阅读说明：本技术 温控电路和发光装置 (Temperature control circuit and light emitting device ) 是由 李文禹 张剑 谷红生 姜晓宁 李鹏 李兴亮 张晶 赵元培 于 2020-12-21 设计创作，主要内容包括：本申请公开了一种用于LED灯的温控电路和发光装置。温控电路包括调节模块和滞回过温保护模块。调节模块用于在LED灯的温度升高至预设调控区间范围内时,调节LED灯的驱动电流以抑制LED灯的温度升高；滞回过温保护模块用于在LED灯的温度大于第一阈值时关闭LED灯,并在LED灯的温度由第一阈值降低到第二阈值时重新启动LED灯。本申请的LED温控电路带有滞回功能的过温保护模块和电流随温度自适应的调节模块,从而同时具有过温保护和温度自适应调节功能,可以避免LED灯过温工作,延长LED灯的使用寿命。此外,过温保护模块还增加了重新启动LED灯的温度滞回区间可以避免LED闪烁,进一步延长LED灯的寿命。(The application discloses a temperature control circuit and a light emitting device for an LED lamp. The temperature control circuit comprises an adjusting module and a hysteresis over-temperature protection module. The adjusting module is used for adjusting the driving current of the LED lamp to inhibit the temperature rise of the LED lamp when the temperature of the LED lamp rises to be within the range of a preset adjusting and controlling interval; the hysteresis over-temperature protection module is used for turning off the LED lamp when the temperature of the LED lamp is greater than a first threshold value, and restarting the LED lamp when the temperature of the LED lamp is reduced from the first threshold value to a second threshold value. The LED temperature control circuit has the over-temperature protection module with the hysteresis function and the current adjusting module with the temperature self-adaption, so that the over-temperature protection and temperature self-adaption adjusting functions are achieved, over-temperature work of the LED lamp can be avoided, and the service life of the LED lamp is prolonged. In addition, the over-temperature protection module also increases the temperature hysteresis interval for restarting the LED lamp, so that the LED lamp can be prevented from flickering, and the service life of the LED lamp is further prolonged.)

1. A temperature control circuit for an LED lamp, the temperature control circuit comprising:

the adjusting module is used for adjusting the driving current of the LED lamp to inhibit the temperature rise of the LED lamp when the temperature of the LED lamp rises to be within a preset adjusting and controlling range; and

the hysteresis over-temperature protection module is used for turning off the LED lamp when the temperature of the LED lamp is greater than a first threshold value, and restarting the LED lamp when the temperature of the LED lamp is reduced from the first threshold value to a second threshold value.

2. The temperature-controlled circuit of claim 1, wherein the hysteretic over-temperature protection module comprises: the temperature sensing circuit comprises a temperature sensing element, a first resistor, a second resistor, a first operational amplifier, a third resistor and a fourth resistor;

one end of the first resistor is connected with a first power supply, and the other end of the first resistor is connected with the temperature sensing element and the second resistor; the temperature sensing element is connected with the first resistor and the ground and is used for measuring the temperature of the LED lamp in real time;

one end of the second resistor is connected with the first resistor and the temperature sensing element, and the other end of the second resistor is connected with the first input end of the first operational amplifier;

the third resistor is connected with the second input end and the output end of the first operational amplifier;

the fourth resistor is connected to the second input terminal of the first operational amplifier and ground.

3. The temperature control circuit of claim 2, wherein the output voltage of the output terminal of the first operational amplifier is a difference between the input voltage of the first input terminal and the reference voltage.

4. The temperature control circuit according to claim 1, further comprising a constant current driving module for outputting a constant driving current.

5. The temperature control circuit according to claim 4, further comprising a first MOS transistor and a second MOS transistor, wherein the first MOS transistor is connected to the over-temperature hysteresis protection module, and the second MOS transistor is connected to the constant current driving module.

6. The temperature control circuit according to claim 1, further comprising a third MOS transistor, a fourth MOS transistor, a fifth MOS transistor and a sixth MOS transistor, wherein the third MOS transistor and the fourth MOS transistor are a set of current mirrors, and the fifth MOS transistor and the sixth MOS transistor are a set of current mirrors.

