Control system for keeping LED brightness constant

Abstract

The utility model discloses a control system for keeping LED brightness constant, and belongs to the technical field of brightness control. The sampling circuit is used for collecting simulated temperature collection signals; the single chip microcomputer control circuit is connected with the sampling circuit and outputs a digital pulse width modulation signal based on the temperature acquisition signal; the constant-current driving circuit is connected with the single chip microcomputer control circuit, the input end of the constant-current driving circuit receives the pulse width modulation signal, and the constant-current driving circuit outputs a light source driving signal based on the pulse width modulation signal; and the light source circuit is connected with the output end of the constant-current driving circuit and receives a light source driving signal. The technical scheme has the beneficial effects that the function of keeping the brightness of the LED constant in different temperature environments is realized, the consistency and the reliability of a light source are favorably kept, and the product performance and the user experience are improved.

Description

Technical Field

[0001] The utility model relates to the technical field of brightness control, in particular to an LED brightness control system. Background Art

[0002] The temperature characteristics of LEDs (Light-Emitting Diodes) result in significant differences in brightness between extreme high and low temperatures, especially for red LEDs. Using a 25°C brightness as a benchmark, the brightness at -40°C can be over 40% higher than the benchmark, while at 105°C, the LED brightness can be over 50% lower than the benchmark.

[0003] In the prior art, based on the above-mentioned characteristics of LED lamps, for LED lamps that need to work in environments with large temperature differences, if effective control is not performed, the brightness fluctuations of the LED at different temperatures will make it impossible to achieve the design requirements, affecting the consistency and reliability of the light source, thereby reducing product performance and user experience. Utility Model Content

[0004] The purpose of this utility model is to provide a control system that keeps the LED brightness constant to solve the above technical problems;

[0005] A control system for maintaining constant LED brightness, comprising:

[0006] A sampling circuit for collecting analog temperature acquisition signals;

[0007] A single-chip microcomputer control circuit is connected to the sampling circuit, and the single-chip microcomputer control circuit outputs a digital pulse width modulation signal based on the temperature acquisition signal;

[0008] a constant current driving circuit connected to the single-chip control circuit, wherein an input end of the constant current driving circuit receives the pulse width modulation signal, and the constant current driving circuit outputs a light source driving signal based on the pulse width modulation signal;

[0009] The light source circuit is connected to the output end of the constant current driving circuit and receives the light source driving signal.

[0010] Preferably, the sampling circuit includes:

[0011] a first resistor, wherein a first end of the first resistor is connected to an input voltage source, and a second end of the first resistor is connected to the temperature acquisition signal;

[0012] The second resistor is a thermistor provided in the temperature environment to be collected, a first end of the second resistor is connected to the second end of the first resistor, and a second end of the second resistor is grounded.

[0013] Preferably, the single-chip microcomputer control circuit includes a control chip, and an acquisition pin of the control chip receives the temperature acquisition signal;

[0014] The first power pin of the control chip is connected to the input voltage source;

[0015] The first analog ground pin of the control chip is grounded;

[0016] The analog power pin of the control chip is connected to the input voltage source;

[0017] The first digital ground pin of the control chip is grounded;

[0018] The second power pin of the control chip is connected to the input voltage source;

[0019] The second digital ground pin of the control chip is grounded;

[0020] The third power pin of the control chip is connected to the input voltage source.

[0021] Preferably, the constant current driving circuit includes a power management chip, and a first dimming pin and a second dimming pin of the power management chip obtain the pulse width modulation signal;

[0022] The constant current driving circuit further includes:

[0023] a first capacitor, wherein a first end of the first capacitor is connected to a first power input pin of the power management chip, and a second end of the first capacitor is grounded;

[0024] a second capacitor, wherein a first end of the second capacitor is connected to the second end of the first capacitor, and a second end of the second capacitor is connected to a second power input pin of the power management chip;

[0025] a third capacitor, wherein a first end of the third capacitor is connected to the first end of the first capacitor, and a second end of the third capacitor is grounded;

[0026] a fourth capacitor, wherein a first end of the fourth capacitor is connected to the second end of the third capacitor, and a second end of the fourth capacitor is connected to the second end of the second capacitor;

[0027] a fifth capacitor, wherein a first end of the fifth capacitor is connected to the first end of the third capacitor, and a second end of the fifth capacitor is grounded;

[0028] a sixth capacitor, wherein a first end of the sixth capacitor is connected to the second end of the fifth capacitor, and a second end of the sixth capacitor is connected to the second end of the fourth capacitor.

