JP6235367B2 - VEHICLE LAMP, ITS DRIVE DEVICE, AND CONTROL METHOD THEREOF - Google Patents

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 the 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 a 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 the pedestrian. is there.

  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 1r includes a light source 10 and a driving device 20r. 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. The light source 10 includes a plurality of light emitting elements 12_1 to 12_N associated with N sub-regions. Each light emitting element 12 is a semiconductor device such as an LED (light emitting diode) or an LD (laser diode), and is arranged so as to irradiate a corresponding sub-region. The driving device 20r changes the high beam orientation by controlling each of the light emitting elements 12_1 to 12_N to be on (lighted) and off (light off). Alternatively, the driving device 20r adjusts the effective luminance by PWM (pulse width modulation) control of the light emitting element 12 at a high frequency.

The driving device 20r includes a current source 30, a plurality of bypass circuits 40_1 to 40_N, and a controller 50. The current source 30 receives a battery voltage V _BAT (also referred to as an input voltage _VIN ) from the battery 2 via the switch 4, and stabilizes the drive current I _DRV flowing through the light source 10 to a certain target amount.

The plurality of bypass circuits 40_1 to 40_N are associated with the plurality of light emitting elements 12_1 to 12_N. The bypass circuit 40 is configured to be switched on and off. When the i-th bypass circuit 40_i is turned on, the drive current I _DRV flows to the bypass circuit 40_i instead of the light emitting element 12_i. When the light emitting element 12_i is turned off and the bypass circuit 40_i is turned off, the drive current I _DRV is Lights through the light emitting element 12_i.

  An upstream processor (for example, an electronic control unit ECU) 6 that controls the vehicular lamp 1r determines a sub-region to be irradiated with a high beam based on a state in front of the vehicle, and instructs the controller 50 of the driving device 20r. The controller 50 controls the states of the bypass circuits 40_1 to 40_N based on the control command from the processor 6. Specifically, the light emitting element 12 corresponding to the sub-region to be irradiated is selected, the bypass circuit 40 parallel to the selected light emitting element 12 is turned off, and the bypass circuit 40 parallel to the remaining light emitting elements 12 is turned on. State.

  The light source 10 and the driving device 20r are connected via wiring. When this wiring is cut (open failure), the light emitting element 12 cannot be turned on, or the light emitting element 12 cannot be actively controlled to be turned off. Therefore, means for detecting an abnormality such as a short circuit failure or an open failure is mounted on the driving device 20r.

When a drive current I _DRV flows through a certain light emitting element 12_i and is normally lit, the voltage drop (forward voltage) of the light emitting element 12_i is included in a predetermined voltage range (referred to as a normal voltage range), and an open failure or When a short circuit fault occurs, the voltage drop deviates from the normal voltage range. Therefore, it is possible to detect an abnormality by monitoring the detection voltage Vs between both ends of each light emitting element 12 (that is, the forward voltage Vf of the light emitting element 12). For example, when the typical value of the forward voltage Vf of the light emitting element 12 when the predetermined drive current I _DRV flows is 4V, the lower limit V _THL of the normal voltage range is set to 1.5V and the upper limit V _THH is set to 5.5V. Is done.

JP 2008-205357 A

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

  Attention is paid to the first and second light-emitting elements 12_1 and 12_2. A node connecting the light emitting elements 12_1 and 12_2 is called a first node ND1, a node connecting the bypass circuits 40_1 and 40_2 is called a second node ND2, and (i) connecting the first node ND1 and the light emitting element 12_1. Consider the failure mode in which the first wiring L1_1 is disconnected and (ii) the failure mode in which the second wiring L2_1 connecting the first node ND1 and the second node ND2 is disconnected.

In the failure mode in which the first wiring L1_1 is disconnected, the drive current I _DRV flows through the bypass circuit 40_1 in parallel with the light emitting element 12, and the voltage Vs1 between the output terminals OUT1 and OUT2 is the upper limit value 5. It becomes higher than 5V. Therefore, this failure mode can be detected based on the detection voltage Vs1 between the terminals OUT1 and OUT2.

