Fault detection circuit and passenger monitoring device

Abstract

A failure detection circuit (1) comprises: a first substrate (PL1) on which is mounted a drive circuit (21) that outputs a drive voltage; and a second substrate (PL2) on which are mounted a plurality of light-emitting elements (31–33) that are driven by the drive voltage output from the drive circuit and are connected in series to each other, and a failure detection unit (40) that detects one or more failures among the plurality of light-emitting elements, wherein the first substrate and the second substrate are configured as separate substrates.

Description

[Technical field]

[0001] The present disclosure relates to a fault detection circuit and an occupant monitoring device. [Background technology]

[0002] Conventionally, there is known a lighting control circuit for controlling lighting of a vehicle lamp using a semiconductor light emitting element such as an LED (Light Emitting Diode) as a light source. For example, Patent Document 1 discloses a lighting control circuit for a vehicle lamp, which includes a control means for controlling a current and a voltage to N (N is a positive integer) semiconductor light sources connected in series, with electrostatic protection elements connected in parallel to the N semiconductor light sources as loads, a disconnection detection means for outputting a disconnection detection signal when the current of the N semiconductor light sources shows an abnormal value, a plurality of voltage drop detection means for detecting that the sum of the voltages across the plurality of semiconductor light sources is lower than the sum of the forward voltages of the plurality of semiconductor light sources, with a plurality of semiconductor light sources being detection targets among the N semiconductor light sources, and a voltage drop logic means for outputting a logical sum of the detection outputs of the plurality of voltage drop detection means as a disconnection detection signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-86413 A Summary of the Invention [Problem to be solved by the invention]

[0004] Semiconductor light-emitting elements such as LEDs may be used as light sources for various devices other than vehicle lighting. For example, in a driver monitoring system (DMS), a plurality of IR-LEDs (Infra-Red LEDs) connected in series are used as a light source for irradiating passengers in the vehicle cabin. In this case, in order to reliably irradiate passengers with infrared rays, it is desirable that the IR-LEDs be able to change the direction of infrared radiation by adjusting the installation angle of the board on which the IR-LEDs are mounted in the vehicle cabin, where the installation space is limited.

[0005] On the other hand, fault detection is also necessary for IR-LEDs used as illumination light sources in passenger monitoring devices. Therefore, it is conceivable to apply the fault detection method in the lighting control circuit described in Patent Document 1 to fault detection of IR-LEDs used in passenger monitoring devices. However, the lighting control circuit described in Patent Document 1 does not take into consideration varying the irradiation direction of light emitted from the semiconductor light source. Therefore, it has been difficult to apply the fault detection method described in Patent Document 1 to fault detection of IR-LEDs used in passenger monitoring devices.

[0006] The present disclosure has been made to solve the above-mentioned problems, and aims to obtain a fault detection circuit that is capable of adjusting the direction of light emitted by a light-emitting element and detecting a fault in the light-emitting element. [Means for solving the problem]

[0007] The fault detection circuit of the present disclosure comprises a first substrate on which a drive circuit that outputs a drive voltage is mounted, and a second substrate on which a plurality of light-emitting elements connected in series with each other and driven by the drive voltage output from the drive circuit are mounted, and a fault detection unit for detecting a fault in one or more of the plurality of light-emitting elements, the first substrate and the second substrate being configured as separate substrates. The fault detection unit includes resistors arranged in parallel with each of the multiple light-emitting elements, first transistors arranged in parallel with each of the resistors, second transistors arranged in parallel with each of the first transistors and connected in series with each other, a third transistor that outputs a signal indicating the logical product of each of the output signals of the second transistors, and a fourth transistor that outputs an inverted signal of the output signal of the third transistor as a fault detection signal. Effect of the Invention

[0008] According to the present disclosure, it is possible to obtain a failure detection circuit that is capable of adjusting the direction of light emitted by a light-emitting element and detecting a failure in the light-emitting element. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing an example of the configuration of an occupant monitoring device including a failure detection circuit according to a first embodiment; [Diagram 2] 2 is a diagram illustrating a configuration example of a fault detection circuit according to the first embodiment; [Diagram 3] 5 is a diagram showing an example of an installation angle of a first substrate and a second substrate in the first embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Embodiment 1

[0011] Fig. 1 is a diagram showing an example of the configuration of a driver monitoring system (DMS) 10 including a fault detection circuit 1 according to embodiment 1. The driver monitoring system 10 shown in Fig. 1 is mounted on, for example, a vehicle 100, and monitors a driver of the vehicle 100.

[0012] 1, the occupant monitoring device 10 includes a camera (imaging device) 11, a floodlight 12, and a control device (ECU) 13. The occupant monitoring device 10 starts operation when the main power supply of the vehicle 100 is turned on (for example, when the ignition is turned on), and ends operation when the main power supply is turned off.

