CN103167669A - Light-emitting diode (LED) drive circuit - Google Patents
Light-emitting diode (LED) drive circuit Download PDFInfo
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- CN103167669A CN103167669A CN2011104175340A CN201110417534A CN103167669A CN 103167669 A CN103167669 A CN 103167669A CN 2011104175340 A CN2011104175340 A CN 2011104175340A CN 201110417534 A CN201110417534 A CN 201110417534A CN 103167669 A CN103167669 A CN 103167669A
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Abstract
The invention discloses a light-emitting diode (LED) drive circuit with temperature feedback to solve the problem of overhigh temperature of the LED drive circuit. The existing LED drive chip can stop working at the overhigh temperature to cause an LED to flicker. The LED drive chip comprises an error amplifier, and further comprises an over-temperature identification module and a voltage control module, wherein the over-temperature identification module is used for identifying over temperature of the LED drive chip, the voltage control module is used for replacing an original reference voltage, connected with an equidirectional input end of the error amplifier, with a new reference voltage under the condition that the identification module identifies the over temperature, and voltage values of the new reference voltage are less than that of the original reference voltage. An output result COMP of the error amplifier is further changed. The LED drive chip further comprises a pulse-width modulation (PWM) comparator. Due to the fact that the COMP is closely differed from current of the LED, the current flowing through the LED is further controlled, and then the temperature of the LED drive chip is changed through the feedback.
Description
Technical field
The present invention relates to the LED drive circuit field, relate in particular to the LED drive circuit with overheat protector.
Background technology
In order to prevent that excess Temperature from damaging LED and driving chip, LED drives chip internal and usually was integrated with temperature control circuit at present, when chip temperature surpasses predetermined temperature, crosses temperature control circuit control chip is quit work, and reaches the cooling purpose.But LED drives chip and quits work, and LED is extinguished, and after temperature reduced, LED drove chip and reworks, and LED lights.The flicker of LED will appear like this.
Summary of the invention
The invention provides a kind of LED drive circuit with temperature feedback, can quit work to prevent existing LED drive circuit excess temperature, cause LED the problem of flicker to occur.
LED drive circuit provided by the invention comprises error amplifier, also comprises: the excess temperature identification module is used for identifying the LED drive circuit excess temperature; Voltage control module is used in the situation that the excess temperature identification module identifies excess temperature, with described error amplifier in the same way the former reference voltage that connects of input be replaced by new reference voltage, the magnitude of voltage of described new reference voltage is lower than the magnitude of voltage of former reference voltage.
LED drive circuit provided by the invention comprises error amplifier, and the excess temperature identification module is used for identifying LED and drives the chip excess temperature; Voltage control module is used in the situation that the excess temperature identification module identifies excess temperature, with described error amplifier in the same way the former reference voltage that connects of input be replaced by new reference voltage, the magnitude of voltage of described new reference voltage is lower than the magnitude of voltage of former reference voltage.
LED drive circuit provided by the invention and LED circuit when excess temperature by reduce error amplifier in the same way the voltage that connects of incoming end realized that LED drives the cooling of chip and LED, need not to allow LED drive chip quits work, can quit work thereby avoided existing LED to drive the chip excess temperature, cause LED the problem of flicker to occur.
The present invention utilizes the forward conduction voltage of diode to become the characteristic of negative correlation with temperature, makes the circuit structure that detects the LED chip temperature simple, is easy to realize.
Description of drawings
The LED drive circuit structural representation that Fig. 1 provides for the embodiment of the present invention;
Fig. 2 is a kind of concrete structure schematic diagram of voltage control module in the embodiment of the present invention;
Fig. 3 is LED drive circuit partial interior structure chart in the embodiment of the present invention;
Fig. 4 is LED reference voltage and LED_OTP_EN signal generating circuit structure chart.
Embodiment
In existing overheat protector scheme, in case LED drives the chip excess temperature, LED driving chip will quit work, and flicker will appear in LED, and LED drives chip current I=V
ref/ R
Sense, wherein Vref is that LED drives the interior error amplifier of the chip reference voltage of input access in the same way, R
SenseBe current sense resistor, if described reference voltage can reduce, the electric current that flows through power tube also can reduce, and the conduction loss of power tube and switching loss all can reduce, and drives chip power-consumption thereby reduce LED.Along with chip power-consumption reduces, chip temperature also can descend.
Based on above-mentioned thinking, the embodiment of the present invention proposes following LED drive circuit, to avoid having now the problems such as causing security incident that quits work when LED drives the chip excess temperature.
The LED drive circuit structural representation that Fig. 1 provides for the embodiment of the present invention, in conjunction with this figure, described LED drives chip 10, comprising:
Excess temperature identification module 11 is used for identifying LED and drives chip 10 excess temperatures;
Due to the magnitude of voltage of the new reference voltage magnitude of voltage lower than former reference voltage, so after adopting new reference voltage, the temperature that LED drives chip can reduce.
