JP6425983B2 - Lighting circuit, vehicle lamp - Google Patents

Description

  The present invention relates to a vehicle lamp used for a car or the like.

  Conventionally, halogen lamps and HID (High Intensity Discharge) lamps have mainly been used as light sources for vehicle lamps, especially headlights, but in recent years semiconductor light sources such as LEDs (light emitting diodes) have been used instead of them. Development of vehicle lamps is underway.

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

  In another light source, the laser diode generates blue excitation light instead of ultraviolet light. The phosphor receiving blue excitation light generates fluorescence having a spectral distribution in a wavelength range (green to red) longer than the excitation light. The excitation light irradiated to the phosphor is scattered by the phosphor and passes through the phosphor with a loss of coherence. The phosphor outputs white light containing scattered blue light and green to red fluorescence.

  For example, a laser light source is used as an additional high beam that illuminates further than the high beam. FIG. 1 is a block diagram of a lamp system 1200 with an additional high beam. The left and right lamps (vehicle lamps) 1300L, 1300R are similarly configured.

  The vehicular lamp 1300 includes a semiconductor light source (laser diode) 302, a lamp ECU 310, and a lighting circuit 320. The lamp ECU 310 is connected to the vehicle ECU 202 via a bus 203 such as a controller area network (CAN) or a local interconnect network (LIN).

The power supply of the high beam lighting circuit (not shown) and the power supply of the additional high beam lighting circuit 320 are shared. Switch 312 of lamp ECU 310 is provided on a supply path of battery voltage V _BAT from battery 204 to lighting circuit 320. A CPU (Central Processing Unit) 314 controls on / off of the switch 312 based on a command from the vehicle ECU 202, vehicle speed information, etc., and controls turning on / off of the high beam and the additional high beam.

  In order to produce a sense of luxury, it is desirable that the light quantity of the additional high beam be gradually increased or decreased with time. This is called gradual change lighting and gradual change off. The gradual change lighting can be realized by utilizing the gradual rise of the constant current converter 322 after the switch 312 is turned on. On the other hand, the output current of constant current converter 322 can not be gradually decreased only by turning off switch 312.

  Thus, the lighting circuit 320 is provided with a gradual change light-off circuit 324. The gradual change point on / off circuit 324 controls the constant current converter 322 based on the on / off instruction signal S1 from the CPU 314 to execute the gradual change lighting and the gradual change on / off.

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

  For example, it is assumed that the high level of the on / off instruction signal S1 is assigned to turn on the semiconductor light source 302 and the low level is assigned to turn off the semiconductor light source 302. At this time, if the signal line 304 through which the on / off instruction signal S1 propagates is shorted (shorted to the power supply line), the control of the on / off instruction signal S1 by the CPU 314 is disabled. The problem of dazzling surrounding vehicles arises. When the logic level of the on / off instruction signal S1 is switched, the signal line 304 can not be turned off when the semiconductor light source 302 should be turned off when the signal line 304 is grounded (shorted to the ground). Alternatively, depending on the output form of the on / off instruction signal S1 of the lamp ECU 310 and the reception form of the on / off instruction signal S1 of the gradual change point on / off circuit 324, the same problem may occur due to the disconnection of the signal line 304. Such a problem may occur regardless of the presence or absence of gradual change lighting and gradual change off. The same is true for the low beam and the high beam as well as the additional high beam.

  Here, switching on of the semiconductor light source 302 in two modes is considered. In this case, if one more control signal is output from the CPU 314 to the lighting circuit 320 in addition to the on / off instruction signal S1, one signal line is added, which results in cost increase and wiring increase. This leads to an increase in the probability of failure or failure.

  The present invention has been made in such a situation, and one of the exemplary objects of an aspect of the present invention is to control on / off and two modes with one signal line, and to transmit / off indication signal. It is an object of the present invention to provide a lighting circuit capable of extinguishing the semiconductor light source when an abnormality occurs in the signal line.

  One embodiment of the present invention relates to a lighting circuit that turns on or off a semiconductor light source in response to a lighting on / off instruction signal from a processor. The lighting on / off instruction signal has a pulse shape having a first duty ratio when instructing lighting in the first mode, and a pulse having a second duty ratio different from the first duty ratio when instructing lighting in the second mode. It is a constant level when instructing to turn off. The lighting circuit determines whether the lighting on / off instruction signal is in the form of a pulse, and determines the duty ratio of the lighting on / off instruction signal and a pulse input determination circuit that generates a lighting determination signal that is asserted when the lighting is on. The mode determination circuit generates a mode determination signal indicating the determination result, and when the lighting determination signal is asserted, the driving current is supplied to the semiconductor light source in the mode corresponding to the mode determination signal, and the lighting determination signal is negated. And driving circuit for stopping supply of driving current to the semiconductor light source.

The processor can not control the on / off instruction signal if an abnormality such as disconnection, short-circuit or ground fault occurs in the line transmitting the on / off instruction signal, but in any case, the on / off instruction signal has a constant level Maintained. Therefore, according to this aspect, the semiconductor light source can be turned off not only when the processor instructs to turn off but also when an abnormality occurs, and the safety can be enhanced.
Moreover, lighting and lighting and two modes can be controlled by one signal line.

