Lucent

The PWM section features peak current mode control (with a ramp signal available to add slope compensation), programmable soft-start, accurate maximum duty cycle clamp, peak current limit and high-current output gate driver. The oscillator for the combination controller is available in two versions. In UCC28510, UCC28511, UCC28512, and UCC28513, the PWM and the PFC circuits are switched at the same frequency. In the UCC28514, UCC28515, UCC28516, and UCC28517, the PWM stage frequency is twice that of the PFC frequency. The PWM stage is suppressed until the PFC output has reached 90% of its programmed value during startup. During line dropout and turn off, the device allows the PWM stage to operate until the PFC output has dropped to 47% (UCC28512, UCC28513, UCC28516, and UCC28517) or 71% (UCC28510, UCC28511, UCC28514, and UCC28515) of its nominal value. See available options table on page 1 for a summary of options.