Lighting circuit and vehicle lamp

Abstract

The present invention comprises: a drive circuit that supplies a drive current to a light source; and a control circuit that includes a storage unit and that controls the drive circuit. The storage unit stores first information relating to the drive current in a light-increasing mode in which the brightness of the turned-off light source is gradually increased to a first brightness, and second information relating to the drive current in a first dimming mode in which the brightness of the light source is gradually reduced from the first brightness and the light source is turned off. The control circuit controls the drive circuit on the basis of a first instruction by using the first and second information so that the light source is turned off in the first dimming mode after the light source is turned on in the light-increasing mode, and controls the drive circuit on the basis of a second instruction by using a portion of the second information so that the light source is turned off in a second dimming mode in which the light source is turned off by gradually reducing the brightness of the light source from a second brightness darker than the first brightness.

Description

Lighting circuit and vehicle lighting fixture

[0001] The present invention relates to a lighting circuit and a vehicle lamp.

[0002] As a lighting circuit applied to a vehicle lamp, for example, Patent Document 1 discloses a lighting circuit that adjusts the brightness of a light source by combining control that adjusts the magnitude of a drive current using a switching element (DC dimming) and PWM control of a switch provided in a supply path of the drive current to the light source. Patent Document 1 also discloses that the brightness of the light source is changed smoothly (gradually) by using a table (information) that associates conditions related to the drive current (duty ratio) with a dimming rate.

[0003] JP 2013-258003 A

[0004] However, if there are multiple controls (e.g., dimming modes) that gradually change the brightness of the light source depending on the situation in which the light source is turned on, it is necessary to prepare a table for each, which is a significant burden on development.

[0005] An object of the present invention is to provide a lighting circuit that can reduce the development burden.

[0006] The main invention for achieving the above object is a lighting circuit comprising: a drive circuit that supplies a drive current to a light source; and a control circuit including a memory unit and that controls the drive circuit, wherein the memory unit stores first information regarding the drive current in a brightening mode in which the brightness of the light source that has been turned off is gradually reduced to a first brightness, and second information regarding the drive current in a first dimming mode in which the brightness of the light source is gradually reduced from the first brightness and the light source is turned off; and the control circuit controls the drive circuit using the first and second information based on a first instruction so that the light source is turned on in the brightening mode and then turned off in the first dimming mode, and controls the drive circuit using a part of the second information based on a second instruction so that the light source is turned off in a second dimming mode in which the brightness of the light source is gradually reduced from a second brightness that is lower than the first brightness and the light source is turned off.

[0007] According to the present invention, it is possible to provide a lighting circuit that can reduce the development burden.

[0008] It is a schematic circuit diagram of the vehicular lamp 1 of the present embodiment. It is an explanatory diagram of signal conditions in each lighting mode. It is an explanatory diagram of the pick-up lighting mode. It is an explanatory diagram of a table T1 of gradual lighting and a table T2 of gradual extinction in the pick-up mode. It is an explanatory diagram of the farewell lighting mode. It is an explanatory diagram of a table (part of table T2) of gradual extinction in the pick-up mode.

[0009] <Cross-reference to related applications> This application claims priority to Japanese patent application No. 2023-174145, filed on October 6, 2023, the contents of which are incorporated by reference.

[0010] At least the following matters will become clear from the description of this specification and the accompanying drawings.

[0011] In this embodiment, unless otherwise specified, "connection" refers to a state in which two components are electrically connected. Therefore, "connection" includes not only cases in which two components are connected by wiring but also cases in which two components are connected by, for example, a resistor.

[0012] 1 is a schematic circuit diagram of a vehicle lamp 1 according to this embodiment. The vehicle lamp 1 according to this embodiment includes a light source 3 and a lighting circuit 10.

[0013] The light source 3 is illuminated by a drive current Ik supplied from a lighting circuit 10, which will be described later. In this embodiment, the light source 3 is used as a daytime running lamp (DRL) and a clearance lamp (CLL). The DRL is a lamp that is illuminated during the day to notify pedestrians, drivers of oncoming vehicles, and the like of the presence of a moving vehicle, and is also called a daytime running light. The CLL is a lamp that indicates the width of the vehicle and its presence, and is also called a sidelight or small lamp. As will be described later, the DRL illuminates brighter than the CLL.