  Note that "the on / off instruction signal is in the form of a pulse" means that the on / off instruction signal alternates between a predetermined potential and a high impedance state (Hi-Z) in addition to the state where the two different potentials alternate. Including the state. The phrase "the on / off instruction signal is at a constant level" includes a state in which the on / off instruction signal maintains a high impedance state as well as a state in which the on / off instruction signal maintains a predetermined potential.

  The mode determination circuit compares the voltage of the capacitor with a predetermined voltage, and the charge / discharge circuit which charges the capacitor when the on / off instruction signal is at the first level and discharges the capacitor when the on / off instruction signal is at the second level. And a comparison circuit that outputs a mode determination signal having a level according to the comparison result.

The mode determination signal may be a first level indicating a first mode when the voltage of the capacitor is higher than a predetermined voltage, and may be a second level indicating a second mode when the voltage of the capacitor is lower than the predetermined voltage. The charge and discharge circuit may be configured to reduce the discharge rate when the mode determination signal is at the first level.
According to this aspect, when the voltage of the capacitor becomes higher than the predetermined voltage, the discharge rate is reduced and the voltage of the capacitor is increased. Therefore, switching from the first mode to the second mode can be delayed. This is particularly effective in the case of performing gradual change off.

In the first mode, the semiconductor light source may be lit at a first light quantity, and in the second mode, the semiconductor light source may be lit at a second light quantity smaller than the first light quantity. The mode determination unit may change the determination signal after a predetermined delay time has elapsed when the duty ratio of the on / off instruction signal changes from the first duty ratio to the second duty ratio.
By setting the delay time to be longer than the time constant at the time of gradual change off, it is possible to prevent the mode determination signal from affecting the gradual change off.

In the first mode, the semiconductor light source may be lit at a first light quantity, and in the second mode, the semiconductor light source may be lit at a second light quantity smaller than the first light quantity. The drive circuit may generate a reference signal that changes in binary according to the mode determination signal, and may stabilize the drive current to a target amount according to the reference signal.
Thereby, the light quantity at the time of lighting can be controlled by one signal line.

  The light source comprises a laser diode for emitting excitation light, and a phosphor provided on the optical axis of the excitation light and emitting fluorescence by being excited by the excitation light, and is a white output light including the spectrum of the excitation light and the fluorescence May be configured to generate

  Another aspect of the present invention relates to a vehicle lamp. A vehicular lamp includes a semiconductor light source and a processor that generates a lighting on / off instruction signal instructing lighting on / off of the semiconductor light source based on information from an electronic control unit (ECU), and the lighting circuit according to any of the above And. The lighting on / off instruction signal has a pulse shape having a first duty ratio when instructing lighting in the first mode, and a pulse having a second duty ratio different from the first duty ratio when instructing lighting in the second mode. It is a constant level when instructing to turn off.

The pulse input determination circuit charges (or discharges) the capacitor in response to the edge of the on / off instruction signal, and discharges (or charges) the capacitor when the edge is not detected, the voltage of the capacitor, And a determination unit that generates a lighting determination signal based on a comparison result of predetermined threshold voltages.
When the on / off instruction signal is in the form of a pulse, the edge is periodically detected, and thus the capacitor is periodically charged (or discharged) to increase (or decrease) the voltage of the capacitor. On the other hand, when the lighting on / off instruction signal is at a constant level, the capacitor is continuously discharged without being charged (or discharged), so the voltage of the capacitor decreases (or increases). Therefore, according to this aspect, it is possible to determine the on state and the off state based on the voltage of the capacitor.

The charge / discharge circuit includes an edge detection circuit that detects an edge of a lighting on / off instruction signal, a current source that supplies a current to the capacitor in response to an output of the edge detection circuit, a discharge path that discharges the capacitor, and a voltage of the capacitor And a comparison transistor input to the control terminal.
In the lit state, the current source repeatedly charges the capacitor in response to the periodic edge, thereby increasing the capacitor voltage and turning on the comparison transistor. In the light-off state, the capacitor is discharged by the discharge path, so that the capacitor voltage decreases and the comparison transistor is turned off. Accordingly, it is possible to determine the on state and the off state in response to the on / off of the comparison transistor.

  The edge detection circuit may include a differentiation circuit that differentiates the on / off instruction signal.

The pulse input determination circuit may include a retriggerable monostable multivibrator that receives a trigger signal according to the on / off instruction signal at its trigger input.
When the on / off indication signal is in the on state, the retriggerable monostable multivibrator is repeatedly triggered by the trigger signal in response to the on / off indication signal, so that its output sustains an unstable output. Conversely, the output of the retriggerable monostable multivibrator maintains a stable output when the on / off indication signal is off. Therefore, it is possible to determine the on / off state based on the output state of the retriggerable monostable multivibrator.

  The pulse input determination circuit may further include a low pass filter provided downstream of the retriggerable monostable multivibrator. In this case, the sensitivity from the unlit state to the lit state can be reduced and erroneous lighting can be prevented.

The pulse input determination circuit includes an edge detection circuit that detects an edge of a lighting on / off instruction signal, a retrigger impossible monostable multivibrator that receives a trigger signal according to the output of the edge detection circuit at its trigger input, and retrigger impossible And a low pass filter provided downstream of the monostable multivibrator.
When the on / off instruction signal is in the off state, the output of the non-retriggerable monostable multivibrator continues the stable output. On the other hand, when the on / off instruction signal is in the on state, the output of the retrigger impossible monostable multivibrator becomes an unstable output in response to the trigger signal and returns to the stable state temporarily after a certain time constant time elapses, It becomes an unstable output again according to the next trigger signal. That is, the output of the non-retriggerable monostable multivibrator repeats a steady state and an unstable state. Then, by inserting a low pass filter in the subsequent stage and removing the short stable state, it is possible to determine the on state and the off state.

