Showing papers on "Inductor published in 2014"

Optimal ZVS Modulation of Single-Phase Single-Stage Bidirectional DAB AC–DC Converters

Abstract: A comprehensive procedure for the derivation of optimal, full-operating-range zero voltage switching (ZVS) modulation schemes for single-phase, single-stage, bidirectional and isolated dual active bridge (DAB) ac-dc converters is presented. The converter topology consists of a DAB dc-dc converter, receiving a rectified ac line voltage via a synchronous rectifier. The DAB comprises primary and secondary side full bridges, linked by a high-frequency isolation transformer and a series inductor. ZVS modulation schemes previously proposed in the literature are either based on current-based or energy-based ZVS analyses. The procedure outlined in this paper for the calculation of optimal DAB modulation schemes (i.e., combined phase-shift, duty-cycle, and switching frequency modulation) relies on a novel, more accurate, current-dependent charge-based ZVS analysis, taking into account the amount of charge that is required to charge the nonlinear parasitic output capacitances of the switches during commutation. Thereby, the concept of “commutation inductance(s)” is shown to be an essential element in achieving full-operating-range ZVS. The proposed methods are applied to a 3.7 kW, bidirectional, and unity power factor electric vehicle battery charger which interfaces a 400 V dc-bus with the 230 Vac, 50-Hz utility grid. Experimental results obtained from a high-power-density, high-efficiency converter prototype are given to validate the theoretical analysis and practical feasibility of the proposed strategy.

Modeling of Mutual Coupling Between Planar Inductors in Wireless Power Applications

Abstract: This paper presents a compact model of mutual inductance between two planar inductors, which is essential to design and optimize a wireless power transmission system. The tracks of the planar inductors are modeled as constant current carrying filaments, and the mutual inductance between individual filaments is determined by Neumann's integral. The proposed model is derived by solving Neumann's integral using a series expansion technique. This model can predict the mutual inductance at various axial and lateral displacements. Mutual coupling between planar inductors is computed by a 3-D electromagnetic (EM) solver, and the proposed model shows good agreement with these numerical results. Different types of planar inductors were fabricated on a printed circuit board (PCB) or silicon wafer. Using these inductors, wireless power links were constructed for applications like implantable biomedical devices and contactless battery charging systems. Mutual inductance was measured for each of the cases, and the comparison shows that the proposed model can predict mutual coupling suitably.

Ultraflat Interleaved Triangular Current Mode (TCM) Single-Phase PFC Rectifier

Abstract: This paper presents the analysis and realization of a topology suitable to realize a power factor correction (PFC) rectifier with a thickness of only a few millimeters. The low height of the converter requires all components to be integrated into the printed circuit board (PCB). Still reasonable dimensions of the converter PCB are feasible (221 mm × 157 mm for a 200 W PFC rectifier), since PCB-integrated inductors and capacitors allow for high energy densities due to their large surface area which facilitates a low thermal resistance to ambient. A multicell totem-pole PFC rectifier employing a soft-switching modulation scheme over the complete mains period is identified as an adequate topology. The mode of operation is entitled triangular current mode (TCM) due to the triangular-shaped inductor currents. The modulation technique requires a reliable description of the switching transition of a half-bridge in order to provide accurate timing parameters. For this purpose, a simplified model of the nonlinear MOSFETs' output capacitances facilitates closed-form analytical expressions for duty cycle and switching frequency. Furthermore, this paper details the control of three interleaved converter cells which yields a reduction of the input current ripple. A 200 W TCM PFC rectifier with a low height of 5 mm has been realized and measurement results are provided in order to validate the theoretical considerations. The presented TCM PFC rectifier achieves an efficiency of 94.6% and a power factor of 99.3% at nominal power.

A Switched-Capacitor-Based Active-Network Converter With High Voltage Gain

Abstract: The voltage gain of traditional boost converter is limited due to the high current ripple, high voltage stress across active switch and diode, and low efficiency associated with large duty ratio operation. High voltage gain is required in applications, such as the renewable energy power systems with low input voltage. A high step-up voltage gain active-network converter with switched-capacitor technique is proposed in this paper. The proposed converter can achieve high voltage gain without extremely high duty ratio. In addition, the voltage stress of the active switches and output diodes is low. Therefore, low voltage components can be adopted to reduce the conduction loss and cost. The operating principle and steady-state analysis are discussed in detail. A prototype with 20-40-V input voltage, 200-V output voltage, and 200-W output power has been established in the laboratory. Experimental results are given to verify the analysis and advantages of the proposed converter.

