Atmosphere lamp temperature control circuit

Abstract

An atmosphere lamp temperature control circuit comprises an MCU and is characterized in that the MCU is provided with at least one PWM channel, each PWM channel is in cascade connection with at least one LED drive circuit, and each LED drive circuit is connected with an LED lamp set; and the MCU controls all the corresponding LED lamp groups through each PWM channel. The MCU calculates the channel current of each PWM channel according to the chromatographic value and the brightness level of the LED lamp group, limits the channel current value of each PWM channel through the threshold current, and adjusts the duty ratio of each PWM channel according to the adjustment proportion after the threshold current is exceeded, so that the sum of the channel currents of all the PWM channels tends to the threshold current, the working temperature of the LED lamp group is reduced, and the service life of the LED lamp group is prolonged. And the channel current utilization rate of the PWM channel is improved.

Description

Technical Field

[0001] This utility model relates to the field of automotive lighting technology, and in particular to an ambient lighting temperature control circuit. Background Technology

[0002] With the development of new energy vehicles, the development of in-car ambient lighting is also advancing rapidly, no longer satisfied with the simple functions of traditional single-color light on and off. The demand for multi-color gamut and multi-LED lighting is now experiencing explosive growth.

[0003] As customers' demands for color and functionality increase, the problem of LED overheating is becoming more and more serious. Overheating of LEDs accelerates the aging of the LED chips, thereby reducing their lifespan. It also leads to accelerated light decay, decreased luminous flux, and a gradual reduction in brightness, ultimately affecting the lighting effect.

[0004] In addition, overheating of LEDs can cause malfunctions in other electronic components, leading to increased electrical impedance and current, which may eventually damage electronic components due to overheating. It may also cause aging and damage to the insulation layer of wires, and even cause safety problems such as fires.

[0005] To address this, traditional ambient lighting currently reduces the operating temperature of LEDs by limiting luminous flux. However, this method is too crude and reduces channel utilization. Since different colors have different duty cycles under the same luminous flux limit, maximizing channel current utilization cannot be guaranteed. In other words, under a constant current source circuit, limiting the luminous flux does not guarantee that the current for some colors will reach its maximum. Utility Model Content

[0006] The purpose of this invention is to provide an ambient light temperature control circuit that makes the sum of the channel currents of all PWM channels approach the threshold current, thereby reducing the operating temperature of the LED light group and improving the channel current utilization rate of the PWM channels.

[0007] An ambient light temperature control circuit includes an MCU, the key feature of which is that the MCU is provided with at least one PWM channel, each PWM channel is cascaded with at least one LED driver circuit, and each LED driver circuit is connected to a group of LED lights;

[0008] The MCU controls all corresponding LED groups through each PWM channel;

[0009] The channel current of the PWM channel corresponds one-to-one with the driving current and operating temperature of the LED lamp group. The larger the channel current of the PWM channel, the larger the driving current of the LED lamp group, and the higher the ambient temperature of the LED lamp group.

[0010] The MCU controls the sum of the channel currents of all PWM channels to tend towards a set value by controlling the duty cycle, thereby preventing the LED light group from operating at too high a temperature.

[0011] The LED driving circuit includes a PNP transistor Q2. The base of the transistor Q2 is connected to the PWM channel via resistor R2. The emitter of the transistor Q2 is connected to the power supply VCC via resistor R3. The collector of the transistor Q2 is connected to the front end of resistor R4. The rear end of resistor R4 is grounded via resistor R5, and the common terminal of both is connected to the LED lamp group.

[0012] The base of transistor Q2 is also connected to the collector of transistor Q1, which is a PNP transistor. The base of transistor Q1 is connected to the emitter of transistor Q2, and the emitter of transistor Q1 is connected to the power supply VCC.

[0013] The power supply VCC is also connected to the PWM channel via resistor R1.

