Electric lamp and discharge devices: systems – Current and/or voltage regulation – Automatic regulation
Reexamination Certificate
2000-12-20
2001-11-13
Philogene, Haissa (Department: 2881)
Electric lamp and discharge devices: systems
Current and/or voltage regulation
Automatic regulation
C315S291000, C315S098000, C315S2090SC, C315SDIG004, C315SDIG007
Reexamination Certificate
active
06316888
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a ballast for at least one gas discharge lamp and to a method for operating a ballast for at least one gas discharge lamp.
PRIOR ART
Such a ballast and such a method are disclosed in WO 94/06261. FIGS. 2
a
and 2
b
illustrated there show the control signals of the two switches in the undimmed operating state, that is to say when maximum power is being fed to the gas discharge lamp, while FIGS. 3
a
and 3
b
there show the control signals of the two switches in the dimmed operating state, that is to say when reduced power is being fed. The pulse duty factor, which is mentioned several times below, may be defined as a quotient of the time interval in which the control signal assumes the high voltage value, and the sum of the periods of the high and the low voltage values, referred to a pulse period. It may be seen that the pulse duty factor of one switch has been changed and, specifically, has been reduced in this case starting from a value of 50% in accordance with FIG. 2
a
there, to a value of less than 50%. However, it has emerged in practice that the gas discharge lamp can shine unevenly, particularly at low temperatures, if the switches are operated in accordance with FIGS. 3
a
and 3
b
of the citation. This is undesirable, for example, when gas discharge lamps are used as exterior lighting.
SUMMARY OF THE INVENTION
It is therefore the object of the present invention to develop a ballast of the type mentioned at the beginning in such a way that this disadvantage is avoided.
A further object of the present invention consists in developing a method for operating a ballast of the type mentioned at the beginning in such a way that uneven shining of the gas discharge lamp is prevented.
The invention is based on the finding that dimmed operation with the aid of control signals provided by the control circuit in accordance with FIGS. 3
a
and 3
b
from WO 94/06261 leads to a different temperature of the two lamp electrodes. As experiments have shown, uneven shining no longer occurs when the two electrodes of the gas discharge lamp are subjected to essentially the same thermal load.
The solution according to the invention offers not only advantages in the case of dimmed operation of a gas discharge lamp—rather, it can also be used for the purpose of making a prescribed ballast available by varying the pulse duty factor in an inventive way for operating the most varied gas discharge lamps with completely different lamp parameters, in particular lamp powers. In other words, a ballast is dimensioned such that for the purpose of operating the gas discharge lamp, which requires maximum power, it works with a pulse duty factor of 50%. All other lamps which are to be operated with the same ballast are then operated with a pulse duty factor of less than 50% without fear of these lamps shining unevenly.
In one embodiment of the solution according to the invention, the first and second switches are operated in a push-pull fashion, that is to say while one switch is receiving an input signal at a high level, the other switch is receiving one at a low level, and vice versa. In a development of the basic idea of the invention, it is then possible to provide that the pulse duty factor of the two switches is changed periodically with the aid of the control circuit. This is preferably to be seen in that the pulse duty factor is controlled with the aid of the control circuit such that the sum of the ON times of the first switch is the same on average as the sum of the ON times of the second switch.
It can be provided in a particularly advantageous way that the first and second switches are operated with N different pulse duty factors, in which case N≧2 and the change between the different pulse duty factors is performed with a period which is determined in the shortest case by virtue of the fact that each pulse duty factor is carried out only precisely once before a change is made to the next one, and which is determined in the longest case by the thermal inertia of the first and second electrodes. The reason for the last-named limit is that it is impermissible to maintain a pulse duty factor until the two electrodes acquire markedly different thermal loads. The result here is different time periods, depending on the physical properties of the electrodes with which a gas discharge lamp is fitted.
N=2 in the case of a concrete exemplary embodiment, the first pulse duty factor being D and the second pulse duty factor being E=100%−D.
While it is possible in the case of the above-named field of use of the invention, that is to say a ballast for gas discharge lamps of different powers, to use the control circuit to store the pulse duty factor appropriate for the respective lamp, it is possible over and above this also to provide an input of the control circuit via which the pulse duty factor can be changed by an operator, for example in order to dim the gas discharge lamp.
REFERENCES:
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patent: 4682080 (1987-07-01), Ogawa et al.
patent: 4725762 (1988-02-01), Jagschitz
patent: 4920299 (1990-04-01), Presz et al.
patent: 5103138 (1992-04-01), Orenstein et al.
patent: 5365151 (1994-11-01), Spiegel et al.
patent: 5367225 (1994-11-01), Pacholok et al.
patent: 5485061 (1996-01-01), Ukita et al.
patent: 5583402 (1996-12-01), Moisin et al.
patent: 6140771 (2000-10-01), Luger et al.
patent: 43 32 059 (1994-03-01), None
patent: 0 306 086 (1989-03-01), None
patent: 2.067.690 (1971-08-01), None
patent: 94/06261 (1994-03-01), None
patent: 99/01013 (1999-01-01), None
Bessone Carlo S..
Patent-Treuhand-Gesellschaft Fuer Elektrische Gluehlampen MBH
Philogene Haissa
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