Lighting system

Abstract

To provide an illumination system for supplying DC power to a plurality of luminaires, the illumination system being capable of performing lighting control of the luminaires depending on variations in supply voltage.SOLUTION: An illumination system 1 comprises: a DC power supply unit for supplying DC power; DC power supply lines 3A, 3B connected to its output end; and a plurality of luminaires 4A to 4C connected in parallel to the lines. The luminaire 4A includes: an LED row in which a plurality of LEDs are connected; and a control circuit for performing lighting control of the LED row depending on variations in supply voltage from the DC power supply unit to the LED row. The DC power supply unit is a combination of AC-DC conversion units 2A, 2B for converting AC power to DC power and renewable energy power supplies 5, 6. When supply voltage of the power supplies 5, 6 has been varied, lighting control of the LED row is performed depending on the variation. In changeover of a supply source of power between the renewable energy power supplies 5, 6 and the AC-DC conversion units 2A, 2B, the changeover is performed smoothly without interruption of supply power.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a lighting system that supplies DC power to a plurality of lighting fixtures, and particularly to a lighting fixture equipped with a dimming function.

Background Art

[0002] The Intergovernmental Panel on Climate Change has set a goal of substantially zeroing greenhouse gas (CO2) emissions by 2050, and various technological developments are being made in accordance with this goal. In the lighting of roads, public facilities, etc. that support social infrastructure, light-emitting diodes (LEDs) have been widely used due to advantages such as low power consumption and long life in the past, but further technological development is required.

[0003] Since semiconductor light-emitting elements such as LEDs emit light by DC power, consideration is being given to switching the power supply system for a plurality of lighting fixtures in streetlights, tunnel lighting, ceiling lighting, etc. from the conventional AC power supply system to a DC power supply system (hereinafter referred to as a DC power supply system). That is, a common DC power supply unit is provided, commercial AC power is converted into DC power by the DC power supply unit, and the converted DC power is supplied to a plurality of lighting fixtures via positive and negative power supply lines.

[0004] The DC power supply system is more compatible with renewable energy. For example, when using solar power generation or wind power generation as a power source, it is expected that the conversion from the generated DC power to AC power becomes unnecessary and no power loss occurs during conversion. Similarly, when using a storage battery for backup during a power outage, there is also an expectation that the DC power of the storage battery can be supplied as it is. In addition, in the conventional AC power supply system, in order to switch from AC power to the DC power of the storage battery during a power outage, control is required to detect the disconnection from the AC power source and then connect to the storage battery, resulting in the lighting fixture being temporarily turned off. In contrast, in the DC power supply system, it becomes possible to always connect to the storage battery, and it is expected to avoid temporary turning off during a power outage.

[0005] On the other hand, due to the characteristics of LEDs, even a slight change in the applied DC voltage or temperature causes a large change in the flowing current. Therefore, generally, a constant current circuit is provided to keep the LED current constant to avoid a decrease in the light quality of lighting fixtures or damage to the LEDs. For example, the lighting system of Patent Document 1 includes a DC power supply unit, DC power supply lines on the positive and negative sides connected thereto, and a plurality of lighting fixtures connected in parallel to the DC power supply lines. The lighting fixtures are provided with a constant current circuit that keeps the LED current constant by the operation of a switching element that repeatedly turns on and off at high speed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] The inventors focused on the fact that a DC power supply system inherently has a large allowable voltage fluctuation range, and thought that if the lighting fixtures can be dimmed according to the change when the supply voltage from the DC power supply unit to the lighting fixtures changes, for example, it is possible to realize a lighting system that can effectively utilize renewable energy such as linking the illuminance of the lighting fixtures to the change in the surrounding environment (such as the amount of sunlight), and have been intensively developing. However, the constant current circuit of Patent Document 1 detects the LED current value from a current detection resistor connected in series with the LED, and adjusts the duty of the switching element so that this current value becomes a predetermined magnitude. Therefore, even if the supply voltage from the DC power supply unit is increased or decreased, the LED current is only controlled to be constant, and the illuminance of a plurality of LEDs cannot be changed according to the supply voltage.

[0008] An object of the present invention is to provide a lighting system that can dim lighting fixtures according to a change in supply voltage in a lighting system that supplies DC power to a plurality of lighting fixtures.

