WO2022091973A1

WO2022091973A1 - Vehicle lamp fitting and lighting circuit

Info

Publication number: WO2022091973A1
Application number: PCT/JP2021/039106
Authority: WO
Inventors: 賢菊池; 紀人高橋; 光治眞野; 雄太丸山
Original assignee: 株式会社小糸製作所
Priority date: 2020-10-29
Filing date: 2021-10-22
Publication date: 2022-05-05
Also published as: JPWO2022091973A1

Abstract

A scanning-type light source (200A) includes a semiconductor light source (212), and performs scanning with light emitted from the semiconductor light source (212). A LED driver (320A) can dim, through pulse modulation in multiple levels, the quantity of light of the semiconductor light source (212) at each scanning position, in synchronization with the scanning by the scanning-type light source (200A). A series switch (323) is provided in series with the semiconductor light source (212). A step-down converter (322) of a constant current output is connected to a series-connection circuit of the semiconductor light source (212) and the series switch (323), and generates driving current (Iout). A driver circuit (324) causes, so as to obtain target light distribution, switching of the series switch (323) on the basis of a pulse dimming signal (PWM_DIM) which is pulse-modulated and in which the same waveform is repeated for each scanning.

Description

Vehicle lighting and lighting circuits

This disclosure relates to lighting fixtures for vehicles used in automobiles and the like.

Vehicle lighting fixtures can generally switch between low beam and high beam. The low beam illuminates the vicinity of the own vehicle with a predetermined illuminance, and the light distribution rule is set so as not to give glare to the oncoming vehicle or the preceding vehicle, and is mainly used when traveling in an urban area. On the other hand, the high beam illuminates a wide area and a distant place in front with a relatively high illuminance, and is mainly used when traveling at high speed on a road where there are few oncoming vehicles and preceding vehicles. Therefore, although the high beam has better visibility by the driver than the low beam, there is a problem that glare is given to the driver and pedestrian of the vehicle existing in front of the vehicle.

In recent years, ADB (Adaptive Driving Beam) technology that dynamically and adaptively controls the light distribution pattern of high beams based on the surrounding conditions of the vehicle has been put into practical use. The ADB technique detects the presence or absence of a preceding vehicle, an oncoming vehicle, or a pedestrian in front of the vehicle, dims the area corresponding to the vehicle, and reduces glare given to the vehicle.

As a method for realizing the ADB function, a shutter method for controlling an actuator, a rotary method, an LED array method, etc. have been proposed. In the shutter method and the rotary method, the width of the light-off area (light-shielding area) can be continuously changed, but the number of light-off areas is limited to one. In the LED array method, it is possible to set a plurality of extinguishing areas, but the width of the extinguishing area is limited by the irradiation width of the LED chip, so that the extinguishing area is discrete.

The applicant has proposed a scanning method as an ADB method that can solve these problems (see Patent Documents 2 and 3). The scan method is to incident light on a rotating reflector (blade mirror), reflect the incident light at an angle according to the rotation position of the reflector, scan the reflected light in front of the vehicle, and turn on and off the light source. A desired light distribution pattern is formed in front of the vehicle by changing the light distribution pattern according to the rotation position of the vehicle.

In the scan method described in Patent Document 3, the light source is turned on and off (on and off) in a time-division manner while keeping the amount of drive current flowing through the light source constant during one scan. Therefore, it was easy to realize a glare-free function that shields a predetermined area from light, but the illuminance in the irradiation area was restricted to a substantially constant level.

Patent Document 4 discloses a specific method for forming a light distribution using a scan-type vehicle lamp. In this technique, a light distribution is formed by a multi-channel light source. Each of the multi-channel light sources is responsible for a part of the horizontal range, and the scan range of each light source is shifted horizontally while partially overlapping the scan range of the other light sources. There is. The amount of light of each light source is controlled by so-called DC dimming (analog dimming), and is variable in units of one scan due to the limitation of response speed. With this lamp, the illuminance at each scanning position can be controlled by combining multiple light sources on, off, and the amount of light, and it is now compatible with various light distribution patterns other than the glare-free function (for example, electronic swivel). There is.

Japanese Unexamined Patent Publication No. 2008-205357 Japanese Unexamined Patent Publication No. 2012-224317 Japanese Unexamined Patent Publication No. 2010-6109 Japanese Unexamined Patent Publication No. 2018-187979

FIG. 1 is a block diagram of a vehicle lamp 100R according to a comparative technique examined by the present inventors. The vehicle lamp 100R includes a scanning optical system 2, a plurality of LEDs 4_1 to 4_N, a plurality of LED drivers 10, and a light distribution controller 20. A plurality of LEDs 4_1 to 4_N are connected in series every two (or three) to form a plurality of M LED strings 6_1 to 6_M. The LED driver 10 is provided for each LED string 6. The reason why the two LEDs are connected in series is to reduce the number of LED drivers.

The LED driver 10_1 includes a constant current output buck converter 12 and a drive circuit 14 for bypass switches SW1 and SW2 and bypass switches SW1 and SW2 provided in parallel with LEDs 4_1 and 4_2. The LED drivers 10_1 to 10_M are similarly configured.

The scanning optical system 2 horizontally scans the emitted beams BM ₁ to BM _N of the plurality of LEDs 4_1 to 4_N on the virtual vertical screen 900 in front of the vehicle. By scanning the emitted beams BM ₁ to BM _N , individual light distribution patterns PTN ₁ to PTN _N are formed. A plurality of individual light distribution patterns PTN ₁ to PTN _N are formed in different ranges in the horizontal direction. By synthesizing a plurality of individual light distribution patterns PTN ₁ to PTN _N , a synthetic light distribution of the entire vehicle lamp 100R is formed.

Focus on one LED_i. When the corresponding bypass switch SWi is turned on for a certain period of time during scanning, no current is supplied to the LED4_i, so that the LED_i can be turned off. When an oncoming vehicle or a preceding vehicle (referred to as a vehicle in front) is present in front of the vehicle, the bypass switch SWi is turned on while the emitted beam of LED_i passes through the existing range of the vehicle in front. As a result, the existing range of the vehicle in front can be shielded from light.

The scanning frequency by the scanning optical system 2 needs to be set higher than 60 Hz so that the scanning is not perceived by the human eye. For example, it is set to about 200 Hz, and one scanning cycle is 5 ms. In the comparative technique, the light amount (luminance) of each LED is controlled by analog dimming (DC dimming), but it is difficult to dynamically change the output current I _OUT of the switching converter 12 within a scanning cycle of 5 ms. Therefore, the output current I _OUT is constant during one scan cycle, and therefore the illuminance of the irradiated portion included in one individual light distribution pattern PTN _i is uniform. When it is desired to form a bright part and a dark part in the final synthetic light distribution, it is necessary to control the brightness of each of the individual light distribution patterns PTN ₁ to PTN _N and superimpose them.

The present inventors have studied that in the vehicle lamp 100R of FIG. 1, the light intensity of each of the LEDs 4_1 to 4_N is changed within one scanning cycle by PWM-controlling the bypass switches SW1 to SWN.

Focus on one LED driver 10_1. Consider a situation in which the bypass switch SW1 is fixed to off and the bypass switch SW2 is switched. When the bypass switch SW2 is switched, the current I _LED2 flowing through the LED4_2 rings at the turn-off timing of the switch, that is, at the timing when the LED4_2 is turned on. This phenomenon is explained by charging / discharging the electric charge of the output capacitor C1 of the switching converter 12. FIG. 2 is a diagram (measurement result) showing a ringing waveform of the driving current of the LED.

The initial state is the state in which the bypass switch SW1 is off and the bypass switch SW2 is on. At this time, the output voltage V _OUT of the switching converter 12 becomes _VF . _VF is a forward voltage of one LED.

When the bypass switch SW2 is turned off, the switching converter 12 needs to raise its output voltage V _OUT to 2 × VF, and has to charge the output capacitor C1 with the charge of _C × _VF . Therefore, immediately after the turn-off of the bypass switch SW2, a part of the output current I _OUT is consumed as the charging current of the capacitor C1, so that the output current I _OUT is insufficient. In the switching converter 12, feedback is applied so that the insufficient current approaches the target value, but the output current I _OUT rings due to the resonance of the inductor of the switching converter 12.

When the bypass switch SW2 is switched in this way, the current I _LED2 of the LED4_2 in parallel with the bypass switch SW2 rings. Not only that, the current I _LED1 of the LED4_1 that is always lit will also be ringing.

When the duration of ringing (hereinafter referred to as ringing time) was measured by an experiment, it was about 30 to 50 μs.

The PWM frequency of a general non-scanning lamp is about 300 Hz, and the PWM cycle is 3.3 ms. In this case, the ringing time of 50 μs is only about 5% of the PWM cycle, and the influence of ringing on the gradation control is small.

However, in the scanning lamp of FIG. 1, when the scanning frequency is 100 to 200 Hz, the PWM frequency needs to be several times or more, that is, several kHz. It can be said that this is a very high frequency as compared with the PWM frequency of about 300 Hz in a general non-scan type lamp.

For example, in a scanning lamp, when the PWM frequency is 20 kHz, the PWM cycle is 50 μs, which is about the same as the ringing time of 50 μs. Therefore, in the configuration of FIG. 1, it is practically difficult to perform PWM dimming at several tens of kHz by using the bypass switches SW1 and SW2.

1. 1. A certain aspect of the present disclosure has been made in view of the above problems, and one of its exemplary purposes is to provide a scan type vehicle lamp capable of PWM dimming.
2. 2. One aspect of the present disclosure has been made in view of the subject, and one of its exemplary purposes is to provide a vehicle lamp capable of PWM dimming over a wide range.
3. 3. One aspect of the present disclosure is made in such a situation, and one of its exemplary purposes is to provide a vehicle lamp capable of detecting an abnormality in a short switch in a lighting circuit that performs pulse dimming by a short switch. be.
4. One aspect of the present disclosure has been made in such circumstances, one of which is an exemplary purpose of optimizing signal processing scheduling in a scanning lamp.

1. 1. The vehicle lighting fixture of a certain aspect of the present disclosure includes a scanning light source and a lighting circuit. The scanning light source includes a semiconductor light source and scans the emitted light of the semiconductor light source. The lighting circuit is configured to be capable of dimming 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 lighting circuit consists of a series switch installed in series with the semiconductor light source, a constant current output buck converter connected to the series connection circuit of the series switch and the semiconductor light source, and pulse tuning pulse-modulated to obtain the desired light distribution. It is equipped with a driver circuit that switches the series switch based on the optical signal.

2. 2. The vehicle lighting fixture of a certain aspect of the present disclosure includes a semiconductor light source and a lighting circuit capable of dimming the light amount of the semiconductor light source in multiple gradations by pulse modulation. The lighting circuit consists of a series switch installed in series with the semiconductor light source, a constant current output buck converter connected to the series connection circuit of the series switch and the semiconductor light source, and a series switch based on a pulse-modulated pulse dimming signal. It is equipped with a driver circuit to drive. The buck converter includes an output circuit including a switching transistor and an output capacitor, and a converter controller that feedback-controls the switching transistor so that the detected value of the output current of the buck converter during the on period of the series switch approaches a predetermined target value. An overshoot suppression circuit that acts on at least one of the output circuit and converter controller in synchronization with the pulse dimming signal so that the overshoot immediately after the series switch of the drive current flowing through the semiconductor light source is turned on is suppressed. Be prepared.

Another aspect of the present disclosure is a lighting circuit. This lighting circuit is a lighting circuit capable of dimming the light amount of the semiconductor light source in multiple gradations by pulse modulation, and is connected to a series switch provided in series with the semiconductor light source and a series connection circuit of the series switch and the semiconductor light source. It is equipped with a constant current output buck converter and a driver circuit that drives a series switch based on a pulse-modulated pulse dimming signal. The buck converter includes an output circuit including a switching transistor and an output capacitor, and a converter controller that feedback-controls the switching transistor so that the detected value of the output current of the buck converter during the on period of the series switch approaches a predetermined target value. An overshoot suppression circuit that acts on at least one of the output circuit and converter controller in synchronization with the pulse dimming signal so that the overshoot immediately after the series switch of the drive current flowing through the semiconductor light source is turned on is suppressed. Be prepared.

3. 3. The vehicle lighting fixture of a certain aspect of the present disclosure includes a semiconductor light source and a lighting circuit capable of dimming the light amount of the semiconductor light source in multiple gradations by pulse modulation. The lighting circuit is connected to a series switch provided in series with the semiconductor light source and a series connection circuit between the series switch and the semiconductor light source, (i) outputs a constant current during the on period of the series switch, and (ii) turns off the series switch. A buck converter that stops the switching operation during the period and maintains substantially the same output voltage as the previous on period, a driver circuit that drives the series switch based on the pulse-modulated pulse dimming signal, and the series switch off. If the output voltage of the buck converter deviates from the normal range during the period, an abnormality detection circuit for determining an abnormality of the series switch is provided.

