JP2008124303A - Drive controller of semiconductor light-emitting element, projection display device having drive controller, and method of them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology which can estimate a temperature of a semiconductor light-emitting element accurately. <P>SOLUTION: A plurality of power supply processings which contain a first power supply processing in which a current flowing in the semiconductor light-emitting element is greater than zero, and a second power supply processing in which a current is greater than the first power supply processing are repeatedly executed, respectively. Then, in at least each of the first power supply processing and the second power supply processing, at least one of a current value and a voltage value is measured. Further, the temperature of the semiconductor light-emitting element is estimated by utilizing a measurement result in each of a plurality of operating states in which a current is greater than zero. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a drive control device for a semiconductor light emitting element, a projection display device having the drive control device, and methods thereof.

  Conventionally, a semiconductor light emitting element has been used as a light source. As such a semiconductor light emitting element, for example, a light emitting diode (hereinafter also referred to as “LED”) is used. In recent years, a technique of using an LED as a light source of a projection display device is also known. Since such a device requires a large amount of light, a large amount of power is supplied to the LED. As a result, the temperature of the LED tends to increase. On the other hand, when the temperature of the LED (particularly the junction temperature) rises to an excessively high temperature, the LED is greatly deteriorated. In order to suppress an excessive temperature rise while maintaining a large amount of light, it is important to acquire the temperature of the LED with high accuracy. Here, a technique for calculating the junction temperature of an LED with reference to the current-voltage characteristics of the LED is known.

JP 2005-115350 A

  However, since there are individual differences in the characteristics of the semiconductor light emitting device, the temperature accuracy may decrease. Such a problem is not limited to the case where the semiconductor light emitting element is used as the light source of the projection display apparatus, but is a problem common to various apparatuses using the semiconductor light emitting element as the light source.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a technique capable of accurately estimating the temperature of a semiconductor light emitting element.

  In order to solve at least a part of the problems described above, a drive control device according to a first aspect of the present invention is a drive control device that drives a semiconductor light emitting element, and a current flowing through the semiconductor light emitting element is greater than zero. Repetitively executing each of the plurality of power supply processes including one power supply process and a second power supply process in which a current flowing through the semiconductor light-emitting element is larger than the first power supply process. A power supply unit for supplying variable power to the semiconductor light emitting element and lighting the semiconductor light emitting element; a sensor for measuring at least one of a current value flowing through the semiconductor light emitting element and a voltage value applied to the semiconductor light emitting element; A current flowing through the semiconductor light emitting element including an operation state in which the first power supply process is executed and an operation state in which the second power supply process is executed And a temperature estimation unit that estimates a temperature of the semiconductor light emitting device by using the measurement result of the sensor in each of the plurality of operating states greater than zero.

  According to this drive control device, the temperature of the semiconductor light emitting element is estimated using the measurement results of the sensor in each of a plurality of operating states in which the current flowing through the semiconductor light emitting element is greater than zero. Can be estimated with high accuracy.

  In the drive control apparatus, the temperature estimation unit may obtain ratio information correlated with a ratio between a change in current value and a change in voltage value in a range where the current flowing through the semiconductor light emitting element is greater than zero. While determining using a measurement result, it is good also as estimating the temperature of the said semiconductor light-emitting device using the said ratio information.

  According to this configuration, the temperature of the semiconductor light emitting element is estimated using ratio information correlated with the ratio between the change in the current value and the change in the voltage value in the range where the current flowing through the semiconductor light emitting element is greater than zero. Therefore, the temperature of the semiconductor light emitting element can be estimated with high accuracy.

  In each of the drive control devices, the power supply unit includes: a constant current power source that supplies a constant current according to a current setting value to the semiconductor light emitting element; and a current setting unit that controls the current setting value, In the first power supply process, the current setting unit sets the current set value to a predetermined first set value that is greater than zero, and in the second power supply process, the current setting unit includes the first set value. The current setting value may be set to a larger predetermined second setting value, and the sensor may include a voltage sensor that measures a voltage value applied to the semiconductor light emitting element.

  According to this configuration, it is easy to suppress an excessive increase in the current flowing through the semiconductor light emitting element.

  In the drive control device, the power supply unit includes: a constant current power source that supplies a constant current according to a current setting value to the semiconductor light emitting element; and a current setting unit that controls the current setting value. In the 1 power supply process, the current setting unit sets the current set value to a predetermined first set value greater than zero, and in the second power supply process, the current setting unit determines that the current set value is greater than the first set value. The current setting value is set to a large predetermined second setting value, the sensor includes a voltage sensor that measures a voltage value applied to the semiconductor light emitting element, and the temperature estimation unit includes the ratio information as the ratio information, A difference between a first voltage that is a measurement result of the voltage sensor in the first power supply process and a second voltage that is a measurement result of the voltage sensor in the second power supply process may be used.

  According to this configuration, it is easy to suppress an excessive increase in the current flowing through the semiconductor light emitting element. Furthermore, the temperature can be easily estimated.

  A projection display device according to a second aspect of the present invention is a projection display device that displays an image based on image data, and includes a semiconductor light emitting element used as a light source and light emitted from the semiconductor light emitting element. A projection light conversion unit that converts image projection light for projecting an image; an image processing unit that controls the projection light conversion unit based on image data; and the first aspect that drives the semiconductor light emitting element. The drive control apparatus which concerns, and the temperature corresponding | compatible process part which performs the process which suppresses that the temperature estimated by the said drive control apparatus exceeds the predetermined upper limit is provided.

  According to this projection display apparatus, since the process for suppressing the temperature of the semiconductor light emitting element accurately estimated from exceeding the predetermined upper limit value is executed, the semiconductor light emitting element is deteriorated due to the high temperature. Can be suppressed appropriately.

