SL Corp. Exhibit 1025
`
`

`
`(19) Japan Patent Office (JP)
`
`(12) Japanese Unexamined Patent
`Application Publication (A)
`
`(11) Japanese Unexamined Patent
`Application Publication Number
`2000-185593
`(P2000-185593A)
`(43) Publication date: July 4, 2000 (2000.7.4)
`
`(51) Int. Cl.6
`B60Q 1/04
`1/14
`
`Identification codes
`
`FI
`B60Q
`
`1/04
`1/14
`
`Theme Codes
`3K039
`
`E
`F
`
`Request for examination Not yet requested Number of claims: 13 OL (Total of 9 pages)
`
`(21) Application number
`
`(22) Date of application
`
`Japanese Patent Application
`H10-364677 A
`Dec. 22, 1998
`
`(71) Applicant
`
`(72) Inventor
`
`(72) Inventor
`
`(72) Inventor
`
`(74) Agent
`
`000002303
`STANLEY ELECTRIC K.K.
`2-9-13 Naka Meguro, Meguro-ku, Tokyo-to
`NOBUHARU FUKUWA
`1790-13 Takagasaka, Machida-shi, Tokyo-to
`KATSUTOSHI FUKAZAWA
`5-15-20-302 Higashi Kashiwagaya, Ebina-shi,
`Kanagawa-shi
`HIDEKI KITAMURA
`39-6-207 Umegaoka, Aoba-ku, Yokohama-shi,
`Kanagawa-ken
`100066061 Patent attorney HIROYUKI TANBA
`
`(54) (TITLE OF THE INVENTION) VEHICLE LAMP CONTROL DEVICE
`
`Continued on last page
`
`(57) [ABSTRACT]
`[PROBLEM] To simplify circuitry and increase output precision at low
`cost and be able to respond to errors in a lighting control device for
`vehicle lamps, in particular for cases where discharge lamps are used
`as headlamps, for example.
`[Means for Solving the Problem] A lighting circuit of a discharge
`lamp 5 having a DC/DC converter 2, which is a DC voltage boosting
`circuit, a DC/AC inverter 3, and a launch circuit 4 is controlled by a
`lighting control circuit 19, and vertical and horizontal optical axis
`adjustment, etc., of
`the discharge lamp 5 is controlled by a
`microcomputer 20. The microcomputer 20 outputs to a lighting
`control circuit 19 a setting value of a lamp current based on a lamp
`voltage detected by a voltage detection circuit 22, and the lighting
`control circuit 19 controls output of the lighting circuit on the basis of
`the setting value of the lamp current and the detection value of the
`lamp current detected by a current detection circuit 21.
`
`

`
`Japanese Unexamined Patent Application Publication 2000-185593
`(2)
`
`[SCOPE OF PATENT CLAIMS]
`[CLAIM 1] A vehicle lamp control device, comprising a lamp
`control circuit that performs optical axis adjustment of a lamp, a
`lighting circuit that supplies lighting power to a lamp, a lighting
`control circuit
`that controls the lighting circuit, a voltage
`detection circuit
`that detects a lamp voltage, and a current
`detection circuit that detects a lamp current, wherein the lamp
`control circuit outputs to the lighting control circuit a setting
`value of the lamp current on the basis of the lamp voltage
`detected by the voltage detection circuit and the lighting control
`circuit controls output of the lighting circuit on the basis of the
`setting value of the lamp current and a detection value of the
`lamp current detected by the current detection circuit.
`[CLAIM 2]
`The vehicle lamp control device as claimed in
`claim 1, wherein the lighting circuit has a direct current voltage
`boosting circuit that boosts the current from a direct current
`source and a direct current–alternating current
`inverter that
`converts direct current
`into alternating current and supplies
`lighting current to a lamp, and a headlamp using a discharge
`lamp is lighted as the lamp.
`[CLAIM 3]
`The vehicle lamp control device as claimed in
`claim 1 or claim 2, wherein the lamp control circuit is provided
`with at
`least either leveling functionality whereby a vertical
`optical axis of
`the lamp is controlled or cornering light
`distribution functionality that adjusts a horizontal optical axis.
`[CLAIM 4]
`The vehicle lamp control device as claimed in
`claim 2 or claim 3, wherein the lamp control circuit is constituted
`by a microcomputer and a polarity-switching control signal for
`alternating
`current
`lighting
`is
`output
`to
`the
`direct
`current–alternating current inverter.
