Linear power-down control circuit for over-temperature protection of LED lamps

Abstract

The present invention relates to a linear power-down control circuit for over-temperature protection of an LED lamp. After obtaining power from the front-end power supply module, the reference voltage source module stabilizes the voltage and outputs the reference voltage source Vcc. The constant current control module samples the loop current of the front-end power supply. The over-temperature power regulation and shutdown module outputs the reference voltage Vr to the constant current control module. The constant current control module adjusts the constant current output to the maximum voltage limit module according to the reference voltage Vr. The maximum voltage limit module controls the current feedback to the front-end power supply module according to the constant current to control the output current of the front-end power supply module. The linear power-down control circuit for over-temperature protection of the LED lamp according to the present invention linearly reduces the output power of the LED lamp as the ambient temperature rises, realizing the reliability of the LED drive power supply while ensuring the lighting function of the LED lamp as much as possible.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and particularly to a linear power-down control circuit for over-temperature protection of LED lights. Background Art

[0002] At present, for the LED driver power supplies (LED control devices) on the market, during the process of being used in conjunction with LED lights, the LED lights will generate heat during operation, and the LED driver power supplies may also be applied to high-temperature working environments.

[0003] However, when the ambient temperature around the LED driver power supply exceeds its rated operating temperature, the service life of the LED driver power supply will be significantly shortened.

[0004] Therefore, on the premise of ensuring the lighting function of the LED lights as much as possible, it has become an urgent technical problem to extend the service life of the LED driver power supply as much as possible. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies in the prior art, and provide a linear power-down control circuit for over-temperature protection of LED lights, which linearly reduces the output power of the LED lights as the surrounding temperature rises, realizing that while ensuring the lighting function of the LED lights as much as possible, the reliability of the LED driver power supply is also ensured.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A linear power-down control circuit for over-temperature protection of LED lights includes: a front-end power supply module, a constant current control module, a maximum voltage limiting module, a reference voltage source module, and an over-temperature power adjustment and shutdown module;

[0008] The front-end power supply module supplies power to the LED lights; the front-end power supply module also supplies power to the maximum voltage limiting module and the reference voltage source module respectively;

[0009] After taking power from the front-end power supply module, the reference voltage source module stabilizes the voltage and outputs a reference voltage source Vcc; the reference voltage source Vcc supplies power to the constant current control module, the maximum voltage limiting module, and the over-temperature power adjustment and shutdown module respectively;

[0010] The constant current control module samples the loop current of the front-end power supply module; the over-temperature power adjustment and shutdown module outputs a reference voltage Vr to the constant current control module;

[0011] The constant current control module adjusts the constant current output to the maximum voltage limiting module according to the reference voltage Vr; the maximum voltage limiting module controls the current to the front-end power module according to the constant current feedback to control the output current of the front-end power module.

[0012] In one embodiment, the constant current control module includes: amplifier U1A, follower U1B, comparator U2B, resistor RS1, resistor R2, resistor R3, resistor R7, resistor R10, resistor R11, resistor R18, resistor R19, resistor R23, resistor R25, resistor R29, capacitor C5, capacitor C7 and capacitor C8;

[0013] The resistor RS1 is connected in series in the output loop of the front-end power module; the resistor RS1 is connected in series with the resistor R10 and then connected to the positive input terminal of the amplifier U1A; the positive input terminal of the amplifier U1A is also connected in series with the resistor R25 and then grounded; the capacitor C8 is connected in parallel with the resistor R25;

[0014] The negative input terminal of the amplifier U1A is connected in series with the resistor R29 and then grounded; the output terminal of the amplifier U1A is connected in series with the resistor R23 and then connected to the negative input terminal of the amplifier U1A; the capacitor C7 is connected in parallel with the resistor R23; the output terminal of the amplifier U1A is connected in series with the resistor R18 and then connected to the negative input terminal of the comparator U2B;

[0015] The positive input terminal of the comparator U2B is connected in series with the resistor R7 and then connected to the output terminal of the follower U1B; the negative input terminal of the comparator U2B is connected in series with the capacitor C5 and the resistor R19 in sequence and then connected to the output terminal of the comparator U2B; the output terminal of the comparator U2B is connected in series with the resistor R11 and used as the output terminal of the constant current control module to output a constant current to the front-end power module;

[0016] The negative input terminal of the follower U1B is connected in series with the resistor R2 and then connected to the output terminal of the follower U1B; the positive input terminal of the follower U1B is connected in series with the resistor R3 and used as the reference voltage control terminal of the constant current control module to be connected to the output terminal of the over-temperature power regulation and shutdown module.

