Circuit for automatically adjusting color or hue of LED

Abstract

The utility model provides a circuit for automatically adjusting the color or hue of an LED, which comprises a first temperature detection unit, a second temperature detection unit, a first switch combination circuit, a second switch combination circuit, a switch control circuit, a triode Q3, a first unidirectional conduction circuit, a second unidirectional conduction circuit, a light emitting diode LED1, a light emitting diode LED2 and a light emitting diode LED3, the input end of the first temperature detection unit is connected with input voltage, and the output end outputs first temperature detection voltage reflecting environment temperature. The input end of the second temperature detection unit is connected with the input voltage, and the output end of the second temperature detection unit outputs second temperature detection voltage reflecting the environment temperature. Compared with the prior art, according to the utility model, the triode is controlled to carry out LED switching by using the change of the resistance value of the thermistor at different temperatures, the control of a single chip microcomputer is not needed, the switching of the LED color or hue can be realized, and the circuit cost is lower.

Description

[Technical field]

[0001] The utility model relates to the technical field of circuit design, in particular to a circuit for automatically adjusting the color or hue of an LED. [Background technology]

[0002] Car interior ambient lighting is the development trend of car cabin lighting. As the quality of life of users improves, the demand for cabin lighting will also increase. For car cabin ambient lighting or reading light products, displaying the same hue or color in different environments will appear monotonous. If the hue or color of the LED is automatically adjusted according to the ambient temperature, it will bring a different experience to the user. When the ambient temperature is high, the LED is adjusted to cool light or cool tones, and from a visual perspective, the user will feel refreshed. When the ambient temperature is low, the LED is adjusted to warm light or warm tones, and from a visual perspective, the user will feel warm.

[0003] Please refer to Figure 1 As shown, it is a functional block diagram of a lamp with intelligent color tone control in the prior art, and its patent number is CN205014149U. The patent solution is to detect through a thermistor sensor, transmit the signal to the microcontroller through an operational amplifier, and the microcontroller controls the current of the constant current source, thereby controlling the current flowing through the LED, thereby controlling the LED color tone.

[0004] but, Figure 1 The prior art solution shown has the following problems:

[0005] ①. It needs to be controlled by a single-chip microcomputer. If the product does not have a single-chip microcomputer or the single-chip microcomputer has no spare GPIO (General-purpose input / output) port, this function cannot be realized;

[0006] ② This solution can only adjust the hue of the LED by adjusting the constant current source power supply, but cannot achieve the function of adjusting the color;

[0007] ③. This solution uses single-chip microcomputer and operational amplifier components, which are relatively expensive.

[0008] Therefore, it is necessary to propose a new technical solution to solve the above problems. [Contents of the utility model]

[0009] One of the purposes of the utility model is to provide a circuit for automatically adjusting the color or hue of an LED, which utilizes the change in resistance of a thermistor at different temperatures to control a transistor to switch the LED. It does not require a single-chip microcomputer for control, and can achieve switching of the LED color or hue, with a low circuit cost.

[0010] According to one aspect of the utility model, the utility model provides a circuit for automatically adjusting the color or hue of an LED, which includes: a first temperature detection unit, whose input end is connected to an input voltage Vin, and whose output end A outputs a first temperature detection voltage VA reflecting the ambient temperature; a second temperature detection unit, whose input end is connected to the input voltage Vin, and whose output end B outputs a second temperature detection voltage VB reflecting the ambient temperature; a first switch combination circuit, whose first connection end is connected to a power supply voltage Vbus, whose second connection end is connected to a node H, and whose control end is connected to an output end A of the first temperature detection unit; a second switch combination circuit, whose first connection end is connected to the power supply voltage Vbus, whose second connection end is connected to a node I, and whose control end is connected to the second temperature detection unit. The output terminal B of the unit is connected; the switch control circuit, a first input terminal of which is connected to the input voltage Vin, and a second input terminal of which is connected to the node E; the transistor Q3, a first connection terminal of which is connected to the node J, a second connection terminal of which is grounded, and a control terminal of which is connected to the output terminal C of the switch control circuit; a first unidirectional conduction circuit, one end of which is connected to the node H, and the other end of which is connected to the node E; a second unidirectional conduction circuit, one end of which is connected to the node I, and the other end of which is connected to the node E; a light-emitting diode LED1, a positive electrode of which is connected to the node H, and a negative electrode of which is grounded; a light-emitting diode LED2, a negative electrode of which is connected to the node J, and a positive electrode of which is connected to the power supply voltage Vbus; a light-emitting diode LED3, a positive electrode of which is connected to the node I, and a negative electrode of which is grounded.