[0029] Preferably, the constant current driving circuit further includes:

[0030] a third resistor, wherein a first end of the third resistor is connected in series with a seventh capacitor and is grounded, and a second end of the third resistor is connected to a fault alarm pin of the power management chip;

[0031] an eighth capacitor, wherein a first end of the eighth capacitor is grounded, and a second end of the eighth capacitor is connected to a power supply pin of the power management chip and the second end of the seventh capacitor respectively;

[0032] a fourth resistor, wherein a first end of the fourth resistor is connected to the second end of the eighth capacitor, and a second end of the fourth resistor is respectively connected to the first enable pin and the second enable pin of the power management chip;

[0033] a fifth resistor, wherein a first end of the fifth resistor is connected to the first end of the fourth resistor, and a second end of the fifth resistor is respectively connected to the second dimming pin, the second enable pin and the first dimming pin of the power management chip.

[0034] Preferably, the constant current driving circuit further includes:

[0035] a first diode, wherein a cathode of the first diode is connected to the first end of the fifth capacitor and the second end of the sixth capacitor, and an anode of the first diode is connected to the negative electrode of the first channel current detection pin of the power management chip;

[0036] a ninth capacitor, wherein a first end of the ninth capacitor is connected to the positive electrode of the first channel current detection pin of the power management chip, and a second end of the ninth capacitor is grounded;

[0037] a sixth resistor, wherein a first end of the sixth resistor is connected to the first gain pin of the power management chip, and a second end of the sixth resistor is connected in series with a tenth capacitor;

[0038] a first inductor, wherein a first end of the first inductor is connected to a first switch pin of the power management chip and a second end of the tenth capacitor respectively;

[0039] a seventh resistor, wherein a first end of the seventh resistor is connected to the SPI output pin of the power management chip, and a second end of the seventh resistor is connected to the power supply pin of the power management chip;

[0040] a second inductor, wherein a first end of the second inductor is connected to the second switch pin of the power management chip, and a second end of the second inductor is connected in series with an eleventh capacitor and is grounded;

[0041] an eighth resistor, wherein a first end of the eighth resistor is connected to the second gain pin of the power management chip, a second end of the eighth resistor is connected in series with a twelfth capacitor, and a second end of the twelfth capacitor is connected to the first end of the second inductor;

[0042] A second diode, wherein the cathode of the second diode is connected to the first end of the fifth capacitor and the second end of the sixth capacitor, and the anode of the second diode is connected to the negative electrode of the second channel current detection pin of the power management chip.

[0043] Preferably, the constant current driving circuit further includes:

[0044] a ninth resistor, wherein a first end of the ninth resistor is connected to the anode of the first diode, and a second end of the ninth resistor is connected to the positive electrode of the first channel current detection pin of the power management chip;

[0045] a tenth resistor, wherein a first end of the tenth resistor is connected to the first end of the ninth resistor, and a second end of the tenth resistor is connected to the second end of the ninth resistor;

[0046] an eleventh resistor, wherein a first end of the eleventh resistor is connected to the first end of the tenth resistor, and a second end of the eleventh resistor is respectively connected to the second end of the tenth resistor and the second end of the first inductor;

[0047] a thirteenth capacitor, a first end of the thirteenth capacitor being connected to the first end of the eleventh resistor, and a second end of the thirteenth capacitor being grounded;

[0048] a fifth diode, wherein a cathode of the fifth diode is connected to the first end of the eleventh resistor, and an anode of the fifth diode is connected to the second end of the thirteenth capacitor;

[0049] a third inductor, wherein a first end of the third inductor is connected to the first end of the thirteenth capacitor, and a second end of the third inductor is connected to the output end;

[0050] a fifteenth resistor, wherein a first end of the fifteenth resistor is connected to the second end of the third inductor, and a second end of the fifteenth resistor is grounded;

[0051] a fourteenth capacitor, a first end of the fourteenth capacitor being connected to the output end, and a second end of the fourteenth capacitor being connected to the second end of the fifteenth resistor;

[0052] a third diode, wherein a cathode of the third diode is connected to the first end of the first inductor, and an anode of the third diode is grounded;

[0053] a fourth diode, wherein an anode of the fourth diode is connected to the anode of the third diode, and a cathode of the fourth diode is connected to the first end of the second inductor.

[0054] Preferably, the constant current driving circuit further includes:

[0055] a twelfth resistor, wherein a first end of the twelfth resistor is connected to the positive electrode of the second channel current detection pin of the power management chip, and a second end of the twelfth resistor is connected to the anode of the second diode;

[0056] a thirteenth resistor, wherein a first end of the thirteenth resistor is connected to the first end of the twelfth resistor, and a second end of the thirteenth resistor is connected to the second end of the twelfth resistor;

[0057] a fourteenth resistor, wherein a first end of the fourteenth resistor is connected to the first end of the thirteenth resistor and the first end of the eleventh capacitor respectively, and a second end of the fourteenth resistor is connected to the second end of the thirteenth resistor;

[0058] a fourth inductor, wherein a first end of the fourth inductor is connected to the second end of the fourteenth resistor, and a second end of the fourth inductor is connected to the output end;

[0059] a sixth diode, wherein a cathode of the sixth diode is connected to the second end of the fourteenth resistor, and an anode of the sixth diode is grounded;

[0060] a fifteenth capacitor, wherein a first end of the fifteenth capacitor is connected to the first end of the fourth inductor, and a second end of the fifteenth capacitor is grounded;

[0061] a sixteenth resistor, wherein a first end of the sixteenth resistor is connected to the second end of the fourth inductor, and a second end of the sixteenth resistor is grounded;

[0062] A sixteenth capacitor, wherein a first end of the sixteenth capacitor is connected to the output end, and a second end of the sixteenth capacitor is grounded.

