Multi-phase DC-DC Converter 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%.

Robust fixed-order [formula omitted] controller synthesis for multi-phase converters with input voltage feed-forward

Generated DC voltages of batteries, fuel cells, or supercapacitors as power sources connected in series with DC-DC converters change according to operating conditions. In such cases, the output voltage stability of the multi-phase DC-DC converters is an issue, particularly being subject to noises in the input voltage and load current disturbances. Input voltage feed-forward (IVFF) compensation approaches can improve the output voltage stability of the DC-DC converters in such scenarios. This paper proposes a robust fixed-order H∞ based IVFF control framework by considering sensor noise, input voltage, and load current disturbances to improve output voltage stability and reference tracking performance. The mismatched disturbance transfer functions depending on parasitic resistances are derived to include in the controller synthesis process. An iterative convex-concave optimization-based robust fixed-order controller design algorithm is proposed to optimize the feedback and feed-forward controllers under the stability and performance constraints. This algorithm allows the designing of the controllers simultaneously. The feed-forward controller, whose structure is independent of the system transfer functions, is optimized without any model inversion or extra design steps. The performance of the proposed controller is compared with an integral linear quadratic regulator controller, a sliding mode PID controller augmented with a nonlinear disturbance observer, and a fixed-order robust controller designed with non-smooth techniques. Real-time implementation of the fixed-order control systems is performed on a 2-leg 200 W interleaved boost converter. The performances are discussed under external disturbance effects to show the validity of the proposed control approach.

Inversely Coupled Inductors With Small Volume and Reduced Power Loss for Switching Converters

The letter presents a patent of lateral coupled inductor structure and its applications in single-phase and multiphase DC-DC converters. The CPUs, GPUs and FPGAs in the latest servers and artificial intelligence systems are powered by multiphase DC-DC switching converters and require high current, small size, fast transient response and high efficiency. This single-turn lateral coupled-inductor structure reduces magnetic core size through inverse coupling and minimizes inductor DCR power loss for high-current applications. The coupled inductor can be embedded inside a motherboard or a power module. The letter illustrates different implementations of the patent and provides solutions to the artificial intelligence systems that require high current and small volume of the power converters.

Common Mode Conductive Noise Cancellation for Multiphase Converter Using Auxiliary Winding

A multiphase DC-DC converter consisting of a coupled inductor and fast switching devices enables power electronics equipment to achieve a high power density. However, with such devices, the fast voltage transition generates substantial common mode (CM) noise. However, there are very few studies on CM noise reduction for multiphase converters using a coupled inductor. Therefore, in this paper, a CM noise reduction method is proposed for a multiphase DC-DC converter that hardly lowers the power density.

A fully integrated multiphase switched-capacitor DC-DC converter with PFM control and charge sharing loss reduction

A fully integrated high efficiency switched-capacitor (SC) DC-DC converter with pulse frequency modulation (PFM) control is presented. The small signal model of the multiphase-interleaving SC converter is given and it is verified through the simulation and the measurement results. For high efficiency, this design set the dominant pole at the output of the error amplifier (EA) and the 14-phase interleaving topology can push the non-dominant pole away from the Unit Gain Frequency (UGF) for the loop stability. By combining the flying-well and the deep n-well (DNW) isolation techniques, the proposed high-density MOS capacitor can reduce both the parasitic loss and the charge sharing loss of the converter. The conversion ratio of the converter is 2:1 under 3.3V power supply. This SC DC-DC converter is fabricated in the 40 nm CMOS process. It obtains the peak efficiency of 86.2% and the output power-density of 226 mW/mm2. It maintains the efficiency above 80% from 8 mA to 50 mA load condition.