[0011] Compared with the prior art, the utility model utilizes the change of the resistance value of thermistor at different temperatures to control the triode to switch the LED, does not need single chip microcomputer for control, can realize the switching of LED color or tone, and has low circuit cost.

Brief Description of the Drawings

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the following briefly introduces the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0013] Figure 1 This is a functional block diagram of a lamp with intelligent color tone control in the prior art;

[0014] Figure 2 The figure is a schematic diagram of a circuit for automatically adjusting the color or hue of an LED in one embodiment of the utility model. [Specific implementation method]

[0015] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0016] The "one embodiment" or "embodiment" referred to herein refers to specific features, structures or characteristics that may be included in at least one implementation of the present invention. The "in one embodiment" that appears in different places in this specification does not all refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments. Unless otherwise specified, the words "coupled", "connected", "connected" and "connected" in this document that indicate electrical connection all mean direct or indirect connection. For example, A is connected to B, which includes both direct electrical connection between A and B and A is connected to B through electrical components or circuits. In the present utility model, "greater than" means greater than, and "less than or equal to" means less than or equal to.

[0017] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", "front", "back", "left", "right", "vertical", "perpendicular", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0018] Please refer to Figure 2 As shown, it is a schematic diagram of a circuit for automatically adjusting LED color or hue in one embodiment of the utility model. Figure 2 The circuit for automatically adjusting LED color or hue shown includes a first temperature detection unit 210, a second temperature detection unit 220, a first switch combination circuit 230, a second switch combination circuit 240, a switch control circuit 250, a transistor Q3, a first unidirectional conduction circuit 260, a second unidirectional conduction circuit 270, a light-emitting diode LED1, a light-emitting diode LED2 and a light-emitting diode LED3.

[0019] Among them, the input end of the first temperature detection unit 210 is connected to the input voltage Vin, and its output end A outputs a first temperature detection voltage VA reflecting the ambient temperature; the input end of the second temperature detection unit 220 is connected to the input voltage Vin, and its output end B outputs a second temperature detection voltage VB reflecting the ambient temperature; the first connection end of the first switch combination circuit 230 is connected to the power supply voltage Vbus, the second connection end is connected to the node H, and the control end is connected to the output end A of the first temperature detection unit 210; the first connection end of the second switch combination circuit 240 is connected to the power supply voltage Vbus, the second connection end is connected to the node I, and the control end is connected to the output end B of the second temperature detection unit 220; The first input terminal of the switch control circuit 250 is connected to the input voltage Vin, and the second input terminal thereof is connected to the node E; the first connection terminal of the transistor Q3 is connected to the node J, the second connection terminal thereof is grounded, and the control terminal thereof is connected to the output terminal C of the switch control circuit 250; one end of the first unidirectional conducting circuit 260 is connected to the node H, and the other end thereof is connected to the node E; one end of the second unidirectional conducting circuit 270 is connected to the node I, and the other end thereof is connected to the node E; the positive electrode of the light-emitting diode LED1 is connected to the node H, and the negative electrode thereof is grounded; the negative electrode of the light-emitting diode LED2 is connected to the node J, and the positive electrode thereof is connected to the power supply voltage Vbus; the positive electrode of the light-emitting diode LED3 is connected to the node I, and the negative electrode thereof is grounded.

[0020] The first switch combination circuit 230 includes a transistor Q1, a transistor Q2, a resistor R2, and a resistor R5. Among them, the first connection end of the transistor Q1 is connected to the power supply voltage Vbus, the second connection end thereof is connected to the node H, and the control end thereof is connected to the node D; one end of the resistor R2 is connected to the power supply voltage Vbus, and the other end thereof is connected to the node D; the first connection end of the transistor Q2 is connected to the node D via the resistor R5, the second connection end thereof is grounded, and the control end thereof is connected to the output end A of the first temperature detection unit 210.

[0021] The second switch combination circuit 240 includes a transistor Q5, a transistor Q6, a resistor R13, and a resistor R18. Among them, the first connection end of the transistor Q5 is connected to the power supply voltage Vbus, the second connection end thereof is connected to the node I, and the control end thereof is connected to the node G; one end of the resistor R13 is connected to the power supply voltage Vbus, and the other end thereof is connected to the node G; the first connection end of the transistor Q6 is connected to the node G via the resistor R18, the second connection end thereof is grounded, and the control end thereof is connected to the output end B of the second temperature detection unit 220.

