control unit

Abstract

It can accurately calculate the temperature of a light-emitting diode with a simple structure. [Solution] The control unit 20 comprises an LED 30, a control unit 40, and a temperature sensor 23. The control unit 40 is made of an integrated circuit and includes a drive circuit 41 that adjusts and supplies power to the LED 30, and controls the LED 30 through the power supply by the drive circuit 41. The temperature sensor 23 is built into the control unit 40 and detects the temperature of the control unit 40 (sensor temperature THS). The control unit 40 detects the supplied power WL supplied to the LED 30 by the drive circuit 41 through the execution of a power detection process 54 of the software 50. The control unit 40 calculates the temperature of the LED 30 based on the sensor temperature THS and the supplied power WL through the execution of an LED temperature calculation process 55 of the software 50.

Description

Technical Field

[0001] The present invention relates to a control unit.

Background Art

[0002] Patent Document 1 describes a control unit for controlling a light-emitting diode. This control unit includes a light-emitting diode, a control unit for controlling the light-emitting diode, and a temperature sensor for detecting the temperature of the light-emitting diode. The control unit controls the light-emitting diode based on the temperature detected by the temperature sensor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above control unit, a temperature sensor for detecting the temperature of the light-emitting diode is provided separately from the light-emitting diode and the control unit. Therefore, it causes an increase in the number of components by the number of temperature sensors, and it becomes necessary to secure a place for arranging the temperature sensor.

Means for Solving the Problems

[0005] Each aspect of the device for solving the above problems will be described. [Aspect 1] A control unit comprising: a light-emitting diode; a power adjustment and supply unit consisting of an integrated circuit that adjusts and supplies power to the light-emitting diode, and controls the light-emitting diode through the power supply by the power adjustment and supply unit; a temperature sensor built into the control unit that detects the temperature of the control unit; a power detection unit that detects the power supplied to the light-emitting diode by the power adjustment and supply unit; and a temperature calculation unit that calculates the temperature of the light-emitting diode based on the temperature of the control unit detected by the temperature sensor and the power supplied by the power detection unit.

[0006] The inventors of this application have found a strong correlation between the temperature of the control unit, detected by a temperature sensor built into the control unit, the power supplied to the light-emitting diode from the power adjustment and supply unit of the control unit, and the temperature of the light-emitting diode. Therefore, with the above configuration, the temperature of the light-emitting diode can be accurately calculated based on the above correlation, more specifically, based on the temperature of the control unit and the power supplied to the light-emitting diode. Moreover, with the above configuration, by using a control unit with a built-in temperature sensor, the temperature of the light-emitting diode can be calculated using the temperature of the control unit detected by the temperature sensor. Therefore, even when it is necessary to obtain the temperature of the light-emitting diode, it is not necessary to install a separate temperature sensor in addition to the control unit and the light-emitting diode.

[0007] [Aspect 2] The control unit according to [Aspect 1], wherein the temperature calculation unit calculates the temperature difference between the actual temperature of the control unit and the actual temperature of the light-emitting diode based on the power supply detected by the power detection unit, and calculates the temperature of the light-emitting diode by subtracting the temperature difference from the temperature of the control unit detected by the temperature sensor.

[0008] The inventors of this application have found a strong correlation between the power supplied to the light-emitting diode from the power adjustment supply unit of the control unit and the difference between the temperature of the control unit, detected by a temperature sensor built into the control unit, and the actual temperature of the light-emitting diode. Therefore, with the above configuration, the temperature difference can be determined based on the power supply, and by subtracting this temperature difference from the temperature of the control unit detected by the temperature sensor, the temperature of the light-emitting diode can be calculated with high accuracy.

[0009] [Aspect 3] A control unit according to [Aspect 1] or [Aspect 1], further comprising a temperature correction unit that corrects the power supplied to the light-emitting diode based on the temperature of the light-emitting diode calculated by the temperature calculation unit.

[0010] Light-emitting diodes (LEDs) have the characteristic that their illumination state, such as brightness and color, changes with temperature. With the above configuration, the LEDs can be controlled so that their illumination state reaches the desired state according to the temperature calculated with high accuracy by the temperature calculation unit.

[0011] [Aspect 4] The control unit according to [Aspect 3], wherein the light-emitting diode is a full-color light-emitting diode incorporating three monochromatic light-emitting elements: a red light-emitting element, a green light-emitting element, and a blue light-emitting element; the power adjustment supply unit supplies the power to each of the three monochromatic light-emitting elements while adjusting the supply power separately; and the temperature correction unit performs a correction of the supply power based on the temperature of the light-emitting diode only for the red light-emitting element among the three monochromatic light-emitting elements.

[0012] All three monochromatic light-emitting elements have the characteristic of changing luminous intensity with temperature. Of the three monochromatic light-emitting elements, the red light-emitting element shows a particularly large degree of change in luminous intensity with respect to temperature changes compared to the other two.

[0013] With the above configuration, by performing temperature compensation on the supplied power for the red light-emitting element, which exhibits a particularly large degree of change in luminous intensity with respect to temperature changes, the lighting state of the other two light-emitting diodes can be brought to a suitable state without performing temperature compensation on the supplied power. Moreover, with the above configuration, there is no need to construct temperature compensation controls for the green and blue light-emitting elements, thus simplifying the control structure for controlling the light-emitting diodes.

