Lighting device and illumination system

Abstract

To provide a lighting device and an illumination system, where voltage of both ends of a light source part can be detected appropriately.SOLUTION: There is provided a lighting device comprising: a conversion circuit that sets reference potential of a light source part to common potential through a switching element and converts input first DC power to second DC power corresponding to the light source part by switching of the switching element; and a control circuit for controlling operation of the conversion circuit. The conversion circuit includes: an input voltage detection section for detecting voltage of the first DC power; and an output voltage detection section for detecting difference voltage between the voltage of the first DC power and voltage of the second DC power. The control circuit includes a calculation circuit for calculating the voltage of the second DC power by subtracting the difference voltage from the voltage of the first DC power on the basis of detection results of the input voltage detection section and the output voltage detection section.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a lighting device and a lighting system.

Background Art

[0002] There is a lighting device including a light source unit having a light source and a lighting device for lighting the light source unit. There is also a lighting system including a plurality of lighting devices. The lighting device has a conversion circuit that converts the input DC power into another DC power corresponding to the light source unit and supplies the converted DC power to the light source unit to light the light source unit. The conversion circuit has a switching element and performs DC power conversion by switching the switching element.

[0003] In addition, the lighting device detects the voltage across both ends of the light source unit and detects an abnormality of the light source unit based on the voltage across both ends of the light source unit. When the lighting device detects an abnormality of the light source unit, the lighting device stops supplying DC power from the conversion circuit to the light source unit or the like.

[0004] In the conversion circuit of such a lighting device, a low-side switch type circuit in which the light source unit as a load is located on the high-side with respect to the switching element may be used. In a low-side switch type circuit, since the reference potential of the light source unit is not directly connected to the common potential (ground potential) of the conversion circuit, there is a possibility that the voltage across both ends of the light source unit cannot be appropriately detected. For example, when the input voltage fluctuates, the detected value of the voltage across both ends of the light source unit also fluctuates, and there is a possibility that it cannot be determined whether the voltage fluctuation is due to an abnormality of the light source unit or a voltage fluctuation accompanying the input voltage fluctuation.

[0005] Therefore, in the lighting device and the lighting system, it is desired to be able to appropriately detect the voltage across both ends of the light source unit even in a conversion circuit in which the reference potential of the light source unit is not directly connected to the common potential.

Prior Art Documents

Patent Documents

[0006] Patent Document 1 Japanese Patent Application Laid-Open No. 2011-100666 Summary of the Invention Problems to be Solved by the Invention

[0007] The problem to be solved by the present invention is to provide a lighting device and a lighting system capable of appropriately detecting the voltages at both ends of a light source unit. Means for Solving the Problems

[0008] According to an embodiment of the present invention, there is provided a lighting device for lighting a light source unit having a light source, the lighting device including a switching element, setting a reference potential of the light source unit to a common potential via the switching element, converting an input first DC power into a second DC power corresponding to the light source unit by switching of the switching element, and supplying the second DC power to the light source unit to light the light source unit; a conversion circuit; a control circuit for controlling the operation of the conversion circuit; the conversion circuit having an input voltage detection unit for detecting a voltage of the first DC power and an output voltage detection unit for detecting a voltage of a difference between the voltage of the first DC power and the voltage of the second DC power; the control circuit determining a magnitude of the voltage of the first DC power based on a detection result of the input voltage detection unit, determining a magnitude of the difference voltage based on a detection result of the output voltage detection unit, and calculating a voltage of the second DC power by subtracting the magnitude of the difference voltage from the determined magnitude of the voltage of the first DC power; and a control unit for detecting an abnormality of the light source unit based on a calculation result of the voltage of the second DC power. Effects of the Invention

[0009] According to an embodiment of the present invention, it is possible to provide a lighting device and a lighting system capable of appropriately detecting the voltages at both ends of a light source unit. Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0011] Hereinafter, each embodiment will be described with reference to the drawings. Note that the drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the ratio of the sizes between parts, etc. are not necessarily the same as those in reality. Also, even when representing the same part, the dimensions and ratios may be represented differently in the drawings. In the present specification and each drawing, the same reference numerals are given to the same elements as those described above with respect to the previously shown drawings, and detailed descriptions are appropriately omitted.

[0012] FIG. 1 is a block diagram schematically showing the lighting device according to the embodiment. As shown in FIG. 1, the lighting device 2 includes a light source unit 4 and a lighting device 10.

[0013] The light source unit 4 has a light source 4a. The light source 4a is, for example, a light emitting diode (LED). The light source 4a may be, for example, an organic light emitting diode (OLED), an inorganic electroluminescence light emitting element, an organic electroluminescence light emitting element, or other field emission type light emitting elements. The light source 4a may be, for example, an incandescent lamp. The light source 4a may be any light source that lights up in response to the supply of DC power.

[0014] The light source unit 4 has, for example, a plurality of light sources 4a connected in series. The light source unit 4 may have, for example, a plurality of light sources 4a connected in series and in parallel. However, the number of light sources 4a provided in the light source unit 4 may be one. The number of light sources 4a provided in the light source unit 4 may be any number. The plurality of light sources 4a may be composed of light sources that emit light of the same color, or may be composed of light sources that emit light of different colors.

[0015] The light source unit 4 has a first connection point 4p on the high potential side and a second connection point 4n on the low potential side. The first connection point 4p and the second connection point 4n are constituted by, for example, contacts, connection terminals, connection wirings, etc. The light source 4a is provided between the first connection point 4p and the second connection point 4n. For example, the plurality of light sources 4a are connected in series between the first connection point 4p and the second connection point 4n. The light source unit 4 is connected to the lighting device 10 via the first connection point 4p and the second connection point 4n. Note that the first connection point 4p and the second connection point 4n are the points where the lighting device 10 and the light source unit 4 are electrically connected, respectively. Also, the first connection point 4p and the second connection point 4n may be provided in the lighting device 10.

