Lighting circuit

Abstract

A lighting circuit, which is applied to a vehicle lamp including a plurality of light sources, is provided with: a voltage division circuit that divides a power supply voltage applied to a power supply line into a plurality of voltages that differ from each other; a timer circuit including a first resistor to which the power supply voltage is applied via the power supply line, and a first capacitor connected to the first resistor; a control circuit that sequentially lights the plurality of light sources on the basis of the plurality of voltages of the voltage division circuit and the voltage of the first capacitor; and a first discharge circuit that discharges the first capacitor during a first period when the power supply voltage is applied to the power supply line.

Description

Technical Field

[0001] The invention relates to a lighting circuit. Background Art

[0002] As vehicle lamps, for example, vehicle direction indicators (hereinafter also referred to as "turn signal lamps") that use a so-called sequential method of lighting a plurality of light sources in sequence are known (for example, Patent Document 1). Power is supplied from a vehicle battery to a lighting circuit used in such a vehicle lamp.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2016 / 104282 Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] However, in general, turn signal lamps are provided on the left and right sides of the front and rear of the vehicle body, and are respectively supplied with power from the above-mentioned battery. However, since the wiring lengths from the battery to each turn signal lamp are different, the timing of lighting may vary due to differences in wiring resistance, etc.

[0008] An object of the present invention is to provide a lighting circuit capable of improving the accuracy of lighting timing.

[0009] (II) Technical solution

[0010] The main purpose of the present invention to achieve the above-mentioned purpose is a lighting circuit, which is applied to a vehicle lamp including a plurality of light sources, and comprises: a voltage-dividing circuit, which divides the power supply voltage applied to a power line into a plurality of voltages different from each other; a timer circuit, which comprises a first resistor and a first capacitor, the first resistor being applied with the power supply voltage via the power line, the first capacitor being connected to the first resistor; a control circuit, which lights up the plurality of light sources in sequence based on the plurality of voltages of the voltage-dividing circuit and the voltage of the first capacitor; and a first discharge circuit, which discharges the first capacitor within a first period if the power supply voltage is applied to the power line.

[0011] (III) Beneficial effects

[0012] According to the present invention, it is possible to provide a lighting circuit capable of improving the accuracy of lighting timing. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 1 is a diagram showing a configuration of a vehicle lamp 1 including a lighting circuit 10 according to the present embodiment.

[0014] Figure 2 1 is a diagram showing an example of the shut-off circuit 13 .

[0015] Figure 3 1 is a diagram showing an example of the timer circuit 15 and the discharge circuit 16 .

[0016] Figure 4 1 is a diagram showing an example of the reset circuit 17 .

[0017] Figure 5A It is a diagram showing an example of the switch circuit 18 .

[0018] Figure 5B It is a diagram showing an example of the switch circuit 19 .

[0019] Figure 6 It is a diagram for explaining the operation of the lighting circuit 10 . DETAILED DESCRIPTION

[0020] <Cross-reference to related applications>

[0021] This application claims priority based on Japanese patent application No. 2022-164727 filed on October 13, 2022, and cites the contents thereof.

[0022] At least the following matters are apparent from the description of this specification and the accompanying drawings.

[0023] In addition, in this embodiment, unless otherwise specified, "connection" refers to a state of electrical connection. Therefore, "connection" includes not only a case where two components are connected via wiring but also a case where two components are connected via a resistor, for example.

[0024] ======Present Implementation Method======

[0025] <<Structure of vehicle lamp 1>>

[0026] Figure 1 1 is a diagram showing a configuration of a vehicle lamp 1 including a lighting circuit 10 according to the present embodiment.

[0027] The vehicle lamp 1 of the present embodiment is a turn signal lamp (vehicle direction indicator lamp), which lights up the light emitting elements of the light source in a sequential manner based on the voltage Vbat of the vehicle battery 2. In the vehicle of the present embodiment, four positions, namely, the left and right sides of the front of the vehicle body and the left and right sides of the rear of the vehicle body, are provided with light emitting elements corresponding to the turn signal lamp. Figure 1 The vehicle lamp 1 has the same structure. Here, one of them is taken as an example for description.

[0028] In addition, the vehicle lamp 1 of this embodiment is also used as a hazard warning light. In the case of a turn signal, either one of the left and right lights up (flashes), and in the case of danger, all lights up (flashes). In the following description, the vehicle lamp 1 is sometimes simply referred to as a lamp.

[0029] Here, generally speaking, the distance from the battery 2 to each lamp of the vehicle is different, so the length of the wiring (wire harness) that supplies power from the battery 2 to each lamp is different. For example, when the battery 2 is installed in the front of the vehicle, the length of the wiring from the battery 2 to the rear lamp is much longer than the length of the wiring from the battery 2 to the front lamp.

[0030] Due to the difference in the length of the wiring to each lamp (in other words, the difference in the magnitude of the wiring resistance), etc., the timing of lighting of each lamp of the vehicle may vary. Therefore, in this embodiment, as described later, the accuracy of the timing of lighting is improved.

[0031] The vehicle lamp 1 includes a switch 4 , a lighting circuit 10 , light sources 21 to 24 , and resistors Rd1 and Rd2 .

[0032] The switch 4 is an element for applying the voltage Vbat of the vehicle battery 2 to the power line L1 of the vehicle lamp 1. The switch 4 is, for example, a mechanical contact relay, a non-contact relay using a semiconductor element, or the like.

[0033] The voltage Vbat of the battery 2 is applied to one end of the switch 4, and the other end is connected to the power line L1.

[0034] Therefore, when the switch 4 is turned on, the voltage Vbat of the battery 2 is applied to the power line L1 via the switch 4. In this embodiment, the voltage applied to the power line L1 by turning on the switch 4 is referred to as the power voltage VCC. Hereinafter, the power voltage VCC may be simply referred to as the voltage VCC.

[0035] On the other hand, when the switch 4 is turned off, the voltage VCC is no longer applied to the power line L1. As a result, the voltage of the power line L1 drops to zero due to, for example, the influence of the resistance between the power line L1 and the ground, the circuit, etc.

