JP2008230544A - Vehicular lighting fixture lighting circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular lighting fixture lighting circuit capable of detecting failure generated on a single light source unit regardless of in-series connection or in-parallel connection of a plurality of light source units. <P>SOLUTION: The vehicular lighting fixture lighting circuit 10 is provided with a lighting control part 13 for receiving feeding of electric power from a power source and feeding a desired current to a light source part 11 for lighting-control of the light source part 11 constituted by the plurality of light source units 12; and a failure determination part 15 for determining whether or not failure is generated on the respective light source units 12 of the light source part 11 when the light source part 11 is lighted by the lighting control part 13. The failure determination part 15 obtains a voltage V between terminals of the respective light source units 12, sets the largest voltage of the obtained respective voltages V between terminals to a reference voltage. When mere one of the values obtained by reducing the respective voltages V between terminals from the reference voltage is larger than the previously set threshold value Th, it is determined that failure is generated on any one of the respective light source units 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vehicular lamp lighting circuit that lights a light source unit formed of a plurality of light source units.

  2. Description of the Related Art Conventionally, some lamps used in vehicles have a light source unit formed of a plurality of light source units, and an LED unit configured by using an LED (light emitting diode) is adopted as the light source unit. There is something. In such a vehicular lamp, when a failure occurs in any one of the LED units, for example, when a short-circuit failure occurs in one LED unit, a desired light distribution or brightness is not obtained due to the failure. However, there is a possibility that the lit state may be turned on, and the occupant may not be aware of this state. For this reason, some vehicle lamps have a vehicle lamp lighting circuit that can detect that a failure has occurred in any of the LED units.

As an example of such a vehicular lamp lighting circuit, a plurality of LED units are connected in series to form a light source unit, one LED unit randomly selected from the plurality of LED units is set as a reference in advance, and the reference By comparing the value of the voltage between the terminals of the LED unit with the value obtained by dividing the voltage between the terminals of the light source unit by the number of LED units connected in series therewith, a failure occurs in the reference LED unit. There is one that detects occurrence or failure of any of a plurality of LED units (for example, see Patent Document 1). In this vehicular lamp lighting circuit, one side to be relatively compared is a value obtained by dividing the voltage between the terminals of the light source unit by the number of LED units, so that it is possible to detect that a failure has occurred in a single LED unit. it can.
Japanese Patent Laid-Open No. 2006-210219

  However, in the above-described conventional vehicular lamp lighting circuit, one side to be relatively compared is a value obtained by dividing the voltage between the terminals of the light source unit by the number of LED units. Since the variation in the voltage between the terminals of the light source unit is also divided by the number of LED units, it is difficult to accurately detect that a failure has occurred in each LED unit.

  The present invention has been made in view of the above problems, and is for a vehicle capable of detecting a failure occurring in a single light source unit regardless of whether a plurality of light source units are connected in series or in parallel. It is an object to provide a lamp lighting circuit.

  In order to solve the above-described problem, a vehicle lamp lighting circuit according to claim 1 includes: a lighting control unit that supplies a desired current to the light source unit for lighting control of the light source unit configured by a plurality of light source units; A vehicle lamp lighting circuit including a failure determination unit that determines whether or not a failure has occurred in each of the light source units of the light source unit in a scene where the light source unit is turned on by the lighting control unit, The failure determination unit acquires a voltage between the terminals of each light source unit, sets the largest voltage among the acquired voltages between the terminals as a reference voltage, and a value obtained by subtracting the voltage between the terminals from the reference voltage If any one of the light source units is larger than a preset threshold value, it is determined that a failure has occurred in any of the light source units.

  According to the configuration described above, if any one of the differences between the largest inter-terminal voltage set as the reference voltage and the other inter-terminal voltage is larger than the threshold, it is determined that a failure has occurred. Because of the configuration, for example, when a failure that causes disconnection in one light source unit (hereinafter referred to as an open failure of the light source unit) occurs, the voltage between the terminals of the light source unit is relative to the voltage between other terminals. Since the reference voltage protrudes beyond the threshold value from the voltage between the other terminals, it is determined that all the differences are larger than the threshold value and a failure has occurred. When a failure that causes a short circuit in the light source unit (hereinafter referred to as a short-circuit failure of the light source unit) occurs, the voltage between the terminals of the light source unit decreases relative to the voltage between other terminals. So that the difference from the reference voltage of the terminal voltage of the light source unit is determined that a failure is greater than the threshold value has occurred. For this reason, in the light source unit, even when an open failure occurs or a short failure occurs, the failure can be detected appropriately.

