Showing papers by "J.M. Alonso published in 2015"

Large-Signal Characterization of Power Inductors in EV Bidirectional DC–DC Converters Focused on Core Size Optimization

Abstract: This paper is focused on core size optimization of power inductors in bidirectional dc–dc converters. It presents an experimental large-signal characterization procedure for power inductors in electric vehicle applications and a method to obtain an inductance reference value for the power inductor in dc–dc converters' simulation studies. It discusses the importance of the inductor design project by describing important constraints such as core size and saturation. The main contribution of this paper is related to the proposed dc flux cancelation technique in the bidirectional converter. A variable inductor prototype is used to replace the power inductor in order to decrease core size by improving the ripple content of the inductor current. The saturation level of the core is controlled by means of an auxiliary winding whether the converter operates in buck or boost mode. Experimental results validate the proposed methodology showing more than 50% reduction in magnetic material for similar current levels.

On the prediction of Hodgkin lymphoma treatment response

Abstract: Purpose The cure rate in Hodgkin lymphoma is high, but the response along with treatment is still unpredictable and highly variable among patients. Detecting those patients who do not respond to treatment at early stages could bring improvements in their treatment. This research tries to identify the main biological prognostic variables currently gathered at diagnosis and design a simple machine learning methodology to help physicians improve the treatment response assessment.

Optimization of a Front-End DCM Buck PFP for an HPF Integrated Single-Stage LED Driver

Abstract: There is currently a trend in power electronics to avoiding the use of electrolytic capacitors in LED drivers, provided that their expected life span is much lower than that of the LEDs, thus reducing the reliability of the entire LED fixture. This paper presents an optimization study about the determination of the minimal bus capacitance needed for reducing the power factor preregulator (PFP) stage dc-link capacitor down to values that are available in metalized-film technology. This optimization study will be applied to the buck converter, which is an interesting topology for high power factor (HPF) LED drivers due to its low component count, HPF, low output voltage, and lower voltage stress on semiconductors than the boost or buck–boost PFPs, which yields to lower efficiency decline under dimming operation. This way, a 70-W integrated buck–flyback converter is developed and proposed with an metalized-film polypropylene (MKP) dc-link capacitor, intended for outdoor applications where a high reliability is pursued, and capable of driving several LED lamps in different configurations. The experimental results show the accuracy of the theoretical predictions, confirming the feasibility of the buck converter as a high-performance PFP.

Finite element analysis of a variable inductor for an RSCC based LED lamp driver

Abstract: This paper presents a finite element analysis (FEA) of a variable inductor (VI) used to control a resonant switched capacitor converter (RSCC) based LED Driver. As it is well known, resonant converters are generally preferred due to their easily achieved soft-switching as well as soft-starting. In the RSCC based LED driver, the average current flowing through the LEDs is controlled by means of a variable inductance placed in the resonant circuit. The VI is the device responsible for providing the required variable inductance. The RSCC operation with VI control, the operating principle of the VI and typical modelling techniques are briefly presented. In addition, a simplified design procedure for VIs, based on E, EF and EFD cores, is proposed. The FEA of the VI used in the LED lamp driver, based on a double gapped “EFD” core, is presented. The performed FEA simulations describe the behavior of the electromagnetic device and help understanding the non-linear characteristics of this element.

Dimmable LED driver with variable inductor based on a resonant switched-capacitor topology

Abstract: This paper proposes a new 48 V DC-fed dimmable LED driver based on a Resonant Switched-Capacitor Topology (RSCT) where the analog-based dimming feature is accomplished by means of a variable inductor (VI). The proposed topology is based on the classic RSCT step-up double mode converter and it provides a simple and cost-effective solution while guaranteeing a wide dimming range. In order to implement an analog-based dimming the control of the dc current in the LED lamp is required. This technique proposes to replace the resonant inductor by a VI, which will control the rms value of the resonant current, and therefore the mean value of the LED lamp current. In order to evaluate the feasibility and performance of this method a 22 W LED lamp and driver prototypes were built. The most relevant experimental results are presented and briefly described.

