Light emitting circuit

Abstract

A light emitting circuit includes a first voltage source, a plurality of first light emitting diodes, a plurality of first resistive elements, a first impedance element, a second voltage source, a plurality of second light emitting diodes, a plurality of second resistive elements, and a second impedance element. The first voltage source has a first anode and a first cathode. The plurality of first light-emitting diodes are arranged in parallel, and each first light-emitting diode is provided with a first input end and a first output end. One end of the first resistor element is connected with the first output end, and the other end is connected with the first cathode. The other end of the first impedance element is connected with the first input end. The second voltage source has a second anode and a second cathode. The plurality of second light-emitting diodes are arranged in parallel, and each second light-emitting diode is provided with a second input end and a second output end. One end of the second resistor element is connected with the second output end and the other end is connected with the second cathode. One end of the second impedance element is connected with the first anode and the other end is connected with the second input end.

Description

Technical Field

[0001] The present invention relates to a lighting circuit, in particular to a lighting circuit having a cold-color-temperature light-emitting diode and a warm-color-temperature light-emitting diode. Background Art

[0002] When manufacturing a light-emitting diode, there are certain variations in its optoelectronic characteristics such as color, luminous flux, or voltage. Therefore, before leaving the factory, classification and grading operations will be performed first to group light-emitting diodes with similar characteristics together to ensure that the light-emitting diodes in the same batch can meet the specifications and standards required by customers. However, even if the classification and grading procedures have been carried out before leaving the factory, there may still be some differences in the optoelectronic characteristics between the light-emitting diodes leaving the factory in the front and back batches. When multiple light-emitting diodes are provided on a lighting circuit, these differences are also likely to be highlighted and affect the product quality. Therefore, how to reduce the variability in the output light between each light-emitting diode or between lighting circuits containing multiple light-emitting diodes to make it more consistent is an urgent problem to be solved in the industry.

[0003] In addition, when a lighting circuit simultaneously includes multiple cold-color-temperature light-emitting diodes and multiple warm-color-temperature light-emitting diodes and performs mixed lighting through the two, due to the color differences between the light-emitting diodes, it is more difficult to obtain an ideal or predetermined color-temperature output during mixed lighting. Summary of the Invention

[0004] In view of the above requirements, the present invention provides a lighting circuit that can reduce the variability in the output light of light-emitting diodes, compensates for the inherent differences between individual light-emitting diodes in a hardware manner, and can also reduce the complexity of material preparation.

[0005] According to an embodiment of the present invention, a lighting circuit is provided. The lighting circuit includes a first voltage source, a plurality of first light-emitting diodes, a plurality of first resistance elements, a first impedance element, a second voltage source, a plurality of second light-emitting diodes, a plurality of second resistance elements, and a second impedance element. The first voltage source has a first positive electrode and a first negative electrode. The plurality of first light-emitting diodes are cold-color-temperature light-emitting diodes, and the plurality of first light-emitting diodes are connected in parallel. Each first light-emitting diode has a first input end and a first output end. One end of each first resistance element is connected to the first output end of a first light-emitting diode, and the other end of each first resistance element is connected to the first negative electrode of the first voltage source. One end of the first impedance element is connected to the first positive electrode of the first voltage source, and the other end of the first impedance element is connected to the first input end of each first light-emitting diode. The second voltage source has a second positive electrode and a second negative electrode. The plurality of second light-emitting diodes are warm-color-temperature light-emitting diodes, and the plurality of second light-emitting diodes are connected in parallel. Each second light-emitting diode has a second input end and a second output end. One end of each second resistance element is connected to the second output end of a second light-emitting diode, and the other end of each second resistance element is connected to the second negative electrode of the second voltage source. One end of the second impedance element is connected to the first positive electrode of the second voltage source, and the other end of the second impedance element is connected to the second input end of each second light-emitting diode.

[0006] In some embodiments of the present invention, the first voltage source provides a first driving voltage. The voltage from the first input end of the plurality of first light-emitting diodes to the first negative electrode of the first voltage source is a first set voltage. When a first current flows through each first light-emitting diode, the forward voltage of the first light-emitting diode is between a first maximum forward voltage and a first minimum forward voltage. The resistance value of each first resistance element = (first set voltage - (first maximum forward voltage + first minimum forward voltage) / 2) / first current.

[0007] In some embodiments of the present invention, the first driving voltage is 5V, the first set voltage is 4.5V, the first current is 20mA, the first maximum forward voltage is 2.9V, and the first minimum forward voltage is 2.7V.

