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BLOCK DIAGRAM

•

1

µA ICC when Disabled

•

PWM Control for LCD Supply

•

Zero Voltage Switched (ZVS) on

Push-Pull Drivers

•

Open Lamp Detect Circuitry

•

4.5V to 20V Operation

•

Non-saturating Transformer

Topology

•

Smooth 100% Duty Cycle on

Buck PWM and 0% to 95% on

Flyback PWM

The UC1871 Family of IC’s is optimized for highly efficient fluorescent lamp

control. An additional PWM controller is integrated on the IC for applications re-

quiring an additional supply, as in LCD displays. When disabled the IC draws

only 1

µA, providing a true disconnect feature, which is optimum for battery

powered systems. The switching frequency of all outputs are synchronized to

the resonant frequency of the external passive network, which provides Zero

Voltage Switching on the Push-Pull drivers.

Soft-Start and open lamp detect circuitry have been incorporated to minimize

component stress. An open lamp is detected on the completion of a soft-start

cycle.

The Buck controller is optimized for smooth duty cycle control to 100%, while

the flyback control ensures a maximum duty cycle of 95%.

Other features include a precision 1% reference, under voltage lockout, flyback

current limit, and accurate minimum and maximum frequency control.

Resonant Fluorescent Lamp Driver

FEATURES

DESCRIPTION

UDG-92061-1

UC1871

UC2871

UC3871

Note: Pin numbers refer to DIL-18 and SOIC-18 packages only.