[0016] The lighting device 10 has a first conversion circuit 21, a second conversion circuit 22 (conversion circuit), and a control circuit 23.

[0017] The first conversion circuit 21 is connected to the power supply PS. The first conversion circuit 21 (lighting device 10) is detachably connected to the power supply PS via, for example, a connector (not shown). The power supplied by the power supply PS is, for example, AC power. The first conversion circuit 21 converts the AC power supplied from the power supply PS into first DC power. The first conversion circuit 21 is an AC-DC conversion circuit. The power supply PS is, for example, a commercial power supply. The power supply PS may be, for example, a home generator or the like.

[0018] The second conversion circuit 22 converts the first DC power input from the first conversion circuit 21 into second DC power corresponding to the light source unit 4. The second conversion circuit 22 is a DC-DC conversion circuit. The second conversion circuit 22 lights the light source 4a of the light source unit 4 by supplying the converted second DC power to the light source unit 4. The light source 4a irradiates light in response to the supply of the second DC power from the second conversion circuit 22.

[0019] The control circuit 23 controls the operations of the first conversion circuit 21 and the second conversion circuit 22. For example, upon receiving a command from the outside, the control circuit 23 controls the conversion of AC power into first DC power by the first conversion circuit 21 and the conversion of the first DC power into second DC power by the second conversion circuit 22.

[0020] Note that the power supplied from the power source PS may be DC power. In this case, for example, the power source PS can use a battery or the like, and accordingly, the first conversion circuit 21 can be omitted. The second conversion circuit 22 may convert, for example, the first DC power input from the power source PS into second DC power corresponding to the light source unit 4. The configuration for inputting the first DC power to the second conversion circuit 22 is not limited to the above, and any configuration capable of appropriately inputting the first DC power to the second conversion circuit 22 may be used.

[0021] FIG. 2 is a block diagram schematically showing the second conversion circuit and the control circuit according to the embodiment. As shown in FIG. 2, the second conversion circuit 22 has a first input terminal 22a, a second input terminal 22b, a first output terminal 22c, and a second output terminal 22d. The first input terminal 22a is electrically connected to the high-potential-side output terminal of the first conversion circuit 21. The second input terminal 22b is electrically connected to the low-potential-side output terminal of the first conversion circuit 21. Thereby, the first DC power is input from the first conversion circuit 21 to the second conversion circuit 22.

[0022] The first input terminal 22a is the input terminal on the high potential side among a pair of input terminals that receive the input of the first DC power. The second input terminal 22b is the input terminal on the low potential side among a pair of input terminals that receive the input of the first DC power. Also, the potential of the second input terminal 22b is set to a common potential (ground potential). The common potential may be any potential that serves as a reference for the circuit operation of the second conversion circuit 22 (lighting device 10).

[0023] The first output terminal 22c is the output terminal on the high potential side, and the second output terminal 22d is the output terminal on the low potential side. The potential of the first output terminal 22c is higher than the potential of the second output terminal 22d. The first output terminal 22c is electrically connected to, for example, the first input terminal 22a.

[0024] The second conversion circuit 22 is electrically connected to the light source unit 4 via the first output terminal 22c and the second output terminal 22d. The first output terminal 22c is electrically connected to the first connection point 4p of the light source unit 4. The second output terminal 22d is electrically connected to the second connection point 4n of the light source unit 4. The first output terminal 22c and the second output terminal 22d are a pair of output terminals that are connected to the light source unit 4 and output the second DC power to the light source unit 4.

[0025] For example, when the light source 4a is a light-emitting diode, the first output terminal 22c is connected to the anode of the light source 4a, and the second output terminal 22d is connected to the cathode of the light source 4a. When the light source unit 4 has a plurality of light sources 4a (light-emitting diodes) connected in series or (and) in parallel, the first output terminal 22c is connected to the anode of at least one light source 4a located on one end side of the plurality of light sources 4a connected in series or (and) in parallel, and the second output terminal 22d is connected to the cathode of at least one light source 4a located on the other end side of the plurality of light sources 4a connected in series. Thereby, the light source 4a of the light source unit 4 is lit by the second DC power output from the first output terminal 22c and the second output terminal 22d.

[0026] The second conversion circuit 22 includes a switching element 30, an inductor 32, a diode 34, and an output capacitor 36.

[0027] The switching element 30 has a first main terminal 30a, a second main terminal 30b, and a control terminal 30c. The switching element 30 has an on state and an off state. The on state is a state in which current flows between the pair of main terminals 30a and 30b. The off state is a state in which the current flowing between the pair of main terminals 30a and 30b is interrupted. The switching element 30 switches between the on state and the off state according to the magnitudes of the voltages applied between the pair of main terminals 30a and 30b and to the control terminal 30c.

[0028] Note that the off state may be a state in which a weak current that does not affect the operation of the second conversion circuit 22 flows between the pair of main terminals 30a and 30b. In other words, the on state of the switching element 30 is a first state in which current flows between the pair of main terminals 30a and 30b, and the off state is a second state in which the magnitude of the current flowing between the pair of main terminals 30a and 30b is smaller than that in the first state. The switching element 30 is, for example, a FET. The switching element 30 may be a bipolar transistor or the like. The switching element 30 may be any element capable of switching between the on state and the off state.

