Vehicle lighting fixtures

Abstract

In the present invention, a scanning-type light source (200A) includes a semiconductor light source (212), and scans a beam (BM) from the semiconductor light source (212) in the horizontal direction of the light distribution. An illumination circuit (300I) is synchronized with the scanning of the scanning-type light source (200A), and can modulate the amount of light of the semiconductor light source (212) at individual scanning positions in multiple gradations using pulse modulation. The pulse-modulation period TPWM is such that TPWM <A×(θSPOT / θSCAN)×TSCAN, where θSPOT is the horizontal width of an instantaneous irradiation spot (SPT), θSCAN is the total scanning angle, and TSCAN is the scanning cycle, A being a constant that is less than or equal to 1.

Description

[Technical field]

[0001] The present disclosure relates to a vehicle lamp for use in an automobile or the like. [Background technology]

[0002] Vehicle lamps are generally capable of switching between low beam and high beam. Low beam illuminates the vicinity of the vehicle with a predetermined illuminance, and light distribution regulations are established so as not to cause glare to oncoming vehicles or preceding vehicles, and is mainly used when driving in urban areas. On the other hand, high beam illuminates a wide range and distant area ahead with a relatively high illuminance, and is mainly used when driving at high speed on roads with few oncoming vehicles or preceding vehicles. Therefore, high beam has better visibility for the driver than low beam, but has the problem of causing glare to drivers of vehicles and pedestrians in front of the vehicle.

[0003] In recent years, ADB (Adaptive Driving Beam) technology has been put to practical use, which dynamically and adaptively controls the high beam light distribution pattern based on the surrounding conditions of the vehicle. The system detects the presence or absence of preceding vehicles, oncoming vehicles, and pedestrians ahead of the vehicle and reduces the glare given to the vehicle by dimming the areas corresponding to the vehicles.

[0004] Methods proposed to realize the ADB function include the shutter method, which controls an actuator, the rotary method, and the LED array method. The shutter and rotary methods make it possible to continuously change the width of the off-area (light-blocking area), but the number of off-areas is limited to one. The LED array method makes it possible to set multiple off-areas, but the width of the off-area is limited by the irradiation width of the LED chip, so it is discrete.

[0005] The applicant has proposed a scanning method as an ADB method capable of solving these problems (see Patent Documents 2 and 3). The scanning method forms a desired light distribution pattern in front of the vehicle by irradiating light onto a rotating reflector (blade mirror), reflecting the incident light at an angle according to the rotational position of the reflector, and scanning the reflected light in front of the vehicle while changing the on / off state of the light source according to the rotational position of the reflector.

[0006] In the scanning method described in Patent Document 3, the amount of drive current flowing through the light source is kept constant during one scan, while the light source is switched on and off in a time-division manner. Therefore, it was easy to realize a glare-free function that blocks light from a specified area, but the illuminance of the illuminated area was essentially restricted to a constant value.

[0007] Patent Document 4 discloses a specific method of forming a light distribution by a scanning type vehicle lamp. In this technology, a light distribution is formed by a light source of multiple channels. Each of the light sources of the multiple channels is responsible for a part of the horizontal range, and the scanning range of each light source is shifted in the horizontal direction while overlapping with the scanning range of the other light sources. The light amount of each light source is controlled by so-called DC dimming (analog dimming), and is variable in units of one scan due to the constraint of the response speed. In this lamp, the illuminance at each scanning position can be controlled by a combination of on / off and light amount of the multiple light sources, and it is adapted to correspond to various light distribution patterns other than the glare-free function (for example, electronic swivel, etc.). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2008-205357 A [Patent Document 2] JP 2012-224317 A [Patent Document 3] JP 2010-6109 A [Patent Document 4] JP 2018-187979 A Summary of the Invention [Problem to be solved by the invention]

[0009] The technology of Patent Document 4 requires light sources and lighting circuits for many channels to form one light distribution, resulting in a complex structure and complicated control of the light sources to form the desired light distribution.

[0010] The present disclosure has been made in consideration of such problems, and one exemplary purpose of an embodiment of the present disclosure is to provide a vehicle lamp capable of generating various light distribution patterns other than a glare-free function. [Means for solving the problem]

[0011] An aspect of the present disclosure relates to a vehicle lamp used together with a camera. The vehicle lamp includes a scanning light source that includes a semiconductor light source and scans an instantaneous illumination spot based on the light emitted from the semiconductor light source in the horizontal direction of light distribution, and a lighting circuit that can adjust the light amount of the semiconductor light source at each scanning position in multiple gradations by pulse modulation in synchronization with the scanning of the scanning light source. The horizontal width of the instantaneous illumination spot is set to θ SPOT , the total scan angle is θ SCAN , the scanning period is T SCAN Then, the period of the pulse modulation is T PWM teeth, T PWM <A×(θ SPOT / θ SCAN )×T SCAN A is a constant A≦1.

[0012] An aspect of the present disclosure relates to a vehicle lamp used together with a camera. The vehicle lamp includes a scanning light source that includes a semiconductor light source and scans an instantaneous illumination spot based on the light emitted from the semiconductor light source in the horizontal direction of light distribution, and a lighting circuit that can adjust the light amount of the semiconductor light source at each scanning position in multiple gradations by pulse modulation in synchronization with the scanning of the scanning light source. The horizontal width of the instantaneous illumination spot is set to θ SPOT , the scan speed is v θThen, the period of the pulse modulation is T PWM teeth, T PWM <θ SPOT / v θ A is a constant A≦1.