After LED driving chip temperature is reduced to normal temperature, optionally, LED drives chip 10 can also comprise voltage reply module 14, be used for when LED driving chip temperature is reduced to normal temperature, with error amplifier 13 in the same way the new reference voltage that connects of input 130 be replaced by former reference voltage, drive the properties of chip to guarantee LED.
New reference voltage can have various ways to obtain, and can also can generate simultaneously former reference voltage and new reference voltage by former reference voltage is turned down acquisition, then when needs adopt new reference voltage, switches.
Fig. 2 is a kind of concrete structure schematic diagram of voltage control module in the embodiment of the present invention, and voltage control module 12 can have various structures, and structure shown in Figure 2 specifically comprises:
Reference voltage generates submodule 120, is used for generating former reference voltage and new reference voltage;
Reference voltage switching submodule 121 be used for to receive reference voltage and generates former reference voltage and the new reference voltage that submodule 120 generates, and when excess temperature, with export to error amplifier 13 in the same way the former reference voltage of input switch to new reference voltage.
Such scheme has realized that by the reduction of reference voltage level LED drives the reduction of chip temperature, has solved the problem of prior art.
The embodiment of the present invention proposes and can also control submodule 15 by drive the interior LED temperature that arranges of chip 10 at LED in addition, be used for driving chip 10 not during excess temperature at LED excess temperature and LED, with error amplifier 13 in the same way the former reference voltage that connects of input be replaced by the LED reference voltage, the magnitude of voltage of described LED reference voltage is lower than the magnitude of voltage of former reference voltage.Wherein LED excess temperature condition can have multiple choices according to actual conditions, and for example can surpass 150 degrees centigrade is excess temperature.
Fig. 3 is that in the embodiment of the present invention, LED drives chip part cut-away view, the wherein new reference voltage Vref of structural generation shown in label 42/2 and former reference voltage Vref, the voltage that generates is connected to logic choice structure 41, if LED drives the chip excess temperature, the CHIP_OTP_EN signal is high level " 1 ", logic choice structure 41 is exported new reference voltage Vref/2, with error amplifier 40 in the same way the former reference voltage Vref that connects of input 400 be replaced by new reference voltage Vref/2, make LED drive the chip cooling; When LED driving chip is reduced to normal temperature, the CHIP_OTP_EN signal is low level " 0 ", if this moment, LED_OTP_EN was low level " 0 ", the logic choice structure 41 former reference voltage Vref of output, be replaced by former reference voltage Vref in the new reference voltage Vref of input 400 connections/2 in the same way with error amplifier 40.
LED_OTP_EN is high level " 1 " when the LED excess temperature, if this moment, the CHIP_OTP_EN signal was low level " 0 ", logic choice structure 41 is exported LED reference voltage VREF_IN, with error amplifier 40 in the same way the former reference voltage Vref that connects of input 400 be replaced by LED reference voltage VREF_IN, thereby reduce the LED temperature, after the LED temperature is reduced to normal temperature, LED_OTP_EN is low level " 0 ", the logic choice structure 41 former reference voltage Vref of output, just error amplifier 40 in the same way the LED reference voltage VREF_IN that connects of input 400 be replaced by former reference voltage Vref.
Fig. 4 is LED reference voltage and LED_OTP_EN signal generating circuit structure chart, VREF_IN is obtained by the collector electrode of NPN triode and base stage connected structure and conventional, electric-resistance R1 dividing potential drop, if the LED drive circuit temperature rises, the base voltage of triode descends, thereby VREF_IN reduces lower than former reference voltage Vref, LED_OTP_EN signal output high level " 1 " makes LED reference voltage VREF_IN substitute former reference voltage Vref, reaches LED and reduces the temperature purpose.After the temperature decline of LED was enough hanged down, the base voltage of triode rose again, and enable signal LED_OTP_EN can become low level " 0 ", and chip is got back to normal operating conditions.
By changing the reference voltage of error amplifier positive input when the variations in temperature, further change the Output rusults COMP of error amplifier, because the size of COMP and the size of current that flows through LED closely differ, further controlled the electric current that flows through LED.Feed back again the variations in temperature that makes LED drive chip.
The embodiment of the present invention also provides LED circuit, and this LED circuit comprises that LED drives chip, and what the structure of LED driving chip can adopt is the structure that above-described embodiment LED drives chip.Optionally, LED drives chip and also comprises: LED excess temperature identification module is used for identifying the LED excess temperature; The LED temperature control modules, be used for identifying LED excess temperature and LED at LED excess temperature identification module and drive chip not during excess temperature, with error amplifier in the same way the former reference voltage of input switch to the LED reference voltage, the magnitude of voltage of described LED reference voltage is lower than former reference voltage.
Wherein the LED reference voltage can raise and reduce along with temperature, and temperature is higher, and the LED reference voltage is lower, and the LED temperature reduces more fast more.Optionally, LED circuit also comprises: LED reference voltage generation module is used for generating LED reference voltage, described LED reference voltage and temperature negative correlation.The structure of LED reference voltage generation module can be with reference to structure shown in Figure 4.