[0029] The first main terminal 30a is electrically connected to one end of the inductor 32. The other end of the inductor 32 is electrically connected to the second output terminal 22d. The second main terminal 30b is electrically connected to the second input terminal 22b. Therefore, the potential of the second main terminal 30b is set to the common potential. Thus, the switching element 30 is provided between the second output terminal 22d and the second input terminal 22b. In this example, the switching element 30 is provided between the second output terminal 22d and the second input terminal 22b via the inductor 32. In other words, in this example, a series connection body of the switching element 30 and the inductor 32 is provided between the second output terminal 22d and the second input terminal 22b.

[0030] The anode of diode 34 is electrically connected to the connection point between the first main terminal 30a and one end of the inductor 32. The cathode of diode 34 is electrically connected to the wiring path between the first input terminal 22a and the first output terminal 22c. In other words, the cathode of diode 34 is electrically connected to the first input terminal 22a and the first output terminal 22c. Diode 34 is, for example, a freewheeling diode.

[0031] One end of the output capacitor 36 is electrically connected between the connection point with the cathode of diode 34 and the first output terminal 22c in the wiring path between the first input terminal 22a and the first output terminal 22c.

[0032] The other end of the output capacitor 36 is electrically connected to the connection point between the other end of the inductor 32 and the second output terminal 22d. In other words, the output capacitor 36 is electrically connected between the first output terminal 22c and the second output terminal 22d at a position closer to the first output terminal 22c and the second output terminal 22d than the inductor 32 and the diode 34.

[0033] In the second conversion circuit 22, when the switching element 30 is turned on, a direct current is supplied to the light source unit 4, which is a load, by the direct current power input through the first input terminal 22a and the second input terminal 22b, and at the same time, the output capacitor 36 is charged and energy is stored in the inductor 32.

[0034] Then, when the switching element 30 is turned off, the energy stored in the inductor 32 is supplied to the light source unit 4 through the diode 34.

[0035] Thus, the second conversion circuit 22 converts the input first DC power into second DC power corresponding to the light source unit 4 by switching the switching element 30. The second conversion circuit 22 is a buck chopper circuit. The second conversion circuit 22 converts the input first DC power into second DC power corresponding to the light source unit 4 by stepping down the voltage of the first DC power by switching the switching element 30. The second conversion circuit 22 is, for example, a constant current circuit. The second conversion circuit 22 supplies, for example, a substantially constant DC current to the light source unit 4.

[0036] In the second conversion circuit 22, the second connection point 4n on the low potential side of the light source unit 4 is not directly connected to the common potential portion of the second conversion circuit 22. In the second conversion circuit 22, the second connection point 4n on the low potential side of the light source unit 4 is not directly connected to, for example, the second input terminal 22b. In other words, in the second conversion circuit 22, the reference potential of the light source unit 4 is not directly connected to the common potential of the second conversion circuit 22. In the second conversion circuit 22, the reference potential of the light source unit 4 is set to the common potential of the second conversion circuit 22 via the switching element 30. The second connection point 4n is electrically connected to the common potential portion (second input terminal 22b) via the switching element 30. The second conversion circuit 22 is, for example, a low-side switch type buck chopper circuit in which the light source unit 4 as a load is located on the high side with respect to the switching element 30.

[0037] Note that the configuration of the second conversion circuit 22 is not limited to the above, and may have any configuration that has a switching element 30 provided between the second output terminal 22d and the second input terminal 22b, sets the reference potential of the light source unit 4 to the common potential of the second conversion circuit 22 via the switching element 30, and can convert the first DC power into the second DC power by switching the switching element 30.

[0038] The second conversion circuit 22 further includes an input voltage detection unit 40 and an output voltage detection unit 50. The input voltage detection unit 40 is a circuit for detecting the voltage of the first DC power input from the first input terminal 22a and the second input terminal 22b. In other words, the input voltage detection unit 40 detects the voltage between the first input terminal 22a and the second input terminal 22b. The input voltage detection unit 40 is provided between the first input terminal 22a and the second input terminal 22b. Thereby, the reference potential of the input voltage detection unit 40 is set to the common potential.

[0039] The input voltage detection unit 40 has, for example, two resistor elements 41 and 42 connected in series between the first input terminal 22a and the second input terminal 22b. The input voltage detection unit 40 can detect a voltage having a magnitude corresponding to the voltage of the first DC power according to the voltage division ratio of the two resistor elements 41 and 42.

[0040] The input voltage detection unit 40 inputs the detection result of the voltage of the first DC power (the detection result of the voltage having a magnitude corresponding to the voltage of the first DC power) to the control circuit 23. For example, the connection point between the resistor element 41 and the resistor element 42 is connected to the control circuit 23. Thereby, a voltage corresponding to the voltage of the first DC power and the voltage division ratio of the resistor elements 41 and 42 is input to the control circuit 23 as the detection result of the voltage of the first DC power.

[0041] Note that the configuration of the input voltage detection unit 40 is not limited to the above, and any configuration may be used as long as the reference potential is set to the common potential and the magnitude of the voltage of the first DC power can be appropriately detected. The input voltage detection unit 40 may be, for example, a circuit that detects the difference between the potential of the first input terminal 22a and the potential of the second input terminal 22b. However, as described above, by detecting the voltage of the first DC power according to the voltage division ratio of the two resistor elements 41 and 42, an increase in the number of components and the need for expensive components can be suppressed, and the voltage of the first DC power can be appropriately detected with a simpler configuration.

