24P022-O
Luminance Enhancement of Xenon Fluorescent Lamps by Burst Pulse Drive
バーストパルス駆動によるキセノン蛍光ランプの輝度向上
Masaya Yamada, Yudai Yamamoto, Hideki Motomura and Masafumi Jinno
山田真也, 山本雄大, 本村英樹, 神野雅文
Department of Electrical and Electronic Engineering, Ehime University
3 Bunkyo-cho, Matsuyama 790-8577 Japan
愛媛大学 大学院理工学研究科 〒790-8577 松山市文京町3
In the environmental point of view, non-toxic and environmentally friendly products are demanded. For
fluorescent lamps, mercury-free ones are developed and xenon is used as a substitute for mercury.
However, their total flux and the efficacy is not enough for general lighting. The authors tried a novel
driving voltage waveform to solve this problem. By using a burst pulse drive, i.e. by applying a successive
sub-pulse (triangle waveform) after the main pulse (rectangular waveform), the maximum luminance wasenhanced, because of suppression of power injection concentration during the main pulse application.
However, the lamp efficacy decreased on the contrary, because of depletion of the metastable atoms by
step-wise ionization.

1. Introduction
In the environmental point of view, non-toxic
and environmentally friendly products aredemanded. Fluorescent lamps contain mercury as
phosphor exciting UV (ultraviolet) radiator.
Xenon plasmas radiate fairly strong VUV(vacuum ultraviolet) emissions and they are themost promising candidate of substitution for
mercury. Although xenon fluorescent lamps areused for special purpose, such as for image
scanners and photocopies, the lamps for generallighting with enough total flux and the efficacy
have not been realized yet.
Since xenon atom has high excitation level(8.3 eV for resonance level), xenon fluorescentlamps are driven by pulsed voltage and strong
VUV emissions from non-equilibrium plasma areutilized. However, excess ionization of xenon
atoms by high voltage pulse can result in low
efficiency. The authors tried suppressing theexcess ionization and tried exciting xenon atoms
to the resonant and metastable levels with highefficiency by burst pulse drive; the idea is toionize xenon atoms and initiate the plasma by
first main high voltage pulse, and then to excite
xenon atoms by successive low voltage sub-pulse.
This paper discusses experimental results ofluminance enhancement of xenon fluorescentlamps by burst pulse drive.
2. Experimental Procedure
The cold cathode xenon fluorescent lamp madefor the experiment had following specification.
The xenon filling pressure was 6.7 kPa. The
distance between the electrodes was 50 mm, theinside and outside diameter were 26 and 30 mm
respectively. Tri-band phosphor for plasma
display panel was coated on the inside of thelamp. In this study, a triangle waveform was usedfor the sub-pulse, as shown in Fig. 1. The pulse
repetition frequency and the pulse width of thefirst main pulse were set at 17 kHz and 5 srespectively. The luminance of the lamp surface
was measured at the center of the lamp with aluminance meter (Topcon, SR-3). The amplitude
and the duration of the sub-pulse were optimized
by monitoring the lamp luminance.
3. Results and Discussion
Figure 2 shows the luminance vs. the power
consumption when (a) the amplitude and (b) theduration of the sub-pulse were changed. The input
power was set within the range in which a stablediffuse positive column was obtained; this meansthat if the input power was over the range shownin Fig. 2 for each condition, the positive column

Fig. 1. An example of the schematic of the burstpulse.

(a)W/o sub-pulse
With sub-pulse, amplitude ratio=0.1
With sub-pulse, amplitude ratio=0.2
With sub-pulse, amplitude ratio=0.3(a)W/o sub-pulse
With sub-pulse, Amplitude ratio=0.2,
Duration=45 s(b)
W/o sub-pulse(b)
W/o sub-pulse
With sub-pulse, duration=35 sWith sub-pulse, duration=45 sWith sub-pulse, duration=53.8 sWith sub-pulse, Amplitude ratio=0.2,Duration=45 s

Fig. 3. An example of (a) the applied voltage and(b) the lamp current.

Fig. 2. The luminance vs. the power consumption
when (a) the amplitude and (b) the duration of the
sub-pulse were changed.

constricted and the discharge turned to thefilamentary mode. It is found that the maximum
input power under which the stable diffuse
discharge was obtained increased by applying the
sub-pulse and by increasing its amplitude andduration. As a result, maximum luminanceincreased with the amplitude ratio of sub- to main
pulse of 0.2 and the duration of the sub-pulse of
45 s. When the sub-pulse was applied, the power
injection occurred during both main andsub-pulse. On the other hand, when the only main
pulse was applied, power injection concentrated
for the short time range during the main pulse
application; this resulted in the positive column
constriction at the lower threshold value of theinput power. On the contrary, however, the lamp
efficacy dropped with sub-pulse application,
which was against the hypothesis described inSec. 1. Figure 3 shows an example of (a) theapplied voltage and (b) the lamp current. It isfound that the lamp current during the sub-pulse
application is not small. It means the ionization
rate during the sub-pulse application is not smallin spite of low voltage amplitude. This can be
resulted from the step-wise ionization, which
requires lower electron energy than directionization. Thus, sub-pulse application resulted indepletion of the metastable atoms and efficacy
drop. Optimization of waveform etc. is necessary
as a future task.
4. Conclusion
A novel driving voltage waveform for
mercury-free xenon fluorescent lamps isintroduced. By using a burst pulse drive, i.e. byapplying a successive sub-pulse after the mainpulse, the maximum luminance was enhanced,
because of suppression of power injection
concentration during the main pulse application.
However, the lamp efficacy decreased on thecontrary, because of depletion of the metastableatoms by step-wise ionization.
Acknowledgment

This work was partly supported by the Grant
for Industrial Technology Research (financial
support to young researchers) No. 06A39007d
from The New Energy and the Industrial
Technology Development Organization (NEDO)
of Japan.