[0013] The camera 11 is attached, for example, to a position (for example, near a meter) close to the front of the driver's seat on the instrument panel of the vehicle 100. The shooting range of the camera 11 is set so as to include a spatial area in which the face of an occupant (driver) would normally be located when the occupant sits in the driver's seat. In other words, the camera 11 is positioned so as to be able to shoot an image of the face of the occupant sitting in the driver's seat from the front.

[0014] This camera 11 repeatedly captures the faces of the occupants at regular intervals (e.g., 30 times per second) while the occupant monitoring device 10 is in operation, and outputs the captured images (i.e., images including the faces) obtained as a result of the capture to the control device 13 in the order in which they were captured.

[0015] Camera 11 mainly uses near-infrared light when taking pictures. Specifically, a filter that blocks almost all light other than near-infrared light is attached to camera 11, and the camera takes pictures using the light received through the filter.

[0016] The floodlight 12 is a device for irradiating mainly near-infrared light onto the face of the occupant sitting in the driver's seat. The near-infrared light irradiated by the floodlight 12 is reflected by the occupant's face, so that the captured image of the face taken by the camera 11 becomes clear without being significantly affected by the external environment.

[0017] A light-emitting element (IR-LED) that emits near-infrared light, for example, is used as the floodlight 12. The floodlight 12 is attached, for example, to a position on the instrument panel of the vehicle 100, close to the front of the driver's seat. The floodlight 12 is disposed so that infrared light is emitted to a spatial region where the face of the occupant would normally be located when the occupant sits in the driver's seat.

[0018] In addition, the floodlight 12 may be configured to emit light in accordance with the timing of the image capture by the camera 11 based on control from the control device 13, or may be configured to continue emitting light at all times while the occupant monitoring device 10 is operating.

[0019] The control device (ECU) 13 is composed of a microcomputer having a CPU, RAM, ROM, flash memory, I / O, etc., all of which are not shown. The CPU reads a program from the ROM, loads it into the RAM, and executes it, and during the execution, obtains information from the flash memory, camera 11, etc., as necessary. The operation of the control device 13 is realized by such operations of the CPU, etc.

[0020] Specifically, the control device 13 sequentially determines the facial movement state of the occupant based on the captured image of the occupant's face received from the camera 11, and executes a predetermined process based on the determination result. Here, the facial movement state of the occupant refers to the state of the occupant's facial movement. For example, the face direction, eye opening degree (i.e., the degree to which the eyelids are open), and gaze direction (i.e., the direction in which the occupant is looking) are each a type of facial movement state.

[0021] <Fault detection circuit 1> The failure detection circuit 1 is provided in, for example, an occupant monitoring device 10. In this case, the failure detection circuit 1 detects a failure of an LED used in a projector 12.

[0022] A configuration example of the fault detection circuit 1 is shown in Fig. 2. The fault detection circuit 1 includes a first substrate PL1 and a second substrate PL2, as shown in Fig. 2, for example. The first substrate PL1 and the second substrate PL2 are configured as separate substrates. Note that the LEDs that are the subject of fault detection by the fault detection circuit 1, i.e., the IR-LEDs used in the floodlight 12, are mounted on the second substrate PL2 in a state in which a plurality of them are connected in series. In the example of Fig. 2, three IR-LEDs 31 to 33 (hereinafter also simply referred to as "LEDs 31 to 33") are mounted on the second substrate PL2 in a state in which they are connected in series.

[0023] On the other hand, the first substrate PL1 is mounted with a drive circuit LED-DR21. The LED-DR21 outputs a drive voltage for driving the LEDs 31-33 and also controls the operation of the LEDs 31-33.

[0024] The first substrate PL1 and the second substrate PL2 are arranged in the vehicle 100, separated from each other, in a state where they are connected by a connection line (e.g., a vehicle harness). For example, the first substrate PL1 is arranged in a state where it is housed inside the above-mentioned control device (ECU) 13. On the other hand, the second substrate PL2 is arranged in a state where it is housed inside the above-mentioned floodlight 12. At this time, both the first substrate PL1 and the second substrate PL2 are configured so that their own installation angles can be arbitrarily adjusted, regardless of the installation angle of the other substrate. The first substrate PL1 and the second substrate PL2 will be described below.

[0025] <First board PL1> The first substrate PL1 is mounted with a drive circuit LED-DR21. The LED-DR21 has a positive terminal connected to a connection line L1 and a negative terminal connected to a connection line L2.

[0026] The LED-DR21 generates a drive voltage having a predetermined voltage value from the positive terminal. As a result, the LED-DR21 supplies a direct current (hereinafter also simply referred to as "current") for driving the LEDs 31 to 33 mounted on the second substrate PL2 to the LEDs 31 to 33 via the connection line L1. In the following description, the voltage of the connection line L1 when the LED-DR21 generates the drive voltage is also referred to as the "input voltage."

