Lighting equipment

Abstract

To uniform lightness of a plurality of serially connected LEDs when the plurality of serially connected LEDs is lighten in a duty ratio less than 100%.SOLUTION: An illumination device 1 comprises: a plurality of serially connected LEDs 11 to 14; FRT circuits 21 to 24 having switches SW1 to SW4 parallely connected to each LED; and a control unit 100 that controls lightness of each LED by a PWM control by controlling a duty ratio corresponding to a disconnection time of each switch. In the control unit, a target value of the duty ratio with respect to a first switch SW1 corresponding to a first LED 11 is set to be a first target value when the duty ratio is set to be less than 100%, and the two or more LEDs are lighted by being deviated in terms of time with a predetermined luminance, and a target of the duty ratio with respect to a second switch SW2 corresponding to a second LED 12 positioned in the downstream side of the first LED 11 in a current flow direction is set to be a second target larger than the first target value.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a lighting device comprising a number of LEDs connected in series. [Background technology]

[0002] Conventionally, a lighting device for a vehicle equipped with a plurality of LEDs arranged in a row has been known as a lighting device (see Patent Document 1). With this technology, it is possible to inform the occupant of the direction of movement of an object approaching the vehicle by sequentially lighting up the plurality of LEDs individually. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-16289 A Summary of the Invention [Problem to be solved by the invention]

[0004] The inventor of the present application is considering reducing power consumption by connecting multiple LEDs in series. Specifically, he is considering a structure in which a FET circuit having a switch for switching the supply and stop of current to the LED is connected in parallel to each of the multiple LEDs connected in series. In this structure, it is possible to light only the target LED by disconnecting the switch corresponding to the LED to be lit and connecting the other switches. Also, in this structure, it is possible to change the brightness of the LED by controlling the duty ratio corresponding to the switch disconnection time.

[0005] However, in this structure, for example, when a current is supplied to the most downstream LED in the current flow direction, the current is supplied to the most downstream LED via each FET circuit corresponding to the LED other than the most downstream, so that a part of the current escapes from each FET circuit other than the most downstream, and the brightness of the most downstream LED may be lower than the desired brightness. Such a decrease in brightness is not particularly noticeable when the duty ratio is a large value close to 100%, but becomes noticeable when the duty ratio is reduced.

[0006] Therefore, an object of the present invention is to make the brightness of a plurality of LEDs arranged in series uniform when the LEDs are illuminated with a duty ratio of less than 100%. [Means for solving the problem]

[0007] The lighting device of the present invention, which solves the above-mentioned problems, includes a plurality of LEDs connected in series with each other, a FET circuit having a switch provided corresponding to each of the plurality of LEDs and connected in parallel to the LEDs, and a control unit that controls the brightness of the LEDs by PWM control by controlling a duty ratio corresponding to the disconnection time of the switch. When the control unit sets the duty ratio to less than 100% and causes two or more of the LEDs to start emitting light at a predetermined brightness with a time lag, the control unit sets a target value of the duty ratio for a first switch corresponding to a first LED to a first target value, and sets a target value of the duty ratio for a second switch corresponding to a second LED located downstream of the first LED in the current flow direction to a second target value greater than the first target value.

[0008] According to this configuration, when the duty ratio is set to less than 100% and two or more LEDs are caused to start emitting light at a predetermined brightness with a time lag, the control unit sets the target value of the duty ratio for the first switch to a first target value and the target value of the duty ratio for the second switch to a second target value greater than the first target value, so that when the second LED is caused to emit light, even if a part of the current escapes from the FET circuit corresponding to the first LED, the second LED is supplied with current for a long time corresponding to the duty ratio that is the second target value greater than the first target value. Therefore, it is possible to prevent the brightness of the downstream second LED from decreasing, and it is possible to make the brightness of the first LED and the second LED the same.

[0009] Also, the disconnection period of the first switch and the disconnection period of the second switch may not overlap.

[0010] Here, if current is supplied to both the first LED and the second LED at the same time, the downstream second LED will accumulate charge first, and the first LED will not accumulate charge easily, causing a problem of reduced brightness of the upstream first LED. In response to this, by making the disconnection period of the first switch and the disconnection period of the second switch not overlap, it is possible to prevent current from being supplied to both the first LED and the second LED at the same time, allowing each LED to emit light satisfactorily.

[0011] The control unit may sequentially turn off two or more switches within a cycle period corresponding to one cycle of the PWM control.

[0012] According to this configuration, two or more switches are turned off in sequence during a very short period such as a cycle period, so that two or more LEDs can appear to light up simultaneously.

[0013] In addition, the control unit may cause two or more of the LEDs to emit light sequentially by performing a process of turning off only one switch for two or more switches within a cycle period corresponding to one cycle of the PWM control.

