Flyback converter design with EMC improvement for railway applications

Nowadays, switched mode DC-DC power supplies are widely used in industry. The flyback converter is at the forefront of the railway application due to its wide input voltage range at low powers, input and output isolation, reliability, and simplicity of design. This paper aims to design a flyback converter with an EMC filter and dimmable feature for use in led lighting designs in railway systems with high efficiency and low cost according to the equivalents in the literature and industry using hard switching technique and passive RC snubber. The power losses of the flyback converter circuit were calculated theoretically, and all the theoretical relations were simulated in the LTspice program. Additionally, the EMC filter circuit was designed and implemented according to the desired flyback converter specifications. The prototype of the designed flyback converter was implemented with an input voltage range of 77-137.5 Vdc, a rated output voltage of 24 Vdc, an output voltage of 20 Vdc in dimming mode, and the output current of 1.5 A. Then, electrical, thermal performances as well as EMC tests were performed experimentally. The converter reaches approximately 90% efficiency at rated power. The designed flyback converter complies with EN 50155 and EN 50121 railway standards.