Academic literature on the topic 'Resonant converter with Piezoelectric transformers'

Piezoelectric transformers (PTs) allow the design of promising power supply applications, increasing efficiency, reducing size, facilitating the achievement of high transformation ratio, besides providing high immunity against electromagnetic noise. Due to the electrical equivalent model having resonant characteristics, some resonant topologies are used to build these power supplies, i.e. the Class-E converter. In order to make easier the analysis of high order converters, it's possible to use a normalized analysis method. The control of the Class-E converter using PTs is implemented through the switching frequency and duty cycle variation. The static gain is achieved though the switching frequency variation, while the duty cycle is adjusted with the purpose of achieving soft switching for different frequencies and loads. This paper shows a normalized analysis of this process, including a normalized frequency and load variation, without the need of design parameters. Experimental results for a 3W step-down converter are shown for a universal 85-260VAC input and out put voltage 6 V DC, to validate the proposed method.

In this paper, a new constant-frequency quasi-resonant converter is proposed. Compared with the traditional LLC converter, the proposed converter can effectively reduce the range of the operating frequency. The output voltage is changed to adjust the reactance of the resonant cavity. The proposed converter has a better loss factor. To verify the theoretical analysis and soft-switching condition, a 250 W, 100 V output prototype was built and compared with the full-bridge LLC converter. Analysis and experimental results verify that a smaller operating frequency range and volume of the transformers, a soft-switching condition, and a higher overall efficiency are achieved with the proposed converter.

In this paper, high-efficiency bidirectional LLC resonant converters with primary auxiliary windings in transformers of resonant circuits are proposed. Even though resonant capacitors are used on the primary and secondary sides, the proposed converter can operate, regardless of the direction of the power flow, with the high gain characteristics of the LLC resonant converter without the mutual coupling of resonant capacitors. The operation principles and gain characteristics of the proposed bidirectional DC–DC converters are described in detail. A 3.3 kW prototyped bidirectional LLC resonant converter for interfacing 750 VDC buses was built and tested to verify the effectiveness and applicability of this proposed converter.

Within the electronics industry there is a continual demand for DC-DC power converters that achieve high power density at low cost. Since a piezoelectric transformer (PT) has an electrical equivalent circuit that is similar to several resonant converter topologies, a PT can be used to replace many of the reactive components in these topologies with a single ceramic component, thereby offering potential savings in cost, size, and mass. The first part of this thesis presents a new equivalent circuit model for one of the most promising types of PT, the radial mode Transoner. This model relates the electrical characteristics of the PT to the physical dimensions and material properties. Considerable insight is then gained about how to design these devices to meet a particular set of converter specifications whilst simultaneously maximising PT power density. The second part of this thesis concerns the effect of the rectifier topology on PT power density. Using concepts from material science, together with equivalent circuit models of both the PT and the rectifier topologies, it is shown that a given PT will always achieve a higher thermally limited maximum output power when used in an AC-output topology compared to a DC-output topology. The half-bridge inductor-less PT-based converter topology is particularly attractive because it requires no additional components between the half-bridge and the rectifier. However, it is difficult to achieve zero-voltage-switching (ZVS) without significantly compromising PT power density when using this topology. The third part of this thesis details the development and experimental verification of a new model for the ZVS condition. Using a normalisation scheme and numerical optimisation techniques, the requirements for achieving inductor-less ZVS are accurately quantified for the first time. The impact of these requirements on PT power density is assessed, and design guidelines for maximising PT power density are given.

