Ph.D. Dissertation Fast Transient and High Efficiency Voltage-Regulated PWM Buck Converters Jung-Duk Suh Department of Electrical and Computer Engineering The Graduate School Sungkyunkwan University 2019

 

Ph.D. Dissertation Fast Transient and High Efficiency Voltage-Regulated PWM Buck Converters 

Jung-Duk Suh

 Department of Electrical and Computer Engineering 

The Graduate School Sungkyunkwan University 

2019 

 Abstract Fast Transient and High Efficiency Voltage-Regulated PWM Buck Converters This dissertation proposes three pulse-width modulation (PWM) buck converter architectures; two for fast load transient and one for high efficiency. A fast load transient response for small overshoot or undershoot is very important to designing switching regulator because dynamic voltage scaling is regarded as an effective power management solution. The transient response in the conventional voltage mode converter is limited since a type-3 compensator with large capacitors is used. So, it is important to improve slow transient response problems. Also, improving the efficiency under the light load condition of switching regulators is a very important design because of many portable devices stay in standby mode. In common PWM buck converters, the switching loss is dominant in the light load. So, to improve the performance of PWM buck converters in terms of the light-load efficiency, the switching power consumption should be minimized. In this dissertation, to overcome the speed limitation of the PWM control and the light load efficiency, PWM buck converters that can improve both the load transient response and the light load efficiency are proposed. First, a DC-DC converter with active ramp tracking control (ARTC) is presented. When the difference between the output voltage and reference voltage is increased to the threshold voltage in the load transient situation, the ramp bias voltages change and generate a full duty signal to the power switches. This helps restore the output voltage to the reference voltage, improving the load transient response speed and decreasing the overshoot/undershoot at the output voltage. The proposed converter with ARTC improves the load transient response speed and decreases the overshoot/undershoot at the output voltage. This proposed buck converter with ARTC can reduce the overshoot/undershoot at the output by up to 61.1% and the recovery time up to 60.0 % for a 450-mA load current step. Second, a DC-DC converter with inductor current slope control (ICSC) is presented. In load transient period, the slope of the inductor current is increased two times by connecting the parallel inductor of same size as main inductor. It can recover the output voltage quickly and have a consistent fast response time regardless of the load current step size and output voltage. This proposed buck converter with ICSC simulated in a 65-nm CMOS technology reduces the overshoot/undershoot at the output by up to 54.4% and the recovery time up to 82.6% for a 450-mA load current step. Third, a DC-DC converter with chargerecycling gate-voltage swing control is presented. This proposed converter with charge-recycling gate-voltage swing control can improve the power efficiency by reducing the gate-driving loss at the light load. This proposed converter controls the gate-voltage swing with charge-recycling structure according to the load current and has the gate-driving loss reduced by up to 87.7% and 47.2% compared to the conventional full-swing and low-swing designs, respectively. The maximum power conversion efficiency was 90.3% when the input and output voltages are 3.3 V and 1.8 V, respectively.

LINK: http://www.riss.kr/search/detail/DetailView.do?p_mat_type=be54d9b8bc7cdb09&control_no=f17df0f4a93a1c12ffe0bdc3ef48d419&keyword=pwm%20converters

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Active gate switching control of IGBT to improve efficiency in high power density converters- AUTOR Ghorbani, Hamidreza- Universitat Politècnica de Catalunya. Departament d'Enginyeria Electrònica Document-Doctoral thesis

 Active gate switching control of IGBT to improve efficiency in high power density converters 

 Thesis submitted in partial fulfilment of the requirement for the PhD degree issued by the Universitat Politècnica de Catalunya, in its Electronic Engineering Program 

BY Hamidreza Ghorbani 

Director: Dr. Prof. Jose Luis Romeral Martinez Co-Director: Dr. Eng. Vicent Sala -May 2019 

