JP2015147445A - Vehicle lighting appliance and its drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly detect a variety of failure modes.SOLUTION: A drive device 200 is used together with a plurality of light sources 102, and constitutes a vehicle lighting appliance 100. A plurality of drive units 202 are arranged correspondingly to a plurality of the light sources 102, receive common input voltages V, respectively, and supply drive voltages to the corresponding light sources 102, and can stabilize a current Iflowing in the corresponding light source 102 to a target current Iwhich corresponds to target luminance. A controller 212 controls a converter 210 so that one of a source current Iflowing out to the corresponding light source 102 from the converter 210 and a sink current Iflowing into the converter 210 from the corresponding light source 102 coincide with the target current each other. An abnormality detection circuit 214 detects an abnormality on the basis of the other of the source current Iand the sink current I.

Description

  The present invention relates to a vehicular lamp used in an automobile or the like.

  In general, a vehicular lamp can be switched between a low beam and a high beam. The low beam illuminates the neighborhood with a predetermined illuminance, and the light distribution regulation is determined so as not to give glare to the oncoming vehicle and the preceding vehicle, and is mainly used when traveling in an urban area. On the other hand, the high beam illuminates a wide area in front and a distant area with a relatively high illuminance, and is mainly used when traveling at high speed on a road with few oncoming vehicles and preceding vehicles. Therefore, although the high beam is more visible to the driver than the low beam, there is a problem that glare is given to the driver or pedestrian of the vehicle existing in front of the vehicle.

  In recent years, ADB (Adaptive Driving Beam) technology has been proposed that dynamically and adaptively controls the alignment pattern of a high beam based on the state around the vehicle. The ADB technology reduces glare given to a vehicle or pedestrian by detecting the presence of a preceding vehicle, an oncoming vehicle or a pedestrian in front of the vehicle, and dimming a region corresponding to the vehicle or pedestrian. is there.

JP 2005-329819 A

  A vehicle lamp having an ADB function will be described. FIG. 1 is a block diagram of a vehicular lamp having an ADB function according to a comparative technique. This comparison technique should not be recognized as a known technique.

  The vehicular lamp 100r includes a plurality of light sources 102_1 to 102_N and a driving device 200r. In ADB, the high beam irradiation area is divided into a plurality of N (N is a natural number of 2 or more) sub-areas. Then, a plurality of light sources 102_1 to 102_N arranged to irradiate a plurality of sub-regions are provided. The driving device 200r changes the orientation of the high beam by controlling each of the light sources 102_1 to 102_N to be on (lit), off (dark), or brightness.

Drive device 200r receives battery voltage V _BAT (also referred to as input voltage _VIN ) from battery 2 via switch 4. The drive device 200r includes a plurality of drive units 202_1 to 202_N associated with the plurality of light sources 102_1 to 102_N. The i (1 ≦ i ≦ N) -th driving unit 202 — i supplies the corresponding light source 102 — i with the driving current I _DRVi according to the target luminance. For example, the light source 102 is an LED string (also referred to as an LED module) including a plurality of LEDs (light emitting diodes) connected in series.

  Each of the plurality of drive units 202_1 to 202_N is configured to be independently controllable on and off, and the amount of drive current in the on (lighted) state can be independently set.

  An upstream processor that controls the vehicular lamp 100 determines a sub-region to be irradiated with a high beam based on a state in front of the vehicle, and selects a light source 102 to be lit. Then, the processor instructs the drive unit 202 corresponding to the light source 102 to be turned on, and instructs the drive unit 202 corresponding to the other sub-region to turn off.

  As a result of studying the vehicular lamp 100r shown in FIG. 1, the present inventors have recognized the following problems.

  The drive device 200r and the plurality of light sources 102_1 to 102_N are electrically connected via the cable harness 108. In order to improve the reliability of the vehicular lamp 100, it is required to detect an abnormality such as a disconnection (open) or a short between different channels in the wiring or connector portion of the cable harness 108.

Now, focus on two channels CH1 and CH2. The following combinations are conceivable for shorting between adjacent channel wirings.
(I) Short-circuit between cathode (K1) of first channel CH1 and cathode (K2) of second channel CH2 (ii) Short-circuit between anode (A1) of first channel CH1 and cathode (K2) of second channel CH2 (iii) ) Short circuit between cathode (K1) of first channel CH1 and anode (A2) of second channel CH2 (iv) Short circuit between anode (A1) of first channel CH1 and anode (A2) of second channel CH2

In each channel, the drive unit 202 detects a current (source current) flowing in the light source 102 and feeds back the output voltage V _OUT , in other words, the anode of the LED, so that the source current I _SRC approaches the target current I _REF. It is assumed that the forward voltage Vf between the cathodes is adjusted.