4. A vehicle lighting fixture of an aspect of the present disclosure includes a semiconductor light source, a motor, and a plurality of mirrors attached to the rotor of the motor at intervals from each other, and the emitted light of the semiconductor light source is reflected and scanned by the plurality of mirrors. It includes a scanning light source and a lighting circuit that controls a drive current supplied to the semiconductor light source in synchronization with scanning of the scanning light source and controls the amount of light of the semiconductor light source. The lighting circuit turns off the semiconductor light source in a plurality of blank periods in which the optical axis of the semiconductor light source crosses the distance between the plurality of mirrors, and the distance between the plurality of mirrors is non-uniform.

It should be noted that an arbitrary combination of the above components and a mutual replacement of the components and expressions of the present disclosure among methods, devices, systems and the like are also effective as aspects of the present disclosure.

1. 1. According to an aspect of the present disclosure, in a scan type vehicle lamp, PWM dimming is possible at a PWM frequency of several tens of kHz.
2. 2. According to one aspect of the present disclosure, PWM dimming is possible in a wide range.
3. 3. According to certain aspects of the present disclosure, anomalies in the short switch can be detected.
4. According to certain aspects of the present disclosure, signal processing scheduling can be optimized for scanning lamps.

It is a block diagram of the lamp for a vehicle which concerns on the comparative technique examined by the present inventors. It is a figure which shows the ringing waveform of the driving current of LED. It is a figure which shows the lighting fixture for a vehicle which concerns on Embodiment 1. FIG. 4 (a) and 4 (b) are diagrams illustrating the formation of glare-free light distribution by vehicle lamps. 5 (a) and 5 (b) are diagrams illustrating the formation of a partially dimmed light distribution by a vehicle lamp. 6 (a) and 6 (b) are diagrams illustrating an electronic swivel by a vehicle lamp. It is a block diagram which shows the structural example of a lighting circuit. It is a circuit diagram which shows the structural example of the LED driver. FIG. 9A is a diagram showing current control by a series switch, and FIG. 9B is a diagram showing current control by a bypass switch. It is a circuit diagram which shows the structural example of the LED driver. It is a figure which shows the lighting fixture for a vehicle which concerns on Embodiment 2. It is a block diagram which shows the structural example of the lighting circuit of FIG. It is a figure which shows the lighting fixture for a vehicle which concerns on Embodiment 3. It is a block diagram of a vehicle lamp equipped with a short-circuit abnormality detection function. 15 (a) and 15 (b) are diagrams illustrating the operation of the vehicle lamp of FIG. 14. It is a circuit diagram of the abnormality detection circuit which concerns on one Example. It is a figure which shows the IV characteristic of a semiconductor light source. It is a figure explaining the determination process 1 of an abnormality detection circuit. It is a figure explaining the determination process 2 of an abnormality detection circuit. It is a figure explaining the determination process 3 of an abnormality detection circuit. It is a figure which shows the structural example of a scanning optical system. It is a figure which shows the blank period corresponding to the space between two blades. FIG. 23A is a diagram illustrating position detection in a 4-pole motor, and FIG. 23B is a diagram illustrating rotation detection in a 2-pole motor. It is a figure explaining the overshoot of the drive current I _LED with PWM dimming in the LED driver of FIG. It is a circuit diagram of the LED driver which concerns on one Embodiment. It is a circuit diagram of the LED driver which concerns on Example 1. FIG. FIG. 6 is an operation waveform diagram of the LED driver of FIG. 26. It is a circuit diagram which shows the structural example of the overshoot suppression circuit. FIG. 8 is an operation waveform diagram of the overshoot suppression circuit of FIG. 28. It is a circuit diagram of the modification of the overshoot suppression circuit of FIG. 28. It is an operation waveform diagram of the overshoot suppression circuit of FIG. It is a circuit diagram of the LED driver which concerns on Example 2. FIG. It is operation waveform diagram of the LED driver which concerns on Example 2. FIG. It is an operation waveform diagram of the overshoot suppression circuit which concerns on Example 2. FIG. It is a circuit diagram of the LED driver which concerns on Example 3. FIG. It is an operation waveform diagram of the LED driver of FIG. 35. It is a circuit diagram which shows the structural example of the overshoot suppression circuit which concerns on Example 3. FIG. It is a circuit diagram of the modification of the overshoot suppression circuit of FIG. 37. It is a circuit diagram of the LED driver which concerns on Example 4. FIG. It is an operation waveform diagram of the LED driver of FIG. 39.

(Outline of Embodiment)
Some exemplary embodiments of the present disclosure will be outlined. This overview simplifies and describes some concepts of one or more embodiments for the purpose of basic understanding of embodiments, as a prelude to the detailed description described below, and is an invention or disclosure. It does not limit the size. Also, this overview is not a comprehensive overview of all possible embodiments and does not limit the essential components of the embodiments. For convenience, "one embodiment" may be used to refer to one embodiment (examples or modifications) or a plurality of embodiments (examples or modifications) disclosed herein.

1. 1. The vehicle lamp according to the embodiment includes a semiconductor light source, and the light amount of the semiconductor light source at each scanning position is pulse-modulated in synchronization with the scanning of the scanning light source and the scanning light source that scans the emitted light of the semiconductor light source. It is equipped with a lighting circuit that can be dimmed with multiple gradations. The lighting circuit consists of a series switch installed in series with the semiconductor light source, a constant current output buck converter connected to the series connection circuit of the series switch and the semiconductor light source, and pulse tuning pulse-modulated to obtain the desired light distribution. It is equipped with a driver circuit that switches the series switch based on the optical signal.

In this configuration, the output current of the buck converter is cut off and the continuity is switched at high speed by the series switch, so it is not necessary to change the output voltage of the buck converter in steps. As a result, ringing of the output current due to charging / discharging of the output capacitor can be suppressed, and dimming by high-speed pulse modulation of several kHz to several tens of kHz becomes possible. Further, since the amount of light of one semiconductor light source can be changed within one scanning cycle, not only partial shading but also partial dimming can be realized, and the degree of freedom of the light distribution pattern can be increased. ..

"Pulse modulation" includes pulse width modulation (PWM), pulse frequency modulation (PFM), pulse density modulation (PDM), etc., and switches the drive current flowing through the light source at high speed to obtain the time average value of the drive current. It may include varying modulation schemes.

In one embodiment, the scanning light source includes a plurality of semiconductor light sources, and a lighting circuit may be provided for each semiconductor light source. As a result, even if the output current of the step-down inverter of one channel is ringing, the other channels are not affected.

In one embodiment, the buck converter is a converter controller that switches and drives the output circuit including the switching transistor and the switching transistor so that the detected value of the output current of the buck converter during the on period of the series switch approaches a predetermined target value. And may be included.

In one embodiment, the converter controller may stop the switching drive of the switching transistor during the off period of the series switch.

2. 2. The vehicle lamp according to the embodiment includes a semiconductor light source and a lighting circuit capable of dimming the light amount of the semiconductor light source in multiple gradations by pulse modulation. The lighting circuit consists of a series switch installed in series with the semiconductor light source, a constant current output buck converter connected to the series connection circuit of the series switch and the semiconductor light source, and a series switch based on a pulse-modulated pulse dimming signal. It is equipped with a driver circuit to drive. The buck converter includes an output circuit including a switching transistor and an output capacitor, and a converter controller that feedback-controls the switching transistor so that the detected value of the output current of the buck converter during the on period of the series switch approaches a predetermined target value. An overshoot suppression circuit that acts on at least one of the output circuit and converter controller in synchronization with the pulse dimming signal so that the overshoot immediately after the series switch of the drive current flowing through the semiconductor light source is turned on is suppressed. Be prepared.

According to this configuration, the series switch cuts off the output current of the buck converter and switches the continuity at high speed, so it is not necessary to change the output voltage of the buck converter in steps. As a result, ringing of the drive current due to charging / discharging of the output capacitor can be suppressed, and dimming by high-speed pulse modulation of several kHz to several tens of kHz becomes possible.

The present inventors have recognized that when the output current of a constant current output buck converter is switched at high speed by a series switch, the output current exceeds the target amount and overshoot occurs immediately after the series switch is turned on. According to one embodiment, by providing an overshoot suppression circuit that operates in synchronization with the pulse dimming signal, overshoot of the drive current immediately after the turn-on of the series switch can be suppressed.

In one embodiment, the overshoot suppression circuit may discharge the output capacitor in synchronization with the pulse dimming signal. The drive current is affected by the charge current and discharge current of the output capacitor, and the drive current can be indirectly controlled by controlling the charge amount of the output capacitor.

In one embodiment, the overshoot suppression circuit may discharge the output capacitor during the off period of the series switch. By reducing the charge amount of the output capacitor during the off period, the discharge current from the output capacitor immediately after the turn-on of the subsequent series switch can be reduced, and the drive current can be prevented from overshooting.

In one embodiment, the overshoot suppression circuit includes a first capacitor with a grounded first end, which initializes the charge of the first capacitor during the on period of the series switch, based on the pulse dimming signal, of the series switch. During the off period, the second end of the first capacitor may be connected to the output capacitor. This allows the output capacitor to be discharged during the off period of the series switch.

In one embodiment, the overshoot suppression circuit may forcibly discharge the output capacitor immediately after the series switch is turned on. In other words, the overshoot suppression circuit may sink current from the output capacitor immediately after the series switch is turned on. As a result, it is possible to prevent the drive current from overshooting immediately after the turn-on.

In one embodiment, the overshoot suppression circuit includes a first capacitor with a grounded first end, which initializes the charge of the first capacitor during the off period of the series switch, based on the pulse dimming signal, of the series switch. The second end of the first capacitor may be connected to the output capacitor during the on period. As a result, the output capacitor can be forcibly discharged immediately after the turn-on of the series switch.

In one embodiment, the overshoot suppression circuit is provided between the first switch provided between the second end of the first capacitor and the output line, and the second end of the first capacitor and the constant voltage node. 2 switches and may be included.

In one embodiment, the constant voltage node may be a ground line.

In one embodiment, the constant voltage node may be the output of a constant voltage source. In this case, the amount of electric charge to be discharged can be controlled according to the output voltage of the constant voltage source.

In one embodiment, the overshoot suppression circuit may act on the converter controller to change the internal signal that correlates with the duty cycle of the switching transistor generated by the converter controller. The waveform of the coil current of the buck converter changes according to the duty cycle of the switching transistor, but the waveform of the coil current can be controlled by changing the internal signal, so that the drive current can be indirectly controlled.

In one embodiment, the overshoot suppression circuit may forcibly reduce the internal signal that correlates with the duty cycle of the switching transistor generated by the converter controller during the off period of the series switch. As a result, the internal signal that correlates with the duty cycle is reduced during the off period, so that the buck converter starts operating from the state where the switching duty cycle is lowered immediately after the turn-on, so that the coil current increases. The speed slows down. This can prevent the drive current from overshooting.

In one embodiment, the converter controller comprises an error amplifier that generates an error signal according to an error between the detected value and the target value of the output current of the step-down converter, a feedback capacitor connected to the output of the error amplifier, and a voltage of the feedback capacitor. It may include a pulse modulator which produces a pulse signal having a duty cycle according to the above. The overshoot suppression circuit includes a second capacitor with the first end grounded, which initializes the charge of the second capacitor during the series switch on period and the series switch off period based on the pulse dimming signal. The second end of the capacitor may be connected to the output of the error amplifier. By using the voltage of the feedback capacitor as an internal signal, the duty cycle can be forcibly lowered.

In one embodiment, the overshoot suppression circuit may forcibly reduce the internal signal having a correlation with the duty cycle of the switching transistor generated by the converter controller immediately after the turn-on of the series switch. As a result, the duty cycle of the switching transistor decreases immediately after the turn-on, so that the rate of increase in the coil current slows down. This can prevent the drive current from overshooting.

In one embodiment, the converter controller comprises an error amplifier that generates an error signal according to an error between the detected value and the target value of the output current of the step-down converter, a feedback capacitor connected to the output of the error amplifier, and a voltage of the feedback capacitor. It may include a pulse modulator which produces a pulse signal having a duty cycle according to the above. The overshoot suppression circuit includes a second capacitor whose first end is grounded, and based on the pulse dimming signal, initializes the charge of the second capacitor during the off period of the series switch, and during the on period of the series switch, the second. The second end of the capacitor may be connected to the output of the error amplifier. By using the voltage of the feedback capacitor as an internal signal, the duty cycle can be forcibly lowered.

In one embodiment, the overshoot suppression circuit is provided between a third switch provided between the second end of the second capacitor and the output of the error amplifier, and between the second end of the second capacitor and the constant voltage node. The fourth switch may be included.

In one embodiment, the constant voltage node may be a ground line.

In one embodiment, the constant voltage node may be the output of a constant voltage source. In this case, the reduction width of the duty cycle of the switching transistor can be controlled according to the output voltage of the constant voltage source.

