Buck LED Driver with PWM Input

Abstract

This Project aims to design and construct a simple buck LED driver with PWM input control, and using a switching mode regulator with a chaotic signal to give a PWM control for the LED driver. By contrast, using a chaotic signal to produce a PWM will have a wider frequency spectrum than the microcontroller produces. Human's eyes will more comfortable to see a wider frequency spectrum than fixed frequency PWM lighting. The LED driver is made by using a simple switch-mode buck converter. It is a constant current LED driver built without MCU control. There is a current regulating function that can control the brightness of the LED, and input controls the output with PWM. This makes the LED driver can building block for other MCU with no change any design. The LED driver is designed with using RCD circuit to reduce the switching low in order to drop the heat of MOSFET. AC to DC converter, switching mode regulator comparator circuit and Chua's circuit, which is other student's FYP 20 years ago, is given by Prof. WONG, Hei. But the circuits are not working now, so I have to study and try to rebuild it. Unfortunately, I just finished the AC to DC converter and working with the Chua's circuit. 220AC to 12-0-12DC converter, which is provided by two regulators, 7812 and 7912, is made for supply power to the LED driver, switching mode regulator, comparator circuit and Chua's circuit. I tried to construct the chaotic signal of higher frequency which is obtained by changing the values of inductor and capacitor of Chua's circuit. However, the result is still not good. The waveforms were being observed by CRO.