Electric lamp and discharge devices: systems – Current and/or voltage regulation – Automatic regulation
Reexamination Certificate
2001-05-24
2002-11-05
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Current and/or voltage regulation
Automatic regulation
C315S225000, C315S226000, C315SDIG007
Reexamination Certificate
active
06476568
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gas discharge lamp lighting device used as a light source such as a lamp for use with a vehicle display of a projection type.
2. Description of the Prior Art
FIG. 17
is a schematic circuit diagram showing the structure of a prior art gas discharge lamp lighting device as disclosed in Japanese patent application publication (TOKKAIHEI) No. 12-82592. In
FIG. 17
, reference numeral
1
denotes a direct-current power supply such as a battery, and numeral
2
denotes a DC/DC converter for adjusting electric power supplied from the direct-current power supply
1
and for outputting the adjusted electric power supply. The DC/DC converter
2
includes a transformer
2
a
, an FET (field effect transistor)
2
a
, and a diode
2
c
. Reference numeral
3
denotes a ground, numeral
4
denotes a shunt resistor used for detection of an electric current IL flowing through a gas discharge lamp
12
, and numeral
50
denotes an H-type full bridge circuit (referred to as “H-bridge” hereafter) that consists of a plurality of FETs
50
a
to
50
d
, and that converts the DC power adjusted by the DC/DC converter
2
to AC power. The gas discharge lamp
12
is driven by the AC power to which the DC power is converted by the H-bridge
50
.
Furthermore, reference numeral
13
denotes an interface circuit (referred to as I/F from here on) that accepts a lamp voltage VL from a cathode-side output of the DC/DC converter
2
, and that accepts a lamp electric current IL from an H-bridge side end of the shunt resistor
4
, and numeral
14
denotes a control circuit for controlling the FET
2
b
of the DC/DC converter
2
based on the lamp voltage VL and the lamp electric current IL, which are detected successively by way of the I/F
13
, and a predetermined circuit impedance so that the electric power supplied to the gas discharge lamp
12
reaches a predetermined value.
In operation, when causing the gas discharge lamp
12
to start to light, the DC/DC converter
2
adjusts the DC electric power supplied from the direct-current power supply
1
and outputs the adjusted. DC electric power, and the H-bridge
50
then converts the adjusted DC electric power from the DC/DC converter
2
to AC power so as to drive the lamp
12
. The lamp voltage VL detected at the cathode side of the output of the DC/DC converter
2
is raised up to −400V as shown in FIG.
18
. The gas discharge lamp
12
is made to light up after the lamp voltage VL is further increased up to about 20 kV at its peak, and, after that, the lamp is put in a stable lighting status at −90V. In the meanwhile, the DC/DC converter
2
is controlled by the control circuit
14
. The control circuit
14
controls the FET
2
b
of the DC/DC converter
2
based on the lamp voltage VL and the lamp electric current IL, which are detected successively by way of the I/F
13
, so that the electric power supplied to the lamp
12
reaches a predetermined value.
After the lamp
12
is made to light up, the control circuit
14
applies the AC voltage to the lamp
12
by alternately Switching between a switching mode of turning on the FETs
50
a
and
50
d
of the H-bridge
50
and turning off the other FETs
50
b
and
50
c
of the H-bridge
50
, and another switching mode of turning off the FETs
50
a
and
50
d
of the H-bridge
50
and turning on the other FETs
50
b
and
50
c
of the H-bridge
50
.
By the way, it is preferable that the electric power supplied to the lamp
12
put in the stable lighting status is 34 watts. The control circuit
14
does not simply control the electric power supplied to the lamp
12
based on only the lamp voltage VL and the lamp electric current IL so that it reaches 34 watts. By estimating the on-resistance of each of the FETs
50
a
to
50
d
of the H-bridge
50
in advance so as to make an estimate of the circuit impedance, the control circuit
14
performs the control operation based on the lamp voltage VL, the lamp electric current IL, and the circuit impedance estimated beforehand so that the electric power supplied to the lamp
12
reaches 34 watts even if there is a power loss due to the on-resistance of each of the FETs
50
a
to
50
d
of the H-bridge
50
.
