JP5371914B2 - LED lighting device for headlamp and inspection method - Google Patents

Description

  The present invention relates to an LED lighting device for a headlamp that lights an LED (Light Emitting Diode) as a light source of an in-vehicle headlamp, and an inspection method for the LED lighting device for the headlamp.

  As a light source used for an in-vehicle headlamp, a long-life and maintenance-free LED has been widely used instead of a conventional halogen bulb. This LED has a long life span and can secure the necessary brightness with a small amount of power, and can maintain a generally stable brightness by simple control that supplies a constant current, making it suitable as an in-vehicle light source. It is.

However, the LED has a property that the temperature of the LED rises due to self-heating due to lighting (energization), and a property that the LED becomes dark when the LED becomes high temperature even if the LED is turned on at a constant current because the amount of light emission changes depending on the temperature. There is. Therefore, it is bright when the temperature immediately after lighting is low, and when the temperature rises as the lighting time elapses, it tends to become dark as the temperature rises. The following Patent Documents 1 to 4 are known as conventional examples for correcting variations in the amount of light emission of LEDs or a decrease due to temperature.
Incidentally, since the emission color and light emission amount of the LED vary even at room temperature, the desired characteristics cannot be obtained even if the circuit constant of the lighting device is fixed to a specific value. In other words, a desired color and brightness cannot be obtained unless appropriate LED selection and correction for individual LEDs are performed.
In addition, since the forward voltage of an LED having a constant voltage characteristic has a variation that cannot be ignored, it is common to light the LED by applying a constant current to reduce the influence of the variation.

  Patent Document 1 is a drive control device that lights an LED used in a color printer with a constant current, and a drive profile necessary for emitting a target light quantity by measuring temporal changes in drive voltage and light quantity in advance. Create and remember. When the LED is lit, the system controller refers to the drive profile to determine the drive voltage, and controls the current to flow through the LED so that the determined drive voltage is obtained.

  Patent Document 2 is a backlight device that lights red, green, and blue LEDs for color liquid crystal display, and stores an initial current amount of the LED and a correction amount corresponding to the temperature of the initial current amount in advance. deep. When the LED is lit, the drive unit corrects the initial current amount according to the temperature of the LED detected by the temperature sensor, and activates the LED.

  Patent Document 3 is a light emitting device that lights an LED disposed on the back side of a liquid crystal, and stores correspondence information between the light emission intensity and temperature of the LED in advance. When the LED is turned on, the light emission intensity control means controls the light emission intensity according to the temperature of the LED detected by the temperature measurement means.

  Patent Document 4 is an illumination device that turns on an LED for a projector, and stores in advance a value related to power supply to each of a plurality of LEDs with respect to an ambient temperature so as to obtain a predetermined emission color as an initial value. When the LED is lit, the adjustment means changes the amount of power supplied to the LED according to the ambient temperature during actual use.

JP 2005-286290 A JP 2006-171893 A JP 2006-253502 A JP 2007-87816 A

  Conventional LEDs have a small current that can be energized, and even if large power is applied, the effect of securing the brightness that meets the demand is low. Therefore, in conventional LED lighting applications, the temperature rise due to heat generation and the amount of light emission associated therewith In general, lighting is performed in a range where the energization current is small so as to avoid the decrease in current. In the current region for lighting conventional LEDs, the LEDs generally exhibit constant voltage characteristics. Therefore, it is possible to turn on with almost constant power simply by energizing with a constant current (with constant current) and taking the voltage into consideration. There was no need to consider lighting at constant power. In any of the above Patent Documents 1 to 4, constant current control is performed because it does not relate to an in-vehicle headlamp that uses a high-power LED as a light source, and constant power control considering voltage is not performed.

  On the other hand, in the LED with a large light emission amount realized by the progress of the LED, a large amount of power is input to obtain a large light emission amount, and thus self-heating increases. For this reason, the simple lighting control in which a constant current is applied has a problem that the light emission amount is significantly reduced due to self-heating.

  FIG. 8 shows a forward voltage (FIG. 8 (a)), energization current (FIG. 8 (b)), and supplied power (FIG. 8 (c)) applied to the LED when the LED is lit by conventional constant current control. It is a graph which shows. When the LED is turned on by the constant current control shown in FIG. 8B, since the LED temperature is low immediately after the start of lighting, the voltage correlated with the temperature is high (A part in FIG. 8A). If the temperature of the LED rises after a lapse of time after the start of lighting, the forward voltage decreases (part B in FIG. 8A). Since the supply power is also reduced by this forward voltage drop (FIG. 8C), the light emission amount proportional to the supply power is also reduced. Therefore, in a large light emitting LED that turns on a large amount of power, a constant brightness is always maintained immediately after lighting, and the brightness does not change. In other words, in order to emit a high-quality brightness, a constant that takes voltage into account is used. It is necessary to perform power control.

  The present invention has been made to solve the above-described problems, and is used for a headlamp in which an LED is turned on with the same brightness from immediately after turning on to stable lighting to improve the quality of the headlamp. An object of the present invention is to provide an LED lighting device and an inspection method.

  An LED lighting device for a headlamp according to the present invention includes a power supply unit that supplies power by converting a voltage supplied from a power source into a voltage for LED lighting, a voltage detection unit that detects a voltage applied to the LED, and an LED A current detection unit that detects a current flowing through the power supply, a control unit that operates the power supply unit based on the detection values of the voltage detection unit and the current detection unit, and an LED that is in a stable lighting state when it is lit before the current lighting operation. A storage unit that stores the power supplied to the LED as a target power value, and the control unit supplies a constant output power equal to the target power value to the LED during a period from the start of lighting until the LED reaches a stable lighting state. Power control is performed, and constant current control is performed to output a predetermined current value set in advance when the LED reaches a stable lighting state.

  In the method for inspecting the LED lighting device for headlamps according to the present invention, during the period from the start of lighting until the LED reaches a lighting stable state, constant power control is performed to supply output power equivalent to the target power value to the LED. In the inspection process when manufacturing a headlamp LED lighting device that performs constant current control to output a predetermined current value set in advance when a stable lighting state is reached, an inspection resistor equivalent to the headlamp LED during stable lighting Is connected to a resistor having a resistance value lower than that of the inspection resistor, and the constant power control is switched to the constant current control.

  The method for inspecting the LED lighting device for headlamps according to the present invention performs constant power control for supplying output power equivalent to the target power value to the LED during the period from the start of lighting to the stable lighting state of the LED. When the LED reaches a stable lighting state, constant current control is performed to output a predetermined current value set in advance. In the power control, stable lighting is performed in the manufacturing process of the headlamp LED lighting device that reduces the output current by the intermittent operation of the power supply unit. When measuring the output current at the time of stable lighting by connecting a test resistor equivalent to the LED for the headlamp at the time, the output current value at the timing when the current of intermittent output current flows is the output at the time of stable lighting It is measured as a current value.

