Current-mode flyback controller with secondary-side regulation (SSR) for offline applications

UCC28750 is a

highly-integrated current-mode, continuous-conduction-capable, PWM controller optimized for

high performance, low standby power, and cost effective offline flyback converter

applications using an opto-coupler. During light-load conditions the device enters frequency

foldback and burst modes, improving light-load efficiency. The burst-mode algorithm used in

UCC28750 controls the minimum effective switching frequency to prevent audible noise during

light-load conditions. Frequency dithering improves EMI performance, and is active in

normal, frequency foldback, and power boost operations.

UCC28750

provides protection features that enable a robust converter design with minimal external

components. Output over-power protection (OPP) and cycle-by-cycle over-current limit protect

the load and power-stage components from electrical stress. Over-voltage and under-voltage

lockout (OVLO and UVLO) prevent switching in unwanted input conditions. The FLT pin provides

line brown-out sensing and protection, or external over-temperature and over-voltage

protection, depending on the device variant. The FLT pin is also used to disable the device

through external control by pulling the pin to ground, regardless of the device variant.