Control method for enabling color temperature to be consistent during color mixing of double-color COB (Chip On Board)

Abstract

The invention relates to the technical field of color temperature adjustment of a double-color COB, in particular to a control method for enabling color temperatures to be consistent during color mixing of a double-color COB. Comprising the following steps: S1, in a double-color COB circuit in which a first LED chip and a second LED chip with different color temperature values are connected in parallel, connecting the first LED chip with a first switch tube in series, connecting the second LED chip with a second switch tube in series, and matching established and complementary conduction duty ratios to the first switch tube and the second switch tube respectively so as to control the ratio of current flowing through the first LED chip and the second LED chip, the brightness ratio of the first LED chip to the second LED chip is realized, and then a set color temperature value is output through color mixing of the double-color COB; s2, matching established and complementary conduction duty ratios to a first switching tube and a second switching tube respectively; according to the invention, the color temperature of the LED lamp can be accurately controlled, so that the color temperature consistency of the lamps in the same batch is good, that is, the light source colors of the lamps are consistent.

Description

Technical Field

[0001] The present invention relates to the technical field of two-color COB color temperature adjustment, and in particular to a control method for making the color temperature of a two-color COB consistent when mixing colors. Background Art

[0002] In the lighting industry, a two-color COB light source is an LED lamp bead formed by mixing and packaging two LED chips with different color temperatures. It is usually used in application scenarios that require both warm light and cold light effects. The characteristics of a two-color COB light source are that it can emit light of different color temperatures on the same lamp bead at the same time, thus forming a comfortable and natural lighting effect in the lighting space. This light source has excellent color and temperature adjustment capabilities. It can control the color temperature and brightness of the emitted light by adjusting the current of the two LED chips according to different needs and scenarios. A relatively simple approach is to control the current value of the two LED chips by connecting different resistance values ​​in series, thereby achieving the control of the brightness ratio. However, this control method has poor color temperature consistency between lamps during mass production due to the deviation of the resistor and the forward voltage VF value of the lamp bead. That is, among the 10 lamps produced in the same batch, the light source colors of the 10 lamps may not be consistent after power-on, which cannot meet the customer's requirements for the product.

[0003] In the prior art, the patent document with the authorization announcement number CN108834261B is disclosed: a circuit control system and method with adjustable color temperature of mixed light. The patent document has two driving sources, the first driving source and the second driving source, and is a constant voltage method. The high cost is not conducive to the marketization of the product; in the prior art, the patent document with the authorization announcement number CN107113940B is disclosed: a correlated color temperature control system and method. The patent document is a constant voltage power supply to power the LED, and a resistor is connected in series in the LED circuit to limit the current. This technical solution has little competitiveness in the current market that pursues energy saving and high efficiency. In addition, the patent document uses two control signals, one to control the color temperature and the other to control the brightness. The control structure is complex and not energy-saving and efficient. A control method for making the color temperature consistent when mixing two-color COB is proposed to solve the problems existing in the prior art. Summary of the invention

[0004] The purpose of the present invention is to provide a control method for making the color temperature consistent when mixing two-color COB colors, so as to solve the problem in the prior art that the current value of two LED chips is controlled by series resistors to achieve control of the brightness ratio. Under this control method, the light source color is inconsistent between multiple lamps produced in the same batch.