[0022] The first unidirectional conducting circuit 260 includes a diode D1 and a resistor R15 . The anode of the diode D1 is connected to the node H, the cathode of the diode D1 is grounded via the resistor R15 , and the cathode of the diode D1 is connected to the node E.

[0023] The second unidirectional conducting circuit 270 includes a diode D2 and a resistor R19. The anode of the diode D2 is connected to the node I, the cathode of the diode D2 is grounded via the resistor R19, and the cathode of the diode D2 is connected to the node E.

[0024] The switch control circuit 250 includes a resistor R7, a resistor R8, a resistor R10, a resistor R11 and a transistor Q4. Among them, one end of the resistor R7 is connected to the input voltage Vin, and the other end thereof is connected to the output terminal C (or node C) of the switch control circuit 250; one end of the resistor R8 is connected to the output terminal C of the switch control circuit 250, and the other end thereof is grounded; the first connection end of the transistor Q4 is connected to the output terminal C of the switch control circuit 250, the second connection end thereof is grounded, and the control end thereof is connected to the node F; one end of the resistor R10 is connected to the node F, and the other end thereof is connected to the node E; one end of the resistor R11 is connected to the node F, and the other end thereof is grounded. The selection of resistors R7 and R8 needs to satisfy that when the ambient temperature is greater than the low temperature threshold TL and less than the high temperature threshold TH, the voltage division on the resistor R8 is greater than the turn-on voltage value of the transistor Q3. The selection of resistors R10 and R11 needs to satisfy that when the node E is at a high level, the voltage division on the resistor R11 is greater than the turn-on voltage value of the transistor Q4. The low temperature threshold TL is smaller than the high temperature threshold TH.

[0025] When the ambient temperature is lower than the low temperature threshold TL, the first temperature detection voltage VA output by the first temperature detection unit 210 is greater than the turn-on voltage value of the transistor Q2; when the ambient temperature is higher than the low temperature threshold TL, the first temperature detection voltage VA output by the first temperature detection unit 210 is less than the turn-on voltage value of the transistor Q2.

[0026] exist Figure 2In the specific embodiment shown, the first temperature detection unit 210 includes a resistor R3, a thermistor NTC1, a resistor R4, and a resistor R6. Among them, one end of the resistor R3 is connected to the input voltage Vin, and the other end thereof is connected to the output terminal A (or node A) of the first temperature detection unit 210 via the resistor R4; one end of the resistor R6 is connected to the output terminal A of the first temperature detection unit 210, and the other end thereof is grounded; one end of the thermistor NTC1 is connected to the other end of the resistor R3, and the other end thereof is grounded. The thermistor NTC1 (Negative Temperature Coefficient thermistor) is a negative temperature coefficient thermistor (i.e., the resistance of the thermistor is related to the temperature, and when the temperature rises, the resistance of the thermistor will decrease). The resistance value of the thermistor NTC1 when the ambient temperature is the low temperature threshold TL is understood through the curve of the thermistor NTC1; the selection of resistors R3, R4, and R6 needs to meet the following requirements: when the ambient temperature is lower than the low temperature threshold TL, the voltage at the output terminal A (i.e., node A) of the first temperature detection unit 210 is greater than the turn-on voltage value of the transistor Q2; when the ambient temperature is higher than the low temperature threshold TL, the voltage at the output terminal A (i.e., node A) of the first temperature detection unit 210 is less than the turn-on voltage value of the transistor Q2. It can also be said that the thermistor NTC1 is a negative temperature coefficient thermistor, and the selection of resistors R3, R4, R6 and thermistor NTC1 needs to satisfy that when the ambient temperature is lower than the low temperature threshold TL, the voltage at the output terminal A (i.e., node A) of the first temperature detection unit 210 is greater than the turn-on voltage value of the transistor Q2; when the ambient temperature is higher than the low temperature threshold TL, the voltage at the output terminal A (i.e., node A) of the first temperature detection unit 210 is less than the turn-on voltage value of the transistor Q2.

[0027] When the ambient temperature is lower than the high temperature threshold TH, the second temperature detection voltage VB output by the second temperature detection unit 220 is lower than the turn-on voltage value of the transistor Q6; when the ambient temperature is higher than the high temperature threshold TH, the second temperature detection voltage VB output by the second temperature detection unit 220 is higher than the turn-on voltage value of the transistor Q6.

