HF920B Flyback Regulator with EMI Optimization Monolithic Power Systems (MPS) HF920B Flyback Regulator comes with a monolithic, 900V MOSFET. The HF920B is an enhanced version of the HF920 with EMI optimization. It provides excellent power regulation with very few external components for AC/DC applications that require high reliability, such as smart meters, large appliances, industrial controls, and products powered by AC grids.