Design and analysis of a novel zero-voltage-transition interleaved boost converter for renewable power applications

High-efficiency stepping up operation is an important feature of the converters used in renewable power applications due to the low voltage level of photo-voltaic arrays and fuel cells. Decreasing the switching losses of the converters is an effective solution for increasing the converter efficiency, especially in high-power applications. This article presents a novel zero-voltage-transition (ZVT) interleaved dc–dc boost converter that can be used in renewable power sources to reduce switching losses. The auxiliary circuit used in the proposed converter is composed of only one auxiliary switch and a minimum number of passive components without an important increase in the cost and complexity. The main advantage of the proposed converter is that it not only provides ZVT in the boost switches but also provides soft switching in the auxiliary switch. Another advantage of the proposed topology is that the semiconductor devices used in the converter do not have any additional voltage or current stresses. Also, it has a simple structure, low cost and ease of control. In this article, a detailed steady-state analysis of the proposed converter is presented. The theoretical analysis is verified via simulation and experimental studies which are in very good agreement.     

A novel self-excited forward DC-DC converter withzero-voltage-switched resonant transitions using a saturable core

A novel self-excited forward DC-DC power converter is proposed. The turn-on and turn-off of the switch are zero-voltage-switching with resonant transition. A saturable core is used to achieve the self-excitation and the zero-voltage-switched resonant transition. The voltage waveform across the switch is trapezoidal with sinusoidal transitions, and the current waveform flowing through the switch is quasisquare. The switching losses, the conduction losses and the stresses of the switch are significantly reduced in the proposed power converter. The output voltage is determined by the ON duty ratio of the switch as in a PWM converter. Two methods to modulate the ON duty ratio are proposed. Both methods results in variable-frequency operation. Experiments on two 5 V, 20 A DC-DC power converters show good performance     

High step-up converter with coupled-inductor

In this study, a high step-up converter with a coupled-inductor is investigated. In the proposed strategy, a coupled inductor with a lower-voltage-rated switch is used for raising the voltage gain (whether the switch is turned on or turned off). Moreover, a passive regenerative snubber is utilized for absorbing the energy of stray inductance so that the switch duty cycle can be operated under a wide range, and the related voltage gain is higher than other coupled-inductor-based converters. In addition, all devices in this scheme also have voltage-clamped properties and their voltage stresses are relatively smaller than the output voltage. Thus, it can select low-voltage low-conduction-loss devices, and there are no reverse-recovery currents within the diodes in this circuit. Furthermore, the closed-loop control methodology is utilized in the proposed scheme to overcome the voltage drift problem of the power source under the load variations. As a result, the proposed converter topology can promote the voltage gain of a conventional boost converter with a single inductor, and deal with the problem of the leakage inductor and demagnetization of transformer for a coupled-inductor-based converter. Some experimental results via examples of a proton exchange membrane fuel cell (PEMFC) power source and a traditional battery are given to demonstrate the effectiveness of the proposed power conversion strategy.     

Switch failure diagnosis based on inductor current observation for boost converters

Face to the growing number of applications using DC–DC power converters, the improvement of their reliability is subject to an increasing number of studies. Especially in safety critical applications, designing fault-tolerant converters is becoming mandatory. In this paper, a switch fault-tolerant DC–DC converter is studied. First, some of the fastest Fault Detection Algorithms (FDAs) are recalled. Then, a fast switch FDA is proposed which can detect both types of failures; open circuit fault as well as short circuit fault can be detected in less than one switching period. Second, a fault-tolerant converter which can be reconfigured under those types of fault is introduced. Hardware-In-the-Loop (HIL) results and experimental validations are given to verify the validity of the proposed switch fault-tolerant approach in the case of a single switch DC–DC boost converter with one redundant switch.     