[0063] Preferably, the first power ground pin, the second power ground pin, the third power ground pin and the second analog ground pin of the power management chip are grounded.

[0064] Preferably, the light source circuit includes:

[0065] a first LED lamp, wherein an anode of the first LED lamp is connected to the output end;

[0066] a second LED lamp, wherein the anode of the second LED lamp is connected to the cathode of the first LED lamp;

[0067] A third LED lamp has an anode connected to a cathode of the second LED lamp, and a cathode of the third LED lamp is grounded.

[0068] The beneficial effects of the utility model are: achieving the function of maintaining constant LED brightness under different temperature environments, helping to maintain the consistency and reliability of the light source, and improving product performance and user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 It is a connection block diagram of the control system of the utility model;

[0070] Figure 2 It is a circuit diagram of the sampling circuit of the utility model;

[0071] Figure 3 This is a circuit diagram of the single chip microcomputer control circuit of the utility model;

[0072] Figure 4 This is a circuit diagram of the constant current drive circuit of the utility model;

[0073] Figure 5 It is a circuit diagram of the light source circuit of the utility model;

[0074] Figure 6 This is a flow chart of a control method for maintaining constant LED brightness according to the present invention. DETAILED DESCRIPTION

[0075] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0076] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other.

[0077] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0078] A control system that keeps the LED brightness constant, such as Figures 1 to 5 Shown, including,

[0079] A sampling circuit 1 for collecting a simulated temperature acquisition signal Vntc;

[0080] The single-chip microcomputer control circuit 2 is connected to the sampling circuit 1, and the single-chip microcomputer control circuit 2 outputs a digital pulse width modulation signal DIM based on the temperature acquisition signal Vntc;

[0081] The constant current driving circuit 3 is connected to the single chip control circuit 2, the input end of the constant current driving circuit 3 receives the pulse width modulation signal DIM, and the constant current driving circuit 3 outputs the light source driving signal based on the pulse width modulation signal DIM;

[0082] The light source circuit 4 is connected to the output terminal LED+ of the constant current driving circuit 3 and receives the light source driving signal.

[0083] Specifically, the utility model provides a control system for maintaining constant LED brightness, which is used for controlling special lamps with large temperature differences in the working environment and low brightness change rate. It includes a hardware layer and a software layer. The hardware layer includes a sampling circuit 1, a single-chip microcomputer control circuit 2, a constant current drive circuit 3, and a light source circuit 4.

[0084] In a preferred embodiment, the sampling circuit 1 includes:

[0085] A first resistor R1, wherein a first end of the first resistor R1 is connected to an input voltage source VCC, and a second end of the first resistor R1 is connected to a temperature acquisition signal Vntc;

[0086] The second resistor R2 is a thermistor disposed in the temperature environment to be collected, a first end of the second resistor R2 is connected to the second end of the first resistor R1 , and a second end of the second resistor R2 is grounded.

[0087] Specifically, the first resistor R1 is a current limiting resistor, and the rated measurement range of the second resistor R2 is -40° C. to 150° C. The sampling circuit 1 can calculate the temperature value by using an algorithm that converts the NTC resistance value into temperature through a single chip microcomputer.

[0088] In a preferred embodiment, the single chip control circuit 2 includes a control chip U2, and an acquisition pin PA1 of the control chip U2 receives a temperature acquisition signal Vntc;

[0089] The first power supply pin VDD1 of the control chip U2 is connected to the input voltage source VCC;

[0090] The first analog ground pin VSSA of the control chip U2 is grounded;

[0091] The analog power pin VDDA of the control chip U2 is connected to the input voltage source VCC;

[0092] The first digital ground pin VSS1 of the control chip U2 is grounded;

[0093] The second power supply pin VDD2 of the control chip U2 is connected to the input voltage source VCC;

[0094] The second digital ground pin VSS2 of the control chip U2 is grounded;

[0095] The third power pin VDD3 of the control chip U2 is connected to the input voltage source VCC.

[0096] Specifically, the control chip U2 is based on STM32F030C8T6, and collects the temperature acquisition signal Vntc of the sampling circuit 1 through the AD conversion function of the acquisition pin PA1, outputs the pulse width modulation signal DIM through the PWM function of the output pin PB7, and controls the output current of the constant current drive circuit 3 by changing the PWM duty cycle.

