JP2015154704A - Vehicle lamp and driving device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make high-accuracy output current control compatible with robust overcurrent detection.SOLUTION: A DC/DC converter 30 generates a drive voltage Vby boosting, dropping or inverting an input voltage Vand supplies the generated drive voltage to a light source 10. A bypass circuit 40 is provided in parallel with a light-emitting element 12 to which the bypass circuit is correspondent. A current controller 52 performs hysteresis control in which, when a first current flowing between the light source 10 and a ground terminal of the DC/DC converter 30 reaches a predetermined higher target value, a switching element of the DC/DC converter 30 is turned off and when the first current is reduced to a predetermined lower target value, the switching element of the DC/DC converter 30 is turned on. A dimming controller 54 switches ON/OFF of an N pieces of bypass circuits 40. An overcurrent detection circuit 60 detects an overcurrent state by comparing a second current Ivia an output terminal OUT of the DC/DC converter 30 with a predetermined overcurrent threshold value.

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 a high-beam light distribution pattern 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.

  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 drive device 20r changes the light distribution of the high beam by controlling on (lighting) and off (light extinction) of each of the plurality of light emitting elements 12_1 to 12_N. Alternatively, the driving device 20r adjusts the effective luminance (PWM dimming) by controlling the light emitting element 12 by PWM (pulse width modulation) at a high frequency.

  The drive device 20r includes a DC / DC converter 30, a plurality of bypass circuits 40_1 to 40_N, and a controller 50r.

The DC / DC converter 30 receives a battery voltage V _BAT (also referred to as an input voltage _VIN ) from the battery 2 via the switch 4 and supplies a driving voltage _VOUT to the light source 10. The controller 50r includes a current controller 52r and a dimming controller 54r.

Current controller 52r is the driving current _{I OUT} flowing through the light source 10 is stabilized 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 i-th bypass circuit 40_i is turned on, the drive current _{I OUT} to flow to the light emitting element 12_i rather than bypass circuit 40_i, the light emitting element 12_i is turned off, the bypass circuit 40_i is turned off, the driving current _{I OUT} 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 dimming controller 54r. The dimming controller 54r 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.

JP 2004-140885 A

  As a result of studying the vehicular lamp 1r shown in FIG. 1, the present inventor has come to recognize the following problems.

As described above, the current controller 52r detects a driving current I _OUT flowing through the light source 10, a detection signal indicating the current I _OUT is to approach the target value, adjusting on the switching transistor M1, the duty ratio of the off . As a current detection method, a detection resistor Rs is inserted on a current path to be detected, and the magnitude of the current is often detected based on a voltage drop of the detection resistor Rs.

  Here, a circuit in which the detection resistor Rs is provided between the output terminal of the DC / DC converter 30 and the inductor L1 as shown in FIG. 1 will be considered. In this case, the potential Vsp at one end E1 and the potential Vsn at the other end E2 of the detection resistor Rs are input to the current controller 52r, and the current controller 52r controls the switching transistor M1 based on the potential difference Vsp−Vsn. It becomes.

If the impedance of the bypass circuit 40 in the on state is sufficiently small, the voltage between both ends in the on state is substantially zero. When the bypass circuit 40 is turned off in the opposite, the voltage across it is equal to the corresponding voltage drop of the light emitting element 12_I (forward voltage) Vf when the driving current I _OUT flows. Therefore, in the state where k of the N bypass circuits are off and the rest are on, the output voltage _VOUT is k × Vf. That is, when the on / off of the plurality of bypass circuits 40 is dynamically controlled, the output voltage _VOUT also dynamically varies.

When the detection resistor Rs is inserted at the position shown in FIG.
Vsn = V _OUT
Vsp = I _OUT × Rs + Vsn = I _OUT × Rs + V _OUT

In a state where the output voltage V _OUT is stable at a certain level, it is possible to amplify the difference between Vsp and Vsn with high accuracy using an amplifier, and therefore it is possible to detect the drive current I _OUT with high accuracy. It is. However, in the driving device 20r of FIG. 1 in which the output voltage _VOUT varies in response to the on / off of the bypass circuit 40, the detection accuracy is significantly deteriorated due to problems such as amplifier responsiveness, and the luminance accuracy is lowered.

