WO2013140280A2

WO2013140280A2 - Lighting system with lifetime indicator and method for estimating the remaining life time of a lighting system

Info

Publication number: WO2013140280A2
Application number: PCT/IB2013/051528
Authority: WO
Inventors: Franciska Elisabeth EVERTZ; Jeroen Johannes Maria ZAAL; Willem Dirk Van Driel
Original assignee: Koninklijke Philips NV
Current assignee: Koninklijke Philips NV
Priority date: 2012-03-22
Filing date: 2013-02-26
Publication date: 2013-09-26
Anticipated expiration: 2014-09-22
Also published as: WO2013140280A3

Description

Lighting system with lifetime indicator and method for estimating the remaining life time of a lighting system

FIELD OF THE INVENTION

The present invention relates to the field of lighting systems, more particularly to a lighting system comprising a lifetime indicator. The present invention also relates to a method for estimating the remaining lifetime of a lighting system.

BACKGROUND OF THE INVENTION

Modern lamps, and in particular LED lamps, luminaires and modules, show long lifetimes, even up to 40.000 firs are claimed. Due to their long lifetime, the health or remaining lifetime for these types of lamps can not be judged easily. This means that often lamps are still being used while their light level is too low or that the lamps are thrown away before the end of their lifetime. This problem becomes more relevant if the lifetime of a lamp is longer and/or if the lamp is more expensive. Both are currently valid for LED lamps.

During refurbishments or maintenance of hotels, homes or offices it would be economically beneficial to know if lamps are either at the end of their lives or if the lamps can be re-used.

Several methods for establishing the lifetime of a lamp or a lighting system with a long lifetime are known today. US-5,625,616, for example, discloses a deterioration estimating method for a light emitting device and a light emission driving apparatus using the method. A current detector detects a driving current Im flowing through a light emitting device (laser diode). A temperature sensor is arranged in the vicinity of the light emitting device and a microcomputer is supplied with the outputs of the current detector and temperature sensor. A temperature correction coefficient specific to the light emitting device, obtained based on a driving current value IT1 at a temperature Tl and a driving current value IT2 at a temperature T2 (gt;Tl), is stored in memory. A deterioration threshold current Id for a detected temperature Ti is calculated and when the deterioration threshold current Id for the detected temperature Ti is exceeded by the detected current, a driver is controlled so as to inhibit the supply of the driving current to the light emitting device. Since the operating temperature also is taken into consideration, deterioration of the light emitting device can be accurately estimated, thereby preventing erroneous recording/reproduction of data. A drawback with the system is that it is very complicated and expensive. SUMMARY OF THE INVENTION

It is an object of the present invention to overcome or alleviate problems of the prior art by creating a lighting system having a simple, inexpensive and accurate lifetime indicator.

According to a first aspect of the invention, this and other objects are achieved by a lighting system comprising a light source arranged for emitting light, a temperature sensor adapted to detect a temperature of said lighting system when in an on-state, a control unit connected to said temperature sensor, said control unit being adapted to calculate a temperature difference between said temperature detected by said temperature sensor and a default temperature preset in said control unit, and an indicator connected to said control unit and adapted to display said temperature difference. It is known that during lifetime of such a lighting system the degradation of materials causes an increase in the temperature of the lighting system. Therefore, the increase in temperature can directly be related to the lifetime of the lighting system. This is advantageous in that the lighting system is equipped with a built-in lifetime indicator which is extremely inexpensive and simple.

The indicator may be adapted to display a colour dependent on said temperature difference, said colour may correspond to an estimated remaining lifetime of said lighting system. The colour may be green - indicating that no action is required - when said temperature difference is in a first range, preferably between 0°C and 10°C, yellow - indicating a new measurement within 3-6 months - when said temperature difference is in a second range, preferably between 11 °C and 40°C, and red - indicating replacement of said lighting system within 3 months - when said temperature difference is in a third range, preferably larger than 40°C. This is advantageous in that it will be easy for a user to determine the estimated remaining lifetime of the lighting system by reading said indicator.

The control unit may be preset to conduct said calculation every third month, which is a preferred time period for conducting the calculation in order to establish the estimated remaining lifetime of the lighting system.

The light source may comprise a lamp with a long lifetime, such as a LED lamp, which is advantageous in that the lighting system can be successfully used for up to 40.000 hours.

The temperature sensor may be an infrared temperature sensor, which is a preferred temperature sensor for the present lighting system. An infrared temperature sensor is cheap and accurate. The default temperature may be manually inputted. The default temperature may differ between different types of lamps. Therefore, the default temperature may be read from the lighting system when first installing it and thereafter inputted manually into the control unit. This way, the calculation of the remaining lifetime of the lighting system will be as accurate as possible.

According to a second aspect of the invention, a method for estimating the remaining lifetime of a lighting system is provided. The method comprises measuring a temperature of said lighting system, when in an on-state, by means of a temperature sensor, calculating a temperature difference between said temperature detected by said temperature sensor and a default temperature of said lighting system, and estimating the remaining lifetime of said lighting system based on said temperature difference. This is advantageous in that the lighting system is equipped with a built-in lifetime indicator which is extremely inexpensive and simple. Additionally, by performing regular calculations in the control unit, the indicator will be very accurate and reliable.

The method may further comprise displaying said temperature difference on an indicator. The temperature difference may displayed by means of a colour corresponding to the estimated remaining lifetime of said lighting system. This is advantageous in that it will be easy for a user to determine the estimated remaining lifetime of the lighting system by reading said indicator.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the [element, device, component, means, etc]" are to be interpreted openly as referring to at least one instance of said element, device, component, means, etc., unless explicitly stated otherwise.

