JP2019192565A - Vehicular lighting fixture - Google Patents

Abstract

To provide a vehicular lighting fixture capable of detecting disconnection in multiple light source circuits that are mutually connected in parallel with a simple configuration.SOLUTION: A vehicular lighting fixture 1 includes: a light source unit 10 having a master light source circuit 12 and one or more slave light source circuits 13, that are mutually connected in parallel; a first current mirror circuit 30 for allowing a current to flow in each one of the one or more slave light source circuits 13 in accordance with a current flowing in the master light source circuit 12; and a disconnection detection section 40 for detecting disconnection concerning the multiple light source circuits 11. The disconnection detection section 40 includes: a second current mirror circuit 41 for allowing a detection current to flow in a disconnection detection line Ld that is connected to the master light source circuit 12 in parallel in accordance with a current flowing in the master light source circuit 12; and a determination section 42 for determining disconnection on the basis of a fluctuation of a detection current.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a vehicular lamp.

  A vehicle lamp using a semiconductor element such as an LED as a light source has been proposed because of its high luminous efficiency and excellent design. In this type of vehicle lamp, a light source unit is known that employs a configuration in which a plurality of light source circuits each composed of a plurality of light emitting elements connected in series are connected in parallel.

  For example, Patent Document 1 discloses a current driving circuit that causes a built-in light emitting element to emit light by a constant current output from a constant current circuit. This current driving circuit is configured to connect a series of light emitting units in which a plurality of light emitting elements are connected in series, a light emitting unit in which a plurality of light emitting elements are connected in parallel, and a current flowing through one series light emitting circuit among the plurality of series light emitting circuits. A current mirror circuit for inputting to the circuit.

  Further, for example, Patent Document 2 discloses a light source unit group lighting device that lights a light source unit group in which a plurality of light source units are provided in parallel by a lighting instruction signal input from an input unit. This light source unit group lighting device controls a lighting switch unit based on information on a lighting switch unit that controls energization to the light source unit group, a disconnection detection unit that detects whether each light source unit is disconnected, and whether there is a disconnection. And a switch control unit.

JP 2017-5185 A JP 2008-168706 A

  However, according to the technique disclosed in Patent Document 1, there is a problem that there is no function of detecting disconnection, and it is impossible to recognize that the light source circuit (series light emitting circuit) is disconnected. In addition, the circuit does not stop even when the wire is disconnected, and the light source circuit continues to be lit. Therefore, when there is a request to turn off the light in the event of an abnormality, this cannot be met. Furthermore, since the current corresponding to the disconnected system flows to other light source circuits, the amount of light varies, but it cannot cope with the variation.

  On the other hand, the technique disclosed in Patent Document 2 discloses a function of detecting disconnection of each light source circuit (light source unit). However, according to this method, it is necessary to provide an electronic component and a signal wiring for each light source circuit, and there is a disadvantage that the cost increases according to the number of light source circuits.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a vehicular lamp that can detect disconnection of a plurality of light source circuits connected in parallel with each other with a simple configuration.

  In order to solve this problem, the present invention provides a vehicular lamp that is driven by a current output from a constant current circuit. In this vehicular lamp, a plurality of light source circuits composed of a plurality of light emitting elements connected in series are connected in parallel, one light source circuit is provided as a master light source circuit, and the remaining light source circuits are used as one or more slave light source circuits. A light source unit, a first current mirror circuit for causing a current to flow in each of the one or more slave light source circuits in accordance with a current flowing in the master light source circuit, and a break detection unit for detecting a break in each of the light source circuits. Have. Then, the disconnection detection unit is configured to disconnect the second current mirror circuit for supplying a detection current to the disconnection detection line connected in parallel to the master light source circuit in accordance with the current flowing in the master light source circuit, and based on the fluctuation of the detection current. And a determination unit for determining.

  Here, according to the present invention, when any one or more slave circuits are disconnected, the detection current increases according to the current flowing in the disconnected slave circuit, and when the master light source circuit is disconnected, the detection current is detected. The working current is preferably stopped.