Further, in the vehicle lamp 1r, it detects the overcurrent state of the output current I _OUT, is possible to achieve an appropriate circuit protection (over-current protection) is required.

  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 capable of achieving both high-accuracy output current control and robust overcurrent detection.

  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 drive device includes an input terminal that receives an input voltage, and an output terminal to which the light source is connected, and a DC / DC converter that generates a drive voltage by stepping up, stepping down, or inverting the input voltage and supplies the drive voltage to the light source. , N of the plurality of light emitting elements (N is a natural number), N bypass circuits provided in parallel with the corresponding light emitting elements, and the light source and the ground terminal of the DC / DC converter When the first current flowing during the period reaches a predetermined upper target value, the switching element of the DC / DC converter is turned off. When the first current decreases to the predetermined lower target value, the switching element of the DC / DC converter is turned on. Current controller for performing hysteresis control, dimming controller for switching on and off N bypass circuits, and a second via an output terminal of the DC / DC converter By comparing the flow to a predetermined over-current threshold, comprising an overcurrent detection circuit for detecting an overcurrent condition, the.

  According to this aspect, the output current of the DC / DC converter is subjected to hysteresis control based on the detection signal based on the ground voltage, and is stabilized to the target value. As the N bypass circuits are turned on and off, the output voltage of the DC / DC converter fluctuates dynamically. However, the detection signal based on the ground voltage is not affected by fluctuations in the output voltage. Current control becomes possible. In addition, since overcurrent protection is performed based on the second current passing through the output terminal of the DC / DC converter, overcurrent caused by a ground fault (ground short) of the output terminal is also detected. Is possible. Thus, highly accurate output current control and robust overcurrent detection can both be achieved.

  The drive device may further include a filter that filters the output of the overcurrent detection circuit.

  The overcurrent detection circuit may generate a detection signal that is asserted when the second current reaches a predetermined upper overcurrent threshold and negated when the second current falls to the lower overcurrent threshold.

  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 above-described driving device that drives the light source.

  According to an aspect of the present invention, both highly accurate output current control and robust overcurrent detection can be achieved.

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 an operation | movement waveform diagram of the normal state of a drive device. It is an operation | movement waveform diagram of the drive device which concerns on the comparison technique of FIG. It is an operation | movement waveform diagram of the overcurrent state of a drive device. It is a perspective view of a lamp unit (lamp assembly) provided with the vehicle lamp of FIG. It is an operation | movement waveform diagram of the overcurrent state of the drive device which concerns on a 1st modification. FIGS. 8A and 8B are circuit diagrams of a part of the driving apparatus according to the second modification.

  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 including the driving device 20 according to the embodiment. The drive device 20 is used together with the light source 10 as in FIG. 1 and constitutes the vehicular lamp 1 as a whole.

  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 DC / DC converter 30, a plurality of bypass circuits 40_1 to 40_N, a controller 50, and an overcurrent detection circuit 60.

The DC / DC converter 30 supplies a driving current I _OUT corresponding to the target luminance to the light source 10. For example, the DC / DC converter 30 is a step-down converter, and includes an input terminal IN, an output terminal OUT, a ground terminal GND, an input capacitor C1, a switching transistor M1, a rectifier diode D1, and an inductor L1. An input voltage _VIN is input to the input terminal IN. The light source 10 is connected to the output terminal OUT. Since the topology of the DC / DC converter 30 is general, the description thereof is omitted.

  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 controller 50 controls the DC / DC converter 30 and the plurality of bypass circuits 40_1 to 40_N. The controller 50 includes a current controller 52 and a dimming controller 54.

Current controller 52 detects the driving current _{I OUT,} the detected driving current _{I OUT} is to approach the target amount, the feedback control of the switching state of the switching transistor M1 of the DC / DC converter 30.