[0005] The technical solution of the present invention is: a control method for making the color temperature consistent when mixing two-color COB, comprising: S1. In a two-color COB circuit in which a first LED chip and a second LED chip with different color temperature values ​​are connected in parallel, a first switch tube is connected in series to the first LED chip, and a second switch tube is connected in series to the second LED chip, and a predetermined and complementary conduction duty cycle is matched to the first switch tube and the second switch tube, respectively, so as to control the current ratio flowing through the first LED chip and the second LED chip, realize the brightness ratio of the first LED chip and the second LED chip, and further realize the two-color COB mixed color output of the predetermined color temperature value; S2. The method of matching the predetermined and complementary conduction duty ratios to the first switch tube and the second switch tube is: S21. Test the actual color temperature values ​​of the first LED chip and the second LED chip in the two-color COB at different current ratios. Assume that the nominal current of the two-color COB is HmA, the current flowing through the first LED chip gradually increases from 0mA to HmA, and the current flowing through the second LED chip correspondingly gradually decreases from HmA to 0mA. The increase and decrease steps of the current flowing through the first LED chip and the second LED chip are both 5%-12% of HmA; and in each test experiment, the sum of the current flowing through the first LED chip and the current flowing through the second LED chip is equal to HmA; S22. Store the one-to-one correspondence between the conditions and results of each test experiment in a table; S23. Generate a curve graph based on the correspondence between the current value flowing through the first LED chip or the current value flowing through the second LED chip and the actual color temperature value obtained by the test, with the current value as the X coordinate and the color temperature value as the Y coordinate; S24. According to the trend line of the curve graph, a quadratic polynomial function is fitted with the X-axis as the independent variable and the Y-axis as the dependent variable; S25. The ratio of the current flowing through the first LED chip and the second LED chip required for any color temperature value within the range of the color temperature value of the first LED chip and the color temperature value of the second LED chip can be obtained through a quadratic polynomial function, thereby obtaining a predetermined and complementary conduction duty ratio for the first switch tube and the second switch tube respectively; S26. Install the two-color COB in the whole lamp, and calibrate the first switch tube and the second switch tube to match the predetermined and complementary conduction duty ratios by measuring the color temperature value of the whole lamp.

[0006] Preferably, the first switch tube and the second switch tube are any one of a MOSFET tube, a power switch, and a triode.

[0007] Preferably, in step S21, the rising and falling steps of the current flowing through the first LED chip and the second LED chip are both 10% of HmA.

[0008] Preferably, the output end of the dual-color COB circuit is connected to a frequency modulation main control chip; the frequency modulation main control chip generates a pair of complementary PWM waveforms to control the conduction duty cycle of the first switch tube and the second switch tube; assuming that the conduction duty cycle of the first switch tube controlled by the main control chip is D1, and the conduction duty cycle of the second switch tube controlled by the main control chip is D2, then D1+D2=1.

[0009] Preferably, the frequency modulation main control chip is any one of a frequency modulation chip and an MCU chip.

[0010] Preferably, a toggle switch is provided in the dual-color COB circuit.

[0011] Compared with the prior art, the advantages of the present invention are: The present invention connects a first switch tube in series with the first LED chip and a second switch tube in series with the second LED chip in a two-color COB circuit having a first LED chip and a second LED chip with different color temperature values ​​in parallel, and matches a predetermined and complementary conduction duty cycle to the first switch tube and the second switch tube respectively, so as to control the current ratio flowing through the first LED chip and the second LED chip, realize the brightness ratio of the first LED chip and the second LED chip, and further realize the two-color COB mixed color output of a predetermined color temperature value; the present invention can accurately control the current value of the first LED chip and the second LED chip in the two-color COB, thereby realizing accurate control of the color temperature of LED lamps, so that the color temperature consistency of lamps in the same batch is good, that is, the light source color of each lamp is consistent after power-on; and it helps users solve the problem of inconsistent color temperature between different lamps when multiple lamps are installed in the same space. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 This is a table of relevant data of the actual color temperature values ​​of the first LED chip and the second LED chip in the test of the two-color COB at different current ratios described in this embodiment; Figure 2 The Excel file generated in this embodiment takes the current value flowing through the first LED chip of COB1 as the X coordinate and the average value of the actual color temperature values ​​of COB1 and COB2 as the Y coordinate, and at the same time, according to the curve, takes the X axis as the independent variable and the Y axis as the dependent variable, fits a schematic diagram of a quadratic polynomial function; Figure 3 The table of data of the actual color value of the whole lamp measured by configuring five groups of conduction duty ratios for the first switch tube and the second switch tube according to this embodiment; Figure 4 For the present embodiment Figure 3The table of data on the difference between the theoretical color temperature value after fine-tuning the conduction duty cycle and the actual color temperature of the whole lamp; Figure 5 For the present embodiment Figure 4 The table of theoretical color temperature values ​​after fine-tuning the conduction duty cycle in the lamp and the calculated color temperature values ​​of the whole lamp; Figure 6 For the present embodiment Figure 5 The table of data of the measured color temperature value of the whole lamp after fine-tuning the conduction duty cycle in; Figure 7 The table of data for matching the range of the conduction duty ratios of the first switch tube connected in series with the first LED chip and the second switch tube connected in series with the second LED chip when the whole lamp has five color temperatures of 2700K, 3000K, 3500K, 4000K and 5700K as described in the final version of this embodiment; Figure 8 Schematic diagram of the dual-color COB circuit of this embodiment.

