JP2018200802A - Lighting fixture for vehicle and lighting circuit of light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting circuit capable of maintaining a switching operation of a switching converter even if a main controller becomes inoperable. SOLUTION: A first controller 510 has a lamp current ILAMP generated by a converter controller 210 based on a first detection signal VCS1 generated by a first current detecting means 212 provided on an output side of a switching converter 210. The first control pulse SCNT1 is generated so as to approach the target amount IREF1. The second controller 520 generates the second control pulse SCNT2 so that the lamp current ILAMP does not become zero in the inoperable state of the first controller 510. The driver circuit 530 drives the switching converter 210 based on the first control pulse SCNT1 and the second control pulse SCNT2. [Selection diagram] Fig. 2

Description

  The present invention relates to a lighting circuit for a semiconductor light source.

  In general, a vehicular lamp can be switched between a low beam and a high beam. The low beam illuminates the neighborhood with a predetermined illuminance, and the light distribution regulation is determined so as not to give glare to the oncoming vehicle and the preceding vehicle, and is mainly used when traveling in an urban area. On the other hand, the high beam illuminates a wide area in the front and a distant area with a relatively high illuminance, and is mainly used when traveling at high speed on a road with few oncoming vehicles and preceding vehicles. Therefore, although the high beam is more visible to the driver than the low beam, there is a problem that glare is given to the driver or pedestrian of the vehicle existing in front of the vehicle.

  In recent years, ADB (Adaptive Driving Beam) technology has been proposed that dynamically and adaptively controls a high-beam light distribution pattern based on the state around the vehicle. ADB technology detects the presence of preceding vehicles, oncoming vehicles, and pedestrians in front of the vehicle, and reduces glare given to the vehicle or pedestrian by dimming or turning off the area corresponding to the vehicle or pedestrian. Is.

  FIG. 1 is a circuit block diagram of a vehicular lamp 100R examined by the present inventors. The vehicle lamp 100R includes a lighting circuit 200R and a light source 300.

  The light source 300 includes a plurality of N (N ≧ 2) light emitting elements 302_1 to 302_N connected in series. The lighting circuit 200R is configured to be able to independently control turning on / off of each light source 300 by a bypass method. The lighting circuit 200R includes a constant current circuit 202R, a bypass circuit 280, and a bypass controller 290.

The constant current circuit 202R generates a drive current (lamp current) I _LAMP that is stabilized to a target value. Bypass circuit 280 includes a plurality of bypass switches _SWB 1 _{~SWB N.} Each bypass switch SWB _i (1 ≦ i ≦ N) is provided between both ends of the corresponding light emitting element 302 — i. The bypass controller 290 controls each of the plurality of bypass switches SWB _{1 to} SWB _{N to} be turned on and off so that a desired light distribution pattern is obtained. When the i-th bypass switch SWB _i is off, the lamp current I _LAMP flows to the light emitting element 302 — i, and thus the light emitting element 302 — i is turned on. When the i-th bypass switch SWB _i is on, the lamp current I _LAMP flows around the bypass switch SWB _i and no current flows through the light-emitting element 302 — _i, and thus the light-emitting element 302 — i is turned off.

The constant current circuit 202R includes a switching converter 204, a sense resistor R _S , a current detection circuit 206, and a converter controller 208.

Sense resistor _{R S} is provided on a path of lamp current _{I LAMP,} a voltage drop occurs which is proportional to the lamp current _{I LAMP} across it. Current detecting circuit 206 generates a current detection signal _{V CS} based on the voltage drop across the sense resistor _{R S.}

The switching converter 204 is a step-down (Buck) converter or a step-up (Boost) converter. Converter controller 208, the detection signal _{V CS} is closer to the reference voltage _{V REF} corresponding to the target value of the lamp current, and controls the switching converter 204.

JP 2014-189990 A

  As a result of examining the vehicular lamp 100R of FIG. 1, the present inventors have recognized the following problems. This problem should not be regarded as a general recognition of those skilled in the art.

Depending on the light distribution pattern, a period in which all of the plurality of light-emitting elements 302_1 to 302_N are turned off (all turned off) may occur. A sufficiently long all-off state can be realized by stopping the constant current circuit 202R and setting the lamp current I _LAMP to zero.

However, in a situation where a short all-off state occurs repeatedly (for example, a situation where each bypass switch of the bypass circuit 280 is PWM-controlled), the constant current circuit 202R cannot be stopped in the all-off state. Because, when the constant current circuit 202R delay occurs to stabilize the operation state from the stopped state, during this delay, since the lamp current I _LAMP is not stabilized to the target current, the luminance of the light emitting element is not This is because it becomes stable. Therefore, the constant current circuit 202 needs to continue to generate a constant lamp current I _LAMP even in the fully extinguished state.

However, in the vehicular lamp 100R of FIG. 1, the sense resistor _RS is inserted on the anode side (high side) of the light source 300, and the current detection circuit 206 is powered from the output of the switching converter 204. Since the voltage _VL between both ends of the light source 300 (bypass circuit 280) is substantially reduced to zero during the fully extinguished state, the output voltage V _O of the switching converter 204 is also very low. As a result, insufficient supply voltage of the current detection circuit 206, can no longer generate a detection signal _{V CS} correlated with the lamp current _{I LAMP,} the switching converter 204 is uncontrollable.

  The present invention has been made in view of such a problem, and one of exemplary purposes of an aspect thereof is to provide a lighting circuit capable of maintaining the switching operation of the switching converter even when the main controller becomes inoperable. It is in.