Obviously, those skilled in the art can carry out various changes and modification and not break away from the spirit and scope of the present invention the present invention.Like this, if within of the present invention these are revised and modification belongs to the scope of claim of the present invention and equivalent technologies thereof, the present invention also is intended to comprise these changes and modification interior.
Claims (9)
1. the LED drive circuit with temperature feedback, comprise error amplifier, it is characterized in that, comprising: the excess temperature identification module is used for identifying LED and drives the chip excess temperature; Voltage control module is used in the situation that the excess temperature identification module identifies excess temperature, with described error amplifier in the same way the former reference voltage that connects of input be replaced by new reference voltage, the magnitude of voltage of described new reference voltage is lower than the magnitude of voltage of former reference voltage; Also comprise the PWM comparator, be used for producing cut-off signals.
2. LED drive circuit as claimed in claim 1, is characterized in that, described voltage control module specifically comprises: reference voltage generates submodule, is used for generating former reference voltage and new reference voltage; The reference voltage switching submodule be used for to receive reference voltage and generates former reference voltage and the new reference voltage that submodule generates, and when excess temperature, with export to error amplifier in the same way the former reference voltage of input switch to new reference voltage.
3. LED drive circuit as claimed in claim 1, is characterized in that, new reference voltage level and former reference voltage level 1/2 to 1/3.
4. LED drive circuit as claimed in claim 1, is characterized in that, the excess temperature condition is: LED drives chip temperature higher than 150 degrees centigrade.
5. LED drive circuit as claimed in claim 1, it is characterized in that, described voltage control module also specifically comprises: the LED temperature is controlled submodule, be used for driving chip not during excess temperature at LED excess temperature and LED, with error amplifier in the same way the former reference voltage that connects of input be replaced by the LED reference voltage, the magnitude of voltage of described LED reference voltage is lower than former reference voltage.
6. LED drive circuit as claimed in claim 1, is characterized in that, comprises that also voltage replys module, be used for when temperature is reduced to normal value, described error amplifier in the same way input connect former reference voltage.
7. LED drive circuit as claimed in claim 1, is characterized in that, also comprises: LED excess temperature identification module is used for identifying the LED excess temperature; The LED temperature control modules, be used for identifying LED excess temperature and LED at LED excess temperature identification module and drive chip not during excess temperature, with error amplifier in the same way the former reference voltage of input switch to the LED reference voltage, the magnitude of voltage of described LED reference voltage is lower than former reference voltage.
8. LED drive circuit as claimed in claim 1, is characterized in that, also comprises: LED reference voltage generation module is used for generating LED reference voltage, described LED reference voltage and temperature negative correlation.
9. LED drive circuit as claimed in claim 1, it is characterized in that, described LED drives chip and comprises that also voltage replys module, be used for when temperature is reduced to normal value, with described error amplifier in the same way the LED reference voltage that connects of input be replaced by former reference voltage.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011104175340A CN103167669A (en) | 2011-12-14 | 2011-12-14 | Light-emitting diode (LED) drive circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011104175340A CN103167669A (en) | 2011-12-14 | 2011-12-14 | Light-emitting diode (LED) drive circuit |
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| Publication Number | Publication Date |
|---|---|
| CN103167669A true CN103167669A (en) | 2013-06-19 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2011104175340A Pending CN103167669A (en) | 2011-12-14 | 2011-12-14 | Light-emitting diode (LED) drive circuit |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103607822A (en) * | 2013-11-25 | 2014-02-26 | 广东欧珀移动通信有限公司 | Over-temperature protection method and device of flashlight of terminal |
| CN107390764A (en) * | 2017-07-25 | 2017-11-24 | 珠海格力节能环保制冷技术研究中心有限公司 | Thermal-shutdown circuit and method, air conditioner |
| CN108076554A (en) * | 2016-11-10 | 2018-05-25 | 华润矽威科技（上海）有限公司 | Reference voltage declines initial temperature point conditioned circuit and LED constant current driving power chip |
-
2011
- 2011-12-14 CN CN2011104175340A patent/CN103167669A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103607822A (en) * | 2013-11-25 | 2014-02-26 | 广东欧珀移动通信有限公司 | Over-temperature protection method and device of flashlight of terminal |
| CN103607822B (en) * | 2013-11-25 | 2015-08-12 | 广东欧珀移动通信有限公司 | A kind of method of overheat protector of photoflash lamp of terminal and device |
| CN108076554A (en) * | 2016-11-10 | 2018-05-25 | 华润矽威科技（上海）有限公司 | Reference voltage declines initial temperature point conditioned circuit and LED constant current driving power chip |
| CN108076554B (en) * | 2016-11-10 | 2019-08-23 | 华润矽威科技（上海）有限公司 | Reference voltage declines initial temperature point conditioned circuit and LED constant current driving power chip |
| CN107390764A (en) * | 2017-07-25 | 2017-11-24 | 珠海格力节能环保制冷技术研究中心有限公司 | Thermal-shutdown circuit and method, air conditioner |
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Application publication date: 20130619 |