Nowadays the developments of power supplies in military, industrial or commercial applications are growing rapidly, not only to achieve the highest efficiency but also to focus on the size and weight minimization which are playing a major role in this area. Therefore, the research trends in dc-dc, ac-dc, dc-ac, ac-ac topologies are still continuously developing into the direction of new topologies, new control concepts, new materials and devices to achieve highest efficiency and smallest size. The cost per unit is also one of the most important points of power supplies. Also, with new control methods and new ways of manufacturing, for example, the cost per unit might be reduced. Also, a simplified control concept might help to avoid discrete circuits, especially, at low power levels. The last mentioned statement is demonstrated, for instance, by the concept of the Link-Switch of the company Power Integration where an extremely small number of components are necessary. With the target of minimization, this research work explores the possibility to replace conventional electromagnetic transformers considered as the most bulky devices in power supplies by piezoelectric transformers (PT) for innovative off-line power supplies. Several control methods for a load resonant converter focusing on class-E topology utilizing PT, were developed in order to investigate and to select an appropriate control method capable of improving the efficiency and reducing the size of the converter. Efficiency should be understood in this way as maximum reliability at minimum power losses. Different controllers were evaluated for optimizing the effect of disturbances of line and load variations. The ZVS condition for a wide input voltage range and a wide output load range can be achieved by a method called duty-cycle tracking. Further, with an improved design of the PT containing an auxiliary tap, the ZVS condition can be obtained by a method called turn-on synchronization. The controlled output voltage, current or power is achieved by a variable frequency control. Further, the dynamic modeling for open loop and closed loop of load resonant converters, focused on the class-E topology, was introduced. The transient behavior of the output voltage of the open loop against perturbations such as the input voltage change, the switching frequency change, and the output load change is treated by replacing the complete circuit of the class-E converter by simple equivalent circuit models. The results from the analysis of the open loop dynamic behavior are applied to modeling the closed loop class-E converter with several control methods. The methods of linearization for exact solution and heuristic approximation for the steady state analysis were purposed. These models of linearization were implemented with the controller in its topologies to investigate the sufficient accuracy of obtained results of the regulation. Besides, the linearization models were used to observe the stability condition of the proposed control loops. Finally, the evaluation of a well-known classical control such P, I, PI, PD, PID and a simplified controller for a fixed load application by matching an appropriate switching frequency according to the input voltage, into the load resonant converter, considering class-E topology, were presented. Also, the optimum design of the controller for a load resonant converter was discussed and derived
Die Entwicklung von Stromversorgungen in militärischen, industriellen und kommerziellen Anwendungen nimmt bis heute tendenziell stark zu. Nicht nur zur Erzielung höchster Wirkungsgrade, sondern auch im Hinblick auf Baugrößen- und Gewichtsminimierung, welche eine vorrangige Rolle spielen, ist diese Tendenz zu verzeichnen. Diesbezüglich gehen die Forschungstrends bei DC-DC, AC-DC, DC-AC und AC-AC Topologien in Richtung neuer Topologien, neuer Regelungskonzepte, sowie neuer Materialien und Bauelemente, um den höchsten Wirkungsgrad bei kleinster Baugröße zu erreichen. Die Gerätekosten sind ebenso ein sehr wichtiger Punkt bei Stromversorgungen. Auch durch neue Regelungsmethoden und durch neue Herstellungsverfahren können die Gerätekosten beispielsweise reduziert werden. Ebenso kann ein vereinfachtes Regelungskonzept dazu verhelfen, dass diskrete Schaltungen, speziell im unteren Leistungsbereich, vermieden werden. Letzteres wird beispielsweise beim Konzept des Link-Switch der Firma Power Integration verdeutlicht, indem extern wenige Bauelemente benötigt werden. Mit dem Ziel der Miniaturisierung wird in dieser Forschungsarbeit die Möglichkeit untersucht, konventionelle elektromagnetische Transformatoren, welche in Stromversorgungen als besonders voluminös gelten, durch piezoelektrische Transformatoren (PT) bei der Herstellung innovativer Netzstromversorgungen zu ersetzen. Verschiedene Regelungsmethoden für Lastresonanzkonverter, mit dem Fokus auf eine Klasse- E-Topologie mit PT, wurden hierzu entwickelt. Dies hatte zum Ziel, ein geeignetes Regelungsverfahren zu erarbeiten und auszuwählen, welches eine verbesserte Effizienz bei reduzierter Konverter-Baugröße aufzuweisen hat. Effizienz soll hierbei verstanden werden als maximale Zuverlässigkeit bei minimalen Leistungsverlusten. Verschiedene Reglertypen wurden entworfen um die Effekte der Störungen durch Netzspannungs-und Lastvariationen regelungstechnisch zu optimieren. Die Nullspannungsschaltungsbedingung (ZVS-Bedingung) über einen weiten Bereich der Eingangspannung und einen weiten Lastbereich kann durch einen sogenannte Duty-Cycle-Nachführung mit der Frequenz erreicht werden. Weiterhin kann durch eine verbesserte Ausführung des PT auf Basis einer Hilfsanzapfung die ZVSBedingung durch eine sogenannte Einschaltsynchronisation erreicht werden. Geregelte Ausgangsspannung, Ausgangsstrom oder Ausgangsleistung werden über eine Frequenzstellung erreicht. Die dynamische Modellierung der offenen und geschlossenen Regelschleife eines Lastresonanzkonverters, wieder im Hinblick auf die Klasse-E, wird im weiteren vorgestellt. Das transiente Verhalten der Ausgangsspannung der offenen Regelschleife gegenüber Störungen durch Eingangsspannungsänderung, durch Schaltfrequenzänderung oder durch Ausgangslaständerung, wird durch den Ersatz der Klasse-E-Schaltung durch einfache Äquivalenzmodelle behandelt. Die Ergebnisse der Analyse des Verhaltens des offenenen Regelkreises werden verwendet, um den Klasse-E-Konverter mit geschlossener Regelschleife unter Verwendung verschiedener vorgestellter Regelungsmethoden zu modellieren. Methoden der Linearisierung für die exakte Lösung und für eine heuristische Approximation der statischen Analyse des eingeschwungenen Zustands werden vorgeschlagen. Diese Methoden der Linearisierung werden zusammen mit den Reglermodellen in deren jeweilige Topologie implementiert um die ausreichende Genauigkeit der erhaltenen Resultate des Regelungsverhaltens zu beurteilen. Weiterhin werden diese Linearisierungsmodelle dazu verwendet, die Stabilitätskriterien der vorgeschlagenen Regelschleife zu überwachen. Schlussendlich wird die Bestimmung der bekannten klassischen Regler (P, I, PI, PD, PID), sowie eines vereinfachten Konstantlaststellers durch geeignete Anpassung der Schaltfrequenz an die Eingangsspannung, für Lastresonanzkonverter, wieder mit Blick auf die Klasse-E, vorgestellt. Außerdem wird der optimierte Reglerentwurf für Lastresonanzkonverter diskutiert und abgeleitet

