JP2017123241A - Video display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video display device by which even when a fault light source exists in plural serially connected light sources, the existence of the fault light source is notified while maintaining the light emission of the light sources.SOLUTION: A video display device includes a failure drive unit 120 provided in association with n light sources 11 connected in series. When there is a failure light source, the failure drive unit 120 is configured to maintain the light emission of normal light sources as light sources other than the failure light source out of the n light sources. When there is a fault light source, a notifying unit 50 performs notification processing of notifying existence of the fault light source.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a video display device including a plurality of light sources connected in series.

  From the standpoints of reducing environmental pollutants and reducing power consumption, a light emitting diode (LED) is used as a light source for backlights used in video display devices such as liquid crystal display devices instead of conventional cold cathode tubes. ) Has been used. LEDs have better luminous efficiency than cold cathode tubes.

  In addition, the backlight of the video display device is required to emit light with uniform luminance to the video display area. The backlight is generally provided with a plurality of LEDs connected in series. Thereby, the said several LED is driven efficiently.

  When a plurality of LEDs connected in series are used, there is a problem that when any of the plurality of LEDs has an open failure, the plurality of LEDs are turned off. When the plurality of LEDs are turned off, the video display device cannot display a video.

  In order to solve the above problems, Patent Document 1 discloses a technique related to a plurality of LEDs connected in series (hereinafter, also referred to as “related technique A”). Specifically, in the related art A, a protection circuit configured to allow the lighting device to emit light even when there are open LEDs among the plurality of LEDs included in the lighting device is provided. . The lighting device of Related Technology A is assumed to be used as a backlight of a display (video display device), for example.

  Hereinafter, a failed light source that cannot emit light is also referred to as a “failed light source”. In the following, a light source that is not broken and can emit light normally is also referred to as a “normal light source”.

Japanese Patent No. 4952292

  In a backlight using a plurality of light sources connected in series, if the backlight continues to be driven in the presence of a failed light source, an excessive load may be applied to the normal light source, and the backlight may fail. is there.

  Therefore, when a faulty light source exists, a configuration capable of notifying that the faulty light source exists is required. Related technology A cannot satisfy the request.

  The present invention has been made to solve such a problem, and even when a failure light source exists in a plurality of light sources connected in series, the failure light source exists while maintaining the light emission of the light source. An object of the present invention is to provide a video display device capable of notifying the user.

  In order to achieve the above object, an image display device according to an aspect of the present invention includes a light source unit that emits light used to display an image, and the light source unit is supplied with current. It is composed of n (integer greater than or equal to 2) light sources that emit light, the n light sources are connected in series, and the video display device further determines whether or not a fault light source exists in the n light sources. A failure determination unit that determines whether the failure light source is associated with the n light sources, and the failure drive unit includes the n light sources when the failure light source exists. The image display device is configured to maintain light emission of a normal light source that is a light source other than the faulty light source, and the video display device further notifies, when the faulty light source is present, that the faulty light source exists. The notification part which performs is provided.

  According to the present invention, the video display device includes a failure-time drive unit provided in association with the n light sources connected in series. The failure drive unit is configured to maintain light emission of a normal light source that is a light source other than the failure light source among the n light sources when the failure light source is present. When the faulty light source exists, the notification unit performs a notification process for notifying that the faulty light source exists.

  Thereby, even when a fault light source exists in a plurality of light sources connected in series, it is possible to notify that the fault light source exists while maintaining the light emission of the light source.

It is a block diagram which shows the structure of the video display apparatus concerning Embodiment 1 of this invention. It is a flowchart of the failure handling process which the video display apparatus concerning Embodiment 1 of this invention performs. It is a figure for demonstrating the deformation | transformation structure A which concerns on the modification 1 of Embodiment 1 of this invention. It is a block diagram of a video display device showing a characteristic functional configuration. It is a hardware block diagram of a video display apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same components are denoted by the same reference numerals. The names and functions of the components having the same reference numerals are the same. Therefore, a detailed description of some of the components having the same reference numerals may be omitted.

<Embodiment 1>
FIG. 1 is a block diagram showing a configuration of video display apparatus 1000 according to Embodiment 1 of the present invention. Note that FIG. 1 shows an external device 500 that is not included in the video display device 1000 for the sake of explanation. The external device 500 is, for example, a PC (Personal Computer) to which a display (not shown) is connected. The video display device 1000 is a device that displays video. The video display device 1000 is, for example, a liquid crystal display device that operates using liquid crystal.

  Referring to FIG. 1, video display apparatus 1000 includes a backlight 100, a control unit 20, a network interface 30, a memory 40, a notification unit 50, and a video display unit (not shown). The video display unit is a module for displaying video. The video display unit is, for example, a liquid crystal display panel.

  The backlight 100 emits light Lt that is used to display an image. An image display unit (not shown) of the image display apparatus 1000 displays an image using the light Lt emitted from the backlight 100.

  The backlight 100 includes a light source unit 110, a failure drive unit 120, a voltage detection unit 130, and a voltage control unit 140.

  The light source unit 110 emits the light Lt described above. The light source unit 110 includes light sources 11-1 to 11-n (an integer of 2 or more). Each of the light sources 11-1 to 11-n is a light source that emits light. Hereinafter, each of the light sources 11-1 to 11-n is also simply referred to as “light source 11”. That is, the light source unit 110 includes n (an integer of 2 or more) light sources 11.

  The light source 11 is an LED. In this case, the light source 11 has two terminals, an anode terminal and a cathode terminal. The light source 11 emits light when supplied with current. The n light sources 11 are electrically connected in series. Each of the n light sources 11 has the same configuration and the same characteristics. In addition, the light source 11 is not limited to LED, For example, a laser may be sufficient.

  One end of the light source unit 110 constituting the n light sources 11 is connected to the node Nda. The other end of the light source unit 110 is connected to the node Ndb. Specifically, the anode terminal of the light source 11-1 among the n light sources 11 is connected to the node Nda. The cathode terminal of the light source 11-n among the n light sources 11 is connected to the node Ndb.

  The accidental failure mode of the light source 11 includes a short circuit failure and an open failure. The short circuit failure is a failure in which two terminals of the light source 11 are short-circuited. An open failure is a failure in which two terminals of the light source 11 are in an open state.

