Output Current Ripple Research Articles

Design Considerations of Multi-Phase Buck DC-DC Converter

The main objective of this article is to propose a rational methodology for designing multi-phase step-down DC-DC converters, which can find applications both in engineering practice and in power electronics education. This study discusses the main types of losses in the multi-phase synchronous buck converter circuit (transistors’ conduction losses, high-side MOSFET’s switching losses, reverse recovery losses in the body diode, dead time losses, output capacitance losses in the MOSFETs, gate charge losses in MOSFETs, conduction losses in the inductor, and losses in the input and output capacitors) and provides analytical dependencies for their calculation. Based on the control examples for applications characterized by low voltage and high output current, the multi-phase buck converter’s output and input current ripples are analyzed and compared analytically and graphically (3D plots). Furthermore, graphical results of the converter efficiency at different numbers of phases (N = 2, 4, 6, 8, and 12) are presented. An analysis of the impact of various parameters on power losses is conducted. Thus, a discussion on assessing the factors influencing the selection of the number of phases in the multi-phase synchronous buck converter is presented. The proposed systematized approach, which offers a fast and accurate method for calculating power losses and overall converter efficiency, reduces the need for extensive preliminary computational procedures and achieves optimized solutions. Simulation results for investigating power losses in 8-phase multi-phase synchronous buck converters are also presented. The relative error between analytical and simulation results does not exceed 4%.

A Review on Control Methods of SEPIC Converters

In recent years, electric vehicles have witnessed a surge in popularity due to their energy-saving and eco-friendly attributes. Unlike conventional internal combustion engine vehicles, electric vehicles exhibit superior performance and operational efficiency. Within the realm of modern electric vehicles, power electronic circuits, notably including DC-DC converters, play a pivotal role. Among these converters, single- ended primary-inductor converters (SEPIC) find extensive use in scenarios where minimizing input and output ripple currents is essential. The primary objective of this project is to conceive and put into action advanced controllers for SEPIC converters, catering to a diverse range of applications, encompassing battery-powered devices, solar energy systems, and LED lighting systems. Key Words: DC-DC converter, SEPIC converter, PID, SMC, ASMC, Fuzzy logic Control.

Analysis and Design Considerations of Input Parallel Output Series-Phase Shifted Full Bridge Converter for a High-Voltage Capacitor Charging Power Supply System

Capacitor charging power supply (CCPS) is used for impulse-power applications such as electromagnetic rail guns, flash lamps, medical sterilization, and rock crushing, among many other application fields. This paper describes the design and analysis of an Input Parallel Output Series-Phase Shifted Full Bridge converter for CCPS. The proposed system has a low output current ripple to improve the lifetime of the high-voltage pulsed capacitor. Design considerations of topology's electrical parameters such as HF transformer's leakage inductor and output inductor for the CCPS application are presented. The intermediate DC-link capacitance is provided as an energy storage element to minimize the disturbances (power variation) on the source for the CCPS application. Analysis and sizing of the capacitance for two different charging methods are analyzed and compared. A controller design procedure for the Active Front End Converter (AFEC) is also included to ensure near-constant power drawn, rejecting the load disturbances. Finally, a complete design procedure for the whole CCPS system is presented. Design and simulation results are presented for a rated system, followed by experimental results from a scaled-down hardware prototype to validate the design.

A High Efficiency Δ-Lr-Y Type Three-Phase Interleaved LLC Converter With Less Transformer Loss

Y-type three-phase interleaved LLC has advantages in high-power applications with small output current ripple. However, the traditional Y-type three-phase interleaved LLC has large winding current under low output voltage and high power (LVHP) applications, which affects the efficiency and power density. In this paper, a high efficiency delta-type three-phase interleaved LLC topology with less transformer losses was proposed. This paper verifies that the transformer loss of the proposed topology is lower than that of the traditional Y-type topology based on the loss model and simulation. Furthermore, considering the coupling between three-phase transformers, a more accurate soft-switching analysis method and the first harmonic gain formula of the proposed topology are given. According to the analysis results, compared with the traditional Y-type topology, only half of the magnetizing current was needed to achieve soft-switching. Meanwhile, the length of the transformer air gap is one-third of the traditional Y-type topology, which can reduce the fringing loss. Finally, a 3 kW prototype was designed and verified. Compared with the Y-type, this paper achieves 19.2% loss reduction.