[0028] exist Figure 2In the specific embodiment shown, the second temperature detection unit 220 includes a resistor R16, a thermistor NTC2, a resistor R14, and a resistor R17. Among them, one end of the thermistor NTC2 is connected to the input voltage Vin, and the other end thereof is connected to the output end B (or node B) of the second temperature detection unit 220 via the resistor R14; one end of the resistor R17 is connected to the output end B of the second temperature detection unit 220, and the other end thereof is grounded; one end of the resistor R16 is connected to the other end of the thermistor NTC2, and the other end thereof is grounded. The thermistor NTC2 (Negative Temperature Coefficient thermistor) is a negative temperature coefficient thermistor (i.e., the resistance of the thermistor is related to the temperature, and when the temperature rises, the resistance of the thermistor will decrease). The resistance value of the thermistor NTC2 when the ambient temperature is the high temperature threshold TH is understood through the curve of the thermistor NTC2; the selection of resistors R14, R16, and R17 needs to meet the following requirements: when the ambient temperature is lower than the high temperature threshold TH, the voltage at the output terminal B (i.e., node B) of the second temperature detection unit 220 is lower than the turn-on voltage value of the transistor Q6; when the ambient temperature is higher than the high temperature threshold TH, the voltage at the output terminal B (i.e., node B) of the second temperature detection unit 220 is higher than the turn-on voltage value of the transistor Q6. It can also be said that the thermistor NTC2 is a negative temperature coefficient thermistor, and the selection of resistors R14, R16, R17 and thermistor NTC2 needs to meet the following requirements: when the ambient temperature is lower than the high temperature threshold TH, the voltage at the output terminal B (i.e., node B) of the second temperature detection unit 220 is lower than the turn-on voltage value of the transistor Q6; when the ambient temperature is higher than the high temperature threshold TH, the voltage at the output terminal B (i.e., node B) of the second temperature detection unit 220 is higher than the turn-on voltage value of the transistor Q6.

[0029] exist Figure 2In the specific embodiment shown, the transistor Q1 is a PNP transistor, and the first connection end, the second connection end and the control end of the transistor Q1 are respectively the emitter, the collector and the base of the PNP transistor; the transistor Q2 is an NPN transistor, and the first connection end, the second connection end and the control end of the transistor Q2 are respectively the collector, the emitter and the base of the NPN transistor; the transistor Q3 is an NPN transistor, and the first connection end, the second connection end and the control end of the transistor Q3 are respectively the collector, the emitter and the base of the NPN transistor. The transistor Q4 is an NPN transistor, and the first connection terminal, the second connection terminal and the control terminal of the transistor Q4 are respectively the collector, the emitter and the base of the NPN transistor; the transistor Q5 is a PNP transistor, and the first connection terminal, the second connection terminal and the control terminal of the transistor Q5 are respectively the emitter, the collector and the base of the PNP transistor; the transistor Q6 is an NPN transistor, and the first connection terminal, the second connection terminal and the control terminal of the transistor Q6 are respectively the collector, the emitter and the base of the NPN transistor.

[0030] exist Figure 2 In the specific embodiment shown, the first temperature detection unit 210 further includes a capacitor C1, one end of which is connected to the other end of the resistor R3, and the other end of which is grounded; the second temperature detection unit 220 further includes a capacitor C4, one end of which is connected to the other end of the thermistor NTC2, and the other end of which is grounded; the switch control circuit 250 further includes a capacitor C2 and a capacitor C3, one end of which is connected to the output terminal C (or node C) of the switch control circuit 250, and the other end of which is grounded; one end of the capacitor C3 is connected to the node F, and the other end of which is grounded. Among them, the capacitors C1, C2, C3, and C4 are filter capacitors that filter out clutter in the circuit and prevent the transistor from being mis-conducted.

[0031] Figure 2 The circuit for automatically adjusting LED color or hue shown also includes resistor R1, resistor R9 and resistor R12, wherein one end of resistor R1 is connected to the cathode of light-emitting diode LED1, and the other end thereof is grounded; one end of resistor R9 is connected to the cathode of light-emitting diode LED2, and the other end thereof is connected to node J; one end of resistor R12 is connected to the cathode of light-emitting diode LED3, and the other end thereof is grounded.

[0032] The following is a detailed introduction Figure 2 The working principle of the circuit for automatically adjusting the color or hue of an LED is shown.