`[CLAIM 5]
`The vehicle lamp control device as claimed in any
`one of claims 2–4, wherein the lighting control circuit compares
`detection values of output voltage and output current from the
`direct current voltage boosting circuit and setting values for
`limiting output thereof, and controls output of the direct current
`voltage boosting circuit on the basis of results of the comparison.
`[CLAIM 6]
`The vehicle lamp control device as claimed in any
`one of claims 1–5, wherein operation of the lighting circuit is
`stopped when the lamp control circuit detects an error on the
`basis of the detection value of the lamp voltage and the detection
`value of the lamp current.
`[CLAIM 7]
`The vehicle lamp control device as claimed in any
`one of claims 1–6, wherein the lighting control circuit
`is
`constituted by a CMOS transistor, and the lighting control circuit
`and the lamp control circuit are formed on one semiconductor
`chip in an integrated manner.
`[CLAIM 8]
`The vehicle lamp control device as claimed in any
`one of claims 1–7, wherein the lamp control circuit has two
`systems for left and right lamps, one of the control circuits
`adjusting the vertical optical axis of both of the lamps and
`another of the control circuits adjusting the horizontal axis of
`both of the lamps.
`[CLAIM 9]
`The vehicle lamp control device as claimed in
`claim 8, wherein the two lamp control circuits comprise
`microcomputers having memory with identical content, and
`
`control is performed by using an external signal to selecting
`either a control program that adjusts the vertical optical axis or a
`control program that adjusts the horizontal optical axis.
`[CLAIM 10]
`The vehicle lamp control device as claimed in
`claim 8 or claim 9, wherein the two lamp control circuits perform
`at
`least
`either mutual
`information exchange
`through a
`communication port or
`information exchange with another
`external device.
`[CLAIM 11]
`The vehicle lamp control device as claimed in any
`one of claims 8–10, wherein, if there are two lamps, left and right,
`the left and right lamps have functionality for light distribution
`switching control between a traveling beam and a passing beam.
`[CLAIM 12]
`The vehicle lamp control device as claimed in any
`one of claims 1–11, wherein the lamp control circuit has a
`common memory that stores parameters for correcting output
`characteristics of optical axis adjustment sensors that differ by
`vehicle model.
`The vehicle lamp control device as claimed in any
`[CLAIM 13]
`one of claims 1–12, wherein the lamp control circuit has an
`added control function other than an adjustment function for the
`vertical and horizontal optical axes.
`[DETAILED DESCRIPTION OF THE INVENTION]
`[0001]
`[TECHNICAL FIELD TO WHICH THE INVENTION BELONGS] The
`present
`invention relates to a vehicle lamp control device
`particularly suited to automobile headlights using discharge
`lamps.
`[0002]
`[PRIOR ART] Lighting devices in which discharge lamps are used
`as automobile headlights and are instantly lighted by applying a
`starting current that is several multiples of the rated current when
`starting the discharge lamps have been proposed. FIG. 3 is a
`block diagram showing a circuit configuration of a discharge
`lamp lighting device.
`lighting device comprises a DC/DC
`[0003] This type of
`converter 2 that inputs a DC voltage from a DC power source 1
`such as a battery and boosts the DC voltage, a DC/AC inverter 3
`that converts the DC into AC and supplies the AC to a discharge
`lamp 5, and a launch circuit 4 that generates a high-voltage pulse
`for launching that initiates discharge when lighting the discharge
`lamp 5 (when starting). Output of the DC/DC converter 2 is
`detected by a current detection element 6 and a voltage detection
`element 7, a control circuit 8 controls the DC/DC converter 2 on
`the basis of the detection values, and the DC/AC inverter 3 is
`controlled by an inverter driver 9.
`[0004] In the lighting device thus configured, lamp power from
`starting of the discharge lamp 5 until stabilization is achieved is
`controlled by a lighting control portion inside the DC/DC
`converter 2 in accordance with lamp voltage and lamp current. If
`an error occurs in input voltage, output voltage, or output current,
`functionality is provided for stopping operation by means of a
`protection circuit.