  According to the present invention, the power supplied to the LED during the stable lighting state when lighting before the current lighting operation is stored as the target power value, and the LED is in the stable lighting state from the start of lighting in the current lighting operation. Since the constant power control is performed so that the output power of the power supply unit is equal to the target power value during the period up to, the LED with the same brightness until the stable lighting state where the LED temperature is stable immediately after lighting It is possible to provide a headlamp lighting device with improved quality as a headlamp light.

  According to the present invention, in the manufacturing process, a resistor having a low resistance value is once connected to lower the output voltage, and then switched to an inspection resistor that generates a voltage drop corresponding to the forward voltage of the LED during stable lighting. By measuring the current value that flows through the inspection resistor, it is possible to output a predetermined current value that is supplied during stable lighting immediately after the start of lighting, making it easier to inspect the output current value during constant current control, and productivity Can be improved.

  According to the present invention, in the manufacturing process, the current value at the timing when the current is flowing is measured during the constant power control in which the output current is intermittently output and the comb-shaped rectangular wave is output. The output current value during constant current control supplied during stable lighting can be inspected and productivity can be improved.

It is a block diagram which shows the structure of the LED lighting device which concerns on Embodiment 1 of this invention. It is a figure explaining the lighting operation of the LED lighting device which concerns on Embodiment 1, Fig.2 (a) is a forward voltage of an LED unit, FIG.2 (b) is an energization current, FIG.2 (c) is supply electric power. It is a graph to show. 3 is a flowchart showing the operation of the LED lighting device according to Embodiment 1. 4 is a flowchart showing an abnormality determination / abnormality notification operation of the LED lighting device according to Embodiment 1; It is a flowchart which shows operation | movement of the LED lighting device which concerns on Embodiment 2 of this invention. It is a flowchart which shows operation | movement of the LED lighting device which concerns on Embodiment 3 of this invention. It is a graph which shows the electric current which the power supply part of the LED lighting device which concerns on Embodiment 5 of this invention outputs. It is a figure explaining the conventional constant current control, Fig.8 (a) is a forward voltage of LED, FIG.8 (b) is an energizing current, FIG.8 (c) is a graph which shows supplied electric power.

Embodiment 1 FIG.
An LED lighting device 1 shown in FIG. 1 is a vehicle-mounted device that lights an LED unit 10 used as a vehicle-mounted headlamp, and includes a power supply unit 2 that converts a voltage supplied from a power supply 11 into a voltage for lighting the LED unit 10, and an LED. Voltage detection unit 3 that detects a voltage applied to the unit 10, a current detection unit 4 that detects a current to be supplied to the LED unit 10, and lighting information such as a target power value supplied to the LED unit 10 in a stable lighting state A control unit 6 that controls the power supply unit 2 based on lighting information, a temperature detection interface (hereinafter referred to as I / F) 7 that inputs an output signal of the temperature sensor 12 to the control unit 6, Communication I / F8 which communicates with the external communication apparatus 13 and Output I / F9 which outputs the signal which the control part 6 emits to the vehicle-mounted failure state display apparatus 14 are provided.

  The LED unit 10 is a light source for a headlamp formed by connecting a plurality of LEDs in series. As described above, the LED unit 10 to be controlled by the first embodiment also has a property that the temperature rises due to self-heating due to lighting (energization), and the light emission amount changes depending on the temperature, so that the LED unit 10 lights at a constant current. However, it has the property of becoming darker if the LED becomes hot. Therefore, when the conventional constant current control as shown in FIG. 8 is performed, when lighting is started, the supply power (light emission amount) is reduced due to a voltage drop due to self-heating, and the temperature of the LED unit 10 is increased over time. It stabilizes while becoming, and it stabilizes with the light emission amount lower than the light emission amount immediately after lighting start.

  Therefore, in the LED lighting device 1 according to the first embodiment, a lighting operation combining constant power control and constant current control is performed to keep the light emission amount constant regardless of the elapsed time. 2A and 2B are diagrams for explaining the lighting operation of the LED lighting device 1 according to the first embodiment. FIG. 2A is a forward voltage of the LED unit 10, FIG. 2B is an energization current, and FIG. c) is a graph showing the supplied power. When time elapses after the lighting starts, the voltage decreases as the temperature of the LED unit 10 increases due to self-heating (A part in FIG. 2A), and the voltage changes when the temperature stabilizes while eventually becoming high. Is also stable (part C in FIG. 2A). The power value (b portion in FIG. 2 (c)) when the voltage is stable (hereinafter, stable lighting state) is stored in the storage unit 5 as the target power value, and the LED unit 10 is used at the next lighting operation. From the start of lighting at a low temperature until the stable lighting state is reached, the same power as the target power value stored at the time of previous lighting is turned on to light up at the same brightness as at the time of stable lighting. After that, when the temperature of the LED unit 10 rises due to lighting (energization) and the voltage is stabilized, the control unit 6 switches from constant power control to constant current control and supplies the constant current to light it.

Next, a specific example of the LED lighting device 1 that realizes the lighting operation shown in FIG. 2 will be described.
The power supply unit 2 is a coil that boosts the battery voltage of the power supply 11 to the voltage of the LED unit 10 (the sum of the forward voltages of the LEDs connected in series) (denoted as the transformer 2a in this figure), The DC / DC converter includes a switching element such as an FET (Field Effect Transistor) 2b that interrupts the primary side and a rectifying element such as a rectifier diode 2c that rectifies a voltage output from the coil. Further, the LED lighting device 1 has a connector portion (not shown) that inputs power from the power source 11 and outputs power to the LED unit 10.

  The voltage detection unit 3 detects a voltage applied from the power supply unit 2 to the LED unit 10 and inputs the voltage to the control unit 6. The current detection unit 4 detects a current flowing from the power supply unit 2 to the LED unit 10 and inputs the detected current to the control unit 6.

  The storage unit 5 is a storage element that stores lighting information such as an electric power value and a current value necessary for controlling the lighting of the LED unit 10, and is backed up like an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory. A nonvolatile memory element that does not require a power supply is used. A part of the lighting information may be stored in a ROM (not shown) of a microcomputer (hereinafter, CPU (Central Processing Unit)) 6a.