7. The temperature control circuit of claim 1, wherein the adjusting module is configured to adjust a first current output by the temperature control circuit according to a temperature rise, and adjust a second current flowing through the LED lamp by adjusting a magnitude of the first current to suppress the temperature rise.

8. The temperature control circuit of claim 1, wherein the regulation module comprises a current source circuit comprising: the temperature sensing device comprises a temperature sensing element, a first resistor, a fifth resistor, a sixth resistor, a second operational amplifier, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor and a Darlington tube;

one end of the first resistor is connected with a first power supply, and the other end of the first resistor is connected with the temperature sensing element and the fifth resistor; the temperature sensing element is connected with the first resistor and the ground and is used for measuring the temperature of the LED lamp in real time;

one end of the fifth resistor is connected with the first resistor and the temperature sensing element, and the other end of the fifth resistor is connected with the first input end of the second operational amplifier;

the sixth resistor is connected with the second input end of the second operational amplifier and the ground;

the seventh resistor and the eighth and tenth resistors are connected in series to the first input terminal and the second input terminal of the second operational amplifier, the eighth resistor is connected to one end of the seventh resistor and the first input terminal of the second operational amplifier, and the ninth resistor is connected to the other end of the seventh resistor and the second input terminal of the second operational amplifier;

the tenth resistor is connected with the output end of the second operational amplifier and the base electrode of the Darlington tube, and the emitting electrode of the Darlington tube is connected with the other end of the seventh resistor.

9. The temperature control circuit of claim 7, wherein the conditioning module further comprises: the self-adaptive adjusting unit is used for controlling the seventh mos tube to be turned on and outputting the first current to adjust a second current flowing through the LED lamp when the temperature of the LED lamp rises to be within the range of the preset adjusting interval.

10. A light-emitting device, comprising an LED lamp and the temperature control circuit of claims 1 to 9, wherein the temperature control circuit is connected to the LED lamp.

Technical Field

The application relates to the technical field of LED lighting circuit control, in particular to a temperature control circuit and a light-emitting device.

Background

Compared with the traditional luminescent lamp, the Light Emitting Diode (LED) lamp has the advantages of high energy saving, long service life, multiple and changeable colors, environmental protection and the like, thereby being widely applied in various fields.

However, the current LED driving circuit is not well matched with the LED lamp, and the operating temperature of the LED driving circuit seriously affects the operating life of the LED, and the higher the temperature is, the shorter the life is.

Disclosure of Invention

In view of this, embodiments of the present application provide a temperature control circuit and a light emitting device.

The application provides a temperature control circuit for an LED lamp. The temperature control circuit comprises an adjusting module and a hysteresis over-temperature protection module. The adjusting module is used for adjusting the driving current of the LED lamp to inhibit the temperature rise of the LED lamp when the temperature of the LED lamp rises to be within a preset adjusting and controlling range; the hysteresis over-temperature protection module is used for turning off the LED lamp when the temperature of the LED lamp is greater than the first threshold value, and restarting the LED lamp when the temperature of the LED lamp is reduced from the first threshold value to a second threshold value.

In certain embodiments, the hysteretic over-temperature protection module comprises: the temperature sensing circuit comprises a temperature sensing element, a first resistor, a second resistor, a first operational amplifier, a third resistor and a fourth resistor; one end of the first resistor is connected with a first power supply, and the other end of the first resistor is connected with the temperature sensing element and the second resistor; the temperature sensing element is connected with the first resistor and the ground and is used for measuring the temperature of the LED lamp in real time; one end of the second resistor is connected with the first resistor and the temperature sensing element, and the other end of the second resistor is connected with the first input end of the first operational amplifier; the third resistor is connected with the second input end and the output end of the first operational amplifier; the fourth resistor is connected to the second input terminal of the first operational amplifier and ground.

In some embodiments, the output voltage of the output terminal of the first operational amplifier is a difference between the input voltage of the first input terminal and the reference voltage.

In some embodiments, the temperature control circuit further includes a constant current driving module, and the constant current driving module is configured to output a constant driving current.

In some embodiments, the temperature control circuit further includes a first MOS transistor and a second MOS transistor, the first MOS transistor is connected to the hysteresis over-temperature protection module, and the second MOS transistor is connected to the constant current driving module.