[0014] When the PWM channel outputs a low-level signal, the constant current circuit composed of transistors Q2 and Q1 is turned on, which gradually stabilizes the current flowing through the LED lamp group, thereby driving the LED lamp group with constant current, keeping the brightness of the LED lamp group stable, uniformly increasing the brightness and color of the LED lamp group, reducing the temperature rise of the LED lamp group, preventing the LED lamp group from overheating, delaying the light decay of the LED, and extending its service life.

[0015] Furthermore, the MCU is provided with a power drive terminal LC3, which is connected to an enable power circuit, which is connected to the power supply VS and the power supply VCC.

[0016] The MCU is also equipped with a signal input terminal LIN_In and a signal output terminal LIN_Out, which are connected to the ECU.

[0017] The signal input terminal LIN_In and the signal output terminal LIN_Out are connected to the ECU via the LIN bus.

[0018] Furthermore, the enabling power supply circuit includes an NPN transistor Q14. The base of transistor Q14 is connected to the power drive terminal LC3 via resistor R28. The base of transistor Q14 is grounded via resistor R31 and also via capacitor C1. The emitter of transistor Q14 is grounded. The collector of transistor Q14 is connected to the base of transistor Q13 via resistor R30. Transistor Q13 is a PNP transistor. The base of transistor Q13 is connected to the power supply VS via resistor R29. The emitter of transistor Q13 is connected to the power supply VS. The collector of transistor Q13 is connected to the power supply VCC and also via capacitor C2.

[0019] The MCU controls the power supply VCC to turn on and off by enabling the power supply circuit. When the MCU sends a high-level signal, the power supply VCC is in the on state; when the MCU sends a low-level signal, the power supply VCC is in the off state, thereby preventing equipment damage, extending equipment life and saving energy.

[0020] Furthermore, the MCU is equipped with three PWM channels: PWM_R channel, PWM_B channel, and PWM_G channel.

[0021] The PWM_R channel is connected to the LED group with a red light emission color via the LED driving circuit.

[0022] The PWM_B channel is connected to the blue LED group via the LED driver circuit;

[0023] The PWM_G channel is connected to the LED group with a green light emission color via the LED driver circuit.

[0024] The PWM_R channel, PWM_B channel, and PWM_G channel can combine color values ​​to mix red, blue, and green LEDs to produce a variety of colors, thus meeting various lighting design needs.

[0025] The working principle of the ambient light temperature control circuit is as follows:

[0026] S1: The MCU matches the color spectrum value of each LED group according to the selected color of each LED group, and calculates the channel current of each PWM channel in turn according to the color spectrum value and brightness level of each LED group.

[0027] S2: The MCU determines whether the sum of the channel currents of all PWM channels is greater than the threshold current;

[0028] If the sum of the channel currents of all PWM channels is less than or equal to the threshold current, the MCU drives the LED driver circuit according to the current channel current.

[0029] If the sum of the channel currents of all PWM channels is greater than the threshold current, the MCU calculates the adjustment ratio based on the threshold current and the sum of the channel currents of all PWM channels.

[0030] S3: The MCU calculates the adjustment channel current of all PWM channels according to the adjustment ratio, and calculates the adjustment duty cycle of each PWM channel in turn based on the adjustment channel current of all PWM channels.

[0031] S4: The MCU drives each LED driver circuit according to the adjusted duty cycle of each PWM channel.

[0032] The channel current value of the PWM channel corresponds one-to-one with the operating temperature value of the LED lamp group. The larger the channel current, the higher the ambient temperature value of the LED lamp group. The MCU calculates the channel current of each PWM channel based on the color spectrum value and the brightness level of the LED lamp group, and limits the channel current value of each PWM channel through the threshold current. After the threshold current is exceeded, the MCU adjusts the duty cycle of each PWM channel according to the adjustment ratio, so that the sum of the channel current of all PWM channels tends to the threshold current, thereby preventing the operating temperature of the LED lamp group from rising and improving the channel current utilization rate of the PWM channel.