The control unit 6 reads the lighting information from the ROM of the storage unit 5 or the CPU 6a, executes calculation by the CPU 6a to control the power supply unit 2, and communicates with the external communication device 13 via the communication I / F 8. Or reporting an abnormality occurrence of the LED unit 10 to the in-vehicle failure state display device 14 via the output I / F 9. Further, the CPU 6a has a timer (timer 6b) that measures an arbitrary time by using a clock signal supplied from a clock generation circuit (not shown). This timer constitutes a first timing unit, a second timing unit, or a third timing unit.
In addition, you may comprise the function of the control part 6 and the memory | storage part 5 in the function of CPU6a. In that case, the storage unit 5, temperature detection I / F7, communication I / F8, and output I / F9 are stored using the EEPROM or flash memory, A / D converter, communication port, and input / output port installed in the CPU 6a. What is necessary is just to make it the structure which operates.

Moreover, each component except the temperature sensor 12 of the LED lighting device 1 may be housed in a housing, and a part of the housing may be used as a heat sink that releases heat generated by the housed member. .
Since the temperature sensor 12 and the temperature detection I / F 7 are not used in the first embodiment but are used in the third embodiment, details will be described in a third embodiment to be described later.

Next, the operation of the LED lighting device 1 will be described.
In the first embodiment, during the period from the start of lighting to the stable lighting state, the constant power that outputs the same power as the power supplied to the LED during the stable lighting state when lighting before the current lighting operation. This is an example of an LED lighting device that performs control and performs constant current control that outputs a constant current when the current lighting reaches a stable lighting state. The forward voltage is increased by the temperature of the LED rising due to self-heating. The output voltage is input until the output current reaches a predetermined current, and the power equivalent to the output power at the previous lighting is output.
It should be noted that the temperature rise of the LED unit 10 due to self-heating has converged, and the elapsed time that the temperature of the LED unit 10 will be in a substantially stable state, in other words, from the start of lighting where the light emission amount will be generally stable. Since the elapsed time can be empirically grasped, the empirical elapsed time is set to a predetermined time, and when the predetermined time has elapsed, an operation of switching from the constant power control to the constant current control is performed. Here, it is assumed that the LED unit 10 almost reaches a stable lighting state after 3 minutes from the start of lighting, and the time for switching from constant power control to constant current control is 3 minutes after starting lighting (part C of FIG. 2A). Set to.
Further, the power output at the time when an empirical elapsed time that will surely reach a stable state is reached is stored as a target power value for use in the next lighting operation. Here, the time for acquiring the target power value is set to 5 minutes after starting lighting (part D in FIG. 2A).

  If the current value (set current value) output to the LED unit 10 at the time of stable lighting is a known value, the voltage value at the time of stable lighting (in FIG. 2A) is used instead of the target power value. B section) may be stored in the storage section 5 as the target voltage value. In this case, the product of the target voltage value and the set current value may be used as the target power value.

FIG. 3 is a flowchart showing the operation of the LED lighting device 1.
When a current is supplied to the LED lighting device 1 (lighting operation is started), first, in step ST1, the CPU 6a performs a predetermined initial process. That is, a current value prepared in advance is set, and the values of timers 0 to 2 are reset.

The CPU 6a repeats the lighting operation of the LED unit 10 every 1 ms (steps ST2 to ST5).
Timer 0 is a timer that counts 1 ms, and increments the counter until timer 0 reaches 1 ms (steps ST2 and ST3). When timer 0 reaches 1 ms ("YES" in step ST3), the value of timer 0 is reset and the values of timers 1 and 2 are incremented in subsequent step ST4. Then, control is performed so that the power supply unit 2 outputs the current L (the detected current detected by the current detection unit 4 is changed to the current L) (step ST5).

The CPU 6a measures the voltage supplied to the LED unit 10 every 10 ms by the voltage detector 3, and calculates and updates the current L of the output current based on the target power value stored in the previous lighting and the detected voltage ( Steps ST6 to ST9).
Timer 1 is a timer that counts 10 ms. Steps ST2 to ST5 are repeated until timer 1 reaches 10 ms. When timer 1 reaches 10 ms (“YES” in step ST6), the value of timer 1 is reset in subsequent step ST7. . Then, the CPU 6a detects the output voltage of the power supply unit 2 with the voltage detection unit 3 (step ST8), and obtains the current L = (target power value / detection voltage) to be applied to the LED unit 10 at that time (step ST9). . Alternatively, current L = {(target voltage value × set current value) / detected voltage} is obtained.

  The timer 2 serves as both a timer that counts 3 minutes from the start of lighting and a timer that counts 5 minutes from the start of lighting. If the current L obtained in step ST9 is smaller than the set current value and the stable lighting state has not been reached (step ST10 “NO”) and the value of the timer 2 is earlier than 3 minutes (step ST11 “ NO "), it returns to step ST2 again, and the lighting operation which outputs the electric current L is performed.

  When 3 minutes have elapsed from the start of lighting (timer 2 counts 3 minutes) (step ST11 “YES”), it is determined that the LED unit 10 is in a stable lighting state. At this time, if the output current (current L) during the constant power control is different from the set current value for the constant current control, the output current may change abruptly. Then, the brightness of the LED unit 10 also changes suddenly, flickers, and is easily visually recognized. Therefore, when the set current value stored in the storage unit 5 is higher than the current current L (step ST12 “YES”), the current current L is increased by 0.1 mA in the subsequent step ST13. Thus, when switching from constant power control to constant current control, the control unit 6 increases the current L by 0.1 mA every 10 ms counted by the timer 1 and approaches the set current value. The change of the current L to be performed becomes slow, and the flicker of light emission can be made inconspicuous.

  When the current L exceeds the set current value during the constant power control before the lapse of 3 minutes from the start of lighting (step ST10 “YES”), the CPU 6a sets the constant power control without waiting for the lapse of 3 minutes. Switching to the current control, the set current value is set to the current L (step ST14), and the power supply unit 2 is controlled so that the output current becomes constant at the set current value. Alternatively, in step ST10, the output power (= current L × detected voltage) is equal to or higher than the target power value (or the power value obtained from the target voltage value × the set current value) during the constant power control before 3 minutes have elapsed from the start of lighting. The constant power control may be switched to the constant current control when the detected voltage becomes, or may be switched to the constant current control when the detected voltage becomes equal to or lower than the target voltage value.

  Alternatively, in step ST10, if the difference between the current L and the set current value (or the difference between the output power and the target power value or the difference between the detected voltage and the target voltage value) reaches within 2%, for example, it is determined that they are substantially equal. You may make it switch from electric power control to constant current control. Thereby, the change of the current at the time of switching from the constant power control to the constant current control becomes continuous, the flicker of the LED unit 10 is eliminated, and the quality as the light of the headlamp is improved.

  Also, when the current L is increased by 0.1 mA every 10 ms and the current L exceeds the set current value (“NO” in step ST12), the constant power control is switched to the constant current control to detect the current. The power supply unit 2 is controlled so that the detection current of the unit 4 becomes constant at the set current value (step ST14).