[0014] [Aspect 5] The control unit according to [Aspect 3], wherein the light-emitting diode incorporates a plurality of monochromatic light-emitting elements of different colors, the power adjustment supply unit supplies the power to each of the plurality of monochromatic light-emitting elements while adjusting the supply power, and the temperature correction unit performs a correction of the supply power based on the temperature of the light-emitting diode so that the relationship between temperature and luminous intensity of one of the plurality of monochromatic light-emitting elements matches the relationship between temperature and luminous intensity of the other monochromatic light-emitting elements.

[0015] According to the above configuration, although the luminosity of multiple monochromatic light-emitting elements changes in response to temperature changes, the degree of change in luminosity in response to temperature changes can be made consistent across the multiple monochromatic light-emitting elements. Therefore, the ratio (percentage) of the luminous flux emitted individually by the multiple monochromatic light-emitting elements can be precisely adjusted without regard to the temperature of the light-emitting diodes. Consequently, the color of the mixed visible light emitted from the multiple monochromatic light-emitting elements, i.e., the color of the light emitted by the light-emitting diodes, can be set to the desired color with high precision. [Effects of the Invention]

[0016] According to the present invention, the temperature of a light-emitting diode can be calculated accurately with a simple structure. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 is a schematic diagram showing the general configuration of a control unit and its surroundings according to one embodiment. [Figure 2]FIG. 2 is a schematic diagram showing the configuration of the control unit of this embodiment. [Figure 3] FIG. 3 is a flowchart showing a series of processes of software executed by the control unit of this embodiment. [Figure 4] FIG. 4 is a chromaticity diagram defined in JIS Z8785. [Figure 5] FIG. 5 is a characteristic diagram showing the relationship between the temperature and luminous intensity of the LED of the control unit of this embodiment. [Figure 6] FIG. 6 is an explanatory diagram schematically showing the correction mode by the temperature correction processing of this embodiment. [Figure 7] FIG. 7 is a flowchart showing a series of processes of software executed by the control unit of this embodiment. [Figure 8] FIG. 8 is an explanatory diagram schematically showing the correction mode by the temperature correction processing of the modification. [Figure 9] FIG. 9 is a flowchart showing a series of processes of software executed by the control unit of this modification.

MODE FOR CARRYING OUT THE INVENTION

[0018] Hereinafter, an embodiment of the control unit will be described with reference to FIGS. 1 to 7. As shown in FIG. 1, the control unit 20 includes a light emitting diode (hereinafter, LED 30) and a control unit 40 that controls the LED 30. The control unit 20 is attached inside the passenger compartment of the vehicle 10. The vehicle 10 is provided with a power supply device 11 and a lamp ECU 12. The power supply device 11 is connected to the control unit 20 and supplies power to the control unit 20. The lamp ECU 12 is constituted by a microcomputer or the like and is connected to the control unit 20. An operation unit 13 operated by the occupant is connected to the lamp ECU 12. When the operation unit 13 is operated, the lamp ECU 12 outputs a lighting instruction signal to the control unit 40 of the control unit 20.

[0019] <Control Unit 20> The control unit 20 includes, in addition to the LED 30 and control unit 40, a housing 21, a circuit board 22, and a temperature sensor 23. The housing 21 is a roughly rectangular box with a lid and bottom. The housing 21 houses the LED 30, control unit 40, circuit board 22, and temperature sensor 23. The circuit board 22 is located inside the housing 21. The circuit board 22 is equipped with the LED 30 and the control unit 40. The control unit 40 is composed of a microcomputer or the like. The control unit 40 is made of an integrated circuit and includes a drive circuit 41 as a power adjustment and supply unit that adjusts and supplies power to the LED 30. The control unit 40 controls the LED 30 through the power supply by the drive circuit 41. The temperature sensor 23 is built into the control unit 40. The temperature sensor 23 detects the temperature of the control unit 40 (hereinafter referred to as the sensor temperature THS).

[0020] <led30> LED30 is a full-color light-emitting diode that incorporates three monochromatic light-emitting elements 30R, 30G, and 30B. Specifically, LED30 incorporates a red light-emitting element 30R that emits red light, a green light-emitting element 30G that emits green light, and a blue light-emitting element 30B that emits blue light.

[0021] The control unit 40 of the control unit 20 receives a power supply voltage from the power supply device 11, and also receives an LED 30 lighting instruction signal from outside the control unit 20, specifically from the lamp ECU 12. Based on the input lighting instruction signal, the control unit 40 controls the drive circuit 41 to adjust the current flowing to the LED 30, in other words, by adjusting the power supplied to the LED 30, thereby controlling the LED 30 to be lit in a state corresponding to the lighting instruction signal. Specifically, the control unit 40 adjusts and supplies current (power) to each of the three monochromatic light-emitting elements 30R, 30G, and 30B individually through the control of the drive circuit 41 based on the lighting instruction signal. In this embodiment, the power supplied to the LED 30 is adjusted through pulse width modulation control, or so-called PWM control, by the operation of the drive circuit 41. Examples of the lighting state of the LED 30 include brightness and color.

