WO2016043171A1

WO2016043171A1 - Led illumination device

Info

Publication number: WO2016043171A1
Application number: PCT/JP2015/076091
Authority: WO
Inventors: 洋治椋田
Original assignee: 株式会社ステラージアＬｅｄ
Priority date: 2014-09-16
Filing date: 2015-09-15
Publication date: 2016-03-24
Also published as: JP2017201572A

Abstract

　An LED illumination device 10, provided with an LED illumination unit 11 having an LED 13 mounted on a substrate 12, and a driving control circuit 20 for supplying a driving current to the LED illumination unit 11. The driving control circuit 20, when starting the supplying of the current to the LED illumination unit 11, incrementally increases the supplied current amount I to a prescribed driving current value I0 set in advance.

Description

LED lighting device

The present invention relates to an LED lighting device including an LED lighting unit having LEDs mounted on a substrate.

The LED illumination device is configured to supply a drive current to an LED mounted on a substrate to cause the LED to emit light, and to irradiate the illumination area with light. In such an LED lighting device, a high output type LED may be mounted in order to obtain brighter illumination light. A high-power type LED generates a large amount of heat during operation, and its luminous efficiency decreases as the temperature of the LED chip increases. Therefore, it is used while appropriately dissipating heat.

In order to improve heat dissipation, a heat dissipating means such as a radiator is attached to the substrate on which the LED is mounted via a heat conductive material having a low thermal resistance. In this case, the heat generated by the LED chip is transmitted from the chip to the heat dissipator as the heat dissipating means via the die bond portion, the LED package, the substrate, and the heat conducting material, and is radiated from the heat dissipating means to the air.

When the LED is radiated with the above-described configuration, when the LED chip is turned from the non-lighting state to the lighting state (especially, the lighting state with the highest luminance) by turning on the power, the temperature of the chip itself rises due to the heat generated from the LED chip, and then die-bonded. The temperature of the part, LED package and substrate rises. Further, heat is transmitted to the heat dissipating means such as a radiator through the heat conducting material, and the temperature of the heat dissipating means rises. At this time, a time lag in temperature rise occurs in each part of the heat transfer path from the chip to the heat dissipating means, and a certain amount of time is required until each part comes into a thermal equilibrium state after the power is turned on. As a result, a transient temperature difference occurs between the chip, the LED package, the substrate, and the heat dissipation means.

When a transient temperature difference occurs, transient thermal stress can occur in each part of the heat transfer path from the chip to the heat dissipation means. In particular, a large thermal stress is transiently applied to the die bond portion provided between the chip and the LED package, the electrode portion of the LED package, and the connection portion between the heat radiation terminal and the substrate. And when such transient thermal stress is applied every time the power is turned on, thermal stress accumulates due to long-term use of the LED lighting device, cracks occur in the die bond part and the connection part between the LED and the substrate, etc. In some cases, disconnection may occur. Then, even if the LED chip itself has a long life, the life of the LED lighting device as a whole is lost by causing cracks at each connection part from the LED chip to the substrate and causing a connection failure.

In particular, in a cold district where the outside air temperature is below a few dozen degrees Celsius to below a few tens of degrees Celsius, the entire LED lighting device including the LED chip and the substrate is cooled to the outside air temperature in a non-lighting state. When the power is turned on in such a temperature state and a large driving current is supplied so that the lighting state with the highest luminance is achieved, the temperature of the LED chip rapidly increases. If it does so, the thermal stress mentioned above will become larger and the possibility of a crack generation will increase significantly.

The present invention has been made in view of such problems, and one of the exemplary purposes thereof is to reduce a temperature difference temporarily generated between the LED chip and the substrate when the power is turned on. It is to improve the reliability of the LED lighting device by reducing the thermal stress applied to the connecting portion between them.