[0008] In some embodiments of the present invention, the first driving voltage is 5V, the first set voltage is 4.5V, the first current is 20mA, the first maximum forward voltage is 3.1V, and the first minimum forward voltage is 2.9V.

[0009] In some embodiments of the present invention, the first driving voltage is 5V, the first set voltage is 4.5V, the first current is 20mA, the first maximum forward voltage is 3.3V, and the first minimum forward voltage is 3.1V.

[0010] In some embodiments of the present invention, a first voltage source provides a first driving voltage. The voltage from the first input ends of a plurality of first light-emitting diodes to the first negative electrode of the first voltage source is a first set voltage. The current flowing through each first light-emitting diode is a first current. The number of first light-emitting diodes is N. The impedance value of the first impedance element = (first driving voltage - first set voltage) / (first current * N * chromaticity adjustment value), where the chromaticity adjustment value is less than or equal to 1.2 and greater than or equal to 0.8.

[0011] In some embodiments of the present invention, the first driving voltage is 5V, the first set voltage is 4.5V, the first current is 20mA, and the chromaticity adjustment value is selected from one of the following: 1.2, 1.15, 1.1, 1.05, 1, 0.95, 0.9, 0.85, and 0.8.

[0012] In some embodiments of the present invention, the first impedance element is composed of a plurality of resistors connected in parallel.

[0013] In some embodiments of the present invention, a second voltage source provides a second driving voltage. The voltage from the second input ends of a plurality of second light-emitting diodes to the second negative electrode of the second voltage source is a second set voltage. When a second current flows through each second light-emitting diode, the forward voltage of the second light-emitting diode is between a second maximum forward voltage and a second minimum forward voltage. The resistance value of each second resistor element = (second set voltage - (second maximum forward voltage + second minimum forward voltage) / 2) / second current.

[0014] In some embodiments of the present invention, the second driving voltage is 5V, the second set voltage is 4.5V, the second current is 20mA, the second maximum forward voltage is 2.9V, and the second minimum forward voltage is 2.7V.

[0015] In some embodiments of the present invention, the second driving voltage is 5V, the second set voltage is 4.5V, the second current is 20mA, the second maximum forward voltage is 3.1V, and the second minimum forward voltage is 2.9V.

[0016] In some embodiments of the present invention, the second driving voltage is 5V, the second set voltage is 4.5V, the second current is 20mA, the second maximum forward voltage is 3.3V, and the second minimum forward voltage is 3.1V.

[0017] In some embodiments of the present invention, a second voltage source provides a second driving voltage. The voltage from the second input ends of a plurality of second light-emitting diodes to the second negative electrode of the second voltage source is a second set voltage, the current flowing through each second light-emitting diode is a second current, the number of the second light-emitting diodes is N, and the impedance value of the second impedance element = (the second driving voltage - the second set voltage) / (the second current * N * chromaticity adjustment value), where the chromaticity adjustment value is less than or equal to 1.2 and greater than or equal to 0.8.

[0018] In some embodiments of the present invention, the second driving voltage is 5V, the second set voltage is 4.5V, the second current is 20 mA, and the chromaticity adjustment value is selected from one of the following: 1.2, 1.15, 1.1, 1.05, 1, 0.95, 0.9, 0.85, and 0.8.

[0019] In some embodiments of the present invention, the second impedance element is composed of a plurality of resistors connected in parallel.

[0020] In some embodiments of the present invention, a first light-emitting diode among a plurality of first light-emitting diodes and a second light-emitting diode among a plurality of second light-emitting diodes are encapsulated together in a dual-color light-emitting diode.

[0021] In some embodiments of the present invention, the first impedance element is selected from one of the following: a single resistor, a plurality of resistors connected in series, and a plurality of resistors connected in parallel.

[0022] In some embodiments of the present invention, the second impedance element is selected from one of the following: a single resistor, a plurality of resistors connected in series, and a plurality of resistors connected in parallel.

[0023] In some embodiments of the present invention, the first resistance element is selected from one of the following: a single resistor, a plurality of resistors connected in series, and a plurality of resistors connected in parallel.

[0024] In some embodiments of the present invention, the second resistance element is selected from one of the following: a single resistor, a plurality of resistors connected in series, and a plurality of resistors connected in parallel. Description of the Drawings

[0025] Figure 1 is a light-emitting circuit provided according to a first embodiment of the present invention.

[0026] Figure 2 is a schematic diagram of the ranges of cold-color-temperature light-emitting diodes with different grades on the chromaticity coordinate.

[0027] Figure 3 is a schematic diagram of the ranges of warm-color-temperature light-emitting diodes with different grades on the chromaticity coordinate.