[0097] In a preferred embodiment, the constant current driving circuit 3 includes a power management chip U1, and the first dimming pin DIM1 and the second dimming pin UDIM2 of the power management chip U1 are connected to the output pin PB7 of the control chip U2 to obtain the pulse width modulation signal DIM;

[0098] The constant current driving circuit 3 also includes,

[0099] A first capacitor C1, wherein a first end of the first capacitor C1 is connected to a first power input pin VIN1 of the power management chip U1, and a second end of the first capacitor C1 is grounded;

[0100] A second capacitor C2, wherein a first end of the second capacitor C2 is connected to the second end of the first capacitor C1, and a second end of the second capacitor C2 is connected to a second power input pin VIN2 of the power management chip U1;

[0101] a third capacitor C3, where a first end of the third capacitor C3 is connected to the first end of the first capacitor C1, and a second end of the third capacitor C3 is grounded;

[0102] a fourth capacitor C4, wherein a first end of the fourth capacitor C4 is connected to the second end of the third capacitor C3, and a second end of the fourth capacitor C4 is connected to the second end of the second capacitor C2;

[0103] a fifth capacitor C5, wherein a first end of the fifth capacitor C5 is connected to the first end of the third capacitor C3, and a second end of the fifth capacitor C5 is grounded;

[0104] a sixth capacitor C6, where a first end of the sixth capacitor C6 is connected to the second end of the fifth capacitor C5, and a second end of the sixth capacitor C6 is connected to the second end of the fourth capacitor C4;

[0105] The constant current driving circuit 3 also includes,

[0106] The third resistor R3, the first end of the third resistor R3 is connected in series with a seventh capacitor C7 and grounded, and the second end of the third resistor R3 is connected to the fault alarm pin of the power management chip U1

[0107] An eighth capacitor C8, a first end of the eighth capacitor C8 is grounded, and a second end of the eighth capacitor C8 is connected to a power supply pin VCC1 of the power management chip U1 and a second end of the seventh capacitor C7 respectively;

[0108] a fourth resistor R4, wherein a first end of the fourth resistor R4 is connected to the second end of the eighth capacitor C8, and a second end of the fourth resistor R4 is respectively connected to the first enable pin EN1 and the second enable pin EN2 of the power management chip U1;

[0109] a fifth resistor R5, wherein a first end of the fifth resistor R5 is connected to a first end of the fourth resistor R4, and a second end of the fifth resistor R5 is respectively connected to a second dimming pin UDIM2, a second enable pin EN2, and a first dimming pin DIM1 of the power management chip U1;

[0110] The constant current driving circuit 3 also includes,

[0111] A first diode D1, wherein a cathode of the first diode D1 is connected to a first end of the fifth capacitor C5 and a second end of the sixth capacitor C6, and an anode of the first diode D1 is connected to a negative electrode ISN1 of a first channel current detection pin of the power management chip U1;

[0112] A ninth capacitor C9, wherein a first end of the ninth capacitor C9 is connected to the positive electrode ISP1 of the first channel current detection pin of the power management chip U1, and a second end of the ninth capacitor C9 is grounded;

[0113] A sixth resistor R6, a first end of the sixth resistor R6 is connected to the first gain pin BST1 of the power management chip U1, and a second end of the sixth resistor R6 is connected in series with a tenth capacitor C10;

[0114] A first inductor L1, wherein a first end of the first inductor L1 is connected to a first switch pin SW1 of the power management chip U1 and a second end of a tenth capacitor C10 respectively;

[0115] a seventh resistor R7, wherein a first end of the seventh resistor R7 is connected to the SPI output pin SO of the power management chip U1, and a second end of the seventh resistor R7 is connected to the power supply pin VCC1 of the power management chip U1;

[0116] a second inductor L2, wherein a first end of the second inductor L2 is connected to the second switch pin SW2 of the power management chip U1, and a second end of the second inductor L2 is connected in series with an eleventh capacitor C11 and grounded;

[0117] an eighth resistor R8, wherein a first end of the eighth resistor R8 is connected to the second gain pin BST2 of the power management chip U1, a second end of the eighth resistor R8 is connected in series with a twelfth capacitor C12, and a second end of the twelfth capacitor C12 is connected to the first end of the second inductor L2;

[0118] a second diode D2, wherein a cathode of the second diode D2 is connected to a first end of the fifth capacitor C5 and a second end of the sixth capacitor C6, and an anode of the second diode D2 is connected to a negative electrode ISN2 of a second channel current detection pin of the power management chip U1;

[0119] The constant current driving circuit 3 also includes,

[0120] a ninth resistor R9, wherein a first end of the ninth resistor R9 is connected to the anode of the first diode D1, and a second end of the ninth resistor R9 is connected to the positive electrode ISP1 of the first channel current detection pin of the power management chip U1;

[0121] a tenth resistor R10, wherein a first end of the tenth resistor R10 is connected to a first end of the ninth resistor R9, and a second end of the tenth resistor R10 is connected to a second end of the ninth resistor R9;