Balancing scheme for phase current and flying‐capacitor voltage in three‐level DC–DC converter

A balancing scheme for phase current and voltage of the flying capacitor in a fully integrated multi-level multi-phase DC-DC converter is proposed. The proposed balancing scheme based on the ripple voltage of the flying capacitor can simultaneously mitigate the imbalance of phase current and voltage of the flying capacitor. A mathematical analysis shows the proposed scheme can obtain the current information of the flying capacitor during charging and discharging operations and finally obtain the average inductor-current value. A prototype 4-phase 350 MHz three-level DC-DC converter shows <;4.7% voltage imbalance of the flying capacitor and <;36 mA phase-current imbalance at output voltage and maximum load current of 0.9 V and 1.2 A, respectively.

Control of a Multiphase Buck Converter, Based on Sliding Mode and Disturbance Estimation, Capable of Linear Large Signal Operation

Power-hardware-in-the-loop systems enable testing of power converters for electric vehicles (EV) without the use of real physical components. Battery emulation is one example of such a system, demanding the use of bidirectional power flow, a wide output voltage range and high current swings. A multiphase synchronous DC-DC converter is appropriate to handle all of these requirements. The control of the multiphase converter needs to make sure that the current is shared equally between phases. It is preferred that the closed-loop dynamic model is linear in a wide range of output currents and voltages, where parameter variations, control signal limits, dead time effects, and so on, are compensated for. In the case presented in this paper, a cascade control structure was used with inner sliding mode control for phase currents. For the outer voltage loop, a proportional controller with output current feedforward compensation was used. Disturbance observers were used in current loops and in the voltage loop to compensate mismatches between the model and the real circuit. The tuning rules are proposed for all loops and observers, to simplify the design and assure operation without saturation of control signals, that is, duty cycle and inductor current reference. By using the proposed control algorithms and tuning rules, a linear reduced order system model was devised, which is valid for the entire operational range of the converter. The operation was verified on a prototype 4-phase synchronous DC-DC converter.

Multi-Phase DC-DC Converter with Bi-Directional Power Flow Ability for FCEV

Multi-Phase DC-DC Converter with Bi-Directional Power Flow Ability for FCEV

Fuzzy-Logic-Based Mean Time to Failure (MTTF) Analysis of Interleaved Dc-Dc Converters Equipped with Redundant-Switch Configuration

Interleaved dc-dc converters in sensitive applications necessitate an enhanced reliability. An interleaved converter equipped with redundant components can fulfill the reliability requirements. Mean Time to Failure (MTTF), as a reliability index, can be used to evaluate the expected life span of the mentioned converters. The Markov model is a helpful tool to calculate the MTTF in such systems. Different scientific reports denote different failure rates with different weight for power elements. Also, in reliability reports, failure rates of active and passive components are uncertain values. In order to approximate the failure rates fuzzy-logic-based Markov models are proposed in this paper. Then it is used to evaluate the MTTF of an interleaved multi-phase dc-dc converter, which is equipped with parallel and standby switch configurations. For the first time, fuzzy curves for MTTFs of the converters and 3D reliability function are derived in this paper. The reliability analyses give an insight to find the appropriate redundant-switch configurations for interleaved dc-dc converters under different conditions. Simulation and experimental results are provided to lend credence to the viability of the studied redundant-switch configurations in interleaved dc-dc boost converter.

Hybrid Energy Storage System With Active Power-Mix Control in a Dual-Chemistry Battery Pack for Light Electric Vehicles

This paper demonstrates a hybrid energy storage system (HESS), comprised of lithium-ion (LI) and lead-acid (PbA) batteries, for a utility light electric vehicle. While LI batteries have superior energy density, lower internal resistance, and longer lifetime than PbA batteries, the module cost is typically three times higher. The objective of this paper is to design an HESS that: 1) is cost competitive with a PbA single energy storage system (SESS) and 2) maintains most of the performance benefits of a conventional LI SESS. This is done by minimizing the Peukert effect and thus increasing the usable energy of the PbA battery. The proposed modular multiphase dc-dc converter achieves stable interleaving operation, and the traditional noninverting buck-boost converter is modified to allow intermodule balancing. A simple power-mix algorithm with active intramodule state-of-charge balancing is proposed, and the modular hybrid battery system is demonstrated experimentally with low-cost embedded hardware. The cost and the performance of the HESS are assessed side by side with PbA and LI SESS configurations. The HESS has a total projected cost midway between the SESS PbA cost and the SESS Li cost, while providing 23% efficiency (range/kWh) increases over the SESS PbA vehicle.

