U.S. patent number RE31,486 [Application Number 06/380,074] was granted by the patent office on 1984-01-03 for rapid starting of gas discharge lamps.
This patent grant is currently assigned to Chadwick-Helmuth Company, Inc.. Invention is credited to James G. Helmuth.
United States Patent |
RE31,486 |
Helmuth |
January 3, 1984 |
Rapid starting of gas discharge lamps
Abstract
A starting device for a gas discharge lamp, to whose electrodes
AC voltage is applied, comprises: a. first means electrically
connected with at least one lamp electrode to apply to the lamp a
transient voltage pulse which initially changes in amplitude in a
polarity direction relatively in opposition to the polarity of the
main voltage simultaneously supplied to the electrodes, b. said
first means including circuitry to cause said pulse to thereafter
change in amplitude in a polarity direction in aid of the polarity
of the main voltage simultaneously supplied to the electrodes.
Inventors: |
Helmuth; James G. (Monrovia,
CA) |
Assignee: |
Chadwick-Helmuth Company, Inc.
(El Monte, CA)
|
Family
ID: |
27008885 |
Appl.
No.: |
06/380,074 |
Filed: |
May 20, 1982 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
510440 |
Sep 30, 1974 |
03944876 |
Mar 16, 1976 |
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Current U.S.
Class: |
315/205; 315/273;
315/276; 315/289; 315/DIG.7 |
Current CPC
Class: |
H05B
41/19 (20130101); H05B 41/042 (20130101) |
Current International
Class: |
H05B
41/19 (20060101); H05B 41/04 (20060101); H05B
41/00 (20060101); H05B 41/18 (20060101); H05B
041/16 (); H05B 041/24 () |
Field of
Search: |
;315/DIG.2,DIG.5,DIG.7,205,207,208,273,274,275,276,289 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1037008 |
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Feb 1959 |
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DE |
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1764645 |
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Dec 1972 |
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DE |
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1589306 |
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Mar 1973 |
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DE |
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47-10920 |
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Jun 1972 |
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JP |
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47-41876 |
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Oct 1972 |
|
JP |
|
47-39334 |
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Nov 1972 |
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JP |
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49-275 |
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Jan 1974 |
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JP |
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49-61965 |
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Jun 1974 |
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JP |
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1065310 |
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Apr 1967 |
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GB |
|
1183542 |
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Mar 1970 |
|
GB |
|
1210153 |
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Oct 1970 |
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GB |
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1222699 |
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Feb 1971 |
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GB |
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Primary Examiner: Demeo; Palmer C.
Attorney, Agent or Firm: Haefliger; William W.
Claims
I claim:
1. In a starting device for a gas discharge lamp to which main AC
voltage is supplied via lamp electrodes,
a. first means electrically connected with at least one lamp
electrode to apply to the lamp a .[.transient voltage pulse.].
.Iadd.succession of transient voltage pulses of declining
amplitudes .Iaddend.which initially .[.changes.]. .Iadd.change
.Iaddend.in amplitude in a polarity direction relatively in
opposition to the polarity of the main voltage simultaneously
supplied to .Iadd.at least one of .Iaddend.the electrodes,
b. said first means including circuitry to cause said .[.pulse.].
.Iadd.pulses .Iaddend.to thereafter change in amplitude in a
polarity direction in aid of the polarity of the main voltage
simultaneously supplied to .Iadd.at least one of .Iaddend.the
electrodes, whereby the lamp may be re-started when hot.
2. The device of claim 1 wherein said circuitry includes series
connected capacitance and inductance characterized as causing said
pulse to have a transient wave form, of a frequency substantially
higher than the frequency of said main AC voltage.
3. The device of claim 2 including control means connected with
said circuitry, to effect pulse production in response to
predetermined change in amplitude of said main AC voltage.
4. The device of claim 3 wherein said control means includes zener
diode means connected with at least one of said lamp electrodes,
capacitance connected in series with said zener diode means to
charge when the zener diode means conducts, and elements to
discharge said capacitance when the voltage thereon reaches a
predetermined level.
5. The device of claim 1 including second means to produce
ionization of gas within the lamp during application of said
voltage pulse to the lamp electrode.
6. In a starting device for a gas discharge lamp to which main AC
voltage is supplied via lamp electrodes,
a. first means electrically connected with at least one lamp
electrode to apply to the lamp a transient voltage pulse which
initially changes in amplitude in a polarity direction relatively
in opposition to the polarity of the main voltage simultaneously
supplied to the electrodes,
b. said first means including circuitry to cause said pulse to
thereafter change in amplitude in a polarity direction in aid of
the polarity of the main voltage simultaneously supplied to the
electrodes, whereby the lamp may be re-started when hot,
c. and second means to produce ionization of gas within the lamp
during application of said voltage pulse to the lamp electrode,
said second means including an ion gun at the exterior of the lamp
and proximate thereto, and other circuitry to apply an auxiliary
multi-kilovolt pulse to the gun.
