DE202005021520U1 - Lamp, in particular for installation in or for attachment to a piece of furniture or a showcase, with a cold cathode tube - Google Patents

Abstract

Lamp, with a cold cathode tube (12, 38) as a light source and with one of the cold cathode tubes (12, 38) upstream, electrical circuit (50) in an electrical ballast (14, 40), the or the power supply to the cold cathode tube (12, 38), wherein the electrical circuit (50) comprises a current control circuit having the voltage applied to the cold cathode tube (12, 38) Operating current as a function of a detected actual current flow or a detected actual voltage, and between the electrical circuit (50) and the cold cathode tube (12, 38) a power switching stage (52) is provided, the input side to the output of a regulator (56) of the current control loop is connected, characterized by a Training for installation in or for attachment to a piece of furniture or a Showcase in a lamp housing (10, 30) both the Cold cathode tube (12) and the electric ballast (14, 40) are housed, and the power switching stage (52) a Full bridge converter in resonance technology includes.

Description

The The present invention relates to a lamp with a cold cathode tube according to the preamble of claim 1.

to Interior lighting of showcases, drawers or cupboards are used as light sources so-called cold cathode tubes, which develop little heat compared to other bulbs. Only by this low heat development is it possible the bulb in a small, enclosed space like a Drawer, a showcase or a cabinet to integrate, too when the heat generated by the cold cathode tube Nevertheless, in individual cases can lead to considerable temperatures. These in the closed drawer, showcase or in the closed Cabinet pent-up heat can cause cracking in the wood and / or damage to the cold cathode tube to lead. In extreme cases, the cold cathode tube burst and possibly the furniture may catch fire, especially then when an electrode defect occurs.

To avoid overheating of such cold cathode tubes is in the DE 101 01 275 C2 proposed to regulate the operating current based on the temperature present at the cold cathode tube. It should be achieved by adjusting the operating current, a constant temperature in the cold cathode tube.

From the AT 407 461 B a control for a discharge lamp is known in which the operating current applied by means of pulse width and / or pulse packet modulation to the cold cathode lamp, wherein in determining the operating current, a lamp temperature dependent on the correction factor is taken into account according to the lamp-specific correlation of luminance, lamp current and lamp temperature is determined.

From that The present invention is based on the object, to provide a lamp of the type mentioned above, where the cold cathode tube does not overheat and has a long life.

there the invention is based on the finding that such after the Gas discharge principle working cold cathode tubes one need as constant operating current to to burn optimally. Deviations from the ideal current of usually 5 mA can reduce the life of a cold cathode tube reduce considerably.

When technical solution to this problem is inventively a Lamp proposed according to the features of claim 1. An advantageous development of this lamp is the dependent claim 2 to remove.

A formed according to this technical teaching lamp has the advantage that via the current control circuit permanently on (within the usual Tolerances) constant operating current applied to the cold cathode tubes can be, resulting in a long life of the cold cathode tubes leads. The direct capture of the Actual current and / or the actual voltage is a quick reaction deviating operating conditions, so that the operating current can be kept within a narrow tolerance range.

The Use of a resistance sensor to detect the actual current and / or the actual voltage on the cold cathode tube has the advantage that here with a resistance sensor both measured values can be captured and that the values are very precise be recorded. At the same time is such a resistance sensor cost-effective and space-saving.

The Attaching the resistance sensor directly to the cold cathode tube has the advantage that this makes it a very direct and unadulterated Recording the measured values is achieved.

According to the invention between this circuit and the cold cathode tubes, a power switching stage provided, preferably a full bridge converter in Includes resonance technology. This has the advantage that hereby in a cost effective manner a precisely controllable Power supply can be realized.

One Another advantage of the resistance sensor is that over the measured at the resistance sensor Current or voltage drop can be detected, whether a defect is present at the lamp, in particular whether the cold cathode tube is broken or not. Detects the current control loop such Defective, the power supply to the cold cathode tube immediately interrupted. This will be another power supply and eventually associated overheating of the cold cathode tube avoided. Another advantage is that the cold cathode tube is no longer under power and thus replaced safely can be.

A Cold cathode tube in which the operating current is constant held, has the advantage that thereby the cold cathode tube is ideal, resulting in a long life of the cold cathode tube leads. It is understood that any performance adjustments, for example, when the cold cathode tube overheats, by changing the operating voltage, so that the operating current kept constant even in these cases can be.

Further Advantages of the lamp according to the invention arise from the accompanying drawing and those described below Embodiments. Likewise, the above mentioned and the still further features according to the invention in each case individually or in any combination with each other. The mentioned embodiments are not exhaustive Enumerating to understand, but rather have exemplary Character. Show it:

1 a schematic representation of a first embodiment of a lamp according to the invention;

2 a schematic representation of a second embodiment of a lamp according to the invention;

3 a schematic diagram of a circuit according to the invention.

In 1 a lamp according to the invention is shown, in which in a lamp housing 10 both the cold cathode tube 12 , as well as an electric ballast 14 are housed. In this case, the electrical connection between the circuit 14 and the cold cathode tube 12 over extremely short cables or over an appropriate track 16 on the board 18 respectively.

In close proximity to the cold cathode tube 12 is a measuring resistor 20 arranged, whose resistance increases with increasing temperature. Furthermore, in the case 10 a non-contact switch 22 provided, with which the cold cathode tube can be switched on and off.

By using the electric ballast 14 for controlling the power supply to the cold cathode tube 12 It is possible to build everything very small and all components in the housing 10 accommodate. This is the case 10 around a closed housing, to facilitate the installation of this lamp in a piece of furniture or a showcase. This lamp then only needs to be connected to a 12 V, 110 V or 230 V power source. This eliminates the known from the prior art laying a cable between the electric ballast and the cold cathode tube and the associated expense.

