Peter Pišljar (2012) High efficency LED lamp driving circuit. EngD thesis.
The purpose of this thesis was to build a high efficency driver for LED lamp. Lamp uses two high brightness LED diodes Cree XML. This LEDs achieve light output of 100 lumens per watt, with maximum power rating of 10W. With two such LEDs lamp achieves light output of 2000 lumens at 20W. In the first chapter LEDs and their driving circuits are described. Chapter continues with basic equations for buck converter and a description of using the buck converter as a part of circuit for controlling LEDs. The thesis covers hardware and software aspect of the lamp. The second chapter provides descriptions of designing and building the hardware part. Hardware is designed arround ATTiny861 microcontroler. Microcontroler manages all lamp functions including LED control. LED controller is based on a buck converter which converters higher input voltage to lower. In the third chapter simulation of hardware is described. Simulations were made with SPICE simulator. SPICE is general purpose open source program for analysis and simulation of analog electronic circuits. The fourth chapter provides descriptions of software which runs on the microcontroler. Software is constantly checking current over LEDs and properly corrects the duty cycle. Besides controling LEDs software it also monitors battery level and circuit temperature. A single button is ussed to switch betwen diferent modes of operation. At the end tests were made to assure correct working of the designed circuit.
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