Output Filter Inductor Research Articles

A zero-voltage zero-current soft switching DC/DC converter

A novel three-level zero-voltage zero-current switching (ZVZCS) DC/DC converter is proposed in this paper. A tapped-inductor is used to replace the normal output filter inductor, so that the circulating current in the zero-state can be reset to zero. The reset voltage and the reset time can be set conveniently just by simply changing the winding ratio of the tapped inductor. The converter achieves a zero-current tuning off for inner switching, and a zero-voltage tuning on for outer switching. No circulating current exists in the zero state, so that the loss in the on-state is reduced, and the efficiency can be improved. The experimental results verify that the ZVZCS has low voltage stress, zero-voltage and zero-current switching.

Interleaved Three-Phase Forward Converter Using Integrated Transformer

An interleaved three-phase forward converter using an integrated transformer is proposed in this paper. This type of converter has the attractive features of flexible voltage conversion ratio, high output current (due to the parallel connection of outputs), near-zero output-current ripple (due to the output-current-ripple cancellation), fast transient response (due to the small effective output-filtering inductance), and is particularly suitable for high-output-current and low-output-voltage applications such as telecommunication and computer systems. The integrated transformer of the proposed converter consists of three step-down transformers on a single magnetic core. The z-parameter (gyrator) model and the equivalent-circuit model of the integrated transformer are derived. Based on the equivalent-circuit model, the principle of operation of the proposed converter is explained. The analysis and design criteria of the basic circuit, the operation of the regenerative LC snubber circuit, the simulation, and experimental verification are also described.

A Sampled-Data Reduced Order Dynamic Model for a Self-Sustained Series-Parallel Resonant Converter

SummaryResonant converters are well known in many industrial applications due to their high operating frequency and lossless switching. The series parallel hybrid type converter has been known as the most promising resonant topology, as it provides a considerably wide operating range with optimized ratings of components. Unfortunately, it has a wide range of operating frequency under the conventional variable frequency control (VF). The self-sustained oscillation control (SSOC) technique was proposed in 1997 in order to further reduce the range of regulating frequency necessary for zero voltage switching (ZVS) and consequently optimize the converter design to achieve a more compact size and consequently lower cost. However, optimizing the converter design at such high frequencies is not an easy task. The first step for achieving this objective is to have a sound and accurate mathematical model for the converter. This paper describes a simple fifth-order dynamic model with a more systematic approach based on the sampled data technique; it has the advantages of being more accurate, easily computed, and has a lower order than its continuous time predecessor found in [1], which was of a seventh order model. In this paper, the complete analysis, modeling, and design of the seriesparallel resonant converter with an inductive output filter under the SSOC is investigated and verified.

A Single-Phase Inverter System for PV Power Injection and Active Power Filtering With Nonlinear Inductor Consideration

This paper proposes a single-phase two-wire inverter system for photovoltaic (PV) power injection and active power filtering (APF) with nonlinear inductor consideration. The proposed system can fully or partially perform APF, process PV power, eliminate harmonic currents, improve power factor, and take into account the nonlinear effect of its output filter inductor. In the system, even though only the utility current is sensed, both APF and maximum power point tracking features can be still achieved, reducing the number of current sensors and cost significantly. To prevent output current from exceeding switch ratings, inverter current is properly controlled through a current estimator and a defined limit circle. A self-learning algorithm is also proposed to determine nonlinear inductance, which can increase the accuracy of the estimated current. Simulations and experimental results have verified the feasibility of the proposed PV inverter system and the algorithm.

Zero-Voltage and Zero-Current-Switching PWM Hybrid Full-Bridge Three-Level Converter

This paper proposes a zero-voltage and zero-current-switching pulsewidth modulation hybrid full-bridge three-level (ZVZCS PWM H-FB TL) converter, which has a TL leg and a two-level leg. The voltage stress of the switches of the TL leg is half of the input voltage, and the switches can realize ZVS, so MOSFETs can be adopted; the voltage stress of the switches of the two-level leg is the input voltage, and the switches can realize ZCS, so IGBT can be adopted. The secondary rectified voltage is a TL waveform having lower high-frequency content compared with that of the traditional FB converters, which leads to the reduction of the output filter inductance. The input current of the converter has quite little ripple, so the input filter can also be significantly reduced. The operation principle of the proposed converter is analyzed and verified by the experimental results. Several ZVZCS PWM H-FB TL converters are also proposed in this paper.

Zero-Voltage-Switching PWM Three-Level Converter With Current-Doubler-Rectifier

This paper proposes a zero-voltage-switching (ZVS) pulse-width modulation three-level converter with current-doubler-rectifier, which achieves ZVS for all the switches under wide load range and in a wide line range. The rectifier diodes commutate naturally, therefore no oscillation occurs. The determination of the output filter inductance and the blocking capacitor is discussed in details. The experimental results are presented to verify the operation principle of the proposed converter.