[0013] Any combination of the above components, or mutual substitution of components or expressions between methods, devices, systems, etc., are also effective as aspects of the present invention or the present disclosure. Furthermore, the description in this section (Means for Solving the Problems) does not explain all essential features of the present invention, and therefore, subcombinations of the described features may also constitute the present invention. Effect of the Invention

[0014] According to an aspect of the present disclosure, in a scanning type vehicle lamp, various light distribution patterns other than the glare-free function can be generated. [Brief description of the drawings]

[0015] [Figure 1] 1 is a diagram showing a vehicle lamp according to a first embodiment. [Diagram 2] 2(a) and (b) are diagrams for explaining the formation of a glare-free light distribution by a vehicle lamp. [Diagram 3] 3(a) and (b) are diagrams for explaining the formation of a partially dimmed light distribution by a vehicle lamp. [Figure 4] 4(a) and (b) are diagrams for explaining electronic swivel by a vehicle lamp. [Diagram 5] FIG. 13 is a diagram showing a vehicle lamp according to a comparative technique. [Figure 6] 10A and 10B are diagrams illustrating light distribution formed by a vehicle lamp according to a comparative technique. [Figure 7] FIG. 2 is a block diagram showing a configuration example of a lighting circuit. [Figure 8] FIG. 2 is a circuit diagram showing a configuration example of an LED driver. [Figure 9]FIG. 11 is a circuit diagram showing another example of the configuration of the LED driver. [Figure 10] FIG. 13 is a circuit diagram showing yet another example configuration of the LED driver. [Figure 11] FIG. 11 is a diagram showing a vehicle lamp according to a second embodiment. [Figure 12] 12 is a block diagram showing a configuration example of the lighting circuit of FIG. 11. [Figure 13] 1 is a diagram showing a vehicle lamp according to an embodiment of the present invention; [Figure 14] FIG. 13 is a diagram showing an example of the intensity distribution of an instantaneous irradiation spot. [Figure 15] FIG. 11 is a diagram showing a light distribution pattern when the PWM frequency is changed. [Figure 16] FIG. 13 is a diagram showing an example of the intensity distribution of an instantaneous irradiation spot. [Figure 17] FIG. 11 is a diagram showing a light distribution pattern when the PWM frequency is changed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] (Overview of the embodiment) A summary of some exemplary embodiments of the present disclosure will be described. This summary is intended to provide a simplified summary of some concepts of one or more embodiments in order to provide a basic understanding of the embodiments as a prelude to the detailed description that follows, and is not intended to limit the scope of the invention or disclosure. Furthermore, this summary is not intended to be a comprehensive overview of all possible embodiments, nor is it intended to limit essential components of the embodiments. For convenience, the term "one embodiment" may be used to refer to one embodiment (example or variant) or multiple embodiments (examples or variants) disclosed in this specification.

[0017] A vehicle lamp according to one embodiment is used together with a camera. The vehicle lamp includes a semiconductor light source, a scanning light source that scans an instantaneous illumination spot based on light emitted from the semiconductor light source in a horizontal direction of light distribution, and a lighting circuit that adjusts the light amount of the semiconductor light source at each scanning position in multiple gradations by pulse modulation in synchronization with the scanning of the scanning light source.

[0018] According to this configuration, by adopting pulse modulation, the light amount of the light source can be changed at high speed according to the scanning position within one scanning period. Therefore, compared to DC dimming (analog dimming) that keeps the light amount constant within one scanning period, the variation of light distribution that can be formed by one light source is increased. As a result, the number of light sources and lighting circuits can be reduced or the control can be simplified compared to the conventional method.

[0019] "Pulse modulation" includes pulse width modulation (PWM), pulse frequency modulation (PFM), pulse density modulation (PDM), and other modulation methods that rapidly switch the drive current flowing through the light source to change the time-average value of the drive current.

[0020] When using a scanning vehicle light with a camera, the scanning frequency f SCA N is the camera frame rate f FRAME If the scanning frequency is not higher than f, stripes may appear in the image captured by the camera. SCAN is the frame rate f FRA ME In other words, the scanning period T SCAN (1 / f SCAN ) is the imaging period 1 / f FRAME be defined as shorter.

[0021] When scanning and pulsed light modulation are used in combination, the inventors PWM It has been discovered that, depending on the type of camera used, stripes may appear in the image. When stripes appear, this can cause problems such as reducing the accuracy of image recognition.

[0022] The instantaneous irradiation spot has a finite width θ SPOT The angle at which the instantaneous irradiation spot is scanned (total scan angle) is θ SCAN When the instantaneous irradiation spot is SPOT The transit time τ required to move is τ = (θ SPOT / θ SCAN)×T SCAN It becomes.

[0023] Pulse modulation period T PWM However, we realized that when the transit time is longer than τ or is on the same order of magnitude as τ, light and dark areas appear on the screen, which are captured as stripes in the camera image.

[0024] To solve this problem, in one embodiment, the horizontal width of the instantaneous illumination spot is set to θ SP OT , the total scan angle is θ SCAN , the scanning period is T SCAN Then, the period of the pulse modulation is T PWM teeth, T PWM <A×(θ SPOT / θ SCAN )×T SCAN A is a constant that satisfies A≦1. This can suppress the appearance of stripes.

