The Texas Instruments UCC28703DBVT is an offline flyback controller designed for isolated AC-DC power supplies. It operates from a Vcc range of 9 V to 35 V with a startup threshold of 21 V, and switches between 1 kHz and 130 kHz. The controller drives an external MOSFET — there is no internal power switch. Typical applications include chargers, adapters, and auxiliary housekeeping supplies where isolation is required.
The 21 V startup voltage sets the bias winding and bulk capacitor design. The 1 kHz to 130 kHz switching range supports valley-switching or quasi-resonant operation, which helps manage EMI and light-load efficiency. Because the controller has no internal switch, the designer must select an external MOSFET and budget for its gate drive — this is the dominant BOM cost alongside the transformer. Fault protection includes current limiting and overvoltage shutdown, which simplifies the secondary-side feedback loop and reduces external component count.