An LED illumination device according to an aspect of the present invention includes an LED illumination unit having an LED mounted on a substrate, and a drive control circuit that supplies a drive current to the LED illumination unit. When starting the current supply to the LED lighting unit, the drive control circuit increases the supply current amount stepwise up to a predetermined drive current value set in advance.

According to this aspect, since the amount of current supplied to the LED lighting unit increases step by step, the temperature increase rate of the chip in the LED is reduced compared to the case where a predetermined drive current value is supplied simultaneously with power-on. be able to. Moreover, the temperature rise rate in each part of the heat dissipation path from the LED chip to the substrate can be reduced, and the temperature difference that occurs transiently in each part of the heat dissipation path can be reduced. Thereby, the thermal stress added to each connection part between an LED chip and a board | substrate can be reduced, and generation | occurrence | production of the crack resulting from a thermal stress can be prevented. Even when the LED lighting device is used for a long period of time, since thermal stress is difficult to accumulate, the occurrence of poor connection due to cracks or the like can be suppressed, and the reliability and life of the LED lighting device can be improved.

A temperature sensor that detects the temperature of the LED lighting unit or its surroundings may be further provided. When the detected temperature before the start of current supply falls below a predetermined temperature reference value, the drive control circuit compares the period from the start of current supply until the supply current amount reaches a predetermined drive current value, as compared to the case where the detected temperature is lower than the predetermined temperature reference value. The amount of supply current may be increased step by step so as to be longer.

The drive control circuit increases the number of steps when the supply current amount is gradually increased to the predetermined drive current value when the detected temperature before the start of the current supply is lower than the predetermined temperature reference value compared to the case where the detected temperature is not the case. May be.

When the detected temperature before the start of current supply falls below a predetermined temperature reference value, the drive control circuit supplies each stage when the supply current amount is increased stepwise up to a predetermined drive current value compared to the case where the detected temperature is not the case. You may lengthen the period which maintains an electric current amount, respectively.

The drive control circuit may lengthen the period during which the supply current amount at each stage is maintained each time the supply current amount is increased step by step.

The drive control circuit receives power supply from an external power source, and when the power supply voltage of the external power source exceeds the first voltage reference value, the drive control circuit sets the amount of current supplied to the LED lighting unit to a predetermined drive current. The value may be reduced to a current value obtained by multiplying the value by the first ratio.

A temperature sensor that detects the temperature of the LED lighting unit or its surroundings may be provided. When the power supply voltage from the external power source exceeds the first voltage reference value and the detected temperature exceeds the first temperature reference value, the drive control circuit sets the amount of current supplied to the LED lighting unit to a predetermined drive current value. May be reduced to a current value obtained by multiplying by a second ratio smaller than the first ratio.

When the power supply voltage of the external power supply exceeds a second reference voltage value that is greater than the first voltage reference value, the drive control circuit reduces the amount of current supplied to the LED lighting unit to a predetermined drive current value that is less than the second ratio. The current value multiplied by the third ratio may be decreased, or the current supply to the LED lighting unit may be stopped.

When the detected temperature exceeds a second temperature reference value that is greater than the first temperature reference value, the drive control circuit is configured to multiply the predetermined drive current value by the third ratio by the amount of current supplied to the LED lighting unit. Or the current supply to the LED lighting unit may be stopped.

According to the present invention, the reliability of the LED lighting device is improved by reducing the temperature difference generated between the LED chip and the substrate when the power is turned on and reducing the thermal stress applied to the connection portion between the LED chip and the substrate. Can be increased.

