Electric lamp and discharge devices: systems – Automatic substitution of the load device or electrode
Reexamination Certificate
2001-07-31
2003-02-25
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Automatic substitution of the load device or electrode
C315S074000, C315S307000
Reexamination Certificate
active
06525479
ABSTRACT:
The invention relates to a method and ballast for operating a lamp fitted with a fluorescent tube.
E 0 889 675 A1 discloses two ballasts with which several different types of fluorescent tubes can be operated under optimised operating conditions. However, the degree of optmisation of the operating conditions of a fluorescent tube that can be achieved with these ballasts leaves much to be desired.
One of the ballasts pursuant to EP 0 889 675 A1 provides for a preheating phase of the electrodes. It is a ballast for hot-start fluorescent tubes. With a ballast of this kind, the electrodes projecting into the interior of the tube at the ends of the discharge tube of the fluorescent tube are preheated. The electrodes, which are provided with an emitter material, emit ions in this process, causing the gas contained in the discharge tube to become electrically conductive. Only after this preheating phase is the so-called discharge path of the fluorescent tube ignited. This procedure spares the electrodes. The electrode resistance of the fluorescent tube that occurs is measured during the preheating phase, in order to draw an indirect conclusion as to the electrode temperature and perform gentle preheating.
Moreover, according to EP 0 889 675 A1, conclusions as to he type of fluorescent tube are said to be drawn with the aid of the electrode resistance measured. The fluorescent tube is initially supplied with a low current and the electrode temperature is measured indirectly. If the initial current is insufficient to heat the electrodes to an expected temperature, the current is increased in steps, until the electrode resistance or the expected electrode temperature is reached. However, as there are different types of lamps that have the same or very similar electrode resistance values at operating temperature, the electrode resistance is not a definitive criterion for distinguishing between lamp types. When using the known ballast, optimum operating conditions can only be set if the lamp types to be recognised have substantially different electrode resistances.
In another ballast known from EP 0 889 675 A1, the simple method of measuring the lamp voltage is applied in order to determine the type of fluorescent tube, rather than the more complex measurement of the electrode resistance. As the indirect measurement of the temperature via the electrode resistance is eliminated, this design falls back on the sample method of measuring the lamp voltage. Owing to the absence of optimised preheating, the electrodes of the fluorescent tube are subject to elevated wear when using this ballast. Furthermore, unequivocal distinction between different lamp types is again impossible if they have identical or very similar lamp voltages. Likewise, optimum operating conditions can only be set with this ballast if the lamp types to be recognised have markedly different lamp voltages.
The object of the invention is therefore to propose a simple method, and a ballast for implementing the method, by means of which a large number of commercially available types of fluorescent tubes can be operated with a higher degree of optimisation.
According to the invention, the object is solved by a method for operating a lamp fitted with a fluorescent tube, where the operating data of certain recognisable lamp types, i.e. at least the rated lamp voltage, the rated lamp current and the preheating currents and preheating times for preheating the electrodes are stored in a register, where the preheating currents are allocated to predefined electrode resistance ranges, the electrode resistance is measured during a preheating phase, the preheating current allocated to the measured electrode resistance and the allocated preheating time are set, the fluorescent tube is operated with a dimming current of known intensity for a predetermined time during a starting phase following on from the preheating phase, the prevailing lamp voltage of the fluorescent tube is measured after the starting phase, the register is then searched for the rated lamp voltage that comes closest to the measured lamp voltage of the fluorescent tube and the operating data required for operation of the fluorescent tube and allocated to the measured lamp voltage by the register are then set.
The recognition of the lamp type in the present invention is based on the principle of lamp voltage measurement during the starting phase of the fluorescent tube. However, the electrode resistance is also known, having been determined during the preceding preheating phase, thus providing another selection criterion for accurate determination of the lamp type. Thus, the method according to the invention not only provides electrode-sparing hot-starting of the fluorescent tube, but also permits accurate determination of the lamp type.
The term “operating data” is not taken only to mean the parameters required directly for operation of the fluorescent tube. It is also possible to store operating data, such as maximum lamp voltages and currents, electrode resistances and temperatures, that occur under abnormal operating conditions, for instance in order to bring about a safety shutdown, if appropriate.
To be able to understand the invention, it must be pointed out that the register can be used to store operating data, such as the rated lamp voltage and the rated lamp current, in direct form or, alternatively, in the form of other values that are linked to the operating data by way of correlation.
The invention also includes the option of altering and setting operating data of the fluorescent tube directly or of setting them indirectly via variables naturally linked to them. For example, the dimming current and the lamp current can be set by altering the frequency of the alternating current applied to the fluorescent tube in operation.
The term “short-term” operation is intended to mean a predefined operating period amounting to between a few seconds and several minutes.
The dimming current set at the beginning of the starting phase is equal to the lowest rated lamp current stored in the register, or is greater than this. If it corresponds to the lowest of the stored rated lamp currents, a fluorescent tube with a low rated lamp current cannot be overloaded, even after long-term operation under these conditions. However, as the starting phase lasts only a few seconds to minutes even fluorescent tubes whose rated lamp current is lower than the dimming current will not fail.
Favourably, an optimised dimming current is set during the start phase whose current intensity is sufficient for the operation of a fluorescent tube whose rated lamp current is greater than the optmised dimming current, and which does not destroy a fluorescent tube whose rated lamp current is lower than the optimised dimming current.
For lamp types with rated lamp currents higher than the optimised dimming current, the optimised dimming current supplies enough energy to generate sufficient luminous intensity. A dimmed setting lasting a few seconds to several minutes is acceptable, as sufficient brightness is already achieved.
For simplicity, the lowest preheating current stored in the register is set at the start of the first stage of the preheating phase, which is divided into several stages. After the first stage of the preheating phase, a first YES/NO query checks whether the electrode resistance falls within one of the predefined electrode resistance ranges. In the event of a YES decision, a further stage of the preheating phase as triggered, during which the preheating current of the previous stage is retained and the starting phase subsequently initiated. A NO decision triggers a further stage of the preheating phase where the next higher preheating current stored in the register is set at the beginning of this stage. After a predefined time, either the starting phase is initiated or a further YES/NO query is performed, followed by the same process steps as after the first YES/NO query.
For simplicity, the number of YES/NO queries is predetermined and can be defined for the required ballast either i
Keggenhoff Ralf
Mertens Ferdinand
Brooks & Kushman P.C.
Trilux-Lenze GmbH & Co. KG
Vu Jimmy T.
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