[0027] The LED-DR21 also includes a voltage monitor terminal 22 that is a terminal for monitoring the voltage value of the input voltage. The voltage monitor terminal 22 is connected to the connection line L1 via a signal line and a resistor. The LED-DR21 constantly monitors the input voltage via the voltage monitor terminal 22, and detects the occurrence of a failure in the LEDs 31 to 33 based on the voltage value of the input voltage.

[0028] <Second board PL2> The second substrate PL2 is equipped with three LEDs 31-33 connected in series and driven by a driving voltage output from LED-DR21, and a fault detection unit 40 that detects a fault in one or more of the three LEDs 31-33.

[0029] For ease of explanation, an example in which three LEDs 31 to 33 are connected in series will be described here, but the number of LEDs is not limited to this, and may be any number as long as it is more than one. For ease of explanation, the left end in the left-right direction of Fig. 2 and the upper end in the up-down direction of Fig. 2 will be referred to as "one end", and the right end in the left-right direction of Fig. 2 and the lower end in the up-down direction of Fig. 2 will be referred to as "the other end".

[0030] On the second substrate PL2, of the three LEDs 31 to 33 connected in series, the LED 31 at one end has an anode connected to the positive terminal of LED-DR21 via a connection line L1, and a cathode connected to the anode of the LED 32 adjacent to the other end of the LED 31.

[0031] The anode of the LED 32 is connected to the cathode of the LED 31 adjacent to one end of the LED 32 , and the cathode is connected to the anode of the LED 33 adjacent to the other end of the LED 32 .

[0032] The anode of the LED 33 at the other end is connected to the cathode of the LED 32 adjacent to one end of the LED 33, and the cathode is connected to the negative terminal of the LED-DR21 via a connection line L2. The connection line L2 is connected to ground via a resistor 50.

[0033] <Failure detection unit 40> The failure detection section 40 detects a failure in one or more of the three LEDs 31 to 33. Here, the failures detected by the failure detection section 40 include both an open failure and a short failure.

[0034] The failure detection section 40 includes resistors 41 to 49, first transistors 51 to 53, second transistors 61 to 63, a third transistor 71, and a fourth transistor 81.

[0035] <Resistance 41~49> The resistors 41 to 43 are provided in parallel with the LEDs 31 to 33, respectively. Specifically, the resistor 41 has one end connected to the anode of the LED 31, and the other end connected to the cathode of the LED 31. Similarly, the resistor 42 has one end connected to the anode of the LED 32, and the other end connected to the cathode of the LED 32. Moreover, the resistor 43 has one end connected to the anode of the LED 33, and the other end connected to the cathode of the LED 33. The resistance values ​​of the resistors 41 to 43 are set to be larger than the on-resistances of the LEDs 31 to 33.

[0036] One end of the resistor 44 is connected to the collector terminal of the first transistor 51, and the other end is connected to the base terminal of the second transistor 61. Similarly, one end of the resistor 45 is connected to the collector terminal of the first transistor 52, and the other end is connected to the base terminal of the second transistor 62. Moreover, one end of the resistor 46 is connected to the collector terminal of the first transistor 53, and the other end is connected to the base terminal of the second transistor 63.

[0037] The resistor 47 has one end connected to the emitter terminal of the second transistor 63, and the other end connected to the base terminal of the third transistor 71. The resistor 48 has one end connected to the positive terminal of the LED-DR21, and the other end connected to the collector terminal of the third transistor 71. The resistor 49 has one end connected to the positive terminal of the LED-DR21, and the other end connected to the collector terminal of the fourth transistor 81.

[0038] <First transistors 51 to 53> The first transistors 51-53 are PNP transistors, and are provided in parallel with the resistors 41-43, respectively.

[0039] Specifically, the first transistor 51 has an emitter terminal connected to the anode of the LED 31, and a base terminal connected to the cathode of the LED 31. In addition, the collector terminal is connected to the base terminal of the second transistor 61 corresponding to the first transistor 51 via a resistor 44.

[0040] Similarly, the first transistor 52 has an emitter terminal connected to the anode of the LED 32, a base terminal connected to the cathode of the LED 32, and a collector terminal connected via a resistor 45 to the base terminal of a second transistor 62 corresponding to the first transistor 52.

[0041] The first transistor 53 has an emitter terminal connected to the anode of the LED 33, and a base terminal connected to the cathode of the LED 33. The collector terminal is connected to the base terminal of a second transistor 63 corresponding to the first transistor 53 via a resistor 46.

[0042] <Second transistors 61 to 63> The second transistors 61 to 63 are NPN transistors, and are provided in parallel to the first transistors 51 to 53, respectively, and are connected in series to each other.