[0014] The light source 3 includes light-emitting elements D1 to D4 and resistors R1 and R2. The light-emitting elements D1 and D2 and the resistor R1 are connected in series, and the light-emitting elements D3 and D4 and the resistor R2 are connected in series. The series-connected light-emitting elements D1 and D2 and the resistor R1, and the series-connected light-emitting elements D3 and D4 and the resistor R2 are connected in parallel between the drive circuit 13 of the lighting circuit 10 and ground.

[0015] In this embodiment, light-emitting diodes (LEDs) are used as the light-emitting elements D1 to D4. However, the light-emitting elements D1 to D4 are not limited to LEDs and may be other semiconductor light-emitting elements such as laser diodes (LDs) or organic EL elements.

[0016] Resistors R1 and R2 are used to suppress variations in the current flowing through each column. For example, if there is variation in the forward drop voltage of light-emitting elements D1 to D4, there will also be variation in the current (i.e., brightness) flowing through the two parallel paths. By providing resistors R1 and R2, it is possible to suppress such variations.

[0017] As described above, the light source 3 of this embodiment is provided with two sets of two series-connected light emitting elements and resistors in parallel (two parallel sets), but this is not limited to this. For example, it may be provided with only one series connection, or three or more parallel connections. Furthermore, each row may have one light emitting element, or three or more light emitting elements.

[0018] Although not shown, the vehicle lamp 1 of this embodiment also includes a low beam (Lo) light source and a high beam (Hi) light source. Each light source is lit by a drive current Ik supplied from a drive circuit 13 of the lighting circuit 10, which will be described later. For this reason, the lighting circuit 10 of this embodiment is configured to adjust the magnitude and duration of the drive current Ik supplied to the light source depending on the lighting mode (details will be described later). For example, when the light source 3 of this embodiment is lit as CLL, the duration for supplying the drive current Ik to the light source 3 is shortened (effectively reducing the current amount), thereby reducing brightness compared to DRL.

[0019] The lighting circuit 10 is a circuit that controls the turning on and off of each light source (light source 3 in this embodiment) of the vehicle lamp 1. The lighting circuit 10 receives a power supply voltage Vbat (hereinafter simply referred to as voltage Vbat) from the vehicle battery 2 and a CXPI (Clock Extension Peripheral Interface) signal from the vehicle's ECU 100. CXPI is a communication method that conforms to an in-vehicle communication protocol established by the Society of Automotive Engineers of Japan for the purpose of reducing and multiplexing wire harnesses. Based on the power from the battery 2, the lighting circuit 10 outputs a drive current Ik to the light source (light source 3 in this embodiment) in response to an instruction (CXPI signal) from the ECU 100, thereby turning on the light source 3 (the configuration of the lighting circuit 10 will be described later).

[0020] The vehicle ECU 100 outputs a CXPI signal to the lighting circuit 10 according to the operation status of the user. Here, "operation" refers to an operation for lighting the light source 3 in one of the lighting modes. This "operation" is not limited to the user operating a part of the vehicle (e.g., an indicator), but also includes, for example, operating the vehicle's keyless entry system or unlocking or locking the doors by bringing a smart key close to the vehicle.

[0021] "Keyless" refers to a device that can remotely lock and unlock vehicle doors, while "smart key" refers to a device that instructs the vehicle to unlock the doors when it is within a specified range of the vehicle.

[0022] <<Configuration of the Lighting Circuit 10>> As shown in FIG. 1, the lighting circuit 10 includes a VCC circuit 11, a drive circuit 13, an IF (Interface) circuit 15, a microcomputer 17, a PMOS transistor Q1, and an NMOS transistor Q2.

[0023] The PMOS transistor Q1 is provided between the drive circuit 13 and the light source 3, and the NMOS transistor Q2 is provided between the light source 3 and ground. A signal S1 is applied to the gate of the PMOS transistor Q1 from the microcomputer 17, and a signal S2 is applied to the gate of the NMOS transistor Q2 from the microcomputer 17. To turn on the light source 3, the microcomputer 17 sets the signal S1 to a low level and the signal S2 to a high level. This turns on the PMOS transistor Q1 and the NMOS transistor Q2, and causes the drive current Ik output from the drive circuit 13 to flow to ground via the light emitting elements D1 and D2, resistor R1, light emitting elements D3 and D4, and resistor R2 of the light source 3.