More specifically, the current controller 52 performs hysteresis control based on the first current I _OUT1 that flows between the light source 10 and the ground terminal GND of the DC / DC converter 30. Current controller 52, the first current _{I OUT1} reaches a predetermined upper desired value _{I REFH} off the switching transistor M1, turn on the switching transistor M1 when the first current _{I OUT1} is reduced to a predetermined lower target value _{I REFL} To do.

The first current I _OUT1 is detected by a first detection resistor Rs1 provided on the path of the first current I _OUT1 , specifically, between the light source 10 of the DC / DC converter 30 and the ground terminal GND. The first end E1 of the first detection resistor Rs1 is grounded, and the second end E2 is connected to the light source 10. The first detection resistor Rs1, the voltage drop which is proportional to the first current _{I OUT1} (referred to as the first detection _{voltage) Vs1 (= I OUT1 × Rs1} ) is generated. The current controller 52 receives the voltage at the second end E2 of the first detection resistor Rs1, that is, the first detection voltage Vs1. The current controller 52 compares the first detection voltage Vs1 with the two target voltages V _REFH and V _REFL corresponding to the upper target value I _REFH and the lower target value I _REFL , and the output current I _OUT according to the comparison result. Hysteresis control.

  The dimming controller 54 individually controls ON and OFF of the N bypass circuits 40_1 to 40_N. Specifically, the dimming controller 54 switches the N bypass circuits 40_1 to 40_N based on instructions for turning on / off each of the N light emitting elements 12_1 to 12_N. The dimming controller 54 may perform PWM control on the bypass circuit 40_i in accordance with the target luminance of the light emitting element 12_i.

The overcurrent detection circuit 60 detects an overcurrent state by comparing the second current _IOUT2 passing through the output terminal OUT of the DC / DC converter 30 with a predetermined overcurrent threshold _IOCP . When an overcurrent state is detected by the overcurrent detection circuit 60, the current controller 52 stops switching of the switching transistor M1 and applies overcurrent protection.

The second current I _OUT2 is detected by a second detection resistor Rs2 provided on the path of the second current I _OUT2 , specifically, between the inductor L1 of the DC / DC converter 30 and the output terminal OUT. The second detection resistor Rs2 may be provided between the inductor L1 and the cathode of the diode D1.

The second detection resistor Rs2, a voltage drop proportional to the second current _{I OUT2} (second detection _{voltage) Vs2 (= I OUT2 × Rs2} ) is generated. The overcurrent detection circuit 60 receives the voltages Vs2p and Vs2n at both ends of the second detection resistor Rs2, and applies the second detection voltage Vs2 corresponding to the potential difference between them to a threshold voltage V corresponding to the _overcurrent threshold I _OCP. compared with _OCP, when _{Vs2> V OCP,} it asserts an overcurrent detection signal _{S OCP.}

The above is the configuration of the driving device 20. Next, the operation will be described.
FIG. 3 is an operation waveform diagram of the drive device 20 in a normal state.
Focusing on a certain cycle, while the switching transistor M1 is on, the coil current I _L flowing through the inductor L1, that is, the output current I _OUT increases. As the output current I _OUT increases, when the first detection voltage Vs1 increases and reaches the upper target voltage V _REFH , the switching transistor M1 is turned off. While the switching transistor M1 is off, the coil current I _L flowing through the inductor L1, that is, the output current I _OUT decreases. As the output current I _OUT decreases, when the first detection voltage Vs1 decreases and decreases to the lower target voltage V _REFL , the switching transistor M1 is turned off. The current controller 52 stabilizes the output current _IOUT within the target range by repeating this control.

When the dimming controller 54 switches the bypass circuit 40 at time t0, the output voltage _VOUT changes abruptly. The first detection voltage Vs1 is a voltage drop of the first detection resistor Rs1 provided on the ground terminal GND side, and is generated based on the ground voltage V _GND = 0V. Therefore, even if the output voltage _VOUT varies, the first detection voltage Vs1 is not affected by the fluctuation.