[0017] In one embodiment, the maximum voltage limiting module includes: resistor R9, resistor R12, resistor R14, resistor R20, resistor R26, capacitor C2, capacitor C3, capacitor C4, capacitor C9, diode D1, optocoupler PC1 and three-terminal voltage regulator U4;

[0018] One end of the resistor R9 takes power V from the front-end power module 0, the other end is grounded after being successively connected in series with the resistor R14 and the resistor R26; the capacitor C3 is connected in parallel with the resistor R9;

[0019] The input end of the three-terminal voltage regulator U4 is connected to the node between the resistor R14 and the resistor R26, and the grounding end of the three-terminal voltage regulator U4 is grounded; the output end of the three-terminal voltage regulator U4 is successively connected in series with the capacitor C4 and the resistor R20 and then connected to the node between the resistor R14 and the resistor R26; the output end of the three-terminal voltage regulator U4 is also connected in series with the resistor R12 and then connected to the negative electrode of the diode D1;

[0020] The positive electrode of the diode D1 is successively connected in series with the resistor R5 and the resistor R4 and then connected to the reference voltage source Vcc; the capacitor C2 is connected in parallel with the resistor R4; the input end of the optocoupler PC1 is connected in parallel with the resistor R5; the output end of the optocoupler PC1 is fed back to the front-end power module to control the output current of the front-end power module;

[0021] The negative electrode of the diode D1 is also connected in series with the capacitor C9 and then grounded.

[0022] In one embodiment, the reference voltage source module includes: a resistor R6, a resistor R8, a resistor R21, a capacitor C6, a triode Q1, and a zener diode ZD1;

[0023] One end of the resistor R6 takes power V from the front-end power module 0 , the resistor R8 is connected in parallel with the resistor R6; the other end of the resistor R6 is connected to the collector of the triode Q1; the base of the triode Q1 is connected to the negative electrode of the zener diode ZD1; the base of the triode Q1 is also connected in series with the resistor R21 and then connected to the collector of the triode Q1; the positive electrode of the zener diode ZD1 is grounded;

[0024] The emitter of the triode Q1 is connected in series with the capacitor C6 and then grounded; the emitter of the triode Q1 serves as the output end of the maximum voltage limiting module to output the reference voltage source Vcc.

[0025] In one embodiment, the over-temperature power regulation and shutdown module includes: a resistor R13, a resistor R15, a resistor R16, a resistor R17, a resistor R22, a resistor R24, a resistor R27, a resistor R28, a resistor R30, a triode Q2, a three-terminal voltage regulator U3, and a thermistor RT1;

[0026] One end of the resistor R15 is connected to the reference voltage source Vcc of the highest voltage limiting module, and the other end is connected to the output end of the three-terminal voltage regulator U3; the ground terminal of the three-terminal voltage regulator U3 is grounded; the input end of the three-terminal voltage regulator U3 is grounded after being connected in series with the resistor R27; the input end of the three-terminal voltage regulator U3 is also connected in series with the resistor R24 and then connected to the other end of the resistor R15;

[0027] The other end of the resistor R15 is also connected in series with the resistor R13, the resistor R16 and the resistor R17 in sequence and then connected to the collector of the triode Q2; the emitter of the triode Q2 is grounded; a resistor R30 is connected across the base and the emitter of the triode;

[0028] The other end of the resistor R15 is also connected in series with the thermistor RT1 and the resistor R22 in sequence and then connected to the base of the triode Q2;

[0029] The node between the resistor R16 and the resistor R17 serves as the output end of the over-temperature power regulation and shutdown module to output the reference voltage Vr to the reference voltage control end of the constant current control module.