[0033] When the ambient temperature is normal temperature, LED2 emits light, and LED1 and LED3 do not emit light. Specifically, when the ambient temperature is normal temperature, that is, the ambient temperature is between the low temperature threshold TL and the high temperature threshold TH, since the selection of resistors R7 and R8 meets, when the ambient temperature is greater than the low temperature threshold TL and less than the high temperature threshold TH, the voltage division on resistor R8 is greater than the turn-on voltage value of transistor Q3, that is, the voltage of node C is greater than the turn-on voltage value of transistor Q3, therefore, transistor Q3 is turned on, the power supply voltage Vbus supplies power to LED2, resistor R9 is a current limiting resistor, and LED2 can emit light. The selection of resistor R9 needs to consider the brightness of LED2, and needs to be selected according to actual needs. Since the selection of resistors R3, R4, R6 and NTC1 meets, when the ambient temperature is greater than the low temperature threshold TL, the first temperature detection voltage VA output by the first temperature detection unit 210 is less than the turn-on voltage value of transistor Q2, so at normal temperature, transistor Q2 is turned off, thereby transistor Q1 is turned off, and LED1 does not emit light. Since the selection of resistors R14, R16, R17, and NTC2 satisfies, when the ambient temperature is less than the high temperature threshold TH, the second temperature detection voltage VB output by the second temperature detection unit 220 is less than the turn-on voltage value of the transistor Q6, so the transistor Q6 is turned off at normal temperature, and thus the transistor Q5 is turned off, so that LED3 does not emit light. Since the transistors Q1 and Q5 are turned off at normal temperature, the diodes D1 and D2 are cut off, the node E is at a low level, and the transistor Q4 is turned off. Therefore, at normal temperature, only LED2 emits light. That is to say, when the ambient temperature is between the low temperature threshold TL and the high temperature threshold TH, the transistors Q1 and Q2 are turned off, and LED1 does not emit light; the transistors Q5 and Q6 are turned off, and LED3 does not emit light; the transistor Q3 is turned on, the transistor Q4 is turned off, and LED2 emits light; the diodes D1 and D2 are both cut off.

[0034] When the ambient temperature is low, LED1 emits light, and LED2 and LED3 do not emit light. Specifically, when the ambient temperature is low, that is, the ambient temperature is less than the low temperature threshold TL, according to the selection of resistors R3, R4, R6 and thermistor NTC1, when the ambient temperature is less than the low temperature threshold TL, the voltage of the output terminal A (i.e., node A) of the first temperature detection unit 210 is greater than the turn-on voltage value of the transistor Q2. At this time, the transistor Q2 is turned on, and the voltage of node D is the voltage value of the power supply voltage Vbus minus the body diode voltage drop of the transistor Q1. The transistor Q1 is turned on, and the power supply voltage Vbus supplies power to LED1. The resistor R1 is a current limiting resistor, and LED1 can emit light. The selection of resistor R1 needs to consider the brightness of LED1 and needs to be selected according to actual needs. At this time, the diode D1 is forward-conducted, and the voltage of node E is the voltage value of the power supply voltage Vbus minus the voltage drop of the diode D1. The role of the diode D1 is that when the transistor Q5 is turned on, the voltage of node E will not supply power to LED1, so as to achieve the effect of single LED emitting light. Since node E is at a high level at this time, and the selection of resistors R10 and R11 is satisfied, when node E is at a high level, the voltage division on resistor R11 (i.e., the voltage of node F) is greater than the turn-on voltage value of transistor Q4, so that transistor Q4 is turned on, node C is pulled down, so that transistor Q3 is turned off, and LED2 does not emit light. According to the selection of resistors R14, R16, R17, and thermistor NTC2, when the ambient temperature is less than the high temperature threshold TH, the voltage of the output terminal B (i.e., node B) of the second temperature detection unit 220 is less than the turn-on voltage value of transistor Q6, so under low temperature conditions, the voltage of node B will also be less than the turn-on voltage value of transistor Q6, so that transistor Q6 is turned off, and thus transistor Q5 is turned off, so that LED3 does not emit light. Since transistor Q5 is turned off, node E is at a high level, so diode D2 is turned off. Therefore, under low temperature conditions, only LED1 emits light. LED1 can select a high color temperature LED or other warm color LED, so that when the ambient temperature is low, the LED can be warm light or warm tone, and the user will feel warm from a visual perspective. That is to say, when the ambient temperature is less than the low temperature threshold TL, transistors Q1 and Q2 are turned on, LED1 emits light; transistors Q5 and Q6 are turned off, LED3 does not emit light; transistor Q3 is turned off, transistor Q4 is turned on, LED2 does not emit light; diode D1 is forward-conducted, and diode D2 is cut off.

