Study of output power variation due to component tolerances in LC/sub s/C/sub p/ resonant inverters applied to HPS lamp control

The aim of this paper is to incorporate the analysis of component tolerance in the design criteria of resonant inverters applied to the control of high-pressure sodium (HPS) lamps. This method may also be considered for metal halide (MH) lamps. The design accepts a large load variation without exceeding the lamp power limits given by the standard. The analysis is focused on the selection of the most suitable value of the resonant network in order to achieve a good repeatability of the circuit performance. The study is based on the analysis of the lamp power sensitivity regarding the lamp aging and the tolerance of the circuit components. The proposed design is validated with experimental results and a statistical study by the Monte Carlo method.     

Power-mode-controlled power-factor corrector for electronic ballast

Medium- to high-power electronic ballasts are designed with two power conversion stages. The power-factor corrector (PFC) stabilizes the voltage supplied to the second stage and forces the utility current to meet the required standard. The inverter section stabilizes the arc in the lamp, and keeps the lamp power under the specified values. This paper proposes that the PFC section is to provide the power stability of the system while the inverter section operates in open loop. Consequences of this solution are: the power variation in the lamp caused by its aging is prevented, the complex dynamic of the lamp has no influence in the design, some extra voltage is available to achieve the lamp ignition, warmup time is reduced, and dimming control is easily implemented by modifying either the power reference or the bias value in the PFC control circuit. The inverter section is a half-bridge LC/sub p/C/sub s/ resonant inverter designed to require minimum variation of the input voltage to supply constant power to the lamp. In this way the operation point suffers little changes and no overdimensioning of the PFC and inverter components is necessary to meet the power source condition.     

Shotgun wounds in children. Not just accidents

OBJECTIVE: To characterize the demographic characteristics of shotgun wounds in children and adolescents across various regions within a state. DESIGN: Retrospective case study. SETTING: Accredited trauma centers in Pennsylvania. PATIENTS: All patients less than 18 years old who sustained shotgun wounds. DATA COLLECTION: Patient data were collected from the Pennsylvania Trauma Systems Foundation statewide trauma registry for January 1987 through December 1994. Data reviewed included age, race, sex, region, nature of injury, assailant, location of incident, length of stay in the hospital and intensive care unit, Injury Severity Score, organs injured, death, and discharge disposition. RESULTS: Over 8 years there were 95 shotgun wounds in patients with a mean +/- SD age of 14.0 +/- 3.7 years; the male-to-female ratio was 5.8:1. The incidence of shotgun wounds in urban areas increased threefold during the second half of the study; the incidence in nonurban regions was unchanged. Eighteen deaths (19%) occurred, 17 (94%) within 24 hours and 10 (56%) because of intracranial injury. Overall, unintentional shotgun wounds were most common (n = 46 [48%]), followed by assaults (n = 37 [39%]) and suicides (n = 8 [8%]). The highest per capita incidence of shotgun wounds occurred in urban areas, typically the result of an assault (n = 30 [73%]). In nonurban areas, shotgun wounds were usually unintentional (n = 36 [67%]); 34 (63%) occurred in the home. In contrast, in urban areas, 26 shotgun wounds (63%) occurred on the street. Overall, 14 fatal shotgun wounds (78%) occurred in the home. Operative intervention was required for 57 patients (60%). Ultimately, 67 patients (71%) were discharged to home. CONCLUSIONS: In urban areas, shotgun wounds are increasing in incidence, often occur on the street, and often result from assault. In nonurban areas, shotgun wounds are usually unintentional, often occur in the home, and are more often lethal than shotgun wounds in urban areas. Multiple-organ injury, surgery, and lengthy hospital stays are common.     

Helmet laws and motorcycle rider death rates

We investigated motorcycle rider death rates between states with full motorcycle helmet laws and those without. This was done using both unadjusted bivariate analyses and multivariate random-effects generalized least squares regression models of rider death rates. Multivariate models were adjusted for the competing influences of several explanatory variables, including the existence of a motorcycle helmet law. From 1994 to 1996, states with helmet laws experienced a median death rate of 6.20 riders per 10000 registered motorcycles and states without helmet laws experienced a median death rate of 5.07 riders per 10000 registered motorcycles (P = 0.008). After controlling for other factors that affect motorcycle rider fatalities (most notably population density and temperature), death rates in states with full helmet laws were shown to be lower on average than deaths rates in states without full helmet laws (P = 0.740). Our study weakens the claim that rider death rates are significantly lower in states without full motorcycle helmet laws.     

Electronic ballast for 150 W HPS lamps with compensated outputpower

A simple design method for a class-D series-parallel (LCC) resonant inverter suitable for electronic ballast applications is proposed. Variations in the power delivered to the lamp, caused by the lamp aging, are limited to fulfil the standards. This design results in cost-effective circuits, as its functionality is aimed at simplifying the power stage     

Design of LC/sub p/C/sub s/ resonant inverters as a power source for HID lamp ballast applications

This paper presents a new criterion for the design of resonant inverters for driving high-intensity-discharge (HID) lamps. The proposed converter behaves almost as a power source, for a wide load range, regardless of the lamp aging. In order to achieve good repeatability, the analysis of lamp power sensitivity regarding the tolerance of the circuit components is carried out. The design is validated with experimental results and a statistical simulation by the Monte Carlo method.     

Analysis, design and experimental results of a high-frequency power supply for spark erosion

The LC/sub s/C/sub p/ resonant converter finds a new application in an electrical discharge machining (EDM) power supply, which is designed for the purpose of developing small size EDM systems. The switching frequency is tuned to the natural resonant frequency where the converter tends to act as a current source. In this way, three effects are achieved: 1) the necessary over-voltage is generated, first to ionize the dielectric and then to establish the electric discharge, 2) a constant current is supplied during the machining of the workpiece, providing the circuit with inherent protection under short circuit conditions, and 3) overall stability is guaranteed despite the equivalent negative resistance of the dielectric breakdown. The proposed control achieves an optimum and stable operation using tap water as dielectric fluid preventing the generation of undesired impulses and keeping the distance between the electrode and the workpiece within the optimum stable range. The EDM power supply has been validated to perform operations in a nuclear power plant application.     

Contributions to the design and control of LCsCp resonant inverters to drive high-power HPS lamps

This paper presents the design criteria for full-bridge series-parallel (LC_sC_p) resonant inverters suitable for driving high-power high-intensity discharge lamps. By using the properties derived from the transfer functions of the inverter, a soft startup method is proposed. The lamp ignition is carried out maintaining the voltage and current variables below prefixed peak values, with the addition of no extra components to the power stage for this purpose. In steady-state operation, the proposed control minimizes the reactive voltamperes in the resonant tank. Moreover, the variation of the power delivered to the lamp, caused by the lamp aging, is limited in order to fulfil the standard. This design provides cost-effective circuits, simplifying the DC-AC power stage of an electronic ballast. The experimental results are given for high-pressure sodium lamps of the Sylvania SHP250W type