[0025] Instantaneous irradiation spot speed v θ v θ =θ SCAN / T SCAN Therefore, the transit time τ is θ SPOT / v θ Therefore, in one embodiment, the horizontal width of the instantaneous irradiation spot is defined as θ SPOT , the scan speed is v θ Then, the period of the pulse modulation is T PW M teeth, T PWM <A×θ SPOT / v θ A is a constant that satisfies A≦1. This can suppress the appearance of stripes.

[0026] The constant A can be determined according to the intensity distribution of the instantaneous irradiation spot. For example, when a beam with a rectangular intensity distribution is assumed, A ≒ 1. In the case of a Gaussian distribution, A must be set smaller, for example, A ≦ 0.5. For example, if A ≦ 0.2, stripe projection can be suppressed for various intensity distributions.

[0027] In one embodiment, the scanning light source may further include, in addition to the semiconductor light source, a reflector that receives light emitted from the semiconductor light source and scans the reflected light in front of the vehicle by repeating a predetermined periodic motion. The lighting circuit may generate a pulse-modulated control waveform in synchronization with the motion of the reflector and switch a drive current supplied to the semiconductor light source in response to the control waveform.

[0028] In one embodiment, the lighting circuit may include a series switch provided in series with the semiconductor light source, and a constant current driver connected to the series connection circuit of the series switch and the semiconductor light source. The lighting circuit may switch the series switch with a duty cycle according to the scanning position.

[0029] In the prior art (Patent Document 4), two semiconductor light sources are connected in series, and a bypass switch is provided in parallel with each semiconductor light source. In this configuration, when one bypass switch is switched at a frequency sufficiently higher than the scanning frequency, the other semiconductor light source is affected. In contrast, by driving each semiconductor light source individually with a series switch, the effect of driving one channel on the other channel can be eliminated.

[0030] In one embodiment, the constant current driver may include a switching converter and a converter controller that drives the switching converter such that a detected value of an output current of the switching converter approaches a predetermined target value.

[0031] (Embodiment) Hereinafter, the present disclosure will be described with reference to the drawings based on preferred embodiments. The same or equivalent components, parts, and processes shown in each drawing will be given the same reference numerals, and duplicated descriptions will be omitted as appropriate. In addition, the embodiments are not intended to limit the disclosure, but are merely examples, and all features and combinations thereof described in the embodiments are not necessarily essential to the disclosure.

[0032] In this specification, "a state in which component A is connected to component B" includes not only a case in which component A and component B are directly physically connected to each other, but also a case in which component A and component B are indirectly connected to each other via other components that do not substantially affect the electrical connection state between them or that do not impair the function or effect achieved by their combination.

[0033] Similarly, "a state in which component C is provided between components A and B" includes not only the case in which components A and C, or components B and C, are directly connected to each other, but also the case in which they are indirectly connected to each other via other components that do not substantially affect the electrical connection between them or that do not impair the functions or effects achieved by their combination.

[0034] In this specification, symbols attached to electrical signals such as voltage signals and current signals, or circuit elements such as resistors and capacitors, represent the respective voltage values, current values, resistance values, or capacitance values ​​as necessary.

[0035] Fig. 1 is a diagram showing a vehicle lamp 100A according to embodiment 1. The vehicle lamp 100A in Fig. 1 has a scanning type ADB function and forms various light distribution patterns in front of the vehicle. The vehicle lamp 100A mainly includes a scanning light source 200A, a lighting circuit 300A, and a light distribution controller 400.

[0036] The light distribution controller 400 receives information (sensor information) S1 from sensors such as a camera and LiDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging), and information (vehicle information) S2 such as vehicle speed and steering angle, and determines a light distribution pattern. The light distribution controller 400 may be housed in a lamp body or may be provided on the vehicle side. The light distribution controller 400 transmits information (light distribution pattern information) S3 instructing a light distribution pattern to the vehicle lamp 100. The light distribution controller 400 is also called an ADB ECU (Electronic Control Unit).

[0037] The scanning light source 200A includes a light source unit 210A, a scanning optical system 220, and a projection optical system 230. The light source unit 210A includes one semiconductor light source 212 and a heat sink (not shown). The semiconductor light source 212 may be an LED (light emitting diode) or a laser diode. The scanning optical system 220 scans the emitted light (beam) BM from the semiconductor light source 212 in front of the vehicle.

[0038] In this embodiment, the scanning optical system 220 includes a motor 222 and one or more M (two in this example) blade mirrors 224_1, 224_2. The M (M≧2) blade mirrors are attached at positions shifted by 360 / M°, and in this example, two blade mirrors are attached at positions shifted by 180°.

[0039] The optical axis of the semiconductor light source 212 is oriented so that its output beam BM is incident on one of the M blade mirrors.

[0040] At a certain time, the light BM incident on the blade mirror 224 is reflected at a reflection angle according to the position of the blade mirror 224 (rotation angle of the rotor), and forms an instantaneous irradiation spot SPT on a virtual vertical screen 900 in front of the vehicle. The instantaneous irradiation spot SPT has a width Δv in the horizontal direction (H direction) and a width Δh in the vertical direction (V direction). The rotation of the blade mirror 224 changes the reflection angle, i.e., the emission direction of the reflected beam BMr, and the position (scanning position) of the instantaneous irradiation spot SPT in the horizontal direction (H direction) moves. By repeating this operation at high speed, for example at 50 Hz or more, a light distribution pattern PTN is formed in front of the vehicle.

