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 controllers integrate control and drive signals for both PFC and PWM stages into a single device, offering significant performance and cost advantages.
· The UCC28521/28 series features an average current mode control architecture with input voltage feedforward, differing primarily in their trailing-edge modulation schemes.
· The UCC28528 is specifically designed for low power auxiliary supplies, with its PWM stage not turning off with the falling bulk voltage.

FEATURES

· Provides control of both PFC and PWM power stages in one device.
· Features trailing-edge PFC and trailing-edge PWM modulation.
· Built-in sequencing for PFC and PWM turn-on.
· Offers 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.