This application note describes the functioning of the STEVAL-ILL026V1 non-isolated 3 W offline LED driver power supply designed using the VIPER22A-E low power offline SMPS primary switcher from STMicroelectronics. The circuit regulates the load current to 350 mA and generates about 10 V. The load is composed of three high-brightness (HB) LEDs, connected in series. The project does not provide safety isolation between the input and output. This document provides the power supply specification, circuit diagrams, the complete bill of materials, and reports the results of circuit testing.