 Abstract

 Insulated gate bipolar transistor (IGBT) power semiconductors are widely employed in industrial applications. This power switch capability in high voltage blocking and high current-carrying has expanded its use in power electronics. However, efficiency improvement and reducing the size of products is one of main tasks of engineers in recent years. In order to achieve high-density power converters, attentions are focused on the use of fast IGBTs. Therefore, for achieving this desire the trend is designing more effective IGBT gate drivers. In gate drive (GD) controlling, the main issue is maintaining transient behavior of the MOS-channel switch in well condition; when it switches fast to reduce losses. It is well known that fast switching has a direct effect on the efficiency improvement; meanwhile, it is the major reason of appearing electromagnetic interference (EMI) problems in switched-mode power converters. Nowadays the most expectant of an active gate driver (AGD) is actively adjusting the switching transient through simple circuit implementation. Usually its performance is compared with the conventional gate driver (CGD) with fixed driving profile. As a result a proposed AGD has the capability of increasing the switching speed while minimizing the switching stress. Different novel active gate drivers (as feed-forward and closed-loop topologies) have been designed and analysed in this study. To improve the exist trade-off between switching losses and EMI problem, all effective factors on this trade-off are evaluated and considered in proposed solutions. Theoretical developments include proposed controlling methods and simulated efficiency of IGBTs switching control. The efficiency improvement has been pursued with considering EMI study in the proposed active gate controller. Experimental tests have been conducted to verify the design and validate the results. Beside technical aspects, cost study has also considered in the closed-loop GD. The proposed gate drivers are simple enough to allow its use in real industrial applications. 

RESUMEN

 Los semiconductores de potencia (IGBT) se emplean ampliamente en aplicaciones industriales. La capacidad de este interruptor de bloqueo en alta tensión y conducción de alta corriente ha ampliado su uso en la electrónica de potencia. Sin embargo, la mejora de la eficiencia y la reducción del tamaño de los convertidores de potencia es una de las tareas principales de los ingenieros de diseño. Para lograr convertidores de potencia de alta densidad y eficiencia, se requiere el uso de IGBT rápidos. Por lo tanto, la tendencia es diseñar controladores de puerta para IGBT más efectivos. En el control de la unidad de puerta (GD), el problema principal es mantener el comportamiento transitorio del conmutador del canal MOS bajo control, cuando conmuta a lata frecuencia para reducir las pérdidas. Es bien sabido que la conmutación rápida tiene un efecto directo en la mejora de la eficiencia; Sin embargo, la alta frecuencia de conmutación es la razón principal de la aparición de problemas de interferencia electromagnética (EMI) en los convertidores de potencia de modo conmutado. En la actualidad, la acción más directa para un controlador de puerta activo (AGD) consiste en el ajuste activo del transitorio de conmutación a través de la implementación de un circuito simple. Para evaluar su eficiencia, su rendimiento se compara con el controlador de puerta convencional (CGD) con perfil de conducción fijo. Los resultados muestran que la propuesta de AGD tiene la capacidad de aumentar la velocidad de conmutación mientras minimiza el stress. En este estudio se han diseñado y analizado diferentes controladores de puerta activa novedosos (como topologías de control en avance y de bucle cerrado). Para mejorar el balance existente entre la reducción de pérdidas y los problemas de EMI, todos los factores que afectan a las pérdidas y la EMI se evalúan y se consideran en las soluciones propuestas. Los desarrollos teóricos incluyen el análisis y desarrollo de los métodos de control propuestos, la simulación de la operación del control de conmutación del IGBT, y la validación experimental. Además de los aspectos técnicos de eficiencia y emisiones electromagnéticas, el estudio de costes también se ha considerado en los análisis de AGD. Los resultados muestran que los controladores de puerta propuestos son lo suficientemente eficientes y económicos como para permitir su uso en aplicaciones industriales reales [-]

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 https://upcommons.upc.edu/bitstream/handle/2117/168574/THG1de1.pdf?sequence=1&isAllowed=y

Active gate drivers for high-frequency application of SiC MOSFETs by Paredes Camacho, Alejandro Universitat Politècnica de Catalunya. Departament d'Enginyeria Electrònica Doctoral thesis

 Abstract 

The trend in the development of power converters is focused on efficient systems with high power density, reliability and low cost. The challenges to cover the new power converters requirements are mainly concentered on the use of new switching-device technologies such as silicon carbide MOSFETs (SiC). SiC MOSFETs have better characteristics than their silicon counterparts; they have low conduction resistance, can work at higher switching speeds and can operate at higher temperature and voltage levels. Despite the advantages of SiC transistors, operating at high switching frequencies, with these devices, reveal new challenges. The fast switching speeds of SiC MOSFETs can cause over-voltages and over-currents that lead to electromagnetic interference (EMI) problems. For this reason, gate drivers (GD) development is a fundamental stage in SiC MOSFETs circuitry design. The reduction of the problems at high switching frequencies, thus increasing their performance, will allow to take advantage of these devices and achieve more efficient and high power density systems. This Thesis consists of a study, design and development of active gate drivers (AGDs) aimed to improve the switching performance of SiC MOSFETs applied to high-frequency power converters. Every developed stage regarding the GDs is validated through tests and experimental studies. In addition, the developed GDs are applied to converters for wireless charging systems of electric vehicle batteries. The results show the effectiveness of the proposed GDs and their viability in power converters based on SiC MOSFET devices. 