[0028] Description of the Reference Numerals:

[0029] 1: Light-emitting circuit

[0030] 10: First voltage source

[0031] 101: First positive electrode

[0032] 102: First negative electrode

[0033] 11: Second voltage source

[0034] 111: Second positive electrode

[0035] 112: Second negative electrode

[0036] 12: First light-emitting diode

[0037] 121: First input terminal

[0038] 122: First output terminal

[0039] 13: First resistance element

[0040] 14: First impedance element

[0041] 15: Second light-emitting diode

[0042] 151: Second input terminal

[0043] 152: Second output terminal

[0044] 16: Second resistance element

[0045] 17: Second impedance element

[0046] 18: Dual-color light-emitting diode

[0047] 19: Ideal center grading position

[0048] 20: Ideal center grading position Detailed implementation manners

[0049] Embodiments are provided below for detailed description. The embodiments are only used as examples for illustration and will not limit the scope of protection of the present invention.

[0050] According to a first embodiment of the present invention, a light-emitting circuit is provided. This light-emitting circuit can be applied to electronic devices with backlight requirements or light effects on the housing, such as keyboards, mice, headphones, or hosts.

[0051] Please refer to Figure 1, the light-emitting circuit 1 provided by the first embodiment includes a first voltage source 10, a second voltage source 11, a plurality of first light-emitting diodes 12, a plurality of first resistance elements 13, a first impedance element 14, a plurality of second light-emitting diodes 15, a plurality of second resistance elements 16, and a second impedance element 17. The first voltage source 10 and the second voltage source 11 can be separately provided or integrated into the same voltage source, and the present invention does not limit this.

[0052] The first voltage source 10 has a first positive electrode 101 and a first negative electrode 102, and the first voltage source 10 provides a first driving voltage. The plurality of first light-emitting diodes 12 are cold-color-temperature light-emitting diodes, and the color temperature value of the cold color temperature is greater than 5000K. The plurality of first light-emitting diodes 12 are connected in parallel, and each first light-emitting diode 12 has a first input terminal 121 and a first output terminal 122. One end of each first resistance element 13 is connected to the first output terminal 122 of a first light-emitting diode 12, and the other end of each first resistance element 13 is connected to the first negative electrode 102 of the first voltage source 10. One end of the first impedance element 14 is connected to the first positive electrode 101 of the first voltage source 10, and the other end of the first impedance element 14 is connected to the first input terminal 121 of each first light-emitting diode 12.

[0053] The second voltage source 11 has a second positive electrode 111 and a second negative electrode 112, and the second voltage source 11 provides a second driving voltage. The plurality of second light-emitting diodes 15 are warm-color-temperature light-emitting diodes, and the color temperature value of the warm color temperature is less than 5000K. The plurality of second light-emitting diodes 15 are connected in parallel, and each second light-emitting diode 15 has a second input terminal 151 and a second output terminal 152. One end of each second resistance element 16 is connected to the second output terminal 152 of a second light-emitting diode 15, and the other end of each second resistance element 16 is connected to the second negative electrode 112 of the second voltage source 11. One end of the second impedance element 17 is connected to the first positive electrode 111 of the second voltage source 11, and the other end of the second impedance element 17 is connected to the second input terminal 151 of each second light-emitting diode 15.

[0054] Please refer to Table 1 below, which shows an example of the forward voltage specification recorded in the specification when the light-emitting diodes leave the factory. It can be understood from Table 1 that even though the light-emitting diodes have been classified into the same level when leaving the factory, the forward voltage will still vary under the condition of the same flowing current.

[0055]

[0056] Table 1

[0057] In order to reduce the variation in the forward voltage of each light-emitting diode and to unify the specifications of the resistors used in conjunction with each light-emitting diode, thereby reducing the complexity of component preparation, when setting or selecting a resistor, the present invention calculates the appropriate resistor value according to the following formula.

[0058] In this embodiment, assume that the voltage from the first input terminal 121 of a plurality of first light-emitting diodes 12 to the first negative terminal 102 of the first voltage source 10 is a first set voltage, and when a first current flows through each first light-emitting diode 12, the forward voltage of the first light-emitting diode 12 is known to be between a first maximum forward voltage and a first minimum forward voltage. At this time, the resistance value of each first resistor element 13 = (first set voltage - (first maximum forward voltage + first minimum forward voltage) / 2) / first current. For example, when a plurality of first light-emitting diodes 12 are shipped from the factory and have been classified into the V1 classification in Table 2, and when the first driving voltage provided by the first voltage source 10 is 5V, the first set voltage is 4.5V, and the first current is 20 mA, it can be known from the specification table that the first maximum forward voltage of these first light-emitting diodes 12 is 2.9V, and the first minimum forward voltage is 2.7V. Under the above conditions, the resistance value of the first resistor element selected in this embodiment to be used in conjunction with the first light-emitting diode 12 = (4.5 - (2.9 + 2.7) / 2) / 0.02 = 85 Ω.