[0014] According to this configuration, by performing the process of turning off only one switch within a cycle period on two or more switches, it is possible to make two or more LEDs, for example, appear to light up in sequence.

[0015] In this case, the control unit may turn off a predetermined switch a plurality of times, and then turn off a switch different from the predetermined switch a plurality of times.

[0016] Furthermore, when the control section sets the duty ratio to a predetermined value or more, the control section may set target values ​​of the duty ratios for the plurality of switches to the same value.

[0017] When the duty ratio is set to a specified value or above, even if some current leaks from the FET circuit, it does not have much effect on the brightness of the downstream LED. Therefore, by setting the target duty ratio for each switch to the same value, it is possible to prevent control from becoming too complicated.

[0018] The LEDs may be arranged side by side in a predetermined direction.

[0019] According to this configuration, it is possible to perform control so that the multiple LEDs are illuminated in sequence from one side in a predetermined direction so that light flows along the predetermined direction.

[0020] The lighting device may also include a frame that can be attached to a vehicle.

[0021] According to this configuration, the lighting device can be effectively used as lighting for the vehicle. Effect of the Invention

[0022] According to the present invention, when a plurality of LEDs arranged in series are illuminated with a duty ratio of less than 100%, the brightness of the plurality of LEDs can be made uniform.

[0023] In addition, by ensuring that the disconnection period of the first switch and the disconnection period of the second switch do not overlap, it is possible to prevent current from being supplied to both the first LED and the second LED at the same time, allowing each LED to emit light satisfactorily.

[0024] In addition, by sequentially turning off two or more switches during a very short period, such as a cycle period corresponding to one cycle of PWM control, two or more LEDs can be made to appear to be lit simultaneously.

[0025] Furthermore, by performing the process of turning off only one switch within a cycle period on two or more switches, it is possible to make two or more LEDs appear to light up in sequence, for example.

[0026] Also, by performing the process of turning off only one switch within a cycle period multiple times for a specific switch, the apparent brightness of the LED corresponding to the specific switch can be increased. Similarly, by turning off a switch other than the specific switch multiple times, the apparent brightness of the LED corresponding to this switch can be increased. Therefore, when two or more LEDs are made to light up in sequence, the apparent brightness of each LED can be increased.

[0027] Furthermore, when the duty ratio is set to a predetermined value or more, the target values ​​of the duty ratios for the switches are set to the same value, thereby making it possible to prevent the control from becoming complicated.

[0028] Furthermore, by arranging a plurality of LEDs in a line in a predetermined direction, it is possible to control the plurality of LEDs to light up in sequence from one side in the predetermined direction so that the light flows along the predetermined direction.

[0029] Furthermore, by providing the lighting device with a frame that can be attached to a vehicle, the lighting device can be effectively used as lighting for the vehicle. [Brief description of the drawings]

[0030] [Figure 1]FIG. 2A is a perspective view showing a vehicle door in which a lighting device is installed, and FIG. 2B is a perspective view showing the lighting device. [Diagram 2] FIG. 2 is a diagram showing a circuit of a lighting device. [Diagram 3] FIG. 13 is a diagram showing a table for setting a target value of a duty ratio. [Figure 4] 11(a) to 11(d) are diagrams showing the current flow when multiple LEDs are illuminated in sequence from the upstream. [Diagram 5] 4 is a flowchart showing the operation of a control unit. [Figure 6] Time chart (a) shows the ON / OFF state of each switch when full lighting is performed with a duty ratio of about 10%, and time chart (b) shows the ON / OFF state of each switch when full lighting is performed with a duty ratio of 100%. [Figure 7] This is a time chart (a) showing the ON / OFF state of each switch when performing flow lighting processing with a duty ratio of about 10%, and a time chart (b) showing the ON / OFF state of each switch when performing flow lighting processing with a duty ratio of 100%. [Figure 8] 13 is a time chart showing a first modified example in which the flow lighting process is performed with a duty ratio of about 10%. [Figure 9] 13 is a time chart showing a second modified example in which the flowing lighting process is performed with a duty ratio of about 10%. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in Fig. 1(a), the lighting device 1 is a lighting device for a vehicle that is installed on a door DR of the vehicle. As shown in Fig. 1(b), the lighting device 1 includes a first LED 11, a second LED 12, a third LED 13, and a fourth LED 14, and a frame F that supports the LEDs 11 to 14. Note that, for convenience of explanation, in this embodiment, the number of LEDs is four, but the number of LEDs may be more than that, for example, eight.

[0032] The LEDs 11 to 14 are arranged in a predetermined direction, specifically in the front-rear direction. The LEDs 11 to 14 are arranged in the order of the first LED 11, the second LED 12, the third LED 13, and the fourth LED 14 from front to rear. The frame F can be attached to a door DR of a vehicle.