[0035] When the ambient temperature is high, LED3 emits light, and LED1 and LED2 do not emit light. Specifically, when the ambient temperature is high, that is, the ambient temperature is greater than the high temperature threshold TH, according to the selection of resistor R14, resistor R16, resistor R17 and thermistor NTC2, when the ambient temperature is greater than the high temperature threshold TH, the voltage of the output terminal B (i.e., node B) of the second temperature detection unit 220 is greater than the turn-on voltage value of the transistor Q6, at which time the transistor Q6 is turned on, and the voltage of node G is the voltage value of the power supply voltage Vbus minus the body diode voltage drop of the transistor Q5, the transistor Q5 is turned on, the power supply voltage Vbus supplies power to LED3, R12 is a current limiting resistor, and LED3 can emit light. The selection of resistor R12 needs to consider the brightness of LED3, and needs to be selected according to actual needs. At this time, the diode D2 is forward-conducted, and the voltage of node E is the power supply voltage Vbus minus the voltage drop of the diode D2. The function of the diode D2 is that when the transistor Q1 is turned on, the voltage of the node E will not supply power to LED3, so as to achieve the effect of single LED luminescence. Since node E is at a high level at this time, and the selection of resistors R10 and R11 meets the requirements, when node E is at a high level, the voltage division on resistor R11 (i.e., the voltage of pole F) is greater than the turn-on voltage value of transistor Q4, so that transistor Q4 is turned on, node C is pulled down, so that transistor Q3 is turned off, and LED2 does not emit light. According to the selection of resistors R3, R4, R6, and thermistor NTC1, when the ambient temperature is greater than the low temperature threshold TL, the voltage of the output terminal A (i.e., node A) of the first temperature detection unit 210 is less than the turn-on voltage value of transistor Q2, so under high temperature conditions, the voltage of node A will also be less than the turn-on voltage value of transistor Q2, so that transistor Q2 is turned off, and thus transistor Q1 is turned off, so that LED1 does not emit light. Therefore, under high temperature conditions, only LED3 emits light. LED3 can select LEDs with low color temperature or other cold color light LEDs, so that when the ambient temperature is high, the LED is cold light or cold color tone, and from a visual perspective, the user will feel refreshed. That is to say, when the ambient temperature is greater than the high temperature threshold TH, transistor Q1 and transistor Q2 are turned off, and LED1 does not emit light; transistor Q5 and transistor Q6 are turned on, and LED3 does not emit light; transistor Q3 is turned off, transistor Q4 is turned on, and LED2 does not emit light; diode D1 is cut off, and diode D2 is forward-conducted.

[0036] It should be noted that the power supply voltage Vbus in the present invention can be consistent with the input voltage Vin, and other DC power supplies can also be used for power supply. The colors of LED1, LED2 and LED3 in the present invention are different; or the tones of LED1, LED2 and LED3 are different. In a preferred embodiment, LED1 is warmer than LED2, and LED3 is cooler than LED2; LED1 is warmer than LED2, and LED3 is cooler than LED2.

[0037] In summary, the circuit for automatically adjusting LED color or hue provided by the utility model has the following beneficial effects:

[0038] 1. The utility model does not require single chip microcomputer control and can automatically adjust the LED color or hue according to the ambient temperature.

[0039] 2. The utility model can choose to change the LED color or change the LED color temperature according to actual needs, with more choices.

[0040] 3. The utility model does not require the use of an operational amplifier or a single-chip microcomputer, and the circuit cost is low.

[0041] It should be noted that any changes made by those skilled in the art to the specific implementation of the present invention do not deviate from the scope of the claims of the present invention. Accordingly, the scope of the claims of the present invention is not limited to the aforementioned specific implementation.

Claims

1. A circuit for automatically adjusting the color or hue of an LED, characterized in that: It includes: A first temperature detection unit, whose input terminal is connected to the input voltage Vin, and whose output terminal A outputs a first temperature detection voltage VA reflecting the ambient temperature; A second temperature detection unit, whose input terminal is connected to the input voltage Vin, and whose output terminal B outputs a second temperature detection voltage VB reflecting the ambient temperature; A first switch combination circuit, a first connection end of which is connected to the power supply voltage Vbus, a second connection end of which is connected to the node H, and a control end of which is connected to the output end A of the first temperature detection unit; A second switch combination circuit, a first connection end of which is connected to the power supply voltage Vbus, a second connection end of which is connected to the node I, and a control end of which is connected to the output end B of the second temperature detection unit; A switch control circuit, a first input terminal of which is connected to the input voltage Vin, and a second input terminal of which is connected to the node E; A transistor Q3, a first connection end of which is connected to the node J, a second connection end of which is grounded, and a control end of which is connected to the output end C of the switch control circuit; A first unidirectional conducting circuit, one end of which is connected to the node H, and the other end of which is connected to the node E; A second unidirectional conducting circuit, one end of which is connected to the node I, and the other end of which is connected to the node E; A light emitting diode LED1, whose anode is connected to the node H and whose cathode is grounded; A light emitting diode LED2, a cathode of which is connected to the node J, and an anode of which is connected to the power supply voltage Vbus; The light emitting diode LED3 has an anode connected to the node I and a cathode connected to the ground.