7. In a starting device for a gas discharge lamp to which main AC
voltage is supplied via lamp electrodes,
a. first means electrically connected with at least one lamp
electrode to apply to the lamp a transient voltage pulse which
initially changes in amplitude in a polarity direction relatively
in opposition to the polarity of the main voltage simultaneously
supplied to the electrodes,
b. said first means including circuitry to cause said pulse to
thereafter change in amplitude in a polarity direction in aid of
the polarity of the main voltage simultaneously supplied to the
electrodes,
c. and second means to produce ionization of gas within the lamp
during application of said voltage pulse to the lamp electrode,
said second means including an ion gun, and other circuitry to
apply an auxiliary voltage pulse to the gun, said other circuitry
including a transformer T.sub.2 connected with said gun and also
having an intermediate tap, capacitance connected between said tap
and the main voltage input to the lamp, and there being means to
suddenly discharge said capacitor to approximately coincide with
said application of said voltage pulse to the lamp electrode.
8. In a starting device for a gas discharge lamp to which main AC
voltage is supplied via lamp electrodes,
a. first means electrically connected with at least one lamp
electrode to apply to the lamp a transient voltage pulse which
initially changes in amplitude in a polarity direction relatively
in opposition to the polarity of the main voltage simultaneously
supplied to the electrodes,
b. said first means including circuitry to cause said pulse to
thereafter change in amplitude in a polarity direction in aid of
the polarity of the main voltage simultaneously supplied to the
electrodes, and
c. ballast circuitry connected between a source of main AC voltage
and the lamp, said circuitry including an autotransformer and a
gate controlled bilaterally conductive device connected in series
between source terminals, the autotransformer having an
intermediate tap connected with a lamp electrode.
9. The device of claim 8 including an inhibit circuit connected
between said tap and a source terminal to which said bilaterally
conductive device is directly connected, and a pulse generator
responsive to the output of the inhibit circuit to control the gate
of said bilaterally conductive device.
10. For use in combination with a gas discharge lamp to which main
AC voltage is supplied, a ballast circuit connected between the AC
source and the lamp, the source having terminals, the lamp having
two electrodes, said ballast circuit comprising
a. an autotransformer and a gate controlled bilaterally conductive
device connected in series between said source terminals, and
b. the autotransformer having an intermediate tap connected with
one lamp electrode,
c. the other lamp electrode being electrically connected with a
source terminal to which the bilaterally conductive device is also
electrically connected.
11. The ballast of claim 10 including an inhibit circuit connected
between said tap and the source terminal to which said bilaterally
conductive device is directly connected, and a pulse generator
responsive to the output of the inhibit circuit to control the gate
of said device. .Iadd.
12. A starting device for a gas discharge lamp to which a low
frequency main AC voltage and a succession of multiple transient
ignition voltage oscillations per half wave of higher frequency
than that of the main AC voltage and in a polarity direction in aid
of and/or in opposition to the polarity of the main voltage are
supplied via lamp electrodes, said ignition voltage oscillations
being produced in a capacitive inductive oscillatory circuit,
characterized in that the oscillatory circuit is connected for the
supply of pulses (16), always performing an initial ignition
amplitude change (16a) in opposition to the polarity of the main AC
voltage (15) and subsequently an ignition amplitude change (16b) in
a polarity direction in aid of the polarity of the main AC voltage.
.Iaddend. .Iadd.
13. In a starting device for a gas discharge lamp to which main AC
voltage is supplied via lamp electrodes, the combination
comprising
(a) first means including circuitry and control means and connected
with at least one lamp electrode for applying to the lamp transient
voltage pulses,
(b) said circuitry for generating and applying said transient
voltage pulses including series connected capacitance and
inductance, said series connected capacitance and inductance being
arranged to cause each of the pulses initially changing in
amplitude in a polarity direction relatively in opposition to the
polarity of the main AC voltage simultaneously supplied to the
electrode and thereafter changing in amplitude in a polarity
direction in aid of the polarity of the main voltage, said series
connected capacitance and inductance defined to generate in each
half cycle of the main AC voltage a sequence of transient voltage
pulses of declining amplitudes all of which are in a polarity
direction relatively in opposition to the polarity of the main
voltage simultaneously supplied to the electrodes, the first pulse
of said sequence of transient voltage pulses having the largest
amplitude, whereby the lamp may be immediately re-started when hot,
and
(c) said control means connected with said circuitry to effect
pulse production in response to a predetermined change in amplitude
of said main AC voltage. .Iaddend. .Iadd.
