This reference design is a compact and thermally efficient design intended to be used as a bias supply for half-bridge converters. A DCM Flyback with UCC3813-4 controller is used to generate two isolated 12V supplies for half-bridge converter primary driving circuitry. One 5V is generated at the secondary side for secondary rectifier driving circuitry and controller. The second winding at secondary side can be used to sense input voltage level while the Flyback converter is operating.