[0036] In addition, in this embodiment, all the lines connected to the switch 4 (inside and outside of the lighting circuit 10) are used as the power line L1. The power line L1 is a wiring for supplying a voltage VCC to the circuit inside the lighting circuit 10. In addition, a grounding line (not shown) is also provided in the vehicle lamp 1. The grounded part in each circuit of the vehicle lamp 1 means that it is connected to the grounding line.

[0037] When the voltage VCC is applied to the power line L1, the lighting circuit 10 sequentially lights up the light sources 21 to 24. The lighting circuit 10 will be described in detail later. The lighting circuit 10 is a module having a plurality of circuits and terminals A to H mounted on a substrate, wherein the plurality of circuits are used to light up the light sources 21 to 24 (light emitting elements D1 to D4).

[0038] The light source 21 includes a light emitting element D1 that is first lit. The light emitting element D1 of this embodiment uses a light emitting diode (LED). However, the light emitting element D1 is not limited to an LED, and may be, for example, a laser diode (LD), an organic EL element, or other semiconductor light emitting element, or a halogen lamp, etc. (the same applies to the light emitting elements D2 to D4 described later). The anode of the light emitting element D1 is connected to the drive circuit 11 and the NMOS transistor Q1 (described later) via the terminal D of the lighting circuit 10. In addition, the cathode of the light emitting element D1 is connected to the NMOS transistor Q2 (described later) via the terminal E.

[0039] The light source 22 includes a light emitting element D2 which is turned on after the light emitting element D1 of the light source 21 is turned on. The anode of the light emitting element D2 is connected to the cathode of the light emitting element D1. The cathode of the light emitting element D2 is connected to an NMOS transistor Q3 (described later) via a terminal F.

[0040] The light source 23 includes a light emitting element D3 which is turned on after the light emitting element D2 of the light source 22 is turned on. The anode of the light emitting element D3 is connected to the cathode of the light emitting element D2. The cathode of the light emitting element D3 is connected to an NMOS transistor Q4 (described later) via a terminal G.

[0041] The light source 24 includes a light emitting element D4 which is turned on after the light emitting element D3 of the light source 23 is turned on. The anode of the light emitting element D4 is connected to the cathode of the light emitting element D3. The cathode of the light emitting element D4 is grounded via the terminal F.

[0042] The resistors Rd1 and Rd2 are resistors for adjusting the magnitude of the input current Iin supplied from the vehicle battery 2 to the vehicle lamp 1, and are provided outside the lighting circuit 10 in the present embodiment. One end of the resistor Rd1 is connected to the power line L1, and the other end is connected to the switch circuit 18 via the terminal B. In addition, one end of the resistor Rd2 is connected to the power line L1, and the other end is connected to the switch circuit 19 via the terminal C.

[0043] <Allowable range of input current>

[0044] In addition, a detection device (not shown) is provided in the vehicle in which the vehicle lamp 1 of the present embodiment is assembled, and the detection device detects whether or not there is a disconnection in the light emitting elements D1 to D4 of the vehicle lamp 1 based on the input current Iin from the battery 2. For example, when the vehicle lamp 1 is in operation, when the current value of the input current Iin is less than a threshold value (a threshold value on the lower limit side: hereinafter also referred to as a lower limit value), the detection device detects that there is a disconnection in any of the light emitting elements D1 to D4 of the vehicle lamp 1.

[0045] Therefore, when the vehicle lamp 1 operates in a normal state, the current value of the input current Iin needs to be greater than the lower limit value so as not to mistakenly detect that the light emitting elements D1 to D4 are disconnected. In addition, here, "normal state" refers to, for example, a state in which no disconnection occurs in the light emitting elements D1 to D4 of the light sources 21 to 24 of the vehicle lamp 1. In addition, "disconnection of the light emitting element" refers to, for example, a state in which the resistance value between the cathode and the anode of the light emitting element is sufficiently greater than the normal resistance value.

[0046] On the other hand, if the power consumption in the vehicle lamp 1 is larger than necessary, the input current Iin to the vehicle lamp 1 also increases, so that the current from the battery 2 may exceed the rated current, for example.

[0047] Therefore, when the vehicle lamp 1 is operating, a threshold value on the upper limit side (hereinafter also referred to as an upper limit value) is also defined for the input current Iin flowing from the battery 2 to the vehicle lamp 1 .

[0048] Therefore, in the vehicle lamp 1 of the present embodiment, the input current Iin supplied from the battery 2 needs to be within a range (permissible range) defined by the lower limit value and the upper limit value.

[0049] The lighting circuit 10 of the present embodiment, when supplied with power from the battery 2, makes the input current Iin fall within the permissible range and sequentially lights the light sources 21 to 24. Specifically, the magnitude of the input current Iin is adjusted by the adjustment current Id described later.

[0050] <<Structure of Lighting Circuit 10>>

[0051] like Figure 1 As shown, the lighting circuit 10 is constructed to include a driving circuit 11, a disconnection detection circuit 12, an extinguishing circuit 13, a power supply circuit 14, a timer circuit 15, a discharge circuit 16, a reset circuit 17, switch circuits 18 and 19, resistors R1 to R5, R11 to R18, comparators COM1 to COM4, ​​NMOS transistors Q1 to Q4 and terminals A to H.

[0052] The drive circuit 11 is a regulator that generates a predetermined drive current Iout based on the power supplied from the battery 2. The predetermined drive current Iout is used to drive the light emitting elements D1 to D4 of the light sources 21 to 24 as loads. In addition, the method for generating the constant current may be a switching method or a linear method.

[0053] The disconnection detection circuit 12 detects whether there is a disconnection in the light emitting elements D1 to D4 of the light sources 21 to 24 (that is, whether there is an abnormality in at least any one of the light sources 21 to 24). In addition, the disconnection detection circuit 12 is equivalent to a "detection circuit". Here, if any one of the light emitting elements D1 to D4 is disconnected, the resistance value between the anode and the cathode of the light emitting element after the disconnection is very large. In such a state, if the driving current Iout is supplied to the light emitting elements D1 to D4, the output voltage Vout of the driving circuit 11 increases significantly. Therefore, it is possible to detect whether the light sources 21 to 24 are abnormal based on the output voltage Vout of the driving circuit 11.

