JP2014049255A - Led light flux control device, and road illuminating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an LED light flux control device capable of constantly controlling a light flux of an LED with a high accuracy without using a sensor such as an optical sensor and a temperature sensor.SOLUTION: An LED light flux control device comprises: a constant current power supply part 11 performing constant current drive of an LED 5; a switching transistor 12 connected in series to the LED 5; voltage dividing resistors 13 and 14 dividing a both-end voltage (a forward voltage Vf) of the LED 5; a differential amplifier circuit 15 amplifying a difference between the divided voltage and a reference voltage Vf; an A/D converter 16 performing A/D conversion of output voltage ΔVf; and a CPU 17 turning on and off the switching transistor 12 to control the LED 5 in a PWM system. The CPU 17 calculates a light flux corresponding to an actual forward voltage calculated from an output of the A/D converter 16 by using known characteristics of the forward voltage and a light flux, and controls a PWM duty ratio so that the light flux of the LED 5 becomes a target value.

Description

  The present invention relates to an LED light flux control device and a road illumination device that light an LED with a constant light flux (brightness).

  2. Description of the Related Art In recent years, an LED (light emitting diode) is employed as a light source in a road lighting device or the like that is installed at an upper portion of a support column that stands on the side of a road and illuminates a road below.

  As a technique for controlling the luminous flux (brightness) of the LED, there is a technique for measuring the luminous flux with an optical sensor and controlling it to a target luminous flux.

  Further, since the luminous flux of the LED greatly depends on the temperature (particularly the junction temperature), the ambient temperature of the LED is measured by a temperature sensor, and the luminous flux is estimated from the ambient temperature and controlled.

  In addition, an LED driving circuit has been devised in which an operational amplifier for driving an LED is fed back with a forward voltage of the LED to suppress a change in light flux depending on temperature (see Patent Document 1).

Patent No. 3000667

  In the method using an optical sensor or a temperature sensor, the cost increases as much as the sensor is provided. In particular, in an illuminating device using a plurality of light source modules, it is necessary to provide a sensor for each light source module, resulting in a large increase in cost.

  On the other hand, although the LED drive circuit disclosed in Patent Document 1 can suppress the fluctuation of the luminous flux depending on the temperature to some extent, it is not sufficient.

  In particular, in the road lighting device, the heat capacity of the housing is large, and since it takes a relatively long time for the temperature to rise and stabilize after the power is turned on, it is required to suppress fluctuations in brightness during that time.

  The present invention is intended to solve the above-described problem, and an LED light flux control device and a road that can control the light flux emitted from an LED uniformly with high accuracy without using a sensor such as an optical sensor or a temperature sensor. The object is to provide a lighting device.

  The gist of the present invention for achieving the object lies in the inventions of the following items.

[1] a driving source for driving the light emitting diode at a constant current;
A measurement unit for measuring the forward voltage of the light emitting diode;
From the information indicating the characteristic of the intensity of the luminous flux emitted by the light emitting diode with respect to the forward voltage of the light emitting diode, the value of the luminous flux with respect to the forward voltage measured by the measuring unit is obtained to obtain the luminous flux emitted by the light emitting diode. A controller that repeatedly performs light flux stabilization control for controlling a driving state of the light emitting diode by the driving source so as to be a predetermined target value;
An LED light flux control device comprising:

  In the above invention, the forward voltage of the light emitting diode is measured, the luminous flux of the light emitting diode is obtained from the measured value, and the driving state of the light emitting diode is controlled so that this luminous flux becomes the target value. Thereby, the fluctuation of the brightness depending on the temperature is eliminated.

[2] The period of the light flux stabilization control is made longer than before the convergence when the rate of change of the forward voltage measured by the measurement unit converges to a predetermined value or less. LED light flux control device.

  In the above invention, after the forward voltage is stable, that is, after the temperature is stabilized, the control period of the light flux stabilization control is made longer than before the stabilization. Thereby, the processing load of the control performed by the CPU or the like is reduced.