LCL-filter design for robust active damping in grid-connected converters

Abstract: Grid-connected converters employ LCL-filters, instead of simple inductors, because they allow lower inductances while reducing cost and size. Active damping, without dissipative elements, is preferred to passive damping for solving the associated stability problems. However, large variations in the grid inductance may compromise system stability, and this problem is more severe for parallel converters. This situation, typical of rural areas with solar and wind resources, calls for robust LCL-filter design. This paper proposes a design procedure with remarkable results under severe grid inductance variation. The procedure considers active damping using lead-lag network and capacitor current feedback. Passive damping is also discussed. The design flow, with little iteration and no complex algorithms, selects the proper ratios between the switching and resonance frequency, the grid and converter inductance, and the filter capacitance and total inductance. An estimation for the grid current total harmonic distortion (THD) is also proposed. Simulation and experiments validate the proposals.

High-Conversion-Ratio Bidirectional DC–DC Converter With Coupled Inductor

Abstract: In this paper, a high-conversion-ratio bidirectional dc-dc converter with coupled inductor is proposed. In the boost mode, two capacitors are parallel charged and series discharged by the coupled inductor. Thus, high step-up voltage gain can be achieved with an appropriate duty ratio. The voltage stress on the main switch is reduced by a passive clamp circuit. Therefore, the low resistance RDS(ON) of the main switch can be adopted to reduce conduction loss. In the buck mode, two capacitors are series charged and parallel discharged by the coupled inductor. The bidirectional converter can have high step-down gain. Aside from that, all of the switches achieve zero voltage-switching turn-on, and the switching loss can be improved. Due to two active clamp circuits, the energy of the leakage inductor of the coupled inductor is recycled. The efficiency can be further improved. The operating principle and the steady-state analyses of the voltage gain are discussed. Finally, a 24-V-input-voltage, 400-V-output-voltage, and 200-W-output-power prototype circuit is implemented in the laboratory to verify the performance.

Pulsewidth Modulation of Z-Source Inverters With Minimum Inductor Current Ripple

Abstract: This paper proposes the pulsewidth modulation (PWM) strategy of Z-source inverters (ZSIs) with minimum inductor current ripple. In existing PWM strategy with single-phase shoot-through, the shoot-through time interval is divided into six equal parts, therefore the three phase legs bear the equal shoot-through time interval. In this manner, the allotment and arrangement of the shoot-through state is easy to realize, but the inductor current ripple is not optimized. This causes to use relatively large inductors. In the proposed PWM strategy, the shoot-through time intervals of three phase legs are calculated and rearranged according to the active state and zero state time intervals to achieve the minimum current ripple across the Z-source inductor, while maintaining the same total shoot-through time interval. The principle of the proposed PWM strategy is analyzed in detail, and the comparison of current ripple under the traditional and proposed PWM strategy is given. Simulation and experimental results on the series ZSI are shown to verify the analysis.

An Adjustable-Speed PFC Bridgeless Buck–Boost Converter-Fed BLDC Motor Drive

Abstract: This paper presents a power factor corrected (PFC) bridgeless (BL) buck-boost converter-fed brushless direct current (BLDC) motor drive as a cost-effective solution for low-power applications. An approach of speed control of the BLDC motor by controlling the dc link voltage of the voltage source inverter (VSI) is used with a single voltage sensor. This facilitates the operation of VSI at fundamental frequency switching by using the electronic commutation of the BLDC motor which offers reduced switching losses. A BL configuration of the buck-boost converter is proposed which offers the elimination of the diode bridge rectifier, thus reducing the conduction losses associated with it. A PFC BL buck-boost converter is designed to operate in discontinuous inductor current mode (DICM) to provide an inherent PFC at ac mains. The performance of the proposed drive is evaluated over a wide range of speed control and varying supply voltages (universal ac mains at 90-265 V) with improved power quality at ac mains. The obtained power quality indices are within the acceptable limits of international power quality standards such as the IEC 61000-3-2. The performance of the proposed drive is simulated in MATLAB/Simulink environment, and the obtained results are validated experimentally on a developed prototype of the drive.