[0043] Specifically, among the second transistors 61 to 63, the second transistor 61 corresponding to the LED 31 at one end has a collector terminal connected to the positive terminal of the LED-DR21, and a base terminal connected to the collector terminal of the first transistor 51 corresponding to the second transistor 61 via a resistor 44. Also, the emitter terminal is connected to the collector terminal of the second transistor 62 adjacent to the second transistor 61 at the other end side.

[0044] Of the second transistors 61 to 63, the second transistor 62 corresponding to the LED 32 between one end and the other end has a collector terminal connected to the emitter terminal of the second transistor 61 adjacent to one end of the second transistor 62, and a base terminal connected to the collector terminal of the first transistor 52 corresponding to the second transistor 62 via a resistor 45. The emitter terminal is also connected to the collector terminal of the second transistor 63 adjacent to the other end of the second transistor 62.

[0045] Among the second transistors 61 to 63, the second transistor 63 corresponding to the LED 33 at the other end has a collector terminal connected to the emitter terminal of the second transistor 62 adjacent to one end side of the second transistor 63, and a base terminal connected via a resistor 46 to the collector terminal of the first transistor 53 corresponding to the second transistor 63. The emitter terminal is also connected to the base terminal of the third transistor 71.

[0046] <Third transistor 71> The third transistor 71 is an NPN transistor, and outputs a signal indicating the logical product of the output signals of the second transistors 61 to 63. Specifically, the collector terminal of the third transistor 71 is connected to the positive terminal of the LED-DR21 via a resistor 48, and the base terminal is connected to the emitter terminal of the second transistor 63 corresponding to the LED 33 at the other end via a resistor 47. The emitter terminal is also connected to the negative terminal of the LED-DR21.

[0047] <Fourth transistor 81> The fourth transistor 81 is an NPN transistor, and outputs an inverted signal of the output signal of the third transistor 71 as a fault detection signal. Specifically, the collector terminal of the fourth transistor 81 is connected to the positive terminal of the LED-DR21 via the resistor 49, and the base terminal is connected to the collector terminal of the third transistor 71. Also, the emitter terminal is connected to the negative terminal of the LED-DR21.

[0048] In the failure detection circuit 1 configured as above, the three LEDs 31-33 configure an element unit together with the resistors 41-43, the first transistors 51-53, and the second transistors 61-63 provided corresponding to the LEDs 31-33. In the failure detection circuit 1, the LEDs 31-33 are configured so that each element unit can be mounted on the second substrate PL2.

[0049] Next, an operation example of the fault detection circuit 1 shown in Fig. 2 will be described. In the following explanation, the operation example of the fault detection circuit 1 will be described in three cases: (1) when all three LEDs are operating normally (no fault has occurred) (hereinafter also referred to as "normal operation"), (2) when one or more of the three LEDs have a short circuit failure (hereinafter also referred to as "short circuit failure"), and (3) when one or more of the three LEDs have an open circuit failure (hereinafter also referred to as "open circuit failure").

[0050] In addition, in the operation example of the failure detection circuit 1, in a state (initial state) before LED-DR21 outputs a drive voltage, the first transistors 51-53, the second transistors 61-63, the third transistor 71, and the fourth transistor 81 are all off.

[0051] (1) During normal operation First, the LED-DR21 outputs a drive voltage. This generates a current in the connection line L1. The LED-DR21 also starts monitoring the input voltage via the voltage monitor terminal 22.

[0052] At this time, since the resistance value of resistor 41 is larger than the on-resistance of LED 31, most of the current generated in connection line L1 flows to LED 31, and then to LEDs 32 to 33. As a result, LEDs 31 to 33 operate (emit light), and a predetermined forward voltage (Vf) is generated in each LED. This forward voltage generates a potential difference between the emitter and base of first transistors 51 to 53, and first transistors 51 to 53 are turned on.

[0053] When the first transistors 51 to 53 are turned on, a current flows to the base terminals of the second transistors 61 to 63, and the second transistors 61 to 63 are also turned on. When the second transistors 61 to 63 are turned on, a current flows to the base terminal of the third transistor 71, and the third transistor 71 is also turned on.

[0054] When the third transistor 71 is turned on, no current flows from the connection line L1 to the base terminal of the fourth transistor 81, and the fourth transistor 81 remains off. When the fourth transistor 81 remains off, the voltage value of the input voltage monitored by the LED-DR21 via the voltage monitor terminal 22 becomes substantially the same as the voltage value of the drive voltage output by the LED-DR21. In this case, the LED-DR21 does not detect an LED failure. The failure detection circuit 1 operates as described above while the LEDs 31 to 33 continue to operate normally.

[0055] (2) In case of a short circuit For example, assume that during normal operation, only LED31 of the three LEDs has a short circuit. At this time, most of the current generated in the connection line L1 flows through LED31, but since LED31 has a short circuit, no forward voltage is generated in LED31. As a result, in the first transistor 51, no voltage drop occurs between the emitter and base, and the emitter and base become at the same potential. This turns the first transistor 51 off. When the first transistor 51 turns off, no current flows through the base terminal of the second transistor 61, and the second transistor 61 also turns off.

