An agile supply modulator with improved transient performance for power efficient linear amplifier employing envelope tracking techniques

This article presents an agile supply modulator with optimal transient performance that includes improvement in rise time, overshoot and settling time for the envelope tracking supply in linear power amplifiers. For this purpose, we propose an on-demand current source module: the bang-bang transient performance enhancer (BBTPE). Its objective is to follow fast variations in input signals with reduced overshoot and settling time without deteriorating the steady-state performance of the buck regulator. The proposed approach enables fast system response through the BBTPE and an accurate steady-state output response through a low switching ripple and power efficient dynamic buck regulator. Fast output response with the help of the added module induces a slower rise of inductor current in the buck converter that further helps the proposed system to reduce both overshoot and settling time. This article also introduces an efficient selective tracking of envelope signal for linear PAs. To demonstrate the feasibility of the proposed solution, extensive simulations and experimental results from a discrete system are reported. The proposed supply modulator shows 80% improvement in rise time along with 60% reduction in both overshoot and settling time compared to the conventional dynamic buck regulator-based solution. Experimental results using the LTE 16-QAM 5 MHz standard shows improvement of 7.68 dB and 65.1% in adjacent channel power ratio (ACPR) and error vector magnitude (EVM), respectively.Peer ReviewedPostprint (author's final draft

‘Bang-Bang’ technique in supply modulation for linear wideband RF power amplifiers

This paper deals with the design techniques of power efficient switching regulators intended for linear power amplifiers employing envelope tracking techniques in wideband wireless standards. The bottlenecks involve a tradeoff between ripple voltage, slew rate and bandwidth. The slew rate limitation is identified as the main challenge, then a ‘bang-bang’ slew enhancement technique is proposed. This approach enables the use of efficient supply modulators in wideband power amplifiers. The proposed scheme does not significantly degrade PA efficiency and preserves the stability of the switching regulator. The prototype has been implemented using the TSMC 0.18 µm technology; schematic simulation results in Cadence® are presented to prove the concept.Postprint (published version

Supply modulator for linear wideband RF power amplifiers

Este artículo trata de las técnicas de diseño de reguladores de potencia conmutados de alta eficiencia destinados a alimentar amplificadores de potencia (PAs) lineales, empleando técnicas de seguimiento para estándares inalámbricos de banda ancha. Los cuellos de botella presentados implican un compromiso entre tensión, slew rate y ancho de banda. De hecho, la limitación de slew rate es identificada como el principal desafío. Por tanto, se propone una técnica de mejora del slew rate denominada “bang-bang”. Este enfoque permite el uso de moduladores de alimentación eficientes para la alimentación de los mencionado amplificadores de potencia de banda ancha. El esquema propuesto no degrada significativamente la eficiencia del PA y preserva, e incluso mejora, la estabilidad del regulador conmutado. El prototipo ha sido implementada utilizando la tecnología de TSMC 0,18 μm. Resultados de simulación post-layout en Cadence® son presentados para demostrar la viabilidad del diseño llevado a cabo.This paper deals with the design techniques of power efficient switching regulators intended for linear power amplifiers (PAs) employing envelope tracking techniques in wideband wireless standards. The bottlenecks involve a tradeoff between ripple voltage, slew rate and bandwidth. The slew rate limitation is identified as the main challenge; thus a ‘bang-bang’ slew-enhancement technique is proposed. This approach enables the use of efficient supply modulators in wideband power amplifiers. The proposed scheme does not significantly degrade PA efficiency and preserves, and even improves, the stability of the switching regulator. The prototype has been implemented using the TSMC 0.18 μm technology; schematic simulation results in Cadence® are presented to prove the concept.Peer Reviewe

Buck derived converters based on gallium nitride devices for Envelope Tracking applications

Envelope tracking (ET) is a technique designed to enhance the efficiency of radio frequency power amplifiers (RF PA). It is based on providing the voltage to the RF PA with variations that mimic the shape of the envelope of the communication signal that the RF PA is processing. As the bandwidth of these signals can be around several megahertz, the switching frequency of the switching mode power supply designed for ET applications has to be very high. The good switching characteristics of Gallium Nitride devices makes them suitable for this application. This paper presents two multiphase converters to be used as envelope modulators in envelope tracking application

