-Mobility Application

A nonisolated integrated multiple output synchronous buck converter is proposed in this article to cater the auxiliary power supply requirements of e-mobility. The converter provides independently controlled multiple outputs with reduced switch count as compared to conventional separate buck converters as well as conventional synchronous buck converter. The operating principle and working of the proposed converter are discussed in detail for better understanding. As the dynamic behavior of the converter is similar to the conventional buck converter, a simple controller is designed and implemented in this work. The converter is simulated in MATLAB-Simulink. A laboratory prototype of single input–quadruple output (SIQO) converter is developed and operated under closed loop condition to validate and demonstrate its advantages. The prototype is developed by designing two inductors on a single core for increased compactness and reduced cost of the converter. Each output of the converter can be independently controlled by varying the duty ratio of the related switch, thereby eliminating the effective cross regulation problem. The efficiency of the proposed SIQO converter is 93.6%, with four output ports, which is higher than its category of converters reported earlier. A significant improvement in the calculated efficiency is observed with the replacement of conventional switches and diodes of the converter by SiC switches (96.1%).

A Highly Integrated Tri-Path Hybrid Buck Converter With Reduced Inductor Current and Self-Balanced Flying Capacitor Voltage

This paper presents a single-stage tri-path buck converter with reduced inductor current and self-balanced flying capacitor voltage. The proposed converter introduces capacitor paths to reduce the average inductor current and inductor current ripple, hence decreasing the conduction loss. Operating with two states per conversion cycle, it exhibits a relatively low voltage conversion ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${D}$ </tex-math></inline-formula> /(1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$+\,\,2{D}$ </tex-math></inline-formula> ). Besides, it realizes a self-balanced flying capacitor voltage in the charge redistribution phase. Similar to the conventional buck converter, the proposed converter in continuous-current mode only has two complex poles. Therefore, we design a Type-III compensator to obtain a good transient response. Moreover, the circuit does not require extra supplies for gate drivers due to the reutilization of the flying capacitor voltages, eliminating additional circuit and power overheads. The proposed converter, validated in a 65-nm standard CMOS technology, regulates a 0.7 V – 1 V output voltage from a 3.3 V – 4 V input voltage, delivering a maximum output power of 270 mW. The peak efficiency is 84%, with a switching frequency up to 5 MHz.

Stability Analysis of Coupled-Inductor-Based Buck Converter: Participation Factors Approach

A coupled-inductor-based fourth-order buck converter is introduced in this article. The salient features of this topology are lower source current ripples like in conventional buck converter with input filter, no need of connecting an additional damping network across the input filter capacitor, additional flexibility provided by the coupling in the performance tuning, and the existing input <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> – <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_m</i> structure itself acts as a ripple steering network. The detailed steady-state analysis is evolved and conditions for source current ripple reductions are formulated. Subsequently, small-signal analysis is established and a proportional plus integral plus derivative type controller is designed to ensure load voltage regulation. To enhance the dynamic performance, a two-loop voltage-mode controller is designed. The stability analysis of the closed-loop coupled-inductor-based buck converter is carried out through the eigenvalue sensitivity and participation factors approach. The impact of converter parameters on the converter system stability is discussed. In comparison with the single-loop voltage-mode controller, the two-loop voltage-mode controller is able to ensure that the closed-loop poles stay away from the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">jω</i> -axis and, thus, the two-loop voltage-mode controller exhibits better dynamic performance. Analytical findings are validated on a 75 W, 60 to 36 V prototype converter. Steady-state and dynamic performance characterizing measurement results are given for validation of the concept.

Buck converter with magnetic-coupled inductors for power factor corrector

The step-down dc-to-dc converter for application in power factor corrector is proposed and analysed in this paper. Unlike a conventional buck converter containing a single inductor and output capacitor, the proposed converter uses two magnetic-coupled inductors and two output capacitors connected in series. The output voltage of such a coupled inductor buck converter is equal to the sum of voltages of these capacitors. The direct interaction of the input voltage occurs only with a part of the output voltage. This allows increasing a conduction angle in the power factor corrector (PFC) on the basis of the proposed converter and, as a result, reducing the total harmonic distortions and increasing a power factor to satisfy current standard requirements. A detailed analysis of the operation of the proposed converter is presented. The reliability of the analysis is confirmed by a small discrepancy between the results of calculation, modeling and experiment.

High-Efficiency Flicker-Free LED Driver with Soft-Switching Feature.