Nowadays the developments of power supplies in military, industrial or commercial applications are growing rapidly, not only to achieve the highest efficiency but also to focus on the size and weight minimization which are playing a major role in this area. Therefore, the research trends in dc-dc, ac-dc, dc-ac, ac-ac topologies are still continuously developing into the direction of new topologies, new control concepts, new materials and devices to achieve highest efficiency and smallest size. The cost per unit is also one of the most important points of power supplies. Also, with new control methods and new ways of manufacturing, for example, the cost per unit might be reduced. Also, a simplified control concept might help to avoid discrete circuits, especially, at low power levels. The last mentioned statement is demonstrated, for instance, by the concept of the Link-Switch of the company Power Integration where an extremely small number of components are necessary. With the target of minimization, this research work explores the possibility to replace conventional electromagnetic transformers considered as the most bulky devices in power supplies by piezoelectric transformers (PT) for innovative off-line power supplies. Several control methods for a load resonant converter focusing on class-E topology utilizing PT, were developed in order to investigate and to select an appropriate control method capable of improving the efficiency and reducing the size of the converter. Efficiency should be understood in this way as maximum reliability at minimum power losses. Different controllers were evaluated for optimizing the effect of disturbances of line and load variations. The ZVS condition for a wide input voltage range and a wide output load range can be achieved by a method called duty-cycle tracking. Further, with an improved design of the PT containing an auxiliary tap, the ZVS condition can be obtained by a method called turn-on synchronization. The controlled output voltage, current or power is achieved by a variable frequency control. Further, the dynamic modeling for open loop and closed loop of load resonant converters, focused on the class-E topology, was introduced. The transient behavior of the output voltage of the open loop against perturbations such as the input voltage change, the switching frequency change, and the output load change is treated by replacing the complete circuit of the class-E converter by simple equivalent circuit models. The results from the analysis of the open loop dynamic behavior are applied to modeling the closed loop class-E converter with several control methods. The methods of linearization for exact solution and heuristic approximation for the steady state analysis were purposed. These models of linearization were implemented with the controller in its topologies to investigate the sufficient accuracy of obtained results of the regulation. Besides, the linearization models were used to observe the stability condition of the proposed control loops. Finally, the evaluation of a well-known classical control such P, I, PI, PD, PID and a simplified controller for a fixed load application by matching an appropriate switching frequency according to the input voltage, into the load resonant converter, considering class-E topology, were presented. Also, the optimum design of the controller for a load resonant converter was discussed and derived.
Die Entwicklung von Stromversorgungen in militärischen, industriellen und kommerziellen Anwendungen nimmt bis heute tendenziell stark zu. Nicht nur zur Erzielung höchster Wirkungsgrade, sondern auch im Hinblick auf Baugrößen- und Gewichtsminimierung, welche eine vorrangige Rolle spielen, ist diese Tendenz zu verzeichnen. Diesbezüglich gehen die Forschungstrends bei DC-DC, AC-DC, DC-AC und AC-AC Topologien in Richtung neuer Topologien, neuer Regelungskonzepte, sowie neuer Materialien und Bauelemente, um den höchsten Wirkungsgrad bei kleinster Baugröße zu erreichen. Die Gerätekosten sind ebenso ein sehr wichtiger Punkt bei Stromversorgungen. Auch durch neue Regelungsmethoden und durch neue Herstellungsverfahren können die Gerätekosten beispielsweise reduziert werden. Ebenso kann ein vereinfachtes Regelungskonzept dazu verhelfen, dass diskrete Schaltungen, speziell im unteren Leistungsbereich, vermieden werden. Letzteres wird beispielsweise beim Konzept des Link-Switch der Firma Power Integration verdeutlicht, indem extern wenige Bauelemente benötigt werden. Mit dem Ziel der Miniaturisierung wird in dieser Forschungsarbeit die Möglichkeit untersucht, konventionelle elektromagnetische Transformatoren, welche in Stromversorgungen als besonders voluminös gelten, durch piezoelektrische Transformatoren (PT) bei der Herstellung innovativer Netzstromversorgungen zu ersetzen. Verschiedene Regelungsmethoden für Lastresonanzkonverter, mit dem Fokus auf eine Klasse- E-Topologie mit PT, wurden hierzu entwickelt. Dies hatte zum Ziel, ein geeignetes Regelungsverfahren zu erarbeiten und auszuwählen, welches eine verbesserte Effizienz bei reduzierter Konverter-Baugröße aufzuweisen hat. Effizienz soll hierbei verstanden werden als maximale Zuverlässigkeit bei minimalen Leistungsverlusten. Verschiedene Reglertypen wurden entworfen um die Effekte der Störungen durch Netzspannungs-und Lastvariationen regelungstechnisch zu optimieren. Die Nullspannungsschaltungsbedingung (ZVS-Bedingung) über einen weiten Bereich der Eingangspannung und einen weiten Lastbereich kann durch einen sogenannte Duty-Cycle-Nachführung mit der Frequenz erreicht werden. Weiterhin kann durch eine verbesserte Ausführung des PT auf Basis einer Hilfsanzapfung die ZVSBedingung durch eine sogenannte Einschaltsynchronisation erreicht werden. Geregelte Ausgangsspannung, Ausgangsstrom oder Ausgangsleistung werden über eine Frequenzstellung erreicht. Die dynamische Modellierung der offenen und geschlossenen Regelschleife eines