  In addition, since the voltage between the terminals of each light source unit is compared, it can be used to determine the failure while maintaining the ratio of the fluctuation of the voltage between the terminals due to the failure occurring in each light source unit with respect to the reference voltage. Therefore, the failure can be detected easily and accurately.

  Furthermore, since it is the structure which compares the voltage between terminals of each light source unit, the fall of the detection accuracy by accumulation of the allowable error range of each light source unit can be prevented.

    The vehicular lamp lighting circuit according to claim 2 is the vehicular lamp lighting circuit according to claim 1, wherein the light source unit includes a plurality of the light source units connected in series, and the failure determination unit. Obtains the voltage between both ends of each light source unit as a comparison light source potential converted into a potential proportional to the magnitude of each voltage between both ends with a predetermined reference potential as a reference, and uses each comparison light source potential. And determining whether or not a failure has occurred.

  According to the configuration described above, since the comparison light source potential based on the predetermined reference potential is used, the comparison at the time of determining the failure can be made simple and accurate.

  The vehicular lamp lighting circuit according to claim 3 is the vehicular lamp lighting circuit according to claim 2, wherein the lighting control unit detects the value of the output voltage or the output current. In a scene having supply value detection means and applying a desired voltage to the light source part for lighting control of the light source part, the output voltage or output current detected by the supply value detection means is within a predetermined range. If it is outside, a failure detection signal is output to the failure determination unit.

  According to the configuration described above, such a failure can be detected when, for example, an open failure such as detachment of the light source unit or a short failure between both ends of the light source unit occurs.

  In the vehicular lamp lighting circuit of the present invention, it is possible to detect a failure occurring in a single light source unit regardless of whether the plurality of light source units are connected in series or in parallel.

  Embodiments of a vehicle lamp lighting circuit 10 according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a perspective view schematically illustrating a vehicle C in which the vehicular lamp lighting circuit 10 according to the first embodiment is employed, and FIG. 2 is a configuration diagram schematically illustrating the configuration of the vehicular lamp lighting circuit 10. It is.

  As shown in FIG. 1, the vehicle lamp lighting circuit 10 is applied as a circuit for lighting a light source unit 11 that constitutes a light emitting unit as a headlamp of the vehicle C, and is provided in a passenger compartment (not shown). The light source unit 11 is turned on / off in accordance with the operation performed by the headlamp lighting switch 18 (see FIG. 2). The light source unit 11 is configured by combining a plurality of LED units 12. In the first embodiment, five LED units 12a, 12b, 12c, 12d, and 12e having the same rating are connected in series. . Although not shown, each LED unit 12 is configured by connecting a single LED (light emitting diode) or at least two LEDs in series. The vehicle lamp lighting circuit 10 detects whether or not a failure has occurred in each LED unit 12 while performing lighting control of the light source unit 11. As shown in FIG. 2, the vehicular lamp lighting circuit 10 includes a lighting control unit 13, a comparison potential generation unit 14, and a failure determination unit 15.

  The lighting control unit 13 includes a control supervision part 16 and a supply value detection part 17. The control supervision part 16 has a power supply terminal Ts connected to the power supply circuit (23) and a GND terminal Tg which is set to the ground level (potential). Further, the control control part 16 is connected to both ends of the light source unit 11 through a pair of connection lines 19 and 20. In the first embodiment, the power terminal Ts is connected to the battery 23 as the power circuit mounted on the vehicle C via the switch circuit 24, and the switch circuit 24 is connected to the headlamp lighting switch 18. . The switch circuit 24 interrupts the electrical path from the battery 23 to the power supply terminal Ts in accordance with the operation performed on the headlamp lighting switch 18. When the switch circuit 24 is turned on and power is supplied from the battery 23, the control control unit 16 supplies a desired current to the light source unit 11 (a desired voltage corresponding to the light source unit 11 is supplied to the light source unit 11. The light source unit 11 is turned on.

  The supply value detection part 17 is connected to the connection point a and the connection point b and bridges the connection line 19 and the connection line 20, and the voltage (output voltage) applied to the light source unit 11 by the control supervision part 16. The detected output voltage value is output to the control control unit 16.