  Subsequently, in step ST15, it is determined whether or not an abnormality has occurred in the LED unit 10. The abnormality determination / abnormality notification process will be described later.

  When 5 minutes have elapsed from the start of lighting (timer 2 counts 5 minutes) (step ST16 “YES”), the CPU 6a multiplies the detection voltage of the voltage detection unit 3 by the set current value to calculate the target power value, and the storage unit 5 (Or the voltage detected by the voltage detector 3 is stored as a target voltage). This target power value is a value shown in part b of FIG. 2C, and the target voltage value is a value shown in part B of FIG. During the next lighting operation, constant power control is performed using the target power value (target voltage value) stored during the current lighting operation, so that the LED unit has the same power as the stable lighting state when the current lighting is performed. 10 can be input. As a result, in the next lighting operation, it is possible to light with the same brightness as that at the time of stable lighting from the start of lighting.

Next, the abnormality determination / abnormality notification process of step ST15 will be described using the flowchart of FIG.
The abnormality determination / abnormality notification process is performed when the LED unit 10 is stably lit. When the process is started, first, in step ST15-1, the CPU 6a calculates a current abnormality determination voltage value (hereinafter, abnormality determination voltage value). This abnormality determination voltage value is a voltage value in a stable lighting state of the LED unit 10 connected to the LED lighting device 1, and {(target power value / set current value) − (voltage of one LED × 0.5) }. Alternatively, it is obtained from {target voltage value− (voltage of one LED × 0.5)}. In the first time, an abnormality determination voltage value is calculated using a preset target power value (or target voltage value), and thereafter, the abnormality is detected using the latest stored target power value (or target voltage value). The determination voltage value is recalculated and updated.

In step ST15-2, the CPU 6a compares the voltage of the LED unit 10 (detection voltage of the voltage detection unit 3) with the abnormality determination voltage value, and if the detected voltage is equal to or lower than the abnormality determination voltage value, an abnormality has occurred. Judgment is made (step ST15-2 “YES”). That is, if the detected voltage at the time of the current determination decreases by more than ½ of the voltage of one LED from the latest target voltage value (= target power value / set current value), it is determined that an abnormality has occurred. Then, a signal indicating that an abnormality has occurred in the LED unit 10 is output from the control unit 6 to the failure state display device 14 via the output I / F 9, and the abnormality is given to the driver by the signal generated by the failure state display device 14. (Step ST15-3), and the process returns to the flowchart of FIG. In addition to this abnormality notification, the lighting operation stop control of the LED unit 10 may be performed.
On the other hand, if it is determined that there is no abnormality (step ST15-2 “NO”), the process directly returns to the flowchart of FIG.

  Thus, by calculating the abnormality determination voltage value during the current lighting operation using the target power value (or target voltage value) stored in the storage unit 5 during the previous lighting operation, Since it can be detected that the voltage of the LED unit 10 has suddenly changed, it can be determined that an abnormality has occurred in the LED unit 10.

When the abnormality determination voltage value is not calculated from the target power value (or target voltage value), it is necessary to calculate the abnormality determination voltage value from the typical LED voltage (rated value, etc.). Therefore, the voltage change when one LED is short-circuited is hidden in the voltage variation of the entire LED units 10 connected in series, and a short-circuit of one LED cannot be detected.
For example, if the rated value of the forward voltage of one LED is 3V, the actual voltage value is 2.9V, and the number of LED units 10 connected in series is 20, the actual voltage of the LED unit 10 is 58V. On the other hand, if the variation in the LED voltage is 10%, the voltage of the LED unit 10 is assumed to be 60 ± 6V.
If one of the 20 LEDs is short-circuited, the voltage of the LED unit 10 is 55.1V, but it is hidden within the range of 60 ± 6V variation and one LED is short-circuited. It cannot be detected.

  On the other hand, if the abnormality determination voltage value (56.5 V = 58−3 × 0.5) calculated using the target power value (or target voltage value) derived from the detected voltage in the actual stable lighting state, When the voltage of the LED unit 10 becomes 55.1V, it can be determined that one LED is short-circuited by comparison with the abnormality determination voltage value 56.5V.

  In the above description, a value that is equal to or more than ½ the LED voltage from the target voltage value derived from the detected voltage is used as the abnormality determination voltage value. However, the target voltage value (58 V in the above example) is directly determined as abnormal. In this case, a short circuit of one LED can be detected.

By the way, when the first lighting operation without the previous lighting information is performed, control is performed using a standard value prepared in advance in the ROM of the CPU 6a.
In addition, it is also possible to set information from the communication device 13 via the communication I / F 8, and the lighting operation is performed in the storage unit 5 in addition to the target power value or the target voltage value necessary for constant power control. As lighting information necessary for the above, a predetermined current value (set current value) at the time of stable lighting necessary to obtain a desired brightness, a time for switching from constant power control to constant current control, and the next lighting operation The time for acquiring the target power value used for the constant power control can be set in advance.

  As described above, the LED lighting device 1 according to Embodiment 1 converts the voltage supplied from the power source 11 into the voltage for lighting the LED unit 10 and supplies the power, and the voltage applied to the LED unit 10. The voltage detection unit 3 for detecting the current, the current detection unit 4 for detecting the current to be supplied to the LED unit 10, and the power supplied to the LED unit 10 during the stable lighting state when it is lit before the current lighting operation The storage unit 5 that stores the power value and the power source unit 2 so that the product of the detection voltage of the voltage detection unit 3 and the detection current of the current detection unit 4 becomes the target power value during the period from the start of lighting to the stable lighting state. And a control unit 6 that performs constant current control for controlling the output current of the power supply unit 2 so that the detected current becomes a predetermined current value when a stable lighting state is reached. Constitution It was. For this reason, the LED unit 10 can be lit with the same brightness from immediately after lighting to stable lighting, and a headlamp LED lighting device with improved quality as a headlamp light can be provided.

  Further, according to the first embodiment, the storage unit 5 uses, as the target voltage value, the voltage applied to the LED unit 10 during the stable lighting state when the lighting is performed before the current lighting operation, instead of the target power value. The control unit 6 calculates the target power value from the target voltage value stored in the storage unit 5 and performs constant power control during the period from the start of lighting to the stable lighting state, leading to a stable lighting state. For example, the constant current control is performed so that the detection current of the current detection unit 4 becomes a set current value. For this reason, if the set current value for constant current control is known, even if the target voltage value is used instead of the target power value, the LED unit 10 can be lit at the same brightness from immediately after lighting until stable lighting. The LED lighting device for headlamps with improved quality as the light of the headlamps can be provided.