[0030] In one embodiment, the front-end power supply module includes: an AC-DC conversion unit, a surge protection capacitor EC1, a surge protection capacitor EC2, a resistor R1 and a capacitor C1;

[0031] The AC-DC conversion unit converts the external AC power into a DC voltage V 0 ; the output end of the AC-DC conversion unit is grounded after being connected in series with the surge protection capacitor EC2, and the resistor R1 and the surge protection capacitor EC2 are grounded; the surge protection capacitor EC1 is connected in parallel with the resistor R1; the capacitor C1 is connected in parallel with the surge protection capacitor EC1 and then serves as the output end to supply power to the LED lamp.

[0032] The linear power reduction control circuit for LED lamp over-temperature protection disclosed by the present invention linearly reduces the output power of the LED lamp as the temperature around the LED lamp rises, realizing ensuring the lighting function of the LED lamp as much as possible, and at the same time ensuring the reliability of the LED driving power supply and extending the service life of the LED driving power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0034] Figure 1It is the principle block diagram of the linear power reduction control circuit for over-temperature protection of the LED lamp in the present invention;

[0035] Figure 2 It is the circuit schematic diagram of the linear power reduction control circuit for over-temperature protection of the LED lamp in the present invention. Specific embodiments

[0036] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. The preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0037] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there can also be a middle element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be a middle element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only embodiments.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0039] As Figure 1 shown, the present invention relates to a linear power reduction control circuit 10 for over-temperature protection of an LED lamp, including: a front-end power supply module 20, a constant current control module 30, a maximum voltage limiting module 40, a reference voltage source module 50, and an over-temperature power adjustment and shutdown module 60.

[0040] As Figure 1 shown, the front-end power supply module 20 supplies power to the LED lamp 100. The front-end power supply module 20 also supplies power to the maximum voltage limiting module 40 and the reference voltage source module 50 respectively. After taking power from the front-end power supply module 20, the reference voltage source module 50 stabilizes the voltage and outputs a reference voltage source Vcc. The reference voltage source Vcc supplies power to the constant current control module 30, the maximum voltage limiting module 40, and the over-temperature power adjustment and shutdown module 60 respectively.

[0041] As Figure 1As shown, the constant current control module 30 samples the loop current of the front-end power supply module; the over-temperature power regulation and shutdown module 60 outputs a reference voltage Vr to the constant current control module 30. The constant current control module 30 adjusts the constant current output to the maximum voltage limit module 40 according to the reference voltage Vr. The maximum voltage limit module 40 controls the current to the front-end power supply module 20 based on the constant current feedback to control the output current of the front-end power supply module 20.

[0042] As Figure 2 shown, in this embodiment, the front-end power supply module 20 includes: an AC-DC conversion unit, a surge protection capacitor EC1, a surge protection capacitor EC2, a resistor R1, and a capacitor C1. The AC-DC conversion unit (AC TO DC unit) converts the external AC power into a DC voltage V 0 . The output terminal of the AC-DC conversion unit is grounded in series with the surge protection capacitor EC2, and the resistor R1 is connected in parallel with the surge protection capacitor EC2. The surge protection capacitor EC1 is connected in parallel with the resistor R1; the capacitor C1 is connected in parallel with the surge protection capacitor EC1 and then used as an output terminal to supply power to the LED lamp 100.

[0043] After the AC-DC conversion unit of the front-end power supply module 20 converts the external AC power into a DC voltage, it is subjected to primary filtering by the surge protection capacitor EC2 to obtain the DC voltage V 0 ; the DC voltage V 0 respectively supplies power to the maximum voltage limit module 40 and the reference voltage source module 50.

[0044] In addition, after the DC voltage V 0 obtained after primary filtering by the surge protection capacitor EC2 is subjected to secondary filtering by the surge protection capacitor EC1 and tertiary filtering by the capacitor C1, it supplies power to the LED lamp 100.

[0045] As Figure 2 shown, in this embodiment, the reference voltage source module 50 is a linear voltage regulator circuit. The reference voltage source module 50 includes: a resistor R6, a resistor R8, a resistor R21, a capacitor C6, a triode Q1, and a zener diode ZD1.