  The control control unit 16 is connected to the failure determination unit 15 via the connection line 21. When the output voltage value detected by the supply value detection unit 17 is out of a predetermined range, the supply abnormality signal is detected as a failure determination unit. 15 to send. The supply value detection part is provided as a supply value detection part 17 ′ that detects the value of the output current that flows through the connection line 19 at the position indicated by the alternate long and short dash line, that is, from the control control part 16 to the light source unit 11. It may be. In this case, the control control unit 16 may be configured to transmit a supply abnormality signal to the failure determination unit 15 when the value of the output current from the supply value detection unit 17 ′ is out of a predetermined range. In order to acquire the voltage between the terminals of each LED unit 12 of the light source unit 11 that is turned on by the control control unit 16, a comparison potential generation unit 14 is provided.

  The comparison potential generation unit 14 includes five voltage conversion circuits 22a, 22b, 22c, 22d, and 22e (hereinafter simply referred to as voltage conversion circuit 22 when collectively referred to). The five voltage conversion circuits 22 are configured to correspond to the five LED units 12, that is, the voltage conversion circuit 22a is connected to the connection point c and the connection point d so that the voltage between the terminals of the LED unit 12a can be obtained. The conversion circuit 22b is connected to the connection point d and the connection point e so that the voltage between the terminals of the LED unit 12b can be acquired, and the voltage conversion circuit 22c is connected to the connection point e and the connection point f so that the LED unit 12c The voltage between the terminals can be acquired, the voltage conversion circuit 22d is connected to the connection point f and the connection point g, and the voltage between the terminals of the LED unit 12d can be acquired, and the voltage conversion circuit 22e is connected to the connection point g and the connection point. The voltage between the terminals of the LED unit 12e can be acquired by being connected to h.

  In addition, each voltage conversion circuit 22 is connected to the GND terminal Tg via the control general part 16 of the lighting control unit 13 (in FIG. 2, connected to the GND terminal of the control general part 16). Each voltage conversion circuit 22 converts the voltage between the terminals of the corresponding LED unit 12 into a potential with reference to the ground, and generates comparison light source potentials V1, V2, V3, V4, and V5 (see FIG. 3). . Each comparison light source potential V does not need to be equal to the absolute value of the voltage between the terminals of each LED unit 12, and each has a magnitude equal to the absolute value of the voltage between the terminals of each LED unit 12. What is necessary is just to be converted into a potential with reference to the ground. Each voltage conversion circuit 22 outputs the generated comparison light source potentials V1, V2, V3, V4, and V5 (see FIG. 3) to the failure determination unit 15.

  As shown in FIG. 3, the failure determination unit 15 causes each LED unit 12 to fail using the comparison light source potentials V1, V2, V3, V4, and V5 acquired from the comparison potential generation unit 14 (each voltage conversion circuit 22). It is determined whether or not the error has occurred. This will be described in detail below.

  The failure determination unit 15 compares the comparison light source potentials V1, V2, V3, V4, and V5 with each other and selects the largest one (in the first embodiment, the comparison light source potential V4 is applicable). The comparative light source potential (V4) is set to the reference potential.

  Next, the failure determination unit 15 determines whether or not the other comparison light source potentials (V1, V2, V3, V5) are within a predetermined range as the reference potential (comparison light source potential V4), that is, the reference potential ( It is determined whether or not a value obtained by subtracting the other comparison light source potentials (V1, V2, V3, V5) from the comparison light source potential V4) is equal to or less than a predetermined threshold Th described later.

  If the values obtained by subtracting the other comparison light source potentials (V1, V2, V3, V5) from the reference potential (comparison light source potential V4) are all equal to or less than the threshold Th, the failure determination unit 15 displays the graph shown in FIG. When other comparative light source potentials V1, V2, V3, and V5 exist within a predetermined range (Na) with reference to the comparative light source potential V4, it is determined that no failure has occurred in any of the LED units 12. .

  On the other hand, the failure determination unit 15 determines that when at least one value obtained by subtracting the other comparison light source potentials (V1, V2, V3, V5) from the reference potential (comparison light source potential V4) is equal to or greater than the threshold Th, FIG. In the graph shown in FIG. 4, when any one of the other comparison light source potentials V1, V2, V3, and V5 exists outside the predetermined range (Na) with reference to the comparison light source potential V4 (see FIGS. 4 and 5), each LED unit. 12 is determined that a failure has occurred, and a failure detection signal is output to the vehicle control output terminal To. Although not shown, the vehicle control output terminal To is connected to a display control unit that controls lightning display in the vehicle interior of the vehicle C. When the failure detection signal is transmitted to the display control unit, A display for notifying that a failure has occurred in the headlamp is displayed on the electronic display. The notification to the occupant in the passenger compartment may be, for example, one that generates a warning sound as long as the occupant can recognize the occurrence of the failure, and is visually recognized by an electric display. It is not limited.

