Due to the low-voltage loop bandwidth required to maintain proper PFC and ignore the slight ripple at twice line frequency on the output, the response of ordinary controllers to input voltage and load transients are also slow. However, the Q_VFF function effectively handles the line transient response with the exception of any minor adjustments needed within a Q_VFF level. Load transients on the other hand can only be handled by the voltage loop; therefore, the UCC28070A has been designed to improve its transient response by pulling up on the output of the voltage amplifier (V_VAO) with an additional 100μA of current in the event the voltage on VSENSE drops below 93% of regulation (2.79V). During a soft-start cycle, when V_VSENSE is ramping up from the 0.75V PFC Enable threshold, the 100μA correction current source is disabled to ensure the gradual and controlled ramping of output voltage and current during a soft start.