[0046] As Figure 2 shown, one end of the resistor R6 takes power V 0 from the front-end power supply module 20, and the resistor R8 is connected in parallel with the resistor R6; the other end of the resistor R6 is connected to the collector of the triode Q1; the base of the triode Q1 is connected to the negative electrode of the zener diode ZD1; the base of the triode Q1 is also connected to the collector of the triode Q1 in series with the resistor R21. The positive electrode of the zener diode ZD1 is grounded. The emitter of the triode Q1 is grounded in series with the capacitor C6; the emitter of the triode Q1 serves as the output terminal of the maximum voltage limit module 40 to output the reference voltage source Vcc.

[0047] As Figure 2As shown, the reference voltage source module 50 obtains the DC voltage V from the front-end power supply module 20 0 , and after current limiting through resistor R6 and resistor R8, it is input to transistor Q1; a stable reference voltage source Vcc is output from the emitter of transistor Q1. In this embodiment, the output reference voltage source Vcc is filtered by capacitor C6 to further ensure the stability of the reference voltage source Vcc.

[0048] As Figure 1 shown, the reference voltage source Vcc output by the reference voltage source module 50 supplies power to the constant current control module 30, the maximum voltage limit module 40, and the over-temperature power regulation and shutdown module 60 respectively. The reference voltage source module 50 provides a stable and reliable voltage for the constant current control module 30, the maximum voltage limit module 40, and the over-temperature power regulation and shutdown module 60.

[0049] As Figure 2 shown, in this embodiment, the constant current control module 30 includes: amplifier U1A, follower U1B, comparator U2B, resistor RS1, resistor R2, resistor R3, resistor R7, resistor R10, resistor R11, resistor R18, resistor R19, resistor R23, resistor R25, resistor R29, capacitor C5, capacitor C7, and capacitor C8. Resistor RS1 is connected in series with resistor R10 and then connected to the positive input terminal of amplifier U1A. The positive input terminal of amplifier U1A is also connected to ground in series with resistor R25; capacitor C8 is connected in parallel with resistor R25.

[0050] As Figure 2 shown, the negative input terminal of amplifier U1A is connected to ground in series with resistor R29; the output terminal of amplifier U1A is connected to the negative input terminal of amplifier U1A in series with resistor R23; capacitor C7 is connected in parallel with resistor R23; the output terminal of amplifier U1A is connected to the negative input terminal of comparator U2B in series with resistor R18.

[0051] As Figure 2 shown, the positive input terminal of comparator U2B is connected to the output terminal of follower U1B in series with resistor R7; the negative input terminal of comparator U2B is connected to the output terminal of comparator U2B in series with capacitor C5 and resistor R19 in sequence; the output terminal of comparator U2B is connected to the output terminal of the constant current control module 30 in series with resistor R11 to output a constant current to the front-end power supply module 20;

[0052] The negative input terminal of follower U1B is connected to the output terminal of follower U1B in series with resistor R2; the positive input terminal of follower U1B is connected to the output terminal of the over-temperature power regulation and shutdown module 60 in series with resistor R3 as the reference voltage control terminal of the constant current control module 30.

[0053] As Figure 2As shown, in this embodiment, the over-temperature power regulation and shutdown module 60 includes: resistor R13, resistor R15, resistor R16, resistor R17, resistor R22, resistor R24, resistor R27, resistor R28, resistor R30, triode Q2, three-terminal voltage regulator U3, and thermistor RT1.

[0054] As Figure 2 shown, one end of resistor R15 is connected to the reference voltage source Vcc of the maximum voltage limit module 40, and the other end is connected to the output terminal of three-terminal voltage regulator U3; the ground terminal of three-terminal voltage regulator U3 is grounded; the input terminal of three-terminal voltage regulator U3 is grounded after being connected in series with resistor R27; the input terminal of three-terminal voltage regulator U3 is also connected in series with resistor R24 and then connected to the other end of resistor R15. The other end of resistor R15 is also connected to the collector of triode Q2 after being connected in series with resistor R13, resistor R16, and resistor R17 in sequence; the emitter of triode Q2 is grounded; a resistor R30 is connected across the base and emitter of the triode. The other end of resistor R15 is also connected to the base of triode Q2 after being connected in series with thermistor RT1 and resistor R22 in sequence. The node between resistor R16 and resistor R17 serves as the output terminal of the over-temperature power regulation and shutdown module 60 to output the reference voltage Vr to the reference voltage control terminal of the constant current control module 30.