[0041] In this embodiment, the light distribution pattern PTN formed by one beam BM is a light distribution pattern that covers the entire horizontal range −θ MAX ~+θ MAX That is, the scanning light source 200A scans the reflected beam BMr over the entire range in the horizontal direction. For example, MAX The angle is about 20 to 25°. Note that the entire range refers to the entire range that can be irradiated by the scan, and does not include the range that is irradiated by a light source other than the scan.

[0042] The lighting circuit 300A adjusts the light amount of the semiconductor light source 212 at each scanning position, i.e., the intensity of the beam BM, in multiple gradations by pulse modulation in synchronization with the scanning of the scanning light source 200A so that the light distribution pattern specified by the light distribution pattern information S3 is obtained. In this embodiment, the driving current I LED The average amount of light is changed to change the amount of light (PWM dimming) from semiconductor light source 212. The PWM frequency is set to be sufficiently higher than the scanning frequency, and is desirably set to, for example, several kHz to several hundred kHz.

[0043] The lighting circuit 300A generates a current I OUT The amount of current may be changed. In other words, PWM dimming and DC dimming may be used in combination. The above is the configuration of the vehicular lamp 100A. Next, the operation will be described.

[0044] 2(a) and (b) are diagrams for explaining the formation of a glare-free light distribution by the vehicle lamp 100A. The glare-free light distribution 910 in FIG. 2 includes a light-shielding portion 912 and irradiated portions 914 and 916. FIG. 2(a) shows the light distribution on a virtual vertical screen, and FIG. 2(b) shows the operating waveform of the vehicle lamp 100A corresponding to the light distribution in FIG. 2(a). Note that the vertical and horizontal axes of the waveform diagrams and time charts referred to in this specification are appropriately enlarged or reduced for ease of understanding, and each waveform shown is simplified, exaggerated, or emphasized for ease of understanding.

[0045] For example, the lighting circuit 300A controls the driving current I LED The duty cycle of the driving current I LED The duty cycle of is 0%.

[0046] 3(a) and (b) are diagrams for explaining the formation of a partially dimmed light distribution by a vehicle lamp 100A. Fig. 3(a) shows the horizontal illuminance distribution of light distribution on a virtual vertical screen, and Fig. 3(b) shows the operating waveform of the vehicle lamp 100A corresponding to the light distribution of Fig. 3(a). The partially dimmed light distribution 920 shown in Fig. 3(a) includes two dimmed parts 922, 924 and three non-dimmed parts 926, 927, 928.

[0047] For example, the lighting circuit 300A controls the driving current I LED The duty cycle is fixed at 100%, and in the sections corresponding to the dimming parts 922 and 924, the driving current I LED The duty cycles of the driving current I LED Partial dimming can be achieved by PWM control.

[0048] 4(a) and (b) are diagrams for explaining electronic swivel by the vehicle lamp 100A. FIG. 4(a) shows the brightest light distribution at the center, and FIG. 4(b) shows the brightest light distribution at the right side. With this vehicle lamp 100A, the driving current I LED By controlling this with PWM, an electronic swivel function can be realized.

[0049] The above is the operation of the vehicular lamp 100A. The advantages of the vehicular lamp 100A become clearer when compared with a comparative technique. The comparative technique will now be described. Figure 5 is a diagram showing a vehicular lamp 100R according to the comparative technique.

[0050] In a vehicle lamp 100R according to the comparative technique, a light source unit 210R includes a plurality of semiconductor light sources 212_1 to 212_N. 1 ~BM N are scanned in different horizontal ranges on the virtual vertical screen 900, and the output beam BM 1 ~BM N By scanning, multiple individual light distribution patterns PTN 1 ~PTN N The light distribution formed by the vehicle lamp 100R is a plurality of individual light distribution patterns PTN 1 ~PTN N It is a superposition of.

[0051] The lighting circuit 300R supplies a driving current I LED1 ~I LEDN The lighting circuit 300R supplies a driving current I LE D1 ~I LEDN Each of the lighting circuits 300R can be turned on and off. In addition, the lighting circuit 300R controls the driving current I LED1 ~I LEDN Although the amount of current during each ON period can be controlled, the amount of current can only be switched for each scan.

[0052] FIG. 6 is a diagram for explaining the formation of light distribution by a vehicle lamp 100R according to a comparative technique. Here, N=6 channels. A plurality of individual light distribution patterns PTN 1 ~PTN 6 By overlapping them, a light distribution pattern with a brighter left front is formed in this example.

[0053] Returning to the first embodiment. According to the vehicle lamp 100A of the first embodiment, by adopting pulse modulation, the light amount of the light source can be changed at high speed in one scanning cycle according to the scanning position. Therefore, compared with the conventional analog dimming that keeps the light amount constant in one scanning cycle, the variation of the light distribution that can be formed by one light source is increased. As a result, compared with the conventional, the number of light sources and lighting circuits can be reduced, or the control can be simplified.

[0054] The present disclosure is understood as the block diagram and circuit diagram of Fig. 1, and extends to various devices and circuits derived from the waveform diagrams of Fig. 3 and Fig. 4, or the above description, and is not limited to a specific configuration. Below, more specific configuration examples are described, not for the purpose of narrowing the scope of the present disclosure, but for the purpose of making the essence of the disclosure and the circuit operation easier and clearer to understand.