  Hereinafter, the failed light source 11 that is included in the light source unit 110 and that cannot emit light is also referred to as a “failed light source”. The failed light source is the light source 11 that has failed due to short circuit or the light source 11 that has failed due to open circuit. Hereinafter, the light source 11 in which a short circuit has failed is also referred to as a “short circuit failure light source”. In the following, the light source 11 that has an open failure is also referred to as an “open failure light source”. In the following, the light source 11 that is not broken and can emit light normally is also referred to as a “normal light source”. When a faulty light source is present, the normal light source is a light source other than the faulty light source among the n light sources included in the light source unit 110.

  The failure drive unit 120 is configured to maintain light emission of light sources 11 (normal light sources) other than the failure light source among the n light sources when a failure light source exists in the n light sources 11.

  The failure-time drive unit 120 is provided in association with the n light sources 11. Specifically, the failure-time drive unit 120 includes bypass circuits 12-1 to 12-k (an integer greater than or equal to 2). Hereinafter, each of the bypass circuits 12-1 to 12-k is also simply referred to as “bypass circuit 12”. That is, the failure-time drive unit 120 includes k (an integer greater than or equal to 2) bypass circuits.

  In the present embodiment, as an example, the value of k is the same as the value of n. That is, in the video display device 1000 of the present embodiment, the number of light sources 11 and the number of bypass circuits 12 are the same. Each of the k bypass circuits 12 is electrically connected in parallel to the n light sources 11.

  The bypass circuit 12, the voltage detection unit 130, and the voltage control unit 140 will be described later.

  The control unit 20 has a function of performing control, arithmetic processing, and the like for each component included in the video display device 1000. The control unit 20 is, for example, a CPU (Central Processing Unit). Although details will be described later, the control unit 20 has a function of determining whether there is a fault light source that is an open fault light source or a short-circuit fault light source.

  The network interface 30 is an interface having a function of communicating with the external device 500. The network interface 30 communicates with the external device 500 via a network such as the Internet, for example. The network interface 30 is connected to the control unit 20. Therefore, the control unit 20 can communicate with the external device 500 via the network interface 30.

  As an example, the external device 500 is installed in a place (remote place) very far from the place where the video display apparatus 1000 is installed. The place where the external device 500 is installed is not limited to the above place, and may be, for example, in the vicinity of the video display apparatus 1000.

  The memory 40 stores data and the like. The memory 40 is a non-volatile memory such as NVRAM (Non-Volatile RAM), for example. Therefore, the memory 40 can store various data and the like even when the power of the video display apparatus 1000 is off. The control unit 20 is configured to be accessible to the memory 40.

  The control unit 20 controls the notification unit 50. The notification unit 50 performs processing for notifying the operation state of the video display apparatus 1000 according to the control of the control unit 20. Specifically, the notification unit 50 performs a process for notifying that a faulty light source exists, for example. For example, the notification unit 50 includes a light source capable of emitting colored light. The color light is, for example, green light.

  Next, the bypass circuit 12, the voltage detection unit 130, and the voltage control unit 140 will be described in detail.

  The voltage control unit 140 is electrically connected to the control unit 20 via the node Nda. The voltage controller 140 generates a drive voltage VL. The drive voltage VL is an analog voltage. The drive voltage VL is supplied to the node Nda. In the following, the current supplied to the light source 11-1 when the drive voltage VL is supplied to the node Nda is also referred to as “drive current If”. The drive voltage VL is a voltage for supplying the drive current If to the first light source 11 (light source 11-1) among the n light sources 11. The drive current If is a current for causing at least one of the n light sources 11 to emit light.

  Each of the k bypass circuits 12 has the same configuration and the same characteristics. As described above, the k bypass circuits 12 are electrically connected to the n light sources 11 in parallel. For example, the bypass circuit 12-1 is electrically connected in parallel to the light source 11-1. Each of the k bypass circuits 12 includes a switch Sw and resistors Ra and Rb.

  The switch Sw is, for example, an NPN bipolar transistor. The resistor Ra is provided between the collector and base of the switch Sw. The resistor Rb is provided between the base and emitter of the switch Sw. Note that the resistance value of the resistor Ra is larger than the resistance value of the resistor Rb.

  Hereinafter, the current flowing through each of the resistors Ra and Rb is also referred to as “resistance current”. In the following, the state where each of the n light sources 11 is a normal light source is also referred to as a “normal state Stn”. Hereinafter, the drive current If flowing in each of the n light sources 11 in the normal state Stn is also referred to as “normal current Ifn” or “Ifn”.

  The resistance values of the resistors Ra and Rb are set so that the resistance current is sufficiently smaller than the normal current. The resistance values of the resistors Ra and Rb are set so that the resistance current is, for example, a current in the range of 1/10 to 1/100 times the normal current Ifn.

  Hereinafter, a voltage generated between two terminals of the light source 11 when the drive current If flows through the light source 11 is also referred to as a “forward voltage VF”. Hereinafter, the forward voltage VF of the normal light source when the light source 11 is a normal light source is also referred to as “forward voltage VFn” or “VFn”.

  Hereinafter, the voltage between the base and the emitter in the switch Sw included in the bypass circuit 12 is also referred to as “voltage VBE” or “VBE”. Hereinafter, the voltage between the collector and the emitter in the switch Sw included in the bypass circuit 12 is also referred to as “voltage VCE” or “VCE”. The voltage VCE is a forward voltage of the bypass circuit 12.

  Hereinafter, the state in which the light source 11 connected in parallel to the bypass circuit 12 is an open failure light source is also referred to as an “open failure existing state”.

  When the voltage VCE applied to the switch Sw included in the bypass circuit 12 rises above the forward voltage VFn in the open fault existence state, the bypass circuit 12 is set so that the state of the switch Sw becomes a conduction state described later. The resistance values of the included resistors Ra and Rb are set.

  Specifically, when the voltage VCE applied to the switch Sw rises above the forward voltage VFn in the open fault existence state, the voltage generated in the resistor Rb by the resistors Ra and Rb The resistance values of the resistors Ra and Rb are set so as to be equal to the voltage VBE. Note that when the voltage generated in the resistor Rb becomes equal to the voltage VBE of the switch Sw, the state of the switch Sw becomes a conductive state described later.