Maximum Efficiency Point Tracking Technique for $LLC$ -Based PEV Chargers Through Variable DC Link Control

Abstract: In this paper, a variable dc link technique is proposed to track the maximum efficiency point of the $LLC$ converter for plug-in electric vehicle battery-charging applications over a wide battery state-of-charge (SOC) range. With the proposed variable dc link control approach, the dc link voltage follows the battery pack voltage. The operating point of the $LLC$ converter is always constrained to the proximity of the primary resonant frequency so that the circulating current in the magnetizing inductor and the turning-off currents of MOSFETs are minimized. In comparison with conventional approaches, the proposed variable dc link voltage methodology demonstrates efficiency improvement across the wide SOC range. Efficiency improvements of 2.1% at the heaviest load condition and 9.1% at the lightest load condition are demonstrated.

A 55 nm triple gate oxide 9 metal layers SiGe BiCMOS technology featuring 320 GHz f T / 370 GHz f MAX HBT and high-Q millimeter-wave passives

Abstract: This paper presents the first 55 nm SiGe BiCMOS technology developed on a 300 mm wafer line in STMicroelectronics. The technology features Low Power (LP) and General Purpose (GP) CMOS devices and 0.45 µm2 6T-SRAM bit cell. High Speed (HS) HBT exhibits 320 GHz f T and 370 GHz f MAX associated with a CML ring oscillator gate delay τ D of 2.34 ps. Transmission lines, capacitors, high-Q varactors and inductors dedicated to millimeter-wave applications are also available.

An Active Power-Decoupling Method for Single-Phase AC–DC Converters

Abstract: This paper presents an active topology for power decoupling in single-phase ac-dc converters, featuring the effective suppression of low-frequency power ripple which is an inherent problem in single-phase energy conversion systems. This topology is composed of an H-bridge circuit and a ripple power-decoupling circuit. The ripple power-decoupling circuit shares one bridge arm with the H-bridge circuit so it has less additional components: just one IGBT, one diode, and an energy-storage inductor. Its modulation strategy is properly devised to coordinate the operation of decoupling circuit and H-bridge circuit. To enhance the power-decoupling performance, a direct ripple power-cancellation method based on energy-storage inductor is proposed. A multiresonant controller with feed-forward control is introduced for fast and precise current tracking. The effectiveness of this topology has been verified by detailed simulation studies as well as the laboratory prototype experiment results.

A Unified Control Strategy for Three-Phase Inverter in Distributed Generation

Abstract: This paper presents a unified control strategy that enables both islanded and grid-tied operations of three-phase inverter in distributed generation, with no need for switching between two corresponding controllers or critical islanding detection. The proposed control strategy composes of an inner inductor current loop, and a novel voltage loop in the synchronous reference frame. The inverter is regulated as a current source just by the inner inductor current loop in grid-tied operation, and the voltage controller is automatically activated to regulate the load voltage upon the occurrence of islanding. Furthermore, the waveforms of the grid current in the grid-tied mode and the load voltage in the islanding mode are distorted under nonlinear local load with the conventional strategy. And this issue is addressed by proposing a unified load current feedforward in this paper. Additionally, this paper presents the detailed analysis and the parameter design of the control strategy. Finally, the effectiveness of the proposed control strategy is validated by the simulation and experimental results.

Electronic Tuning of Misaligned Coils in Wireless Power Transfer Systems

Abstract: The misalignment and displacement of inductively coupled coils in a wireless power transfer system (WPT) can degrade the power efficiency and limit the amount of power that can be transferred. Coil misalignment leads the primary coil driver to operate in an untuned state which causes nonoptimum switching operation and results in an increase in switching losses. This paper presents a novel method to electronically tune a Class-E inverter used as a primary coil driver in an inductive WPT system to minimize the detrimental effects of misalignment between the inductively coupled coils which may occur during operation. The tuning method uses current-controlled inductors (saturable reactors) and a variable switching frequency to achieve optimum switching conditions regardless of the misalignment. Mathematical analysis is performed on a Class-E inverter based on an improved model of a resonant inductive link. Experimental results are presented to confirm the analysis approach and the suitability of the proposed tuning method.

