The UCG28826 is a high frequency, quasi-resonant (QR) AC/DC flyback converter with integrated 650V primary-side GaN FET suitable for use in power supplies up to 65W without PFC and 120W with a PFC front-end. This device gives the benefit of GaN integration to achieve high power density designs with high switching frequency, up to 500kHz. The UCG28826 features industry's first auxless flyback architecture with self-bias to give a compact and low cost power supply design without the need for an auxiliary winding in the transformer. The self bias feature reduces losses to improve efficiency in wide output voltage applications like USB-PD chargers by eliminating the need for a low dropout regulator (LDO) and its associated losses to generate the device bias. The UCG28826 supports continuous conduction mode (CCM) operation for upto 4ms for transient output power of up to 130W (two times the 65W nominal output power) at low-line input without the need for a transformer designed for such transient load conditions, saving space and cost. This device also includes frequency foldback and burst modes for higher efficiency operation during light load and no-load conditions, respectively. The X-cap discharge circuit discharges the X-capacitor in the input EMI filter to 0V within less than 1s to prevent the user from an electric shock at the time of unplugging the power supply from the wall socket. The UCG28826 overcomes the system design limitations of integrated converters by offering resistor programmable options for maximum flexibility to the user to optimize performance at the desired operating point. The device also includes many in-built protections such as output over-voltage, over-current, overload, short-circuit and over-temperature conditions with auto-restart and latch response for a robust power supply design preventing any damage during such fault conditions.