Means for Solving the Problem

[0009] The inventors have successfully developed a control circuit for dimming a semiconductor light-emitting element in response to a change in the supply voltage from a DC power supply unit, and have thus completed the present invention. That is, the lighting system according to the present invention includes a DC power supply unit that supplies DC power, a DC power supply line connected to the output terminal of the DC power supply unit, a plurality of lighting fixtures connected in parallel to the DC power supply line, A lighting system for tunnel lighting, wherein the DC power supply line is arranged along the tunnel, and the plurality of lighting fixtures are arranged at intervals along the tunnel. Each wherein the lighting fixture has a light-emitting element array in which a plurality of semiconductor light-emitting elements are connected, has a plurality of, and the plurality of light emitting element arrays are configured to be switchable from series connection to parallel connection by turning on or off a switch element. and a control circuit that dims the light-emitting element array in response to a change in the supply voltage from the DC power supply unit to lighting fixture thereof. By turning on or off the switch element to switch the connection state of the plurality of This is characterized by having paths Here, the AC-DC conversion unit includes a transformer, the a voltage variable unit that changes the supply voltage of the AC-DC conversion unit As, a device for changing the turns ratio of the transformer, and a rectifying element connected to the secondary side of the transformer, and is characterized by having the same. Here, it is preferable that the DC power supply unit has an AC-DC conversion unit that converts AC power into DC power, a renewable energy power source, a storage battery, or a combination thereof.

[0010] When the lighting system having the above configuration is used, when the supply voltage from the DC power supply unit (for example, an AC-DC conversion unit, a renewable energy power source, a storage battery, etc.) changes, the control circuit can dim the light-emitting element array in response to the change. Further, when the DC power supply unit is composed of at least two types of power sources among an AC-DC conversion unit, a renewable energy power source, and a storage battery, and it is desired to sequentially switch the supply source of DC power in accordance with a change in the supply voltage of each, since it is DC, that is, simply the power source with the higher supply voltage preferentially becomes the supply source, the supply source can be smoothly switched without interruption of the supplied power. Therefore, a mechanism for controlling the switching of the DC power supply unit is not required. Subsequently, the control circuit can dim the light-emitting element array in response to the supply voltage of the switched DC power supply unit. When the supply voltage of the DC power supply unit changes in this way, the lighting fixture is dimmed according to the change. Therefore, dimming control such as changing the illuminance of the lighting fixture in conjunction with changes in the surrounding environment (such as the amount of sunlight) becomes possible.

[0011] Further, the DC power supply unit has at least an AC-DC conversion unit that converts AC power into DC power and a renewable energy power source, and it is preferable that the supply voltage of the renewable energy power source is higher than the supply voltage of the AC-DC conversion unit.

[0012] Renewable energy power sources (such as solar power generation and wind power generation) have the characteristic that the supplyable voltage changes due to changes in the surrounding environment (such as the amount of sunlight and wind speed). According to the above configuration, while ensuring a predetermined illuminance by the supply voltage from the AC-DC conversion unit, during the period when the supply voltage of the renewable energy power source (such as solar power generation and wind power generation) is higher than the supply voltage of the AC-DC conversion unit, the renewable energy with a low environmental load is preferentially supplied. Therefore, the consumption of commercial AC power can be suppressed, and there are merits such as reduction of environmental load and reduction of the burden of electricity charges. In addition, during the period when the supply voltage of solar power generation is higher than the supply voltage of the AC-DC conversion unit (when the amount of sunlight is large), the lighting fixture can be dimmed according to the amount of sunlight. For example, during the daytime when sunlight is strong, the illuminance of the lighting fixture can be increased (or decreased), and during the evening when sunlight is weak, the illuminance of the lighting fixture can be decreased (or increased), etc., so that the effective use of renewable energy can be achieved.

[0013] Further, the DC power supply unit has at least an AC-DC conversion unit that converts AC power into DC power and a storage battery, and the storage battery supplies DC power to the DC power supply line via a diode, and it is preferable that the supply voltage of the storage battery is lower than the supply voltage of the AC-DC conversion unit.

[0014] According to the above configuration, during the period when the AC-DC conversion unit maintains a supply voltage equal to or higher than a certain level, since the supply voltage is higher than the supply voltage of the storage battery, the storage battery does not supply DC power. When a power outage or the like causes the AC-DC conversion unit to be unable to maintain the supply voltage and the supply voltage becomes lower than the supply voltage of the storage battery, the supply of DC power from the storage battery is started. Therefore, when there is a power outage of AC power or the like, the lighting fixture can continue to light without going out.

[0015] Further, the DC power supply unit preferably has at least an AC-DC conversion unit that converts AC power into DC power, and the AC-DC conversion unit preferably has a voltage variable unit that changes the supply voltage of the AC-DC conversion unit. Furthermore, the voltage variable unit is preferably configured to receive a dimming signal from the outside and change the supply voltage of the AC-DC conversion unit according to the dimming signal.