[3] driving a plurality of light emitting diodes;
The controller according to [1] or [2], wherein when the forward voltage measured by the measuring unit is out of a predetermined normal range, it is determined that some of the light emitting diodes are faulty. LED luminous flux control device.

  In the above invention, when a plurality of light emitting diodes connected in series are driven and a part of them is broken, the change in the forward voltage as a whole of the plurality of light emitting diodes connected in series is more rapid than the fluctuation depending on the temperature. Therefore, the failure is detected by holding it.

[4] The LED luminous flux control device according to [3], wherein the luminous flux of the remaining normal light emitting diodes is strengthened to compensate for the decrease in luminous flux due to the failure.

  For example, when some of the plurality of light emitting diodes are short-circuited, the luminous flux of other normal light emitting diodes is strengthened to compensate for the decrease in the luminous flux as a whole. In addition, when a large number of light emitting diodes in the instrument are divided into a plurality of groups and driven by different LED light flux control devices for each group, when an open failure occurs in any group, To compensate for the decrease in luminous flux due to the failure, the brightness of other groups is increased.

[5] A switching transistor for turning on and off the driving of the light emitting diode by the driving source,
The measurement unit includes a voltage dividing resistor that divides the voltage across the light emitting diode, and
A differential amplifier circuit that amplifies the difference between the divided voltage output from the voltage dividing resistor and a reference voltage; and an A / D converter that performs A / D conversion on the output voltage of the differential amplifier circuit;
The control unit controls the driving state of the light emitting diode by a pulse width modulation method by turning on and off the switching transistor, converts the forward voltage of the light emitting diode from the output value of the A / D converter, The LED light flux control apparatus according to any one of [1] to [4], wherein the light flux stabilization control is performed based on a forward voltage obtained by the conversion.

  In the above invention, the CPU controls the brightness by the PWM duty ratio.

[6] A road lighting device for lighting a road from above,
A housing having an irradiation port covered with a light-transmitting plate;
A plurality of light emitting diodes housed in the housing;
The LED light flux control device according to any one of [1] to [5], which drives the plurality of light emitting diodes;
A road lighting device characterized by comprising:

  In the above invention, the brightness of the road lighting device is controlled to be constant without depending on the temperature.

[7] A plurality of light emitting modules in which a plurality of light emitting diodes are arranged,
A plurality of LED light flux control devices are provided for each light emitting module,
[6], wherein the plurality of LED light flux control devices cooperate to increase the brightness of another light emitting module to compensate for a decrease in brightness caused by a failure in one light emitting module. Road lighting equipment.

  In the above invention, each light emitting module is driven by a separate LED light flux control device, and when a failure (for example, an open failure) occurs in any of the light emitting modules, the reduction of the light flux due to the failure is reduced to the other light emitting modules. Increase the brightness of to compensate.

  According to the LED light beam control device and the road lighting device according to the present invention, the light beam emitted from the LED can be controlled to be constant with high accuracy without using a sensor such as an optical sensor or a temperature sensor.

It is a circuit diagram which shows the structure of the LED light beam control apparatus which concerns on embodiment of this invention. It is a figure which shows the timing which samples the forward direction voltage of LED driven by PWM with an AD converter. It is a figure which shows the characteristic of ambient temperature-forward voltage. It is a figure which shows the characteristic of ambient temperature-relative light beam. It is a figure which shows the characteristic of a forward direction voltage-relative light beam. It is a flowchart which shows the process which CPU of a LED light beam control apparatus performs. It is a figure which shows the example of installation of the road illuminating device which concerns on embodiment of this invention. 1 is a perspective view showing a road lighting device according to an embodiment of the present invention. It is a figure which shows the front of the road illuminating device which concerns on embodiment of this invention, a lower surface, an upper surface, a back surface, and a side surface. It is a figure which shows the inside (array of a light emitting module) of the road lighting apparatus which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a circuit configuration of an LED light flux control device 10 according to an embodiment of the present invention. The LED light flux control device 10 fulfills a function of driving the LED 5 so as to keep a light flux emitted from a light emitting diode (hereinafter referred to as an LED 5) to be driven at a predetermined target value.