One embodiment of the present invention relates to a lighting circuit that drives a light source. The lighting circuit includes a switching converter and a converter controller that controls the switching converter. The converter controller controls the first control pulse so that the lamp current generated by the converter controller approaches the first target amount based on the first detection signal generated by the first current detection means provided on the output side of the switching converter. Based on the first controller and the second control pulse, the second controller for generating the second control pulse so that the lamp current does not become zero in the inoperable state of the first controller. And a driver circuit for driving the switching converter.
According to this aspect, even when the main first controller becomes inoperable, the switching operation of the switching converter can be maintained by using the second control pulse generated by the second controller.

  The light source may include a plurality of light emitting elements connected in series. The lighting circuit may further include a plurality of bypass switches each connected in parallel with the corresponding light emitting element. The inoperable state of the first controller may be a completely unlit state in which all bypass switches are turned on.

  The second controller generates a second control pulse based on a second detection signal generated by a second current detection unit different from the first current detection unit so that the lamp current approaches the second target amount. Also good. Thereby, the lamp current in the fully extinguished state can be controlled to a predetermined amount.

  The second current detection means may be provided on the input side of the switching converter. In this case, the second controller may be supplied with a constant voltage from the previous DC power supply as the power supply voltage.

  The second controller may be a controller in an upper detection / off time setting mode (off time fixed mode). As a result, it is only necessary to detect the coil current during the on-time, and it is not necessary to detect the coil current during the off-time, so that the second controller can be simplified and the degree of freedom of the position of the second resistor is increased.

  The second controller may operate as an overcurrent protection circuit during a period in which the first controller can operate. By sharing the second controller and the overcurrent protection circuit, an increase in circuit area or the number of parts can be suppressed.

  The second controller compares the second detection signal corresponding to the voltage drop of the second sense resistor with an upper threshold value that defines the peak value of the output current of the switching converter, and the second detection signal becomes the upper threshold value. A comparator that generates an off signal that is asserted upon reaching, and a pulse generator that generates a second control pulse that transitions to an off level in response to the assertion of the off signal and then transitions to an on level. .

  The upper threshold may take a first value when the first controller is inoperable and may take a second value higher than the first value when the first controller is operable. The second value may be set higher than the target value of the lamp current generated by the switching converter. As a result, the second controller can function as an overcurrent protection circuit. In addition, the lamp current can be reduced during the all-off period, wasteful power consumption can be reduced, and heat generation can be suppressed.

  The first controller may be a ripple control controller. The first controller may be a hysteresis control controller. As a result, it is possible to follow high-speed load fluctuations accompanying high-speed switching of the bypass switch.

  The lighting circuit may include a determination circuit that compares the voltage across the light source with a predetermined threshold voltage. When the voltage across the light source becomes lower than the threshold voltage, it may be determined that the first controller is inoperable.

  The determination circuit may also be used as a short circuit detection circuit. Thereby, an increase in the circuit area or the number of parts can be suppressed.

  The lighting circuit may further include a bypass controller that controls the plurality of bypass switches. The inoperable state of the first controller may be determined according to a control signal from the bypass controller. Since the bypass controller knows the states of the plurality of bypass switches at each time, the bypass controller can detect or predict that the first controller will become inoperable.

  Another aspect of the present invention relates to a vehicular lamp. The vehicular lamp includes a light source including a plurality of light emitting elements connected in series, and any one of the lighting circuits described above for lighting the light source.

  It should be noted that any combination of the above-described constituent elements, and those in which constituent elements and expressions of the present invention are mutually replaced between methods, apparatuses, systems, and the like are also effective as an aspect of the present invention.

  According to an aspect of the present invention, the switching operation of the switching converter can be maintained even when the first controller is inoperable.

It is a circuit block diagram of the vehicular lamp examined by the present inventors. It is a block diagram of a lamp system provided with the vehicle lamp which concerns on embodiment. It is an operation | movement waveform diagram of the vehicle lamp of FIG. It is a block diagram of the lighting circuit which concerns on one Example. It is a figure which shows the specific structural example of a converter controller. It is a figure explaining operation | movement of a 2nd controller. FIG. 3 is a simplified block diagram of a driver IC. It is a circuit diagram of a lighting circuit provided with the driver IC of FIG. It is a perspective view of a scan-type vehicle lamp. 10A to 10D are diagrams for explaining the formation of a light distribution pattern.

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

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

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

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

FIG. 2 is a block diagram of a lamp system 1 including the vehicular lamp 100 according to the embodiment. The lamp system 1 includes a battery 2, a vehicle ECU 4, and a vehicle lamp 100. Vehicle lamp 100 receives DC voltage (battery voltage) V _BAT from battery 2. Further, it is connected to the vehicle ECU 4 via a CAN (Controller Area Network), a LIN (Local Interconnect Network), or the like.

  The vehicular lamp 100 includes a lighting circuit 200, a light source 300, and a lamp ECU (Electronic Control Unit) 400. The lamp ECU 400 is connected to the vehicle ECU 4 and controls the lighting circuit 200 based on control signals and information from the vehicle ECU 4. From the vehicle ECU 4 to the lamp ECU 400, information indicating the host vehicle and surrounding conditions is transmitted in addition to an instruction to turn on and off. This information includes information on the position of the vehicle ahead and pedestrian, vehicle speed, and the like.

  The lamp ECU 400 includes a switch 402 and a processor 404. The switch 402 is provided on a power supply voltage supply path from the battery 2 to the lighting circuit 200. The processor 404 is a CPU (Central Processing Unit) or a microcomputer, and controls the switch 402 based on an on / off instruction from the vehicle ECU 4. When the switch 402 is turned on in response to a lighting command from the vehicle side, power is supplied to the lighting circuit 200. Further, the processor 404 determines a light distribution pattern based on information from the vehicle ECU 4 and controls the lighting circuit 200.