[0033] 2, the LEDs 11 to 14 are connected in series to one another. The LEDs 11 to 14 are arranged in the following order from upstream to downstream in the flow direction of the current Io: first LED 11, second LED 12, third LED 13, and fourth LED 14. The fourth LED 14 is grounded.

[0034] The lighting device 1 further includes a plurality of FET circuits 21-24, a constant current circuit 31, a step-up DC / DC converter 32, a noise filter 33, diodes 34 and 35, a regulator 36, and a control unit 100. The first LED 11 is connected to a power source PS via the constant current circuit 31, the step-up DC / DC converter 32, the noise filter 33, and the diode 34. This keeps the current Io flowing from the constant current circuit 31 to the first LED 11 constant. In this embodiment, the power source PS is an external power source separate from the lighting device 1, but the power source may be built into the lighting device 1.

[0035] The control unit 100 is connected to a power supply PS via a regulator 36 and a diode 35. Thus, a voltage regulated by the regulator 36 is applied to the control unit 100. A noise filter 33 is connected to a wiring connecting the regulator 36 and the diode 35.

[0036] The multiple FET circuits 21-24 are provided corresponding to the multiple LEDs 11-14, respectively. In the following description, the FET circuits corresponding to the first LED 11, the second LED 12, the third LED 13, and the fourth LED 14, respectively, are also referred to as the first FET circuit 21, the second FET circuit 22, the third FET circuit 23, and the fourth FET circuit 24.

[0037] The first FET circuit 21 includes a first switch SW1, resistors R1 and R2, a capacitor C, and a Zener diode ZD. The first switch SW1 is connected in parallel to the first LED 11. The first switch SW1 can be switched between a connected state in which a current is permitted to flow between the drain D and the source S and a disconnected state in which a current is prohibited to flow between the drain D and the source S by controlling a voltage (hereinafter also referred to as a "switching voltage") applied to the gate G. Specifically, the first switch SW1 is in a connected state when the switching voltage is not applied, and in a disconnected state when the switching voltage is applied.

[0038] When the first switch SW1 is in a connected state, the current Io flows toward the downstream second LED 12 via the first switch SW1 so as to bypass the first LED 11. When the first switch SW1 is in a disconnected state, the current Io flows through the first LED 11, causing the first LED 11 to emit light.

[0039] The resistor R1, the capacitor C, and the Zener diode ZD are each connected in parallel to the first switch SW1. More specifically, one end of the resistor R1, the capacitor C, and the Zener diode ZD is connected to the drain D of the first switch SW1, and the other end is connected to the gate G of the first switch SW1. The resistor R2 is connected to the gate G and the control unit 100.

[0040] The second FET circuit 22, the third FET circuit 23, and the fourth FET circuit 24 have the same structure as the first FET circuit 21. In the following description, the switches SW2 to SW4 provided in the second FET circuit 22, the third FET circuit 23, and the fourth FET circuit 24, respectively, are also referred to as the second switch SW2, the third switch SW3, and the fourth switch SW4.

[0041] The vehicle includes an illuminance sensor 51 and an operation unit 52. The illuminance sensor 51 is a sensor that detects the brightness of the external environment, such as the vehicle interior or the outside of the vehicle. A signal detected by the illuminance sensor 51 is output to the control unit 100. The operation unit 52 has buttons and the like that are operated by the occupant, and outputs to the control unit 100 a turn-on instruction for operating the lighting device 1 in a predetermined manner or a turn-off instruction for turning off the lighting device 1 in response to the operation of the occupant.

[0042] The lighting instruction is an instruction to light the LEDs 11-14 at a predetermined brightness, and in this embodiment, includes an all-on instruction and a flowing instruction. The all-on instruction is an instruction to light the LEDs 11-14 so that all of the LEDs 11-14 appear to the occupant as if they are all on at the same time. The flowing instruction is an instruction to light the LEDs 11-14 sequentially so that the light emitted from the LEDs 11-14 appears to the occupant to flow in the front-rear direction.

[0043] The control unit 100 includes a CPU, RAM, ROM, input / output circuits, etc., and executes control by performing various arithmetic processing based on input from an illuminance sensor 51 provided in the vehicle and programs and data stored in the ROM. Specifically, the control unit 100 has a function of controlling the brightness of the LEDs 11-14 by PWM control by controlling a duty ratio corresponding to the disconnection time of the switches SW1-SW4. Furthermore, when the multiple LEDs 11-14 are caused to emit light, the control unit 100 is configured to stagger the timing at which current supply to each of the LEDs 11-14 is started so that the start of light emission of each of the LEDs 11-14 is staggered.

