CN102131324A - Thermal foldback control circuit and control method of light-emitting diode (LED) - Google Patents
Thermal foldback control circuit and control method of light-emitting diode (LED) Download PDFInfo
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- CN102131324A CN102131324A CN2010100007604A CN201010000760A CN102131324A CN 102131324 A CN102131324 A CN 102131324A CN 2010100007604 A CN2010100007604 A CN 2010100007604A CN 201010000760 A CN201010000760 A CN 201010000760A CN 102131324 A CN102131324 A CN 102131324A
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Abstract
The invention discloses a thermal foldback control circuit and a control method of a light-emitting diode (LED). The thermal foldback control circuit and the control method of the LED are used for sensing the temperature of the LED and the temperature of a control chip of the LED and gradually reducing a driving current of the LED before overheating of the LED or the control chip so as to avoid the twinkle of the LED caused by the startup of an overheating protecting mechanism due to the overheating of the control chip. The thermal foldback control circuit comprises an outside heat-sensing end for receiving an outside heat-sensing signal related to the temperature of the LED, a heat-controllable circuit for sensing the temperature of the control chip so as to determine an inside heat-sensing signal and a multi-path sensing circuit for connecting the outside heat-sensing end and the heat-controllable circuit and triggering a heat-regulating signal to regulate the driving current intelligently and further regulate the temperatures of the LED and the control chip automatically when the outside heat-sensing signal surpasses a first threshold signal or the inside heat-sensing signal surpasses a second threshold signal.
Description
Technical field
The present invention relates to the controller of a kind of light-emitting diode (LED), particularly about the heat of a kind of LED (thermal foldback) control circuit and the method for turning back.
Background technology
Overtemperature protection mechanism (Over Temperature Protection; OTP) be the technology of protection controller chip, when its temperature at controller chip rose to set point, the closing controller chip burnt to avoid controller chip.Hot foldback technique is the mechanism of protection LED, when its temperature at LED rises to set point, reduces the drive current of LED, continues to raise with the temperature of avoiding LED.The design of existing LED light fixture focuses on safety and the heat radiation of LED itself; therefore LED and its drive circuit branch are arranged; and be in particular LED and keep and to supply cross-ventilated space; to reduce the temperature of its surface contact; and drive circuit is set in the airtight space mostly; heat radiation is difficult for; therefore; sometimes be the temperature that the temperature of the controller chip of drive circuit is higher than LED on the contrary; touching OTP makes controller chip enter hot protected mode; cause the drive current of LED to be cut off, the phenomenon of LED thereby generation flicker.
Summary of the invention
One of purpose of the present invention, the heat that is to propose a kind of LED turn back control circuit and method are progressively adjusted the drive current of LED according to variations in temperature.
One of purpose of the present invention is to propose a kind of simple circuit and method, detects the variations in temperature of LED and controller chip simultaneously, and intelligence is regulated the drive current of LED according to this, and then the temperature of regulating LED and controller chip voluntarily.
For reaching above-mentioned purpose, the heat that the invention provides a kind of light-emitting diode control circuit of turning back, the drive current of the controlled device chip controls of this light-emitting diode is lighted, and this heat control circuit of turning back comprises:
The external heat sense terminal, the external heat detection signal of the temperature correlation of reception and this light-emitting diode;
Hot controlable electric current is detected the temperature of this controller chip, determines the internal heat detection signal according to this; And
The multichannel circuit for detecting, connect this external heat sense terminal and this hot controlable electric current, when this external heat detection signal surpasses the first door signal or this internal heat detection signal and surpasses the second door signal, trigger the thermal conditioning signal and regulate this drive current, and then regulate the temperature of this light-emitting diode and this controller chip voluntarily with intelligence.
For reaching above-mentioned purpose, the present invention also provides a kind of heat of light-emitting diode control method of turning back, and the drive current of the controlled device chip controls of this light-emitting diode is lighted, and this heat control method of turning back comprises:
(A) the external heat detection signal of the temperature correlation of reception and this light-emitting diode;
(B) detect the temperature of this controller chip with decision internal heat detection signal; And
(C) when this external heat detection signal surpassed the first door signal or this internal heat detection signal and surpasses the second door signal, intelligence was regulated this drive current, and then the temperature of regulating this light-emitting diode and this controller chip voluntarily.
According to the present invention, the control circuit of a kind of LED and method monitor the temperature of this light-emitting diode and the temperature of controller chip thereof simultaneously, judge that what person is higher, determine that again the position of hygral equilibrium is accurate.The present invention can detect the temperature of the controller chip of the temperature of this light-emitting diode and this light-emitting diode; before this light-emitting diode or this controller chip are overheated; just progressively reduce the drive current of this light-emitting diode, avoid causing starting overtemperature protection mechanism and causing LED flash because this controller chip is overheated.