  The light source 300 includes a plurality of N (N ≧ 2) light emitting elements 302_1 to 302_N connected in series. The lighting circuit 200 is configured to be able to independently control turning on / off of each light source 300 by a bypass method.

  The lighting circuit 200 includes a constant current circuit 202, a bypass circuit 280, and a bypass controller 290, similarly to the lighting circuit 200R of FIG. The bypass circuit 280 and the bypass controller 290 are the same as those in FIG. Note that the function of the bypass controller 290 may be implemented in the processor 404.

  The constant current circuit 202 includes a switching converter 210, first current detection means 212, second current detection means 214, and converter controller 500. The switching converter 210 is a step-down (Buck) converter, a step-up (Boost) converter, or a step-up / step-down Cuk converter.

Converter controller 500 controls switching converter 210 such that lamp current I _LAMP approaches its target amount I _REF . First current detecting means 212 is provided on the output side of the switching converter 210, the lamp current _{I LAMP} directly monitored, to generate a first detection signal _{V CS1} corresponding to the lamp current _{I LAMP.} The first current detection means 212 may be a combination of the sense resistor _RS and the current detection circuit 206 in FIG.

The second current detection means 214 is provided separately from the first current detection means 212, and the second detection signal V _CS2 indicating the lamp current I _LAMP in the fully extinguishing state where the first current detection means 212 becomes inoperable. Can be generated. Second current detection means 214, by monitoring the current or voltage having a correlation with the lamp current _{I LAMP,} it can be said that indirectly monitors the lamp current _{I LAMP.} The second current detection unit 214 may be, for example, an input current of the switching converter 210, a coil current flowing through the coil of the switching converter 210, a current flowing through the switching element of the switching converter 210, or the like.

Converter controller 500 includes first controller 510, second controller 520, driver circuit 530, and determination circuit 540. The first controller 510 generates the first control pulse _SCNT1 based on the first detection signal _VCS1 generated by the first current detection unit 212. The first controller 510 controls at least one of the duty ratio, frequency, on-time, and off-time of the first control pulse _SCNT1 so that the lamp current I _LAMP approaches the first target amount I _REF1 .

When the first current detection unit 212 is provided on the output side of the switching converter 210, as described with reference to FIG. 1, the power supply voltage of the first current detection unit 212 is insufficient when the light source 300 is completely turned off. The correlation between the 1 detection signal V _CS1 and the lamp current I _LAMP is lost, and the first controller 510 becomes inoperable.

The second controller 520 generates the second control pulse _SCNT2 so that the lamp current I _LAMP does not become zero when the first controller 510 is inoperable. The second controller 520 preferably generates the second control pulse _SCNT2 by feedback. Specifically, the second controller 520 controls the second control pulse S so that the lamp current I _LAMP approaches the second target amount I _REF2 based on the second detection signal V _CS2 generated by the second current detection unit 214. Control at least one of the duty ratio, frequency, on-time, and off-time of _CNT2 .

The second target amount I _REF2 may be the same as the first target amount I _REF1 , but is preferably smaller than that. In the following description, I _REF2 <I _{REF1 is} assumed.

  The configuration of the first controller 510 and the second controller 520 and the pulse generation method are not particularly limited. For example, the controller architecture of voltage mode, peak current mode, and average current mode may be adopted, or the architecture of ripple control (hysteresis control, bottom detection / on time setting, upper detection / off time setting) may be adopted. Good. In addition, when controlling the light source 300 by a bypass system, since the quick response is calculated | required, it is preferable that the 1st controller 510 and the 2nd controller 520 are controllers of a ripple control. Note that the second controller 520 may continue to operate during a period in which the first controller 510 is operating normally.

The driver circuit 530 drives the switching converter 210 based on the first control pulse _SCNT1 and the second control pulse _SCNT2 . The driver circuit 530 may select one of the first control pulse _SCNT1 and the second control pulse _SCNT2 to generate the gate drive signal _SGATE . Alternatively, the driver circuit 530 may generate the gate drive signal S _GATE by combining the first control pulse S _CNT1 and the second control pulse S _CNT2 .

The above is the configuration of the vehicular lamp 100. Next, the operation will be described.
FIG. 3 is an operation waveform diagram of the vehicular lamp 100 of FIG. Here, N = 3. In the period T ₀ , all the bypass switches SWB _{1 to} SWB ₃ are off, and all the light emitting elements 302_1 to 302_3 emit light. Output voltage _{V O} of the switching converter 210 at this time is 3 × _{V F.} V _F is a forward voltage of the light emitting element 302. Note that the lamp current I _LAMP is indicated by a straight line, but actually, a ripple may be included.

In the period _{T 1,} the bypass switch SWB ₁ is emitting element 302_1 turned on is turned off. Output voltage _{V O} of the switching converter 210 at this time is 2 × _{V F.} In the period _{T 2,} the bypass switch _SWB 1, SWB ₂ is emitting element 302_1,302_2 turned on is turned off. Output voltage _{V O} of the switching converter 210 at this time is 1 × _{V F.}

During the period T _{0 to} T ₂ , the power supply voltage of the first current detection unit 212 exceeds the minimum operating voltage V _MIN of the first current detection unit 212, and the first current detection unit 212 and the first controller 510 operate. Is possible. Therefore, the lamp current I _LAMP is stabilized at the first target amount I _REF1 .

Period _{T 3,} all of the bypass switches _SWB 1 _{~SWB 3} is turned on, it is fully turned off state in which all of the light emitting element 302_1～302_3 is turned off. At this time, the output voltage V _O of the switching converter 210 is substantially zero. When the output voltage V _O becomes zero, the power supply voltage of the first current detection means 212 is lower than the minimum operating voltage V _MIN and the first controller 510 becomes inoperable. In this state, the second controller 520 is enabled and the second control pulse _SCNT2 is generated. As a result of driving the switching converter 210 by the second control pulse _SCNT2 , the lamp current I _LAMP is stabilized to the second target amount _IREF2 .