3. 3. The vehicle lamp according to the embodiment includes a semiconductor light source and a lighting circuit capable of dimming the light amount of the semiconductor light source in multiple gradations by pulse modulation. The lighting circuit is connected to a series switch provided in series with the semiconductor light source and a series connection circuit between the series switch and the semiconductor light source, (i) outputs a constant current during the on period of the series switch, and (ii) turns off the series switch. A buck converter that stops the switching operation during the period and maintains substantially the same output voltage as the previous on period, a driver circuit that drives the series switch based on the pulse-modulated pulse dimming signal, and the series switch off. If the output voltage of the buck converter deviates from the normal range during the period, an abnormality detection circuit for determining an abnormality of the series switch is provided.

In PWM dimming by the bypass switch, when a short-circuit failure that the bypass switch cannot be turned off occurs, the LED is turned off, which is a preferable state from the viewpoint of not giving glare. On the other hand, in pulse dimming by the series switch, when the series switch cannot be turned off or a short circuit occurs (generally called short circuit abnormality), a current flows through the semiconductor light source and glare occurs on the oncoming vehicle or the preceding vehicle. Will be given. According to the above configuration, the switching of the buck converter is stopped during the off period of the series switch. Therefore, when a short circuit error occurs in the series switch, the output of the buck converter is output by the path including the series switch with the short circuit error and the semiconductor light source. The charge is discharged and the output voltage drops. Therefore, by monitoring the output voltage of the buck converter during the off period of the series switch, a short circuit abnormality of the series switch can be detected.

In one embodiment, the abnormality detection circuit may have an abnormality determination condition that the output voltage of the buck converter falls below a predetermined threshold value during the off period of the series switch. This enables reliable detection.

In one embodiment, the predetermined threshold value may be set higher than the lighting start voltage of the semiconductor light source and lower than the forward voltage Vf when the semiconductor light source is lit.

In one embodiment, the vehicle lighting fixture may further include a scanning optical system that scans the emitted light of the semiconductor light source. The pulse dimming signal may be generated so that the series switch is turned off for a predetermined period of time at the scan-scan break. The abnormality detection circuit may detect an abnormality of the series switch based on the output voltage of the buck converter in a predetermined period. By inserting a predetermined period during which the series switch is always turned off between scans and using this predetermined period for abnormality detection, abnormality detection is performed using a short off period within the pulse modulation cycle. Compared to the case, it is possible to detect anomalies with a margin of time.

In one embodiment, the abnormality detection circuit may make a provisional determination state when the output voltage falls below the threshold value in a predetermined period, and may make a final determination when the provisional determination state is established over a predetermined number of scans. This makes it possible to prevent erroneous detection of abnormalities.

In one embodiment, the abnormality detection circuit is a comparison circuit that compares the output voltage of the step-down converter with a threshold value and generates a detection signal that becomes a predetermined level when the output voltage of the step-down converter is lower than the threshold value. When the detection signal reaches a predetermined level in the period, the provisional determination state is set, and when the provisional determination state is established over a predetermined number of scans, the signal processing unit for the main determination may be included.

In one embodiment, the abnormality detection circuit may have an abnormality determination condition that the output voltage of the buck converter is not constant. When the series switch is normal, the output voltage of the buck converter is kept substantially constant, whereas when a short circuit error occurs in the series switch, the on / off control of the series switch (that is, switching of the buck converter) is performed. The output voltage of the buck converter vibrates in conjunction with the operation / stop of. Therefore, an abnormality can be detected by monitoring whether the output voltage is constant or vibrating.

In one embodiment, the abnormality detection circuit may be subject to an abnormality determination condition that the switching state of the output voltage of the buck converter is maintained for a predetermined determination time.

In one embodiment, the anomaly detection circuit is a comparison circuit that compares the output voltage of the buck converter with a threshold value and generates a detection signal that reaches a predetermined level when the output voltage of the buck converter is lower than the threshold value. When the state in which the signal is a pulse signal continues for a predetermined time, the signal processing unit for determining the abnormal state may be included.

In one embodiment, the anomaly detection circuit compares the output voltage of the buck converter with a threshold and generates a detection signal that reaches a predetermined level when the output voltage of the buck converter is lower than the threshold. It may include a signal processing unit that counts the number of times the signal has transitioned to a predetermined level and determines that the signal is in an abnormal state when the count value exceeds a predetermined threshold value.

In one embodiment, the abnormality detection by the abnormality detection circuit may be disabled after the operation of the buck converter is started until the output voltage exceeds a predetermined voltage. This can prevent erroneous detection.

The lighting circuit according to one embodiment is connected to a series switch provided in series with the semiconductor light source and a series connection circuit of the series switch and the semiconductor light source, and (i) outputs a constant current during the on period of the series switch, and (ii). ) A buck converter that stops the switching operation during the off period of the series switch and maintains substantially the same output voltage as the immediately preceding on period, and a driver circuit that drives the series switch based on the pulse-modulated pulse dimming signal. , An abnormality detection circuit for determining an abnormality of the series switch when the output voltage of the buck converter deviates from the normal range during the off period of the series switch is provided.

4. A vehicle lamp according to an embodiment includes a semiconductor light source, a motor, and a plurality of mirrors attached to the rotor of the motor at intervals from each other, and scans the emitted light of the semiconductor light source by being reflected by the plurality of mirrors. It includes a type light source and a lighting circuit that controls a drive current supplied to the semiconductor light source in synchronization with scanning of the scanning type light source and controls the amount of light of the semiconductor light source. The lighting circuit turns off the semiconductor light source in a plurality of blank periods in which the optical axis of the semiconductor light source crosses the distance between the plurality of mirrors, and the distance between the plurality of mirrors is non-uniform.

According to this configuration, it is possible to intentionally create a long blank period and a short blank period by making the intervals of a plurality of mirrors non-uniform. This allows the vehicle lamps to perform different processes during the long blank period and the short blank period, making it easier to optimize signal processing scheduling.

In one embodiment, the vehicle lighting fixture may further include a pulse dimming signal generator that generates an off-level pulse dimming signal in a section where the optical axis of the semiconductor light source passes through the space between a plurality of mirrors. .. The lighting circuit is connected to a series switch provided in series with the semiconductor light source and a series connection circuit between the series switch and the semiconductor light source, (i) outputs a constant current during the on period of the series switch, and (ii) turns off the series switch. It may include a buck converter that stops the switching operation during the period and maintains substantially the same output voltage as the immediately preceding on period, and a driver circuit that drives the series switch based on the pulse dimming signal.

In one embodiment, the lighting circuit is an abnormality detection circuit that determines that the series switch is abnormal when the output voltage of the buck converter deviates from the normal range in the longest blank period corresponding to the widest interval among the intervals of the plurality of mirrors. May be further provided.

When detecting a short abnormality during the off period, that is, during the blank period, the blank period becomes shorter in inverse proportion to the rotation speed of the motor, so that the higher the scanning frequency, the more difficult it becomes to detect the short abnormality. In one embodiment, instead of shortening one blank period, another blank period is lengthened, so that the short blank abnormality can be detected by utilizing the long blank period.

In one embodiment, the motor is a two-pole motor, and the lighting circuit may detect the rotation position of the motor based on the Hall signal. In this case, it is possible to discriminate between a long blank period and a short blank period based on the waveform of the Hall signal.

In one embodiment, the vehicle lighting fixture may include a microcontroller. The microcontroller may perform a predetermined process in the longest blank period corresponding to the widest spacing of the plurality of mirrors.

In one embodiment, the number of mirrors may be two. In this case, two scan cycles and two blank periods are included in one rotation of the motor.

(Embodiment)
Hereinafter, the present disclosure will be described with reference to the drawings based on the preferred embodiments. The same or equivalent components, members, and processes shown in the drawings shall be designated by the same reference numerals, and duplicate description thereof will be omitted as appropriate. Further, the embodiment is not limited to the disclosure but is an example, and all the features and combinations thereof described in the embodiment are not necessarily essential to the disclosure.

In the present specification, the "state in which the member A is connected to the member B" means that the member A and the member B are physically directly connected, and the member A and the member B are electrically connected to each other. It also includes cases of being indirectly connected via other members that do not substantially affect the connection state or impair the functions and effects performed by the combination thereof.

Similarly, "a state in which the member C is provided between the member A and the member B" means that the member A and the member C, or the member B and the member C are directly connected, and their electricity. It also includes cases of being indirectly connected via other members that do not substantially affect the connection state or impair the functions and effects performed by the combination thereof.

Further, in the present specification, the reference numerals attached to electric signals such as voltage signals and current signals, or circuit elements such as resistors and capacitors have their respective voltage values, current values, resistance values, and capacitance values as necessary. It shall be represented.

FIG. 3 is a diagram showing a vehicle lamp 100A according to the first embodiment. The vehicle lamp 100A of FIG. 1 has a scan-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.

The light distribution controller 400 receives and distributes information (sensor information) S1 and information (vehicle information) S2 such as vehicle speed and steering angle from sensors such as cameras and LiDAR (Light Detection and Ringing, Laser Imaging Detection and Ringing). Determine the light pattern. The light distribution controller 400 may be housed in the lamp body or may be provided on the vehicle side. The light distribution controller 400 transmits information (light distribution pattern information) S3 indicating a light distribution pattern to the vehicle lamp 100. The light distribution controller 400 is also referred to as an ADB ECU (Electronic Control Unit).

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). An LED (light emitting diode), a laser diode, or the like can be used as the semiconductor light source 212. The scanning optical system 220 scans the emitted light (beam) BM of the semiconductor light source 212 in front of the vehicle.

In the present embodiment, the scanning optical system 220 includes a motor 222 and one or a plurality of M (two in this example) blade mirrors 224_1224_2. The M blade mirrors (M ≧ 2) are mounted at 360 / M ° offset positions, and in this example, the two blade mirrors are mounted at 180 ° offset positions.

The optical axis of the semiconductor light source 212 is directed so that the emitted beam BM irradiates one of the M blade mirrors.

At a certain time, the incident light BM on the blade mirror 224 is reflected at a reflection angle corresponding to the position of the blade mirror 224 (rotation angle of the rotor), and an instantaneous irradiation spot SPT is formed on the 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, that is, the emission direction of the reflected beam BMr, and the horizontal (H direction) position (scanning position) of the instantaneous irradiation spot SPT moves. By repeating this operation at high speed, for example, at 50 Hz or higher, a light distribution pattern PTN is formed in front of the vehicle.

In the present embodiment, the light distribution pattern PTN formed by one beam BM extends over the entire horizontal range of the vehicle lamp 100A to _−θMAX to + _θMAX . That is, the scanning light source 200A scans the reflected beam BMr over the entire horizontal range. For example, θ _MAX is about 20 to 25 °. The entire range is the entire range that can be irradiated by scanning, and does not include the range irradiated by a light source other than scanning.

The lighting circuit 300A determines the amount of light of the semiconductor light source 212 at each scanning position, that is, the intensity of the beam BM, in synchronization with the scanning of the scanning light source 200A so that the light distribution pattern indicated by the light distribution pattern information S3 can be obtained. Dimming with multiple gradations by pulse modulation. In the present embodiment, the average amount of drive current I _LEDs flowing through the semiconductor light source 212 is changed by PWM (pulse width modulation), and the amount of light of the semiconductor light source 212 is changed (PWM dimming). The PWM frequency is set sufficiently higher than the scanning frequency, and it is desirable that the PWM frequency is, for example, several kHz to several hundred kHz.

The lighting circuit 300 may change the amount of current I _OUT in a scanning cycle or a control cycle longer than that. That is, PWM dimming and DC dimming may be used together. The above is the configuration of the vehicle lamp 100A. Next, the operation will be described.

4 (a) and 4 (b) are diagrams illustrating the formation of glare-free light distribution by the vehicle lamp 100A. The glare-free light distribution 910 of FIG. 4A includes a light-shielding portion 912 and an irradiation portion 914,916. 4 (a) shows the light distribution on the virtual vertical screen, and FIG. 4 (b) shows the operation waveform of the vehicle lamp 100A corresponding to the light distribution of FIG. 4 (a). The vertical and horizontal axes of the waveform charts and time charts referred to in the present specification are appropriately enlarged or reduced for easy understanding, and each waveform shown is also simplified for easy understanding. It is made, or exaggerated or emphasized.

For example, the lighting circuit 300 sets the duty cycle of the drive current I _LED of the semiconductor light source 212 to a non-zero value (100% constant value in this example) in the section corresponding to the

irradiation portions

914 and 916, and corresponds to the light shielding portion 912. In this section, the duty cycle of the drive current I _LED is set to 0%.

5 (a) and 5 (b) are diagrams illustrating the formation of a partially dimmed light distribution by the vehicle lamp 100A. 5 (a) shows the horizontal illuminance distribution of the light distribution on the virtual vertical screen, and FIG. 5 (b) shows the operation waveform of the vehicle lamp 100A corresponding to the light distribution of FIG. 5 (a). The partial dimming distribution 920 shown in FIG. 5A includes two dimming portions 922,924 and three non-dimming portions 926,927,928.