Due to the compact design of the electrical circuit, the housing 10 also be made very compact. In the in 1 illustrated embodiment, the housing 10 rectangular in cross-section and has an edge length of 10 mm by 10 mm.

At the in 2 illustrated lamp is an alternative embodiment. In this embodiment, the housing 30 from a soil 32 and a lid 34 which are lockable to each other. In this case is on a holding plate 36 a meandering curved cold cathode tube 38 , an electric ballast 40 , a temperature measuring resistor 42 and a non-contact switch 44 assembled. Again, it is due to the compact design of the electrical circuit 44 possible to mount everything in the smallest space and in the very compact housing 30 to integrate. In this case, the housing has 30 a height of about 8 mm and a diameter of about 70 mm.

In 3 is an electrical circuit 50 shown, for example, in the electric ballast 14 according to the lamp 1 or in the electric ballast 40 according to the lamp 2 is used. This electrical circuit 50 controls a power switching stage 52 connected to the cold cathode tube 12 . 38 connected is. In this case, the power switching stage comprises 52 a full-bridge transducer in resonance technology, as known from the prior art. Furthermore, the electrical circuit comprises 50 a regulator 56 and a limit memory 58 , as well as a voltage divider 60 , The following is the operation of the electric circuit 50 as described in more detail below: The temperature measuring resistor 20 . 42 permanently measures the existing temperature. The current temperature is proportional to the resistance. In the limit memory 58 is stored a temperature limit, which was determined experimentally. Now raises the temperature in the housing 10 . 30 so strong that the resistance in the temperature measuring resistor 20 . 42 increases so much that the limit is reached, so controls the controller 56 the power switching stage 52 to the effect that the power supply to the cold cathode tube 12 . 38 for a predetermined time T is reduced by 10% to 95%, preferably 80%. This process is repeated until the temperature at the cold cathode tube 12 . 38 fell below the threshold.

At the same time, the electrical circuit is detected 50 over the resistance sensor 54 the current flow or the voltage at the cold cathode tube 12 . 38 , For example, in the case that the cold cathode tube 12 . 38 is defective, increases the current or voltage drop at the resistance sensor 54 drastically, so that the limit provided for this is exceeded. This recognizes the electrical circuit 50 in that there is a defect and interrupts the power supply to the cold cathode tube 12 . 38 Completely. Since the lamp is no longer under power / voltage now required repair work can be carried out without risk.

In another, not shown embodiment the electrical circuit is designed such that upon reaching a stored in the limit memory temperature upper limit for example, 80 ° C, the power supply to the cold cathode tube is lowered by 10% to 95%, preferably 80%. The remains Reduced power supply maintained until the temperature a likewise stored in the limit memory temperature lower limit has reached, for example, 50 ° C. In this case will then the power supply reduced to the old value, until the temperature reaches the upper temperature limit has reached again. This procedure can be repeated as often as desired and causes the temperature on the cold cathode tube always remains in a given temperature interval.

In yet another embodiment, not shown here the power supply will reach after reaching the lower temperature limit not to the original height, but only up to 90% of the original performance. Should the heat development at the cold cathode tube despite only 90% power also to a temperature increase up lead to the temperature upper limit, the above becomes Repeat process, if necessary several times.

At the resistance sensor 54 the current operating current is measured and in the controller 56 with a predetermined limit from the limit memory 58 compared. If the two values deviate from one another beyond the usual tolerances, the controller regulates 56 the operating current accordingly.

Continue on the resistance sensor 54 the current operating voltage measured and in the controller 56 with a predetermined limit from the limit memory 58 compared. If the two values deviate from one another beyond the usual tolerances, the controller regulates 56 the operating current accordingly.

In the event that the cold cathode tube 12 . 38 should overheat once the operating voltage of the cold cathode tube 12 . 38 lowered and the operating current kept constant at 5 mA. As a result, the power of the cold cathode tube can be throttled at a constant operating current, so that the cold cathode tube cools.

10

casing

12

Cold cathode tube

14

electrical ballast

16

conductor path

18

circuit board

20

Temperature-sensing resistor

22

switch

30

casing

32

ground

34

blanket

36

Retaining plate

38

Cold cathode tube

40

electrical ballast

42

Temperature-sensing resistor

44

switch

50

electrical circuit

52

Power switching stage

54

RTD

56

regulator

58

limit memory

60

voltage divider

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10101275 C2 [0003]
• AT 407461 B [0004]

Claims (2)

Lamp, with a cold cathode tube ( 12 . 38 ) as a light source and with one of the cold cathode tubes ( 12 . 38 ) upstream, electrical circuit ( 50 ) in an electric ballast ( 14 . 40 ), the or the power supply to the cold cathode tube ( 12 . 38 ), whereby the electrical circuit ( 50 ) has a current control loop that the on the cold cathode tube ( 12 . 38 ) adjusts operating current as a function of a detected actual current flow or a detected actual voltage, and between the electrical circuit ( 50 ) and the cold cathode tube ( 12 . 38 ) a power switching stage ( 52 ) is provided, the input side to the output of a controller ( 56 ) is connected to the power control circuit, characterized by a design for installation in or for attachment to a piece of furniture or a showcase, in a lamp housing ( 10 . 30 ) both the cold cathode tube ( 12 ) as well as the electrical ballast ( 14 . 40 ), and the power switching stage ( 52 ) comprises a full-bridge converter in resonance technology. Lamp according to Claim 1, characterized by an ohmic resistance sensor ( 54 ), which on the cold cathode tube ( 12 . 38 ) is directly connected and detects the actual current flow and / or the actual voltage.