An Overview of Equivalent Circuit Modeling Techniques of Frequency Selective Surfaces and Metasurfaces

Abstract: Circuit analysis of frequency selective surfaces is reviewed with the aim to underline range of validity of different models and their advantages in terms of simplicity and physical insight. The circuit approach is based on an equivalent representation of the FSSs with series or shunt connections of inductances and capacitances. Dense non-resonant periodic surfaces (i.e.: grid or patch arrays) can be analyzed analytically by computing the values of inductors or capacitors via the homogenization theory. As the lattice period increases with respect to the operating wavelength or the element shape becomes resonant, a fully analytical circuital approach fails, in particular, in the presence of thin substrates. However, simple circuit approaches can still be employed by deriving lumped parameters values via a quick pre-processing and then generalizing them. The results are accurate up to the resonant frequency region of the element. By including an additional lumped element it is possible, taking into account the effect of the first high order Floquet harmonic. The multi-mode formulation is also able to catch the highly nonlinear response of FSS screens in the grating lobe region provided that the current profile of the element does not change significantly.

Isolated Coupled-Inductor-Integrated DC–DC Converter With Nondissipative Snubber for Solar Energy Applications

Abstract: This paper proposes an isolated coupled-inductor-integrated dc-dc converter with a nondissipative snubber for solar energy applications. The proposed converter realizes high step-up voltage gain without incurring a high coupled inductor turns ratio by adapting a dual-voltage doubler circuit. In addition, the energy in the coupled inductor leakage inductance can be recycled via a nondissipative snubber on the primary side. Thus, the system efficiency is improved. Finally, a laboratory prototype for demonstrating the performance of the proposed circuit is implemented with a 200-W solar array simulator, a 24-V solar voltage, and a 200-V output voltage. The experimental results show that the peak efficiency of the proposed converter is about 96%.

Deadbeat Control Strategy of Circulating Currents in Parallel Connection System of Three-Phase PWM Converter

Abstract: Module parallel connection for three-phase VSC can increase the system level effectively. However, the circulating currents problem will occur. The circulating currents will distort the three-phase currents, increase the power loss and decrease the system efficiency. A novel deadbeat circuiting currents control method is proposed in this paper. Based on the analysis of the average model of parallel system, a circuiting currents deadbeat controller is designed while presenting the design method. The control strategy is realized by adjusting the voltage zero vector of space-vector pulse-width modulation in each paralleled module. No additional hardware is needed through the method. Fast dynamic response can be achieved and the performance of circulating currents is better compared with conventional PI controller. This method can be applied to common dc-link double parallel three-phase voltage converters with communication line. The validity of proposed theory was verified by simulation and experimental results. It is shown that the parallel converters can operate with different line inductor or different line currents by using this novel control strategy.

Positive/negative lossy/lossless grounded inductance simulators employing single VDCC and only two passive elements

Abstract: Actively simulated grounded inductors have been used in several applications ranging from filter to oscillator design as well as cancellation of parasitic inductances. In this paper, new grounded inductance simulators employing only one voltage differencing current conveyor (VDCC) and two passive components are proposed. Two new topologies for realizing positive and negative lossless inductances and four different topologies for realizing lossy inductances are proposed. The aim of this paper is to present new inductance simulators using the minimum number of active and passive components. The proposed inductance simulators can be tuned electronically by changing the biasing current of the VDCC. Moreover, the circuits do not require any conditions of component matching. Finally, using one of the proposed inductance simulators a third-order high-pass filter is constructed. The performance of the proposed filter is verified and simulated by using SPICE.

Micropower Design of a Fully Autonomous Energy Harvesting Circuit for Arrays of Piezoelectric Transducers

Abstract: This paper presents a self-powered energy harvesting circuit based on synchronous charge extraction with a single shared inductor for power conversion from arrays of independent piezoelectric transducers. The number of handled elements can be easily increased at the expense of few additional components and without affecting performance. The energy harvesting circuit was characterized with three 0.5 × 12.7 × 31.8 mm3 piezoelectric cantilevers subject to different types of vibrations. Throughout all operating conditions, the circuit was able to extract the maximum power independently from every transducer. Compared to passive energy harvesting interfaces, the output power is significantly higher, with worst-case increases ranging from +75% to +184%. The circuit starts up passively and is based on ultralow power active control, which consumes during operation at 3 V a fraction of the extra harvested power as low as 10 μW per source. As part of the best tradeoff between harvested and intrinsic power, an overall energy efficiency up to 74% was achieved.