For example, in the lighting circuit 300, the duty cycle of the drive current I _LED of the semiconductor light source 212 is fixed to 100% in the section corresponding to the non-dimming portion (irradiation portion) 926,927,928, and the duty cycle is fixed to the dimming portion 922,924. In the corresponding section, the duty cycle of the drive current I _LED is 50% and 25%, respectively. According to the vehicle lamp 100A, partial dimming can be realized by PWM-controlling the drive current I _LED flowing through a single semiconductor light source.

6 (a) and 6 (b) are diagrams illustrating an electronic swivel by a vehicle lamp 100A. FIG. 6A shows the brightest light distribution in the center, and FIG. 6B shows the brightest light distribution on the right side. According to the vehicle lamp 100A, the electronic swivel function can be realized by PWM-controlling the drive current I _LED flowing through a single semiconductor light source.

A specific configuration example of the lighting circuit 300 will be described. FIG. 7 is a block diagram showing a configuration example of the lighting circuit 300.

The light distribution controller 400 receives sensor information S1 and vehicle information S2. The light distribution controller 400 detects the situation in front of the vehicle, specifically, the presence / absence of an oncoming vehicle, a preceding vehicle, the presence / absence of a pedestrian, and the like based on the sensor information S1. Further, the light distribution controller 400 detects the current vehicle speed, steering angle, and the like based on the vehicle information S2. Based on these information, the light distribution controller 400 determines a light distribution pattern to be irradiated to the front of the vehicle, and transmits information (light distribution pattern information) S3 instructing the light distribution pattern to the lighting circuit 300.

The lighting circuit 300 changes the light amount (luminance) of the semiconductor light source 212 in multiple gradations by PWM dimming while synchronizing with the rotation of the blade mirror 224 based on the light distribution pattern information S3. For example, the lighting circuit 300 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.

The position detector 302 is provided to detect the position of the blade mirror 224, in other words, the scanning position of the current beam. The position detector 302 generates a position detection signal S4 indicating the timing at which the predetermined reference point of the blade mirror 224 passes the predetermined position. For example, the reference portion may be the end portion (separation) of the two blade mirrors 224, or may be the center of each blade mirror, and may be any location.

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 corresponding to the position of the rotor, that is, 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 by a Hall comparator that compares a pair of Hall signals.

The position detection method of the blade mirror 224 by the position detector 302 is not limited to the one using a Hall element. For example, the position detector 302 may generate the position detection signal S4 by using an optical or other 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 surface side of the blade mirror 224 toward the photosensor. Then, the blade mirror 224 may be provided with a slit or a pinhole. This makes it possible to detect when the slit or pinhole passes over the photo sensor. The slit may be a gap between the two blade mirrors 224. Further, the light source for position detection may be an infrared light source or a semiconductor light source 212. As described above, there may be various variations in the configuration of the position detector 302.

The PWM signal generation unit 310 generates a pulse dimming signal PWM_DIM in synchronization with the movement of the blade mirror 224. The duty cycle of one scan cycle of the pulse dimming signal PWM_DIM is defined based on the light distribution pattern. For example, when the rotation speed of the motor 222 is 6000 rpm (100 Hz) and the number of blade mirrors is two, the scanning frequency is 100 Hz × 2 = 200 Hz, and the scanning cycle is 5 ms. The PWM signal generation unit 310 may be implemented by combining the microcontroller 304 and the software program, or may be implemented only by hardware. The microcontroller 304 and the LED driver 320 may be mounted on one substrate or may be arranged in one housing.

The frequency of the pulse dimming signal PWM_DIM is set higher than 200 Hz, and can be, for example, several kHz to several tens of kHz. The duty cycle of the pulse dimming signal PWM_DIM determines the amount of light of the semiconductor light source 212, and the duty cycle may be set for each PWM cycle or may be set for each of a plurality of PWM cycles. good.

The LED driver 320 supplies a drive current I _LED to the semiconductor light source 212. The current amount of the drive current I _LED is stabilized to a predetermined target value, and the LED driver 320 switches the drive current I _LED according to the pulse dimming signal PWM_DIM.

FIG. 8 is a circuit diagram showing a configuration example (320A) of the LED driver 320. The LED driver 320A includes a buck 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 may be inserted between the cathode and the ground.

The buck converter 322 is a constant current output switching converter and includes an output circuit 326 and a converter controller 328. The output circuit 326 includes a switching transistor MH, a synchronous rectifying transistor ML, an inductor L1, and an output capacitor C1. The converter controller 328 switches and controls the switching transistor MH and the synchronous rectifying transistor ML of the output circuit 326 so that the output current I _OUT of the buck converter 322 approaches a predetermined target amount while the series switch 323 is on.

The control method of the 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 / differential) compensator, or a hysteresis control controller.

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 in the same IC as the converter controller 328.

The converter controller 328 stops the switching of the switching transistor MH and the synchronous rectifying transistor ML when the pulse dimming signal PWM_DIM is at the off level indicating the off of the series switch 323.

The above is the configuration of the LED driver 320A. In this LED driver 320A, since the output current I _OUT of the buck converter 322 is cut off and the continuity is switched at high speed by the series switch 323, it is not necessary to change the output voltage V _OUT of the buck converter 322 in a stepwise manner. As a result, ringing of the output current I _OUT due to charging / discharging of the output capacitor C1 can be suppressed, and dimming by high-speed pulse modulation of several kHz to several tens of kHz becomes possible.

FIG. 9A is a diagram showing current control by a series switch, and FIG. 9B is a diagram showing current control by a bypass switch. These waveforms show one cycle of PWM dimming, the PWM frequency is 5 kHz (200 μs cycle), and the duty cycle is 50%.

As shown in FIG. 9B, in the PWM dimming by the bypass switch, ringing occurs in the output current of the buck converter 322, that is, the LED current, whereas in the PWM dimming by the series switch, FIG. 9 (a). ), The ringing of the LED current can be suppressed. As a result, gradation control by PWM dimming becomes possible even in a region where the duty cycle is small.

Further, during the period when the series switch 323 is off, the converter controller 328 stops switching between the switching transistor MH and the synchronous rectifying transistor ML. As a result, the voltage V _OUT of the output capacitor C1 is kept constant during the period when the series switch 323 is off, so that the fluctuation amount of the output voltage V _OUT immediately after the series switch 323 is turned on can be brought close to zero. .. As a result, ringing of the output current I _OUT can be further suppressed.

FIG. 10 is a circuit diagram showing a configuration example of the LED driver 320A. The LED driver 320A includes a control IC (Integrated Circuit) 340. In addition to the converter controller 328, the control IC 340 integrates a switching transistor MH, a synchronous rectifier transistor ML, and a driver circuit 324.

The output circuit 326 includes a current detection resistor Rcs. The voltage across the current detection resistor Rcs is fed back to the ISP / ISN pin of the control IC. The transconductance amplifier 330 generates a current corresponding to an error of the current detection signal Vcs, which is the potential difference between the two terminals ISP and ISN, and the reference voltage Vref. The output of the transconductance amplifier 330 is connected to the Vc pin via the sample hold circuit 332. A resistor Rc and a capacitor Cc are connected to the Vc pin. The resistance Rc and the capacitor Cc also serve as a phase compensation circuit. The resistance Rc may be omitted. The capacitor Cc is charged and discharged according to the output current of the transconductance amplifier 330, so that an error voltage Vc is generated in the Vc pin. Due to the feedback, this error voltage Vc increases or decreases so that the current detection signal Vcs approaches the reference voltage Vref. The transconductance amplifier 330 and the phase compensation circuits Rc and Cc are grasped as an error amplifier.

The on-time control unit 334 is a pulse width modulator, and generates a control pulse Spwm having a duty cycle corresponding to an error voltage Vc. The frequency of this control pulse Spwm is set even higher than the pulse dimming signal PWM_DIM. The configuration of the on-time control unit 334 is not particularly limited, but may include an oscillator that generates a periodic voltage such as a triangular wave or a sawtooth wave, and generate a control pulse Spwm by comparing the periodic voltage and the error voltage Vc. ..

The gate driver 336 drives the switching transistor MH and the synchronous rectifying transistor ML according to the control pulse Spwm.

The PWM signal generation unit 310 is composed of a microcontroller. A pulse dimming signal PWM_DIM generated by the PWM signal generation unit 310 is input to the PWM pin of the control IC 340. The driver circuit 324 receives the pulse dimming signal PWM_DIM and drives the series switch 323. In this embodiment, the series switch 323 is a polyclonal transistor, and the driver circuit 324 outputs a signal obtained by inverting the pulse dimming signal PWM_DIM from the PWMG pin.

The pulse dimming signal PWM_DIM is input to the sample hold circuit 332. The sample hold circuit 332 connects the output of the transconductance amplifier 330 to the Vc pin and the input of the on-time control unit 334 during the on-level (high) period in which the pulse dimming signal PWM_DIM instructs the series switch 323 to turn on. Further, the sample hold circuit 332 maintains the connection between the Vc pin and the input of the on-time control unit 334 during the off-level (low) period in which the pulse dimming signal PWM_DIM instructs the series switch 323 to be turned off, while maintaining the connection of the transconductance amplifier 330. The output is cut off from the Vc pin and the on-time control unit 334. As a result, the error voltage Vc of the Vc pin is held during the period when the pulse dimming signal PWM_DIM is off, and when the next pulse dimming signal PWM_DIM is turned on, the error voltage Vc is immediately returned to the appropriate voltage level. Can be made to.

The pulse dimming signal PWM_DIM is input to the gate driver 336. The gate driver 336 selectively switches the switching transistor MH and the synchronous rectifying transistor ML according to the control pulse Spwm during the period when the pulse dimming signal PWM_DIM is on level (high). Further, the gate driver 336 stops switching between the switching transistor MH and the synchronous rectifying transistor ML during the period when the pulse dimming signal PWM_DIM is off level (low). Specifically, the gate driver 336 fixes both the switching transistor MH and the synchronous rectifying transistor ML to off during the period when the pulse dimming signal PWM_DIM is off level.

(Embodiment 2)
FIG. 11 is a diagram showing a vehicle lamp 100B according to the second embodiment. Differences from the first embodiment will be described.

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 directed so that the respective emitted beams BM ₁ to BM _N irradiate one of the M blade mirrors. Here, only the light beam of the emitted beam BM ₂ of the semiconductor light source 212_2 is shown as a representative.

At a certain time, the incident light BM ₂ on the blade mirror 224 is reflected at a reflection angle corresponding to the position of the blade mirror 224 (rotation angle of the rotor), and an instantaneous irradiation spot SPT ₂ is formed on the virtual vertical screen 900 in front of the vehicle. do. The instantaneous irradiation spot SPT ₂ has a predetermined width in each of the horizontal direction (H direction) and the vertical direction (V direction). As the blade mirror 224 rotates, the reflection angle changes, the emission direction of the reflected beam BMr ₂ changes as shown by the broken line, and the horizontal (H direction) position (scanning position) of the instantaneous irradiation spot SPT ₂ moves. do. By repeating this operation at high speed, for example, at 50 Hz or higher, an individual light distribution pattern PTN ₂ is formed in front of the vehicle.

The same applies to the other beams BM ₁ , BM ₃ to BM _N , and the individual light distribution pattern PTN _i is formed by scanning the i-th reflected beam BM r _i .

For example, the individual light distribution patterns PTN ₁ to PTN _N formed by the beams BM ₁ to BM _N are formed at different heights on the virtual vertical screen 900. By synthesizing a plurality of individual light distribution patterns PTN ₁ to PTN _N , the light distribution pattern PTN_ALL of the entire vehicle lamp 100 is formed. The individual light distribution patterns PTNs adjacent to each other in the vertical direction may slightly overlap each other in the vertical direction.

In the second embodiment, at least one of the plurality of individual light distribution patterns PTN ₁ to PTN _N extends over the entire horizontal range of the vehicle lamp 100 to _−θMAX to + _θMAX . That is, the scanning light source 200B scans at least one of the plurality of beams BMr ₁ to BMr _N over the entire horizontal range. In the example of FIG. 11, all the individual light distribution patterns PTN ₁ to PTN _N extend over the entire horizontal range −θ _MAX to + θ _MAX .

The lighting circuit 300B adjusts the light intensity of each of the semiconductor light sources 212_1 to 212_N at each scanning position, that is, the intensity of the beams BM ₁ to BM _N in multiple gradations in synchronization with the scanning of the scanning light source 200B. .. The lighting circuit 300B may change the amount of current I _OUT in a scanning cycle or a control cycle longer than that. That is, PWM dimming and DC dimming may be used together.

FIG. 12 is a block diagram showing a configuration example of the lighting circuit 300B of FIG. 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. The PWM signal generation unit 310 generates pulse dimming signals PWM_DIM_1 to PWM_DIM_N for a plurality of LED drivers 320_1 to 320_N so that the desired light distribution can be obtained. The i-th (1 ≦ i ≦ N) LED driver 320 supplies a PWM-modulated drive current I _LEDi to the corresponding semiconductor light source 212_i. The configuration of the LED driver 320 is the same as that of the first embodiment.