[0022] Here, since the LED 30 has the characteristic that its lighting state, such as brightness and color, changes depending on its temperature, the temperature of the LED 30 affects its lighting state. The control unit 40 adjusts the power supplied to the LED 30 based on its temperature in order to ensure that the lighting state of the LED 30 is the desired state, even if such an effect occurs. In other words, the control unit 40 controls the LED 30 so that its lighting state is the desired state by adjusting the power supplied to the LED 30 based on its temperature. As a result, the lighting state, such as brightness and color, of the LED 30 is ensured to be the desired state regardless of the temperature of the LED 30.

[0023] In this embodiment, the control unit 20 is provided with a function of calculating the temperature of the LED 30 by using the temperature sensor 23 built in the control unit 40. As a result, the temperature of the LED 30 can be calculated without providing a temperature sensor separately from the control unit 40 and the LED 30, so it is not necessary to secure a place for installing the temperature sensor or to incur the cost of installation.

[0024] <Configuration for calculating the temperature of the LED 30> As shown in FIG. 2, the control unit 40 includes an A / D converter 43 and a function of executing software 50. The A / D converter 43 A / D-converts the detection value detected by the temperature sensor 23 as the temperature of the control unit 40 and outputs it to the software 50, and also A / D-converts the power supply voltage input to the control unit 40 and outputs it to the software 50. The software 50 receives the detection value and the voltage value from the A / D converter 43, and also receives the lighting instruction signal input from the lamp ECU 12 to the control unit 40.

[0025] The software 50 executes a sensor temperature detection process 51 for obtaining the temperature of the control unit 40 (hereinafter, sensor temperature THS) based on the detection value input from the A / D converter 43. Further, the software 50 executes a power supply voltage detection process 52 for obtaining the power supply voltage VB based on the voltage value input from the A / D converter 43. Furthermore, the software 50 executes a current amount determination process 53 for obtaining the current amount (hereinafter, supply current amount IL) supplied to the LED 30 based on the index value of the operation state of the drive circuit 41 (specifically, each operation instruction value TR, TG, TB described later).

[0026] The software 50 executes a power detection process 54 for detecting the power supplied to the LED 30 (hereinafter, supply power WL) based on the obtained power supply voltage VB and supply current amount IL. When the software 50 executes the power detection process 54, the control unit 40 serves as a power detection unit for detecting the supply power WL supplied to the LED 30.

[0027] As described above, the software 50 executes an LED temperature calculation process 55 to calculate the temperature of the LED 30 (hereinafter referred to as LED temperature THL) based on the detected supply power WL and the sensor temperature THS obtained above. When the software 50 executes the LED temperature calculation process 55, the control unit 40 acts as a temperature calculation unit that calculates the LED temperature THL based on the sensor temperature THS detected by the temperature sensor 23 and the supply power WL detected by the power detection process 54.

[0028] Figure 3 is a flowchart showing a series of processes performed by the software 50 to calculate the temperature of the LED 30. This series of processes is repeated at predetermined intervals. Step 101 (S101) in the flowchart corresponds to the sensor temperature detection process 51. Steps S102, S103, S104, and S105 in the flowchart correspond to the power supply voltage detection process 52, the current amount determination process 53, the power detection process 54, and the LED temperature calculation process 55, respectively.

[0029] In the LED temperature calculation process 55 described above, the sensor temperature THS obtained by the sensor temperature detection process 51, in other words, the temperature of the control unit 40 detected by the temperature sensor 23, is acquired at predetermined intervals. In addition, the LED temperature calculation process 55 also acquires the supplied power WL detected by the power detection process 54 at predetermined intervals. In the LED temperature calculation process 55, the difference between the actual temperature of the control unit 40 and the actual temperature of the LED 30 (hereinafter referred to as the temperature difference ΔT) is calculated based on the latest supplied power WL. Then, the temperature of the LED 30 (the LED temperature THL) is calculated by subtracting this temperature difference ΔT from the latest sensor temperature THS.

[0030] Specifically, there is a relationship shown by the following formula "THS = THL + ΔT... (1)" among the sensor temperature THS, the temperature difference ΔT, and the LED temperature THL. By transforming formula (1), a formula "THL = THS - ΔT... (2)" for calculating the LED temperature THL can be obtained. And formula (2) is stored in advance in the memory of the control unit 40 as an arithmetic expression F1.

[0031] The temperature difference ΔT can be calculated using the following formula "ΔT = a × WL + b... (3)" based on the latest supply power WL, coefficient a, and constant b. The inventor of the present application has found that there is a strong correlation between the supply power WL supplied from the drive circuit 41 of the control unit 40 to the LED 30, the difference between the temperature of the control unit 40 detected by the temperature sensor 23 built in the control unit 40 and the actual temperature of the LED 30. This is considered to be related to the following (Item 1) to (Item 3). (Item 1) The heat generation associated with the power adjustment and supply by the drive circuit 41 is the main cause of the temperature rise of the control unit 40. (Item 2) The heat generation associated with the energization of the LED 30 is the main cause of the temperature rise of the LED 30. (Item 3) In the control unit 20, the inside of the housing 21 is heated by the heat generated by the control unit 40 and the heat generated by the LED 30, so the influence of the heat generation of the control unit 40 affects the temperature of the LED 30.