RESUMEN

La tendencia en el diseño y desarrollo de convertidores de potencia está enfocada en realizar sistemas eficientes con alta densidad de potencia, fiabilidad y bajo costo. Los retos para cubrir esta tendencia están centrados principalmente en el uso de nuevas tecnologías de dispositivos de conmutación tales como, MOSFETs de carburo de silicio (SiC). Los MOSFETs de SiC presentan mejores características que sus homólogos de silicio; tienen baja resistencia de conducción, pueden trabajar a mayores velocidades de conmutación y pueden operar a mayores niveles de temperatura y tensión. A pesar de las ventajas de los transistores de SiC, existen problemas que se manifiestan cuando estos dispositivos operan a altas frecuencias de conmutación. Las rápidas velocidades de conmutación de los MOSFETs de SiC pueden provocar sobre-voltajes y sobre-corrientes que conllevan a problemas de interferencia electromagnética (EMI). Por tal motivo, el desarrollo de controladores de puertas es una etapa fundamental en los MOSFETs de SiC para eliminar los problemas a altas frecuencias de conmutación y aumentar su rendimiento. En consecuencia, aprovechar las ventajas de estos dispositivos y lograr sistemas más eficientes y con alta densidad de potencia. En esta tesis, se realiza un estudio, diseño y desarrollo de controladores activos de puerta para mejorar el rendimiento de conmutación de los MOSFETs de SiC aplicados a convertidores de potencia de alta frecuencia. 

 VIEW FULL DOCTORAL THESIS

https://upcommons.upc.edu/bitstream/handle/2117/328186/TAPC1de1.pdf?sequence=1&isAllowed=y

Stability improvement and control optimization of isolated two-stage AC-DC-DC converter systems Authors: Feng, Fan -Engineering::Electrical and electronic engineering::Power electronics -Nanyang Technological University

STABILITY IMPROVEMENT AND CONTROL OPTIMIZATION OF ISOLATED TWO-STAGE AC-DC-DC CONVERTER SYSTEMS by FENG FAN

 School of Electrical & Electronic Engineering -2020

 A thesis submitted to the Nanyang Technological University in partial fulfilment of the requirement for the degree of Doctor of Philosophy 2020 

 Abstract: Driven by the ever-increasing energy demand and the desire for carbon footprint reduction, the power industry is under a wave of transformation from the current grid into the smart grid. As the trend of the grid transformation continues, a significantly high penetration level of renewable energy resources, in parallel with other emerging technologies such as the energy storage and electric vehicles, is to be expected. Since many types of renewables and energy storage devices, e.g., solar photovoltaic, batteries and supercapacitors, etc., are treated as DC sources, the multi-stage converter system is usually employed as the interface between the AC grid and DC networks. Specifically, the dual active bridge (DAB)-based two-stage AC-DC-DC converter is highly related to the distributed systems because of its advantages such as the high power density, soft switching properties, galvanic isolation and less passive components. Therefore, the stability and reliability of the two-stage AC-DC-DC converters are at the core of the distributed system operations. However, despite its control benefits, the two-stage AC-DC-DC converter system may suffer instability issues. This thesis aims to investigate and overcome the instability issues of the two-stage AC-DC-DC converter system. First, the existing primary stability criteria and stabilization methods for the non-isolated two-stage converter systems have been reviewed and summarized. The terminal impedances of the sub-converters are useful tools to determine the stability of the two-stage converter systems. The forbidden regions for the voltage-source and current-source systems have been discussed. To satisfy these stability criteria, the terminal impedances of the sub-converters should be modified via passive or active damping methods. The research gap for the isolated two-stage AC-DC-DC converter has been identified as well. To analyze the stability of the DAB-based two-stage AC-DC-DC converter, the full-order impedance model of the DAB converter is derived for the first time in this thesis. Since the high-frequency ac conversion stage of the DAB converter naturally violates the small ripple assumption of the traditional state-space modeling, the generalized averaging approach is applied for the DAB impedance derivation. The derived impedance model can provide fully continuous-time representations that are capable of describing the ac conversion stage of the DAB converter. Furthermore, based on the developed impedance model, the influences of the DAB circuit parameters on the stability of the two-stage converter are analyzed. The analysis results offer instructive implications to fine-tune the design rules of the DAB converters. Bearing the mind that the impedance model of the DAB converter is closely related to the modulation schemes, the impacts of three typical modulation methods on the DAB impedances are analyzed and compared. An interesting phenomenon is found that the open-loop impedances of Single Phase-Shift (SPS)-based and Dual Phase-Shift (DPS)-based DAB converters present the characteristics of the parallel-connected inductor and capacitor, while the open-loop impedance of Cooperative Triple Phase-Shift (CTPS)-based DAB converter presents the resistor characteristics. The optimal modulation scheme in terms of stability performance for the two-stage converter is pointed out. This can help engineers find a more stable modulation scheme of the DAB converter in practical cascaded applications.