14. The combination of claim 13 including additional means to
produce ionization of gas within the lamp during application of
said voltage pulses to the lamp electrode, said additional means
including an ion gun at the exterior of the lamp and proximate
thereto, and other circuitry to apply an auxiliary multi-kilovolt
pulse to the gun. .Iaddend.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to the starting of gas discharge
lamps, and more particularly concerns overcoming problems relating
to such starting.
Gas discharge lamps such as mercury vapor lamps have come into
widespread use, two examples being sources of ultraviolet light
employed in print reproduction, and street lamps. Although such
lamps are clean and efficient devices, as compared with carbon arc
lights, they have presented two long standing problems. First, they
require objectionably long warm-up times, i.e up to about 5 minutes
in certain cases; and secondly, there is the practical
impossibility of re-starting a warmed-up mercury vapor lamp (should
it be even momentarily turned off) until it cools. Therefore, for
repetitive on-off duty, it has been the practice to leave the lamp
on all the time, and resort to a mechanical shutter which is moved
to control exposure. Such shutters, however, are subject to
mechanical failure, and resultant prolonged human exposure to a
mercury vapor lamp in ON condition can cause serious damage to the
eyes and skin.
SUMMARY OF THE INVENTION
It is a major object of the invention to overcome both of the above
problems, enabling powering of gas lamps only when needed and
thereby additionally producing energy savings, extension of lamp
life and elimination of physical damage to humans otherwise
resulting from prolonged exposure to lamp rays. Further, mercury
vapor lamps used as street lights can be restarted immediately
after power interruptions (as for example may be due to lightning,
and short power failures), enhancing traffic and pedestrian
safety.
Basically, the starting device comprises means to apply to the lamp
one or more transient voltage pulses or spikes which initially
change in amplitude in a polarity direction relatively in
opposition to the polarity of the main voltage simultaneously
supplied to the electrodes; further, each pulse thereafter is
typically caused to change in amplitude in a polarity direction in
aid of the polarity of the main voltage then being applied to the
electrodes. As a result, a rapid start of the lamp is achieved.
It is another object of the invention to provide circuitry to
achieve the above; with pulse oscillation frequency much greater
than the main AC voltage frequency. Such circuitry may typically
include series connected inductance and capacitance, and control
means electrically connected with the capacitance to effect
capacitor discharge and pulse production in response to
predetermined increase or decrease in the amplitude level of the
main AC voltage; accordingly, pulse production may be achieved when
the main AC voltage is near maximum absolute value, to aid the
start; also, when the main AC voltage drops below that level, the
command of pulse production is terminated.
It is a further object of the invention to provide second means to
produce ionization of the gas within the lamp during application of
voltage pulses to the lamp electrodes, such second means typically
including an ion gun, and other circuitry including inductance and
capacitance to apply an auxiliary voltage pulse to the gun in
synchronism with pulse application to the lamp electrodes.
It is an additional object of the invention to provide unusually
effective ballast circuitry between the main AC source and the
lamp, such ballast shortening the time from start to full light
out, without drawing excessive current from the mains and without
applying excessive power to the lamp.
These and other objects and advantages of the invention, as well as
the details of illustrative embodiments, will be more fully
understood from the following description and drawings, in
which:
DRAWING DESCRIPTION
FIG. 1 is a circuit diagram;
FIGS. 2 and 3 are wave forms related to the operation of the FIG. 1
circuit;
FIG. 4 is a circuit diagram;
FIGS. 5 and 6 are wave forms related to the operation of the FIG. 4
circuit; and
FIG. 7 is a circuit diagram.
DETAILED DESCRIPTION
Referring first to FIG. 1, it illustrated one preferred form of
starting device for a discharge lamp 10 to which main AC voltage is
supplied via input terminals 11 and 12, ballast 13, and lamp
electrodes 10a and 10b. The main AC voltage waveform appears at 15
in FIGS. 2 and 3.
In accordance with the invention, first means is electrically
connected with at least one lamp electrode to apply to the lamp a
transient voltage pulse which initially changes in amplitude in a
polarity direction relatively in opposition to the polarity of the
main voltage 15 simultaneously supplied to the electrodes. See for
example the sharp initial amplitude change at 16a of pulse 16 in
FIG. 2, the pulse being applied at 20 to electrode 10b in FIG. 1.