[0059] Similarly, when a plurality of first light-emitting diodes 12 are shipped from the factory and have been classified into the V2 classification in Table 1, and when the first driving voltage provided by the first voltage source 10 is 5V, the first set voltage is 4.5V, and the first current is 20 mA, it can be known from the specification table that the first maximum forward voltage of these first light-emitting diodes 12 is 3.1V, and the first minimum forward voltage is 2.9V. Under the above conditions, the resistance value of the first resistor element 13 selected in this embodiment to be used in conjunction with the first light-emitting diode 12 = (4.5 - (3.1 + 2.9) / 2) / 0.02 = 75 Ω. Similarly, when a plurality of first light-emitting diodes 12 are shipped from the factory and have been classified into the V3 classification in Table 1, and when the first driving voltage provided by the first voltage source 10 is 5V, the first set voltage is 4.5V, and the first current is 20 mA, it can be known from the specification table that the first maximum forward voltage of these first light-emitting diodes 12 is 3.3V, and the first minimum forward voltage is 3.1V. Under the above conditions, the resistance value of the first resistor element 13 selected in this embodiment to be used in conjunction with the first light-emitting diode 12 = (4.5 - (3.3 + 3.1) / 2) / 0.02 = 65 Ω.

[0060] In addition, for multiple second light-emitting diodes 15 belonging to the warm color temperature category, when selecting the matching second resistor element 16, the logic also follows the architecture of the aforementioned first light-emitting diode 12 and first resistor element 13. In this embodiment, assume that the voltage from the second input terminal 151 of the multiple second light-emitting diodes 15 to the second negative electrode 112 of the second voltage source 11 is a second set voltage, and when a second current flows through each second light-emitting diode 15, the forward voltage of the second light-emitting diode 15 is known to be between a first maximum forward voltage and a first minimum forward voltage. At this time, the resistance value of each second resistor element 16 = (second set voltage - (second maximum forward voltage + second minimum forward voltage) / 2) / second current. For example, when the multiple second light-emitting diodes 15 are shipped from the factory, they have been classified into the V1 grading in Table 1, and when the second driving voltage provided by the second voltage source 11 is 5V, the second set voltage is 4.5V, and the second current is 20mA, it can be known from the specification table that the second maximum forward voltage of these multiple second light-emitting diodes 15 is 2.9V, and the second minimum forward voltage is 2.7V. Under the above conditions, the resistance value of the second resistor element 16 selected in this embodiment to match the second light-emitting diode 15 = (4.5 - (2.9 + 2.7) / 2) / 0.02 = 85Ω.

[0061] Similarly, when the multiple second light-emitting diodes 15 are shipped from the factory and have been classified into the V2 grading in Table 1, and when the second driving voltage provided by the second voltage source 11 is 5V, the second set voltage is 4.5V, and the second current is 20mA, it can be known from the specification table that the second maximum forward voltage of these multiple second light-emitting diodes 15 is 3.1V, and the second minimum forward voltage is 2.9V. Under the above conditions, the resistance value of the second resistor element 16 selected in this embodiment to match the second light-emitting diode 15 = (4.5 - (3.1 + 2.9) / 2) / 0.02 = 75Ω. Similarly, when the multiple second light-emitting diodes 15 are shipped from the factory and have been classified into the V3 grading in Table 1, and when the second driving voltage provided by the second voltage source 11 is 5V, the second set voltage is 4.5V, and the second current is 20mA, it can be known from the specification table that the second maximum forward voltage of these multiple second light-emitting diodes 15 is 3.3V, and the second minimum forward voltage is 3.1V. Under the above conditions, the resistance value of the second resistor element 16 selected in this embodiment to match the second light-emitting diode 15 = (4.5 - (3.3 + 3.1) / 2) / 0.02 = 65Ω.