[0044] Specifically, a cycle period Ts corresponding to one cycle of PWM control is divided into a number of sections corresponding to the number of LEDs, and the start of each section is set as the timing to start supplying current to each of the LEDs 11 to 14. In this embodiment, since the number of LEDs is four, the timing to start supplying current is set as follows. The timing to supply current to the first LED 11 is set to coincide with the start of the cycle period Ts corresponding to one cycle of PWM control. The timing to supply current to the second LED 12 is set to a point Ts / 4 ahead of the start of the cycle period Ts. The timing to supply current to the third LED 13 is set to a point Ts / 2 ahead of the start of the cycle period Ts. The timing to supply current to the fourth LED 14 is set to a point 3·Ts / 4 ahead of the start of the cycle period Ts.

[0045] The control unit 100 can execute a full lighting process for lighting the LEDs 11-14 so that all of the LEDs 11-14 appear to be lit simultaneously to the passenger, and a flowing lighting process for lighting the LEDs 11-14 sequentially so that the light emitted from the LEDs 11-14 appears to the passenger to be flowing in the front-rear direction. Specifically, the control unit 100 executes the full lighting process or the flowing lighting process based on a lighting instruction output from the operation unit 52.

[0046] In the flowing lighting process, the control unit 100 performs a process for turning off only one switch for each of the switches SW1 to SW4 within a cycle period Ts corresponding to one cycle of PWM control, as shown in Fig. 7(a) and (b), thereby sequentially lighting up the multiple LEDs 11 to 14. Here, the process for turning off only one switch is a process for switching the switch from ON to OFF, in other words, a process for starting turning off. The full lighting process will be described in detail later.

[0047] Based on the signal from the illuminance sensor 51, the control unit 100 has a function of determining whether the external environment is in a dark state, such as at night, where the brightness is relatively low. When the control unit 100 determines that the external environment is in a dark state, it sets the target brightness of the LEDs 11 to 14 to a smaller first brightness corresponding to the dark state. Also, when the control unit 100 determines that the external environment is not in a dark state, that is, in a relatively bright state, such as during the day, it sets the target brightness to a second brightness greater than the first brightness.

[0048] Based on the set target brightness and the table shown in Figure 3, the control unit 100 has a function of setting the target value of the duty ratio for each of the switches SW1 to SW4. Specifically, when the control unit 100 sets the target brightness to the larger second brightness, it sets the target value of the duty ratio for each of the switches SW1 to SW4 to the same value, for example, 100%.

[0049] When the control unit 100 sets the target brightness to the smaller first brightness, it sets the target values of the duty ratio for each of the switches SW1 to SW4 to different values. Specifically, the control unit 100 sets the target value of the duty ratio for the first switch SW1 to the first target value (10%), and the target value of the duty ratio for the second switch SW2 to a second target value (10 + a%) greater than the first target value. Also, the control unit 100 sets the target value of the duty ratio for the third switch SW3 to a third target value (10 + b%) greater than the second target value, and the target value of the duty ratio for the fourth switch SW4 to a fourth target value (10 + c%) greater than the third target value. Here, the magnitude relationship of a, b, and c is a < b < c. The reason for making the target values different will be described in detail later.

[0050] When performing the full lighting process at the second luminance, the control unit 100 turns off (OFF) the multiple switches SW1 to SW4 at approximately the same time with a duty of 100% as shown in FIG. 6(b). Specifically, the control unit 100 switches each of the switches SW1 to SW4 from ON to OFF within a cycle period Ts corresponding to the first cycle of the PWM control, and then maintains each of the switches SW1 to SW4 OFF for a plurality of cycle periods Ts. When performing the full lighting process at the first luminance, the control unit 100 turns off (OFF) the multiple switches SW1 to SW4 sequentially within a cycle period Ts corresponding to one cycle of the PWM control as shown in FIG. 6(a). In addition, when performing the full lighting process at the first luminance, the turn-off periods T1 to T4 of the switches SW1 to SW4 are set so as not to overlap with each other.

[0051] Here, the reason why the switches SW1 to SW4 are sequentially turned off during the full lighting process at the first brightness is as follows. In a circuit in which the LEDs 11 to 14 are connected in series as in this embodiment, if the switches SW1 to SW4 are simultaneously turned off at a small duty ratio of about 10%, electric charges accumulate in sequence starting from the fourth LED 14 at the most downstream, causing the LEDs located upstream to have a poorer start-up of light emission, resulting in a difference in brightness between the LEDs 11 to 14. In contrast, the above-mentioned problem is solved by sequentially turning off the switches SW1 to SW4 during the full lighting process at the first brightness. However, when the switches SW1 to SW4 are sequentially turned off at a small duty ratio of about 10%, another problem occurs due to leakage of the current Ic as shown in Figs. 4(b) to (d). Therefore, this problem is solved by setting the target value of the duty ratio for each switch SW1 to SW4 to a different value as described above.

