| (19) |
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(11) |
EP 2 312 912 A2 |
| (12) |
EUROPEAN PATENT APPLICATION |
| (43) |
Date of publication: |
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20.04.2011 Bulletin 2011/16 |
| (22) |
Date of filing: 31.05.2010 |
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| (51) |
International Patent Classification (IPC):
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| (84) |
Designated Contracting States: |
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AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL
NO PL PT RO SE SI SK SM TR |
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Designated Extension States: |
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BA ME RS |
| (30) |
Priority: |
03.06.2009 SI 200900157
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| (71) |
Applicant: Technoplast, d.o.o. |
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4273 Bjejska Dobrava (SI) |
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| (72) |
Inventor: |
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- Kuster, Dragotin
2230 Lenart (SI)
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| (74) |
Representative: Pipan, Marjan |
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Kotnikova 5
1000 Ljubljana
1000 Ljubljana (SI) |
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| (54) |
Circuit for a temperature control of a LED diode |
(57) The subject of the invention is a circuit for a temperature control of a LED diode
providing a possibility of changing luminous intensity of the LED diode as a function
of ambient temperature, wherein an analogue voltage signal is generated as a function
of detected temperature on a sensor circuit (1), wherein this signal is compared to
a ramp frequency, which is internally set on a regulator (3) by means of a resistor
(2) and the signal of the regulator (3) generated based on the intersection point
between the ramp frequency and the generated analogue voltage signal determines the
current, the size of which depends on the width of the signal of the regulator (3)
generated as a function of detected temperature on the sensor circuit (1). Figure
3 should appear in publication.
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[0001] The subject of the invention is a circuit for a temperature control of a LED diode
providing a possibility of changing luminous intensity of the LED diode as a function
of ambient temperature. The described circuit can be used for controlling illumination
as well, e.g. of car lamps and car fog lamps. The invention belongs to class F21V29/00
of the international patent classification.
[0002] The technical problem successfully solved by the circuit of the invention is high
sensitivity of the luminous intensity of a LED diode to ambient temperature and consequently
increase/decrease of the luminous intensity of LED diodes.
[0003] A solution to set technical problem relates to a problem of heating of luminous elements
comprising LED diodes. A problem of excess heating of luminous elements comprising
one or several LED diodes needs to be solved by means of adequate mechanical cooling
systems or a structure of a housing of luminous elements that are effective in deflecting
heat.
[0004] The circuit of the invention detects the temperature of a chip of the LED diode and
controls the increase/decrease of the current running through the LED diode. By applying
an adequate combination of NTC and PTC resistors and belonging elements for a proper
functioning of the circuit it is possible to prepare such control voltage curve that
will adequately generate current through the LED diode as a function of temperature
of the chip of the LED diode.
[0005] The invention will now be explained in more detail by way of an embodiment and the
belonging drawings, representing in:
Figure 1 a block diagram of the circuit of the invention;
Figure 2 curve of dependence of luminous intensity on the temperature of the LED diode;
Figure 3 control circuit structure.
[0006] According to the invention the problem is solved by a circuit for a temperature control
of a LED diode generating an analogue voltage signal as a function of detected temperature
on a sensor circuit 1 consisting of an NTC and a PTC resistor. This signal is compared
to a ramp frequency, which is internally set on a regulator 3. Based on the intersection
point between the ramp frequency and the generated analogue voltage signal an adequate
signal of the regulator 3 is generated at the output terminal of the regulator 3,
said signal opening a FET transistor and a diode port in an adequate width, through
which current flows, the size of the current depending on the width of the signal
of the regulator 3 generated as a function of detected temperature on the sensor circuit
1.
[0007] Figure 2 shows curves representing the situation on NTC and PTC resistors and the
curve of voltage and current through the LED diode and herewith sensitivity of the
luminous intensity of the LED diode to temperature.
[0008] The circuit of the invention operates in the entire temperature range between -40°
and 105°. Proper operation of the circuit of the invention is subject to adequate
cooling by means of a cooler that can be arranged on the bottom side under the LED
diode.
1. A circuit for a temperature control of a LED diode,
characterized in that
an analogue voltage signal is generated as a function of detected temperature on a
sensor circuit (1), wherein this signal is compared to a ramp frequency, which is
internally set on a regulator (3) by means of a resistor (2) and the signal of the
regulator (3) generated based on the intersection point between the ramp frequency
and the generated analogue voltage signal determines the current, the size of which
depends on the width of the signal of the regulator (3) generated as a function of
detected temperature on the sensor circuit (1).