A new family of zero-voltage-transition PWM converters with dual active auxiliary circuits

A new family of active auxiliary circuits that allow the power switch in single switch, pulsewidth modulated converters to operate with zero-voltage switching is proposed in this paper. The main feature of an auxiliary circuit belonging to this family is that the auxiliary switch can operate with a zero-current switching turn-on and turn-off without increasing the peak current stresses of the main switch. This is an improvement over previous proposed auxiliary circuits where either the auxiliary switch operates with a hard turn-off or the circuit itself increases the peak stresses of the main switch. In this paper, the fundamental principles behind the proposed family of active auxiliary circuits are explained. Based on these principles, an example auxiliary circuit is systematically derived and presented along with several other auxiliary circuits belonging to the new family. The operation of a boost converter operating with the example auxiliary circuit is discussed in detail, and general guidelines for the design and implementation of auxiliary circuits belonging to the new family are given. The feasibility of the example auxiliary circuit is confirmed by experimental results obtained from a 500-W, 100-kHz boost converter laboratory prototype.     

Soft-switched DC/DC converter with PWM control

In this paper, a new power converter with two variations is proposed. A novel asymmetrical pulse-width-modulation (PWM) control scheme is used to control the power converter under constant switching frequency operation. The modes of operation for both variations are discussed. The DC characteristics, which can be used in the design of the power converters, are also presented. Two 50 W power converters were built to verify the characteristics of the converters. Due to the zero-voltage-switching (ZVS) operation of the switches and low device voltage and current stresses, these power converters have high full- and partial-load efficiencies. They are, therefore, potential candidates for high-efficiency high-density power supply applications     

A zero-voltage-switched PWM boost converter with an energyfeedforward auxiliary circuit

A zero-voltage-switched (ZVS) pulsewidth-modulated (PWM) boost converter with an energy feedforward auxiliary circuit is proposed in this paper. The auxiliary circuit, which is a resonant circuit consisting of a switch and passive components, ensures that the converter's main switch and boost diode operate with soft switching. This converter can function with PWM control because the auxiliary resonant circuit operates for a small fraction of the switching cycle. Since the auxiliary circuit is a resonant circuit, the auxiliary switch itself has both a soft turn on and turn off, resulting in reduced switching losses and electromagnetic interference (EMI). This is unlike other proposed ZVS boost converters with auxiliary circuits where the auxiliary switch has a hard turn off. Peak switch stresses are only slightly higher than those found in a conventional PWM boost converter because part of the energy that would otherwise circulate in the auxiliary circuit and drastically increase peak switch stresses is fed to the load. In this paper, the operation of the converter is explained and analyzed, design guidelines are given, and experimental results obtained from a prototype are presented. The proposed converter is found to be about 2%-3% more efficient than the conventional PWM boost converter     

A generalized program for extracting the control characteristics ofresonant converters via the state-plane diagram

This paper presents a generalized computer program that can be used to derive the control characteristics of resonant power converters from their state-plane trajectories. It has been shown that the geometrical properties of the state-plane trajectory can be used to derive the control characteristics of a given resonant power converter topology. These characteristics are essential in determining the design parameters such as power converter gain, component stresses and required feedback controllers. The main program consists of several subroutines, each of which is associated with a segment of the state-plane trajectory. Such a program will make it faster and easier for a design engineer to obtain the design parameters of any given resonant topology     

A Soft-Switched Full-Bridge Single-Stage AC-to-DC Converter With Low-Line-Current Harmonic Distortion

A single-phase high-frequency transformer-isolated soft-switching single-stage ac-to-dc converter with low-line-current distortion is presented. The circuit configuration is obtained by integrating two discontinuous current mode (DCM) boost converters with a DCM full-bridge buck converter. The zero-voltage switching for the top switches is achieved automatically, whereas bottom switches are aided by zero-voltage transition circuits. The output voltage is regulated by duty-cycle control at constant switching frequency. The intervals of operation and steady-state analysis are presented. A systematic design procedure is presented with a 1-kW converter design example. PSPICE simulation and experimental results obtained from a 1-kW laboratory prototype are presented for a wide variation in line and load conditions.     

