thesis

Designing and Implementing a Micro-controller based Primary-side Sensing Flyback Converter for LEDs Driver

Abstract

The fast development of LED and its applications has enabled a new generation of lighting device with higher efficiency and long lifespan. By employing a primary-side sensing flyback converter and the PIC18F micro-controller series, an LED driver could achieve two important features: (1) the compatibility with the available lighting fixtures, and (2) reducing unit price. The flyback converter was chosen for its simplicity, competitive low cost, and its ability to provide a constant output current, a necessarily important factor to an LED driver. Meanwhile, the PIC18F micro-controller series offer numerous advanced features which include but not limited to pulse-width modulation (PWM), 10-bit 13-channel Analog-to-Digital Converter (ADC) etc., which suitably meet the requirements for regulating a primary-side sensing flyback converter. The design process was first conducted in simulation stage with aid from Matlab®-Simulink and Cadence OrCAD Capture CIS (PSpice). By using PI based control scheme and making full use of built-in Analog Behavioral Modelling (ABM) blocks, the simulation-relevant difficulties due to lacking of appropriate model for the PIC18F series micro-controller were completely solved. The simulation results matched well with the intended design specifications: the output voltage is 32 VDC while the load current is 350 mA. More importantly, the simulation results demonstrated the feasibility of deploying a primary-side sensing flyback converter in conjunction with a PIC18F micro-controller as an LED driver. Next, a demo printed-circuit board (PCB) was layout by using OrCAD PCB Editor. Finally, the PIC18F4550 micro-controller was programmed to undertake control tasks of the LED driver. The experimental results reflect the project\u27s success with all the parts of the driver harmoniously work as expected

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