[0055] As Figure 2 shown, the negative input terminal of follower U1B is connected in series with resistor R2 and then connected to the output terminal of follower U1B; the positive input terminal of follower U1B is connected in series with resistor R3 and serves as the reference voltage control terminal of the constant current control module 30 and is connected to the output terminal of the over-temperature power regulation and shutdown module 60.

[0056] As Figure 2 shown, the constant current control module 30 samples the output current of the front-end power supply module 20 through resistor RS1 and amplifies it through an amplifier circuit composed of amplifier U1A, resistor R10, resistor R25, resistor R29, resistor R23, and capacitor C8, and then inputs it to the negative input terminal of comparator U2B;

[0057] Meanwhile, the over-temperature power regulation and shutdown module 60 senses the ambient temperature around the LED lamp 100 through thermistor RT1; the over-temperature power regulation and shutdown module 60 outputs a corresponding reference voltage Vr to the positive input terminal of follower U1B according to the detected ambient temperature around the LED lamp 100; the reference voltage Vr is input to the positive input terminal of comparator U2B after passing through follower U1B;

[0058] The current on the current sampling resistor RS1 is amplified by an amplifier circuit and then input to the negative input terminal of the comparator U2B for comparison with the reference voltage Vr. When the current on the current sampling resistor RS1 increases, the input voltage at the negative input terminal of the comparator U2B is greater than the reference voltage Vr, and the comparator U2B outputs a low level. Conversely, when the current on the current sampling resistor RS1 decreases, the input voltage at the negative input terminal of the comparator U2B is less than the reference voltage Vr, and the comparator U2B outputs a high level (constant current value).

[0059] As Figure 2 shown, in this embodiment, the maximum voltage limiting module 40 includes: resistor R9, resistor R12, resistor R14, resistor R20, resistor R26, capacitor C2, capacitor C3, capacitor C4, capacitor C9, diode D1, optocoupler PC1, and three-terminal voltage regulator U4.

[0060] As Figure 2 shown, one end of the resistor R9 takes power V 0 from the front-end power module 20, and the other end is grounded after being sequentially connected in series with resistor R14 and resistor R26; the capacitor C3 is connected in parallel with the resistor R9.

[0061] As Figure 2 shown, the input terminal of the three-terminal voltage regulator U4 is connected to the node between the resistor R14 and the resistor R26, and the grounding terminal of the three-terminal voltage regulator U4 is grounded; the output terminal of the three-terminal voltage regulator U4 is sequentially connected in series with the capacitor C4 and the resistor R20 and then connected to the node between the resistor R14 and the resistor R26; the output terminal of the three-terminal voltage regulator U4 is also connected in series with the resistor R12 and then connected to the negative electrode of the diode D1.

[0062] As Figure 2 shown, the positive electrode of the diode D1 is sequentially connected in series with the resistor R5 and the resistor R4 and then connected to the reference voltage source Vcc; the capacitor C2 is connected in parallel with the resistor R4. The input terminal of the optocoupler PC1 is connected in parallel with the resistor R5; the output terminal of the optocoupler PC1 is fed back to the front-end power module 20 to output the current of the front-end power module 20. The negative electrode of the diode D1 is also connected in series with the capacitor C9 and then grounded.

[0063] As Figure 2 shown, the resistors R9, R14, and R26 obtain the DC voltage V 0 from the front-end power module 20 and are fed back to the three-terminal voltage regulator U4; after internal reference comparison by the three-terminal voltage regulator U4, the conduction amounts of the resistors R4, R5, diode D1, resistor R12, and optocoupler PC1 are controlled, and then the output current of the front-end power module 20 is adjusted by the feedback of the optocoupler PC1 to the AC-to-DC unit.

