Electric lamp and discharge devices: systems – Pulsating or a.c. supply – Induction-type discharge device load
Reexamination Certificate
1999-09-20
2001-01-30
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Pulsating or a.c. supply
Induction-type discharge device load
C315S224000, C315S225000, C315SDIG007
Reexamination Certificate
active
06181080
ABSTRACT:
The invention relates to a circuit arrangement for operating at least one electrodeless discharge lamp.
I. Technical Field
The term electrodeless discharge lamp in this case denotes a gas discharge lamp which is excited by induction. This gas discharge lamp has a light-transmitting discharge vessel with an ionizable filling enclosed therein, which filling can be excited to effect the gas discharge. The gas discharge is excited by means of one or more induction coils with a closed ferrite core which are fixed on the exterior of the discharge vessel. The induction coils, to which a high-frequency AC voltage is applied, are arranged in such a way that they feed an electric field into the discharge vessel, which excites the ionizable filling in the interior of the discharge vessel to effect the gas discharge. This gas discharge has—in contrast to the gas discharge which takes place in the widely used fluorescent lamps having electrodes which project into the discharge vessel—an annularly closed discharge path. A more detailed description of an electrodeless discharge lamp is disclosed for example in the international published Patent Application WO 97/10610. The invention relates, in particular, to a circuit arrangement for operating an electrodeless discharge lamp of this type.
II. Prior Art
A prior art arrangement is described in U.S. Pat. No. 5,063,332, for example. This circuit arrangement has a half-bridge invertor with a resonant circuit connected down-stream, to which the induction coil of an electrodeless discharge lamp is connected. One disadvantage of this circuit arrangement is that it still operates even in the absence of a lamp.
SUMMARY OF THE INVENTION
The object of the invention is to provide a circuit arrangement for operating at least one electrodeless discharge lamp which generates the ignition voltage required for igniting the gas discharge only when at least one lamp is connected to the electrical terminals of the circuit arrangement which are provided therefor.
The invention's circuit arrangement for operating at least one electrodeless discharge lamp has at least one voltage input for supplying voltage to the circuit arrangement and electrical terminals for at least one electrodeless discharge lamp and, according to the invention, is equipped with supervisory means which ascertain the presence or the absence of the at least one electrodeless discharge lamp and enable the provision of the ignition and/or operating voltage for the at least one electrodeless discharge lamp only when the at least one electrodeless discharge lamp is connected to the electrical terminals. These measures ensure that the ignition or operating voltage required for operation of the lamp is not generated in the absence of a lamp. Specifically, with no lamp connected, the extremely high ignition voltage would lead to the circuit arrangement being destroyed. If, on the other hand, the at least one electrodeless discharge lamp is connected to the electrical terminals, then the magnetic losses in the at least one induction coil of the electrodeless discharge lamp attenuate the ignition voltage prior to lamp ignition to such a great extent that a destructive effect on the components of the circuit arrangement is avoided. Unless at least one induction coil of at least one electrodeless discharge lamp is connected, no ignition attempts are made.
It is advantageous for the circuit arrangement according to the invention to have at least one voltage converter and one control circuit for the at least one voltage converter and also a load circuit connected downstream of the at least one voltage converter where the supervisory means interact with the control circuit in such a way that the control circuit generates driving pulses for the at least one voltage converter only when the at least one electrodeless discharge lamp is connected to the electrical terminals. As a result, the voltage converter can begin operating only when the at least one electrodeless discharge lamp is connected to the electrical terminals provided therefor. The voltage converter is advantageously designed as an inverter with a resonant circuit connected downstream, with the result that the ignition voltage required for igniting the gas discharge in the at least one electrodeless discharge lamp can be generated in a simple manner by the method of resonant increase. The control circuit of the voltage divider is advantageously designed as an integrated circuit.
The supervisory means of the circuit arrangement according to the invention advantageously have a current path and a current or voltage detector, where the current path has a first electrical resistance if the at least one discharge lamp is connected to the circuit arrangement, and a different electrical resistance if no discharge lamp is connected to the circuit arrangement, and where the current or voltage detector monitors the current flow or the voltage drop in the current path. The current path is advantageously designed in such a way that it is interrupted in the absence of the at least one electrodeless discharge lamp. Furthermore, the electrical terminals for the at least one electrodeless discharge lamp are advantageously arranged in the current path. In order to be able to ascertain the presence or the absence of the at least one electrodeless discharge lamp using simple means, it is advantageous for at least one induction coil of the at least one electrodeless discharge lamp to be arranged in the current path. The current path is advantageously a DC path.
A circuit arrangement for operating at least one electrodeless discharge lamp having at least one voltage input for supplying voltage to the circuit arrangement and electrical terminals for at least one electrodeless discharge lamp that has proved to be particularly advantageous is one which has at least one voltage converter and one control circuit, designed as an integrated circuit, for the at least one voltage converter and also a load circuit connected downstream of the at least one voltage converter, and which has, as the supervisory means which ascertain the presence or the absence of the at least one electrodeless discharge lamp at the electrical terminals and enable the provision of the ignition or operating voltage for the at least one electrodeless discharge lamp only when the at least one electrodeless discharge lamp is connected to the electrical terminals, a current path which is connected to a voltage supply terminal of the integrated circuit and is interrupted in the absence of the at least one electrodeless discharge lamp at the electrical terminals. In the absence of a lamp, the integrated circuit driving the at least one voltage converter consequently receives no supply voltage, with the result that the voltage converter cannot start operating—despite the mains voltage switched on at the voltage input of the circuit arrangement.
In accordance with another preferred exemplary embodiment, the supervisory means advantageously comprise a tap in the load circuit of the at least one voltage converter and a monitoring element, where the electrical potential at this tap has a first value if the at least one discharge lamp is connected to the circuit arrangement, and has a second, different value if no discharge lamp is connected to the circuit arrangement, and where the monitoring element monitors the electrical potential at the tap and generates an evaluation signal for the control circuit of the at least one voltage converter, said evaluation signal corresponding to the electrical potential. The monitoring element is advantageously designed as a logic circuit which is integrated into the control circuit or connected upstream of the control circuit.
REFERENCES:
patent: 5063332 (1991-11-01), El-Hamamsy et al.
patent: 5237242 (1993-08-01), Takahashi et al.
patent: 5574336 (1996-11-01), Konopka et al.
patent: 5783908 (1998-07-01), Toda et al.
patent: 5925983 (1999-07-01), Toda et al.
patent: 197 13 935 (1997-10-01), None
patent: 196 50 110 (1998-06-01), None
patent: 0016542 (1980-10-01), None
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Bessone Carlo S.
Patent-Treuhand-Gesellschaft Fuer Elektrische Gluehlampen MBH
Tran Thuy Vinh
Wong Don
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