[0122] an eleventh resistor R11, wherein a first end of the eleventh resistor R11 is connected to a first end of the tenth resistor R10, and a second end of the eleventh resistor R11 is respectively connected to a second end of the tenth resistor R10 and a second end of the first inductor L1;

[0123] a thirteenth capacitor C13, wherein a first end of the thirteenth capacitor C13 is connected to the first end of the eleventh resistor R11, and a second end of the thirteenth capacitor C13 is grounded;

[0124] a fifth diode D5 , wherein a cathode of the fifth diode D5 is connected to the first end of the eleventh resistor R11 , and an anode of the fifth diode D5 is connected to the second end of the thirteenth capacitor C13 ;

[0125] a third inductor L3 , wherein a first end of the third inductor L3 is connected to a first end of the thirteenth capacitor C13 , and a second end of the third inductor L3 is connected to the output terminal LED+;

[0126] a fifteenth resistor R15, wherein a first end of the fifteenth resistor R15 is connected to the second end of the third inductor L3, and a second end of the fifteenth resistor R15 is grounded;

[0127] a fourteenth capacitor C14, wherein a first end of the fourteenth capacitor C14 is connected to the output terminal LED+, and a second end of the fourteenth capacitor C14 is connected to a second end of the fifteenth resistor R15;

[0128] a third diode D3 , wherein a cathode of the third diode D3 is connected to the first end of the first inductor L1 , and an anode of the third diode D3 is grounded;

[0129] a fourth diode D4, where an anode of the fourth diode D4 is connected to the anode of the third diode D3, and a cathode of the fourth diode D4 is connected to the first end of the second inductor L2;

[0130] The constant current driving circuit 3 also includes,

[0131] a twelfth resistor R12, wherein a first end of the twelfth resistor R12 is connected to the positive electrode ISP2 of the second channel current detection pin of the power management chip U1, and a second end of the twelfth resistor R12 is connected to the anode of the second diode D2;

[0132] a thirteenth resistor R13, wherein a first end of the thirteenth resistor R13 is connected to the first end of the twelfth resistor R12, and a second end of the thirteenth resistor R13 is connected to the second end of the twelfth resistor R12;

[0133] a fourteenth resistor R14, wherein a first end of the fourteenth resistor R14 is respectively connected to the first end of the thirteenth resistor R13 and the first end of the eleventh capacitor C11, and a second end of the fourteenth resistor R14 is connected to the second end of the thirteenth resistor R13;

[0134] a fourth inductor L4 , wherein a first end of the fourth inductor L4 is connected to the second end of the fourteenth resistor R14 , and a second end of the fourth inductor L4 is connected to the output terminal LED+;

[0135] a sixth diode D6 , wherein a cathode of the sixth diode D6 is connected to the second end of the fourteenth resistor R14 , and an anode of the sixth diode D6 is grounded;

[0136] a fifteenth capacitor C15, wherein a first end of the fifteenth capacitor C15 is connected to the first end of the fourth inductor L4, and a second end of the fifteenth capacitor C15 is grounded;

[0137] a sixteenth resistor R16, wherein a first end of the sixteenth resistor R16 is connected to the second end of the fourth inductor L4, and a second end of the sixteenth resistor R16 is grounded;

[0138] The sixteenth capacitor C16 has a first end connected to the output terminal LED+ and a second end grounded.

[0139] Specifically, the power management chip U1 of the constant current drive circuit 3 is MPQ7210, and the maximum output current is set by the sampling resistors: the tenth resistor R10, the eleventh resistor R11, the twelfth resistor R12, the thirteenth resistor R13, the fourteenth resistor R14, and the ninth resistor R9. The first dimming pin DIM1 and the second dimming pin UDIM2 of the power management chip U1 receive PWM signals to control the output current.

[0140] In a preferred embodiment, the first power ground pin PGND1 , the second power ground pin PGND2 , the third power ground pin PGND3 and the second analog ground pin AGND of the power management chip U1 are grounded.

[0141] In a preferred embodiment, the light source circuit 4 includes:

[0142] A first LED lamp LED1, wherein the anode of the first LED lamp LED1 is connected to the output terminal LED+;

[0143] a second LED lamp LED2, wherein the anode of the second LED lamp LED2 is connected to the cathode of the first LED lamp LED1;

[0144] The third LED lamp LED3 has an anode connected to the cathode of the second LED lamp LED2 , and a cathode of the third LED lamp LED3 is grounded.

[0145] Specifically, the light source circuit 4 is based on GA CSHPM1.23 and can change the brightness of the LED according to the magnitude of the output current of the constant current driving circuit 3 .