The failure mode in which the second wiring L2_1 cuts, the driving current _{I DRV} is flowing through the light emitting element 12_1 and 12_2. Therefore, the sum Vs1 + Vs2 of the two detection voltages between the output terminals OUT1 and OUT3 is Vf × 2 = 8V.
Vs1 + Vs2 = Vf × 2

Here, Vs1 and Vs2 are determined as follows according to the impedances Zo1 and Zo2 of the bypass circuits 40_1 and 40_2, respectively.
Vs1 = Zo1 / (Zo1 + Zo2) × Vf × 2
Vs2 = Zo2 / (Zo1 + Zo2) × Vf × 2
Therefore, in the state of Zo1≈Zo2, Vs1≈Vs2≈Vf, and the detection voltages Vs1 and Vs2 both remain in the normal voltage range, and a situation in which an abnormality cannot be detected may occur.

  This problem occurs not only when ADB control is performed, but also when the vehicular lamp 1r shown in FIG. 1 is used for luminance control.

  The present invention has been made in view of such a situation, and one of the exemplary purposes of an aspect thereof is to provide a drive device that can reliably detect various abnormal states.

  An aspect of the present invention relates to a drive device that is used with a light source including a plurality of light emitting elements connected in series and constitutes a vehicular lamp. The driving device is associated with a current source that supplies a driving current to the light source and N (N is an integer of 2 or more) light emitting elements among the plurality of light emitting elements, and each is provided in parallel with the corresponding light emitting element. (I) N bypass circuits, (i) N abnormality detection circuits that are associated with the N light emitting elements and are configured to be able to detect an abnormality based on a voltage across each of the corresponding bypass circuits; And (ii) a controller that switches the N bypass circuits in accordance with a control pattern having a predetermined switching period during the abnormality determination period. . When attention is paid to any two adjacent light emitting elements, the driving device is configured so that there is an unbalanced period in which the impedance desired on the corresponding bypass circuit side is different from each of the two light emitting elements for each switching period. The

  A line connecting the first node connecting the i-th light-emitting element and the (i + 1) -th light-emitting element and the second node connecting the i-th bypass circuit and the (i + 1) -th bypass circuit is opened. When a failure occurs, the impedance viewed from the i-th light emitting element is different from the impedance viewed from the (i + 1) -th light emitting element in the unbalance period, so the i-th bypass circuit and the (i + 1) -th bypass circuit Therefore, the voltage across at least one of the two is out of the predetermined voltage range, so that an abnormality can be reliably detected.

The controller may shift to the abnormality determination period when an abnormality is detected by at least one abnormality detection circuit in the normal lighting control period.
In this case, the abnormality can be temporarily determined during the normal lighting control period, and the abnormality can be determined during the abnormality determination period.

The control pattern may be determined so that there is an unbalance period in which one of two adjacent bypass circuits is off and the other is on for each switching period.
As a result, during the unbalance period, the impedance desired on the corresponding bypass circuit side can be made different from each of the two adjacent light emitting elements.

The control pattern may be determined so that the on / off duty ratios of two adjacent bypass circuits are different.
Accordingly, a period in which one of the two adjacent bypass circuits is on and the other is off can be set regardless of the switching phase of the two adjacent bypass circuits.

  The control pattern may be determined so that two adjacent bypass circuits have the same on / off duty ratio and different phases.

The driving device according to an aspect may further include a delay circuit that is inserted between the controller and the N bypass circuits and configured to give different delays to the control signals for the two adjacent bypass circuits.
As a result, the switching phase and / or on-time of two adjacent bypass circuits can be made different.

The driving device according to an aspect may further include an unbalance circuit that constantly varies the impedance desired on the corresponding bypass circuit side from each of the two adjacent light emitting elements.
As a result, the impedance desired on the corresponding bypass circuit side can be made different from each of the two adjacent light emitting elements at all times regardless of the control pattern of the N bypass circuits.

  Another aspect of the present invention relates to a vehicular lamp. The vehicular lamp includes a light source including a plurality of light emitting elements connected in series, and the driving device according to any one of the above-described aspects that drives the light source.

  According to an aspect of the present invention, an abnormality 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 the vehicular lamp which concerns on 1st Embodiment. FIGS. 3A and 3B are waveform diagrams showing control patterns. 4A to 4C are waveform diagrams showing control patterns. It is a circuit diagram of a bypass circuit and an abnormality detection circuit. It is an operation | movement waveform diagram of lighting control period Ta and abnormality determination period Tb. It is a circuit diagram of the drive device concerning a 2nd embodiment. It is a block diagram of the drive device concerning a 3rd embodiment. It is a perspective view of a lamp unit (lamp assembly) provided with the vehicle lamp of FIG.