[0033] The formula for calculating the channel current of the PWM channel is as follows:

[0034]

[0035] Among them, a 色 To select a color-matching chromatographic value, the chromatographic value range is [0, 255], I max This is the maximum channel current of the PWM channel. The maximum channel current of the PWM channel is the channel current of the PWM channel when the color value is 255 and the brightness level is 100%.

[0036] The formula for calculating the sum of the channel currents of all PWM channels is:

[0037]

[0038] Among them, I n This represents the channel current of the nth PWM channel, where n is the number of PWM channels.

[0039] The formula for calculating the adjustment ratio is:

[0040]

[0041] Among them, I 阈 For the threshold current, I 总 This is the sum of the channel currents of all PWM channels.

[0042] The formula for calculating the adjustment channel current of the PWM channel is:

[0043] I 调 =I×k

[0044] Where I is the channel current of the PWM channel, and k is the adjustment ratio.

[0045] The formula for calculating the duty cycle of the PWM channel is:

[0046]

[0047] Among them, I 调 The current is the adjustment channel current for the PWM channel, where m is the total number of pulses in one cycle, and I... max This is the maximum channel current of the PWM channel.

[0048] Beneficial effects: 1. This utility model can make the sum of the channel currents of all PWM channels approach the threshold current, thereby preventing the reduction of the operating temperature of the LED lamp group and improving the channel current utilization rate of the PWM channels.

[0049] 2. Transistors Q2 and Q1, along with the power supply VCC, drive the LED light group with constant current, ensuring stable brightness, uniform brightness and color of the LED light group, reducing temperature rise, preventing overheating, delaying light decay, and extending the lifespan of the LEDs.

[0050] 3. The MCU controls the opening and closing of the power supply VCC through the enable power supply circuit. When the MCU sends a high-level signal, the power supply VCC is in the open state; when the MCU sends a low-level signal, the power supply VCC is in the closed state, thereby preventing equipment damage, extending equipment life, and saving energy.

[0051] 4. Set up three PWM channels to drive red, blue, and green LED light groups respectively. Red, blue, and green can be mixed to produce a variety of colors by combining their color chromatogram values, thereby meeting various lighting design needs. Attached Figure Description

[0052] Figure 1 Schematic diagram of the working principle of the ambient light temperature control circuit;

[0053] Figure 2 This is the MCU circuit diagram;

[0054] Figure 3 Circuit diagram of cascaded LED driver circuit for PWM_R channel;

[0055] Figure 4 Circuit diagram of cascaded LED driver circuit for PWM_B channel;

[0056] Figure 5 Circuit diagram of cascaded LED driver circuit for PWM_G channel;

[0057] Figure 6 Circuit diagram for enabling power supply. Detailed Implementation

[0058] The specific embodiments and working principle of this utility model will be further described in detail below with reference to the accompanying drawings.

[0059] like Figure 2As shown, the ambient light temperature control circuit includes an MCU, which has PWM_R channel, PWM_B channel, PWM_G channel, power drive terminal LC3, signal input terminal LIN_In and signal output terminal LIN_Out.

[0060] like Figure 3 As shown, the PWM_R channel is connected to the first LED driver circuit and the second LED driver circuit.

[0061] The first LED driving circuit includes a PNP transistor Q2. The base of transistor Q2 is connected to the PWM channel via resistor R2. The emitter of transistor Q2 is connected to the power supply VCC via resistor R3. The collector of transistor Q2 is connected to the front end of resistor R4. The rear end of resistor R4 is grounded via resistor R5. The common terminal of both is connected to the first LED group with a red light emission color.

[0062] The base of transistor Q2 is also connected to the collector of transistor Q1, which is a PNP transistor. The base of transistor Q1 is connected to the emitter of transistor Q2, and the emitter of transistor Q1 is connected to the power supply VCC.