[0055] A specific example of the configuration of the lighting circuit 300A will be described below. Fig. 7 is a block diagram showing an example of the configuration of the lighting circuit 300A.

[0056] The light distribution controller 400 receives sensor information S1 and vehicle information S2. Based on the sensor information S1, the light distribution controller 400 detects the situation ahead of the vehicle, specifically, the presence or absence of an oncoming vehicle, a preceding vehicle, a pedestrian, etc., based on the sensor information S1. The light distribution controller 400 also detects the current vehicle speed, steering angle, etc., based on the vehicle information S2. Based on this information, the light distribution controller 400 determines a light distribution pattern to be irradiated ahead of the vehicle, and transmits information (light distribution pattern information) S3 instructing the light distribution pattern to the lighting circuit 300A.

[0057] The lighting circuit 300A changes the light amount (brightness) of the semiconductor light source 212 in multiple gradations by PWM dimming based on the light distribution pattern information S3 and in synchronization with the rotation of the blade mirror 224. For example, the lighting circuit 300A mainly includes a position detector 302, a PWM signal generation unit 310, and a constant current driver (hereinafter referred to as an LED driver) 320.

[0058] The position detector 302 is provided to detect the position of the blade mirror 224, in other words, the current scanning position of the beam. The position detector 302 generates a position detection signal S4 that indicates the timing when a predetermined reference point of the blade mirror 224 passes a predetermined position. For example, the reference point may be the ends (discrepancies) of the two blade mirrors 224, or the center of each blade mirror, or any other point.

[0059] A Hall element may be attached to the motor 222 that rotates the blade mirror 224. In this case, the Hall signal from the Hall element has a periodic waveform that corresponds to the position of the rotor, i.e., the position of the blade mirror. The position detector 302 may detect the timing at which the polarity of the Hall signal is inverted, and specifically may be configured with a Hall comparator that compares a pair of Hall signals.

[0060] The method of detecting the position of the blade mirror 224 by the position detector 302 is not limited to using a Hall element. For example, the position detector 302 may generate the position detection signal S4 by using an optical or other type of rotary encoder that detects the position of the rotor of the motor 222. Alternatively, the position detector 302 may include a photosensor provided on the back side of the blade mirror 224 and a light source for position detection that irradiates light from the front side of the blade mirror 224 toward the photosensor. A slit or a pinhole may be provided in the blade mirror 224. This makes it possible to detect the timing when the slit or pinhole passes over the photosensor. The slit may be the gap between two blade mirrors 224. The light source for position detection may be an infrared light source or a semiconductor light source 212. As described above, the configuration of the position detector 302 may have various variations.

[0061] The PWM signal generating unit 310 generates a pulse dimming signal PWM_DIM in synchronization with the movement of the blade mirror 224. The duty cycle of one scanning period of the pulse dimming signal PWM_DIM is determined based on the light distribution pattern. For example, when the rotation speed of the motor 222 is 6000 rpm (100 Hz) and there are two blade mirrors, the scanning frequency is 100 Hz x 2 = 200 Hz, and the scanning period is 5 ms. The PWM signal generating unit 310 may be implemented as a combination of the microcontroller 304 and a software program, or may be implemented only by hardware. The microcontroller 304 and the LED driver 320 may be mounted on a single board, or may be arranged in a single housing.

[0062] The frequency of the pulse dimming signal PWM_DIM is set to be higher than 200 Hz, and may be, for example, several kHz to several tens of kHz. The duty cycle of the pulse dimming signal PWM_DIM defines the light amount of the semiconductor light source 212, and the duty cycle may be set for each PWM period or may be set for multiple PWM periods.

[0063] The LED driver 320 supplies a driving current I LED The drive current I LED The amount of current in the LED driver 320 is stabilized at a predetermined target value, and the LED driver 320 controls the driving current I LED Switching.

[0064] 8 is a circuit diagram showing a configuration example (320A) of the LED driver 320. The LED driver 320A includes a step-down converter 322, a series switch 323, and a driver circuit 324. The series switch 323 and the semiconductor light source 212 are connected in series. In this example, the series switch 323 is inserted on the anode side of the semiconductor light source 212, but it may be inserted between the cathode and ground.

[0065] The step-down converter 322 is a switching converter that outputs a constant current, and includes an output circuit 326 and a converter controller 328. The output circuit 326 includes a switching transistor MH, a synchronous rectifier transistor ML, an inductor L1, and an output capacitor C1. The converter controller 328 controls the output current I of the step-down converter 322 during the period when the series switch 323 is on. OUT The switching of the switching transistor MH and the synchronous rectification transistor ML of the output circuit 326 is controlled so that the current approaches a predetermined target amount.

[0066] The control method of converter controller 328 is not particularly limited, and may be an analog controller using an error amplifier, a digital controller including a PID (proportional-integral-derivative) compensator, or a hysteresis control controller.

[0067] The driver circuit 324 drives the series switch 323 in response to the pulse dimming signal PWM_DIM. The driver circuit 324 may be integrated into the same IC as the converter controller 328.

[0068] When the pulse dimming signal PWM_DIM is at an off level instructing the series switch 323 to be turned off, the converter controller 328 stops switching of the switching transistor MH and the synchronous rectification transistor ML.

[0069] 9 is a circuit diagram showing another example configuration (320B) of the LED driver 320. The LED driver 320B includes a step-down converter 322, a bypass switch SW2, and a driver circuit 324. The step-down converter 322 may include an output circuit 326 and a converter controller 328, similar to FIG. 8. The step-down converter 322 outputs an output current I stabilized to a predetermined target amount. OUT Generate.

