DESCRIPTION

· The UCC28521 and UCC28528 are combination PFC/PWM controllers designed for off-line power systems requiring compliance with IEC1000−3−2 harmonic reduction standards.
· These devices integrate control and drive signals for both PFC and PWM stages into a single unit, enhancing performance and reducing costs.
· Based on the UCC28511, they feature an average current mode control architecture with input voltage feedforward.
· The UCC28521/28 utilize a trailing-edge modulation scheme for PFC/PWM stages, with the UCC28528 specifically designed for low power auxiliary supplies without turning off the PWM stage at falling bulk voltage.

FEATURES

· Control of both PFC and PWM power stages in one device.
· Trailing-edge PFC and trailing-edge PWM modulation.
· Built-in sequencing for PFC and PWM turn-on.
· 2-A source and 3-A sink gate drive for both PFC and PWM stages.
· Typical 16-ns rise time and 7-ns fall time into 1-nF loads.
· PFC features include average-current-mode control, highly-linear multiplier, input voltage feedforward, improved load transient response, accurate power limiting, and zero power detect.
· PWM features include peak-current-mode control, 1:1 PFC:PWM frequency option, programmable maximum duty cycle limit up to 90%, and programmable soft-start.

APPLICATIONS

· High-efficiency server and desktop power supplies.
· High-efficiency telecom AC-DC converters.