Evolution of Very High Frequency Power Supplies

Abstract: The ongoing demand for smaller and lighter power supplies is driving the motivation to increase the switching frequencies of power converters. Drastic increases however, come along with new challenges, namely the increase of switching losses in all components. The application of power circuits used in radio frequency transmission equipment helps to overcome those. However, those circuits were not designed to meet the same requirements as power converters. This paper summarizes the contributions in the recent years in the application of very high frequency (VHF) technologies in power electronics, which show the results of the recent advances and describes the remaining challenges. The presented results include a self-oscillating gate drive, air-core inductor optimizations, an offline LED driver with a power density of 8.9 W/cm 3 , and a 120-MHz, 9-W dc powered LED driver with 89% efficiency as well as a bidirectional VHF converter. The challenges to be solved before VHF converters can be used effectively in industrial products are within those three categories: 1) components; 2) circuit architectures; and 3) reliability testing.

Design and Performance of an Adaptive Low-DC-Voltage-Controlled LC-Hybrid Active Power Filter With a Neutral Inductor in Three-Phase Four-Wire Power Systems

Abstract: This paper proposes an adaptive low-dc-link-voltage-controlled LC coupling hybrid active power filter ( LC-HAPF) with a neutral inductor, which can compensate both dynamic reactive power and current harmonics in three-phase four-wire distribution power systems. Due to its adaptive low-dc-link-voltage characteristic, it can obtain the least switching loss and switching noise and the best compensating performances, compared with the conventional fixed and newly adaptive dc-voltage-controlled LC-HAPFs. The design procedures of the dc-link voltage controller are discussed, so that the proportional and integral gains can be designed accordingly. Moreover, the general design procedures for the adaptive dc-voltage-controlled LC-HAPF with a neutral inductor are also given. The validity and effectiveness of the adaptive dc-link voltage-controlled LC -HAPF with a neutral inductor are confirmed by experimental results obtained from a 220-V 10-kVA laboratory prototype compared with the conventional fixed and adaptive dc-link voltage-controlled LC-HAPFs without a neutral inductor.

High-gain weakly nonlinear flux-modulated Josephson parametric amplifier using a SQUID-array

Abstract: We have developed and measured a high-gain quantum-limited microwave parametric amplifier based on a superconducting lumped LC resonator with the inductor L including an array of eight superconducting quantum interference devices (SQUIDs). This amplifier is parametrically pumped by modulating the flux threading the SQUIDs at twice the resonator frequency. Around 5 GHz, a maximum gain of 31 dB, a product amplitude gain x bandwidth above 60 MHz, and a 1 dB compression point of -123 dBm at 20 dB gain are obtained in the nondegenerate mode of operation. Phase-sensitive amplification-deamplification is also measured in the degenerate mode and yields a maximum gain of 37 dB. The compression point obtained is 18 dB above what would be obtained with a single SQUID of the same inductance, due to the smaller nonlinearity of the SQUID array.

Combined Unipolar and Bipolar PWM for Current Distortion Improvement During Power Compensation

Abstract: To eliminate leakage ground current while achieve high efficiency, many transformerless photovoltaic inverters with unipolar pulse width modulation (UP-PWM) have been proposed and verified with real power injection only. However, in 2011, German standard VDE-AR-N 4105 updated the requirement that the inverters should satisfy the power factor from 0.9 leading to 0.9 lagging at power level higher than 4.6 kVA. When compensating the reactive power under a leading power factor, the inverter with UP-PWM might not have sufficient voltage to magnetize the inductor, which results in current distortion at zero crossing. It is hard to comply with the requirement of 1% displacement-factor accuracy. The reactive power can be well compensated with a bipolar PWM (BP-PWM) scheme; however, this will result in high current ripple and high switching loss. In this study, for reducing the current distortion under leading power factors and increasing the inductor current in the negative power region, UP-PWM is changed to BP-PWM. While in the positive power region, the inverter operation is still kept with UP-PWM to yield higher efficiency and lower current ripple. The proposed combination of UP-PWM and BP-PWM can improve the current distortion and reduce THD, while still can sustain high efficiency even with the power factors other than unity. Experimental results measured from a 5 kVA PV inverter have verified the analysis and discussion of the proposed approach.