[0064] The working principle of the linear power-down control circuit 10 for over-temperature protection of the LED lamp is as follows (please refer to it together)Figure 1 and Figure 2 ):

[0065] When the temperature around the LED lamp 100 is within the rated temperature range, the front-end power module 20 provides a constant current to the LED lamp 100. At this time, the LED lamp 100 outputs a constant power and the illumination brightness is stable. Specifically:

[0066] When the LED lamp 100 operates at a higher voltage (higher than the preset maximum voltage value), the resistors R9, R14, and R26 of the maximum voltage limiting module 40 detect the output voltage V of the front-end power module 20 0 The voltage value is too high and is fed back to the input end of the three-terminal voltage regulator U4; it is transmitted to the optocoupler PC1 through the output end of the three-terminal voltage regulator U4, and then fed back to the front-end power module 20 to reduce the output voltage of the front-end power module 20; at this time, the comparator U2B does not work;

[0067] When the LED lamp 100 operates at a lower voltage (lower than the preset maximum voltage value), the voltage values detected by the resistors R9, R14, and R26 of the maximum voltage limiting module 40 are too low. At this time, the three-terminal voltage regulator U4 has no output and does not control the optocoupler PC1; at this time, the constant current control module 30 operates in the maximum current state;

[0068] That is to say, when the internal resistance of the load LED lamp 100 is large, its operating voltage is high, and the three-terminal voltage regulator U4 of the maximum voltage limiting module 40 limits the output voltage of the front-end power module 20 through the optocoupler PC1; at this time, the LED lamp 100 cannot operate in the maximum current state due to the voltage limiting effect of the maximum voltage limiting module 40, and thus fails to reach the constant current threshold; that is, at this time, the constant current control module 30 does not start the constant current operation, and the comparator U2B does not participate in the constant current operation;

[0069] When the internal resistance of the load LED lamp 100 is small, the operating current of the load LED lamp 100 is large, and the operating current exceeds the current threshold limited by the comparator U2B of the constant current control module 30; at this time, the constant current control module 30 starts the constant current operation, and the comparator U2B adjusts the current to make the current constant at the preset current constant value; at this time, the current constant value adjusted by the comparator U2B is fed back to the front-end power module 20 through the optocoupler PC1 to ensure that the LED lamp 100 is in a constant current state;

[0070] When the temperature around the LED lamp 100 exceeds the rated temperature range, the thermistor RT1 detects the temperature around the LED lamp 100 in real time; the over-temperature power adjustment and shutdown module 60 adjusts the reference voltage Vr at the positive input terminal of the follower U1B in real time according to the temperature change, so as to transfer the changed reference voltage Vr to the positive input terminal of the comparator U2B, and then change the reference comparison voltage of the comparator U2B, thereby changing the output current of the constant current control module 30; it should be noted that the voltage input by the thermistor RT1 to the reference voltage Vr changes linearly with the change of temperature, so the output current of the constant current control module 30 also changes linearly; therefore, the power reduction of the LED lamp 100 also decreases linearly with the temperature detected by the thermistor RT1;

[0071] It can be understood that the current output by the comparator U2B is fed back to the AC-DC unit through the optocoupler PC1 to adjust the output current of the front-end power module 20; thus, the output power of the LED lamp 100 is adaptively changed, ensuring the reliability of the LED drive power supply while trying to ensure the lighting function of the LED lamp 100;

[0072] In the present invention, the change of the output current of the LED lamp 100 and the change of the temperature detected by the thermistor RT1 are in a linear relationship, that is, the change of the output power of the LED lamp 100 and the change of the temperature detected by the thermistor RT1 are in a linear relationship; as the temperature around the LED lamp 100 changes, the output power of the LED lamp 100 changes linearly with the temperature;

[0073] The working principle of the over-temperature power adjustment and shutdown module 60 is as follows:

[0074] When the temperature exceeds the rated temperature, as the temperature rises, the resistance value of the thermistor RT1 decreases; the circuit branch composed of the thermistor RT1, the resistor R22, and the resistor R30 provides drive for the triode Q2;