[0052] The reason why the target value of the duty ratio is set to a different value when the target luminance is set to the first luminance will be described below with reference to Fig. 4. Note that Fig. 4 illustrates a simplified circuit configuration.

[0053] As shown in Fig. 4(a), when only the first switch SW1 corresponding to the first LED 11 at the most upstream is turned off with a duty of 10%, a current Io flows through the first LED 11 for a period corresponding to the 10% duty, and the first LED 11 lights up at a first brightness. As shown in Fig. 4(b), when only the second switch SW2 corresponding to the second LED 12 is turned off with a duty of 10%, a current Ic, which is a part of the current Io, leaks from the first FET circuit 21 located upstream of the second switch SW2. Therefore, in this case, a current (Io-Ic) smaller than the current Io flows through the second LED 12 for a period corresponding to the duty of 10%, and the second LED 12 lights up at a brightness smaller than the first brightness.

[0054] 4(c), when only the third switch SW3 is turned off with a duty of 10%, the current Ic leaks from each of the two FET circuits 21, 22 located upstream of the third switch SW3. Therefore, in this case, a current (Io-2Ic) smaller than the current (Io-Ic) when only the second LED 12 is illuminated flows through the third LED 13, and the luminance of the third LED 13 becomes smaller than the luminance of the second LED 12.

[0055] 4(d), when only the fourth switch SW4 is turned off with a duty of 10%, the current Ic leaks from each of the three FET circuits 21-23 located upstream of the fourth switch SW4. Therefore, in this case, a current (Io-3Ic) smaller than the current (Io-2Ic) when only the third LED 13 is illuminated flows through the fourth LED 14, and the luminance of the fourth LED 14 becomes smaller than the luminance of the third LED 13.

[0056] 3, the relationship of the target values ​​of the duty ratios for the switches SW1 to SW4 when the target brightness is the first brightness is set to first target value (10%)<second target value (10%+a)<third target value (10%+b)<fourth target value (10%+c), thereby making it possible to make the LEDs 11 to 14 shine at the first brightness. Note that in this embodiment, for the sake of convenience, the currents leaking from the FET circuits 21 to 23 are all designated as Ic, but in reality, the current leaking from the FET circuit 22 is smaller than the current leaking from the FET circuit 21, and the current leaking from the FET circuit 23 is smaller than the current leaking from the FET circuit 22.

[0057] Next, the operation of the control unit 100 will be described in detail. 5, the control unit 100 determines whether or not there is a lighting instruction (S1). If it is determined in step S1 that there is no lighting instruction (No), the control unit 100 ends this process.

[0058] When it is determined in step S1 that a lighting instruction has been issued (Yes), the control unit 100 acquires a signal from the illuminance sensor 51 (S2). After step S2, the control unit 100 determines the target luminance of the LEDs 11 to 14 based on the signal from the illuminance sensor 51 (S3). In detail, when the control unit 100 determines that the external environment is in a relatively dark state, it sets the target luminance to a first luminance, and when it determines that the external environment is not in a dark state, it sets the target luminance to a second luminance that is greater than the first luminance.

[0059] After step S3, the control unit 100 sets target values ​​of the duty ratios for the switches SW1 to SW4 based on the target luminance and the table shown in Fig. 3 (S4). After step S4, the control unit 100 starts supplying a current Io to a circuit having the LEDs 11 to 14 (S5).

[0060] After step S5, the control unit 100 determines whether the target value of the duty ratio is less than 100% (S6). If it is determined in step S6 that the target value is less than 100% (Yes), the control unit 100 determines whether the lighting instruction is a full lighting instruction for executing a full lighting process (S7).

[0061] If it is determined in step S7 that the turn-on instruction is an all-on instruction (Yes), the control unit 100 sequentially turns off the switches SW1 to SW4 at their respective target duty ratios within the cycle period Ts (S8). After step S8, the control unit 100 determines whether or not there is a turn-off instruction (S9).

[0062] If it is determined in step S9 that a turn-off instruction has been issued (Yes), the control unit 100 ends this process. If it is determined in step S9 that a turn-off instruction has not been issued (No), the control unit 100 returns to the process of step S6.

[0063] If it is determined in step S7 that the lighting instruction is not a full lighting instruction, that is, that it is a flowing lighting instruction for executing a flowing lighting process (No), the control unit 100 turns off only one switch in the cycle period Ts at a target duty ratio in response to the flowing lighting instruction (S10), and proceeds to the process of step S9. Specifically, in the first control cycle, in step S10, the control unit 100 turns off the first switch SW1 at a duty ratio of a first target value (10%). After that, when it is determined as No in step S9 and the second control cycle is entered, in step S10, the control unit 100 turns off the second switch SW2 at a duty ratio of a second target value (10%+a). Similarly, in each step S10 in the third and fourth control cycles, the control unit 100 turns off the third switch SW3 and the fourth switch SW4 at the duty ratios of their respective target values ​​(10%+b, 10%+c).