Design and Performance Evaluation of an Automatic Dimmable Fault-Adaptive LED Driver Circuit

In this paper, an automatic, fault-adaptive, and dimmable LED driver circuit and LED lamp module is designed and simulated. The designed LED driver can automatically operate and dim (18–72) W LED modules assembled with unknown series-parallel combination of 3 W LED chips on universal AC input (Vrms=(90–265) V, 50/60 Hz). The unique feature of the modelled LED driver circuit is its ability to monitor and detect failure of any connected LED chip and then adapt to provide optimised light output from the LED modules under faulty conditions. The proposed LED driver circuit and LED lamp module are simulated in MATLAB Simulink environment to evaluate the electrical performance. The operation of the simulated LED driver circuit from 100 % to 30 % of rated light output and during occurrence of fault is satisfactory and in compliance with IEC61000–3–2:2014 and IEEE Standard P1789. Input power factor of the simulated LED driver ranges from 0.74 to 0.99, THD from 3.33 % to 30.63 %, and output current ripple from 4.6 % to 20 % under operation of all connected LED modules.

Development of DSP-based TPS fully digital correction magnet power supply

The Taiwan Photon Source (TPS) is a third-generation 3 GeV synchrotron accelerator light source. After successfully operating for ten years since its first light in 2013, various subsystems are undergoing updates. In the context of magnet power supply upgrades, the trend toward digitization and high-precision modulation control is driving advancements worldwide. This study focuses on developing a fully digital correction magnet power supply (FDCMPS) based on a digital signal processor (DSP). The prototype utilizes a low-power, floating-point DSP with multiple communication functionalities as the core control unit. The output current is converted into digital values using current sensors and high-precision analog-to-digital converters. Discrete PI compensator algorithms are implemented within the DSP to generate pulse-width modulation (PWM) waveforms, driving a full-bridge (H-bridge) converter configuration with metal-oxide-semiconductor field-effect transistors (MOSFET). This forms a complete, fully digital closed-loop current control system. A virtual control interface is designed to operate the FDCMPS state. The control loop design of the prototype has been validated and demonstrates stable output bipolar current performance. When tested with a 0.1 V input reference signal, the prototype achieves a -3 dB bandwidth of 2.03 kHz. Finally, a hardware prototype circuit was constructed in the power supply laboratory, with an input voltage of 48 V, an output current of 10 A, and a maximum power of 400 W. Overall, the developed fully digital correction magnet power supply prototype showcases stable and high-performance output bipolar current performance. The system achieves total harmonic distortion of output current ripple within 0.3 mA peak to peak and long-term stability within ± 15 ppm. The successful implementation of the prototype establishes a solid foundation for advancing magnet power supply technology at the TPS.

A ZVS Three-Level Synchronous Buck Converter With Simple LC Circuit

This brief presented a new soft-switching auxiliary circuit for the three-level buck converter with synchronous rectification (TLBC-SR). The new zero voltage switching (ZVS) auxiliary circuit only employs one inductor and one capacitor, and has the features as full soft-switching conditions, high efficiency, low output current ripples, and simple modulation control method. The detailed operation principle and soft-switching design method are also given. Finally, an experimental prototype is built to verify the proposed ZVS TLBC-SR. The experimental results show that all switches operate under zero voltage switching (ZVS) conditions, and the peak efficiency of the prototype is up to 96.85%@100kHz.

A Novel Light-Emitting Diode Streetlight Driver Circuit Applied to a Direct Current-Input Voltage Source

With the global advocacy of green lighting and the urgent need for energy saving and carbon reduction, more and more street lighting applications have entered the era of being replaced by light-emitting diode (LED) lighting sources. This paper presents a new LED streetlight driving circuit applied to a direct current (DC)-input voltage source, which consists of a buck converter combined with a flyback converter to reduce the number of circuit components required and to recover the leakage energy of the transformer to improve energy conversion efficiency. In addition, this study also completed the analysis of the operational principle of the new LED streetlight driving circuit, and developed a prototype LED streetlight driver with DC-input voltage of 48V and output power of 72 W (36 V/2 A). Finally, the measurement results of the prototype circuit show that the output voltage ripple rate was less than 15%, the output current ripple rate was less than 6%, and the circuit efficiency was as high as 91%.