2. The circuit for automatically adjusting LED color or hue according to claim 1, characterized in that: The first switch combination circuit includes a transistor Q1, a transistor Q2, a resistor R2, and a resistor R5, wherein a first connection end of the transistor Q1 is connected to the power supply voltage Vbus, a second connection end thereof is connected to the node H, and a control end thereof is connected to a node D; one end of the resistor R2 is connected to the power supply voltage Vbus, and the other end thereof is connected to the node D; a first connection end of the transistor Q2 is connected to the node D via the resistor R5, a second connection end thereof is grounded, and a control end thereof is connected to an output end A of the first temperature detection unit; The second switch combination circuit includes a transistor Q5, a transistor Q6, a resistor R13, and a resistor R18. The first connection end of the transistor Q5 is connected to the power supply voltage Vbus, the second connection end thereof is connected to the node I, and the control end thereof is connected to the node G; one end of the resistor R13 is connected to the power supply voltage Vbus, and the other end thereof is connected to the node G; the first connection end of the transistor Q6 is connected to the node G via the resistor R18, the second connection end thereof is grounded, and the control end thereof is connected to the output end B of the second temperature detection unit.

3. The circuit for automatically adjusting LED color or hue according to claim 2, characterized in that: The first unidirectional conduction circuit includes a diode D1 and a resistor R15, wherein the anode of the diode D1 is connected to the node H, the cathode of the diode D1 is grounded via the resistor R15, and the cathode of the diode D1 is connected to the node E; The second unidirectional conducting circuit comprises a diode D2 and a resistor R19, wherein the anode of the diode D2 is connected to the node I, the cathode of the diode D2 is grounded via the resistor R19, and the cathode of the diode D2 is connected to the node E; The switch control circuit includes a resistor R7, a resistor R8, a resistor R10, a resistor R11 and a transistor Q4, one end of the resistor R7 is connected to the input voltage Vin, and the other end thereof is connected to the output end C of the switch control circuit; one end of the resistor R8 is connected to the output end C of the switch control circuit, and the other end thereof is grounded; a first connection end of the transistor Q4 is connected to the output end C of the switch control circuit, a second connection end thereof is grounded, and a control end thereof is connected to a node F; one end of the resistor R10 is connected to the node F, and the other end thereof is connected to the node E; one end of the resistor R11 is connected to the node F, and the other end thereof is grounded.

4. The circuit for automatically adjusting LED color or hue according to claim 3, characterized in that: When the ambient temperature is between the low temperature threshold TL and the high temperature threshold TH, the transistors Q1 and Q2 are turned off, and the LED1 does not emit light; the transistors Q5 and Q6 are turned off, and the LED3 does not emit light; the transistor Q3 is turned on, the transistor Q4 is turned off, and the LED2 emits light; the diodes D1 and D2 are both cut off; When the ambient temperature is lower than the low temperature threshold TL, the transistors Q1 and Q2 are turned on, and the LED1 emits light; the transistors Q5 and Q6 are turned off, and the LED3 does not emit light; the transistor Q3 is turned off, the transistor Q4 is turned on, and the LED2 does not emit light; the diode D1 is forward-conducted, and the diode D2 is cut off; When the ambient temperature is greater than the high temperature threshold TH, the transistor Q1 and the transistor Q2 are turned off, and the LED1 does not emit light; the transistor Q5 and the transistor Q6 are turned on, and the LED3 does not emit light; the transistor Q3 is turned off, the transistor Q4 is turned on, and the LED2 does not emit light; the diode D1 is cut off, and the diode D2 is forward-conducted.

5. The circuit for automatically adjusting LED color or hue according to claim 4, characterized in that: The selection of the resistors R7 and R8 needs to satisfy the requirement that when the node E is at a high level, the divided voltage on the resistor R8 is greater than the turn-on voltage value of the transistor Q3; The selection of the resistors R10 and R11 needs to satisfy the following requirement: when the ambient temperature is lower than the low temperature threshold TL or higher than the high temperature threshold TH, the voltage divided by the resistor R11 is higher than the turn-on voltage value of the transistor Q4. The low temperature threshold TL is smaller than the high temperature threshold TH.