[0146] The software layer includes temperature acquisition module and list module, refer to Figure 6 Sampling circuit 1, based on an NTC thermistor, is used to monitor the temperature of the LED lamp in real time. The resistance of the NTC (thermistor) decreases as the temperature rises, accurately reflecting the operating temperature of the LED lamp. When the LED lamp temperature is within the operating temperature range, the LED drive current is obtained by querying the table module according to the current temperature. By querying the temperature and preset drive current relationship table, the optimal drive current for the LED at a specific temperature is obtained. Based on the drive current provided by the table module, the single-chip microcomputer control circuit 2 outputs a corresponding PWM (pulse width modulation signal) to adjust the brightness of the LED lamp. Based on the table lookup result, the corresponding PWM duty cycle is output to achieve a constant current drive circuit 3 that drives the LED lamp to a specified brightness according to the specified output current.

[0147] The temperature detection module uses the following formula to obtain the resistance value of the NTC:

[0148]

[0149] Wherein, Rntc represents the resistance value of the NTC, Vntc represents the voltage value of the NTC, Intc represents the current value of the NTC, VCC represents the voltage value of the input voltage, and R1 represents the first resistor.

[0150] The list module stores the output current value corresponding to the NTC temperature at constant brightness. The list content is the DCDC output current value corresponding to the NTC temperature value under the condition of maintaining constant brightness under actual testing in 1°C steps over the full temperature range (the current value is expressed in the form of PWM duty cycle in the list module).

[0151] The performance and lifespan of LEDs are significantly affected by temperature. Excessively high temperatures can reduce the LED's luminous efficiency, shorten its lifespan, or even damage it. By monitoring the temperature in real time, the system can promptly adjust the LED's operating state to maintain it within a safe range, thereby improving the LED's reliability and lifespan.

[0152] The use of a list module allows the LED drive current to be adaptively adjusted based on the current temperature. For example, the LED current is increased in high temperatures and decreased in low temperatures to maintain brightness. This dynamic adjustment improves energy efficiency and ensures consistent light output.

[0153] With stable brightness output, users can enjoy consistent lighting effects when using LED lights. The combination of temperature control and PWM dimming ensures that the LED lights can still provide ideal lighting in different environmental conditions, improving user satisfaction.

[0154] This utility model enables LED lamps to maintain constant brightness within an ambient temperature range of -40°C to 105°C. The temperature acquisition module uses a microcontroller's analog-to-digital converter (ADC) function to collect NTC resistor values ​​and calculate temperature. By measuring the NTC resistor value, the microcontroller (such as an Arduino or other microcontroller) converts the resistance value into a temperature value using analog-to-digital conversion (ADC). The MCU's ADC module converts the collected analog voltage value into a digital signal and calculates the current ambient temperature. This temperature information is used for subsequent brightness adjustment. The table module calibrates the LED drive current and the ambient temperature value collected by the NTC at a specified brightness level within an ambient temperature range of -40°C to 105°C in 1°C increments. The relationship between the NTC resistor value and the LED drive current is recorded, allowing for quick reference and adjustment in actual applications. When the ambient temperature changes, the microcontroller quickly determines the required current value by consulting a pre-established table of temperature-drive current relationships, ensuring the LED maintains the desired brightness. This continuous collection of the relationship between ambient temperature and drive current creates a feedback mechanism. The drive circuit automatically adjusts the output current based on temperature changes to maintain constant LED brightness. Without adding any additional electronic devices, brightness control under different ambient temperatures can be achieved using only software control methods, which has high industrial application value.

[0155] The above description is only a preferred embodiment of the present invention and does not limit the implementation method and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A control system for maintaining constant LED brightness, characterized in that: include, A sampling circuit (1) for collecting an analog temperature acquisition signal (Vntc); A single-chip microcomputer control circuit (2) is connected to the sampling circuit (1), and the single-chip microcomputer control circuit (2) outputs a digital pulse width modulation signal (DIM) based on the temperature acquisition signal (Vntc); A constant current drive circuit (3) is connected to the single chip control circuit (2), wherein an input end of the constant current drive circuit (3) receives the pulse width modulation signal (DIM), and the constant current drive circuit (3) outputs a light source drive signal based on the pulse width modulation signal (DIM); The light source circuit (4) is connected to the output end (LED+) of the constant current driving circuit (3) and receives the light source driving signal.

2. The control system for maintaining constant LED brightness according to claim 1, characterized in that: The sampling circuit (1) comprises: a first resistor (R1), wherein a first end of the first resistor (R1) is connected to an input voltage source (VCC), and a second end of the first resistor (R1) is connected to the temperature acquisition signal (Vntc); A second resistor (R2) is a thermistor disposed in a temperature environment to be collected, a first end of the second resistor (R2) is connected to a second end of the first resistor (R1), and a second end of the second resistor (R2) is grounded.

3. The control system for maintaining constant LED brightness according to claim 2, characterized in that: The single-chip control circuit (2) comprises a control chip (U2), and an acquisition pin (PA1) of the control chip (U2) receives the temperature acquisition signal (Vntc); The first power supply pin (VDD1) of the control chip (U2) is connected to the input voltage source (VCC); A first analog ground pin (VSSA) of the control chip (U2) is grounded; The analog power pin (VDDA) of the control chip (U2) is connected to the input voltage source (VCC); The first digital ground pin (VSS1) of the control chip (U2) is grounded; The second power supply pin (VDD2) of the control chip (U2) is connected to the input voltage source (VCC); The second digital ground pin (VSS2) of the control chip (U2) is grounded; The third power supply pin (VDD3) of the control chip (U2) is connected to the input voltage source (VCC).