[0016] According to the above configuration, since the voltage variable unit is provided in the AC-DC conversion unit which is the DC power supply unit, the supply voltage of the AC-DC conversion unit can be actively changed, and the lighting fixture can be lit at a desired illuminance. Also, if the voltage variable unit is configured to change the supply voltage according to a dimming signal from the outside, remote control of dimming and automatic dimming according to detection values of sensors or the like can be realized.

[0017] Further, the DC power supply unit preferably has at least an AC-DC conversion unit that converts AC power into DC power, and the AC-DC conversion unit preferably has a rectifier circuit with a phase number of 6 or more. According to the above configuration, the harmonics contained in the DC power from the AC-DC conversion unit are less than those in the lighting system of a conventional switching power supply, the generation of electromagnetic noise is suppressed, and a highly reliable lighting system can be provided.

[0018] Further, the light emitting element array has a bypass path that bypasses at least one semiconductor light emitting element among the plurality of semiconductor light emitting elements constituting the light emitting element array, and a semiconductor switching element is provided on the bypass path. Preferably, the control circuit is configured to change the opening degree of the semiconductor switch element according to the magnitude of the supply voltage applied to the light emitting element array.

[0019] In the above configuration, for example, when the supply voltage of the DC power supply unit is maximum, it is assumed that the opening degree of the semiconductor switch element in the bypass path is set to be fully open. Since all the current flows through the light emitting element array, the light emitting element array reaches the maximum brightness (dimming rate 100%). Then, when the supply voltage decreases, the control circuit changes the opening degree of the semiconductor switch element in the direction from fully open to closed accordingly. As a result, the amount of bypassed current increases according to the closing degree, and the illuminance of the semiconductor light emitting element provided with the bypass path decreases. In this way, dimming of the light emitting element array according to the supply voltage is executed. Not limited to the above, for example, when the supply voltage is maximum, the opening degree of the semiconductor switch element may be set to be fully closed so that the amount of current flowing through the bypass path is maximum (the current flowing through the light emitting element array is minimum). The light emitting element array becomes the darkest. Then, as the supply voltage decreases, the control circuit changes the opening degree of the semiconductor switch element in the direction from fully closed to open. As a result, the amount of bypassed current decreases according to the opening degree, and the current flowing through the semiconductor light emitting element provided with the bypass path increases, so the illuminance increases.

[0020] Further, the DC power supply unit preferably has at least an AC-DC conversion unit that converts AC power into DC power, and the AC-DC conversion unit is preferably provided at both ends of the DC power supply line. By providing the AC-DC conversion unit at both ends of the DC power supply line as in this configuration, even if a trouble such as a disconnection occurs in one AC-DC conversion unit, it is possible to avoid the lighting fixture being completely turned off due to the power supply from the other AC-DC conversion unit.

[0021] Further, the DC power supply unit preferably includes at least a storage battery and a battery checker that detects the deterioration status of the storage battery. According to this configuration, the deterioration status of the storage battery can be confirmed remotely.

[0022] Furthermore, the lighting system according to the present invention preferably further includes a resistance midpoint grounding circuit connecting between the DC power supply lines of the positive and negative electrodes and the ground point. According to this configuration, during energization, the resistance midpoint grounding circuit acts as a safety circuit, and it is possible to detect deterioration of the insulation resistance of the DC power supply line.

[0023] Furthermore, the lighting system according to the present invention The plurality of light emitting element arrays preferably further includes an arc suppression circuit connecting between the terminals of the lighting fixture , the arc suppression circuit suppresses the generation of an arc when the switch element is released. . According to this configuration, when the switch is released, the arc suppression circuit acts as a safety circuit, preventing the generation of an arc and avoiding disconnection.

[0024] Furthermore, the lighting system according to the present invention is for tunnel lighting, and it is preferable that the DC power supply line is arranged along the tunnel, and the plurality of lighting fixtures are arranged at intervals along the tunnel. Here, the lighting system for tunnel lighting preferably further includes an illuminance sensor provided outside the tunnel, the DC power supply unit has at least an AC-DC conversion unit that converts AC power into DC power, and the AC-DC conversion unit preferably has a voltage variable unit that changes the supply voltage according to the illuminance measured by the illuminance sensor.