Further, the pulse is thereafter caused to change in amplitude in a
polarity direction in aid of the polarity of the main voltage 15.
See for example the sharp amplitude change at 16b of pulse 16 in
FIG. 2, it being clear that the pulse oscillation frequency is much
greater than the frequency of the main AC voltage. One or more such
pulses are typically applied, as for example at 16, 17 and 18
during one half cycle of the main voltage wave; further, pulses 19,
20 and 21 are shown as applied during the next half cycle, the
latter pulses being reversed in initial amplitude change direction
relative to pulses 16-18. A time axis expanded version of pulse 19
is shown in FIG. 3, the shape of the pulse being altered as shown
by the broken lines 19a upon the occurrence of lamp conduction.
In the circuitry example as shown in FIG. 1, the means to produce
the pulses typically includes series connected capacitance C.sub.3
and inductance T.sub.1 characterized as causing the pulse to have
the illustrated transient wave form. Further, control means is
connected with such circuitry to effect pulse production in
response to predetermined change in amplitude of the main AC
voltage, as during each half cycle of the latter. Such control
means may with unusual advantage include Zener diode means as at
120 and 121 connected back-to-back and in series with the ballast
13, as via leads 22 and 23. The Zener diodes are also connected in
series with capacitance 24, via diode 25, so that the capacitance
24 will become charged when the Zeners conduct in response to
increase of the main voltage to predetermined level, on each half
cycle. When the capacitance charges to predetermined voltage level,
the diode 25 conducts, firing the triac Q.sub.1.
Upon conduction of the latter via path 26 between main power heads
23 and 23a, the capacitor C.sub.1 is discharged through the primary
of the pulse transformer T.sub.1. The latter may typically produce
a medium voltage pulse (7-15 KV, for example) applied, as
described, across the lamp electrodes (C.sub.3 being low impedance
to the pulse). The energy of one pulse is normally insufficient to
establish full conduction in the arc region of the lamp, reliance
being placed on a succession of such places (as at 16-18)
superposed on the main voltage to alter the ionization state of the
gas within the lamp, and free charges, thereby to initiate lamp
conduction. When the lamp conducts, the voltage at lead 22 falls,
disabling the pulse generator A that includes elements 120, 121, 24
and 25 previously described. Should the lamp ever stop conducting
while main power is applied, the starting cycle will automatically
repeat.
With respect to the connection of T.sub.1 to oppose the main
voltage, it would normally appear that such a connection is
incorrect. It is found, in this regard, that after T.sub.1 delivers
an initial pulse, conduction ceases momentarily but, within the
lamp, due to the reverse conduction in oppsitions to main voltage,
a condition is brought into existance which aids the main voltage.
While the exact nature of such condition is not understood, it is
thought that the reverse current within the lamp creates a cloud of
electrons produced by secondary emission at the electrode which
then becomes the cathode for the main current flow.
Also provided is what may be referred to as second means to produce
ionization of gas within the lamp during application of the voltage
pulse to the lamp electrode by transformer T.sub.1. Such second
means may with unusual advantage include an ion gun 126, and other
circuitry to apply an auxiliary voltage pulse to the gun. For
example, that circuitry may include a transformer T.sub.2 whose end
taps are connected between the gun and lead 23a, T.sub.2 having an
intermediate tap 27 connected via a capacitor C.sub.2 and resistor
R with lead 23. When the triac Q.sub.1 is fired as described, the
capacitor C.sub.2 is discharged through the primary of T.sub.2,
which causes T.sub.2 to produce a relatively very high voltage
(i.e., 15-20 KV) pulse at relatively low current applied to the
gun. This produced ionization of the gas in the Townsend region in
the gun; however, the ionization level is not sufficient (if the
lamp is hot and the mercury is vaporized, as in a Sylvania type
H377 lamp, for example) to enable the main voltage to cause
conduction. On the other hand, such ionization assists the lower
voltage from T.sub.1 to cause reverse current flow, allowing the
relatively very low voltage from the mains, plus the second cycle
of T.sub.1 output, to cause forward current to bring the lamp into
full conduction. Typically, the ionization level will be sufficient
for T.sub.1 voltage to cause high reverse current (0.5 to 2 amps)
to flow for a short time (5-20.mu. second, for example) in the
lamp.
If T.sub.2 is not employed, the voltage level from T.sub.1 must be
higher in order to first ionized the gas and then to produce the
reverse current, as described above. It should also be noted that
if T.sub.1 is connected with conventional polarity so as to aid the
main voltage, and/or if T.sub.1 does not produce a second
oscillatory pulse after the initial pulse (i.e. a second pulse such
as 17 after initial pulse 16, for example), very much more energy
is required from T.sub.1 to bring the lamp into main
conduction.
