JP5005967B2 - Light source system - Google Patents

Description

  The present invention relates to a light source including a plurality of light emitting elements and a light source system using the light source.

  Light emitting elements such as light emitting diodes (hereinafter referred to as “LEDs”) and semiconductor lasers are used in various light emitting devices. In particular, a light source in which a plurality of light emitting elements are integrated on a substrate is applied to a liquid crystal backlight light source, an indicator light source, a display light source, a reading sensor light source, and the like. However, a light source in which a plurality of light emitting elements are integrated has problems such as deterioration of a substrate on which the light emitting elements are mounted due to heat generated from the light emitting elements.

In order to solve the above problems, Patent Documents 1 and 2 propose light sources capable of controlling the current value input to the LED in accordance with the junction temperature (Tj) of the LED. According to this light source, an increase in Tj of the LED can be suppressed.
JP 2004-319595 A JP 2005-324656 A

  However, in the light sources disclosed in Patent Document 1 and Patent Document 2, since the input current value is uniformly controlled for all the LEDs, for example, the Tj of the LED mounted at the center of the substrate and the end of the substrate There is a possibility that the temperature distribution in the substrate surface becomes non-uniform due to a difference in Tj of the LED mounted on the board. For this reason, the light source may cause problems such as warping of the substrate.

  The present invention solves the above-described conventional problems, and provides a light source capable of making the temperature distribution in the substrate surface uniform and a light source system using the light source.

In the light source system of the present invention, a first circuit in which a plurality of first light emitting elements made of light emitting diodes are connected in series and a plurality of second light emitting elements made of light emitting diodes are mounted in series. A light source system, wherein the first light emitting element is arranged on a substrate so as to surround the second light emitting element from at least three sides, and is connected to the first circuit and the second circuit The first circuit and the second circuit can be electrically cut off, and the current control unit is configured such that a current value input to the second light emitting element is the first light emission. The difference between the junction temperature of the first light-emitting element and the junction temperature of the second light-emitting element is controlled to be about 1 ° C. by controlling the current value to be smaller than the current value supplied to the element .

According to the optical source system of the present invention, to easily emitting element temperature rises, that over other light emitting elements to reduce the making current, it is possible to uniform the temperature distribution in the substrate plane. Thereby, for example, problems such as substrate warpage can be prevented, and the life of the light source system can be extended.

  The light source of the present invention includes a substrate on which a first circuit and a second circuit are formed, at least three first light-emitting elements mounted on the first circuit, mounted on the second circuit, and a plurality of the first light-emitting elements. And at least one second light emitting element surrounded by one light emitting element.

Base material constituting the above substrate is not particularly limited, for example, or a ceramic substrate made of Al ₂ O _3, AlN or the like, a composite substrate or the like containing an inorganic filler and a thermosetting resin can be used. Or in order to improve the heat dissipation of the said board | substrate, the laminated base material which formed the electrically insulating layer (for example, the said composite base material) on the metal base material which consists of aluminum etc. can also be used. The thickness of the base material is, for example, about 0.5 to 3 mm.

  Examples of the first and second light emitting elements include a red LED that emits red light having a wavelength of 590 to 650 nm, a green LED that emits green light having a wavelength of 500 to 550 nm, and a blue light having a wavelength of 450 to 500 nm. A blue LED or the like that emits light can be used. As the red LED, for example, an LED using an AlInGaP-based material can be used. Moreover, as said green LED and said blue LED, LED using InGaAlN type material can be used, for example. In the present invention, the number of the first light emitting elements is not particularly limited as long as it is three or more. Further, the number of the second light emitting elements surrounded by the first light emitting elements is not particularly limited as long as at least one is provided.

When the light source system of the present invention is used as a white light source system, a blue LED is used as the first and second light emitting elements, and a phosphor layer is formed so as to cover the first and second light emitting elements. do it. For example, a phosphor paste that absorbs light emitted from the first and second light emitting elements and emits fluorescence is dispersed in silicone resin or the like to form a phosphor paste, and the fluorescent light is formed on the first and second light emitting elements. The phosphor layer may be formed by applying a body paste. Examples of the phosphor include phosphors emitting green light, such as garnet structure system Y ₃ (Al, Ga) ₅ O ₁₂ : Ce ³⁺ , silicate system (Ba, Sr) ₂ SiO ₄ : Eu ²⁺ , Sialon type Ca—Al—Si—O—N: Eu ²⁺ , silicate type (Sr, Ca) ₂ SiO ₄ : Eu ²⁺ , garnet structure type (Y, Gd) ₃ Al ₅ O ₁₂ : Ce ³⁺ Phosphors emitting yellow light, nitridosilicate Sr ₂ Si ₅ N ₈ : Eu ²⁺ , nitridoaluminosilicate CaAlSiN ₃ : Eu ²⁺ , oxonitridoaluminosilicate Sr ₂ Si ₄ AlON ₇ : Eu ^{2 +} , Phosphors emitting red light such as sulfide-based CaS: Eu ²⁺ can be used.