Description of drawings
Fig. 1 is a schematic diagram according to an embodiment of the invention;
Fig. 2 is the embodiment of hot controlable electric current;
Fig. 3 is the embodiment of hot controlable electric current; And
Fig. 4 is to use the embodiment of multi-door bank signal.
Specific embodiment
Below in conjunction with Figure of description the specific embodiment of the present invention is done detailed description.Obviously, described embodiment only is a part of embodiment of the present invention, and other embodiment that those skilled in the art is obtained under the prerequisite of not paying creative work belongs to protection scope of the present invention.
Fig. 1 is a schematic diagram according to an embodiment of the invention, and LED array 10 couples power Vcc through resistance R 1, and controller chip 12 connects LED arrays 10, is used for controlling the drive current Iled of LED array 10.Controller chip 12 comprises BJT 14 connects with LED array 10, so the collector current Ic of BJT 14 equals the drive current Iled of LED array 10.Driver 16 connects the base stage of BJT 14, with the collector current Ic of control BJT 14.As prior art, controller chip 12 has light modulation (dimming) pin DIM and connects driver 16, is used for accepting the light modulation input, with the brightness of control LED array 10.Controller chip 12 also comprises the heat control circuit 18 of turning back, and is used to provide the thermal conditioning signal and gives driver 16, regulates the collector current Ic of BJT 14 according to this.The temperature of thermistor NTCR detecting LED array 10 produces external heat detection signal VTO according to this and gives controller chip 12.When temperature raise, the resistance value of thermistor NTCR descended, and made external heat detection signal VTO reduce.The heat control circuit 18 of turning back has external heat sense terminal 20, receive external heat detection signal VTO, the temperature of hot controlable electric current 22 detecting controller chips 12 itself, produce internal heat detection signal VTI, and multichannel circuit for detecting 24 is according to external heat detection signal VTO and internal heat detection signal VTI decision thermal conditioning signal.In multichannel circuit for detecting 24, comparator 26 has two positive input terminals and receives external heat detection signal VTO and internal heat detection signal VTI respectively, itself and door signal VTH are compared, produce and compare signal to voltage generator 28, produce overheated detecting voltage Vt according to this, hysteresis comparator 30 more overheated detecting voltage Vt with produce the thermal conditioning signal from the feedback voltage Vf of LED array 10.Resistance R 1 so feedback voltage because drive current Iled flows through
Vf=Vcc-Iled * R1, formula 1
It is the function of drive current Iled.The door signal VTH of comparator 26 is provided by the voltage source 32 of temperature influence not.Voltage generator 28 comprises current source 34 and determines overheated detecting current It according to comparing signal, and resistance R 2 is connected between the positive input terminal of power Vcc and hysteresis comparator 30, overheated detecting current It flows through resistance R 2 and produces cross-pressure, thereby determines overheated detecting voltage
Vt=Vcc-It * R2, formula 2
It is the function of overheated detecting current It.In one embodiment, the initial value of overheated detecting current It is zero.When the LED of outside array 10 temperature internal temperature too high or controller chip 12 is too high, the comparison signal that comparator 26 produces makes current source 34 increase its overheated detecting current It, thereby reduce overheated detecting voltage Vt, hysteresis comparator 30 thereby triggering thermal conditioning signal, cause driver 16 to reduce the collector current Ic of BJT 22, but still keep 10 work of LED array.After each thermal conditioning signal was triggered, driver 16 will reduce by a predetermined difference with collector current Ic, unless the temperature of controller chip 12 is elevated to the set point of OTP, just can touch OTP mechanism closing controller chip 12.Therefore, no matter be that the temperature of the temperature of LED array 10 or controller chip 12 is too high, all can impel collector current Ic to reduce, but LED array 10 is still kept at work.By comparator 26, can judge that what person of internal temperature of outside LED array 10 temperature and controller chip 12 is higher, determine that again the position of hygral equilibrium is accurate.This detecting structure is more flexible, and the user can have the setting of more grasp lamp temperatures protections.
Above-mentioned hot controlable electric current 22 can be the bipolarity junction transistor, and this bipolarity junction transistor has base-emitter voltage and changes this internal heat detection signal in response to variations in temperature.Fig. 2 is the embodiment of hot controlable electric current 22, and it uses a simple BJT circuit to produce internal heat detection signal VTI.The base of BJT 36-emitter voltage VBE is about 0.7V under normal temperature, when temperature raise, VBE can reduce, and cause its collector current Ic to increase, so internal heat detection signal VTI descends.Can be by adjust setting the initial value of resistance R set decision internal heat detection signal VTI, the resistance value of setting resistance R set is high more, and then the initial value of internal heat detection signal VTI is low more, and in other words, the critical temperature of controller chip 12 self is low more.As shown in Figure 3, set up capacitor C, can improve the stability of internal heat detection signal VTI at the output of hot controlable electric current 22.For reducing the area of controller chip 12, the embodiment of Fig. 3 is arranged on controller chip 12 outsides with the setting resistance R set of hot controlable electric current 10, but in other embodiments, also can be arranged on controller chip 12 inside with setting resistance R set.