[0032] In this embodiment, based on the results of various experiments and simulations by the inventor, the relationship between the supply power WL and the temperature difference ΔT (for example, the above formula (3)) has been obtained. And that relationship is stored in advance in the memory of the control unit 40 as an arithmetic expression F2.

[0033] In the above LED temperature calculation process 55, based on the supply power WL, the temperature difference ΔT is obtained from the above arithmetic expression F2. And based on the obtained temperature difference ΔT and the sensor temperature THS detected by the temperature sensor 23, the LED temperature THL is calculated from the above arithmetic expression F1.

[0034] <Configuration for controlling the LED 30> As described above, the control unit 40 (Figure 2) controls the drive circuit 41 based on the lighting instruction signal input from the lamp ECU 12 and adjusts the power supplied to the LED 30, thereby controlling the LED 30 to be lit in a state corresponding to the lighting instruction signal.

[0035] Specifically, the software 50 executes an operation instruction value calculation process 56 to determine control instruction values ​​for the operation of the drive circuit 41 (all of which will be described later as red operation instruction value TR, green operation instruction value TG, and blue operation instruction value TB) based on the above-mentioned lighting instruction signal.

[0036] Furthermore, the software 50 executes a temperature correction process 57 to correct the power supplied to the LED 30 (specifically, the control instruction value mentioned above) based on the LED temperature THL calculated by the LED temperature calculation process 55. When the software 50 executes the temperature correction process 57, the control unit 40 acts as a temperature correction unit that corrects the power supplied to the LED 30 based on the LED temperature THL calculated by the LED temperature calculation process 55.

[0037] Furthermore, the software 50 outputs the above-mentioned operation instruction values ​​TR, TG, and TB to the drive circuit 41 of the control unit 40, thereby operating the drive circuit 41 and executing an LED control process 58 that controls the LED 30.

[0038] The above-mentioned operation instruction values ​​TR, TG, and TB are indicator values ​​of the operating state of the drive circuit 41 (more specifically, the amount of current output from the drive circuit 41). In the current amount determination process 53, as described above, the supply current amount IL supplied to the LED 30 is determined based on the operation instruction values ​​TR, TG, and TB, which are indicator values ​​of the operating state of the drive circuit 41.

[0039] LED30 generates mixed-color light by mixing the visible light emitted from three monochromatic light-emitting elements 30R, 30G, and 30B. The control unit 20 is positioned inside the vehicle so that the mixed-color light generated as described above is irradiated onto a predetermined target area.

[0040] Figure 4 shows a chromaticity diagram as defined in JIS Z8785 (Photometry - CIE Physical Photometry System). A chromaticity diagram is a diagram that represents the color of light in XY planar coordinates. All colors are represented on the chromaticity diagram. The bell-shaped curved portion of the chromaticity diagram is called the "monochromatic locus (spectral locus)" and represents the monochromatic colors red, orange, yellow, green, blue, indigo, and blue-violet by wavelength. All colors inside this monochromatic locus are mixtures. The straight line at the bottom is called the "pure violet locus" and represents colors that do not exist in the spectrum, such as "violet, red-violet, and their mixtures."

[0041] In the chromaticity diagram above, the proportion of "red" increases as X increases, and the proportion of "blue" increases as X decreases. Similarly, the proportion of "green" increases as Y increases, and the proportion of "blue" increases as Y decreases. In the chromaticity diagram above, the point where the chromaticity coordinates are X=0.333 and Y=0.333 represents the chromaticity point of achromatic (white) and is called the white point W. As you move away from this white point W, the saturation increases (the colors become more vivid), and this point becomes the monochromatic light with the maximum saturation on the monochromatic locus.

[0042] The dominant wavelength of the mixed-color light can be changed by controlling the power supplied to the three monochromatic light-emitting elements 30R, 30G, and 30B. In other words, by adjusting the output of the three monochromatic light-emitting elements 30R, 30G, and 30B, the ratio (proportion) of red, green, and blue luminous flux in the mixed-color light can be adjusted to any desired color.

[0043] As shown in Figure 5, the luminous intensity of LED 30 changes depending on the temperature of LED 30. Figure 5 shows the "temperature-luminous intensity" characteristics, which are the relationship between temperature and luminous intensity for each monochromatic light-emitting element 30R, 30G, and 30B.

[0044] As shown by the solid line in Figure 5, in the red light-emitting element 30R, the luminous intensity decreases as the temperature of LED 30 (specifically, the temperature of the red light-emitting element 30R) increases. Therefore, in the red light-emitting element 30R, a constant luminous intensity can be obtained regardless of the temperature of LED 30 by increasing the power supply as the temperature of LED 30 increases. Also, as shown by the dashed line in Figure 5, in the green light-emitting element 30G, the luminous intensity decreases as the temperature of LED 30 (specifically, the temperature of the green light-emitting element 30G) increases. Therefore, in the green light-emitting element 30G, a constant luminous intensity can be obtained regardless of the temperature of LED 30 by increasing the power supply as the temperature of LED 30 increases. Furthermore, as shown by the dashed line in Figure 5, in the blue light-emitting element 30B, the luminous intensity increases as the temperature of LED 30 (specifically, the temperature of the blue light-emitting element 30B) increases. Therefore, in the blue light-emitting element 30B, a constant luminous intensity can be obtained regardless of the temperature of LED 30 by decreasing the power supply as the temperature of LED 30 increases.