  Further, according to the first embodiment, it is determined that the stable lighting state is reached when an arbitrary time has elapsed, and the constant power control is switched to the constant current control. For this reason, it is possible to switch from constant power control to constant current control by determining a stable lighting state with a simple configuration.

  Further, according to the first embodiment, the difference between the power calculated from the detection voltage of the voltage detection unit 3 and the detection current of the current detection unit 4 and the target power value, or the detection voltage of the current detection unit 4 and the target voltage value When the difference value has reached a predetermined value or less, it is determined that the stable lighting state has been reached, and the constant power control is switched to the constant current control. For this reason, it is possible to switch from constant power control to constant current control by determining a stable lighting state with a simple configuration.

  Further, according to the first embodiment, the control unit 6 is configured to smoothly change the output current of the power supply unit 2 to the set current value when switching from constant power control to constant current control. For this reason, when the control is switched, the current supplied to the LED unit 10 changes continuously, flickering is eliminated, and the quality of the headlamp can be improved.

  Further, according to the first embodiment, the control unit 6 stores the power calculated from the detection voltage and the detection current when a predetermined time has elapsed from the start of lighting in the storage unit 5 as the target power value, or this The detection voltage is stored in the storage unit 5 as a target voltage value. For this reason, it is possible to store the power or voltage of the LED unit 10 during stable lighting with a simple configuration. Even if the lighting operation is repeatedly performed, the lighting control can be performed using the newly stored target power value or target voltage value, so that it is possible to perform the lighting control with a light emission amount without a sense of incongruity.

  Moreover, according to Embodiment 1, since the memory | storage part 5 was comprised with the non-volatile memory element, the lighting device of a simple structure is realizable.

  Further, according to the first embodiment, the ROM or the storage unit 5 of the CPU 6a is configured such that the target power value or the target voltage value used for the first constant power control, the set current value used for the constant current control, and the constant power control. The time for switching from constant current control to constant current control is stored in advance. For this reason, abnormal lighting operation can be avoided in the first lighting. In addition, a unique set current value can be set for each LED unit 10 connected to the LED lighting device 1, and variations in the amount of light emission can be absorbed.

  According to the first embodiment, the target power value or the target voltage value used for the first constant power control stored in advance in the storage unit 5 is configured to be able to communicate with the external communication device 13, and the constant current. If the setting current value used for control and the time for switching from constant power control to constant current control can be set even after the LED lighting device 1 is assembled, the lighting device having the same configuration has different characteristics. It can also be applied to a headlamp composed of LEDs.

  Further, according to the first embodiment, the control unit 6 is configured to compare the detection voltage of the voltage detection unit 3 and a predetermined abnormality determination voltage value to determine whether the LED unit 10 has an abnormality. Therefore, abnormality can be determined based on the actual voltage of the LED unit 10 during normal lighting, and the accuracy of failure determination can be increased.

  Further, according to the first embodiment, the control unit 6 updates the abnormality determination voltage value to a value based on the target power value or the target voltage value each time the target power value or the target voltage value is stored in the storage unit 5. Therefore, the abnormality can be determined from the voltage change of the LED unit 10, and the abnormality of the LED unit 10 can be determined with high accuracy with a simple configuration.

  Further, according to the first embodiment, when the control unit 6 determines that an abnormality has occurred in the LED unit 10, the output I / F 9 that outputs a signal indicating the occurrence of abnormality to an in-vehicle device such as the failure state display device 14 is output. It was configured to provide. For this reason, it is possible to notify the driver of the abnormality of the LED unit 10 from another in-vehicle device that has received a signal indicating the occurrence of the abnormality, prompting an early response, and avoiding the danger caused by the abnormality.

Embodiment 2. FIG.
The LED lighting device 1 according to the second embodiment has the same configuration as that of the LED lighting device 1 shown in FIG. 1 and will be described below with reference to FIG. In the second embodiment, it is determined that the light emission amount of the LED unit 10 is stable from the fact that the detection voltage of the LED unit 10 detected by the voltage detection unit 3 is stable, and the change amount of the detection voltage per unit time is When it reaches a predetermined value or less, it is configured to switch from constant power control to constant current control.
In addition, the power value (or voltage value) at the time when a predetermined time has elapsed since the switching from constant power control to constant current control is used as the target power value (or target voltage value) used in the constant power control at the next lighting operation. To be stored in the storage unit 5.

  Here, it is assumed that the LED unit 10 will be in a stable lighting state if the amount of change per 10 seconds of the detection voltage detected by the voltage detection unit 3 is 100 mV or less, and the change in voltage for switching from constant power control to constant current control. Set the amount to 100 mV per 10 seconds. The time for acquiring the target power value is set to 30 seconds (E section in FIG. 2A) from the time of switching to constant current control (C section in FIG. 2A).

FIG. 5 is a flowchart showing the operation of the LED lighting device 1 according to the second embodiment.
When the LED lighting device 1 starts a lighting operation, first, in step ST101, the CPU 6a performs a predetermined initial process. That is, the CPU 6a sets a current value prepared in advance and resets the values of timers 0, 1, 3, and 4, respectively.

  Steps ST2 to ST10 in FIG. 5 are the same processes as steps ST2 to ST10 in FIG. As in the first embodiment, the timer 0 is a timer that counts 1 ms, and the CPU 6a repeats the lighting operation of the LED unit 10 every 1 ms. The timer 1 is a timer that counts 10 ms, and calculates the current L of the output current from the target power value stored in the previous lighting and the detected voltage based on the detection voltage measured by the voltage detection unit 3 every 10 ms. (Steps ST6 to ST9).

  The timer 3 is a timer that counts a unit time of 10 seconds as a reference for detecting the amount of voltage change. Steps ST2 to ST10 are repeated until the timer 3 reaches 10 seconds, and when the timer 3 reaches 10 seconds (step ST102 “YES” "), The value of the timer 3 is reset in the following step ST103. Then, the CPU 6a determines that the LED unit 10 has not reached the stable lighting state if the amount of change in the detected voltage detected by the voltage detection unit 3 in the previous and current step ST8 is 100 mV or more (step ST104 “YES”). Then, the process returns to step ST2. On the other hand, if the amount of change is smaller than 100 mV (step ST104 “NO”), it is determined that the LED unit 10 is in a stable lighting state, and the process proceeds to steps ST12 to ST14. Note that steps ST12 to ST14 in FIG. 5 are the same processes as steps ST12 to ST14 in FIG.

  The timer 4 is a timer that counts 30 seconds from the time when the constant power control is switched to the constant current control. After switching to the constant current control in step ST14, the value of the timer 4 is incremented to start counting ( Step ST105). When the timer 4 reaches 30 seconds (“YES” in step ST106), the target voltage value is calculated by multiplying the detected voltage detected by the voltage detection unit 3 in step ST17 followed by the set current value and stored in the storage unit 5. Alternatively, the detected voltage at that time is stored in the storage unit 5 as a target voltage value.