  In addition, the resistance values of the resistors Ra and Rb are set so that the forward voltage of the bypass circuit 12 is larger than the forward voltage VFn by the resistors Ra and Rb included in the bypass circuit 12 in the open failure existence state. The

  Hereinafter, the state of the switch Sw that allows the current If to flow through the switch Sw is also referred to as a “conduction state”. In the conductive switch Sw, the current If can flow from the collector to the emitter. The conduction state is also a state of the bypass circuit 12 in which the drive current If can flow through the bypass circuit 12.

  In the following, the state of the switch Sw in which the current If cannot be passed through the switch Sw is also referred to as “non-conduction state” or “cut-off state”. In the non-conducting switch Sw, the current If cannot flow from the collector to the emitter. The non-conducting state is also a state of the bypass circuit 12 in which the drive current If cannot flow through the bypass circuit 12.

  That is, each bypass circuit 12 is configured such that the state of each bypass circuit 12 is either a conduction state or a non-conduction state. When each of the n light sources 11 is a normal light source, the state of each bypass circuit 12 is a non-conductive state.

  Voltage detector 130 includes a resistor Rf and an error amplifier 131. The resistor Rf is a current detection resistor for detecting the drive current If. The resistor Rf is electrically connected in series with the n light sources 11. Specifically, one end of the resistor Rf is connected to the node Ndb. The other end of the resistor Rf is grounded.

  Hereinafter, a voltage generated in the resistor Rf when a current flows through the resistor Rf is also referred to as “voltage VRf” or “VRf”. As described above, the drive current If flowing in each of the n light sources 11 in the normal state Stn is also referred to as “normal current Ifn” or “Ifn”.

  In the present embodiment, the resistance values of the resistors Ra and Rb of each bypass circuit 12 are set so that the current value of the normal current Ifn is the same as or equivalent to the current value of the current flowing through the resistor Rf. Is done. Therefore, in the normal state Stn, the voltage VRf that satisfies the voltage VRf = Rf × Ifn is generated in the resistor Rf.

  The error amplifier 131 is an operational amplifier. Error amplifier 131 includes terminals T1, T2, and T3. A reference voltage Vref (hereinafter also referred to as “Vref”) is supplied to a terminal T3 which is a non-inverting input terminal. The reference voltage Vref is a voltage indicating a constant voltage value. In the normal state Stn, the voltage value of the reference voltage Vref and the resistance value of the resistor Rf are set so that VRf = Vref is established when the normal current Ifn flows through each of the n light sources 11 described above. The That is, VRf = Vref is established in the normal state Stn. Further, the voltage VRf is supplied to the terminal T2, which is an inverting input terminal.

  The error amplifier 131 outputs the voltage Vct from the terminal T1 according to the comparison result between the voltage VRf and the reference voltage Vref. The voltage Vct is supplied to the voltage controller 140.

  Hereinafter, the voltage value of the voltage Vct output from the error amplifier 131 is also referred to as “voltage value Vctv” or “Vctv”. Hereinafter, the voltage value Vctv of the voltage Vct output from the error amplifier 131 in the normal state Stn is also referred to as “voltage value Vctvn” or “Vctvn”.

  Hereinafter, the voltage value of the drive voltage VL generated by the voltage controller 140 is also referred to as “voltage value VLv” or “VLv”. Hereinafter, the voltage value VLv of the drive voltage VL generated by the voltage controller 140 in the normal state Stn is also referred to as “voltage value VLvn” or “VLvn”. When the voltage value of the voltage Vct is the voltage value Vctvn, the voltage control unit 140 generates a drive voltage VL indicating the voltage value VLvn.

  Hereinafter, the drive voltage VL generated by the voltage control unit 140 in the normal state Stn is also referred to as “normal state voltage”. In the normal state Stn, with the generation of the drive voltage VL that is a normal state voltage, the drive current If flows sequentially to the n light sources 11 that are normal light sources. Thereby, in the normal state Stn, each of the n light sources 11 emits light normally.

  Hereinafter, the voltage value of the normal state voltage is also referred to as “normal state voltage value Vini” or “Vini”. The memory 40 stores a normal state voltage value Vini in advance. The normal state voltage value Vini is stored in the memory 40 after the production of the video display device 1000 is completed, for example.

  For example, it is assumed that the operator performs an operation for storing the normal state voltage value Vini in the memory 40 (hereinafter also referred to as “storage operation M”) on the external device 500. In this case, the external device 500 causes the control unit 20 to perform a process of storing the normal state voltage value Vini in the memory 40 in accordance with the storage operation M.

  The voltage control unit 140 changes the voltage value of the drive voltage VL according to the voltage value of the voltage Vct supplied from the error amplifier 131 so that VRf = Vref is satisfied. When the voltage VRf = Vref is established, the drive current If flowing through the resistor Rf is a current that satisfies If = Vref / Rf.

  As described above, the reference voltage Vref is a voltage indicating a constant voltage value. Therefore, the voltage control unit 140 changes the voltage value of the drive voltage VL so that the current value of the drive current If becomes constant.

  Hereinafter, an example will be described. For example, assume that there is one open failure light source and VRf <Vref is satisfied. In this case, the error amplifier 131 performs a voltage increase process A1. In the voltage increase process A1, the error amplifier 131 increases the voltage value (Vctv) of the voltage Vct. Hereinafter, a voltage value that is q (a real number greater than 1) times Vctv is also referred to as “voltage value Vctvq” or “Vctvq”. For example, q is 1.1.

  Specifically, in the voltage increase process A1, the error amplifier 131 supplies, for example, the voltage Vct indicating the voltage value Vctvq to the voltage control unit 140.

  When the voltage value of the voltage Vct is the voltage value Vctvq, the voltage control unit 140 performs a voltage increase process A2 for increasing VLv.

  Specifically, in the voltage increase process A2, the voltage control unit 140 supplies, for example, the drive voltage VL indicating a voltage value q times VLv to the node Nda and the control unit 20. Note that the voltage increase process A1 and the voltage increase process A2 are repeated until VRf = Vref is satisfied.

  For example, it is assumed that there is one short-circuit fault light source and VRf> Vref is satisfied. In this case, the error amplifier 131 performs a voltage reduction process B1. Hereinafter, a voltage value that is w (a real number satisfying 0 <w <1) times Vctv is also referred to as “voltage value Vctvw” or “Vctvw”. For example, w is 0.9.

  In the voltage reduction process B1, the error amplifier 131 supplies, for example, the voltage Vct indicating the voltage value Vctvw to the voltage control unit 140.