  In the projection display device, the power supply unit supplies the fluctuating power to the semiconductor light emitting element during display of the image, and the temperature estimation unit converts the temperature of the semiconductor light emitting element according to the supply of the fluctuating power. May be estimated.

  According to this configuration, it is possible to accurately estimate the temperature of the semiconductor light emitting element even during image display.

  The present invention can be realized in various forms. For example, a semiconductor light emitting element driving method and driving apparatus, a projection display device having a semiconductor light emitting element as a light source, a control method therefor, and a semiconductor as a light source Illumination device having a light emitting element and control method thereof, computer program for realizing the function of the method or device, recording medium recording the computer program, data signal including the computer program and embodied in a carrier wave, Or the like.

Next, embodiments of the present invention will be described in the following order based on examples.
A. First embodiment:
B. Second embodiment:
C. Third embodiment:
D. Fourth embodiment:
E. Variation:

A. First embodiment:
FIG. 1 is an explanatory diagram showing a projector 200 as an embodiment of the present invention. The projector 200 includes three light-emitting diodes 210R, 210G, and 210B (hereinafter also referred to as “LEDs 210R, 210G, and 210B”) that emit light of three colors, red R, green G, and blue B, and these three colors. Liquid crystal light valves 240R, 240G, and 240B that respectively modulate the three color lights, a cross dichroic prism 250 that synthesizes the modulated three color lights, and a projection lens system that projects the synthesized three color lights onto the screen SC. 260, a cooling fan 400 that sends cooling air to each of the three LEDs 210R, 210G, and 210B, and a control unit 300 that controls the entire projector 200.

  The liquid crystal light valve 240R for red converts light incident from the red LED 210R as a light source into light for projecting an image (corresponding to “image projection light” in the claims). The same applies to “green liquid crystal light valve 240G, green LED 210G” and “blue liquid crystal light valve 240B, blue LED 210B”. That is, each of the three liquid crystal light valves 240R, 240G, and 240B corresponds to a “projection light conversion unit” in the claims. Note that such a projection light conversion unit is not limited to a liquid crystal light valve, and projects an image of light emitted from a light emitting diode by modulating the intensity of light at each pixel position in the projected image. It is possible to employ various devices that convert image projection light for the purpose. For example, DMD (Digital Micromirror Device, trademark of TI (Texas Instruments)) may be used.

  FIG. 2 is an explanatory diagram illustrating the configuration of the control unit 300. The control unit 300 includes three power supply modules 310R, 310G, and 310B, three current setting value monitors 320R, 320G, and 320B, three voltage sensors 330R, 330G, and 330B, a temperature estimation module 340, and a temperature corresponding process. A module 350 and an image processing module 360 are provided.

  The three power supply modules 310R, 310G, and 310B supply power to the three light emitting diode light sources 210R, 210G, and 210B, respectively. The red power supply module 310R includes a constant current power source 314R and a current setting module 312R. The constant current power source 314R maintains the current flowing through the red LED 210R at the current set value according to the current set value set by the current setting module 312R. As will be described later, the current setting module 312R varies the current setting value. Thereby, the fluctuating power is supplied to the red LED 210R. The configurations and operations of the power supply modules 310G and 310B for the other colors are the same as those of the power supply module 310R for red.

  The three current setting value monitors 320R, 320G, and 320B acquire the current current setting values of the three power supply modules 310R, 310G, and 310B, respectively, and output the acquired current setting values to the temperature estimation module 340. It can also be said that the output information (current set value) is information for specifying the current I. In this manner, the three current set value monitors 320R, 320G, and 320B each function as a current specifying unit that specifies the current current I.

  The three voltage sensors 330R, 330G, and 330B measure the voltages applied to the three LEDs 210R, 210G, and 210B, respectively, and output the measured voltage values to the temperature estimation module 340.

  The temperature estimation module 340 estimates the temperature of each of the three LEDs 210R, 210G, and 210B based on the information acquired from the three current setting value monitors 320R, 320G, and 320B and the three voltage sensors 330R, 330G, and 330B. To do. Details of the temperature estimation will be described later.

  The temperature correspondence processing module 350 executes processing for suppressing the estimated temperatures Ter, Teg, and Teb of the LEDs 210R, 210G, and 210B from exceeding predetermined upper limit values of the LEDs 210R, 210G, and 210B, respectively. In the first embodiment, the temperature correspondence processing module 350 increases the driving speed of the cooling fan 400 (FIG. 1) as the estimated temperature is closer to the upper limit value. As a result, the higher the estimated temperature of each LED 210R, 210G, 210B, the stronger the LED 210R, 210G, 210B is cooled, so that the estimated temperature of each LED 210R, 210G, 210B is suppressed from exceeding the respective upper limit value. The

  The image processing module 360 controls the liquid crystal light valves 240R, 240G, and 240B based on image data supplied from an external device (not shown) (for example, a personal computer or a DVD player). As a result, an image represented by the image data is displayed on the screen SC (FIG. 1).

  In the first embodiment, each component of the control unit 300 is configured by an electronic circuit that realizes the function of each component. Various configurations can be adopted as the configuration of the electronic circuit. As an electronic circuit that performs data processing (for example, the temperature estimation module 340), for example, a dedicated electronic circuit such as ASIC (Application Specific Integrated Circuits) may be employed.

  FIG. 3 is a graph illustrating temperature estimation. This graph shows the current-voltage characteristics of the LED. The horizontal axis indicates the voltage V applied to the LED, and the vertical axis indicates the current I flowing through the LED. The voltage V indicates a forward voltage, and the current I indicates a forward current. As shown in the figure, the current I increases rapidly as the voltage V increases. However, when the voltage V is smaller than a certain threshold value Vt larger than zero, the current I is almost zero. This is because the voltage threshold Vt required to pass current through the LED is greater than zero.