Development of an active power filter based on wide-bandgap semiconductors

Pla de Doctorat Industrial, Generalitat de CatalynuaElectrical and electronic equipment needs sinusoidal currents and voltages to function properly. Equipment such as computers, household appliances, electric vehicle chargers, and LED lights can distort the grid and worsen grid quality. Distorted electrical grids can cause malfunctions, reduce service life, and decrease the performance of connected equipment. Industry commonly solves these problems using active power filters, which can minimise the harmonics of the grid, eliminate undesirable reactive power, and restore balance to unbalanced power grids. This thesis deals with the design and implementation of an active power filter based on wide-bandgap semiconductors, which have properties that are superior to classical silicon devices. An active power filter’s design must take advantage of these benefits to build converters that are smaller, more efficient, and consume fewer resources. However, wide-bandgap semiconductors also present design challenges. Because the most commonly used active power filters in the industry are based on two-level voltage source converters, the research for this doctoral thesis focuses on this converter topology. Moreover, its main objective is to contribute new modulation techniques that are specially designed to work with wide-bandgap semiconductors. The proposed modulations consider different aspects, such as the computational cost of the algorithms, converter losses, and the electromagnetic distortion generated. First, this thesis presents a hexagonal sigma-delta (H-S¿) modulation based on sigma-delta (S¿) modulation. The properties of this modulation are studied, and the technique is compared with other widely used modulations. The comparison considers efficiency, harmonic distortion, the electromagnetic compatibility of the converter, and the type of wideband semiconductor used. In addition, a fast algorithm is mathematically developed to simplify the presented modulation and reduce its computational cost. Secondly, this thesis presents a family of sigma-delta modulations specially designed to improve electromagnetic compatibility: the reduced common-mode voltage sigma-delta (RCMV-S¿) modulations. These modulations avoid using the vectors that generate the maximum common-mode voltage, which significantly reduces the generated electromagnetic distortion without affecting the performance of the converter and its harmonic distortion. Finally, the proposed modulations are applied in a wide-bandgap power converter working as an active filter. Thus, it is verified that the techniques presented in this thesis will obtain satisfactory results when implemented in commercial active power filters.Els equips elèctrics i electrònics necessiten corrents i tensions sinusoïdals per funcionar correctament. Existeixen equips com els ordinadors, els electrodomèstics, els carregadors de vehicle elèctric o les llums LED, que poden distorsionar la xarxa i empitjorar la qualitat d'aquesta. Les xarxes elèctriques distorsionades poden causar el mal funcionament dels equips que s'hi connecten, reduir la seva vida útil i també empitjorar la seva eficiència. A la industria és habitual utilitzar filtres actius per a solucionar aquests problemes. Els filtres actius permeten minimitzar els harmònics presents a la Δxarxa, eliminar la potència reactiva no desitjada i equilibrar xarxes elèctriques desequilibrades. Aquesta tesi tracta sobre el disseny i la implementació d'un filtre actiu basat en semiconductors de banda ampla. Aquests semiconductors presenten propietats superiors als clàssics dispositius de silici. El disseny d'un filtre actiu ha d'aprofitar aquests avantatges per a construir convertidors més petits, eficients i que consumeixin menys recursos. Tanmateix, els semiconductors de banda ampla també presenten problemes que el disseny ha de solucionar. Els filtres actius més utilitzats en la indústria són els basats en convertidors de font de tensió (voltatge source converters) amb dos nivells. La recerca d'aquesta tesi doctoral està focalitzada en aquesta topologia de convertidor, i el seu principal objectiu és l’aportació de noves tècniques de modulació especialment dissenyades per treballar amb semiconductors de banda ampla. Les modulacions proposades tenen en compte diferents aspectes: el cost computacional dels algoritmes, les pèrdues del convertidor i la distorsió electromagnètica generada. En primer lloc, es presenta una modulació sigma-delta hexagonal (H-__) que es basa en la modulació sigma-delta (ΣΔ). S'estudien les propietats d'aquesta modulació i la tècnica es compara amb altres modulacions àmpliament usades. La comparativa realitzada considera l’eficiència, la distorsió harmònica, la compatibilitat electromagnètica del convertidor i el tipus de semiconductor de banda ampla emprat. Addicionalment, es desenvolupa matemàticament un algoritme ràpid per simplificar la modulació presentada i reduir el seu cost computacional. En segon lloc, es presenta una família de modulacions sigma-delta especialment dissenyades per millorar la compatibilitat electromagnètica: les modulacions sigmadelta amb tensió en mode comú reduïda (RCMV-ΣΔ ). Aquestes modulacions eviten fer servir els vectors que generen la màxima tensió en mode comú. D'aquesta manera es redueix significativament la distorsió electromagnètica generada sense afectar de forma notable al rendiment del convertidor ni a la seva distorsió harmònica. Finalment, les modulacions proposades s'apliquen en un convertidor de potència, basat en semiconductors de banda ampla, que treballa com a filtre actiu. Això es verifica que les tècniques presentades en aquesta tesi poden ser implementades en filtres actius comercials obtenint resultats satisfactoris.Postprint (published version