[0042] The output voltage detection unit 50 is provided between the second output terminal 22d and the second input terminal 22b. In other words, the output voltage detection unit 50 is provided between the second output terminal 22d and the second main terminal 30b of the switching element 30. Thereby, the reference potential of the output voltage detection unit 50 is set to the common potential.

[0043] The output voltage detection unit 50 is a circuit for detecting the voltage difference between the voltage of the first DC power input from the first input terminal 22a and the second input terminal 22b and the voltage of the second DC power output from the first output terminal 22c and the second output terminal 22d to the light source unit 4. In other words, the output voltage detection unit 50 detects the voltage difference between the voltage of the first DC power and the voltage between the first connection point 4p and the second connection point 4n of the light source unit 4.

[0044] The output voltage detection unit 50 has, for example, two resistor elements 51 and 52 connected in series between the second output terminal 22d and the second input terminal 22b. The output voltage detection unit 50 enables the detection of a voltage having a magnitude corresponding to the voltage difference between the voltage of the first DC power and the voltage of the second DC power according to the voltage division ratio of the two resistor elements 51 and 52.

[0045] The output voltage detection unit 50 inputs the detection result of the voltage difference between the voltage of the first DC power and the voltage of the second DC power (the detection result of a voltage having a magnitude corresponding to the voltage difference between the voltage of the first DC power and the voltage of the second DC power) to the control circuit 23. For example, the connection point between the resistor element 51 and the resistor element 52 is connected to the control circuit 23. Thereby, the voltage difference between the voltage of the first DC power and the voltage of the second DC power and the voltage corresponding to the voltage division ratio of the resistor elements 51 and 52 are input to the control circuit 23 as the detection result of the voltage difference between the voltage of the first DC power and the voltage of the second DC power.

[0046] Note that the configuration of the output voltage detection unit 50 is not limited to the above. The reference potential may be set to a common potential, and any configuration capable of appropriately detecting the magnitude of the voltage difference between the voltage of the first DC power and the voltage of the second DC power may be used. The output voltage detection unit 50 may be, for example, a circuit that detects the difference between the potential of the second output terminal 22d and the potential of the second input terminal 22b. However, as described above, by detecting the voltage difference between the voltage of the first DC power and the voltage of the second DC power based on the voltage division ratio of the two resistor elements 51 and 52, an increase in the number of components or the need for expensive components can be suppressed, and the voltage difference between the voltage of the first DC power and the voltage of the second DC power can be appropriately detected with a simpler configuration.

[0047] The control circuit 23 is electrically connected to the control terminal 30c of the switching element 30. The control circuit 23 controls the switching of the switching element 30. That is, the control circuit 23 switches between the on state and the off state of the switching element 30. The control circuit 23 switches between the on state and the off state of the switching element 30 according to the voltage (drive signal) input to the control terminal 30c. For example, the control circuit 23 generates a DC voltage across a pair of terminals of the output capacitor 36 by switching the switching element 30. In this way, the control circuit 23 is connected to the control terminal 30c of the switching element 30 and controls the switching of the switching element 30 to control the conversion of the first DC power to the second DC power by the second conversion circuit 22. As a result, the second DC power is supplied from the second conversion circuit 22 to the light source unit 4.

[0048] The control circuit 23 stops the supply of the second DC power from the second conversion circuit 22 to the light source unit 4 by, for example, turning off the switching element 30. Further, the control circuit 23 can change the voltage value and current value of the second DC power supplied to the light source unit 4 by, for example, changing the period (duty ratio) of the on-state and off-state of the switching element 30. Thereby, for example, the brightness of the light emitted from the light source unit 4 can be changed. The control circuit 23 changes the period of the on-state and off-state of the switching element 30 according to a dimming signal (control signal) input from the outside, and causes the light source unit 4 to emit light with a brightness corresponding to the dimming level of the dimming signal.

[0049] The control circuit 23 includes an arithmetic circuit 60 and a control unit 62. The arithmetic circuit 60 calculates the voltage of the second DC power based on the detection result of the input voltage detection unit 40 and the detection result of the output voltage detection unit 50. In other words, the arithmetic circuit 60 calculates the voltage (load voltage) between the first connection point 4p and the second connection point 4n of the light source unit 4 based on the detection result of the input voltage detection unit 40 and the detection result of the output voltage detection unit 50.

[0050] In the circuit configuration shown in FIG. 2, when the voltage of the first DC power is the input voltage V1, the voltage of the second DC power is the load voltage V2, and the voltage applied to the resistance elements 51 and 52 is V3, the relationship V1 = V2 + V3 holds for the input voltage V1.

[0051] The arithmetic circuit 60 determines the magnitude of the voltage of the first DC power based on the detection result of the input voltage detection unit 40. The arithmetic circuit 60 determines the magnitude of the voltage of the first DC power by, for example, performing a proportional operation on the voltage input from the input voltage detection unit 40. Similarly, the arithmetic circuit 60 determines the magnitude of the voltage difference between the voltage of the first DC power and the voltage of the second DC power based on the detection result of the output voltage detection unit 50. The arithmetic circuit 60 calculates the voltage of the second DC power by subtracting the magnitude of the voltage difference from the determined magnitude of the voltage of the first DC power. In other words, the arithmetic circuit 60 calculates the voltage of the second DC power (load voltage V2) using the formula V2 = V1 - V3.

[0052] The arithmetic circuit 60 inputs the arithmetic result of the voltage of the second DC power to the control unit 62. For the arithmetic circuit 60, for example, a microcontroller (MCU) is used. The reference potential of the arithmetic circuit 60 is set to be substantially the same potential as the common potential of the second conversion circuit 22. However, the arithmetic circuit 60 is not limited to a microcontroller, and any circuit (any element) whose reference potential is set to be substantially the same potential as the common potential of the second conversion circuit 22 and which can calculate the voltage of the second DC power based on the detection result of the input voltage detection unit 40 and the detection result of the output voltage detection unit 50 may be used.