マルチフェーズ方式DC-DCコンバータの数学的モデリングにおける低次元化手法の提案

マルチフェーズ方式DC-DCコンバータの数学的モデリングにおける低次元化手法の提案

Analysis and Verification of Inductor Coupling Effect in Interleaved Multiphase DC-DC Converters

Interleaved multiphase synchronous buck converters are often used to power computer CPU, GPU, and memory to meet the demands for increasing load current and fast current slew rate of the processors. This paper reports and explains undesired coupling between discrete inductors in typical commercial multiphase applications where space is limited. In this paper, equations of coupling coefficient are derived for single-turn and multiturn Ferrite core inductors commonly used in multiphase converters and are verified by Maxwell static simulation. The influence of the coupling effect on inductor current waveforms is demonstrated by Maxwell transient simulation and confirmed by experiments. The analysis provides a useful tool for mitigating the coupling effect in multiphase converters to avoid early inductor saturation and interference between phases. Design guidelines and recommendations are provided to minimize the unwanted coupling effect in multiphase converters.

English

Multiphase dc-dc converters are widely used in modern power electronics applications due to their advantages over single-phase converters. Such advantages include reduced current stress in both the switching devices and passive elements, reduced output current ripple, increase in output voltage and overall efficiency and so on. The output current ripple of a converter can be significantly reduced by virtue of the interleaving connection. This paper presents a design and simulation of an interleaved high step up DC-DC converter with PID controller. The control strategy of the converter is based on a Proportional-Integral-Derivative (PID) controller. The proposed converter achieves a high step-up voltage-conversion ratio without extreme duty ratio and the numerous turns-ratios of a coupled inductor and reduction in the input current ripple with the efficiency higher than 97%.The PID controller is used in the feedback to reduce the rise time and steady state error. The proposed interleaved high step up DC-DC converter model along with PID controller is modeled using SIMULINK and the simulation results are presented in this paper to authenticate the proposed scheme.

High-Efficiency Multiphase DC–DC Converter for Fuel-Cell-Powered Truck Auxiliary Power Unit

This paper presents the design and control of a high-efficiency multiphase dc-dc converter for a truck auxiliary power unit (APU) fed by a fuel-cell stack. The power-stage design methodology and the operation of the designed power stage used to achieve high efficiency are described in detail. To operate the designed converter as a truck APU, the mode transfer control scheme, where smooth transitions of the voltage and current control modes are necessary, is proposed, and the current controller design procedure is described. A 5-kW four-phase dc-dc converter prototype is built with the proposed power-stage configuration, and the proposed control strategy is applied to control the dc-dc converter. The efficiency of the converter is more than 99.5% at near 10% load and above 98% from 10% to 100% load range. Simulations and experimental results are provided to verify the feasibilities of dc-dc converter operation and the proposed control strategy in the truck APU application.

Analysis and Design of Coupled Inductors for Two-Phase Interleaved DC-DC Converters

Multiphase dc-dc converters are widely used in modern power electronics applications due to their advantages over single-phase converters. Such advantages include reduced current stress in both the switching devices and passive elements, reduced output current ripple, and so on. Although the output current ripple of a converter can be significantly reduced by virtue of the interleaving effect, the inductor current ripple cannot be reduced even with the interleaving PWM method. One way to solve this problem is to use a coupled inductor. However, care must be taken in designing the coupled inductor to maximize its performances. In this paper, a detailed analysis of a coupled inductor is conducted and the effect of a coupled inductor on current ripple reduction is investigated extensively. From this analysis, a UU core based coupled inductor structure is proposed to maximize the performance of the coupled inductor.