In some embodiments, the temperature control circuit further includes a third MOS transistor, a fourth MOS transistor, a fifth MOS transistor, and a sixth MOS transistor, where the third MOS transistor and the fourth MOS transistor are a set of current mirrors, and the fifth MOS transistor and the sixth MOS transistor are a set of current mirrors.

In some embodiments, the adjusting module is configured to adjust a first current output by the temperature control circuit with an increase in temperature, and adjust a second current flowing through the LED lamp by adjusting a magnitude of the first current to suppress the increase in temperature.

In some embodiments, the regulation module comprises a current source circuit comprising: the temperature sensing device comprises a temperature sensing element, a first resistor, a fifth resistor, a sixth resistor, a second operational amplifier, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor and a Darlington tube; one end of the first resistor is connected with a first power supply, and the other end of the first resistor is connected with the temperature sensing element and the fifth resistor; the temperature sensing element is connected with the first resistor and the ground and is used for measuring the temperature of the LED lamp in real time; one end of the fifth resistor is connected with the first resistor and the temperature sensing element, and the other end of the fifth resistor is connected with the first input end of the second operational amplifier; the sixth resistor is connected with the second input end of the second operational amplifier and the ground; the seventh resistor and the eighth and tenth resistors are connected in series to the first input terminal and the second input terminal of the second operational amplifier, the eighth resistor is connected to one end of the seventh resistor and the first input terminal of the second operational amplifier, and the ninth resistor is connected to the other end of the seventh resistor and the second input terminal of the second operational amplifier; the tenth resistor is connected with the output end of the second operational amplifier and the base electrode of the Darlington tube, and the emitting electrode of the Darlington tube is connected with the other end of the seventh resistor.

In certain embodiments, the adjustment module further comprises: the self-adaptive adjusting unit is used for controlling the seventh mos tube to be turned on and outputting the first current to adjust a second current flowing through the LED lamp when the temperature of the LED lamp rises to be within the range of the preset adjusting interval.

The present application further provides a light emitting device. The lighting device comprises an LED lamp and the temperature control circuit of any one of the preceding claims, wherein the temperature control circuit is connected with the LED lamp.

The LED temperature control circuit has the over-temperature protection module with the hysteresis function and the current adjusting module with the temperature self-adaption, so that the over-temperature protection and temperature self-adaption adjusting functions are achieved, over-temperature work of the LED lamp can be avoided, and the service life of the LED lamp is prolonged. In addition, the over-temperature protection module also increases the temperature hysteresis interval for restarting the LED lamp, so that the LED lamp can be prevented from flickering, and the service life of the LED lamp is further prolonged.

Drawings

The foregoing and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic diagram of a temperature control circuit according to some embodiments of the present application;

FIG. 2 is a schematic diagram of a current source circuit of a conditioning module in a temperature control circuit according to some embodiments of the present application;

fig. 3 is a circuit schematic diagram of a hysteretic over-temperature protection module in a temperature control circuit according to some embodiments of the present disclosure.

Detailed Description

Reference will now be made in detail to embodiments of the present application, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining the present application and should not be construed as limiting the present application.

Compared with the traditional luminescent lamp, the Light Emitting Diode (LED) lamp has the advantages of high energy saving, long service life, multiple and changeable colors, environmental protection and the like, thereby being widely applied in various fields. However, the existing driving circuit of the LED lamp cannot be well matched with the LED lamp, and has the problems of mismatched service life, low efficiency, poor heat dissipation, and the like. It will be appreciated that the operating temperature of the circuit significantly affects the operating life of the LED lamp, with higher temperatures leading to shorter lifetimes.

To solve this problem, referring to fig. 1, the present application provides a temperature control circuit 100 for an LED lamp. The temperature control circuit 100 includes a regulation module 10 and a hysteresis overheat protection module 20. The adjusting module 10 is configured to adjust a driving current of the LED lamp to suppress a temperature increase of the LED lamp when the temperature of the LED lamp increases to a preset adjusting range. The hysteresis over-temperature protection module 20 is used for turning off the LED lamp when the temperature of the LED lamp is greater than a first threshold value, and restarting the LED lamp when the temperature of the LED lamp is reduced from the first threshold value to a second threshold value.