[0024] Although detailed explanation is omitted, low beam (Lo) and high beam (Hi) lamps (light sources) are also provided in the same manner, and by switching the current path under the control of a bypass switch (PMOS transistor), a drive current Ik is supplied from the drive circuit 13 to each of them, causing them to light up.

[0025] The VCC circuit 11 is a power supply circuit that generates a voltage VCC of a predetermined level (for example, 5 V) from a voltage Vbat (for example, 12 V) for operating each circuit (for example, the microcomputer 17) of the lighting circuit 10.

[0026] The drive circuit 13 converts the input voltage Vbat into an output voltage corresponding to the light source 3, and generates a drive current Ik to supply to the light source 3. As shown in FIG. 1 , the drive circuit 13 of this embodiment includes a current output circuit 131 and a dimmer switch 132.

[0027] The current output circuit 131 includes a switching element 131a (for example, a MOS transistor) and a switching control circuit 131b.

[0028] The switching control circuit 131b controls the on / off (switching) of the switching element 131a in response to a control signal Sb input from the microcomputer 17. The microcomputer 17 receives a detection result of the current value of the drive current Ik from a current detection circuit (not shown). The switching control circuit 131b controls the switching of the switching element 131a based on the control signal Sb input from the microcomputer so that the drive current Ik becomes a target value.

[0029] Based on this switching, the current output circuit 131 generates and outputs a drive current Ik according to the control signal Sb. The current output circuit 131 corresponds to an "output circuit." In this embodiment, the switching frequency of the current output circuit 131 is, for example, 280 kHz (the frequency of the control signal Sb is approximately 10 kHz), which is higher than the frequency of the PWM control of the dimmer switch 132 described below.

[0030] The duty ratio of the control signal Sb indicates the reduction rate (dimming rate) of the drive current Ik. For example, when the duty ratio of the control signal Sb is 0%, the drive current Ik output from the current output circuit 131 is at its maximum, and as the duty ratio of the control signal Sb increases, the drive current Ik decreases. This duty ratio does not indicate the rate at which the switching element 131a is actually turned on. Therefore, even if the duty ratio of the control signal Sb is 0%, the switching element 131a is not fixed to either on or off. Specifically, the duty ratio of 280 kHz is fixed, and only the duty ratio of 10 kHz changes.

[0031] The dimmer switch 132 is provided between the current output circuit 131 and the light source 3, and is controlled to be turned on and off based on the PWM signal Sa from the microcomputer 17. When the dimmer switch 132 is turned on, the drive current Ik is supplied to the light source 3. When the dimmer switch 132 is turned off, the drive current Ik is no longer supplied to the light source 3.

[0032] The PWM signal Sa is a rectangular wave (pulse-shaped) signal for blinking the light source 3 at a high frequency (e.g., 200 Hz). The dimmer switch 132 turns on and off in accordance with the duty ratio of the PWM signal Sa, and the brightness (luminance) of the light source 3 is adjusted.

[0033] The duty ratio of the PWM signal Sa is the proportion of the period during which the PWM signal Sa is at a high level (hereinafter referred to as an H level) in one cycle. The period during which the PWM signal Sa is at an H level is substantially equal to the length of the period during which the drive current Ik is supplied to the light source 3. Similarly, the length of the period during which the PWM signal Sa is at a low level (hereinafter referred to as an L level) is substantially equal to the length of the period during which the drive current Ik is not supplied to the light source 3. Therefore, when the duty ratio of the PWM signal Sa increases, the proportion of the period during which the drive current Ik is supplied to the light source 3 increases (the light source 3 becomes brighter). Conversely, when the duty ratio of the PWM signal Sa decreases, the proportion of the period during which the drive current Ik is not supplied to the light source 3 increases (the light source 3 becomes dimmer).