[0075] As the temperature rises, the voltage at the base of the triode Q2 continuously increases until the base voltage of the triode Q2 rises to turn on the triode Q2;

[0076] When the triode Q2 is in the conduction state, with the change of temperature, the base circuit of the triode Q2 also changes accordingly, thereby adjusting the conduction degree of the triode Q2; after the triode Q2 amplifies the current at its base, the output reference voltage Vr is adjusted to the reference voltage control terminal through the resistors R16 and R17 at the collector;

[0077] When the temperature rises to a preset limit value, the reference voltage Vr output by the temperature detection and regulation module to the reference voltage control terminal is 0; at this time, the reference voltage Vr input to the positive input terminal of the follower U1B is 0, and the voltage at the positive input terminal of the comparator U2B is 0, so the output terminal of the comparator U2B is 0, which makes the conduction amount of the optocoupler PC1 0, and the output current of the front-end power supply module 20 is 0.

[0078] The control circuit of the present invention is realized by electronic components with simple structure and low cost, linearly adjusts the output power of the LED lamp as the temperature rises, and finally turns off the LED lamp when the temperature rises to the threshold value; it realizes ensuring the lighting function of the LED lamp as much as possible while ensuring the reliability of the LED drive power supply.

[0079] The above embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A linear power-down control circuit for over-temperature protection of LED lights, characterized in that, it includes: a front-end power supply module, a constant current control module, a maximum voltage limit module, a reference voltage source module, an over-temperature power regulation and shutdown module; The front-end power supply module supplies power to the LED lights; The front-end power supply module also supplies power to the maximum voltage limit module and the reference voltage source module respectively; After taking power from the front-end power supply module, the reference voltage source module stabilizes the voltage and outputs a reference voltage source Vcc; the reference voltage source Vcc supplies power to the constant current control module, the maximum voltage limit module, and the over-temperature power regulation and shutdown module respectively; The constant current control module samples the loop current of the front-end power supply module; the over-temperature power regulation and shutdown module outputs a reference voltage Vr to the constant current control module; The constant current control module adjusts the constant current output to the maximum voltage limit module according to the reference voltage Vr; The maximum voltage limit module controls the current feedback to the front-end power supply module according to the constant current to control the output current of the front-end power supply module; The constant current control module includes: amplifier U1A, follower U1B, comparator U2B, resistor RS1, resistor R2, resistor R3, resistor R7, resistor R10, resistor R11, resistor R18, resistor R19, resistor R23, resistor R25, resistor R29, capacitor C5, capacitor C7 and capacitor C8; The resistor RS1 is connected in series in the output loop of the front-end power supply module; the resistor RS1 is connected in series with the resistor R10 and then connected to the positive input terminal of the amplifier U1A; the positive input terminal of the amplifier U1A is also connected in series with the resistor R25 and then grounded; the capacitor C8 is connected in parallel with the resistor R25; The negative input terminal of the amplifier U1A is connected in series with the resistor R29 and then grounded; the output terminal of the amplifier U1A is connected in series with the resistor R23 and then connected to the negative input terminal of the amplifier U1A; the capacitor C7 is connected in parallel with the resistor R23; the output terminal of the amplifier U1A is connected in series with the resistor R18 and then connected to the negative input terminal of the comparator U2B; The positive input terminal of the comparator U2B is connected in series with the resistor R7 and then connected to the output terminal of the follower U1B; the negative input terminal of the comparator U2B is connected in series with the capacitor C5 and the resistor R19 in sequence and then connected to the output terminal of the comparator U2B; the output terminal of the comparator U2B is connected in series with the resistor R11 and used as the output terminal of the constant current control module to output a constant current to the front-end power supply module; The negative input terminal of the follower U1B is connected in series with the resistor R2 and then connected to the output terminal of the follower U1B; the positive input terminal of the follower U1B is connected in series with the resistor R3 and used as the reference voltage control terminal of the constant current control module to be connected to the output terminal of the over-temperature power regulation and shutdown module; The maximum voltage limiting module includes: resistor R9, resistor R12, resistor R14, resistor R20, resistor R26, capacitor C2, capacitor C3, capacitor C4, capacitor C9, diode D1, optocoupler PC1, and three-terminal voltage regulator U4; One end of the resistor R9 draws power V from the front-end power supply module 0 , and the other end is grounded after being successively connected in series with the resistor R14 and the resistor R26; the capacitor C3 is connected in parallel with the resistor R9; The input terminal of the three-terminal voltage regulator U4 is connected to the node between the resistor R14 and the resistor R26, and the ground terminal of the three-terminal voltage regulator U4 is grounded; the output terminal of the three-terminal voltage regulator U4 is connected to the node between the resistor R14 and the resistor R26 after sequentially connecting the capacitor C4 and the resistor R20 in series; the output terminal of the three-terminal voltage regulator U4 is also connected to the negative electrode of the diode D1 after connecting the resistor R12 in series; The positive electrode of the diode D1 is connected to the reference voltage source Vcc after sequentially connecting the resistor R5 and the resistor R4 in series; the capacitor C2 is connected in parallel with the resistor R4; the input terminal of the optocoupler PC1 is connected in parallel with the resistor R5; the output terminal of the optocoupler PC1 is fed back to the front-end power module to control the output current of the front-end power module; The negative electrode of the diode D1 is also connected to the ground after connecting the capacitor C9 in series; The over-temperature power regulation and shutdown module includes: resistor R13, resistor R15, resistor R16, resistor R17, resistor R22, resistor R24, resistor R27, resistor R28, resistor R30, triode Q2, three-terminal voltage regulator U3, and thermistor RT1; One end of the resistor R15 is connected to the reference voltage source Vcc of the maximum voltage limiting module, and the other end is connected to the output terminal of the three-terminal voltage regulator U3; the ground terminal of the three-terminal voltage regulator U3 is grounded; the input terminal of the three-terminal voltage regulator U3 is connected to the ground after connecting the resistor R27 in series; the input terminal of the three-terminal voltage regulator U3 is also connected to the other end of the resistor R15 after connecting the resistor R24 in series; The other end of the resistor R15 is also connected to the collector of the triode Q2 after sequentially connecting the resistor R13, the resistor R16, and the resistor R17 in series; the emitter of the triode Q2 is grounded; a resistor R30 is connected across the base and the emitter of the triode; The other end of the resistor R15 is also connected to the base of the triode Q2 after sequentially connecting the thermistor RT1 and the resistor R22 in series; The node between the resistor R16 and the resistor R17 serves as the output terminal of the over-temperature power regulation and shutdown module to output the reference voltage Vr to the reference voltage control terminal of the constant current control module.