  In addition, three graphs G1, G2, and G3 are shown in this graph. The order in which the ratio (slope) of the change of the current I with respect to the change of the voltage V is large is the order of the first graph G1, the second graph G2, and the third graph G3. These graphs G1, G2, and G3 show the same LED characteristics. However, the first graph G1 shows a case where the LED temperature (junction temperature) is higher than the second graph G2, and the third graph G3 shows a case where the LED temperature is lower than the second graph G2. Thus, in the example of FIG. 3, the higher the temperature, the larger the ratio (slope) of the change in current I with respect to the change in voltage V. By utilizing such characteristics, the LED temperature (junction temperature) can be estimated from the ratio between the change in voltage V and the change in current I.

  In the graph of FIG. 3, the slopes k1, k2, and k3 of the three graphs G1, G2, and G3 are shown. These slopes k1, k2, and k3 all represent slopes (ratio of change in current I with respect to change in voltage V) derived from two operating points at which current I is greater than zero. Here, the operating point means a combination of the current I and the voltage V. That is, the operation point represents the operation state of the LED. One operation point is represented by one point in the current-voltage characteristic graph. In the example of FIG. 3, the slopes k1 and k2 from the operating point where the current I is a predetermined first current IL larger than zero and the operating point where the current I is a predetermined second current IH larger than the first current IL. , K3 is determined. In the first embodiment, the temperature estimation module 340 (FIG. 2) estimates the LED temperature from such an inclination.

  FIG. 4 is a graph showing a correspondence relationship between the estimated temperature Te and the gradient k. As described above, the higher the temperature, the larger the ratio (inclination k) of the change in the current I to the change in the voltage V. Therefore, in the graph of FIG. 4, the estimated temperature Te is set so as to increase as the slope k increases. The temperature estimation module 340 (FIG. 2) estimates the temperature of each of the three LEDs 210R, 210G, and 210B according to such a correspondence relationship. Such correspondence is experimentally determined in advance for each LED 210R, 210G, 210B.

  FIG. 5 is a graph showing individual differences in current-voltage characteristics. In this graph, two graphs GA and GB are shown. These two graphs GA and GB show the characteristics of two LEDs of the same type, respectively. The LED temperature is the same. By the way, even if it is LED of the same kind, an individual difference may arise in the voltage threshold value Vt. Two graphs GA and GB in FIG. 5 respectively show the characteristics of two LEDs having such individual differences. In the example of FIG. 5, the first voltage threshold VtA of the first graph GA is smaller than the second voltage threshold VtB of the second graph GB. Further, since the temperatures of the LEDs are the same, the slope in the range where the current I is greater than zero (the ratio of the change in the current I to the change in the voltage V) is substantially the same between the two graphs GA and GB.

  In the graph of FIG. 5, the slopes kA and kB of the two graphs GA and GB are shown. These inclinations kA and kB are calculated in the same manner as in the example of FIG. Further, these inclinations kA and kB are substantially the same. On the other hand, the slopes jA and jB of the comparative example are also shown in this graph. These comparison slopes jA and jB are slopes derived from the operating point at which the current I is zero and the operating point at which the current I is the second current IH. Here, as an operating point where the current I is zero, an operating point where the voltage V is zero is typically used.

  The difference dVH of the voltage V between the two graphs GA and GB when the current I is the current value IH appears as a difference between the comparison gradients jA and jB. That is, although the actual temperature is the same, the slope jA of the first graph GA is larger than the slope jB of the second graph GB. Therefore, if the temperature is estimated using the comparative inclinations jA and jB, the accuracy of temperature estimation may be reduced due to individual differences. For example, in the example of FIG. 5, there is a possibility that the difference between the temperature estimated from the first graph GA having a large comparison gradient jA and the temperature estimated from the second graph GB having a small gradient jB in the comparative example may be large. is there. Such a problem can occur when an operating point where the current I is zero is used regardless of the magnitude of the voltage V at that operating point (I = 0). Such a problem may also occur when using an operating point where the current I is zero and estimating the temperature using three or more operating points.

  On the other hand, the slopes kA and kB in the embodiment are substantially the same when the temperature is the same regardless of the individual difference between the voltage thresholds VtA and VtB. As a result, the temperatures estimated from the two graphs GA and GB are almost the same.

  Thus, in the estimation method of the first embodiment, the temperature of the LED is estimated using two operating points in a range where the current I is larger than zero without using the operating point where the current I is zero. The As a result, the influence of individual differences among LEDs can be alleviated, and the estimation accuracy of LED temperatures can be increased. In particular, in the estimation method of the first embodiment, the temperature of the LED is estimated using the ratio between the change in the current I and the change in the voltage V in a range where the current is greater than zero. As a result, it is possible to improve the estimation accuracy of the LED temperature.

  FIG. 6 is a flowchart showing a procedure of control processing executed by the control unit 300 (FIG. 2). This flowchart shows a control process related to the LEDs 210R, 210G, and 210B. When displaying an image, the control unit 300 executes processing according to this flowchart. This control process is executed for each of the RGB colors. In the following description, a process related to red R will be described as a representative process.

  In the first step S100, the power supply module 310R (FIG. 2) starts supplying variable power to the red LED 210R. The red LED 210R is lit by the supply of this variable power.

  FIG. 7 is a timing chart for explaining a drive signal (power) supplied to the red LED 210R by the power supply module 310R (FIG. 2). The horizontal axis indicates time, and the vertical axis indicates current I and voltage V.

  The power supply module 310R (FIG. 2) generates a first power supply process P1 for maintaining the current I at a predetermined first current ILr larger than zero, and a current I for a predetermined second current IHr larger than the first current ILr. The second power supply process P2 to be maintained is repeatedly executed. Specifically, the current setting module 312R maintains the current set value at the first current ILr only during the first time TLr (P1), and the current set value is maintained at the second current IHr only during the second time THr. The process of maintaining (P2) is repeatedly executed. The constant current power source 314R adjusts the voltage V so that the current I is maintained at the current set value. In the example of FIG. 7, in the first power supply process P1, the voltage V is maintained at a relatively small first voltage VLr, and in the second power supply process P2, the voltage V is maintained at a relatively large second voltage VHr. . As described above, the power supply module 310R supplies the fluctuating power to the red LED 210R.

