JP2018008656A - Lighting fixture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicular lighting fixture capable of properly dealing with light leakage abnormality.SOLUTION: A light source 10 includes a laser diode 12. A lighting circuit supplies a stabilized lamp current Ito the laser diode 12 in a normal state. An abnormality detector 40 detects one part of output light 24 of the light source 10, and when the abnormality of the output light 24 is detected, asserts an abnormality detection signal S1. A protection device 50, in response to the assertion of the abnormality detection signal S1, acts on the output light 24 of the light source 10, and lowers the density of light 25 emitted from a vehicular lighting fixture 1.SELECTED DRAWING: Figure 3

Description

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

  Conventionally, halogen lamps and HID (High Intensity Discharge) lamps have been mainstream as light sources for vehicle lamps, particularly headlamps, but in recent years, semiconductor light sources such as LEDs (light emitting diodes) have been used instead. Vehicle lamps are being developed.

  In order to further improve the visibility, a vehicular lamp provided with a laser diode (also referred to as a semiconductor laser) and a phosphor instead of an LED is disclosed (for example, see Patent Document 1). In the technique described in Patent Document 1, ultraviolet light, which is excitation light emitted from a laser diode, is irradiated to a phosphor. The phosphor receives white light and generates white light. The white light generated by the phosphor is irradiated in front of the lamp, thereby forming a predetermined light distribution pattern. In the technique described in Patent Document 1, excitation light is not irradiated in front of the vehicle.

  FIG. 1 is a cross-sectional view of a light source of a vehicular lamp studied by the present inventor. The light source 10 mainly includes a laser diode 12, a phosphor 14, an optical system 16, and a housing 18. The light source 10 is common to the technique of Patent Document 1 in that it includes a laser diode 12 and a phosphor 14.

  The laser diode 12 in FIG. 1 generates blue excitation light 20 instead of ultraviolet light. The excitation light 20 is collected on the phosphor 14 by the optical system 16. The optical system 16 is configured by a lens, a reflecting mirror, an optical fiber, or a combination thereof. The phosphor 14 that has received the blue excitation light 20 generates fluorescence 22 having a spectral distribution in a longer wavelength region (green to red) than the excitation light 20. The excitation light 20 applied to the phosphor 14 is scattered by the phosphor 14 and passes through the phosphor 14 in a state where coherence is lost. For example, the phosphor 14 is supported by being fitted into an opening provided in the housing 18.

  FIG. 2 is a diagram illustrating a spectrum of the output light 24 of the light source 10. The output light 24 of the light source 10 includes blue excitation light 20a that has passed through the phosphor 14 and green to red fluorescence 22 emitted from the phosphor 14, and has a spectral distribution of white light.

  That is, in the light source of Patent Document 1, excitation light that is ultraviolet light is not used as part of the emitted light that irradiates the front of the vehicle, whereas in the light source 10 of FIG. It is used as a part of the emitted light from the lighting.

  As a result of studying the light source 10 of FIG. 1, the present inventor has recognized the following problems. In the light source 10 of FIG. 1, when an abnormality such as the phosphor 14 is broken or the phosphor 14 is detached from the housing 18, the excitation light 20 generated by the laser diode 12 is strong without being scattered by the phosphor 14. It is emitted directly with coherence, which is undesirable.

JP 2004-241142 A International Publication No. 10/070720 Pamphlet

  In order to solve this problem, the present inventor examined the following comparative techniques. In this comparison technique, the leakage of the excitation light 20 is detected by an optical sensor or the like. When light leakage is detected, the supply of the lamp current to the light source 10 is stopped and the light emission is stopped. This comparison technique should not be recognized as a known technique.

  This is not preferable because light emission from the light source 10 stops when light leakage is erroneously detected due to noise or the like. This problem can be solved by adding a correction that stops the supply of the lamp current and stops the light emission when the light leakage state is detected for a predetermined time (determination time). However, with this correction, the excitation light 20 is emitted during the determination time even in a situation where light leakage is actually occurring.

  The white light from the light source 10 may be reflected by a reflector and radiated forward of the vehicle. In such a lamp, when light leakage occurs, the non-scattering excitation light 20 is concentrated on a part of the reflector. Therefore, if an opening is provided in a part of the reflector, light leakage can be prevented from being reflected forward of the vehicle. However, this opening is lost during normal operation, and the luminance is lowered.

  The present invention has been made in such a situation, and one of exemplary purposes of an embodiment thereof is to provide a lamp that can appropriately cope with a light leakage abnormality.