According to this vehicle lamp 100B, the resolution in the height direction can be improved as compared with the first embodiment.

A modified example of the second embodiment will be described. In the above explanation, all of the plurality of light distribution patterns PTN ₁ to PTN _N are spread over the entire range, but not limited to this, and some of them are spread over a part of the range, not the entire range. You may.

In the second embodiment, the entire light distribution is vertically divided into a plurality of regions, and a plurality of individual light distribution patterns PTN ₁ to PTN _N are associated with the plurality of regions, but this is not the case. Some of the plurality of individual light distribution patterns PTN ₁ to PTN _N may completely overlap.

(Embodiment 3)
FIG. 13 is a diagram showing a vehicle lamp 100C according to the third embodiment. Similar to the second embodiment, the light source unit 210C includes a plurality of semiconductor light sources 212_1 to 212_N. In the first embodiment or the second embodiment, the emitted beams BM ₁ to BM _N of the semiconductor light sources 212_1 to 212_N are irradiated over the entire range of the horizontal scan, but in the third embodiment, the emitted beams BM ₁ to BM _N are emitted. , Different horizontal ranges are scanned on the virtual vertical screen 900, and the scanning of the emitted beams BM ₁ to BM _N forms a plurality of individual light distribution patterns PTN ₁ to PTN _N. The light distribution formed by the vehicle lamp 100R is a superposition of a plurality of individual light distribution patterns PTN ₁ to PTN _N.

The lighting circuit 300C can be configured in the same manner as the lighting circuit 300B of the second embodiment.

(Short abnormality detection of series switch)
When PWM dimming is performed by the series switch, if a short circuit error occurs in the series switch, the drive current I _LED to the semiconductor light source 212 cannot be cut off, the semiconductor light source 212 lights up, and the correct light distribution cannot be formed. Specifically, the dimming cannot be sufficiently performed, which may cause glare on the oncoming vehicle and the preceding vehicle.

Note that the short-circuit abnormality cannot cut off the current supply to the semiconductor light source 212 even if the pulse dimming signal PWM_DIM is turned off, such as an abnormality in which the series switch cannot be turned off or an abnormality in which both ends of the series switch are short-circuited. It means an abnormality.

The following describes vehicle lamps that can detect short-circuit abnormalities in series switches.

FIG. 14 is a block diagram of a vehicle lamp 100F having a short abnormality detection function. The vehicle lamp 100F includes a semiconductor light source 212, an LED driver 320F, and a PWM signal generation unit 310. The PWM signal generation unit 310 generates a pulse dimming signal PWM_DIM pulse-modulated so as to form a desired light distribution pattern.

The LED driver 320F includes a buck converter 322, a series switch 323, and a driver circuit 324, similarly to the LED driver 320A of FIG. These functions and operations are as described above. That is, the buck converter 322 outputs a constant current during the on period (i) of the series switch 323 (the period during which the pulse dimming signal PWM_DIM is on level). Further, the buck converter 322 stops the switching operation during the off period of the (ii) series switch 323 (the period during which the pulse dimming signal PWM_DIM is at the off level), and has substantially the same output voltage V _OUT , that is, the semiconductor as the immediately preceding on period. It is configured to maintain the forward voltage of the light source 212.

The LED driver 320F further includes an abnormality detection circuit 370. When the output voltage V _OUT of the buck converter 322 deviates from the normal range during the off period of the series switch 323, the abnormality detection circuit 370 determines that the series switch 323 is abnormal and asserts the abnormality detection signal (fail signal) FAIL. The fail signal FAIL is transmitted to the PWM signal generation unit 310 or an upper block such as another microcontroller, processor, or ECU. The PWM signal generation unit 310 that has received the fail signal FAIL may stop the generation of the pulse dimming signal PWM_DIM and turn off the semiconductor light source 212.

15 (a) and 15 (b) are diagrams illustrating the operation of the vehicle lamp 100F of FIG. Here, an operation for one scan is taken as an example when forming a light distribution including two light-shielding portions and one dimming portion.

The operation when the series switch 323 is normal will be described with reference to FIG. 15 (a). The pulse dimming signal PWM_DIM is an off-level (low) in the light-shielding portion, a pulse signal having a duty cycle according to the dimming rate in the dimming portion, and an on-level (high) in the other portion. Take.

When the pulse dimming signal PWM_DIM is high (on level), the series switch 323 conducts, so that the constant current I _OUT generated by the buck converter 322 is supplied to the semiconductor light source 212, and the drive current I flows through the semiconductor light source 212. The _LED is stabilized to a constant current I _OUT . At this time, the output voltage V _OUT of the buck converter ₃₂₂ becomes equal to the forward voltage VF of the semiconductor light source 212.

When the pulse dimming signal PWM_DIM is low (off level), the series switch 323 is cut off, so that the drive current I _LED flowing through the semiconductor light source 212 becomes 0A. Further, since the switching operation of the buck converter 322 is stopped and charging / discharging to the output capacitor C1 does not occur, the output voltage V _OUT is kept at a substantially constant level.

Thus, when the series switch 323 is normal, the output voltage V _OUT of the buck converter 322 is in a certain voltage range near the forward voltage _VF regardless of whether the series switch 323 is on or off (this). Is included in the normal range).

The operation when a short-circuit abnormality occurs in the series switch 323 will be described with reference to FIG. 15 (b). The pulse dimming signal PWM_DIM is the same as that in FIG. 15 (a).

Even if a short-circuit error occurs, when the pulse dimming signal PWM_DIM is high (on level), it operates in the same way as normal, but when the pulse dimming signal PWM_DIM is low (off level), it is for vehicles. The lamp 100F behaves differently from the normal state.

That is, even if the pulse dimming signal PWM_DIM is low (off level), the series switch 323 cannot be cut off, so that the drive current I _LED continues to flow in the semiconductor light source 212. However, since the switching of the buck converter 322 is stopped while the pulse dimming signal PWM_DIM is low, the drive current I _LED is covered by the discharge of the output capacitor C1 of the buck converter 322. Therefore, as the discharge progresses, the drive current I _LED decreases with time. Since the low section of the pulse dimming signal PWM_DIM is long in the light-shielded portion, when the output capacitor C1 is discharged and drops to the lighting start voltage V _MIN shown in FIG. 17, the drive current I _LED drops to 0 A. At this point, the discharge of the output capacitor C1 is stopped, so that the output voltage V _OUT is near the lighting start voltage V _MIN . On the other hand, in the dimmed portion, since the low section of the pulse dimming signal PWM_DIM is short, the drive current I _LED may not decrease to 0A.

In this way, when a short-circuit abnormality of the series switch 323 occurs, the drive current I _LED hardly decreases in the dimmed portion, which may cause glare to the oncoming vehicle or make it difficult for the driver to recognize the target. ..

Focusing on the low section of the pulse dimming signal PWM_DIM at the time of a short-circuit abnormality, the output capacitor C1 is discharged via the semiconductor light source 212, so that the output voltage V _OUT drops. As a result, it can be seen that it deviates from the normal range described in FIG. 15 (a).

According to this embodiment, the output voltage V _OUT can be detected by utilizing the difference in the behavior of the output voltage V _OUT at the time of short circuit abnormality and the normal state.

Hereinafter, a specific configuration of the abnormality detection circuit 370 and a specific signal processing will be described based on some examples.

FIG. 16 is a circuit diagram of the abnormality detection circuit 370 according to the embodiment. The abnormality detection circuit 370 includes a comparison circuit 372 and a signal processing unit 374. The comparison circuit 372 includes resistors R31 and R32 and a voltage comparator COMP1. The output voltage V _OUT of the buck converter 322 is divided by a voltage divider circuit including resistors R31 and R32. The voltage comparator COMP1 compares the output voltage V _OUT'after voltage division with a predetermined threshold voltage _VTH , and generates a detection signal S _DET indicating the comparison result. The detection signal S _DET is a binary signal indicating whether or not the output voltage V _OUT of the buck converter 322 is included in the normal range. In this configuration, _VSHORT = _VTH × (R31 + R32) / R32 is the threshold value (lower limit) in the normal range.

For example, in the normal state, V _OUT > V _SHORT , and the detection signal S _DET at this time keeps high. When a short-circuit abnormality occurs, every time the pulse dimming signal PWM_DIM becomes an off level, V _OUT <V _SHORT becomes V OUT <V SHORT, and the detection signal S _DET becomes low. By binarizing with the comparison circuit 372, it becomes easy to determine a short circuit abnormality by digital signal processing using a microcontroller or a logic circuit.

The signal processing unit 374 determines the presence or absence of a short-circuit abnormality based on the detection signal S _DET , and when the abnormality is detected, asserts the fail signal FAIL. Specifically, in the signal processing unit 374, the detection signal S _DET reaches a predetermined level (low), that is, the output voltage V _OUT of the buck converter 322 becomes a predetermined threshold value V _SHORT during the off period of the series switch 323. It is a condition of abnormality judgment that it is less than.

The signal processing unit 374 can be implemented by combining a microcontroller and software. In this case, the PWM signal generation unit 310 and the signal processing unit 374 may be mounted on the same microcontroller. The signal processing unit 374 may be configured by a hardware logic circuit.

FIG. 17 is a diagram showing the IV characteristics of the semiconductor light source 212. The horizontal axis represents the voltage V _LED between both ends of the semiconductor light source 212, and the vertical axis represents the current. The lower limit threshold V _SHORT in the normal range may be set higher than the lighting start voltage V _MIN of the semiconductor light source 212 and lower than the forward voltage _VF when the semiconductor light source 212 is lit.

Immediately after the start of operation of the buck converter 322, the output voltage V _OUT is 0 V, so that an abnormality cannot be determined based on the output voltage V _OUT . Therefore, the abnormality detection by the abnormality detection circuit 370 is invalidated after the operation of the buck converter 322 is started until the output voltage V _OUT exceeds a predetermined voltage.

Subsequently, a specific example of the determination process by the abnormality detection circuit 370 will be described.

(Judgment process 1)
FIG. 18 is a diagram illustrating the determination process 1 of the abnormality detection circuit 370. FIG. 18 shows the waveform at the time of short circuit abnormality. As shown in FIG. 3, the vehicle lamp 100 includes a scanning optical system 220. The pulse dimming signal PWM_DIM is generated so that the series switch 323 is turned off for a predetermined period (referred to as blank period _TBLANK ) at the break between scans. For example, when the scanning optical system 220 includes a plurality of blade mirrors 224, the gap between the blade mirrors can be set as a blank period _TBLANK .

For example, when the scanning frequency is 200 Hz, the scanning period _TSCAN is 5 ms. When the PWM frequency is 20 kHz, the PWM cycle is 50 μs. The blank period _TBLANK may be set longer than the PWM cycle of 50 μs, for example 70 μs.

The abnormality detection circuit 370 detects an abnormality of the series switch 323 based on the output voltage V _OUT of the step-down converter 322 in the blank period _TBLANK . The abnormality detection circuit 370 sets a tentative determination state when the output voltage V _OUT falls below the threshold value V _SHORT in the blank period _TBLANK . Then, when the provisional determination state is established over a predetermined number of scans, the final determination may be performed.

Specifically, the signal processing unit 374 acquires the position of the blank period _TBLANK based on the position detection signal S4, and the detection signal _SDET transitions to a predetermined level (low) during the blank period _TBLANK . Is a condition for determining a short circuit abnormality. When the provisional determination state in which the detection signal S _DET becomes low in the blank period _TBLANK is established several times M a predetermined number of times, the fail signal FAIL is asserted. For example, the signal processing unit 374 includes a counter, and counts up the counter each time the detection signal S _DET of the blank period _TBLANK becomes low. Then, when the count value reaches a predetermined value M, the fail signal FAIL is asserted. If the low detection signal S _DET cannot be detected before the count value reaches the predetermined value M, the counter may be reset. That is, in the determination process 1, the short-circuit abnormality is detected by focusing only on the hatched portion of the detection signal S _DET in FIG.

The advantages of the determination process 1 will be described. If the blank period _TBLANK is not provided, the short circuit abnormality cannot be detected unless the pulse dimming signal PWM_DIM transitions to low. In the first determination process, by inserting the blank period _TBLANK , an opportunity for abnormality determination is always given once per scan. This makes it possible to reliably detect a short circuit abnormality in a short time.

The PWM dimming section and the low section of the detection signal S _DET are narrow pulses shorter than 50 μs. Therefore, in order to use the detection signal S _DET in the PWM dimming section, a high-speed signal processing unit 374 is required. Further, when the duty cycle of the pulse dimming signal PWM_DIM is large (when the low section is short), the output voltage V _OUT may not fall below the threshold value V _SHORT . In the blank period _TBLANK longer than the PWM cycle, the output voltage V _OUT surely falls below the threshold value V _SHORT , so that a low-level detection signal S _DET can be generated, and a short-circuit abnormality can be detected stably.