It is a block diagram which shows the structure of the LED lighting apparatus which concerns on 1st embodiment. It is sectional drawing which shows the detailed structure of the LED illumination unit of FIG. It is sectional drawing which shows the structure of each LED of FIG. It is a graph which shows an example of control of the supply current amount at the time of power-on by a drive control circuit. It is a graph which shows the temperature change of each part of the LED lighting apparatus which concerns on embodiment. It is a graph which shows the temperature change of each part of the LED lighting apparatus which concerns on a comparative example. It is a graph which shows another example of control of the supply current amount at the time of power-on by a drive control circuit. It is a graph which shows another example of control of the supply current amount at the time of power-on by a drive control circuit. It is a block diagram which shows the structure of the LED lighting apparatus which concerns on 2nd embodiment. It is a flowchart which shows the operation example with respect to the voltage fluctuation of a drive control circuit. It is a flowchart which shows another operation example with respect to the voltage fluctuation of a drive control circuit.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description, the same elements are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate.

(First embodiment)
FIG. 1 is a block diagram showing a configuration of an LED lighting device 10 according to the first embodiment. The LED lighting device 10 includes an LED lighting unit 11, a drive control circuit 20, and a temperature sensor 21.

FIG. 2 is a cross-sectional view showing a detailed configuration of the LED lighting unit 11. The LED lighting unit 11 includes a substrate 12, a plurality of LEDs 13 mounted on the substrate 12, a heat conductive sheet 14 provided on the back surface of the substrate 12, and a heat dissipation member 15 thermally connected to the heat conductive sheet 14. And including.

Each LED 13 is mounted on the substrate 12, and the chip inside the LED emits light by the drive current I from the drive control circuit 20, and irradiates the light within a predetermined irradiation range. The heat conductive sheet 14 has a known configuration and is made of a material having high thermal conductivity. The heat radiating member 15 is similarly a well-known structure, for example, is comprised with a metal material with high heat conductivity. The heat dissipating member 15 has a plurality of heat dissipating fins 15a for enhancing the heat dissipating effect.

FIG. 3 is a cross-sectional view showing the structure of each LED 13. The LED 13 includes a lens portion 13a, a package 13b, a chip 13c, a die bond portion 13d, a chip electrode 13e, a bonding wire 13f, and an electrode terminal 13g. The lens unit 13a converges light emitted from the chip 13c in a predetermined direction. The chip 13c is bonded onto the die bond portion 13d provided on the upper surface of the package 13b. The two chip electrodes 13e provided on the upper surface of the chip 13c are respectively connected to electrode terminals 13g provided on the upper surface of the package 13b by bonding wires 13f. The electrode terminal 13g is formed so as to wrap around the lower surface of the package 13b, and is electrically connected to the electrode portion 12a provided on the substrate 12 by the solder 16.

The LED 13 preferably has a heat dissipation terminal 13h. The heat radiating terminal 13h is formed near the center of the lower surface of the package 13b. The heat radiating terminal 13 h is thermally connected to the heat radiating electrode portion 12 b provided on the substrate 12 by the solder 16. As shown in FIG. 2, the back surface of the substrate 12 is thermally connected to the heat radiating member 15 via the heat conductive sheet 14. The heat generated by each LED 13 is conducted through the substrate 12, the heat conductive sheet 14 and the heat radiating member 15, and is radiated from the heat radiating member 15 into the air.

1, the temperature sensor 21 detects the ambient temperature T of the LED lighting unit 11 and sends a detection signal to the drive control circuit 20. The drive control circuit 20 calculates the detected temperature based on the detection signal from the temperature sensor 21. The temperature sensor 21 may be provided in the vicinity of the LED lighting unit 11 or may be provided in the LED lighting unit 11.

The drive control circuit 20 receives the supply of the AC voltage from the external power supply 22 and controls the supply current amount I output to the LED lighting unit 11. The drive control circuit 20 adjusts the supply current I to the LED illumination unit 11 to a preset drive current value I0 and outputs it to the LED illumination unit 11. For example, the drive control circuit 20 switches the supply current amount I between the minimum drive current for low-luminance light emission and the maximum drive current that gives the maximum luminance, or the supply current amount between the minimum drive current and the maximum drive current. The amount I of current supplied to the LED lighting unit 11 is adjusted by continuously changing it.