6. The circuit for automatically adjusting LED color or hue according to claim 5, characterized in that: When the ambient temperature is lower than the low temperature threshold TL, the first temperature detection voltage VA output by the first temperature detection unit is greater than the turn-on voltage value of the transistor Q2; when the ambient temperature is higher than the low temperature threshold TL, the first temperature detection voltage VA output by the first temperature detection unit is less than the turn-on voltage value of the transistor Q2; When the ambient temperature is lower than the high temperature threshold TH, the second temperature detection voltage VB output by the second temperature detection unit is lower than the turn-on voltage value of the transistor Q6; When the ambient temperature is greater than the high temperature threshold TH, the second temperature detection voltage VB output by the second temperature detection unit is greater than the turn-on voltage value of the transistor Q6.

7. The circuit for automatically adjusting LED color or hue according to claim 6, characterized in that: The first temperature detection unit includes a resistor R3, a thermistor NTC1, a resistor R4 and a resistor R6, one end of the resistor R3 is connected to the input voltage Vin, and the other end thereof is connected to the output end A of the first temperature detection unit via the resistor R4; one end of the resistor R6 is connected to the output end A of the first temperature detection unit, and the other end thereof is grounded; one end of the thermistor NTC1 is connected to the other end of the resistor R3, and the other end thereof is grounded; The second temperature detection unit includes a resistor R16, a thermistor NTC2, a resistor R14 and a resistor R17, one end of the thermistor NTC2 is connected to the input voltage Vin, and the other end thereof is connected to the output end B of the second temperature detection unit via the resistor R14; one end of the resistor R17 is connected to the output end B of the second temperature detection unit, and the other end thereof is grounded; one end of the resistor R16 is connected to the other end of the thermistor NTC2, and the other end thereof is grounded.

8. The circuit for automatically adjusting LED color or hue according to claim 7, characterized in that: The thermistor NTC1 is a negative temperature coefficient thermistor, and the selection of the resistors R3, R4, R6 and the thermistor NTC1 needs to satisfy that when the ambient temperature is lower than the low temperature threshold TL, the voltage at the output terminal A of the first temperature detection unit is higher than the turn-on voltage value of the transistor Q2; when the ambient temperature is higher than the low temperature threshold TL, the voltage at the output terminal A of the first temperature detection unit is lower than the turn-on voltage value of the transistor Q2; The thermistor NTC2 is a negative temperature coefficient thermistor, and the selection of the resistor R14, the resistor R16, the resistor R17 and the thermistor NTC2 needs to satisfy that when the ambient temperature is lower than the high temperature threshold TH, the voltage at the output terminal B of the second temperature detection unit is lower than the turn-on voltage value of the transistor Q6; When the ambient temperature is greater than the high temperature threshold TH, the voltage at the output terminal B of the second temperature detection unit is greater than the turn-on voltage value of the transistor Q6.

9. The circuit for automatically adjusting LED color or hue according to claim 8, characterized in that: The transistor Q1 is a PNP transistor, and the first connection end, the second connection end and the control end of the transistor Q1 are respectively the emitter, the collector and the base of the PNP transistor; The transistor Q2 is an NPN transistor, and the first connection end, the second connection end and the control end of the transistor Q2 are respectively the collector, the emitter and the base of the NPN transistor; The transistor Q3 is an NPN transistor, and the first connection end, the second connection end and the control end of the transistor Q3 are respectively the collector, the emitter and the base of the NPN transistor; The transistor Q4 is an NPN transistor, and the first connection end, the second connection end and the control end of the transistor Q4 are respectively the collector, the emitter and the base of the NPN transistor; The transistor Q5 is a PNP transistor, and the first connection end, the second connection end and the control end of the transistor Q5 are respectively the emitter, the collector and the base of the PNP transistor; The transistor Q6 is an NPN transistor, and the first connection end, the second connection end and the control end of the transistor Q6 are respectively the collector, the emitter and the base of the NPN transistor.

10. The circuit for automatically adjusting LED color or hue according to any one of claims 1 to 9, characterized in that: The colors of LED1, LED2 and LED3 are different; or The LED1, LED2 and LED3 have different tones.

11. The circuit for automatically adjusting LED color or hue according to claim 10, characterized in that: The LED1 has a warmer tone than the LED2, and the LED3 has a cooler tone than the LED2; The LED1 emits warmer light than the LED2, and the LED3 emits cooler light than the LED2.

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