  The power supply module 310R adjusts the brightness (light quantity) of the red LED 210R by adjusting at least one of the pulse width (second time THr) and the pulse interval (first time TLr). Such control is also called PWM control (Pulse Width Modulation Control). The brightness adjustment of the red LED 210R is performed according to a user instruction to the control unit 300, for example.

  Further, both the first current ILr and the second current IHr are set in advance to a value smaller than a predetermined maximum rated current of the red LED 210R. As a result, it is possible to suppress an excessive current from flowing through the red LED 210R, and thus it is possible to suppress the red LED 210R from being deteriorated due to the excessive current.

  Thereafter, the power supply module 310R continues to supply variable power.

  In the next step S110 of FIG. 6, the temperature estimation module 340 (FIG. 2) acquires the voltage V when the current I is the first current ILr. The temperature estimation module 340 receives the current current set value from the current set value monitor 320R and receives the current voltage V from the voltage sensor 330R. In step S110, the temperature estimation module 340 acquires the voltage V when the current set value is the first current ILr. In this embodiment, the acquired voltage V is the first voltage VLr (FIG. 7).

  In the next step S120, the temperature estimation module 340 acquires the voltage V when the current I is the second current IHr. Specifically, the temperature estimation module 340 acquires the voltage V when the current set value is the second current IHr. In this embodiment, the acquired voltage V is the second voltage VHr (FIG. 7).

  In the next step S130, the temperature estimation module 340 estimates the temperature of the red LED 210R. This temperature estimation is performed according to the method described with reference to FIGS. The temperature estimation module 340 calculates the slope k from the operating point (ILr, VLr) in the first power supply process P1 and the operating point (IHr, VHr) in the second power supply process P2. Then, the temperature estimation module 340 determines the estimated temperature Ter of the red LED 210R from the inclination k according to the correspondence relationship shown in FIG.

  In the first embodiment, the current I is repeatedly set to each of two predetermined values ILr and IHr. That is, the current difference between the two operating points is a predetermined value. As a result, the slope k is uniquely determined from the voltage difference between the two operating points. Therefore, the temperature estimation module 340 may estimate the temperature from the voltage difference (VHr−VLr) without calculating the slope k. FIG. 8 is a graph showing the correspondence between the voltage difference dV and the estimated temperature Ter. The horizontal axis indicates the voltage difference dV, and the vertical axis indicates the estimated temperature Ter. In the graph of FIG. 8, the estimated temperature Ter is set so as to decrease as the voltage difference dV increases. The temperature estimation module 340 may determine the estimated temperature Ter from the voltage difference dV according to this correspondence. In this example, since it is not necessary to calculate the slope k, the temperature can be estimated easily. And the structure of the temperature estimation module 340 can be simplified. The voltage difference dV is correlated with the ratio between the change in voltage V and the change in current I. Therefore, the voltage difference dV corresponds to “ratio information” in the claims.

  Note that the correspondence between the slope k and the estimated temperature Ter, and the correspondence between the voltage difference dV and the estimated temperature Ter are experimentally determined in advance. In addition, the correspondence actually used is stored in advance in a memory (not shown) included in the temperature estimation module 340. Various formats can be adopted as the format for defining the correspondence. For example, the correspondence may be defined by a function in which the input value is the slope k (or voltage difference dV) and the output value is the estimated temperature Ter. Further, a correspondence relationship between the slope k (or voltage difference dV) and the estimated temperature Ter may be determined using a so-called lookup table.

  In the case where the temperature is estimated from the difference dV between the two voltages VHr and VLr as in the example illustrated in FIG. 8, the temperature estimation module 340 also includes information for specifying the current I (in the first embodiment, the current setting value). ) Is preferably used for temperature estimation. Specifically, the voltage value received from the voltage sensor 330R is specified using the information for specifying the current I, which of the first current ILr and the second current IHr corresponds to the current value. It is preferable to do. In this way, erroneous estimation of temperature can be suppressed.

  In the next step S140 of FIG. 6, the temperature estimation module 340 (FIG. 2) outputs the determined estimated temperature Ter to the temperature corresponding processing module 350. The temperature handling processing module 350 executes processing for suppressing the received estimated temperature Ter from exceeding a predetermined upper limit value of the red LED 210R. In the first embodiment, the temperature corresponding processing module 350 changes the driving speed of the cooling fan 400 (FIG. 1) according to the estimated temperature Ter. The temperature corresponding processing module 350 increases the driving speed of the cooling fan 400 as the estimated temperature Ter is closer to the upper limit value. As a result, the higher the estimated temperature Ter is, the stronger the red LED 210R is cooled, so that the temperature of the red LED 210R is suppressed from exceeding the upper limit value. Various temperatures can be adopted as the upper limit value. However, it is preferable to employ a temperature lower than the maximum rated temperature of the red LED 210R as the upper limit value.

  The processes in steps S110 to S140 described above are repeatedly executed.

  As described above, the processing relating to red R has been described as a representative processing, but the processing in steps S100 to S130 is executed for each color of red R, green G, and blue B. The process for green G and blue B is the same as the process for red R described above. However, various settings (for example, the correspondence between the slope k and the estimated temperature, the correspondence between the voltage difference dV and the estimated temperature, the current setting value, the pulse width, the pulse interval, etc.) are set for each color. To be determined. For example, the first current ILg and the second current IHg related to the green G are preset to values smaller than the maximum rated current of the green LED 210G, and the first current ILb and the second current IHb related to the blue B are set to the maximum ratings of the blue LED 210B. A value smaller than the current is preset. Then, the temperature estimation module 340 determines the estimated temperature Teg of the green LED 210G from the two operation points related to the green G (“ILg, VLg”, “IHg, VHg”), and the two operation points related to the blue B (“ILb, VLb ”,“ IHb, VHb ”), the estimated temperature Teb of the blue LED 210B is determined.