  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 1 according to the first embodiment. The vehicular lamp 1 includes a light source 10 and a driving device 20. The light source 10 includes a plurality of light emitting elements 12_1 to 12_N connected in series. The driving device 20 is used together with the light source 10 and constitutes the vehicular lamp 1. The light emitting element 12 is, for example, an LED (light emitting diode).

  The drive device 20 includes a current source 30, a plurality of bypass circuits 40_1 to 40_N, a controller 50, and a plurality of abnormality detection circuits 60_1 to 60_N.

The current source 30 supplies a driving current I _DRV corresponding to the target luminance to the light source 10. For example, current source 30 includes a step-up or step-down converter and its control circuit. Control circuit detects a driving current I _DRV, the detected driving current I _DRV is to approach the target amount may be feedback-controlled switching states of the converter. The type of the converter and the current control method are not particularly limited, and a known technique may be used.

  The plurality of bypass circuits 40_1 to 40_N are associated with N (N is an integer of 2 or more) light emitting elements 12 among the plurality of light emitting elements 12. In the present embodiment, a case where bypass circuits 40 are provided for all the light emitting elements 12 will be described. The bypass circuit 40_i is provided in parallel with the corresponding light emitting element 12_i. The bypass circuit 40_i can be switched between an on state and an off state, and is configured to form a bypass path parallel to the light emitting element 12_i in the on state.

  The abnormality detection circuits 60_1 to 60_N are associated with N light emitting elements. The i-th abnormality detection circuit 60_i is configured to be able to detect an abnormality based on the voltage Vsi across the corresponding bypass circuit 40_i (that is, the corresponding light emitting element 12_i).

  (I) In the normal lighting control period Ta, the controller 50 switches the N bypass circuits 40_1 to 40_N based on the lighting / extinguishing instructions of the N light emitting elements 12_1 to 12_N. The controller 50 may perform PWM control of the bypass circuit 40_i in accordance with the target luminance of the light emitting element 12_i.

The controller 50, for (ii) abnormality determination period Tb, according to the control pattern having a predetermined switching period _{T SW,} switching the N-number of the bypass circuit 40_1～40_N.

The abnormality detection circuit 60_i is configured to be able to determine the presence / absence of an abnormality based on the detection voltage Vsi between both ends of the corresponding bypass circuit 40_i. Specifically, the presence or absence of abnormality is determined by comparing the detection voltage Vsi with a predetermined upper threshold voltage V _THH and a lower threshold voltage V _THL .

  For example, when an abnormality is detected by any of the abnormality detection circuits 60 in the normal lighting control period Ta, the controller 50 makes a provisional determination as an abnormal state and transitions to the abnormality determination period Tb. Whether this state is present is determined. For example, in the abnormality determination period Tb, the abnormality state may be determined when an abnormality is continuously detected for a predetermined time. As a result, erroneous detection due to the influence of noise can be prevented, or a short-time abnormal state that does not require protection can be masked.

The ON time of the i-th bypass circuit 40_i in the abnormality determination period Tb is T _ON i, and the OFF time is T _OFF i. The control pattern is
T _ON i> T _OFF i
It is desirable to set so as to satisfy. For example, the on-duty T _ON i / (T _ON i + T _OFF i) may be 80% or more, more preferably 90% or more.

The impedance desired from the i-th light emitting element 12_i to the inside of the driving device 20, that is, the impedance desired from the light emitting element 12_i to the corresponding bypass circuit 40_i side is defined as Zoi. In this case the drive device 20 according to the present embodiment, in each switching cycle _{T SW,} any adjacent two light emitting elements 12_i, 12_ (i + 1) wanted from each impedance Zoi, Zo (i + 1) is different from the unbalance A period T _UB is configured to exist.

In this embodiment, each switching cycle T _SW, two adjacent bypass circuit 40_i, one is off 40_ (i + 1), by the other defines the control pattern so that a period for turning on existing unbalance The period T _UB is secured. It is understood that Zoi approaches zero when the bypass circuit 40_i is on and Zoi takes a relatively large value when it is off.

  Hereinafter, some examples of the control pattern will be described.

  FIGS. 3A and 3B are waveform diagrams showing control patterns. Hereinafter, N = 4, and control signals S1_1 to S1_4 instructing on / off of each of the bypass circuits 40_1 to 40_4 are shown.