  In the present invention, it is preferable that the disconnection detection line includes a resistor that converts a change in detection current into a change in detection voltage, and the determination unit determines disconnection based on the change in detection voltage.

  According to the vehicular lamp according to the present invention, disconnection of a plurality of light source circuits connected in parallel to each other can be detected with a simple configuration.

The block diagram which shows typically the vehicle lamp which concerns on this embodiment Timing chart showing voltage fluctuation of detection voltage

  Hereinafter, the vehicular lamp 1 according to the present embodiment will be described. Here, FIG. 1 is a configuration diagram schematically showing the vehicular lamp 1 according to the present embodiment.

  The vehicular lamp 1 is mainly composed of a light source unit 10, a power supply circuit 20, a first current mirror circuit 30, and a disconnection detector 40. The vehicle lamp 1 is turned on by supplying a current from the power supply circuit 20 to the light source unit 10.

  The light source unit 10 includes a plurality of light source circuits connected in parallel to each other, four light source circuits 11 in this embodiment. Each light source circuit 11 includes a plurality of light emitting elements, for example, LEDs, connected in series. The anode side of each light source circuit 11 is commonly connected to the power supply line Lp, and the cathode side thereof is connected to the first current mirror circuit 30. In the present embodiment, among these four light source circuits 11, one light source circuit 11 is called a master light source circuit 12, and the remaining light source circuits 11 are called slave light source circuits 13, respectively.

  The power supply circuit 20 is a circuit that outputs a constant current, and can change the output voltage. For the power supply circuit 20, for example, a constant current output type DC / DC converter or the like can be used. A DC power source (not shown) such as a battery mounted on the vehicle is connected to the power circuit 20. The power supply circuit 20 is connected to a power supply line Lp for supplying an input current to the light source unit 10.

  The first current mirror circuit 30 distributes the current supplied from the power supply circuit 20 to each light source circuit 11 so that the current flowing through each light source circuit 11 becomes equal. Specifically, the first current mirror circuit 30 has a function of flowing current to each of the three slave light source circuits 13 in accordance with the current flowing to the master light source circuit 12. The first current mirror circuit 30 includes transistors Q1 to Q4 connected to each light source circuit 11 in series.

  The transistors Q1 to Q4 are NPN-type bipolar transistors, and are connected in series to the master light source circuit 12 and the three slave light source circuits 13, respectively. Specifically, the transistor Q1 is connected to the master light source circuit 12. The remaining transistors Q2 to Q4 are connected to the three slave light source circuits 13, respectively.

  The collector terminals of the transistors Q1 to Q4 are connected to the cathode side of the master light source circuit 12 and the slave light source circuit 13.

  The emitter terminals of the transistors Q1 to Q4 are connected to the ground line Lg via resistors R1 to R4. The resistors R1 to R4 function as emitter resistors. The resistance values of the resistors R1 to R4 are selected so that the voltage between both ends becomes a predetermined voltage. By providing the resistors R1 to R4, a potential difference is generated by the current flowing through the resistors R1 to R4. Thereby, variations in the base-emitter voltages of the transistors Q1 to Q4 can be absorbed, and the current flowing through each light source circuit 11 can be stabilized.

  The base terminals of the transistors Q1 to Q4 are commonly connected.

  Further, the transistor Q5 is connected to the first current mirror circuit 30. The transistor Q5 is connected between the power supply line Lp and the transistors Q1 to Q4, and is Darlington connected to the individual transistors Q1 to Q4. The collector terminal of the transistor Q5 is connected to the power supply line Lp, and its emitter terminal is commonly connected to the base terminals of the individual transistors Q1 to Q4. The base terminal of the transistor Q5 is connected to a connection point A between an emitter terminal of a transistor Q6, which will be described later, and a collector terminal of the transistor Q1.

  The disconnection detection unit 40 detects disconnection for each of the light source circuits 11. The disconnection detection unit 40 includes a second current mirror circuit 41 and a determination unit 42.

  The second current mirror circuit 41 has a function of causing a detection current to flow through the disconnection detection line Ld connected in parallel to the master light source circuit 12 in accordance with the current flowing through the master light source circuit 12. The second current mirror circuit 41 includes transistors Q6 and Q7. The transistors Q6 and Q7 are NPN bipolar transistors.