  Here, when the failure determination unit 15 determines that a failure has occurred in any of the LED units 12, the failure determination unit 15 outputs a failure detection signal to the control control unit 16 of the lighting control unit 13. The light control unit 16 to which the failure detection signal is input may be configured to turn off the light source unit 11 regardless of the operation performed on the headlamp lighting switch 18. It is stipulated by laws and regulations that if any of the LED units 12 fails, the light source unit 11 must be turned off when the amount of light in the light source unit 11 does not satisfy the prescribed standard. Because there are cases.

  Next, a process for detecting a failure occurring in the light source unit 11 in the vehicular lamp lighting circuit 10 will be described with reference to FIGS.

  3 to 5 are schematic graphs showing the comparative light source potential V in each LED unit 12 on the vertical axis, and FIG. 3 shows a case where each LED unit 12 is in a normal state. Shows a case where the LED unit 12c has a short circuit failure, and FIG. 5 shows a case where the LED unit 12e has an open failure. 3 to 5 are graphs schematically showing a process for detecting a failure in the vehicular lamp lighting circuit 10 for easy understanding of the explanation, and the magnitude of the comparison light source potential V shown in each of the graphs. Is different from the actual one.

  In the light source unit 11 of the vehicular lamp lighting circuit 10, as shown in FIG. 3, even when each LED unit 12 having the same standard is in a normal state, the terminal voltage (comparison light source potential) is in the lighting state. V) is not necessarily uniform due to the tolerance of each LED unit 12. In order to determine the presence or absence of a failure while taking into account variations due to this allowable error, the failure determination unit 15 sets a threshold value Th. For example, by making this threshold Th equal to the allowable error of the LED unit 12 to be mounted, it is possible to prevent erroneous detection of a failure due to variation due to the allowable error. Note that the threshold Th is not limited to the first embodiment, which may be a criterion for appropriately determining whether or not a failure has occurred, and is equal to the allowable error of the LED unit used.

  The failure determination unit 15 selects the largest one of the comparison light source potentials V input from the voltage conversion circuits 22 and sets this as the reference potential. In the example shown in FIG. 3, the comparative light source potential V4 is the reference potential.

  The failure determination unit 15 determines whether or not a value obtained by subtracting the remaining comparison light source potentials V1, V2, V3, and V5 from the reference potential V4 is larger than the threshold value Th, in other words, by the threshold Th from the reference potential V4. Whether or not a failure has occurred in each LED unit 12 by determining whether or not the remaining comparative light source potentials V1, V2, V3, and V5 exist within the range of the subtracted value (normal range Na in FIG. 3). Judge whether or not.

  Here, it is assumed that a short circuit failure has occurred in the LED unit 12c. Then, as shown in FIG. 4, since the comparison light source potential V3 becomes small (substantially 0 because of a short failure), the comparison light source potential V3 exists outside the normal range Na, that is, from the comparison light source potential V4 to the comparison light source potential. The value obtained by subtracting V3 becomes larger than the threshold value Th. Then, the failure determination unit 15 does not have the comparison light source potential V3 in the normal range Na (even one of the remaining comparison light source potentials V1, V2, V3, and V5 is not in the normal range Na. Therefore, it is determined that a failure has occurred in any of the LED units 12, and a failure detection signal is output.

  It is assumed that an open failure has occurred in the LED unit 12e. Then, as shown in FIG. 5, when the comparison light source potential V5 becomes large (because it is an open failure, it is assumed that no current flows through each voltage conversion circuit 22 (even if it flows), the LED unit 12a, 12b, 12c, and 12d no longer flow current, so that the voltage applied across the light source unit 11 is substantially the voltage across the terminals of the LED unit 12e). Since the light source potential V5 is the largest, the comparative light source potential V5 is set as the reference potential. Then, since the comparative light source potential V5 is larger than the remaining comparative light source potentials V1, V2, V3, and V4, the normal range Na is formed with a relatively large value, so that the comparative light source potential is formed. V1, V2, V3, and V4 exist outside the normal range Na, that is, all values obtained by subtracting the comparative light source potentials V1, V2, V3, and V4 from the comparative light source potential V5 are all greater than the threshold value Th. Then, the failure determination unit 15 does not have the comparison light source potentials V1, V2, V3, and V4 in the normal range Na (the normal range Na is set to one of the remaining comparison light source potentials V1, V2, V3, and V4). Therefore, it is determined that a failure has occurred in any of the LED units 12, and a failure detection signal is output.