[0053] The control unit 62 is electrically connected to the control terminal 30c of the switching element 30. As described above, the control unit 62 controls the switching of the switching element 30 to control the conversion of the first DC power to the second DC power by the second conversion circuit 22. The control unit 62 is, for example, a control IC. For example, the reference potential of the control unit 62 is also set to be substantially the same potential as the common potential of the second conversion circuit 22, similar to the arithmetic circuit 60. In other words, the reference potential of the control circuit 23 is set to be substantially the same potential as the common potential of the second conversion circuit 22.

[0054] Further, the control unit 62 detects an abnormality of the light source unit 4 based on the arithmetic result of the voltage of the second DC power input from the arithmetic circuit 60. The control unit 62 determines that the light source unit 4 is normal when the voltage of the second DC power input from the arithmetic circuit 60 (the voltage between the first connection point 4p and the second connection point 4n of the light source unit 4) is within a predetermined range.

[0055] The control unit 62 determines that the light source unit 4 is abnormal when the voltage of the second DC power input from the arithmetic circuit 60 is less than the lower limit value. When the voltage of the second DC power is less than the lower limit value, for example, a short-circuit fault or an open-circuit fault occurs in the light source 4a of the light source unit 4, and it is considered that the voltage between both ends of the light source unit 4 has decreased. Therefore, when the control unit 62 determines an abnormality of the light source unit 4, it stops the operation of converting the first DC power to the second DC power by the second conversion circuit 22 and stops the supply of the second DC power to the light source unit 4.

[0056] The rated value (target value) of the voltage of the second DC power is, for example, 20V. The lower limit value of the voltage of the second DC power is, for example, 15V. Thus, when the voltage of the second DC power drops by about 25% with respect to the rated value, for example, the control unit 62 determines that the light source unit 4 is abnormal and stops the operation of the second conversion circuit 22.

[0057] When the voltage of the second DC power becomes equal to or higher than the upper limit value, for example, the control unit 62 may determine that the light source unit 4 is abnormal and stop the operation of the second conversion circuit 22 and the supply of the second DC power to the light source unit 4. In other words, when detecting an overvoltage of the voltage applied across the light source unit 4, the control unit 62 may determine that the light source unit 4 is abnormal and stop the operation of the second conversion circuit 22 and the supply of the second DC power to the light source unit 4.

[0058] For example, there is a configuration in which a resistor element is connected in parallel to the light source unit 4 to detect the voltage of the second DC power. However, in such a configuration, since the reference potential of the light source unit 4 is not directly connected to the common potential of the second conversion circuit 22, it is difficult to appropriately detect the voltage of the second DC power. For example, when the input voltage (the voltage of the first DC power) fluctuates, the voltage of the second DC power also fluctuates, and it becomes impossible to distinguish whether the voltage fluctuation is due to an abnormality of the light source unit 4 or due to the voltage fluctuation accompanying the fluctuation of the input voltage.

[0059] Therefore, with the method of detecting the voltage of the second DC power using the resistor element connected in parallel to the light source unit 4, the detection accuracy of the voltage of the second DC power decreases. Also, the reference potential of the control unit 62 is set substantially equal to the common potential of the second conversion circuit 22. Therefore, when the control unit 62 determines the abnormality of the light source unit 4 based on the voltage of the second DC power detected by the resistor element connected in parallel to the light source unit 4, for example, when the input voltage fluctuates, the light source unit 4 may be determined to be abnormal and the light source unit 4 may be turned off unintentionally. In other words, there is a possibility that the false detection of the abnormality of the light source unit 4 increases in the control unit 62.

[0060] On the other hand, in the lighting device 10 according to the present embodiment, the second conversion circuit 22 includes an input voltage detection unit 40 and an output voltage detection unit 50, and the arithmetic circuit 60 determines the magnitude of the voltage of the first DC power based on the detection result of the input voltage detection unit 40, and determines the magnitude of the voltage of the difference between the voltage of the first DC power and the voltage of the second DC power based on the detection result of the output voltage detection unit 50, and calculates the voltage of the second DC power by subtracting the magnitude of the voltage of the difference from the magnitude of the determined voltage of the first DC power.

[0061] The reference potentials of the input voltage detection unit 40, the output voltage detection unit 50, and the arithmetic circuit 60 are all set to a common potential. Therefore, in the lighting device 10 according to the present embodiment, even when there is a fluctuation in the input voltage, the influence of the fluctuation in the input voltage is suppressed, and the voltage of the second DC power (the voltage between the first connection point 4p and the second connection point 4n of the light source unit 4) can be detected more appropriately.

[0062] Thus, in the lighting device 10 according to the present embodiment, the voltage of the second DC power can be detected more appropriately. In the lighting device 10 according to the present embodiment, the detection accuracy of the voltage of the second DC power can be improved. Further, thereby, in the lighting device 10 according to the present embodiment, false detection of an abnormality of the light source unit 4 can be suppressed, and the light source unit 4 can be prevented from being turned off unintentionally.

[0063] For example, it is also conceivable to detect the voltage of the second DC power by a circuit that detects the difference between the potential of the first output terminal 22c and the potential of the second output terminal 22d. However, in this case, there are concerns about an increase in the number of components and an increase in component costs. In the lighting device 10 according to the present embodiment, the voltage of the second DC power can be accurately detected with a simpler configuration compared to the case of using a circuit that detects a difference. In the lighting device 10 according to the present embodiment, for example, while suppressing an increase in the number of components and costs, high-precision of the voltage of the second DC power can be realized.