Lastresonanzkonverters, wieder im Hinblick auf die Klasse-E, wird im weiteren vorgestellt. Das transiente Verhalten der Ausgangsspannung der offenen Regelschleife gegenüber Störungen durch Eingangsspannungsänderung, durch Schaltfrequenzänderung oder durch Ausgangslaständerung, wird durch den Ersatz der Klasse-E-Schaltung durch einfache Äquivalenzmodelle behandelt. Die Ergebnisse der Analyse des Verhaltens des offenenen Regelkreises werden verwendet, um den Klasse-E-Konverter mit geschlossener Regelschleife unter Verwendung verschiedener vorgestellter Regelungsmethoden zu modellieren. Methoden der Linearisierung für die exakte Lösung und für eine heuristische Approximation der statischen Analyse des eingeschwungenen Zustands werden vorgeschlagen. Diese Methoden der Linearisierung werden zusammen mit den Reglermodellen in deren jeweilige Topologie implementiert um die ausreichende Genauigkeit der erhaltenen Resultate des Regelungsverhaltens zu beurteilen. Weiterhin werden diese Linearisierungsmodelle dazu verwendet, die Stabilitätskriterien der vorgeschlagenen Regelschleife zu überwachen. Schlussendlich wird die Bestimmung der bekannten klassischen Regler (P, I, PI, PD, PID), sowie eines vereinfachten Konstantlaststellers durch geeignete Anpassung der Schaltfrequenz an die Eingangsspannung, für Lastresonanzkonverter, wieder mit Blick auf die Klasse-E, vorgestellt. Außerdem wird der optimierte Reglerentwurf für Lastresonanzkonverter diskutiert und abgeleitet.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Piezoelectric transformers (PTs) allow the design of promising power supply applications, increasing efficiency, reducing size, facilitating the achievement of high transformation ratio, besides providing high immunity against electromagnetic noise. Due to the electrical equivalent model having resonant characteristics, some resonant topologies are naturally suitable for these power supplies, i.e. the Class- E, Half-Bridge, Full-Bridge and Push-pull. Among these topologies, the Class-E converter has a highlight of having one controlled switch. The static gain of the Class-E is changed through the switching frequency variation, while the duty cycle is adjusted with the purpose of achieving soft switching for different switching frequencies and loads. The analisys of this process becomes complex when the system has a high number of reactive elements. One way to simplify this analisys is applying a normalized methodology. On this regard, the first result of this work is the normalized analisys of the functionally of the Class-E converter, including normalized load and switching frequency variation. This allows choosing one optimum point for the static design, without the necessity of design parameters. The main objective of this analisys is the obtention of the duty cycle behavior in order to have soft switching for all operation points. In a second moment, a small-signal model was derived using the generalized averaging method, through Fourier series aproximation. The model describes the relevant poles and zeros of the system, being accurate enough for different loads and switching frequencies. The behavior of resonant converters changes considerably for different operating points; therefore it is important to have a model that represents the system well. The normalized analisys allowed simplifying the small-signal model derivation, once soft switching is achieved for all the operation points. Experimental measurements validate either the normalized or the small signal derivation methodologies. The measurements were achieved for a 3W step-down converter, with universal 85-265 V AC input and 6 V DC output.
Os Transformadores Piezoelétricos (PTs) permitem o projeto de aplicações promissoras para fontes de alimentação até 100W, melhorando a eficiência, reduzindo o tamanho, facilitando a obtenção de grandes relações de transformação, além de proporcionar alta imunidade contra ruídos eletromagnéticos e interferências. Os PTs apresentam modelo elétrico ressonante, trazendo a necessidade de implementação juntamente com topologias de conversores ressonantes, como por exemplo os conversores: Classe-E, Meia Ponte, Ponte Completa e Push-pull. Dentre estas topologias, o conversor Classe-E se destaca por apresentar somente um interruptor controlado. O ganho estático do conversor Classe-E é obtido através da variação da freqüência de chaveamento, e a razão cíclica muda para atender as condições de comutação suave para diferentes freqüências e cargas. A análise deste processo se torna complexa à medida que o sistema apresenta inúmeros elementos reativos. Uma maneira de simplificar esta análise é utilizar uma metodologia normalizada. Devido a isso, o primeiro resultado deste trabalho é a análise normalizada do funcionamento do conversor piezoelétrico Classe- E, incluindo variação normalizada da frequênciade operação e da carga. Isso permite escolher um ponto ótimo de projeto estático, sem a necessidade de parâmetros de projeto. O objetivo principal desta análise normalizada é a obtenção do comportamento da razão cíclica para obter comutação suave em todos os pontos de operação. Em um segundo momento, um modelo de pequenos sinais foi derivado utilizando a metodologia do modelo médio generalizado, através de aproximação por series de Fourier. O modelo descreve os pólos e zeros relevantes do sistema, sendo suficientemente preciso para diferentes cargas e da frequencias de operação. O comportamento de conversores ressonantes varia consideravelmente para diferentes pontos de operação, pois isso um modelo que permita avaliar estes pontos de maneira precisa se faz importante. A análise normalizada permitiu simplificar a derivação do modelo de pequenos sinais, uma vez que garante a operação em comutação suave. Para validar a metodologia apresentada, são mostrados resultados experimentais para um conversor abaixador de 3W, entrada universal de 85-260 V AC e saída de 6 V DC.