  Further, in the vehicular lamp lighting circuit 10, when an open failure occurs between both terminals of the light source unit 11 due to, for example, the light source unit 11 being detached, the output voltage increases greatly. For example, between the two terminals of the light source unit 11 When the short circuit failure occurs between the two terminals of the light source unit 11 due to, for example, getting wet due to an unforeseen situation, the output voltage decreases greatly. Therefore, the control control unit 16 determines the value of the output voltage detected by the supply value detection unit 17. Is out of the predetermined range, a supply abnormality signal is transmitted to the failure determination unit 15. Upon receiving this supply abnormality signal, the failure determination unit 15 outputs a failure detection signal.

  Thus, in the vehicular lamp lighting circuit 10, when each LED unit 12 is normal, it is determined that the variation based on the allowable error of each LED unit 12 is a failure in any one of the LED units 12 ( Even if a short-circuit failure occurs in each LED unit 12 (see FIG. 4) or an open failure occurs (see FIG. 5) Can be detected.

  Further, in the vehicular lamp lighting circuit 10, even when a short failure occurs or an open failure occurs between both terminals of the light source unit 11, the failure can be detected appropriately.

  Further, the vehicular lamp lighting circuit 10 is configured to determine whether or not a value obtained by subtracting the other comparative light source potential V from the reference potential is equal to or less than a threshold Th with the largest comparative light source potential V as a reference potential. Therefore, the failure can be detected appropriately. This is because, as in the past, when a random LED unit is used as a reference, it cannot be determined how much tolerance the LED unit has. This is because the maximum amount of allowable error needs to be set both above and below the LED unit, so that the accuracy of failure detection is reduced.

  Since the vehicular lamp lighting circuit 10 is configured to compare the voltage between the terminals of each LED unit 12, a state in which the ratio of the fluctuation of the voltage between the terminals due to a failure occurring in each LED unit 12 with respect to the reference voltage is maintained. Therefore, it is possible to detect a failure easily and accurately.

  In the vehicular lamp lighting circuit 10, the voltage between the terminals of each LED unit 12 is relatively compared using each comparison light source potential V generated by the comparison potential generation unit 14 (each voltage conversion circuit 22). Thus, even if the voltage between the terminals of each LED unit 12 is a large value, each comparative light source potential V is set to a magnitude that is easy to handle in the failure determination unit 15, thereby reducing the burden on various elements constituting the failure determination unit 15. In addition, the failure determination unit 15 can have a simple configuration.

  Since the vehicular lamp lighting circuit 10 is configured to compare the voltage between the terminals of each LED unit 12, it is determined whether or not a failure has occurred in each LED unit 12 based on the allowable error range of each LED unit 12. Therefore, the failure can be detected easily and accurately.

  Therefore, in the vehicle lamp lighting circuit 10 according to the first embodiment, it is possible to appropriately detect a failure that has occurred in the single light source unit (LED unit 12).

  Next, the vehicle lamp lighting circuit 100 according to the second embodiment will be described. The vehicular lamp lighting circuit 100 according to the second embodiment corresponds to a light source unit 110 configured by connecting five LED units 120 in parallel as shown in FIG. The vehicular lamp lighting circuit 100 has the same basic configuration as the vehicular lamp lighting circuit 10 of the first embodiment, and therefore, the same functional parts are denoted by the same reference numerals as those of the first embodiment, and the detailed description thereof will be given. Is omitted. 6 is a configuration diagram schematically showing the configuration of the vehicular lamp lighting circuit 100, and FIG. 7 is a diagram illustrating each light source in FIG. 3 is a configuration diagram equivalently showing the periphery of a unit 110. FIG.

  In the vehicle lamp lighting circuit 100, as shown in FIG. 6, the light source unit 110 is configured by connecting five LED units 120 (120a, 120b, 120c, 120d, 120e) in parallel. In the light source unit 110, one end side of each LED unit 120 is connected to a connection line 190 extending from the control control part 16 of the lighting control unit 13 (the connection line 190 is connected in parallel as a common power line on the supply side). The other end side of the unit 120 is connected to the control control unit 16 via five connection lines 200 (200a, 200b, 200c, 200d, 200e).

