JP7620184B2 - Lighting equipment - Google Patents

Description

The present invention relates to a lighting device that includes multiple LEDs connected in series.

Conventionally, a lighting device for a vehicle equipped with multiple LEDs arranged in a row is 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 multiple LEDs individually.

JP 2018-16289 A

The inventors of the present application are considering reducing power consumption by connecting multiple LEDs in series. Specifically, they are considering a structure in which a FET circuit having a switch for switching on and off the supply 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 targeted LED by disconnecting the switch corresponding to the LED to be illuminated 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.

However, in this structure, for example, when 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 LEDs other than the most downstream, so there is a risk that part of the current will escape from each FET circuit other than the most downstream, causing the brightness of the most downstream LED to be lower than the desired brightness. And, this reduction in brightness is not particularly noticeable when the duty ratio is a large value close to 100%, but it becomes noticeable when the duty ratio is reduced.

The present invention aims to make the brightness of multiple LEDs uniform when the LEDs are arranged in series and illuminated with a duty ratio of less than 100%.

The lighting device of the present invention, which solves the above-mentioned problems, includes a plurality of LEDs connected in series with each other, an FET circuit provided corresponding to each of the plurality of LEDs and having a switch connected in parallel to the LED, 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.

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. Therefore, even if part of the current escapes from the FET circuit corresponding to the first LED when the second LED is caused to emit light, current is supplied to the second LED 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 match the brightness of the first LED and the second LED.

The disconnection period of the first switch and the disconnection period of the second switch may be made not to overlap.

Here, if current is supplied to both the first LED and the second LED at the same time, charge accumulates in the downstream second LED first, and charge does not accumulate easily in the first LED, resulting in a problem of reduced brightness of the upstream first LED. In response to this, by preventing the disconnection period of the first switch from overlapping with the disconnection period of the second switch, 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.

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

With this configuration, two or more switches are turned off sequentially during a very short period such as a cycle period, so two or more LEDs can appear to be illuminated simultaneously.

The control unit may also cause two or more LEDs to emit light sequentially by performing a process for turning off only one switch for two or more switches within a cycle period corresponding to one cycle of the PWM control.

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

In this case, the control unit may turn off a specific switch multiple times, and then turn off a switch different from the specific switch multiple times.

In addition, when the control unit sets the duty ratio to a predetermined value or more, the target values of the duty ratios for the multiple switches may be set to the same value.

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

The LEDs may also be arranged side by side in a specific direction.

With this configuration, it is possible to control multiple LEDs to light up in sequence from one side of a specified direction so that the light flows in that direction.

The lighting device may also have a frame that can be attached to a vehicle.

This configuration allows the lighting device to be effectively used as vehicle lighting.

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

In addition, by preventing the disconnection period of the first switch from overlapping with the disconnection period of the second switch, 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.

In addition, by turning off two or more switches sequentially 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 illuminated simultaneously.

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

In addition, 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 illuminated in sequence, the apparent brightness of each LED can be increased.

In addition, when the duty ratio is set to a predetermined value or greater, the target value of the duty ratio for each switch can be set to the same value, which helps prevent the control from becoming complicated.

In addition, by arranging multiple LEDs in a line in a specific direction, it is possible to control the multiple LEDs to light up in sequence from one side of the specific direction so that the light flows along the specific direction.

In addition, 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.

1A is a perspective view showing a vehicle door on which a lighting device is installed, and FIG. 1B is a perspective view showing the lighting device. FIG. 2 is a diagram showing a circuit of a lighting device. FIG. 13 is a diagram showing a table for setting a target value of a duty ratio. 1A to 1D are diagrams showing the flow of current when multiple LEDs are illuminated in sequence from the upstream. 4 is a flowchart showing the operation of a control unit. FIG. 1A is a time chart showing the ON/OFF states of each switch when full lighting processing is performed with a duty ratio of about 10%, and FIG. 1B is a time chart showing the ON/OFF states of each switch when full lighting processing is performed with a duty ratio of 100%. FIG. 1A is a time chart showing the ON/OFF state of each switch when performing flow lighting processing with a duty ratio of about 10%, and FIG. 1B is a time chart showing the ON/OFF state of each switch when performing flow lighting processing with a duty ratio of 100%. 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%. 13 is a time chart showing a second modified example in which the flow lighting process is performed with a duty ratio of about 10%.