In the period _{T 4} followed, the bypass switch SWB ₁ is turned off, the output voltage _{V O} is 1 × _{V F} becomes, the first current detection means 212 and the first controller 510 are operable. As a result, the switching converter 210 is driven by the first control pulse _SCNT1 , and the lamp current I _LAMP is stabilized at the first target amount _IREF1 .

The operation of the vehicular lamp 100 has been described above.
The operation of the vehicular lamp 100 is clarified by comparison with the following comparative technique. In the comparative technique, the switching converter 210 is completely stopped and the lamp current I _LAMP becomes zero in the fully extinguished state T ₃ . Usually, after the switching converter 210 is completely stopped, soft start control is performed when the operation is resumed. _Therefore , a large delay occurs until the lamp current I _LAMP returns to the original target current.

According to the vehicle lamp 100 according to the embodiment with respect to this, even in a fully turned off state T _3, can be based on the second control pulse S _CNT2 continues switching operation of the switching converter 210, the lamp current I _LAMP can be kept non-zero. Accordingly, when the light emitting element 302 is turned on next time, the soft start control becomes unnecessary, and the light emitting element 302 can be turned on promptly.

In addition, the lamp current I _LAMP in the all-off state T ₃ does not contribute to the light emission of the light emitting element 302 and is wasted. By setting the second target amount I _REF2 to be lower than the first target amount I _REF1 , the power consumption in the bypass circuit 280 can be reduced, and the heat generation amount can be reduced. This means that a small and inexpensive component having a smaller heat capacity can be selected as the bypass switch SWB.

  The present invention covers various devices, circuits, and methods that can be grasped from the block diagram and circuit diagram of FIG. 2 or derived from the above description, and is not limited to a specific configuration. In the following, more specific embodiments and modifications will be described in order not to narrow the scope of the present invention but to help understanding the essence and circuit operation of the invention and to clarify them.

FIG. 4 is a block diagram of a lighting circuit 200A according to an embodiment. The switching converter 210 is a step-down converter and includes a switching transistor M ₁ , an inductor L ₁ , and a rectifying element D ₁ . First current detection means 212 includes a first sense resistor _{R S1} provided on a path of lamp current _{I LAMP,} first current detection for converting the voltage drop across the first sense resistor _{R S1} to the first detection signal _{V CS1} Circuit 216 is included.

Next, a configuration example of the converter controller 500A will be described. The first controller 510 includes a controller for hysteresis control. More specifically, in the vicinity of the first target quantity _{I REF1,} upper threshold _{I UPPER1} and bottom threshold _{I BOTTOM1} is defined. When the first detection signal V _CS1 reaches the voltage V _UPPER1 corresponding to the upper threshold value I _UPPER1 , the first controller 510 causes the first control pulse _SCNT1 to transition to an off level (for example, low), and the first detection signal V _CS1 is, drops to the voltage _{V BOTTOM1} corresponding to the bottom threshold _{I BOTTOM1,} shifts the first control pulse _{S CNT1} oN level (e.g., high).

The second current detection unit 214 is provided on the input side of the switching converter 210, monitors the input current I _IN of the switching converter 210, and generates a second detection signal V _CS2 corresponding to the lamp current I _LAMP . In the period of the switching transistor _{M 1} is turned on, input current _{I IN} is consistent with the output current _{I LAMP.} In the period of the switching transistor _{M 1} is turned off, the second detection signal _{V CS2} does not have a correlation with the lamp current _{I LAMP.}

For example, the second current detection means 214 includes a second sense resistor _{R S2} provided on a path of the input current _{I IN,} the second current to convert the voltage drop across the second sense resistor _{R S2} to the second detection signal _{V CS2} A detection circuit 218 is included. Instead of the second sense resistor R _S2, it may be utilized on-resistance of the switching transistor M _1.

Supply voltage of the second current detection circuit 218, the input voltage _{V IN} or the input voltage _{V IN} of the lighting circuit 200A may be an internal voltage stabilized. As a result, the second current detection circuit 218 can continue to operate even in the fully extinguished state.

The second controller 520 may be a controller in an upper detection / off time setting mode. Specifically, the second controller 520 defines an upper threshold value I _UPPER2 based on the second target amount I _REF2 . When the second detection signal V _CS2 reaches the voltage V _UPPER2 corresponding to the upper threshold value I _UPPER2 , the second controller 520 transitions the second control pulse _SCNT2 to an off level (for example, low). When a certain off time T _OFF elapses, the second control pulse S _CNT2 is _shifted to an on level (for example, high). The off time T _OFF may be constant or adjustable. According to the upper detection off time setting method, since the current information in the OFF period of the switching transistor M ₁ is not required, it generates a second control pulse S _CNT2 based on the second detection signal V _CS2.

  Converter controller 500A may further include a determination circuit 540. The determination circuit 540 determines whether or not the first controller 510 is operable. If the first circuit 510 is inoperable, the determination circuit 540 asserts the determination signal DET and enables the second controller 520.

FIG. 5 is a diagram illustrating a specific configuration example of the converter controller 500A. The first controller 510 includes a hysteresis comparator. The hysteresis comparator includes a variable voltage source 512 and a comparator 514, for example. Variable voltage source 512, depending on the state of the output of the comparator 514 (first control pulse _{S CNT1),} outputs one of the two voltages _{V UPPER1, V BOTTOM1.} The comparator 514 compares the first detection signal V _CS1 with the output of the variable voltage source 512 and generates the first control pulse S _CNT1 .