As described above, according to the drive device 20 according to the embodiment, the output current I _OUT can be stabilized with high accuracy without being affected by the fluctuation of the output voltage _VOUT accompanying the control of the bypass circuit 40. This advantage becomes clear by comparison with the waveform diagram of FIG. FIG. 4 is an operation waveform diagram of the drive device 20r according to the comparative technique of FIG.

When the output voltage _VOUT changes at time t0, the potential Vsn at one end of the detection resistor Rs changes accordingly. The current controller 52r amplifies the potential difference between the voltages Vsp and Vsn across the detection resistor Rs to generate the detection voltage Vs, and performs hysteresis control based on the detection voltage Vs. However, the linearity of the detection voltage Vs and the potential difference (Vsp−Vsn) is lost if it cannot follow the fluctuation of the voltage Vsn due to the response delay τ of the amplifier. As a result, the output current I _OUT deviates from the target range. Since the output current I _OUT corresponds to the brightness of the lamp, if the output current I _OUT varies, it will be recognized as flicker.

  According to the drive device 20 according to the embodiment, the current detection for hysteresis control is performed with reference to the ground voltage, so that the problem that occurs in the comparison technique can be solved.

FIG. 5 is an operation waveform diagram of the overcurrent state of the driving device 20.
When the overcurrent state is entered, the output current _IOUT increases. When the second current I _OUT2 exceeds the threshold value I _OCP and the state continues for a certain time, the overcurrent detection circuit 60 asserts the _overcurrent detection signal S _OCP (high level). When the overcurrent detection signal S _OCP is asserted, the current controller 52 stops switching of the switching transistor M1. When the switching of the switching transistor M1 stops, the output current I _OUT decreases. When the second current I _OUT2 eventually falls below the threshold value I _OCP , the overcurrent detection signal S _OCP is negated, the overcurrent protection state is released, and switching of the switching transistor M1 is resumed. This operation is repeated if the event causing the overcurrent persists.

  Here, in the driving device 20, current detection for overcurrent protection is performed based on a second detection resistor Rs2 provided on the output terminal OUT side, separately from the first detection resistor Rs1 for hysteresis control. Yes.

  In the examination stage, the present inventors also examined a configuration for performing overcurrent protection using the first detection resistor Rs1. This configuration has the advantage that one detection resistor is sufficient, but there is a problem that an overcurrent state due to a ground fault (called output short-circuit) of the wiring from the output terminal OUT to the light source 10 cannot be detected. This is because the voltage level of the second end E2 of the first detection resistor Rs1 is included in the voltage range near the ground voltage regardless of whether or not there is an output short circuit.

  On the other hand, in the drive device 20 according to the embodiment, when an output short circuit occurs, the voltage Vs2n at one end of the second detection resistor Rs2 input to the overcurrent detection circuit 60 decreases to near the ground voltage 0V, which is normal. Deviation from the voltage range of the hour. The same applies to the voltage Vs2p at the other end of the second detection resistor Rs2. Therefore, according to the driving device 20, it is possible to detect an overcurrent state due to an output short circuit.

In the overcurrent detection based on the voltage drop of the second detection resistor Rs2, the accuracy of the current detection can be reduced due to the fluctuation of the output voltage _VOUT accompanying the on / off control of the bypass circuit 40. However, the reduction in current detection accuracy does not pose a problem by setting the threshold I _OCP in consideration of the decrease in current detection accuracy for overcurrent detection.

  Finally, the use of the vehicular lamp 1 will be described. FIG. 6 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 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.

(First modification)
In the driving device 20 according to the embodiment, overcurrent protection is performed based on the comparison result between the second current _IOUT2 and the predetermined threshold value _IOCP . In a DC / DC converter with hysteresis control, the response delay is very small, so when an event that causes an overcurrent state continues, the cycle of repetition of operation and stop shown in FIG. 5 may become very short. is there. Therefore, in the first modification, a hysteresis is set in the threshold value I _OCP of the _overcurrent detection circuit 60.