[0064] In the lighting device 10 according to the present embodiment, the input voltage detection unit 40 has two resistor elements 41 and 42 connected in series between the first input terminal 22a and the second input terminal 22b, and detects the voltage of the first DC power according to the voltage division ratio of the two resistor elements 41 and 42. Thereby, as described above, an increase in the number of components and the need for expensive components can be suppressed, and the voltage of the first DC power can be appropriately detected with a simpler configuration.

[0065] In the lighting device 10 according to the present embodiment, the output voltage detection unit 50 has two resistor elements 51 and 52 connected in series between the second output terminal 22d and the second input terminal 22b, and detects the voltage of the difference between the voltage of the first DC power and the voltage of the second DC power according to the voltage division ratio of the two resistor elements 51 and 52. Thereby, as described above, an increase in the number of components and the need for expensive components can be suppressed, and the voltage of the difference between the voltage of the first DC power and the voltage of the second DC power can be appropriately detected with a simpler configuration.

[0066] In the lighting device 10 according to the present embodiment, when the voltage of the second DC power input from the arithmetic circuit 60 becomes less than the lower limit value, the control unit 62 stops the operation of converting the first DC power to the second DC power by the second conversion circuit 22 and stops the supply of the second DC power to the light source unit 4. Thereby, for example, it is possible to suppress the continuous use of the light source unit 4 in a faulty state, and to further improve the safety of the lighting device 2 and the lighting device 10.

[0067] Also, in the lighting device 10 according to the present embodiment, as described above, the detection accuracy of the voltage of the second DC power can be improved. For example, when a plurality of light sources 4a are directly connected, a short circuit failure of one of the plurality of light sources 4a connected in series can also be detected.

[0068] For example, when a light-emitting diode with a forward voltage of 2V is used as the light source 4a and ten of these light sources 4a are connected in series, the rated value of the voltage of the second DC power is approximately 20V. When the voltage of the second DC power input from the arithmetic circuit 60 drops from 20V to 18V, for example, the control unit 62 detects a short-circuit failure of one light source 4a.

[0069] When the control unit 62 detects a short-circuit failure of one light source 4a, for example, it increases the current supplied to the light source unit 4 so as to compensate for the luminance of the failed light source 4a, and increases the luminance of the light emitted from the remaining light sources 4a.

[0070] Thus, in the lighting device 10 according to this embodiment, for example, it is also possible to detect a short-circuit failure of a predetermined number of the light sources 4a among the plurality of light sources 4a connected in series, and perform luminance adjustment according to the number of failed light sources 4a when a predetermined number of light sources 4a fail. The control unit 62 detects a short-circuit failure of a predetermined number of the light sources 4a among the plurality of light sources 4a connected in series based on the calculation result of the voltage of the second DC power. When a predetermined number of light sources 4a fail, it increases the current supplied to the light source unit 4 so as to compensate for the luminance of the failed light sources 4a, and increases the luminance of the light emitted from the remaining light sources 4a, thereby performing luminance adjustment according to the number of failed light sources 4a. The control unit 62 increases the current supplied to the light source unit 4 according to the number of failed light sources 4a, for example, by controlling the switching of the switching element 30. The control unit 62 increases the current supplied to the light source unit 4 according to the number of failed light sources 4a, for example, by increasing the duty ratio. Thereby, even when a predetermined number of light sources 4a fail, a decrease in the luminance of the light emitted from the light source unit 4 can be suppressed. In this case, when the number of failed light sources 4a becomes equal to or more than a preset number, for example, the control unit 62 may stop the operation of the second conversion circuit 22.

[0071] FIG. 3 is a block diagram schematically showing the lighting system according to the embodiment. Note that components that are substantially the same as those in the above embodiment in terms of function and configuration are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in FIG. 3, the lighting system 100 includes a plurality of lighting devices 2. In this example, the lighting system 100 includes two lighting devices 2. However, the number of lighting devices 2 provided in the lighting system 100 is not limited to two and may be any number.

[0072] In the lighting system 100, control circuits 23 provided in each of the plurality of lighting devices 10 communicate with each other. For example, control units 62 of the control circuits 23 provided in each of the plurality of lighting devices 10 communicate with each other. The communication between the control circuits 23 may be wired communication or wireless communication. The form of communication between the control circuits 23 may be any form that enables appropriate communication between the control circuits 23.

[0073] When the control unit 62 communicates with the control units 62 of other lighting devices 10 and detects an abnormality in the light source unit 4 based on the calculation result of the voltage of the second DC power input from the arithmetic circuit 60, the control unit 62 transmits the detection of the abnormality in the light source unit 4 to the control units 62 of other lighting devices 10. For example, when the control unit 62 detects an abnormality in the light source unit 4, the control unit 62 stops the operation of the second conversion circuit 22, turns off the light source unit 4, and transmits the detection of the abnormality in the light source unit 4 to the control units 62 of other lighting devices 10.

[0074] The abnormality of the light source unit 4 transmitted to the control units 62 of other lighting devices 10 may be an abnormality in which the voltage of the second DC power is less than the lower limit value, or an abnormality of a short circuit failure of a predetermined number of light sources 4a among the plurality of light sources 4a connected in series.