Specifically, the maximum value of the preset regulation and control interval range may be the first threshold, that is, when the temperature exceeds the preset regulation and control interval range, the temperature control circuit 100 may control to turn off the LED lamp through the hysteresis over-temperature protection module 20, and restart the LED lamp when the temperature of the LED lamp is reduced from the first threshold to the second threshold. Wherein the temperature range interval between the first threshold value and the second threshold value is a temperature hysteresis interval. Therefore, the second threshold may be a temperature value within the preset regulation range, or may be a temperature value lower than the preset regulation range.

For example, the preset regulation and control interval range is [40 ° and 70 °, the first threshold may be 70 °, and when the temperature of the LED lamp exceeds the first threshold, the temperature control circuit 100 may control the LED lamp to be turned off through the hysteresis over-temperature protection module 20, so that the LED lamp can be prevented from over-temperature operation, and the service life of the LED lamp is prolonged. When the temperature of the LED lamp is decreased from 70 ° to 50 °, the hysteresis over-temperature protection module 20 controls to restart the LED lamp, [50 °, 70 ° ] is a temperature hysteresis interval. The second threshold may also be lower than the preset regulation and control range, for example, the second threshold is 30 °, and when the temperature of the LED lamp decreases from 70 ° to 30 °, the over-temperature hysteresis protection module 20 controls to restart the LED lamp, [30 °, 70 ° ] is the temperature hysteresis range. The problem of LED lamp scintillation can effectively be avoided through setting up the temperature hysteresis interval, further prolong the life of LED lamp.

The LED temperature control circuit has the over-temperature protection module 20 with the hysteresis function and the adjusting module 10 with the current adaptive to the temperature, so that the over-temperature protection and temperature adaptive adjusting functions are achieved, over-temperature work of an LED lamp can be avoided, and the service life of the LED lamp is prolonged. In addition, the over-temperature protection module 20 also increases the temperature hysteresis interval for restarting the LED lamp, so as to prevent the LED from flickering, and further prolong the service life of the LED lamp.

Referring to fig. 1, the temperature control circuit 100 includes a first MOS transistor M27 and a second MOS transistor M30, the first MOS transistor M27 is connected to the hysteresis over-temperature protection module 20, and the second MOS transistor M30 is connected to the constant current driving module 30.

Specifically, the working principle of the constant current driving module 30 is as follows: when the current passing through M30 increases, the voltage of R7 increases, and the voltage U at the inverting terminal of the third operational amplifier U6A is enabled by the feedback action of R7_–And is increased. The negative feedback structure enables the output voltage of the third operational amplifier U6A to be reduced, namely the grid voltage of the switching tube M30 is reduced, and M30The leakage current is reduced and dynamic equilibrium is reached so that the current flowing out of M30 remains constant. U due to clamping action of operational amplifier₊＝U_–Thus determining the current I of R7₀As shown in the following formula:

the clamping action is a measure for limiting the potential of a certain point to a specified potential, and the clamping action is an overvoltage protection technology.

The temperature control circuit 100 further includes a third MOS transistor M28, a fourth MOS transistor M29, a fifth MOS transistor M31, and a sixth MOS transistor M33, where the third MOS transistor M28 and the fourth MOS transistor M29 are a set of current mirrors, and the fifth MOS transistor M31 and the sixth MOS transistor M33 are a set of current mirrors.

It can be understood that, since the MOS transistor is equivalent to a switching valve, and the state of the MOS transistor can be divided into three states, which are: the MOS tube valve comprises a saturation region, an amplification region and a cut-off region, wherein the saturation region refers to the fully-opened state of the MOS tube valve, the amplification region refers to the opening process of the MOS tube valve, and the cut-off region refers to the closed state of the MOS tube valve. Specifically, the third MOS transistor M28, the fourth MOS transistor M29, the fifth MOS transistor M31, and the sixth MOS transistor M33 are all in a saturation region, that is, M28 and M29, and M31 and M33 are all in a fully open state of the valve.