  As described above, the LED lighting device 1 according to Embodiment 2 determines that the stable lighting state has been reached when the amount of change per unit time of the detection voltage detected by the voltage detection unit 3 reaches a predetermined value or less, and thus the constant lighting state. It was configured to switch from power control to constant current control. For this reason, the stable lighting state can be determined with a simple configuration, and the constant power control can be switched to the constant current control.

  Further, according to the second embodiment, the time after switching from constant power control to constant current control is measured, and the power calculated from the detected voltage and the detected current when the measurement time reaches a predetermined time is set as the target power. A value is stored in the storage unit 5 or a detection voltage is stored in the storage unit 5 as a target voltage value. For this reason, it is possible to shorten the time from determining the stable lighting state to storing the power or voltage. Even if the lighting operation is repeatedly performed, the lighting control can be performed using the newly stored target power value or target voltage value, so that it is possible to perform the lighting control with a light emission amount without a sense of incongruity.

In the second embodiment, the condition for switching from constant power control to constant current control is detected when the current L obtained in step ST9 exceeds the set current value (step ST10 “YES”) and detection per 10 seconds. Two conditions are set when the voltage change amount is smaller than 100 mV (step ST104 “NO”), but when three minutes have passed since the start of lighting as in the first embodiment (step ST11 “FIG. 3”). “YES”) may be added as a condition.
Thereby, for example, when the temperature of the LED unit 10 at the time of stable lighting is different and the voltage change amount of the LED unit 10 does not become a predetermined value or less for a long time even when the same power is supplied, a predetermined time has elapsed from the start of lighting. It is possible to forcibly switch to the constant current control at the time, and it is possible to maintain a lighting operation with no sense of incongruity even if the surrounding conditions change.

By the way, in the second embodiment, as in the first embodiment, when the first lighting operation without lighting information is performed, the control is performed using the standard value prepared in advance in the ROM of the CPU 6a.
In addition, it is also possible to set information from the communication device 13 via the communication I / F 8, and the lighting operation is performed in the storage unit 5 in addition to the target power value or the target voltage value necessary for constant power control. As lighting information necessary for the above, a predetermined current value (set current value) at the time of stable lighting necessary to obtain a desired brightness, a time for switching from constant power control to constant current control, and the next lighting operation The time for acquiring the target power value used for the constant power control can be set in advance.

Embodiment 3 FIG.
The LED lighting device 1 according to the third embodiment has the same configuration as that of the LED lighting device 1 shown in FIG. 1 and will be described below with reference to FIG. In the third embodiment, a temperature sensor 12 such as a thermistor is mounted on the substrate on which the LED of the LED unit 10 is mounted, and the temperature of the LED or its ambient temperature is measured. The analog signal output from the temperature sensor 12 is input to the control unit 6 via the temperature detection I / F 7. Then, it is determined that the light emission amount of the LED unit 10 is stable from the temperature of the LED unit 10 detected by the temperature sensor 12 or the ambient temperature of the LED unit 10 being stable, and the amount of change in the detected temperature per unit time is When it reaches a predetermined value or less, it is configured to switch from constant power control to constant current control.

  Here, assuming that the amount of change per 10 seconds of the detected temperature detected by the temperature sensor 12 is 1 ° C. or less, the LED unit 10 reaches a stable lighting state, and the voltage for switching from constant power control to constant current control is set. The amount of change is set to 1 ° C. per 10 seconds. In addition, the time for acquiring the target power value is 30 seconds (the E part in FIG. 2A) from the time of switching to the constant current control (the C part in FIG. 2A) as in the second embodiment. Set to.

FIG. 6 is a flowchart showing the operation of the LED lighting device 1 according to the third embodiment.
When the LED lighting device 1 starts the lighting operation, first, in step ST201, the CPU 6a performs a predetermined initial process. That is, the CPU 6a sets a current value prepared in advance and resets the values of the timers 0, 1, 3, and 4, respectively.

  Steps ST2 to ST10 in FIG. 6 are the same processes as steps ST2 to ST10 in FIGS. However, in step ST202 in the middle, the CPU 6a acquires the temperature of the LED unit 10 detected by the temperature sensor 12.

  The timer 3 is a timer that counts a unit time of 10 seconds as a reference for detecting the amount of temperature change. Steps ST2 to ST10 are repeated until the timer 3 reaches 10 seconds, and when the elapsed time by the timer 3 reaches 10 seconds (step In step ST204 “YES”), the value of timer 3 is reset in the following step ST204. Then, the CPU 6a determines that the LED unit 10 has not reached the stable lighting state if the change amount of the detected temperature detected by the temperature sensor 12 in the previous and current step ST202 is 1 ° C. or more (step ST205 “YES”). Then, the process returns to step ST2. On the other hand, if the amount of change is smaller than 1 ° C. (step ST205 “NO”), it is determined that the LED unit 10 is in a stable lighting state, and the process proceeds to steps ST12 to ST14, ST17, ST105, ST106. Steps ST12 to ST14 and ST17 in FIG. 6 are the same as steps ST12 to ST14 and ST17 in FIG. Also, the processing in steps ST105 and ST106 in FIG. 6 is the same as that in steps ST105 and ST106 in FIG.

  As described above, the LED lighting device 1 according to Embodiment 3 includes the temperature sensor 12 that detects the temperature of the LED unit 10 or the surrounding temperature, and the amount of change per unit time of the detected temperature detected by the temperature sensor 12 is large. When it reached below a predetermined value, it was judged that it was in a stable lighting state, and it was configured to switch from constant power control to constant current control. For this reason, the stable lighting state can be determined with a simple configuration, and the constant power control can be switched to the constant current control.

In the third embodiment, the condition for switching from the constant power control to the constant current control is determined when the current L obtained in step ST9 exceeds the set current value (step ST10 “YES”) and detection per 10 seconds. Two conditions are set when the temperature change amount is smaller than 1 ° C. (step ST205 “NO”), but when three minutes have passed since the start of lighting as in the first embodiment (step ST11 in FIG. 3). “YES”) may be added as a condition.
Thereby, for example, when the temperature of the LED unit 10 at the time of stable lighting is different and the temperature change amount of the LED unit 10 does not become a predetermined value or less over a long time even when the same power is supplied, a predetermined time has elapsed from the start of lighting. It is possible to forcibly switch to the constant current control at the time, and it is possible to maintain a lighting operation with no sense of incongruity even if the surrounding conditions change.

  In addition, after the transition to the stable lighting state in the second and third embodiments, the abnormality determination / abnormality notification process described in the first embodiment may be performed.