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, in this embodiment, for convenience of explanation, the number of LEDs is four, but the number of LEDs may be more than that, for example, eight.

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

As shown in FIG. 2, the multiple LEDs 11 to 14 are connected in series with each other. The multiple 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.

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 ensures that the current Io flowing from the constant current circuit 31 to the first LED 11 is always 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.

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

The multiple FET circuits 21 to 24 are provided corresponding to the multiple LEDs 11 to 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.

The first FET circuit 21 has 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 that allows current to flow between the drain D and the source S and a disconnected state that prohibits current 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 no switching voltage is applied, and in a disconnected state when a switching voltage is applied.

When the first switch SW1 is in a connected state, the current Io flows through the first switch SW1 toward the downstream second LED 12, bypassing 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.

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.

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.

The vehicle is equipped with 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 specified manner or a turn-off instruction for turning off the lighting device 1 in response to the operation of the occupant.

The lighting instruction is an instruction to light the multiple LEDs 11-14 at a specified brightness, and in this embodiment includes an all-on instruction and a flowing lighting instruction. The all-on instruction is an instruction to light the multiple LEDs 11-14 so that all of the multiple LEDs 11-14 appear to the occupant to be on at the same time. The flowing lighting instruction is an instruction to light the multiple LEDs 11-14 sequentially so that the light emitted from the multiple LEDs 11-14 appears to the occupant to flow in the forward and backward directions.

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 through PWM control by controlling the duty ratio corresponding to the disconnection time of the switches SW1-SW4. Furthermore, when multiple LEDs 11-14 are illuminated, the control unit 100 is configured to stagger the timing at which current supply to each of the LEDs 11-14 begins so that the start of illumination of each of the LEDs 11-14 is staggered in time.

Specifically, the 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 there are four LEDs, 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.

The control unit 100 is capable of executing a full lighting process in which the multiple LEDs 11-14 are illuminated so that all of the multiple LEDs 11-14 appear to the occupant to be illuminated simultaneously, and a flowing lighting process in which the multiple LEDs 11-14 are illuminated in sequence so that the light emitted from the multiple LEDs 11-14 appears to the occupant to be flowing in the front-to-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.

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

The control unit 100 has a function of determining whether the brightness of the external environment is relatively dark, such as at night, based on a signal from the illuminance sensor 51. If the control unit 100 determines that the brightness of the external environment is dark, it sets the target brightness of the LEDs 11 to 14 to a smaller first brightness that corresponds to a dark state. If the control unit 100 determines that the brightness of the external environment is not dark, that is, that the external environment is relatively bright, such as during the day, for example, it sets the target brightness to a second brightness that is greater than the first brightness.

The control unit 100 has a function of setting the target value of the duty ratio for each of the switches SW1 to SW4 based on the set target brightness and the table shown in FIG. 3. Specifically, when the control unit 100 sets the target brightness to the large 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%.

When the control unit 100 sets the target luminance to a small first luminance, it sets the target value of the duty ratio for each switch SW1 to SW4 to a different value. Specifically, the control unit 100 sets the target value of the duty ratio for the first switch SW1 to a first target value (10%), and the target value of the duty ratio for the second switch SW2 to a second target value (10+a%) that is larger than the first target value. The control unit 100 also sets the target value of the duty ratio for the third switch SW3 to a third target value (10+b%) that is larger 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%) that is larger than the third target value. Here, the magnitude relationship between a, b, and c is a<b<c. The reason for making the target values different will be described in detail later.

When the control unit 100 performs the full lighting process at the second brightness, 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 switch SW1 to SW4 from ON to OFF during a cycle period Ts corresponding to the first cycle of the PWM control, and then maintains each switch SW1 to SW4 OFF for multiple cycle periods Ts. When the control unit 100 performs the full lighting process at the first brightness, the control unit 100 turns off (OFF) the multiple switches SW1 to SW4 sequentially during 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 brightness, the turn-off periods T1 to T4 of the switches SW1 to SW4 are set so as not to overlap with each other.