  Further, in the vehicle lamp lighting circuit 100, since one end side of each LED unit 120 is connected to the common connection line 190, a common reference potential (ground level in the first embodiment) is applied as in the first embodiment. Since it is possible to compare the magnitudes without converting them to reference potentials, there is no equivalent to the comparison potential generation unit 14 (each voltage conversion circuit 22) of the vehicular lamp lighting circuit 10, and a failure determination unit. 150 is configured to acquire the voltage between the terminals of each LED unit 120. That is, the failure determination unit 150 is connected to the connection line 190 at the connection point o, is connected to the connection line 200a at the connection point p, and can acquire the voltage between the terminals of the LED unit 120a, and is connected at the connection point q. The voltage between the terminals of the LED unit 120b can be acquired by being connected to the line 200b, the voltage between the terminals of the LED unit 120c can be acquired at the connection point r, and the connection line 200d can be acquired at the connection point s. Is connected to the connection line 200e at the connection point t, and the terminal voltage of the LED unit 120e can be acquired. Determination of whether or not a failure has occurred in any of the LED units 120 in the failure determination unit 150 is the same as that of the failure determination unit 150 of the first embodiment.

  Further, the vehicle lamp lighting circuit 100 is provided with a supply value detection portion 170 that detects the output current of the connection line 190, similar to the supply value detection portion 17 'of the vehicle lamp lighting circuit 10 of the first embodiment. .

  Next, a process for detecting a failure occurring in the light source unit 110 in the vehicle lamp lighting circuit 100 will be described with reference to FIGS. 3 to 5. For this description, each LED unit of the light source unit 110 is described. FIG. 7 which is a configuration diagram showing 120 converted equivalently is used. As shown in FIG. 7, each LED unit 120 is configured such that the other end is connected to the control control section 16 and connected to the ground level via various circuits (not shown) in the control control section 16. Equivalently, it is configured to be connected to the ground level via a resistor R having an equal size. Here, as in Example 1, each LED unit 120 is in a normal state as shown in FIG. 3 (the LED unit 120d has the largest inter-terminal voltage V4), and a short circuit failure has occurred in the LED unit 120c. The case is shown in FIG. 4, and the case where an open failure occurs in the LED unit 120e is shown in FIG.

  The failure determination unit 150 selects the largest one of the inter-terminal voltages V input from each voltage conversion circuit 22 and sets this as a reference voltage. In the example shown in FIG. 3, the inter-terminal voltage V4 is the reference voltage. The failure determination unit 150 determines whether or not a value obtained by subtracting the remaining inter-terminal voltages V1, V2, V3, and V5 from the reference voltage V4 is larger than the threshold value Th, in other words, by the threshold Th from the reference voltage V4. Whether or not a failure has occurred in each LED unit 120 by determining whether or not the remaining terminal voltages V1, V2, V3, and V5 exist within the subtracted value range (normal range Na in FIG. 3). Judge whether or not.

  Here, it is assumed that a short circuit failure has occurred in the LED unit 120c. Then, as shown in FIG. 4, the inter-terminal voltage V3 becomes small (because of a short circuit failure, the voltage drop amount at the LED unit 120c is substantially zero, and the voltage drop amount at the resistor R in series therewith is the light source. Therefore, the voltage V3 between the terminals is outside the normal range Na, that is, the voltage V3 between the terminals is changed from the voltage V4 between the terminals. The value obtained by subtracting is larger than the threshold value Th. Then, the failure determination unit 150 does not have the terminal voltage V3 in the normal range Na (even one of the remaining terminal voltages V1, V2, V3, V5 does not exist in the normal range Na. Therefore, it is determined that a failure has occurred in any of the LED units 120, and a failure detection signal is output.

  Further, it is assumed that an open failure has occurred in the LED unit 120e. Then, as shown in FIG. 5, the inter-terminal voltage V5 becomes large (since it is an open failure, no current flows through the resistor R connected in series with the LED unit 120e, and the inter-terminal voltage of the LED unit 120e becomes the light source. The voltage applied across both ends of the unit 110 is equal to the potential of the connection line 190 as viewed from the ground level, whereas the other LED units 120a, 120b, 120c, and 120d are applied across the light source unit 110. Therefore, the inter-terminal voltage V5 is the largest among the inter-terminal voltages V, and the inter-terminal voltage V5 is used as a reference voltage. Then, since the inter-terminal voltage V5 is larger than the remaining inter-terminal voltages V1, V2, V3, and V4, the normal range Na is formed with a relatively large value, and the inter-terminal voltage V1, V2, V3, and V4 exist outside the normal range Na, that is, all the values obtained by subtracting the inter-terminal voltages V1, V2, V3, and V4 from the inter-terminal voltage V5 are all greater than the threshold Th. Then, the failure determination unit 150 does not have the inter-terminal voltages V1, V2, V3, V4 in the normal range Na (the normal range Na is set to one of the remaining inter-terminal voltages V1, V2, V3, V4). Therefore, it is determined that a failure has occurred in any of the LED units 120, and a failure detection signal is output.