  The LED light flux control device 10 includes a power supply unit 11 and a constant current circuit 18 for driving the LED 5 at a constant current, a switching transistor 12 interposed between the power supply unit 11 and the constant current circuit 18, and a voltage across the LED 5. A voltage dividing resistor (first resistor 13 and second resistor 14) that divides (forward voltage), a differential amplifier circuit 15 that amplifies the voltage difference between the divided voltage and the reference voltage, and A / A CPU (Central Processing Unit) 17 having a built-in D (analog to digital) converter 16 is included.

Specifically, the output of the power supply unit 11 is connected to the emitter of a PNP switching transistor 12. The collector of the switching transistor 12 is connected to the anode of the LED 5 via the constant current circuit 18, and the cathode of the LED 5 is grounded. The voltage between the anode of the LED 5 and the ground is set to Vf ₁ . The voltage Vf ₁ is a forward voltage of the LED 5.

One end of the first voltage dividing resistor 13 is connected to the anode of the LED 5, and the other end of the first resistor 13 is connected to one end of the second resistor 14 and the input of the differential amplifier circuit 15. The other end of the second resistor 14 is grounded. The resistance value of the first resistor 13 is R1, and the resistance value of the second resistor 14 is R2. The voltage at the connection point between the first resistor 13 and second resistor 14: the (divided voltage voltage input to the differential amplifier circuit 15) and Vf _2.

A reference voltage Vf ₀ is separately input to the differential amplifier circuit 15, and the differential amplifier circuit 15 amplifies the difference voltage between the reference voltage Vf ₀ and the divided voltage Vf ₂ by B times. The output voltage of the differential amplifier circuit 15 is assumed to be ΔVf. The output ΔVf of the differential amplifier circuit 15 is input to the A / D converter 16 built in the CPU 17 and converted into a digital value.

  The CPU 17 takes in the output of the A / D converter 16 and outputs a PWM (Pulse Width Modulation) signal for controlling on / off of the switching transistor 12 to the base of the switching transistor 12. CPU17 controls the drive state of LED5 by a PWM system.

  The operation of the LED light flux control device 10 will be described.

The constant current circuit 18 drives the LED 5 with a constant current. Dividing resistor (first resistor 13 and second resistor 14), by dividing the forward voltage Vf ₁ of the LED 5, and converts the Vf ₁ to manageable voltage Vf _2. Vf ₂ is expressed by the following equation (1).

Since the amount of change in the forward voltage is very small (several tens of mV to several hundred mV), the amount of change in the forward voltage is multiplied by B by the differential amplifier circuit 15. ΔVf is the amount of change in the forward voltage, and Vf ₀ is a reference voltage for calculating the amount of change in the forward voltage. For example, the forward voltage when the junction temperature is 25 ° C. is adopted. ΔVf is expressed by the following equation (2).

The CPU 17 takes in ΔVf by A / D conversion by the A / D converter 16 and calculates Vf ₁ that is a forward voltage of the LED 5. Vf ₁ is expressed by the following equation (3).

  As shown in FIG. 2, the A / D conversion is performed in synchronization with the timing when the output voltage of the constant current circuit 18 driven by PWM is High. In FIG. 2, the A / D conversion timing is indicated by an arrow 21.

In order to make Vf ₁ more accurate, the CPU 17 samples N times and calculates an average value Vfave. Vfave is expressed by the following equation (4).

  Here, when the LED 5 is one in which M LEDs are connected in series, the forward voltage of one LED is expressed by the following equation (5).