[0064] If it is determined in step S6 that the target value of the duty ratio is not less than 100%, that is, is 100% (No), the control unit 100 determines whether the lighting instruction is a full lighting instruction (S11). If it is determined in step S11 that the lighting instruction is a full lighting instruction (Yes), the control unit 100 turns off each of the switches SW1 to SW4 substantially simultaneously with a duty ratio of 100% (S12), and proceeds to the process of step S9.

[0065] If it is determined in step S11 that the lighting instruction is not a full lighting instruction, i.e., a flowing lighting instruction (No), the control unit 100 turns off only one switch with a duty ratio of 100% within the cycle period Ts in accordance with the flowing lighting instruction (S13), and proceeds to processing in step S9.

[0066] Next, an example of a specific operation of the control unit 100 will be described in detail. When turning on all the illumination devices 1, the occupant operates the operation unit 52 to output a full-on instruction from the operation unit 52 to the control unit 100. Upon receiving the full-on instruction, the control unit 100 determines Yes in step S1 and acquires a signal related to brightness from the illuminance sensor 51 (S2).

[0067] If the external environment is nighttime when the full lighting instruction is given, the control unit 100 determines that the external environment is dark based on the signal from the illuminance sensor 51, and sets the target luminance to the first luminance (S3). After that, the control unit 100 sets target values ​​of the duty ratio corresponding to the first luminance for each switch SW1 to SW4 based on the table of Fig. 3 (S4). As a result, the target values ​​are set for the switches SW1 to SW4 in order from the first switch SW1, which is the most upstream, as 10%, 10%+a, 10%+b, and 10%+c, with higher target values ​​being set for the switches further downstream.

[0068] Thereafter, the control unit 100 executes the processes of steps S5 to S8, and sequentially and individually flows the current Io flowing through the circuit to each of the LEDs 11 to 14, as shown in Fig. 4(a) to (d). At this time, the current flowing through each of the LEDs 11 to 14 becomes smaller from the upstream to the downstream, such as Io, Io-Ic, Io-2Ic, and Io-3Ic, due to the influence of the leakage current Ic. However, since the target values ​​of the duty ratios of the switches SW1 to SW4 are higher for the downstream switches, the brightness of each of the LEDs 11 to 14 can be made uniform to the first brightness. Also, as shown in Fig. 6(a), each of the switches SW1 to SW4 is turned off within a very short cycle period Ts, so that each of the LEDs 11 to 14 can be made to appear to be illuminated approximately at the same time, and therefore, at night, the occupant can feel that each of the LEDs 11 to 14 is appearing to be all lit up.

[0069] If the external environment is daytime when the full lighting instruction is given, the control unit 100 determines that the external environment is not dark based on the signal from the illuminance sensor 51, and sets the target luminance to the second luminance (S3). After that, the control unit 100 sets the target value of the duty ratio corresponding to the second luminance for each of the switches SW1 to SW4 based on the table in Fig. 3. As a result, the target value of each of the switches SW1 to SW4 is set to the same value (100%).

[0070] Thereafter, the control unit 100 executes the processes of steps S5, S6, S11, and S12 to turn off the switches SW1 to SW4 substantially simultaneously with a duty ratio of 100%, as shown in Fig. 6(b). At this time, charges are accumulated in sequence starting from the fourth LED 14, which is the most downstream, so that some difference occurs in the brightness of the LEDs 11 to 14, but since the effect of the difference is negligible at a duty ratio of 100%, the occupants can feel that the LEDs 11 to 14 are all lit up with the same second brightness during the daytime.

[0071] When the lighting device 1 is to be turned on in a flowing manner, the occupant operates the operation unit 52 to output a flowing lighting instruction from the operation unit 52 to the control unit 100. Upon receiving the flowing lighting instruction, the control unit 100 performs the processes of steps S1 to S3 to set a target luminance according to the brightness of the external environment.

[0072] If the external environment when the moving lighting instruction is given is nighttime, the control unit 100 sets the target luminance to the first luminance in step S3. After that, the control unit 100 sets the target value of the duty ratio corresponding to the first luminance for each of the switches SW1 to SW4 based on the table of FIG. 3 (S4).