[0054] The disconnection detection circuit 12 of this embodiment determines whether the output voltage Vout of the driving circuit 11 is higher than a predetermined value, and if the output voltage Vout is higher than the predetermined value, it detects that any one of the light emitting elements D1 to D4 is disconnected. Furthermore, if the disconnection detection circuit 12 detects that there is a disconnection, it changes the level of the connection line L2 connected to the extinguishing circuit 13 from a high level (hereinafter referred to as an H level) to a low level (hereinafter referred to as an L level).

[0055] If the disconnection detection circuit 12 detects a disconnection, the extinguishing circuit 13 stops the operation of the driving circuit 11 to extinguish the light sources 21 to 24. In addition, based on the disconnection detection result of the disconnection detection circuit 12, the extinguishing circuit 13 controls the switch circuits 18 and 19 so that the current does not flow through the resistors Rd1 and Rd2 to prevent the resistors Rd1 and Rd2 from consuming unnecessary power. In addition, the details of the extinguishing circuit 13 will be described later.

[0056] The power circuit 14 is a circuit that generates a voltage Vdd (for example, 5 V) for operating each circuit of the lighting circuit 10 based on a voltage VCC (for example, 13 V) of the power line L1 .

[0057] When the voltage VCC is applied to the power supply line L1 , the timer circuit 15 outputs a voltage (voltage V1 to be described later) that changes with time. The timer circuit 15 will be described in detail later.

[0058] When the voltage VCC is applied to the power line L1, the discharge circuit 16 discharges the capacitor 52 (described later) of the timer circuit 15 for a certain period of time, thereby stopping the operation of the timer circuit 15. In this embodiment, the discharge circuit 16 corresponds to the "first discharge circuit". The details of the discharge circuit 16 will be described later.

[0059] If the voltage VCC is no longer applied to the power line L1, the reset circuit 17 outputs an H-level signal SR for resetting each circuit of the lighting circuit 10 for a certain period of time. Based on the H-level signal SR, for example, the capacitor 52 (described later) of the timer circuit 15 and the capacitor 66 (described later) of the discharge circuit 16 are discharged. In this embodiment, the reset circuit 17 corresponds to the "second discharge circuit". In addition, the details of the reset circuit 17 will be described later.

[0060] The switch circuits 18 and 19 are circuits for adjusting the magnitude of the input current Iin flowing through the power line L1 by turning on or off the current paths connecting the resistors Rd1 and Rd2 from the power line to the ground. In the present embodiment, the switch circuit 18 is equivalent to the "first current adjustment circuit" and the resistor Rd1 is equivalent to the "second resistor". In addition, the switch circuit 19 is equivalent to the "second current adjustment circuit" and the resistor Rd2 is equivalent to the "third resistor". The details of the switch circuits 18 and 19 will be described later.

[0061] Resistors R1 to R5 are connected in series between the power line L1 and the ground, and divide the voltage VCC applied to the power line L1 into multiple different voltages. In addition, resistors R1 to R5 are equivalent to a "voltage divider circuit". Figure 1 As shown, resistors R5, R4, R3, R2, and R1 are connected in sequence from the power line L1 (voltage VCC) side to the ground side. In addition, the connection point between the resistor R5 and the resistor R4 is a node N4, the connection point between the resistor R4 and the resistor R3 is a node N3, the connection point between the resistor R3 and the resistor R2 is a node N2, and the connection point between the resistor R2 and the resistor R1 is a node N1.

[0062] When voltage VCC is applied to power line L1, resistors R1 to R5 generate voltages obtained by dividing voltage VCC at connection points (nodes N1 to N4) of the resistors. Node N4 has the highest voltage and node N1 has the lowest voltage.

[0063] The voltages of the nodes (N1 to N4) of the resistors R1 to R5 are applied to the non-inverting input terminals (+ terminals) of the comparators COM1 to COM4, ​​respectively. In addition, the output voltage (voltage V1 described later) of the timer circuit 15 is applied to the inverting input terminals (- terminals) of the comparators COM1 to COM4, ​​respectively.

[0064] Furthermore, the comparators COM1 to COM4 compare the voltages of the -terminal and the +terminal, respectively, and output in accordance with the result. Specifically, the comparators COM1 to COM4 of the present embodiment are open drain type, and if the voltage of the +terminal is greater than the voltage of the -terminal, an open circuit (hereinafter also referred to as high impedance) voltage is output, and if the voltage of the +terminal is less than the voltage of the -terminal, an L level (ground level) voltage is output. In addition, the same is true for the other comparators (comparators 61, 75, 85) described later.

[0065] Resistors R11, R12, R13, R14, R15, R16, R17, R18 are connected in series, and when voltage VCC is applied to power line L1, voltage VCC is divided. At this time, the resistance value of each resistor (resistors R11 to R18) is set to generate a divided voltage that turns on NMOS transistors Q1 to Q4.

[0066] The NMOS transistors Q1 to Q4 have a switch function that turns on and off according to a voltage applied to a gate. In the present embodiment, the NMOS transistors Q1 to Q4 are elements that control the lighting or extinguishing of each of the light sources 21 to 24 .

[0067] The drain of the NMOS transistor Q1 is connected to the terminal D, and the source is grounded. The gate of the NMOS transistor Q1 is connected to a connection point between the resistor R11 and the resistor R12, and is also connected to an output of the comparator COM1.

[0068] The drain of the NMOS transistor Q2 is connected to the terminal E, and the source is grounded. The gate of the NMOS transistor Q2 is connected to a connection point between the resistor R13 and the resistor R14, and is connected to an output of the comparator COM2.

[0069] The drain of the NMOS transistor Q3 is connected to the terminal F, and the source is grounded. The gate of the NMOS transistor Q3 is connected to a connection point between the resistor R15 and the resistor R16, and is connected to an output of the comparator COM3.

[0070] The drain of the NMOS transistor Q4 is connected to the terminal G, and the source is grounded. The gate of the NMOS transistor Q4 is connected to a connection point between the resistor R17 and the resistor R18, and is also connected to an output of the comparator COM4.

[0071] For example, when the output of comparator COM1 is at an L level, the voltage at the connection point between resistors R11 and R12 is lower than the threshold voltage of NMOS transistor Q1, and NMOS transistor Q1 is turned off. On the other hand, when the output of comparator COM1 is high impedance, a divided voltage based on the voltage VCC of resistors R11 and R12 is applied to the gate of NMOS transistor Q1, and NMOS transistor Q1 is turned on. The relationship between comparators COM2 to COM4 and NMOS transistors Q2 to Q4 is the same, so their description is omitted. In addition, comparators COM1 to COM4, ​​resistors R11 to R18, and NMOS transistors Q1 to Q4 are equivalent to a "control circuit".