  In the failure mode (i), the light sources 102_1 and 102_2 of both the first channel CH1 and the second channel CH2 are normally lit. This failure mode (i) need not be detected as an abnormal state.

  In the failure mode (ii), the light source 102_1 of the first channel CH1 is turned off, and the light source 102_2 of the second channel CH2 is normally turned on. In the first channel CH1, an abnormality (short circuit) can be detected based on the decrease in the voltage between the anode (A1) and the cathode (K1).

  In the failure mode (iii), the light source 102_1 of the first channel CH1 is normally turned on and the light source 102_2 of the second channel CH2 is turned off. In the second channel CH2, an abnormality (short circuit) can be detected based on the decrease in the voltage between the anode (A2) and the cathode (K2).

In the failure mode (iv), the source currents I _SRC1 and I _{SRC2 of the} light sources 102_1 and 102_2 are stabilized to the target currents I _REF1 and I _REF2 , respectively, and thus their total current is stabilized to I _REF1 + I _REF2 . Here, if the impedance of the current path including the light source 102_1 and the current path including the light source 102_2 are equal, I _REF1 + I _REF2 is equally divided into the two light sources 102_1 and 102_2.

  However, the impedance of the light source 102 generally varies from channel to channel. Specifically, even when the number of LEDs constituting each light source 102 is equal, the forward voltage of each LED has manufacturing variations, so that the impedance of the current path of each channel is non-uniform. Alternatively, when the number of LEDs constituting the light source 102 is made different for each channel, the impedance of the current path of each channel becomes more uneven.

Assume that Z1> Z2 when the failure mode (iv) occurs. Z1 is the impedance of the current path of the first channel CH1, and Z2 is the impedance of the current path of the second channel CH2. In this case, the current I _REF1 + I _REF2 generated by the drive units 202_1 and 202_2 is concentrated on the light source 102_2 of the second channel CH2. As a result, heat generation of the light source 102_2 becomes a problem, or the reliability of the light source 102_2 may be affected.

  Even in such a situation, an abnormality cannot be detected in the drive units 202_1 and 202_2 because the source current and voltage to be generated by each of the drive units 202_1 and 202_2 are normally generated.

  The present invention has been made in view of such circumstances, and one of the exemplary purposes of an aspect thereof is to provide a vehicular lamp and a driving apparatus thereof that can reliably detect various failure modes.

  An aspect of the present invention relates to a drive device that is used with a plurality of light sources and constitutes a vehicular lamp. The driving device is provided corresponding to a plurality of light sources, each receives a common input voltage, supplies the driving voltage to the corresponding light source, and stabilizes the current flowing through the corresponding light source to the target current corresponding to the target luminance. A plurality of drive units configured to be configurable. Each of the drive units has one of the converter that boosts, steps down, or inverts the input voltage, the source current that flows from the converter to the corresponding light source, and the sink current that flows from the corresponding light source to the converter matches the target current And a controller that controls the converter, and an abnormality detection circuit that detects an abnormality based on the other of the source current and the sink current.

  According to this aspect, all failure modes can be detected, and the reliability of the circuit element can be improved.

  The abnormality detection circuit may be configured such that the detection accuracy is lower than the detection accuracy of the controller. The abnormality detection circuit only needs to have an accuracy capable of detecting whether or not an abnormality has occurred, and is not required to have an accuracy required for current feedback control. According to this aspect, the circuit configuration can be simplified, and the circuit area and cost can be reduced.

  The abnormality detection circuit may stop the abnormality detection operation during the turn-off period of the corresponding light source. As a result, it is possible to exclude a state in which the current to be monitored is reduced when the light is actively turned off by the control from the abnormality determination target.

The abnormality detection circuit may determine that an abnormality has occurred when a state in which the detected current is lower than the threshold value continues for a predetermined time during the lighting period of the corresponding light source.
As a result, it is possible to mask a very short time abnormality that does not require circuit protection or to prevent erroneous detection of abnormality due to the influence of noise or the like.

  The threshold value may be a predetermined value. Alternatively, the threshold value may depend on the target current.