Fault Diagnosis of PWM DC–DC Converters Based on Magnetic Component Voltages Equation

Abstract: Switch fault diagnosis is an important design aspect for pulse width modulation (PWM) dc-dc power converters. It can prevent power converters from further damage, and also make preparations for remedial actions. In this paper, a fast switch fault diagnostic method is proposed for PWM dc-dc converters operating in continuous conduction mode. The proposed method utilizes the magnetic component (inductor or transformer) voltage for fault diagnosis. Based on the real-time voltage measurement and switch gate-driver signals, characteristics of switch open-circuit faults and short-circuit faults are rapidly extracted, and thus, switch faults can be quickly detected. The magnetic component voltage can be measured by an auxiliary winding in the magnetic core, and gate-driver signals can be easily got from the control circuit. Moreover, the fault detection can be implemented by a low-cost logical hardware circuit, and this circuit can be integrated into the control circuit. The fault diagnosis principle, design considerations, and implementation are discussed in this paper. Experiments are conducted to verify the theoretical analysis.

Wireless Power Transfer Using Class E Inverter With Saturable DC-Feed Inductor

Abstract: Resonant converters used as coil drivers in inductive links generally operate efficiently at optimum switching conditions for constant load values and ranges. Changes in load and range can shift the operation of the coil driver to a nonoptimum switching state which results in higher switching losses and reduced output power levels. This paper presents a method to adapt to variations in range for a Class E inverter used as a coil driver in a wireless power transfer (WPT) system based on inductive coupling. It is shown that by controlling the duty cycle of the inverter's switch and the value of its dc-feed inductance, the Class E inverter can be tuned to operate at optimum switching conditions as the distance between the coils of the WPT system changes. Mathematical analysis is presented based on a linear piecewise state-space representation of the inverter and the inductive link. Extensive experimental results are presented to verify the performed analysis and validity of the proposed tuning procedure.

Nonlinear Modeling of Eddy-Current Couplers

Abstract: Analytical models play an important role in the design of electromagnetic devices by providing computationally efficient solutions. In this paper, by combining magnetic equivalent circuit approaches and Faraday's and Ampere's laws, a model for radial-flux eddy-current couplers is developed, which can easily handle complex geometries as well as account for iron saturation, all material properties, and three-dimensional (3-D) parameters. The characteristics and the design considerations of a surface-mounted permanent-magnet structure are presented. Also, a procedure aimed at an optimal design of the yoke thicknesses is utilized. Moreover, 2-D and 3-D finite-element methods are employed in the analyses and evaluation of the model. Finally, sensitivity analysis is performed to explore the impacts of the machine parameters on the device performance.

Methodology for switching characterization evaluation of wide band-gap devices in a phase-leg configuration

Abstract: Double pulse tester (DPT) is a widely accepted method to evaluate the switching behavior of power devices. Considering the high switching-speed capability of wide band-gap (WBG) devices, the test results become significantly sensitive to the alignment of voltage and current (V-I) measurement. Also, because of the shoot-through current induced by Cdv/dt, during the switching transient of one device, the switching losses of its complementary device in the phase-leg is non-negligible. This paper summarizes the key issues of DPT, including layout design, measurement considerations, grounding effects and data processing. Among them, the latest probes for switching waveform measurement are compared, the methods of V-I alignment are discussed, and the impact of grounding effects induced by probes on switching waveforms are investigated. Also, for the WBG devices in a phase-leg configuration, a practical method is proposed for switching loss evaluation by calculating the difference between the input energy supplied by a dc capacitor and the output energy stored in a load inductor. Based on a phase-leg power module built with 1200 V SiC MOSFETs, the test results show that regardless of V-I timing alignment, this method can accurately indicate the switching losses of both the upper and lower switches by detecting only one switching current.