  In step S140, the temperature processing module 350 (FIG. 2) sets the cooling fan 400 so that the estimated temperatures Ter, Teg, and Teb of all the LEDs 210R, 210G, and 210B do not exceed the predetermined upper limit values. To drive. That is, the temperature correspondence processing module 350 increases the drive speed of the cooling fan 400 in response to at least some of the three estimated temperatures Ter, Teg, and Teb approaching the corresponding upper limit values.

  As described above, in the first embodiment, the temperature estimation module 340 uses the value representing the ratio between the change in the current I and the change in the voltage V in the range where the current I is greater than zero to each LED 210R, Since the temperatures of 210G and 210B are estimated, it is possible to alleviate the influence of individual differences of LEDs and to increase the estimation accuracy of LED temperatures.

  In the first embodiment, the constant current power supplies 314R, 314G, and 314B are used to supply power to the LEDs 210R, 210G, and 210B, so that it is possible to easily suppress an excessive increase in the current flowing through the LEDs.

  Further, in the first embodiment, the temperature correspondence processing module 350 executes a process for suppressing the estimated temperatures of the respective LEDs 210R, 210G, and 210B from exceeding the respective upper limit values, so that the LEDs 210R, 210G, and 210B have a high temperature. Deterioration can be suppressed. In addition, it is preferable to employ | adopt the temperature lower than the maximum rated temperature of each LED210R, 210G, 210B as an upper limit of each RGB color.

  In the first embodiment, in the first power supply process P1 (FIG. 7) where the current I is relatively small, a current I larger than zero flows through the LED. Then, the power supply modules 310R, 310G, and 310B (FIG. 2) repeatedly execute the first power supply process P1 and the second power supply process P2 (FIG. 7). As a result, both image display and temperature estimation can be executed in parallel. That is, two operating points for temperature estimation can be acquired while the LED is emitting light for displaying an image without affecting the display image. In other words, two operation points can be acquired during image display.

  Therefore, in the first embodiment, the image processing module 360 (FIG. 2) controls the liquid crystal light valves 240R, 240G, and 240B based on the image data independently of the control processing shown in FIG. In other words, the control process shown in FIG. 6 is executed during image display. As a result, the temperature estimation module 340 can accurately estimate the temperatures of the LEDs 210R, 210G, and 210B even during the display of an image. That is, accurate temperature estimation is possible even when image display is performed continuously. And even if the temperature corresponding | compatible process module 350 is displaying the image, it can suppress that the estimated temperature of each LED210R, 210G, 210B exceeds each upper limit. In addition, you may perform acquisition of an operating point (FIG. 6: step S110, S120) when the image is not displayed, ie, when LED for emitting the light for displaying an image is not emitted.

B. Second embodiment:
FIG. 9 is an explanatory diagram showing another embodiment of the control unit of the projector 200 (FIG. 1). There are two differences from the control unit 300 shown in FIG. The first difference is that the three current set value monitors 320R, 320G, and 320B are omitted. The second difference is that the temperature estimation module 340x estimates the temperature using the measurement result of the voltage V without using the information specifying the current I. Other components of the control unit 300x are the same as those of the control unit 300 shown in FIG.

  The power supply module 310R repeatedly sets the current flowing through the red LED 210R to each of two predetermined values ILr and IHr, as in the first embodiment described above. The voltage sensor 330R repeatedly outputs a relatively low measurement result VLr and a relatively high measurement result VHr. Therefore, the temperature estimation module 340x executes the processing of steps S110 and S120 in FIG. 6 by acquiring the latest two measurement results VLr and VHr without considering the current I. The other steps of the control process of FIG. 6 are executed in the same manner as in the first embodiment. In step S130, the temperature estimation module 340x determines the estimated temperature Ter by using the difference between two different measurement results VHr and VLr without specifying the current corresponding to each measurement result VLr and VHr. can do. At this time, the temperature estimation module 340x determines the estimated temperature Ter according to the correspondence shown in FIG. Similarly, temperature estimation is performed for the other colors (green G, blue B).

  As described above, in the second embodiment, the temperature estimation is performed without using the information specifying the current current I. Therefore, the current set value monitors 320R, 320G, and 320B can be omitted. As a result, the configuration of the control unit 300x can be simplified.

C. Third embodiment:
FIG. 10 is an explanatory diagram showing another embodiment of the control unit of the projector 200 (FIG. 1). The only difference from the control unit 300 shown in FIG. 2 is that three current sensors 320aR, 320aG, and 320aB are provided instead of the three current set value monitors 320R, 320G, and 320B. Other components of the control unit 300a are the same as those of the control unit 300 shown in FIG.

  The three current sensors 320aR, 320aG, and 320aB measure the currents flowing through the three LEDs 210R, 210G, and 210B, respectively, and output the measured current values to the temperature estimation module 340. The temperature estimation module 340 performs the processes of steps S110 and S120 in FIG. 6 based on the current values received from the current sensors 320aR, 320aG, and 320aB. The other steps of the control process of FIG. 6 are executed in the same manner as in the first embodiment.

  As described above, in the third embodiment, in addition to the voltage V applied to the LED, the current I flowing through the LED is actually measured, so that the slope k can be calculated with high accuracy. As a result, the temperature estimation accuracy can be increased.