  The plurality of drive units and the plurality of light sources may be detachably connected via a cable harness.

  Another aspect of the present invention relates to a vehicular lamp. The vehicular lamp includes a plurality of light sources and any one of the driving devices described above.

  According to an aspect of the present invention, various failure modes can be reliably detected.

It is a block diagram of the vehicular lamp which has the ADB function which concerns on a comparison technique. It is a block diagram of a vehicular lamp provided with the drive device concerning an embodiment. It is a circuit diagram which shows the structural example of a drive unit. It is a circuit diagram which shows the structural example of an abnormality detection circuit. FIG. 5 is an operation waveform diagram of the abnormality detection circuit of FIG. 4. It is a perspective view of a lamp unit provided with a vehicular lamp.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. The embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

In this specification, “the state in which the member A is connected to the member B” means that the member A and the member B are electrically connected to each other in addition to the case where the member A and the member B are physically directly connected. It includes cases where the connection is indirectly made through other members that do not substantially affect the general connection state, or that do not impair the functions and effects achieved by their combination.
Similarly, “the state in which the member C is provided between the member A and the member B” refers to the case where the member A and the member C or the member B and the member C are directly connected, as well as their electric It includes cases where the connection is indirectly made through other members that do not substantially affect the general connection state, or that do not impair the functions and effects achieved by their combination.

  Further, in this specification, electrical signals such as voltage signals and current signals, or symbols attached to circuit elements such as resistors and capacitors indicate the respective voltage values, current values, resistance values, and capacitance values as necessary. It shall represent.

  FIG. 2 is a block diagram of the vehicular lamp 100 including the driving device 200 according to the embodiment. The drive device 200 is used together with a plurality of light sources 102_1 to 102_N, as in FIG. 1, and constitutes the vehicle lamp 100 as a whole.

The driving device 200 includes a plurality of driving units 202_1 to 202_N. The plurality of drive units 202_1 to 202_N are provided corresponding to the plurality of light sources 102_1 to 102_N. i-th driving unit 202_i, respectively, receive a common input voltage _{V IN,} supplies a driving voltage to the corresponding light source 102_I, corresponding to current _{I DRVi} flowing through the light source 102_I the target current _{I REFi} in accordance with the target brightness It is configured to be stable.

Each of the plurality of drive units 202 includes a converter 210, a controller 212, and an abnormality detection circuit 214. Focusing on the i-th channel CHi, the converter 210_i boosts, steps down, or inverts the input voltage _VIN . Controller 212_i from converter 210_I, so that the corresponding source current flows to the light source 102_i that _{I SRCI,} one of the sink current _{I SNKi} from the corresponding light source 102_i into the converter 210_I matches the target current _{I REFi,} The switching operation of the converter 210_i is controlled. For example, the controller 212 - i, a microcomputer or processor (not shown), a signal S1_i instructing target current _{I REFi,} on the corresponding light source 102_I (lit) and off signals S2_i instructing (off) is input. The internal configuration of the controller 212 is not particularly limited, and a known circuit may be used. As a control method of the controller 212, voltage mode control, peak current mode control, average current mode control, hysteresis control (bang-bang control), etc. are known, and any of them may be used.

The controller 212_i of each channel, (a) the source current _{I SRCI} is either its is kept to the target current _{I REFi,} (b) the anode of the corresponding light sources 102 (Ai) - voltage between the cathode (Ki) normal Whether it is within the range can be determined.

Abnormality detection circuit 214_i detects an abnormality based on the other of the source current _{I SRC} and sink current _{I SNK.} The abnormality detection circuit 214 asserts (for example, high level) the determination signal S3_1 when normal, and negates (for example, low level) the determination signal S3_1 when abnormal. Controller 212_i in this embodiment controls the converter 210 based on the source current _{I SRC,} the abnormality detection circuit 214_i shall perform abnormality detection based on the sink current _{I SNK.}

  The above is the overall configuration of the driving device 200 and the vehicular lamp 100. Next, the operation will be described.

In the normal state, the converter 210_i of the i-th channel CHi is to stabilize the source current _{I SRCI} to the target value _{I REFi.}

Focus on any two channels CHi and CHj (i ≠ j). The following combinations are conceivable for the short circuit between the wirings of the two channels.
(I) Short-circuit between the cathode (Ki) of the i-th channel CHi and the cathode (Kj) of the j-th channel CHj (ii) Short-circuit between the anode (Ai) of the i-th channel CHi and the cathode (Kj) of the j-th channel CHj (iii) ) Short circuit between the cathode (Ki) of the i-th channel CHi and the anode (Aj) of the j-th channel CHj. (Iv) Short circuit between the anode (Ai) of the i-th channel CHi and the anode (Aj) of the second channel CHj.