  The collector terminal of the transistor Q6 is connected to the cathode side of the master light source circuit 12, and the emitter terminal thereof is connected to the collector terminal of the transistor Q1. The base terminal of the transistor Q6 is commonly connected to the base terminal of the transistor Q7.

  The collector terminal of the transistor Q7 is connected to the power supply line Lp, and the emitter terminal thereof is connected to the ground line Lg via the resistor R5. A disconnection detection line Ld is configured by a path from the connection point with the power supply line Lp to the ground line Lg through the collector terminal of the transistor Q7, the emitter terminal of the transistor Q7, and the resistor R5.

  The transistor Q8 is connected to the second current mirror circuit 41. The transistor Q8 is connected between the power supply line Lp and the transistors Q6 and Q7, and is Darlington connected to the individual transistors Q6 and Q7. The collector terminal of the transistor Q8 is connected to the power supply line Lp, and the emitter terminal thereof is commonly connected to the base terminals of the transistors Q6 and Q7. The base terminal of the transistor Q8 is connected to a connection point B between the cathode side of the master light source circuit 12 and the collector terminal of the transistor Q6.

  The determination unit 42 determines the disconnection of the light source unit 10 based on the voltage fluctuation of the disconnection detection line Ld due to the fluctuation of the detection current, that is, the fluctuation of the detection voltage Va. The determination unit 42 includes a resistor R5, a first comparator 43, and a second comparator 44.

  The resistance value of the resistor R5 is selected so that the voltage between both ends becomes a predetermined voltage when the light source unit 10 is not disconnected. By providing the resistor R5, a potential difference (detection voltage Va) is generated by a current (detection current) flowing through the disconnection detection line Ld. At this time, the current change of the detection current appears as a voltage change of the detection voltage Va. The resistor R5 has a function of converting a change in the detection current into a change in the detection voltage Va. Through this potential difference (detection voltage Va), the voltage change of the disconnection detection line Ld can be recognized.

  The non-inverting input terminal (+) of the first comparator 43 and the inverting input terminal (−) of the second comparator 44 are respectively connected to the connection point between the emitter terminal of the transistor Q7 and the resistor R5.

  The first comparator 43 compares the detection voltage Va input to the non-inverting input terminal (+) with the first determination voltage Vref1 input to the inverting input terminal (−) to thereby detect the first disconnection detection signal S1. Is generated. The first disconnection detection signal S1 is at a high level if the detection voltage Va is higher than the first determination voltage Vref1, and is at a low level if the detection voltage Va is lower than the first determination voltage Vref1.

  The second comparator 44 compares the second determination voltage Vref2 input to the non-inverting input terminal (+) with the detection voltage Va input to the inverting input terminal (−) to thereby generate the second disconnection detection signal S2. Is generated. The second disconnection detection signal S2 is at a high level if the second determination voltage Vref2 is higher than the detection voltage Va, and is at a low level if the second determination voltage Vref2 is lower than the detection voltage Va.

  The determination result by the determination unit 42, that is, the first disconnection detection signal S1 and the second disconnection detection signal S2 are set to an upper control unit that sets the output current of the power supply circuit 20 or informs the state of the light source unit 10 (Not shown).

  Hereinafter, the disconnection detection process in the vehicle lamp 1 according to the present embodiment will be described. Here, FIG. 2 is a timing chart showing voltage fluctuations of the detection voltage Va. In the figure, (a) is a timing chart showing a state in which no disconnection occurs in any of the light source circuits 11. (B) is a timing chart showing a state in which a disconnection has occurred in any of the slave light source circuits 13, and (c) is a timing chart showing a state in which a disconnection has occurred in the master light source circuit 12.

