JP4274536B2 - Semiconductor light emitting device - Google Patents

Description

  The present invention relates to a semiconductor light-emitting device that mainly uses white light and is used for an illumination device using a light-emitting element or a liquid crystal backlight.

  As a conventional semiconductor light emitting device, the one shown in FIG. 3 is known (for example, see Patent Document 1). 3A is a plan view of the semiconductor light emitting device, and FIG. 3B is a schematic cross-sectional view taken along the line AA of FIG. 1A. In FIG. 3B, hatching is omitted.

  The semiconductor light emitting device 1a includes a blue (B) light emitting diode element 1b, a red (R) light emitting diode element 1c, and a green (G) light emitting diode element 1d on a lead frame (or substrate) in one package. The reflector plate 1f is provided around the light emitting portion composed of the three light emitting diode elements 1b to 1d.

  As shown in FIG. 4, the driving circuit of the semiconductor light emitting device has a driving voltage applied to the three light emitting diode elements 1b to 1d from a common power supply voltage (Vcc) in series with each of the light emitting diode elements 1b to 1d. The protective resistors 1g, 1h, and 1i inserted in are controlled to have appropriate values.

  FIG. 5 shows a characteristic curve of drive current and drive voltage for each light emitting diode element.

  The driving voltage of the red light emitting diode element is greatly different from that of the green and blue light emitting diode elements even with the same driving current. Therefore, in the drive circuit, when the same power supply voltage is used, the value of the resistor 1h corresponding to the red light emitting diode element 1c is increased, thereby increasing the voltage drop.

Further, as a method of adjusting the luminance and color tone of the semiconductor light emitting device, there is a method of adjusting the luminance and color tone of the entire semiconductor light emitting device by changing the luminance by changing the current of each light emitting diode element. Other adjustment methods include a method of changing the pulse width or duty ratio when each light emitting diode element is pulse-driven with a constant peak current to each light emitting diode element, or a predetermined method using the adjustment method as described above. There is also a method of performing feedback control by monitoring with an external sensor so that the luminance and color tone are kept constant after the adjustment is completed.
Japanese Patent Laid-Open No. 10-173242

  By the way, in recent years, semiconductor light emitting devices are required to have a high output in order to ensure the function of a conventional lamp or a camera strobe. This requirement can be accommodated to some extent by increasing the current value.

  However, when the current value is increased, a decrease in light conversion efficiency and a heat generation of the semiconductor light emitting device itself become a problem due to heat generation accompanying an increase in current. In addition, as described above, the resistance related to the red light emitting diode element has a larger resistance value than the resistance related to the light emitting diode elements of the other colors. Cause. Of course, with respect to each of the green and blue light emitting diode elements having a high driving voltage, heat generation inside the light emitting diode element becomes a problem.

  As described above, increasing the drive current for higher output causes heat generation and decreases the light conversion efficiency, so that the power supply cannot be efficiently converted into the light output. That is, the amount of heat generated by the drive circuit and the light emitting diode element is lost.

  Further, since the temperature of the light emitting diode element rises with heat generation, the emission wavelength and the light output change. Thereby, even if it adjusts brightness | luminance and a color tone once, there exists a difficulty that a brightness | luminance and a color tone change after adjustment.

  Furthermore, such luminance and color tone also vary with time. Therefore, a monitoring sensor is installed outside the semiconductor light emitting device, and feedback control is performed based on the measurement result. In this case, the semiconductor light emitting device and the monitoring sensor are Since they are not integrated, there is a problem that the position is shifted due to a change with time, and the detection accuracy of the monitor varies due to dirt or dust adhesion.

  The present invention has been made in order to solve such a problem of the prior art, and it is possible to suppress heat generation accompanying an increase in drive current and to achieve high output in a state in which fluctuations in characteristics are reduced. An object of the present invention is to provide a semiconductor light emitting device that can be used.