[0062] As can be understood from the above description, in order to ensure that the color temperatures output by light-emitting diodes of the same color temperature are consistent during operation, in this embodiment, the differences in the forward voltage variations of individual light-emitting diodes are taken into account. After referring to the specification sheet of the reference light-emitting diode and understanding the forward voltage grading of the batch of light-emitting diodes, the average value of the maximum forward voltage and the minimum forward voltage is used as the preset forward voltage for multiple light-emitting diodes, and resistors of the same specification are selected and installed accordingly to match each light-emitting diode. In this way, the complex material preparation problem faced when multiple specifications of resistors need to be prepared can be solved. According to the above description, if the assembly manufacturer knows that the first light-emitting diode 12 or the second light-emitting diode 15 in this batch of incoming materials belongs to the V1, V2, or V3 grading, when arranging and installing the first resistor element 13 and the second resistor element 16, only resistors of the same specification, such as 85Ω, 75Ω, or 65Ω, need to be prepared.

[0063] In the light-emitting circuit 1 provided by the present invention, a dual-color light-emitting diode can be used, which is formed by encapsulating the die of the first light-emitting diode 12 and the die of the second light-emitting diode 15 together to form a single dual-color light-emitting diode 18.

[0064] The light-emitting circuit 1 provided by the present invention can also drive the cold-color-temperature first light-emitting diode 12 and the warm-color-temperature second light-emitting diode 15 to perform mixed light, and then output a specific color temperature. When performing mixed light, the ratio of the current flowing through the cold-color-temperature first light-emitting diode 12 and the current flowing through the warm-color-temperature second light-emitting diode 15 will be appropriately adjusted to achieve the desired ideal color temperature. However, the optoelectronic characteristics of each batch of light-emitting diodes are different, and it is not easy to mix an ideal color temperature. For example, when driving a light-emitting diode with a certain voltage, if the forward voltage of the cold-color-temperature light-emitting diodes in this batch is relatively high, its input current will be lower than the preset value, resulting in a lower brightness. After mixed light, the overall output color temperature will be warmer. Another example is that when the brightness (luminous flux) of the cold-color-temperature light-emitting diodes in this batch is low, or the color coordinates (color) of the cold-color-temperature light-emitting diodes are relatively warm, after mixed light, the overall color temperature will also be warmer, resulting in a deviation from the ideal preset value. Therefore, before performing mixed light, it is also necessary to make the cold-color-temperature light-emitting diodes or warm-color-temperature light-emitting diodes in this batch be close to or have the ideal preset color temperature, so that the subsequent mixed light can be more accurate.

[0065] In view of the above requirements, the present invention also proposes a design that can reduce the differences in the variation of the color between the cold-color-temperature and warm-color-temperature light-emitting diodes. Please first refer to Table 2 and Figure 2, which is an illustration of the grading table of cold - color - temperature light - emitting diodes in terms of color and the distribution of these color gradings on the chromaticity diagram. Table 2 shows that the light - emitting diodes belonging to the cold - color - temperature can be divided into four grades on the grading table, including B1, B2, B3, and B4. And the four groups of X - coordinates and Y - coordinates marked by each grade can define the color change range belonging to this grade in the Figure 2 chromaticity diagram. Figure 2 shows the relative relationship between the color change ranges of the four grades B1, B2, B3, and B4 and the ideal central grading position 19 on the coordinate axes. Through calculation or estimation, the variation degrees between the four grades B1, B2, B3, and B4 and the ideal central grading position 19 can be obtained, and then the resistance value of the first impedance element 14 can be adjusted accordingly for compensation.

[0066]

[0067] Table 2

[0068] When setting the resistance value of the first impedance element 14 in the light - emitting circuit provided in this embodiment, the parameter of the chromaticity adjustment value is added, and the resistance value of the first impedance element is adjusted according to the variation degree between the grading of the batch of cold - color - temperature light - emitting diodes received and the ideal central grading position 19. For example, in this embodiment, it is assumed that the first voltage source 10 provides a first driving voltage, the voltage from the first input terminal 121 of the plurality of first light - emitting diodes 12 to the first negative electrode 102 of the first voltage source 10 is the first set voltage, the current flowing through each first light - emitting diode 12 is a first current, and the number of the first light - emitting diodes 12 connected in parallel is N. At this time, the impedance value of the first impedance element 14=(first driving voltage - first set voltage) / (first current * N * chromaticity adjustment value), and the chromaticity adjustment value is less than or equal to 1.2 and greater than or equal to 0.8.

[0069] For example, if the light - emitting circuit 1 is provided with 17 first light - emitting diodes 12 connected in parallel and these 17 first light - emitting diodes 12 have been classified as the B1 grade in Table 2 at the time of leaving the factory, and through tests or calculations, it is judged that compared with the ideal central grading position 19, the color temperature of this B1 grade is too cold, and the difference ratio is about - 15%. Therefore, the chromaticity adjustment value is set to 0.85. At this time, if the first driving voltage provided by the first voltage source 10 is 5V, the first set voltage is 4.5V, and the first current is 20mA, then the impedance value of the first impedance element 14=(5 - 4.5) / (0.02 * 17 * 0.85)=1.73Ω. Through the above - mentioned hardware correction, the cold - color - temperature light - emitting diodes belonging to different grades can be compensated by adjusting the resistance value of the first impedance element 14, so that the plurality of first light - emitting diodes 12 output a color temperature that meets the ideal.