[0013] Among them: 1. toggle switch, 2. frequency modulation main control chip, 3. first switch tube, 4. second switch tube, 5. second LED chip, 6. first LED chip. DETAILED DESCRIPTION

[0014] The present invention is further described in detail below in conjunction with specific embodiments: In the description of the invention, it is necessary to understand that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the 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 cannot be understood as a limitation on the invention.

[0015] A control method for making the color temperature of a two-color COB consistent when mixing colors, comprising: S1. In a two-color COB circuit in which a first LED chip 6 and a second LED chip 5 with different color temperature values ​​are connected in parallel, a first switch tube 3 is connected in series to the first LED chip 6, and a second switch tube 4 is connected in series to the second LED chip 5, and a predetermined and complementary conduction duty cycle is matched to the first switch tube 3 and the second switch tube 4 respectively, so as to control the current ratio flowing through the first LED chip 6 and the second LED chip 5, realize the brightness ratio of the first LED chip 6 and the second LED chip 5, and then realize the two-color COB mixed color output of the predetermined color temperature value; a toggle switch 1 is provided in the two-color COB circuit to select the color temperature gear of the whole lamp; the first switch tube 3 and the second switch tube 4 are any one of MOSFET tube, power switch and triode, and MOSFET tube is preferred in terms of economic benefit and performance; the specific two-color COB circuit is as follows Figure 8 As shown; S2. The method of matching the predetermined and complementary conduction duty ratios to the first switch tube 3 and the second switch tube 4 is as follows: S21. Test the actual color temperature values ​​of the first LED chip 6 and the second LED chip 5 in the two-color COB under different current ratios. Assume that the nominal current of the two-color COB is HmA, the current flowing through the first LED chip 6 gradually increases from 0mA to HmA, and the current flowing through the second LED chip 5 correspondingly gradually decreases from HmA to 0mA, and the increase and decrease steps of the current flowing through the first LED chip 6 and the second LED chip 5 are both 5%-12% of HmA; considering the number of experiments and experimental accuracy, the increase and decrease steps of the current flowing through the first LED chip 6 and the second LED chip 5 in step S21 are preferably 10% of HmA.

[0016] And in each test experiment, the sum of the current flowing through the first LED chip 6 and the current flowing through the second LED chip 5 is equal to HmA; S22. Store the one-to-one correspondence between the conditions and results of each test experiment in a table; S23. Generate a graph based on the correspondence between the current value flowing through the first LED chip 6 or the current value flowing through the second LED chip 5 and the actual color temperature value obtained by the test, with the current value as the X coordinate and the color temperature value as the Y coordinate; S24. According to the trend line of the curve graph, a quadratic polynomial function is fitted with the X-axis as the independent variable and the Y-axis as the dependent variable; S25. The ratio of the current flowing through the first LED chip 6 and the second LED chip 5 required for any color temperature value within the color temperature range of the first LED chip 6 and the second LED chip 5 can be obtained through a quadratic polynomial function, and then the predetermined and complementary conduction duty ratios for the first switch tube 3 and the second switch tube 4 can be matched respectively; S26. Install the two-color COB in the whole lamp, and calibrate the first switch tube 3 and the second switch tube 4 to match the predetermined and complementary conduction duty ratios by measuring the color temperature of the whole lamp.