According to another aspect of the present invention, there is provided a semiconductor light-emitting device including at least three light-emitting elements that emit red, green, and blue, respectively, wherein at least one of the red, green, and blue light-emitting elements is a semiconductor laser. One of the three light-emitting elements is a light-emitting diode element, and emits light emitted from the front surface of the semiconductor laser element near the center of the light-emitting portion composed of the at least three light-emitting elements in the direction of the emission axis. A reflecting mirror is disposed around the light emitting part, and the reflecting mirror reflects a part of the emitted light in the light emitting axis direction and reflects the remaining part of the light. dimension setting so as to reach the plate has been made, further, provided with a photodiode for receiving light output of each light emitting element, respectively, each of the photodiodes A drive circuit that controls each light emitting element so as to obtain a predetermined luminance and color tone based on the electrical output captured by the child, the drive circuit performs control by increasing / decreasing the current value of the semiconductor laser element, and the light emitting diode The element is controlled by pulse width modulation , whereby the above object is achieved.
The invention described gun specification are as follows.
According to a first aspect of the present invention, there is provided a semiconductor light-emitting device including at least three light-emitting elements that emit red, green, and blue, respectively, wherein at least one of the red, green, and blue light-emitting elements is a semiconductor. It is a laser element, and the above object is achieved by this. There are three types of light emitting elements, but the number is not limited to three. Actually, for example, a total of four light emitting devices are possible by using two green light emitting elements with low luminance. Also, red is also mass-produced for semiconductor lasers, and it is realistic that any one of these colors is red, but blue and the like may change in the future.

  In this semiconductor light emitting device, the light emitting element of at least one of the three colors is a semiconductor laser element suitable for higher output with higher luminance than the light emitting diode element. It is easy to increase the output of the semiconductor light emitting device in a state in which heat generation is suppressed and fluctuations in characteristics are reduced. In this case, since the green and blue semiconductor laser elements are under development, the use of such green and blue semiconductor laser elements becomes very expensive. Therefore, if a red semiconductor laser element that is currently mass-produced is used for the red light emitting element as in the present invention, the cost can be reduced.

The second shot light of the semiconductor light emitting device, the semiconductor light-emitting device of the first invention, in the vicinity of the semiconductor laser element, and characterized in that the photo diode for receiving the light emitted from the semiconductor laser element is disposed To do.

  In this semiconductor light emitting device, since the photodiode element receives the light emitted from the semiconductor laser element, feedback control can be realized by using the detection value of the photodiode element for monitoring. Note that the photodiode element also has a function of reflecting light emitted from the semiconductor laser element.

The third shot light of the semiconductor light emitting device, the semiconductor light-emitting device of the second invention, said photodiode element with formed on the submount, only the semiconductor laser element on the submount is die-bonded It is characterized by.

  In this semiconductor light emitting device, the amount of received light captured by the photodiode element can be adjusted by changing the position of the submount.

The fourth shot light of the semiconductor light-emitting device, reflected by the semiconductor light-emitting device of the first invention, near the center of the at least consists of three light-emitting element emitting portion, the light emitted from the front surface of the semiconductor laser device in the light-emitting axis direction The reflection mirror for making it arrange | position is arrange | positioned.

  In this semiconductor light emitting device, the output light from the front surface of the semiconductor laser element can be reflected in the direction of the light emitting axis by the reflection mirror, so that the output of the semiconductor light emitting device is further improved.

The fifth shots light of the semiconductor light emitting device, the semiconductor light-emitting device of the fourth aspect of the present invention, a photodiode element is installed in place of the reflecting mirror, and wherein the reflecting while receiving radiation by said photodiode element.

  In this semiconductor light emitting device, since the received light is reflected and reflected by the photodiode element, the function as a monitor and the function as a reflection mirror can be shared by the photodiode element, thereby achieving miniaturization. .

Remains with the sixth shot light of the semiconductor light emitting device, the semiconductor light-emitting device of the fourth aspect of the present invention, the reflector around the light emitting portion is provided, the reflection mirror reflects a part of the emitted light in the light-emitting axis direction The size is defined so that a part of the light reaches a part of the reflector.

  In this semiconductor light emitting device, the reflection mirror reflects a part of the emitted light from the semiconductor laser element in the direction of the light emitting axis and the remaining part reaches the reflecting plate, thereby further improving the output of the semiconductor light emitting device. In addition, the color mixing with other color lights is improved. At this time, the dimension definition of the reflection mirror includes setting the height and size of the reflection mirror to appropriate values and setting the distance between the reflection mirror and the semiconductor laser element to appropriate values.

Seventh rounds light of the semiconductor light emitting device, the semiconductor light-emitting device of the second invention or the fifth invention, based on the electrical output said photodiode element is captured, the as the light output of the semiconductor laser element becomes constant A drive circuit for controlling the current value of the semiconductor laser element is provided.

