Lighting device, and illumination device

Abstract

To provide a lighting device capable of preventing a light source from turning off without emitting light at the specified dimming rate due to individual differences in lighting devices, and an illumination device.SOLUTION: A lighting device 10 includes a lighting circuit 1, a bypass circuit 2, and a control circuit 3. The lighting circuit 1 supplies lighting power to a light source 4. The bypass circuit 2 is connected in parallel with the light source 4. The control circuit 3 is configured to control the lighting circuit 1 so that the output current I3 of the lighting circuit 1, which is the sum of the first current I1 flowing through the light source 4 and the second current I2 flowing through the bypass circuit 2 is set to the target value. The second current I2 flowing through the bypass circuit 2 is a current less than the lower limit of the control range of the output current I3 of the lighting circuit 1 by the control circuit 3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure generally relates to lighting devices and illumination devices, and more particularly to a lighting device that lights up a light source and an illumination device including the lighting device. [Background technology]

[0002] Patent Document 1 describes an illumination device including a lighting device and a light source. The lighting device includes a lighting circuit, a control unit (control circuit), and a bypass resistor (bypass circuit). The bypass resistor is connected in parallel with the light source. The control unit controls the lighting circuit so that an output current of the lighting circuit, which is the sum of a current flowing through the light source and a current flowing through the bypass resistor, matches a target value. The bypass resistor is set so that a current equal to or greater than the lower limit of the range of output current controllable by the control unit flows through the bypass resistor. In this lighting device, a current equal to or greater than the lower limit of the range of output current controllable by the control unit flows through the bypass resistor, thereby expanding the lower limit control range of the current flowing through the light source. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-40750 Summary of the Invention [Problem to be solved by the invention]

[0004] In the lighting device described in Patent Document 1, when the output current of the lighting circuit is controlled to a current with a deeper dimming ratio, the current flowing through the light source may become zero due to variations caused by individual differences in the lighting device. In this case, the light source does not emit light at the specified dimming ratio and is turned off.

[0005] An object of the present disclosure is to provide a lighting device and an illumination device that can prevent a light source from being turned off without emitting light at a specified dimming rate due to variations due to individual differences in lighting devices. [Means for solving the problem]

[0006] A lighting device according to an aspect of the present disclosure includes a lighting circuit, a bypass circuit, and a control circuit. The lighting circuit supplies lighting power to a light source. The bypass circuit is connected in parallel with the light source. The control circuit controls the lighting circuit so that an output current of the lighting circuit, which is a sum of a first current flowing through the light source and a second current flowing through the bypass circuit, matches a target value. The second current flowing through the bypass circuit is a current less than a lower limit value of a control range of the output current of the lighting circuit by the control circuit.

[0007] An illumination device according to an embodiment of the present disclosure includes the lighting device and the light source, the light source including at least one LED. Effect of the Invention

[0008] The lighting device and illumination device according to one aspect of the present disclosure have the advantage that it is possible to prevent the light source from being turned off without emitting light at a specified dimming rate due to variations due to individual differences in the lighting device. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic circuit diagram of a lighting device and an illumination device according to the first embodiment. [Diagram 2] FIG. 2 is an explanatory diagram illustrating the relationship between the output current of the lighting circuit in Comparative Example 2 and the variation in the second current. [Diagram 3] FIG. 3 is an explanatory diagram illustrating the variation in the first current in the second comparative example. [Figure 4] FIG. 4 is an explanatory diagram illustrating the relationship between the output current of the lighting circuit and the variation in the second current in the first embodiment. [Diagram 5] FIG. 5 is an explanatory diagram illustrating the variation in the first current in the first embodiment. [Figure 6] FIG. 6 is a schematic circuit diagram of a lighting device and an illumination device according to the second embodiment. [Figure 7]FIG. 7 is an explanatory diagram illustrating the relationship between the two first currents flowing through the two light sources constituting the illumination light and the color temperature of the illumination light in Comparative Example 4. In FIG. [Figure 8] FIG. 8 is an explanatory diagram illustrating the relationship between two first currents flowing through two light sources that constitute illumination light and the color temperature of the illumination light in the second embodiment. [Figure 9] FIG. 9 is a schematic circuit diagram of a lighting device and an illumination device according to the third embodiment. [Figure 10] FIG. 10 is an explanatory diagram illustrating the relationship between the three first currents flowing through the three light sources constituting the illumination light and the color temperature of the illumination light in Comparative Example 5. [Figure 11] FIG. 11 is an explanatory diagram illustrating the relationship between the three first currents flowing through the three light sources constituting the illumination light and the color temperature of the illumination light in Comparative Example 6. [Figure 12] FIG. 12 is an explanatory diagram illustrating the relationship between three first currents flowing through three light sources that constitute illumination light and the color temperature of the illumination light in the third embodiment. [Figure 13] FIG. 13 is a schematic circuit diagram of a lighting device and an illumination device according to the fourth embodiment. [Figure 14] FIG. 14 is a schematic circuit diagram of a lighting device and an illumination device according to the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a lighting device and an illumination device according to an embodiment will be described with reference to the drawings. Each figure described in the following embodiment is a schematic diagram, and the size and thickness ratio of each component do not necessarily reflect the actual dimensional ratio. In addition, the configuration described in the following embodiment is merely one example of the present disclosure. The present disclosure is not limited to the following embodiment, and various modifications are possible depending on the design, etc., as long as the effects of the present disclosure can be achieved.