  One embodiment of the present invention relates to a lamp. The lamp includes a light source including a light emitting element, a lighting circuit that supplies a stabilized lamp current to the light emitting element, an abnormality detector that asserts an abnormality detection signal when an abnormality in output light of the light source is detected, and an abnormality detection signal And a protective device that acts on the output light of the light source and reduces the density of the light emitted from the lamp in response to the assertion of.

  According to this aspect, when an abnormality occurs, it is possible to prevent the light emitted from the light source from being directly irradiated to the front of the vehicle.

  In addition to the light emitting element, which is a laser diode that emits excitation light, the light source includes a phosphor that emits fluorescence when excited by the excitation light, and is configured to generate white output light including the excitation light and the fluorescence spectrum. The abnormality detector may detect light leakage abnormality of the light source.

  The protection device may insert the protection member on the optical path of the output light in response to the assertion of the abnormality detection signal.

  The protective member may diffuse the output light of the light source. The protective member may be a diffusing lens or a diffusing plate. The protective member may also have a function of diffusing the output light of the lamp when the vehicle travels on a curve.

  The protective member may attenuate the output light of the light source. The protective member may absorb or reflect a part of the output light of the light source.

  The protective member may have an electro-optic effect that can electrically control polarization and refractive index. The protective member may include a translucent piezoelectric ceramic (PLZT) or a liquid crystal device.

  The protection device may include a solenoid actuator that displaces the protection member. The solenoid actuator may include a solenoid and a drive circuit that drives the solenoid by chopper. The drive circuit may include a signal generator that generates a pulsed solenoid drive signal and a transistor that switches according to the solenoid drive signal.

The drive circuit may further include an abnormality determination circuit that monitors a switching node where a pulse signal should be generated during transistor switching, and detects an abnormality based on the signal of the switching node and the solenoid drive signal.
If an abnormality occurs in the wiring, terminals, harness, etc. between the drive circuit and the solenoid, and a DC voltage is applied to the solenoid, the current flowing through the solenoid increases, causing overheating, etc. By detecting such an abnormality, the reliability can be improved.

  The abnormality determination circuit may include a coincidence circuit that determines whether or not the logic values of the switching node signal and the solenoid drive signal match, and may determine whether there is an abnormality based on the output of the coincidence circuit.

  The drive circuit may further include an abnormality determination circuit that monitors a switching node where a pulse signal should be generated during transistor switching, and determines that an abnormality occurs when no pulse signal is generated at the switching node. Since abnormality can be detected by the abnormality determination circuit, reliability can be improved.

In addition, or alternatively, the abnormality determination circuit may determine that an abnormality occurs when a pulse signal having a period longer than a predetermined period is generated in the switching node.
If an abnormality occurs in the signal generator and the period of the solenoid drive signal becomes longer, the solenoid will be driven at a higher duty ratio than in the normal state, causing heat generation, etc. Therefore, reliability can be improved.

  The drive circuit monitors a switching node where a pulse signal should be generated during switching of the transistor, and determines an abnormality when the duty cycle (duty ratio) of the pulse signal generated at the switching node is higher than a threshold value A determination circuit may be further included.

  The threshold value may change according to at least one of the power supply voltage and the solenoid temperature.

  The abnormality determination circuit smoothes the voltage of the switching node and generates a duty cycle detection voltage proportional to the duty cycle, a voltage source that generates a threshold voltage, and the duty cycle detection voltage as a threshold voltage. A comparator for comparison.

  The voltage source may decrease the threshold voltage according to the power supply voltage. The voltage source may decrease the threshold voltage depending on the temperature.

  The voltage source may include a resistance voltage dividing circuit and a variable current source connected in parallel with the lower resistance of the resistance voltage dividing circuit.

  The drive circuit may further include a switch that cuts off a current flowing through the solenoid when the abnormality determination circuit detects an abnormality. Thereby, the solenoid and the transistor can be protected.

  According to an aspect of the present invention, it is possible to appropriately cope with a light source abnormality.

It is sectional drawing of the light source of the vehicle lamp which this inventor examined. It is a figure which shows the spectrum of the output light of a light source. It is a block diagram of the vehicular lamp which concerns on embodiment. It is an operation | movement waveform diagram of the vehicle lamp of FIG. It is a circuit diagram of the solenoid actuator which concerns on a 1st structural example. 6A and 6B are operation waveform diagrams of the solenoid actuator of FIG. It is a circuit diagram of the solenoid actuator which concerns on a 2nd structural example. 8A and 8B are operation waveform diagrams of the abnormality determination circuit of FIG. It is a circuit diagram of the solenoid actuator which concerns on a 3rd structural example. FIG. 10 is a circuit diagram illustrating a configuration example of the duty cycle comparator of FIG. 9. FIG. 10 is a circuit diagram showing a modification of the duty cycle comparator of FIG. 9. FIG. 12 is a circuit diagram illustrating a specific configuration example of the duty cycle comparator of FIG. 11. FIG. 12 is a circuit diagram showing another modification of the duty cycle comparator of FIG. 11. It is a perspective view of a lamp unit provided with the vehicular lamp concerning an embodiment.