  In the light source of the present invention, the first circuit and the second circuit can be electrically cut off. Since the second light-emitting element is surrounded by the first light-emitting element, the heat dissipating property is lowered and the temperature is likely to rise as compared with the first light-emitting element. In the present invention, since the first circuit and the second circuit can be electrically disconnected, the first light-emitting element in which the current applied to the second light-emitting element that easily rises in temperature is relatively difficult to rise in temperature. The current can be controlled to be smaller than the input current. Thereby, the temperature distribution in the substrate surface can be made uniform. Therefore, according to the light source of the present invention, for example, problems such as substrate warpage can be prevented, and the life of the light source can be extended. Moreover, since a wasteful input current can be reduced, energy saving is facilitated.

  The first circuit and the second circuit are only required to be electrically cut off. For example, the first circuit and the second circuit are formed independently without being in electrical contact with each other. Alternatively, the first circuit and the second circuit may be connected via an open / close switch.

  Next, the light source system of the present invention will be described. The light source system of the present invention further includes a current control unit connected to the first and second circuits in addition to the configuration of the light source of the present invention. The current controller controls the current value input to the second light emitting element to be smaller than the current value input to the first light emitting element. Thereby, as described above, the temperature distribution in the substrate surface can be made uniform. Therefore, according to the light source system of the present invention, for example, problems such as substrate warpage can be prevented, and the life of the light source system can be extended. Moreover, since a wasteful input current can be reduced, energy saving is facilitated. In addition, the said current control part can use the arithmetic processing unit etc. which are used for a computer, for example.

  In the light source system of the present invention, the current control unit determines a current value input to each of the first and second light emitting elements based on a voltage value applied to each of the first and second light emitting elements. It may be a light source system to be controlled. When the light source system is turned on, the voltage value applied to each of the first and second light emitting elements varies depending on the degree of temperature rise of the first and second light emitting elements. By controlling the current value supplied to each based on the applied voltage value, it becomes easier to make the temperature distribution in the substrate surface uniform.

  Embodiments of the present invention will be described below with reference to the drawings. Note that in the drawings to be referred to, components having substantially the same function are denoted by the same reference numerals, and redundant description may be omitted.

  FIG. 1 is a schematic plan view of a light source according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a light source system according to an embodiment of the present invention using the light source shown in FIG. In FIG. 1, the circuit is omitted.

  As shown in FIG. 1, the light source 1 includes a substrate 11, twelve first light emitting elements 13 disposed in a region X on the substrate 11, and four second light sources disposed in a region Y on the substrate 11. The light emitting element 15 and 20 third light emitting elements 17 disposed in the region Z on the substrate 11 are included. The second light emitting element 15 is surrounded by the first light emitting element 13, and the first light emitting element 13 is surrounded by the third light emitting element 17. As shown in FIG. 2, the first to third light emitting elements 13, 15, and 17 are mounted on the first to third circuits 12, 14, and 16, respectively. The first to third circuits 12, 14, and 16 are each provided with a constant current control unit 18 that maintains the current flowing through the circuits at a constant value. Further, the first to third circuits 12, 14, and 16 are formed so as to be electrically cut off from each other. Reference numeral 20 is a terminal provided in each of the first to third circuits 12, 14, and 16.

  As shown in FIG. 2, the light source system 2 includes the light source 1 described above and a central control unit 19 connected to each constant current control unit 18. Based on the voltage value applied to each of the first and second light emitting elements 13 and 15, the central control unit 19 converts the current value input to the second light emitting element 15 into the current input to the first light emitting element 13. Control to be smaller than the value. Thereby, since the temperature distribution in the surface of the substrate 11 can be made uniform, problems such as warpage of the substrate 11 can be prevented. The central control unit 19 corresponds to the “current control unit” described above.

  Further, the central control unit 19 inputs the current value input to the first light emitting element 13 to the third light emitting element 17 based on the voltage value applied to each of the first and third light emitting elements 13 and 17. The current is controlled to be smaller than the current value. Thereby, since the temperature distribution in the surface of the substrate 11 can be made more uniform, problems such as warpage of the substrate 11 can be reliably prevented.