  The edge detection circuit may include a differentiation circuit that differentiates the on / off instruction signal.

The pulse input determination circuit charges the capacitor, a charge / discharge circuit that charges the capacitor when the on / off instruction signal is at the first level, and discharges the capacitor when the on / off instruction signal is at the second level, And a determination unit that compares the voltage and the second voltage and determines whether to turn on or off based on the comparison result. The charge rate and the discharge rate of the charge and discharge circuit may be defined such that the voltage of the capacitor is included between the first voltage and the second voltage when the on / off instruction signal is in a pulse form.
Thus, it can be determined whether the on / off instruction signal S1 is in the form of a pulse.

  According to an aspect of the present invention, lighting and extinguishing and two modes can be controlled by one signal line, and the semiconductor light source is extinguished when an abnormality occurs in the signal line through which the stimulable and extinguishing instruction signal propagates. it can.

FIG. 7 is a block diagram of a lamp system with an additional high beam. It is a block diagram of a vehicular lamp provided with a lighting circuit concerning an embodiment. FIG. 5 is an operation waveform diagram of the vehicle lamp of FIG. 2; FIG. 5 is a circuit diagram showing an example of configuration of a pulse input determination circuit and a mode determination circuit. 5 (a) and 5 (b) are operation waveform diagrams of the pulse input determination circuit of FIG. 6A and 6B are operation waveform diagrams of the pulse input determination circuit of FIG. FIGS. 7A and 7B are circuit diagrams of the pulse input determination circuit of the first modification. FIGS. 8A and 8B are operation waveform diagrams of the pulse input determination circuit of FIG. 7B. FIG. 13 is a circuit diagram of a pulse input determination circuit according to a second modification. FIG. 16 is a circuit diagram of a pulse input determination circuit according to a third modification.

  Hereinafter, the present invention will be described 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 duplicating descriptions will be omitted as appropriate. In addition, the embodiments do not limit the invention and are merely examples, and all the features and combinations thereof described in the embodiments are not necessarily essential to the invention.

In the present specification, “the state in which the member A is connected to the member B” means that the members A and B are electrically connected in addition to the case where the members A and B are physically and directly connected. It also includes the case of indirect connection via other members that do not substantially affect the connection state of the connection or do not impair the function or effect provided by the connection.
Similarly, "a state where 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 It also includes the case of indirect connection via other members that do not substantially affect the connection state of the connection or do not impair the function or effect provided by the connection.

  In the present specification, reference numerals attached to electric signals such as voltage signals and current signals or circuit elements such as resistors and capacitors indicate respective voltage values, current values, or resistance values and capacitance values as necessary. It shall represent.

  FIG. 2 is a block diagram of a vehicular lamp 300 including the lighting circuit 400 according to the embodiment. The vehicle lamp 300 may be an additional high beam, a low beam, or a normal high beam, as in FIG. 1. The entire lamp system 200 is shown in FIG.

  The vehicular lamp 300 includes a semiconductor light source 302, a lamp ECU 310, and a lighting circuit 400. The lighting circuit 400 turns on or off the semiconductor light source 302 in response to the on / off instruction signal S1 from the processor (CPU) 314. The semiconductor light source 302 is, for example, a laser diode.

In the present embodiment, the on / off instruction signal S1 generated by the CPU 314 has a pulse shape in the lighting state φ _ON instructing lighting, and has a constant level (steady state) in the lighting off state φ _OFF instructing lighting. The lighting state φ _ON may be a state in which the on / off instruction signal S1 alternately transitions between two different potentials (high level and low level, high level and intermediate level, intermediate level and low level, etc.). Alternatively, the lighting state φ _ON may be a state in which the on / off instruction signal S1 alternates between a predetermined potential (high level, low level or intermediate level) and a high impedance state. Further, the light-off state φ _OFF may be a state in which the light-on / off instruction signal S1 maintains a predetermined potential (high level, low level or intermediate level). Alternatively, the light-off state φ _OFF may be a state in which the light-on / off instruction signal S1 is maintained in the high impedance state.

  In the present embodiment, lighting circuit 400 is configured to be able to switch between two lighting modes. The two modes are selected in accordance with the duty ratio (pulse width) of the pulse lighting on / off instruction signal S1. That is, the on / off instruction signal S1 is in the form of a pulse having a first duty ratio in the first mode, and in the form of a pulse having the second duty ratio in the second mode.

  As an example, the first mode (also referred to as a normal mode) is a mode in which the semiconductor light source 302 emits light with a normal light amount during normal traveling, and the second mode (also referred to as a test mode) is a semiconductor during maintenance. In this mode, the light source 302 is caused to emit light at a light quantity (second light quantity) smaller than the normal light quantity (first light quantity). The test mode can be used at the time of inspection of adjustment of the optical axis, abnormality of the fluorescent material, and the like. It should be noted that in general PWM dimming, the duty ratio of the on / off instruction signal S1 is proportional to the light amount, while the light amount in each mode of the present embodiment is irrelevant to the duty ratio. I want to.