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

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

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

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

  FIG. 3 is a block diagram of the vehicular lamp 1 according to the embodiment. The vehicular lamp 1 includes a light source 10, a lighting circuit 30, an abnormality detector 40, and a protection device 50.

  As shown in FIG. 1, the light source 10 includes a laser diode 12 that is a light emitting element that emits excitation light 20, and a phosphor 14 that emits fluorescence when excited by the excitation light 20, and includes the excitation light 20 and fluorescence. The white output light 24 including the spectrum is generated.

The lighting circuit 30 supplies a stabilized drive current (lamp current I _LAMP ) to the laser diode 12 of the light source 10. The lighting circuit 30 includes a switching converter 32 and a converter controller 34. The switching converter 32 is, for example, a step-down converter, and steps down a voltage V _BAT from a power source such as a battery (not shown) and supplies it to the light source 10. Converter controller 34 controls switching converter 32 such that lamp current I _LAMP approaches a predetermined target value. The converter controller 34 may be a PWM or PFM controller including an error amplifier, or may be a Bang-Bang control controller.

  The abnormality detector 40 detects a part of the output light 24 of the light source 10 and, when detecting the abnormality of the output light 24, asserts the abnormality detection signal S1 (for example, high level). In the present embodiment, the abnormality detector 40 determines light leakage abnormality caused by the abnormality of the phosphor 14. Examples of the abnormality of the phosphor 14 include, but are not limited to, cracking, detachment, and aging deterioration of the phosphor 14. The abnormality detector 40 may detect a light leakage abnormality based on the ratio of the light amount of the excitation light 20 and the light amount of the fluorescence 22 included in the output light 24. Specifically, when the ratio of the excitation light to the fluorescence becomes higher than a predetermined value, it can be determined that the light leakage is abnormal.

For the anomaly detector 40, the technique described in Japanese Patent Application Laid-Open No. 2006-058370 may be used. For example, the abnormality detector 40 includes a first photosensor 42_1, a second photosensor 42_2, and a determination unit 44. The first photosensor 42_1 is sensitive to the wavelength of the excitation light 20 and is substantially insensitive to the wavelength of the fluorescence 22. First photo sensor 42_1 receives a portion of the output light 24, to generate a first current _{I SC1} corresponding to the intensity of the excitation light 20 that has passed through the phosphor 14. On the other hand, the second photosensor 42_2 is sensitive to the wavelength of the fluorescence 22 and is substantially insensitive to the wavelength of the excitation light 20. Second photosensor 42_2 receives a portion of the output light 24, to generate a second current _{I SC2} corresponding to the intensity of the fluorescence 22 phosphor 14 emits.

The determination unit 44 determines the presence / absence of light leakage abnormality based on the relative relationship (for example, ratio) between the first current I _SC1 and the second current I _SC2 . When the light source 10 is normal, the ratio of the first current I _SC1 and the second current I _SC2 is included in a certain normal range. However, when the leakage light abnormality occurs, the first current I _SC1 becomes relatively large. The ratio deviates from the normal range.

Although the configuration and processing of the determination unit 44 are not particularly limited, for example, the following processing may be performed. The first current I _SC1 is converted to the first detection voltage V ₁ with the first gain α ₁ , and the second current I _SC2 is converted to the second detection voltage V ₂ with the second gain α ₂ . The first compares the detection voltages _{V 1} and the second detection voltage _{V 2,} <normal when _{V 2,} V 1> V 1 may be determined to be abnormal when the _{V 2.}

  The vehicular lamp 1 may include a reflector 26 that reflects the output light 24 of the light source 10. The reflector 26 is provided with an opening (or slit) 28, and the light detection element 42 of the abnormality detector 40 is provided on the back surface of the reflector 26. The light detection element 42 determines whether there is an abnormality in the light source 10 based on the light that has passed through the opening 28.

  The opening 28 is desirably provided at a location where the non-scattering excitation light 20 is concentrated in the reflector 26 when light leakage occurs. Thereby, when the light source 10 is abnormal, the non-scattering excitation light 20 can be prevented from being reflected forward of the vehicle. That is, the aperture 28 has both a function of extracting a part of the output light 24 for abnormality detection and a function of removing the non-scattering excitation light 20 at the time of abnormality.

  The vehicular lamp 1 may include other optical systems instead of or in addition to the reflector 26.