A novel interleaved DC-DC buck converter is proposed to drive high-brightness light-emitting diodes (LEDs). The circuit configuration mainly consists of two buck converters, which are connected in parallel and use interleaved operation. Through interleaved operation, the power capability of the converter is doubled. Traditionally, two individual inductors are used in the two buck converters. The difference between conventional parallel-operated buck converters using two energy storage inductors and the proposed circuit is that the proposed circuit uses two small inductors and a coupled inductor that replace the two inductors of the buck converters. In this way, both buck converters can be designed to operate in discontinuous-current mode (DCM), even if the magnetizing inductance of the coupled inductor is large. Therefore, the freewheeling diodes can achieve zero-current switching off (ZCS). Applying the principle of conservation of magnetic flux, the magnetizing current is converted between the two windings of the coupled inductor. Because nearly constant magnetizing current continuously flows into the output, the output voltage ripple can be effectively reduced without the use of large-value electrolytic capacitors. In addition, each winding current can drop from positive to negative, and this reverse current can discharge the parasitic capacitor of the active switch to zero volts. In this way, the active switches can operate at zero-voltage switching on (ZVS), leading to low switching losses. A 180 W prototype LED driver was built and tested. Our experimental results show satisfactory performance.

Analogous Mode Implementation of State Space Based Control of Buck Converter

Abstract The new requirements for point-of-load converters include the dynamic behavior, leading to the need for improvements in the control system for the conventional buck converter. Usually, the regulator design, in order to secure stability at parameter or mode variation, aims a zero steady-state error and a phase margin over 60 degrees. The design based on Venable’s K-factor method (Venable, 1983) helps achieve this topic. A more modern control design method based on State Space is used progressively on digital platforms. This paper extends the merits of the State Space based design procedure with an analogous mode implementation.

Stable Convergence Control of the Buck Converter Based on Iterative Learning Method

To enhance the stability and robustness of the DC converter, a two-dimensional (2D) iterative learning control method suitable for the Buck converter is proposed. This control method is derived through a continuous-discrete model. Combining the error dynamics equation and the iterative learning method(ILM) described with Roesser theory, effective learning rules and sufficient conditions for convergence are obtained. By contrast with the iterative learning algorithm of the conventional Buck converter, this algorithm clarifies the learning gain, deeply learns the structure and parameters of the converter, and obtains an accurate learning dynamics model. Moreover, numerical simulations of the Buck converter with specific circuit parameters are also conducted. The simulation results demonstrate that the control learning rules are less restrictive with a swift transient response, which are robust without complex feedback compensation circuits. Thereby, it elucidates a new approach to the application of the Buck converter.

A two‐phase non‐inverting buck‐boost converter for an RL load

There is an increase in renewable energy sources, which are regarded as current sources, where DC-DC converters are widely used which require more suitable loads for driving current type loads. This paper uses a duality approach to show that the converter circuit can apply to the current type loads without too much voltage variation. It illustrates the derived steps for a conventional buck converter by using graph formation. To validate the duality approach, five original switching converters are detailed. A current source with an R-L load (CSRL) converter is used for current-based applications, such as electrical motors, electromagnetic relays, or light-emitting diodes (LEDs). This study proposes a two-phase non-inverting buck-boost converter with an R-L load which is suitable for driving current-based applications. The design procedure and steady-state analysis are presented. SIMPLISTM software is used to simulate the topologies. This method for operation mode and formula derivation is like in voltage type circuit structures, and this study has sufficient mathematical analysis capabilities. For demonstration, a 650 W VSRL converter is implemented to verify the feasibility of the method. The corresponding circuit topology of the conventional circuit can be illustrated by using the duality approach rapidly.

Active Cross-Commutated (ACC) Buck Converter

To address the hard-switching issue of conventional buck converter and high-voltage/current stress issue of soft-switched converter like resonant cross-commutated buck converter, a new soft-switched dc–dc topology with two-phase operation is proposed in this article. The ac current generated from the floating half bridge of one phase is injected into the switching node of another phase to realize zero-voltage switching for all MOSFETs and zero-current switching for the low-side MOSFETs. This method is named as active cross-commutation (Acc). The benefits of AccBuck converter include soft switching, low-voltage stress of low-side switches, low current stress for all switches, and fixed switching frequency. The operation principles with and without parasitic output capacitance ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oss</sub> ) are analyzed by using the state-plane method. Clamped diodes are added to reduce the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oss</sub> -related ringing. The analytical formula of voltage gain is derived, which is related to the duty ratio, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oss</sub> , inductance, load current, and switching frequency. A prototype was fabricated to demonstrate the proposed converter. During the fixed-duty-ratio operation, the converter achieves 97.8% peak efficiency and 1410 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> power density at 50 A output current, 54 V input, and 9 V output. The calculated load line and regulation capability are also verified experimentally.

