F.J. Diaz

Microcontroller Power Mode Stabilized Power Factor Correction Stage for High Intensity Discharge Lamp Electronic Ballast

This paper presents new design considerations and a control strategy for a two-stage ballast system; power factor correction (PFC) and resonant inverter (RI), for high intensity discharge lamps. The ballast includes a microcontroller whose proposed algorithm implements a power loop and a voltage loop, both to control the PFC, and generates the transistor drive signals of the RI. The power loop adjusts the lamp power in steady state and the voltage loop controls the PFC during the ignition and warm-up time. System stability is studied to verify that the PFC stage provides the ballast with the required stability in long and medium term, while the short term stability is assured by the high output impedance of the LCC inverter, operating in open loop at constant switching frequency. The resulting performance of the ballast shows improvements in ignition repeatability, warm-up time reduction, robustness of the resonant inverter operation, and simple and accurate power control, including dimming operation

Digital Control of a Low-Frequency Square-Wave Electronic Ballast With Resonant Ignition

This paper proposes a two-stage low-frequency square-wave (LFSW) electronic ballast with digital control. The first stage of the ballast is a power factor correction (PFC) stage, and the second is a full-bridge (FB) converter used for both lamp ignition and LFSW drive. As a novelty for LFSW ballasts, ignition is achieved without an additional igniter circuit by operating the FB during start-up as a high-frequency resonant inverter. After ignition, the converter operates as an LFSW inverter to avoid exciting acoustic resonances by controlling the FB as a buck converter and regulating alternately positive or negative current to the lamp. Lamp power is regulated by adjusting the average current supplied by the PFC stage. Another contribution of this paper is to utilize digital control as a simple solution to achieve multimode control, including resonant lamp ignition, LFSW transitions, and lamp current and power regulation.

Effects of voltage sags on different types of ballasts for 150-W HPS lamps

Nowadays, energy efficiency is a hot topic in a very demanding environment. In this way, improvements in lighting applications, which is a significant point of energy consumption, could be very much welcomed. Electronic ballast may serve to this goal since they are focused on achieving energy savings, reduction in the utility line harmonic content and reactive power, as well as on implementing dimming control and some other parameter of interest in lighting applications. On the other hand, power quality problems are very common in our power system and any new electric device should be designed taking into account these events. One of the typical problems in electrical distribution systems are voltage sags. These have a great incidence on the electrical equipment connected to the network in the same area. The sags cause more damages than the rest of disturbances because these have a greater frequency of occurrence. In this work, the effects of voltage sags on several 150-W high- pressure sodium lamps combined with two different types of electronic ballast have been studied. One of the ballasts supplies the required voltage to minimize the reactive component in the resonant inverter, while the other regulates the power supplied by the utility line to be constant in long term, the resonant inverter being also in open loop at constant switching frequency providing the short term stability. The results of these electronic ballasts will be compared with those obtained with the traditional electromagnetic ballast. The influence of the lamp age will be also considered in the approach. The final goal of this study is to improve the performance of the ballast prototypes under voltage sags.

Low-frequency square-wave electronic ballast with resonant ignition using digital mode and power control

The paper proposes the use of a single full-bridge (FB) inverter and LC filter in HID electronic ballast, realizing both the functions of a resonant circuit for lamp ignition and a current controlled low frequency square wave inverter for normal operation. Ignition is achieved by resonance when the converter is controlled as a FB inverter at the resonant frequency of the LC filter. After ignition the converter operates as a LF square wave inverter by controlling the FB to act alternately as a Buck converter supplying positive or negative current. While ignition occurs at the LC filter resonance, the Buck converter switching frequency is selected significantly higher to attenuate high frequency harmonics and avoid exciting acoustic resonances. System stability is achieved by controlling the input current to the FB (output current of the PFC front-end), resulting in a power mode control provided that the voltage supplied by the PFC stage is constant. A digital control circuit selects the different operation modes of the FB converter according to the lamp requirements.

TIG Welding Machines

A new dc and pulsed dc TIG welding power supply has been designed. Power modules connected in parallel with interleaving operation achieve scalable output current with no reduction of the single module performance and limiting the output current ripple. The resonant converter is supplied by an active rectifier from the AC mains with a reduction of mains current peak by five times.

A genome-wide association study suggests the HLA Class II region as the major susceptibility locus for IgA vasculitis

The genetic component of Immunoglobulin-A (IgA) vasculitis is still far to be elucidated. To increase the current knowledge on the genetic component of this vasculitis we performed the first genome-wide association study (GWAS) on this condition. 308 IgA vasculitis patients and 1,018 healthy controls from Spain were genotyped by Illumina HumanCore BeadChips. Imputation of GWAS data was performed using the 1000 Genomes Project Phase III dataset as reference panel. After quality control filters and GWAS imputation, 285 patients and 1,006 controls remained in the datasets and were included in further analysis. Additionally, the human leukocyte antigen (HLA) region was comprehensively studied by imputing classical alleles and polymorphic amino acid positions. A linkage disequilibrium block of polymorphisms located in the HLA class II region surpassed the genome-wide level of significance (OR = 0.56, 95% CI = 0.46–0.68). Although no polymorphic amino acid positions were associated at the genome-wide level of significance, P-values of potential relevance were observed for the positions 13 and 11 of HLA-DRB1 (P = 6.67E-05, P = 1.88E-05, respectively). Outside the HLA, potential associations were detected, but none of them were close to the statistical significance. In conclusion, our study suggests that IgA vasculitis is an archetypal HLA class II disease.