The DC Inductor Current Ripple Reduction Method for a Two-Stage Power Conversion System

This paper proposes a method for minimizing the inductor current ripple of a DC–DC converter in a two-stage power conversion system consisting of a grid-connected PWM converter and an interleaved multiphase three-level DC–DC converter. To reduce the output voltage ripple, the three-level DC–DC converter is configured in parallel and operated interleaved. However, a circulating current generated by the interleaved operation increases the inductor current ripple of each DC–DC converter and causes system loss and inductor saturation. In this paper, the inductor and output current ripple of the interleaved three-phase three-level DC–DC converter is mathematically analyzed and the effect of the DC–DC converter’s duty ratio and output voltage on each current ripple is described. Based on this analysis, a method is proposed for controlling the optimal DC link voltage through the PWM converter, so that the DC–DC converter is controlled with the duty ratio that minimizes the inductor current ripple. The simulation and experimental results under various operating conditions are presented to verify the feasibility of the proposed control method.

An E-Core Based Integrated Coupled Inductor for Interleaved Boost Converter

Interleaving in a boost converter is beneficial for lowering input and output current ripples through ripple cancellation due to phase-shift between channel currents. However, interleaving does not affect the channel current ripple. The channel current comprises circulating Differential Mode (DM) current and Common Mode (CM) boost current, whose ripples constitute the total channel current ripple. Inverse coupling between channel inductors effectively lowers channel current ripple while maintaining the same input and output current ripples. However, with a single inverse coupled inductor, its leakage inductance, which serves as a boost inductor, depends on the winding arrangement and is challenging to balance in both channels. To overcome this, the inverse coupled inductor can be implemented as a cascade of inverse (DM inductance) and direct (CM inductance) coupled inductors. The DM and CM currents and their ripples then depend on CM and DM inductances, respectively. Nonetheless, this approach results in increased size and count of magnetic cores. In this paper, an Integrated Magnetic Structure (IMS), based on a gapped EE-core, is proposed that combines both CM and DM inductances in a single core. The CM and DM inductances are independent and depend on separate winding turns. A reluctance model is derived, and a design procedure is developed where core parameters are expressed in terms of converter parameters. Finally, the proposed IMS concept is validated through a 300 W, 100 V to 168 V prototype, switching at 70 kHz.

Design and implementation of a temperature-compensated corrector magnet power supply for the Taiwan Photon Source

The Taiwan Photon Source (TPS) is a widely recognised 3 GeV synchrotron light source. It has demonstrated exceptional performance in average beam downtime and meeting international standards over its successful ten-year operation. Regular equipment updates are conducted for all subsystems to ensure continuous improvement and maintain an optimal research facility environment. This study focuses on designing and implementing a temperature-compensated corrector magnet power supply for the TPS. The power supply incorporates a high-bandwidth, compact, cost-effective, bipolar, and highly precise shunt resistor as the current feedback component. A temperature control copper box and temperature compensation circuit are employed to improve the thermal equilibrium time of the output current. A laboratory-developed TPS-corrected magnet power supply with temperature compensation control has been successfully developed through these measures. The prototype exhibits a maximum output current of 10 A and operates at a voltage of 40 V. Metal-oxide-semiconductor field-effect transistors (MOSFETs) are utilised as the power switch in a full-bridge (H-bridge) configuration with a driving frequency of 40 kHz. The output current ripple is effectively maintained at 100 μA for a 10 A output, and the stabilisation time is achieved within 5 minutes. The control loop design of the prototype has been verified to achieve fast and stable output current performance. The completed prototype demonstrated a -3 dB bandwidth of 2.57 kHz when tested with an input reference signal of 0.1 V. Finally, a hardware prototype circuit was constructed in the power supply laboratory, featuring an input voltage of 48 V, an output current of 10 A, and a maximum power capacity of 400 W.

Impact of Parameter Mismatch on Three-Phase Dual-Active-Bridge Converters

Three-phase dual active bridge converters (DAB3) are a widely used topology in battery charging applications thanks to their numerous advantages, such as bidirectional power flow, galvanic isolation, low output current ripple, and inherent soft-switching. In such applications, three single-phase transformers are commonly employed as the AC-link to simplify manufacturing and reduce costs. These transformers’ leakage inductance can be utilized instead of the external leakage inductance to achieve high power density. However, the assumption of uniformity in these inductances is not always accurate as they can vary significantly during fabrication. This study presents a comprehensive analysis of the impact of transformer leakage inductance variation, which can deviate by up to 24% from the desired value. The effects of this variation are investigated from different perspectives, including power transfer, soft-switching range, root-mean-square (RMS) current, and the temperature rise of the transformer winding. Although the power transfer and total copper loss of transformers are changed insignificantly even under highly mismatched leakage inductance, the currents and thermal distribution among phases are considerably impacted. Based on statistical probability, a maximum leakage inductance variation threshold of 10–15% compared to the desired value is recommended to ensure the maximum acceptable temperature rise among phases. Experimental results are presented to validate the analysis.