  Based on the calculated Vfe, the CPU 17 controls the duty ratio of the PWM signal so that the luminous flux emitted from the LED 5 is maintained at a predetermined target value.

  The ambient temperature and forward voltage characteristics of the LED 5 are represented in FIG. 3, and the ambient temperature and relative luminous flux characteristics of the LED 5 are represented in FIG. 3 and 4 are characteristics when the current If flowing through the LED 5 is 700 mA. The relative luminous flux in FIG. 4 shows a value when the luminous flux when driving at 700 mA is 1.

  If the characteristics of FIGS. 3 and 4 are integrated, the characteristics of the forward voltage and the relative luminous flux are as shown in FIG. FIG. 5 also shows the characteristics when the drive current If of the LED 5 is 700 mA. 3 to 5 are characteristics when the number of LEDs is one.

  The CPU 17 stores, in an internal ROM (Read Only Memory) or the like, characteristics indicating the relationship between the forward voltage and the relative light flux, for example, in an approximate expression or a table format. The CPU 17 obtains the relative luminous flux corresponding to the calculated Vfe from the above characteristics, and estimates the luminous flux emitted by the LED 5 at the present time. Then, the CPU 17 obtains a PWM duty ratio so that the luminous flux emitted from the LED 5 becomes a target value, and outputs a PWM signal having the duty ratio.

  The luminous flux φ emitted from the LED 5 (per LED) is expressed by the following equation (6).

ここで、Ｌ：相対光束、Ｄ：ＰＷＭのデューティ比、φ_Ｖ：Ｉｆ＝７００ｍＡのときの光束、φ：現在の光束、とする。φ_Ｖは予め測定されてＲＯＭに記憶されている。

Here, L: relative luminous flux, D: PWM duty ratio, φ _V : luminous flux when If = 700 mA, φ: current luminous flux. phi _V is stored in the ROM previously been measured.

  The following equation (7) is an equation for obtaining the duty ratio D obtained by modifying the equation (6). If the target value is substituted as the current value of the light flux φ, the duty ratio for driving the LED 5 is derived so that the target value of the light flux is emitted. The CPU 17 outputs a PWM signal having the obtained duty ratio.

  The LED light flux control device 10 performs control so that the light flux emitted from the LED 5 always becomes a constant value (target value) by repeatedly performing the above-described control (light flux stabilization control). Thereby, even if the ambient temperature of LED5 changes, the light beam which LED5 radiates | emits can be kept constant. In particular, even when the temperature of the LED 5 greatly fluctuates immediately after the power is turned on, the luminous flux emitted from the LED 5 can be kept constant.

<Frequency control period>
Immediately after the LED 5 is turned on, the temperature change of the LED 5 is large (fast), so the change of the luminous flux is also large (fast). Therefore, the light beam stabilization control cycle is shortened. However, since the luminous flux is stabilized after the temperature of the LED 5 is stabilized, the luminous flux can be kept constant even if the period is extended. Further, if the cycle is lengthened, the load on the CPU 17 is reduced accordingly.

  Therefore, it is determined that the luminous flux of the LED 5 is stable, and in a stable state, the luminous flux stabilization control cycle is controlled to be longer than before stabilization. Specifically, if the difference between the current Vfe and the previous Vfe is within a range of −0.1 V to 0.1 V, for example, for 10 seconds continuously, it is determined that the sampling is stable. Increase the period. If the sampling period for A / D conversion is Q and the number of samplings for obtaining Vfe is N, the light flux stabilization control period is approximately Q × N, and therefore the A / D conversion sampling period Q is Increasing the length results in a longer light flux stabilization control period.