(Judgment process 2)
FIG. 19 is a diagram illustrating the determination process 2 of the abnormality detection circuit 370. FIG. 19 shows the waveform at the time of short circuit abnormality. In the determination process 2, the blank period _TBLANK is not essential.

In the determination process 2, the abnormality detection circuit 370 constantly monitors the detection signal S _DET , and a state in which the detection signal S _DET is not a DC signal (DC state), in other words, a pulse signal (pulse state) is a predetermined determination. If the time τ _{DET continues} , it is determined that the condition is abnormal and the fail signal FAIL is asserted.

For example, the signal processing unit 374 generates a provisional determination signal DC / PULSE indicating whether the detection signal S _DET is in the pulse state or the DC state. A state in which the detection signal S _DET is continuously high for a predetermined time or longer may be a DC state, and a state in which the detection signal S DET is continuously high may be a pulse state. When the temporary determination signal DC / PULSE is high indicating the pulse state for a predetermined determination time τ _DET , the signal processing unit 374 determines that the temporary determination signal DC / PULSE is an abnormal state and asserts the fail signal FAIL. The signal processing unit 374 may be implemented by using the timer resource of the microcontroller.

The determination process 1 requires timing synchronization with the blank period _TBLANK , whereas the determination process 2 has an advantage that timing synchronization is not required.

(Judgment process 3)
FIG. 20 is a diagram illustrating the determination process 3 of the abnormality detection circuit 370. FIG. 20 shows the waveform at the time of short circuit abnormality. In the determination process 3, the blank period _TBLANK is not essential.

In the determination process 3, the abnormality detection circuit 370 constantly monitors the detection signal S _DET , the number of times the detection signal S _DET transitions to low, in other words, the number of low pulses generated on the detection signal S _DET , in other words, the detection signal S. The number of negative edges of the _DET is counted, and when the count value exceeds a predetermined threshold value K, it is determined as an abnormal state.

From a certain point of view, some of the determination processes 1 to 3 can be regarded as a condition for abnormality determination that the output voltage V _OUT of the buck converter 322 is not constant and lasts for a predetermined time. From another point of view, it is understood that some of the determination processes 1 to 3 require that the switching state of the output voltage V _OUT of the buck converter 322 lasts for a predetermined determination time as a condition for abnormality determination. Will be done.

(Judgment process 4)
In the embodiment, the abnormality determination is performed after binarizing the output voltage V _OUT , but this is not the case. For example, a high-speed A / D converter may capture a waveform of an output voltage V _OUT , and the presence or absence of an abnormality may be determined based on the waveform.

(Shape of blade mirror)
FIG. 21 is a diagram showing a configuration example of the scanning optical system 220. The scanning optical system 220 includes a motor 222 and a plurality of blade mirrors 224. In this example, the number of blade mirrors 224 is two. The blade mirrors 224_1224_2 are attached to the rotor (rotating shaft) of the motor 222 with a gap (hereinafter referred to as mirror spacing) 226_1.226_2. In the scanning optical system 220 of FIG. 21, the distance between the two mirrors 226_1, 226_2 is non-uniform, and d1> d2.

The mirror spacing 226_1,226_2 cannot reflect the emitted light of the semiconductor light source 212. Also, the edge of the blade mirror may be less accurate than the center. Therefore, the blank period _TBLANKi is set so as to include the period in which the optical axis of the semiconductor light source 212 crosses the mirror interval 226_i (i = 1, 2), and the semiconductor light source 212 is turned off in the blank period _TBLANKi . As a result, the blank period _TBLANK1 corresponding to the mirror interval 226_1 is longer than the blank period _TBLANK2 corresponding to the mirror interval 226_1.
T _BLANK1 > T _BLANK2

FIG. 22 is a diagram showing a blank period T _BALNK corresponding to the distance between the two blades. BM indicates the optical axis (beam spot) of the semiconductor light source. When there are two blade mirrors, two scanning cycles T _SCAN are included in the cycle _TROT of one rotation of the motor 222. Each time the motor rotates, a long blank period _TBLANK1 and a short blank period _TBLANK2 are alternately generated.

According to this configuration, a long blank period _TBLANK1 and a short blank period _TBLANK2 can be intentionally created by making the spacing between the plurality of blade mirrors non-uniform. As a result, it becomes possible to cause the vehicle lamp to perform different processing in the long blank period _TBLANK1 and the short blank period _TBLANK2 , and it becomes easy to optimize the scheduling of signal processing.

Hereinafter, a specific example of signal processing will be described.

-Short anomaly detection As described in the determination process 1 for short abnormality detection of the series switch described above, consider a case where short anomaly detection is performed by using the blank period _TBLANK of the semiconductor light source. In the blank period _TBLANK , the blank period is shortened in inverse proportion to the rotation speed of the motor. Therefore, the higher the scanning frequency, the more difficult it is to detect a short circuit abnormality. In this case, of the plurality of blank periods T _BLANK1 and T _BLANK2 , one of the T _{BLANK 2} is shortened, and the other T _{BLANK 1} is lengthened, so that the longer blank period T _{BLANK 1} is used to detect a short abnormality. It will be possible to do it reliably.

The microcontroller 304 for vehicle lighting performs various tasks (processes). The microcontroller 304 may perform a predetermined process in the longest blank period _TBLANK1 corresponding to the widest spacing of the plurality of mirrors. For example, the microcontroller 304 may perform a relatively heavy task during a long blank period _TBLANK1 and a relatively light task during a short blank period _TBLANK2 .

Alternatively, if there is a task to be executed at a rate of once for each rotation of the motor, the task may be executed in the long blank period _TBLANK1 .

(Regarding the distinction between blank periods)
When making the mirror spacing non-uniform, it is necessary to distinguish between long blank periods and short blank periods.

Generally, in the case of a motor provided with a permanent magnet on the rotor side, the rotation information of the motor can be acquired by using a Hall element. In many applications, it is common to use a motor with four or more poles. FIG. 23A is a diagram illustrating position detection in a 4-pole motor. H + and H- indicate the hall signal, and the FG signal indicates the comparison result of the hall signal.

In the case of a 4-pole motor, the output H + (FG signal) of the Hall element repeats the same waveform twice within one rotation of the motor. Therefore, it is not possible to distinguish between a long blank period and a short blank period based on the Hall signal H + or the FB signal.

Therefore, a two-pole motor may be used to distinguish between a long blank period and a short blank period. FIG. 23B is a diagram illustrating rotation detection in a two-pole motor. By using a two-pole motor, the cycle of the FG signal matches the rotation cycle of the motor, so it is possible to distinguish between the blank periods _TBLANK1 and _TBLANK2 based on the position of the edge of the FG signal. ..

The method for detecting the blank periods T _{BLANK 1} and T _{BLANK 2} is not limited to this. For example, apart from the semiconductor light source 212, a position detection light source that is always lit and a light receiving element that detects the emitted light of the position detection light source may be provided facing each other so as to sandwich the blade mirror. The output of the light receiving element becomes zero during the period when the emitted light of the position detecting light source is blocked by the blade mirror, and the output of the light receiving element becomes non-zero during the period when the emitted light of the position detecting light source passes through the mirror interval. Since the length of time during which the output of the light receiving element becomes non-zero differs depending on the widths d1 and d2 of the mirror interval, it is possible to distinguish between the blank periods _TBLNK1 and _TBLANK2 .

Alternatively, one position detection magnet may be added to the rotor or blade of the motor, and the magnetic field of the position detection magnet may be detected by the Hall element.

(Suppression of overshoot)
When PWM dimming is performed by the series switch, the drive current I _LED may overshoot immediately after the turn-on of the series switch. When the drive current I _LED overshoots, the duty cycle of PWM dimming and the linearity of the amount of light are lost in the region where the on-time of the series switch is short, and gradation control becomes impossible.

FIG. 24 is a diagram illustrating overshoot of the drive current I _LED due to PWM dimming in the LED driver 320A of FIG. While the pulse dimming signal PWM_DIM from time t ₀ to t ₁ is on level (high), the drive current I _LED is supplied to the semiconductor light source 212, and the voltage drop V _LED of the semiconductor light source 212 is the forward voltage _VF . Become.

When the pulse dimming signal _{PWM_DIM} transitions to the off level (low) at time t1, the series switch 323 is immediately turned off. On the other hand, the energy stored in the inductor _L1 of the output circuit 326 is supplied to the output capacitor C1 of the output circuit 326 as a current signal (coil current) IL (with hatching), and the output capacitor C1 is charged. As a result, the voltage of the output capacitor C1 is higher than VF by _ΔV .

When the pulse dimming signal PWM_DIM transitions to the on level (high) at time t ₂ , the series switch 323 turns on. At this time, the voltage of the output capacitor C1 decreases from _VF + _ΔV toward VF. That is, the electric charge (with hatching) corresponding to the potential difference ΔV, the discharge current from the output capacitor C1 flows into the semiconductor light source 212 via the series switch 323. The drive current I _LED flowing through the semiconductor light source 212 is the sum of the constant current IL flowing through the inductor _L1 of the output circuit 326 and the discharge current I _DIS of the output capacitor C1. That is, the discharge current caused by the surplus charge (Q = ΔV × C1) of the output capacitor C1 causes the overshoot of the drive current I _LED .

Hereinafter, a technique for suppressing overshoot of the drive current I _LED by the series switch will be described.

FIG. 25 is a circuit diagram of the LED driver 320D according to the embodiment. The LED driver 320D supplies an intermittent drive current I _LED corresponding to the PWM signal (pulse dimming signal) PWM_DIM to the semiconductor light source 212. The LED driver 320D includes a buck converter 322D, a series switch 323, and a driver circuit 324.

The buck converter 322D includes an overshoot suppression circuit 350 in addition to the output circuit 326 and the converter controller 328.

A pulse dimming signal PWM_DIM is input to the overshoot suppression circuit 350. The overshoot suppression circuit 350 is connected to at least one of the output circuit 326 and the converter controller 328 in synchronization with the pulse dimming signal PWM_DIM so that the overshoot of the drive current I _LED immediately after the series switch 323 is turned on is suppressed. It works. In the figure, the broken line (i) conceptually shows the function or configuration acting on the output circuit 326, and the broken line (ii) conceptually shows the function or configuration acting on the converter controller 328. "Acting" may include forcibly changing the voltage of a certain node, changing the circuit constant of a circuit element, and the like.

By providing the overshoot suppression circuit 350 that operates in synchronization with the pulse dimming signal PWM_DIM, it is possible to suppress the overshoot of the drive current I _LED immediately after the turn-on of the series switch 323.

Hereinafter, a configuration example of the overshoot suppression circuit 350 will be described.

(Example 1)
In the first embodiment, the overshoot suppression circuit 350 discharges the output capacitor C1 of the output circuit 326 in synchronization with the pulse dimming signal PWM_DIM, and forcibly changes the output voltage V _OUT of the buck converter 322.

FIG. 26 is a circuit diagram of the LED driver 320Da according to the first embodiment. In the first embodiment, the overshoot suppression circuit 350a is connected to the output line 327 of the output circuit 326. The overshoot suppression circuit 350a discharges the output capacitor C1 during the off period of the series switch 323, and makes the output voltage V _{OUT of the buck converter 322 higher than the output voltage V OUT} _of the buck converter 322 during the on period of the series switch 323. Decrease.

FIG. 27 is an operation waveform diagram of the LED driver 320Da of FIG. 26. The drive current I _LED'and the output voltage V _OUT ' of the alternate long and short dash line show the waveform (FIG. 24) when the overshoot suppression circuit 350a is not provided.

During the period t ₀ to t ₁ when the pulse dimming signal _{PWM_DIM} is on level, the output voltage V _OUT becomes VF.

At time t1, the pulse dimming signal _{PWM_DIM} transitions to the off level. The overshoot suppression circuit 350Da forcibly discharges the output capacitor C1 when the pulse dimming signal PWM_DIM becomes an off level (low), and forcibly lowers the output voltage V _OUT below the voltage level of the broken line. By lowering the output voltage V _OUT of the buck converter 322D during the off period, the discharge current from the output capacitor C1 can be reduced immediately after the turn-on, and the overshoot of the drive current I _LED can be prevented. If the voltage level V _LOW of the output voltage _V _OUT during the off period is set lower than VF, a part of the coil current IL of the buck converter _322D is used to charge the output capacitor C1 of the output circuit 326 immediately after the turn-on. As it is used, this can further suppress overshoot.

FIG. 28 is a circuit diagram showing a configuration example of the overshoot suppression circuit 350a. The overshoot suppression circuit 350a includes a first capacitor C11, a first switch SW11, a second switch SW12, and a switch controller 352. The first end of the first capacitor C11 is grounded. The overshoot suppression circuit 350a initializes the charge of the first capacitor C11 when the pulse dimming signal PWM_DIM is on level, and sets the second end of the first capacitor C11 when the pulse dimming signal PWM_DIM is off level. Connect to the output line 327.