The control patterns in FIGS. 3A and 3B are determined so that the on / off duty ratios of any two adjacent bypass circuits are different.
In FIG. 3A, the control pattern is determined so that all the bypass circuits 40_1 to 40_4 have different on / off duty ratios.

  In FIG. 3B, the control pattern is determined so that the duty ratio of the odd-numbered bypass circuit 40 and the duty ratio of the even-numbered bypass circuit 40 are different.

4A to 4C are waveform diagrams showing control patterns. 4A to 4C, the control patterns are determined such that the two adjacent bypass circuits 40_i and 40_ (i + 1) have the same duty ratio and different phases. In FIG. 4A, the phases of the two bypass circuits 40_i and 40_ (i + 1) are shifted by T _SW / 2. In FIG. 4B, the off period T _OFF is shifted so as to be adjacent. In FIG. 4C, the phases of the four bypass circuits 40_1 to 40_4 are shifted by T _SW / 4.

  When the controller 50 is configured by a microcontroller or CPU, the control patterns shown in FIGS. 3 and 4 can be realized by software using a timer built in the microcontroller.

Next, configuration examples of the bypass circuit 40 and the abnormality detection circuit 60 will be described.
FIG. 5 is a circuit diagram of the bypass circuit 40 and the abnormality detection circuit 60. FIG. 5 shows only the configuration corresponding to the i-th light emitting element 12_i.

  The bypass circuit 40_i includes a bypass transistor M1, a gate resistor R1, a Zener diode ZD1, and a diode D1. The bypass transistor M1 is provided in parallel with the corresponding light emitting element 12. A control signal S1_i from the controller 50 is input to the gate of the bypass transistor M1 through the gate resistor R1. The diode D1 and the Zener diode ZD1 are provided in series between the gate and source of the bypass transistor M1.

The abnormality detection circuit 60 includes a short detection circuit 62, an open detection circuit 64, and an output circuit 66. The short detection circuit 62 detects a short circuit failure of the light emitting element 12_i based on the voltage Vsi across the light emitting element 12_i. A control signal S1_i is input to the base of the first transistor Q1 via the resistor R2. A voltage Vsi ′ obtained by dividing the detection voltage Vsi by the resistors R3 and R4 is input to the base of the first transistor Q1. The collector of the first transistor Q1 is pulled up by the resistor R5 and input to the base of the second transistor Q2. The first transistor Q1 is turned off when the control signal S1_i is at a low level and the detection voltage Vsi is lower than a predetermined lower threshold voltage V _THL , that is, when a short circuit failure of the light emitting element 12_i is suspected. Sometimes the second transistor Q2 is turned on.

  The open detection circuit 64 includes a resistor R6 and a third transistor Q3. The voltage Vy at the connection node between the Zener diode ZD1 and the diode D1 is input to the base of the third transistor Q3 via the resistor R6. A Zener voltage of the Zener diode ZD1 is Vz, a forward voltage of the diode D1 is Vf, and a gate-source voltage of the transistor M1 is Vgs. When the light emitting element 12_i has an open failure, the Zener diode ZD1 becomes conductive, and the detection voltage Vs is clamped to a certain voltage level (≈Vz + Vf + Vgs). Vz and Vf are designed so that the third transistor Q3 is turned on in this state.

The collector of the transistor Q2 of the short detection circuit 62 and the collector of the transistor Q3 of the open detection circuit 64 are connected in common, and the logical sum (OR) S10 of the two detection results is input to the output circuit 66. The input of the output circuit 66 becomes a low level when an open failure or a short failure occurs, and becomes a high level when no failure occurs. The output circuit 66 logically inverts the OR output S10 of the two detection circuits 62 and 64 in the previous stage, and outputs a level-shifted output. The output circuit 66 includes a fourth transistor Q4, resistors R7 to R10, and a capacitor C10. The fourth transistor Q4 and the resistor R9 are inverters that invert the signal S10. Resistor R10 and capacitor C1 constitute a low-pass filter. The output circuit 66 generates an abnormality detection signal S2_i that is at a high level (power supply voltage V _CC ) in an abnormal state in which an open failure or a short failure occurs, and is at a low level (ground voltage V _GND ) in a normal state.

  The configurations of the bypass circuit 40 and the abnormality detection circuit 60 are not limited to those shown in FIG.