[0072] <Extinguishing circuit 13>

[0073] Figure 2 1 is a diagram showing an example of the shut-off circuit 13 .

[0074] The extinguishing circuit 13 is configured to include inverters 30A and 30B, a capacitor 31 , and Schottky barrier diodes 38 a to 38 c .

[0075] The capacitor 31 is an element that is charged by application of the voltage Vdd and holds the charge for operating the inverters 30A and 30B.

[0076] The inverter 30A is a circuit that inverts and outputs the logic level of the connection line L2 from the disconnection detection circuit 12, and includes a PNP transistor 32, a diode 33, and a resistor 34 connected in series. For example, when the level of the connection line L2 is at an H level, the PNP transistor 32 is turned off, so that the node NA connected to the diode 33 and the resistor 34 becomes an L level. On the other hand, when the level of the connection line L2 is at an L level, the PNP transistor 32 is turned on, so that the node NA becomes an H level.

[0077] The inverter 30B is a circuit that inverts the logic level of the node NA and outputs it, and includes an NMOS transistor 35 and resistors 36 and 37 connected in series. Here, for example, when the level of the node NA is at an H level, the NMOS transistor 35 is turned on, so that the level of the node NB connected to the NMOS transistor 35 and the resistor 36 becomes an L level. In addition, when the level of the node NA is at an L level, the NMOS transistor 35 is turned off, so that the level of the node NB becomes an H level.

[0078] In this embodiment, the node NA, which is the output of the inverter 30A, is connected to the gate electrode of the NMOS transistor 35, which is the input of the inverter 30B. In addition, the node between the resistors 36 and 37 of the inverter 30B and the base electrode of the PNP transistor 32, which is the input of the inverter 30A, are connected via the connection line L2. Therefore, the extinguishing circuit 13 operates as a holding circuit that holds the logic level of the connection line L2.

[0079] When disconnection detection is performed and the extinguishing circuit 13 holds a signal at an L level, the Schottky barrier diode 38 a generates an L level signal S10 at the anode for stopping the operation of the driving circuit 11 .

[0080] When disconnection detection is performed and the extinguishing circuit 13 holds an L-level signal, the Schottky barrier diode 38 b generates an L-level signal S11 at the anode for turning off an NMOS transistor 81 (described later) of the switch circuit 18 .

[0081] When disconnection detection is performed and the extinguishing circuit 13 holds an L-level signal, the Schottky barrier diode 38 c generates an L-level signal S12 at the anode for turning off an NMOS transistor 91 (described later) of the switch circuit 19 .

[0082] In addition, in the present embodiment, the Schottky barrier diodes 38 a to 38 c are used, but the present invention is not limited to the Schottky barrier diodes, and for example, general rectifying diodes may be used.

[0083] <Timer circuit 15>

[0084] Figure 3 1 is a diagram showing an example of the timer circuit 15 and the discharge circuit 16 .

[0085] like Figure 3 As shown, the timer circuit 15 is configured to include a resistor 51 , a capacitor 52 , and an NPN transistor 53 .

[0086] A voltage VCC is applied to one end of the resistor 51 via the power supply line L1. The resistor 51 corresponds to a "first resistor".

[0087] The capacitor 52 is connected between the other end of the resistor 51 and the ground. The connection point between the resistor 51 and the capacitor 52 is a node NC. The voltage of the node NC (hereinafter also referred to as voltage V1) becomes the output of the timer circuit 15. The capacitor 52 corresponds to the "first capacitor".

[0088] When the voltage VCC is applied to the resistor 51, a current corresponding to the resistance value of the resistor 51 flows toward the capacitor 52. The capacitor 52 accumulates electric charge and is charged, so the voltage V1 of the node NC gradually rises. As described above, the voltage V1 is applied to the non-inverting input terminal (-terminal) of the comparator COM1 to COM4. In addition, as described later, the voltage V1 is supplied to the switch circuit 18.

[0089] The NPN transistor 53 is an element for discharging the capacitor 52. The collector of the NPN transistor 53 is connected to the node NC, and the emitter is grounded. In addition, a signal SR from a reset circuit 17 described later is applied to the base of the NPN transistor 53. When the signal SR is at an H level, the NPN transistor 53 is turned on. As a result, the charge accumulated in the capacitor 52 is discharged.

[0090] <Discharge circuit 16>

[0091] like Figure 3 As shown, the discharge circuit 16 is configured to include a comparator 61 , resistors 62 to 65 , a capacitor 66 , and an NPN transistor 67 .

[0092] The + terminal of the comparator 61 is connected to a connection point (hereinafter referred to as a node ND) between the resistors 62 and 63 that divide the voltage VCC, and a divided voltage based on the power supply voltage VCC of the resistors 62 and 63 is applied. In addition, the - terminal of the comparator 61 is connected to a connection point (hereinafter referred to as a node NE) between the resistors 64 and 65 that divide the voltage VCC, and a divided voltage based on the power supply voltage VCC of the resistors 64 and 65 is applied. In addition, the output of the comparator 61 is connected to the node NC of the timer circuit 15.

[0093] Then, the comparator 61 outputs high impedance if the voltage of the + terminal is greater than the voltage of the - terminal, and outputs a voltage of L level (ground level) if the voltage of the + terminal is less than the voltage of the - terminal. In addition, the resistance values ​​of the resistors 62, 63 and the resistors 64, 65 are set so that the voltage of the node ND is slightly higher than the voltage of the node NE in the initial state (the state in which the capacitor 66 is not charged).

[0094] The capacitor 66 is provided between the node NE and the ground. Therefore, when the voltage VCC is applied to the power supply line L1, current flows to the capacitor 66 via the resistor 64 and the node NE. As a result, the capacitor 66 is charged, and the voltage of the node NE also rises, and soon (after a certain period of time) becomes higher than the voltage of the node ND.

[0095] Therefore, when the voltage VCC is applied to the power supply line L1, the output of the comparator 61 is at an L level for a certain period of time, and then, when the voltage of the node NE is higher than the voltage of the node ND, it becomes a high impedance. During the certain period of time, since the output of the comparator 61 is at an L level, the discharge circuit 16 discharges the capacitor 52 of the timer circuit 15 via the comparator 61.