[0070] The bypass switch SW2 is connected in parallel with the semiconductor light source 212. The driver circuit 324 drives the bypass switch SW2 in response to the pulse dimming signal PWM_DIM. During the off-period of the bypass switch SW2, an output current I OUT is the drive current I LED During the on-period of the bypass switch SW2, the output current I OUT flows through the bypass switch SW2, so the drive current I LED will be zero.

[0071] 10 is a circuit diagram showing yet another example configuration (320C) of the LED driver 320. The LED driver 320C includes a constant voltage converter 327 and a constant current source 329. The constant voltage converter 327 outputs an output voltage V OUT The constant current source 329 is connected in series with the semiconductor light source 212. The constant current source 329 can be switched on and off, and generates a drive current I stabilized at a predetermined amount during the on period. LED The constant current source 329 is turned on and off in response to the pulse dimming signal PWM_DIM.

[0072] The configuration of the LED driver 320 is not limited to the example shown here.

[0073] (Embodiment 2) 11 is a diagram showing a vehicle lamp 100B according to embodiment 2. Differences from embodiment 1 will be described.

[0074] The light source unit 210B of the scanning light source 200B includes a plurality of N (N≧2) semiconductor light sources 212_1 to 212_N. The optical axes of the semiconductor light sources 212_1 to 212_N are aligned along the axis of each of the emitted beams BM 1 ~BM N is directed to be irradiated onto one of the M blade mirrors. Here, the output beam BM 2 Only the rays of are shown as representative.

[0075] At a certain time, the incident light BM 2 is reflected at a reflection angle according to the position of the blade mirror 224 (rotation angle of the rotor) and instantaneously irradiated onto a virtual vertical screen 900 in front of the vehicle. 2 Instantaneous irradiation spot SPT 2 has a predetermined width in both the horizontal direction (H direction) and the vertical direction (V direction). The rotation of the blade mirror 224 changes the reflection angle, and the reflected beam BMr 2 The direction of the light emitted changes, and the instantaneous irradiation spot SPT 2 By repeating this operation at high speed, for example at 50 Hz or more, an individual light distribution pattern PTN is displayed in front of the vehicle. 2 is formed.

[0076] Another beam BM 1 ,B.M. 3 ~BM N Similarly, for the i-th reflected beam BMr i By scanning, individual light distribution patterns PTN i is formed.

[0077] For example, Beam BM 1 ~BM N Individual light distribution pattern PTN formed by 1 ~PTNN are formed at different heights on the virtual vertical screen 900. 1 ~PTN N These are combined to form a light distribution pattern PTN_ALL for the entire vehicle lamp 100. The individual light distribution patterns PTN adjacent to each other in the vertical direction may slightly overlap each other in the vertical direction.

[0078] In the second embodiment, a plurality of individual light distribution patterns PTN 1 ~PTN N At least one of the horizontal directions of the vehicle lamp 100B is within the entire range -θ MAX ~+θ MAX That is, the scanning light source 200B emits a plurality of beams BMr 1 ~BMr N In the example of FIG. 11, at least one of the individual light distribution patterns PTN is scanned over the entire range in the horizontal direction. 1 ~PTN N is the total horizontal range -θ MAX ~+θ MAX It has spread to.

[0079] The lighting circuit 300B controls the light amount of each of the semiconductor light sources 212_1 to 212_N at each scanning position, that is, the beam BM 1 ~BM N The lighting circuit 300B adjusts the intensity of the current I OUT In other words, PWM dimming and DC dimming can be used together.

[0080] Fig. 12 is a block diagram showing an example of the configuration of the lighting circuit 300B of Fig. 11. The lighting circuit 300B includes a plurality of LED drivers 320_1 to 320_N corresponding to the plurality of semiconductor light sources 212_1 to 212_N. A PWM signal generating unit 310 generates pulse dimming signals PWM_DIM_1 to PWM_DIM_N for the plurality of LED drivers 320_1 to 320_N so as to obtain a desired light distribution. The i-th (1≦i≦N) LED driver 320 supplies a PWM-modulated drive current I LEDi The configuration of the LED driver 320 is the same as that of the embodiment 1. The microcontroller 304 and the plurality of LED drivers 320_1 to 320_N may be mounted on a single board, or may be arranged in a single housing.

[0081] According to this vehicular lamp 100B, the resolution in the height direction can be improved compared to the first embodiment.

[0082] A modification of the second embodiment will be described. In the above description, a plurality of light distribution patterns PTN 1 ~PTN N Although all of the above are extended in the entire range, this is not limited thereto, and some of them may extend in a part of the range rather than in the entire range.

[0083] In the second embodiment, the entire light distribution is divided into a plurality of regions in the vertical direction, and a plurality of individual light distribution patterns PTN are arranged in the plurality of regions. 1 ~PTN N However, this is not necessarily the case. 1 ~PTN N Some of them may completely overlap.

[0084] (About the frequency of pulse modulation) 13 is a diagram showing a vehicular lamp 100I according to an embodiment. The vehicular lamp 100I is used together with a camera 2. The camera 2 may be built into the vehicular lamp 100I, or may be provided on the vehicle side.