  When the voltage value of the voltage Vct is the voltage value Vctvw, the voltage control unit 140 performs a voltage reduction process B2 for reducing VLv.

  Specifically, in the voltage reduction process B2, the voltage control unit 140 supplies, for example, the drive voltage VL indicating a voltage value w times VLv to the node Nda and the control unit 20. Note that the above-described voltage reduction processing B1 and voltage reduction processing B2 are repeatedly performed until VRf = Vref is established.

  The control unit 20 has an AD converter function. Specifically, the control unit 20 performs AD conversion on the drive voltage VL that is an analog voltage every predetermined time. The predetermined time is, for example, any time in the range of 0.1 second to 5 seconds. The controller 20 acquires a voltage value VLv that is a digital signal value by performing AD conversion on the drive voltage VL. Thereby, the control unit 20 always grasps the voltage value VLv of the drive voltage VL.

  Next, processing performed by the video display apparatus 1000 (hereinafter also referred to as “failure handling processing”) will be described. The failure handling process is repeatedly performed every predetermined time. The predetermined time is, for example, any time in the range of 1 second to 5 seconds. FIG. 2 is a flowchart of the failure handling process.

  Here, the following premise Pr1 is considered. In the premise Pr1, the state of the video display apparatus 1000 is the normal state Stn. That is, in the assumption Pr1, each of the n light sources 11 constituting the light source unit 110 is a normal light source.

  Hereinafter, the switch Sw included in the bypass circuit 12-1 is also referred to as “switch Sw1”. In the following description, the above-described voltage VBE in the switch Sw1 is also referred to as “voltage VBE1” or “VBE1”. Hereinafter, the forward voltage VF generated in the light source 11-1 when the drive current If flows through the light source 11-1 is also referred to as “forward voltage VF1” or “VF1”.

  Next, the operation of each light source 11 and each bypass circuit 12 immediately before the failure handling process in the premise Pr1 is described. As an example, operations of the light source 11-1 and the bypass circuit 12-1 will be described.

  When the drive current If flows through the light source 11-1 in the normal state Stn, the aforementioned forward voltage VF1 is generated in the light source 11-1. When the forward voltage VF1 is generated in the premise Pr1, the relationship of the following formula 1 regarding the forward voltage VF1 of the light source 11-1, the voltage VBE1 of the switch Sw1, and the resistors Ra and Rb included in the bypass circuit 12-1. Is established.

  When the relationship of Formula 1 is satisfied, the state of the switch Sw1 is a non-conduction state (cut-off state). Therefore, in the premise Pr1, the drive current If does not flow between the collector and the emitter in the switch Sw1.

  In the premise Pr1, the drive current If does not flow between the collector and the emitter in the switch Sw included in each bypass circuit 12 except the bypass circuit 12-1 among the k bypass circuits 12. Therefore, in the premise Pr1, the driving current If flows through the n light sources 11 sequentially. Thereafter, the drive current If flows through the resistor Rf.

  Thus, VRf = Vref is established in the premise Pr1. Therefore, the error amplifier 131 outputs the voltage Vct indicating the voltage value Vctvn as described above. Therefore, in the premise Pr1, as described above, the voltage control unit 140 generates the drive voltage VL indicating the voltage value VLvn.

  Next, the failure handling process in the premise Pr1 will be described. In the failure handling process, first, the process of step S110 is performed.

  In step S110, a voltage value acquisition process is performed. In the voltage value acquisition process, the control unit 20 acquires the voltage value VLv of the drive voltage VL by performing AD conversion on the drive voltage VL generated by the voltage control unit 140.

  In step S110 in the premise Pr1, the control unit 20 acquires the voltage value VLv (VLvn) of the drive voltage VL by performing AD conversion on the drive voltage VL.

  In step S120, although the details will be described later, the control unit 20 determines whether or not an open failure light source exists. If YES in step S120, the process proceeds to step S142 described later. On the other hand, if NO at step S120, the process proceeds to step S130. In step S120 in the premise Pr1, it is determined NO, and the process proceeds to step S130.

  In step S130, although the details will be described later, the control unit 20 determines whether or not a short-circuit fault light source exists. If YES in step S130, the process proceeds to step S143 described later. On the other hand, if NO at step S130, the process proceeds to step S141. In step S130 in the premise Pr1, it is determined NO, and the process proceeds to step S141.

  In steps S120 and S130, the control unit 20 determines whether there is a fault light source that is an open fault light source or a short-circuit fault light source. That is, the control unit 20 is a failure determination unit.

  In step S141, an external notification process N1 is performed. In the external notification process N1, the control unit 20 transmits a normal message to the external device 500 via the network interface 30. The normal message is, for example, a message indicating that there is no faulty light source in the video display apparatus 1000.

  The external device 500 displays a normal message on a display connected to the external device 500. Thereby, for example, a user operating the external device 500 can know that there is no faulty light source in the video display apparatus 1000.

  In step S151, a notification process N1 is performed. The notification process N1 is a process for performing a normal notification process for notifying the user that there is no faulty light source. The normal notification process is, for example, a process for maintaining the state where the notification unit 50 emits colored light (for example, green light).

  In the notification process N1, for example, the control unit 20 controls the notification unit 50 so as to perform a normal notification process. Thereby, the state where the notification unit 50 emits colored light is maintained. Thus, the failure handling process in the premise Pr1 ends.

  Next, the following premise Pr2 is considered. In the assumption Pr2, one open failure light source exists as an example in the n light sources 11 constituting the light source unit 110. The open failure light source is, for example, the light source 11-1. In the premise Pr2, light sources other than one open failure light source among the n light sources 11 are normal light sources.

  In the following, the bypass circuit 12 connected in parallel to the open failure light source is also referred to as an “open correspondence bypass circuit”. When the open failure light source is the light source 11-1, the open corresponding bypass circuit is the bypass circuit 12-1. Although details will be described later, when an open failure light source exists in the n light sources 11, the open correspondence bypass circuit connected in parallel to the open failure light source is in a conductive state.

  Next, the operation of each light source 11 and each bypass circuit 12 immediately before the failure handling process in the premise Pr2 is performed will be described. As an example, operations of the light source 11-1 and the bypass circuit 12-1 will be described.

