This offline flyback reference design uses the UCC28740 controller to generate 3 isolated outputs (5 V at 30 mA: 15 V at 20 mA: 15 V at 20 mA) from an AC input (180 VAC - 264 VAC). The design can provide 750-mW output power. The UCC28740 uses an optical coupler to regulate the 5-V output and to improve transient response. The valley-switching technique reduces switching losses and keeps the efficiency high.