  In the failure mode (i), the light sources 102_i and 102_j of both the i-th channel CHi and the j-th channel CHi are normally lit. This failure mode (i) need not be detected as an abnormal state.

In the failure mode (ii), the light source 102_i of the i-th channel CHi is turned off, and the light source 102_j of the j-th channel CHj is normally turned on. Then, in the i-th channel CHi, anode (Ai) - cathode (Ki) or deviating voltages of the normal range and decreases during, the source current _{I SRCI} deviates from the target current _{I REFi,} abnormal by the controller 212_i (Short) can be detected. Further, since the sink current _{I SNK} decreases, abnormality by the abnormality detection circuit 214_i can detect.

In the failure mode (iii), the light source 102_j of the j-th channel CHj is turned off and the light source 102_i of the i-th channel CHi is normally turned on. In the j-th channel CHj, the voltage between the anode (Ai) and the cathode (Ki) decreases and deviates from the normal range, or the source current I _SRCj deviates from the target current I _REFj. (Short) can be detected. Further, since the sink current _{I SNK} decreases, abnormality by the abnormality detection circuit 214_i can detect.

In the failure mode (iv), the light source 102_I, the total current of 102_j _is stabilized _I REFi ₊ I _REFj. If a relationship of Zi> Zj is established between the impedance Zi of the path including the light source 102_i and the impedance Zj of the path including the light source 102_j, the current generated by the driving device 200 is concentrated on the light source 102_j, and the light source Almost no flow in 102_i. Then, the sink current _{I SNKj} of the j channel CHj is increased, it becomes possible to sink current _{I SNKi} of the i channel CHi is reduced, abnormality is detected by the abnormality detecting circuit 214_j or 214_I.

  The above is the principle of the vehicular lamp 100 and the driving device 200. Thus, according to the vehicular lamp 100 and the drive device 200 according to the embodiment, various failure modes can be reliably detected.

  Next, a specific configuration example of the drive unit 202 will be described. FIG. 3 is a circuit diagram illustrating a configuration example of the drive unit 202.

The converter 210 in FIG. 3 boosts the input voltage _VIN and generates an output voltage _VOUT . The converter 210 includes an input capacitor C11, an inductor L1, a switching transistor M1, a diode D1, and output capacitors C12 and C13. Since the topology of the converter 210 is a general boost converter, description thereof is omitted. Converter 210 applies input voltage _VIN to the cathode of light source 102 and output voltage _VOUT to its anode. Therefore, a drive voltage of V _OUT −V _IN is applied between both ends of the light source 102.

The controller 212 is an IC (Integrated Circuit) configured to control the converter 210. The ground (GND) terminal of the controller 212 is grounded, and the drive (DRV) terminal is connected to the gate of the switching transistor M1. A signal S1a instructing the target current I _REF is input from a processor (not shown) to the current control (ICTRL) terminal of the controller 212. The pulse width modulation dimming (PWMDIM) terminal of the controller 212 is supplied with a signal S1b that indicates the duty ratio between the lighting period and the extinguishing period when the light source 102 is PWM driven.

On the path of the source current _{I SRC,} is inserted first resistor Rs1 for current detection, are across the first resistor Rs1, the voltage drop Vs1 proportional to the source current _{I SRC} is generated. A voltage across the first resistor Rs1 is input to the current detection terminals IS + and IS− of the controller 212. Controller 212, a current detection terminal IS +, the potential difference between the IS- Vs1 is to match the reference voltage _{V REF} in accordance with the target current _{I REF,} adjusts the duty ratio of the switching signal S4 to the gate of the switching transistor M1. A noise removing capacitor C14 may be provided in parallel with the first resistor Rs1.

The controller 212 has an overvoltage detection function. An output voltage V _OUT ′ divided by the resistors R11 and R12 is input to an overvoltage protection (OVP) terminal of the controller 212. Inside the controller 212, the voltage V _OUT ′ can be compared with a predetermined threshold value V _OVP to detect an overvoltage state. When detecting an overvoltage state, the controller 212 asserts an abnormal signal FLT (for example, high level), notifies an external processor, and stops driving the light source 102.