  Although the light source and the light source system of the present invention have been described above, the present invention is not limited to the above embodiment. For example, as shown in FIG. 3, the region X does not have to surround all around the region Y. Further, as shown in FIG. 4, the region Y may be surrounded by four divided regions X.

  Examples of the present invention will be described below. The present invention is not limited to this example.

As an example of the present invention, the light source system shown in FIG. 2 was produced using the light source shown in FIG. As the substrate, a substrate made of Al ₂ O ₃ (24 mm × 30 mm, thickness: 1 mm) was used. As the first to third light emitting elements, blue LEDs (1 mm × 1 mm, thickness: 300 μm) made of a GaN-based material were used.

(Relationship between junction temperature and voltage)
The light source system of the above embodiment was placed in a thermostat maintained at 19 ° C., 38 ° C., 57 ° C., and 73 ° C., and left for 1 hour. Each element was selected arbitrarily, the temperature of the main surface on the light extraction side of each light emitting element was measured, and the value was defined as the junction temperature (Tj). At the same time, a current of 1 mA was applied to each of the first to third light emitting elements, and the voltage applied to each light emitting element (voltage applied per one) was measured. The results are shown in FIG. As shown in FIG. 5, regarding the relationship between Tj and voltage, there was no difference between the first to third light emitting elements.

(Relationship between input current value and Tj)
Each of the first to third light emitting elements of the light source system of the above embodiment was turned on for 1 hour by applying the same current (50 mA, 100 mA, 150 mA, 200 mA and 250 mA), and then each light emitting element. The voltage applied to each (voltage applied per one) was measured, and Tj was calculated from the value. The results are shown in FIG. As shown in FIG. 6, for the third light emitting element, Tj was relatively stable, but for the first and second light emitting elements, Tj tended to increase as the input current value increased. . Therefore, when the central control unit calculates the Tj in the same manner as described above after supplying currents of 150 mA, 125 mA and 200 mA to the first to third light emitting elements and lighting them for 1 hour, these Tj are calculated. The difference was about 1 ° C. In addition, when the central controller calculated the Tj in the same manner as described above after applying currents of 150 mA, 120 mA and 150 mA to the first to third light emitting elements and lighting them for 1 hour, respectively, The difference in Tj was about 1 ° C.

  The light source and the light source system of the present invention are used, for example, in lighting devices used for general lighting, production lighting (sign lights, etc.), automotive lighting (especially headlights), large street displays, projectors, etc. This is useful for display devices and the like.

It is a schematic plan view of the light source which concerns on one Embodiment of this invention. It is a schematic block diagram of the light source system which concerns on one Embodiment of this invention using the light source shown in FIG. It is a schematic plan view of the light source which shows the modification of FIG. It is a schematic plan view of the light source which shows the modification of FIG. It is a graph which shows the relationship between junction temperature and voltage in the light source system of the Example of this invention. It is a graph which shows the relationship between the input electric current value and junction temperature in the light source system of the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Light source system 11 Board | substrate 12 1st circuit 13 1st light emitting element 14 2nd circuit 15 2nd light emitting element 16 3rd circuit 17 3rd light emitting element 18 Constant current control part 19 Central control part 20 Terminal

Claims (3)

A first circuit in which a plurality of first light emitting elements made of light emitting diodes are connected in series and mounted; and a second circuit in which a plurality of second light emitting elements made of light emitting diodes are connected in series;
The light source system, wherein the first light emitting element is arranged on a substrate so as to surround the second light emitting element from at least three sides,
A current control unit connected to the first circuit and the second circuit;
The first circuit and the second circuit can be electrically disconnected,
The current control unit controls the current value input to the second light emitting element to be smaller than the current value input to the first light emitting element, so that the junction temperature of the first light emitting element and the second A light source system characterized in that a difference from a junction temperature of a light emitting element is about 1 ° C. A third circuit in which a plurality of third light emitting elements made of light emitting diodes are connected in series and mounted;
The third light emitting element is arranged on the substrate so as to surround the first light emitting element from at least three sides,
The third circuit is connected to the current control unit, and can be electrically disconnected from the first circuit and the second circuit,
The current control unit controls the current value input to the third light emitting element to be larger than the current value input to the first light emitting element, so that the junction temperature of the third light emitting element and the first The light source system according to claim 1, wherein a difference from a junction temperature of the light emitting element is about 1 ° C.   3. The light source system according to claim 1, wherein current values of the first light emitting element, the second light emitting element, and the third light emitting element are controlled based on voltage values applied to the respective light emitting elements. .

Images