Electric lamp and discharge devices: systems – Current and/or voltage regulation
Reexamination Certificate
2000-02-03
2002-01-22
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Current and/or voltage regulation
C315S246000, C315S360000
Reexamination Certificate
active
06340869
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for operating a direct current metal halide arc lamp, to an associated circuit arrangement, and to a direct current metal halide arc lamp with a fill that is especially well suited to these purposes.
For example, direct current metal halide arc lamps are needed for projection applications. For good color reproduction, the spectrum at the location of the highest luminance, that is, upstream of the cathode, should include sufficient proportions of the primary colors, i.e., blue, green and red. It is known to use the fill elements of indium for blue and lithium for red. In typical projection lamps, however, the primary color red is especially lacking, since the radiation of the element lithium is emitted predominantly not from the site of highest luminance but from the jacket of the arc instead. It is true that the proportion of red in the light generated can be enhanced by increasing the proportion of lithium, but then it must be remembered that lithium predominantly has very long-wave emissions, thus producing a very dark red component. Since the spectral sensitivity of the human eye drops off markedly at the long-wave edge, then to the extent that the red component is based on the lithium emissions, a correspondingly enhanced spectral power must be generated if the desired light flux is to be generated. On the other hand, it has been found that adding lithium to the lamp fill increases the so-called color separation effect; that is, various spectral ranges of the light generated are generated at different sites in the lamp; this worsens the light quality for projection purposes, which is expressed in color fringes at the boundary or peripheral regions of projected images.
Corresponding problems arise in the operation of rectangular alternating current lamps.
PRIOR ART
For generating a discharge with enhanced brightness, it is known from German Patent Disclosure DE 39 20 675 to operate a short-arc discharge lamp with a constant base current, on which a periodic pulsed current is imposed. The pulse length is in the range from 0.03 to 3 ms, and the intervals between pulses vary between 0.1 and 10 ms. Triggering a direct current arc lamp with a signal whose intervals between pulses are in this range would cause the direct current arc lamp to go out, especially if an additional base current of high constant amplitude is not used. No relationship between the trigger signal and the spectrum of the light generated can be learned from this reference.
European Patent Disclosure EP 0 443 795 and U.S. Pat. Nos. 5,047,695 and 5,198,727 describe DC discharges with AC “ripples” superimposed on them; the AC ripples are in the frequency range between 20 and 200 kHz for acoustically tightening the arc.
SUMMARY OF THE INVENTION
It is therefore the object of the present invention to propose a method for operating a direct current metal halide arc lamp, in particular a direct current metal halide arc lamp for projection purposes, or a rectangular alternating current lamp, by means of which the photometric data are improved. It is also an object of the present invention to describe an associated circuit arrangement, as well as a direct current lamp with a fill that is especially well suited to operation according to the invention.
According to the invention, this object is attained by the characteristics of the independent claims.
The fundamental concept of the invention is to operate the direct current metal halide arc lamp with a clocked voltage signal. The signal is cyclically clocked during a period T
ein
to an ON amplitude and during the subsequent period T
aus
to a voltage of quantitatively lesser amplitude.
Advantageously, the time period T
ein
is between 10 and 100 &mgr;s, and the time period T
aus
is between 1 and 50 &mgr;s. The same is true for the operation according to the invention of rectangular alternating current lamps.
The invention offers the advantage of markedly increasing the radiation, upstream of the cathode, of the element lithium, or other elements of group
1
A, that is, the red component. Since the normal calibration curve x
&lgr;
is at its maximum in this spectral region, the tristimulus value x rises compared to y. Thus by adding an element with radiation lines in the range from 520 to 580 nm, such as thallium at 535.1 nm, the y value can be increased without exceeding the Planckian locus, and without the perceived color shifting toward greenish. Increasing the y value also increases the useful light flux. Surprisingly, in the operation according to the invention of direct current metal halide arc lamps, the change in convective flow conditions in the lam causes a marked reduction in the electrode temperatures, especially for the anode that is usually overloaded in metal halide d.c. lamps. This leads to an improvement in the light flux drop over time, or so-called maintenance, since there is a reduction in blackening and electrode consumption. The result is a longer service life of the direct current arc lamp.
In the circuit arrangement of the invention, it has proved especially advantageous to select the operation of the pulsator such that in the pulsator output signal, the voltage is essentially 0 V during the period T
aus
. The same is correspondingly true for the circuit arrangement of the invention for operating a rectangular alternating current lamp; that is, in this case the amplitude values are U
n
and −U
n
during the time periods T
aus
and T′
aus
(see FIG.
4
), and advantageously both are essentially 0 V.
To prevent acoustical resonances, the time period T
ein
or T′
ein
can be varied periodically, for instance being swept with a sweep frequency of 50 to 500 Hz, preferably 100 Hz. The time period T
aus
or T′
aus
can either be constant or be varied as well. If T
aus
or T′
aus
is varied, then especially advantageously it is possible to perform a variation with adaptation to the variation of T
ein
and T′
ein
, with the goal that the minimal voltage value generated in the signal downstream of the starter for triggering the rectangular alternating current lamp remains quantitatively constant despite the variation of T
ein
and T′
ein
, respectively. Other advantageous embodiments are described in the dependent claims.
REFERENCES:
patent: 4373146 (1983-02-01), Bonazoli et al.
patent: 4410837 (1983-10-01), Suzuki et al.
patent: 4680509 (1987-07-01), Fallier, Jr. et al.
patent: 4904903 (1990-02-01), Pacholok
patent: 4937505 (1990-06-01), Deglon et al.
patent: 5047695 (1991-09-01), Allen et al.
patent: 5198727 (1993-03-01), Allen et al.
patent: 5932976 (1999-08-01), Maheshwari et al.
patent: 6111359 (2000-08-01), Work et al.
patent: 22 36 973 (1973-02-01), None
patent: 27 05 540 (1973-08-01), None
patent: 25 25 408 (1975-12-01), None
patent: 36 36 901 (1988-05-01), None
patent: 39 20 675 (1990-01-01), None
patent: 43 01 184 (1994-07-01), None
patent: 43 01 256 (1994-07-01), None
patent: 0 334 355 (1989-09-01), None
patent: 0 443 795 (1991-08-01), None
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Patent-Treuhand-Gesellschaft für Elektrische Glühlampen mbH
Tran Thuy Vinh
LandOfFree
Method for operating direct current metal halogen arc lamp... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for operating direct current metal halogen arc lamp..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for operating direct current metal halogen arc lamp... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2821132