1 Features

1• Controls Boost Preregulator to Near-Unity Power

Factor

• Limits Line Distortion

• World Wide Line Operation

• Overvoltage Protection

• Accurate Power Limiting

• Average Current Mode Control

• Improved Noise Immunity

• Improved Feed-Forward Line Regulation

• Leading Edge Modulation

• 150-μA Typical Start-Up Current

• Low-Power BiCMOS Operation

• 12-V to 17-V Operation

• Frequency Range of 6 kHz to 220 kHz

2 Applications

• PC Power

• Consumer Electronics

• Lighting

• Industrial Power Supplies

• IEC6100-3-2 Compliant Supplies Less Than

300 W

3 Description

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.