[0063] The second LED driving circuit includes a PNP transistor Q4. The base of the transistor Q4 is connected to the PWM channel via resistor R6, the emitter of the transistor Q4 is connected to the power supply VCC via resistor R7, the collector of the transistor Q4 is connected to the front end of resistor R8, the rear end of resistor R8 is grounded via resistor R9, and the common terminal of both is connected to the second LED group with a red light color.

[0064] The base of transistor Q4 is also connected to the collector of transistor Q3, which is a PNP transistor. The base of transistor Q3 is connected to the emitter of transistor Q4, and the emitter of the gate-off transistor Q3 is connected to the power supply VCC.

[0065] The power supply VCC is also connected to the PWM_R channel via resistor R1.

[0066] like Figure 4 As shown, the PWM_B channel is connected to the third LED driver circuit and the fourth LED driver circuit;

[0067] The third LED driving circuit includes a PNP transistor Q6. The base of transistor Q6 is connected to the PWM channel via resistor R11, the emitter of transistor Q6 is connected to the power supply VCC via resistor R12, the collector of transistor Q6 is connected to the front end of resistor R13, the rear end of resistor R13 is grounded via resistor R14, and the common terminal of both is connected to the third LED group with a blue light emission color.

[0068] The base of transistor Q6 is also connected to the collector of transistor Q5, which is a PNP transistor. The base of transistor Q5 is connected to the emitter of transistor Q6, and the emitter of transistor Q5 is connected to the power supply VCC.

[0069] The fourth LED driving circuit includes a PNP transistor Q8. The base of the transistor Q8 is connected to the PWM channel via resistor R15, the emitter of the transistor Q8 is connected to the power supply VCC via resistor R16, the collector of the transistor Q8 is connected to the front end of resistor R17, the rear end of resistor R17 is grounded via resistor R18, and the common terminal of both is connected to the fourth LED group with a blue light emission color.

[0070] The base of transistor Q8 is also connected to the collector of transistor Q7, which is a PNP transistor. The base of transistor Q7 is connected to the emitter of transistor Q8, and the emitter of transistor Q7 is connected to the power supply VCC.

[0071] The power supply VCC is also connected to the PWM_B channel via resistor R10.

[0072] like Figure 5 As shown, the PWM_G channel is connected to the fifth LED driver circuit and the sixth LED driver circuit;

[0073] The fifth LED driving circuit includes a PNP transistor Q10. The base of the transistor Q10 is connected to the PWM channel via resistor R20, the emitter of the transistor Q10 is connected to the power supply VCC via resistor R21, the collector of the transistor Q10 is connected to the front end of resistor R22, the rear end of resistor R22 is grounded via resistor R23, and the common terminal of both is connected to the fifth LED group with a green light color.

[0074] The base of transistor Q10 is also connected to the collector of transistor Q9, which is a PNP transistor. The base of transistor Q9 is connected to the emitter of transistor Q10, and the emitter of transistor Q9 is connected to the power supply VCC.

[0075] The sixth LED driving circuit includes a PNP transistor Q12. The base of the transistor Q12 is connected to the PWM channel via resistor R24, the emitter of the transistor Q12 is connected to the power supply VCC via resistor R25, the collector of the transistor Q12 is connected to the front end of resistor R26, the rear end of resistor R26 is grounded via resistor R27, and the common terminal of both is connected to the sixth LED group with a green light color.

[0076] The base of transistor Q12 is also connected to the collector of transistor Q11, which is a PNP transistor. The base of transistor Q11 is connected to the emitter of transistor Q12, and the emitter of transistor Q11 is connected to the power supply VCC.

[0077] The power supply VCC is also connected to the PWM_G channel via resistor R19.