In the present embodiment, in the lighting state φ _ON1 of the first mode, the on / off instruction signal S1 has a high level (for example, power supply voltage V _DD ) and a low level (ground voltage V _GND ) at a first duty ratio (for example, 50%). Repeatedly, in the second mode lighting state φ _ON2 , the on / off instruction signal S1 repeats high level and low level with the second duty ratio (for example, 10%), and in the off state φ _OFF , the on / off instruction signal S1 is low. It is fixed to the level (ground voltage V _GND ).

  The lighting circuit 400 includes a pulse input determination circuit 402, a mode determination circuit 404, and a drive circuit 410. The pulse input determination circuit 402 receives the on / off instruction signal S1, and determines whether the on / off instruction signal S1 is in the form of a pulse. The pulse input determination circuit 402 asserts the lighting determination signal S2 when the lighting on / off instruction signal S1 is in a pulse shape.

  The mode determination circuit 404 determines the duty ratio of the on / off instruction signal S1, and generates a mode determination signal S5 indicating the determination result. Mode determination signal S5 has a second level (for example, low level) when lighting on / off instruction signal S1 has a second duty ratio, that is, when the second mode is instructed, lighting on / off instruction signal S1 has a second duty ratio. When not having it, that is, when the first mode is designated, it becomes the first level (for example, high level).

Driving circuit 410, when the lighting decision signal S2 is asserted (e.g., high level), the mode corresponding to the mode decision signal S5, and supplies the drive current I _LD to the semiconductor light source 302, the lighting decision signal S2 is negated (e.g. when the low level) by the stops supplying the drive current I _LD to the semiconductor light source 302.

Drive circuit 410 includes, for example, converter 412 and lighting control circuit 414. Converter 412 includes a switching converter (DC / DC converter) which receives power supply voltage V _Hi supplied via switch 312 and boosts or lowers it. The topology of the converter 412 is not particularly limited, and may be selected according to the type, the number, etc. of the semiconductor light sources 302.

The lighting control circuit 414 detects the current I _LD flowing through the semiconductor light source 302, and controls the converter 412 such that the detected current I _LD matches the reference value I _REF according to the target light amount of the semiconductor light source 302. . The reference value I _REF is switched according to the mode determined by the mode determination circuit 404. The type of the lighting control circuit 414 is not particularly limited, and a controller of pulse width modulation, a controller of pulse frequency modulation, a controller of hysteresis control, or the like can be used. When implementing the function of gradual change lighting, the lighting control circuit 414 may gradually increase the reference value I _REF in response to the assertion of the lighting determination signal S2. Further, when implementing the function of gradual change and extinction, the lighting control circuit 414 may gradually decrease the reference value I _REF triggered by the negation of the lighting determination signal S2.

  The above is the basic configuration of the vehicular lamp 300. Subsequently, the operation will be described.

FIG. 3 is an operation waveform diagram of the vehicle lamp 300 of FIG. Before time t1, the signal line 304 is normal, and the on / off instruction signal S1 is correctly transmitted. In the section A, the CPU 314 generates a pulse on / off instruction signal S1 having a duty ratio of 50% in order to turn on the semiconductor light source 302 in the first mode. When the signal line 304 is normal, the input signal of the pulse input determination circuit 402 is also in the form of pulses, and the pulse input determination circuit 402 asserts the lighting determination signal S2. The mode determination circuit 404 outputs a high level mode determination signal S5 indicating that the mode is the first mode. The lighting control circuit 414 uses the assertion of the lighting determination signal S2 as a trigger to gradually increase the driving current _ILD supplied to the semiconductor light source 302 toward the target amount I _REF1 of the first mode, and gradually change lighting, and thereafter , the drive current _{I LD} is stabilized at the target value _{I REF1,} keeping the light intensity of the semiconductor light source 302 constant.

In the section B, the CPU 314 generates a low level lighting on / off instruction signal S1 to turn off the semiconductor light source 302. As a result, since no pulse is observed at the input of the pulse input determination circuit 402, the pulse input determination circuit 402 negates the lighting determination signal S2. The lighting control circuit 414 causes the drive current _ILD supplied to the semiconductor light source 302 to be gradually decreased with the use of the negate of the lighting determination signal S2 as a trigger to gradually change off. As will be described later, it is desirable that the mode determination signal S5 make a level transition after a certain delay time τ since the on / off instruction signal S1 becomes constant. Thereby, it is possible to prevent the decrease in the target current I _REF accompanying the change of the mode determination signal S5 from affecting the gradual change and extinction.

In section C, the CPU 314 generates a pulse on / off instruction signal S1 having a duty ratio of 10% in order to turn on the semiconductor light source 302 in the second mode. Since the signal line 304 is normal, the input signal of the pulse input determination circuit 402 is also in the form of pulses, and the pulse input determination circuit 402 asserts the lighting determination signal S2. The mode determination circuit 404 outputs a low level mode determination signal S5 indicating that it is the second mode. The lighting control circuit 414 uses the assertion of the lighting determination signal S2 as a trigger to gradually increase the drive current _ILD supplied to the semiconductor light source 302 toward the target amount I _REF2 of the second mode, and gradually change lighting, and thereafter , the drive current _{I LD} is stabilized at the target value _{I REF2,} keeping the light intensity of the semiconductor light source 302 constant.