The first switch SW11 is provided between the second end of the capacitor C11 and the output line 327, and the second switch SW12 is provided between the second end of the capacitor C11 and the ground. The switch controller 352 turns off the first switch SW11 and turns on the second switch SW12 when the pulse dimming signal PWM_DIM is on level, and turns on the first switch SW11 when the pulse dimming signal PWM_DIM is off level. 2 Switch SW12 is turned off.

FIG. 29 is an operation waveform diagram of the overshoot suppression circuit 350a of FIG. 28. VC11 indicates the voltage of the first capacitor _C11 . During the period when the pulse dimming signal PWM_DIM is on level, the second switch SW12 is turned on, and the voltage VC11 of the first capacitor _C11 becomes 0V. During the period when the pulse dimming signal PWM_DIM is off level, the first switch SW11 is turned on, the first capacitor C11 is connected to the output capacitor C1, and the charge is transferred from the output capacitor C1 to the first capacitor C11. As a result, the output voltage V _OUT generated in the output capacitor C1 is reduced. The above is the operation waveform diagram of the overshoot suppression circuit 350a of FIG. 28.

FIG. 30 is a circuit diagram of a modification (350a') of the overshoot suppression circuit 350a of FIG. 28. The overshoot suppression circuit 350a'includes a constant voltage source 354 in addition to the overshoot suppression circuit 350a of FIG. 28. The constant voltage source 354 produces a predetermined voltage V _ADJ . The second switch SW12 is provided between the second end of the first capacitor C11 and the output node of the constant voltage source 354.

FIG. 31 is an operation waveform diagram of the overshoot suppression circuit 350a'of FIG. 30. During the period when the pulse dimming signal PWM_DIM is on level, the second switch SW12 is turned on, and the voltage _VC11 of the first capacitor _C11 becomes the constant voltage VADJ. During the period when the pulse dimming signal PWM_DIM is off level, the first switch SW11 is turned on, the first capacitor C11 is connected to the output capacitor C1, and the charge is transferred from the output capacitor C1 to the first capacitor C11. As a result, the output voltage V _OUT generated in the output capacitor C1 is reduced. The reduced voltage level V _LOW'can be adjusted according to the constant voltage V _ADJ .

(Example 2)

FIG. 32 is a circuit diagram of the LED driver 320Db according to the second embodiment. In the second embodiment, as in the first embodiment, the overshoot suppression circuit 350b forcibly discharges the electric charge from the output capacitor C1 in synchronization with the pulse dimming signal PWM_DIM, but the timing of the discharge is different.

The LED driver 320Db according to the second embodiment can be configured in the same manner as the LED driver 320Da in FIG. The LED driver 320Db includes an overshoot suppression circuit 350b.

The overshoot suppression circuit 350b forcibly discharges the output capacitor C1 immediately after the series switch 323 is turned on.

FIG. 33 is an operation waveform diagram of the LED driver 320Db according to the second embodiment. The drive current I _LED'of the alternate long and short dash line shows the waveform (FIG. 24) when the overshoot suppression circuit 350b is not provided.

While the pulse dimming signal PWM_DIM from time t ₀ to t ₁ is on level (high), the drive current I _LED is supplied to the semiconductor light source 212, and the voltage drop V _LED of the semiconductor light source 212 is the forward voltage _VF . Become.

When the pulse dimming signal _{PWM_DIM} transitions to the on level ( _high ) at time t2, and when the series switch 323 is turned on, the voltage of the output capacitor C1 decreases from VF + _ΔV toward VF, and the surplus charge Q = ΔV × C is emitted as a discharge current.

At this time, the overshoot suppression circuit 350b forcibly discharges the output capacitor C1. The overshoot suppression circuit 350b can also be grasped as a current source that sucks in the sink current _ISINK immediately after the turn-on of the series switch 323. As a result, a part of the current supplied to the semiconductor light source 212 flows into the overshoot suppression circuit 350b, so that the overshoot of the drive current I _LED can be suppressed.

Return to Fig. 28. The overshoot suppression circuit 350b is configured in the same manner as the overshoot suppression circuit 350a of FIG. 28. However, the control of the switch by the switch controller 352 is reversed. Specifically, the switch controller 352 of the overshoot suppression circuit 350b turns off the first switch SW11 and turns on the second switch SW12 when the pulse dimming signal PWM_DIM is off level, and the pulse dimming signal PWM_DIM is on level. At this time, the first switch SW11 is turned on and the second switch SW12 is turned off.

FIG. 34 is an operation waveform diagram of the overshoot suppression circuit 350b according to the second embodiment. While the pulse dimming signal PWM_DIM is off level, the second switch SW12 is discharged and the voltage VC11 of the first capacitor _C11 becomes zero. Further, while the pulse dimming signal PWM_DIM is off level, the output capacitor C1 takes a voltage level higher than Vf.

When the pulse dimming signal PWM_DIM transitions to the on-level, the output capacitor C1 and the first capacitor C11 are connected, and charge transfer occurs. At this time, the electric charge that moves from the output capacitor C1 to the first capacitor C11 is the sink current _ISINK , and the output capacitor C1 is discharged by this sink current _ISINK .

As a modification of the second embodiment, the overshoot suppression circuit 350b'in FIG. 30 may be used. In this case, the amount of sink current _ISINK can be adjusted according to the voltage V _ADJ .

(Example 3)
FIG. 35 is a circuit diagram of the LED driver 320Dc according to the third embodiment. The overshoot suppression circuit 350c acts on the converter controller 328 in synchronization with the pulse dimming signal PWM_DIM to change the internal signal having a correlation with the duty cycle of the switching transistor MH generated by the converter controller 328.

The converter controller 328 includes an error amplifier 360, a pulse width modulator 362, and a driver 364. The error amplifier 360 amplifies the error between the detected value Vcs of the output current I _OUT of the buck converter 322 and the target value Vref, and generates an error signal Verr. The pulse width modulator 362 generates a pulse signal Spwm having a duty cycle corresponding to the error signal Verr. The driver 364 drives the switching transistor MH and the synchronous rectifying transistor ML according to the pulse signal Spwm.

The overshoot suppression circuit 350c can use the output signal of the error amplifier 360 included in the converter controller 328, in other words, the input signal of the pulse width modulator 362 as an internal signal.

The overshoot suppression circuit 350c forcibly lowers the error voltage Verr, which is an internal signal, during the off period of the series switch 323.

The above is the configuration of the LED driver 320Dc. Next, the operation will be described. FIG. 36 is an operation waveform diagram of the LED driver 320Dc of FIG. 35. The alternate long and short dash line indicates the operation when the overshoot suppression circuit 350c is not provided.

While the pulse dimming signal _{PWM_DIM} from time t ₀ to t ₁ is on level (high), the drive current I _LED is supplied to the semiconductor light source 212, and the output voltage V _OUT becomes the forward voltage VF.

When the pulse dimming signal _{PWM_DIM} transitions to the off level (low) at time t1, the series switch 323 is immediately turned off. On the other hand, the energy stored in the inductor _L1 of the output circuit 326 is supplied to the output capacitor C1 of the output circuit 326 as a current signal (coil current) IL, and the output capacitor C1 is charged. As a result, the voltage of the output capacitor C1 is higher than VF by _ΔV .

When the pulse dimming signal PWM_DIM becomes an off level, the overshoot suppression circuit 350c forcibly lowers the error voltage Verr.

_At time t2, the pulse dimming signal PWM_DIM transitions to the on-level. At this time, the excess charge C1 × ΔV of the output capacitor C1 is discharged as the discharge current I _DIS .

On the other hand, when the pulse dimming signal _{PWM_DIM} transitions to the on _- level at time t2, the error voltage Verr becomes low, so that the rate of increase of the coil current IL slows down. That is, immediately after the turn-on of the series switch 323, the coil current _IL decreases. As a result, overshoot of the drive current I _LED , which is the sum of the coil current _{IL and the discharge current I DIS} _of the output capacitor C1, is suppressed.

When the control IC 340 of FIG. 10 is used, the transconductance amplifier 330, the sample hold circuit 332, the resistor Rc, and the capacitor Cc of FIG. 10 are grasped as the error amplifier 360. Further, the on-time control unit 334 of FIG. 10 can be grasped as a pulse width modulator 362. Therefore, the overshoot suppression circuit 350c may change the voltage of the Vc pin in FIG. 10 as an internal signal.

FIG. 37 is a circuit diagram showing a configuration example of the overshoot suppression circuit 350c according to the third embodiment. As described above, the control IC 340 has a Vc pin, and a feedback capacitor Cc is externally attached to the Vc pin.

The overshoot suppression circuit 350c includes a second capacitor C12, a third switch SW13, a fourth switch SW14, and a switch controller 356. The first end of the second capacitor C12 is grounded. The third switch SW13 is provided between the second end of the second capacitor C12 and the Vc pin which is the output of the error amplifier. The fourth switch SW14 is provided between the second end of the second capacitor C12 and the ground.

The switch controller 356 complementaryly switches the third switch SW13 and the fourth switch SW14 in synchronization with the pulse dimming signal PWM_DIM. Specifically, the switch controller 356 initializes the charge of the second capacitor C12 by turning off the third switch SW13 and turning on the fourth switch SW14 when the pulse dimming signal PWM_DIM is on level. When the pulse dimming signal PWM_DIM is at the off level, the switch controller 356 turns on the third switch SW13 and turns off the fourth switch SW14, and outputs the second end of the second capacitor C12 to the output of the error amplifier, that is, the control IC 340. Connect with Vc pin.

FIG. 38 is a circuit diagram of a modification (350c') of the overshoot suppression circuit 350c of FIG. 37. The overshoot suppression circuit 350c'includes a constant voltage source 358 in addition to the overshoot suppression circuit 350c of FIG. 37. The constant voltage source 358 produces a predetermined voltage V _ADJ . The fourth switch SW14 is provided between the second end of the second capacitor C12 and the output node of the constant voltage source 358.

According to this modification, the amount of decrease in the error voltage Vc can be controlled according to the voltage level of the voltage _VADJ .

(Example 4)
FIG. 39 is a circuit diagram of the LED driver 320Dd according to the fourth embodiment. Similar to the third embodiment, the overshoot suppression circuit 350d according to the fourth embodiment forcibly lowers the internal signal Verr in synchronization with the pulse dimming signal PWM_DIM, but the operation timing thereof is different. Specifically, the overshoot suppression circuit 350d generates a sink current _ISINK immediately after the turn-on of the series switch 323, and lowers the internal signal Verr.

FIG. 40 is an operation waveform diagram of the LED driver 320Dd of FIG. 39. The alternate long and short dash line indicates the operation when the overshoot suppression circuit 350d is not provided.

On the other hand, when the pulse dimming signal PWM_DIM transitions to the on _- level at time t2, the error voltage Verr is forcibly lowered. As a result, the rate of increase of the coil current IL _slows down. That is, immediately after the turn-on of the series switch 323, the coil current _IL decreases. As a result, overshoot of the drive current I _LED , which is the sum of the coil current _{IL and the discharge current I DIS} _of the output capacitor C1, is suppressed.

The overshoot suppression circuit 350d can be configured in the same manner as the overshoot suppression circuit 350c of FIG. 37 or the overshoot suppression circuit 350c'of FIG. 38, and the switches SW13 and S14 can be operated in the opposite phase to that of the third embodiment. Just do it.

That is, the switch controller 356 of the overshoot suppression circuit 350d initializes the charge of the second capacitor C12 by turning off the third switch SW13 and turning on the fourth switch SW14 when the pulse dimming signal PWM_DIM is at the off level. .. Further, the switch controller 356 turns on the third switch SW13 and turns off the fourth switch SW14 when the pulse dimming signal PWM_DIM is on level, and outputs the second end of the second capacitor C12 to the output of the error amplifier, that is, the control IC 340. Connect to the Vc pin of. As a result, the error voltage Verr, which is an internal signal, can be reduced immediately after the turn-on of the series switch 323.

The LED driver 320D with an overshoot suppression function described with reference to FIGS. 24 to 40 can be suitably combined with, but is not limited to, a scanning type vehicle lamp. For example, in an array type vehicle lighting equipment, when the frequency of PWM dimming is set as high as several kHz to several tens of kHz, it is effective to perform PWM dimming with a series switch, and at that time, the drive current I _LED . The LED driver 320D can be used to suppress the overshoot.

The embodiments merely show the principles and applications of the present invention, and the embodiments include many modifications and arrangement changes within a range that does not deviate from the ideas of the present invention defined in the claims. Is recognized.

