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 Instruments 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, low-offset (±2 mV) current amplifier to reduce distortion at light load
The UCC3817A/18A family of PFC Controllers is directly pin for pin compatible with the
UCC3817/18 family of devices. Only the output stage of UCC3817A family has been modified to allow
use of a smaller external gate drive resistor values. For some power supply designs where an
adequately high enough gate drive resistor can not be used, the UCC3817A/18A family offers a more
robust output stage at the cost of increasing the internal gate resistances. The gate drive of the
UC3817A/18A family however remains strong at ±1.2 A of peak current capability.
UCC3817A offers an on-chip shunt regulator with low start-up current, suitable for
applications utilizing a bootstrap supply. UCC3818A is intended for applications with a fixed
supply (VCC). Both devices are available in the 16-pin D, N and PW packages.
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