[0034] The IF circuit 15 is a device (CXPI transceiver) for performing CXPI communication with the ECU 100 of the vehicle.

[0035] When the IF circuit 15 receives a CXPI signal from the vehicle ECU 100, it demodulates the received signal and transmits it as an instruction signal to the microcomputer 17. In this embodiment, the CXPI signal includes a DRL signal that instructs the DRL to be turned on or off, a CLL signal that instructs the CLL to be turned on or off, and a WEL signal that instructs gradual on / off (described later). Note that the communication method is not limited to CXPI, and other communication methods (e.g., CAN communication or LIN communication) may be used.

[0036] The microcomputer 17 operates when a voltage VCC is applied to it, and controls each circuit (e.g., the drive circuit 13) of the lighting circuit 10. The microcomputer 17 includes a storage unit 171 and an arithmetic processing unit 172. The microcomputer 17 corresponds to a "control circuit."

[0037] The storage unit 171 includes memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and stores programs executed (processed) by the arithmetic processing unit 172, various information for controlling the lighting of the light source 3 (tables described later), and the like.

[0038] The arithmetic processing unit 172 is, for example, a CPU (Central Processing Unit), and realizes various functions by executing programs stored in the storage unit 171 .

[0039] In this embodiment, the microcomputer 17 determines the values ​​(duty ratios) of the PWM signal Sa and the control signal Sb based on the instruction signal received via the IF circuit 15 and the information stored in the storage unit 171, and outputs them to the drive circuit 13. As a result, the drive current Ik is generated in the drive circuit 13, and the current supplied to the light source 3 is adjusted.

[0040] More specifically, the microcomputer 17 sets the duty ratio of the control signal Sb in accordance with the lighting mode, and controls the on / off of the switching element 131a to adjust the magnitude of the drive current Ik. Furthermore, the microcomputer 17 controls the on / off of the dimmer switch 132 using the duty ratio of the PWM signal Sa, and adjusts the proportion of the period during which the drive current Ik is supplied to the light source 3. This adjusts the brightness of the light source 3.

[0041] <<Operation of the Lighting Circuit 10>> The lighting circuit 10 turns on the light source 3 based on instructions of the CXPI signal received from the vehicle ECU 100. In the vehicle lamp 1 of this embodiment, the light source 3 has four lighting modes (DRL lighting mode, CLL lighting mode, welcome lighting mode, and farewell lighting mode).

[0042] FIG. 2 is an explanatory diagram of signal conditions in each lighting mode. In FIG. 2, ON of signal S1 indicates "L level" (OFF indicates "H level"). Furthermore, ON of the WEL signal, DRL signal, WEL signal, and signal S2 indicates "H level," and OFF indicates "L level." For example, when turning on light source 3, signal S1 becomes L level and signal S2 becomes H level, thereby turning on both PMOS transistor Q1 and NMOS transistor Q2, and enabling light source 3 to be turned on. In FIG. 2, the values ​​(%) of PWM signal Sa and control signal Sb indicate duty ratios.

[0043] <DRL Lighting Mode> As described above, the DRL lighting mode is a mode in which the light source 3 is turned on to notify pedestrians, drivers of oncoming vehicles, and the like of the presence of a vehicle during the day.

[0044] When the light source 3 is turned on as a DRL, the DRL signal is ON (H level), and the CLL signal and WEL signal are OFF (L level), as shown in Fig. 2. The instruction (instruction signal) at this time corresponds to the "fourth instruction." In this case, the microcomputer 17 sets the duty ratio of the PWM signal Sa to 100% and the duty ratio (dimming rate) of the control signal Sb to 0%.

[0045] When the duty ratio (dimming rate) of the control signal Sb is 0% and the dimmer switch 132 is on, the current value of the drive current Ik output from the current output circuit 131 corresponds to a "predetermined value." Furthermore, when the duty ratio of the PWM signal Sa becomes 100%, the dimmer switch 132 is fixed to on (the on period is the longest). Therefore, the light source 3 lights up brightly. The duty ratio (100%) of the PWM signal Sa at this time corresponds to a "third duty ratio."