In the section D, when the CPU 314 generates a low level on / off instruction signal S1 to instruct the semiconductor light source 302 to turn off, the pulse input determination circuit 402 negates the lighting determination signal S2. The lighting control circuit 414 causes the drive current _ILD supplied to the semiconductor light source 302 to be gradually decreased with the use of the negate of the lighting determination signal S2 as a trigger to gradually change off.

It is assumed that the signal line 304 is shorted at time t1. When the signal line 304 is shorted, the on / off instruction signal S1 is fixed to the high level voltage. At this time, no pulse is observed at the input terminal of the pulse input determination circuit 402, so that the lighting determination signal S2 remains negated. Therefore, the drive current _ILD is not supplied to the semiconductor light source 302, and the turn-off is maintained.

  As described above, according to the lighting circuit 400 according to the embodiment, the semiconductor light source 302 is turned off not only when the processor 314 instructs to turn off, but also when an abnormality such as a short-circuit, ground or disconnection occurs. And can enhance safety.

  In addition, it is possible to switch between the two modes with one signal line 304 without adding a control line for mode selection.

  The present invention extends to various circuits that can be understood from the block diagram of FIG. 2 and the above description, and a specific configuration example thereof will be described below.

  FIG. 4 is a circuit diagram showing a configuration example of the pulse input determination circuit 402c and the mode determination circuit 404.

The on / off instruction signal S1 in FIG. 4 is defined as follows.
・ First mode (normal mode)
High impedance / GND 200Hz, duty 50%
・ Second mode (test mode)
High impedance / GND 200Hz, duty 10%
Turn off High impedance fixed The duty ratio is the ratio of the GND section to the cycle.

  Mode determination circuit 404 includes a capacitor C4, a charge / discharge circuit 450, and a comparison circuit 452. One end of the capacitor C4 is grounded. The charge / discharge circuit 450 charges the capacitor C4 when the on / off instruction signal is at the first level (for example, high impedance), and discharges the capacitor C4 when the on / off instruction signal S1 is at the second level (GND level). The charge path is the transistor Tr9 and the resistor R10. The discharge path is the resistors R11 and R9 and the transistor Tr7.

  When the on / off instruction signal S1 is high impedance, the transistor Tr1 is off, and the signal S1 'becomes low level. Therefore, the transistor Tr9 is turned on, and the capacitor C4 is charged. When the on / off instruction signal S1 is at the GND level, the transistor Tr1 is on and the signal S1 'is at the high level. Therefore, the transistor Tr9 is turned off, and the capacitor C4 is discharged.

If the section in which the on / off instruction signal S1 is at the GND level is long, the voltage V _{C4 of the} capacitor C4 rises, and if the section in which the on / off instruction signal S1 is high impedance is long, the voltage V _{C4 of the} capacitor C4 decreases. That is, the capacitor voltage V _C4 changes in accordance with the duty ratio of the on / off instruction signal S1.

The comparison circuit 452 compares the voltage V _{C4 of the} capacitor C4 with the predetermined voltage V _TH and outputs a mode determination signal S5 having a level corresponding to the comparison result. The comparison circuit 452 includes resistors R12 and R13, a transistor Tr6, and a resistor R15. The resistors R12 and R13 divide the power supply voltage Vcc. The divided voltage Vcc 'is input to the source of the transistor Tr6 which is a P-channel MOSFET.

When capacitor voltage V _C4 is higher than Vcc′−V _{GS (} TH 6 ₎ , transistor Tr 6 is off, mode determination signal S 5 is low, and when capacitor voltage V _{C 4} is lower than Vcc′− V _{GS (} TH 6 ₎ , The transistor Tr6 is turned on, and the mode determination signal S5 is at high level. V _{GS (TH6)} is a threshold voltage between the gate and the source of the transistor Tr6.

That the comparison circuit 452, can adjust the threshold voltage _{V TH} in accordance with the division ratio of the _{Vcc'-V GS (TH6)} is the threshold voltage _{V TH,} and the resistors R12, R13. A voltage comparator may be used as the comparison circuit 452.

The charge / discharge circuit 450 is configured to decrease the discharge speed when the mode determination signal S5 is at low level, that is, when the capacitor voltage V _C4 is higher than Vcc′−V _{GS (TH6)} . The switching of the discharge rate is associated with on and off of the transistor Tr7. When the mode determination signal S5 is at low level, the transistor Tr7 is turned off, and the discharge path is only the resistor R11. When the mode determination signal S5 is at high level, the transistor Tr7 is turned on, the discharge path is a parallel circuit of the resistor R11 and the resistor R9, and the discharge speed is increased.

When the GND duty ratio is large (50%), that is, in the normal mode, the capacitor voltage V _C4 becomes high, the transistor Tr6 is turned off, and the mode determination signal S5 becomes low level. When the GND duty ratio is small (10%), that is, in the test mode, the capacitor voltage V _C4 becomes low, the transistor Tr6 is turned on, and the mode determination signal S5 becomes high level.

The mode determination signal S5 generated by the mode determination circuit 404 is input to the subsequent variable voltage source 406. The variable voltage source 406 is a part of the lighting control circuit 414 of FIG. The variable voltage source 406 generates a reference signal V _REF ′ that changes in binary according to the level of the mode determination signal S5. The reference signal V _REF 'indicates the target amount of the drive current I _LD .