In the prior art gas discharge lamp lighting device constructed as above, since a high voltage of 400V or less is applied to the H-bridge
50
, each of the FETs which constitute the H-bridge
50
has to withstand a high voltage of 400V. The unit price of FETs having such a high voltage breakdown is high, and the above-mentioned H-bridge of the prior art gas discharge lamp lighting device uses as much as four FETs with such a high unit price. The inverter circuit structure, by using the H-bridge as mentioned above, therefore obstructs downsizing of the gas discharge lamp lighting device and a reduction in the cost of the device. A decrease in the number of FETs included in the H-bridge
50
and a reduction in the voltage applied to the H-bridge are therefore challenges for the prior art gas discharge lamp lighting device.
On the other hand, Japanese patent application publication (TOKKAIHEI) No. 8-195288 discloses another prior art gas discharge lamp lighting device for driving a gas discharge lamp by applying AC power to the lamp using two semiconductor switching elements (transistors) and a capacitor without the use of an H-bridge like the above-mentioned H-bridge of FIG.
18
.
FIG. 19
is a schematic circuit diagram showing the structure of the other prior art gas discharge lamp lighting device. In
FIG. 19
, reference numeral
61
denotes a gas discharge lamp, numeral
62
denotes a lighting device, numeral
63
denotes a battery, numeral
64
denotes a transistor, numeral
65
denotes a diode, numeral
66
denotes a choke coil, numeral
67
denotes a capacitor, numeral
68
denotes a control circuit, numeral
69
denotes a step-down chopper circuit, numeral
70
denotes a direct-current power supply, numerals
71
and
72
denote transistors, numeral
73
denotes a capacitor, numeral
74
denotes an inverter circuit, numeral
75
denotes an inductor, numeral
76
denotes a start circuit, numeral
77
denotes a lamp voltage detector, numeral
78
denotes a driving circuit, numeral
79
denotes a control unit, numeral
80
denotes a lamp electric current detector, and numeral
81
denotes a detector for detecting electric power applied to the lamp
61
.
In operation, electric power from the battery
63
within the direct-current power supply
70
is adjusted by the step-down chopper circuit
69
, and is furnished. to the inverter circuit
74
. The transistor
71
is turned on and the transistor
72
is turned off in the inverter circuit
74
. As a result, an electric current flows from the step-down chopper circuit
69
into the discharge lamp
61
by way of the capacitor
73
, and the electric current is then supplied to the gas discharge lamp
61
while the capacitor
73
is charged up. By turning off the transistor
71
and turning on the transistor
72
, the electric charge stored in the capacitor
73
is then made to flow to the gas discharge lamp
61
as an electric current flowing in the opposite direction to that of the above-mentioned electric current flowing from the step-down chopper circuit
69
to the gas discharge lamp
61
. Thus, by alternately switching between a state in which the capacitor
73
is charged up with the supply of the electric current from the transistor
71
to the gas discharge lamp
61
and another state in which the electric current is supplied from the capacitor
73
to the lamp
61
by turning off the transistor
71
and turning on the transistor
72
, an AC current is made to flow into the gas discharge lamp
61
.
A problem with the prior art gas discharge lamp lighting device is that when switched into the phase in which the electric current is made to flow from the capacitor
73
to the gas discharge lamp
61
and the polarity of the current flowing through the gas discharge lamp is then reversed, the AC gas discharge can
Iwata Akihiko
Kinoshita Hidehiko
Urakabe Takahiro
Leydig , Voit & Mayer, Ltd.
Tran Thuy Vinh
LandOfFree
Gas discharge lamp lighting device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Gas discharge lamp lighting device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gas discharge lamp lighting device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2980457