[0085] The basic configuration of the vehicular lamp 100I is the same as that of Fig. 1, and includes a scanning light source 200A and a lighting circuit 300I. The scanning light source 200A includes a semiconductor light source 212, and scans an instantaneous irradiation spot SPT based on the light emitted from the semiconductor light source 212 in the horizontal direction of light distribution. The lighting circuit 300I adjusts the light amount of the semiconductor light source 212 at each scanning position in multiple gradations by pulse modulation in synchronization with the scanning of the scanning light source 200A.

[0086] Frame rate of camera 2, f FRAME For the scanning frequency f of the vehicle lamp, 24 fps, 30 fps, 60 fps, 120 fps, etc. are selected. When a scanning type vehicle lamp is used with a camera, the scanning frequency f of the vehicle lamp is SCAN is the camera frame rate f FRAME If the scanning frequency is not higher than f, stripes may appear in the image captured by the camera. SCAN is the frame rate f FRAME In other words, the scanning period T SCAN (1 / f SCAN ) is the imaging period 1 / f FRAME For example, the scanning frequency f SCAN is 200Hz, and the scanning period T SCAN is 1 / f SCAN =5ms.

[0087] The instantaneous irradiation spot SPT has a finite width θ SPOT For example, this width θ SPO T is the spread angle, which is several degrees, specifically, about 1° to 2°. Also, the scanning range θ SCAN (=2×θ MAX ) is, for example, 10° to 20°.

[0088] The instantaneous irradiation spot SPT has an angular width θ SPOT The transit time τ required to move only τ = (θ SPOT / θ SCAN )×T SCAN It becomes.

[0089] The instantaneous irradiation spot SPT is one scanning period T SCAN Between them, θ SCAN Since it moves, its speed is v θ v θ =θ SCAN / T SCAN It becomes.

[0090] The inventors have determined that the period of the pulse modulation T PWM However, we realized that when the transit time is longer than τ or is about the same, there will be areas that are not sufficiently illuminated by light or that are not illuminated at all, resulting in light and dark areas on the screen that appear as stripes in the camera image.

[0091] To solve this problem, in one embodiment, the horizontal width of the instantaneous illumination spot is set to θ SP OT , the total scan angle is θ SCAN , the scanning period is T SCAN Then, the period of the pulse modulation is T PWM teeth, T PWM <A×(θ SPOT / θ SCAN )×T SCAN This can suppress the appearance of stripes. A is a constant that satisfies A≦1 and corresponds to the intensity distribution of the instantaneous irradiation spot.

[0092] Instantaneous irradiation spot speed v θ v θ =θ SCAN / T SCAN Therefore, the transit time τ is θ SPOT / v θ Therefore, in one embodiment, the horizontal width of the instantaneous irradiation spot is defined as θ SPOT , the scan speed is v θ Then, the period of the pulse modulation is T PW M teeth, T PWM <A×θ SPOT / v θ may be satisfied.

[0093] The constant A will be explained. The intensity distribution of the instantaneous irradiation spot SPT in the horizontal scanning direction (θ direction) is Ψ(θ). This instantaneous irradiation spot SPT is moved horizontally at a speed v θ When scanning with, the intensity distribution of the instantaneous irradiation spot SPOT on the screen at time t is Ψ(θ-v θ t) It becomes.

[0094] When scanning and pulse modulation are combined, the intensity distribution on the screen at time t is Ψ(θ-v θ t) f PWM (t,θ) f PWM (t, θ) is a function showing the waveform of the pulse width modulation. For ease of understanding, when forming a uniform light distribution, the function of the pulse width modulation is a function f of only time t. PWM The period of the pulse width modulation can be expressed as T PWM , duty cycle is d, then f PWM (t) is (t%T PWM ) <dのとき、1、(t%T PWM )>d, then it is 0. A%B is the modulo operator that indicates the remainder when A is divided by B.

[0095] The intensity distribution of the light formed on the screen is the integral of the instantaneous illumination spot and is expressed by the following equation. I(θ)=∫ 0:TPWM f PWM (t) Ψ(θ-v θ ·t)dt ∫ 0:TPWM g(t)dt is the function g(t) in the range 0 to T PWM Represents the integral in

[0096] Fig. 14 shows an example of the intensity distribution of the instantaneous irradiation spot SPOT. Here, a beam having a rectangular function intensity distribution in the horizontal direction is considered. The spot diameter is 2°.

[0097] FIG. 15 shows the light distribution pattern when the PWM frequency is changed. Here, the instantaneous irradiation spot is scanned over a range of 10°. The scanning period T SCA N The pulse width is 5 ms and the PWM modulation duty cycle is 25%.

[0098] A flat light distribution is formed at PWM frequencies of 4 kHz, 2 kHz, and 1 kHz, but when the frequency is slowed down to 500 Hz, ripples, or stripes, occur and a uniform light distribution cannot be formed.

[0099] In this example, at PWM frequencies higher than 1 kHz, stripes in the camera image are negligible or not a problem, but at 0.5 kHz, they become a problem. In other words, it is preferable to set the PWM frequency to 1 kHz or higher, and the upper limit of the PWM period is 1 ms. θ SPOT = 2°, θ SCAN = 10°, T SCAN = 5 ms, so τ = (θ SPOT / θ SCAN )×T SCAN =1ms Therefore, assuming a rectangular beam, the coefficient A is 1, and the condition for generating a light distribution with suppressed stripes is T PWM <θ SPOT / v θ It becomes.

