UCC28740/Q1 Flyback Controllers Texas Instruments UCC28740/Q1 Constant-Current Flyback Controllers are an isolated-flyback power-supply controller that provides Constant-Voltage (CV) using an optical coupler to improve transient response to large-load steps. Constant-Current (CC) regulation is accomplished through Primary-Side Regulation (PSR) techniques. These devices process information from opto-coupled feedback and an auxiliary flyback winding for precise high-performance control of output voltage and current.