The heat of the present invention control circuit 18 of turning back can judge it is the temperature height of LED array 10 or the internal temperature height of controller chip 12 automatically, and then beginning intelligence is regulated the drive current Iled of LED array 10, make it to raise and minimizing gradually with the internal temperature of controller chip 12 or the temperature of LED array 10, to relax the trend that temperature rises, reach the effect of the temperature of conditioning controller chip 12 inside and LED array 10 voluntarily, the generation probability of cease operation that reduces LED array 10 because controller chip 12 is overheated.
In the embodiment in figure 1, the temperature monitoring of the temperature monitoring of internal controller chip 12 and external LED array 10 all uses same door signal VTH, but in other embodiments, also can be respectively the temperature of LED array 10 and the temperature of controller chip 12 different door signal VTH1 and VTH2 are set, as shown in Figure 4, use two comparators 38 and 40 to compare respectively, voltage generator 28 is given in result's warp relatively or door 42 generations relatively signal.
More than; only be preferred embodiment of the present invention, but protection scope of the present invention is not limited thereto, anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range that claim was defined.
Claims (22)
1. the heat of the light-emitting diode control circuit of turning back, the drive current of the controlled device chip controls of this light-emitting diode is lighted, and it is characterized in that, and this heat control circuit of turning back comprises:
The external heat sense terminal, the external heat detection signal of the temperature correlation of reception and this light-emitting diode;
Hot controlable electric current is detected the temperature of this controller chip, determines the internal heat detection signal according to this; And
The multichannel circuit for detecting, connect this external heat sense terminal and this hot controlable electric current, when this external heat detection signal surpasses the first door signal or this internal heat detection signal and surpasses the second door signal, trigger the thermal conditioning signal and regulate this drive current, and then regulate the temperature of this light-emitting diode and this controller chip voluntarily with intelligence.
2. the heat as claimed in claim 1 control circuit of turning back is characterized in that, this external heat sense terminal connects thermistor.
3. the heat as claimed in claim 1 control circuit of turning back is characterized in that this hot controlable electric current comprises the bipolarity junction transistor, and this bipolarity junction transistor has base-emitter voltage and changes this internal heat detection signal in response to variations in temperature.
4. the heat as claimed in claim 1 control circuit of turning back is characterized in that, this hot controlable electric current connects sets resistance, to determine the initial value of this internal heat detection signal.
5. the heat as claimed in claim 1 control circuit of turning back is characterized in that this first door signal and this second door signal are equal to each other.
6. the heat as claimed in claim 5 control circuit of turning back is characterized in that this multichannel circuit for detecting comprises:
Comparator, relatively this external heat detection signal and this first door signal, and this internal heat detection signal and this second door signal are to produce relatively signal;
Voltage generator connects this comparator, produces overheated detecting voltage according to this comparison signal; And
Hysteresis comparator, relatively this overheated detecting voltage with from the feedback voltage of this light-emitting diode, to produce this thermal conditioning signal.
7. the heat as claimed in claim 6 control circuit of turning back is characterized in that this voltage generator comprises:
Current source produces overheated detecting current according to this comparison signal; And
Resistance connects this current source;
Wherein, flow through this resistance of this overheated detecting current produces this overheated detecting voltage.
8. the heat as claimed in claim 6 control circuit of turning back is characterized in that this feedback voltage is the function of this drive current.
9. the heat as claimed in claim 1 control circuit of turning back is characterized in that this first door signal and this second door signal are unequal each other.
10. the heat as claimed in claim 9 control circuit of turning back is characterized in that this multichannel circuit for detecting comprises:
First comparator, relatively this external heat detection signal and this first door signal;
Second comparator, relatively this internal heat detection signal and this second door signal;
Or door, produce this comparison signal according to the comparative result of this first and second comparator;
Voltage generator connects and is somebody's turn to do or door, produces overheated detecting voltage according to this comparison signal; And
Hysteresis comparator, relatively this overheated detecting voltage with from the feedback voltage of this light-emitting diode, to produce this thermal conditioning signal.
The control circuit 11. heat as claimed in claim 10 is turned back is characterized in that, this voltage generator comprises:
Current source produces overheated detecting current according to this comparison signal; And
Resistance connects this current source;
Wherein, flow through this resistance of this overheated detecting current produces this overheated detecting voltage.