In addition, when the LED lighting unit 11 is turned on, that is, when the current supply to the LED lighting unit 11 is started, the drive control circuit 20 increases the supply current amount I stepwise to obtain a predetermined drive current value I0. Control is performed so that

FIG. 4 is a graph showing an example of control of the supply current amount I when the power is turned on by the drive control circuit 20. The drive control circuit 20 sets the current I1 when the power is turned on at time t0 (= 0), sets the current I2 (I2> I1) at time t1 (t1 = t0 + Δt), and sets the current t2 (t2 = t0 + Δt × 2). The current is I3 (I3> I2) and the desired drive current I0 (I0> I3) is obtained at time t3 (t3 = t0 + Δt × 3). That is, the drive control circuit 20 increases the supply current amount I in four stages from when the power is turned on, and adjusts it to the drive current value I0 set in the final stage.

FIG. 5A is a graph showing a temperature change of each part of the LED lighting device according to the embodiment. As shown in FIG. 5A, the temperature of each part of the LED lighting unit 11 is changed by increasing the amount of current I supplied to the LED lighting unit 11 stepwise. In the graph shown in FIG. 5A, T1 indicates the temperature of the PN junction of the chip 13c, T2 indicates the temperature of the chip 13c, T3 indicates the temperature of the package 13b, and T4 indicates the temperature immediately below the LED 13 mounting portion of the substrate 12. T5 indicates the temperature of the heat dissipating member 15 in the vicinity of the LED 13, and T6 indicates the temperature of the heat dissipating member 15 at a position away from the LED 13.

5A, when the power is turned on at time t0, a supply current I1 is output from the drive control circuit 20 to the LED illumination unit 11, and the chip 13c inside the LED generates heat due to the supply current I1. Heat generated in the chip 13c is conducted from the die bond portion 13d to the heat radiating member 15 through the LED package 13b, the substrate 12, and the heat conductive sheet 14, and is radiated from the fins 15a of the heat radiating member 15 to the air. As a result, the temperature of each part of the LED illumination unit 11 rises, as indicated by reference numerals T1 to T6 in FIG. 5A. In particular, as indicated by reference numeral T1, the temperature of the PN junction portion of the chip 13c rapidly increases at the same time as the power is turned on and then gradually decreases.

Similarly, at times t1, t2, and t3, supply currents I2, I3, and I0 flow, and the supply current amount increases by the difference from the immediately preceding supply currents I1, I2, and I3. As a result, as indicated by reference numerals T1 to T6 in FIG. 5A, the temperature of each part rises stepwise as the supply current amount increases stepwise.

FIG. 5B is a graph showing a temperature change of each part of the LED lighting device according to the comparative example. FIG. 5B shows a temperature change when a desired drive current value I0 is supplied to the LED lighting unit 11 at the same time as the power is turned on. In the comparative example, since the desired drive current value I0 is supplied simultaneously with the power-on, as shown in the graph of FIG. 5B, the temperatures T1 to T6 of each part rapidly increase. As a result, the temperature difference of each part of the LED lighting unit 11 becomes transiently large.

On the other hand, according to the present embodiment shown in FIG. 5A, the increase amount (I1, I2-I1, I3-I2, I0-I3) of the supply current I at each time t0 to t3 is the final drive current value I0. Since it is comparatively small, the rapid temperature rise of each part of the LED lighting unit 11 is suppressed. In particular, it is possible to suppress a rapid temperature rise in the connection portion between the chip 13c and the package 13b and the connection portion between the package 13b and the substrate 12, and to reduce a temperature difference generated in each connection portion. Thereby, thermal stress applied to each connection portion when the power is turned on is reduced, occurrence of cracks and the like in the connection portion due to repeated power on is suppressed, and occurrence of contact failure in the connection portion is reduced.