[0073] Thereafter, the control unit 100 performs the process of steps S5 to S7 and S10, and performs the process of turning off only one switch at the target duty ratio within the cycle period Ts for each switch SW1 to SW4 in response to the sequential lighting instruction, as shown in Fig. 7(a). At this time, a leakage current Ic occurs as in the full lighting process, but since the target value of the duty ratio is higher for the downstream switch, the brightness of each LED 11 to 14 can be adjusted to the first luminance.

[0074] 7(a) is an example in which the flowing lighting instruction is an instruction to light each of the LEDs 11-14 in sequence from the upstream, so the switches SW1-SW4 are turned off in sequence from the upstream. Therefore, when the flowing lighting instruction is an instruction to light each of the LEDs in sequence from the downstream, the control unit 100 turns off each of the switches SW1-SW4 in sequence from the downstream in response to this flowing lighting instruction. Note that when the external environment is daytime when the flowing lighting instruction is given, the only difference is the target value of the duty ratio, and the operation is the same, so a description thereof will be omitted.

[0075] The vehicle seat of this embodiment as described above can provide the following advantages. When the duty ratio is set to less than 100% and the multiple LEDs 11-14 are caused to emit light at a first brightness, the target duty ratio is set to be larger for the more downstream LEDs and each LED 11-14 is caused to emit light with a time lag, thereby almost eliminating the effect of the leakage current Ic and making the brightness of each LED 11-14 uniform.

[0076] By making the disconnection periods T1 to T4 of the switches SW1 to SW4 not overlap, it is possible to prevent current from being supplied to two or more LEDs at the same time, so that the LEDs 11 to 14 can emit light satisfactorily.

[0077] Since the switches SW1 to SW4 are turned off in sequence during a very short period such as the cycle period Ts, the LEDs 11 to can appear to light up simultaneously.

[0078] By performing a process for turning off only one switch within a cycle period Ts for each of the switches SW1 to SW4, it is possible to make each of the LEDs 11 to 14 appear to light up in sequence.

[0079] When the duty ratio is set to a predetermined value or above, even if some current leaks from the FET circuit, it does not have much effect on the brightness of the downstream LEDs. Therefore, by setting the target value of the duty ratio for each of LEDs 11 to 14 to the same value (100%), it is possible to prevent the control from becoming complicated.

[0080] Since the LEDs 11 to 14 are arranged in a predetermined direction, flowing lighting in which light flows in a predetermined direction can be achieved.

[0081] Since the lighting device 1 includes the frame F that can be attached to the door DR of a vehicle, the lighting device 1 can be effectively used as lighting for the vehicle.

[0082] Although the embodiment of the present invention has been described above, the present invention can be practiced by appropriately modifying it as shown in the following other forms. In the following description, the same components as those in the above embodiment are given the same reference numerals, and the description thereof will be omitted.

[0083] In the above embodiment, in the flow lighting process, each of the switches SW1 to SW4 is turned off once from the upstream side, but the present invention is not limited to this, and in the flow lighting process, each of the switches SW1 to SW4 may be turned off multiple times from the upstream side. That is, the control unit 100 may turn off a switch other than the specified switch multiple times after turning off a specified switch multiple times.

[0084] 8, the control unit 100 may be configured to perform the process of turning off only one switch within a cycle period Ts twice for the first switch SW1, twice for the second switch SW2, twice for the third switch SW3, and twice for the fourth switch SW4, in that order. This allows the light of the LEDs 11-14 to flow slowly.

[0085] In addition, when the process of turning off only one switch within a cycle period is performed multiple times on a specific switch, only the specific switch may be turned off during all of a plurality of consecutive cycle periods, or only the specific switch may be turned off during a portion of two or more of the plurality of consecutive cycle periods.

[0086] In the above embodiment, when the switching is performed with a duty ratio of 10%, the disconnection periods of the switches are not overlapped, but the present invention is not limited to this, and the disconnection periods may overlap as long as the timing of the start of disconnection of each switch is shifted. Specifically, for example, as shown in FIG. 9, the duty ratio for a specific switch may be gradually increased and then gradually decreased to perform the switching with a duty ratio of 10%. In this case, for example, at time t1, the disconnection period of the first switch SW1 and the disconnection period of the second switch SW2 overlap, but the timing of the start of disconnection of each switch is shifted, so that each LED can be well lit. Also, in this embodiment, the duty ratio for each switch gradually increases and then gradually decreases, so that the light from each LED can be beautifully lit.

[0087] In the embodiment, the occupant operates the operation unit 52, and the operation unit 52 outputs a turn-on instruction to the control unit 100. However, the present invention is not limited to this. For example, the turn-on instruction may be output from an ECU (Electronic Control Unit) provided in the vehicle to the control unit 100. Specifically, for example, when the ECU determines that another vehicle is approaching the vehicle based on a signal from a sensor (e.g., an ultrasonic sensor) that detects the approach of another vehicle to the vehicle, the ECU may output a flowing turn-on instruction to the control unit 100. In this case, when the ECU determines that another vehicle is approaching from behind, the ECU may output a flowing turn-on instruction to turn on the LEDs 11-14 in sequence from the rear, and when the ECU determines that another vehicle is approaching from the front, the ECU may output a flowing turn-on instruction to turn on the LEDs 11-14 in sequence from the front.