[0025] According to the above configuration, in tunnel lighting, when the illuminance (amount of sunlight) outside the tunnel changes, the supply voltage of the AC-DC conversion unit is changed according to the detection value of the illuminance sensor, and in conjunction with this, the lighting fixture is dimmed. For example, when it is bright outside the tunnel, the inside of the tunnel is also brightened, and when it is dark outside the tunnel, the inside of the tunnel is also darkened, so that dimming control of tunnel lighting can be realized. In this configuration, it is not necessary to individually transmit a dimming signal according to the detection value of the illuminance sensor to a large number of lighting fixtures, and dimming can be achieved only by changing the supply voltage in the AC-DC conversion unit. Therefore, the configuration of dimming control of tunnel lighting can be realized simply and inexpensively.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0027] Embodiments of a tunnel lighting system of the present invention will be specifically described with reference to the drawings.

[0028] FIG. 1 is a schematic diagram showing the overall configuration of a tunnel lighting system. This lighting system 1 includes AC-DC converters 2A and 2B provided at both ends of the lighting system as a main power source of DC power, a positive DC power supply line 3A connecting the positive output terminals of the AC-DC converters 2A and 2B, a negative DC power supply line 3B connecting the negative output terminals thereof, a plurality of LED luminaires 4A to 4C connected in parallel to the DC power supply lines 3A and 3B, a solar power generator 5 as a first auxiliary power source, a wind power generator 6 as a second auxiliary power source, a storage battery 7 as an emergency power source, and a resistance midpoint earthing circuit 8 which is a safety circuit.

[0029] A pair of DC power supply lines 3A and 3B are arranged along the tunnel, and the AC-DC converters 2A and 2B are installed near the entrance and exit of the tunnel. Even if one of the AC-DC converters becomes inoperable, the power supply from the other AC-DC converter continues, so it is possible to avoid the tunnel being completely darkened. Also, the AC-DC converters 2A and 2B are connected to an illuminance sensor 9 outside the tunnel by a signal line to obtain the illuminance signal outside the tunnel detected by the illuminance sensor 9. FIG. 2(A) shows the circuit configuration of a center-tapped rectifier circuit as a specific example of the AC-DC converter 2A. The AC-DC converter 2A includes a transformer T that converts the AC voltage from an AC power source, diodes D1 and D2 each having an anode connected to both ends of the secondary coil of the transformer T, and a load tap changer 21 that functions as a voltage variable section. The cathodes of the two rectifying elements D1 and D2 are connected to form a positive output terminal, which is connected to the positive DC power supply line 3A. Also, the midpoint of the secondary coil of the transformer T forms a negative output terminal, which is connected to the negative DC power supply line 3B. The AC-DC converter 2B on the opposite side has the same configuration as the AC-DC converter 2A. They convert AC power into DC power and apply a voltage (positive potential) to the positive terminal of the LED lighting fixtures 4A to 4C via the positive DC power supply line 3A. The load tap changer 21 is a device that changes the turns ratio of the transformer T according to the illuminance signal from the illuminance sensor 9 and is used to change the supply voltage of the DC power according to the illuminance outside the tunnel.

[0030] Note that in FIG. 2, a single-phase AC-DC conversion section is illustrated. However, if three-phase AC is converted to DC using a rectifier circuit with six or more phases, the harmonics will be even fewer, and DC power that is less likely to generate noise can be supplied. For example, a 12-phase rectifier circuit or a 24-phase rectifier circuit may be used.

[0031] In the AC-DC converter 2C of the modified example shown in Fig. 2(B), both ends of the secondary coil of the transformer T are branched, and via additional diodes D3 and D4, these branched lines are connected to each other, and DC power is output to the DC power supply line 3C of the positive electrode of another system. Then, if the two positive DC power supply lines 3A and 3C are arranged along the tunnel and the positive electrode terminals of the lighting fixtures are connected to both DC power supply lines 3A and 3C, it is possible to avoid the lighting fixtures from going out due to the disconnection of either one of the DC power supply lines.

[0032] Next, a plurality of LED lighting fixtures 4A to 4C are arranged at intervals along the tunnel, and their respective positive electrode terminals are connected to the positive DC power supply line 3A via diodes D5 to D7 for preventing reverse current. The negative electrode terminals are connected to the negative DC power supply line 3B. A specific example of the lighting fixture 4A will be described later with reference to Figs. 5 to 8.

[0033] Next, both the solar power generator 5 and the wind power generator 6 have their positive output terminals connected to the positive DC power supply line 3A via diodes D8 and D9. When the outputs of the generators 5 and 6 reach the voltage of the DC power supply line 3A, these renewable energies are supplied to the DC power supply line 3A.

