Hella Saturnus Slovenia is a company that develops and manufactures lighting equipment for the automotive industry, and therefore deals with different voltage converters, as various electronic assemblies (e.g. headlights) require a different voltage to that provided by the car battery. For my diploma, I decided to build one of these converters, a SEPIC (single-ended primary-inductor converter) converter, which can also be used for in-house testing in the future. SEPIC is a type of switching DC/DC converter that transforms the input voltage to a higher or lower level, depending on the application. It works on the principle of energy exchange between the inductors and capacitors in the circuit.
I have designed the converter with the LM51571-Q1 controller from Texas Instruments. The converter I have designed allows the conversion of a varying input voltage to a constant selected output voltage. I used calculations to determine the appropriate components for the operation of the converter. The schematic and the layout of the circuit were drawn in KiCad. During testing of the PCB, the performance was as expected. The output voltage was constant, without fluctuations. The electromagnetic compatibility (EMC) of the circuit was in accordance with the IEC standard CISPR 25:2021 class 4, which means that the circuit does not yet meet the required class 5 of the automotive standard.
Despite the performance of the circuit, improvements could be made, particularly in the area of EMC. The circuit complies with the IEC CISPR 25:2021 class 4 standard, but for use in vehicles it is necessary to achieve a class 5, which has certain stricter maximum EMI values. Electromagnetic interference could possibly be limited by the use of a shield can or a ferrite bead.
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