  In this semiconductor light emitting device, the current value of the semiconductor laser element is changed so that the light output of the semiconductor laser element is constant by replacing the light emitting diode element with the red light emitting element, which originally has a low driving voltage and low luminance, from the light emitting diode element. By performing so-called APC driving for controlling the light emission, it is possible to provide a semiconductor light-emitting device that has high luminance and whose light output does not fluctuate due to a temperature change or a change with time. Further, since the current is driven by APC, there is no voltage drop due to a resistor (protective resistor) inserted in series with the semiconductor laser element, and the device can be driven with an optimum voltage. Therefore, there is no power consumed by the voltage drop, and the temperature rise due to heat generation can be reduced.

  By the way, the temperature characteristic of the semiconductor laser element is much stricter than that of the light emitting diode element, so that another drive circuit and light output must be monitored. However, since the driving voltage of the red light emitting diode element is greatly different from the driving voltage of the light emitting diode elements of other colors in the prior art, the circuit is different from the driving circuit of the other blue or green light emitting diode elements. In addition, since a general semiconductor laser element drive circuit also performs feedback control by an external or internal monitor, it is not necessary to devise a new drive circuit for drive control. Technical semiconductor laser device drive circuits can be used.

Eighth rounds light of the semiconductor light emitting device, the semiconductor light-emitting device of the first invention, the respective light emitting elements light output incorporates a photodiode for receiving respective, predetermined on the basis of the electrical output each photodiode element is captured A driving circuit for controlling each light emitting element so as to obtain luminance and color tone is provided.

  In this semiconductor light emitting device, a photodiode element as a monitoring sensor is incorporated in the semiconductor light emitting device and integrated with the light emitting element, so that the semiconductor laser element changes with time and the semiconductor laser element and sensor change with time. It is possible to prevent positional deviation due to changes, sensor contamination, and the like.

Ninth rounds light of the semiconductor light emitting device, the semiconductor light-emitting device of the first invention, among the three light emitting elements, one is a light emitting diode element, further, a photodiode for receiving light output of each light emitting element, respectively And a driving circuit that controls each light emitting element so as to obtain a predetermined luminance and color tone based on an electrical output captured by each photodiode element. The driving circuit has a current value for the semiconductor laser element. Control by increase / decrease is performed, and control by pulse width modulation is performed on the light-emitting diode element.

  In this semiconductor light emitting device, since there is a threshold current for driving the semiconductor laser element, unlike the light emitting diode element, the current value is increased or decreased rather than the control by the pulse width modulation (PWM) for controlling the duty ratio and the pulse width. The control can be controlled more easily.

  As described above in detail, in the case of the present invention, the light emitting element of at least one of the three color light emitting elements is a semiconductor laser element suitable for high output with higher luminance than the light emitting diode element. It is easy to increase the output of the semiconductor light-emitting device in a state in which heat generation accompanying an increase in drive current is suppressed and fluctuations in characteristics are reduced. In this case, since the green and blue semiconductor laser elements are under development, the use of such green and blue semiconductor laser elements becomes very expensive. Therefore, if a red semiconductor laser element currently mass-produced is used for the red light emitting element as in the present invention, the cost can be reduced.

  The present invention will be specifically described below.

  1A and 1B are diagrams showing a semiconductor light emitting device according to an embodiment of the present invention. FIG. 1A is a plan view of the semiconductor light emitting device, and FIG. 1B is a schematic cross-sectional view taken along the line AA. In FIG. 1B, hatching is omitted.

  The semiconductor light emitting device 4a is assembled as a single package, and a blue light emitting diode element 4h and a green light emitting diode element 4g as light emitting elements are provided in a predetermined lead frame in the package. A submount 4j is formed on the lead frame 4c. A Si photodiode element 4d is formed on the submount 4j, and a red semiconductor laser element 4e as a light emitting element is die-bonded. Yes.

  An annular reflecting plate 4i is provided outside the light emitting portion having the three elements 4h, 4g, and 4e so as to surround them. The reflection plate 4i is formed so that the inside is low and the outside is high, and the incident light is reflected in the front direction (upward in the drawing) of the device 4a.

  A reflection mirror 4f is provided between the blue light-emitting diode element 4h and the green light-emitting diode element 4g and in the vicinity of the center of the light-emitting portion. The reflection mirror 4f is a front surface of the red semiconductor laser element 4e. A part of the radiated light emitted from the incident light and the remaining radiated light not reflected by the reflecting mirror 4f and the radiated light emitted from the rear of the red semiconductor laser element 4e are directed toward the front surface of the device 4a by the reflector 4i. It is reflected in the light emitting axis direction (upward in the figure). The radiated light emitted from the blue light emitting diode element 4h and the green light emitting diode element 4g is incident on the reflecting plate 4i and reflected upward. In the illustrated example, six electrical terminals 4b are provided on the side surface of the semiconductor light emitting device 4a.