An ion gun of the type referred to is described in my prior
application Ser. No. 371,396, filed June 19, 1973, now U.S. Pat.
No. 3,870,924.
Referring now to FIG. 4, improved ballast circuitry is shown in
combination with lamp 10, which is of the medium to high pressure
type, such as the Sylvania Model previously referred to. Such
ballast shortens the time (i.e. from 3-5 minutes as in conventional
to only a few seconds, i.e. 15 seconds for example) from start to
full light out without drawing excessive current from the mains and
without applying excessive power to the lamp.
The circuit essentially comprises an autotransformer T.sub.3 and a
gate controlled bilaterally conductive device such as triac Q.sub.2
connected in series between the mains 11 and 12; an inhibit circuit
51 connected between leads 23 and 23a; and a pulse generator 52
responsive to the output at 53 of the inhibit circuit to control
firing of the triac, as shown. Note that the pulse generator output
is connected to the triac gate at 54.
In operation, when power is applied to the cold lamp 10 which is
non-conductive, the voltages V.sub.1 and V.sub.2 as indicated are
essentially the same as at the mains, (i.e. 240 VAC, for example)
as is clear from FIG. 5, and there is no voltage change across
T.sub.3. Therefore, V.sub.2 across Q2 has the same phase and
amplitude as V.sub.1. The latter commands the inhibit circuit which
prevents the pulse generator from operation when its V.sub.2
command has the same phase as V.sub.3. Therefore, Q.sub.2 does not
conduct, and full supply voltage remains applied to the lamp to
assist starting.
When the cold lamp conducts via the exciting inductance L.sub.2,
(typically at about 70MH), V.sub.1 becomes low due to the small
voltage drop across the lamp (i.e. 20 volts, for example), and
there is then a large voltage gradient along T.sub.3. This causes
V.sub.2 to tend to be of opposite phase from V.sub.1. The inhibit
circuit then no longer prevents the pulse generator from operating,
and Q.sub.2 conducts. T.sub.3 can now operate as an
autotransformer, delivering high currents (e.g. 30 AMPS, for
example) to the lamp while drawing much less current (e.g. 14 amps)
from the main. The ratio of these two currents is determined by the
position of the tap 55 (e.g. 40% for example) and the magnitude
determined by the inductance of L.sub.1 (e.g. 8 MH) and the voltage
drop across the lamp. As the lamp warms, voltage across the lamp
increases leaving less voltage across L.sub.2. Thus, the lamp
current decreases.
When the voltage V.sub.1 increases sufficiently, Q.sub.2 will not
conduct at the beginning of each half cycle of lamp current;
voltage V.sub.1 lags the main voltage since, when O.sub.2 is off,
current is supplied by the exciting inductance L.sub.2 and the lamp
voltage is in phase with this lamp current. Thus, voltage V.sub.2
will be of the same polarity as V.sub.1 and Q.sub.2 not triggered
until the main voltage is at high enough value during the half
cycle to drive V.sub.2 to reverse polarity. Then triac Q.sub.2
conducts for the remainder of the half cycle. This action continues
until Q.sub.2 no longer conducts at any time, and the lamp is
powered directly from the mains via the leakage inductance
L.sub.2.
Benefits of this system over prior ballasts include rapid warm-up
without excessive mains current; approximate constant power to the
lamp during warm-up: since lamp current and lamp voltage are
inversely related, this prevents thermal shock or other damage to
the lamp due to excessive power input; independence of changes in
lamp parameters or line voltage; since circuit action demands that
sufficient voltage (up to the maximum available from the mains) is
applied to the lamp to maintain conduction, no adjustments need be
made for lamp aging, installation of new lamps, normal changes in
mains voltage, etc.; and reversible action; i.e. should the lamp
for some reason cool, appropriate higher current will automatically
be provided to return lamp quickly to full output conditions.
FIG. 7 combines the circuits of FIGS. 1 and 4, with all the
benefits of each, into a superior lamp starting circuit. Note that
L.sub.1 of FIG. 4 has been included into T.sub.1 of FIG. 1 by
adjusting T.sub.1 for the desired exciting inductance.
The invention is applicable to mercury and/or metal additive
mercury lamps, an example of the latter being Sylvania Type MP2000.
In this case, the T.sub.1 voltage applicable to the lamp electrodes
would be in the range 15KV to 30KV, to hot re-strike, the ion gun
also being usable.
* * * * *