In the normal mode in which the mode determination signal S5 is at low level, the transistor Tr8 is turned off, and the reference signal V _REF 'is high, that is, the amount of light is large. On the contrary, in the test mode in which the mode determination signal S5 is at the high level, the transistor Tr8 is turned on, and the reference signal V _REF 'is low, that is, the light amount is small.

5 (a) and 5 (b) are operation waveform diagrams of the pulse input determination circuit 402c of FIG. FIG. 5A shows the case where the GND duty ratio is 10% and 50%. When the GND duty ratio is small, the capacitor voltage V _C4 is maintained at the low level, and the mode determination signal S5 is at the high level. Conversely, when the GND duty ratio is large, the capacitor voltage V _C4 increases, and the mode determination signal S5 becomes low level.

  The waveform at the time of light extinction is shown by FIG.5 (b). When the on / off instruction signal S1 changes from a pulse to a GND level, the mode determination signal S5 does not change immediately, and transitions to a low level after a long delay time (about 3 seconds). This is because the discharge speed of the capacitor C4 is changed according to the mode determination signal S5. It is desirable that this delay time be set longer than a time constant for changing the light quantity at the time of gradual change and extinction.

If the mode determination signal S5 transitions to the high level immediately after the on / off instruction signal S1 changes from the pulse shape to the GND level, the reference signal V _REF 'generated by the variable voltage source 406 decreases and the gradual change extinguishment is performed. Before that, the light amount of the semiconductor light source 302 is reduced instantaneously. On the other hand, in the mode determination circuit 404 of FIG. 4, the reference signal V _REF 'can be changed without affecting the gradual change and extinction by delaying the transition of the mode determination signal S5 to the high level. it can.

  Subsequently, the pulse input determination circuit 402c will be described. The pulse input determination circuit 402c utilizes a non-retriggerable monostable multivibrator 436 that can be configured with a small number of elements.

  The pulse input determination circuit 402 c includes an edge detection circuit 422, a monostable multivibrator 436, a low pass filter 438, and an output circuit 440. The edge detection circuit 422 detects a positive edge of the on / off instruction signal S1.

  For example, the edge detection circuit 422 can be configured using a differentiation circuit (high pass filter). Specifically, the edge detection circuit 422 includes a transistor Tr1, a resistor R1, a capacitor C1, a diode D1, and resistors Rb2 and R2. The capacitor C1, the resistor Rb2 and the resistor R2 form a differentiating circuit. The time constant of the differentiating circuit is determined according to the combined resistance of the resistors Rb2 and R2 and the capacitance value of the capacitor C1. The diode D1 is a clamper that prevents swinging to a negative voltage due to the negative edge of the on / off instruction signal S1.

  The monostable multivibrator 436 receives at its trigger input 437 a trigger signal S3 according to the output of the edge detection circuit 422. A low pass filter 438 is provided downstream of the monostable multivibrator 436. The output circuit 440 binarizes the output of the low pass filter 438 and outputs it.

6A and 6B are operation waveform diagrams of the pulse input determination circuit 402c of FIG. 6 (a) and 6 (b) show waveforms when the on / off instruction signal S1 has a duty ratio of 10% and 50%. According to the pulse input determination circuit 402c of FIG. 4, the lighting state φ _ON can be determined regardless of the duty ratio.

  The present invention has been described above based on the embodiments. It is understood by those skilled in the art that this embodiment is an exemplification, and that various modifications can be made to the combination of each component and each processing process, and such a modification is also within the scope of the present invention. is there. Hereinafter, such modifications will be described.

  In the embodiment, the case where the first mode is the normal mode and the second mode is the test mode is described, but the present invention is not limited thereto. For example, the present invention can also be used when it is necessary to change the amount of light according to the environment (speed, time zone, presence or absence of a preceding vehicle, presence or absence of a pedestrian, etc.) while traveling. Further, the number of modes is not limited to two, and three or more discrete duty ratios may be used to enable selection of three or more modes.

  Further, the vehicle lamp 300 is not limited to the additional high beam, and may be a normal high beam or a low beam. The semiconductor light source 302 is not limited to a laser diode, and may be an LED or the like.

Further, the means for the lighting control circuit 414 to switch the target light amount I _REF in accordance with the mode determination signal S5 is not limited to one using the variable voltage source 406 of FIG. In addition, as the specific circuit configuration of the gradual change lighting and the gradual change extinction, a known technique or a technique which can be used in the future may be used.

Subsequently, a modified example of the pulse input determination circuit 402 will be described.
FIGS. 7A and 7B are circuit diagrams of the pulse input determination circuit 402a according to the first modification. As shown in FIG. 7A, the pulse input determination circuit 402a includes a charge / discharge circuit 420, a capacitor C2, and a determination unit 430. The potential at one end of the capacitor C2 is fixed. The charge / discharge circuit 420 charges the capacitor C2 in response to the edge of the on / off instruction signal S1, and discharges the capacitor C2 when the edge is not detected. Note that the charging operation and the discharging operation of the charge and discharge circuit 420 may be changed. Determination unit 430 generates lighting determination signal S2 based on the comparison result of voltage V _{C2 of} capacitor C2 and a predetermined threshold voltage V _TH .