[0056] On the other hand, since the LEDs 32 to 33 are operating normally, the first transistors 52 to 53 and the second transistors 62 to 63 all remain on.

[0057] When the second transistor 61 is turned off, even if the second transistors 62 to 63 are on, no current flows through the second transistors 61 to 63 as a whole, and therefore no current flows through the base terminal of the third transistor 71. As a result, the third transistor 71 is also turned off. In this case, the third transistor 71 being turned off is synonymous with the third transistor 71 outputting a signal indicating the logical product (AND) of the output signals from the second transistors 61 to 63.

[0058] When the third transistor 71 is turned off, a current from the connection line L1 flows to the base terminal of the fourth transistor 81 via the resistor 48, and the fourth transistor 81 is turned on. In this case, the fourth transistor 81 being turned on is synonymous with the fourth transistor 81 outputting an inverted signal of the output signal of the third transistor 71.

[0059] When the fourth transistor 81 is turned on, the connection lines L1 and L2 are shorted. Then, the voltage value of the input voltage monitored by the LED-DR21 via the voltage monitor terminal 22 becomes approximately 0. When the voltage value of the input voltage becomes approximately 0, the LED-DR21 detects an LED failure. In this case, the fourth transistor 81 being turned on is synonymous with the fourth transistor 81 outputting a failure detection signal.

[0060] The above operation is the same when one or more of the three LEDs fail due to a short circuit. For example, the above operation is the same not only when only LED 32 or only LED 33 fails due to a short circuit, but also when, for example, LED 31 and LED 32 fail due to a short circuit, or when all three LEDs 31 to 33 fail due to a short circuit.

[0061] (3) When an open fault occurs For example, let us assume that during normal operation, only LED31 of the three LEDs experiences an open circuit fault. At this time, a current generated in the connection line L1 flows to LED32 via resistor 41. At this time, a voltage drop occurs in resistor 41, and a potential difference occurs between the emitter and base of first transistor 51. However, this potential difference is small and does not turn on the first transistor 51. As a result, the first transistor 51 turns off.

[0062] After the first transistor 51 is turned off, the fault detection circuit 1 operates in the same manner as in the case of the short fault described above. That is, when the first transistor 51 is turned off, no current flows through the base terminal of the second transistor 61, and the second transistor 61 is also turned off.

[0063] On the other hand, since the LEDs 32 to 33 are operating normally, the first transistors 52 to 53 and the second transistors 62 to 63 all remain on.

[0064] When the second transistor 61 is turned off, even if the second transistors 62 to 63 are on, no current flows through the second transistors 61 to 63 as a whole, and therefore no current flows through the base terminal of the third transistor 71. As a result, the third transistor 71 is also turned off. In this case, the third transistor 71 being turned off is synonymous with the third transistor 71 outputting a signal indicating the logical product (AND) of the output signals from the second transistors 61 to 63.

[0065] When the third transistor 71 is turned off, a current from the connection line L1 flows to the base terminal of the fourth transistor 81 via the resistor 48, and the fourth transistor 81 is turned on. In this case, the fourth transistor 81 being turned on is synonymous with the fourth transistor 81 outputting an inverted signal of the output signal of the third transistor 71.

[0066] When the fourth transistor 81 is turned on, the connection lines L1 and L2 are shorted, and the voltage value of the input voltage monitored by the LED-DR21 via the voltage monitor terminal 22 becomes approximately 0. In this case, the LED-DR21 detects an LED failure. In this case, the fourth transistor 81 being turned on is synonymous with the fourth transistor 81 outputting a failure detection signal.

[0067] The above operation is the same when one or more of the three LEDs have an open circuit failure. For example, the above operation is the same not only when only LED32 or only LED33 has an open circuit failure, but also when, for example, LED31 and LED32 have an open circuit failure, or when all three LEDs 31 to 33 have an open circuit failure.

[0068] Thus, according to the first embodiment, the failure detection circuit 1 can accurately detect a failure (short failure and open failure) that occurs in one or more of a plurality of LEDs in a state in which the plurality of LEDs are connected in series. Also, according to the first embodiment, the failure detection section 40, which is a main part of the failure detection circuit 1, can be configured by a simple circuit using only a plurality of transistors and resistors. For example, for the above-mentioned three LEDs 31 to 33, the failure detection section 40 can be configured by using only eight transistors (reference numerals 51 to 53, 61 to 63, 71, and 81) and nine resistors (reference numerals 41 to 49).

[0069] In particular, when IR-LEDs are used as the LEDs, the forward voltage of IR-LEDs is smaller than that of other LEDs, and the forward voltage of each IR-LED tends to vary widely. Therefore, in the past, when multiple IR-LEDs were connected in series, it was sometimes difficult to detect a short circuit failure that occurred in one of them.