  Hereinafter, the above-described voltage VCE in the switch Sw1 is also referred to as “voltage VCE1”. The voltage VCE1 is a forward voltage of the bypass circuit 12-1. Further, as described above, the forward voltage VF of the light source 11-1 is also referred to as “forward voltage VF1” or “VF1”.

  In the premise Pr2, the light source 11-1 is an open failure light source. For this reason, the resistors Ra and Rb included in the bypass circuit 12-1 make the voltage generated in the resistor Rb equal to the voltage VBE1 of the switch Sw1 included in the bypass circuit 12-1. Therefore, the state of the switch Sw1 included in the bypass circuit 12-1 becomes a conductive state. That is, the state of the bypass circuit 12-1 connected in parallel to the open failure light source (light source 11-1) is a conductive state. At this time, the voltage VCE1 of the switch Sw1 is expressed by the following Expression 2.

  Hereinafter, the voltage calculated by the equation of VBE1 × (Ra + Rb) / Rb−VF1 is also referred to as “increased voltage Vx”.

  When an open failure light source is present, VRf <Vref is satisfied, and thus the above-described voltage increase processing A1 and voltage increase processing A2 are performed until VRf = Vref is satisfied. As a result, the drive current IF flowing through the resistor Rf becomes a constant value (Vref / Rf). Further, the voltage increase process A1 and the voltage increase process A2 are performed, so that the voltage value VLv of the drive voltage VL supplied by the voltage control unit 140 increases.

  Specifically, the voltage value VLv in the premise Pr2 increases by the increased voltage Vx from the voltage value VLv in the normal state Stn. Further, due to the resistors Ra and Rb, the forward voltage (VCE1) of the bypass circuit 12-1 that is an open-response bypass circuit becomes larger than the forward voltage VF1 of the light source 11-1 (normal light source) in the normal state Stn.

  That is, when there is an open failure light source, the voltage control unit 140 sets the normal voltage in a state where the light source 11 provided in association with the forward voltage of the bypass circuit 12 in the conductive state is a normal light source. A drive voltage VL is generated to make the voltage larger than the forward voltage VF of the light source.

  The drive voltage VL indicating the increased VLv is supplied to the control unit 20.

  In step S110 of the failure handling process in the premise Pr2, the control unit 20 performs AD conversion on the increased drive voltage VL to obtain the voltage value VLv of the drive voltage VL.

  Hereinafter, a value obtained by adding the threshold value Vth1 to the above-described normal state voltage value Vini is also referred to as “open threshold Vhop” or “Vtop”. The open threshold Vthop is a value for determining that one or more open failure light sources exist. The threshold value Vth1 is set so as to satisfy the following Expression 3, for example.

  When VLv is equal to or higher than Vthop, the control unit 20 determines that there are one or more open failure light sources in the n light sources 11. Note that Vth1 is not limited to the above, and may be set to an arbitrary value depending on the number of open failure light sources to be detected.

  For example, in the state where one open failure light source exists, the voltage value VLv increased by performing the above-described voltage increase processing A1, A2 until VRf = Vref is satisfied may be set as the threshold value Vth1.

  In step S120, the control unit 20 determines whether there is a fault light source that is an open fault light source by using the drive voltage VL (normal state voltage) generated in the normal state Stn.

  Specifically, the control unit 20 determines that there is an open failure light source when the voltage value VLv of the drive voltage VL generated in the state where the failed light source is present is equal to or greater than the open threshold Vtop.

  When step S120 in the premise Pr2 is performed, the voltage value VLv is greater than or equal to the open threshold Vhop. Therefore, the control unit 20 determines that an open failure light source exists. Thereby, a process transfers to step S142.

  In step S142, the control unit 20 performs an external notification process A1. The external notification process A1 is a process for notifying the external device 500 that there is a fault light source that is an open fault light source. In the external notification process A1, for example, the control unit 20 transmits a release notification message to the external device 500 via the network interface 30. The open notification message is a message indicating that an open failure light source exists in the video display device 1000, for example.

  The external device 500 displays a release notification message on a display connected to the external device 500. Thereby, for example, a user who operates the external device 500 can know that an open failure light source exists in the video display apparatus 1000.

  In step S152, the notification unit 50 performs notification processing B1. The notification process B1 is a process for notifying the user that there is a fault light source that is an open fault light source. Hereinafter, the process in which the notification unit 50 causes the colored light to blink at a constant period is also referred to as “light blinking process L1”. In the notification process B1, for example, a light blinking process L1 is performed.

  The light blinking process L1 is a process in which the notification unit 50 emits colored light every 3 seconds, for example. Note that the user knows in advance that the light blinking process L1 is a process indicating that an open failure light source exists.

  In the notification process B1, for example, the control unit 20 controls the notification unit 50 so as to perform the light blinking process L1. Thereby, the notification part 50 performs the light blink process L1 which blinks colored light. Thus, the failure handling process in the premise Pr2 ends.

  The user can know that there is an open failure light source in the video display apparatus 1000 by performing the light blinking process L1 in the video display apparatus 1000.

  That is, when the above-described steps S120, S142, and S152 are performed, and there is a fault light source that is an open fault light source, the notification unit 50 performs the external notification process A1 and the notification process B1.

  Next, the following premise Pr3 is considered. In the premise Pr3, one short-circuit fault light source exists as an example in the n light sources 11 constituting the light source unit 110. The short circuit fault light source is, for example, the light source 11-1. Further, in the premise Pr3, light sources other than one short-circuit failure light source among the n light sources 11 are normal light sources.

  Next, the operation of each light source 11 and each bypass circuit 12 immediately before the failure handling process in the premise Pr3 is described. As an example, operations of the light source 11-1 and the bypass circuit 12-1 will be described.

  In the premise Pr3, the light source 11-1 is a short-circuit fault light source. Therefore, the state of bypass circuit 12-1 (switch Sw1) maintains a non-conduction state. As a result, the forward voltage VF1 of the light source 11-1 is approximately 0V. Therefore, VRf> Vref is established.

  In this case, the above-described voltage reduction processing B1 and voltage reduction processing B2 are performed until VRf = Vref is established. As a result, the drive current IF flowing through the resistor Rf becomes a constant value (Vref / Rf). Further, by performing the voltage decrease process B1 and the voltage decrease process B2, the voltage value VLv of the drive voltage VL supplied by the voltage control unit 140 is decreased by the value of VF1.

