Electric lamp and discharge devices: systems – Pulsating or a.c. supply – Discharge control discharge device load
Reexamination Certificate
2002-07-10
2004-02-03
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Pulsating or a.c. supply
Discharge control discharge device load
C315S219000, C315S282000, C315S291000
Reexamination Certificate
active
06686704
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a lamp lighting apparatus and a projector which uses the lamp lighting apparatus, and more particularly to a lamp lighting apparatus which uses a metal halide lamp or the like and a projector which uses the lamp lighting apparatus.
A lamp lighting apparatus generates a high voltage for lighting and applies the high voltage to both of electrodes of a lamp to cause glow discharge to be produced by a glow switch or the like provided in the lamp. Then, the glow discharge changes into arc discharge in an arc tube to light the lamp.
A typical lamp lighting apparatus shown in
FIG. 8
includes an active filter, for example. Referring to
FIG. 8
, the lamp lighting apparatus comprises a down converter
52
which receives a DC voltage E
1
normally of approximately 300 to 400 Vdc from a DC power supply and converts the DC voltage E
1
once into a DC voltage V
1
of approximately 50 to 100 Vdc, a controller
53
which inputs a control signal C
1
obtained by comparing a detection power W
1
from a power detection section
59
hereinafter described and a reference power W
2
with each other to the down converter
52
to control the DC voltage V
1
to keep a fixed power, a full bridge
54
which converts the DC voltage V
1
of approximately 50 to 100 Vdc into an AC current having a frequency of approximately 90 to 200 Hz which is necessary to keep discharge of a lamp
62
and supplies the resulting AC current to the lamp
62
, a controller
55
which sets a reference frequency fs of a drive signal for driving the full bridge
54
and controls on/off of the drive signal, an igniter
56
including an ignition outputting transformer T
2
which generates a high voltage of 5 to 20 kV for lighting of the lamp
62
and transmits an AC voltage V
2
of approximately 50 to 100 V for keeping of arc discharge, a voltage control section
60
for controlling the igniter
56
, a voltage detection section
57
which detects a voltage value of the AC voltage V
2
to be supplied from the full bridge
54
to the igniter
56
, a current detection section
59
which detects a current value of AC current I
2
to be supplied from the full bridge
54
to the igniter
56
, a power detection section
58
which detects a detection power W
1
from the voltage detected by the voltage detection section
57
and the current detected by the current detection section
58
, and a connector
61
for establishing a connection to the lamp
62
. It is to be noted that, when the present lamp lighting apparatus is applied to a projector, the controller
53
can be used also as a system controller, and if a power switch not shown is depressed and the controller
53
discriminates a power supply off state, then the controller
53
, for example, opens a contact of a relay to switch off supply of the DC voltage E
1
and enters a standby state. Then, if the power switch is depressed again and the controller
53
discriminates a power supply on state, then the present lamp lighting apparatus enters a normal operation mode and closes the contact of the relay to supply the DC voltage E
1
.
The voltage control section
60
performs control for producing a high voltage of 5 to 20 kV upon lighting of the lamp
62
. An exemplary configuration of the voltage control section
60
is shown in FIG.
9
. Referring to
FIG. 9
, the voltage control section
60
shown includes a resister R
31
and a capacitor C
31
which form a series circuit to which a DC power supply DC of 300 Vdc is supplied, a boosting transformer T
31
connected to a node between the resister R
31
and the capacitor C
31
through a switching element H
31
such as a SIDAC, a diode D
31
and a discharging gap element H
32
which are connected to a secondary winding N
2
of the boosting transformer T
31
and form a series circuit, and a capacitor C
32
which is connected to a node between the diode D
31
and the discharging gap element H
32
and which forms a parallel circuit together with the secondary winding N
2
of the boosting transformer T
31
. The output side of the discharging gap element H
32
is connected to a terminal T
5
, and the output side of the secondary winding N
2
of the boosting transformer T
31
and the capacitor C
32
which form the parallel circuit is connected to a terminal T
6
.
Referring back to
FIG. 8
, the full bridge
54
is formed from a full bridge including, for example, field effect transistors (FETs) or the like. The gates of the FETs are controlled between on and off based on the reference frequency fs set by the controller
55
.
Consequently, the full bridge
54
can convert the DC voltage V
1
into an AC current having a frequency of approximately 90 to 200 Hz and can supply an AC current I
2
necessary to keep lighting of the lamp
62
to the lamp
62
through the igniter
56
and the connector
61
which has a Lo terminal and a Hi terminal.
Referring to
FIGS. 8 and 9
, in the voltage control section
60
having the connection scheme described above, a voltage of 300 Vdc of the DC power supply first charges the capacitor C
31
through the resister R
31
. Then, if the charging voltage of the capacitor C
31
reaches, for example, 200 V, then the switching device H
31
enters into a conducting state, and as a result, an excitation current flows to the primary side of the boosting transformer T
31
while the capacitor C
31
discharges. The charging voltage of the capacitor C
31
drops as a result of the discharge just described, and finally, the switching device H
31
enters into a non-conducting state and the excitation current does not flow to the boosting transformer T
31
any more. Then, the voltage from the DC power supply charges the capacitor C
31
again through the resister R
31
.
By the repeating cycle described above, a pulse voltage raised to 2 to 3 kV can be repetitively obtained on the secondary side of the boosting transformer T
31
.
The pulse voltage repetitively charges the capacitor C
32
through the diode D
31
on the secondary side of the boosting transformer T
31
, and as a result, a charging voltage of the capacitor C
32
gradually rises. If this charging voltage reaches, for example, 1 kV, then the discharging gap element H
32
starts discharge and an excitation current flows to the primary side of the outputting transformer T
2
of the igniter
56
while the capacitor C
32
discharges. The charging voltage drops as the capacitor C
32
discharges, and finally, the discharging gap element H
32
stops the discharge and the excitation current does not flow to the outputting transformer T
2
. Then, the raised pulse voltage charges the capacitor C
32
again through the diode D
31
.
By the repeating cycle described above, a pulse voltage raised to, for example, 5 kV can be obtained on the secondary side of the outputting transformer T
2
and the lamp
62
is lit.
The lamp
62
may be, for example, a discharge lamp
11
such as a metal halide lamp shown in FIG.
10
. Referring to
FIG. 10
, the discharge lamp
11
has a pair of electrodes
26
and
27
of the same structure arranged in a spaced relationship from each other in a translucent airtight vessel
25
formed from, for example, a heat resisting glass material so that they may have a predetermined electrode space distance L therebetween. The electrodes
26
and
27
are driven with an AC current.
The electrodes
26
and
27
are connected to metal conductors
30
and
31
sealed in seal sections
28
and
29
formed at both ends of the airtight vessel
25
. The metal conductor
30
is connected to a terminal Hi of a connector
17
and the other metal conductor
31
is connected to another terminal Lo. Further, the seal section
28
of the airtight vessel
25
is fixed to a central portion of a reflector
32
having a hemispherical shape.
Then, a discharging medium which includes, for example, rare gas, cesium, rare earth metal, and halogen in addition to mercury and wherein the encapsulated amount of cesium is within a predetermined range is encapsulated in the airtight vessel
25
. Thus, since steam of the several k
Maioli Jay H.
Sony Corporation
Vo Tuyet T.
Wong Don
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