Constant-frequency control of quasi-resonant converters

An additional independent control needed to eliminate the undesirable variable switching frequency of quasi-resonant (QR) converters is obtained by replacing the output rectifier by an active switch. The concept is applicable to all classes of converters. Compared to QR converters with conventional switch realization, constant-frequency quasi-resonant (CF-QR) converters exhibit the same type of switching transitions and similar switch voltage and current stresses. Advantages of CF-QR converters are not restricted to the constant-frequency control. In all classes, operation at zero load is possible, so that the available load range is unlimited. The range of attainable, conversion ratios is significantly extended in the classes of zero-voltage quasi-square-wave (CF-ZV-QSW) and zero-voltage multiresonant (CF-ZV-MR) topologies. A practical design example of a 25 W CF-ZV-MR buck converter is constructed and evaluated. The converter operates at 2 MHz from zero load to full load, with a full-load efficiency of 83%. Simple duty ratio control is used to maintain the output voltage constant for all loads. The circuit is inherently immune to the short-circuit condition at the output. Disadvantages of CF-QR converters are the increased gate-drive losses and increased complexity of the power stage and the control circuitry     

A nonlinear resonant switch

A resonant switch is introduced that uses linear tank elements. Zero-current switching is obtained even through the peak transistor voltage and current stresses can approach those of an equivalent ideal pulsewidth-modulated converter. Reduced switching loss without a substantial increase in conduction loss is therefore possible. An approximate analysis is outlined, and transistor peak-voltage and current stresses are shown to be much lower than those of linear resonant switch technologies. Single-transistor implementations of the buck, boost, and buck-boost nonlinear resonant switch converters are given. Results are presented which experimentally prove the validity of the nonlinear resonant switch concept, as well as that of the approximate analysis     

PWM zero-voltage switching boost-derived converters with outputisolation

In this paper, the basic operations and steady-state analysis for three modified boost-derived power converter topologies are presented. Unlike the conventional boost topology, these power converters provide electrical isolation and zero-voltage switching, while having identical component stresses as those in the conventional boost power converters. Zero-voltage switching and proper transformer-core resetting are achieved from the resonance that occurs between the parasitic capacitance of the power switch and the transformer magnetizing inductance. By introducing a lossless clamping circuit, the voltage stresses across the switching devices are limited to the reflected output voltage to the primary side     

A true ZCZVT commutation cell for PWM converters

This paper introduces a true zero-current and zero-voltage transition (ZCZVT) commutation cell for DC-DC pulsewidth modulation (PWM) converters operating with an input voltage less than half the output voltage. It provides zero-current switching (ZCS) and zero-voltage switching (ZVS) simultaneously, at both turn on and turn off of the main switch and ZVS for the main diode. The proposed soft-switching technique is suitable for both minority and majority carrier semiconductor devices and can be implemented in several DC-DC PWM converters. The ZCZVT commutation cell is placed out of the power path, and, therefore, there are no voltage stresses on power semiconductor devices. The commutation cell consists of a few auxiliary devices, rated at low power, and it is only activated during the main switch commutations. The ZCZVT commutation cell, applied to a boost converter, has been analyzed theoretically and verified experimentally. A 1 kW boost converter operating at 40 kHz with an efficiency of 97.9% demonstrates the feasibility of the proposed commutation cell     

A PFC voltage regulator with low input current distortion derived from a rectifierless topology

This paper presents an ac-dc converter topology for realization of power factor correction (PFC) voltage regulators for applications where the mains frequency is high and a low input current harmonic is required, e.g., in aircraft power systems. The proposed converter represents a minimal configuration consisting of two basic converters, which can be systematically derived from a previously proposed general synthesis procedure for rectifierless ac-dc converters. The proposed PFC converter has incorporated a control method which drastically reduces the circulating power and hence raises the efficiency to a level comparable to existing PFC converters. The proposed PFC converter can completely eliminate any crossover distortion, which can be significant for supply systems having a high mains frequency. In addition, the proposed converter allows bidirectional energy flow ensuring all inductors work in continuous conduction mode hence eliminating the distortion due to the abrupt change of dynamic response when the operating mode changes. Analysis and design of the power and control circuits will be given and discussed. An experimental system will be presented for verification purposes.     

Performance Comparison of Single-Stage Three-Level Resonant AC/DC Converter Topologies

In this paper, the performance of different three-level resonant converters is studied for single-stage power factor correction operation. These converters are suitable for power ranges higher than that in the currently available single-stage converters, due to their high efficiency and reduced component stresses. All the converters presented here are characterized by their ability to regulate the output voltage as well as the dc bus voltage. This leads to lower voltage stresses, wider input voltage range, higher output power applications, and improved efficiencies compared to existing single-stage topologies. Due to the availability of more degrees of freedom in the presented converters, two types of control strategies can be used for this purpose: variable frequency asymmetrical pulsewidth modulation control and variable frequency phase-shift modulation control. Three resonant converters will be studied in this paper and their performances as well as the applicability of the aforementioned control methods for each converter are compared. A 2.3-kW, 48-V converter with input voltage range of 90-265 V_rms is used to study the performance of each case.     