  If each light source 11 other than the light source 11-n is a short-circuit failure light source, an operation similar to that of the light source 11-1 in the premise Pr3 occurs in the light source 11.

  The drive voltage VL indicating the decreased VLv is supplied to the control unit 20.

  In step S110 of the failure handling process in the premise Pr3, the control unit 20 acquires the decreased voltage value VLv by performing AD conversion on the drive voltage VL indicating the decreased voltage value VLv.

  Hereinafter, the value obtained by adding the threshold value Vth2 to the above-described normal state voltage value Vini is also referred to as “short circuit threshold value Vthcs” or “Vthcs”. The threshold value Vth2 is a value for determining that one or more short-circuit fault light sources exist.

  The threshold value Vth2 is set to a voltage value VLv that is decreased by performing the above-described voltage reduction processing B1 and B2 until VRf = Vref is satisfied, for example, in a state where one short-circuit fault light source exists. Therefore, when VLv is equal to or lower than Vthcs, the control unit 20 determines that one or more short-circuit fault light sources exist.

  In step S120 in the premise Pr3, it is determined NO, and the process proceeds to step S130.

  In step S130, the control unit 20 determines whether there is a fault light source that is a short-circuit fault light source by using the drive voltage VL (normal state voltage) generated in the normal state Stn.

  Specifically, when the voltage value VLv of the drive voltage VL generated in the state where the fault light source is present is equal to or lower than Vthcs, the control unit 20 determines that a short-circuit fault light source exists.

  When step S130 in the premise Pr3 is performed, the voltage value VLv is equal to or less than the short circuit threshold Vthcs. Therefore, the control unit 20 determines that there is a short circuit fault light source. Thereby, a process transfers to step S143.

  In step S143, the control unit 20 performs an external notification process A2. The external notification process A2 is a process for notifying the external device 500 that there is a fault light source that is a short-circuit fault light source. In the external notification process A2, for example, the control unit 20 transmits a short circuit notification message to the external device 500 via the network interface 30. The short circuit notification message is, for example, a message indicating that a short circuit failure light source exists in the video display apparatus 1000.

  The external device 500 displays a short circuit notification message on a display connected to the external device 500. Thereby, for example, the user who operates the external device 500 can know that the short-circuit fault light source exists in the video display apparatus 1000.

  In step S153, the notification unit 50 performs notification processing B2. The notification process B2 is a process for notifying the user that there is a fault light source that is a short-circuit fault light source.

  Hereinafter, the process in which the notification unit 50 causes the colored light to blink at a constant period is also referred to as “light blinking process L2”. Note that the color light blinking pattern in the light blinking process L2 is different from the color light blinking pattern in the light blinking process L1 described above. In the notification process B2, for example, a light blinking process L2 is performed.

  The light blinking process L2 is a process in which the notification unit 50 emits colored light, for example, every second. The user knows in advance that the light blinking process L2 is a process indicating that a short-circuit fault light source exists.

  In the notification process B2, for example, the control unit 20 controls the notification unit 50 so as to perform the light blinking process L2. Thereby, the notification part 50 performs the light blink process L2 which blinks colored light. Thus, the failure handling process in the premise Pr3 ends.

  The user can know that there is a short-circuit failure light source in the video display apparatus 1000 by performing the light blinking process L2 in the video display apparatus 1000.

  That is, when the above-described steps S130, S143, and S153 are performed, and there is a fault light source that is a short-circuit fault light source, the notification unit 50 performs external notification processing A2 and notification processing B2.

  If each light source 11 other than the light source 11-n is a short-circuit failure light source, the light source 11 performs the same processing as the above-described failure handling processing in the premise Pr3.

  As described above, according to the present embodiment, the video display apparatus 1000 includes the failure-time drive unit 120 provided in association with the n light sources 11 connected in series. The failure drive unit 120 is configured to maintain light emission of a normal light source that is a light source other than the failure light source among the n light sources when a failure light source is present. When there is a faulty light source, the notification unit 50 performs a notification process for notifying that the faulty light source exists.

  Thereby, even when a fault light source exists in the plurality of light sources 11 connected in series, it is possible to notify that the fault light source exists while maintaining the light emission of the light source 11.

  Further, in the present embodiment, it is possible to maintain the light emission of the normal light source even when there is a faulty light source. Therefore, even when a faulty light source exists, the video display apparatus 1000 can maintain displaying video using the light Lt emitted from the light source unit 110 (backlight 100). Thereby, occurrence of the following situation X can be prevented.

  The situation X is a situation where, for example, the video display device cannot display a video (electronic advertisement) indicating an advertisement. Thereby, it is possible to prevent a disadvantage from occurring in the company that provides the advertisement. The situation X is a situation in which, for example, the video display device cannot display highly important video (content) such as emergency broadcast. Therefore, the video display apparatus 1000 of the present embodiment can be used as an apparatus that is required to continue displaying video.

  In the present embodiment, when there is an open failure light source, the voltage control unit 140 generates a drive voltage VL that increases the voltage value VLv by the increased voltage Vx from the voltage value VLv in the normal state Stn. Thereby, even when an open failure light source exists, it can suppress that the light quantity of the light Lt which the light source part 110 (backlight 100) inject | emits becomes small.

  For this reason, it is possible to suppress the deterioration of the quality of the video displayed using the light Lt. Therefore, even when the video displayed on the video display device 1000 indicates an advertisement, for example, it is possible to prevent the advertisement image from deteriorating.

  In the present embodiment, when there is a fault light source that is an open fault light source or a short-circuit fault light source, a notification process B1 or a notification process B2 for notifying the user that a fault light source exists is performed.

  As a result, the user can be prompted to repair the failed light source or replace the failed light source. Therefore, the user can perform repair of a failed light source, arrangement of a replacement for the failed light source, and the like in a period in which the display quality of the video display device 1000 is less deteriorated. Therefore, the period during which the display quality of the video display apparatus 1000 is degraded can be shortened.

  In the present embodiment, when there is a fault light source that is an open fault light source or a short-circuit fault light source, an external notification process A1 or an external notification process A2 is performed to notify the external device 500 that a fault light source exists. Is called.

  Here, it is assumed that the external device 500 is installed in a remote place with respect to the place where the video display apparatus 1000 is installed, for example. In this case, the user operating the external device 500 can know from the remote location that there is a fault light source that is an open fault light source or a short-circuit fault light source.