[0017] The output end of the two-color COB circuit is connected to the frequency modulation main control chip 2; the frequency modulation main control chip 2 generates a pair of complementary PWM waveforms to control the conduction duty ratio of the first switch tube 3 and the second switch tube 4; assuming that the conduction duty ratio of the first switch tube 3 controlled by the main control chip is D1, and the conduction duty ratio of the second switch tube 4 controlled by the main control chip is D2, then D1+D2=1. The frequency modulation main control chip 2 is any one of a frequency modulation chip and an MCU chip.

[0018] Specifically, the method of matching the established and complementary conduction duty cycles to the first switch tube 3 and the second switch tube 4 is described in detail by taking a 40W two-color COB with a nominal current of 1000mA as an example; when measuring a single two-color COB, there may be different characteristics of individual cases. It is more accurate to measure two or three to obtain the average value, thereby avoiding the problem of deviation in the color temperature of a two-color COB; therefore, in this embodiment, when testing the actual color temperature values ​​of the first LED chip 6 and the second LED chip 5 in the two-color COB at different current ratios, two identical 40W two-color COBs with a nominal current of 1000mA are used for testing, and finally the actual color temperatures of the two two-color COBs are taken. The color temperature of the first LED chip 6 in the two identical dual-color COBs is 2700K, and the color temperature of the second LED chip 5 is 5700K; the two identical dual-color COBs are respectively recorded as COB1 and COB2; in COB1 and COB2, the current flowing through the first LED chip 6 is gradually increased from 0mA to 1000mA, and the current flowing through the second LED chip 5 is correspondingly gradually reduced from 1000mA to 0mA, and the increase and decrease steps of the current flowing through the first LED chip 6 and the second LED chip 5 are both 5% of 1000mA, that is, 50mA; the conditions and results of each test experiment are stored in a table in a one-to-one correspondence relationship, and then the result is obtained. Figure 1 .

[0019] Will Figure 1 The current flowing through the first LED chip 6 of COB1 and the average value of the actual color temperature values ​​of COB1 and COB2 are made into a table, and a curve chart is generated with the current flowing through the first LED chip 6 of COB1 as the X coordinate and the average value of the actual color temperature values ​​of COB1 and COB2 as the Y coordinate (such as Figure 2 As shown), Excel can fit a quadratic polynomial function based on the curve with the X axis as the independent variable and the Y axis as the dependent variable: (like Figure 2As shown); According to this quadratic polynomial function, when the required color temperature value y is known, the current value x flowing through the first LED chip 6 of COB1 can be solved, x / 1000 is the conduction duty cycle of the first switch tube 3 connected in series with the first LED chip 6, and 1-x / 1000 is the conduction duty cycle of the second switch tube 4 connected in series with the second LED chip 5.