[0070] For example, a conventional method for detecting a short circuit when multiple IR-LEDs are connected in series is to have the LED-DR monitor the voltage on the anode side of each IR-LED, and when that voltage falls below a threshold voltage, detect a short circuit in that IR-LED.

[0071] However, as mentioned above, IR-LEDs have a smaller forward voltage than other LEDs, and the forward voltage of each individual IR-LED tends to vary greatly. Therefore, when multiple IR-LEDs are connected in series, with the above-mentioned conventional method, the LED-DR may not be able to detect a short circuit in an IR-LED, or the LED-DR may mistakenly detect a short circuit in an IR-LED even when there is no short circuit.

[0072] To address this issue, one option would be to have the LED-DR monitor the voltage across each IR-LED. However, with this method, if the IR-LEDs are on a separate board from the LED-DR, it could result in an increase in the amount of wiring connecting the boards, or an increase in the number of monitor terminals on the LED-DR.

[0073] In this regard, in the first embodiment, even when a plurality of IR-LEDs are connected in series, a short circuit failure occurring in one or more of the plurality of IR-LEDs can be accurately detected. Moreover, in the first embodiment, even when a short circuit failure of each IR-LED is detected, there is no need to increase the number of wirings connecting the first substrate PL1 and the second substrate PL2, or to increase the number of monitor terminals of the LED-DR.

[0074] According to the first embodiment, the first substrate PL1 and the second substrate PL2 are installed apart from each other while being connected via the connection lines L1 and L2 as described above. For example, the first substrate PL1 is accommodated inside the control device 13 installed in the vehicle 100, and the second substrate PL2 is accommodated inside the floodlight 12 installed in the vehicle 100. At this time, the floodlight 12 and the control device 13 are located at positions physically separated from each other in the vehicle 100.

[0075] In this state, the first substrate PL1 and the second substrate PL2 are configured so that the installation angle of one substrate can be arbitrarily adjusted regardless of the installation angle of the other substrate. Here, the installation angle refers to, for example, the pitch angle, yaw angle, and roll angle.

[0076] An example of the installation angles of the first substrate PL1 and the second substrate PL2 is shown in Fig. 3. The installation angles of both substrates are expressed by, for example, a pitch angle, a yaw angle, and a roll angle as shown in Fig. 3.

[0077] For example, the installation angle of the first substrate PL1 can be adjusted arbitrarily, regardless of the installation angle at which the second substrate PL2 is installed. Similarly, the installation angle of the second substrate PL2 can be adjusted arbitrarily, regardless of the installation angle at which the first substrate PL1 is installed.

[0078] In particular, in the first embodiment, the installation angle of the second substrate PL2 on which the serially connected LEDs are mounted can be adjusted arbitrarily regardless of the installation angle of the first substrate PL1, so that the degree of illumination of the LEDs for the occupants can be easily adjusted. In addition, in this case, the worker does not need to make any changes to the wiring of the connection lines L1 and L2 that connect the first substrate PL1 and the second substrate PL2, so the workability is extremely good.

[0079] Furthermore, as described above in the first embodiment, each of the LEDs 31 to 33 configures an element unit together with the resistors 41 to 43, the first transistors 51 to 53, and the second transistors 61 to 63 provided corresponding to each of the LEDs 31 to 33. In the first embodiment, each of the LEDs 31 to 33 is configured so that each element unit can be mounted on the second substrate PL2.

[0080] For example, in the first embodiment, consider a case where an operator adds a fourth LED 34 (not shown) to the second substrate PL2. In this case, the operator configures the LED 34, a resistor 44 connected in parallel to the LED 34, a first transistor 54 connected in parallel to the resistor 44, a second transistor 64 connected in parallel to the first transistor 54, and a resistor (none of which are shown) connecting the collector terminal of the first transistor 54 and the base terminal of the second transistor 64 as one element unit. Then, the operator adds the element unit between the connection line L1 and the base terminal of the third transistor 71, for example.

[0081] In this case, the worker only needs to add the element unit between the connection line L1 and the base terminal of the third transistor 71, and does not need to modify the configuration related to other wiring (e.g., connection lines L1 and L2, the wiring of the third transistor 71, and the wiring of the fourth transistor 81) and terminals (e.g., the voltage monitor terminal 22). Furthermore, even if the worker adds an element unit, there is no need for the worker to increase the number of connection lines connecting the first substrate PL1 and the second substrate PL2. Furthermore, even in this case, the worker only needs to add two transistors and two resistors for each additional LED, and the size and number of components of the failure detection section 40 do not increase excessively.

[0082] Thus, in embodiment 1, even when an operator adds LEDs to the second substrate PL2, the LEDs can be easily added on an element unit basis without making significant changes to the existing wiring and terminal configuration.