  In the related art A described above, even when there is an open failure LED, it is possible to maintain the lighting of the LED by the operation of the protection circuit. However, in the configuration in which the lighting device of Related Technology A is used as a backlight of a video display device, when the number of LEDs that have failed to open increases, the luminance of the video, the uniformity of the luminance of the video, and the like decrease. For this reason, the display quality of the video display device is remarkably lowered, and there is a problem that the user feels uncomfortable.

  In addition, when a conventional video display device is installed at a location (remote location) that is very far from the location where the user is, the user can check whether the video display device displays the video normally. I can't confirm. For this reason, the video display device continues to display video with degraded display quality without the user knowing that the light source has failed. For this reason, there is a problem that the impression of the image becomes worse for the user.

  In addition, in a conventional video display device that uses a plurality of light sources connected in series, there is a problem in that when there is a short-circuited light source, a part of the video becomes dark and the quality of the video is significantly reduced.

  Therefore, the video display apparatus 1000 of the present embodiment is configured as described above. Therefore, the video display apparatus 1000 can solve the above problems.

<Modification 1 of Embodiment 1>
The configuration of the first modification of the present embodiment is a configuration in which a plurality of light sources 11 are provided in association with one bypass circuit 12 (hereinafter also referred to as “modified configuration A”).

  The video display apparatus 1000 to which the modified configuration A is applied includes n light sources 11 and k bypass circuits 12 connected in series. The light source unit 110 includes n light sources 11.

  In the modified configuration A, the value of k is smaller than the value of n. That is, in the video display device 1000 to which the modified configuration A is applied, the number of the light sources 11 is larger than the number of the bypass circuits 12. In the modified configuration A, each bypass circuit 12 is connected in parallel to different u (an integer satisfying 2 ≦ u <n) light sources 11 connected in series among the n light sources 11. The value of u is smaller than the value of n.

  As an example, a modified configuration A in a state where the value of n is twice the value of k will be described with reference to FIG.

  FIG. 3 is a diagram for explaining a modified configuration A according to the first modification of the first embodiment of the present invention. Referring to FIG. 3, in modified configuration A, for example, each bypass circuit 12 is connected in parallel to two different light sources 11 connected in series among n light sources 11.

  Note that the number of light sources 11 connected in parallel to each bypass circuit 12 may be three or more.

  With the above modified configuration A, the number of bypass circuits 12 can be made smaller than the number of bypass circuits 12 in the configuration of the first embodiment. That is, the number of components (bypass circuit 12) can be reduced by the modified configuration A. Therefore, cost reduction of the video display apparatus 1000 can be realized.

(Function block diagram)
Hereinafter, among the functions of the video display apparatus 1000, the video display apparatus 1000 showing the main functions related to the present invention is also referred to as “video display apparatus BL10”. The video display device BL10 shows only the characteristic functional configuration of the video display device 1000.

  FIG. 4 is a block diagram of the video display device BL10 showing a characteristic functional configuration. The video display device BL10 functionally includes a light source unit BL1, a failure drive unit BL2, a failure determination unit BL3, and a notification unit BL4.

  The light source unit BL1 emits light used to display an image. The light source unit BL1 corresponds to the light source unit 110. The light source unit BL1 includes n (an integer of 2 or more) light sources that emit light when supplied with current. The n light sources are connected in series.

  The failure driving unit BL2 is provided in association with the n light sources. The failure time drive unit BL2 corresponds to the failure time drive unit 120. The failure determination unit BL3 determines whether or not a failure light source exists in the n light sources. The failure determination unit BL3 corresponds to the control unit 20. In addition, when a failure light source is present, the failure-time drive unit BL2 is configured to maintain light emission of a normal light source that is a light source other than the failure light source among the n light sources.

  When there is a faulty light source, the notification unit BL4 performs a notification process for notifying that the faulty light source exists. The notification unit BL4 corresponds to the notification unit 50.

(Other variations)
As described above, the video display device according to the present invention has been described based on the embodiment, but the present invention is not limited to the embodiment. The present invention also includes modifications made to the embodiments that would occur to those skilled in the art without departing from the spirit of the present invention. That is, within the scope of the invention, the present invention can be freely combined with the embodiments and the modified examples of the embodiments, or can be appropriately modified and omitted with the modified examples of the embodiments and the embodiments. is there.

  The video display apparatus 1000 according to the present invention may not include all the components shown in FIG. That is, the video display apparatus 1000 may include only the minimum components that can realize the effects of the present invention. For example, the video display apparatus 1000 may be configured without the network interface 30. In this configuration, the control unit 20 has the function of the network interface 30.

  In addition, the function of the control unit 20 that operates as a failure determination unit included in the video display device 1000 may be realized by a processing circuit. That is, the video display apparatus 1000 includes a processing circuit. The processing circuit is a circuit for determining whether or not a faulty light source is present in n light sources connected in series.

  The processing circuit may be dedicated hardware. The processing circuit may be a processor that executes a program stored in the memory. The processor is, for example, a CPU (Central Processing Unit), a central processing unit, an arithmetic unit, a microprocessor, a microcomputer, a DSP (Digital Signal Processor), or the like.

  Hereinafter, the configuration in which the processing circuit is dedicated hardware is also referred to as “configuration Cs1”. In the following, the configuration in which the processing circuit is a processor is also referred to as “configuration Cs2”. In the following, a configuration that realizes the function of the control unit 20 that operates as a failure determination unit by a combination of hardware and software is also referred to as “configuration Cs3”.

  In the configuration Cs1, the processing circuit is, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. Applicable. The function of the control unit 20 may be realized by a single processing circuit.

  Note that a configuration in which all or a part of each component included in the video display apparatus 1000 is represented by hardware is as follows, for example. Hereinafter, a video display device in which all or a part of each component included in the video display device 1000 is represented by hardware is also referred to as a “video display device hd10”.

  FIG. 5 is a hardware configuration diagram of the video display device hd10. Referring to FIG. 5, program recording / playback apparatus hd10 includes a processor hd1 and a memory hd2. The memory hd2 is, for example, a nonvolatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM, or an EEPROM. Further, for example, the memory hd2 is a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD, or the like.