The second controller 520 includes a comparator 522 and a pulse generator 524. The comparator 522 compares the second detection signal V _CS2 with the voltage V _UPPER2 corresponding to the upper threshold value I _UPPER2 , and is asserted (for example, high level) when the second detection signal V _CS2 reaches the voltage V _UPPER2. Generate signal _OFF . The pulse generation unit 524 generates the second control pulse _SCNT2 that transitions to the off level in response to the assertion of the off signal and then transitions to the on level. The pulse generator 524 includes a flip-flop 526 and an off-time timer 528. An off signal S _OFF is input to the reset terminal of the flip-flop 526. Off-time timer 528, the second control pulse _{S CNT2} is from the transition to the off-level, after the lapse of the off-time _{T OFF,} asserts the ON signal _{S ON.} The on signal _SON is input to the set terminal of the flip-flop 526. Note that the configuration of the flip-flop 526 is not limited to that shown in FIG.

The determination circuit 540 may include a comparator 542 that compares a voltage corresponding to the voltage across the light source 300 (load voltage V _L ) with a predetermined threshold voltage V _TH . Determination circuit 540 may compare output voltage V _O of switching converter 210 with threshold voltage V _TH . The determination signal DET generated by the comparator 542 is asserted (high level) in a fully extinguished state and negated (low level) in a lit state. By defining smaller than the forward voltage V _F of the threshold voltage V _TH of the light emitting element 302, it can detect the full off state on the grounds that a Vo <V _F. The comparator 542 may also be used as a short circuit detection circuit. In other words, in addition to the fully extinguished state, the short circuit state of the output of the lighting circuit 200 may be treated as the inoperability of the first controller 510.

When the second controller 520 is configured as an upper detection / off time setting mode controller, the second controller 520 operates as an overcurrent protection circuit rather than being completely stopped during a period in which the first controller 510 can operate. You may let them. In this case, the second upper threshold value I _UPPER2 may be switched between the first value I _TH1 and the second value I _TH2 . Specifically, when the first controller 510 is inoperable, the upper threshold value I _UPPER2 of the second controller 520 may be set to the first value I _TH1 corresponding to the second target amount I _REF2 . In a state where the first controller 510 is operable, the upper threshold value I _UPPER2 may be set to the second value I _TH2 corresponding to the _overcurrent threshold value I _OCP higher than the first target amount I _REF1 .

Specifically, when the determination signal DET is asserted, the voltage generated by the voltage source 523 is the first level V _REF2 corresponding to the second target amount I _REF2 , and when the determination signal DET is negated, the voltage source 523 The voltage to be generated may be the second level V _OCP corresponding to the _overcurrent threshold I _OCP .

FIG. 6 is a diagram for explaining the operation of the second controller 520. In a state where at least one light emitting element 302 is lit (referred to as a lit state), the determination signal DET is negated. Before the time t ₀ , the first controller 510 is operating normally, and the switching transistor M ₁ is controlled according to the first control pulse S _CNT1 generated by the first controller 510, and the lamp current I _LAMP is It is stabilized to within the range of _{I UPPER1} and _{I BOTTOM1} corresponding to 1 target amount _{I REF1.} When the first controller 510 is normal, the second controller 520 does not affect the control of the switching transistor _{M 1.}

Prior to time t ₀ , the value of the upper threshold value I _UPPER2 of the second controller 520 is the second value I _TH2 corresponding to the overcurrent threshold value I _OCP2 . Abnormality in the first controller 510 generates at time _{t 0.} In an abnormal state, the value of the upper threshold value I _UPPER2 of the second controller 520 decreases to the first value I _TH1 that defines the second target amount I _REF2 .

At time _{t 1,} the off signal _{S OFF} is asserted in the second controller 520. Then, the ON signal S _ON is asserted at time t ₂ after the elapse of the _OFF time T _OFF , the second control pulse S _CNT2 and the gate drive signal S _GATE are turned on, and the switching transistor M ₁ is turned on. When the switching transistor _{M 1} is turned on, input current _{I IN} is increased, the second detection signal _{V CS2} increases. When I _IN > I _OCP , in other words, when V _CS2 > V _OCP , the second controller 520 asserts the off signal S _OFF , the second control pulse S _CNT2 transits to the off level, and the gate drive signal S _GATE is turned off level, the switching transistor _{M 1} is turned off. Then, off-on signal _{S ON} to the time _{t 4} after the elapse of the time _{T OFF} is asserted, the second control pulse _{S CNT2} is changed to the on level.

  Next, an embodiment in which the same function as that of the lighting circuit 200A of FIG. 4 is implemented using a commercially available LED driver IC (Integrated Circuit) will be described. Here, the LED driver IC will be described by taking LM3409, etc., manufactured by TEXAS INSTRUMENTS, USA as an example.

  FIG. 7 is a simplified block diagram of the driver IC 600. The driver IC 600 can be understood as an integration of the driver circuit 530, the second controller 520, and the second current detection circuit 218 of FIG.

  The driver IC 600 incorporates an upper detection / off time setting type controller. In this embodiment, the controller built in the driver IC 600 is used as the second controller 520 (and overcurrent protection circuit) in FIG.

PGATE terminal of the driver IC600 is connected to the gate of the switching transistor _{M 1.} The current setting (IADJ) terminal is a terminal for setting the peak current I _UPPER used in the upper detection / off time setting method. The CSP terminal and the CSN terminal for current detection are connected to the second sense resistor _RS2 . A voltage V _CS2 proportional to the input current I _IN is generated between the CSP terminal and the CSN terminal.