Sink current On path _{I SNK,} second resistor Rs2 for current detection is inserted, between the two ends of the second resistor Rs2, a voltage drop Vs2 proportional to the sink current _{I SNK} occurs. The abnormality detection circuit 214 detects an abnormality by comparing the voltage drop of the second detection resistor Rs2 with the threshold value V _SHRT . The threshold value V _SHRT may be a predetermined value or a value corresponding to the target current I _REF .

  The abnormality detection circuit 214 is configured so that the detection accuracy is lower than the detection accuracy of the controller 212. This is because the abnormality detection circuit 214 only needs to have an accuracy capable of detecting whether or not an abnormality has occurred, and is not required to have an accuracy required for current feedback control. Thereby, a circuit structure can be simplified and a circuit area and cost can be reduced.

  Preferably, the abnormality detection circuit 214 is configured to stop the abnormality detection operation during the turn-off period of the corresponding light source 102. In other words, in the light extinction period, the determination signal S3 is fixed at a level (asserted) indicating normality.

In addition, the abnormality detection circuit 214 is configured to determine an abnormality when a state in which the detected current _ISNK is lower than the threshold value continues for a predetermined time τ during the lighting period of the corresponding light source 102. As a result, it is possible to mask a very short time abnormality that does not require circuit protection or to prevent erroneous detection of abnormality due to the influence of noise or the like.

  FIG. 4 is a circuit diagram illustrating a configuration example of the abnormality detection circuit 214. Abnormality detection circuit 214 mainly includes transistors Q1 to Q4, resistors R21 to R24, and a diode D21.

  Transistors Q1 and Q2 form a current mirror circuit, and transistor Q1 is biased by resistor R21. A capacitor C21 and a resistor R22 are connected to the collector of the transistor Q2. Transistor Q3 is provided in parallel with capacitor C21. The transistor Q3 is controlled in synchronization with the light source 102 being turned on and off, and is turned on when the light source 102 is turned off and turned off when the light source 102 is turned on.

The following relational expressions hold for the base-emitter voltages Vbe1 and Vbe2 of the transistors Q1 and Q2.
Vbe1 = Vbe2 + Rs2 × I _SNK

While the light source 102 is turned off, the transistor Q3 is on, so the voltage V _{C21 of the} capacitor _C21 is zero.

While the light source 102 is lit, the transistor Q3 is turned off. When the circuit is normal, when that is that a sufficiently large sink current _{I SNK} flows, the second resistor Rs2, a large voltage drop Rs2 × _{I SNK} occurs. At this time, the base-emitter voltage Vbe2 of the transistor Q2 decreases, and the transistor Q2 is turned off. Since the current _{I Q2} is not supplied at this time the capacitor C21, the voltage _{V C21} of the capacitor C21 becomes zero.

The voltage V _{C21 of the} capacitor C21 is level-shifted by the diode D21 and the resistor R23, and the level-shifted voltage V _R23 is input to the base of the transistor Q4. When the circuit is normal, the transistor Q4 is off, and therefore the determination signal S3 is high (asserted). The diode D21 and the resistor R23 may be a combination of other circuit elements.

During the light source 102 is lit, when the circuit is abnormal, that is, when the sink current _{I SNK} decreases, the voltage drop across Rs2 × _{I SNK} of the second resistor Rs2 decreases. At this time, the base-emitter voltage Vbe2 of the transistor Q2 increases and the transistor Q2 is turned on. At this time, the current _{I Q2} is supplied from the transistor Q2 in the capacitor C21, it is charged. As a result, the voltage V _{C21 of the} capacitor C21 increases. The rising speed at this time depends on the capacitance values of the resistor R22 and the capacitor C21.

With the increase in the voltage _{V C21} of the capacitor C21, the base voltage _{V R23} of transistor Q4 rises. When the base voltage of the transistor Q4 exceeds 0.7V, the transistor Q4 is turned on and the determination signal S3 is negated (low level).

  Further, in the driving apparatus 200 of FIG. 4, when the determination signal S3 is input to the controller 212 and not only an overvoltage state but also an abnormality is detected by the abnormality detection circuit 214, the abnormality signal FLT is asserted, It is possible to notify the microcomputer.