`[0005] In order to perform this control operation, a control circuit
`8 constituted mainly by an analog circuit or a microcomputer is
`provided. Specifically, a setting value of the lamp power is found
`
`

`
`Japanese Unexamined Patent Application Publication 2000-185593
`(3)
`
`as computation output by the control circuit 8 on the basis of
`which the DC/DC converter 2 is subjected to power output
`control such as PWM or the like to perform lamp power control,
`and if an input or output error occurs operation is stopped in the
`form of a protection operation.
`[0006] Thus, with the control circuit of an illumination discharge
`lamp lighting device for an automobile, there are protection items
`such as output short currents that are limited by each cycle of the
`PWM oscillation frequency in a PWM controller that requires
`rapid feedback control for which analog circuitry is more suited
`and there are protection items that have a long monitoring cycle,
`such as computation of power setting values and output open
`stopping that are possible with microcomputer control, and
`therefore it cannot be said in general that one or the other is more
`advantageous as a control circuit configuration of a discharge
`lamp lighting device. There are also cases where dedicated ICs
`are used in which the analog control circuitry is customized.
`[0007] There have been practical implementations of automatic
`optical axis adjustment functions whose purpose is to prevent
`glare against oncoming vehicles through active control of the
`optical axis of the headlamps. FIG. 4 shows an example of a
`circuit configuration of this auto leveling.
`[0008] In FIG. 4, 10 is a headlamp unit onto which the discharge
`lamp 5 is mounted, and into which a reflector 11 and a motor 12
`for optical axis adjustment are incorporated. 13 is a motor driver
`that drives the motor 12, and 14 is a microcomputer into which
`are input signals from a lamp switch 15, a vehicle speed sensor
`16, and vehicle height sensors 17 and 18 in front and back of a
`vehicle.
`[0009] There are large advantages in including this auto leveling
`function in discharge lamp headlamps, which are at least twice as
`bright as halogen bulbs,
`increasing their marketability. As a
`control circuit for implementing an auto leveling function that
`performs automatic adjustment of the optical axis, an amount of
`control of an actuator that moves the optical axis can be varied in
`accordance with signals input from the vehicle height sensors 17
`and 18, the vehicle speed sensor 16, the lamp switch 15, and so
`on. The detection level of the vehicle height sensors 17 and 18
`has to be set according to where they are installed on the
`suspension. Microcomputers are generally more suited to cases
`where accurate control values are required for various inputs like
`this, and optimization is relatively easy.
`[0010] It is effective to use a common housing for device units in
`cases where combination of the discharge lamp lighting device
`attached to a headlamp unit 10 and the auto leveling device is
`considered. FIG. 5 shows a configuration of a conventional
`discharge lamp lighting device with added auto leveling function.
`When a combined control unit is attached to the headlamp unit
`10, a single unit results, which can reduce the number of process
`steps involved and is effective in reducing costs. Combination of
`these lamp control units is therefore moving forward. In FIG. 5,
`19 is a lighting control circuit
`that controls lighting of the
`discharge lamp 5.
`[0011] For example, JP H10-35358 A describes a discharge lamp
`lighting device in which a leveling function, etc., is provided that
`
`adjusts light distribution of the headlamps. It also states that
`control is easily done when using a microcomputer in cases
`where vehicle height sensor information, etc., differs from model
`to model depending on factors such as the tightness of the
`suspension. Aside from the auto level function, a lamp cleaner is
`described as a third function and adding a function for cornering
`light distribution in parallel as a fourth function, as well as the
`microcomputer of the lighting device sending malfunction data
`out of the device, and so on.
`[0012]
`[PROBLEMS TO BE SOLVED BY THE INVENTION] The following
`problems have existed in conventional vehicle lamp control
`devices with this type of auto leveling functionality.
`[0013] (1) A microcomputer control portion of the auto leveling
`device was simply added to a conventional discharge lamp
`lighting device which performed control operations for boosting
`circuits using dedicated IC’s, protection operations when errors
`occur, meaning that
`the dedicated control
`IC and the
`microcomputer have been needed in order to combine control
`functionality, and therefore costs have not fallen even when
`circuits have been integrated.
`involving circuit
`impossible
`[0014]
`(2) Combination is
`functionality if lighting of discharge lamps is controlled using
`only the dedicated IC. Moreover, in cases where lighting control
`is done using only the microcomputer power source control of
`the boosting circuit has also been necessary, which makes the
`processing load on the microcomputer larger. There is therefore a
`need to select a high-performance microcomputer, which
`eliminates any cost-related advantages.