An ever present trend in the power conversion industry is to get higher performance at a lower cost. In a computer server system, the front-end converter, supplying the load subsystems, is typically a multiple output power supply. The power supply unit is custom designed and its output voltages are fully regulated, so it is not very efficient or cost effective. Most of the load systems in this application are supplied by point-of-load converters (POLs). By leaving the output voltage regulation aspect to POLs, the front-end converter does not need to be a fully regulated, multiple output converter. It can be replaced by a dc-dc transformer (DCX), which is a semi-regulated or unregulated, single output dc-dc converter. A DCX can be made using a modular design to simplify expansion of the system capacity. To realize this concept, the DCX block must have a current sharing feature. The current sharing method for a resonant DCX is discussed in this work. To simplify the system architecture, the current sharing method is based on the droop method, which requires no communication between paralleled units. With this method, the current sharing error is inversely proportional to the droop voltage. In traditional DCX implementations, the droop voltage depends on the resistive voltage drops in the power stage, which is not sufficient to achieve the desired current sharing error. The resonant converter has the inherent characteristic that its conversion gain depends on the load current, so the virtual droop resistance can realized by the resonant tank and the droop voltage can be obtained without incurring conduction loss. An LLC resonant converter is investigated for its droop characteristic. The study shows the required droop voltage is achievable at very high switching frequency. To lower the switching frequency, a notch filter is introduced into the LLC resonant tank to increase the sensitivity of the conversion gain versus the operating frequency. The design of the multi-element resonant tank is discussed. Depending soly on the resonant tank, the droop characteristic is largely varied with the component tolerance in the resonant tank. The current sharing error becomes unacceptable. The active droop control is imposed to make the output regulation characteristic insensitive to the component tolerance. The proposed resonant DCX has simpler circuit structure than the fully regulated resonant converter. Finally simulation and experimental results are presented to verify this concept.
Master of Science