[0078] like Figure 6 As shown, the power drive terminal LC3 is connected to an enable power circuit, which includes an NPN transistor Q14. The base of transistor Q14 is connected to the power drive terminal LC3 via resistor R28, and the base of transistor Q14 is grounded via resistor R31. The base of transistor Q14 is also grounded via capacitor C1. The emitter of transistor Q14 is grounded. The collector of transistor Q14 is connected to the base of transistor Q13 via resistor R30. Transistor Q13 is a PNP transistor. The base of transistor Q13 is also connected to the power supply VS via resistor R29. The emitter of transistor Q13 is connected to the power supply VS. The collector of transistor Q13 outputs the power supply VCC, and the collector of transistor Q13 is also grounded via capacitor C2.

[0079] The signal input terminal LIN_In and the signal output terminal LIN_Out are connected to the ECU via the LIN bus.

[0080] like Figure 1 As shown, the working principle of the ambient light temperature control circuit is as follows:

[0081] S1: The MCU matches the color spectrum value of each LED group according to the selected color of each LED group, and calculates the channel current of each PWM channel in turn according to the color spectrum value and brightness level of each LED group.

[0082] The formula for calculating the channel current of the PWM channel is:

[0083]

[0084] Among them, a 色 To select a color-matching chromatographic value, the chromatographic value range is [0, 255], I max This is the maximum channel current of the PWM channel. The maximum channel current of the PWM channel is the channel current of the PWM channel when the color value is 255 and the brightness level is 100%.

[0085] The formula for calculating the sum of the channel currents of all PWM channels is:

[0086]

[0087] Among them, I n This represents the channel current of the nth PWM channel, where n is the number of PWM channels.

[0088] For example: the color spectrum value of a red LED light group is 100, the color spectrum value of a blue LED light group is 250, and the color spectrum value of a green LED light group is 150. If the brightness level of all LED light groups is 60%, then:

[0089] The channel current of the PWM_R channel is:

[0090]

[0091] The channel current of PWM_B is:

[0092]

[0093] The channel current of the PWM_G channel is:

[0094]

[0095] The sum of the channel currents for all PWM channels is:

[0096] I 总 =I1+I2+I3=7.2+18+10.8=36mA

[0097] S2: The MCU determines whether the sum of the channel currents of all PWM channels is greater than the threshold current;

[0098] If the sum of the channel currents of all PWM channels is less than or equal to the threshold current, the MCU drives the LED driver circuit according to the current channel current.

[0099] If the sum of the channel currents of all PWM channels is greater than the threshold current, the MCU calculates the adjustment ratio based on the threshold current and the sum of the channel currents of all PWM channels.

[0100] The formula for calculating the adjustment ratio is:

[0101]

[0102] Among them, I 阈 For the threshold current, I 总 This is the sum of the channel currents of all PWM channels.

[0103] Adjustment Figure 3 , 4By determining the resistance values ​​of resistors R3, R7, R12, R16, R21, and R25 in section 5, the relationship between the channel current of each PWM channel and the operating temperature of the corresponding LED group can be obtained. This relationship can then be used to determine the threshold current I. 阈 .

[0104] For example, if the threshold current is 30mA, the sum of the channel currents of all PWM channels, referring to the example above, is as follows:

[0105] The adjustment ratio is:

[0106]

[0107] S3: The MCU calculates the adjustment channel current of all PWM channels according to the adjustment ratio, and calculates the adjustment duty cycle of each PWM channel in turn based on the adjustment channel current of all PWM channels.

[0108] The formula for calculating the adjustment channel current of the PWM channel is:

[0109] I 调 =I×k

[0110] Where I is the channel current of the PWM channel, and k is the adjustment ratio;

[0111] The formula for calculating the adjustment duty cycle of the PWM channel is:

[0112]

[0113] Among them, I 调 The current is the adjustment channel current for the PWM channel, where m is the total number of pulses in one cycle, and I... max This is the maximum channel current of the PWM channel.

