The XYS3580 buck-boost converter is explained. Major components and the datasheet are reviewed. Setting voltage, current, maximum power, maximum time, and capacity are shown. Short-circuit protection, constant current, charging a lithium battery, and undervoltage protection were tested. The input and output voltages are shown. The XYS3580 is tested as a step-down and step-up converter with 1A to 5A. A thermal image is shown, and the output ripple voltage is measured and shown.