Level shifter 610 includes resistors R ₂₁ and R ₂₂ and a V / I conversion circuit 612. The V / I conversion circuit 612 generates a current I _ADJ that is proportional to the voltage V _IADJ input to the IADJ terminal. A voltage drop I _ADJ × R ₂₁ corresponding to the upper threshold value I _UPPER2 is generated in the resistor R ₂₁ , and V _CSP −I _ADJ × R ₂₁ is generated at one end on the low potential side. Voltage drop across the resistor R ₂₂ is substantially zero. The level shifter 610 corresponds to the second current detection circuit 218 and the voltage source 523 in FIG.

The comparator 614 corresponds to the comparator 522 in FIG. The comparator 614 compares the voltage at one end of each of the two resistors R ₂₁ and R ₂₂ and generates an off signal S _OFF . That is, the comparator 614 compares V _CSP -I _ADJ × R ₂₁ and V _CSP -R _S2 × I _IN . This is equivalent to comparing I _ADJ × R ₂₁ and R _S2 × I _IN . The off signal S _OFF is asserted when I _IN > I _ADJ × R ₂₁ / R _S2 .

The IADJ terminal of the driver IC 600 is a setting pin for setting the upper threshold value I _UPPER2 (and I _OCP ). A voltage VI _ADJ having a level corresponding to I _OCP is input to the IADJ terminal when the first controller 510 is operable, and a voltage VI _ADJ having a level corresponding to I _UPPER2 is input when the first controller 510 is inoperable. Is done.

An off time setting capacitor is externally attached to the COFF terminal. The GND terminal is grounded. The VIN pin input voltage _{V IN} is supplied.

The pulse generator 616 includes a logic circuit 620 and an off time timer circuit 622. When the output S _{OFF of the} comparator 614 is asserted, the logic circuit 620 shifts the second control pulse _SCNT2 to the off level and gives a start trigger to the off-time timer circuit 622. The logic circuit 620 corresponds to the flip-flop 526 in FIG. 5, and the off-time timer circuit 622 corresponds to the off-time timer 528 in FIG.

Off-time timer circuit 622 starts operating in response to the start trigger, after the lapse of the off-time T _OFF, asserts the ON signal S _ON. For example, the off-time timer circuit 622 compares the voltage V _{COFF of the} COFF terminal with a predetermined voltage V _OFF with a switch provided in parallel with the external capacitor C _tm between the COFF terminal and the ground. A comparator. Also the COFF terminal, the charging voltage _{V C} is applied via a resistor _{R tm.} The switch of the off-time timer circuit 622 is turned on when V _COFF > V _OFF and discharges the capacitor C _tm . The off time can be set according to the capacitance value of the capacitor C _tm , the charging voltage V _C , and the resistance value R _tm . Logic circuit 620 transits the second control pulse _{S CNT2} in response to the assertion of the on signal _{S ON} to the on-level.

The output of the driver circuit 530 is connected to the gate of the switching transistor _{M 1} through the PGATE terminal.

The driver IC 600 includes an enable (EN) terminal, and is enabled when a high level is input to the enable terminal. Driver IC600 while the low level is input to the enable terminal becomes a disabled state, the gate output PGATE is fixed to the low level, the switching transistor M ₁ is turned off.

FIG. 8 is a circuit diagram of a lighting circuit 200B including the driver IC 600 of FIG. An enable terminal of the driver IC 600, the first control pulse _{S CNT1} of the first controller 510 has generated is input. That entire driver IC600 in response to the first control pulse _{S CNT1} is turned on, by turning off, the PGATE terminal, the gate drive signal _{S GATE} according to the first control pulse _{S CNT1} occurs. When the first controller 510 becomes inoperable, the enable terminal EN is fixed at a high level, and the gate drive signal S _GATE corresponding to the second control pulse S _CNT2 generated inside the driver IC 600 is generated at the PGATE terminal. .

The determination circuit 540 compares the load voltage V _L supplied to the light source 300 with the threshold voltage V _TH and generates a determination signal DET. When the determination signal DET indicates a lighting state, the first voltage level is supplied to the IADJ terminal, whereby the upper current in the driver IC 600 is set to I _OCP and the overcurrent protection function is enabled. . When the determination signal DET indicates a fully extinguished state, the second voltage level is supplied to the IADJ terminal, whereby the upper current inside the driver IC 600 is set to I _UPPER2 , and the upper detection / off time setting mode is set. As a result, the second control pulse _SCNT2 is generated. That is, the second controller 520 is enabled. A ripple removing filter 270 may be inserted between the switching converter 210 and the light source 300.

  Although the lighting circuit 200 can be mounted on various vehicle lamps 100, it can be suitably used particularly for scan-type lamps. FIG. 9 is a perspective view of a scan-type vehicle lamp. The vehicle lamp 100 of FIG. 9 can select a plurality of light distribution modes according to the traveling scene.

  The vehicular lamp 100 mainly includes a light source unit 110, a scanning optical system 120, a projection optical system 130, and the lighting circuit 200 described above. The light source unit 110 includes a plurality of light emitting units 112. The light source unit 110 and the light emitting unit 112 correspond to the light source 300 and the light emitting element 302 in FIG. The plurality of light emitting units 112 are connected to a lighting circuit 200 (not shown) via a connector 114. The light emitting unit 112 includes a semiconductor light source such as an LED (light emitting diode) or an LD (semiconductor laser). One light emitting unit 112 constitutes a minimum unit for controlling brightness and lighting. One light emitting unit 112 may be one LED chip (LD chip), or may include a plurality of LED chips (LD chips) connected in series and / or in parallel.