  In response to the assertion of the abnormality detection signal S1, the protection device 50 acts on the output light 24 of the light source 10, and reduces the density of the light (emitted light) 25 emitted from the vehicular lamp 1. The density of the emitted light 25 can be grasped as energy per unit solid angle, or can be grasped as energy per unit area (irradiation intensity) in the irradiation region.

  For example, the protection device 50 includes a protection member 52 and an actuator 54. The protection member 52 is attached to the actuator 54, and its position or posture can be controlled. In response to the assertion of the abnormality detection signal S1, the actuator 54 of the protection device 50 displaces the protection member 52 and mechanically inserts it in the optical path of the output light 24 of the light source 10. For example, the protection member 52 may diffuse the output light 24 of the light source 10. The protection member 52 may be a diffusion plate or a diffusion lens.

  The outgoing light 25 indicated by a solid line in FIG. 3 indicates a normal optical path, and the outgoing light 25 ′ indicated by a one-dot chain line indicates an abnormal optical path.

Further, the lighting circuit 30 reduces the lamp current I _LAMP when the abnormality detection signal S1 is asserted for a predetermined determination time τ. The lamp current I _LAMP after the decrease may be zero, or may be a current amount that does not dazzle the person in front of the vehicle. Thereby, it is possible to prevent the light source 10 from continuing to emit strong light in an abnormal state.

The above is the basic configuration of the vehicular lamp 1. Next, the operation will be described. FIG. 4 is an operation waveform diagram of the vehicular lamp 1 of FIG. Prior to time t0, the lighting circuit 30 is normal, and the lamp current I _LAMP is stabilized at the normal target value I _{LAMP (REF)} .

  At time t0, a laser leakage abnormality occurs in the light source 10. As a result, the balance between the laser light and the fluorescence contained in the output light 24 of the light source 10 is lost. The abnormality detector 40 detects the abnormality of the light source 10 based on the ratio of the laser light and the fluorescence, and asserts the abnormality detection signal S1.

  When the abnormality detection signal S <b> 1 is asserted, the protection device 50 immediately inserts the protection member 52 into the optical path of the output light 24. Thereby, the emitted light 25 from the vehicular lamp 1 is diffused, and the density of the emitted light 25 decreases.

When assertion of the abnormality detection signal S1 continues for the determination time τ, the lamp current I _LAMP decreases at time t1, and the density of the emitted light 25 further decreases.

  The operation of the vehicular lamp 1 has been described above. According to the vehicular lamp 1, the energy density per prescribed solid angle in the irradiation direction can be reduced by the protection device 50 when the light source 10 is abnormal, so that safety can be improved.

Further, since the safety immediately after the occurrence of an abnormality is secured by the protection device 50, it is not necessary to shorten the determination time τ until the converter controller 34 decreases the lamp current I _LAMP more than necessary. Thereby, when the abnormality detection signal S1 is erroneously asserted due to noise, it is possible to prevent the lamp current I _LAMP from decreasing and the luminance from decreasing.

  In addition, since the safety immediately after the occurrence of the abnormality is secured by the protective device 50, the opening 28 provided in the reflector 26 can be made small. As a result, loss during normal operation can be reduced.

  Next, a specific configuration example of the protection device 50 will be described. The protection device 50 preferably reduces the density of the emitted light 25 in as short a time as possible in response to the assertion of the abnormality detection signal S1, and thus the actuator 54 is required to operate at high speed. Further, when the protective member 52 is a lens or a diffusion plate, the weight of the protective member 52 is increased, and thus a large output is required for the actuator 54. In order to satisfy such a requirement, a solenoid actuator can be used as the actuator 54.

  FIG. 5 is a circuit diagram of the solenoid actuator 60 according to the first configuration example. The solenoid actuator 60 includes a solenoid 62 and a drive circuit 64. The drive circuit 64 includes a signal generator 66, a gate driver 68, and a transistor M11. The signal generator 66 generates a pulsed solenoid drive signal S2 in response to the assertion of the abnormality detection signal S1. The gate driver 68 drives the transistor M11 according to the solenoid drive signal S2. A rectifier diode D11 is provided in parallel with the solenoid 62.

  If an abnormality occurs in the drive circuit 64 itself, the wiring connecting the solenoid 62 and the drive circuit 64, a harness, a terminal, or the like, the chopping control of the drive current flowing through the solenoid 62 cannot be performed. Due to such an abnormality, when a DC voltage is constantly applied to the solenoid 62, the current flowing through the solenoid 62 increases, which may cause heat generation due to overcurrent. In order to detect such an abnormality, the drive circuit 64 further includes an abnormality determination circuit 70. Examples of the abnormality include a power line (power supply short circuit) of the line connecting the solenoid 62 and the transistor M11, a short circuit failure of the transistor M11, a failure of the gate driver 68, and the like.