One end of M28 is connected with M30, one end of M33 is connected with the LED lamp, the other end of M28 is connected with M29 to form a group of current mirror images, one end of M31 is connected with M29, and the other end of M31 is connected with M33 to form a second group of current mirror images. Thus, the current I flowing through M30₀After the mirror action of M28 and M29, the mirror action of M31 and M33 generates a corresponding mirror current KI at M33₀For driving the LED lamp. Through the above process, the driving current of the LED lamp at this time is:

wherein K is K1K2, where K1 is the width to length ratio of M29 to M28, and K2 is the width to length ratio of M31 to M33. The width-length ratio is the ratio of the width to the length of a conducting channel of the MOS tube, and the larger the width-length ratio is, the larger the rated current (Id) of the MOS tube passes, namely the width-length ratio is in direct proportion to Id.

The internal circuits of the regulation module 10 and the hysteretic over-temperature protection module 20 and the operation principle thereof will be described in detail below.

Referring to fig. 1 and 2, the adjusting module 10 includes a current source circuit PTAT. The current source circuit PTAT is I in FIG. 1_PTATA circuit represented in a symbol. The current source circuit PTAT includes: the temperature sensing element NTC1, a first resistor R3, a fifth resistor R5, a sixth resistor R29, a second operational amplifier U6A, a seventh resistor R31, an eighth resistor R2, a ninth resistor R33, a tenth resistor R27 and a Darlington tube (Q1 and Q3). One end of the first resistor R3 is connected with the first power supply 3.3V, and the other end of the first resistor R3 is connected with the temperature sensing element NTC1 and the fifth resistor R5; the temperature sensing element NTC1 is connected with the first resistor R3 and the ground, and the temperature sensing element NTC1 is used for measuring the temperature of the LED lamp in real time.

One end of the fifth resistor R5 is connected with the first resistor R3 and the temperature sensing element NTC1, and the other end of the fifth resistor R5 is connected with the first input end 3 of the second operational amplifier U6A; one end of the sixth resistor R29 is connected to the second input terminal 2 of the second operational amplifier U6A and ground; the seventh resistor R31 is connected in series with the eighth resistor R2 and the tenth resistor R27 at the first input terminal 3 and the second input terminal 2 of the second operational amplifier U6A, the eighth resistor R2 is connected with one end of the seventh resistor R31 and the first input terminal 3 of the second operational amplifier U6A, and the ninth resistor R33 is connected with the other end of the seventh resistor R31 and the second input terminal 2 of the second operational amplifier U6A; the tenth resistor R27 is connected with the output terminal 1 of the second operational amplifier U6A and the base electrodes of the Darlington tubes (Q1 and Q3), and the emitter electrodes of the Darlington tubes are connected with the other end of the seventh resistor R31. As can be seen from FIG. 2, the first current I_PTATIs the current through the seventh resistor R31. The model of the second operational amplifier 6A may be TL082idr, the model of darlington tube (Q1 and Q3) is 2SCI6233, the resistance values of R5, R29, R2 and R33 may be 10K Ω, and the resistance values of R27 and R31 may be 100 Ω. It should be noted that the values labeled in fig. 2 are only one example that can be implemented, and the temperature control circuitThe various components in the circuit 100 can be provided with elements of different models or different resistances to form the temperature control circuit 100.

Referring to fig. 1, the adjusting module 10 further includes: the adaptive adjusting unit 11 and a seventh mos tube M32, the seventh mos tube M32 is connected with the LED lamp in parallel, and the first current I_PTATA second current I passing through the seventh mos tube M32 and the LED lamp_LEDThe combined flow was into a sixth mos tube M33.

The adaptive adjusting unit 11 is used for controlling the seventh mos tube M32 to be turned on and outputting a first current I when the temperature of the LED lamp rises to the preset adjusting range_PTATTo regulate a second current I flowing through the LED lamp_LED。

When the temperature of the LED lamp rises to the preset regulation range, the regulating module 10 is configured to regulate the first current I output by the temperature control circuit 100 along with the temperature rise of the LED lamp_PTATBy regulating the first current I_PTATAdjusts the second current I flowing through the LED lamp_LEDThereby suppressing an increase in the temperature of the LED lamp. Understandably, as can be seen from FIG. 1, the second current I_LEDAnd a first current I_PTATThe sum equals the current I through M33₃₃I.e. the branch to which the LED lamp is connected in parallel with the branch to which the adjusting module 10 is connected. Therefore, when the regulating module 10 regulates the first current I_PTATWhen the second current I becomes larger_LEDIs equal to I₃₃Subtract I_PTATThen, I_LEDThe value of (a) becomes small; when the regulating module 10 regulates the first current I_PTATWhen the second current I becomes smaller_LEDIs equal to I₃₃Subtract I_PTATThen, I_LEDThe value of (c) becomes large.