Scan optics 120 receives light emitted L ₁ of the light source 110, (in the figure, H direction) transverse the reflected light L ₂ at the front of the vehicle by repeating a predetermined periodic motion scanned in. The projection optical system 130 projects the reflected light _{L 2} of the scanning optical system 120 on the virtual screen 10 in front of the vehicle. The projection optical system 130 can be configured by a reflection optical system, a transmission optical system, or a combination thereof.

Specifically, the scanning optical system 120 includes a reflector 122 and a motor 124. The reflector 122 is attached to the rotor of the motor 124 and performs a rotational motion. In the present embodiment, two reflectors 122 are provided, and the emitted light L ₂ is scanned twice by one rotation of the motor 124. Therefore, the scanning frequency is twice the rotational speed of the motor. The number of reflectors 122 is not particularly limited.

At a certain time t ₀ , the emitted light L ₁ of the light source unit 110 is reflected at an angle according to the position of the reflector 122 (rotor rotation angle), and the reflected light L _{2 at} that time is reflected on the virtual screen 10 in front of the vehicle. , One irradiation region 12 is formed. In FIG. 1, the irradiation area 12 is shown as a rectangle for simplification of explanation, but the irradiation area 12 is not necessarily rectangular as described later.

When the position of the reflector 122 changes at another time t ₁ , the reflection angle changes, and the reflected light L ₂ ′ at that time forms an irradiation region 12 ′. Further, when the position of the reflector 122 changes at another time t ₂ , the reflection angle changes, and the reflected light L ₂ ″ at that time forms an irradiation region 12 ″.

  By rotating the scanning optical system 120 at a high speed, the irradiation region 12 scans the virtual screen 10, thereby forming a light distribution pattern in front of the vehicle.

  10A to 10D are diagrams for explaining the formation of a light distribution pattern. FIG. 10A shows a layout of a plurality of light emitting units 112 in the light source unit 110. In the present embodiment, the number of the plurality of light emitting units 112 is nine.

  The plurality of light emitting units 112 are arranged in two or more stages in the height direction, and are arranged in three stages in this example, and the number of light emitting units 112 in the lowest stage is the largest. Thereby, a region with high illuminance can be formed in the vicinity of the H line on the virtual screen.

  The vehicular lamp 100 according to the present embodiment forms a light distribution pattern by superimposing light distribution by scanning and light distribution by non-scanning. In addition to the plurality of light emitting units 112_1 to 112_9 for scanning, the light source unit 110 includes at least one light emitting unit 113_1 and 113_2 for widely irradiating the front of the vehicle without scanning. Light emitted from the light emitting units 113_1 and 113_2 is irradiated onto the virtual screen 10 via an optical system (not shown) different from the scan optical system 120.

  FIG. 10B is a diagram showing irradiation spots formed on the virtual screen 10 by the light emitted from the light emitting units 112 and 113 when the reflector 122 is at a predetermined position.

An irradiation spot formed by the light emitting unit 112 for scanning is referred to as a condensed spot Sc. Sc _i represents a condensing spot formed by the i-th (1 ≦ i ≦ 9) light emitting unit 112 — i. A set of the plurality of focused spots Sc _{1 to} Sc ₉ in FIG. 10B corresponds to the irradiation region 12 in FIG.

The irradiation spot formed on the virtual screen 10 by the light emitting unit 113 for diffusion is referred to as a diffusion spot Sd. Sd _i represents a condensing spot formed by the i-th light emitting unit 113_i. The diffusion spot Sd is independent of the rotation of the reflector 122. A set of diffusion spots Sd ₁ and Sd ₂ is referred to as a diffusion region 14.

  FIG. 10B shows only the irradiation spots Sc and Sd by the right lamp. When the right side lamp and the left side lamp are configured symmetrically, a left side lamp is formed by horizontally inverting the irradiation spot of FIG.

FIG. 10C shows a region (referred to as a scan region) SR through which each focused spot Sc passes when the reflector 122 is rotated. SR _i indicates a region through which the i-th focused spot Sc _i passes. A set of scan areas SR _{1 to} SR ₉ , in other words, an area where the irradiation area 12 is scanned is referred to as a light collection area 15. The condensing region 15 overlaps with the diffusion region 14.

  FIG. 10D shows the illuminance distribution in the horizontal direction of the light distribution pattern in the vicinity of the H line formed by the lowermost light emitting units 112_1 to 112_5.

  The light distribution pattern actually formed is a superposition of the light distribution pattern of the right lamp and the light distribution pattern of the left lamp. In this example, the light collection region 15 of the right lamp and the light collection region 15 of the left lamp substantially overlap each other. Further, the diffusion area 14 of the right lamp mainly emits the right side from the V line, and the diffusion area 14 (not shown) of the left lamp mainly emits the left side from the V line.

  As described above, the plurality of light emitting units 112_1 to 112_9 for scanning are arranged so that the respective emitted lights irradiate different places on the virtual screen. As shown in FIG. 10A, a plurality of light emitting units 112 may be arranged in a U shape. By arranging in a U-shape (or an E-shape in FIG. 10), the right end and the left end of the first, second, and third-stage condensing regions can be aligned.

The correspondence between the plurality of light emitting units 112 and the channels is, for example, as follows.
First channel CH ₁ = light emitting unit 112_1, 112_2
Second channel CH ₂ = light emitting unit 112_3
Third channel CH ₃ = light emitting units 112_4 and 112_5
Fourth channel CH ₄ = light emitting units 112_6 and 112_7
5th channel CH ₅ = light emitting unit 112_8, 112_9
Emitting unit 113_1,113_2 for diffusion regions, a sixth channel CH _6.

  The plurality of light emitting units 112 are arranged in three stages in the height direction, and the light emitting units 112 that irradiate the same height are classified into the same channel so that the same amount of driving current is supplied. A plurality of light emitting units 112 included in the same channel are connected in series so as to form one light source 300.

