Electric lamp and discharge devices: systems – Current and/or voltage regulation
Reexamination Certificate
1999-10-13
2001-02-20
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Current and/or voltage regulation
C315S2090SC, C315S048000, C315S245000, C315S082000
Reexamination Certificate
active
06191540
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to power supply systems for automobile vehicle headlight discharge lamps.
It has recently been proposed to use a square-wave alternating current at a frequency in the order of 200 Hz to 1 kHz to power automobile vehicle headlight discharge lamps. Compared with direct current operation, alternating current operation considerably increases the service life of the lamp.
BRIEF SUMMARY OF THE INVENTION
As shown in
FIGS. 1 and 2
, systems providing a power supply of this type (referred to as “ballast circuits” by the skilled person) generally include a DC/DC converter
1
powered at the battery voltage of the vehicle (12 V) and a DC/AC converter
2
between the discharge lamp
3
of the headlight and a capacitor C
0
at the output of the DC/DC converter
1
. A module
4
which generates a high-voltage pulse for igniting the lamp
3
is connected in series with the lamp to the output of the DC/AC converter
2
.
The DC/AC converter
2
usually comprises four switches
5
configured as an H-bridge and controlled by control electronics (not shown).
The igniting module can comprise a resistor and a capacitor in series with the discharge lamp, for example. A module of this type is described in DE-U-91 11890, for example.
FIG. 3
is a graph showing the supply voltage of the discharge lamp
3
as a function of time during the igniting stage. The graph shows that the voltage at the terminals of the lamp
3
is first raised to a breakdown value (in the order of 12 kV to 25 kV, depending on the lamp). After this igniting pulse, the arc voltage of the lamp
3
falls over a period of a few microseconds from 400 V to less than 120 V (as low as 30 V in some cases).
The igniting stage is then followed by a stage in which the power rises and which precedes the nominal alternating current operating stage (in which the maximum voltages—imposed by the lamp—are in the order of 65 V to 115 V).
During the period of the igniting stage in which the arc voltage falls, the power supply system must supply sufficient power to the lamp
3
to maintain the current in said lamp
3
, at the voltages imposed by the lamp
3
, as otherwise the arc is extinguished and the lamp
3
must be ignited again.
At present, two techniques are mainly used.
In one of these techniques (FIG.
1
), the capacitor C
0
and the converter
1
supply power direct to the discharge lamp
3
.
However, this requires the converter
1
, the capacitor C
0
and the H-bridge to be rated to withstand voltages of 500 V and above, which gives rise to problems of overall size in particular.
In the other technique (FIG.
2
), a circuit between the H-bridge
2
and the converter
1
with its capacitor C
0
includes a second capacitor C
1
in series with a short-circuit comprising a resistor R
1
shunting a resistor R
2
and a diode D
2
and which is charged to a voltage higher than the output voltage of the converter
1
.
It is this capacitor C
1
which powers the discharge lamp
3
throughout the part of the igniting stage in which the lamp voltage falls.
However, that solution requires the addition of bulky components.
Also, the H-bridge must again be rated to withstand voltages of 500 V and above.
The object of the invention is therefore to propose a discharge lamp power supply system that does not have the drawbacks of the aforementioned circuits and which in particular enables the components of the converters on the upstream side of the discharge lamp to be rated to withstand voltages of 200 V and below rather than voltages of 500 V.
To this end, the invention provides a power supply system for an automobile vehicle headlight discharge lamp, the system including a DC/DC converter with a capacitor at its output, a DC/AC converter powered by the voltage across said capacitor, and a module for generating a high-voltage breakdown pulse for connection in series with said discharge lamp to the output of the DC/AC converter, characterised in that it further includes a module for heating the electrodes of the discharge lamp for connection in series with the discharge lamp and the high-voltage pulse generator module and adapted to deliver a voltage which, at the terminals of said discharge lamp, is added to the voltage across the capacitor at the output of the DC/DC converter, and which decreases after the high-voltage breakdown pulse.
A system of the above kind advantageously has the following additional features, individually or in all technically feasible combinations:
the electrode-heating module includes means for short-circuiting it if the arc voltage of the lamp falls below a given threshold,
said module includes a capacitor and means for charging said capacitor,
the capacitor is connected in series with the module for generating a high-voltage pulse,
the capacitor is connected in parallel with the primary of a transformer whose secondary is connected in series with the module for generating a high-voltage pulse,
the system includes a switch for short-circuiting the capacitor of the electrode-heating module,
the system includes a switch controlling discharging of the capacitor of the electrode-heating module into the primary of the transformer of said module,
the DC/AC converter is an H-bridge including a capacitor half-bridge and a switch half-bridge,
the electrode-heating module is included in the module for generating a high-voltage pulse.
The invention also includes an automobile vehicle headlight including a reflector, at least one discharge lamp disposed at the back of said reflector and a power supply system for said lamp, characterised in that said system is a power supply system of the aforementioned type.
REFERENCES:
patent: 4431945 (1984-02-01), Kawashima et al.
patent: 5198727 (1993-03-01), Allen et al.
patent: 5343125 (1994-08-01), Bernitz et al.
patent: 5355055 (1994-10-01), Tary
patent: 91 11 890 (1991-01-01), None
patent: 0 485 866 (1992-05-01), None
patent: 0 684 755 (1995-11-01), None
Herzberger Erick
Nicolai Jean-Marc
Morgan & Finnegan , LLP
Philogene Haissa
Valeo Vision
LandOfFree
Devices for powering a motor vehicle headlight discharge lamp does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Devices for powering a motor vehicle headlight discharge lamp, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Devices for powering a motor vehicle headlight discharge lamp will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2564374