If the drive circuit 64 is normal, the transistor M11 switches according to the solenoid drive signal S2, and a pulse signal synchronized with the solenoid drive signal S2 is generated at the switching node N1. On the other hand, if an abnormality occurs in the drive circuit 64 or wiring, the potential of the switching node N1 becomes constant or indefinite, and the correlation with the solenoid drive signal S2 is lost. Therefore, the abnormality determination circuit 70 monitors the switching node N1 where a pulse signal should be generated during switching of the transistor M11, and detects an abnormality based on the signal V _N1 of the switching node _N1 and the solenoid drive signal S2.

For example, the abnormality determination circuit 70 includes a matching circuit 72 that determines whether the logical value of the signal V _N1 of the switching node N1 and the solenoid drive signal S2 matches or does not match. Based on the output (match signal) S3 of the matching circuit 72 The presence or absence may be determined. Abnormality determination circuit 70, instead of the solenoid drive signal S2, may monitor the gate signal V _G of the transistor M11.

  The coincidence circuit 72 may be an XOR (exclusive OR) gate or an XNOR (Negative Exclusive OR) gate. When the solenoid actuator 60 is normal, the coincidence signal S3 takes a logical value (for example, 1) indicating coincidence. When an abnormality occurs in the solenoid actuator 60, the coincidence signal S3 becomes a logical level (for example, 0) indicating disagreement. Or it becomes a pulse signal which repeats 1 and 0. The latch 74 latches when the match signal S3 transitions to a logical value indicating a mismatch.

  Thus, according to the abnormality determination circuit 70, abnormality of the solenoid actuator 60 can be detected. For example, when an abnormality is detected by the abnormality determination circuit 70, the vehicle lamp 1 may notify an ECU (Electronic Control Unit) on the vehicle side.

  Further, when an abnormality is detected by the abnormality determination circuit 70, the drive circuit 64 preferably stops energization of the solenoid 62, and specifically fixes the transistor M11 to be off. The drive circuit 64 may further include a switch M12 provided in a path through which a current flowing through the solenoid 62 passes. When the abnormality determination circuit 70 detects an abnormality, the abnormality determination circuit 70 turns off the switch M12 and interrupts the current flowing through the solenoid 62. As a result, even when the transistor M11 is short-circuited or when the node N1 has a power fault, the current path can be cut off and the reliability can be improved.

  The switch M12 may be inserted in series with the solenoid 62 on a parallel path with the diode D11.

6A and 6B are operation waveform diagrams of the solenoid actuator 60 of FIG. FIG. 6A shows the operation when the solenoid actuator 60 is normal. Since the transistor M11 switches according to the solenoid drive signal S2, the voltage V _{N1 of the} node N1 becomes a pulse signal synchronized with the solenoid drive signal S2, and the coincidence signal S3 becomes a constant value indicating coincidence.

FIG. 6B shows the operation when the solenoid actuator 60 is abnormal. For example, when the node N1 has a power fault, the voltage V _N1 becomes the power supply voltage V _DD (high level). At this time, the coincidence signal S3 is a pulse signal that alternately repeats coincidence and mismatch.

As described above, according to the abnormality determination circuit 70 of FIG. 3, the abnormality can be detected based on the solenoid drive signal S2 and the voltage V _N1 of the switching node N1.

As a modification, the abnormality determination circuit 70 may compare the gate signal V _G of the transistor M11 and the voltage V _N1 of the switching node N1. In this case, when the solenoid actuator 60 is normal, the gate signal V _G and the voltage V _N1 are inverted logic. Therefore, when the solenoid actuator 60 is normal, the coincidence signal S3 is a constant value indicating mismatch, and when the solenoid actuator 60 is abnormal, the coincidence signal S3 is a pulse signal alternately indicating mismatch and coincidence.

Note that the transition timing of the solenoid drive signal S2 (or gate signal V _G ) and the voltage V _N1 of the switching node N1 may be shifted due to a delay. Are superimposed. Accordingly, the latch 74 is preferably configured not to respond to short pulses.

FIG. 7 is a circuit diagram of the solenoid actuator 60a according to the second configuration example. The abnormality determination circuit 70a includes a pulse detector 76 instead of the coincidence circuit 72 of the abnormality determination circuit 70 of FIG. The pulse detector 76 monitors the switching node N1 and determines whether or not a pulse signal is generated at the switching node N1. For example, the pulse detector 76 monitors whether the positive edge (or negative edge) of the signal V _N1 is repeatedly and continuously generated.