[0075] When the control unit 62 receives the detection of the abnormality of the light source unit 4 from the control units 62 of other lighting devices 10, the control unit 62 performs an operation corresponding to the abnormality of the light source unit 4 of the other lighting devices 10. For example, the control unit 62 stops the operation of the second conversion circuit 22 as an operation corresponding to the abnormality of the light source unit 4 of the other lighting devices 10. Thereby, all the lighting devices 2 can be turned off in response to a failure in any one of the plurality of lighting devices 2, and the operations of the plurality of lighting devices 2 can be interlocked.

[0076] For example, when an abnormality occurs in the light source unit 4 of the lighting device 2, the control unit 62 may increase the current supplied to the light source unit 4 so as to compensate for the luminance of the lighting device 2, and perform an operation of increasing the luminance of the light emitted from the light source unit 4 as an operation corresponding to the abnormality of the light source unit 4 of another lighting device 10.

[0077] For example, assume that the lighting system 100 includes ten lighting devices 2, and an abnormality occurs in the light source unit 4 of one of the lighting devices 2. In this case, in the remaining nine lighting devices 2, the current supplied to the light source unit 4 is increased so as to compensate for the luminance of the lighting device 2 in which the abnormality has occurred. Thereby, even if an abnormality occurs in the light source unit 4 of any of the plurality of lighting devices 2, a decrease in the luminance of the light emitted from each lighting device 2 can be suppressed. In this case, the control unit 62 may stop the operation of the second conversion circuit 22, for example, when the number of lighting devices 2 in which an abnormality has occurred in the light source unit 4 becomes equal to or greater than a preset number. Note that the operation corresponding to the abnormality of the light source unit 4 of another lighting device 10 is not limited to the above, and may be any operation corresponding to the abnormality of the light source unit 4 of another lighting device 10.

[0078] As described above, in the lighting system 100, the control unit 62 of each lighting device 10 has a communication function with the control unit 62 of another lighting device 10, and an output function for detecting an abnormality of the light source unit 4 with respect to the control unit 62 of another lighting device 10. Further, the control unit 62 of each lighting device 10 has a function of performing an operation corresponding to an abnormality of the light source unit 4 of another lighting device 10. Thereby, in the lighting system 100, for example, it is possible to interlock the operations of the plurality of lighting devices 2 or perform luminance adjustment according to an abnormality of the light source unit 4 of any of the plurality of lighting devices 2, and the convenience of the lighting system 100 can be further enhanced.

[0079] This embodiment includes the following aspects. (Appendix 1) A lighting device for lighting a light source unit having a light source, A conversion circuit having a switching element, setting a reference potential of the light source unit to a common potential via the switching element, converting the input first DC power into second DC power corresponding to the light source unit by switching of the switching element, and supplying the second DC power to the light source unit to turn on the light source unit; A control circuit for controlling the operation of the conversion circuit; Comprising: The conversion circuit includes: An input voltage detection unit for detecting a voltage of the first DC power; An output voltage detection unit for detecting a voltage of a difference between the voltage of the first DC power and the voltage of the second DC power; Having: The control circuit includes: Based on the detection result of the input voltage detection unit, determining the magnitude of the voltage of the first DC power, based on the detection result of the output voltage detection unit, determining the magnitude of the voltage of the difference, and subtracting the magnitude of the voltage of the difference from the determined magnitude of the voltage of the first DC power to calculate the voltage of the second DC power; an arithmetic circuit; A control unit for detecting an abnormality of the light source unit based on the calculation result of the voltage of the second DC power; A lighting device having:

[0080] (Appendix 2) The conversion circuit has a first input terminal and a second input terminal for receiving the input of the first DC power, The input voltage detection unit has two resistor elements connected in series between the first input terminal and the second input terminal, and is capable of detecting a voltage having a magnitude corresponding to the voltage of the first DC power according to the voltage division ratio of the two resistor elements. The lighting device according to Appendix 1.

[0081] (Appendix 3) The conversion circuit includes: A first input terminal and a second input terminal for receiving the input of the first DC power, A first output terminal and a second output terminal connected to the light source unit, Having: The second input terminal is an input terminal on the low potential side, The second output terminal is an output terminal on the low potential side, The output voltage detection unit has two resistor elements connected in series between the second output terminal and the second input terminal, and enables detection of a voltage having a magnitude corresponding to the voltage difference between the voltage of the first DC power and the voltage of the second DC power according to the voltage division ratio of the two resistor elements. The lighting device according to Addendum 1 or 2.

[0082] (Addendum 4) When the voltage of the second DC power input from the arithmetic circuit becomes less than the lower limit value, the control unit stops the operation of the conversion circuit and stops the supply of the second DC power to the light source unit. The lighting device according to any one of Addenda 1 to 3.

[0083] (Addendum 5) The light source unit has a plurality of the light sources connected in series, Based on the calculation result of the voltage of the second DC power, the control unit detects a short circuit failure of a predetermined number of the plurality of light sources connected in series, and when a failure occurs in the predetermined number of light sources, the brightness of the failed light source is compensated. The lighting device according to any one of Addenda 1 to 3, wherein the current supplied to the light source unit is increased and the brightness of the light emitted from the remaining light sources is increased to perform brightness adjustment according to the number of failed light sources.