  Further, in the vehicular lamp lighting circuit 10, when an open failure occurs between both terminals of the light source unit 110 due to, for example, the light source unit 110 being disconnected, the output current becomes 0, for example, between the two terminals of the light source unit 110. When a short circuit failure occurs between both terminals of the light source unit 110 due to an accidental wetting or the like, the output current greatly increases. Therefore, the control control unit 16 determines that the output voltage value detected by the supply value detection unit 170 Based on being out of the predetermined range, a supply abnormality signal is transmitted to the failure determination unit 150. Upon receiving this supply abnormality signal, the failure determination unit 150 outputs a failure detection signal. Needless to say, the supply value detection portion may be configured to acquire the voltage between both terminals of the light source unit 110, as in the supply value detection portion 17 of the first embodiment. This can be realized by acquiring the potential of the connection line 190 viewed from the ground level.

  Thus, in the vehicular lamp lighting circuit 100, when each LED unit 120 is normal, it is determined that the variation based on the allowable error of each LED unit 120 indicates that a failure has occurred in any one of the LED units 120 ( Even if a short circuit failure occurs in each LED unit 120 (see FIG. 4) or an open failure occurs (see FIG. 5) Can be detected.

  Further, in the vehicular lamp lighting circuit 100, even when a short failure occurs or an open failure occurs between both terminals of the light source unit 110, the failure can be appropriately detected.

  Further, the vehicular lamp lighting circuit 10 is configured to determine whether or not a value obtained by subtracting the voltage V between the other terminals from the reference voltage is equal to or less than a threshold Th with the largest voltage V between the terminals as a reference voltage. Therefore, the failure can be detected appropriately.

  Since the vehicular lamp lighting circuit 100 is configured to compare the voltage between the terminals of each LED unit 120, the ratio of the fluctuation of the voltage between the terminals due to a failure occurring in each LED unit 120 with respect to the reference voltage is maintained. Therefore, it is possible to detect a failure easily and accurately.

  Since the vehicular lamp lighting circuit 100 is configured to compare the voltage between the terminals of each LED unit 120, it is determined whether or not a failure has occurred in each LED unit 120 based on the allowable error range of each LED unit 120. Therefore, the failure can be detected easily and accurately.

  Therefore, in the vehicular lamp lighting circuit 100 according to the second embodiment, a failure that has occurred in a single light source unit (LED unit 120) can be detected appropriately.

  As described above, in the vehicular lamp lighting circuit according to the present invention, the inter-terminal voltage of each light source unit is acquired, the largest voltage among the inter-terminal voltages is set as the reference voltage, and the remaining voltage from the reference voltage is set. Since the configuration in which one of the light source units has failed when the value obtained by subtracting the inter-terminal voltage of each light source unit is greater than the threshold value Th, a plurality of light source units are connected in series. Whether or not a failure has occurred in any one of the light source units by adopting a configuration capable of acquiring the voltage between the terminals of each light source unit as appropriate regardless of whether it is configured in parallel or connected in parallel Can be detected appropriately.

  In the vehicular lamp lighting circuit according to the present invention, a voltage between terminals of each light source unit (LED unit) is acquired, and a failure has occurred in one of them by comparing the voltage between the terminals. For example, even if each light source unit (LED unit) is configured with different ratings, the rated value of each light source unit (LED unit) is uniform. By simply multiplying the obtained inter-terminal voltage by a variable such as, a failure occurring in each light source unit (LED unit) by the same process can be appropriately detected. On the other hand, the conventional vehicle lamp lighting circuit cannot be applied unless the ratio of its allowable error to the rated value of each light source unit (LED unit) is equal.

  Further, in the vehicular lamp lighting circuit according to the present invention, regardless of whether the light source unit is configured by connecting a plurality of light source units in series or connected in parallel, the allowable error range of each light source unit is accumulated. This prevents the detection accuracy from being lowered.