[0045] Thus, all three monochromatic light-emitting elements 30R, 30G, and 30B have the characteristic of changing luminous intensity with temperature. However, as is clear from Figure 5, among the three monochromatic light-emitting elements 30R, 30G, and 30B, the red light-emitting element 30R shows a particularly large degree of change in luminous intensity with respect to temperature changes compared to the other two green light-emitting elements 30G and blue light-emitting elements 30B. Therefore, it can be said that the effect of temperature changes on the emission color of the LED 30 is particularly large for the red light-emitting element 30R, while it is small for the green light-emitting element 30G and blue light-emitting elements 30B.

[0046] Based on this, in this embodiment, the temperature compensation process 57, which brings the lighting state of the LED 30 closer to the desired state according to the temperature of the LED 30, is performed only on the red light-emitting element 30R among the three monochromatic light-emitting elements 30R, 30G, and 30B. As shown in Figure 6, in the temperature compensation process 57, the power supplied to the red light-emitting element 30R is corrected so that the luminous intensity of the red light-emitting element 30R becomes a constant luminous intensity (luminous intensity shown by the dashed line in the figure) regardless of the temperature of the LED 30.

[0047] According to this embodiment, by performing a temperature correction process 57 on the red light-emitting element 30R, which exhibits a particularly large degree of change in luminous intensity with respect to temperature changes, it becomes possible to bring the lighting state of the other two LEDs 30 closer to the desired state without performing the temperature correction process 57 on the other two. Moreover, since it is not necessary to construct temperature correction controls for the other two monochromatic light-emitting elements 30G and 30B, the control structure for controlling the LEDs 30 can be simplified accordingly.

[0048] Figure 7 is a flowchart showing the execution procedure of a series of processes performed by the software 50 to control the LED 30. This series of processes is repeated at predetermined intervals. Steps S201 to S203 in the flowchart correspond to the operation instruction value calculation process 56. Steps S202 and S203 in the flowchart correspond to the temperature compensation process 57. Step S204 in the flowchart corresponds to the LED control process 58.

[0049] As shown in Figure 7, in this process, the above operation instruction value calculation process 56 is first executed at predetermined intervals. In the operation instruction value calculation process 56, control instruction values ​​for the operation of the drive circuit 41 are calculated based on the lighting command signal (S201). Specifically, the control instruction values ​​calculated are the red operation instruction value TR for supplying power to the red light-emitting element 30R, the green operation instruction value TG for supplying power to the green light-emitting element 30G, and the blue operation instruction value TB for supplying power to the blue light-emitting element 30B.

[0050] In this embodiment, the relationship between the lighting command signal when the LED 30 is at a reference temperature (for example, 25 degrees Celsius) and the power supplied to each monochromatic light-emitting element 30R, 30G, and 30B that can realize the lighting state indicated by the lighting command signal is predetermined. This relationship, more specifically the relationship between the lighting command signal and the power supplied to each monochromatic light-emitting element 30R, 30G, and 30B (specifically, the respective operation instruction values ​​TR, TG, and TB), is pre-stored in the memory of the control unit 40 as a calculation map M1. In the processing of S201, the red operation instruction value TR, the green operation instruction value TG, and the blue operation instruction value TB are calculated from the calculation map M1 based on the lighting command signal. In this embodiment, the larger the values ​​of each operation instruction value TR, TG, and TB, the greater the power supplied to the monochromatic light-emitting elements 30R, 30G, and 30B.

[0051] Subsequently, in the operation instruction value calculation process 56, the temperature correction process 57 is executed. In the temperature compensation process 57, first, a correction value KR is calculated to correct the red operation indicator value TR based on the latest LED temperature THL (S202).

[0052] In this embodiment, the relationship between the actual temperature of the LED 30 and the correction value KR, which corrects the operation instruction value TR so that the luminous intensity of the red light-emitting element 30R is the same as the luminous intensity at the reference temperature, has been determined from the results of various experiments and simulations conducted by the inventor. This relationship, more specifically the relationship between the LED temperature THL and the correction value KR, is pre-stored in the memory of the control unit 40 as a calculation map M2. In the processing of S202, the correction value KR is calculated from the calculation map M2 based on the LED temperature THL. Specifically, the correction value KR is calculated to be larger the higher the LED temperature THL is. More specifically, the correction value KR is calculated to be "0" when the LED temperature THL is the reference temperature (see Figure 6). Also, the correction value KR is calculated to be negative (KR<0) when the LED temperature THL is lower than the reference temperature, and positive (KR>0) when the LED temperature THL is higher than the reference temperature.

[0053] Subsequently, in the temperature compensation process 57, the red operation instruction value TR is corrected by the correction value KR (S203). Specifically, the value obtained by adding the correction value KR to the operation instruction value TR (TR+KR) is calculated as the final operation instruction value TR.

[0054] In the above operation instruction value calculation process 56, the operation instruction values ​​TR, TG, and TB, which are control instruction values ​​for the operation of the drive circuit 41, are calculated in this manner. In this process, the LED control process 58 is then executed (S204).