`[0015] (3) When adding functionality other than auto leveling
`functionality to the discharge lamp lighting device, such as
`cornering light distribution control designed to control an angle
`of illumination to the right and left when going around a curve,
`or headlamp cleaner functionality, a second circuit (leveling), a
`third circuit (cleaner), and a fourth circuit (light distribution
`control) which perform these various control operations are
`added in parallel to one of the discharge lamp lighting devices
`for the left and right lamps, meaning that the processing load is
`focused on the microcomputer for the lighting device control on
`one
`of
`the
`lamps,
`and
`therefore
`a
`high-performance
`microcomputer must be used, which is disadvantageous in terms
`of cost.
`[0016] (4) Since malfunction data is only sent outside the
`microcomputer, operations responding thereto by compensating
`cannot be done by the functional lamp if the other one has
`malfunctioned.
`invention was devised in light of these
`[0017] The present
`problems and has as an object to provide a vehicle lamp control
`circuit with which circuitry can be simplified and high precision
`output can be realized at low cost thanks to an optimized control
`configuration, and which is capable of responding to errors.
`[0018]
`[MEANS FOR SOLVING THE PROBLEM] A vehicle lamp control
`device according to the present
`invention is configured as
`follows.
`
`

`
`Japanese Unexamined Patent Application Publication 2000-185593
`(4)
`
`[0019] (1) A vehicle lamp control device comprises a lamp
`control circuit that performs optical axis adjustment of a lamp, a
`lighting circuit that supplies lighting power to a lamp, a lighting
`control circuit
`that controls the lighting circuit, a voltage
`detection circuit
`that detects a lamp voltage, and a current
`detection circuit that detects a lamp current, and the lamp control
`circuit outputs to the lighting control circuit a setting value of the
`lamp current on the basis of the lamp voltage detected by the
`voltage detection circuit and the lighting control circuit controls
`output of the lighting circuit on the basis of the setting value of
`the lamp current and a detection value of the lamp current
`detected by the current detection circuit.
`[0020] (2) In the configuration of (1) above the lighting circuit
`has a direct current voltage boosting circuit
`that boosts the
`current
`from a
`direct
`current
`source
`and
`a
`direct
`current–alternating current inverter that converts direct current
`into alternating current and supplies lighting current to a lamp,
`and a headlamp using a discharge lamp is lighted as the lamp.
`[0021] (3) In the configuration of (1) or (2) above, the lamp
`control circuit
`is provided with at
`least either
`leveling
`functionality whereby a vertical optical axis of the lamp is
`controlled or cornering light distribution functionality that
`adjusts a horizontal optical axis.
`[0022] (4) In the configuration of (2) or (3) above, the lamp
`control circuit
`is constituted by a microcomputer and a
`polarity-switching control signal for alternating current lighting
`is output to the direct current–alternating current inverter.
`[0023] (5) In one of the configurations in (2)–(4) above, the
`lighting control circuit compares detection values of output
`voltage and output current from the direct current voltage
`boosting circuit and setting values for limiting output thereof,
`and controls output of the direct current voltage boosting circuit
`on the basis of results of the comparison.
`[0024]
`(6)
`In one of
`the configurations in (1)–(5) above,
`operation of the lighting circuit is stopped when the lamp control
`circuit detects an error on the basis of the detection value of the
`lamp voltage and the detection value of the lamp current.
`[0025] (7) In one of the configurations in (1)–(6) above, the
`lighting control circuit is constituted by a CMOS transistor, and
`the lighting control circuit and the lamp control circuit are
`formed on one semiconductor chip in an integrated manner.
`[0026] (8) In one of the configurations in (1)–(7) above, the lamp
`control circuit has two systems for left and right lamps, one of
`the control circuits adjusting the vertical optical axis of both of
`the lamps and another of the control circuits adjusting the
`horizontal axis of both of the lamps.
`[0027] (9) In the configuration of (8) above, the two lamp control
`circuits comprise microcomputers having memory with identical
`content, and control is performed by using an external signal to
`selecting either a control program that adjusts the vertical optical
`axis or a control program that adjusts the horizontal optical axis.
`[0028] (10) In the configuration of (8) or (9) above, the two lamp
`control circuits perform at
`least either mutual
`information
`exchange through a communication port or information exchange
`with another external device.