Silicon Photonic Subsystems for Inter-Chip Optical Networks

The continuous growth of electronic compute and memory nodes in terms of the number of I/O pins, bandwidth, and areal throughput poses major integration and packaging challenges associated with offloading multi-Tbit/s data rates within the few pJ/bit targets. While integrated photonics are already deployed in long and short distances such as inter and intra data centers communications, the promising characteristics of the silicon photonic platform set it as the future technology for optical interconnects in ultra short inter-chip distances. The high index contrast between the waveguide and the cladding together with strong thermo-optic and carrier effects in silicon allows developing a wide range of micro-scale and low power optical devices compatible with the CMOS fabrication processes. Furthermore, the availability of photonic foundries and new electrical and optical co-packaging techniques further pushes this platform for the next steps of commercial deployment. The work in this dissertation presents the current trends in high-performance memory and processor nodes and gives motivation for disaggregated and reconfigurable inter-chip network enabled with the silicon photonic layer. A dense WDM transceiver and broadband switch architectures are discussed to support a bi-directional network of ten hybrid-memory cubes (HMC) interconnected to ten processor nodes with an overall aggregated bandwidth of 9.6Tbit/s. Latency and energy consumption are key performance parameters in a processor to primary memory nodes connectivity. The transceiver design is based on energy-efficient micro-ring resonators, and the broadband switch is constructed with 2x2 Mach-Zehnder elements for nano-second reconfiguration. Each transceiver is based on hundreds of micro-rings to convert the native HMC electrical protocol to the optical domain and the switch is based on tens of hundreds of 2x2 elements to achieve non-blocking all-to-all connectivity. The next chapters focus on developing methods for controlling and monitoring such complex and highly integrated silicon photonic subsystems. The thermo-optic effect is characterized and we show experimentally that the phase of the optical carrier can be reliably controlled with pulse-width modulation (PWM) signal, ultimately relaxing the need for hundreds of digital to analog converters (DACs). We further show that doped waveguide heaters can be utilized as \textit{in-line} optical power monitors by measuring photo-conductance current, which is an alternative for the conventional tapping and integration of photo-diodes. The next part concerned with a common cascaded micro-ring resonator in a WDM transceiver design. We develop on an FPGA control algorithm that abstracts the physical layer and takes user-defined inputs to set the resonances to the desired wavelength in a unicast and multicast transmission modes. The associated sensitivities of these silicon ring resonators are presented and addressed with three closed-loop solutions. We first show a closed-loop operation based on tapping the error signal from the drop port of the micro-ring. The second solution presents a resonance wavelength locking with a single digital I/O for control and feedback signals. Lastly, we leverage the photo-conductance effect and demonstrate the locking procedure using only the doped heater for both control and feedback purposes. To achieve the inter-chip reconfigurability we discuss recent advances of high-port-count SiP broadband switches for reconfigurable inter-chip networks. To ensure optimal operation in terms of low insertion loss, low cross-talk and high signal integrity per routing path, hundreds of 2x2 Mach-Zehnder elements need to be biased precisely for the cross and bar states. We address this challenge with a tapless and a design agnostic calibration approach based on the photo-conductance effect. The automated algorithm returns a look-up table for all for each 2x2 element and the associated calibrated biases. Each routing scenario is then tested for insertion loss, crosstalk and bit-error rate of 25Gbit/s 4-level pulse amplitude modulation signals. The last part utilizes the Mach-Zehnder interferometers in WDM transceiver applications. We demonstrate a polarization insensitive four-channel WDM receiver with 40Gbit/s per channel and a transmitter design generating 8-level pulse amplitude modulation signals at 30Gbit/s

Integrated design of high performance pulsed power converters : application to klystron modulators for the compact linear colider (CLIC)