Here, the reason why the multiple 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 multiple LEDs 11 to 14 are connected in series as in this embodiment, when the switches SW1 to SW4 are simultaneously turned off with a small duty ratio of about 10%, electric charge accumulates in the LEDs starting from the fourth LED 14 at the most downstream position, and the LEDs located further upstream have a poorer start-up of light emission, resulting in differences in brightness among the LEDs 11 to 14. In contrast, the above-mentioned problem is solved by sequentially turning off the multiple switches SW1 to SW4 during the full lighting process at the first brightness. However, when the multiple switches SW1 to SW4 are sequentially turned off with a small duty ratio of about 10%, another problem occurs due to leakage of the current Ic as shown in Figures 4(b) to (d), so 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.

Below, the reason for setting the target value of the duty ratio to a different value when the target luminance is set to the first luminance will be explained with reference to FIG. 4. Note that FIG. 4 illustrates a simplified circuit configuration.

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 10% duty, the current Io flows through the first LED 11 for the time corresponding to the 10% duty, and the first LED 11 lights up at the 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 10% duty, a part of the current Io, the current Ic, 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 the time corresponding to the 10% duty, and the second LED 12 lights up at a brightness lower than the first brightness.

As shown in FIG. 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 upstream of the third switch SW3. Therefore, in this case, a current (Io-2Ic) flows through the third LED 13 that is smaller than the current (Io-Ic) when only the second LED 12 is illuminated, and the brightness of the third LED 13 becomes smaller than the brightness of the second LED 12.

As shown in FIG. 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 to 23 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 lit flows through the fourth LED 14, and the brightness of the fourth LED 14 becomes lower than the brightness of the third LED 13.

In this embodiment, as shown in FIG. 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), 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 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.

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 turn-on instruction (S1). If it is determined in step S1 that there is no turn-on instruction (No), the control unit 100 ends this process.

If 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 more detail, if 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 if 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.

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

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).

If it is determined in step S7 that the lighting instruction is a full lighting instruction (Yes), the control unit 100 sequentially turns off each of 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 lighting-off instruction (S9).

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

If the control unit 100 determines in step S7 that the lighting instruction is not a full lighting instruction, that is, that it is a flowing lighting instruction for executing the flowing lighting process (No), then the control unit 100 turns off only one switch in the cycle period Ts at the 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 the first target value (10%). After that, when the control unit 100 determines No in step S9 and enters the second control cycle, in step S10, the control unit 100 turns off the second switch SW2 at a duty ratio of the 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).

If it is determined in step S6 that the target value of the duty ratio is not less than 100%, i.e., that it 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 switch SW1 to SW4 at approximately the same time with a duty ratio of 100% (S12) and proceeds to the processing of step S9.

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 response to the flowing lighting instruction (S13), and proceeds to the processing of step S9.

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).

If the external environment is nighttime when the full lighting command is issued, 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). The control unit 100 then sets the target value of the duty ratio corresponding to the first luminance for each switch SW1 to SW4 based on the table in FIG. 3 (S4). As a result, the target values are set to higher values the more downstream the switch, starting from the first switch SW1, which is the most upstream, in order: 10%, 10%+a, 10%+b, 10%+c.

Then, the control unit 100 executes the processes of steps S5 to S8, and sequentially passes the current Io passed through the circuit to each of the LEDs 11 to 14 individually, 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 luminance. Also, as shown in FIG. 6(a), by turning off each of the switches SW1 to SW4 within a very short cycle period Ts, each of the LEDs 11 to 14 can be made to appear to be illuminated approximately simultaneously, so that at night, the occupant can feel that each of the LEDs 11 to 14 is appearing to be all lit.

If it is daytime when the full lighting command is issued, 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). The control unit 100 then 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. This sets the target value of each of the switches SW1 to SW4 to the same value (100%).

Then, the control unit 100 executes the processes of steps S5, S6, S11, and S12 to turn off each switch SW1 to SW4 at approximately the same time with a duty ratio of 100%, as shown in FIG. 6(b). At this time, the charge accumulates in sequence starting from the fourth LED 14, which is the most downstream, so that some difference occurs in the brightness of each LED 11 to 14. However, at a duty ratio of 100%, the effect of the difference is so small that it can be ignored, so that during the daytime, the occupants can feel that each LED 11 to 14 is fully lit with the same second brightness.

When lighting the lighting device 1 in a flowing manner, the occupant operates the operation unit 52, which outputs a flowing lighting instruction 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.

If the external environment is nighttime when the flowing lighting command is issued, the control unit 100 sets the target brightness to the first brightness in step S3. The control unit 100 then sets the target value of the duty ratio corresponding to the first brightness for each switch SW1 to SW4 based on the table in FIG. 3 (S4).