[0011] (Embodiment 1) (1) Overview An overview of a lighting device 10 and an illumination device 100 according to a first embodiment will be described with reference to FIG.

[0012] The lighting device 100 according to the first embodiment is, for example, architectural lighting (line lighting) that is embedded in at least a part of a ceiling, wall surface, and floor surface as part of a building, and produces a space with a gradation of light. The building is, for example, a residence such as a detached house or an apartment complex, or a non-residential facility such as an office, a store, a factory, a hospital, or a warehouse. As shown in FIG. 1, the lighting device 100 includes a lighting device 10 and a light source 4. The lighting device 10 is a device for supplying lighting power to the light source 4.

[0013] In the field of architectural lighting, a bypass circuit may be connected in parallel with a light source to achieve a deeper (i.e., smaller) dimming ratio (deep dimming). However, in this case, a current larger than a set value may flow through the bypass circuit due to individual differences in lighting device 10, and the light source may turn off without emitting light at the designated dimming ratio.

[0014] In order to solve the above-mentioned problems, a lighting device 10 according to the first embodiment includes a lighting circuit 1, a bypass circuit 2, and a control circuit 3, as shown in FIG. 1. The lighting circuit 1 supplies lighting power to a light source 4. The bypass circuit 2 is connected in parallel with the light source 4. The control circuit 3 controls the lighting circuit 1 so that an output current I3 of the lighting circuit 1 matches a target value. The output current I3 is the sum of a first current I1 flowing through the light source 4 and a second current I2 flowing through the bypass circuit 2. The second current I2 flowing through the bypass circuit 2 is a current less than a lower limit value in a control range of the output current I3 of the lighting circuit 1 by the control circuit 3.

[0015] According to this configuration, the second current I2 flowing through the bypass circuit 2 is a current less than the lower limit of the control range of the output current I3 of the lighting circuit 1 by the control circuit 3. Therefore, when the output current I3 of the lighting circuit 1 is controlled to a current with a deeper dimming ratio, there is an advantage in that it is possible to suppress the light source 4 from being turned off without emitting light at the specified dimming ratio due to the second current I2 becoming larger than the set value due to variations in the second current I2 caused by individual differences in the lighting device 10.

[0016] (2) Details The configurations of a lighting device 10 and an illumination device 100 according to the first embodiment will be described with reference to FIG.

[0017] The illumination device 100 according to the first embodiment includes a lighting device 10 and a light source 4, as shown in FIG.

[0018] (2.1) Light source As shown in FIG. 1, the light source 4 has a plurality of light-emitting elements 41 (four in FIG. 1). Each of the plurality of light-emitting elements 41 is, for example, an LED (Light-Emitting Diode). The plurality of light-emitting elements 41 are connected in series with each other. Therefore, a voltage obtained by multiplying the forward voltage of each light-emitting element 41 by the number of light-emitting elements 41 (hereinafter, referred to as "forward voltage of the light source 4") is applied between both ends of the light source 4. The anode of the light source 4 is connected to a first output terminal T1 of a lighting circuit 1 described later. In addition, the cathode of the light source 4 is connected to a second output terminal T2 of the lighting circuit 1 described later via a detection resistor R1 described later. That is, the light source 4 is connected to the rear stage of the lighting circuit 1 described later.