  In each of the above-described embodiments, a headlamp is shown as an example of a vehicle lamp device according to the present invention. For example, a stop lamp, a tail lamp, a turn lamp, a room lamp, a side turn lamp, and a door mirror turn lamp However, the present invention is not limited to the above-described embodiments.

  Further, in each of the above-described embodiments, the LED unit 12 composed of LEDs is shown as an example of a plurality of light source units used in the light source unit, but any light source unit that can emit light to the outside. For example, a filament valve may be used and is not limited to the above-described embodiment.

  Furthermore, in each of the above-described embodiments, an example in which the light source unit has a plurality of light source units connected in series in Example 1 is shown, and an example in which the light source unit has a plurality of light source units connected in parallel in Example 2 is shown. In any case, the inter-terminal voltage of each light source unit is acquired, the largest voltage among the terminals is set as the reference voltage, and the remaining inter-terminal voltage of each light source unit is determined from the reference voltage. If the value obtained by subtracting is larger than the threshold value Th, any failure may occur in any of the light source units, and the present invention is not limited to the above-described embodiments.

  In each of the above-described embodiments, an example in which each LED unit 12 has a short failure and an open failure has been shown. However, when each LED unit 12 is configured by connecting a plurality of LEDs in series, for example, one of them There may be a situation where one LED has a short-circuit failure and an open failure. Here, when an open failure occurs in a single LED, no current flows through the remaining LEDs, and a failure is detected in the same manner as in each of the above embodiments. In this case, unlike the above-described embodiments, other LEDs in the light source section remain lit at a predetermined voltage. Even in this case, since the voltage between the two terminals of the light source unit is reduced by the voltage drop of the single LED that is short-circuited, for example, when several or more of the plurality of LEDs are short-circuited The threshold value Th may be set from the viewpoint of whether the LED unit is regarded as a failure.

1 is a perspective view schematically showing a vehicle in which a vehicle lamp to which a vehicle lamp lighting circuit of the present invention is applied is adopted. It is a block diagram which shows schematically the structure of a vehicle lamp lighting circuit. It is a graph for demonstrating the operation | movement of determination of the generation | occurrence | production of the failure in a vehicle lamp lighting circuit, and has shown the case where each LED unit is a normal state. It is a graph for demonstrating the operation | movement of judgment of generation | occurrence | production of the failure in a vehicle lamp lighting circuit, and has shown the case where one LED unit has a short circuit failure. It is a graph for demonstrating the operation | movement of judgment of generation | occurrence | production of the failure in a vehicle lamp lighting circuit, and has shown the case where one LED unit has an open failure. It is a block diagram which shows schematically the structure of the vehicle lamp lighting circuit of Example 2. FIG. FIG. 7 is a configuration diagram showing equivalent conversion of each light source unit of the light source unit in FIG. 6.

Explanation of symbols

10, 100 Vehicle lamp lighting circuit 11, 110 Light source unit 12, 120 LED unit (as light source unit) 13 Lighting control unit 15, 150 Failure determination unit 17, 17 ′, 170 Supply value (as supply value detecting means) Detection part Th Threshold V Comparison light source potential

Claims (3)

A lighting control unit for supplying a desired current to the light source unit for lighting control of the light source unit configured by a plurality of light source units, and the light source unit in the scene where the light source unit is lit by the lighting control unit A vehicle lamp lighting circuit including a failure determination unit that determines whether or not a failure has occurred in each light source unit,
The failure determination unit acquires a voltage between the terminals of each light source unit, sets the largest voltage among the acquired voltages between the terminals as a reference voltage, and a value obtained by subtracting the voltage between the terminals from the reference voltage The vehicle lamp lighting circuit according to claim 1, wherein when any one of the light source units is larger than a preset threshold, it is determined that a failure has occurred in any of the light source units. The light source unit is configured by connecting a plurality of the light source units in series,
The failure determination unit acquires the voltage between both ends of each light source unit as a comparison light source potential converted into a potential proportional to the magnitude of each voltage between both ends with respect to a predetermined reference potential, The vehicle lamp lighting circuit according to claim 1, wherein the presence or absence of a failure is determined using a light source potential. The lighting control unit has supply value detection means for detecting a value of an output voltage or an output current, and applies a desired voltage to the light source unit for lighting control of the light source unit. 3. The vehicle according to claim 2, wherein a failure detection signal is output to the failure determination unit when an output voltage or an output current detected by the supply value detection means is outside a predetermined range in a scene where the supply value is detected. Lamp lighting circuit.

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