As can be seen from fig. 2, the operation principle of the internal circuit of the regulating module 10 is as follows: when the temperature of the lamp strip changes, the resistance of the NTC1 changes, which results in a change in the voltage of the positive input terminal of the second operational amplifier U6A. In order to keep the second operational amplifier stable, the current output by the Darlington tubes (Q1, Q3) can be continuously adjusted. When the voltages across the darlington tubes (Q1, Q3) to R31 are regulated to be equal to Ut, the second operational amplifier U6A is stabilized. At this time, a current I flows through R31_PTAT：

Referring to fig. 3, the hysteresis overheat protection module 20 includes: the temperature sensing device comprises a temperature sensing element NTC1, a first resistor R3, a second resistor R4, a first operational amplifier U1A, a third resistor R1 and a fourth resistor R2. One end of the first resistor R3 is connected with a first power supply U₀The other end of the first resistor R3 is connected with the NTC1 and the second resistor R3. The temperature sensing element NTC1 is connected with the first resistor R3 and the ground, and the temperature sensing element NTC1 is used for measuring the temperature of the LED lamp in real time. One end of the second resistor R4 is connected with the first resistor R3 and the temperature sensing element NTC1, and the other end of the second resistor R4 is connected with the first input end 7 of the first operational amplifier U1A; the third resistor R1 is connected with the second input end 6 and the output end 8 of the first operational amplifier U1A; the fourth resistor R2 is connected between the second input terminal 6 of the first operational amplifier U1A and ground. As shown in FIG. 3, the second input terminal 6 of the first operational amplifier U1A is connected to the reference voltage U_{Base of}. Specifically, the temperature sensing element NTC1 may be a thermistor, and may be connected with the LED lamp in a wired or wireless manner to detect the temperature of the LED lamp in real time. The third operational amplifier U1A may be model LM339 shown in FIG. 3.

Specifically, the temperature sensing element NTC1 may be a thermistor. The temperature hysteresis comparison circuit inside the hysteresis over-temperature protection module 20 is shown in fig. 3, where R3 and NTC1 divide the voltage. When the temperature of the LED lamp changes, the resistance of the thermistor NTC1 changes, resulting in the voltage U at the first input terminal 7 (positive terminal) of the first operational amplifier U1A_tAnd (4) changing. Specifically, the higher the temperature of the LED lamp, the smaller the resistance of the thermistor NTC1, the greater the current through the NTC1, and therefore the greater the current through R3, i.e., the voltage U between R3 and NTC1 and at the connection point where R4 is connected to the first operational amplifier U1A_tAlso increases, the voltage U_tIs the voltage at the first input terminal 7 of the first operational amplifier U1A.

Referring to fig. 1, along with the temperature change measured by the NTC1, Uout output by the first operational amplifier U1A can control the saturation or cut-off state of M27, so as to achieve the function of hysteresis over-temperature protection, in which the circuit is short-circuited to stop the operation of the driving circuit of the LED lamp and restart the operation state.

Specifically, when the NTC1 detects that the temperature of the LED lamp is a first threshold, for example, the first threshold is 70 °, the resistance of the NTC1 of the temperature-sensing element becomes small, and the current through the R3 becomes large accordingly, that is, the voltage U between the R3 and the NTC1 and at the connection point where the R4 is connected to the first operational amplifier U1A_tAlso increases, the voltage at REF end is the reference voltage U_{Base of}Is a relative constant value, Uout ═ U_t|-|U_{Base of}If the output Uout is a positive value and slowly increases, according to the increased Uout, the mos tube can control the M27 to be slowly changed from an initial cut-off state to an amplification state and finally to reach a saturation state, so that the M27 is turned on, the circuits at two ends of the R7 are short-circuited, the whole LED driving circuit is short-circuited, and the LED lamp stops working.