[0096] The NPN transistor 67 is an element for discharging the capacitor 66. The collector of the NPN transistor 67 is connected to the node NE, and the emitter is grounded. In addition, a signal SR from a reset circuit 17 described later is applied to the base of the NPN transistor 53. When the signal SR is at an H level, the NPN transistor 53 is turned on. As a result, the charge accumulated in the capacitor 66 is discharged.

[0097] <Reset circuit 17>

[0098] Figure 4 1 is a diagram showing an example of the reset circuit 17 .

[0099] like Figure 4 As shown, the reset circuit 17 is configured to include a diode 71, capacitors 72, 74, 76, and resistors 73, 77a, 77b, 78a, 78b.

[0100] The comparator 75 is operated by applying a voltage VCC via a diode 71 for backflow prevention. In addition, a capacitor 72 and a resistor 73 and a capacitor 74 connected in series are provided in parallel between the cathode of the diode 71 and the ground. In addition, the output of the comparator 75 is connected to the connection point of the resistor 73 and the capacitor 74, and the voltage of the connection point becomes the output (signal SR) of the reset circuit 17.

[0101] The resistors 77a and 77b and the resistors 78a and 78b are connected in series to divide the voltage VCC. In addition, a capacitor 76 is provided in parallel with the resistor 77b at the connection point between the resistor 77a and the resistor 77b.

[0102] A voltage at a connection point between the resistor 77 a and the resistor 77 b is applied to the + terminal of the comparator 75 , and a voltage at a connection point between the resistor 78 a and the resistor 78 b is applied to the − terminal.

[0103] The resistors 77a and 77b and the resistors 78a and 78b are set so that when the voltage VCC is applied to the power supply line L1, the voltage at the connection point of the resistors 78a and 78b becomes higher than the voltage at the connection point of the resistors 77a and 77b.

[0104] Therefore, while the voltage VCC is applied to the power supply line L1, the output of the comparator 75 is at the L level, and the signal SR also becomes at the L level. In addition, during this period, the capacitors 72, 74, and 76 are charged.

[0105] After that, if the voltage VCC is no longer applied to the power supply line L1, the comparator 75 operates for a certain period of time using the charging voltage of the capacitor 72 as a power source. At this time, the voltage at the connection point of the resistors 78a and 78b becomes zero, but the voltage at the connection point of the resistors 77a and 77b becomes greater than zero due to the charging voltage of the capacitor 76. Therefore, the comparator 75 becomes high impedance because the voltage of the + terminal is greater than the voltage of the - terminal, and outputs a voltage based on the charging voltage of the capacitor 74, so that the signal SR becomes H level.

[0106] In this way, when the state where the voltage VCC is applied to the power supply line L1 changes to the state where the voltage VCC is no longer applied, the reset circuit 17 outputs the signal SR at the H level for a certain period of time.

[0107] <Switch Circuits 18, 19>

[0108] Figure 5A It is a diagram showing an example of the switch circuit 18 . Figure 5B It is a diagram showing an example of the switch circuit 19 .

[0109] like Figure 5A As shown, the switch circuit 18 is configured to include an NMOS transistor 81 , a capacitor 82 , resistors 83 , 84 , a comparator 85 , and resistors 86 , 87 .

[0110] The NMOS transistor 81 has a function of a switch that turns on and off according to the voltage applied to the gate. The drain of the NMOS transistor 81 is connected to the resistor Rd1 via the terminal B, and the source is grounded. In addition, the gate of the NMOS transistor 81 is connected to the connection point of the resistors 83 and 84 that divide the voltage Vdd. In addition, the signal S11 is applied to the connection point of the resistors 83 and 84, and the output of the comparator 85 is applied.

[0111] The capacitor 82 is an element for stabilizing the gate voltage of the NMOS transistor 81 , and is provided between the gate of the NMOS transistor 81 and the ground.

[0112] The + terminal of the comparator 85 is connected to the connection point of the resistors 86 and 87 that divide the voltage VCC, and a voltage V1 is applied to one end. If the voltage of the + terminal is lower than the voltage of the - terminal, the comparator 85 outputs an L level, and if the voltage of the + terminal is higher than the voltage of the - terminal, it becomes a high impedance.

[0113] In this embodiment, the resistance values ​​of the resistors 86 and 87 are set so that the divided voltage of the voltage VCC by the resistors 86 and 87 is slightly lower than Figure 1 The voltage of node N3.

[0114] With the above configuration, in the switch circuit 18, when the voltage VCC is applied to the power line L1, the NMOS transistor 81 is turned on, and current starts to be supplied from the power line L1 to the resistor Rd1. In addition, in the switch circuit 18, when the NMOS transistor 81 is turned off based on the signal S11 or the output of the comparator 85, the supply path of the current from the power line L1 to the resistor Rd1 is cut off.

[0115] like Figure 5B As shown, the switch circuit 19 is configured to include an NMOS transistor 91 , a capacitor 92 , and resistors 93 and 94 .

[0116] The NMOS transistor 91 has a switch function that turns on and off according to the voltage applied to the gate. The drain of the NMOS transistor 91 is connected to the resistor Rd1 via the terminal C, and the source is grounded. In addition, the gate of the NMOS transistor 91 is connected to the connection point of the resistors 93 and 94 that divide the voltage Vdd. In addition, the signal S12 is applied to the connection point of the resistors 93 and 94.

[0117] The capacitor 92 is an element for stabilizing the gate voltage of the NMOS transistor 91 , and is provided between the gate of the NMOS transistor 91 and the ground.

[0118] With the above configuration, in the switch circuit 19, when the voltage VCC is applied to the power line L1, the NMOS transistor 91 is turned on, and current starts to be supplied from the power line L1 to the resistor Rd2. In addition, in the switch circuit 19, when the NMOS transistor 91 is turned off based on the signal S12, the current supply path from the power line L1 to the resistor Rd2 is cut off.

[0119] <<<Operation of Lighting Circuit 10>>>

[0120] Figure 6 1 is a diagram for explaining the operation of the lighting circuit 10. Figure 6 In the output of the discharge circuit 16, the portion shaded with diagonal lines indicates high impedance.