4. The control system for maintaining constant LED brightness according to claim 1, characterized in that: The constant current drive circuit (3) comprises a power management chip (U1), and a first dimming pin (DIM1) and a second dimming pin (UDIM2) of the power management chip (U1) obtain the pulse width modulation signal (DIM); The constant current driving circuit (3) further includes: a first capacitor (C1), wherein a first end of the first capacitor (C1) is connected to a first power input pin (VIN1) of the power management chip (U1), and a second end of the first capacitor (C1) is grounded; a second capacitor (C2), wherein a first end of the second capacitor (C2) is connected to a second end of the first capacitor (C1), and a second end of the second capacitor (C2) is connected to a second power input pin (VIN2) of the power management chip (U1); a third capacitor (C3), wherein a first end of the third capacitor (C3) is connected to the first end of the first capacitor (C1), and a second end of the third capacitor (C3) is grounded; a fourth capacitor (C4), wherein a first end of the fourth capacitor (C4) is connected to the second end of the third capacitor (C3), and a second end of the fourth capacitor (C4) is connected to the second end of the second capacitor (C2); a fifth capacitor (C5), wherein a first end of the fifth capacitor (C5) is connected to the first end of the third capacitor (C3), and a second end of the fifth capacitor (C5) is grounded; A sixth capacitor (C6), wherein a first end of the sixth capacitor (C6) is connected to the second end of the fifth capacitor (C5), and a second end of the sixth capacitor (C6) is connected to the second end of the fourth capacitor (C4).

5. The control system for maintaining constant LED brightness according to claim 4, characterized in that: The constant current driving circuit (3) further includes: a third resistor (R3), wherein a first end of the third resistor (R3) is connected in series with a seventh capacitor (C7) and is grounded, and a second end of the third resistor (R3) is connected to a fault alarm pin of the power management chip (U1) an eighth capacitor (C8), wherein a first end of the eighth capacitor (C8) is grounded, and a second end of the eighth capacitor (C8) is respectively connected to a power supply pin (VCC1) of the power management chip (U1) and a second end of the seventh capacitor (C7); a fourth resistor (R4), wherein a first end of the fourth resistor (R4) is connected to a second end of the eighth capacitor (C8), and a second end of the fourth resistor (R4) is respectively connected to a first enable pin (EN1) and a second enable pin (EN2) of the power management chip (U1); a fifth resistor (R5), wherein a first end of the fifth resistor (R5) is connected to a first end of the fourth resistor (R4), and a second end of the fifth resistor (R5) is respectively connected to a second dimming pin (UDIM2), a second enable pin (EN2), and a first dimming pin (DIM1) of the power management chip (U1).

6. The control system for maintaining constant LED brightness according to claim 5, characterized in that: The constant current driving circuit (3) further includes: a first diode (D1), wherein a cathode of the first diode (D1) is connected to a first end of the fifth capacitor (C5) and a second end of the sixth capacitor (C6), and an anode of the first diode (D1) is connected to a negative electrode (ISN1) of a first channel current detection pin of the power management chip (U1); a ninth capacitor (C9), wherein a first end of the ninth capacitor (C9) is connected to the positive electrode (ISP1) of the first channel current detection pin of the power management chip (U1), and a second end of the ninth capacitor (C9) is grounded; a sixth resistor (R6), a first end of the sixth resistor (R6) being connected to a first gain pin (BST1) of the power management chip (U1), and a second end of the sixth resistor (R6) being connected in series with a tenth capacitor (C10); a first inductor (L1), wherein a first end of the first inductor (L1) is respectively connected to a first switch pin (SW1) of the power management chip (U1) and a second end of the tenth capacitor (C10); a seventh resistor (R7), a first end of the seventh resistor (R7) connected to the SPI output pin (SO) of the power management chip (U1), and a second end of the seventh resistor (R7) connected to the power supply pin (VCC1) of the power management chip (U1); a second inductor (L2), wherein a first end of the second inductor (L2) is connected to a second switch pin (SW2) of the power management chip (U1), and a second end of the second inductor (L2) is connected in series with an eleventh capacitor (C11) and is grounded; an eighth resistor (R8), a first end of the eighth resistor (R8) being connected to a second gain pin (BST2) of the power management chip (U1), a second end of the eighth resistor (R8) being connected in series with a twelfth capacitor (C12), and a second end of the twelfth capacitor (C12) being connected to a first end of the second inductor (L2); a second diode (D2), wherein a cathode of the second diode (D2) is connected to the first end of the fifth capacitor (C5) and the second end of the sixth capacitor (C6), and an anode of the second diode (D2) is connected to the negative electrode (ISN2) of the second channel current detection pin of the power management chip (U1).