2. The linear power-down control circuit for over-temperature protection of LED lamps according to claim 1, characterized in that The reference voltage source module includes: resistor R6, resistor R8, resistor R21, capacitor C6, triode Q1, and zener diode ZD1; One end of the resistor R6 draws power V from the front-end power supply module 0 , and the resistor R8 is connected in parallel with the resistor R6; the other end of the resistor R6 is connected to the collector of the triode Q1; the base of the triode Q1 is connected to the negative electrode of the zener diode ZD1; the base of the triode Q1 is also connected to the collector of the triode Q1 in series with the resistor R21; the positive electrode of the zener diode ZD1 is grounded; The emitter of the triode Q1 is connected to the ground after connecting the capacitor C6 in series; the emitter of the triode Q1 serves as the output terminal of the maximum voltage limiting module to output the reference voltage source Vcc.

3. The linear power-down control circuit for over-temperature protection of LED lamps according to claim 1, characterized in that The front-end power supply module includes: an AC-DC conversion unit, a surge protection capacitor EC1, a surge protection capacitor EC2, a resistor R1, and a capacitor C1; The AC-to-DC unit converts the externally connected alternating current into a DC voltage V 0 ; the output terminal of the AC-to-DC unit is grounded after being connected in series with the surge protection capacitor EC2, and the resistor R1 is connected in parallel with the surge protection capacitor EC2; the surge protection capacitor EC1 is connected in parallel with the resistor R1; the capacitor C1 is connected in parallel with the surge protection capacitor EC1 and then serves as an output terminal to supply power to the LED lamp.

Images