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Advanced Control for Very Fast DC-DC Converters Based on Hysteresis of the C-out Current

  • Huerta Oliveres, Santa Concepción
  • Soto de Pecho, Andrés
  • Alou Cervera, Pedro
  • Oliver Ramírez, Jesús Angel
  • García Suárez, Oscar
  • Cobos Márquez, José Antonio
The bandwidth achievable by using voltage mode control or current mode control in switch-mode power supply is limited by the switching frequency. Fast transient response requires high switching frequency, although lower switching frequencies could be more suitable for higher efficiency. This paper proposes the use of hysteretic control of the output capacitor $(C_{out})$ current to improve the dynamic response of the buck converter. An external voltage loop is required to accurately regulate the output voltage. The design of the hysteretic loop and the voltage loop are presented. Besides, it is presented a non-invasive current sensor that allows measuring the current in the capacitor. This strategy has been applied for DVS (dynamic voltage scaling) on a 5 MHz buck converter. Experimental results validate the proposed control technique and show fast transient response from 1.5 V to 2.5 V in 2 $mu{rm s}$.
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Integración de un amplificador de RF de alto rendimiento con un amplificador de envolvente con red de cancelación de rizado mediante la técnica de EER

  • Alou Cervera, Pedro
  • Oliver Ramírez, Jesús Angel
  • Vasic, Miroslav
  • García Suárez, Oscar
  • Díaz López, Daniel
  • Cobos Márquez, José Antonio
  • Patiño Gomez, Moises
  • Tena Ramos, David
  • Ortega González, Francisco Javier
En este artículo se presenta la integración de un amplificador de envolvente de una etapa con un amplificador de clase E mediante la técnica de Kahn o Eliminación y restauración de envolvente (EER). Esta técnica se basa en la combinación de un amplificador de potencia conmutado de alto rendimiento alimentado por una fuente de alimentación modulada. El amplificador de envolvente se ha implementado con un convertidor reductor síncrono con red de cancelación de rizado, lo cual permite reducir la relación entre la frecuencia de conmutación y el ancho de banda de gran señal del amplificador de envolvente, que es uno de los factores de diseño más limitantes en esta aplicación. Para la mejora de la linealidad se ha usado la técnica de predistorsión realizándose una validación experimental. El amplificador de envolvente conmuta a 4MHz y el amplificador de clase E a 100MHz. El rendimiento total obtenido para una modulación de amplitud en cuadratura (QAM) es del 68%, con un relación de potencia del canal adyacente (ACPR) de 40dB. Para una modulación por multiplexación por división de frecuencias ortogonales (OFDM), se ha obtenido un rendimiento total del 57% y un ACPR de 32dB.1
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Application and modeling of GaN FET in 1MHz large signal bandwidth power supply for radio frequency power amplifier

  • Cucak, Dejana
  • Vasic, Miroslav
  • García Suárez, Oscar
  • Oliver Ramírez, Jesús Angel
  • Alou Cervera, Pedro
  • Cobos Márquez, José Antonio
  • Tadjer, Marko Jak
  • Calle Gómez, Fernando
  • Benkhelifa, F.
  • Reiner, R.
  • Waltereit, P.
  • Müller, S.
In this paper, implementation and testing of non- commercial GaN HEMT in a simple buck converter for envelope amplifier in ET and EER transmission techn iques has been done. Comparing to the prototypes with commercially available EPC1014 and 1015 GaN HEMTs, experimentally demonstrated power supply provided better thermal management and increased the switching frequency up to 25MHz. 64QAM signal with 1MHz of large signal bandw idth and 10.5dB of Peak to Average Power Ratio was gener ated, using the switching frequency of 20MHz. The obtaine defficiency was 38% including the driving circuit an d the total losses breakdown showed that switching power losses in the HEMT are the dominant ones. In addition to this, some basic physical modeling has been done, in order to provide an insight on the correlation between the electrical characteristics of the GaN HEMT and physical design parameters. This is the first step in the optimization of the HEMT design for this particular application.
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Review and Comparison of Step-Up Transformerless Topologies for Photovoltaic AC-Module Application

  • Meneses Herrera, David
  • Blaabjerg, Frede
  • García Suárez, Oscar
  • Cobos Márquez, José Antonio
This paper presents a comprehensive review of stepup single-phase non-isolated inverters suitable for ac-module applications. In order to compare the most feasible solutions of the reviewed topologies, a benchmark is set. This benchmark is based on a typical ac-module application considering the requirements for the solar panels and the grid. The selected solutions are designed and simulated complying with the benchmark obtaining passive and semiconductor components ratings in order to perform a comparison in terms of size and cost. A discussion of the analyzed topologies regarding the obtained ratings as well as ground currents is presented. Recommendations for topological solutions complying with the application benchmark are provided.
Proyecto:


Transformer-coupled converter for voltage modulation techniques

  • González Sánchez, Mª Carmen
  • Vasic, Miroslav
  • Alou Cervera, Pedro
  • García Suárez, Oscar
  • Oliver Ramírez, Jesús Angel
  • Cobos Márquez, José Antonio
In high performance digital systems as well as in RF systems, voltage scaling and modulation techniques have been adopted to achieve a more efficient processing of the energy. The implementation of such techniques relies on a power supply that is capable of rapidly adjusting the system supply voltage. In this paper, a pulsewidth modulation multiphase topology with magnetic coupling is proposed for its use in voltage modulation techniques. Since the magnetic coupling in this topology is done with transformers instead of coupled inductors, the energy storage is reduced and very fast voltage changes are achieved. Advantages and drawbacks of this topology have been previously presented in the literature and in this paper, the design criteria for implementing a power supply for the envelope elimination and restoration technique in an RF system are presented along with an implementation of the power supply.
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Comparison of Boost-Based MPPT Topologies for Space Applications

