Electric lamp and discharge devices: systems – Surge generator or inductance in the supply circuit
Reexamination Certificate
2002-09-18
2003-12-09
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Surge generator or inductance in the supply circuit
C315S290000, C315S291000, C315S261000, C315S263000, C315SDIG005
Reexamination Certificate
active
06661184
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention generally relates to a light source device having a high pressure mercury discharge lamp. In particular, the invention can be used, for example, as a light source for a projector.
2. Description of the Related Art
In a light source device for an optical device, such as a liquid crystal projector, a DLP, or the like, a discharge lamp with high radiance (HID lamp) is used. Recently however there has been a demand for a greater amount of mercury to be added to the discharge lamp than in the conventional case in order to make the optical device more radiant. In one such discharge lamp it is necessary to produce a high voltage during start-up by using a starter to subject a discharge space to an insulation breakdown, and thus to start a discharge.
FIG. 19
shows an arrangement of a conventional discharge lamp light source device. In a light source device for an optical device, conventionally a starter (Ui) is used between the electrodes (E
1
, E
2
) to which a high voltage is applied. The secondary winding (Si) of the high voltage transformer (T
1
) of the starter is series connected to the discharge lamp (Li). After starting a discharge, the function of the starter (Ui) is thus no longer necessary. The discharge current supplied to the discharge lamp (Li) must nevertheless flow via the secondary winding (Si) of the high voltage transformer which has a large winding number. To suppress the formation of heat loss in the secondary winding (Si), it is necessary to make the wire diameter of the winding large, resulting in the disadvantage that an increase in the size and weight of the starter (Ui) is inevitable.
As a measure for eliminating this defect, an outside trigger method can be used which is often used for the trigger in a blinking lamp. With this method, besides the first electrode and the second electrode acting as the two main discharge poles, i.e., an arc discharge after starting, there is an auxiliary electrode. Between the auxiliary electrode and the first or second electrode, a high voltage is applied, plasma is produced by a dielectric barrier discharge in the discharge space, and between the first electrode and the second electrode the main discharge is started by means of a voltage applied beforehand (no-load voltage) by means of the plasma.
After starting the discharge in the primary winding and the secondary winding of the high voltage transformer of the starter, no discharge current flows to the discharge lamp. Thus, in the primary and secondary windings of the high voltage transformer of the starter no heat loss forms. Therefore, both an increase in size and an increase in weight of the starter can be avoided.
In a discharge lamp with a large amount of added mercury, the pressure in the discharge lamp is low due to the condensation of the mercury when the discharge lamp is in the cold state. In this case, starting can take place relatively easily. However, the case of a hot discharge lamp, which can occur shortly after turning off the lamp, the pressure in the discharge space is high due to the vaporized mercury. This is disadvantageous in that a hot restart of the lamp is difficult.
The disadvantage of a difficult hot restart for an optical device such as a projector, or the like, is the disadvantage of convenience of use by the user of this device. This disadvantage of difficult restart has furthermore become more and more serious in recent years due to the increase in the amount of mercury added to implement the outside trigger method.
On the other hand, the conventional discharge lamp (Li) and a feed device (Ni) were connected to one another by feed lines (K
1
, K
2
). The starter (Ui) for starting the discharge lamp (Li) was located on a side of the feed circuit. The starter (Ui) produced a high voltage. In the case in which the starter (Ui) produces a pulsed high voltage, the feed lines (K
1
, K
2
) are exposed to a high voltage within a short time, which created strong noise.
Furthermore, “dulling distortion” of the pulsed high voltage is caused by an electrostatic potential which forms between the feed lines (K
1
, K
2
), a conductance in the environment, and by the inductance of the feed lines (K
1
, K
2
). The increase in the voltage between the electrodes (E
1
, E
2
) is therefore reduced. In order to obtain the pulsed voltage necessary for starting the discharge lamp, more energy than necessary must be delivered by the starter (Ui) in the direction of the feed lines (K
1
, K
2
). Moreover, the pulse width is broadened by the “dulling distortion” of the pulsed high voltage. In this way, the possibility of the formation of an insulation breakdown in an unintended area, such as the insulation coating of the high voltage transformer (T
1
) of the starter and the feed lines (K
1
, K
2
) or the like, is increased. In this way, there is the danger of a reduction in reliability.
On the other hand, in the case of a DC starter which produces a relatively slowly increasing high voltage, the insulation breakdown phenomenon takes place more frequently, and in proportion to the higher the voltage and the longer the voltage application time. In this instance, one disadvantage is the possibility that the formation of an insulation breakdown in an unintended area increases even more.
For conventional inventions and concepts for starting a high pressure discharge lamp using the outside trigger method, reference can be made to, for example, Japanese Utility Model SHO 37-8045. Here an arrangement is disclosed in which there is a coil which produces a magnetic force, and controls in the operation of a starter circuit which produces a high voltage in the auxiliary electrode by a magnetic force.
Furthermore, in the invention described in Japanese patent disclosure document HEI 5-54983, an arrangement is disclosed in which in the discharge lamp, such as in a high pressure mercury lamp or the like, there are auxiliary electrodes (outside electrodes) adjacent to one another with a distance of a few millimeters to one another.
SUMMARY OF THE INVENTION
However, in these conventional inventions and concepts, the formation of an insulation breakdown in an unintended area during restart were not considered at all.
An exemplary object of the invention is to eliminate the disadvantages of the prior art. These disadvantages at least are:
an increase in size or an increase in weight of the starter cannot be avoided if heat loss in the windings is to be avoided,
that restart is difficult shortly after turning off and the discharge lamp is hot;
noise concerns;
as a result of capacitive coupling between the feed lines and the conductor in the vicinity of the starter, greater energy than necessary must be delivered in the direction of the feed lines; and
the possibility of the formation of an insulation breakdown in an unintended area increases thus causing a reduction in reliability.
In a first aspect of the invention in a light source device the following components are connected to one another:
a discharge lamp (Ld) in which a pair of main discharge electrodes (E
1
, E
2
) are located opposite to the discharge space (
12
) and moreover an auxiliary electrode (Et) is arranged such that it does not come into contact with the main discharge space (
12
);
a feed circuit (Bx) for supplying a discharge current to the main discharge electrodes (E
1
, E
2
); and
a starter (Ue) which produces a high voltage between one of the electrodes (E
1
, E
2
) for the main discharge and the auxiliary electrode (Et),
an object is achieved in that during the interval during which the starter (Ue) produces a high voltage, a high voltage is also applied at least during part of this interval to the main discharge electrodes (E
1
, E
2
).
The object is achieved in a second aspect of the invention in that in the above described invention the high voltage which is produced by the starter (Ue) and which is applied at least partially overlapping in time to the main discharge electrodes (E
1
, E
2
) is at least 2.5 times as high as the glow discharge
Okamoto Masashi
Takaya Izumi
Yamashita Takashi
Nixon & Peabody LLP
Philogene Haissa
Safran David S.
Ushiodenki Kabushiki Kaisha
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