Electric lamp and discharge devices: systems – Pulsating or a.c. supply – Transformer in the supply circuit
Reexamination Certificate
2001-08-22
2003-09-16
Le, Hoanganh (Department: 2821)
Electric lamp and discharge devices: systems
Pulsating or a.c. supply
Transformer in the supply circuit
C315S2090SC, C315S224000, C315S219000
Reexamination Certificate
active
06621237
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to gas-discharge lamps lighting apparatus and, more particularly, to an gas-discharge lamp lighting apparatus for a vehicle or a display of the projection type.
FIG. 17
shows a construction of an gas-discharge lamp lighting apparatus according to the related art disclosed in the Japanese Laid-Open Patent Application 5-166592.
FIG. 18
shows a pulse generation circuit of an igniter circuit of the related-art gas-discharge lamp lighting apparatus shown in the above-mentioned Application. Referring to
FIGS. 17 and 18
, reference numeral
51
indicates an inverter circuit,
52
indicates an igniter circuit, and
52
a
indicates a pulse generation circuit.
The igniter circuit
52
comprises a pulse generation circuit
52
a
which generates a pulse, and a pulse transformer PT by which the output of this pulse generation circuit
52
a
is stepped up. A secondary winding L
2
of the pulse transformer PT is connected to a high-pressure gas-discharge lamp Lp in series, and the series circuit composed of the gas-discharge lamp Lp and the secondary winding L
2
is connected with both ends of a capacitor C
2
. The pulse generation circuit
52
a
shown in
FIG. 18
comprises a bi-directional switching element S
4
implemented, for example, by a triac, connected to a primary winding L
3
of the pulse transformer PT, a trigger element S
3
triggering the switching element S
4
, a trigger circuit causing a breakover of the trigger element S
3
and comprising a resistor R
2
and a capacitor C
4
, and a charging circuit comprising a resistor R
1
and a capacitor C
3
and supplying a dc current to the series circuit composed of the primary winding L
3
of the pulse transformer PT and the switching element S
4
. An AC power is supplied to the pulse circuit
52
a
via a switch SW. Only when the high-pressure gas-discharge lamp Lp is started, the switch SW supplies AC power to the pulse generation circuit
52
a.
A description will now be given of the operation according to the related art.
In the pulse generation circuit
52
a
shown in
FIG. 18
, the capacitor C
3
is charged via the resistor R
1
when the switch SW is turned on, and the capacitor C
4
is charged via the primary winding L
3
of the pulse transformer PT and the resistor R
2
. When the voltage across the capacitor C
4
reaches a breakover voltage of the trigger element S
3
, the electric charge of the capacitor C
4
is discharged via the trigger element S
3
. As a result, a gate current is supplied to the switching element S
4
for conduction. When the switching element S
4
is turned on, the electric charge built up in the capacitor C
3
is discharged via the primary winding L
3
and the switching element S
4
. A high-voltage pulse corresponding to the turn ratio with respect to the primary winding L
3
is generated in the secondary winding L
2
of the pulse transformer PT. This high-voltage pulse is applied to both ends of the high-pressure gas-discharge lamp Lp via the capacitor C
2
. The high-voltage pulse is applied to the high-pressure gas-discharge lamp Lp so as to be superimposed on the output of the inverter circuit
51
. The high-pressure gas-discharge lamp Lp is ignited by this high-voltage pulse.
Once the high-pressure gas-discharge lamp Lp is started, the switch SW is turned off so that the igniter circuit
52
stops applying the high-voltage pulse to the high-pressure gas-discharge lamp Lp. The output of the inverter circuit
51
keeps the high-pressure gas-discharge lamp Lp lighted in a stable manner.
As described above, the pulse generation circuit, constituting the igniter circuit together with the pulse transformer, comprises the bi-directional switching element, the trigger element that triggers the switching element, the trigger circuit causing a breakover of the trigger element and composed of the resistor R
2
and the capacitor C
4
, and the charging circuit composed of the resistor R
1
and the capacitor C
3
and supplying a dc current to the series circuit composed of the primary winding of the pulse transformer and the switching element. Accordingly, the number of components constructing the igniter circuit is relatively large. As a result of the large number of components, the cost of the gas discharge lamp lighting apparatus is relatively high and the scale of the device is relatively large.
SUMMARY OF THE INVENTION
Accordingly, a general object of the present invention is to provide an gas-discharge lamp lighting apparatus in which the aforementioned problems are eliminated.
Another and more specific object is to provide a small-scale, low-cost gas-discharge lamp lighting apparatus by reducing the number of components constituting an igniter circuit for generating a high-voltage pulse at the discharge starting.
The aforementioned objects can be achieved by an gas-discharge lamp lighting apparatus comprising: power conditioning means regulating a power supplied from a power source, outputting voltages with mutually different levels from two output terminals, and provided with a first capacitor coupled between the two output terminals; a switching circuit unit coupled between the output terminals of the power conditioning means and comprising at least one switching element; and a pulse transformer generating a high-voltage pulse, placed in a circuit connecting the output terminals of the switching circuit unit and an gas-discharge lamp, wherein a first terminal of a primary winding of the pulse transformer is connected to a first output terminal of the power conditioning means via a first output terminal of the switching circuit unit, and a second terminal of the primary winding is directly, or via the switching circuit unit, connected to a second output terminal of the power conditioning means.
The switching circuit unit may comprise one switching element; the first terminal of the primary winding of the pulse transformer may be connected to the second output terminal of the power conditioning means via the one switching element, and the second terminal of the primary winding may be connected to the second output terminal of the power conditioning means, wherein a second capacitor is provided in a circuit connecting the pulse transformer, the gas-discharge lamp and the first output terminal of the power conditioning means, the second capacitor being connected to the gas-discharge lamp in series.
Another switching element may be provided in parallel with the second capacitor.
The switching circuit unit may comprise first and second switching elements, the first terminal of the primary winding of the pulse transformer being connected to the first output terminal of the power conditioning means via the first switching element, and the second terminal of the primary winding being connected to the second output terminal of the power conditioning means via the second switching element, and a second capacitor may be provided in a circuit connecting the pulse transformer, the gas-discharge lamp and the first output terminal of the power conditioning means, the second capacitor being connected to the gas-discharge lamp in series.
A third switching element may be provided in parallel with the second capacitor.
A third capacitor may be connected between a node, connected to the second switching element and the primary winding, and the first output terminal of the power conditioning means.
A parallel circuit formed of a diode and a resistor may be connected between the third capacitor and the node.
A current may be run through the primary winding of the pulse transformer before supplying a current from the second capacitor to the gas-discharge lamp so that a voltage between electrodes of the gas-discharge lamp is larger than a voltage maintained in the second capacitor, and the gas-discharge lamp may be ac driven by alternately performing a current feed from the power conditioning means and a current feed from the second capacitor.
The switching circuit unit may be a full-bridge inverter circuit comprising first through fourth switching elements t
Kinoshita Hidehiko
Urakabe Takahiro
Le Hoang-anh
Mitsubishi Denki & Kabushiki Kaisha
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