[0020] It should be noted that the above-mentioned quadratic polynomial function is for two-color COB, but two-color COB needs to be installed in lamps for use. The secondary optics outside the lamp (such as reflector cups, sunshades) have an impact on the color temperature. The color temperature of the light emitted by the two-color COB has a certain deviation after the secondary optics. In order to overcome this deviation, the color temperature of the two-color COB needs to be compensated. The specific method of compensating the color temperature of the two-color COB is described as follows. The conditions are: the two-color COB is 40W, the nominal current is 1000mA, the color temperature of the first LED chip 6 in the two-color COB is 2700K, and the color temperature of the second LED chip 5 is 5700K. The required whole lamp The color temperature is 2700K, 3000K, 3500K, 4000K, and 5700K, a total of 5 gears; the control method for making the color temperature consistent when the two-color COB is mixed in this embodiment is applied to the whole lamp. In the first step, the first switch tube 3 connected in series with the first LED chip 6 and the second switch tube 4 connected in series with the second LED chip 5 are initially configured with the first group 1, 0, the second group 0.876, 0.124, the third group 0.682, 0.318, the fourth group 0.53, 0.47, and the fifth group 0.09, 0.91 conduction duty ratios, and three groups of whole lamps with the same configuration are used for experiments, and the average value of the measured color temperature of the three groups of whole lamps is taken, as shown in FIG. Figure 3 As shown; the second step is to fine-tune the conduction duty cycle according to the average value of the measured color temperature of the three groups of whole lamps in the first step, as shown Figure 4 As shown; Figure 3-Figure 7 The duty cycle on the left side of each group is provided to the first switch tube 3, and the duty cycle on the right side is provided to the second switch tube 4; relative to Figure 3 , Figure 4 The duty cycle of the first group remains unchanged, and the first LED chip 6 is turned on individually; Figure 3 The second group's 0.876 is rounded off to 0.88, and the corresponding Figure 3 The second group's 0.124 is changed to 0.12; considering Figure 3 The average color temperature of the whole lamp corresponding to the third group of three measurements is 3305.333K, which is far from the required color temperature point of 3500K. Figure 3 The third group's 0.682 increased to 0.69, corresponding to Figure 3 The third group's 0.318 is reduced to 0.31; the fourth group remains unchanged; in order to increase the color temperature a little, Figure 3In the fifth group, 0.09 dropped to 0.08, and 0.91 increased to 0.92; Figure 4 The theoretical color temperature value in Figure 4 Substitute the actual duty cycle into the quadratic polynomial function: The color temperature obtained is the color temperature of the two-color COB; Figure 4 The difference between the measured and whole lamp color temperature is Figure 4 The theoretical color temperature value in Figure 3 The difference between the three measured average values ​​of the whole lamp color temperature in each group is Figure 4 The actual duty cycle is Figure 3 The actual duty cycle of the two is very small, so the second step can still use the first step. Figure 3 The third step is to continue to adjust the color temperature of the whole lamp as needed. Figure 4 The actual duty cycle in the lamp is fine-tuned to make the color temperature of the whole lamp closer to the required color temperature point. The specific duty cycle is fine-tuned as follows: Figure 5 As shown; Figure 5 The theoretical color temperature value is about Figure 5 Substitute the actual duty cycle into the quadratic polynomial function: The color temperature obtained is the color temperature of the two-color COB; Figure 5 The color temperature of the whole lamp is Figure 5 The theoretical color temperature value in minus Figure 4 The difference between the measured color temperature of the whole lamp and the color temperature of the whole lamp is obtained, that is, the calculated color temperature of the whole lamp; the fourth step is based on Figure 5 The color temperature value of the whole lamp in Figure 5 The actual duty cycle in the system is fine-tuned. The specific duty cycle fine-tuning is as follows: Figure 6 As shown, in this step, two groups of whole lamps with the same configuration are used to conduct experiments, and the average value of the measured color temperatures of the two groups of whole lamps is taken; until the fine-tuning in the fourth step can reach the expected color temperature range, Figure 7 That is, when the final version makes the whole lamp have five color temperatures of 2700K, 3000K, 3500K, 4000K and 5700K, the range of conduction duty ratios of the first switch tube 3 connected in series with the first LED chip 6 and the second switch tube 4 connected in series with the second LED chip 5 are matched.

[0021] The present invention provides a control method for making the color temperature of a two-color COB consistent when mixing colors. It has only one driving source, which is more cost-optimized and more conducive to product marketing. At the same time, the present invention uses the color temperature control loop of the rear section of the driving source to accurately control the color temperature of the entire lamp. It is not only energy-saving and efficient, but also has high color temperature accuracy, which can ensure the consistency of color temperature between different lamps and is accepted by the market. The present invention can directly control the brightness by changing the output current of the driving source, which is convenient and flexible, and there is no need to design a control circuit for controlling the brightness.