Single-Stage Active Rectifier With Wide Impedance Conversion Ratio Range for Inductive Power Transfer System Delivering Constant Power

Compared with the constant current (CC) charging mode, the constant power (CP) charging mode can speed up the battery charging rate and free the charger from excessive thermal design problems. However, the range of the battery's equivalent resistance in CP mode is wider than that in CC mode, which makes it difficult to track the optimal resistance of the inductive power transfer (IPT) system for efficiency enhancement. To solve this problem, this paper proposes a single-stage active rectifier (SSAR) integrating an interleaved buck converter with a full-bridge active rectifier (FBAR). Compared with the traditional FBAR, the resistance conversion ratio range of the SSAR is extended from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$[0, 8/\pi ^{2}]$</tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$[0, 8]$</tex-math></inline-formula> , and the output current ripple is reduced due to the interleaved operation. A novel optimal phase angle control strategy is correspondingly proposed for the IPT system with the SSAR, which features advantages of wide impedance conversion ratio range, zero voltage switching (ZVS) turn-on of all MOSFETs, and no communication between the primary and the secondary sides. A 150 W experimental prototype is provided to verify the effectiveness of the proposed rectifier.

An Electrolytic-Capacitor-Less PFC LED Driver With Low DC-Bus Voltage Stress for High Power Streetlighting Applications

This paper presents a single-stage, soft-switching, high power factor, flicker-free LED driver without any electrolytic capacitors for streetlighting application. The proposed LED driver consists of a buck-boost type power factor correction (PFC) circuit integrated with an asymmetric half-bridge LLC resonant converter. The buck-boost type PFC circuit provides a high power factor, low input current harmonics, and low dc bus average voltage. Unlike other methods that use the first harmonic approximation (FHA) analysis or the differential equations in time domain to analysis the LLC circuit, in this paper, a Fourier series-based analysis is proposed. The proposed method provides better accuracy in comparison with the FHA while being simpler than the time domain analyze method. The half-bridge LLC resonant converter is designed such that ZVS is obtained for the entire input voltage range (185 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 265 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$V_{rms}$</tex-math></inline-formula> ), and for 20% to 100% of the full-load power. In addition, a magnetic integration technique is utilized to increase efficiency and reduce converter size. The designed control system enables lowering the output current ripples without using any electrolytic capacitors. To verify the feasibility of the proposed LED driver, a 200 W prototype is implemented. The proposed LED driver achieves maximum efficiency of 94.6%, high PF, and a maximum of 15% output current ripples.

Analysis and Control of Chaos in Current Mode Controlled Superbuck Converter for Photovoltaic Systems

Background: Superbuck converter is a strong nonlinear system. However, with the changes in parameters, Superbuck converter performance may be reduced due to nonlinear phenomena, such as bifurcation, chaos, etc. Current mode controlled Superbuck converters have been extensively applied in photovoltaic (PV) systems that require a stable output voltage. Superbuck converters, as nonlinear circuits, exhibit plentiful nonlinear phenomena, such as bifurcation and chaos. In this study, we analyze and control the nonlinear phenomena in the current mode controlled Superbuck converter. The piecewise switching model and discrete iteration mapping model of the Superbuck converter are established. The evolution process of the Superbuck converter from steady state to bifurcation and chaos is revealed when the reference current, input voltage, and load are used as bifurcation parameters, and the bifurcation forms of the converter are all period-doubling bifurcations. The stability criterion of Superbuck converter under current mode has been deduced from reference current by analyzing the stability of the converter. Through the resonant parametric perturbation (RPP) method, the chaos control of the Superbuck converter has been realized for the first time. The converter changes from a chaotic state to a stable single-cycle state about 0.4ms after control and the output voltage ripple is reduced from 3.905V to 0.679V, which effectively improves the output stability of the converter. Objective: This study aimed to analyze and control nonlinear phenomena in current-mode controlled Superbuck converters. Method: Bifurcation diagram, time-domain waveform diagram, phase portrait and Poincare section are used as analytical methods for the nonlinear dynamic characteristics of Superbuck converters. The chaotic control method of the Superbuck converter is Resonant Parameter Perturbation (RPP). Results: After applying RPP control to the Superbuck converter in the chaotic state, it is converted into a single-cycle stable state in about 0.4ms. After the converter is controlled, the output current ripple is reduced from 0.71479A to 0.31A, and the output voltage ripple is reduced from 3.905V to 0.679V. Conclusion: With the increase in the reference current, the decrease in the input voltage, or the increase in the load, the system enters the chaotic state through the period-doubling bifurcation path. In this study, the chaos control of the Superbuck converter is carried out for the first time, and the control method used is the resonant parametric perturbation method. After RPP control, the converter is changed from an unstable, chaotic state to a stable period state in about 0.4ms.

