Electric lamp and discharge devices: systems – Condenser in the supply circuit – Inductance in the condenser circuit
Reexamination Certificate
2002-09-17
2004-06-08
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Condenser in the supply circuit
Inductance in the condenser circuit
C315S224000, C315S2090SC, C315S291000, C315S307000
Reexamination Certificate
active
06747418
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a device for preheating the two coil electrodes of a fluorescent lamp comprising an AC voltage source, a resonance capacitor, which is arranged serially between the two coil electrodes, and a first inductance, which is coupled between the AC voltage source and one of the two coil electrodes. It additionally relates to a method for preheating the two coil electrodes of a fluorescent lamp.
BACKGROUND ART
In order to explain the problems on which the invention is based,
FIG. 1
illustrates a preheating device of the generic type, known from the prior art. An AC voltage source
10
is formed from a DC voltage source U, two switches S
1
, S
2
and a coupling capacitor C
K
. The two coils W
1
, W
2
of a fluorescent lamp La, in particular a low-pressure fluorescent lamp, are connected in series into the output circuit of an electronic ballast (not illustrated) which comprises an inductance L
1
and also a resonance capacitor C
R
. This circuit provides a very simple method of providing heating of the coils W
1
, W
2
before the ignition of the lamp La.
In the case of this circuit, preheating current I
V
and preheating voltage U
V
are related to the inductance L
1
and the resonance capacitor C
R
as follows:
L1
C
R
-
U
v
I
v
Accordingly, the voltage U
v
across the lamp La during preheating and the preheating current I
v
cannot be chosen independently of one another given predetermined values for the inductance L
1
and the resonance capacitor C
R
. In the case of unfavorable lamp data or a lack of degrees of freedom in the design of the electrical ballast, it is possible, therefore, that adequate coil preheating will not be able to be obtained at the maximum permissible voltage U
v
across the lamp La.
DISCLOSURE OF THE INVENTION
The object of the present invention therefore consists in enabling preheating which suffices for the ignition of the lamp even in the case of unfavorable lamp data or a lack of degrees of freedom in the design of the electrical ballast.
This object is achieved by virtue of the fact that the device of the generic type furthermore comprises a second inductance, which is connected to a point between the AC voltage source and the coil electrode coupled thereto, the second inductance being coupled to the first inductance in such a way that a current flow through the second inductance leads to a reduction of the magnetization of the first inductance.
This measure makes it possible to realize intensified coil preheating which manages with a minimum of additional components. The current through the first inductance L
1
, the so-called lamp inductor, is increased by connecting the second inductance, which is designed in particular as an auxiliary winding fitted on the lamp inductor, in a polarity such that the current flowing therein reduces the magnetization of the first inductance L
1
, that is to say effectively reduces the effective inductance. In accordance with the above formula, a reduction of the effective inductance corresponds to an increase in the preheating current. After preheating, the second inductance is switched out.
By virtue of the present invention, the fixed coupling between the lamp inductor L
1
and the resonance capacitor C
R
is abandoned, so that a higher preheating current can be realized during preheating, on account of the smaller effective inductance, without the permissible maximum lamp voltage being exceeded.
In accordance with a second aspect of the present invention, the above object is also achieved by means of a method for preheating the two coil electrodes of a fluorescent lamp, using a preheating device having an AC voltage source, a resonance capacitor, which is arranged serially between the two coil electrodes, a first inductance, which is coupled between the AC voltage source and one of the two coil electrodes, and a second inductance, which is connected to a point between the AC voltage source and the coil electrode coupled thereto, which comprises the following steps:
firstly, the second inductance is coupled to the first inductance in such a way that a current flow through the second inductance leads to a reduction of the magnetization of the first inductance. Afterward, a current flow through the second inductance is effected during preheating and a current flow through the second inductance is prevented or the coupling between the first and second inductances is interrupted after preheating.
A particularly preferred embodiment comprises a control device by which the current flow through the second inductance or the coupling between the first and second inductances can be controlled. This control device is preferably realized as a switch arranged in series with he second inductance, or a PTC thermistor. For the case where the control device is realized as a switch, it is possible to provide a drive device which closes the switch during preheating and otherwise opens it. For the case where the control device is realized as a PTC thermistor, this driving is unnecessary since said PTC thermistor automatically undergoes transition to the high-impedance state at a specific temperature and thereby prevents a current flow through the second inductance.
The other connection of the second inductance is preferably connected to ground.
REFERENCES:
patent: 5122712 (1992-06-01), Hirschmann
patent: 5493181 (1996-02-01), Shackle et al.
patent: 5825136 (1998-10-01), Rudolph
patent: 5854538 (1998-12-01), Krummel
patent: 5880562 (1999-03-01), Nakagawa et al.
patent: 6194840 (2001-02-01), Chang
patent: 6252357 (2001-06-01), Tanaka et al.
patent: 6281636 (2001-08-01), Okutsu et al.
patent: 6683418 (2004-01-01), Shoji et al.
patent: 0358502 (1990-03-01), None
patent: 0689373 (1995-12-01), None
Patent-Treuhand-Gesellschaft fuer elektrische Gluehlampen mbH
Vu Jimmy T.
Wong Don
LandOfFree
Device and method for preheating the coil electrodes of a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device and method for preheating the coil electrodes of a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device and method for preheating the coil electrodes of a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3359156