  A more specific configuration example of the pulse input determination circuit 402a of FIG. 7A is shown in FIG. 7B. In this example, the assertion (lighting) of the lighting determination signal S2 is low, and the negate (lighting) is high. The charge and discharge circuit 420 includes an edge detection circuit 422, a current source 424, and a discharge path 426. The edge detection circuit 422 detects a positive edge of the on / off instruction signal S1. For example, the edge detection circuit 422 can be configured using a differentiation circuit (high pass filter). Specifically, the edge detection circuit 422 includes a transistor Tr1, a resistor R1, a capacitor C1, a diode D1, and a resistor Rb2. The series connection of the capacitor C1 and the resistor Rb2 forms a differentiating circuit. The diode D1 is a clamper that prevents swinging to a negative voltage due to the negative edge of the on / off instruction signal S1.

  The current source 424 includes transistors Tr2 and Tr3 and a resistor R2. When the positive edge of the on / off instruction signal S1 is detected, a current flows through the transistors Tr2 and Tr3, and a current is supplied to the capacitor C2. When the pulse on / off instruction signal S1 is input and the positive edge is detected at a predetermined interval, the capacitor C2 is repeatedly charged by the current source 424.

  Discharge path 426 includes a resistor Rb4. The charge of the capacitor C2 is discharged through the resistor Rb4. The charge current of the current source 424 is designed to be larger than the discharge current by the discharge path 426.

Determination unit 430 includes a transistor Tr4 and a resistor R3. The capacitor voltage V _C2 is divided by the voltage dividing circuit formed by the discharge path 426, and is input to the base of the transistor Tr4. When the base-emitter voltage of the transistor Tr4 exceeds its threshold (forward voltage Vbe ≒ 0.6 V), the transistor Tr4 is turned on, and the determination signal S2 goes low (assert).

  FIGS. 8A and 8B are operation waveform diagrams of the pulse input determination circuit 402a of FIG. 7B. The potential of the connection node of the capacitor C1 and the resistor Rb2 is Vx. FIG. 8 (a) shows the waveform of the lighting instruction, and FIG. 8 (b) shows the waveform of the lighting instruction. It should be noted that in FIG. 8 (a) and FIG. 8 (b) the time scale of the horizontal axis is different.

  As described above, according to the pulse input determination circuit 402a of FIG. 7B, it can be determined whether or not the pulse on / off instruction signal S1 is input.

  FIG. 9 is a circuit diagram of a pulse input determination circuit 402b according to a second modification. The pulse input determination circuit 402 b includes an input circuit 432 and a retriggerable monostable multivibrator 434. The input circuit 432 includes transistors Tr1 and R1 and generates a trigger signal S3 (inverted logic) according to the on / off instruction signal S1. Monostable multivibrator 434 receives trigger signal S3 at its trigger input. The oscillation cycle of the monostable multivibrator 434 is set to be longer than the cycle of the pulse lighting on / off instruction signal S1.

When the lighting on / off instruction signal S1 is in the lighting state φ _ON , that is, a pulse signal, the monostable multivibrator 434 is repeatedly triggered by the trigger signal S3 according to the lighting on / off instruction signal S1 and therefore its output Q is an unstable output. continue. Conversely, when the on / off instruction signal S1 is in the off state, the output Q of the monostable multivibrator 434 maintains the stable output. Therefore, with the output state Q of the monostable multivibrator 434 as the lighting determination signal S2, the lighting state and the lighting off state can be determined.

FIG. 10 is a circuit diagram of a pulse input determination circuit 402d according to a third modification. The basic configuration of the pulse input determination circuit 402d is the same as that of the pulse input determination circuit 402a of FIG. 7A. The charge / discharge circuit 420d charges the capacitor C2 in response to the on / off instruction signal S1. Specifically, charge / discharge circuit 420d charges capacitor C2 when lighting on / off instruction signal S1 is at the first level (for example, low level), and capacitor C2 when lighting on / off instruction signal S1 is at the second level (for example, high level). Discharge. The charging rate and the discharging rate are determined such that the voltage V _{C2 of the} capacitor C2 is included in the voltage range Va to Vb (Va <Vb) when the on / off instruction signal S1 is in a pulse form. Determination unit 430d asserts lighting determination signal S2 when capacitor voltage V _C2 is included in voltage ranges Va to Vb, and negates lighting determination signal S2 when it is not included.

  For example, charge / discharge circuit 420 d includes a transistor Tr1 and resistors R1 and R2. When the on / off instruction signal S1 is at a low level, the transistor Tr1 is turned on, and the capacitor C2 is charged via the resistor R1. The charge rate is defined by the resistor R1. When the on / off instruction signal S1 is at a high level, the transistor Tr1 is turned off, and the capacitor C2 is discharged through the resistors R1 and R2. The discharge rate is defined by the resistors R1 and R2.

For example, when the duty ratio of the on / off instruction signal S1 is 50%, the capacitor voltage V _C2 is in the vicinity of the midpoint voltage V _CC / 2 between the power supply voltage V _CC and the ground voltage V _GND (= 0 V), The charge rate and the discharge rate may be determined.