Resonance Damping and Harmonic Suppression for Grid-Connected Current-Source Converter

Abstract: Due to the inductor-capacitor (LC) filter, a pulsewidth-modulation (PWM) current-source converter may experience LC resonance. The resonance can be excited by system harmonics either from the PWM process or from the grid voltage distortions and hence results in the line current distorted. In this paper, feedback controls using different variables in the LC filter are first investigated and comprehensively analyzed. It is shown that the inductor-voltage feedback or the capacitor-voltage feedback can damp the current oscillations by increasing the damping ratio, while the inductor-current feedback or the capacitor-current feedback is able to suppress low-order harmonics by raising the resonance frequency. On this basis, a group of combined variable feedback control methods is presented by combining the feedbacks of the inductor/capacitor current and the inductor/capacitor voltage. Thus, not only the current oscillations can be damped, but also the low-order harmonics can be suppressed. Therefore, the line current waveform is improved, and the system performance can be flexibly optimized. A practical design method for feedback gains is also presented in this paper. Finally, the simulation and experimental results verify the feasibility and validity of the proposition.

A Novel Single-Stage High-Power-Factor LED Street-Lighting Driver With Coupled Inductors

Abstract: This paper proposes a single-stage high-power-factor (HPF) LED driver with coupled inductors for street-lighting applications. The presented LED driver integrates a dual buck-boost power-factor-correction (PFC) ac-dc converter with coupled inductors and a half-bridge-type LLC dc-dc resonant converter into a single-stage-conversion circuit topology. The coupled inductors inside the dual buck-boost converter subcircuit are designed to be operated in the discontinuous-conduction mode for obtaining high power-factor (PF). The half-bridge-type LLC resonant converter is designed for achieving soft-switching on two power switches and output rectifier diodes, in order to reduce their switching losses. This paper develops and implements a cost-effective driver for powering a 144-W-rated LED street-lighting module with input utility-line voltage ranging from 100 to 120 V. The tested prototype yields satisfying experimental results, including high circuit efficiency (>89.5%), low input-current total-harmonic distortion ( 0.99), low output-voltage ripple (<; 7.5%), and low output-current ripple (<; 5%), thus demonstrating the feasibility of the proposed LED driver.

Switching power supply device

Abstract: A primary resonant inductor (Lr) and a primary resonant capacitor (Cr) form a primary resonant circuit, and secondary resonant inductors (Ls1, Ls2) and secondary resonant capacitors (Cs1, Cs2) form a secondary resonant circuit. Equivalent mutual inductances (Lms1, Lms2) and equivalent mutual capacitances (Cm1, Cm2, Cm3) are formed between a primary winding (np) and secondary windings (ns1, ns2) by electromagnetic resonance coupling, and a multi-resonant circuit containing an LC resonant circuit is formed on both the primary and secondary sides. Power is transferred from the primary circuit to the secondary circuit. Resonance energy that is not transmitted from the primary winding is retained in the multi-resonant circuit, as is resonance energy that is received by the secondary windings but not supplied as output. In particular, on the secondary side, resonance energy is retained in a current path in which rectification elements are not arranged in series.

A Bandpass Filter Incorporated Into the Inductor Current Feedback Path for Improving Dynamic Performance of the Front-End DC–DC Converter in Two-Stage Inverter

Abstract: The instantaneous output power of a two-stage single-phase inverter pulsates at twice the output voltage frequency, generating second harmonic current (SHC) in the front-end dc-dc converter. To reduce the SHC, this paper proposes a virtual impedance based control strategy. For the case of adopting a resistor as the virtual impedance, a closed-loop parameter design method is presented, revealing that the voltage loop crossover frequency is relatively low under such circumstance. To overcome this problem, a control strategy incorporating a bandpass filter (BPF) into the inductor current feedback path is put forward and a damping resistor is further added into the BPF for the purpose of improving the system stability margin. Hence, the proposed control scheme can not only reduce the SHC significantly, but also improve the dynamic performance of the front-end dc-dc converter effectively while guaranteeing the stability of the converter. Finally, a 1-kVA prototype is built and tested in the laboratory, and the experimental results are presented to verify the effectiveness of the proposed control strategy.