High Output Voltage Based Multiphase Step-Up DC-DC Converter Topology with Voltage Doubler Rectifiers

High Output Voltage Based Multiphase Step-Up DC-DC Converter topology with voltage doubler rectifiers is presented in this paper. High output voltage is obtained due to the series combination of voltage doubler rectifiers on the secondary side of high frequency transformers. This topology is useful in the application where the output voltage is greater than the input. The two loop control strategy has been developed in order to analyze the stable and effective working of the converter topology. Therefore the working mode analysis of the converter topology has been described in detail. The multiphase step-up DC-DC converter topology is first simulated on MATLAB and then a prototype has been designed in order to verify the simulation and experimental results. Finally the simulation and experimental results are found to be satisfactory. DOI: http://dx.doi.org/10.11591/telkomnika.v11i2.1856 Full Text: PDF

Auto-tuning scheme for improved current sharing of multiphase DC–DC converters

In this study, an auto-tuning scheme is presented to realise simple and accurate calibration, for improved current sharing in multiphase DC-DC converters. The proposed control scheme is based on a look-up table method to automatically tune the pre-stored parameters to obtain the same effect as equal output inductance and direct current resistor (DCR). It ensures that time constant is perfectly matched in a conventional DCR current-sensing technique. The proposed scheme provides a low-cost solution with ease of implementation because it is fully designed using a digital control technique without any external phase compensation elements. The proposed scheme is verified on a two-phase interleaved DC-DC buck converter with a 12-V input and a 1-V, 40-A output. Simulation and experimental results are presented to demonstrate the theoretical analysis.

Automated system identification and controller tuning for digitally controlled dc–dc converters

Digital controllers are often used in interleaved multi-phase dc-dc converters. System identification is desirable for precise frequency-domain characterisations and subsequent stability assessment and/or controller design. The digital nature of the feedback signal facilitates the communication between the converter and a processing unit, which is used here to estimate the system parameters by means of system identification in situ . The phase loss, zero-order-hold effect and asynchronised sampling of the digital controller are discussed. Design limitations and desired dynamic behaviours complicate the controller design process and necessitate automated tuning of the controller. Therefore a computer-generated auto-tuning framework is set forth that provides the required controller coefficients to meet desired time and frequency performance criteria. This is an offline optimisation-based process that minimises a cost function formulated using appropriate error terms. The identification results for single- and multi-phase dc-dc converters closely match those obtained from conventional network analysers. Also, the auto-tuning performance is verified in time and frequency domains using hardware measurements and numerical simulations.

An Active Current Reconstruction and Balancing Strategy With DC-Link Current Sensing for a Multi-phase Coupled-Inductor Converter

This paper proposes an active technique to reconstruct and balance the phase currents in multiphase dc-dc converters implementing both of voltage- and current-mode controls. Only one current sensor at the dc link is required to measure and reconstruct the phase currents. Multiple current samples in the pulsewidth modulation switching period are synchronized with the carrier waveforms to actively reconstruct the phase currents using a simple active balancing algorithm that is implemented in a digital controller. The proposed technique improves system performance, stability, and efficiency, and prevents inductor saturation. A 5-kW four-phase dc-dc converter prototype for battery charging application is built to experimentally verify the proposed algorithm.

A Unified Approach to Reliability Assessment of Multiphase DC–DC Converters in Photovoltaic Energy Conversion Systems

A systematic framework for reliability assessment and fault-tolerant design of multiphase dc-dc converters deployed in photovoltaic applications is presented. System-level steady-state models allow a detailed specification of component failure rates, and in turn establish the effects of ambient conditions and converter design on reliability. Markov reliability models are derived to estimate the mean time to system failure. Case studies applied to two- and three-phase, 250-W converters demonstrate that topological redundancy does not necessarily translate to improved reliability for all choices of switching frequency and capacitance. Capacitor voltage rating is found to be the dominant factor that affects system reliability.