[0121] The vehicle lamp 1 of the present embodiment is a turn signal lamp. For example, when the driver of the vehicle operates a turn indicator (not shown) to light the vehicle lamp 1 , a control circuit (not shown) such as a microcomputer controls the switch 4 to turn on and off.

[0122] By turning the switch 4 on and off, a voltage (hereinafter also referred to as the turn voltage Vt) that alternately repeats a period T1 of H level and a period T2 of L level is generated at a specified period. Specifically, during the period T1, the switch 4 is turned on, so that the voltage VCC is applied to the power supply line L1, and thus the turn voltage Vt becomes H level. On the other hand, during the period T2, the switch 4 is turned off, so that the voltage VCC is not applied to the power supply line L1, and thus the turn voltage Vt becomes L level. In Figure 6 it describes approximately one cycle amount of the turn voltage Vt, but the periods T1 and T2 are periodically repeated. In other words, the voltage VCC is periodically applied to the power supply line L1.

[0123] In addition, in Figure 6 it conceptually represents the difference in the rise of the turn voltage Vt caused by the difference in the wiring length (wiring resistance) from the battery 2 to each lamp of the vehicle by solid lines and dashed lines. For example, in the case where the battery 2 is arranged in the front of the vehicle body as in the present embodiment, the solid line represents the front of the vehicle body, and the dashed line represents the rear of the vehicle body. At the rear of the vehicle body far from the battery 2, the wiring resistance becomes larger, so as shown by the dashed line in the figure, the rise is delayed compared with the front of the vehicle body (the rising waveform of the turn voltage Vt is inclined). Hereinafter, the operation in the case of the solid line will be mainly described.

[0124] Before the time t0, the turn voltage Vt is at L level, and the voltage VCC is not applied to the power supply line L1. Therefore, since the power of the battery 2 is not supplied to the lighting circuit 10, the operation of each circuit stops. That is, the output voltage Vout of the lighting circuit 10 is zero, and the light sources 21 to 24 are extinguished. In addition, the outputs of the discharge circuit 16, the timer circuit 15, and the reset circuit 17 are all at L level, and the adjustment current Id flowing through the resistors Rd1 and Rd2 is also zero.

[0125] At the time t0, the switch 4 is turned on, and the turn voltage Vt becomes H level. That is, the voltage VCC is applied to the power supply line L1. As a result, since the voltage Vdd is generated in the power supply circuit 14 of the lighting circuit 10, the NMOS transistors 81 and 91 of the switch circuits 18 and 19 are turned on. By turning on the NMOS transistor 81, the switch circuit 18 starts to supply current to the resistor Rd1 connected to the power supply line L1. In addition, by turning on the NMOS transistor 91, the switch circuit 19 starts to supply current to the resistor Rd2 connected to the power supply line L1.

[0126] At this time, the adjustment current Id flowing from the power line to the resistors Rd1 and Rd2 becomes the sum of the current flowing through the resistor Rd1 and the current flowing through the resistor Rd2. In addition, the input current Iin input to the lighting circuit 10 must be greater than the adjustment current Id. Therefore, by making the magnitude of the adjustment current Id at this time greater than the lower limit value of the input current Iin, it is possible to prevent the vehicle-side detection device from causing the input current Iin to be less than the lower limit value.

[0127] In addition, at this time, due to Figure 3 The discharge circuit 16 is operated, and its output becomes L level, so Figure 3 The capacitor 52 of the timer circuit 15 is discharged (not charged). Therefore, the output (voltage V1) of the timer circuit 15 is zero. Therefore, Figure 1 The outputs of the comparators COM1 to COM4 become high impedance, and the NMOS transistors Q1 to Q4 are all turned on, and the driving current Iout is not supplied to the light emitting elements D1 to D4 (the light sources 21 to 24 remain off). Figure 5A The comparator 85 of the switch circuit 18 has a high impedance because the voltage of the + terminal is higher than the voltage of the - terminal (the output of the timer circuit 15 ).

[0128] At time t1, the output of the discharge circuit 16 becomes high impedance. As a result, the charging of the capacitor 52 of the timer circuit 15 (charging based on the voltage VCC) begins, and the voltage V1 gradually rises. In addition, the period from time t0 to t1 is the period during which the discharge circuit 16 discharges the capacitor 52 of the timer circuit 15, which corresponds to the "first period". Figure 6 As shown, this period is shorter than the period T1 during which the steering voltage Vt is at the H level.

[0129] At time t2, the output (voltage V1) of the timer circuit 15 is higher than the voltage of the node N1. Figure 1 The output of the comparator COM1 becomes L level, and the NMOS transistor Q1 is turned off. Therefore, the drive current Iout flows through the path of terminal D→light source 21 (light emitting element D1)→terminal E→NMOS transistor Q2→ground, and the light source 21 is turned on.

[0130] At time t3, the output (voltage V1) of the timer circuit 15 is higher than the voltage of the node N2. Figure 1 The output of the comparator COM2 becomes L level, and the NMOS transistor Q2 is turned off. Therefore, the drive current Iout flows through the path of terminal D→light source 21 (light emitting element D1)→light source 22 (light emitting element D2)→terminal F→NMOS transistor Q3→ground, and the light sources 21 and 22 are lit.

[0131] At time t4, the output (voltage V1) of the timer circuit 15 is higher than the voltage of the node N3. Figure 1 The output of the comparator COM3 becomes L level, and the NMOS transistor Q3 is turned off. Therefore, the drive current Iout flows through the path of terminal D→light source 21 (light emitting element D1)→light source 22 (light emitting element D2)→light source 23 (light emitting element D3)→terminal G→NMOS transistor Q4→ground, and the light sources 21 to 23 are lit.

[0132] Here, at time t4 (actually before time t4), Figure 5A The voltage of the -terminal of the comparator 85 of the switch circuit 18 shown is greater than the voltage of the +terminal, and the output of the comparator 85 becomes an L level. If the output of the comparator 85 becomes an L level, the voltage at the connection point of the resistors R86 and 87 is lower than the threshold voltage of the NMOS transistor 81, and the NMOS transistor 81 is disconnected, so the supply of current to the resistor Rd1 stops. That is, after the light source 22 (light-emitting element D2) is turned on, the switch circuit 18 cuts off the supply path of the current from the power line L1 to the resistor Rd1. In addition, in this case, the light source 22 is equivalent to the "specified light source". Therefore, as Figure 6 As shown in FIG. 1 , at time t4 , the magnitude of the adjustment current Id decreases. By reducing the adjustment current Id in this way, when the number of light sources to be lit increases, the input current Iin can be made not to exceed the upper limit value (to be within the allowable range).