Dual-Bridge DC–DC Converter: A New Topology Characterized With No Deadtime Operation

Two new topologies characterized by no deadtime and small valued filter inductor, the Dual-Bridge dc-dc converter and the Dual-Bridge dc-dc converter with ZVS, are presented and analyzed. Compared to the conventional Full-Bridge converter, the dc-dc converters with the proposed topologies have lower input current ripple, less stress on power switching components and smaller output filter inductor. Simple self-driven synchronous rectification can be used in the new topologies for high efficiency implementation. Prototype dc-dc converters have been tested for the verification of the principles. Both simulations and experiments verify the feasibility and advantages of the new topologies. The advantages and disadvantages of the topologies are discussed.

Design of 48 V Voltage regulator modules with a novel integrated magnetics

The push-pull forward topology with the current-doubler and synchronous rectifier is a suitable approach for high-input voltage regulator modules (VRMs) used to supply high-performance microprocessors. In order to improve efficiency and reduce size, this paper proposes an improved push-pull forward converter with a novel integrated magnetics. All the magnetic components including input filter inductor, step-down transformer and output filter inductors are integrated into a single EI or EE core. This topology is essentially the modified push-pull converter with the built-in input filter and the coupled-inductor current doubler rectifier. The proposed integrated magnetic structure features a simple core structure, a small leakage inductance and low winding and core losses. A design is given for a 48-V VRM with a 1.2-V and 70-A output, and its experimental results show that the proposed approach can offer a great improvement in efficiency.

Average current-mode control of a two-module DC-DC converter with mutually coupled output filter inductors

A small-signal model is presented for an average current-mode controlled two module DC–DC converter feeding a common resistive load. The recently proposed parallel input/series output buck-based converter works in the continuous conduction mode and uses magnetic coupling between the separate output filter inductors. The sampling effect of current mode control is included in the development of the model which makes it valid up to half the switching frequency. All of the converter power stage transfer functions are analytically expressed, and the effect of the coupling coefficient on the small-signal characteristics is examined. It is found that without damping the natural frequencies of the output filter, the current-mode control scheme loses its superiority over voltage-mode control when the coupling coefficient is increased above a certain level. The converter model is implemented using both MATLAB and the evaluation version of PSPICE.

Decoupled output voltage control of quantum series resonant converter for improved buck-boost operation

A new output voltage control technique is proposed to obtain the improved buck-boost operation of the quantum series resonant power converter (QSRC). The new nonlinear dynamic model of QSRC is first derived and the cross-coupled nonlinear term existing in the output voltage dynamics is decoupled by using control methods such as the periodic control of the boosting switch (PCBS) and the resonant current control (RCC). By applying the state-space averaging concept to the decoupled dynamics, two linear large signal averaged models are obtained for PCBS and RCC schemes. Using the proposed technique, the flux imbalance problem of the isolation transformer and the robustness of the output voltage response can be easily considered. This technique can also be widely applicable to the cascade buck-boost power converter, which can be implemented by inserting a boosting switch between the output filter inductor and the ripple capacitor of the forward power converter. The validity of the proposed scheme is confirmed by the computer simulations and the experiments.

Small-signal and transient behaviour of a two-module DC-DC converter using mutually coupled output filter inductors

Small-signal characteristics and output voltage transients of a voltage-mode controlled two-module DC-to-DC converter feeding a common resistive load are investigated. The parallel-input/series-output converter system works in the continuous current conduction mode (CCM), and uses magnetic coupling between the separate output filler inductors to reduce converter size and weight. A damping circuit can be designed to ensure that the natural frequencies of the output filter are well damped and adequate stability margins are achieved. The converter model is implemented using ‘MATLAB‘ and results are varified against ‘PSPICE’ simulations.

A fixed frequency LCL-Type series resonant converter

A fixed frequency LCL-type series resonant converter (SRC) which uses an inductive output filter is proposed. Steady-state analysis of the converter is presented using complex ac circuit analysis. Based on the analysis, a simple design procedure is given. Detailed space integrated control experiment (SPICE) simulation results are presented to evaluate the performance of the designed converter under varying load and supply voltage conditions. Also, detailed experimental results obtained from a metal-oxide-semiconductor field-effect transistor (MOSFET) based 500 W converter are presented to verify the analysis and SPICE simulation results. The results obtained from the analysis, SPICE simulation and the experimental converter are compared. The proposed converter requires a narrow variation in pulsewidth while maintaining lagging power factor mode of operation for a very wide variation in the load as well as supply voltage.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Feed-forward active filter for output ripple cancellation

An active filter for DC-DC converter ripple cancellation is described and demonstrated. The feed-forward technique used applies to any converter with an output filter inductor. The technique is inherently stable, performs in both continuous and discontinuous conduction modes, and applies to both square-wave and resonant converters. A suitable linear amplifier, combined with a current transformer, implements it with low loss. An adaptive tuning scheme compensates for inductance variation and drift. Operation is demonstrated with buck, push-pull, and boost converter topologies. The result is output ripple below 10 mV RMS, effective on converters with outputs as low as 2 V and currents above 30 A.