  In the configuration Cs2, the processing circuit is the processor hd1. In the configuration Cs2, the function of the control unit 20 is realized by software, firmware, or a combination of software and firmware. Software or firmware is described as a program and stored in the memory hd2.

  In the configuration Cs2, the processing circuit (processor hd1) reads out the program stored in the memory hd2 and executes the program, whereby each function of the control unit 20 is realized. That is, the memory hd2 stores the following programs.

  The program is a program for causing the processing circuit (processor hd1) to execute a step of determining whether or not a faulty light source exists in n light sources connected in series.

  The program also causes a computer to execute a procedure of processing performed by the control unit 20, a method of executing the processing, and the like.

  In the configuration Cs3, some functions of the control unit 20 are realized by dedicated hardware. In the configuration Cs3, some other functions of the control unit 20 are realized by software or firmware.

  For example, some functions of the control unit 20 are realized by the processing circuit reading and executing a program stored in the memory. Further, for example, another part of the function of the control unit 20 is realized by a processing circuit as dedicated hardware.

  Like the configuration Cs1, the configuration Cs2, and the configuration Cs3 described above, the processing circuit can realize the functions described above by hardware, software, firmware, or a combination thereof.

  In addition, the present invention may be realized as a failure handling method in which the operation of a characteristic component included in the video display apparatus 1000 is a step. Further, the present invention may be realized as a program that causes a computer to execute each step included in such a failure handling method. Further, the present invention may be realized as a computer-readable recording medium that stores such a program. The program may be distributed via a transmission medium such as the Internet.

  Further, the failure handling method according to the present invention corresponds to, for example, the failure handling process of FIG.

  All the numerical values used in the above-mentioned embodiment are examples of numerical values for specifically explaining the present invention. That is, the present invention is not limited to the numerical values used in the above embodiments.

  It should be noted that within the scope of the invention, the present invention can be freely combined with the embodiments and modifications of the embodiments, or can be appropriately modified and omitted with reference to the embodiments and modifications of the embodiments. is there.

  For example, the notification unit 50 is not limited to a light source, and may be another component having a function of notifying a user that a faulty light source exists. For example, the notification unit 50 may be a speaker. In the configuration, in each of the notification processes B1 and B2 in FIG. 2, the notification unit 50 outputs a sound for notifying the user that a faulty light source exists.

  For example, the notification unit 50 may be a small display provided separately from the video display unit of the video display device 1000. In this configuration, in each of the notification processes B1 and B2 in FIG. 2, the notification unit 50 displays a message for notifying the user that a faulty light source exists. The message is, for example, the above-described release notification message or the above-described short-circuit notification message.

  Further, for example, the bypass circuit 12 is not limited to the configuration in FIG. 1, and may be configured by a circuit using a Zener diode or the like.

  Further, for example, the switch Sw is not limited to a bipolar transistor, and may be another type of switch. The switch Sw may be, for example, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor).

  For example, the network interface 30 included in the video display apparatus 1000 may be replaced with a serial communication interface.

  11, 11-1, 11-n light source, 12, 12-1, 12-k bypass circuit, 20 control unit, 50, BL4 notification unit, 100 backlight, 110, BL1 light source unit, 120, BL2 failure drive unit 140 Voltage control unit, 1000, BL10, hd10 video display device.

Claims (8)

A video display device,
A light source unit that emits light used to display an image;
The light source unit includes n (integer of 2 or more) light sources that emit light when supplied with current.
The n light sources are connected in series,
The video display device further includes:
A failure determination unit that determines whether or not a failure light source exists in the n light sources;
A failure-time drive unit provided in association with the n light sources,
The failure drive unit is configured to maintain light emission of a normal light source that is a light source other than the failure light source among the n light sources when the failure light source is present,
The video display device further includes:
A video display device comprising: a notification unit that performs a notification process for notifying that the faulty light source is present when the faulty light source is present. The failure-time drive unit includes k (an integer greater than or equal to 2) bypass circuits,
The value of k is the same as the value of n;
The video display device according to claim 1, wherein the k bypass circuits are connected in parallel to the n light sources. The failure-time drive unit includes k (an integer greater than or equal to 2) bypass circuits,
The value of k is smaller than the value of n,
The video display device according to claim 1, wherein each of the bypass circuits is connected in parallel to different u (an integer satisfying 2 ≦ u <n) light sources connected in series among the n light sources. . The video display device further includes:
Voltage control for generating a drive voltage, which is a voltage for supplying a drive current, which is a current for causing at least one of the n light sources to emit light, to a first light source among the n light sources. Part
The state of each bypass circuit is either a conductive state in which the drive current can be passed through the bypass circuit, or a non-conductive state in which the drive current cannot be passed through the bypass circuit. The bypass circuit is configured,
When each of the n light sources is the normal light source, the state of each bypass circuit is the non-conductive state,
The open circuit failure light source that is the failed light source that has an open failure in the n light sources, the state of the bypass circuit connected in parallel to the open failure light source is the conduction state. 4. The video display device according to 3. When the open failure light source is present, the voltage control unit is configured so that the forward voltage of the bypass circuit in the conductive state is associated with the bypass circuit, and the normal light source is in the state where the light source provided is the normal light source. The video display apparatus according to claim 4, wherein a driving voltage for generating a voltage greater than a forward voltage of the light source is generated. The failure determination unit determines whether or not the failure light source exists using a normal state voltage that is the driving voltage generated in a state where each of the n light sources is the normal light source. Has function,
The failure determination unit sets a first threshold value for determining that the open failure light source is present to a value of the driving voltage generated in a state where the failure light source is present, to a value of the normal state voltage. The video display device according to claim 4, wherein when the sum is equal to or greater than the added value, it is determined that the open failure light source exists. The failure determination unit determines whether or not the failure light source exists using a normal state voltage that is the driving voltage generated in a state where each of the n light sources is the normal light source. Has function,
The failure determination unit determines that the value of the drive voltage generated in a state where the failure light source exists is a value of the normal state voltage, and that there is a short-circuit failure light source that is the failure light source that is short-circuited. The video display device according to claim 4, wherein the short-circuit fault light source is determined to be present when the value is equal to or less than a value obtained by adding a second threshold value for performing the operation. The failure determination unit can communicate with an external device,
The video display according to any one of claims 1 to 7, wherein, when the faulty light source exists, the fault determination unit performs an external notification process for notifying the external device that the faulty light source exists. apparatus.

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