7. The control system for maintaining constant LED brightness according to claim 6, characterized in that: The constant current driving circuit (3) further includes: a ninth resistor (R9), wherein a first end of the ninth resistor (R9) is connected to the anode of the first diode (D1), and a second end of the ninth resistor (R9) is connected to the positive electrode (ISP1) of the first channel current detection pin of the power management chip (U1); a tenth resistor (R10), wherein a first end of the tenth resistor (R10) is connected to a first end of the ninth resistor (R9), and a second end of the tenth resistor (R10) is connected to a second end of the ninth resistor (R9); an eleventh resistor (R11), a first end of the eleventh resistor (R11) being connected to the first end of the tenth resistor (R10), and a second end of the eleventh resistor (R11) being connected to the second end of the tenth resistor (R10) and the second end of the first inductor (L1), respectively; a thirteenth capacitor (C13), wherein a first end of the thirteenth capacitor (C13) is connected to the first end of the eleventh resistor (R11), and a second end of the thirteenth capacitor (C13) is grounded; a fifth diode (D5), wherein a cathode of the fifth diode (D5) is connected to the first end of the eleventh resistor (R11), and an anode of the fifth diode (D5) is connected to the second end of the thirteenth capacitor (C13); a third inductor (L3), a first end of the third inductor (L3) connected to the first end of the thirteenth capacitor (C13), and a second end of the third inductor (L3) connected to the output end (LED+); a fifteenth resistor (R15), wherein a first end of the fifteenth resistor (R15) is connected to the second end of the third inductor (L3), and a second end of the fifteenth resistor (R15) is grounded; a fourteenth capacitor (C14), wherein a first end of the fourteenth capacitor (C14) is connected to the output end (LED+), and a second end of the fourteenth capacitor (C14) is connected to the second end of the fifteenth resistor (R15); a third diode (D3), wherein a cathode of the third diode (D3) is connected to the first end of the first inductor (L1), and an anode of the third diode (D3) is grounded; A fourth diode (D4), wherein the anode of the fourth diode (D4) is connected to the anode of the third diode (D3), and the cathode of the fourth diode (D4) is connected to the first end of the second inductor (L2).

8. The control system for maintaining constant LED brightness according to claim 7, characterized in that: The constant current driving circuit (3) further includes: a twelfth resistor (R12), wherein a first end of the twelfth resistor (R12) is connected to the positive electrode (ISP2) of the second channel current detection pin of the power management chip (U1), and a second end of the twelfth resistor (R12) is connected to the anode of the second diode (D2); a thirteenth resistor (R13), wherein a first end of the thirteenth resistor (R13) is connected to the first end of the twelfth resistor (R12), and a second end of the thirteenth resistor (R13) is connected to the second end of the twelfth resistor (R12); a fourteenth resistor (R14), wherein a first end of the fourteenth resistor (R14) is connected to a first end of the thirteenth resistor (R13) and a first end of the eleventh capacitor (C11), respectively, and a second end of the fourteenth resistor (R14) is connected to a second end of the thirteenth resistor (R13); a fourth inductor (L4), wherein a first end of the fourth inductor (L4) is connected to the second end of the fourteenth resistor (R14), and a second end of the fourth inductor (L4) is connected to the output end (LED+); a sixth diode (D6), wherein a cathode of the sixth diode (D6) is connected to the second end of the fourteenth resistor (R14), and an anode of the sixth diode (D6) is grounded; a fifteenth capacitor (C15), wherein a first end of the fifteenth capacitor (C15) is connected to the first end of the fourth inductor (L4), and a second end of the fifteenth capacitor (C15) is grounded; a sixteenth resistor (R16), wherein a first end of the sixteenth resistor (R16) is connected to the second end of the fourth inductor (L4), and a second end of the sixteenth resistor (R16) is grounded; a sixteenth capacitor (C16), wherein a first end of the sixteenth capacitor (C16) is connected to the output end (LED+), and a second end of the sixteenth capacitor (C16) is grounded.

9. The control system for maintaining constant LED brightness according to claim 4, characterized in that: The first power ground pin (PGND1), the second power ground pin (PGND2), the third power ground pin (PGND3) and the second analog ground pin (AGND) of the power management chip (U1) are grounded.

10. The control system for maintaining constant LED brightness according to claim 1, characterized in that: The light source circuit (4) comprises: a first LED lamp (LED1), wherein an anode of the first LED lamp (LED1) is connected to the output terminal (LED+); a second LED lamp (LED2), wherein the anode of the second LED lamp (LED2) is connected to the cathode of the first LED lamp (LED1); A third LED lamp (LED3), wherein the anode of the third LED lamp (LED3) is connected to the cathode of the second LED lamp (LED2), and the cathode of the third LED lamp (LED3) is grounded.

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