[0070] Similarly, when the 17 parallel-connected first light-emitting diodes 12 leave the factory and are classified into the B2 classification in Table 2, and this B2 classification is only slightly colder than the ideal center classification position 19, the chromaticity adjustment value can be set to 0.95. When the first driving voltage provided by the first voltage source 10 is 5V, the first set voltage is 4.5V, and the first current is 20mA, the impedance value of the first impedance element 14 = (5 - 4.5) / (0.02 * 17 * 0.95) = 1.55Ω. Similarly, when the 17 parallel-connected first light-emitting diodes 12 leave the factory and are classified into the B3 classification in Table 2, and the B3 classification is only slightly warmer than the ideal center classification position 19, the chromaticity adjustment value can be set to 1.05 at this time. When the first driving voltage provided by the first voltage source 10 is 5V, the first set voltage is 4.5V, and the first current is 20mA, the impedance value of the first impedance element 14 = (5 - 4.5) / (0.02 * 17 * 1.05) = 1.4Ω. When the 17 parallel-connected first light-emitting diodes leave the factory and are classified into the B4 classification in Table 2, the B4 classification is warmer than the ideal center classification position 19. Therefore, the chromaticity adjustment value can be set to 1.15. When the first driving voltage provided by the first voltage source is 5V, the first set voltage is 4.5V, and the first current is 20mA, the impedance value of the first impedance element = (5 - 4.5) / (0.02 * 17 * 1.15) = 1.28Ω.

[0071] The design proposed by the present invention that can reduce the differences in the variance of each light-emitting diode in terms of color is also applicable to warm-color-temperature light-emitting diodes. Please refer to Table 3 and Figure 3 , which is an illustration of the grading table of warm-color-temperature light-emitting diodes in terms of color and the distribution of these color gradings on the chromaticity diagram. Table 3 shows that warm-color-temperature light-emitting diodes can be divided into four grades on the grading table, including Y1, Y2, Y3, and Y4. Through the four groups of X coordinates and Y coordinates marked by each grading, the color change range belonging to this grading can be defined in the Figure 3 chromaticity diagram. Figure 3 shows the relative relationship on the coordinate axes between the color change ranges of the four grades Y1, Y2, Y3, and Y4 and an ideal center grading position 20. Through experiments or calculations, the degree of variation between the four grades Y1, Y2, Y3, and Y4 and the ideal center grading position 20 can be obtained, and then the resistance value of the second impedance element 17 can be adjusted accordingly for compensation.

[0072]

[0073] Table 3

[0074] For the light-emitting circuit provided in this embodiment, when setting the resistance value of the second impedance element 17, the parameter of the chromaticity adjustment value is also added. The resistance value of the second impedance element 17 is adjusted according to the variation degree between the grading of this batch of warm-color temperature light-emitting diodes received and the ideal central grading position 20. For example, in this embodiment, it is assumed that the second voltage source 11 provides a second driving voltage, the voltage from the second input terminal 151 of the plurality of second light-emitting diodes 15 to the second negative electrode 112 of the second voltage source 11 is the second set voltage, the current flowing through each second light-emitting diode 15 is a second current, and the number of the second light-emitting diodes 15 arranged in parallel is N. At this time, the impedance value of the second impedance element 17 = (the second driving voltage - the second set voltage) / (the second current * N * the chromaticity adjustment value), where the chromaticity adjustment value is less than or equal to 1.2 and greater than or equal to 0.8.

[0075] For example, if the light-emitting circuit 1 is provided with 17 second light-emitting diodes 15 arranged in parallel and has been classified into the Y1 grading in Table 3 when leaving the factory, and it is judged through tests or calculations that the color temperature of this Y1 grading is colder than the ideal central grading position 20, and the difference ratio is about -15%, so the chromaticity adjustment value can be set to 1.15. At this time, if the second driving voltage provided by the second voltage source 11 is 5V, the second set voltage is 4.5V, and the second current is 20mA, then the impedance value of the second impedance element 17 = (5 - 4.5) / (0.02 * 17 * 1.15) = 1.28Ω. Through the above hardware correction, the warm-color temperature light-emitting diodes belonging to different gradings can be compensated by adjusting the resistance value of the second impedance element 17, so that the plurality of second light-emitting diodes 15 output a preset color temperature that meets the ideal.