Determination unit 430 d compares capacitor voltage V _C2 with two threshold voltages Va and Vb. For example, determination unit 430d includes transistors Tr3 and Tr4, resistor R3 and transistor Tr2.
The threshold voltage between the gate and the source of the transistor Tr2 is V _{GS (TH2)} , and the threshold voltage between the gate and the source of the transistor Tr3 is V _{GS (TH3)} .
When V _GS of _{(TH2) <V C2 <V} CC -V GS (TH3), the transistors Tr2, Tr3 is turned both ON, the transistor Tr4 is also turned on, the lighting decision signal S2 is at a high level (≒ _{V CC)} Become. When V _C2 <V _{GS (TH 2)} , the transistor Tr 2 is off and the transistor Tr 3 is turned on, and the lighting determination signal S 2 becomes low level (V _GND ). When V _CC −V _{GS (TH3)} <V _C2 , the transistor Tr2 is on, the transistor Tr3 is off, and the lighting determination signal S2 is at a low level. According to this configuration the first voltage _{Va = V GS (TH2),} as the second voltage _{Vb = V CC -V GS (TH3} ), it can be determined whether the capacitor voltage _{V C2} is included in the voltage range Va~Vb .

Determination unit 430d may be configured as a window comparator including two voltage comparators that compare capacitor voltage V _C2 with voltages Va and Vb, and a logic gate that performs a logic operation on the outputs of the two voltage comparators. .

  While the present invention has been described using specific terms based on the embodiments, the embodiments merely show the principles and applications of the present invention, and the embodiments are defined in the claims. Many variations and modifications of the arrangement can be made without departing from the concept of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Vehicle lamp, 200 ... lamp system, 202 ... vehicle ECU, 204 ... battery, 300 ... vehicle lamp, 302 ... semiconductor light source, 304 ... signal line, 310 ... lamp ECU, 312 ... switch, 314 ... CPU, 320 ... lighting circuit, 322 ... constant current converter, 324 ... gradual change point switching circuit, 400 ... lighting circuit, 402 ... pulse input determination circuit, 404 ... mode determination circuit, 406 ... variable voltage source, 410 ... drive circuit, 412 ... converter 414: lighting control circuit 420: charge / discharge circuit C2: capacitor 422: edge detection circuit 424: current source 426: discharge path 430: determination unit 432: input circuit 434, 436: monostable multi-element Vibrator, 438 ... low pass filter, 440 ... output circuit, C 4 ... capacitor, 450 ... charge / discharge circuit, 45 ... comparison circuit, S1 ... point off instruction signal, S2 ... lighting decision signal, S5 ... mode decision signal.

Claims (6)

A lighting circuit for lighting or extinguishing a semiconductor light source in response to a lighting on / off instruction signal from a processor,
The on / off instruction signal has a pulse shape having a first duty ratio when instructing lighting in the first mode, and has a second duty ratio different from the first duty ratio when instructing lighting in the second mode. It has a pulse shape, and has a constant level when instructing turn-off,
The lighting circuit is
A pulse input determination circuit that determines whether the on / off instruction signal is in the form of a pulse and generates a lighting determination signal that is asserted when the signal is in the form of a pulse;
A mode determination circuit that determines a duty ratio of the on / off instruction signal and generates a mode determination signal indicating a determination result;
When the lighting determination signal is asserted, a drive current is supplied to the semiconductor light source in a mode corresponding to the mode determination signal, and when the lighting determination signal is negated, supply of the drive current to the semiconductor light source Drive circuit to stop the
A lighting circuit comprising: The mode determination circuit
Capacitors,
A charge / discharge circuit which charges the capacitor when the on / off instruction signal is at a first level and discharges the capacitor when the on / off instruction signal is at a second level;
A comparison circuit that compares the voltage of the capacitor with a predetermined voltage and outputs the mode determination signal having a level according to the comparison result;
The lighting circuit according to claim 1, further comprising: The mode determination signal is at a first level indicating the first mode when the voltage of the capacitor is higher than the predetermined voltage, and is a second level indicating the second mode when the voltage of the capacitor is lower than the predetermined voltage. And
The lighting circuit according to claim 2, wherein the charge / discharge circuit is configured to decrease a discharge rate when the mode determination signal is at the first level. In the first mode, the semiconductor light source is turned on with a first light quantity, and in the second mode, the semiconductor light source is turned on with a second light quantity smaller than the first light quantity,
The mode determination circuit is characterized in that the mode determination signal is changed after a predetermined delay time has elapsed since the duty ratio of the on / off instruction signal is changed from the first duty ratio to the second duty ratio. The lighting circuit according to any one of claims 1 to 3. In the first mode, the semiconductor light source is turned on with a first light quantity, and in the second mode, the semiconductor light source is turned on with a second light quantity smaller than the first light quantity,
4. The drive circuit according to claim 1, wherein the drive circuit generates a reference signal that changes in binary according to the mode determination signal, and stabilizes the drive current to a target amount according to the reference signal. The lighting circuit according to any of the above. A vehicle lamp,
Semiconductor light source,
The processor generates an on / off instruction signal instructing on / off of the semiconductor light source based on information from an electronic control unit (ECU), and the on / off instruction signal instructs on / off in the first mode. The pulse shape having a first duty ratio, the pulse shape having a second duty ratio different from the first duty ratio when instructing lighting in the second mode, and the constant level when instructing turning off A processor,
The lighting circuit according to any one of claims 1 to 5, wherein the semiconductor light source is turned on or off according to the on / off instruction signal.
A vehicle lamp comprising:

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