[0100] FIG. 16 is a diagram showing an example of the intensity distribution of the instantaneous irradiation spot SPOT. Here, a Gaussian beam having an intensity distribution of a Gaussian function in the horizontal direction is considered. Here, a beam with a standard deviation of 0.5° is considered. There are various ways to define the beam diameter, but for example, 1 / e 2 If the width at this point is taken as the spot diameter, the spot diameter is 2°.

[0101] FIG. 17 shows the light distribution pattern when the PWM frequency is changed. Here, the instantaneous irradiation spot is scanned over a range of 10°. The scanning period T SCAN The pulse width is 5 ms and the PWM modulation duty cycle is 25%.

[0102] When the PWM frequency is 4 kHz, a flat light distribution is formed, but as the frequency is slowed to 2 kHz and 1 kHz, stripes appear and a uniform light distribution cannot be formed.

[0103] In this example, the stripes in the camera image are negligible or not a problem at 4 kHz and 2 kHz, but they become a problem at 1 kHz. In other words, it is preferable to set the PWM frequency to 2 kHz or higher, and the upper limit of the PWM period is 0.5 ms. θ SPOT = 2°, θ S CAN = 10°, T SCAN = 5 ms, so τ = (θ SPOT / θ SCAN )×T SCAN =1ms Therefore, when the Gaussian distribution is assumed, the constant A is 0.5, and the condition for generating a light distribution with suppressed stripes is as follows: T PWM <0.5×θ SPOT / v θ It becomes.

[0104] The constant A depends on the intensity distribution of the beam as well as the duty cycle of the PWM modulation; the smaller the duty cycle, the smaller the constant A. Also, the smaller the amount of tolerable ripple, the smaller the constant A must be set. Taking these factors into consideration, if the constant A is smaller than 0.2, it can accommodate various intensity distributions and duty cycles of the instantaneous irradiation spot. For example, if A is set to 0.1, the required PWM frequency under the above conditions is 10 kHz. This is much higher than the frequency of general PWM modulation.

[0105] The embodiments are merely examples, and it will be understood by those skilled in the art that there are various modifications in the combination of each component and each treatment process, and that such modifications are also included within the scope of the present disclosure or the present invention. [Industrial Applicability]

[0106] The present disclosure relates to a vehicle lamp for use in an automobile or the like. [Explanation of symbols]

[0107] S1...sensor information, S2...vehicle information, S3...light distribution pattern information, 4...ECU for ADB, S4...position detection signal, PWM_DIM...pulse dimming signal, 8...switch, 100...vehicle lamp, 200...scanning light source, 210...light source unit, 212...semiconductor light source, 220...scanning optical system, 222...motor, 224...blade mirror, 230...projection optical system, 300...lighting circuit, 302...position detector, 310...PWM signal generation unit, 320...LED driver, 400...light distribution controller, 900...virtual vertical screen.

Claims

1. A vehicle lamp used together with a camera, a scanning light source including a semiconductor light source and configured to scan an instantaneous illumination spot based on the emitted light of the semiconductor light source in a horizontal direction of light distribution; a lighting circuit capable of adjusting the light amount of the semiconductor light source at each scanning position in multiple gradations by pulse modulation in synchronization with the scanning of the scanning light source; Equipped with The horizontal width of the instantaneous irradiation spot is θ ＳＰＯＴ , the total scan angle is θ ＳＣＡＮ , the scanning period is T ＳＣＡＮ Then, the period T of the pulse modulation ＰＷＭ teeth, T ＰＷＭ <A×(θ ＳＰＯＴ / i ＳＣＡＮ )×T ＳＣＡＮ and A is a constant corresponding to the intensity distribution of the instantaneous illumination spot, satisfying the above expression (1) above.

2. A vehicle lamp used together with a camera, a scanning light source including a semiconductor light source and configured to scan an instantaneous illumination spot based on the emitted light of the semiconductor light source in a horizontal direction of light distribution; a lighting circuit capable of adjusting the light amount of the semiconductor light source at each scanning position in multiple gradations by pulse modulation in synchronization with the scanning of the scanning light source; Equipped with The horizontal width of the instantaneous irradiation spot is θ ＳＰＯＴ , the scan speed is v θ Then, the period T of the pulse modulation ＰＷＭ teeth, T ＰＷＭ <A×θ ＳＰＯＴ / v θ and A is a constant corresponding to the intensity distribution of the instantaneous illumination spot, satisfying the above expression (1) above.

3. 3. The vehicular lamp according to claim 1, wherein A≦0.

5.

4. In addition to the semiconductor light source, the scanning light source further includes a reflector that receives light emitted from the semiconductor light source and scans the reflected light in front of the vehicle by repeating a predetermined periodic motion, 4. The vehicle lamp according to claim 1, wherein the lighting circuit generates a pulse-modulated control waveform in synchronization with the movement of the reflector, and switches a drive current supplied to the semiconductor light source in response to the control waveform.

5. The lighting circuit includes: a series switch provided in series with the semiconductor light source; a constant current driver connected to a series connection circuit of the series switch and the semiconductor light source; Equipped with 5. The vehicular lamp according to claim 1, wherein the lighting circuit switches the series switch with a duty cycle corresponding to a scanning position.

6. The constant current driver includes: A switching converter; a converter controller that drives the switching converter so that a detected value of an output current of the switching converter approaches a predetermined target value; 6. The vehicle lamp according to claim 5, further comprising:

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