The CPU 17 starts the operation with a sampling period of 20 ms at startup, and thereafter determines the sampling period under the following conditions.
・ For 10 seconds, when | Vfe− _{Vfe_OLD} |> 0.1V, sampling period = 20 ms,
・ For 10 seconds, when | Vfe− _{Vfe_OLD} | ≦ 0.1V, sampling period = 1000 ms
It should be noted, Vfe _{_OLD} represents the last Vfe. Moreover, | Vfe-Vfe _{_OLD} | indicates the absolute value of (Vfe-Vfe _{_OLD).}

  FIG. 6 shows the flow of processing performed by the CPU 17 of the LED light flux control device 10. The CPU 17 repeats this process immediately after the power is turned on.

First, ΔVf input from the differential amplifier circuit 15 is A / D converted and captured by the A / D converter 16 (step S101). Then, the forward voltage Vf ₁ of the LED 5 is calculated from the above equation (3) (step S102). If sampling has not been performed N times (step S103; No), the process returns to step S101. Note that the initial sampling period is 20 ms. If N samplings is completed (step S103; Yes), and calculates the Vfave obtained by averaging the Vf ₁ of N times, further, by dividing the Vfave by the number M of LED which are connected in series, LED1 per The forward voltage Vfe is obtained (step S104).

  Next, a relative luminous flux corresponding to Vfe is obtained from the characteristics of the forward voltage and the relative luminous flux (step S105), and this is substituted into the equation (7), and the duty ratio of PWM at which the luminous flux emitted from the LED 5 becomes the target value. And the duty ratio of the PWM signal is changed to the duty ratio (step S106).

  Next, it is determined whether or not Vfe is stable (step S107). If not stable (step S107; No), the A / D conversion sampling period is set to 20 ms (step S108), and step S101. Return to. If Vfe is stable (step S107; Yes), the A / D conversion sampling period is set to 1000 ms (step S109), and the process returns to step S101.

<Response to failure>
The current Vfave and the previous Vfave are compared, and an open failure or a short failure of the LED 5 is detected. For example, when the forward voltage of one LED 5 is 3.0V, an open failure is determined if the difference between the current Vfave and the previous Vfave is 3.0V or more. If the difference between the current Vfave and the previous Vfave is −3.0 V or less, it is determined that a short circuit failure has occurred. That is,
Vfave-Vfave _{_OLD} ≧ 3.0V ··· it is determined that the open failure Vfave-Vfave _{_OLD} ≦ -3.0V ··· short-circuit failure.

  Thereby, normal LED5 can be dimmed and a suitable light beam can be maintained. For example, it is assumed that the lighting device has a plurality of light emitting modules in which a plurality of LEDs 5 are connected in series, and the LED light flux control device 10 is provided and driven for each light emitting module. At this time, when the above-mentioned failure is detected in one light emitting module, control is performed so as to increase the luminous flux emitted from normal LEDs and other normal light emitting modules in the same light emitting module. To compensate for the decrease in luminous flux.

  For example, when driving a light emitting module in which 14 LEDs are connected in series, if Vfave is 9 V lower than the normal value, it is determined that 3 LEDs have failed. At this time, the luminous fluxes of the remaining 11 normal LEDs and / or other light emitting modules are increased. If Vfave is higher than the normal value by 3 V or more, it is determined that the LED has an open failure. In this case, since all LEDs of the light emitting module in which the open failure has occurred are not lit, the luminous flux of other normal light emitting modules is increased.

  FIG. 7 shows an installation example of the road lighting device 60 that drives the LED 5 by the LED light flux control device 10. The road illumination device 60 is attached to an upper portion of a support column 53 that is erected on the side of the road 52, and illuminates the road 52 and its surroundings from above. The road lighting device 60 is installed at intervals of several tens of meters (for example, 40 m) along the longitudinal direction of the road. In each figure, the arrow L indicates the longitudinal direction (longitudinal direction) of the road 52, and the arrow W indicates the width direction (transverse direction) of the road 52.