`
`[0029] (11) In the configuration of (8) or (10) above, if there are
`two lamps,
`left and right,
`the left and right
`lamps have
`functionality for light distribution switching control between a
`traveling beam and a passing beam.
`[0030] (12) In one of the configurations in (1)–(11) above, the
`lamp control circuit has a common memory that
`stores
`parameters for correcting output characteristics of optical axis
`adjustment sensors that differ by vehicle model.
`[0031] (13) In one of the configurations in (1)–(12) above, the
`lamp control circuit has an added control function other than an
`adjustment function for the vertical and horizontal optical axes.
`[0032]
`[EMBODIMENTS OF THE INVENTION] FIG. 1 is a block diagram
`showing a configuration of embodiment 1 of
`the present
`invention. The same reference numerals as in FIGs. 3–5 show the
`same constituent elements.
`[0033] In FIG. 1, 1 is a DC power source such as a car battery or
`the like, 2 is a DC/DC converter (DC voltage boosting circuit)
`that boosts the DC, 3 is a DC/AC (direct current–alternating
`current) inverter that converts the boosted DC into AC and
`supplies lighting power to a discharge lamp 5 which is a
`headlamp, 4 is a launch circuit that applies a high-voltage pulse
`for launching when starting the discharge lamp 5 and, together
`with the DC/DC converter 2 and the DC/AC inverter 3,
`constitutes a lighting circuit for the discharge lamp 5.
`[0034] 10 is a headlamp unit on which the discharge lamp 5 and
`the lighting circuit are mounted, 11 is a reflector, 12 is a motor
`for optical axis adjustment of the discharge lamp 5, 13 is a motor
`driver that drives the motor 12, 19 is a lighting control circuit
`that controls the DC/DC converter 2, and 20 is a microcomputer
`that constitutes a lamp control circuit that performs the optical
`axis adjustment, receives as inputs signals from a lamp switch 15,
`a vehicle speed sensor 16, and vehicle height sensors 17 and 18
`at
`a
`front
`and a back of
`a vehicle,
`and outputs
`a
`polarity-switching control signal for AC lighting to the DC/AC
`inverter 3.
`[0035] 21 is a current detection circuit that detects a lamp current,
`here detecting a current output by the DC/DC converter 2 with a
`current detection element 6. 22 is a voltage detection circuit that
`detects a lamp voltage, here detecting a voltage output by the
`DC/DC converter 2 with a voltage detection element 7. 23 is a
`dedicated control IC chip 23 that is a semiconductor chip on
`which are formed the lighting control circuit 19 and the
`microcomputer 20 in an integrated fashion, configured by CMOS
`transistors.
`[0036] In the aforementioned configuration, the microcomputer
`20 outputs to a lighting control circuit 19 a setting value of a
`lamp current based on a lamp voltage detected by a voltage
`detection circuit 22, and the lighting control circuit 19 controls
`output of the lighting circuit on the basis of the setting value of
`the lamp current and the detection value of the lamp current
`detected by a current detection circuit 21.
`[0037] Further, the microcomputer 20 is provided with leveling
`functionality that controls a vertical optical axis of the discharge
`lamp 5 and cornering light distribution functionality that adjusts
`
`

`
`Japanese Unexamined Patent Application Publication 2000-185593
`(5)
`
`a horizontal optical axis, and can also be provided with other
`lamp control functionality. Moreover, the microcomputer 20 has
`a shared memory that stores parameters for correcting output
`characteristics of optical axis adjustment sensors that differ by
`vehicle model.
`[0038] The circuit in FIG. 1 is an example of a circuit in which
`an auto leveling device and a discharge lamp lighting device are
`combined. With the present embodiment, parts of the control
`circuit of
`the discharge lamp lighting device that can be
`substituted by microcomputer control are processed by the
`microcomputer for controlling the leveling device, taking into
`account processing power of the microcomputer, and therefore
`some of the control circuitry can be removed, allowing greater
`integration of control circuitry by combining functionality. The
`microcomputer 20 in FIG. 1 is provided with a CPU, a memory,
`an I/O device, an A/D converter, and a D/A converter, not shown
`in the drawings.
`[0039] As regards control of the discharge lamp lighting device,
`the lamp voltage and current are detected, the microcomputer 20
`finds an optimum lamp current to the discharge lamp 5 and sends
`this as a setting value to the lighting control circuit 19 that
`performs DC voltage boosting control using PWM control, and
`control
`is performed accurately every cycle of a switching
`frequency of the DC/DC converter 2 in accordance with a
`detection value of the lamp current.