Effects of Flicker on Different Types of 150-W High-Pressure Sodium Lamps and Ballasts

The limits of the severity of flicker caused by voltage fluctuations is defined in Europe by the standard CENELEC EN 50160. Under normal operating conditions, flicker level will not exceed the long term severity Plt=1 during 95% of the time in one week. This threshold was originally established considering that a lamp with tungsten coiled coil filament of 60 W and 230 V that is gas-filled produces a flicker perceivable by 50% of the population when it is supplied with a voltage that verifies Plt=1. Other light sources like fluorescent lamps and discharge lamps with ballasts exhibit a different behavior under the same supply conditions. This means that the flicker meter should be different for each type of illumination technique ir order to provide accurate information about flicker phenomena. At the same time, lamp age also plays an important role in flicker generation. In this research work, a test system and a methodology able to measure the optical fluctuation produced by different types of lamps and ballast is presented. This experimental platform allows to obtain a correlation between voltage flicker levels and optical flicker perception. It can be considered the first step in the definition of new lamp models. This work also shows that age lamp has a significant correlation with flicker generation.

Control of low-frequency square-wave electronic ballast with resonant ignition using a dsPIC30F2010

The paper proposes the use of a dsPIC30F2010 for implementing the ignition sequence, a double loop control and selecting the operation modes of a low frequency square wave (LFSW) electronic ballast for two-stage HID lamps. The first stage is the power factor correction (PFC) stage, and the second is a single full-bridge (FB) inverter with LC filter. The latter stage performs function of a resonant circuit for lamp ignition and a current controlled low frequency square wave inverter for normal operation. Ignition is achieved at the resonant frequency of the LC filter when the FB converter is working as a resonant inverter. After ignition the converter operates as a LFSW inverter by controlling the FB to act alternately as a Buck converter supplying positive or negative current. While ignition occurs at the LC filter resonance (f0=25kHz), the Buck converter switching frequency (fsw=200kHz) is selected significantly higher to attenuate high frequency harmonics and avoid exciting acoustic resonance. Lamp stability is achieved by controlling the inductor current of the LC filter, and power mode control is achieved adjusting average current supplied by the PFC stage. The microcontroller selects the different operation modes of the FB converter according to the lamp requirements.

Risk Model for Colorectal Cancer in Spanish Population Using Environmental and Genetic Factors: Results from the MCC-Spain study

Colorectal cancer (CRC) screening of the average risk population is only indicated according to age. We aim to elaborate a model to stratify the risk of CRC by incorporating environmental data and single nucleotide polymorphisms (SNP). The MCC-Spain case-control study included 1336 CRC cases and 2744 controls. Subjects were interviewed on lifestyle factors, family and medical history. Twenty-one CRC susceptibility SNPs were genotyped. The environmental risk model, which included alcohol consumption, obesity, physical activity, red meat and vegetable consumption, and nonsteroidal anti-inflammatory drug use, contributed to CRC with an average per factor OR of 1.36 (95% CI 1.27 to 1.45). Family history of CRC contributed an OR of 2.25 (95% CI 1.87 to 2.72), and each additional SNP contributed an OR of 1.07 (95% CI 1.04 to 1.10). The risk of subjects with more than 25 risk alleles (5th quintile) was 82% higher (OR 1.82, 95% CI 1.11 to 2.98) than subjects with less than 19 alleles (1st quintile). This risk model, with an AUROC curve of 0.63 (95% CI 0.60 to 0.66), could be useful to stratify individuals. Environmental factors had more weight than the genetic score, which should be considered to encourage patients to achieve a healthier lifestyle.

Phase-controlled parallel-series (LC p C s ) resonant converter to drive high-brightness power LEDs

This paper presents the analysis and design of a resonant converter suitable to drive high-brightness power LED lamps for outdoor lighting applications. The inverter stage arises from the parallel connection of two class D LCpCs resonant inverters. The output stage is based on a central tap rectifier without electrolytic capacitor. The output current can be precisely adjusted, at constant switching frequency, trough the phase displacement, Ψ, of the control signals of each class D section. The dimming control follows a PWM pattern whose on-state is set by the nominal phase displacement Ψ and the off-state by setting Ψ at 180° where the output current is cancelled out. Therefore, the average lamp current is modified without necessity of extra switches. The fast dynamics of the resonant stage ensures an operation free of instabilities and flicker effect. A 120W prototype has been built to validate the design proposal.