UC1853

UC2853

UC3853

The UC3853 provides simple, yet high performance active power factor

correction. Using the same control technique as the UC1854, this 8-pin de-

vice exploits a simplified architecture and an internal oscillator to minimize

external component count. The UC3853 incorporates a precision multi-

plier/squarer/divider circuit, voltage and current loop error amplifiers, and a

precision voltage reference to implement average current mode control

with RMS line voltage compensation. This control technique maintains con-

stant loop gain with changes in input voltage, which minimizes input line

current distortion over the worldwide input voltage range.

The internal 75kHz oscillator includes an external clock input, allowing syn-

chronization to downstream converters. Additionally, the device features an

overvoltage protection comparator, a clamped MOSFET gate driver which

self-biases low during undervoltage lockout, and low startup and supply

current.

These devices are available in 8-pin plastic and ceramic dual in-line (DIP)

packages, and 8-lead small outline (SOIC) packages. The UC1853 is

specified for operation from –55°C to +125°C, the UC2853 is specified for

operation from –25°C to +85°C, and the UC3853 is specified for operation

from 0°C to +70°C.

High Power Factor Preregulator

•

Complete 8-pin Power Factor

Solution

•

Reduced External Components

•

RMS Line Voltage Compensation

•

Precision Multiplier/Squarer/Divider

•

Internal 75kHz Synchronizable

Oscillator

•

Average Current Mode PWM

Control

•

Overvoltage Protection Comparator

•

High Current, Clamped Gate Driver

BLOCK DIAGRAM

11/97

FEATURES

DESCRIPTION

UDG-94120-1