[0133] At time t5, the output (voltage V1) of the timer circuit 15 is higher than the voltage of the node N4. Figure 1 The output of comparator COM4 becomes L level, and NMOS transistor Q4 is turned off. Therefore, the drive current Iout flows through the path of terminal D→light source 21 (light emitting element D1)→light source 22 (light emitting element D2)→light source 23 (light emitting element D3)→light source 24 (light emitting element D4)→terminal H→ground, and all light sources 21 to 24 are lit.

[0134] At time t6 (after a period T1 from time t0), the steering voltage Vt becomes L level. As a result, the voltage VCC is no longer applied to the power line L1. By no longer applying the voltage VCC to the power line L1, the operation of each circuit stops, and the light sources 21 to 24 are turned off. However, Figure 4 The reset circuit 17 operates with the voltage of the capacitor 72 and outputs a signal of the H level until time t7. The charge of the capacitors of each circuit is discharged by the signal of the H level. Therefore, when the capacitor is charged next, it is always charged from an empty state (a state in which no charge is stored), so the relationship between the charging time and the voltage is accurate.

[0135] In addition, the period from time t6 to time t7 corresponds to the "second period". Figure 6 As shown, this period is shorter than the period T2 during which the steering voltage Vt is at the L level.

[0136] After the period T2 has passed from the time t6, the steering voltage Vt becomes H level. The same operation is then repeatedly performed.

[0137] Here, it is assumed that the discharge circuit 16 is not provided. Figure 6 At time t0, the capacitor 52 of the timer circuit 15 starts to be charged. At this time, in each lamp of the vehicle, if due to wiring resistance, etc., Figure 6 As shown, if there is a difference in the rise of the steering voltage Vt (solid line and dotted line), the charging voltage of the capacitor 52 of each lamp will be different, and there is a possibility that the lighting timing will be uneven.

[0138] In this regard, in the present embodiment, a discharge circuit 16 is provided, and the discharge circuit 16 discharges the capacitor 52 of the timer circuit 15 during a certain period (a period between time t0 and time t1). Therefore, as shown in the figure, even when there is a difference in the rise of the steering voltage Vt, the accuracy of the timing of lighting the lamps at various positions of the vehicle can be improved.

[0139] In addition, the voltage Vbat (voltage VCC) of the battery 2 is not always constant, and varies between 9 and 16 V, for example. In the present embodiment, the resistors R1 to R5 divide the voltage VCC into a plurality of voltages, and the charging voltage of the capacitor 52 of the timer circuit 15 depends on the voltage VCC. Moreover, the lighting circuit 10 sequentially lights up the light sources 21 to 24 based on the comparison between the divided voltages of the resistors R1 to R5 and the charging voltage (voltage V1) of the capacitor 52, so that even when the magnitude of the voltage VCC changes, the accuracy of the timing of lighting can be improved.

[0140] <When disconnection is detected>

[0141] During the period T1, if the disconnection detection circuit 12 detects a disconnection, Figure 2 The extinguishing circuit 13 turns the signals S10, S11, and S12 to L level and keeps them at L level. The driving circuit 11 stops operating due to the L level signal S10. As a result, all the light sources are extinguished. In addition, by turning the signals S11 and S12 to L level, Figure 5A The NMOS transistor 81 of the switch circuit 18 and Figure 5B The NMOS transistor 91 of the switch circuit 19 is turned off together. Therefore, the switch circuit 18 cuts off the current supply path from the power line L1 to the resistor Rd1, and the switch circuit 19 cuts off the current supply path from the power line L1 to the resistor Rd2. Therefore, the current Id is adjusted to zero, which can avoid unnecessary power consumption.

[0142] In addition, in the lighting circuit 10 of the present embodiment, the NMOS transistor Q1 provided between the output of the driving circuit 11 and the light source 21 (specifically, the anode of the light emitting element D1) has a function of turning off the light sources 21 to 24 at the same time. That is, if the NMOS transistor Q1 is turned on, the driving current Iout is no longer supplied to the light emitting elements D1 to D4, so that all the light sources 21 to 24 are turned off. Therefore, when the disconnection detection circuit 12 detects a disconnection, for example, the turning off circuit 13 can be configured to forcibly control the NMOS transistor Q1 to be turned on.

[0143] ===Summary===

[0144] The lighting circuit 10 of the present embodiment has been described above. The lighting circuit 10 is a lighting circuit applied to a vehicle lamp 1 including light sources 21 to 24, and comprises: a circuit (voltage-dividing circuit) composed of resistors R1 to R5; a timer circuit 15; a circuit (control circuit) composed of comparators COM1 to COM4 and NMOS transistors Q1 to Q4, etc.; and a discharge circuit 16. The resistors R1 to R5 divide the power supply voltage VCC applied to the power supply line L1 into a plurality of (four in this case) different voltages. The timer circuit 15 includes a resistor 51 and a capacitor 52, the resistor 51 being applied with the power supply voltage VCC via the power supply line L1, and the capacitor 52 being connected to the resistor 51. The control circuit sequentially lights up the light sources 21 to 24 based on the four voltages divided by the resistors R1 to R5 and the voltage of the capacitor 52. If the power supply voltage VCC is applied to the power supply line L1, the discharge circuit 16 is turned on for a certain period ( Figure 6 During the period from time t0 to t1, the capacitor 52 of the timer circuit 15 is discharged. As a result, when the power supply voltage VCC is applied to the power supply line L1, the timer circuit 15 does not operate immediately (operates after a certain period of time) through the discharge circuit 16, so that, for example, the deviation of the lighting timing caused by the difference in the wiring length from the battery 2 to the position of each lamp on the vehicle body can be suppressed. Therefore, the accuracy of the lighting timing can be improved.