The above is the configuration of the driving device 20. Next, the operation will be described.
FIG. 6 is an operation waveform diagram of the lighting control period Ta and the abnormality determination period Tb. FIG. 6 shows only waveforms corresponding to the light emitting elements 12_1 and 12_2.
In the lighting control period Ta, on / off of the light emitting elements 12_1 and 12_2 is controlled based on a control command from the processor 6. For example, the light emitting element 12_1 is repeatedly turned on and off, and the light emitting element 12_2 is turned off.

  When an abnormality is detected by any of the abnormality detection circuits 60 at time t1, the process proceeds to the abnormality determination period Tb. In the abnormality determination period Tb, the processor 6 controls the bypass circuits 40_1 to 40_N according to a predetermined control pattern. The control pattern is as described with reference to FIG. 3 or FIG.

Attention is focused on the impedance Zo1 that the bypass circuit 40_1 side is desired from the light emitting element 12_1 and the impedance Zo2 that the bypass circuit 40_2 side is desired from the light emitting element 12_2. In the switching cycle _{T SW,} control signal S1_1, S2_2 both high level period, both low-level period, the impedance Zo1 and Zo2 are equal. In contrast, the control signal S1_1 is low, S2_2 of high-level period is a first unbalance period _{T UB1} to be Zo1> Zo2, control signal S1_1 is high level, S2_2 has a low level section, Zo1 <is an unbalanced period _{T UB2} to be Zo2.

As described above, the detection voltages Vs1 and Vs2 are given by the following equations.
Vs1 = Zo1 / (Zo1 + Zo2) × Vf × 2
Vs2 = Zo2 / (Zo1 + Zo2) × Vf × 2
Accordingly, the first unbalanced _{T UB1} Zo1> Zo2 holds, a Vs1> Vs2. Thus in the abnormality detection circuit 60_1, it is possible to detect an abnormal state becomes _{Vs1> V THH.}

Further, the Zo1 <Zo2 holds second unbalanced _{T UB2,} a Vs1 <Vs2. Thus in the abnormality detection circuit 60_2, it is possible to detect an abnormal state becomes _{Vs2> V THH.}

  The above is the operation of the driving device 20. The effects achieved by the drive device 20 are summarized below.

In (Effect 1) drive unit 20, in the abnormality determination period Tb, any adjacent two light emitting elements 12_I, when attention is paid to 12_ (i + 1), for each switching cycle _{T SW,} the respective two light emitting elements, There exist unbalance periods in which the impedances Zo1 and Zo2 desired on the corresponding bypass circuits 40_i and 40_ (i + 1) side are different.

  Thereby, when the second wiring L2_i becomes an open failure, the voltage drop Vf × 2 of the light emitting elements 12_i and 12_ (i + 1) for two stages is detected voltages Vsi and Vs (i + 1) during the unbalance period. The pressure is divided to one of the two. Accordingly, at least one of the detection voltages Vsi and Vs (i + 1) deviates from the normal voltage range, and an abnormal state can be detected.

Of course, even when the first wiring L1_i becomes open failure, since the _{Vsi> V THH,} it is possible to abnormality detected by the abnormality detection circuit 60_I.

(Effect 2) Further, the unbalance period T _UB is realized by a combination of ON and OFF of the adjacent bypass circuits 40_i and 40_ (i + 1). In other words, since the unbalance period T _UB can be introduced by software by devising the pattern of the control signals S1_1 to S1_N, it is also a great advantage that there is almost no increase in hardware.

(Effect 3) In addition, in the abnormality determination period Tb, the control patterns S1_1 to S1_1 are set so that the on-duty T _ON / (T _ON / T _OFF ) of each bypass circuit 40_i increases, specifically, exceeds 80%. S1_N is defined. The effect by this becomes clear by comparison with the following techniques.

In order for the abnormality detection circuit 60_i to detect an abnormality, the corresponding bypass circuit 40_i must be in an off state. Therefore, consider a case where the bypass circuits 40_1 to 40_N are fixed to OFF during the abnormality determination period Tb. In this case, when the open failure in the light emitting element 12_i occurs, the bypass circuit 40_i off, i.e. the impedance is very large bypass circuit 40_i, so that the driving current _{I DRV} flows. When the configuration of FIG. 5 is employed, the voltage Vsi across the bypass circuit 40_i is clamped to the voltage level (Vz + Vf + Vgs) when the light-emitting element 12_i has an open failure. At this time, a large power loss of P = (Vz + Vf + Vgs) × I _DRV occurs in the bypass circuit 40 — i.