An active power factor correction technique for three-phase dioderectifiers

A novel active power factor correction method for power supplies with three-phase front-end diode rectifiers is proposed and analyzed. The implementation of this method requires the use of an additional single switch boost chopper. The combined front-end converter draws sinusoidal AC currents from the AC source with nearly unity input power factor while operating at a fixed switching frequency. It is shown that when the active input power factor correction stage is also used to regulate the converter DC bus voltage, the converter performance can improve substantially in comparison with the conventional three-phase AC-to-DC converters. These improvements include component count reduction, simplified input synchronization logic requirements, and smaller filter refractive components. Theoretical results are verified experimentally. The proposed method has the disadvantage of substantially increasing the current stresses of the switching devices and the high-frequency ripple content of the prefiltered AC input currents     

Voltage and current stress reduction in single-stage power factorcorrection AC/DC converters with bulk capacitor voltage feedback

Single-stage power factor correction (PFC) AC/DC converters integrate a boost-derived input current shaper (ICS) with a flyback or forward DC/DC converter in one single stage. The ICS can be operated in either discontinuous current mode (DCM) or continuous current mode (CCM), while the flyback or forward DC/DC converter is operated in CCM. Almost all single-stage PFC AC/DC converters suffer from high bulk capacitor voltage stress and extra switch current stress. The bulk capacitor voltage feedback with a coupled winding structure is widely used to reduce both the voltage and current stresses in practical single-stage PFC AC/DC converters. This paper presents a detailed analysis of the bulk capacitor voltage feedback, including the relationship between bulk capacitor voltage, input current harmonics, voltage feedback ratio, and load condition. The maximum bulk capacitor voltage appears when the DC/DC converter operates at the boundary between CCM and DCM. This paper also reveals that only the voltage feedback ratio determines the input current harmonics under DCM ICS and CCM DC/DC operation. The theoretical prediction of the bulk capacitor voltage as well as the predicted input harmonic contents is verified experimentally on a 60 W AC/DC converter with universal-line input     

Novel zero-voltage-transition PWM converters

To date, soft-switching techniques applied to the PWM converters, with the exception of a few isolated cases, are subjected to either high switch voltage stresses or high switch current stresses, or both. A new class of zero-voltage-transition PWM converters is proposed, where both the transistor and the rectifier operate with zero-voltage switching and are subjected to minimum voltage and current stresses. Breadboarded converters are constructed to verify the novelty of the proposed new family of converters     

Power electronic converters for motion control

The historical development of power electronic converters to control electrical machines is traced up to the present state of the technology. The fundamental possibilities to control average power in a switching mode are considered and the concepts switching function, converter topology and converter structure defined. A systematic approach to developing more complicated topologies and structures for singular and composite converters is discussed and application to motion control systems given. A functional classification of motion control converters is also related to the switching nature of the power processing, illustrating the fundamental dilemma of this kind of highly efficient power control. The different control possibilities of using power electronic converters with electrical machines in motion control applications (DC drives, AC drives) are reviewed systematically. The paper does not attempt to compile a comprehensive list of all possible converter circuits and variations but focusses on generic issues and technologies. The switching technology in converters and its limitations is related to snubberless, snubbed, and resonant transition-type operation, with reference also to switch drive and converter protection technology. Some future generic possibilities related to electromagnetic integration of switching converters are discussed, also in relation to a motion control application     

Properties and synthesis of passive lossless soft-switching PWMconverters

This paper derives general topological and electrical properties common to all lossless passive soft-switching power converters with defined characteristics, and proposes a synthesis procedure for the creation of new power converters. The synthesis procedure uses the properties to determine all possible locations for the resonant inductors and capacitors added to achieve soft switching. A set of circuit cells is then used to recover the energy stored in these resonant elements. This paper also explains the operation of the circuit cells and the many new passive lossless soft-switching power converters. A family of soft-switching boost converters is given as an example of the synthesis procedure. Experimental waveforms are also shown for a new soft-switching Cuk converter