  • García Suárez, Oscar
  • Alou Cervera, Pedro
  • Oliver Ramírez, Jesús Angel
  • Díaz López, Daniel
  • Meneses Herrera, David
  • Cobos Márquez, José Antonio
  • Soto de Pecho, Andrés
  • Lapeña, Emilio
  • Rancaño, Jesús
Several boost-derived topologies are analyzed and compared for an aerospace application that uses a 100 V voltage bus. All these topologies have been designed and optimized considering the electrical requirements and the reduced number of space-qualified components. The comparison evaluates the power losses, mass, and dynamic response. Special attention has been paid to those topologies that may cancel the inherent right half plane zero (RHP) zero of the boost topology. Experimental results of the less common topologies are presented.
Proyecto:


3-Phase Rectifier System with very demanding dynamic load: Architecture analysis and control strategy

  • Molina Garcia, Jose Maria
  • Zhao, Sisi
  • Oliver Ramírez, Jesús Angel
  • Alou Cervera, Pedro
  • García Suárez, Oscar
  • Cobos Márquez, José Antonio
A distributed power architecture for aerospace application with very restrictive specifications is analyzed. Parameters as volume, weight and losses are analyzed for the considered power architectures. In order to protect the 3 phase generator against high load steps, an intermediate bus (based in a high capacitance) to provide energy to the loads during the high load steps is included. Prototypes of the selected architecture for the rectifier and EMI filter are built and the energy control is validated.
Proyecto:


Interleaved multi-cell isolated three-phase PWM rectifier system for aircraft applications

  • Silva Faúndez, Marcelo Alexis
  • Hensgens, Nico H.
  • Molina García, José María
  • Vasic, Miroslav
  • Oliver Ramírez, Jesús Angel
  • Alou Cervera, Pedro
  • García Suárez, Oscar
  • Cobos Márquez, José Antonio
Recently there has been an important increase in electric equipment, as well as, electric power demand in aircrafts applications. This prompts to the necessity of efficient, reliable, and low-weight converters, especially rectifiers from 115VAC to 270VDC because these voltages are used in power distribution. In order to obtain a high efficiency, in aircraft application where the derating in semiconductors is high, normally several semiconductors are used in parallel to decrease the conduction losses. However, this is in conflict with high reliability. To match both goals of high efficiency and reliability, this work proposes an interleaved multi-cell rectifier system, employing several converter cells in parallel instead of parallel-connected semiconductors. In this work a 10kW multi-cell isolated rectifier system has been designed where each cell is composed of a buck type rectifier and a full bridge DC-DC converter. The implemented system exhibits 91% of efficiency, high power density (10kW/10kg), low THD (2.5%), and n−1 fault tolerance which complies, with military aircraft standards.
Proyecto:


Improvement of the Dynamic Performance of a Multiphase Current Controlled Buck Converter using an Auxiliary Synchronous Buck Converter as an Additional Energy Path

  • Svikovic, Vladimir
  • Alou Cervera, Pedro
  • Oliver Ramírez, Jesús Angel
  • García Suárez, Oscar
  • Cobos Márquez, José Antonio
This work is related to the output impedance improvement of a Multiphase Buck converter with Peak Current Mode Control (PCMC) by means of introducing an additional power path that virtually increases the output capacitance during transients. Various solutions that can be employed to improve the dynamic behavior of the converter system exist, but nearly all solutions are developed for a Single Phase Buck converter with Voltage Mode Control (VMC), while in the VRM applications, due to the high currents, the system is usually implemented as a Multiphase Buck Converter with Current Mode Control. The additional energy path, as presented here, is introduced with the Output Impedance Correction Circuit (OICC) based on the Controlled Current Source (CCS). The OICC is used to inject or extract a current n-1 times larger than the output capacitor current, thus virtually increasing n times the value of the output capacitance during the transients. Furthermore, this work extends the OICC concept to a Multiphase Buck Converter system while comparing proposed solution with the system that has n times bigger output capacitor. In addition, the OICC is implemented as a Synchronous Buck Converter with PCMC, thus reducing its influence on the system efficiency.
Proyecto:


Forward micro-inverter with primary-parallel secondary-series multicore transformer

  • Meneses Herrera, David
  • García Suárez, Oscar
  • Alou Cervera, Pedro
  • Oliver Ramírez, Jesús Angel
  • Prieto López, Roberto
  • Cobos Márquez, José Antonio
This paper presents a primary-parallel secondary-series multicore forward micro-inverter for photovoltaic AC-module application. The proposed solution changes the number of active phases depending on the grid voltage, thus enabling the usage of low-profile unitary turns ratio transformers. Therefore, the transformers are well coupled and the overall performance of the inverter is improved. Due to the multiphase solution the number of devices increases but, the current stress and losses per device are reduced contributing to an easier thermal management. Furthermore, the decoupling capacitor is split between the phases, contributing to a low-profile solution without electrolytic capacitors suitable to be mounted in the frame of a PV module.
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