[0034] The storage battery 7 has its positive output terminal connected to the anode of the diode D10, and the cathode of this diode D10 is connected to the DC power supply line 3A. In addition, a series connection consisting of a diode D11, a switch element SW1, and a resistor R1, whose direction is opposite to that of the diode D10, is connected in parallel to the diode D10. The switch element SW1 turns on when the voltage of the storage battery 7 drops below a specified value (charge start voltage), and charging is started by the voltage of the DC power supply line 3A. Also, the switch element SW1 turns off when the voltage of the storage battery 7 reaches another specified value (charge stop voltage) due to charging, and charging is stopped. These start and stop of charging are automatically executed. In addition, the storage battery 7 has a battery checker 71 and is used to confirm information indicating the voltage value and deterioration state of the storage battery by remote operation.

[0035] Note that in the lighting system 1 of this embodiment, the DC power supply includes a main power supply (AC-DC converters 3A and 3B), an auxiliary power supply (solar power generator 5 and wind power generator 6), and an emergency power supply (storage battery 7). However, it may be only the main power supply, only the auxiliary power supply, or a combination of the main power supply and the auxiliary power supply, a combination of the main power supply and the emergency power supply, or a combination of the auxiliary power supply and the emergency power supply.

[0036] The lighting fixtures 4A to 4C are lighting fixtures with the same configuration. The lighting fixture 4A includes a plurality of LEDs as light sources. These LEDs form LED columns that are groups of a plurality of LEDs, and it has a plurality of such LED columns.

[0037] In addition, the lighting fixture 4A has a control circuit that dims a plurality of LED columns according to the supply voltage from the DC power supply line 3A. A specific example of the control circuit will be described later with reference to FIGS. 5 to 8. Here, the characteristics of the tunnel lighting system 1 using the lighting fixtures 4A to 4C capable of dimming a plurality of LED columns according to the supply voltage will be described.

[0038] FIG. 3 illustrates a case where the relationship between the supply voltage (V) and the dimming rate (%) of the lighting system 1 is linear. In this example, the range of the supply voltage V1 of the AC-DC converter 2A of the main power supply is set to 225 to 300V, the range of the supply voltage V2 (or V3) of the solar power generator 5 (or wind power generator 6) of the auxiliary power supply is set to 300 to 380V, and the range of the supply voltage V4 of the storage battery 7 of the emergency power supply is set to 100 to 190V. That is, the range of the supply voltage (100 to 380V) corresponding to the entire range of the dimming rate (5% to 100%) is divided into a plurality of sections, and different types of DC power supplies are responsible for the power supply in each section.

[0039] In FIG. 3, the supply voltage V2 of the solar power generator 5 is set higher than the supply voltage V1 of the AC-DC converter 2A.

[0040] The solar power generator 5 is likely to have its supply voltage change due to changes in sunlight intensity, but it is also possible to predict the supply voltage based on time zones and weather information. Here, with the setting of V1 < V2, renewable energy such as solar power generation is preferentially supplied during the period when the supply voltage V2 of the solar power generator 5 becomes higher than the supply voltage V1 (225 - 300V) of the AC-DC converter 2A. At the same time, during the period when the solar power generator 5 cannot maintain a supply voltage V2 of 300V or higher, a predetermined illuminance is ensured by the supply voltage V1 from the AC-DC conversion unit, which is the main power source. Note that since the DC power supply system is the basis for switching the power supply source from the solar power generator 5 to the AC-DC converter 2A, simply the power source with the higher supply voltage becomes the preferential power supply source, and the supply power is smoothly executed without interruption.

[0041] Fig. 4 shows an example of the change in illuminance inside the tunnel due to the dimming control of the lighting system 1. The upper graph shows the change in the supply voltage throughout the day, indicating the supply voltage V2 of the solar power generator 5 and the supply voltage V1 of the AC-DC converter 2A. Here, the supply voltage V1 is kept constant. According to the lighting system 1, during the day (from 8:00 to 16:00), the lighting fixtures are dimmed according to the change in the supply voltage V2 of the solar power generator 5, so that, as shown in the lower graph, the illuminance inside the tunnel changes almost in the same way as the change in sunlight intensity outside the tunnel. By means of dimming control such as making the inside of the tunnel bright when it is bright outside the tunnel and making it dark when it is dark outside the tunnel, it is possible to realize illuminance management inside the tunnel that is friendly to drivers using the tunnel.

[0042] FIG. 3 shows that the lighting system 1 can also perform dimming control of the lighting fixtures even within the supply voltage V1 range (225 to 300 V) of the AC-DC converter 2A. That is, the illuminance sensor 9 detects a change in the illuminance (amount of sunlight) outside the tunnel, and based on the illuminance signal, the load tap changers 21 of the AC-DC converters 2A and 2B operate, changing the supply voltage V1 of the AC-DC converters 2A and 2B. Therefore, the control circuits of the lighting fixtures 4A to 4C can perform dimming in conjunction with the change in the supply voltage V1 of the AC-DC converters 2A and 2B, similar to when the supply voltage V2 of the solar power generator 5 changes. Since the supply voltage V1 is collectively adjusted in the AC-DC converters 2A and 2B, it is not necessary to individually transmit the illuminance signal of the illuminance sensor to a large number of lighting fixtures, simplifying the configuration of the dimming control of the tunnel lighting.

