The LM5181 primary-side regulated (PSR) flyback converter is a high-density, cost-effective solution for industrial systems requiring less than 4 W of isolated DC/DC power. This compact, easy-to-use flyback converter with low I_Q can be applied over a wide input voltage range from 4.5 V to 65 V, with operation down to 3.5 V after start-up. Innovative frequency and current amplitude modulation enables high conversion efficiency across the entire load and line range. Primary-side regulation of the isolated output voltage using sampled values of the primary winding voltage eliminates the need for an opto-coupler or an auxiliary transformer winding for feedback. Regulation performance that rivals that of traditional opto-coupler solutions is achieved without the associated cost, solution size, and reliability concerns. The LM5181 converter services a wide range of applications including IGBT-based motor drives, factory automation, and medical equipment.