By the way, in the third embodiment, similarly to the first and second embodiments, when the first lighting operation without lighting information is performed, the standard value prepared in advance in the ROM of the CPU 6a is used. Control.
In addition, it is also possible to set information from the communication device 13 via the communication I / F 8, and the lighting operation is performed in the storage unit 5 in addition to the target power value or the target voltage value necessary for constant power control. As lighting information necessary for the above, a predetermined current value (set current value) at the time of stable lighting necessary to obtain a desired brightness, a time for switching from constant power control to constant current control, and the next lighting operation The time for acquiring the target power value used for the constant power control can be set in advance.

Embodiment 4 FIG.
Here, the inspection method of the LED lighting device 1 according to the first to third embodiments will be described. The LED lighting device 1 according to the fourth embodiment has the same configuration as that of the LED lighting device 1 shown in FIG. 1 and will be described below with reference to FIG.

  When the LED lighting device 1 is operated by a normal lighting operation when inspecting or confirming the output current of the LED lighting device 1, particularly when the output current during stable lighting is inspected or confirmed, first, constant power control is performed, and this constant power control is completed. In order to shift to constant current control after that, in order to inspect or confirm constant current operation, the output current is inspected or confirmed after shifting to constant current control. However, waiting until switching from constant power control to constant current control (waiting for the passage of time) requires a long inspection time, and thus is unacceptable because it impairs productivity in the mass production process.

  Therefore, in the fourth embodiment, when the current L exceeds the set current during the constant power control, or the detection voltage of the voltage detection unit 3 is lower than or substantially equal to the target voltage value, switching to the constant current control is performed. Using the operation (step ST10 in FIGS. 3, 5, and 6), immediately after starting the lighting operation, the voltage is once decreased (current L is increased) and then corresponds to the forward voltage of the LED at the time of stable lighting. Returning to the voltage (current L), the control unit 6 makes the above determination to switch to constant current control so that the output current value corresponding to the stable lighting can be inspected immediately after the lighting operation is started.

  Specifically, before inspecting the characteristics of the stable lighting state by connecting the inspection resistor, a voltage drop lower than the forward voltage at the time of stable lighting of the LED connected to the headlamp LED lighting device is generated ( Connecting a resistor (with a low resistance value) that connects a large current and lowering the output voltage from the forward voltage of the LED during stable lighting (increasing the current L) leads to a stable lighting state in the control unit 6. And switch to the stable lighting state (constant current control). Thereafter, the output current at the time of stable lighting is inspected or confirmed by measuring the current flowing through the inspection resistor.

  As described above, the inspection method according to the fourth embodiment includes the resistance for inspection (LED unit 10 during stable lighting (in the LED lighting device for headlamps) in the manufacturing process of the LED lighting device 1 according to the first to third embodiments. Connect a resistor that generates a voltage drop (small resistance) that is lower than the forward voltage during stable lighting before connecting the resistor corresponding to the connected LED) and inspecting the characteristics of the stable lighting state. Then, the step of measuring the current value to be energized by returning to the inspection resistor after passing the simulation step until the detection voltage detected by the voltage detection unit 3 is lower than the detection voltage when the inspection resistor is connected and the stable lighting state is reached. It was configured to provide. For this reason, by lowering the output voltage once before connecting the test resistor, it is possible to output a predetermined current value that is output during stable lighting even immediately after the start of lighting, and inspection of the output current value during constant current control And the productivity can be improved.

Embodiment 5 FIG.
The LED lighting device 1 according to the fifth embodiment has the same configuration as the LED lighting device 1 shown in FIG. 1 on the drawing, and will be described below with reference to FIG. In the fifth embodiment, the control unit 6 controls the power supply unit 2 by PWM (Pulse Width Modulation) so that the current output from the power supply unit 2 has a rectangular wave shape. However, the PWM control (about 500 Hz) for intermittently reducing the output current by intermittently cutting the output current in a comb shape is the same control method as the PWM control (about 500 kHz) of the FET (switching element) 2 b of the power supply unit 2. Therefore, in order to avoid confusion between the two, the operation in which the power supply unit 2 according to the fifth embodiment outputs a comb-like rectangular wave current is referred to as an intermittent operation.

  In FIG. 7, the output current by the intermittent operation | movement of the power supply part 2 is shown. In the graph, the horizontal axis represents time, and the vertical axis represents current value. When the comb-tooth-shaped rectangular wave current is output by the intermittent operation (at the time of high-level current output), the power supply unit 2 turns on and off the FET 2b according to the pulse signal output from the control unit 6, and the power supply is turned on. A current is supplied from 11 to the transformer 2a, and the rectangular wave boosted by the transformer 2a during the OFF state is rectified by the rectifier diode 2c and output to the LED unit 10 via the voltage detection unit 3. Further, when the current of the rectangular wave current on the comb teeth is stopped by the intermittent operation (when the current on the low level side is output), the power supply unit 2 stops and turns off the pulse signal output from the control unit 6 to the FET 2b. . Therefore, the current supplied to the LED unit 10 by the power supply unit 2 is a comb-like rectangular wave as shown in FIG. Note that the output current (high-level side output current) when the power supply unit 2 is operating and outputting current is set to the set current value for stable lighting, and the ratio of operation time to stop time (duty ratio) is set. If control is performed to reduce the equivalent output current that is energized to the LED unit 10 by adjustment, the output current value (the output current value on the high level) during output is always the same, and the LED unit The luminescent color of 10 does not change.

  Further, even if the output current value is reduced equivalently by the intermittent operation, the current value on the high level side (the output current value when the power supply unit 2 outputs the output current) does not change. If the current value on the high level side is measured when a resistance for inspection (a resistance corresponding to the LED unit 10 at the time of stable lighting) is connected to 1, the constant current control can be performed even when constant power control is performed. The output current value can be easily inspected and productivity can be improved.

  As described above, in the LED lighting device 1 according to the fifth embodiment, the control unit 6 intermittently operates the power supply unit 2 to reduce the output current immediately after starting lighting by making the output current a rectangular wave on the comb teeth. The inspection method of the LED lighting device 1 according to the fifth embodiment is a lighting device, and the current value on the high level side of the comb-like rectangular wave (the output when the power supply unit 2 outputs the output current) By measuring the (current value), the output current value during constant current control can be inspected immediately after lighting during constant power control, and productivity can be improved.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

  DESCRIPTION OF SYMBOLS 1 LED lighting device, 2 Power supply part, 2a transformer, 2b FET, 2c Rectifier diode, 3 Voltage detection part, 4 Current detection part, 5 Memory | storage part, 6 Control part, 6a CPU, 6b Time measuring part, 7 Temperature detection I / F , 8 Communication I / F, 9 Output I / F, 10 LED unit, 11 Power supply, 12 Temperature sensor, 13 Communication device, 14 Failure status display device.