`the
`generates
`also
`20
`[0040]
`The microcomputer
`polarity-switching signal that uses AC to light the discharge lamp
`5 and, regarding control when outputting excess current, such as
`for current control when an output short occurs, sends the signal
`to the lighting lighting [sic] control circuit 19 that performs
`PWM control or the like directly on the basis of the value output
`by the current detection circuit 21, performing monitoring and
`limitation for each switching cycle. Similarly, regarding excess
`voltage output by the DC/DC converter 2, the output value of the
`voltage detection circuit 22 is sent directly to the lighting control
`circuit 19 where control is performed to suppress.
`[0041] Thus, by using a configuration in which items requiring
`control every switching cycle are sent directly to the lighting
`control circuit 19 from the detection portions, errors which occur
`between
`control
`inverters which
`always
`occur with
`microcomputer control can be dealt with immediately. Therefore,
`operation is performed so as to limit output immediately once an
`error arises in lighting device output, preventing breakage.
`[0042] Furthermore, regarding protection stopping during output
`open shorts or the like of the lighting device, the microcomputer
`20 either detects an error and stops the lighting device based on
`the voltage detection value and the current detection value, or
`makes an error determination while the error continues and stops
`the lighting device. Moreover, the microcomputer 20 detects the
`input voltage and/or the mounted state of the discharge lamp 5
`and performs protective stopping. Microcomputer errors are
`monitored with a watchdog timer and the microcomputer 20 is
`reset when an error occurs. In addition to this method, in the
`present embodiment the lighting control circuit 19 can limit
`output to any setting value or lower to deal with excess output
`
`which can cause circuit breakdown without going through the
`microcomputer 20, ensuring the circuitry is protected during an
`error output.
`[0043] Thus, with the present embodiment, in the control circuit
`for the discharge lamp lighting device for vehicle illumination
`configuration of lamp current values whose purpose is to control
`the lamp current in accordance with the lamp voltage, generation
`of a switching signal for the inverter AC output, determinations
`about whether to stop for protective purposes, and so on are done
`by the microcomputer 20 which is shared with the control portion
`of the auto leveling device through combination of control
`portions, and can therefore be integrated into the microcomputer
`20, with the exception of circuits for finding the setting values of
`the lamp current, clock generation circuits, and protection
`determination stop circuits from conventional control circuits.
`Output is controlled as regards errors in lighting device output by
`directly sending a signal to the lighting control circuit 19 from
`the detection circuits 21 and 22, and therefore safety is not
`adversely affected due to a lag in operation caused by control
`intervals which always occur when using a microcomputer for
`control portions.
`[0044] Next, a combined configuration of control circuitry
`according to the present
`embodiment
`is described.
`In
`conventional control circuit configurations, two semiconductor
`chips were needed: a dedicated IC (an ASIC)
`and a
`microcomputer. The biggest
`reason for
`this
`is
`that
`the
`semiconductor processes are different
`for a dedicated IC
`configured using a circuit using bipolar transistors which are
`analog
`circuits with
`outstanding
`characteristics,
`and
`microcomputers which are configured using CMOS transistors
`which have outstanding energy savings. Bi-CMOS technology
`allows combining of these two processes on one semiconductor
`chip, but because the cost of
`the semiconductor becomes
`relatively higher, the cost-lowering effect of using a single chip
`is minimized.
`[0045] In contrast to conventional chips in which it has been
`common to combine dedicated ICs and microcomputers in this
`manner, in the present embodiment the focus is on lowering costs
`through combined control circuit
`integration. Specifically,
`advances in simulation technology have made it possible to
`design CMOS transistors which have characteristics that are just
`as good as those of bipolar transistors. Analog circuits, which
`had been constituted using bipolar transistors for control portions,
`have now been reconfigured using CMOS transistors, and the use
`of
`semiconductor
`processes,
`including
`fine machining
`technologies, which are the same as for the microcomputer
`portions, has allowed integration of the entire control circuit,
`which had been configured using analog circuitry and a
`microcomputer, to be integrated as a one-chip ASIC.
`[0046] This method has made it possible to lower costs and
`reduce sizes by cutting down the two expensive chips—the
`microcomputer and the dedicated IC—to a single dedicated IC.