[0019] (2.2) Lighting device 1, the lighting device 10 includes a lighting circuit 1, a bypass circuit 2, and a control circuit 3. The lighting device 10 further includes a capacitor C1 and a detection resistor R1.

[0020] (2.2.1) Lighting circuit The lighting circuit 1 is a circuit that supplies lighting power to the light source 4. As shown in FIG. 1, the lighting circuit 1 has a switching element Q1, an inductor L1, and a diode D1. The lighting circuit 1 further has a first output terminal T1 and a second output terminal T2. The lighting circuit 1 is a so-called high-side type buck converter circuit. The lighting circuit 1 changes the duty ratio of the output voltage of the lighting circuit 1 by turning on and off the switching element Q1, thereby lighting the light source 4 at a dimming rate according to the duty ratio.

[0021] The switching element Q1 is, for example, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The switching element Q1 has a first terminal, a second terminal, and a control terminal. In the first embodiment, since the switching element Q1 is a MOSFET, the first terminal is a drain, the second terminal is a source, and the control terminal is a gate. The first terminal of the switching element Q1 is connected to the positive electrode of the DC power source 5. The second terminal of the switching element Q1 is connected to the cathode of the diode D1 and to a first end of the inductor L1. The control terminal of the switching element Q1 is connected to the control circuit 3.

[0022] As described above, the first end of the inductor L1 is connected to the second terminal of the switching element Q1 and to the cathode of the diode D1. The first end of the inductor L1 is connected to the positive electrode of the DC power source 5 via the switching element Q1. The second end of the inductor L1 is connected to the first output terminal T1. The first output terminal T1 is the high potential side output terminal of the lighting circuit 1.

[0023] As described above, the cathode of the diode D1 is connected to the second terminal of the switching element Q1 and to the first end of the inductor L1. The anode of the diode D1 is connected to the second output terminal T2. The anode of the diode D1 is also connected to the negative electrode of the DC power source 5 via the second output terminal T2. The second output terminal T2 is an output terminal on the low potential side of the lighting circuit 1.

[0024] The lighting circuit 1 outputs an output current I3 from the first output terminal T1. A lower limit is set for the output current I3 of the lighting circuit 1. The lighting circuit 1 is configured to output only an output current I3 equal to or greater than the lower limit. Therefore, when the lighting circuit 1 is controlled by the control circuit 3 to output an output current I3 less than the lower limit, the lighting circuit 1 outputs the output current I3 of the lower limit and does not output an output current I3 less than the output current I3. In other words, the lower limit of the output current I3 of the lighting circuit 1 is the lower limit of the control range when the control circuit 3 controls the output current I3 of the lighting circuit 1.

[0025] (2.2.2) Bypass circuit As shown in FIG. 1, the bypass circuit 2 includes a transistor Tr1, an operational amplifier OP1, a first resistor (resistor) R2, and a second resistor R3. The transistor Tr1 is, for example, an NPN transistor. In the transistor Tr1, a collector current obtained by amplifying a base current by passing the base current can be passed. That is, the transistor Tr1 is an amplifying element. The bypass circuit 2 is connected in parallel with the light source 4. That is, the bypass circuit 2 is connected in parallel with all of the plurality of light-emitting elements 41 connected in series, but is not connected in parallel with some of the plurality of light-emitting elements 41.

[0026] The collector terminal of the transistor Tr1 is connected to the first output terminal T1 on the high potential side of the lighting circuit 1. The emitter terminal of the transistor Tr1 is connected to the second output terminal T2 on the low potential side of the lighting circuit 1 via a first resistor R2. That is, the first resistor R2 is connected between the output terminals (the first output terminal T1 and the second output terminal T2) of the lighting circuit 1. More specifically, the first resistor R2 is connected between the output terminals of the lighting circuit 1 via the transistor Tr1. Also, the base terminal of the transistor Tr1 is connected to the output terminal of the operational amplifier OP1 via a second resistor R3.