[0046] <CLL lighting mode> As described above, the CLL lighting mode is a mode in which the light source 3 is turned on to indicate the size of the vehicle in the width direction and its presence. The CLL lighting mode corresponds to the "illumination mode."

[0047] When the light source 3 is turned on as CLL, the CLL signal is ON (H level), and the DRL signal and WEL signal are OFF (L level). This instruction (instruction signal) corresponds to a "third instruction." In this case, the microcomputer 17 sets the duty ratio of the PWM signal Sa to 7% and the duty ratio of the control signal Sb to 0%. The drive current Ik output from the current output circuit 131 is the same as in the DRL lighting mode, but because the duty ratio of the PWM signal Sa is small (the time during which the drive current Ik is supplied to the light source 3 is shortened), the light source 3 lights up with a lower brightness (i.e., darker) than in the DRL lighting mode. Note that the duty ratio (7%) of the PWM signal Sa in this case corresponds to a "second duty ratio."

[0048] <Welcome Lighting Mode> The welcome lighting mode is a mode in which the light source 3 is turned on when, for example, the vehicle doors are unlocked. In the welcome lighting mode of this embodiment, the light source 3 first turns on gradually from an off state, gradually increasing in brightness, and then maintains the light at a constant brightness, and then turns off gradually decreasing in brightness. Note that the gradual lighting in the welcome lighting mode corresponds to the "brightening mode," and the gradual extinguishing corresponds to the "first dimming mode." Such gradual lighting and gradual extinguishing are performed based on a table stored in the storage unit 171 of the microcomputer 17.

[0049] FIG. 3 is an explanatory diagram of the welcome lighting mode. From top to bottom, FIG. 3 shows the instruction signals (CLL, WEL), PWM signal Sa, control signal Sb, and current (drive current Ik). The horizontal axis of each diagram in FIG. 3 represents time (sec). FIG. 4 is an explanatory diagram of table T1 for gradual lighting and table T2 for gradual extinguishing in the welcome lighting mode. Each table associates the value (duty ratio) of the PWM signal Sa, the value (duty ratio) of the control signal Sb, and the value of the drive current Ik with each time (elapsed time). Table T1 corresponds to "first information," and table T2 corresponds to "second information."

[0050] The welcome lighting mode will be described below with reference to FIGS. 2, 3, and 4.

[0051] In the initial state, the CLL signal and the WEL signal (and the DRL signal) are both at level L. As shown in Fig. 3, at this time, the duty ratio of the PWM signal Sa is 0% (the dimmer switch 132 is fixed to OFF), the duty ratio of the control signal Sb is 100%, and the drive current Ik is 0 mA (i.e., the light source 3 is turned off).

[0052] For example, when the vehicle doors are unlocked, the CLL signal and the WEL signal both go high at time t1, and the vehicle enters the welcome light mode. The instruction (instruction signal) for executing the welcome light mode at this time corresponds to the "first instruction."

[0053] First, the microcomputer 17 refers to the gradual lighting table T1 shown in Fig. 4 and sets the duty ratio of the PWM signal Sa to 30% and the duty ratio of the control signal Sb to 67%. At this time, the drive current Ik becomes 160 mA, and the light source 3 is turned on. The duty ratio (30%) of the PWM signal Sa corresponds to the "first duty ratio."

[0054] Furthermore, the microcomputer 17 gradually decreases the duty ratio of the control signal Sb (decreases the dimming rate) over time with reference to the gradual lighting table T1 in Fig. 4. As a result, the drive current Ik gradually increases, and the light source 3 gradually becomes brighter, as shown in Fig. 3.

[0055] At time t2, 2080 ms after the start of gradual lighting (time t1), the gradual lighting ends. After that, for a predetermined period (the period until time t3: for example, approximately 13 seconds), the duty ratios of the PWM signal Sa and the control signal Sb do not change, and the drive current Ik is maintained constant (1350 mA). This makes the brightness of the light source 3 constant. Note that the brightness of the light source 3 at this time corresponds to the "first brightness."

[0056] At time t3, the CLL signal changes from H level to L level, causing the microcomputer 17 to execute gradual extinguishing while referring to the gradual extinguishing table T2 in FIG.