`[0047] FIG. 2 is a block diagram showing a configuration of
`embodiment 2 of the present
`invention. The same reference
`numerals as in FIG. 1 show the same constituent elements. In the
`
`

`
`Japanese Unexamined Patent Application Publication 2000-185593
`(6)
`
`drawing, 24 is the aforementioned lamp lighting circuit that has
`the DC/DC converter 2, the DC/AC inverter 3, and the launch
`circuit 4 of FIG. 1.
`[0048] Aside from motorcycles, vehicle headlamps generally
`have light sources for passing beams and driving beams as left
`and right bulbs. If discharge lamps are used for the passing
`beams,
`two discharge lamp lighting devices are needed.
`Accordingly,
`if part of
`the control circuits for
`these are
`constituted by microcomputers,
`two microcomputers
`are
`incorporated, one left and one right. One microcomputer can
`control
`two lamps,
`left and right, as regards auto leveling
`functionality and cornering light distribution functionality.
`[0049] Accordingly,
`the present embodiment
`is a combined
`headlamp control system in which the processing load of
`microcomputers that control the left and right lamps are averaged
`out by the microcomputers for
`the left and right devices.
`Specifically, the microcomputers 20 that perform control for the
`left and right lighting devices operate such that, for example, one
`microcomputer 20 performs auto leveling control and adjusts
`vertical light distribution for the left and right lamps while the
`other microcomputer 20 performs cornering light distribution
`control and adjusts horizontal light distribution for the left and
`right lamps.
`[0050] By thus averaging out the load on the microcomputers 20
`which control the left and right lamps 5 between both devices
`and not focusing all the load on one or the other, both the left and
`right microcomputers 20 can be used in a manner fitting their
`performance capabilities, which allows a combined system to be
`made a low cost.
`[0051] Furthermore, in the present embodiment the memories of
`the microcomputers 20 which control the left and right lamps 5
`are exactly the same, so the following is performed. In other
`words,
`for mask ROMs
`for both the
`left
`and right
`microcomputers to have the same content, control programs for
`auto leveling, cornering light distribution control, and so on are
`all written. The control programs are made to be selectable by
`signals input from outside the microcomputers 20 after mounting
`via input ports (communication ports) as regards auto leveling,
`cornering light distribution control, and so on, which are separate
`from the lighting control needed for the left and right lamps 5.
`[0052] Thus, even if the microcomputers 20 have the same mask
`ROM content,
`it
`is possible, for example,
`to select
`lighting
`control and auto leveling with the left microcomputer 20 and
`lighting control and cornering light distribution control with the
`right microcomputer 20. With this method, different control can
`be selected for the left and right lamps, with the mask ROMs in
`the microcomputers having the same content. Moreover, by
`storing parameters for correcting sensor output characteristics for
`auto leveling, which differ by vehicle model, in EEPROM, the
`same mask can be used for different models, making it possible
`to increase the IC cost savings.
`[0053] The microcomputers 20 which control the left and right
`lamps 5 of the present embodiment may also be provided with
`communication ports
`and exchange
`information between
`themselves or with microcomputers in other devices. Thus, for
`
`example if one lamp 5 does not light up, the light distribution
`axis of the other lamp can be moved to the center of the vehicle
`automatically or the optical axis of the driving beam on the side
`with the malfunction can be lowered to prevent a drop in
`roadway visibility. In other words, total control of the lamps 5
`can be performed. Furthermore, if the front lamps are two-bulb
`discharge lamps, the microcomputer for leveling control can
`perform light distribution switching control between the traveling
`beam and the passing beam.
`[0054] Note that in the above description, leveling functionality,
`cornering light distribution control, and other aspects of lamp
`optical axis control have mainly been discussed in terms of the
`vehicle lamp control device, but naturally it is also possible to
`apply the present invention within the scope of lamp control
`functionality that is controlled by microcomputers, substituting
`the above for providing two-bulb low/high switching control,
`lamp washer control, or other lamp control functionality, or
`adding such functions to what has been discussed above.
`[0055] A configuration as shown in FIG. 6(a) is disclosed in JP
`H10-35358 A, for example, relating to a control configuration for
`headlamps using discharge lamps. In this circuit, a lamp voltage
`signal and a lamp current signal are input into a microcomputer
`101, an optimum power signal is generated on the basis of these
`signals