FIG. 7 is an operation waveform diagram of the overcurrent state of the drive device 20 according to the first modification. The threshold value I _OCP compared with the second current I _OUT2 transitions between the upper threshold value I _OCPH and the lower threshold value I _OCPL . Specifically, during the period when the _overcurrent detection signal S _OCP is asserted (high level), the threshold value I _OCP takes the lower value I _OCPL and during the period when it is negated (low level), the threshold value I _{OCP Takes the} upper value I _OCPH .

  According to this modification, it is possible to prevent the repetition cycle of operation and stop from being shortened when an event that causes an overcurrent state continues.

(Second modification)
FIGS. 8A and 8B are circuit diagrams of a part of the driving device 20a according to the second modification. The drive device 20a further includes a filter 62 that filters the _overcurrent detection signal _SOCP generated by the overcurrent detection circuit 60. The filter 62 in FIG. 8A is an RC filter including a resistor R21 and a capacitor C21.

As shown in FIG. 5, there is a case where it is desired to notify the external processor 6 or the like from the vehicular lamp 1 that the event causing the overcurrent state has continued. However, the overcurrent detection signal S _OCP is a pulse signal that alternately repeats assertion and negation in this state, and may not be detected by an interface provided as a standard in the processor (microcomputer) 6. Therefore, by smoothing the _overcurrent detection signal S _OCP by the filter 62, a DC detection signal S _OCP 'that becomes a high level when the overcurrent state continues can be generated and correctly notified to the processor 6.

The filter 62 in FIG. 8B further includes a diode D21 connected in parallel with the resistor R21 of the RC filter. The response to the positive edge and the negative edge of the _overcurrent detection signal SOCP can be made different by the diode D21. That is, the diode D21 can respond to the assertion of the _overcurrent detection signal _{SOCP at} a high speed and can make the sensitivity to the negate (release of the overcurrent state) insensitive.

(Third Modification)
In the embodiment, the case where a step-down converter is used as the DC / DC converter 30 has been described. However, in the present invention, the topology of the DC / DC converter 30 is not limited thereto. The DC / DC converter 30 may be a Cuk converter, a Sepic converter, or a Zeta converter. Or a forward converter and a flyback converter may be sufficient.

(Fourth modification)
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.

(Fifth modification)
In the lamp unit 500 of FIG. 6, 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 ... DC / DC converter, 40 ... Bypass circuit, 50 ... Controller, 52 ... Current controller 54 ... Dimming controller 60 ... Overcurrent detection circuit 62 ... Filter M1 ... Switching transistor Rs1 ... First detection resistor Rs2 ... Second detection resistor 500 ... Lamp unit 502 ... Cover 504 ... High beam unit, 506... Low beam unit, 508.

Claims (4)

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 DC / DC converter having an input terminal for receiving an input voltage and an output terminal to which the light source is connected, generating a drive voltage by boosting, stepping down or inverting the input voltage, and supplying the drive voltage to the light source;
N bypass circuits that are associated with N (N is a natural number) light emitting elements among the plurality of light emitting elements, and each is provided in parallel with the corresponding light emitting element;
When the first current flowing between the light source and the ground terminal of the DC / DC converter reaches a predetermined upper target value, the switching element of the DC / DC converter is turned off, and the first current is set to the predetermined lower target. A current controller that performs hysteresis control to turn on the switching element of the DC / DC converter when the value drops to a value;
A dimming controller for switching on and off the N bypass circuits;
An overcurrent detection circuit for detecting an overcurrent state by comparing a second current passing through the output terminal of the DC / DC converter with a predetermined overcurrent threshold;
A drive device comprising:   The drive device according to claim 1, further comprising a filter that filters a detection signal indicating a detection result of the overcurrent detection circuit.   The overcurrent detection circuit generates a detection signal that is asserted when the second current reaches a predetermined upper overcurrent threshold and negated when the second current falls to a lower overcurrent threshold. The drive device according to claim 1, wherein: A light source including a plurality of light emitting elements connected in series;
The driving device according to any one of claims 1 to 3, which drives the light source;
A vehicular lamp characterized by comprising:

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