  On the other hand, the power loss of the bypass circuit 40 can be significantly reduced by setting the ON duty of each of the control signals S1_1 to S1_N in the abnormality determination period Tb to be large. Thereby, the reliability of the drive device 20 can be improved, and an inexpensive element having a small rated capacity can be selected as the transistor constituting the bypass circuit 40.

(Effect 4)
Further, as shown in FIG. 6, when an abnormality is detected by at least one abnormality detection circuit 60 in the normal lighting control period Ta, the abnormality determination period Tb is started. As a result, an abnormal state is provisionally determined based on the lighting control period Ta, and when an abnormality is suspected, it is possible to detect the abnormality with high accuracy or robustness by making a transition to the abnormality determination period Tb and performing this determination. .

(Second Embodiment)
In the first embodiment, the case where the controller 50 controls the control signals S1_1 to S1_N for the bypass circuits 40_1 to 40_N to set the unbalance period has been described. In the second embodiment, the unbalance period is set by a hardware configuration.

  FIG. 7 is a circuit diagram of a driving device 20a according to the second embodiment. In FIG. 7, the current source 30 and the abnormality detection circuit 60 are omitted.

  The driving device 20a further includes a delay circuit 70 inserted between the controller 50 and the N bypass circuits 40_1 to 40_N. The delay circuit 70 is configured to give different delays τi and τ (i + 1) to the control signals S1_i and S1_ (i + 1) for any two adjacent bypass circuits 40_i and 40_ (i + 1).

The delay circuit 70 may act on both the positive edge and the negative edge of the control signal S1. In this case, the control patterns shown in FIGS. 4A to 4C can be realized.
The first delay amount may be set equal to the odd number, and the second delay amount may be set equal to the even number. In this case, the control pattern shown in FIG. 4A or 4B can be realized.
One of the first delay amount and the second delay amount may be zero. In this case, the configuration of the delay circuit 70 can be simplified.

  All delay amounts may be set to different values. In this case, the control pattern of FIG. 4C can be realized.

  Further, the delay circuit 70 may act on only one of the positive edge and the negative edge of the control signal S1. For example, the control patterns shown in FIGS. 3A and 3B can be realized by giving different delays only to the positive edge of the control signal.

  The configuration of the delay circuit 70 is not particularly limited. For example, an RC filter, an analog timer circuit, or a one-shot circuit may be used.

  According to the second embodiment, an unbalance period can be set by the delay circuit 70 while the controller 50 generates the same (or different) control signals S1_1 to S1_N.

(Third embodiment)
In the first and second embodiments, the transient unbalance period is realized by a combination of turning on and off the bypass circuits 40_i and 40_ (i + 1). However, the present invention is not limited to this. In the third embodiment, a steady impedance imbalance is introduced.

  FIG. 8 is a block diagram of a driving device 20b according to the third embodiment. The driving device 20b includes an unbalance circuit 80. The unbalance circuit 80 steadily varies the impedances Zoi and Zo (i + 1) at which the corresponding bypass circuits 40_i and 40_ (i + 1) are desired from the two adjacent light emitting elements 12_i and 12_ (i + 1).

  For example, the unbalance circuit 80 includes impedance circuits 82_1 to 82_N provided in parallel with the N bypass circuits 40_1 to 40_N. Any two adjacent impedance circuits 82_i and 82_ (i + 1) have different impedances Zai and Za (i_1).

  The impedance Zoi is a combined impedance of the impedance Zai of the impedance circuit 82_i, the impedance Zbi of the bypass circuit 40_i, and the impedance Zci of the abnormality detection circuit 60_i. Even in the case of Zbi = Zb (i + 1) and Zci = Zc (i + 1), Zai ≠ Za (i_1), and therefore Zoi ≠ Zo (i + 1).

  The specific configuration of the impedance circuit 82 is not particularly limited. For example, resistance elements having different resistance values as shown in FIG. 8 may be used, or diodes, Zener diodes, transistors, or the like may be used. Further, the impedance Zai of an impedance circuit 82_i may be infinite. In this case, the impedance circuit 82_i is omitted.

  According to the third embodiment, even when the controller 50 generates the same control signals S1_1 to S1_N, a steady impedance imbalance can be introduced.