FIG. 6 is a graph showing another example of control of the amount of supplied current when the power is turned on by the drive control circuit 20. In the control example shown in FIG. 4 described above, after the power is turned on, the drive control circuit 20 performs control so as to sequentially increase the supply current at the time Δt that is equally spaced from the times t1, t2, and t3. In the modification, these times t0, t1, t2, and t3 may not be set at equal intervals. For example, as shown in FIG. 6, each time the supply current amount I is increased stepwise, the period for maintaining the supply current amount at each stage may be lengthened. In other words, when the period during which the current amount at each stage is maintained is Δt1 = t1−t0, Δt2 = t2−t0, Δt3 = t3−t2, each stage is increased as the supply currents I1, I2 and I3 are increased. The drive control circuit 20 may control the supply current amount I so that the intervals Δt1, Δt2, and Δt3 are long (Δt1 <Δt2 <Δt3).

According to the present modification, the amount of current I supplied to the LED lighting unit 11 gradually increases as a whole. Therefore, the temperature difference between the respective portions of the LED lighting unit 11 is further reduced, and the temperature applied to each connecting portion. Stress can be suppressed. In particular, the thermal stress applied to each connection portion can be further reduced by gradually increasing the time interval as it approaches the predetermined drive current value I0.

FIG. 7 is a graph showing still another example of the control of the supply current amount when the power is turned on by the drive control circuit 20. In the control example shown in FIG. 4 described above, the case where the drive control circuit 20 performs control so as to sequentially increase the supply current in four stages of I1, I2, I3, and I0 after the power is turned on is shown. In the modified example, when the ambient temperature is low, for example, from about several tens of degrees Celsius to about several tens of degrees Celsius, the supply current may be sequentially increased in multiple stages. That is, based on the detection signal from the temperature sensor 21, the drive control circuit 20 gradually increases the amount of supplied current in multiple steps when the detected temperature, that is, the ambient temperature of the LED lighting unit 11, is lower than the predetermined temperature reference value Ta. You may let them. Thereby, you may make the temperature difference of each part of the LED lighting unit 11 in each step smaller.

For example, as shown in FIG. 7, when the power is turned on at time t10 (= 0), the current is I11. At time t11, the current is I12 (I12> I11). At time t12, the current is I13 (I13> I12). At time t13, current I14 (I14> I13) is set, at time t14, current I15 (I15> I14) is set, at time t15, current I16 (I16> I15) is set, and at time t16, a desired drive current I0 ( I0> I16). That is, the drive control circuit 20 adjusts the supply current amount I to the drive current value I0 set in the final stage by increasing the supply current quantity I in seven stages from the time of power-on.

According to this modification, even if the ambient temperature is very low and there is a large temperature difference from the ambient temperature at the start of driving the LED lighting device 10, the supply current amount I is increased stepwise in seven steps. Thus, the temperature difference between the LED chip and the substrate can be reduced. Thereby, the thermal stress concerning each connection part can be reduced significantly and generation | occurrence | production of the crack etc. in a junction part can be suppressed significantly.

When the temperature detected by the temperature sensor 21 is lower than the predetermined temperature reference value Ta, the drive control circuit 20 increases the amount of supplied current in a stepwise manner up to the predetermined drive current value I0 as compared to the case where the temperature is not. The period of each step may be lengthened. That is, the supply current amount I may be increased stepwise so that the period from when the current supply is started until the supply current amount reaches the predetermined drive current value I0 becomes longer.

According to this modification, when the detected temperature is low, that is, when the temperature difference between the respective parts of the LED lighting unit 11 immediately after the power is turned on, the time during which the current amount of each stage is maintained is lengthened. The temperature can be prevented from rising rapidly. By gradually increasing the amount of current supplied to the LED chip as a whole, the temperature difference that occurs transiently between the LED chip and the substrate is reduced, and the thermal stress applied to each connection is greatly reduced. it can.