Four-Parameter Taylor Series-Based Light-Emitting-Diode Model

Abstract: This paper presents a light-emitting-diode (LED) model based on the four-parameter Taylor series to describe the $V$ – $I$ characteristic of the LED at different junction temperatures. Therefore, in order to precisely model the LED nonlinear characteristics at different junction temperatures, an improved Taylor series-based LED model is proposed according to the four available parameters: 1) maximum operating point; 2) rated operating point; 3) knee point; and 4) temperature coefficient obtained from the LED $V$ – $I$ curves. Furthermore, in order to perform the dc and small-signal simulation and analyses of the LED drivers at different junction temperatures, the proposed model can be used to derive the LED dc and small-signal equivalent resistances at different junction temperatures. Finally, the measured results are compared with the modeled $V$ – $I$ curves, dc equivalent resistances, and small-signal equivalent resistances of the experimental LED at different junction temperatures.

Analysis of low-frequency current ripple transmission in series-resonant LED drivers

Abstract: The use of series-resonant converters (SRCs) in light-emitting diode (LED) drivers has increased due to its simplicity and high efficiency. Furthermore, the use of a SRC provides reduction of the low-frequency ripple in the LED current, originated by the bus voltage ripple. Thus, an analysis of the SRC aiming to define a design methodology to improve the current ripple reduction provided by the SRC is proposed. Moreover, a discussion about the main factors that have influenced ripple reduction and the limits for this attenuation is presented, which have not been explored in the literature hither to.

High-power-factor LED driver based on input current shaper using a flyback converter

Abstract: This paper presents a high-power-factor LED driver implemented by using an input current shaper. A DCM-operated flyback converter is placed between the main rectifier and DC bus, in order to increase the conduction angle of the rectifier diodes and to obtain low current harmonics injected to the mains. Power control stage is performed by a buck converter, which is integrated with the flyback, thus presenting reduced component count. The use of a flyback converter operating as a loss free resistor provides reduced power processing, which increases overall efficiency of the converter. In addition, two-stage configuration allows for bus capacitor reduction, owing to the effect of low frequency filtering provided by the second stage. In this way, electrolytic capacitors can be avoided, thus increasing reliability of the LED driver, which is an essential feature pursued in this type of converters. Analysis and design example of the proposed converter are presented. Experimental results of the proposed converter supplying two 25 V / 2.1 A LEDs are shown. The prototype presented high power factor, PF=0.97, total harmonic distortion of input current satisfying the IEC 61000-3-2 requirements, THD=21.1%, and high efficiency, η=91,2%.

Self-oscillating series-resonant led driver applied to reduce low-frequency current ripple transmission

Abstract: This paper presents the analysis and design of an LED driver based on the series-resonant converter (SRC) and on the self-oscillating command circuit (SOCC). The use of SRC provides a reduction of the low frequency (LF) ripple in the LEDs' current, originated by the voltage ripple in the output of the power factor correction (PFC) stage (bus voltage ripple). The attenuation of the ripple transmission from the bus voltage to the LEDs' current achieves some desired goals: (1) reduction of the bulk capacitance used at the output of the PFC stage, enabling the employment of long-life film capacitors, and (2) increasing of the efficiency of the LED driver because of the low switching losses of the series-resonant converter. The SOCC stamps on the LED driver the low-cost, simplicity, and robustness features. In order to avoid any mismatch between the SRC LF current ripple reduction design guidelines and the SOCC design, a design methodology is presented. Experimental results from a self-oscillating series resonant converter to supply a 10 Watts LED lamp are presented, validating the feasibility of the developed methodology and the proposed analysis.