Specifically, the determination signal S3 is input to the connection point of the resistors R11 and R12 via the transistor Q5 and the resistor R25. When an abnormality is detected by the abnormality detection circuit 214 and the determination signal S3 becomes low level, the transistor Q5 is turned on and the OVP terminal V _OUT ′ is pulled up to near the power supply voltage V _DD . As a result, in the overvoltage detection comparator CMP1, V _OVP <V _OUT ′, so that the abnormal signal FLT becomes high level. When the detection result by the abnormality detection circuit 214 is normal, the determination signal S3 is at a high level and the transistor Q5 is off. In this case, the transistors Q5 and R25 are ignored, so that a voltage obtained by dividing the output voltage _VOUT is input to the OVP terminal, and overvoltage determination is performed.

FIG. 5 is an operation waveform diagram of the abnormality detection circuit of FIG. FIG. 5 shows a state in which a short circuit failure has occurred at time t0 during the lighting period. When a short circuit fault occurs, I _SNK decreases and current I _Q2 flows through transistor Q2. When the capacitor C21 is charged by the current IQ2, the voltage V _{C21 of the} capacitor C21 increases according to the CR time constant. And following this, the base voltage _{V R23} of transistor Q4 is increased. When the base voltage _VR23 becomes larger than the threshold value Vf of the transistor Q4 at time t1, the transistor Q4 is turned on and the determination signal S3 becomes low level. When the voltage V _OUT ′ at the OVP terminal exceeds the threshold voltage V _OVP at time t2, the abnormal signal FLT is asserted (high level).

According to the abnormality detection circuit 214 in FIG. 4, the determination signal S3 is fixed at a high level during the turn-off period of the corresponding light source 102, so that the abnormality detection operation can be stopped. As a result, the state where the sink current _ISNK is reduced when the control is actively turned off can be excluded from the abnormality determination target.

Further, according to the abnormality detection circuit 214 of FIG. 4, when the state where the detected current _ISNK is lower than the threshold value during the lighting period of the corresponding light source 102 continues for a predetermined time τ, it is determined that there is an abnormality. Can do. The predetermined time τ can be set according to the capacitance of the capacitor C21 and the resistance value of the resistor R22.

  Finally, the use of the vehicular lamp 100 will be described. FIG. 6 is a perspective view of a lamp unit (lamp assembly) 500 including the vehicular lamp 100. The lamp unit 500 includes a transparent cover 502, a high beam unit 504, a low beam unit 506, and a housing 508. The vehicle lamp 100 described above can be used for the high beam unit 504, for example. The plurality of light sources 102 are arranged, for example, in a row in the horizontal direction so as to irradiate different areas. Then, in the traveling state of the vehicle, a region to be irradiated is adaptively selected by a vehicle-side controller, for example, an ECU (electronic control unit). Data indicating an area to be irradiated is input to the vehicular lamp 100, and the vehicular lamp 100 turns on the light source 102 corresponding to the instructed area.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are within the scope of the present invention. is there. Hereinafter, such modifications will be described.

(Modification 1)
In the embodiment, the case where the controller 212 performs current control based on the source current I _SRC and the abnormality detection circuit 214 performs abnormality detection based on the sink current I _SNK has been described, but the present invention is not limited thereto. The controller 212 may perform current control based on the sink current _ISNK , and the abnormality detection circuit 214 may perform abnormality detection based on the source current I _SRC .

(Modification 2)
Although the case where converter 210 is a boost converter has been described in the embodiment, the configuration and type of converter 210 are not particularly limited. The converter 210 may employ various known types such as a synchronous rectification type boost converter, flyback converter, forward converter, Cuk converter, SEPIC converter, and Zeta converter. Alternatively, converter 210 may be a step-down converter or a step-up / down converter. Further, the output voltage of converter 210 may be a negative voltage.

(Modification 3)
In the embodiment, the case where the input voltage V _IN and the output voltage V _OUT of the converter 210 are supplied to the cathode and the anode of the light source 102 has been described, but the present invention is not limited thereto. For example, the ground voltage V _GND may be supplied to the cathode of the light source 102 and the output voltage _VOUT may be supplied to the anode. When the converter 210 generates the negative output voltage _VOUT , the input voltage _VIN or the ground voltage _VGND may be supplied to the anode, and the output voltage _VOUT may be supplied to the cathode.

(Modification 4)
In the embodiment, the case where the drive current I _DRV supplied to the light source 102 is stabilized at the target value by adjusting the duty ratio of the switching transistor M1 of the converter 210 has been described, but the present invention is not limited to this. For example, a constant current source that generates a current stabilized to the target current I _REF is connected in series with the light source 102, and the output voltage V _OUT of the converter 210 is connected between both ends of the series connection circuit of the light source 102 and the constant current source. May be supplied.

