Electric lamp and discharge devices: systems – Surge generator or inductance in the supply circuit – Circuit interrupter in the inductance circuit
Reexamination Certificate
2000-05-17
2001-11-27
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Surge generator or inductance in the supply circuit
Circuit interrupter in the inductance circuit
C315S289000, C315S194000, C315S244000, C315S058000
Reexamination Certificate
active
06323604
ABSTRACT:
TECHNICAL FIELD
The invention relates to high-pressure and extra-high-pressure discharge lamps which are becoming increasingly widespread in all sectors of lighting engineering, because of their good luminous efficiency. Owing to their specific properties, they are mostly difficult to start and operate. This holds, in particular, for sodium high-pressure lamps with a relatively high xenon pressure. Because of their outstanding luminous efficiency, these lamps are particularly well suited for street lighting. In this case, they frequently replace existing systems with a substantially lower efficiency, for example mercury-vapor lamps. In addition, in this formulation of the problem, it is also necessary to solve the problem of power reduction (in conjunction with an identical luminous flux), the result of all this being a saving in energy.
The invention also relates to a method for starting and operating a discharge lamp. In particular, a circuit arrangement is described which permits the operation of a sodium high-pressure lamp with a high inert gas filling pressure (typically 2 atm xenon) and a low power output at a ballast inductor for high powers (this arrangement is known as retrofit or plug-in technology), the starting of the lamp being rendered substantially more difficult, in particular, because of the very high cold filling pressure.
PRIOR ART
So far, attempts have been made to solve the problem of the impeded starting of high-pressure discharge lamps (in particular in the case of the replacement of a mercury-vapor discharge lamp by a sodium high-pressure lamp) through, for example, special starting aids, through internal starters or through special starting gas mixtures. In the two first cases, however, the ballast inductor is fully loaded in the process with the starting voltage, while in the latter case the lighting properties of the lamp are impaired.
Adapting sodium high-pressure lamps to existing burning positions for mercury-vapor lamps as regards their electric data (for example magnitude of the inductor current) and lighting data (for example luminous flux) has not yet been satisfactorily solved with previous means.
Circuit arrangements which are particularly suitable for retrofitting applications are described, for example, in DE-A 31 48 821, EP-A 181 666 and EP-A 181 667 and EP 168 087. DE-A 31 48 821 describes, in particular, a circuit, based on a capacitor, for a high-pressure discharge lamp with an auxiliary starting electrode which provides an increased voltage between the two main electrodes. However, these circuits cannot be used to start lamps with a very high cold filling pressure. U.S. Pat. No. 3,732,460 describes a circuit for fast cold and warm starting with pulses of up to 20 kV. The circuit uses a capacitor connected in parallel with the electrodes, as a result of which the no-load voltage can be increased up to three times the value.
Furthermore, circuits with very wide (high-energy) pulses are known; they permit the starting and transfer of arc tubes with a very high cold filling pressure. However, this requires very large, voluminous starting inductors for rectified RF pulses (DE-A 34 26 491). Or a so-called internal starter, which briefly short-circuits the ballast inductor, generates a relatively wide starting pulse. A corresponding arrangement is to be found, for example, in U.S. Pat. No. 5,336,974 and U.S. Pat. No. 5,185,557. However, it is disadvantageous that the ballast inductor is loaded in this case with the entire starting voltage. This is damaging to most ballasts.
There is likewise a multiplicity of proposals with regard to the power reduction of lamps. The conventional technology is based on a phase-gating control such as is described, for example, in U.S. Pat. No. 3,925,705 and DE-A 34 38 003. An RC element is connected in parallel in both cases to a semiconductor switching element (for example a sidac or a diac-controlled triac). In order to avoid the replacement of an already existing ballast, use is made of a retrofit lamp in which a capacitor is arranged in parallel with the discharge vessel in the outer bulb (WO 96/21337 and EP 030 785). A disadvantage in this case is the difficulty of implementation and, in some circumstances, the complicated measures for following the radio-interference regulations.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a circuit arrangement which starts an electrode discharge lamp quickly and simply and requires few electronic components therefor. An additional object is to specify a method for operating such a lamp, and to specify a compact assembly of lamp and circuit arrangement.
The object has been achieved in accordance with the invention by developing a circuit arrangement in which a capacitor connected in parallel with the assigned lamp is charged up to a voltage (transfer voltage) higher than the required and previously exclusively targeted (customary) no-load voltage. The no-load voltage corresponds to the input voltage in the case of conventional ballasts. This voltage is made immediately available to the plasma after breakdown has occurred. The increased voltage is provided by means of at least one of the following measures: by means of the closing operation on a resonant circuit (preferred), by means of a resonant increase or by means of a combination of the two.
The power reduction is performed by means of a phase-gating control known in principle per se (see above). In this case, in order to maintain the maximum permissible radio-interference voltage the capacitor (transfer capacitor) connected in parallel with the lamp can be disconnected from the electrical circuit after starting of the lamp, thus preventing the periodic switching of a low-resistance source to a capacitor.
It has emerged that in the case of discharge lamps the voltage available after the first breakdown is crucial in some cases for the final transfer of the arc.
Discharge lamps with a very high filling pressure (for example sodium-vapor high-pressure lamps with a very high xenon cold filling pressure of typically 1 to 3 bar) can frequently be started only with difficulty, since a high starting voltage is required for the first breakdown, and the transfer proceeds only very hesitantly.
They require pulses with a very high voltage and power for starting and transfer. Moreover, a high transfer voltage favors successful transfer of the arc as early as after the first breakdown.
Surprisingly, it proved possible to find a simple circuit arrangement with the aid of which it was possible to start and operate even lamps which were very unwilling to start, the circuit outlay being very low, and therefore cost-effective and space-saving, with the result that the circuit can be accommodated at least partially in the base of the assigned lamp. Since the starting pulses can be kept relatively narrow (at least two to ten times narrower than in the abovementioned prior art) owing to the principle of a circuit as defined in the invention, there is no need for any voluminous inductors. The ballast inductor is not loaded with the starting voltage.
The invention is suitable, in particular, for so-called retrofit (plug-in) lamps, a typical example being a circuit arrangement for starting and operating a 70 W sodium high-pressure lamp (with 2 atm xenon cold filling pressure) at a burning position for originally a 125 W mercury-vapor lamp, using the original ballast inductor. In a particularly preferred embodiment, the aim is simultaneously to permit the lamp power to be adjusted (preferably reduced).
As defined in the invention, a circuit arrangement has been developed in which a capacitor (transfer capacitor) connected in parallel with the lamp is charged up to a voltage (transfer voltage U
transfer
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) which is higher than the required (customary) no-load voltage. This voltage is made immediately available to the plasma after breakdown has occurred. The increased voltage is preferably provided by means of a closing operation on a resonant circuit.
The present i
Boenigk Michael
Guenther Klaus
Bessone Carlo S.
Patent-Treuhand-Gesellschaft Fuer Elektrische Gluehlampen MBH
Philogene Haissa
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