  In such a scan-type lamp, an all-off state in which a plurality of light emitting units 112 of the same channel are simultaneously turned off can occur intermittently in a scanning cycle. Therefore, power consumption can be suppressed by driving the lighting circuit 200 described above.

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

(First modification)
Turning on / off the plurality of light emitting elements 302 is controlled by a bypass controller 290. Accordingly, the bypass controller 290 knows when the fully extinguished state occurs. Therefore, the determination circuit 540 may determine whether the light is completely off or on based on information from the bypass controller 290. Alternatively, the function of the determination circuit 540 may be implemented in the bypass controller 290.

(Second modification)
In the embodiment, the switching converter 210 is a step-down converter, but may be a step-up converter or a step-up / step-down converter.

(Third Modification)
In the embodiment, the second controller 520 generates the second control pulse _SCNT2 based on the second detection signal _VCS2 from the second current detection unit 214. However, the present invention is not limited to this. The second controller 520 may generate the second control pulse _SCNT2 in a completely open loop. In this case, the level at which the lamp current I _LAMP is stabilized depends on the input voltage, but the second controller 520 can be simplified. For example, the second controller 520 may be configured with an oscillator.

(Fourth modification)
In the embodiment, the inoperable state of the first controller 510 has been described as a fully extinguished state, but the application of the present invention is not limited thereto. Even in lighting circuits other than the bypass system, for example, if the output of the converter is short-circuited (ground fault), the first controller 510 becomes inoperable. By providing the second controller 520, the switching operation of the switching converter 210 can be maintained even in a ground fault state. When the ground fault is temporary, the luminance of the light source 300 can be increased promptly after the cause of the ground fault is removed. If the second target amount I _REF2 is set small, the current flowing through the ground fault path can also be reduced.

  Although the present invention has been described using specific terms based on the embodiments, the embodiments merely show one aspect of the principle and application of the present invention. Many variations and modifications of the arrangement are allowed without departing from the spirit of the present invention defined in the scope.

1 LAMP system, 2 ... battery, 4 ... vehicle ECU, 100 ... vehicle lamp, M 1 _... switching transistors, 300 ... light source, 302 ... light emitting element, 400 ... lamp ECU, 402 ... switch, 404 ... processor, 200 ... Lighting circuit 202 ... Constant current circuit 204 ... Switching converter 206 ... Current detection circuit 208 ... Converter controller ... 210 ... Switching converter 212 ... First current detection means 214 ... Second current detection means 216 ... First current detection circuit, 218 ... second current detection circuit, 280 ... bypass circuit, 290 ... bypass controller, R _S ... sense resistor, SWB ... bypass switch, S _CNT1 ... first control pulse, S _CNT2 ... second control pulse , _{V CS1 ...} first detection signal, _{V CS2 ...} second detection signal, 50 ... Converter controller, 510 ... First controller, 512 ... Variable voltage source, 514 ... Comparator, 520 ... Second controller, 522 ... Comparator, 524 ... Pulse generator, 526 ... Flip-flop, 528 ... Off time timer, 530 ... Driver Circuits 540... Determination circuit 600 Driver IC 610 Level shifter 612 V / I conversion circuit 614 Comparator

Claims (12)

A lighting circuit for driving a light source,
A switching converter;
A converter controller for controlling the switching converter;
With
The converter controller is
Based on a first detection signal generated by a first current detection means provided on the output side of the switching converter, a first control pulse is generated so that the lamp current generated by the converter controller approaches a first target amount. A first controller that
A second controller that generates a second control pulse so that the lamp current does not become zero in an inoperable state of the first controller;
A driver circuit for driving the switching converter based on the first control pulse and the second control pulse;
A lighting circuit comprising: The light source includes a plurality of light emitting elements connected in series,
The lighting circuit further includes a plurality of bypass switches each connected in parallel with a corresponding light emitting element,
2. The lighting circuit according to claim 1, wherein the inoperable state of the first controller is a fully extinguished state in which all bypass switches are turned on.   The second controller controls the second control pulse so that the lamp current approaches a second target amount based on a second detection signal generated by a second current detection unit different from the first current detection unit. The lighting circuit according to claim 1, wherein the lighting circuit is generated.   The lighting circuit according to claim 3, wherein the second current detection unit is provided on an input side of the switching converter.   The lighting circuit according to claim 3, wherein the second controller is a controller in an upper detection / off time setting mode.   The lighting circuit according to claim 5, wherein the second controller operates as an overcurrent protection circuit in an operable state of the first controller. The second controller is
A comparator that compares the second detection signal with an upper threshold that defines a peak value of the output current of the switching converter and generates an off signal that is asserted when the second detection signal reaches the upper threshold When,
A pulse generation unit that generates the second control pulse that transitions to an off level when the off signal is asserted and then transitions to an on level;
The lighting circuit according to claim 3, further comprising:   8. The upper threshold value takes a first value when the first controller is not operable and takes a second value higher than the first value when the first controller is operable. Lighting circuit according to.   A determination circuit that compares the voltage across the light source with a predetermined threshold voltage and determines that the first controller is inoperable when the voltage across the light source becomes lower than the threshold voltage; The lighting circuit according to any one of claims 1 to 8, characterized in that   The lighting circuit according to claim 9, wherein the determination circuit is also used as a short circuit detection circuit. A bypass controller for controlling the plurality of bypass switches;
A determination circuit for determining an inoperable state of the first controller in response to a control signal from the bypass controller;
The lighting circuit according to claim 1, further comprising: A light source including a plurality of light emitting elements connected in series;
The lighting circuit according to any one of claims 1 to 11, wherein the light source is turned on;
A vehicular lamp characterized by comprising:

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