Steady-state analysis of dual converters with circulating-current mode used in four-quadrant DC magnet power supplies

The authors present a steady-state analysis of the dual converter operating in a circulating current mode, with an output low-pass filter, in order to identify the operating conditions of the proposed power supply configuration. In the power supply configuration, interconverter inductors are used to limit the circulating current and an additional low-pass filter is required to reduce output ripple content. The operating conditions of the power supply configuration are identified by closed-form solutions of the instantaneous voltage and current waveforms. The steady-state operation is affected by the low-pass output filter and the effects are examined in terms of the inductance ratio. The effective output filter inductance is the sum of two inductances: one half of the circulating current limiting inductance and the output filter inductance. The Thevenin equivalent circuit of the dual converter with circulating current is identified. >

A novel current-assisted output voltage control technique for switch-mode-rectifier converters

A current-assisted voltage control technique for high-power switch-mode-rectifier (SMR) converters is proposed. This technique implements a fast-forward AC current loop by sensing the current through the output filter capacitor. The control loop forces the AC current component of the output filter inductance to be synchronized with a symmetrical triangular reference waveform. As a result, the converter behaves like a fixed-frequency current-regulated voltage source with a low-output impedance and an increased bandwidth. A small-signal linear model is derived and the dynamic performance of a buck-derived SMR using the proposed control technique is analyzed. Simulation and experimental results are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Rectifier for minimum line-current harmonics and maximum power factor

Rectifier line current harmonics interfere with proper power system operation, reduce rectifier power factor, and limit the power available from a given service. The rectifier's output filter inductance determines the rectifier line current waveform, the line current harmonics, and the power factor. Classical rectifier analysis usually assumes a near-infinite output filter inductance, which introduces significant error in the estimation of line current harmonics and power factor. A quantitative analysis of single and three-phase rectifier line current harmonics and power factor as a function of the output filter inductance is presented. For the single phase rectifier, one value of finite output filter inductance produces maximum power factor and a different value of finite output filter inductance produces minimum line current harmonics. For the three phase rectifier, a near-infinite output filter inductance produces minimum line current harmonics and maximum power factor, and the smallest inductance that approximates a near-infinite inductance is determined. >

PWM-controlled SRC with inductive output filter at constant switching frequency

By using the PWM control scheme in the series resonant power converter (SRC) with inductive output filter, the converter can be operated at a constant frequency. This converter has lower switching loss than the PWM converter and better control characteristics than the ordinary SRC. Since the peak current in the present converter equals the load current, it has the lowest possible peak current stress among converters. The analysis and the performance characteristics of the converter operating at a constant switching frequency are presented. Experimental results are given to confirm the analytical work.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Steady-state analysis and design of the parallel resonant converter

Five basic operating modes of the parallel resonant converter are analyzed. Three of the modes occur when the output filter inductor is removed and the remaining two occur when the filter inductor is large. Closed-form solutions are found for the two most important modes. Analysis results are given graphically so that the designer can use them without lengthy calculation or computer iteration. Switching frequency, peak tank capacitor voltage, and peak tank inductor current are plotted in the output plane. These plots, with a load line superimposed, show how operating point, frequency, and peak stress vary as load conditions change. Use of the output plane plots to minimize component costs is explained. Comparison of the best designs found for the large and zero filter inductance cases shows that removing the filter inductor can reduce both parts count and tank circuit size while peak transistor current remains unchanged. >

Ripple determination for switch-mode DC/DC converters

The state-space average model of a DC/DC convertor is used directly to obtain expressions for the ripple in any state or output of the model. This is used to rederive the current-ripple trade-off conditions in the Cuk convertor in a more straightforward fashion. In addition, it is shown that the buck convertor with input filter inductor and storage inductor coupling, and boost convertor with output filter inductor and storage inductor coupling, have similar ripple behaviour to the Cuk convertor at one port when the other port ripple is zero. For the case of equal input and output current ripples, the coupled inductor boost and buck are shown to be superior to the Cuk convertor.

Optimum Input and Output Filters for a Single-Phase Rectifier Power Supply

The ``optimum'' output filter inductance Lf and the input filter capacitor Ci for a single-phase uncontrolled bridge rectifier employed for low power de-to-dc converters or inverters is established. The filter Ci is optimized to obtain maximum input power factor, minimum filter inductance, and minimum output dc voltage regulation. A design example is provided and theoretical results have been verified on an experimental model.