The UCC3817A and the UCC3818A family provides all the functions necessary for active power factor corrected preregulators. The controller achieves near unity power factor by shaping the ac input line current waveform to correspond to that of the ac input line voltage. Average current mode control maintains stable, low distortion sinusoidal line current. Designed in Texas Instrument's BiCMOS process, the UCC3817A/UCC3818A offers new features such as lower start-up current, lower power dissipation, overvoltage protection, a shunt UVLO detect circuitry, a leading-edge modulation technique to reduce ripple current in the bulk capacitor and an improved, lowoffset (±2 mV) current amplifier to reduce distortion at light load conditions