[0057] That is, the microcomputer 17 gradually increases the value (duty ratio) of the control signal Sb over time, as in the case of gradual lighting (the duty ratio of the PWM signal Sa is fixed at 30%). As a result, the drive current gradually decreases from 1350 mA, and the light source 3 gradually becomes dimmer, as shown in FIG. 3 .

[0058] Then, at time t4, 2080 ms after the start of gradual extinction (time t3), the duty ratio of the control signal Sb becomes 67%, ending the gradual extinction. After that, the duty ratio of the control signal Sb becomes 100%, and the light source 3 is turned off.

[0059] At time ta (duty ratio of signal Sa: 30%, duty ratio of signal Sb: 60%), which is 1830 ms after time t3, the brightness of light source 3 is approximately the same (same luminous flux) as in the CLL lighting mode (duty ratio of signal Sa: 7%, duty ratio of signal Sb: 0%). It is also approximately the same as the brightness at the start of the farewell lighting mode, which will be described later. The brightness of light source 3 at this time corresponds to the "second brightness," and is darker than the brightness ("first brightness") from time t2 to t3.

[0060] <Farewell Lighting Mode> The farewell lighting mode is a mode in which the light source 3 is turned on when, for example, a seating sensor (not shown) in the driver's seat of the vehicle detects that the user has left the seat and the driver's seat door is locked within a predetermined time. In this farewell lighting mode, the light source 3 is first turned on as CLL (CLL lighting mode), and then gradually turned off to gradually dim the light. Note that the gradual turning off in the farewell lighting mode corresponds to the "second dimming mode." The gradual turning off in the farewell mode is also performed based on a table stored in the memory unit 171 of the microcomputer 17.

[0061] As mentioned above, in the CLL lighting mode, the duty ratio of the PWM signal Sa is 7%. Therefore, if the duty ratio of the PWM signal Sa is fixed at 7% and the control signal Sb is changed to gradually turn off the light, a new table different from the table T2 for the welcome mode (the table for gradual turning off) must be created, which increases the development burden. Furthermore, the memory unit 171 requires capacity to store the created table.

[0062] Therefore, in this embodiment, the gradual extinguishing table T2 in the welcoming lighting mode is used to perform the gradual extinguishing in the farewell mode.

[0063] However, the gradual extinction in the farewell lighting mode starts with the light source 3 turned on as CLL (CLL lighting mode). Therefore, the brightness (luminous flux) of the light source 3 at the start of the gradual extinction is set to be the same as that in CLL lighting. Specifically, the drive current Ik at the start of the gradual extinction in the farewell mode is set to be the same as the drive current Ik (290 mA) in the CLL lighting mode. In other words, the farewell lighting mode uses the period from 1830 ms onwards (specifically, times ta to t4 in Figures 3 and 4) in table T2 for the gradual extinction in the welcome lighting mode.

[0064] Fig. 5 is an explanatory diagram of the farewell lighting mode, and Fig. 6 is an explanatory diagram of a table (part of table T2) of gradual extinction in the farewell lighting mode.

[0065] As described above, for example, when a seating sensor (not shown) in the driver's seat of the vehicle detects that the user has left the seat and the driver's door is locked within a predetermined time, the farewell mode is initiated.

[0066] First, the CLL signal goes high, and the CLL lighting mode is activated. That is, the microcomputer 17 sets the PWM signal Sa to 7% and the control signal Sb to 0%. At this time, the drive current Ik is 290 mA.

[0067] At time t5, after a predetermined time (e.g., 16.4 seconds) has elapsed, the WEL signal goes high. This (specifically, the CLL signal goes low and the WEL signal goes high) causes the microcomputer 17 to start gradual extinguishing in the farewell lighting mode. The instruction (instruction signal) used to execute gradual extinguishing in the farewell lighting mode at this time corresponds to the "second instruction."

[0068] First, the microcomputer 17 refers to the table in FIG. 6 (part of table T2 in FIG. 4) and changes the value (duty ratio) of the PWM signal Sa from 7% to 30%, and then changes the value of the control signal Sb from 0% to 60%. The current value at this time is 290 mA, as shown in FIG. 4, which is equal to the current value during CLL lighting in FIG. 5. Therefore, the brightness of the light source 3 is approximately the same as before time t5.