D. Fourth embodiment:
FIG. 11 is an explanatory diagram showing another embodiment of the control unit of the projector 200 (FIG. 1). Unlike the control unit 300 shown in FIG. 2, the control unit 300b uses a constant voltage power supply instead of a constant current power supply. There are three differences from the control unit 300 shown in FIG. The first difference is that the power supply modules 310bR, 310bG, 310bB have voltage setting modules 312bR, 312bG, 312bB and constant voltage power supplies 314bR, 314bG, 314bB, respectively, instead of the current setting module and the constant current power supply. It is a point. The second difference is that current sensors 320bR, 320bG, and 320bB are provided instead of the current setting modules 312R, 312G, and 312B. The third difference is that voltage set value monitors 330bR, 330bG, and 330bB are provided instead of the voltage sensors 330R, 330G, and 330B. Other components of the control unit 300b are the same as those of the control unit 300 shown in FIG.

  The constant voltage power supplies 314bR, 314bG, and 314bB maintain the voltages applied to the LEDs 210R, 210G, and 210B at the voltage setting values according to the voltage setting values set by the voltage setting modules 312bR, 312bG, and 312bB, respectively. The voltage setting modules 312bR, 312bG, and 312bB vary the voltage setting values as shown in the graph of FIG. As a result, fluctuating power similar to that in the first embodiment shown in FIG. 7 is supplied to the LEDs 210R, 210G, and 210B.

  The three current sensors 320bR, 320bG, and 320bB measure currents flowing through the three LEDs 210R, 210G, and 210B, respectively, and output the measured current values to the temperature estimation module 340, respectively. The three voltage setting value monitors 330bR, 330bG, and 330bB acquire the current voltage setting values of the three power supply modules 310bR, 310bG, and 310bB, respectively, and output the acquired voltage setting values to the temperature estimation module 340, respectively. Based on the received information, the temperature estimation module 340 estimates the temperatures of the LEDs 210R, 210G, and 210B, respectively, as in the first embodiment described above.

  As described above, a device having a constant voltage power source may be adopted as the power supply unit that supplies power to the LEDs. If it carries out like this, it can suppress easily that the voltage applied to LED becomes large too much.

  In the fourth embodiment, the temperature is estimated using the voltage setting value (that is, information for specifying the current voltage V), but the voltage V is specified as in the second embodiment shown in FIG. The temperature may be estimated without using the information to be used, or the temperature may be estimated using the measurement result of the voltage V as in the third embodiment shown in FIG.

E. Variation:
In addition, elements other than the elements claimed in the independent claims among the constituent elements in each of the above embodiments are additional elements and can be omitted as appropriate. The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

Modification 1:
In each of the above-described embodiments, the variation form of the power supplied to the LED is not limited to the form shown in FIG. 7, and various forms can be employed. For example, the power supply unit (for example, the power supply modules 310R, 310G, and 310B in FIG. 2) may change the power to a stage that is larger than the number of operating points used for temperature estimation. Further, the power may vary smoothly instead of stepwise. Further, the power may be temporarily set to zero in the process of fluctuation.

Modification 2:
In each of the above-described embodiments, the information supplied from the current set value monitors 320R, 320G, and 320B (FIG. 2) to the temperature estimation module 340 is not limited to the current set value itself, but is an arbitrary value that specifies the current current I. Information can be adopted. For example, in the first embodiment shown in FIGS. 2 and 7, the values that the current I can take are two predetermined values ILr and IHr. Accordingly, each of these two values ILr and IHr can be specified by 1-bit information. Therefore, the current set value monitor 320R uses, as information for specifying the current I, 1-bit information for specifying which of the two current set values ILr and IHr is the current current I, and the temperature estimation module 340. May be supplied. Similarly, when the current set value fluctuates in eight steps, each of these eight current set values can be specified by 3-bit information. Therefore, the current set value monitors 320R, 320G, and 320B may supply the temperature estimation module 340 with 3-bit information that specifies which of the eight current set values the current current has.

  Similarly, as the information supplied to the temperature estimation module 340 from the voltage set value monitors 330bR, 330bG, 330bB (FIG. 11), any information for specifying the current voltage can be adopted. The three voltage set value monitors 330bR, 330bG, and 330bB each function as a voltage specifying unit that specifies the current voltage V.

Modification 3:
In each of the embodiments described above, as the ratio information, various kinds of information correlated with the ratio between the change in the current value flowing through the light emitting diode and the change in the voltage value applied to the light emitting diode can be adopted. . For example, a plurality of operation points may be approximated using an approximate line, and the slope of the approximate line may be used as ratio information. In the fourth embodiment shown in FIG. 11, the difference between the current measurement results between the two operating points may be used as the ratio information. In any case, the correspondence between the ratio information and the estimated temperature may be experimentally determined in advance.

Modification 4:
In each of the above-described embodiments, the method of estimating the temperature of the light emitting diode using the measurement result of the sensor that measures at least one of the current I and the voltage V is not limited to the method using the ratio information, but various methods. The method can be adopted. For example, when the temperature is estimated from the two voltage measurement results VHr and VLr as in the embodiment shown in FIG. 8, a look-up table representing the correspondence between the two voltages VHr and VLr and the estimated temperature Ter is used. Thus, the temperature may be estimated. Such a lookup table may be determined in advance based on, for example, an experiment using a plurality of LEDs having individual differences in current-voltage characteristics.

Modification 5:
In each of the embodiments described above, the temperature estimation module 340 (FIG. 2) uses two operating points for temperature estimation, but may use three or more operating points. For example, three or more operating points may be approximated using an approximate line, and the estimated temperature may be determined from the slope of the approximate line. In the first embodiment shown in FIG. 2, the current flowing through the LED may be repeatedly set to each of three predetermined values (that is, the current varies in three stages). In this case, the temperature may be estimated using a look-up table representing the correspondence between the three voltage measurement results and the estimated temperature. Such a lookup table may be experimentally determined in advance.

  In any case, the temperature estimation module 340 preferably uses a plurality of operating points within a current range greater than zero to estimate the temperature without using operating points where the current I is zero. In this way, as described with reference to FIG. 5, it is possible to reduce the influence of individual differences between LEDs and increase the estimation accuracy of the LED temperature.