[0027] A reference voltage Vref is applied (input) to a non-inverting input terminal of the operational amplifier OP1. An inverting input terminal of the operational amplifier OP1 is connected to a connection point P1 between the emitter terminal of the transistor Tr1 and the first resistor R2. That is, a voltage V3 across the first resistor R2 is input to the inverting input terminal of the operational amplifier OP1. As described above, an output terminal of the operational amplifier OP1 is connected to the base terminal of the transistor Tr1 via the second resistor R3. The operational amplifier OP1 compares the voltage V3 across the first resistor R2 with the reference voltage Vref, and performs feedback control so that the two match.

[0028] Here, as described above, the bypass circuit 2 is connected in parallel with the light source 4. Also, as described above, the light source 4 has a plurality of light-emitting elements (LEDs) 41 connected in series with each other. Therefore, in the lighting device 10 according to the first embodiment, the forward voltage of the light source 4 is applied to the bypass circuit 2.

[0029] The bypass circuit 2 is a circuit for constantly bypassing a part (second current I2) of the output current I3 of the lighting circuit 1, and limiting the first current I1 flowing to the light source 4 to a current obtained by subtracting a certain amount (second current I2) from the output current I3 of the lighting circuit 1. The bypass circuit 2 is configured so that a preset second current I2 always flows through the bypass circuit 2 when the lighting circuit 1 outputs the output current I3. Here, the second current I2 is a current less than a lower limit value in a control range of the output current I3 of the lighting circuit 1 by the control circuit 3. More specifically, if the maximum value of the range of variation in the second current I2 due to individual differences in the lighting device 10 is set to a maximum second current I2_max, the bypass circuit 2 is configured so that the maximum second current I2_max is a current less than the above-mentioned lower limit value.

[0030] The lighting device 10 according to the first embodiment is not configured to detect fluctuations in the forward voltage of the light source 4 by the control circuit 3, and is not configured to input the divided voltage of the bypass circuit 2 to the control circuit 3. In the lighting device 10 according to the first embodiment, the bypass circuit 2 is connected in parallel with the light source 4, and a dummy load that is cut off when the light source 4 is turned on is not connected in parallel with the light source 4. In the lighting device 10 according to the first embodiment, a diode such as a Schottky barrier diode is not connected in parallel with the light source 4. In the lighting device 10 according to the first embodiment, the bypass circuit 2 is not configured to connect a switching element and a load adjustment unit (for example, at least one of a resistor, a variable resistor, a semiconductor switch element, and a resistive switch element) to turn on and off the switching element.

[0031] (2.2.3) Control circuit The control circuit 3 may be realized, for example, by a computer system having one or more processors and one or more memories. In the lighting device 10, the one or more processors execute a program recorded in the memory to realize the functions of the control circuit 3. The program may be pre-recorded in the memory, may be provided via a telecommunication line such as the Internet, or may be provided by recording it on a non-transitory recording medium such as a memory card.

[0032] The control circuit 3 controls the lighting circuit 1 so that the output current I3 of the lighting circuit 1 coincides with a target value (target current). The output current I3 is the sum of a first current I1 flowing through the light source 4 and a second current I2 flowing through the bypass circuit 2, as shown in FIG.

[0033] As described above, the control circuit 3 is connected to the control terminal of the switching element Q1 of the lighting circuit 1. The control circuit 3 is also connected to the dimmer 6. The dimmer 6 is a device for setting a dimming rate of the light source 4. The dimmer 6 outputs a dimming signal corresponding to the dimming rate to the control circuit 3. The dimming signal is, for example, a PWM (Pulse Width Modulation) signal.

[0034] The control circuit 3 sets a target voltage based on a dimming signal from the dimmer 6. The target voltage is a voltage corresponding to a target value (target current) of the output current I3 of the lighting circuit 1. In this manner, the output current I3 of the lighting circuit 1 is determined by the dimming signal input from the dimmer 6 to the control circuit 3. Then, the control circuit 3 outputs a drive signal to the switching element Q1 so that the output voltage of the lighting circuit 1 matches the target voltage. This controls the output current I3 of the lighting circuit 1 to match the target value.

[0035] As described above, a lower limit (for example, a current with a dimming rate of 0.5%) is set for the output current I3 of the lighting circuit 1. Therefore, the control circuit 3 can control the output current I3 of the lighting circuit 1 within a range equal to or greater than the lower limit.

