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Dimming Procedure of Discharge Lamp

IP.com Disclosure Number: IPCOM000117358D
Original Publication Date: 1996-Feb-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 109K

Publishing Venue

IBM

Related People

Ikeda, R: AUTHOR [+5]

Abstract

Disclosed is a method of lighting a discharge lamp. This procedure provides high efficiency of luminance/wattage of the lamp with wider dimming range than other traditional methods.

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This is the abbreviated version, containing approximately 52% of the total text.

Dimming Procedure of Discharge Lamp

      Disclosed is a method of lighting a discharge lamp.  This
procedure provides high efficiency of luminance/wattage of the lamp
with wider dimming range than other traditional methods.

      There is a strong requirement of battery life of portable
electric devices (e.g., NoteBook computer).  Many of those devices
have Liquid Crystal Display (LCD) with backlight and Cathode
Fluorescent Lamp (CFL) is popularly used as a light source.  So the
higher efficiency is required to light the CFL to achieve longer
battery life.  Also, there is another requirement from the point of
ergonomics that the brightness of the LCD should be controlled wider
and wider so that the portable electric device can be used in various
environment, for example well-lighted room, dark room and sunny
outside.

      There are two traditional procedures to control the luminance
of the lamp.  One is to decrease the lamp current by controlling the
input voltage to the inverter by DC/DC converter.  By this method,
the luminance of the lamp can be dimmed without much energy loss,
however, the dimming range cannot be wide, for example, almost
40-50%.  Because the load is a discharge lamp, so there must be
certain voltage level to ignite it, but decreasing the input voltage
makes the drop of the output voltage so the lamp cannot be lit ON at
less than 40% of luminance.  The other traditional way is to turn ON
and OFF the lamp by chopping signal at appropriate frequency which
can not be aware by human eyes.  Decreasing the ON period dims the
lamp.  Without decreasing the input voltage to the inverter, the lamp
can be lit on normally during the ON period, and the dimming range
can be wider about 5% or less.  But by this method, the
luminance/wattage efficiency is worse than the first way.  Fig. 1
shows the w...