[0043] Thus, even after the power supply source is switched from the solar power generator 5 to the AC-DC converter 2A, continuous dimming control within a wide supply voltage range of 225 to 380 V becomes possible because the dimming of the lighting fixtures 4A to 4C continues to be performed in response to changes in the supply voltage. Here, for simplicity, the adjustment of the illuminance inside the tunnel in response to changes in the amount of sunlight has been described, but the lighting system of the present invention can also be applied to dimming control based on conditions other than the amount of sunlight.

[0044] Also, in FIG. 3, the supply voltage V4 of the storage battery 6 is set lower than the supply voltage V1 of the AC-DC converter 2A.

[0045] During the period when the AC-DC converter 2A maintains a supply voltage V1 above a certain level, since the supply voltage V1 is higher than the supply voltage V4 of the storage battery 7, the storage battery 7 does not supply DC power. When the supply of AC power from the outside stops due to a power outage or the like, the supply voltage V1 of the AC-DC converter 2A gradually decreases to 190 V while remaining lit, and power supply from the emergency power supply storage battery 7 is started. Then, lighting continues within the range of the stored power amount of the storage battery 7. Also, as the supply voltage V4 of the storage battery 7 gradually decreases, dimming of the lighting fixtures 4A to 4C is performed in response to the change in the supply voltage V4. That is, the illuminance decreases to the lower limit of the dimming rate (5%), and the lights go out at the timing when the supply voltage V4 becomes 100 V or less.

[0046] Hereinafter, a specific example of the LED lighting fixture 4A will be described with reference to FIGS. 5 to 8.

[0047] The lighting fixture 41 in FIG. 5 has LED columns 51 to 53 composed of a plurality of LEDs. As shown in FIG. 5, the anode of the first LED column 51 is connected to the positive terminal of the lighting fixture 41, and the cathode of the LED column 51 branches. One of the branches is connected to the anode of the second LED column 51, and the other branch is connected to the drain of the field effect transistor (FET1). The source of FET1 further branches, one of the branches is connected to the cathode of the diode D12, and the other branch is connected to the anode of the third LED column 53. The anode of the diode D12 and the cathode of the second LED column 51 merge and are connected to the drain of FET2. Then, the anode of the third LED column 53 and the source of FET2 are connected in series and connected to the negative terminal of the lighting fixture 41 via a constant current control circuit (CC control circuit) 60.

[0048] In the lighting fixture 41 of FIG. 5, the connection state of the plurality of LED columns 51 to 53 is switched from series to parallel by turning on or off the FETs 1 and 2. This will be described with reference to FIGS. 6(A) and 6(B). FIG. 6 shows how the connection state of the five LED columns 51 to 55 is switched from series to parallel. For example, when the supply voltage is the maximum of 380V, the CC control circuit 60 detects the supply voltage and operates the FET control circuit 61 to generate a gate voltage that turns off the FETs 1 to 4. As a result, all the FETs 1 to 4 maintain the off state, and as shown in FIG. 6(A), a series connection circuit of the five LED columns 51 to 55 is formed. That is, the current from the positive terminal flows in the order of LED column 51 → LED column 52 → diode D12 → LED column 53 → diode D13 → LED column 54 → diode D14 → LED column 55. Since the CC control circuit 60 controls the current to be constant, the lighting fixture 41 lights up at a dimming rate of 100%.

[0049] Next, when the supply voltage drops to the threshold value, the CC control circuit 60 operates the FET control circuit 61 so as to generate a gate voltage that turns on FETs 1 to 4. As a result, all of the FETs 1 to 4 are turned on, and as shown in FIG. 6(B), four LED strings 52 to 55 excluding the LED string 51 form a series connection of the LED strings 52 and 54 and a series connection of the LED strings 53 and 55, and a parallel connection circuit that is a parallel connection of the two series connections is formed. That is, the current from the LED string 51 branches, and half of the current flows in the order of LED string 52 → FET2 → LED string 54 → FET4, and the remaining half of the current flows in the order of FET1 → LED string 53 → FET3 → LED string 55, and then they merge. Even after switching to the parallel connection circuit, the CC control circuit 60 controls so that the current becomes constant over the entire plurality of LED strings, so the current flowing through each LED string is halved, and the lighting fixture 41 lights up at a dimming rate of 50%.