[0076] Similarly, when the 17 parallel-connected second light-emitting diodes 15 are classified as the Y2 classification in Table 3 at the time of leaving the factory, and the Y2 classification is only slightly colder compared to the ideal center classification position 20, the chromaticity adjustment value can be set to 1.05 at this time. When the second driving voltage provided by the second voltage source 11 is 5V, the second set voltage is 4.5V, and the second current is 20mA, the impedance value of the second impedance element 17 = (5 - 4.5) / (0.02 * 17 * 1.05) = 1.4Ω. When the 17 parallel-connected second light-emitting diodes 15 are classified as the Y3 classification in Table 3 at the time of leaving the factory, and the Y2 classification is only slightly warmer compared to the ideal center classification position 20, the chromaticity adjustment value can be set to 0.95 at this time. When the second driving voltage provided by the second voltage source 11 is 5V, the second set voltage is 4.5V, and the second current is 20mA, the impedance value of the second impedance element 17 = (5 - 4.5) / (0.02 * 17 * 0.95) = 1.55Ω. Similarly, when the 17 parallel-connected second light-emitting diodes 15 are classified as the Y4 classification in Table 3 at the time of leaving the factory, and the Y4 classification is warmer compared to the ideal center classification position 20, the chromaticity adjustment value can be set to 0.85 at this time. When the second driving voltage provided by the second voltage source 11 is 5V, the second set voltage is 4.5V, and the second current is 20mA, the impedance value of the second impedance element 17 = (5 - 4.5) / (0.02 * 17 * 0.85) = 1.73Ω.

[0077] Through the above design, the lighting circuit 1 provided in this embodiment can drive the cold-color-temperature first light-emitting diode 123 and the warm-color-temperature second light-emitting diode 15 after compensation to perform mixed light, and then accurately output the expected color temperature.

[0078] In addition, in the lighting circuit 1 provided in this embodiment, the first impedance element 14 or the second impedance element 17 is selected from a single resistor that can withstand a large current. In other specific embodiments according to the present invention, the first impedance element 14 or the second impedance element 17 can also be selected from a plurality of resistors connected in series or a plurality of resistors connected in parallel.

[0079] In the lighting circuit 1 provided in this embodiment, the first resistor element 13 or the second resistor element 16 is selected from a single resistor. In other specific embodiments according to the present invention, the first resistor element 13 or the second resistor element 16 can also be selected from a plurality of resistors connected in series or a plurality of resistors connected in parallel.

[0080] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Therefore, any equivalent changes or modifications completed without departing from the concept disclosed by the present invention should be included in the inventive concept of this disclosure.

Claims

1. A lighting circuit, comprising: A first voltage source having a first positive electrode and a first negative electrode; A plurality of first light-emitting diodes, the plurality of first light-emitting diodes being cold-color-temperature light-emitting diodes, the plurality of first light-emitting diodes being connected in parallel, each of the first light-emitting diodes having a first input end and a first output end; A plurality of first resistor elements, one end of each of the first resistor elements being connected to the first output end of one of the first light-emitting diodes, the other end of each of the first resistor elements being connected to the first negative electrode of the first voltage source; A first impedance element, one end of the first impedance element being connected to the first positive electrode of the first voltage source, the other end of the first impedance element being connected to the first input end of each of the first light-emitting diodes; A second voltage source having a second positive electrode and a second negative electrode; A plurality of second light-emitting diodes, the plurality of second light-emitting diodes being warm-color-temperature light-emitting diodes, the plurality of second light-emitting diodes being connected in parallel, each of the second light-emitting diodes having a second input end and a second output end; A plurality of second resistor elements, one end of each of the second resistor elements being connected to the second output end of one of the second light-emitting diodes, the other end of each of the second resistor elements being connected to the second negative electrode of the second voltage source; And A second impedance element, one end of the second impedance element being connected to the first positive electrode of the second voltage source, the other end of the second impedance element being connected to the second input end of each of the second light-emitting diodes.

2. The circuit structure of the light-emitting diode according to claim 1, wherein the first voltage source provides a first driving voltage, the voltage from the first input end of the plurality of first light-emitting diodes to the first negative electrode of the first voltage source is a first set voltage, when a first current flows through each of the first light-emitting diodes, the forward voltage of the first light-emitting diode is between a first maximum forward voltage and a first minimum forward voltage, and the resistance value of each of the first resistor elements = (first set voltage - (first maximum forward voltage + first minimum forward voltage) / 2) / first current.

