Better Efficiency with Linear-Regulator compared to Flyback-Converters in LED Lamps at AC Grids

Conference: PCIM Asia 2015 - International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management
06/24/2015 - 06/26/2015 at Shanghai, China

Proceedings: PCIM Asia 2015

Pages: 5Language: englishTyp: PDF

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Jaschke, R.; Hoffmann, K. F. (Helmut Schmidt University / University of the Federal Armed Forces Hamburg, Faculty of Electrical Engineering, Power Electronics, Holstenhofweg 85, 22043 Hamburg, Germany)

LED lamps replace conventional lighting sources because of longer operating life, no mercury problems and genial luminous efficacy. Conventional LED power supplies at AC grid have a constant LED current regulation with a switched Flyback converter powered of a DC link capacitor, B2-bridge and line filter. Here we take a simple topology with a linear regulator transistor [1] with DC capacitor, B2-bridge without filter. Our LED lamp consists of filament LEDs (100 series LEDs) with a high LED voltage who is a little bit under the minimal capacitor voltage. We show the circuit dimensioning for ?10% grid voltage variation and LED-voltage changing with measured negative voltage temperature coefficients. With measurements and simulations we get efficiencies of 85% to 96%. With a 4 Watt filament LED lamp at the 230V/50Hz grid we have the best efficiency 91% (20deg C) and 96% (-20deg C) with a 108 LED filament lamp and a bigger DC-capacitor. The luminous efficacy goes from 120 Lumen/Watt to 130 Lumen/Watt, that is certificated in the European Area with the Index A++.