[0088] Furthermore, the ECU may output a full-lighting instruction to the control unit 100 when a switch for starting the vehicle is turned on. In this case, the lighting device 1 can be used as indirect lighting that is always turned on. Furthermore, the ECU may output a full-lighting instruction to the control unit 100 when it determines that a door has been opened based on a signal from a sensor that detects whether the door is opened or closed.

[0089] In the above embodiment, when the target luminance is set to the large second luminance, the target values ​​of the duty ratios for the switches SW1 to SW4 are all set to 100%, but the present invention is not limited thereto. For example, when the target luminance is set to a luminance slightly smaller than the second luminance, the target values ​​of the duty ratios for the switches may be set to the same value, for example, 90%. In other words, the control unit may be configured to set the target values ​​of the duty ratios for the switches to the same value when the duty ratio is set to a predetermined value or more.

[0090] In the above embodiment, all of the four LEDs 11 to 14 are illuminated within the cycle period Ts, but the present invention is not limited to this, and two or three LEDs may be illuminated within the cycle period. In other words, at least two of the LEDs may be illuminated within the cycle period.

[0091] In the above embodiment, the number of LEDs is four, but the present invention is not limited to this, and the number of LEDs may be two or more.

[0092] In the above embodiment, the predetermined brightness is a first brightness corresponding to a duty ratio of about 10%, but the present invention is not limited to this, and the predetermined brightness may be, for example, a brightness corresponding to a duty ratio of about 20%.

[0093] The light emission pattern of the multiple LEDs is not limited to the above embodiment and may be any pattern, for example, a pattern in which the first LED 11 and the fourth LED 14 are alternately illuminated.

[0094] In the above embodiment, the lighting device 1 is attached to the door DR of the vehicle, but the lighting device may be attached to a portion of the vehicle other than the door.

[0095] The elements described in the above-mentioned embodiment and modified examples may be implemented in any combination. [Explanation of symbols]

[0096] 1 Lighting equipment 11 1st LED 12 2nd LED 21 First FET circuit 22 Second FET circuit 100 Control section SW1 First switch SW2 Second switch

Claims

1. A plurality of LEDs connected in series with each other; an FET circuit including a switch provided corresponding to each of the plurality of LEDs and connected in parallel to the LED; A control unit controls the brightness of the LED by PWM control by controlling a duty ratio corresponding to a disconnection time of the switch, The control unit is In the case where the duty ratio is set to less than 100% and two or more of the LEDs are caused to start emitting light at a predetermined luminance with a time lag, a target value of a duty ratio for a first switch corresponding to a first LED is set as a first target value; a target value of a duty ratio for a second switch corresponding to a second LED located downstream of the first LED in a current flow direction is set to a second target value greater than the first target value; A lighting device characterized in that two or more of the LEDs are caused to emit light sequentially by performing a process of turning off only one switch within a cycle period corresponding to one cycle of the PWM control such that the turning-off periods of two or more switches do not overlap.

2. The control unit is 2. The lighting device according to claim 1, wherein after a predetermined switch is turned off a plurality of times, a switch different from the predetermined switch is turned off a plurality of times.

3. The control unit is 3. The lighting device according to claim 1, wherein when the duty ratio is to be equal to or greater than a predetermined value, the target values ​​of the duty ratios for the plurality of switches are set to the same value.

4. 4. The lighting device according to claim 1, wherein the LEDs are arranged side by side in a predetermined direction.

5. 5. The lighting device according to claim 1, further comprising a frame capable of being attached to a vehicle.

6. A plurality of LEDs connected in series with each other; an FET circuit including a switch provided corresponding to each of the plurality of LEDs and connected in parallel to the LED; A control unit controls brightness of the LED by PWM control by controlling a duty ratio corresponding to a disconnection time of the switch, The control unit is In the case where the duty ratio is set to less than 100% and two or more of the LEDs are caused to start emitting light at a predetermined luminance with a time lag, a target value of a duty ratio for a first switch corresponding to a first LED is set as a first target value; a target value of a duty ratio for a second switch corresponding to a second LED located downstream of the first LED in a current flow direction is set to a second target value greater than the first target value; A control method characterized by sequentially lighting two or more of the LEDs by performing a process of turning off only one switch within a cycle period corresponding to one cycle of the PWM control such that the turning-off periods of two or more switches do not overlap.

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