This paper presents a Landsman converter fed power factor correction (PFC) based light emitting diode (LED) driver. The application is targeted for high brightness (HB) projection application with brightness control of high brightness red-green-blue (HB-RGB) LED. A pulse width modulation (PWM) technique is used for current control to achieve effective brightness required without compromising the efficiency (overall 85%). This PFC converter is used to feed a dual output flyback DC-DC converter which supplies power to the forced cooling unit and the LED module with galvanic isolation. The brightness control of LED is performed by synchronous buck converter via current modulation. The PFC converter is designed to operate in discontinuous input inductor current mode for inherent PFC at universal AC mains. A prototype of the proposed PFC LED driver is developed and experimentally verified. The power quality parameters of the proposed LED driver are evaluated at rated and light load conditions for universal AC mains (90-265V)with brightness control. The power quality parameters are found within acceptable range of international harmonic standard IEC 61000-3-2 for universal AC mains.

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Introduction:Primary hyperparathyroidism (PHPT) is largely a symptomatic disease with varied systemic manifestations, complicated by coexisting Vitamin D (Vit D) deficiency. Increasing awareness, developments in diagnostics, and Vit D supplementation may have an impact on the disease profile of PHPT.Methods:Clinical, biochemical, and pathological profile of PHPT presenting to a tertiary care center in South India were compared in two groups separated as per the period of presentation (Group A: January 1994–May 2007 - 51 cases and Group B: June 2007–January 2015 - 59 cases).Results:PHPT has remained a disease of female preponderance with similar age of presentation. It is being diagnosed earlier (mean duration of symptoms prior to diagnosis was 38.7 months in Group A, significantly longer than 26 months in Group B). Bone pain and metabolic myopathy were the most common presentations (60%) followed by pathological fracture (16%), renal calculi (13%), and pancreatitis (7%). Pathological fractures have become less frequent. Vit D deficiency is still a widespread co-morbidity. Radionuclide scintigraphy is an effective localizing tool, but ultrasound can be an inexpensive and widely available screening modality.Conclusion:PHPT still remains asymptomatic disease of bones and stones, although it is being diagnosed early. Greater awareness, Vit D supplementation, and better diagnostic tools have made it a disease with lesser morbidity and effective cure.

A single stage single switch AC/DC converter is an integration of input current shaper and a DC/DC cell with a shared controller and one active switch. The converter is applicable for digital input power supply with high input power factor and tight output voltage regulation. The focus of the topology is to reduce the DC bus voltage at light load without compromising with input power factor and voltage regulation. The concept behind this topology is direct power transfer scheme. Using special configuration of DC/DC cell does reduction of DC bus voltage and DC/DC cell works on the principle of series charging and parallel discharging. The power output of this converter can go up to 200 W.

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Summary This article presents a critical conduction mode (CRM)–based power factor correction (PFC) converter for multistring light‐emitting diode (LED) driver. The application is targeted for high power projection application with brightness control of red‐green‐blue LED module. A pulse width modulation (PWM) technique is used for lighting control to achieve required brightness without compromising the efficiency (overall 82%) and power quality. The CRM boost PFC converter is used to feed a dual output flyback DC‐DC converter, which supplies power to the forced cooling unit and the LED modules with galvanic isolation. The brightness control of LED is performed by synchronous buck converter using current PWM modulation. The CRM boost converter–based PFC converter is designed to operate in critical inductor current mode at universal AC mains. A prototype of proposed PFC converter–based LED driver is developed and experimentally verified. The power quality parameters of the proposed LED driver are evaluated at rated and light load conditions for universal AC mains (90–265 V) with brightness control. The power quality parameters are found within acceptable ranges of international harmonic standard IEC 61000‐3‐2 Class C for lighting systems.

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