High power factor dimmable self-oscillating electronic ballast with variable inductor control

Abstract: This paper presents a new high power factor dimmable self-oscillating electronic ballast (DSOEB), in which a variable inductor (VI) is used to control the fluorescent lamp (FL) power. Two different approaches are proposed to provide a wide dimming range using a self-oscillating electronic ballast, and a power factor correction (PFC) stage. In the first one, the VI is placed in the series resonant parallel-loaded filter (SRPLI), controlling the rms value of the lamp current with the dc bus voltage supplied by the PFC stage in a closed loop, and in the second one, the VI is placed in the PFC stage, controlling directly the power feeding the inverter. Experimental results for both topologies are presented to evaluate the preliminary performance of the circuit for a 32 W FL.

Comparative Analysis of Self-Oscillating Electronic Ballast Dimming Methods With Power Factor Correction for Fluorescent Lamps

Abstract: This paper presents a comparative analysis of the performance characteristics among different dimming methods for electronic ballasts using the self-oscillating half-bridge (HB) inverter with a power factor correction (PFC) stage. Initially, a review of common dimming methods presented in the literature is presented, and a general analysis of each dimming method is carried out. Furthermore, the operation of the dimmable self-oscillating electronic ballast with a PFC stage is analyzed in order to evaluate the performance of each different dimming methods used. Finally, a comparison among the different dimming methods implemented with the self-oscillating HB inverter and PFC stage is carried out.

Immunoparesis Recovery as Predictor Marker of Progression After Autologous Stem Cell Transplantation in Multiple Myeloma

Abstract: Context: Localized light chain amyloidosis (LAL) is a rare disease. Systematic data regarding its presentation, management and patient outcomes are limited to small case series. Objective: To systematically describe the Mayo clinic experience of patients with LAL. Design and Setting: We retrospectively reviewed clinical records of 403 patients with biopsy proven LAL seen at the Mayo Clinic between 1969-2014. Results: OF XXXX patients, 403 (XX%) had LAL. Median age at diagnosis was 60 years (range, 13-93) and 51% of them were male. Sites involved included: urothelial (bladder, ureter, renal pelvis) 75 (19%), larynx 51 (13%), lung parenchyma 42 (11%), skin 44 (11%), synovial tissue (9%), tracheobronchial 31 (8%), gastrointestinal tract 30 (8%), seminal vesicles 22 (6%), eyes 23 (6%), pharynx 22 (6%) and other 24 (6%). Typing was performed in 178 (45%) cases. A monoclonal protein was detected in 23 of 351 evaluated (7%) cases, 5 of which had different light restriction from that of LAL. Thirty one (8%) patients had a co-existent autoimmune disease. During a median follow-up of 39 months, no patients progressed to systemic AL. Of 403, 109 (27%) were observed or received supportive care only and 241 (60%) underwent local excision of the amyloid deposits. Sixtyfour (16%) patients required repeated interventions (median 1, range 1-4, upper decile requiring 4 interventions) for progressive disease. Ten year overall survival (OS) and progression free survival were 79% and 61%, respectively and there was no difference according to site of involvement, although patients diagnosed before 2003 fared worse (5 yr. OS 85% vs 95%, p¼0.001). Of the 70 patients that died during the follow-up period, cause of death was known for 29 and death was attributed to LAL in only 2 cases. Conclusions: In the largest series of patients with LAL reported so far we demonstrated that LAL has an excellent prognosis. Treatment is usually local excision for symptom control but 10% of cases carry significant morbidity and require repeated interventions for relapse/ progression. Keywords: Localized, immunoglobulin light chain, amyloidosis.

Digital control applied to single-stage high-power-factor EFL ballast with burst-mode dimming

Abstract: This paper presents the analysis, design and simulation of a digital control strategy for an electronic ballast to supply a 100 W high frequency Electrodeless Fluorescent Lamp (EFL). The electronic topology consists of a single-stage SEPIC power-factor converter associated with a half-bridge asymmetric LCC resonant inverter. In this configuration, the dimming capability based on a low-frequency burst-mode modulation is proposed. The presented digital control is composed of two main strategies: 1) voltage feedback loop for input grid disturbance and lamp parametric variations, 2) and a hysteretic power control loop to maintain a stable lamp power on each operating point. In this initial paper version, simulation results are included to demonstrate the digital control performance.