[0145] In addition, the lighting circuit 10 includes a reset circuit 17. If the voltage VCC is no longer applied to the power line L1, the reset circuit 17 is reset for a certain period of time ( Figure 6 The capacitor 52 is discharged during the period from time t6 to time t7. Thus, the charge of the capacitor 52 can be reliably discharged during the above-mentioned certain period. Therefore, the accuracy of the lighting start timing is further improved.

[0146] In addition, the lighting circuit 10 includes a switch circuit 18. When a voltage VCC is applied to the power line L1, the switch circuit 18 starts to supply current to the resistor Rd1 connected to the power line L1. After a predetermined light source (the light source 22 in this embodiment) among the light sources 21 to 24 is lit based on the voltage of the capacitor 52, the switch circuit 18 cuts off the current supply path from the power line L1 to the resistor Rd1. As a result, when the number of lit light sources increases, the input current Iin can be kept from exceeding the upper limit value.

[0147] In addition, the lighting circuit 10 includes: a switch circuit 19, which starts to supply current to the resistor Rd2 connected to the power line L1 when the voltage VCC is applied to the power line L1; and a disconnection detection circuit 12, which detects whether at least any one of the light sources 21~24 has an abnormality. Moreover, if the disconnection detection circuit 12 detects an abnormality, the switch circuit 18 cuts off the supply path of the current from the power line L1 to the resistor Rd1. In addition, if the disconnection detection circuit 12 detects an abnormality, the switch circuit 19 cuts off the supply path of the current from the power line L1 to the resistor Rd2. Thus, when an abnormality is detected, unnecessary power consumption can be suppressed. In addition, in normal times, by allowing current to flow through the resistors Rd1 and Rd2, the input current Iin can be prevented from being lower than the lower limit value. Therefore, for example, it is possible to prevent the detection device on the vehicle side from erroneously detecting that there is a disconnection in any one of the light-emitting elements D1~D4 due to a small input current Iin.

[0148] The vehicle lamp 1 is a turn signal lamp, and the voltage VCC is periodically applied to the power line L1. It is effective to apply the lighting circuit 10 to such a vehicle lamp 1.

[0149] The above-mentioned embodiments are for easy understanding of the present invention and are not intended to limit the interpretation of the present invention. In addition, the present invention can be changed and improved without departing from its gist, and of course, the present invention includes its equivalents.

[0150] In the above-mentioned embodiment, the vehicle lamp 1 is provided with four light sources 21 to 24 , but the number of light sources is not limited to four, and any number may be more than one.

[0151] In addition, in the aforementioned embodiment, switches (NMOS transistors Q1 to Q4) are respectively provided between the anode of the light emitting element D1 and the cathodes of the light emitting elements D1 to D3 and the ground, and the light sources 21 to 24 are sequentially lit by turning on and off the switches, but the present invention is not limited thereto. For example, the light emitting elements D1 to D4 may be connected in parallel to the switches (NMOS transistors Q1 to Q4), and the light sources 21 to 24 may be sequentially lit by turning on and off the switches.

[0152] In addition, in the above-mentioned embodiment, the case of the turn signal is described, but it can also be applied to the case of the hazard warning. In particular, in the case of the hazard warning, there are many lights that are lit as described above, so the timing of lighting each light can be made consistent through this embodiment, which is more effective.

[0153] Description of reference numerals:

[0154] 1: Vehicle lamp; 2: Battery; 4: Switch; 10: Lighting circuit; 11: Driving circuit; 12: Disconnection detection circuit; 13: Extinguishing circuit; 14: Power supply circuit; 15: Timer circuit; 16: Discharge circuit; 17: Reset circuit; 18, 19: Switching circuit; 21~24: Light source; 31: Capacitor; 32: PNP transistor; 33: Diode; 35: NMOS transistor; 34, 36, 37: Resistor; 38a~38c: Schottky barrier diode; 51: Resistor; 52: Capacitor; 53: NPN transistor; 61: Comparator; 62~65: Resistor; 66: Capacitor; 67: NP N transistor; 71: diode; 72, 74, 76: capacitor; 73, 77a, 77b, 78a, 78b: resistor; 75: comparator; 81, 91: NMOS transistor; 82, 92: capacitor; 83, 84, 86, 87, 93, 94: resistor; 85: comparator; A~H: terminal; D1~D4: light emitting element; R1~R5, R11~R18, Rd1, Rd2: resistor; COM1~COM4: comparator; Q1~Q4: NMOS transistor; VCC: power supply voltage; Vdd: voltage; Vout: output voltage; Iin: input current; Id: adjustment current.

Claims

1. A lighting circuit, which is applied to a vehicle lamp including a plurality of light sources, comprising: A voltage dividing circuit that divides a power supply voltage applied to a power supply line into a plurality of voltages that are different from each other; a timer circuit comprising a first resistor and a first capacitor, wherein the power supply voltage is applied to the first resistor via the power supply line, and the first capacitor is connected to the first resistor; a control circuit configured to sequentially light up the plurality of light sources based on the plurality of voltages of the voltage divider circuit and the voltage of the first capacitor; and The first discharge circuit discharges the first capacitor during a first period when the power supply voltage is applied to the power supply line.

2. The lighting circuit according to claim 1, It is characterized in that A second discharge circuit is provided, and when the power supply voltage is no longer applied to the power supply line, the second discharge circuit discharges the first capacitor during a second period.

3. The lighting circuit according to claim 1, It is characterized in that A first current regulating circuit is provided, and when the power supply voltage is applied to the power supply line, the first current regulating circuit starts to supply current to a second resistor connected to the power supply line, After a predetermined light source among the plurality of light sources is turned on based on the voltage of the first capacitor, the first current regulating circuit cuts off a supply path of current from the power supply line to the second resistor.

4. The lighting circuit according to claim 3, It is characterized in that have: a second current regulating circuit, which starts supplying current to a third resistor connected to the power line when the power voltage is applied to the power line; as well as a detection circuit for detecting whether at least any one of the plurality of light sources is abnormal, If the detection circuit detects an abnormality, the first current regulation circuit cuts off the current supply path from the power line to the second resistor. If the detection circuit detects an abnormality, the second current regulation circuit cuts off a supply path of current from the power line to the third resistor.

5. The lighting circuit according to any one of claims 1 to 4, It is characterized in that The vehicle lamp is a turn signal lamp, The power supply voltage is periodically applied to the power supply line.

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