[0083] Furthermore, even when removing the LEDs from the second substrate PL2, the worker can easily remove the LEDs as element units by following the same procedure as described above, without making any significant changes to the existing wiring and terminal configuration.

[0084] In the above description, the fault detection circuit 1 is provided in the passenger monitoring device 10. However, the fault detection circuit 1 is not limited to this, and can be applied to any device that uses multiple light-emitting elements connected in series with each other.

[0085] As described above, according to the first embodiment, the failure detection circuit 1 includes a first substrate PL1 on which a drive circuit 21 that outputs a drive voltage is mounted, and a second substrate PL2 on which a plurality of light-emitting elements 31-33 connected in series and driven by the drive voltage output from the drive circuit 21, and a failure detection unit 40 that detects a failure of one or more of the plurality of light-emitting elements are mounted, the first substrate PL1 and the second substrate PL2 being configured as separate substrates. As a result, the failure detection circuit 1 according to the first embodiment is capable of adjusting the direction of light emitted by the light-emitting elements and of detecting a failure of the light-emitting elements.

[0086] The fault detection section 40 includes resistors 41-43 provided in parallel with the light-emitting elements 31-33, first transistors 51-53 provided in parallel with the resistors 41-43, second transistors 61-63 provided in parallel with the first transistors 51-53 and connected in series, a third transistor 71 that outputs a signal indicating the logical product of the output signals of the second transistors 61-63, and a fourth transistor 81 that outputs an inverted signal of the output signal of the third transistor 71 as a fault detection signal. As a result, the fault detection circuit 1 according to the first embodiment can configure the fault detection section 40 by a combination of transistors and resistors.

[0087] Each of the light emitting elements 31-33 constitutes an element unit together with the resistors 41-43, the first transistors 51-53, and the second transistors 61-63 provided corresponding to the light emitting element, and the element unit can be mounted on the second substrate PL2. This allows the failure detection circuit 1 according to the first embodiment to easily mount the light emitting elements on an element unit basis.

[0088] In addition, the light-emitting elements 31 to 33 are diodes, the first transistors 51 to 53 are PNP transistors, the second transistors 61 to 63, the third transistor 71, and the fourth transistor 81 are NPN transistors, and the positive terminal of the drive circuit 21 is connected to the anode of the diode at one end of the multiple diodes connected in series, and the negative terminal of the drive circuit 21 is connected to the cathode of the diode at the other end of the multiple diodes. In addition, one end of the resistors 41 to 43 is connected to the anode of the corresponding diode and the other end is connected to the cathode of the corresponding diode, and the emitter terminal of the first transistors 51 to 53 is connected to the anode of the corresponding diode, the base terminal is connected to the cathode of the diode, and the collector terminal is connected to the base terminal of the corresponding second transistors 61 to 63. In addition, the second transistor 61 corresponding to the diode at one end has a collector terminal connected to the positive terminal of the drive circuit 21, a base terminal connected to the collector terminal of the corresponding first transistor 51, and an emitter terminal connected to the collector terminal of the adjacent second transistor 62 at the other end. In addition, the second transistor 63 corresponding to the diode at the other end has a collector terminal connected to the emitter terminal of the adjacent second transistor 62 on one end side, a base terminal connected to the collector terminal of the corresponding first transistor 53, and an emitter terminal connected to the base terminal of the third transistor 71. In addition, the second transistor 62 corresponding to the diode between one end and the other end has a collector terminal connected to the emitter terminal of the second transistor 61 adjacent to one end side, a base terminal connected to the collector terminal of the corresponding first transistor 52, and an emitter terminal connected to the collector terminal of the second transistor 63 adjacent to the other end side. In addition, the third transistor 71 has a collector terminal connected to the positive terminal of the drive circuit 21, a base terminal connected to the emitter terminal of the second transistor 63 corresponding to the diode at the other end, and an emitter terminal connected to the negative terminal of the drive circuit 21. In addition, the fourth transistor 81 has a collector terminal connected to the positive terminal of the drive circuit 21, a base terminal connected to the collector terminal of the third transistor 71, and an emitter terminal connected to the negative terminal of the drive circuit 21. As a result, the failure detection circuit 1 according to the first embodiment can detect a failure in a diode by using a combination of a transistor and a resistor.

[0089] Furthermore, the fault detection unit 40 detects an open fault and a short fault that occurs in one or more of the multiple light-emitting elements 31 to 33 connected in series with each other. This allows the fault detection circuit 1 according to the first embodiment to detect both open faults and short faults as types of faults to be detected.