Then, the control unit 100 executes 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 in response to the floating lighting instruction, for each switch SW1 to SW4, 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 switch further downstream, the brightness of each LED 11 to 14 can be aligned to the first luminance.

In the example shown in FIG. 7(a), 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, if 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 if the external environment when the flowing lighting instruction is given is daytime, the operation is the same except for the target value of the duty ratio, so a description will be omitted.

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 to 14 are caused to emit light at a first luminance, the target value of the duty ratio is set to be larger for the more downstream LEDs and each of the LEDs 11 to 14 is caused to emit light with a time lag, so that the effect of the leakage current Ic can be almost eliminated and the brightness of each of the LEDs 11 to 14 can be made uniform.

By preventing the disconnection periods T1 to T4 of the switches SW1 to SW4 from overlapping, it is possible to prevent current from being supplied to two or more LEDs at the same time, allowing each of the LEDs 11 to 14 to emit light satisfactorily.

Since each switch SW1 to SW4 is turned off in sequence during a very short period such as the cycle period Ts, each LED 11 to 14 can be made to appear to light up simultaneously.

By performing a process for each switch SW1 to SW4 that turns off only one switch within the cycle period Ts, each of the LEDs 11 to 14 can be made to light up sequentially in an apparent sequence.

When the duty ratio is set to a predetermined value or higher, even if some current leaks from the FET circuit, it does not have much effect on the brightness of the downstream LEDs, so 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.

By arranging multiple LEDs 11-14 in a specific direction, it is possible to achieve flowing lighting in which the light flows in a specific direction.

Since the lighting device 1 has a frame F that can be attached to the vehicle door DR, the lighting device 1 can be effectively used as lighting for the vehicle.

Although an embodiment of the present invention has been described above, the present invention can be modified as appropriate and implemented as shown in the other forms below. In the following description, the same components as those in the above embodiment are given the same reference numerals and their description will be omitted.

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. In the flow lighting process, each of the switches SW1 to SW4 may be turned off multiple times from the upstream side. In other words, the control unit 100 may turn off a specific switch multiple times, and then turn off a switch other than the specific switch multiple times.

For example, as shown in FIG. 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, and then twice for the third switch SW3 and twice for the fourth switch SW4, in that order. This allows the light of each of the LEDs 11 to 14 to flow slowly.

When the process of turning off only one switch within a cycle period is performed multiple times on a specific switch, the specific switch may be turned off during all of the multiple consecutive cycle periods, or the specific switch may be turned off during a portion of two or more of the multiple consecutive cycle periods.

In the above embodiment, when the LEDs are turned on in a flowing manner 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 at which each switch starts to be turned off 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 turn on in a flowing manner 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 since the timing at which each switch starts to be turned off is shifted, each LED can be turned on satisfactorily. 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 flowed.

In the above embodiment, the occupant operates the operation unit 52, and the operation unit 52 outputs a turn-on command to the control unit 100. However, the present invention is not limited to this. For example, the turn-on command 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 command 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 command to turn on each of the LEDs 11 to 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 command to turn on each of the LEDs 11 to 14 in sequence from the front.

The ECU may also output a full-light command 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 on. The ECU may also output a full-light command 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 open or closed.

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 to this. For example, even when the target luminance is set to a luminance slightly smaller than the second luminance, the target values of the duty ratios for each switch may be 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 each switch to the same value when the duty ratio is set to a predetermined value or greater.

In the above embodiment, all 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 multiple LEDs may be illuminated within the cycle period.

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.

In the above embodiment, the predetermined brightness is the 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%.

The light emission pattern of the multiple LEDs is not limited to the above embodiment and may be any pattern. For example, the light emission pattern may be such that the first LED 11 and the fourth LED 14 are alternately illuminated.

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 location other than the door of the vehicle.

The elements described in the above embodiments and variations may be combined in any manner.

1 Lighting device 11 First LED
12 Second LED
21 First FET circuit 22 Second FET circuit 100 Control unit SW1 First switch SW2 Second switch

Claims (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 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 . 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. 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. The lighting device according to claim 1, wherein the LEDs are arranged side by side in a predetermined direction. 5. The lighting device according to claim 1, further comprising a frame capable of being attached to a vehicle. 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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