[0069] 6, the microcomputer 17 gradually increases the duty ratio of the control signal Sb over time, thereby gradually decreasing the brightness of the light source 3.

[0070] At time t6, 250 ms after the start of the gradual extinguishing (time t5), the control signal Sb becomes 67%, the drive current Ik becomes 160 mA (the same as time t4 in the welcome lighting mode), and the gradual extinguishing of the farewell lighting mode ends. After that, the control signal Sb becomes 100%, and the light source 3 is turned off.

[0071] As described above, in this embodiment, when executing the gradual extinguishing in the farewell mode, a part of the table T2 for the gradual extinguishing in the welcome mode is used, so there is no need to create a new table for the farewell mode. This reduces the development burden. Also, the capacity required to store the table in the storage unit 171 can be reduced.

[0072] Summary The lighting circuit 10 of this embodiment has been described above. The lighting circuit 10 includes a drive circuit 13 that supplies a drive current Ik to the light source 3, and a microcomputer 17 that includes a memory unit 171 and controls the drive circuit 13. The memory unit 171 stores a table T1 related to the drive current Ik for gradual lighting (brightness increase mode) and a table T2 related to the drive current Ik for gradual extinction (first dimming mode). Based on a welcome lighting command, the microcomputer 17 controls the drive circuit 13 using table T1 and table T2 so that the light source 3 is turned on in gradual lighting mode and then turned off in gradual extinction mode. Based on a farewell lighting command, the microcomputer 17 controls the drive circuit 13 using a portion of table T2 so that the light source 3 is turned off in gradual extinction mode (second dimming mode), in which the brightness of the light source 3 is gradually reduced from the brightness of the light source 3 when it was in CLL mode.

[0073] This eliminates the need to create a table of gradual extinguishing for the farewell lighting mode, thereby reducing the development burden and reducing the capacity required to store the table in the storage unit 171.

[0074] Furthermore, the microcomputer 17 controls the drive circuit 13 based on the lighting instruction of the CLL so that the light source 3 lights up in the CLL lighting mode (illumination mode).

[0075] As a result, when the light source 3 is turned on as a farewell light, it can be gradually turned off from the state in which it is turned on as CLL (same brightness).

[0076] Furthermore, the drive circuit 13 supplies the light source 3 with a drive current Ik having a current value according to the control signal Sb in accordance with the duty ratio of the PWM signal Sa.

[0077] This allows the brightness of the light source 3 to be adjusted by setting the control signal Sb and the PWM signal Sa.

[0078] Furthermore, the microcomputer 17 outputs a control signal Sb that changes the current value of the drive current Ik according to gradual lighting (brightening mode) and gradual extinction (first dimming mode) based on the instruction for welcoming lighting, and a PWM signal Sa with a duty ratio of 30%. Furthermore, the microcomputer 17 outputs a control signal Sb that changes the current value of the drive current Ik according to gradual extinction (second dimming mode) based on the instruction for farewell lighting, and a PWM signal Sa with a duty ratio of 30%.

[0079] As a result, the duty ratio of the PWM signal Sa is the same for the gradual extinction of the welcoming lighting and the farewell lighting, so the same table can be used, reducing the development burden.

[0080] Furthermore, based on the CLL lighting instruction, the microcomputer 17 outputs a control signal Sb that sets the current value of the drive current Ik to a predetermined value (dimming rate 0%) (according to the CLL lighting mode), and a PWM signal Sa with a duty ratio of 7%. The period during which the drive current Ik is supplied to the light source 3 when the duty ratio of the PWM signal Sa is 7% is shorter than the period during which the drive current Ik is supplied to the light source 3 when the duty ratio is 30%.

[0081] This allows the brightness of the light source 3 at the start of the farewell lighting to be adjusted to the brightness of the CLL lighting mode.

[0082] Furthermore, based on the instruction to turn on the DRL, the microcomputer 17 outputs a control signal Sb that sets the current value of the drive current Ik to a predetermined value (dimming rate 0%) and a PWM signal Sa with a duty ratio of 100%. The period during which the drive current Ik is supplied to the light source 3 when the duty ratio of the PWM signal Sa is 100% is longer than the period during which the drive current Ik is supplied to the light source 3 when the duty ratio is 30%.