It is noted that the invention relates to all possible combinations of features recited in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other aspects of the present invention will now be described in more detail, with reference to the appended drawing showing an embodiment of the invention.

Fig. 1 is a schematic view of a lighting system according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION Fig. 1 illustrates a lighting system 1 according to an exemplary embodiment of the present invention. The lighting system 1 has a light source 2 arranged for emitting light, a temperature sensor 3, a control unit 4, and an indicator. The temperature sensor 3 is connected to the control unit 4 and is adapted to detect a temperature of the lighting system 1 , when in an on-state and thus emitting heat. The control unit 4 is adapted to calculate a temperature difference between the temperature detected by the temperature sensor 3 and a default temperature preset in the control unit 4. The indicator is connected to the control unit 4 and is adapted to display the temperature difference calculated by the control unit 4. More specifically, the indicator displays a colour which is based on the temperature difference calculated by the control unit 4. The colour corresponds to an estimated remaining lifetime of the lighting system 1. When the temperature difference is in a range between 0°C and 10°C, the colour is green, which indicates that the lighting system 1 has a remaining lifetime of more than six months. When the temperature difference is in a range between 11 °C and 40°C, the colour is yellow, which indicates that the lighting system 1 has a more uncertain remaining lifetime and that a new measurement should be conducted within three months. When the temperature difference is larger than 40°C, the colour is red, which indicates that the lighting system 1 has a remaining lifetime of less than three months and that it should be replaced shortly. The temperature sensor 3 is an infrared temperature sensor and the control unit 4 is preset to conduct the temperature difference calculation every third month. The default temperature is manually inputted to the control unit 4.

When a lighting system 1 according to the above exemplary embodiment of the present invention is new, the lighting system 1 can easily be tested in order to determine a default temperature of the lighting system 1. This can be done merely by measuring the temperature of the lighting system 1, when in an on-state, by means of the temperature sensor 3. Thereafter, the default temperature is manually inputted in the control unit 4 together with a time period stating how often the temperature difference calculation is to be performed. If the time period is set to three months, the control unit 4 conducts the temperature difference calculation every third month. That is to say, the temperature sensor 3 measures a

temperature of the lighting system 1, when in an on-state. The result is sent to the control unit 4 which in turn calculates the temperature difference by subtracting the default temperature from the temperature detected by the temperature sensor 3. Lastly, the result is submitted to the indicator 5 which displays a colour based on the temperature difference. The colour will accordingly correspond to the estimated remaining lifetime of the lighting system 1. The lifetime indicator 4 could basically be applied to all types of lamps. The indicator 4 is, however, especially suitable for LED lamps, in which the temperature increases during degradation of the material in the lighting system 1.

Naturally, several additional procedures can be used in order to estimate the remaining lifetime of the lighting system 1 according to the present invention using the components included in the lighting system 1.

According to a second aspect of the invention, a method for estimating the remaining lifetime of a lighting system is provided. The method comprises the steps of measuring a temperature of said lighting system, when in an on-state, by means of a temperature sensor, calculating a temperature difference between said temperature detected by said temperature sensor and a default temperature of said lighting system, and estimating the remaining lifetime of said lighting system based on said temperature difference. The method further comprises the step of displaying the temperature difference on an indicator. The temperature difference may be displayed by means of a colour corresponding to the estimated remaining lifetime of the lighting system.

The method can naturally be used separately from the lighting system according to the present invention. For example by using a remote infrared temperature sensor in order to determine the temperature of the system in question and thereafter merely subtract an earlier determined default temperature form the temperature detected by the remote infrared temperature sensor. The resulting temperature difference can then be used in order to establish the remaining lifetime of the system.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

Claims

CLAIMS:

1. A lighting system (1), comprising

a light source (2) arranged for emitting light,

a temperature sensor (3) adapted to detect a temperature of said lighting system (1) when in an on- state,

a control unit (4) connected to said temperature sensor (3),

said lighting system having a default temperature in an on-state, said control unit (4) being adapted to calculate a temperature difference between said temperature detected by said temperature sensor (3) and said default temperature preset in said control unit (4), and

an indicator (5) connected to said control unit (4) and adapted to display said temperature difference.

2. A lighting system (1) according to claim 1, wherein said indicator (5) is adapted to display a colour dependent on said temperature difference.

3. A lighting system (1) according to claim 2, wherein said colour corresponds to an estimated remaining lifetime of said lighting system (1).

4. A lighting system (1) according to any one of the preceding claims, wherein said colour is green when said temperature difference is in a first range, yellow when said temperature difference is in a second range, and red when said temperature difference is in a third range.

5. A lighting system (1) according to claim 4, wherein said first range is between 0°C and 10°C, said second range is between 11 °C and 40°C, and said third range is when larger than 40°C.

6. A lighting system (1) according to any one of the preceding claims, wherein said control unit (4) is preset to conduct said calculation every third month.

7. A lighting system (1) according to any one of the preceding claims, wherein said light source (2) comprises a lamp with a long lifetime, such as a LED lamp.

8. A lighting system (1) according to any one of the preceding claims, wherein said temperature sensor (3) is an infrared temperature sensor.

9. A lighting system (1) according to any one of the preceding claims, wherein said default temperature is manually inputted.

10. Method for estimating the remaining lifetime of a lighting system (1), comprising

measuring a temperature of said lighting system (1), when in an on-state, by means of a temperature sensor (3),

calculating a temperature difference between said temperature detected by said temperature sensor (3) and a default temperature of said lighting system (1), and

estimating the remaining lifetime of said lighting system (1) based on said temperature difference.

11. Method according to claim 10, further comprising displaying said temperature difference on an indicator (5).

12. Method according to claim 10 or 11, wherein said temperature difference is displayed by means of a colour corresponding to the estimated remaining lifetime of said lighting system (1).