Claims (19)

A power supply unit that converts the voltage supplied from the power source into a voltage for lighting the LED and supplies power; and
A voltage detector for detecting a voltage applied to the LED;
A current detection unit for detecting a current flowing through the LED;
A control unit for operating the power supply unit based on detection values of the voltage detection unit and the current detection unit;
A storage unit that stores, as a target power value, the power supplied to the LED during the stable lighting state when it is lit before the current lighting operation;
The control unit performs constant power control for supplying output power equivalent to the target power value to the LED during a period from the start of lighting until the LED reaches a stable lighting state, and the LED reaches a stable lighting state. For example, an LED lighting device for a headlamp that performs constant current control for outputting a predetermined current value set in advance. Instead of storing the power supplied to the LED as a target power value during the stable lighting state when the storage unit is lit before the current lighting operation, the storage unit outputs the voltage output to the LED at that time as the target voltage Remember as a value,
The headlamp according to claim 1, wherein the control unit performs a constant power control by calculating a target power value from a target voltage value stored in the storage unit and a predetermined current value set in advance. LED lighting device. A first time measuring unit for measuring the elapsed time from the start of lighting,
The LED lighting device for a headlamp according to claim 1, wherein the control unit switches from constant power control to constant current control after a predetermined time has elapsed from the start of lighting.   The control unit has a function of detecting a voltage change amount per time unit, and when a change amount of the detection voltage detected by the voltage detection unit reaches a predetermined value or less, a constant current is controlled from a constant power control. The LED lighting device for a headlamp according to any one of claims 1 to 3, wherein the control is switched to control. A temperature detection unit for detecting the temperature of the LED or its surrounding temperature;
The control unit has a function of detecting a temperature change amount per unit time, and when a change amount of the detected temperature detected by the temperature detection unit reaches a predetermined value or less, a constant current is controlled from a constant power control. The LED lighting device for a headlamp according to any one of claims 1 to 3, wherein the control is switched to control.   The control unit is configured such that a difference value between power and a target power value calculated from a detection voltage detected by the voltage detection unit and a detection current detected by the current detection unit, or a difference value between the detection voltage and the target voltage value is a predetermined value. 4. The headlamp LED lighting device according to claim 1, wherein the constant lamp control is switched from the constant power control to the constant current control when reaching a value below the value. 5.   2. The headlamp LED lighting device according to claim 1, wherein when the control unit switches from constant power control to constant current control, the output current is smoothly changed to a predetermined current value. A second time measuring unit for measuring the elapsed time from the start of lighting,
The storage unit uses the detection voltage detected by the voltage detection unit when a predetermined time has elapsed from the start of lighting and the power calculated from the detection current detected by the current detection unit as a target power value, or the detection voltage The LED lighting device for a headlamp according to claim 1, wherein the LED is stored as a target voltage value. A third timer that measures the elapsed time since switching from constant power control to constant current control;
The storage unit uses the detection voltage detected by the voltage detection unit when a predetermined time has elapsed since switching to the constant current control and the power calculated from the detection current detected by the current detection unit as a target power value, Alternatively, the detected voltage is stored as a target voltage value, and the LED lighting device for a headlamp according to claim 1 or 2.   2. The LED lighting device for a headlamp according to claim 1, wherein the power supply unit intermittently reduces an output current value by intermittently outputting an output current in the constant power control.   The headlamp LED lighting device according to claim 1, wherein the storage unit includes a nonvolatile storage element.   3. The headlamp according to claim 1, wherein a target power value or a target voltage value used for the first constant power control and a predetermined current value used for the constant current control are set in advance. LED lighting device.   4. The LED lighting device for a headlamp according to claim 3, wherein a time for switching from constant power control to constant current control is set in advance.   The communication unit takes in at least one of the target power value or target voltage value used for the first constant power control, the predetermined current value used for the constant current control, and the time for switching from the constant power control to the constant current control. 14. The LED lighting device for a headlamp according to claim 12, wherein the LED lighting device is for a headlamp.   The said control part compares the detection voltage which the said voltage detection part detects with predetermined | prescribed abnormality determination voltage value, and determines the presence or absence of abnormality of the said LED, The Claim 1 or Claim 2 characterized by the above-mentioned. LED lighting device for headlamps.   16. The headlamp according to claim 15, wherein the storage unit updates the abnormality determination voltage value to a value based on the target power value or the target voltage value each time the target power value or the target voltage value is stored. LED lighting device. An output unit that outputs a signal indicating the occurrence of abnormality to the outside,
16. The LED lighting device for a headlamp according to claim 15, wherein the output unit outputs the abnormality occurrence signal when it is determined that an abnormality has occurred in the LED. A power supply unit that converts the voltage supplied from the power source into a voltage for lighting the LED and supplies power; and
A voltage detector for detecting a voltage applied to the LED;
A current detection unit for detecting a current flowing through the LED;
A control unit for operating the power supply unit based on detection values of the voltage detection unit and the current detection unit;
A storage unit that stores, as a target power value, the power supplied to the LED during the stable lighting state when it is lit before the current lighting operation;
During the period from the start of lighting until the LED reaches a stable lighting state, the control unit performs constant power control to supply output power equivalent to the target power value to the LED, and the LED reaches a stable lighting state. For example, in the inspection process when manufacturing the LED lighting device for headlamps that performs constant current control that outputs a predetermined current value set in advance, an inspection resistor corresponding to the LED for headlamps during stable lighting is connected and stabilized. Before measuring the output current during lighting, the headlamp LED lighting device is characterized by switching from constant power control to constant current control by connecting a resistor having a resistance value lower than that of the testing resistor. Method. A power supply unit that converts the voltage supplied from the power source into a voltage for lighting the LED and supplies power; and
A voltage detector for detecting a voltage applied to the LED;
A current detection unit for detecting a current flowing through the LED;
A control unit for operating the power supply unit based on detection values of the voltage detection unit and the current detection unit;
A storage unit that stores, as a target power value, the power supplied to the LED during the stable lighting state when it is lit before the current lighting operation;
During the period from the start of lighting until the LED reaches a stable lighting state, the control unit performs constant power control to supply output power equivalent to the target power value to the LED, and the LED reaches a stable lighting state. For example, the constant current control for outputting a predetermined current value set in advance is performed, and in the power control, the output current is reduced by the intermittent operation of the power supply unit. When measuring the output current during stable lighting by connecting a test resistor equivalent to the LED, measure the output current value when the intermittent output current is flowing as the output current value during stable lighting A method for inspecting an LED lighting device for a headlamp.

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