[0083] This allows the light source 3 to be brightly lit in the DRL lighting mode.

[0084] The drive circuit 13 also includes a current output circuit 131 that outputs a drive current Ik in response to the control signal Sb, and a dimmer switch 132 that is provided between the current output circuit 131 and the light source 3 and that turns on and off based on the PWM signal Sa.

[0085] As a result, by setting the control signal Sb and the PWM signal Sa, the current supplied (output) to the light source 3 can be adjusted, and the brightness of the light source 3 can be adjusted.

[0086] The vehicle lamp 1 of this embodiment includes the lighting circuit 10 and the light source 3 described above.

[0087] This makes it possible to realize welcoming and farewell lighting, while also reducing the development burden.

[0088] ===Other Embodiments===The above embodiments are intended to facilitate understanding of the present invention and are not intended to limit the present invention. Furthermore, the present invention may be modified or improved without departing from the spirit thereof, and it goes without saying that the present invention includes equivalents thereof.

[0089] REFERENCE SIGNS LIST 1 Vehicle lighting fixture 2 Battery 3 Light source 10 Lighting circuit 11 VCC circuit 13 Drive circuit 15 IF circuit 17 Microcomputer 100 ECU 131 Current output circuit 131a Switching element 131b Switching control circuit 132 Dimmer switch 171 Storage unit 172 Arithmetic processing unit D1 to D4 Light emitting element R1, R2 Resistor Sa PWM signal Sb Control signal T1, T2 Table

Claims

1. A lighting circuit comprising: a drive circuit which supplies a drive current to a light source; and a control circuit including a memory unit and which controls the drive circuit, wherein the memory unit stores first information regarding the drive current in a brightening mode in which the brightness of the turned-off light source is gradually reduced to a first brightness, and second information regarding the drive current in a first dimming mode in which the brightness of the light source is gradually reduced from the first brightness and the light source is turned off, and the control circuit controls the drive circuit using the first and second information based on a first instruction so that the light source is turned on in the brightening mode and then turned off in the first dimming mode, and controls the drive circuit using a part of the second information based on a second instruction so that the light source is turned off in a second dimming mode in which the brightness of the light source is gradually reduced from a second brightness that is darker than the first brightness and the light source is turned off.

2. A lighting circuit as claimed in claim 1, wherein the control circuit controls the drive circuit based on a third instruction so that the light source is turned on in a lighting mode in which the brightness of the light source is the second brightness.

3. A lighting circuit according to claim 2, wherein the drive circuit supplies the drive current, the value of which corresponds to a control signal, to the light source in accordance with a duty ratio of a PWM signal.

4. A lighting circuit as described in claim 3, wherein the control circuit outputs the control signal for changing the current value of the drive current in accordance with the brightening mode and the first dimming mode based on the first instruction, and the PWM signal with a first duty ratio, and outputs the control signal for changing the current value of the drive current in accordance with the second dimming mode based on the second instruction, and the PWM signal with the first duty ratio.

5. A lighting circuit as claimed in claim 4, wherein the control circuit outputs the control signal for setting the current value of the drive current to a predetermined value in accordance with the lighting mode based on the third instruction, and the PWM signal having a second duty ratio different from the first duty ratio, and the period during which the drive current is supplied to the light source at the second duty ratio is shorter than the period during which the drive current is supplied to the light source at the first duty ratio.

6. A lighting circuit as claimed in claim 5, wherein the control circuit outputs the control signal for setting the current value of the drive current to the predetermined value and the PWM signal of a third duty ratio based on a fourth instruction, and the period during which the drive current is supplied to the light source at the third duty ratio is longer than the period during which the drive current is supplied to the light source at the first duty ratio.

7. A lighting circuit as claimed in claim 3, wherein the drive circuit includes: an output circuit that outputs the drive current in response to the control signal; and a switch that is provided between the output circuit and the light source and that turns on and off based on the PWM signal.

8. A vehicle lamp comprising: a lighting circuit according to any one of claims 1 to 7; and the light source.

Images