碩士
國立聯合大學
電機工程學系碩士班
99
This thesis investigates steady-state electrical characteristics of piezoelectric elements under temperature variations and presents a design procedure of a high-frequency power converter based on piezoelectric transformers for driving light-emitting diodes (LED). Investigations on steady-state responses of piezoelectric elements include piezoelectric transformers and piezoelectric actuators. In this thesis, a set of modified parameters in conventional equivalent circuit of piezoelectric transformers has been derived with the help of experimental studies. The effectiveness of the equivalent circuit with the derived parameters has been verified with results from simulations and practical measurements. In the aspects of designing LED driving circuit on piezoelectric transformers, the basic features of LED driving with AC source are first addressed. Then, a high-frequency power converter based on piezoelectric transformers is designed for driving LED. The proposed high-frequency converter composed of a half-bridge topology and a piezoelectric transformer has a number of advantages; i.e. intrinsic over current protection, lower electric magnetic interferences (EMI) and the current sharing problem in sets of anti-parallel LED array can be solved easily. Considering the requirements in practical applications, issues regarding the improvement of power factor, the elimination of effects of temperature on LED currents have been investigated.

碩士
國立臺灣科技大學
電子工程系
98
This thesis introduces a traditional half-bridge series resonant converter (HB-SRC) and an LLC-type half-bridge series resonant converter (LLC HB-SRC). Then the operating principles are analyzed and the equations of equivalent models are derived. Next, the operating principles and the equivalent circuit models of the proposed half-bridge SRC with dual transformers and resonant tanks are discussed in detail. The Mathcad software is applied to simulate the influences of the quality factor (Q), K factor, characteristics impedance (Zo), and the transformer turn-ratio (Np/Ns) on the frequency response of the voltage gain. The advantages of the proposed converter is that the two transformers can share the output current to reduce the copper losses and the output diode conduction losses. By utilizing two transformers, the presented converter can achieve high efficiency and high power density. Experimental results are recorded for a prototype with an output voltage of 48 V, a rated output power of 800 W, and a resonant frequency of 74 kHz to verify the theoretical analysis. Future works for this research are also included.

碩士
國立雲林科技大學
電機工程系碩士班
100
This paper presents an interleaved pulse-width modulation (PWM) LLC resonant converter with series-parallel connected application. The secondary windings of isolated transformers are connected in series-parallel. Thus the leakage inductance currents at the primary sides and the diode currents at the secondary sides are forced to be balanced. Based on the resonant behavior by the output capacitance of MOSFETs and the leakage inductance of transformers, active switches can be turned on at zero voltage switching (ZVS) and recitifier diodes can be turned off at zero current switching (ZCS) during the transition interval. The benefit of the interleaved pwm scheme can reduce the input/output current ripples, decrease the current stress of all semiconductor components and minimize the electro-magnetic interference (EMI). Finally, the simulation and measured results are presented to confirm the effectiveness of the proposed converter.

碩士
國立臺灣科技大學
電子工程系
104
This thesis presents a single-stage interleaved series resonant converter with dual transformers, which consists of two boost-type power factor corrector (PFC) and two series resonant converter. The PFC stage adopts the voltage-follower control operating under discontinuous conduction mode. It helps to reduce the volume of the boost inductor. The current control loop is not required to reduce the circuit design omplexity. The advantages of the proposed converter are that the two transformers can share the output current to reduce the copper losses and the output diode conduction losses. By utilizing two transformers, the presented converter can achieve high efficiency and high power density. The operating principle of the proposed converter has been analyzed, described and discussed in detail. The simulation using, Mathcad and SIMPLIS, were used for circuit design. The experimental results with the wide input range 180 Vac~240 Vac and an output of 200 V/200 W reveal a maximum efficiency of 89% and a maximum power factor of 0.99.