Understandably, the voltage at the REF terminal is the reference voltage U_{Base of}Is a relative constant value, U_{Base of}Is related to the voltage value U1A' output by the first operational amplifier U1A. When the value of U1A' is positive, the supply voltage V of the positive terminal (terminal 7) of the first operational amplifier U1A⁺Greater than the supply voltage V of the negative terminal (terminal 6)^-For example, as shown in FIG. 3, the supply voltage V is the positive terminal (terminal 7) of the first operational amplifier U1A⁺The voltage is +15V, the power supply voltage of the negative terminal (terminal 6) of the first operational amplifier U1A is +5V, and the voltage U of the REF terminal is at this time_{Base of}Is a V⁺*(R3/(R3+R2))＝15*(R3/(R3+R2))。

When the value of U1A' is negative, the supply voltage V is applied to the positive terminal (terminal 7) of the first operational amplifier U1A⁺Less than the supply voltage V of the negative terminal (terminal 6)^-When, for example, the supply voltage V of the positive terminal (terminal 7) of the first operational amplifier U1A⁺Is +2V, the power supply voltage of the negative terminal (terminal 6) of the first operational amplifier U1A is +5V, and the voltage U of the REF terminal is at this time_{Base of}Is a V^-(R3/(R3+ R2)) -5 (R3/(R3+ R2)). That is, the reference voltage U of the REF terminal_{Base of}May be V⁺(R3/(R3+ R2)) or V^-(R3/(R3+ R2)), and a reference voltage U at the REF end_{Base of}To the positive and negative terminals of the first operational amplifier U1AThe magnitude between the supply voltages at the terminals and the resistance values of R2 and R3 are related.

When the NTC1 detects that the temperature of the LED lamp drops from a first threshold to a second threshold, for example, the second threshold is 40 °, the resistance of the NTC1 of the temperature sensing element becomes large, and the current passing through R3 also becomes correspondingly small, i.e., the voltage U between R3 and NTC1 and at the connection point where R4 is connected to the first operational amplifier U1A_tAlso becomes smaller, the voltage at REF end is the reference voltage U_{Base of}A relatively constant value, then, Uout ═ U_t|-|U_{Base of}I, the output Uout becomes smaller, and accordingly, the control M27 changes slowly from the initial saturation state to the reduction state when U_tLess than | U_{Base of}When Uout is negative, |, M27 eventually returns to the off state. At this time, M27 changes from on state to off state, so that the circuits at both ends of R7 work again, the whole LED driving circuit starts to work, and the LED lamp starts to work.

Understandably, the output voltage U at the output terminal 8 of the first operational amplifier U1A_outIs the input voltage U of the first input terminal 7_tAbsolute value and reference voltage U_{Base of}Difference in absolute value.

Referring to fig. 1, the temperature control circuit 100 further includes a constant current driving module 30, and the constant current driving module 30 is configured to output a constant driving current.

Specifically, the constant current driving module 30 is mainly composed of a voltage reference source 31 (U)_ref) And a third operational amplifier 32, i.e. an inner part of the dashed box in fig. 1. The temperature control circuit 100 can output a constant current through the negative feedback structure of the constant current driving module 30, thereby reducing the power consumption of the circuit. The negative feedback structure is that in fig. 1, a current flowing from the switching tube M30 and flowing through one branch 33 of the resistor R7 is connected to the second input terminal of the third operational amplifier 32, so that the current flowing from the output terminal of the third operational amplifier 32 is shunted to the branch 33 of the resistor R7 through the switching tube M30, and is fed back to the second input terminal of the third operational amplifier 32 by the magnitude of the current shunted to the resistor R7.

The present application also provides a light emitting device 200. The lighting device 200 comprises a temperature control circuit 100 and an LED lamp, and the temperature control circuit 100 is connected with the LED lamp. When the temperature of the LED lamp is within the preset adjusting range, the light emitting device 200 adjusts the driving current passing through the LED lamp through the adjusting module 10 in the temperature control circuit 100, so as to prevent the LED lamp from working at an excessive temperature and prolong the service life of the LED lamp. When the temperature of the LED lamp exceeds the preset regulation range, the light emitting device 200 controls the operation and off state of the LED lamp through the hysteresis over-temperature protection module 20 in the temperature control circuit 100, and in addition, the hysteresis over-temperature protection module 20 is provided with a temperature hysteresis range for restarting the LED lamp, so that the LED can be prevented from flickering, and the service life of the LED lamp can be further prolonged.