Although not limited thereto, the pulse detector 76 can be constituted by a re-triggerable one-shot multivibrator circuit (monostable circuit). The pulse detector 76 generates a signal S4 that is at the first level for a predetermined time Tb from the positive edge of the signal V _{N1 at} the switching node and then returns to the second level. It is desirable that the predetermined time Tb is defined to be longer than the period Ta of the solenoid drive signal S2 and shorter than the time Tc at which the heat generation of the solenoid 62 becomes a problem.
Ta <Tb <Tc

FIG. 8A is an operation waveform diagram of the abnormality determination circuit 70a of FIG. A normal state is indicated before time t0. In a normal state, the voltage V _N1 of the switching node N1 switches with a period Ta. The output S4 of the one-shot multivibrator circuit that is the pulse detector 76 is repeatedly triggered by the voltage V _N1 in a normal state, and maintains a level (high level) indicating an unstable state.

When an abnormality occurs at time t0, the voltage V _N1 becomes a constant voltage. Then, the pulse detector 76 is not triggered, transitions to a level (low level) indicating a stable state after the elapse of time Tb from the last positive edge of the voltage V _N1 , and then maintains the low level.

Thus, according to the abnormality determination circuit 70a of FIG. 7, an abnormality can be detected based on the voltage V _N1 of the switching node N1.

The abnormality determination circuit 70a in FIG. 7 can determine that an abnormality has occurred in the switching node N1 when the pulse signal V _N1 having a period Td longer than the predetermined period Tb is generated. Accordingly, it is possible to detect a case where there is an abnormality in the cycle or duty ratio of the solenoid drive signal S2 generated by the signal generator 66. FIG. 8B is a diagram for explaining detection of the solenoid drive signal S2. The solenoid drive signal S2 is normal before time t0, and the cycle becomes longer at time t0. Then, since the output S4 of the one-shot multivibrator circuit periodically becomes a low level at the same cycle as the solenoid drive signal S2, an abnormal state can be detected.

FIG. 9 is a circuit diagram of a solenoid actuator 60b according to a third configuration example. Depending on the failure mode of the solenoid actuator, a situation may occur in which the duty cycle of the pulse signal V _N1 becomes larger than the normal set value. Therefore, the abnormality determination circuit 70b includes a duty cycle comparator 78 instead of the pulse detector 76 of FIG. Duty cycle comparator 78 determines that solenoid actuator 60b is abnormal when the duty cycle of pulse signal V _N1 generated at switching node N1 is higher than a threshold value.

FIG. 10 is a circuit diagram showing a configuration example of the duty cycle comparator 78 of FIG. The duty cycle comparator 78 c includes a comparator 80, a smoothing circuit 82, and a voltage source 84. The smoothing circuit 82 smoothes the voltage V _N1 of the switching node N1. When the duty cycle of the voltage V _N1 is d _SW and the amplitude is V _DD , the output voltage of the smoothing circuit 82 is
Vx = V _DD × d _SW
And is proportional to the duty cycle d _SW .

The voltage source 84 generates a threshold voltage _VTH . For example, the voltage source 84 may include resistors R21 and R22, and the threshold voltage _VTH may be generated by resistance-dividing the power supply voltage _VDD . When the partial pressure ratio and _{d TH,} the threshold voltage _{V TH} is,
V _TH = V _DD × d _TH
It becomes.

The comparator 80 compares the voltage Vx with the threshold voltage _VTH and outputs a comparison signal S5 indicating the comparison result. For example comparison signal S5, when _{Vx> V TH,} a high level when the _{d SW> d TH} other words. In other words, the duty cycle comparator 78a can detect that the duty cycle of the voltage V _N1 exceeds the threshold value.

FIG. 11 is a circuit diagram showing a modification of the duty cycle comparator 78 of FIG. The smoothing circuit 82d generates a duty cycle detection voltage Vy that is proportional to the duty cycle d _SW of the voltage V _N1 and does not depend on the power supply voltage V _DD .
Vy = V _REG × d _SW

For example, the smoothing circuit 82 d may be configured by a combination of a buffer (or inverter) 90 that uses the constant voltage V _REG as a power source and a low-pass filter 92.

Voltage source 84d generates a variable threshold voltage _{V TH.} For example, it is desirable that threshold voltage V _TH decreases according to power supply voltage V _DD . When the solenoid 62 has a direct current resistance (parasitic resistance) R _DC , the power consumption P is expressed by Equation (6), and increases as the duty cycle d _SW increases.
P = V _DD ² / R _DC × d _SW

Therefore, when the threshold value d _TH of the duty cycle d _SW is lowered so as to be inversely proportional to the square of the power supply voltage V _DD , the solenoid 62 is configured so that the power consumption P of the solenoid 62 does not exceed the threshold value P _TH. The actuator 60d can be operated. That is, in a situation where the power supply voltage V _DD is low, the operation of the solenoid actuator 60 can be continued as much as possible by increasing the threshold value d _TH .