(Second embodiment)
FIG. 8 is a block diagram showing the configuration of the LED lighting device 30 according to the second embodiment. The LED lighting device 30 is different from the LED lighting device 10 according to the above-described embodiment in that the LED lighting device 30 further includes a voltage sensor 31. The voltage sensor 31 has a known configuration and detects the power supply voltage V of the AC voltage applied by the external power supply 22 and outputs it to the drive control circuit 20. Hereinafter, the difference from the LED lighting device 10 will be mainly described.

The drive control circuit 20 operates as follows based on the power supply voltage V detected by the voltage sensor 31 and the ambient temperature T detected by the temperature sensor 21. When the power supply voltage V increases and becomes greater than the first reference voltage value V1 (V> V1), the drive control circuit 20 sets the supply current amount I to a preset first ratio R1 (for example, 90%). ) To decrease. That is, the supply current I is set to I = I0 × R1.

In the drive control circuit 20, the power supply voltage V becomes higher than the first reference voltage V1 (V> V1), and the ambient temperature T exceeds the preset first reference temperature Tb (T> Tb). Sometimes, the supply current I is reduced to a preset second ratio R2 (eg, 75%). That is, the supply current amount I is I = I0 × R2. The second ratio R2 is set to be a value (R1> R2) lower than the first ratio R1.

Further, when the power supply voltage V becomes higher than the second reference voltage V2 (for example, + 14% of the nominal voltage) higher than the first reference voltage V1 (V> V2), the drive control circuit 20 cuts off the current supply. (I = 0), the driving of the LED illumination unit 11 is stopped.

Further, the drive control circuit 20 sets the supply current I in advance when the ambient temperature T exceeds the second reference temperature Tc higher than the first reference temperature Tb (T> Tc) regardless of the power supply voltage V. To a third ratio R3 (eg 50%). That is, the supply current amount I is I = I0 × R3. The third ratio R3 is set to be a value (R2> R3) lower than the second ratio R2.

The LED lighting device 30 increases the supply current amount I in a stepwise manner to a drive current value I0 in the final step, similar to the LED lighting device 10 shown in FIG. Further, the LED lighting device 30 operates as shown in the flowchart of FIG. 9 in a state where the LED lighting unit 11 is stably driven.

FIG. 9 is a flowchart showing an operation example of the drive control circuit 20 with respect to voltage fluctuation. When the ambient temperature T exceeds the second reference temperature Tc (Y in ST1), the drive control circuit 20 decreases the supply current amount I to the third ratio R3, and sets the LED illumination unit as I = I0 × R3 11 (ST2). Thereby, the LED illumination unit 11 drives the LED 13 with the drive current I0 × R3 to emit light.

On the other hand, when the ambient temperature T is equal to or lower than the second reference temperature Tc (N in ST1), the drive control circuit 20 compares the power supply voltage V with the first reference voltage V1 (ST3). When the power supply voltage V is equal to or lower than the first reference voltage V1 (N in ST3), the drive control circuit 20 supplies the supplied current amount I to the LED illumination unit 11 as I0 (ST4). Thereby, the LED illumination unit 11 drives the LED 13 with the drive current I0 to emit light with the maximum luminance.

Further, when the power supply voltage V exceeds the first reference voltage V1 (Y in ST3), the drive control circuit 20 compares the power supply voltage V with the second reference voltage V2 (ST5). When the power supply voltage V exceeds the second reference voltage V2 (Y in ST5), the drive control circuit 20 cuts off the supply current I (I = 0) and stops driving the LED lighting unit 11 ( ST6).

If the power supply voltage V is equal to or lower than the second reference voltage V2 (N in ST5), the drive control circuit 20 compares the ambient temperature T with the first reference temperature Tb (ST7). When the ambient temperature T is equal to or lower than the first reference temperature Tb (N in ST7), the drive control circuit 20 reduces the supply current I to a preset first ratio R1 (for example, 90%), and supplies the supply current I I is set to I = I0 × R1 (ST8). Thereby, the LED illumination unit 11 drives the LED 13 with the drive current I0 × R1 to emit light.

