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Lamp Power Source
yhe tarn p power source
smp and control the power supply to We
Mmp to maintain and stabilize the tamp
K^tscharge, keeptng )Mumfhat!ort at a con-
M a n t ^ e v e ) . _ _ _ _ _ _ _ _ _ _ ^
(j^^tshowsthe tamp power source b)ock diagram.
DC and AC iamp illumination methods are avaiiabfe.
With DC illumination, luminous substances are at-
tracted to the negative electrode, causing discharge to
accumulate toward it. Another drawback is a greater
power ioss which lessens efficiency. Therefore AC
iiiumination is more often used. The iamp driver circuit is
a DC- AC converter used for AC iiiumination of the iamp.
Designed to centre) power supp)y to the tamp, the
chopper circuit consists of switching transistors, choke
coits, diodes, etc. tt generates intermittent current by
switching the switching transistor on and off. The longer
the On time, does the supplied power increase, white the
ionger the Off time, does the supplied power !ower.
Therefore, by varying the on/off time, power supply can
be controlled.
The chopper circuit varies the switching transistor
on/off time to maintain the power suppfy to the tamp at a
constant fevei.
The high- voitage puise generator tights the tamp. The
metat hatide tamp emits tight through arc discharge. To
initiate arc discharge, dielectric breakdown must occur
between the tamp electrodes. The high - voltage putse
generator generates and applies high - vottage putses
with peak values of about 20kV between the lamp's
positive and negative electrodes in order to generate
g!ow discharge. This in turn resutts in dielectric break-
down between the efoctrodos, causing a shift from gtow
discharge to arc discharge.
—4—
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