Electric lamp and discharge devices: systems – Automatic substitution of the power supply
Reexamination Certificate
2000-12-01
2002-12-24
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Automatic substitution of the power supply
C315S088000, C315S129000
Reexamination Certificate
active
06498436
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
the invention relates to a method for operating a lamp, particularly a lamp for medical applications, having at least one discharge lamp which is connected to a supply unit (EVG) which receives electrical energy from a power supply system having an additional safety power supply (ZSV), the emergency power function prompting a changeover to a standby power source in the event of a fault in the power supply, and, after elimination of the fault, prompting a changeover to the power supply for normal operation. In addition, the invention relates to a failsafe lamp, particularly a lamp for medical applications.
2. Discussion of the Prior Art
A power supply system having an additional safety power supply (ZSV) is defined in VDE Regulation VDE 0107; besides the customary mains power supply, the power supply system comprises a standby power source, which is usually supported by a storage battery.
German reference DE 38 07 585 A1 discloses a surgical lamp which has a high-pressure gas discharge lamp as a light source. This lamp is connected to a supply circuit having an emergency power function, whose input can be connected to a DC voltage source having a lower voltage than the operating voltage of the discharge lamp. It comprises a plurality of first voltage converters for transforming the input voltage into the operating voltage of the discharge lamp, whose inputs are connected in parallel and whose outputs are selectively connected in parallel or in series. The multiplicity of voltage converters means that this is a relatively complex desing.
ln addition. German reference DE 195 05 925 A1 (according to U.S. Pat. No. 5,743,628) discloses a medical lamp, particularly a surgical lamp, which has at least one halogen incandescent lamp and one discharge lamp (halogen metal vapor high-pressure lamp) in its housing. In the event of a failure or fault in the static power supply provided for operating the lamp, the supply of power to the lamp is changed over to a standby power source supported by a storage battery, The radiation from the halogen incandescent lamps is available virtually without interruption on account of the thermal inertia of their coil, whereas the discharge lamp is not available for renewed ignition and startup until after a certain cooling phase over a period of several minutes.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a lamp of relatively simple design in which continuous discharge lamp operation is possible even during changeover procedures or in the event of brief voltage drops or voltage failures without renewed ignition procedures. In particular, the intention is to provide a practically failsafe lamp.
Pursuant to this object, and others which will become apparent hereafter, one aspect of the present invention resides in a method in which, if a fault occurs during changeover to the standby power source, a buffer store outputs electrical energy to operate the discharge lamp.
Besides changing over in the case of pure DC voltage operation or pure AC voltage operation for the power supply system and the additional safety power supply, it is also possible to change over between different current types—e.g. from AC voltage to DC voltage or from DC voltage to AC voltage—without impairing the lamp operation, particularly the operating parameters of the discharge lamp.
The buffer store provided is advantageously an electrical capacitor which is at least partly discharged during changeover.
This means that, in the case of a fault during changeover or during a brief voltage drop, the buffer store outputs electrical energy for continuous operation of the discharge lamp.
It is found to be advantageous that, even in the event of brief interruptions, continuous lamp operation is possible without interim ignition operations for the discharge lamp. This means that no inconvenient ignition attempts are made for the discharge lamp during operation. Furthermore, the normal lighting values are quickly restored after the occurrence and elimination of faults. A further advantage can be seen in that the useful life of the lamp is improved on account of reduced loading due to fewer ignition procedures.
In one preferred embodiment of the method, the electrical energy supplied to the supply unit (EVG) first passes through a full-wave rectifier and subsequently a voltage converter containing the buffer store. Energy is subsequently supplied to the discharge lamp via a power-regulated inverter as the output stage.
It is found to be particularly advantageous that the power regulation results in a changeover both from alternating current to direct current and from direct current to alternating current having no effect on the operation of the discharge lamp.
In one preferred embodiment of the invention, while the buffer store is discharging, the discharge lamp is operated in the lower power range for stable illumination (simmer operation). Furthernore, even in the event of a failure in the region of the discharge lamp, at least a certain level of safety should be provided—e.g. in the case of medical application or in the course of a surgical procedure—by virtue of at least standby illumination being ensured by at least one halogen incandescent lamp after an operating fault in the discharge lamp circuit. In the event of a fault in the operation of the discharge lamp or its energy supply, the supply unit (EVG) is used to complete a circuit for operating at least one halogen incandescent lamp. In this context, it is found to be advantageous that an automatic changeover occurs without any significant interruption in the lamp operation.
In addition, in one preferred embodiment of the invention, the operating parameters of the lamp—such as starting procedures or illumination time of the discharge lamp—are determined using a digital computer and are possibly indicated for monitoring purposes. It is found to be advantageous that the user may actually be referred ahead of time to any relevant measures for reliable operation of the lamp.
Another aspect of the invention resides in the supply unit (EVG) having a buffer store which, in the event of a fault occurring or in the event of a fault being eliminated, is provided for outputting electrical energy for operating the discharge lamp during changeover to the standby power source or during changeover to the power supply for normal operation.
The buffer store used is advantageously an electrical capacitor, so that, in the case of a fault during changeover or during a brief voltage drop, the capacitor outputs electrical energy for continuous operation of the discharge lamp.
It is found to be advantageous that, even in the event of brief interruptions, continuous lamp operation is possible without interim ignition operations for the discharge lamp, and no inconvenient ignition attempts are made for the discharge lamp during operation.
In one preferred embodiment of the invention, a full-wave rectifier is provided at the input of the supply unit for the lamp. The output of the full-wave rectifier is connected to a power-regulated inverter via a voltage converter in order to supply the discharge lamp.
It is found to be particularly advantageous that due to the power regulation of the inverter means, changing over the current type (e.g, alternating current—direct current) does not result in any impairment of the operation of the discharge lamp.
To maximize its stored energy, the capacitor is preferably arranged in a DC voltage intermediate circuit of the supply unit. The intermediate circuit operates at an operating voltage in the range from 300 to 400 V and forms, together with a step-down converter connected downstream, a DC voltage converter which is connected via the power-regulated inverter to the discharge lamp for the purpose of supplying energy thereto. In terms of its own energy supply, the DC voltage intermediate circuit is connected to the power supply system via a mains filter, a synchronous rectifier connected upstreain of the filter as a full-wave rectifier and via
Hartge Jörg Eduard
Helten Matthias
Marka Rudolf
Alemu Ephrem
Cohen & Pontani, Lieberman & Pavane
Heraeus Med GmbH
Philogene Haissa
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