Microsemi

Integrated Products Division

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

Page 7

Copyright

Rev. 1.0a, 2006-11-13

RangeMAX

™

LXMG1621-xx

TM

®

HOW THE RANGEMAX WORK S

LAMP VOLTAGE & LAMP CURRENT –

BURST MODE OPERATION

Figure 3 – 50% Burst Duty Cycle

Figure 4 – 2% Burst Duty Cycle

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 3 of Figure 5 photo at right, careful

design consideration was given to controlling lamp start voltage

to softly start current flow. This eliminates current overshoot

that can result in premature cathode wear and reduce lamp life.

Figure 5 – 2% Burst Duty Cycle (Expanded Time Base)

Ramp Gen.

Transformer

Driver

High Voltage

Transformer

Comparator

Ramp

+

-

I

SENSE

V

SENSE

V

BRITE

0.25 -

2.2V

DC

V

SYNC

V

LO

V

HI

V

LO

V

HI

Figure 6 – RangeMAX Simplified Block Diagram

HIGHLIGHTS

voltage to pulse width converter that minimizes system

design work and system noise susceptibility.

This

provides a familiar and convenient interface while

reducing the potential for externally induced noise, which

can cause lamp flicker.

about 95Hz, well beyond standard 50/60Hz video refresh

rates where the eye can perceive pulsing light.

with the burst frequency synchronized to the video frame

rate.

This provides operation with no visible display

disturbances caused by beat frequencies between the

lamps and video frame rates.