Note threshold d _SW is completely without need is inversely proportional to the square of the power supply voltage V _DD, it may be changed to approximate to it, may be inversely proportional to the supply voltage V _DD. Alternatively, the threshold value d _TH may decrease linearly with respect to the power supply voltage V _DD or its square V _DD ² .

For example, the voltage source 84 d includes a voltage dividing circuit 94 and a variable current source 96. The voltage dividing circuit 94 divides the constant voltage V _REG . The variable current source 96 generates a correction current I _ADJ that increases according to the power supply voltage V _DD .
V _TH = V _REG −R21 × I _R21 (1)
I _R21 = I _R22 + I _ADJ = (V _TH / R22 + I _ADJ ) (2)
Substituting equation (2) into equation (1) yields equation (3).
V _TH = V _REG −R21 × (V _TH / R22 + I _ADJ ) (3)
Solving this for V _TH yields equation (4).
V _TH = R22 / (R21 + R22) × (V _REG −R ₂₁ × I _ADJ ) (4)
When R22 / (R21 + R22) × V _REG is written as a threshold value V _TH0 when I _ADJ = 0, Expression (5) is obtained.
_{V TH = V TH0 -R21 × R22} / (R21 + R22) × I ADJ ... (5)
That is, the threshold value V _TH can be lowered as I _ADJ increases. As described above, the correction current _{I ADJ,} by a function of the supply voltage _{V DD,} as the power supply voltage _{V DD} is high, the threshold voltage _{V TH,} it is possible to reduce the turn threshold _{d TH.}

In FIG. 11, the variable current source 96 is connected in parallel with the lower resistor R22 of the voltage dividing circuit 94. However, the variable current source 96 is connected in parallel with the upper resistor R21 so as to source the correction current I _ADJ to the resistor R22. It may be configured. The variable current source 96 may be a variable resistor whose resistance value changes according to the power supply voltage.

  FIG. 12 is a circuit diagram showing a specific configuration example of the duty cycle comparator 78d of FIG. The smoothing circuit 82d includes a buffer 90 and a low-pass filter 92. The low-pass filter 92 is formed integrally with the output stage of the buffer 90.

The variable current source 96 is a square approximation current source of the power supply voltage V _DD . The configuration of the voltage source 84d is not particularly limited, and may be configured with a translinear circuit, for example.

FIG. 13 is a circuit diagram showing another modification of the duty cycle comparator 78 of FIG. In this modification, the variable current source 96e generates a correction current I _ADJ that increases as the temperature rises. The variable current source 96e can also be understood as a V / I conversion circuit that converts the temperature detection signal S6 having a positive correlation with the temperature into the correction current I _ADJ . In the configuration of FIG. 13, the threshold value d _TH can be lowered substantially linearly with respect to the increase in the temperature detection signal S6.

According to the duty cycle comparator 78e of Figure 13, the temperature is low status, can be continued by increasing the threshold value d _TH, as far as possible the operation of the solenoid actuator 60.

  Finally, the use of the vehicular lamp 1 will be described. FIG. 14 is a perspective view of a lamp unit (lamp assembly) 500 including the vehicular lamp 1 according to the embodiment. The lamp unit 500 includes a transparent cover 502, a high beam unit 504, a low beam unit 506, and a housing 508. The vehicle lamp 1 described above can be used for the high beam unit 504, for example. The vehicular lamp 1 includes one or a plurality of light sources 10. Instead of or in addition to the high beam unit 504, the vehicular lamp 1 may be used for the low beam unit 506.

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

  The protection member 52 may attenuate the output light of the light source 10. The protection member 52 may absorb or reflect a part of the output light 24 of the light source 10.

  In FIG. 3, the configuration in which the protection device 50 includes the actuator 54 and moves the protection member 52 has been described, but the configuration is not limited thereto. For example, the protection member 52 may be fixed on the optical path of the output light 24. In this case, the protection member 52 may be configured by a combination of a material having an electro-optic effect capable of electrically controlling polarization and refractive index and other optical elements (other lenses, mirrors, polarizing plates, etc.). . Examples of such materials include, but are not limited to, translucent piezoelectric ceramics (PLZT) and liquid crystal devices. At the time of abnormality, the emitted light 25 of the vehicular lamp 1 can be diffused by changing the polarization and refractive index of the protection member 52.