  First, a state where no disconnection occurs in any of the light source circuits 11 will be described. The constant current supplied from the power supply circuit 20 is evenly distributed by the first current mirror circuit 30 and the second current mirror circuit 41, and flows through each light source circuit 11 and the disconnection detection line Ld. Thereby, each of the master light source circuit 12 and the three slave light source circuits 13 is turned on. The constant current from the power supply circuit 20 is equally divided in the disconnection detection line Ld, the master light source circuit 12 and the three slave light source circuits 13, and the current ILED flowing through each circuit is a constant current output from the power supply circuit 20. Equal value (20% of constant current).

  Here, the current Ic5 input to the collector terminal of the transistor Q5 is a value (ILED / hfe5) obtained by dividing the current ILED by the amplification factor hfe5 of the transistor Q5. In the present embodiment, a sufficiently large amplification factor hfe5 of the transistor Q5 is selected, and the current Ic5 input to the collector terminal of the transistor Q5 is sufficiently small.

  Similarly, current Ic8 input to the collector terminal of transistor Q8 has a value (ILED / hfe8) obtained by dividing current ILED by amplification factor hfe8 of transistor Q8. In the present embodiment, a sufficiently large amplification factor hfe8 of the transistor Q8 is selected, and the current Ic8 input to the collector terminal of the transistor Q8 is sufficiently small.

In the determination unit 42 of the disconnection detection unit 40, the first determination voltage Vref1 input to the inverting input terminal (−) of the first comparator 43 is based on the following condition 1 based on the current ILED and the resistor R5 when there is no disconnection: It is set to satisfy.
<Condition 1>
R5 × ILED <Vref1 <R5 × (ILED + ILED / 4)

Further, the second determination voltage Vref2 input to the non-inverting input terminal (+) of the second comparator 44 is set so as to satisfy the following condition 2 on the basis of the current ILED and the resistor R5 when not disconnected. ing.
<Condition 2>
Vref2 <R5 x ILED

  Therefore, the determination unit 42 disconnects both the master light source circuit 12 and the three slave light source circuits 13 on condition that the detection voltage Va is larger than the second determination voltage Vref2 and smaller than the first determination voltage Vref1. It can be determined that they have not. In this case, the first disconnection detection signal S1 and the second disconnection detection signal S2 output from the determination unit 42 are each at a low level. The upper control unit connected to the determination unit 42 is configured so that both the master light source circuit 12 and the three slave light source circuits 13 are provided on the condition that the first disconnection detection signal S1 and the second disconnection detection signal S2 are each at a low level. It can be recognized that it is not disconnected.

  On the other hand, it is assumed that one of the three slave light source circuits 13 is disconnected. In this case, the current flowing in the disconnected slave light source circuit 13 is divided into the disconnection detection line Ld, the master light source circuit 12, and the remaining two slave light source circuits 13.

The detection voltage Va changes as follows between before disconnection and after disconnection.
<Before disconnection>
Va = R5 × ILED
<After disconnection>
Va = R5 × ILED + R5 × ILED / 4

  The detection voltage Va after the disconnection is higher than the first determination voltage Vref1. Therefore, the determination unit 42 can determine that one of the three slave light source circuits 13 is disconnected on the condition that the detection voltage Va is higher than the first determination voltage Vref1. In this case, the first disconnection detection signal S1 output from the determination unit 42 is at a high level, and the second disconnection detection signal S2 is at a low level. The upper control unit connected to the determination unit 42 is disconnected to one of the three slave light source circuits 13 on condition that the first disconnection detection signal S1 is at a high level and the second disconnection detection signal S2 is at a low level. Can be recognized.

  In contrast, it is assumed that the master light source circuit 12 is disconnected. In this case, the collector current of the transistor Q6 connected in series to the cathode side of the master light source circuit 12 is stopped. For this reason, the operation of the second current mirror circuit 41 is stopped. Then, the current of the disconnection detection line Ld is also stopped.

  The detection voltage Va after the disconnection is smaller than the second determination voltage Vref2. Therefore, the determination unit 42 can determine that the master light source circuit 12 is disconnected on the condition that the detection voltage Va is smaller than the second determination voltage Vref2. In this case, the first disconnection detection signal S1 output from the determination unit 42 is at a low level, and the second disconnection detection signal S2 is at a high level. The upper control unit connected to the determination unit 42 determines that the disconnection has occurred in the master light source circuit 12 on the condition that the first disconnection detection signal S1 is at a low level and the second disconnection detection signal S2 is at a high level. Can be recognized.