[0022] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the scope of protection of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is limited by the attached claims rather than the above description, and it is intended to include all changes within the meaning and scope of the equivalent elements of the claims in the present invention.

Claims

1. A control method for making the color temperature consistent when mixing two-color COB, characterized in that: include: S1. In a two-color COB circuit in which a first LED chip and a second LED chip with different color temperature values ​​are connected in parallel, a first switch tube is connected in series to the first LED chip, and a second switch tube is connected in series to the second LED chip, and a predetermined and complementary conduction duty cycle is matched to the first switch tube and the second switch tube, respectively, so as to control the current ratio flowing through the first LED chip and the second LED chip, realize the brightness ratio of the first LED chip and the second LED chip, and further realize the two-color COB mixed color output of the predetermined color temperature value; S2. The method of matching the predetermined and complementary conduction duty ratios to the first switch tube and the second switch tube is: S21. Test the actual color temperature values ​​of the first LED chip and the second LED chip in the two-color COB at different current ratios. Assume that the nominal current of the two-color COB is HmA, the current flowing through the first LED chip gradually increases from 0mA to HmA, and the current flowing through the second LED chip correspondingly gradually decreases from HmA to 0mA. The increase and decrease steps of the current flowing through the first LED chip and the second LED chip are both 5%-12% of HmA; and in each test experiment, the sum of the current flowing through the first LED chip and the current flowing through the second LED chip is equal to HmA; S22. Store the one-to-one correspondence between the conditions and results of each test experiment in a table; S23. Generate a curve graph based on the correspondence between the current value flowing through the first LED chip or the current value flowing through the second LED chip and the actual color temperature value obtained by the test, with the current value as the X coordinate and the color temperature value as the Y coordinate; S24. According to the trend line of the curve graph, a quadratic polynomial function is fitted with the X-axis as the independent variable and the Y-axis as the dependent variable; S25. The ratio of the current flowing through the first LED chip and the second LED chip required for any color temperature value within the range of the color temperature value of the first LED chip and the color temperature value of the second LED chip can be obtained through a quadratic polynomial function, thereby obtaining a predetermined and complementary conduction duty ratio for the first switch tube and the second switch tube respectively; S26. Install the two-color COB in the whole lamp, and calibrate the first switch tube and the second switch tube to match the predetermined and complementary conduction duty ratios by measuring the color temperature value of the whole lamp.

2. A control method for making the color temperature of a two-color COB consistent when mixing colors according to claim 1, characterized in that: The first switch tube and the second switch tube are any one of a MOSFET tube, a power switch, and a triode.

3. The method for controlling the color temperature of a two-color COB when mixing colors according to claim 1, characterized in that: In step S21, the rising and falling steps of the current flowing through the first LED chip and the second LED chip are both 10% of HmA.

4. The method for controlling the color temperature of a two-color COB when mixing colors according to claim 1, characterized in that: The output end of the dual-color COB circuit is connected to a frequency modulation main control chip; the frequency modulation main control chip generates a pair of complementary PWM waveforms to control the conduction duty cycle of the first switch tube and the second switch tube; assuming that the conduction duty cycle of the first switch tube controlled by the main control chip is D1, and the conduction duty cycle of the second switch tube controlled by the main control chip is D2, then D1+D2=1.

5. A control method for making the color temperature of a two-color COB consistent when mixing colors according to claim 4, characterized in that: The frequency modulation main control chip is any one of a frequency modulation chip and an MCU chip.

6. The method for controlling the color temperature of a two-color COB when mixing colors according to claim 1, characterized in that: A toggle switch is provided in the dual-color COB circuit.

Images