  The protective member 52 is not limited to a transmissive device, and may be a reflective device. For example, the protection member 52 may be a MEMS mirror.

  The abnormality determination method by the determination part 44 is not limited. For example, the determination unit 44 may detect an abnormality of the light source 10 based on the intensity of the excitation light incident on the opening 28 based on the output of the light detection element 42_1.

  The present invention is suitable for a vehicular lamp, particularly a headlamp, but its application is not limited. For example, the present invention can be used for a vehicle-mounted lamp and a light source for road surface drawing. Furthermore, the present invention can be used for a moving means other than a vehicle, and further can be used for a lamp other than the moving means.

  In the embodiment, the abnormality of the light source 10 in FIG. 1 is taken as an example, but the present invention is not limited to this. For example, in a light source that generates white light by mixing two or three colors of laser light or LED light, at least one color of laser light (or LED light) increases beyond an allowable value. Is valid. The light emitted from the light source 10 is not limited to white, and may be monochromatic light.

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

DESCRIPTION OF SYMBOLS 1 ... Vehicle lamp, 10 ... Light source, 12 ... Laser diode, 20 ... Excitation light, 22 ... Fluorescence, 24 ... Output light, 25 ... Output light, 26 ... Reflector, 28 ... Opening, 30 ... Lighting circuit, 32 ... Switching Converter, 34 ... Converter controller, 40 ... Abnormality detector, 42 ... Photodetection element, 44 ... Determination unit, 50 ... Protection device, 52 ... Protection member, 54 ... Actuator, 60 ... Solenoid actuator, 62 ... Solenoid, M11 ... Transistor 64 ... Drive circuit, 66 ... Signal generator, 70 ... Abnormality judgment circuit, 72 ... Match circuit, 74 ... Latch, 76 ... Pulse detector, 78 ... Duty cycle comparator, 80 ... Comparator, 82 ... Smoothing circuit, 84 ... Voltage source, 90 ... Buffer, 92 ... Low pass filter, 94 ... Voltage divider, 96 ... Variable current source, S1 ... Abnormality detection signal S2 ... solenoid drive signal, 500 ... lamp unit, 502 ... cover, 504 ... high beam unit, 506 ... low-beam unit, 508 ... housing.

Claims (10)

A lamp,
A light source including a light emitting element;
A lighting circuit for supplying a stabilized lamp current to the light emitting element in a normal state;
When detecting an abnormality of the output light of the light source, an abnormality detector that asserts an abnormality detection signal;
A protective device that acts on the output light of the light source in response to the assertion of the abnormality detection signal, and reduces the density of light emitted from the lamp;
A lamp characterized by comprising. The light source includes a phosphor that emits fluorescence when excited by the excitation light, in addition to the light emitting element that is a laser diode that emits excitation light, and emits white output light including the excitation light and the fluorescence spectrum. Configured to generate,
The lamp according to claim 1, wherein the abnormality detector detects a light leakage abnormality of the light source.   The lamp according to claim 1, wherein the protection device inserts a protection member on the optical path of the output light in response to the assertion of the abnormality detection signal.   The lamp according to claim 3, wherein the protection member diffuses output light of the light source. The protection device includes a solenoid actuator that displaces the protection member;
The solenoid actuator is
A solenoid,
A drive circuit for chopper-driving the solenoid;
Including
The drive circuit is
A signal generator for generating a solenoid driving signal for chopping driving the solenoid of the solenoid actuator;
A transistor that switches according to the solenoid drive signal;
The lamp according to claim 3 or 4, characterized by comprising:   The drive circuit further includes an abnormality determination circuit that monitors a switching node where a pulse signal should be generated during switching of the transistor and detects an abnormality based on the signal of the switching node and the solenoid drive signal. The lamp according to claim 5.   The abnormality determination circuit includes a matching circuit that determines whether the switching node signal and the logic value of the solenoid drive signal match or not, and determines abnormality based on an output of the matching circuit. 6. The lamp according to 6. The driving circuit monitors a switching node where a pulse signal should be generated during switching of the transistor,
(I) No pulse signal is generated at the switching node,
(Ii) the generation of a pulse signal with a period longer than a predetermined period;
(Iii) the duty cycle of the pulse signal generated at the switching node is greater than a threshold value;
The lamp according to claim 5, further comprising an abnormality determination circuit that uses at least one of the conditions as an abnormality determination condition.   The lamp according to claim 8, wherein the threshold value of (iii) changes according to at least one of a power supply voltage and a temperature of the solenoid.   The lamp according to any one of claims 6 to 9, wherein the drive circuit further includes a switch that cuts off a current flowing through the solenoid when the abnormality determination circuit detects an abnormality.

Images