When the ambient temperature T exceeds the second reference temperature Tb (Y in ST7), the drive control circuit 20 reduces the supply current I to a preset second ratio R2 and reduces the supply current I. I = I0 × R2 (ST9). Thereby, the LED illumination unit 11 drives the LED 13 with the drive current I0 × R2 to emit light.

According to the present embodiment, when the power supply voltage V increases, the supply current amount I is appropriately reduced based on the detection signal from the voltage sensor 31, and a large amount of unintended power is supplied to the LED lighting unit 11. Can be prevented. Thereby, it can suppress beforehand that excessive electric power is supplied to the LED illumination unit 11, and it will be damaged.

In general, when an AC commercial power source or the like is used as a power source, it is known that the AC voltage of the power source fluctuates. Such AC voltage fluctuations need to be absorbed by the drive control circuit 20 when an AC or DC constant voltage power supply is not used. Therefore, when the AC voltage increases, it is necessary to absorb the increase in the AC voltage in the drive control circuit 20, which increases the power consumed by the drive control circuit 20, leading to an increase in the amount of heat generated in the drive control circuit 20. sell. On the other hand, in the present embodiment, when the power supply voltage increases, control is performed so as to reduce the amount of current supplied to the LED lighting unit 11, so that it is possible to prevent more power than expected from flowing to the drive control circuit 20. . Thereby, damage to the LED lighting unit 11 and the drive control circuit 20 can be prevented, and the reliability of the LED lighting device 30 can be improved.

Further, according to the present embodiment, an increase in power consumption due to an increase in the power supply voltage can be reduced by reducing the supply current I when the detected temperature T increases as the power supply voltage of the external power supply 22 increases. . Thereby, while the burden with respect to the power consumption increase in LED lighting unit 11 or drive control circuit 20 is reduced, the further temperature rise of LED lighting device 30 is controlled. Further, when the power supply voltage further increases or the detected temperature further increases, the LED lighting unit 11 and the drive control circuit 20 are protected by further reducing the supply current I or cutting off the current supply. be able to.

FIG. 10 is a flowchart showing another example of operation with respect to voltage fluctuation of the drive control circuit. When the power supply voltage V exceeds the second reference voltage V2 (Y in ST11), the drive control circuit 20 cuts off the current supply to the LED lighting unit 11 and sets I = 0 (ST12). When the power supply voltage V is less than or equal to the second reference voltage V2 (N in ST11), the power supply voltage V is compared with the first reference voltage V1 (ST13). If the power supply voltage V is less than or equal to the first reference voltage V1, (N in ST13), supply current amount I = I0 (ST14).

If the power supply voltage V exceeds the first reference voltage V1 (Y in ST13), the ambient temperature T is compared with the second reference temperature Tc (ST15), and the ambient temperature T exceeds the second reference temperature Tc. If so (Y in ST15), the supply current amount I is reduced to the third ratio R3, and I = I0 × R3 (ST16). If the ambient temperature T is equal to or lower than the second reference temperature Tc (N in ST15) and equal to or lower than the first reference temperature Tb (N in ST17), the supply current amount I is decreased to the first ratio R1, I = I0 × R1 (ST18). If the ambient temperature T exceeds the first reference temperature Tb (Y in ST17), the supply current amount I is reduced to the second ratio R2, and I = I0 × R2.

When the power supply voltage V exceeds the second reference voltage V2, instead of interrupting the current supply to the LED lighting unit 11, the supply current amount I is reduced to the third ratio R3 so that I = I0 × R3 Also good. Further, when the ambient temperature T exceeds the second reference temperature Tc, the current supply to the LED lighting unit 11 may be cut off and I = 0 instead of decreasing the supply current amount I to the third ratio R3. .

