LXM1641-01/-02/-03

PRODUCT DA T ABOOK 1996/1997

9

Copyright © 1999

Rev. 0.7 12/99

High Voltage

Transformer

I

SENSE

V

SENSE

V

BRITE

Transformer

Driver

Ramp

Gen.

Comparator

V

SYNC

Ramp

V

HI1

V

LO

0-2.5V

DC

HOW RANGEMAX WORKS

LAMP VOLTAGE & LAMP CURRENT — Burst Mode Operation

FIGURE 6 — 50% Burst Duty Cycle

FIGURE 7 — 2% Burst Duty Cycle

FIGURE 8 — 2% Burst Duty Cycle (Expanded Time Base)

FIGURE 9 — RangeMAX Block Diagram

Rather than using the traditional dimming technique of

varying lamp current magnitude to adjust light output,

RangeMAX inverters use a fixed lamp current value with

a duty cycle control method.

The lamp current burst width can be modulated from

100% (continuous lamp current) down to a 2% duty cycle,

allowing the lamp to be dimmed to less than 1% of its

full brightness.

As can be seen in Trace 4 of Figure 8, careful design

consideration was given to controlling lamp start voltage

to softly start current flow. This eliminates current over-

shoot that can result in premature cathode wear and re-

duce lamp life.

(770V

(7.6mA

(760V

(6.7mA

(760V

(6.7mA