[0090] According to the first embodiment, the occupant monitoring device 10 is provided with the above-mentioned failure detection circuit 1, and includes an imaging device 11 that images an occupant, a floodlight 12 using a plurality of light-emitting elements 31-33 as a light source for irradiating the occupant with light, and a control device 13 that executes a predetermined process based on an image captured by the imaging device 11, the first board PL1 is disposed inside the control device 13, the second board PL2 is disposed inside the floodlight 12, and the installation angle of one of the first board PL1 and the second board PL2 is adjustable regardless of the installation angle of the other. As a result, the occupant monitoring device 10 according to the first embodiment can arbitrarily adjust the irradiation angle of the light irradiated to the occupant.

[0091] In addition, in the present disclosure, any of the components in the embodiments may be modified, or any of the components in the embodiments may be omitted. [Industrial Applicability]

[0092] INDUSTRIAL APPLICABILITY The present disclosure is suitable for use in a failure detection circuit, since it is possible to adjust the direction of light emitted by a light-emitting element and to detect a failure of the light-emitting element. [Explanation of symbols]

[0093] 1 fault detection circuit, 10 occupant monitoring device, 11 camera (imaging device), 12 floodlight, 13 control device, 21 drive circuit, 22 voltage monitor terminal, 31-33 light emitting element (LED), 40 fault detection section, 41-50 resistor, 51-53 first transistor, 61-63 second transistor, 71 third transistor, 81 fourth transistor, 100 vehicle, L1 connecting line, L2 connecting line, PL1 first board, PL2 second board.

Claims

1. a first substrate on which a drive circuit for outputting a drive voltage is mounted; a second substrate on which are mounted a plurality of light-emitting elements connected in series with each other and driven by a drive voltage output from the drive circuit, and a fault detection unit that detects a fault in one or more of the plurality of light-emitting elements; The first substrate and the second substrate are configured as separate substrates, The failure detection unit A resistor provided in parallel with each of the plurality of light-emitting elements; a first transistor provided in parallel with each of the resistors; second transistors provided in parallel with each of the first transistors and connected in series with each other; a third transistor for outputting a signal indicating a logical product of the output signals of the second transistors; a fourth transistor that outputs an inverted signal of the output signal of the third transistor as a failure detection signal; A fault detection circuit comprising:

2. Each of the light-emitting elements constitutes an element unit together with the resistor, the first transistor, and the second transistor provided corresponding to the light-emitting element, and the element unit can be mounted on the second substrate.

2. The fault detection circuit according to claim 1.

3. the light emitting element is a diode, the first transistor is a PNP transistor; the second transistor, the third transistor, and the fourth transistor are NPN transistors; a positive terminal of the drive circuit is connected to an anode of a diode at one end of a plurality of diodes connected in series; a negative terminal of the drive circuit is connected to the cathode of the diode at the other end of the plurality of diodes; The resistor is One end is connected to the anode of the corresponding diode, and the other end is connected to the cathode of the corresponding diode; The first transistor is an emitter terminal connected to the anode of the corresponding diode, a base terminal connected to the cathode of the diode, and a collector terminal connected to the base terminal of the corresponding second transistor; The second transistor corresponding to the diode at one end is a collector terminal connected to the positive terminal of the drive circuit, a base terminal connected to the collector terminal of the corresponding first transistor, and an emitter terminal connected to the collector terminal of an adjacent second transistor on the other end side; The second transistor corresponding to the diode at the other end is a collector terminal is connected to an emitter terminal of a second transistor adjacent to one end side, a base terminal is connected to a collector terminal of the corresponding first transistor, and an emitter terminal is connected to a base terminal of the third transistor; The second transistor corresponding to the diode between the one end and the other end has a collector terminal connected to an emitter terminal of the second transistor adjacent to the one end side, a base terminal connected to a collector terminal of the corresponding first transistor, and an emitter terminal connected to a collector terminal of the second transistor adjacent to the other end side; The third transistor is a collector terminal connected to the positive terminal of the drive circuit, a base terminal connected to the emitter terminal of the second transistor corresponding to the diode at the other end, and an emitter terminal connected to the negative terminal of the drive circuit; The fourth transistor is The collector terminal is connected to the positive terminal of the drive circuit, the base terminal is connected to the collector terminal of the third transistor, and the emitter terminal is connected to the negative terminal of the drive circuit.

2. The fault detection circuit according to claim 1.

4. The failure detection unit Detects open circuit failures and short circuit failures that occur in one or more of a plurality of light emitting elements connected in series with each other 4. The fault detection circuit according to claim 1, wherein the first and second inputs are connected to the first and second inputs.

5. An occupant monitoring device including the failure detection circuit according to any one of claims 1 to 3, An imaging device for imaging an occupant; a floodlight using the plurality of light-emitting elements as a light source for irradiating the occupant with light; a control device that executes a predetermined process based on an image captured by the imaging device, the first board is disposed inside the control device, and the second board is disposed inside the light projector; The installation angle of one of the first substrate and the second substrate is adjustable regardless of the installation angle of the other substrate. An occupant monitoring device comprising:

Images