S1 ... Sensor information, S2 ... Vehicle information, S3 ... Light distribution pattern information, S4 ... Position detection signal, PWM_DIM ... Pulse dimming signal, 100 ... Vehicle optics, 200 ... Scanning light source, 210 ... Light source unit, 212 ... Semiconductor Light source, 220 ... scanning optical system, 222 ... motor, 224 ... blade mirror, 226 ... mirror spacing, 230 ... projection optical system, 300 ... lighting circuit, 302 ... position detector, 310 ... PWM signal generator, 320 ... LED driver 322 ... Step-down converter, 323 ... Series switch, 324 ... Driver circuit, 326 ... Output circuit, 328 ... Converter controller, 330 ... Transconductance amplifier, 332 ... Sample hold circuit, 334 ... On-time control unit, 336 ... Gate driver, 340 ... control IC, 350 ... overshoot suppression circuit, 370 ... abnormality detection circuit, 400 ... light distribution controller, 900 ... virtual vertical screen.

Claims

A scanning light source that includes a semiconductor light source and scans the emitted light of the semiconductor light source,
A lighting circuit that can adjust the amount of light of the semiconductor light source at each scanning position in multiple gradations by pulse modulation in synchronization with the scanning of the scanning type light source.
Equipped with
The lighting circuit is
A series switch provided in series with the semiconductor light source,
A constant current output buck converter connected to the series switch and the series connection circuit of the semiconductor light source, and
A driver circuit that drives the series switch based on a pulse dimming signal pulse-modulated so that the desired light distribution can be obtained.
A vehicle lighting fixture characterized by being equipped with.
The scanning light source includes a plurality of the semiconductor light sources.
The vehicle lamp according to claim 1, wherein the lighting circuit is provided for each semiconductor light source.
The buck converter
An output circuit including a switching transistor and
A converter controller that switches and drives the switching transistor so that the detected value of the output current of the buck converter during the on period of the series switch approaches a predetermined target value.
The vehicle lamp according to claim 1 or 2, wherein the lamp comprises the above.
The vehicle lamp according to claim 3, wherein the converter controller stops the switching drive of the switching transistor during the off period of the series switch.
The output circuit includes a synchronous rectifying transistor in addition to the switching transistor, and the converter controller is characterized in that the switching transistor and the synchronous rectifying transistor are fixed off during the off period of the series switch. The vehicle lighting equipment according to Item 3.
With a semiconductor light source
A lighting circuit that can adjust the amount of light from the semiconductor light source in multiple gradations by pulse modulation.
Equipped with
The lighting circuit is
A series switch provided in series with the semiconductor light source,
A constant current output buck converter connected to the series switch and the series connection circuit of the semiconductor light source, and
A driver circuit that drives the series switch based on a pulse-modulated pulse dimming signal,
Equipped with
The buck converter
An output circuit that includes a switching transistor and an output capacitor,
A converter controller that feedback-controls the switching transistor so that the detected value of the output current of the buck converter during the on period of the series switch approaches a predetermined target value.
Overshoot acting on at least one of the output circuit and the converter controller in synchronization with the pulse dimming signal so that the overshoot of the drive current flowing through the semiconductor light source immediately after the series switch is turned on is suppressed. Suppression circuit and
A vehicle lighting fixture characterized by being equipped with.
The vehicle lamp according to claim 6, wherein the overshoot suppression circuit discharges the output capacitor in synchronization with the pulse dimming signal.
The vehicle lamp according to claim 7, wherein the overshoot suppression circuit discharges the output capacitor during the off period of the series switch.
The overshoot suppression circuit includes a first capacitor whose first end is grounded and initializes the charge of the first capacitor when the pulse dimming signal is on level indicating the on level of the series switch. The vehicle lamp according to claim 8, wherein the second end of the first capacitor is connected to the output capacitor when the pulse dimming signal is at an off level indicating the off of the series switch.
The vehicle lamp according to claim 6 or 7, wherein the overshoot suppression circuit sinks a current from the output capacitor immediately after the turn-on of the series switch.
The overshoot suppression circuit initializes the charge of the first capacitor when the first end includes a grounded first capacitor and the pulse dimming signal is at an off level indicating the series switch to be off. The vehicle lamp according to claim 7, wherein the second end of the first capacitor is connected to the output capacitor when the pulse dimming signal is at an off level indicating the on of the series switch.
The overshoot suppression circuit is
A first switch provided between the second end of the first capacitor and the output line of the buck converter,
A second switch provided between the second end of the first capacitor and the constant voltage node,
11. The vehicle lighting fixture according to claim 11.
The vehicle lamp according to claim 12, wherein the constant voltage node is a grounding line.
The vehicle lamp according to claim 12, wherein the constant voltage node is an output of a constant voltage source.
The vehicle lamp according to claim 6, wherein the overshoot suppression circuit acts on the converter controller and changes an internal signal having a correlation with the duty cycle of the switching transistor generated by the converter controller.
The vehicle lamp according to claim 15, wherein the overshoot suppression circuit forcibly lowers the internal signal during the off period of the series switch.
The converter controller is
An error amplifier that generates an error signal according to an error between the detected value of the output current of the buck converter and the target value, and an error amplifier.
The feedback capacitor connected to the output of the error amplifier and
A pulse modulator that generates a pulse signal having a duty cycle corresponding to the voltage of the feedback capacitor, and
Including
The overshoot suppression circuit includes a second capacitor whose first end is grounded and initializes the charge of the second capacitor when the pulse dimming signal is on level indicating the on level of the series switch. 13. Vehicle lighting fixtures listed in either.
The vehicle lighting device according to claim 15, wherein the overshoot suppression circuit forcibly lowers the internal signal immediately after the turn-on of the series switch.
The converter controller is
An error amplifier that generates an error signal according to an error between the detected value of the output current of the buck converter and the target value, and an error amplifier.
The feedback capacitor connected to the output of the error amplifier and
A pulse modulator that generates a pulse signal having a duty cycle corresponding to the voltage of the feedback capacitor, and
Including
The overshoot suppression circuit includes a second capacitor whose first end is grounded and initializes the charge of the second capacitor when the pulse dimming signal is at an off level indicating the series switch to be off. 6, 15, wherein the second end of the second capacitor is connected to the output of the error amplifier when the pulse dimming signal is on level indicating the on level of the series switch. The vehicle lighting fixture according to any one of 18.
The overshoot suppression circuit is
A third switch provided between the second end of the second capacitor and the output of the error amplifier,
A fourth switch provided between the second end of the second capacitor and the constant voltage node,
The vehicle lamp according to claim 17 or 19, wherein the lamp comprises the above.
The vehicle lamp according to claim 20, wherein the constant voltage node is a grounding line.
The vehicle lamp according to claim 20, wherein the constant voltage node is an output of a constant voltage source.
It is a lighting circuit that can adjust the amount of light of a semiconductor light source in multiple gradations by pulse modulation.
A series switch provided in series with the semiconductor light source,
A constant current output buck converter connected to the series switch and the series connection circuit of the semiconductor light source, and
A driver circuit that drives the series switch based on a pulse-modulated pulse dimming signal,
Equipped with
The buck converter
An output circuit including a switching transistor and
A converter controller that feedback-controls the switching transistor so that the detected value of the output current of the buck converter during the on period of the series switch approaches a predetermined target value.
Overshoot acting on at least one of the output circuit and the converter controller in synchronization with the pulse dimming signal so that the overshoot of the drive current flowing through the semiconductor light source immediately after the series switch is turned on is suppressed. Suppression circuit and
A lighting circuit characterized by being provided with.
With a semiconductor light source
A lighting circuit that can adjust the amount of light from the semiconductor light source in multiple gradations by pulse modulation.
Equipped with
The lighting circuit is
A series switch provided in series with the semiconductor light source,
It is connected to the series connection circuit of the series switch and the semiconductor light source, (i) outputs a constant current during the on period of the series switch, (ii) stops the switching operation during the off period of the series switch, and turns on immediately before. With a buck converter that maintains substantially the same output voltage as the period,
A driver circuit that drives the series switch based on a pulse-modulated pulse dimming signal,
An abnormality detection circuit that determines that the series switch is abnormal when the output voltage of the buck converter deviates from the normal range during the off period of the series switch.
A vehicle lighting fixture characterized by being equipped with.
24. The vehicle according to claim 24, wherein the abnormality detection circuit is characterized in that the output voltage of the buck converter is below a predetermined threshold value during the off period of the series switch, which is a condition for determining the abnormality. Lighting equipment.
The vehicle lamp according to claim 25, wherein the predetermined threshold value is higher than the lighting start voltage of the semiconductor light source and lower than the forward voltage when the semiconductor light source is lit.
Further, a scanning optical system for scanning the emitted light of the semiconductor light source is provided.
The pulse dimming signal is generated so that the series switch is turned off for a predetermined period of time at the scan-scan break.
The vehicle lamp according to claim 25 or 26, wherein the abnormality detection circuit detects an abnormality of the series switch based on the output voltage of the buck converter in the predetermined period.
The abnormality detection circuit is
If the output voltage falls below the threshold value in the predetermined period, a provisional determination state is set.
The vehicle lamp according to claim 27, wherein when the provisional determination state is established over a predetermined number of scans, the determination is made.
The abnormality detection circuit is
A comparison circuit that compares the output voltage of the buck converter with the threshold value and generates a detection signal that becomes a predetermined level when the output voltage of the buck converter is lower than the threshold value.
When the detection signal reaches the predetermined level in the predetermined period, the provisional determination state is set, and when the provisional determination state is established over the predetermined number of scans, the signal processing unit for the determination is performed.
28. The vehicle lighting fixture according to claim 28.
The vehicle lamp according to claim 24, wherein the abnormality detection circuit is characterized in that the output voltage of the buck converter is not constant as a condition for determining an abnormality.
The vehicle lamp according to claim 24, wherein the abnormality detection circuit is characterized in that the state in which the output voltage of the buck converter is switched is maintained for a predetermined determination time as a condition for abnormality determination.
The abnormality detection circuit is
A comparison circuit that compares the output voltage of the buck converter with the threshold value and generates a detection signal that becomes a predetermined level when the output voltage of the buck converter is lower than the threshold value.
When the state in which the detection signal is a pulse signal continues for a predetermined time, the signal processing unit that determines this as an abnormal state and
30 or 31 for a vehicle according to claim 30 or 31.
The abnormality detection circuit is
A comparison circuit that compares the output voltage of the buck converter with the threshold value and generates a detection signal that becomes a predetermined level when the output voltage of the buck converter is lower than the threshold value.
A signal processing unit that counts the number of times the detection signal has transitioned to the predetermined level and determines that it is in an abnormal state when the count value exceeds a predetermined threshold value.
30 or 31 for a vehicle according to claim 30 or 31.
The vehicle according to any one of claims 24 to 33, wherein the abnormality detection by the abnormality detection circuit is invalidated after the operation of the buck converter is started until the output voltage exceeds a predetermined voltage. Lighting equipment.
It is a lighting circuit that can adjust the amount of light of a semiconductor light source in multiple gradations by pulse modulation.
A series switch provided in series with the semiconductor light source,
It is connected to the series connection circuit of the series switch and the semiconductor light source, (i) outputs a constant current during the on period of the series switch, (ii) stops the switching operation during the off period of the series switch, and turns on immediately before. With a buck converter that maintains substantially the same output voltage as the period,
A driver circuit that drives the series switch based on a pulse-modulated pulse dimming signal,
An abnormality detection circuit that determines that the series switch is abnormal when the output voltage of the buck converter deviates from the normal range during the off period of the series switch.
A lighting circuit characterized by being provided with.
A scanning light source that includes a semiconductor light source, a motor, and a plurality of mirrors attached to the rotor of the motor at intervals from each other, and reflects and scans the emitted light of the semiconductor light source by the plurality of mirrors.
A lighting circuit that controls the drive current supplied to the semiconductor light source in synchronization with the scanning of the scanning light source and controls the amount of light of the semiconductor light source.
Equipped with
The lighting circuit turns off the semiconductor light source during a plurality of blank periods in which the optical axis of the semiconductor light source crosses the distance between the plurality of mirrors, and the distance between the plurality of mirrors is non-uniform. Light source for vehicles.
The optical axis of the semiconductor light source further includes a pulse dimming signal generation unit that generates an off-level pulse dimming signal in a section where the optical axis passes through the space between the plurality of mirrors.
The lighting circuit is
A series switch provided in series with the semiconductor light source,
It is connected to the series connection circuit of the series switch and the semiconductor light source, (i) outputs a constant current during the on period of the series switch, (ii) stops the switching operation during the off period of the series switch, and turns on immediately before. With a buck converter that maintains substantially the same output voltage as the period,
A driver circuit that drives the series switch based on the pulse dimming signal,
An abnormality detection circuit that determines that the series switch is abnormal when the output voltage of the buck converter deviates from the normal range in the longest blank period corresponding to the widest interval among the plurality of mirrors.
36. The vehicle lighting fixture according to claim 36.
The vehicle lamp according to claim 36 or 37, wherein the motor is a two-pole motor, and the lighting circuit detects a rotational position of the motor based on a hall signal.
Equipped with a microcontroller,
The vehicle according to any one of claims 36 to 38, wherein the microcontroller performs a predetermined process in the longest blank period corresponding to the widest spacing of the plurality of mirrors. Lighting equipment.
The vehicle lamp according to any one of claims 36 to 39, wherein the number of mirrors is two.