Modification 6:
As in the second embodiment shown in FIG. 9, temperature estimation using the measurement result of the voltage sensor without using the information specifying the current current (information specifying the current current setting value or the current measurement result). Is also possible when the number of operating points used for temperature estimation is three or more. Usually, the current flowing through the light emitting diode is larger as the voltage is higher. Therefore, when the current flowing through the LED is repeatedly set to each of a plurality of predetermined values, the current corresponding to each of the plurality of measurement results output from the voltage sensor is set to the magnitude of each measurement result. It can be specified by comparing. For example, assume that the current I is repeatedly set to each of three predetermined values I1, I2, and I3 (where I1 <I2 <I3). In this case, three measurement results V1, V2, and V3 are repeatedly output from the voltage sensor (where V1 <V2 <V3). Here, the smallest voltage I1 corresponds to the smallest current I1, the second smallest voltage V2 corresponds to the second smallest current I2, and the third smallest voltage V3 includes the third smallest current I3. Correspond. In this manner, the temperature estimation module 340 can specify a current (that is, an operating point) corresponding to each voltage measurement result without using information for specifying the current current. As a result, the temperature estimation module 340 can accurately estimate the temperature.

  Thus, when the current I is repeatedly set to each of a plurality of predetermined values, the temperature is estimated using the measurement result of the voltage V without using the information specifying the current current I. be able to. Similarly, when the voltage V is repeatedly set to each of a plurality of predetermined values, the temperature is estimated using the measurement result of the current I without using the information specifying the current voltage V. Can do.

Modification 7:
In each of the above-described embodiments, the process using the estimated temperature is not limited to the process by the temperature processing module 350, and various processes can be employed. For example, you may employ | adopt the process which displays estimated temperature on a display apparatus. Further, a process for issuing an alarm in response to the estimated temperature exceeding a predetermined upper limit value may be employed. As a process for issuing an alarm, for example, a process for turning on an alarm lamp or a process for generating an alarm sound using a speaker can be employed. Further, the temperature processing module 350 may be omitted in each of the above-described embodiments.

Modification 8:
In each of the above-described embodiments, as the processing executed by the temperature corresponding processing module 350, any processing that suppresses the estimated temperature from exceeding a predetermined upper limit value can be employed. For example, the LED may be cooled using a cooling unit that can change the cooling capacity. In this case, it is preferable that the temperature corresponding processing module 350 controls the cooling unit using the estimated temperature. Specifically, it is possible to employ a process for increasing the cooling capacity as the estimated temperature is higher. As such a cooling unit, for example, a cooling fan 400 as shown in FIG. 1 can be employed. In this case, as in the above-described embodiments, it is possible to employ a process of increasing the driving speed of the cooling fan 400 as the estimated temperature is higher. At this time, it is preferable to attach a heat sink or heat pipe to the LED to promote heat dissipation. Moreover, as such a cooling part, you may employ | adopt the apparatus which circulates a cooling liquid between LED and a radiator and cools LED. In this case, a process of increasing the flow rate of the coolant as the estimated temperature is higher can be employed. In any case, the correspondence relationship between the estimated temperature and the cooling capacity may be experimentally determined in advance so that the estimated temperature does not exceed the upper limit value. Instead, the cooling capacity may be adjusted by feedback control based on the estimated temperature so that the estimated temperature does not exceed the upper limit value.

  Moreover, you may perform the process which makes the electric power supplied to LED small, so that estimated temperature is near an upper limit. In other words, the process of reducing the power as the estimated temperature is higher may be executed. In this case, the temperature correspondence processing module 350 may output an instruction to adjust the power to the power supply unit (for example, the power supply modules 310R, 310G, and 310B in FIG. 2). The power supply unit may adjust the power according to the received instruction. The correspondence relationship between the power and the estimated temperature may be experimentally determined in advance so that the estimated temperature does not exceed the upper limit value. Instead, the power may be adjusted by feedback control based on the estimated temperature so that the estimated temperature does not exceed the upper limit value. Any method can be adopted as a method of adjusting the power. For example, the current I may be adjusted. Further, at least one of the pulse width (for example, the second time THr in FIG. 7) and the pulse interval (for example, the first time TLr in FIG. 7) may be adjusted. In this case, the average power is adjusted. In addition, when adjusting electric power, it is preferable to adjust all the electric power of three LED210R, 210G, 210B similarly. In this way, it is possible to suppress that some of the three colors of RGB are weaker than other colors.

Modification 9:
The present invention is not limited to the projector 200 (FIG. 1) as in each of the above-described embodiments, and can be applied to various forms. For example, you may apply this invention to the projection television provided with the screen SC and the projector 200 which projects an image on the back side of the screen SC. Further, the present invention may be applied not only to a projection display device that projects such an image but also to various devices that use LEDs as a light source, such as a lighting device and a vehicle headlamp. Moreover, as a semiconductor light-emitting device, not only LED but various light-emitting devices using a semiconductor are employable. For example, a semiconductor laser may be employed. In either case, a drive control device that drives the semiconductor light emitting element and estimates the temperature in a device having the semiconductor light emitting element as a light source, and a process that suppresses the estimated temperature from exceeding a predetermined upper limit value are executed. It is preferable to provide a temperature corresponding processing unit.

Modification 10:
In each of the above embodiments, a part of the configuration realized by hardware may be replaced with software, and conversely, a part of the configuration realized by software may be replaced by hardware. . For example, the function of the temperature estimation module 340 in FIG. 2 may be realized by causing a computer having a CPU and a memory to execute a program.

  In addition, when part or all of the functions of the present invention are realized by software, the software (computer program) can be provided in a form stored in a computer-readable recording medium. In the present invention, the “computer-readable recording medium” is not limited to a portable recording medium such as a flexible disk or a CD-ROM, but an internal storage device in a computer such as various RAMs and ROMs, a hard disk, and the like. An external storage device fixed to the computer is also included.