  The reflection mirror 4f is dimensioned so that a part of the radiated light is reflected in the light emitting axis direction and the remaining part reaches the reflecting plate 4i. The size regulation includes setting the height and size of the reflection mirror 4f to appropriate values, and setting the distance between the reflection mirror 4f and the red semiconductor laser element 4e to appropriate values.

  FIG. 2 shows a drive circuit provided in the semiconductor light emitting device according to the embodiment of the present invention.

  This drive circuit performs the same drive as the prior art to the blue light emitting diode element 4h and the green light emitting diode element 4g. That is, the drive voltage applied to the two light emitting diode elements 4h and 4g from the common power supply voltage (Vcc) is appropriately applied by the protective resistors 4k and 4l inserted in series with the light emitting diode elements 4h and 4g, respectively. The drive is controlled so as to be a value.

  On the other hand, the red semiconductor laser element 4e is driven by receiving a part of the emitted light from the red semiconductor laser element 4e by the Si photodiode element 4d on the submount 4j and converting the current signal converted by the Si photodiode element 4d to A voltage signal is taken out by a resistor 4n connected in series to the Si photodiode element 4d, and is input to an APC (constant light output) circuit 4q through an amplifier 4p. The amount of current to the semiconductor laser element 4e is reduced by the APC circuit 4q. By increasing / decreasing, the optical output of the semiconductor laser element 4e is set to a predetermined constant value. By driving by the APC circuit 4q, the light output from the red semiconductor laser element 4e maintains a constant light output even when there is a temperature change or a change with time.

  In the case of the semiconductor light emitting device of the present embodiment configured as described above, one of the three light emitting elements is the red semiconductor laser element 4e suitable for higher output with higher luminance than the light emitting diode element, so that the drive current It is easy to increase the output of the semiconductor light-emitting device in a state where the heat generation due to the rise in the temperature is suppressed and the variation in characteristics is reduced. In this case, since the blue and green semiconductor laser elements are under development, the use of such blue and green semiconductor laser elements is very expensive. On the other hand, there is an advantage that the cost can be reduced by using the red semiconductor laser element 4e currently mass-produced. However, high output may be achieved by using semiconductor laser elements for the blue and green light emitting elements.

  In the present embodiment, since the photodiode element 4d receives the light emitted from the red semiconductor laser element 4e as an electrical signal in the vicinity of the red semiconductor laser element 4e, the detection value by the photodiode element 4d is By using it for monitoring, feedback control can be realized. Note that the photodiode element 4d also has a function of reflecting light emitted from the red semiconductor laser element 4e.

  In the present embodiment, the photodiode element 4d is formed on the submount 4j, and only the red semiconductor laser element 4e is die-bonded on the submount 4j. Therefore, the position of the submount 4j (or By changing the height, the amount of received light captured by the photodiode element 4d can be adjusted.

  In the present embodiment, the reflection mirror 4f for reflecting the emitted light from the front surface of the red semiconductor laser element 4e in the direction of the emission axis is disposed near the center of the light emitting unit. Since the emitted light from the front surface of the red semiconductor laser element 4e can be reflected in the light emitting axis direction, the output of the semiconductor light emitting device 4a can be further improved.

  In the present embodiment, the reflecting mirror 4f is dimensioned so as to reflect a part of the radiated light in the direction of the light emitting axis and allow the remaining part to reach the reflecting plate 4i. The higher output of 4a can be further improved, and the color mixing with other color lights can be improved. In addition, since the radiated light is reflected upward at the central portion of the semiconductor light emitting device 4a having the reflecting mirror 4f and the periphery having the reflecting plate 4i, the entire light emitting portion of the semiconductor light emitting device 4a shines. It is possible to improve the color mixing property with other colors of emitted light.