  Thus, according to the vehicular lamp 1 of the present embodiment, by using the first current mirror circuit 30, the constant current from the power supply circuit 20 can be evenly distributed to the plurality of light source circuits 11. Thereby, since many light source circuits 11 can be connected in parallel, the series number of the light emitting elements with which each light source circuit 11 is equipped can be reduced, and the voltage which acts on each light source circuit 11 can be reduced. . As a result, the vehicular lamp 1 can be configured with electronic components having a low rated voltage.

  Further, according to the vehicular lamp 1 of the present embodiment, the second current mirror circuit 41 distributes the current to the disconnection detection line Ld according to the current of the master light source circuit 12. Thereby, the detection current flowing in the disconnection detection line Ld varies due to disconnection of the master light source circuit 12 and disconnection of the three slave light source circuits 13. Therefore, the disconnection of the master light source circuit 12 and the three slave light source circuits 13 can be determined by monitoring the fluctuations in the detection current of the disconnection detection line Ld.

  In addition, according to the vehicular lamp 1 of the present embodiment, the disconnection detection unit 40 can be collected on the master light source circuit 12 side without being disposed in each of the light source circuits 11. Thereby, a reduction in the number of parts and a reduction in circuit configuration can be realized. Therefore, disconnection detection can be performed with a simple configuration.

  Moreover, according to the vehicular lamp 1 of the present embodiment, since the disconnection detection unit 40 is provided, the detection result can be used effectively. As a result, the host controller can adjust the output current of the power supply circuit 20 or notify the status of the light source unit 10.

  In the present embodiment, a Darlington-connected transistor Q5 and transistor Q8 are provided. Thereby, the dispersion | variation in an electric current value can be suppressed.

  In the present embodiment, the disconnection detection line Ld includes a resistor R5 that switches the change in the detection current to the change in the detection voltage Va. Thereby, the disconnection can be accurately detected through the voltage comparison by the first comparator 43 and the second comparator 44.

  As mentioned above, although the vehicle lamp which concerns on embodiment of this invention was demonstrated, it cannot be overemphasized that a various deformation | transformation is possible within the scope of the invention, without this invention being limited to embodiment mentioned above. .

  For example, in this embodiment, three slave light source circuits are illustrated. However, the slave light source circuit may be one or more systems, and is not limited to three systems.

DESCRIPTION OF SYMBOLS 1 Vehicle lamp 10 Light source unit 11 Light source circuit 12 Master light source circuit 13 Slave light source circuit 20 Power supply circuit 30 1st current mirror circuit 40 Disconnection detection part 41 2nd current mirror circuit 42 Judgment part 43 1st comparator 44 2nd comparator Ld Disconnection Detection line Lg Ground line Lp Power line Q1-Q8 Transistors R1-R5 Resistance

Claims (3)

In a vehicular lamp driven by a current output from a constant current circuit,
A plurality of light source circuits composed of a plurality of light emitting elements connected in series, and a light source unit including one light source circuit as a master light source circuit and a remaining light source circuit as one or more slave light source circuits;
A first current mirror circuit for causing a current to flow in each of the one or more slave light source circuits according to a current flowing in the master light source circuit;
A disconnection detector for detecting disconnection for each of the light source circuits,
The disconnection detector is
A second current mirror circuit for causing a detection current to flow in a disconnection detection line connected in parallel to the master light source circuit according to a current flowing in the master light source circuit;
A determination unit that determines disconnection based on a change in the detection current;
Vehicular lamp having When one of the one or more slave circuits is disconnected, the detection current increases according to the current flowing in the disconnected slave circuit,
The vehicular lamp according to claim 1, wherein when the master light source circuit is disconnected, the detection current stops. The disconnection detection line includes a resistor that converts fluctuations in the detection current into fluctuations in detection voltage,
The vehicular lamp according to claim 1, wherein the determination unit determines disconnection based on a change in the detection voltage.

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