The control circuit 12. heat as claimed in claim 10 is turned back is characterized in that, this feedback voltage is the function of this drive current.
The control circuit 13. heat as claimed in claim 1 is turned back comprises that more voltage source connects this multichannel circuit for detecting, and this first and second door signal is provided.
The control circuit 14. heat as claimed in claim 1 is turned back is characterized in that, this thermal conditioning signal comprises in order to by this drive current, makes that this light-emitting diode is overheated automatically closes to reduce temperature.
The control method 15. the heat of a light-emitting diode is turned back, the drive current of the controlled device chip controls of this light-emitting diode is lighted, and it is characterized in that, and this heat control method of turning back comprises:
(A) the external heat detection signal of the temperature correlation of reception and this light-emitting diode;
(B) detect the temperature of this controller chip with decision internal heat detection signal; And
(C) when this external heat detection signal surpassed the first door signal or this internal heat detection signal and surpasses the second door signal, intelligence was regulated this drive current, and then the temperature of regulating this light-emitting diode and this controller chip voluntarily.
The control method 16. heat as claimed in claim 15 is turned back is characterized in that, this step B comprises that the variation according to the base-emitter voltage of bipolarity junction transistor changes this internal heat detection signal.
The control method 17. heat as claimed in claim 15 is turned back more comprises the initial value of setting this internal heat detection signal.
The control method 18. heat as claimed in claim 15 is turned back is characterized in that, this first door signal and this second door signal are equal to each other.
The control method 19. heat as claimed in claim 15 is turned back is characterized in that, this first door signal and this second door signal are unequal each other.
The control method 20. heat as claimed in claim 15 is turned back is characterized in that, this step C comprises:
Relatively this external heat detection signal and this first door signal, and this internal heat detection signal and this second door signal produce overheated detecting voltage according to this; And
Relatively this overheated detecting voltage with from the feedback voltage of this light-emitting diode, to determine this thermal conditioning signal.
The control method 21. heat as claimed in claim 20 is turned back is characterized in that, this feedback voltage is the function of this drive current.
The control method 22. heat as claimed in claim 15 is turned back is characterized in that, this step C more comprises by this drive current, makes that this light-emitting diode is overheated automatically closes to reduce temperature.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201010000760.4A CN102131324B (en) | 2010-01-18 | 2010-01-18 | Thermal foldback control circuit and control method of light-emitting diode (LED) |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201010000760.4A CN102131324B (en) | 2010-01-18 | 2010-01-18 | Thermal foldback control circuit and control method of light-emitting diode (LED) |
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| Publication Number | Publication Date |
|---|---|
| CN102131324A true CN102131324A (en) | 2011-07-20 |
| CN102131324B CN102131324B (en) | 2015-03-18 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN201010000760.4A Active CN102131324B (en) | 2010-01-18 | 2010-01-18 | Thermal foldback control circuit and control method of light-emitting diode (LED) |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9265119B2 (en) | 2013-06-17 | 2016-02-16 | Terralux, Inc. | Systems and methods for providing thermal fold-back to LED lights |
| CN114023739A (en) * | 2022-01-10 | 2022-02-08 | 上海奥简微电子科技有限公司 | Temperature sensing circuit and thermal feedback protection circuit |
| CN114035643A (en) * | 2022-01-10 | 2022-02-11 | 上海奥简微电子科技有限公司 | Temperature control protection circuit |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102005018175A1 (en) * | 2005-04-19 | 2006-10-26 | Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH | LED module and LED lighting device with several LED modules |
| US7986112B2 (en) * | 2005-09-15 | 2011-07-26 | Mag Instrument, Inc. | Thermally self-stabilizing LED module |
| KR20090019766A (en) * | 2006-02-10 | 2009-02-25 | 티아이알 테크놀로지 엘피 | Light source intensity control system and method |
| CN201374838Y (en) * | 2009-03-11 | 2009-12-30 | 四川九洲铭伟半导体照明有限公司 | LED driving power source |
-
2010
- 2010-01-18 CN CN201010000760.4A patent/CN102131324B/en active Active
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9265119B2 (en) | 2013-06-17 | 2016-02-16 | Terralux, Inc. | Systems and methods for providing thermal fold-back to LED lights |
| CN114023739A (en) * | 2022-01-10 | 2022-02-08 | 上海奥简微电子科技有限公司 | Temperature sensing circuit and thermal feedback protection circuit |
| CN114035643A (en) * | 2022-01-10 | 2022-02-11 | 上海奥简微电子科技有限公司 | Temperature control protection circuit |
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| CN102131324B (en) | 2015-03-18 |
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