[0055] In the LED control process 58, the red operation instruction value TR, the green operation instruction value TG, and the blue operation instruction value TB are output to the drive circuit 41 of the control unit 40. As a result, the drive circuit 41 is controlled so that power according to the operation instruction value TR is supplied to the red light-emitting element 30R, power according to the operation instruction value TG is supplied to the green light-emitting element 30G, and power according to the operation instruction value TB is supplied to the blue light-emitting element 30B. At this time, the red light-emitting element 30R, the green light-emitting element 30G, and the blue light-emitting element 30B light up in response to the power supplied by the drive circuit 41. As a result, the LED 30 lights up in the desired illumination state.

[0056] <Operation and Effects of This Embodiment> The operation and effects of this embodiment will now be described. (1) The control unit 20 comprises an LED 30, a control unit 40, and a temperature sensor 23. The control unit 40 is made of an integrated circuit and includes a drive circuit 41 that adjusts and supplies power to the LED 30, and controls the LED 30 through the power supply by the drive circuit 41. The temperature sensor 23 is built into the control unit 40 and detects the temperature of the control unit 40 (sensor temperature THS). The control unit 40 detects the supplied power WL supplied to the LED 30 by the drive circuit 41 through the execution of a power detection process 54 of the software 50. The control unit 40 calculates the temperature of the LED 30 (LED temperature THL) based on the sensor temperature THS and the supplied power WL through the execution of an LED temperature calculation process 55 of the software 50.

[0057] The inventors of this application have found a strong correlation between the temperature of the control unit 40, as detected by a temperature sensor 23 built into the control unit 40, the power supplied to the LED 30 from the drive circuit 41 of the control unit 40, and the temperature of the LED 30.

[0058] According to the above configuration, the LED temperature THL can be calculated accurately based on the above correlation, specifically based on the sensor temperature THS and the supplied power WL. Moreover, by using a control unit 40 that incorporates a temperature sensor 23, the LED temperature THL can be calculated using the temperature of the control unit 40 detected by the temperature sensor 23. Therefore, even when it is necessary to obtain the temperature of the LED 30, it is not necessary to install a separate temperature sensor in addition to the control unit 40 and the LED 30. Thus, according to the above configuration, the temperature of the LED 30 can be calculated accurately with a simple structure.

[0059] (2) The control unit 40 calculates the temperature difference ΔT between the actual temperature of the control unit 40 and the actual temperature of the LED 30 based on the supplied power WL by executing the LED temperature calculation process 55 of the software 50. Then, the LED temperature THL is calculated by subtracting the temperature difference ΔT from the sensor temperature THS.

[0060] The inventors of this application have found a strong correlation between the power supply WL supplied to the LED 30 from the drive circuit 41 of the control unit 40 and the temperature difference ΔT, which is the difference between the sensor temperature THS detected by the temperature sensor 23 built into the control unit 40 and the actual temperature of the LED 30.

[0061] According to the above configuration, the temperature difference ΔT is determined based on the above correlation, and more specifically based on the above-mentioned power supply WL. By subtracting this temperature difference ΔT from the sensor temperature THS detected by the temperature sensor 23, the LED temperature THL can be calculated with high accuracy.

[0062] (3) The control unit 40 corrects the power supply WL supplied to the LED 30 based on the calculated LED temperature THL by executing the temperature correction process 57 of the software 50. According to the above configuration, the LED 30, which has the characteristic of changing its lighting state according to its own temperature, can be controlled so that the lighting state of the LED 30 becomes the desired state according to the LED temperature THL, which is calculated with high precision.

[0063] (4) The LED 30 is a full-color light-emitting diode that incorporates three monochromatic light-emitting elements 30R, 30G, and 30B. The drive circuit 41 of the control unit 40 supplies power to each of the three monochromatic light-emitting elements 30R, 30G, and 30B while adjusting the supply power. The control unit 40 performs a correction of the operation instruction value (specifically, the red operation instruction value TR) based on the LED temperature THL only for the red light-emitting element 30R among the three monochromatic light-emitting elements 30R, 30G, and 30B through the execution of the temperature correction process 57 of the software 50.

[0064] With the above configuration, by performing temperature compensation on the supplied power for the red light-emitting element 30R, which exhibits a particularly large degree of change in luminous intensity with respect to temperature changes, the lighting state of the other two LEDs can be brought to a suitable state without performing temperature compensation on the supplied power. Moreover, with the above configuration, there is no need to construct temperature compensation controls for the green light-emitting element 30G and the blue light-emitting element 30B, thus simplifying the control structure for controlling the LEDs 30.

[0065] (5) The control unit 20 includes a housing 21 that houses the LED 30 and the control unit 40. In the control unit 20, the inside of the housing 21 is heated by the heat generated by the control unit 40 and the LED 30, so there is a risk that the heat generated by the control unit 40 may affect the temperature of the LED 30. In this embodiment, the relationship between the power supplied by the drive circuit 41 WL, the sensor temperature THS detected by the temperature sensor 23, and the LED temperature THL is defined so as to include the effect of the heat generated by the control unit 40 on the temperature of the LED 30. This relationship is pre-stored in the memory of the control unit 40 as calculation formulas F1 and F2. According to this embodiment, the LED temperature THL can be calculated with high accuracy, including the effect of the heat generated by the control unit 40, based on these calculation formulas F1 and F2.