  In the present embodiment, as a drive circuit that controls the current value of the red semiconductor laser element 4e so that the optical output of the red semiconductor laser element 4e is constant based on the electrical output captured by the photodiode element 4d. Since the APC circuit 4q is provided, it is possible to provide the semiconductor light emitting device 4a having high luminance and whose light output does not fluctuate due to temperature change or aging change. Further, since the current is driven by the APC circuit 4q, there is no voltage drop due to the resistance (protection resistance) 4m inserted in series with the red semiconductor laser element 4e, and the driving can be performed with an optimum voltage. Therefore, there is no power consumed by the voltage drop, and the temperature rise due to heat generation can be reduced. In this case, the temperature characteristic of the semiconductor laser element is much stricter than that of the light-emitting diode element, so that another drive circuit and light output must be monitored. However, since the driving voltage of the red light emitting diode element is greatly different from the driving voltage of the light emitting diode elements of other colors in the prior art, the circuit is different from the driving circuit of the other blue or green light emitting diode elements. In addition, since a general semiconductor laser element drive circuit also performs feedback control by an external or internal monitor, it is not necessary to devise a new drive circuit for drive control. Technical semiconductor laser device drive circuits can be used.

In the above-described embodiment, the configuration includes both the reflection mirror and the photodiode element. However, the present invention is not limited to this, and the reflection mirror is omitted, and radiation light is received and reflected by the photodiode element. It is good also as a structure.
In the case of this configuration, since the radiated light is received and reflected by the photodiode element, the function as the monitor and the function as the reflection mirror can be shared by the photodiode element, thereby achieving miniaturization.

  In the embodiment described above, the Si photodiode element is formed on the submount. However, the present invention is not limited to this, and a reflection mirror may be formed instead of the Si photodiode element. By doing so, the structure can be simplified and the size can be reduced.

  In the embodiment described above, the Si photodiode element is arranged only for the red semiconductor laser element. However, the present invention is not limited to this, and the Si photodiode element is also arranged in the vicinity of the light emitting diode element. Thus, APC driving may be performed. In this case, it is preferable to control the semiconductor laser element by increasing / decreasing the current value and to control the light emitting diode element by pulse width modulation. The reason for this is that, unlike a light emitting diode element, there is a threshold current for driving a semiconductor laser element, so control by increasing or decreasing the current value is more than control by pulse width modulation (PWM) that controls the duty ratio or pulse width. This is because it can be easily controlled. In addition, it is preferable that a photodiode element as a monitoring sensor is incorporated in the semiconductor light emitting device and integrated with the light emitting element. With this configuration, it is possible to prevent a change in the semiconductor laser element with time, a positional shift due to a change with time in the semiconductor laser element and the sensor, contamination of the sensor, and the like.

  In the field of semiconductor light-emitting devices used mainly for lighting devices using light-emitting elements or liquid crystal backlights that use white light, heat generation due to an increase in drive current is suppressed, and fluctuations in characteristics are reduced. High output can be achieved in the above state.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the semiconductor light-emitting device concerning embodiment of this invention, (a) is a top view of the semiconductor light-emitting device, (b) is typical sectional drawing in the AA line. It is a figure which shows the drive circuit with which the semiconductor light-emitting device concerning embodiment of this invention was equipped. It is a figure which shows the semiconductor light-emitting device of a prior art, (a) is the top view of the semiconductor light-emitting device, (b) is typical sectional drawing in the BB line. It is a figure which shows the drive circuit with which the semiconductor light-emitting device of the prior art was equipped. It is a figure which shows the relationship between the drive current and drive voltage of a light emitting diode.

Explanation of symbols

4a Semiconductor light emitting device 4b Electrical terminal 4c Lead frame 4d Si photodiode 4e Red semiconductor laser element (light emitting element)
4f Reflective mirror 4g Green light-emitting diode element (light-emitting element)
4h Blue light emitting diode element (light emitting element)
4i Reflector 4j Submount 4k, 4l Protection resistance 4m, 4n Resistance 4p Amplifier 4q APC circuit

Claims (1)

In a semiconductor light emitting device incorporating at least three light emitting elements that emit red, green, and blue,
The light emitting element of at least one of the red, green, and blue colors is a semiconductor laser element,
One of the three light emitting elements is a light emitting diode element,
A reflection mirror for reflecting light emitted from the front surface of the semiconductor laser element in the direction of the emission axis is disposed in the vicinity of the center of the light emitting unit composed of the at least three light emitting elements.
A reflecting plate is provided around the light emitting unit, and the reflecting mirror is sized so as to reflect a part of the radiated light in the light emitting axis direction and to make the remaining part reach the reflecting plate,
In addition, a photodiode element that receives the light output of each light emitting element is provided, and a drive circuit that controls each light emitting element to have a predetermined luminance and color tone based on the electrical output captured by each photodiode element. , the drive circuit performs a control by the current value increases or decreases with respect to the semiconductor laser element, a semiconductor light emitting device characterized by performing control by pulse width modulation to the light emitting diode element.

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