  Finally, the use of the vehicular lamp 1 will be described. FIG. 9 is a perspective view of a lamp unit (lamp assembly) 500 including the vehicular lamp 1 of FIG. 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 1 described above can be used for the high beam unit 504, for example. The plurality of light emitting elements 12 are arranged, for example, in a row in the horizontal direction so as to irradiate different regions. 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). The vehicle lamp 1 receives data indicating an area to be irradiated, and the vehicle lamp 1 turns on the light source 10 (light emitting element 12) 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)
When an abnormality is detected in the lighting control period Ta, in addition to or instead of shifting to the abnormality determination period Tb, an abnormality is triggered by a predetermined event such as power-on or power-off of the drive device 20. You may change to determination period Tb.

(Modification 2)
In the third embodiment, the unbalance circuit 80 may be configured integrally with the abnormality detection circuits 60_1 to 60_N. For example, when the abnormality detection circuit 60 has the configuration of FIG. 5, the resistance values of the resistors R3 and R4 may be different in the adjacent abnormality detection circuits 60_i and 60_ (i + 1). In other words, regarding the impedance between both ends of each of the abnormality detection circuits 60_1 to 60_N, the two adjacent ones may be designed to have different values.

(Modification 3)
In the embodiment, the case where the abnormality detection circuit 60 can detect both an open fault and a short fault has been described. However, the present invention is also effective in a configuration that detects only an open fault.

(Modification 4)
As the light source 10, in addition to the LED, a semiconductor light source such as an LD (laser diode) or an organic EL (electroluminescence) may be used.

(Modification 5)
In the lamp unit 500 of FIG. 9, the case where the vehicle lamp 1 of FIG. 3 is used for the high beam unit 504 has been described, but the vehicle lamp 1 may be used for the low beam unit 506 instead of or in addition thereto. .

  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 1 ... Vehicle lamp, 2 ... Battery, 4 ... Switch, 6 ... Processor, 10 ... Light source, 12 ... Light emitting element, 20 ... Drive apparatus, 30 ... Current source, 40 ... Bypass circuit, 50 ... Controller, 60 ... Abnormality detection Circuit 62 62 Short detection circuit 64 Open detection circuit 66 Output circuit 70 Delay circuit 80 Unbalance circuit 500 Lamp unit 502 Cover 504 High beam unit 506 Low beam unit 508 ... enclosure.

Claims (6)

A drive device that is used together with a light source including a plurality of light emitting elements connected in series and constitutes a vehicular lamp,
A current source for supplying a driving current to the light source;
N bypass circuits associated with N (N is an integer greater than or equal to 2) light emitting elements among the plurality of light emitting elements, each provided in parallel with the corresponding light emitting element;
N abnormality detection circuits that are associated with the N light emitting elements, each configured to be able to detect an abnormality based on the voltage across the corresponding bypass circuit;
(I) Switching the N bypass circuits during a normal lighting control period, and (ii) switching the N bypass circuits according to a control pattern having a predetermined switching period during an abnormality determination period. A controller,
With
When attention is paid to any two adjacent light emitting elements, each of the two light emitting elements is configured to have an unbalanced period in which the impedance desired for the corresponding bypass circuit side is different for each switching period. A drive device characterized by the above.   2. The driving device according to claim 1, wherein the controller shifts to the abnormality determination period when an abnormality is detected by at least one abnormality detection circuit in the normal lighting control period.   3. The control pattern according to claim 1, wherein the control pattern is determined so that an unbalance period in which one of two adjacent bypass circuits is off and the other is on exists for each switching period. Drive device.   4. A delay circuit inserted between the controller and the N bypass circuits and configured to give different delays to control signals for two adjacent bypass circuits. The drive apparatus in any one of.   5. The apparatus according to claim 1, further comprising an unbalance circuit provided in parallel with the N bypass circuits and configured to make the impedance desired on the corresponding bypass circuit side different from each of adjacent two light emitting elements. The drive apparatus in any one of. A method for controlling a vehicular lamp, comprising:
The vehicular lamp is
A light source including a plurality of light emitting elements connected in series;
A current source for supplying a driving current to the light source;
N bypass circuits associated with N (N is an integer greater than or equal to 2) light emitting elements among the plurality of light emitting elements, each provided in parallel with the corresponding light emitting element;
With
The control method is:
(I) in a normal lighting control period, switching the N bypass circuits at a duty ratio corresponding to the target luminance of each of the N light emitting elements;
(Ii) switching the N bypass circuits according to a control pattern having a predetermined switching period during the abnormality determination period;
With
The control method is characterized in that, for each switching period, the control pattern is determined such that there is an unbalance period in which one of any two adjacent bypass circuits is on and the other is off.

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