[0066] <Variation> The above embodiment can be implemented with the following modifications. The above embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0067] Instead of calculation formulas F1 and F2, calculation maps M3 and M4 may be defined, or instead of calculation maps M1 and M2, calculation formulas F3 and F4 may be defined. The calculation parameters for the supplied current IL can be arbitrarily changed, not limited to the operation instruction values ​​TR, TG, and TB, as long as they are indicator values ​​of the operating state of the drive circuit 41 that the control unit 40 is aware of. For example, the current or voltage output from the drive circuit 41 can be increased as indicator values ​​of the operating state of the drive circuit 41. With this configuration, the amount of current output from the drive circuit 41 to the LED 30, i.e., the amount of current supplied to the LED 30, can be accurately determined based on the operating state of the drive circuit 41 by the control unit 40.

[0068] • As detection parameters for the supplied power WL, it is possible to use only the supplied current IL, without using the power supply voltage VB, from the power supply voltage VB and the supplied current IL. With this configuration, under the condition that the power supply voltage is approximately constant, the supplied power WL can be accurately detected based on the supplied current IL. Furthermore, in the above configuration, it is possible to use indicator values ​​of the operating state of the drive circuit 41 other than the supplied current IL, such as operation instruction values ​​TR, TG, TB, etc., as detection parameters for the supplied power WL.

[0069] The shape of the housing 21 is not limited to a roughly rectangular box with a lid and bottom. Any shape is acceptable as long as it can accommodate the LED 30, control unit 40, etc., inside, such as a polygonal box, a cylindrical box, or a box with a lid and an open bottom. It is also possible to omit the housing 21.

[0070] The temperature compensation process 57, which is performed to maintain a constant luminous intensity regardless of temperature, is not limited to being performed only on the red light-emitting element 30R among the three monochromatic light-emitting elements 30R, 30G, and 30B, but may also be performed on all three monochromatic light-emitting elements 30R, 30G, and 30B. With this configuration, the lighting state of the LED 30 can be set to the desired state with higher precision compared to the case where the temperature compensation process 57 is performed only on the red light-emitting element 30R. In addition, the temperature compensation process 57 can be performed on only two of the three monochromatic light-emitting elements 30R, 30G, and 30B, or only on the green light-emitting element 30G, or only on the blue light-emitting element 30B.

[0071] The temperature compensation process may be performed so that the temperature-luminosity relationship (hereinafter referred to as the "temperature-luminosity" characteristic) for one of the three monochromatic light-emitting elements 30R, 30G, and 30B matches the "temperature-luminosity" characteristic for the other two. With this configuration, although the luminosity of the monochromatic light-emitting elements 30R, 30G, and 30B changes in response to temperature changes, the degree of change in luminosity in response to temperature changes can be made approximately the same for all three monochromatic light-emitting elements 30R, 30G, and 30B. Therefore, the emitted color of the LED 30 can be set to the desired color with high precision.

[0072] Below, an example of such a control unit will be described with reference to Figures 8 and 9. As shown in Figure 8, in this example, the control unit performs a temperature correction process 67 to match the temperature-luminosity characteristics of the green light-emitting element 30G and the blue light-emitting element 30B to the temperature-luminosity characteristics of the red light-emitting element 30R.

[0073] As shown in Figure 9, in this example, first, based on the lighting command signal, control instruction values ​​for the operation of the drive circuit 41, specifically the red operation instruction value TR, the green operation instruction value TG, and the blue operation instruction value TB, are calculated (S201). In this example, each operation instruction value TR, TG, and TB are calculated using the same processing as in the above embodiment.

[0074] Subsequently, the temperature compensation process 67 is executed. In the temperature correction process 67, first, a correction value KG for correcting the green operation indicator value TG and a correction value KB for correcting the blue operation indicator value TB are calculated based on the latest LED temperature THL (S302).

[0075] In this example, the first and second relationships are determined from the results of various experiments and simulations conducted by the inventor. The first relationship is between the actual temperature of the LED 30 and a correction value KG that allows the green operation instruction value TG to be corrected so that the "temperature-luminosity" characteristic of the green light-emitting element 30G matches the "temperature-luminosity" characteristic of the red light-emitting element 30R. The second relationship is between the actual temperature of the LED 30 and a correction value KB that allows the blue operation instruction value TB to be corrected so that the "temperature-luminosity" characteristic of the blue light-emitting element 30B matches the "temperature-luminosity" characteristic of the red light-emitting element 30R. The first and second relationships, specifically the relationship between the LED temperature THL and the above correction value KG, and the relationship between the LED temperature THL and the above correction value KB, are pre-stored in the memory of the control unit 40 as a calculation map M5.

[0076] In the S302 process, correction values ​​KG and KB are calculated from the calculation map M5 based on the LED temperature THL. Specifically, the higher the LED temperature THL, the smaller the calculated correction value KG and KB. More specifically, when the LED temperature THL is at the reference temperature (see Figure 8), the calculated correction value KG and KB is "0". Also, when the LED temperature THL is lower than the reference temperature, a positive value (KG, KB > 0) is calculated, and when the LED temperature THL is higher than the reference temperature, a negative value (KG, KB < 0) is calculated.