[0084] (Addendum 6) A plurality of lighting devices including a light source unit having a light source and a lighting device for lighting the light source unit, Each of the plurality of lighting devices, has a switching element, sets the reference potential of the light source unit to a common potential via the switching element, converts the input first DC power into a second DC power corresponding to the light source unit by switching of the switching element, and supplies the second DC power to the light source unit. A conversion circuit for lighting the light source unit; A control circuit for controlling the operation of the conversion circuit; and has The conversion circuit includes an input voltage detection unit for detecting the voltage of the first DC power; an output voltage detection unit for detecting the voltage difference between the voltage of the first DC power and the voltage of the second DC power; and the control circuit includes an arithmetic circuit that determines the magnitude of the voltage of the first DC power based on the detection result of the input voltage detection unit, determines the magnitude of the voltage difference based on the detection result of the output voltage detection unit, and calculates the voltage of the second DC power by subtracting the magnitude of the voltage difference from the determined magnitude of the voltage of the first DC power; a control unit that detects an abnormality of the light source unit based on the calculation result of the voltage of the second DC power; and the control unit transmits the detection of the abnormality of the light source unit to the control units of other lighting devices when detecting the abnormality of the light source unit, and performs an operation corresponding to the abnormality of the light source unit of the other lighting devices when receiving the detection of the abnormality of the light source unit from the control units of the other lighting devices. An illumination system.

[0085] Although several embodiments and examples of the present invention have been described, these embodiments or examples are presented as examples and are not intended to limit the scope of the invention. These novel embodiments or examples can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments or examples and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalent scope.

Description of Reference Numerals

[0086] 2… Lighting device, 4… Light source unit, 4a… Light source, 10… Lighting device, 21… First conversion circuit, 22… Second conversion circuit, 23… Control circuit, 30… Switching element, 32… Inductor, 34… Diode, 36… Output capacitor, 40… Input voltage detection unit, 41, 42… Resistance elements, 50… Output voltage detection unit, 51, 52… Resistance elements, 60… Arithmetic circuit, 62… Control unit, 100… Lighting system, PS… Power supply

Claims

1. A lighting device for lighting a light source unit having a light source, comprising a switching element, setting a reference potential of the light source unit to a common potential via the switching element, converting an input first DC power into a second DC power corresponding to the light source unit by switching of the switching element, and supplying the second DC power to the light source unit to light the light source unit; a conversion circuit; a control circuit for controlling the operation of the conversion circuit; and comprising: The conversion circuit has an input voltage detection unit for detecting a voltage of the first DC power; and an output voltage detection unit for detecting a voltage of a difference between the voltage of the first DC power and the voltage of the second DC power; and has: The control circuit discriminates the magnitude of the voltage of the first DC power based on a detection result of the input voltage detection unit, discriminates the magnitude of the voltage of the difference based on a detection result of the output voltage detection unit, and calculates the voltage of the second DC power by subtracting the magnitude of the voltage of the difference from the discriminated magnitude of the voltage of the first DC power; an arithmetic circuit; a control unit for detecting an abnormality of the light source unit based on a calculation result of the voltage of the second DC power; A lighting device having.

2. The conversion circuit has a first input terminal and a second input terminal for receiving an input of the first DC power, The input voltage detection unit has two resistor elements connected in series between the first input terminal and the second input terminal, and enables detection of a voltage having a magnitude corresponding to the voltage of the first DC power by a voltage division ratio of the two resistor elements. The lighting device according to claim 1.

3. The conversion circuit has a first input terminal and a second input terminal for receiving an input of the first DC power, and a first output terminal and a second output terminal connected to the light source unit, and has: The second input terminal is a low-potential side input terminal, The second output terminal is a low-potential side output terminal, The output voltage detection unit has two resistor elements connected in series between the second output terminal and the second input terminal, and enables detection of a voltage having a magnitude corresponding to the voltage of the difference between the voltage of the first DC power and the voltage of the second DC power by a voltage division ratio of the two resistor elements. The lighting device according to claim 1 or 2.

4. The lighting device according to claim 3, wherein when the voltage of the second DC power input from the arithmetic circuit becomes less than the lower limit value, the control unit stops the operation of the conversion circuit and stops the supply of the second DC power to the light source unit.

5. The light source unit has a plurality of the light sources connected in series. The control unit detects a short circuit failure of a predetermined number of the light sources among the plurality of the light sources connected in series based on the calculation result of the voltage of the second DC power, and when a failure occurs in the predetermined number of the light sources, increases the current supplied to the light source unit so as to compensate for the luminance of the failed light source, and increases the luminance of the light emitted from the remaining light sources, thereby performing luminance adjustment according to the number of failed light sources. The lighting device according to claim 3.

6. A plurality of lighting devices including a light source unit having a light source and a lighting device for lighting the light source unit. Each of the plurality of lighting devices has a switching element, sets the reference potential of the light source unit to a common potential via the switching element, converts the input first DC power into second DC power corresponding to the light source unit by switching of the switching element, and supplies the second DC power to the light source unit to light the light source unit, a conversion circuit; a control circuit for controlling the operation of the conversion circuit; and has The conversion circuit has an input voltage detection unit for detecting the voltage of the first DC power; and an output voltage detection unit for detecting the voltage of the difference between the voltage of the first DC power and the voltage of the second DC power; and has The control circuit discriminates the magnitude of the voltage of the first DC power based on the detection result of the input voltage detection unit, discriminates the magnitude of the voltage of the difference based on the detection result of the output voltage detection unit, and subtracts the magnitude of the voltage of the difference from the discriminated magnitude of the voltage of the first DC power to calculate the voltage of the second DC power, an arithmetic circuit; a control unit for detecting an abnormality of the light source unit based on the calculation result of the voltage of the second DC power; and has The control unit transmits the detection of the abnormality of the light source unit to the control units of other lighting devices when detecting the abnormality of the light source unit, and when receiving the detection of the abnormality of the light source unit from the control units of other lighting devices, performs an operation corresponding to the abnormality of the light source unit of the other lighting devices. An illumination system.

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