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https://dr.ntu.edu.sg/bitstream/10356/142948/2/Final%20Thesis.pdf

Development of AC/DC and DC/DC Converters Applied to DC Power Supply with Wide Range of Input Voltage BY TaeHo Bang -Yonsei University Graduate School 2019-Doctor of Philosophy

Development of AC/DC and DC/DC Converters Applied to DC Power Supply with Wide Range of Input Voltage

 A Dissertation Submitted to the School of Electrical and Electronic Engineering and the Graduate School of Yonsei University in partial fulfillment of the requirements for the degree of Doctor of Philosophy 

TaeHo Bang 

December 2018

 Abstract 

This dissertation presents development of AC/DC and DC/DC converters applied to a DC power supply used for various electric devices from home appliances to electric vehicles. In general, the DC power supply consists of electromagnetic interference (EMI) filter for reducing the EMI noise, AC-DC converter to rectify the AC grid voltage into DC voltage and DC-DC converter to supply the power with the suitable voltage level for each device. The EMI filter is essential part of power supply because high speed switching of the converter devices causes undesirable EMI noise. The boost power factor correction (PFC) has widely used for the AC-DC converter because of its simple structure and low cost. In addition, the ability to cope with various AC grid voltages and conditions in different countries is becoming important for PFC converter topologies from the industrial point of view. Meanwhile, full-bridge DC-DC converter is one of the most frequently used topologies in electric vehicle when electrical isolation is required. Isolated DC-DC full-bridge converters are suitable for low DC-DC converter (LDC) which converts high input voltage of the battery into low output voltage level for suppling the power to load of the electrical vehicle. The efficiency of DC-DC converter in electric vehicle are highly related with overall performances including range distance, weight and charging time. Then, improving efficiency without much additional component becomes very important in converter topologies used in electric vehicle. The buck cascaded buck-boost (BuCBB) PFC converter and isolated full-bridge (FB) converter are studied in this dissertation, respectively. 

 First, the BuCBB PFC converter which operates in wide input voltage range to cope with various grid conditions is developed. The converter can operate in buck or boost mode according to the peak value of input voltage. The converter parameters are properly determined to endure voltage and current stress in all operating ranges. In addition, the EMI filter is used to reduce the high frequency switching noise and guarantee continuous input current in buck mode operation. In addition, switching loss is reduced in all operation range by applying zero-voltage-transient pulse-width-modulation (ZVT-PWM) method. In particular, the power factor (PF) depending on the operation modes of the PFC converter including EMI filter is derived with associated mathematical equations in buck and boost mode, respectively. The performances of proposed PFC converter with wide range of input voltage are evaluated by the simulation and experimental test including PF and input current harmonics in all operating ranges. Finally, the efficiency of proposed PFC converter is compared with that of a conventional buck cascaded buck-boost PFC converter in various conditions. And then, a novel control method for FB converter by using the combined phase-shifted and asymmetric pulse-width-modulation (APWM) method is proposed. It reduces the peak and DC offset values of the input-side current of converter. Then, the overall efficiency is consequently improved by reduced the switching losses in its input-side. Moreover, the zero-voltage switching (ZVS) conditions of switches are satisfied in all operating ranges. The phase-shifted duty ratios corresponding to the output currents of converter are optimally selected based on the loss model analysis. Also, the operational features characterized by the proposed phase-shifted asymmetric pulse-width-modulation (PS-APWM) method are investigated under both the continuous and discontinuous current modes of converter. Then, the effectiveness of proposed PS-APWM method is verified with the simulation and practical hardware experimental results. In particular, the experimental test is carried out in a light load condition. Finally, the efficiency of FB converter controlled by the proposed PS-APWM method is compared with that by the conventional phase-shifted or APWM method, which has been separately applied.

ORIGINAL SOURCE:

http://www.riss.kr/search/detail/DetailView.do?p_mat_type=be54d9b8bc7cdb09&control_no=d64f3903ccdb9036ffe0bdc3ef48d419&keyword=topology%20power%20supply

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