  FIG. 8 is a perspective view of the road lighting device 60 as viewed obliquely from above and front. FIG. 9 shows the front, bottom, top, back, and side of the road lighting device 60. The road lighting device 60 includes a housing 61 having a light irradiation port on the lower surface side, a plurality of light emitting modules 70 (see FIG. 10) housed in the housing 61, and an LED light flux control device that drives the light emitting modules 70. 10 or the like. The main part of the housing 61 is a cast product manufactured by pouring molten metal into a mold, cooling and solidifying it.

  A housing 61 of the road lighting device 60 extends forward from the base 62 and a base 62 that houses a metal fitting for fixing the road lighting device 60 to the support 53 and the LED light flux control device 10 that drives the light emitting module 70. In addition, the main body 64 is formed of a horizontally long, substantially rectangular and relatively thin hollow box.

  A substantially rectangular irradiation port 66 is opened on the lower surface of the main body 64. A translucent plate 68 is fitted into the irradiation port 66 with a packing interposed therebetween. The translucent plate 68 is a plate-like member that transmits light, and is made of glass, resin, or the like.

  FIG. 10 shows a state in which the road lighting device 60 with the translucent plate 68 removed is viewed from the lower surface side. A plurality of light emitting modules 70 are accommodated in the main body portion 64 so as to face the irradiation port 66 from the inside of the main body portion 64.

  The light emitting module 70 is configured by arranging a plurality of LEDs 5 on a flat substrate and covering each LED 5 with a lens 75. Here, 14 LEDs 5 covered with lenses 75 are arranged in a 2 × 7 matrix on a rectangular substrate. In the main body 64, the six light emitting modules 70 are arranged in a 3 × 2 matrix and attached. Note that the number of light emitting modules 70 attached can be increased or decreased.

  A plurality of LED light flux control devices 10 are provided for each light emitting module 70. Each LED light flux control device 10 drives one corresponding light emitting module 70. The plurality of LEDs 5 in each light emitting module 70 are connected in series. The LED light flux control device 10 drives 14 LEDs 5 connected in series.

  In the road lighting device 60, the casing 61 is manufactured by casting, and the heat capacity is large. For this reason, it takes a relatively long time for the temperature rise from the start of lighting to stabilize. Therefore, when the light flux stabilization control is not performed by the LED light flux control device 10, the brightness varies over a relatively long time so that the brightness becomes brighter than the target immediately after the start of lighting and gradually becomes darker as the temperature rises.

  However, the road illumination device 60 can maintain the target brightness immediately after the start of lighting because the LED light flux control device 10 performs light flux stabilization control.

  Further, when a short-circuit failure of the LED 5 occurs in any of the light-emitting modules 70, the LED light flux control device 10 that has detected the short-circuit failure controls light emission controlled by the device itself so as to compensate for the decrease in brightness due to the short-circuit failure. Control is performed to increase the brightness of other normal LEDs 5 in the module 70. Or you may make it compensate the fall of the light beam by failure by adjusting the brightness of both the light emitting module in which the short circuit failure occurred, and the other light emitting module.

  When an open failure is detected, the entire light emitting module 70 in which the failure has occurred does not emit light. Therefore, the LED light flux control device 10 that has driven the light emitting module 70 in which the failure has occurred has detected the occurrence of an open failure in another state. The LED luminous flux control device 10 is notified. In response to this, another normal LED light flux control device 10 performs control so that the brightness of the light emitting module 70 driven by the device becomes brighter than usual so as to compensate for the decrease in brightness due to failure. For example, when one of the six light emitting modules 70 has an open failure, the brightness of the other five normal light emitting modules 70 is controlled to increase by 20%.

  One of the plurality of LED light flux control devices 10 is used as a master, information on the occurrence of a failure is collected in the master, and the master instructs the brightness of the control target to all the LED light flux control devices 10. Thus, it may be configured to compensate for the overall brightness reduction due to the failure.

  The embodiment of the present invention has been described with reference to the drawings. However, the specific configuration is not limited to that shown in the embodiment, and there are changes and additions within the scope of the present invention. Are also included in the present invention.