Small Signal Modeling of LLC Converter with LED Load and Quasi-Resonant Controller Based Active Ripple Rejection

This paper has analyzed the defects of the traditional extended description function (EDF) based LLC small signal modeling method when driving light emitting diode (LED) load and proposed an accuracy improvement method. Detailed small signal model modeling methods have been deduced, and the accuracy of different modeling methods has been compared thoroughly. To suppress the second-order harmonic ripple in the direct current link-induced output current ripple, a quasi-resonant controller (QRC) is adopted to realize active ripple rejection (ARR). Considering the frequency of the second-order harmonic ripple changes with the grid voltage frequency, a single-phase software phase lock loop (SPLL) is adopted to extract the frequency of the second-order harmonic. By dynamically regulating the control parameter of the QRC according to the locked second-order frequency, output voltage ripple active rejection ability immune to grid voltage frequency deviation is obtained. Based on the deduced accurate small signal model, the digital controller is designed with stability, steady state and dynamics performance guaranteed. The accuracy of the proposed small signal model, the SPLL and the QRC-based ARR method has been verified at last.

A Single-Switch Soft-Switched High Step-Down Zeta Converter With Low Output Current Ripple

This article proposes a new nonisolated high step-down converter that is derived from Zeta converter. By employing coupled-inductor technique, zero-current switching is achieved for the switch at turn <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and turn <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> . Also, introduced converter incorporates a current ripple cancellation cell, which provides dc output current for full load as well as light load. Another main feature of the proposed converter is using a single switch and a magnetic core. Therefore, high efficiency and high power density are attained. For further efficiency improvement, a synchronous rectifier is employed, which results in efficiency greater than 96% for the entire load range. A 100-W prototype of the proposed converter is designed and implemented to verify the theoretical analysis and confirm its efficiency improvement and advantages.

A Carrier-Based Low Total Current Ripple Modulation Strategy for Parallel Converters With Leakage Current Attenuation

In order to meet the high performance and low leakage current requirements in high power rating photovoltaic applications, an improved carrier-based modulation (ICBM) for parallel converters is presented in this paper. Different from existing methods which are based on PS-PWM, a proper zero-sequence modulation wave is injected into the three-phase modulation waves to achieve low total current ripple based on the root mean square value analysis of output current ripple. Aside from this, the initial phase shift angles for the carriers in each converter are modified to minimize the excitation source of leakage current, while the quality of total output current is not affected. Furthermore, the proposed ICBM is extended to parallel multilevel converters according to the vector shift principle. By using the proposed ICBM, total current ripple reduction and leakage current attenuation in parallel converters can be achieved simultaneously. Experimental results validated the correctness and effectiveness of the proposed method.

Research on control strategy of photovoltaic hydrogen generation system based on Fuzzy PI control

Under the goal of carbon peak and neutrality, the search for efficient and clean green energy has attracted widespread attention. Photovoltaic (PV) hydrogen production has become a research hotspot because of its clean and near-zero carbon emissions. However, due to the influence of natural light, PV power generation is volatile and intermittent, reducing the system’s stability. In order to improve the stability of the system, a large number of power electronic devices and control strategies are applied to the PV hydrogen production system. Among them, the Buck circuit using proportional–integral (PI) control is the most widely used. However, the PI control has a long response time and large ripple, which affects the energy efficiency of PV hydrogen production. This paper proposes a PV hydrogen production system control strategy based on Fuzzy PI control. In the Matlab/Simulink environment, a simulation model of a PV hydrogen production system composed of PV cells, proton exchange membrane electrolyzers, and DC/DC units is built. The DC/DC unit uses a Buck circuit. Simulation analysis compares the output voltage and current ripple of the PV hydrogen production system model under different working conditions using the Fuzzy PI control and classical PI control strategies. Finally, the simulation results verify that the proposed control strategy reduces the system output voltage and current ripple.

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.