The present invention can be implemented in various forms without departing from the spirit of the present invention. For example, in the above-described embodiment, the case where the drive control circuit 20 is configured to increase the supply current in four stages when the power is turned on, or to increase the supply current in seven stages at a low temperature is shown. However, the drive control circuit 20 may increase the supply current step by step in two steps, three steps, or five steps or more depending on the form of use. In this case, the duration of each stage may be uniform, or may be set to become longer or shorter as the supply current I increases.

In the embodiment described above, an AC power supply is adopted as the external power supply 22, but this is not a limitation, and it is obvious that a DC power supply may be adopted.

10 LED lighting device,
11 LED lighting unit 12 Substrate 13 LED
13b LED package 13c chip 14 heat conduction sheet 15 heat radiation member 20 drive control circuit 21 temperature sensor V power supply voltage V1 first reference voltage V2 second reference voltage T ambient temperature Ta predetermined temperature Tb first reference temperature Tc second Reference temperature R1 first proportion R2 second proportion R3 third proportion

Claims

An LED illumination unit having an LED mounted on a substrate, and a drive control circuit for supplying a drive current to the LED illumination unit,
The drive control circuit, when starting to supply current to the LED lighting unit, gradually increases the amount of supplied current to a predetermined driving current value set in advance.
A temperature sensor for detecting the temperature of the LED lighting unit or its surroundings;
When the detected temperature before starting the current supply is lower than the predetermined temperature reference value, the drive control circuit is configured to start supplying the current until the supply current amount reaches the predetermined drive current value, as compared with the case where the detected temperature is not lower than the predetermined temperature reference value. The LED lighting device according to claim 1, wherein the amount of supply current is increased in a stepwise manner so as to lengthen the period.
When the detected temperature before the start of current supply is lower than the predetermined temperature reference value, the drive control circuit increases the supply current amount step by step up to the predetermined drive current value as compared to the case where the detected temperature is not the case. The LED lighting device according to claim 2, wherein the number is increased.
When the detected temperature before the start of current supply is lower than the predetermined temperature reference value, the drive control circuit is configured to increase the supply current amount step by step up to the predetermined drive current value as compared to the case where the detected temperature is not lower. The LED lighting device according to claim 2, wherein each of the periods for maintaining the supply current amount in stages is lengthened.
5. The LED illumination according to claim 1, wherein the drive control circuit lengthens a period during which the supply current amount at each stage is maintained each time the supply current amount is increased step by step. apparatus.
The drive control circuit is supplied with power from an external power source,
The drive control circuit, when the power supply voltage of the external power supply exceeds a first voltage reference value, the amount of current supplied to the LED lighting unit is a current value obtained by multiplying the predetermined drive current value by a first ratio. The LED illumination device according to any one of claims 1 to 5, wherein the LED illumination device is reduced.
A temperature sensor that detects the temperature of the LED lighting unit or its surroundings,
When the power supply voltage from the external power source exceeds the first voltage reference value and the detected temperature exceeds the first temperature reference value, the drive control circuit determines the amount of current supplied to the LED lighting unit when the detected temperature exceeds the first temperature reference value. The LED lighting device according to claim 6, wherein the LED lighting device is reduced to a current value obtained by multiplying a predetermined drive current value by a second ratio smaller than the first ratio.
When the power supply voltage of the external power supply exceeds a second reference voltage value that is larger than the first voltage reference value, the drive control circuit sets the amount of current supplied to the LED lighting unit to the predetermined drive current value. The LED lighting device according to claim 7, wherein a current value obtained by multiplying a third ratio smaller than the second ratio is reduced, or current supply to the LED lighting unit is stopped.
When the detected temperature exceeds a second temperature reference value that is greater than the first temperature reference value, the drive control circuit converts the amount of current supplied to the LED lighting unit to the predetermined drive current value to the third ratio. The LED lighting device according to claim 8, wherein the LED lighting device is reduced to a current value multiplied by or stopped from supplying current to the LED lighting unit.