[0050] In this way, the lighting fixture 41 performs dimming by switching the connection state of the plurality of LED strings 51 to 53 from series to parallel according to the supply voltage.

[0051] In FIG. 5, a specific example of the arc suppression circuit 70 will be described. The arc suppression circuit 70 is connected so as to connect both ends of the connection circuit formed by the plurality of LED strings 51 to 53, and has a circuit configuration including a parallel connection portion of a resistor R2 and a diode D17 and a capacitor C2 connected in series thereto. By providing the arc suppression circuit 70, the generation of an arc at the time of switch release is suppressed, and disconnection or the like can be avoided.

[0052] Also, as in the example shown in FIG. 7, a series connection circuit of a plurality of lighting fixtures 42 to 44 may be connected to the DC power supply lines 3A and 3B of the positive and negative electrodes. However, the CC control circuit 60 is provided only in the last-stage lighting fixture 44. In each of the lighting fixtures 42 to 44, the switching from the series connection to the parallel connection of the LED strings is performed by the FET control circuits 61 to 63.

[0053] In the lighting fixture 45 of FIG. 8, a plurality of LED arrays 51 to 54 are connected in series, and bypass paths are provided for the second and fourth LED arrays 52 and 54. FET1 is connected to the bypass path of the LED array 52, and FET2 is connected to the bypass path of the LED array 54. Here, the major difference from the lighting fixture 41 of FIG. 5 is that FET1 and FET2 can continuously adjust the opening degree (or closing degree) between the drain and the source according to the gate voltage. That is, the current amount in the bypass path is adjusted by the magnitude of the opening degree (or closing degree) of the FET. In the lighting fixture 45, the CC control circuit 80 detects the supply voltage and operates the FET control circuit 81 to generate the gate voltages of FET1 and 2 so that they have an opening degree corresponding to the supply voltage. Further, since the CC control circuit 80 controls so that the current becomes constant over the entire plurality of LED arrays 51 to 54, when the opening degree adjustment of the FET by the FET control circuit 81 is executed, the illuminance of the LED arrays 52 and 54 decreases by the amount of the bypass current. In this way, the illuminance over the entire LED arrays 51 to 54 is continuously changed according to the supply voltage.

[0054] Finally, a specific example of the resistance midpoint grounding circuit 8 will be described with reference to FIG. 9. The resistance midpoint grounding circuit 8 is provided between the DC power supply lines 3A and 3B of the positive and negative electrodes and the ground point. Since the DC power supply lines 3A and 3B are non-grounded DC circuits, the resistance midpoint grounding circuit 8 functions as a circuit for detecting a decrease in the insulation resistance between the DC power supply lines 3A and 3B and the ground point.

[0055] The resistance midpoint grounding circuit 8 has a series connection circuit composed of resistors R3 and R4 with equal resistance values, and a parallel connection circuit of photocouplers 81 and 82 connected with opposite polarities. The series connection circuit of resistors R3 and R4 is connected between the DC power supply lines 3A and 3B of the positive and negative electrodes. Also, the parallel connection circuit of photocouplers 81 and 82 is connected to a circuit connecting the connection point of resistors R and R to the ground point. One terminal of the light receiving element of photocoupler 81 is connected to VCC, and a light emitting diode 83 is connected to the other terminal. When current flows from the ground point toward the connection point of resistors R and R, the light emitting and light receiving actions of photocoupler 81 occur, and the light emitting diode 83 lights up. Similarly, one terminal of the light receiving element of photocoupler 82 is connected to VCC, and another light emitting diode 84 is connected to the other terminal. When current flows from the connection point of resistors R and R toward the ground point, the light emitting and light receiving actions of photocoupler 82 occur, and the light emitting diode 84 lights up.

[0056] In the resistance midpoint grounding circuit 8 with such a configuration, when the resistance value of the insulation resistance of the positive DC power supply line 3A decreases, a weak current flows through the light emitting element of photocoupler 81. The light receiving element captures this weak current, and the light emitting diode 83 lights up. Thereby, the decrease in the insulation resistance of the positive DC power supply line 3A is indicated by the light emission of the light emitting diode 83. Similarly, when the resistance value of the insulation resistance of the negative DC power supply line 3B decreases, a weak current flows through the light emitting element of the opposite-side photocoupler 82. The light receiving element captures this weak current, and the light emitting diode 84 lights up. Thereby, the decrease in the insulation resistance of the negative DC power supply line 3B is indicated by the light emission of the light emitting diode 84.