[0114] For example: if m is 65535, and the maximum channel current of each PWM channel is 30mA, then, following the example above, the adjustment ratio would be:

[0115] The adjustment channel current of the PWM_R channel is:

[0116] I 11 =7.2mA × 0.83 = 5.967mA

[0117] The adjustment channel current of the PWM_B channel is:

[0118] I 21 =18mA × 0.83 = 14.94mA

[0119] The adjustment channel current of the PWM_G channel is:

[0120] I31 =10.8 × 0.83 = 8.964 mA

[0121] The adjustment duty cycle of the PWM_R channel is:

[0122]

[0123] The adjustment duty cycle of the PWM_B channel is:

[0124]

[0125] The adjustment duty cycle of the PWM_G channel is:

[0126]

[0127] S4: The MCU drives each LED driver circuit according to the adjusted duty cycle of each PWM channel;

[0128] For example, referring to the above example, the adjusted duty cycle of the PWM_R channel, the adjusted duty cycle of the PWM_B channel, and the adjusted duty cycle of the PWM_G channel are as follows: the adjusted duty cycle of the PWM_R channel with an output value of 13055 drives the first and second LED driver circuits; the adjusted duty cycle of the PWM_B channel with an output value of 32636 drives the third and fourth LED driver circuits; and the adjusted duty cycle of the PWM_G channel with an output value of 19582 drives the fifth and sixth LED driver circuits.

[0129] Finally, it should be noted that the above are only specific embodiments of this utility model. Of course, those skilled in the art can make modifications and variations to this utility model, such as modifying the value of m, for example, changing the value of m to 256, 2560, etc. These modifications and variations fall within the scope of the claims of this utility model and their equivalents, and should all be considered as within the protection scope of this utility model.

Claims

1. An ambient light temperature control circuit, comprising an MCU, characterized in that, The MCU is equipped with at least one PWM channel, each PWM channel is cascaded with at least one LED driver circuit, and each LED driver circuit is connected to a group of LED lights; The MCU controls all corresponding LED groups through each PWM channel; The LED driving circuit includes a PNP transistor Q2. The base of the transistor Q2 is connected to the PWM channel via resistor R2. The emitter of the transistor Q2 is connected to the power supply VCC via resistor R3. The collector of the transistor Q2 is connected to the front end of resistor R4. The rear end of resistor R4 is grounded via resistor R5, and the common terminal of both is connected to the LED lamp group. The base of transistor Q2 is also connected to the collector of transistor Q1, which is a PNP transistor. The base of transistor Q1 is connected to the emitter of transistor Q2, and the emitter of transistor Q1 is connected to the power supply VCC. The power supply VCC is also connected to the PWM channel via resistor R1.

2. The ambient light temperature control circuit according to claim 1, characterized in that, The MCU is provided with a power drive terminal LC3, which is connected to an enable power circuit. The enable power circuit is connected to the power supply VS and the power supply VCC. The MCU is also equipped with a signal input terminal LIN_In and a signal output terminal LIN_Out, which are connected to the ECU.

3. The ambient light temperature control circuit according to claim 2, characterized in that, The enabling power supply circuit includes an NPN transistor Q14. The base of transistor Q14 is connected to the power drive terminal LC3 via resistor R28. The base of transistor Q14 is grounded via resistor R31 and also via capacitor C1. The emitter of transistor Q14 is grounded. The collector of transistor Q14 is connected to the base of transistor Q13 via resistor R30. Transistor Q13 is a PNP transistor. The base of transistor Q13 is connected to the power supply VS via resistor R29. The emitter of transistor Q13 is connected to the power supply VS. The collector of transistor Q13 is connected to the power supply VCC and also via capacitor C2.

4. The ambient light temperature control circuit according to claim 3, characterized in that, The MCU is equipped with three PWM channels: PWM_R channel, PWM_B channel, and PWM_G channel. The PWM_R channel is connected to the LED group with a red light emission color via the LED driving circuit. The PWM_B channel is connected to the blue LED group via the LED driver circuit; The PWM_G channel is connected to the LED group with a green light emission color via the LED driver circuit.

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