  For example, in the embodiment, the brightness is controlled by the PWM method, but the control method is not limited to this.

  The information indicating the characteristics of the forward voltage and the relative luminous flux may be obtained from, for example, information on the characteristics of the ambient temperature and the forward voltage and the characteristics of the ambient temperature and the relative luminous flux.

  The cycle of light flux stabilization control is not limited to 20 ms and 1000 ms exemplified in the embodiment, and may be set appropriately. However, it is desirable to shorten the cycle immediately after the power is turned on. The change of the period is not limited to two stages, and may be finely changed to three stages or more.

  In the embodiment, an example is shown in which a failure is detected and control is performed to compensate for brightness. However, for example, a failure detection is automatically notified to a management office or the like that manages a road lighting device via a network. It may be configured.

5 ... LED
DESCRIPTION OF SYMBOLS 10 ... LED light beam control apparatus 11 ... Power supply part 12 ... Switching transistor 13 ... 1st resistor 14 ... 2nd resistor 15 ... Differential amplifier circuit 16 ... A / D converter 17 ... CPU
DESCRIPTION OF SYMBOLS 18 ... Constant current circuit 21 ... Sampling timing 52 ... Road 53 ... Post 60 ... Road lighting device 61 ... Case 62 ... Base 64 ... Main part 66 ... Irradiation port 68 ... Translucent plate 70 ... Light emitting module 75 ... Lens

Claims (7)

A driving source for driving the light emitting diode at a constant current;
A measurement unit for measuring the forward voltage of the light emitting diode;
From the information indicating the characteristic of the intensity of the luminous flux emitted by the light emitting diode with respect to the forward voltage of the light emitting diode, the value of the luminous flux with respect to the forward voltage measured by the measuring unit is obtained to obtain the luminous flux emitted by the light emitting diode. A controller that repeatedly performs light flux stabilization control for controlling a driving state of the light emitting diode by the driving source so as to be a predetermined target value;
An LED light flux control device comprising: 2. The LED light beam according to claim 1, wherein when the rate of change of the forward voltage measured by the measuring unit converges to a predetermined value or less, the cycle of the light beam stabilization control is made longer than before the convergence. Control device. Driving multiple light emitting diodes,
3. The LED light beam according to claim 1, wherein the control unit determines that some of the light emitting diodes are faulty when a forward voltage measured by the measurement unit is out of a predetermined normal range. Control device. The LED luminous flux control device according to claim 3, wherein the luminous flux of the remaining normal light-emitting diodes is strengthened to compensate for a decrease in luminous flux due to the failure. A switching transistor for turning on and off the driving of the light emitting diode by the driving source;
The measurement unit includes a voltage dividing resistor that divides the voltage across the light emitting diode, and
A differential amplifier circuit that amplifies the difference between the divided voltage output from the voltage dividing resistor and a reference voltage; and an A / D converter that performs A / D conversion on the output voltage of the differential amplifier circuit;
The control unit controls the driving state of the light emitting diode by a pulse width modulation method by turning on and off the switching transistor, converts the forward voltage of the light emitting diode from the output value of the A / D converter, The LED light flux control apparatus according to any one of claims 1 to 4, wherein the light flux stabilization control is performed based on a forward voltage obtained by the conversion. A road lighting device that illuminates a road from above,
A housing having an irradiation port covered with a light-transmitting plate;
A plurality of light emitting diodes housed in the housing;
The LED light flux control device according to any one of claims 1 to 5, which drives the plurality of light emitting diodes;
A road lighting device characterized by comprising: A plurality of light emitting modules in which a plurality of light emitting diodes are arranged,
A plurality of LED light flux control devices are provided for each light emitting module,
The plurality of LED light flux control devices cooperate to increase the brightness of another light emitting module to compensate for a decrease in brightness caused by a failure occurring in one light emitting module. Road lighting equipment.

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