It is explanatory drawing which shows the projector 200 as one Example of this invention. 3 is an explanatory diagram illustrating a configuration of a control unit 300. FIG. It is a graph explaining temperature estimation. It is a graph which shows the correspondence of estimated temperature Te and inclination k. It is a graph which shows the individual difference of an electric current-voltage characteristic. It is a flowchart which shows the procedure of the control process performed by the control part 300 (FIG. 2). It is a timing chart explaining the drive signal (electric power) supplied to red LED210R by electric power supply module 310R (FIG. 2). It is a graph which shows the correspondence of voltage difference dV and estimated temperature Ter. It is explanatory drawing which shows another Example of the control part of the projector 200 (FIG. 1). It is explanatory drawing which shows another Example of the control part of the projector 200 (FIG. 1). It is explanatory drawing which shows another Example of the control part of the projector 200 (FIG. 1).

Explanation of symbols

200 ... Projector 210B ... Blue LED
210G ... Green LED
210R ... Red LED
240R, 240G, 240B ... Liquid crystal light valve 250 ... Cross dichroic prism 260 ... Projection lens system 300, 300a, 300b, 300x ... Control unit 310R, 310G, 310B, 310bR, 310bG, 310bB ... Power supply module 312R, 312G, 312B ... Current setting module 312bR, 312bG, 312bB ... Voltage setting module 314R, 314G, 314B ... Constant current power supply 314bR, 314bG, 314bB ... Constant voltage power supply 320R, 320G, 320B ... Current setting value monitor 320aR, 320aG, 320aB, 320bR, 320bG, 320bB ... current sensors 330R, 330G, 330B ... voltage sensors 330bR, 330bG, 330bB ... voltage set value monitor 340, 340x ... temperature Degree estimation module 350 ... Temperature-compatible processing module 360 ... Image processing module 400 ... Cooling fan SC ... Screen

Claims (7)

A drive control device for driving a semiconductor light emitting element,
Each of a plurality of power supply processes including a first power supply process in which a current flowing through the semiconductor light-emitting element is greater than zero and a second power supply process in which a current flowing through the semiconductor light-emitting element is greater than the first power supply process Repeatedly supplying the power to the semiconductor light emitting element to supply variable power and turn on the semiconductor light emitting element, and
A sensor for measuring at least one of a current value flowing through the semiconductor light emitting element and a voltage value applied to the semiconductor light emitting element;
In each of a plurality of operation states in which a current flowing through the semiconductor light emitting element is greater than zero, including an operation state in which the first power supply process is being executed and an operation state in which the second power supply process is being executed A temperature estimation unit that estimates the temperature of the semiconductor light-emitting element using a measurement result of the sensor;
A drive control device comprising: The drive control device according to claim 1,
The temperature estimation unit uses the measurement result of the sensor to obtain ratio information correlated with the ratio between the change in the current value and the change in the voltage value in a range where the current flowing through the semiconductor light emitting element is greater than zero. And determining the temperature of the semiconductor light emitting element using the ratio information,
Drive control device. The drive control apparatus according to claim 1 or 2,
The power supply unit
A constant current power source for supplying a constant current according to a current setting value to the semiconductor light emitting element;
A current setting unit for controlling the current set value;
Including
In the first power supply process, the current setting unit sets the current set value to a predetermined first set value greater than zero,
In the second power supply process, the current setting unit sets the current set value to a predetermined second set value larger than the first set value,
The sensor includes a voltage sensor that measures a voltage value applied to the semiconductor light emitting element,
Drive control device. The drive control device according to claim 2,
The power supply unit
A constant current power source for supplying a constant current according to a current setting value to the semiconductor light emitting element;
A current setting unit for controlling the current set value;
Including
In the first power supply process, the current setting unit sets the current set value to a predetermined first set value greater than zero,
In the second power supply process, the current setting unit sets the current set value to a predetermined second set value larger than the first set value,
The sensor includes a voltage sensor that measures a voltage value applied to the semiconductor light emitting element,
The temperature estimation unit includes, as the ratio information, a first voltage that is a measurement result of the voltage sensor in the first power supply process, and a second voltage that is a measurement result of the voltage sensor in the second power supply process. Use the difference between
Drive control device. A projection display device that displays an image based on image data,
A semiconductor light emitting element used as a light source;
A projection light conversion unit that converts light emitted from the semiconductor light emitting element into image projection light for projecting an image;
An image processing unit that controls the projection light conversion unit based on image data;
The drive control device according to any one of claims 1 to 4, which drives the semiconductor light emitting element;
A temperature-corresponding processing unit that executes a process for suppressing the temperature estimated by the drive control device from exceeding a predetermined upper limit;
A projection display device comprising: The projection display device according to claim 5,
The power supply unit supplies the fluctuating power to the semiconductor light emitting element during display of the image,
The temperature estimation unit estimates the temperature of the semiconductor light emitting element according to the supply of the variable power,
Projection display device. A method for estimating the temperature of a semiconductor light emitting device,
Each of a plurality of power supply processes including a first power supply process in which a current flowing through the semiconductor light-emitting element is greater than zero and a second power supply process in which a current flowing through the semiconductor light-emitting element is greater than the first power supply process Repeatedly supplying power to supply power to the semiconductor light emitting element and turn on the semiconductor light emitting element, and
Measuring at least one of a current value flowing through the semiconductor light-emitting element and a voltage value applied to the semiconductor light-emitting element in each of at least the first power supply process and the second power supply process;
In each of a plurality of operation states in which a current flowing through the semiconductor light emitting element is greater than zero, including an operation state in which the first power supply process is being executed and an operation state in which the second power supply process is being executed A temperature estimation step of estimating the temperature of the semiconductor light emitting element using the measurement result of the measurement step;
A method comprising:

Images