A non‐isolated DC‐DC converter with low voltage stress and high step‐down voltage conversion ratio

This work focuses on a new non-isolated interleaved DC-DC converter with very high step-down voltage conversion ratio. By employing the switched/series capacitor concept, along with the proper component interconnection, the converter features a high step-down voltage conversion ratio where, in the private case of equal duty ratios, it is six times higher than the conventional buck converter. This high step-down voltage conversion ratio is achieved with the lowest number of components compared to other similar topologies of the same conversion ratio. Also, due to the blocking/series capacitors, the voltage stress on the switches is reduced, improving the converter efficiency. One of the key features of the proposed converter is the inherent automatic current sharing between the interleaved phases, which in the case of equal duty ratios, is uniformly distributed. To add on, due to the use of only two interleaved phases, the converter has a wide output voltage range, since the duty cycle can be extended to 0.5. To validate the proposed converter operation, a 250 W wide-input/wide-output experimental prototype was built, achieving a peak efficiency of 94%.

A High Step-Down DC–DC Converter With Reduced Inductor Current Ripple and Low Voltage Stress

This article presents a buck converter with a large step-down voltage conversion ratio, reduced ripple in inductor current and low semiconductor voltage stress. The proposed converter produces a lower output voltage at a sufficiently higher duty ratio compared to the conventional buck converter. The step-down voltage conversion ratio is modified by a series-parallel transition of two identical capacitors of a switch-capacitor cell. Two parallelly placed switches and two cross-connected identical capacitors are utilized to design the cell. An extra inductor is placed at the input side to oppose the sudden change in input current due to the series-parallel transition of the two identical capacitors. Therefore, two inductors are required to design the converter. These two inductors are coupled directly. The modified voltage conversion ratio reduces the ripple in inductor currents and output voltage. Direct coupling between the two inductors helps to further reduce the ripple in inductor currents and output voltage. The operating principle, analysis of ripple in inductor currents, and ripple in output voltage are discussed. The analysis of small-signal modeling is carried out and a voltage mode PI-controller is designed to enable the closed-loop operation. Finally, the proposed converter is implemented in hardware and the performance of the proposed converter is verified experimentally.

A study of Comparative analysis of fuzzy logic controller and neural network for dc–dc buck converter

This paper presents the comparative analysis between fuzzy logic controller and neural network for DC-DC Buck converter. The major drawback in the conventional buck converter is when the input voltage or load change, the output voltage also changes which reduces the overall efficiency of the buck converter. So here we are using non linear controllers for buck converter which respond quickly for perturbations and maintains the fixed load voltage even when there are non-linearity’s occurs compared to a linear controllers like P,PI,PID controllers which can’t withstand when perturbations occur. Simplicity, low cost and adaptability to the complex systems without mathematical modeling are the best features of Fuzzy Logic controller and neural networks. The Two implementations are analyzed in detail and simulated in MATLAB/SIMULINK environment and results presented. Proposed approach is implemented on DC to DC step down converter for an input of 230V and performance characteristics like maximum overshoot, settling time and efficiency of the converter are studied.

DG-side earth fault tolerance enhancement based on topology improvement and common and differential mode control strategy

Parallel distributed generation (DG) can extract power from a renewable energy source and supply it to the grid, but the exposure of DG components, such as photovoltaic panels, to the natural environment results in DG-side earth faults and common earth circulating current (CECC) problems. This study proposes an improved topology and a common and differential (C&D) mode control strategy to enhance the earth fault tolerance in parallel DG systems. First, the effects of line resistances and input voltages on CECC are analyzed through a mathematical model, and the disadvantages of the conventional buck converter are identified. Second, an additional switch in a negative pole is designed for the application of the C&D control strategy. Specifically, common-mode algorithm control is used to inhibit CECC, and differential-mode control is applied to ensure current sharing accuracy. Third, an inertial element is added to the reference voltage to restore the bus voltage produced by the differential-mode control strategy. Lastly, an experiment is conducted to verify that the proposed control outperforms conventional control in various conditions.