Ce travail de recherche présente l’étude, conception et validation d’une topologie de convertisseur de puissance pulsé qui compense la chute de tension pour des modulateurs de type klystron de haute performance. Cette topologie est capable de compenser la chute de tension du banc de condensateur principal et, en même temps, de faire fonctionner le modulateur avec une consommation de puissance constante par rapport au réseau électrique. Ces spécifications sont requises par le projet Compact Linear Collider (CLIC) pour les modulateurs klystron de son Drive Beam. Le dimensionnement du système est effectué à partir d’un outil d’optimisation globale développé à partir des modèles analytiques qui décrivent les performances de chaque composant du système. Tous les modèles sont intégrés dans un processus optimal intermédiaire de conception qui utilise des techniques d’optimisation afin de réaliser un dimensionnement optimal du système. Les performances de cette solution optimale intermédiaire sont alors évaluées à l’aide d’un modèle plus fin basé sur des simulations numériques. Une technique d’optimisation utilisant l’approche «space mapping» est alors mise en oeuvre. Si l’écart entre les performances prédites et les performances simulées est important, des facteurs de correction sont appliqués aux modèles analytiques et le processus d’optimisation est relancé. Cette méthode permet d’obtenir une solution optimale validée par le modèle fin en réduisant le nombre de simulations. La topologie finale sélectionnée pour le cahier des charges du modulateur CLIC est validée expérimentalement sur des prototypes à échelle réduite. Les résultats valident la méthodologie de dimensionnement et respectent les spécifications.This research work presents the study, design and validation of a pulsed power converter topology that performs accurate voltage droop compensation for high performance klystron modulators. This topology is capable of compensating the voltage droop of the intermediate capacitor bank and, at the same time, it makes possible a constant power consumption operation of the modulator from the utility grid. These two main specifications are required for the Compact Linear Collider (CLIC) Drive Beam klystron modulators. The dimensioning of the system is performed by developing a global optimization design tool. This tool is first based on developed analytical models describing the performances of each system subcomponent. All these models are integrated into an intermediate design environment that uses nonlinear optimization techniques to calculate an optimal dimensioning of the system. The intermediate optimal solution performances are then evaluated using a more accurate model based on numerical simulation. Therefore, an optimization technique using «space mapping» is implemented. If differences between predicted performances and simulated results are non-negligible, correction factors are applied to the analytical models and the optimization process is launched again. This method makes possible to achieve an optimal solution validated by numerical simulation while reducing the number of numerical simulation steps. The selected final topology for the CLIC klystron modulator is experimentally validated using reduced scale prototypes. Results validate the selected methodology and fulfill the specifications

Design and Advanced Model Predictive Control of Wide Bandgap Based Power Converters

The field of power electronics (PE) is experiencing a revolution by harnessing the superior technical characteristics of wide-band gap (WBG) materials, namely Silicone Carbide (SiC) and Gallium Nitride (GaN). Semiconductor devices devised using WBG materials enable high temperature operation at reduced footprint, offer higher blocking voltages, and operate at much higher switching frequencies compared to conventional Silicon (Si) based counterpart. These characteristics are highly desirable as they allow converter designs for challenging applications such as more-electric-aircraft (MEA), electric vehicle (EV) power train, and the like. This dissertation presents designs of a WBG based power converters for a 1 MW, 1 MHz ultra-fast offboard EV charger, and 250 kW integrated modular motor drive (IMMD) for a MEA application. The goal of these designs is to demonstrate the superior power density and efficiency that are achievable by leveraging the power of SiC and GaN semiconductors. Ultra-fast EV charging is expected to alleviate the challenge of range anxiety , which is currently hindering the mass adoption of EVs in automotive market. The power converter design presented in the dissertation utilizes SiC MOSFETs embedded in a topology that is a modification of the conventional three-level (3L) active neutral-point clamped (ANPC) converter. A novel phase-shifted modulation scheme presented alongside the design allows converter operation at switching frequency of 1 MHz, thereby miniaturizing the grid-side filter to enhance the power density. IMMDs combine the power electronic drive and the electric machine into a single unit, and thus is an efficient solution to realize the electrification of aircraft. The IMMD design presented in the dissertation uses GaN devices embedded in a stacked modular full-bridge converter topology to individually drive each of the motor coils. Various issues and solutions, pertaining to paralleling of GaN devices to meet the high current requirements are also addressed in the thesis. Experimental prototypes of the SiC ultra-fast EV charger and GaN IMMD were built, and the results confirm the efficacy of the proposed designs. Model predictive control (MPC) is a nonlinear control technique that has been widely investigated for various power electronic applications in the past decade. MPC exploits the discrete nature of power converters to make control decisions using a cost function. The controller offers various advantages over, e.g., linear PI controllers in terms of fast dynamic response, identical performance at a reduced switching frequency, and ease of applicability to MIMO applications. This dissertation also investigates MPC for key power electronic applications, such as, grid-tied VSC with an LCL filter and multilevel VSI with an LC filter. By implementing high performance MPC controllers on WBG based power converters, it is possible to formulate designs capable of fast dynamic tracking, high power operation at reduced THD, and increased power density