Explanation of Symbols

[0057] 1 Tunnel lighting system 2A, 2B DC power supply lines 3A, 3B AC-DC converters 4A~4C LED lighting fixtures 5 Solar power generator 6 Wind-solar power generator 7 Storage battery 8 Resistance midpoint grounding circuit 9 Illuminance sensor 21 Tap changer under load 41~45 LED lighting fixtures 51~57 LED arrays 60,80 CC control circuit 61~63,81 FET control circuit 70 Arc suppression circuit

Claims

1. A DC power supply unit that supplies DC power, A DC power supply line connected to the output terminal of the DC power supply unit, A plurality of lighting fixtures connected in parallel to the DC power supply line, wherein the DC power supply line is arranged along a tunnel, and the plurality of lighting fixtures are arranged at intervals along the tunnel. A lighting system for tunnel lighting, Each of the lighting fixtures, Has a plurality of light emitting element arrays in which a plurality of semiconductor light emitting elements are connected, and the plurality of light emitting element arrays are configured to be switchable from series connection to parallel connection by turning on or off a switch element, A lighting system characterized by having a control circuit that dims the plurality of light emitting element arrays by turning on or off the switch element in response to a change in the supply voltage from the DC power supply unit to the lighting fixture to switch the connection state of the plurality of light emitting element arrays.

2. In the lighting system according to Claim 1, The DC power supply unit has at least an AC-DC conversion unit that converts AC power into DC power, The AC-DC conversion unit, A transformer, As a voltage variable unit that changes the supply voltage of the AC-DC conversion unit, a device that changes the turns ratio of the transformer, And a rectifying element connected to the secondary side of the transformer. A lighting system characterized by this.

3. In the lighting system according to Claim 1 or 2, The DC power supply unit has an AC-DC conversion unit that converts AC power into DC power, a renewable energy power source, or a storage battery, or a combination thereof. A lighting system characterized by this.

4. In the lighting system according to any one of Claims 1 to 3, The DC power supply unit has at least an AC-DC conversion unit that converts AC power into DC power and a renewable energy power source, and the supply voltage of the renewable energy power source is higher than the supply voltage of the AC-DC conversion unit. A lighting system characterized by this.

5. In the lighting system according to any one of Claims 1 to 4, The DC power supply unit has at least an AC-DC conversion unit that converts AC power into DC power and a storage battery. The storage battery supplies DC power to the DC power supply line via a diode, and the supply voltage of the storage battery is lower than the supply voltage of the AC-DC conversion unit. A lighting system characterized by this.

6. In the lighting system according to Claim 2, The lighting system is characterized in that the voltage variable unit receives a dimming signal from the outside and is configured to change the supply voltage of the AC-DC conversion unit according to the dimming signal.

7. In the lighting system according to any one of Claims 1 to 6, the DC power supply unit has at least an AC-DC conversion unit that converts AC power into DC power, and the AC-DC conversion unit has a rectifier circuit with six or more phases. The lighting system is characterized by this.

8. In the lighting system according to any one of Claims 1 to 7, the light emitting element array has a bypass path that bypasses at least one semiconductor light emitting element among the plurality of semiconductor light emitting elements that make up the light emitting element array, and a semiconductor switch element is provided on the bypass path. The control circuit is configured to adjust the opening degree of the semiconductor switch element according to the magnitude of the supply voltage applied to the light emitting element array. The lighting system is characterized by this.

9. In the lighting system according to any one of Claims 1 to 8, the DC power supply unit has at least an AC-DC conversion unit that converts AC power into DC power, and the AC-DC conversion unit is provided at both ends of the DC power supply line. The lighting system is characterized by this.

10. In the lighting system according to any one of Claims 1 to 9, the DC power supply unit includes at least a storage battery and a battery checker that detects the deterioration status of the storage battery. The lighting system is characterized by this.

11. In the lighting system according to any one of Claims 1 to 10, A resistance midpoint grounding circuit that connects between the DC power supply lines of the positive and negative electrodes and the ground point is provided. The lighting system is characterized by this.

12. In the lighting system according to any one of Claims 1 to 11, An arc suppression circuit that connects between the terminals of the plurality of light emitting element arrays of the lighting fixture is provided, and the arc suppression circuit suppresses the generation of arcs when the switch element is released. The lighting system is characterized by this.

13. The lighting system for tunnel lighting according to any one of Claims 1 to 12 further includes an illuminance sensor provided outside the tunnel. The DC power supply unit has at least an AC-DC conversion unit that converts AC power into DC power, and the AC-DC conversion unit has a voltage variable unit that changes the supply voltage according to the illuminance measured by the illuminance sensor. The lighting system is characterized by this.

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