[0077] Subsequently, in the temperature compensation process 67, the green operation indicator value TG is corrected by the correction value KG, and the blue operation indicator value TB is corrected by the correction value KB (S303). Specifically, the value obtained by adding the correction value KG to the green operation indicator value TG (TG+KG) is calculated as the final green operation indicator value TG, and the value obtained by adding the correction value KB to the blue operation indicator value TB (TB+KB) is calculated as the final blue operation indicator value TB.

[0078] In this example, the LED control process 58 is executed thereafter (S204). In this example, the LED control process 58 is executed with the same processing content as in the above embodiment. In this example, although the luminous intensity of the three monochromatic light-emitting elements 30R, 30G, and 30B changes in response to temperature changes, the degree of change in luminous intensity in response to temperature changes can be made approximately the same for all three monochromatic light-emitting elements 30R, 30G, and 30B. Therefore, the ratio (proportion) of red, green, and blue luminous flux can be adjusted with high precision, regardless of the temperature of the LED 30. Consequently, the color of the mixed visible light emitted from the three monochromatic light-emitting elements 30R, 30G, and 30B, i.e., the emitted color of the LED 30, can be set to the desired color with high precision. Furthermore, in this example, when the LED temperature THL is high, the power supplied to the three monochromatic light-emitting elements 30R, 30G, and 30B is reduced through the execution of the temperature correction process 67. Therefore, the temperature rise of the LED 30 can be suppressed compared to when the temperature correction process 67 is not performed.

[0079] The processing content of the LED temperature calculation process 55 can be arbitrarily changed as long as it calculates the LED temperature THL based on the supplied power WL and sensor temperature THS. For example, the processing content of the LED temperature calculation process 55 can be defined as follows:

[0080] Based on the results of various experiments and simulations, the relationship between the supplied power WL, the sensor temperature THS, and the LED temperature THL is determined in advance, and this relationship is stored in the memory of the control unit 40 as a calculation map or calculation formula. Then, in the LED temperature calculation process 55, the LED temperature THL is calculated from the above relationship based on the supplied power WL and the sensor temperature THS.

[0081] The LED temperature THL calculated by the LED temperature calculation process 55 may be used in processes other than the temperature correction process 57, such as a process for determining an abnormality in the LED 30. The control unit according to the above embodiment can also be applied to a control unit equipped with a monochromatic light-emitting diode consisting of one monochromatic light-emitting element, or to a control unit equipped with a two-color light-emitting diode consisting of two monochromatic light-emitting elements with different emission colors.

[0082] The control unit according to the above embodiment can also be applied to control units installed in parts of the vehicle 10 other than the passenger compartment (e.g., exterior parts such as doors, trunk compartment), and to control units installed in things other than vehicles (e.g., houses). [Explanation of Symbols]

[0083] 10... Vehicles 11…Power supply device 12... Lamp ECU 13...Operation unit 20…Control Unit 21… Housing 22... Circuit board 23...Temperature sensor 30…Light-emitting diode (LED) 30R…Red light-emitting diode 30G...Green light-emitting element 30B...Blue light-emitting element 40... Control Unit 41…Drive circuit 43…A / D converter 50…Software 51... Sensor temperature detection process 52... Power supply voltage detection process 53...Current amount determination process 54...Power detection process 55...Temperature calculation process 56... Calculation process for operation instruction values 57, 67… Temperature compensation processing 58…LED control processing

Claims

1. Light-emitting diodes and The integrated circuit includes a power adjustment and supply unit that adjusts and supplies power to the light-emitting diode, and a control unit that controls the light-emitting diode through the power supplied by the power adjustment and supply unit. A temperature sensor built into the control unit for detecting the temperature of the control unit, A power detection unit for detecting the power supplied to the light-emitting diode by the power adjustment supply unit, A temperature calculation unit calculates the temperature of the light-emitting diode based on the temperature of the control unit detected by the temperature sensor and the power supply detected by the power detection unit, A control unit equipped with the following features.

2. The temperature calculation unit calculates the temperature difference between the actual temperature of the control unit and the actual temperature of the light-emitting diode based on the power supply detected by the power detection unit, and calculates the temperature of the light-emitting diode by subtracting the temperature difference from the temperature of the control unit detected by the temperature sensor. The control unit according to claim 1.

3. The system includes a temperature correction unit that corrects the power supplied to the light-emitting diode based on the temperature of the light-emitting diode calculated by the temperature calculation unit. The control unit according to claim 1 or 2.

4. The light-emitting diode is a full-color light-emitting diode that incorporates three monochromatic light-emitting elements: a red light-emitting element, a green light-emitting element, and a blue light-emitting element. The power adjustment and supply unit adjusts and supplies the power to each of the three monochromatic light-emitting elements individually. The temperature compensation unit performs a power supply correction based on the temperature of the light-emitting diode only for the red light-emitting element among the three monochromatic light-emitting elements. The control unit according to claim 3.

5. The aforementioned light-emitting diode incorporates multiple monochromatic light-emitting elements with different emission colors. The power adjustment and supply unit adjusts and supplies the power to each of the plurality of monochromatic light-emitting elements individually. The temperature correction unit performs a correction of the supplied power based on the temperature of the light-emitting diode so that the relationship between temperature and luminous intensity for one of the plurality of monochromatic light-emitting elements matches the relationship between temperature and luminous intensity for the other monochromatic light-emitting elements. The control unit according to claim 3.

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