(Modification 5)
The configuration of the abnormality detection circuit 214 is not limited to that of FIG. According to those skilled in the art, it is understood that there is an abnormality detection circuit 214 that can compare the source current I _SNK (or the sink current I _SNK ) with a threshold in addition to the configuration of FIG.

The abnormality detection circuit 214 in FIG. 4 can be grasped as follows.
The abnormality detection circuit 214 includes an I / V conversion circuit (Rs2) that converts the current I _SNK to be detected into a voltage Vs2, and a V / I conversion circuit that generates a current (I _Q2 ) corresponding to the converted voltage Vs2. Q1, Q2, R21), a capacitor C21 charged by the V / I conversion circuit, and a comparison circuit (D21, R23, Q4) for comparing the voltage V _{C21 of the} capacitor _C21 with a predetermined threshold value.

  It will be understood by those skilled in the art that each of the I / V conversion circuit, the V / I conversion circuit, and the comparison circuit may have a configuration different from that of FIG. For example, the comparison circuit may be composed of a voltage comparator. The V / I conversion circuit may be configured using a transconductance amplifier (gm amplifier).

Alternatively, the V / I conversion circuit and the I / V conversion circuit may be omitted, and the voltage drop of the second resistor Rs2 may be compared with a predetermined threshold value. For example, the voltage drop of the second resistor Rs2 may be compared with a predetermined threshold voltage using a voltage comparator. In this case, the threshold voltage may be variable according to the target current I _REF of the drive current I _DRV .

(Modification 6)
In the lamp unit 500 of FIG. 6, the case where the vehicle lamp 100 of FIG. 2 is used for the high beam unit 504 has been described, but the vehicle lamp 100 may be used for the low beam unit 506 instead of or in addition thereto. .

(Modification 7)
In the embodiment, the case where the drive device 200 and the plurality of light sources 102 are detachably connected via the cable harness 108 has been described, but the present invention is not limited thereto. Instead of the cable harness 108, wiring formed on the printed circuit board or a fixed cable that cannot be detached may be used.

(Modification 8)
In the embodiment, the case where the light source 102 is configured by an LED has been described. However, the light source 102 may be configured using another semiconductor light source such as an LD (laser diode) or an organic EL (electroluminescence) element. .

  Although the present invention has been described using specific terms based on the embodiments, the embodiments only illustrate the principles and applications of the present invention, and the embodiments are defined in the claims. Many variations and modifications of the arrangement are permitted without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 2 ... Battery, 4 ... Switch, 100 ... Vehicle lamp, 102 ... Light source, 108 ... Cable harness, 200 ... Drive apparatus, 202 ... Drive unit, 210 ... Converter, 212 ... Controller, 214 ... Abnormality detection circuit, 500 ... Lamp Unit: 502 ... Cover, 504 ... High beam unit, 506 ... Low beam unit, 508 ... Housing.

Claims (6)

A drive device used with a plurality of light sources to constitute a vehicular lamp,
Provided corresponding to the plurality of light sources, each receiving a common input voltage, supplying a driving voltage to the corresponding light source, and stabilizing a current flowing through the corresponding light source to a target current corresponding to a target luminance With a plurality of drive units configured to be possible,
Each of the plurality of drive units is
A converter for stepping up, stepping down or inverting the input voltage;
A controller that controls the converter so that one of a source current flowing from the converter to the corresponding light source and a sink current flowing from the corresponding light source to the converter matches the target current;
An abnormality detection circuit for detecting an abnormality based on the other of the source current and the sink current;
A drive device comprising:   The drive device according to claim 1, wherein the abnormality detection circuit has a detection accuracy lower than that of the controller.   3. The drive device according to claim 1, wherein the abnormality detection circuit stops an abnormality detection operation during a turn-off period of a corresponding light source.   The abnormality detection circuit determines that an abnormality is detected when a state in which the detected current is lower than a threshold value continues for a predetermined time in a lighting period of the corresponding light source. A drive device according to claim 1.   5. The drive device according to claim 1, wherein the plurality of drive units and the plurality of light sources are detachably connected via a cable harness. Multiple light sources;
A driving device according to any one of claims 1 to 5;
A vehicular lamp characterized by comprising:

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