3. The lighting circuit according to claim 2, wherein the first driving voltage is 5V, the first set voltage is 4.5V, the first current is 20mA, the first maximum forward voltage is 2.9V, and the first minimum forward voltage is 2.7V.

4. The lighting circuit according to claim 2, wherein the first driving voltage is 5V, the first set voltage is 4.5V, the first current is 20mA, the first maximum forward voltage is 3.1V, and the first minimum forward voltage is 2.9V.

5. The lighting circuit according to claim 2, wherein the first driving voltage is 5V, the first set voltage is 4.5V, the first current is 20mA, the first maximum forward voltage is 3.3V, and the first minimum forward voltage is 3.1V.

6. The light-emitting circuit as claimed in claim 1, wherein the first voltage source provides a first driving voltage, the voltage from the first input terminal of the plurality of first light-emitting diodes to the first negative electrode of the first voltage source is a first set voltage, the current flowing through each of the first light-emitting diodes is a first current, the number of the first light-emitting diodes is N, and the impedance value of the first impedance element = (first driving voltage - first set voltage) / (first current * N * chromaticity adjustment value), where the chromaticity adjustment value is less than or equal to 1.2 and greater than or equal to 0.

8.

7. The light-emitting circuit as claimed in claim 6, wherein the first driving voltage is 5V, the first set voltage is 4.5V, the first current is 20mA, and the chromaticity adjustment value is selected from one of the following: 1.2, 1.15, 1.1, 1.05, 1, 0.95, 0.9, 0.85, and 0.

8.

8. The circuit structure of the light-emitting diode as claimed in claim 1, wherein the second voltage source provides a second driving voltage, the voltage from the second input terminal of the plurality of second light-emitting diodes to the second negative electrode of the second voltage source is a second set voltage, when a second current flows through each of the second light-emitting diodes, the forward voltage of the second light-emitting diode is between a second maximum forward voltage and a second minimum forward voltage, and the resistance value of each of the second resistance elements = (second set voltage - (second maximum forward voltage + second minimum forward voltage) / 2) / second current.

9. The light-emitting circuit as claimed in claim 8, wherein the second driving voltage is 5V, the second set voltage is 4.5V, the second current is 20mA, the second maximum forward voltage is 2.9V, and the second minimum forward voltage is 2.7V.

10. The light-emitting circuit as claimed in claim 8, wherein the second driving voltage is 5V, the second set voltage is 4.5V, the second current is 20mA, the second maximum forward voltage is 3.1V, and the second minimum forward voltage is 2.9V.

11. The light-emitting circuit as claimed in claim 8, wherein the second driving voltage is 5V, the second set voltage is 4.5V, the second current is 20mA, the second maximum forward voltage is 3.3V, and the second minimum forward voltage is 3.1V.

12. The light-emitting circuit as claimed in claim 1, wherein the second voltage source provides a second driving voltage, the voltage from the second input terminal of the plurality of second light-emitting diodes to the second negative electrode of the second voltage source is a second set voltage, the current flowing through each of the second light-emitting diodes is a second current, the number of the second light-emitting diodes is N, and the impedance value of the second impedance element = (second driving voltage - second set voltage) / (second current * N * chromaticity adjustment value), where the chromaticity adjustment value is less than or equal to 1.2 and greater than or equal to 0.

8.

13. The light-emitting circuit as claimed in claim 12, wherein the second driving voltage is 5V, the second set voltage is 4.5V, the second current is 20mA, and the chromaticity adjustment value is selected from one of the following: 1.2, 1.15, 1.1, 1.05, 1, 0.95, 0.9, 0.85, and 0.

8.

14. The light-emitting circuit according to claim 1, wherein one of the plurality of first light-emitting diodes and one of the plurality of second light-emitting diodes are encapsulated together in a dual-color light-emitting diode.

15. The light-emitting circuit according to claim 1, wherein the first impedance element is selected from one of the following: a single resistor, a plurality of resistors connected in series, and a plurality of resistors connected in parallel.

16. The light-emitting circuit according to claim 1, wherein the second impedance element is selected from one of the following: a single resistor, a plurality of resistors connected in series, and a plurality of resistors connected in parallel.

17. The light-emitting circuit according to claim 1, wherein the first resistor element is selected from one of the following: a single resistor, a plurality of resistors connected in series, and a plurality of resistors connected in parallel.

18. The light-emitting circuit according to claim 1, wherein the second resistor element is selected from one of the following: a single resistor, a plurality of resistors connected in series, and a plurality of resistors connected in parallel.

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