[0036] As described above, a part of the output current I3 of the lighting circuit 1 (the second current I2) flows to the bypass circuit 2, and the remaining current (the first current I1 (=output current I3-second current I2)) flows to the light source 4. That is, in order to pass the first current I1 to the light source 4, the lighting circuit 1 outputs the first current I1 flowing to the light source 4 as the output current I3 by boosting (i.e. increasing) the first current I1 flowing to the light source 4 by the second current I2 flowing to the bypass circuit 2. For this reason, when the dimmer 6 outputs a dimming signal of a desired dimming rate as the dimming rate of the light source 4 to the control circuit 3, the control circuit 3 boosts the target voltage of the output voltage of the lighting circuit 1 by the voltage corresponding to the second current I2 flowing to the bypass circuit 2. Then, the control circuit 3 controls the switching element Q1 so that the output voltage of the lighting circuit 1 coincides with the boosted target voltage. As a result, when a dimming signal with a desired dimming ratio is output from the dimmer 6 to the control circuit 3 as the dimming ratio of the light source 4, the light source 4 can be made to emit light at the desired dimming ratio. Since the desired dimming ratio is a dimming ratio designated by the dimmer 6, in the following description, the desired dimming ratio may be referred to as a "designated dimming ratio."

[0037] (2.2.4) Capacitor and detection resistor A first end of the capacitor C1 is connected to the first output terminal T1 on the high potential side of the lighting circuit 1. A second end of the capacitor C1 is connected to the second end of the detection resistor R1. That is, the second end of the capacitor C1 is connected to the second output terminal T2 on the low potential side of the lighting circuit 1 via the detection resistor R1. In this manner, the capacitor C1 is connected between the output terminals (first output terminal T1, second output terminal T2) of the lighting circuit 1 between the lighting circuit 1 and the light source 4. The capacitor C1 has a function of smoothing the output current I3 of the lighting circuit 1.

[0038] The detection resistor R1 detects the output current I3 of the lighting circuit 1. The first terminal of the detection resistor R1 is connected to the second output terminal T2 on the low potential side of the lighting circuit 1. The second terminal of the detection resistor R1 is connected to the second terminal of the capacitor C1 as described above. That is, the detection resistor R1 is connected between the lighting circuit 1 and the capacitor C1. A voltage V2 is applied between both ends of the detection resistor R1. The voltage V2 is a voltage corresponding to the output current I3. Therefore, the control circuit 3 detects the voltage V2 between both ends of the detection resistor R1 as the output current I3. Then, the control circuit 3 controls the lighting circuit 1 so that the voltage V2 between both ends coincides with the target voltage. The target voltage is a voltage corresponding to the above-mentioned target value (target current).

[0039] (3) Operation Next, the operations of the lighting device 10 and the illumination device 100 according to the first embodiment will be described.

[0040] The control circuit 3 outputs a drive signal to the switching element Q1 of the lighting circuit 1 in a state where a DC voltage V1 is applied to the lighting circuit 1 from the DC power source 5. The control circuit 3 changes the on-width of the switching element Q1 in the drive signal in response to the dimming signal from the dimmer 6. Specifically, the control circuit 3 increases the on-width of the switching element Q1 as the dimming ratio of the lighting device 100 increases, and decreases the on-width of the switching element Q1 as the dimming ratio of the lighting device 100 decreases.

[0041] The switching element Q1 of the lighting circuit 1 is turned on and off by a drive signal from the control circuit 3, so that the first current I1 flows through the light source 4 and the second current I2 flows through the bypass circuit 2. As a result, an output current I3, which is the sum of the first current I1 and the second current I2, flows through the detection resistor R1, and a voltage V2 is generated between both ends of the detection resistor R1. The control circuit 3 detects the voltage V2 between both ends to detect the output current I3 corresponding to the voltage V2 between both ends. Then, the control circuit 3 controls the on / off of the switching element Q1 of the lighting circuit 1 so that the output current I3 of the lighting circuit 1 matches a target value. Specifically, the control circuit 3 controls the on / off of the switching element Q1 of the lighting circuit 1 so that the voltage V2 between both ends of the detection resistor R1 matches a target voltage. As a result, the output current I3 of the lighting circuit 1 is constant current controlled. Also, the dimming rate is changed using the dimmer 6 to change the target voltage, and as a result, the light source 4 can be dimmed.

[0042] (4) Characteristics of the lighting device Next, the characteristics of the lighting device 10 according to the first embodiment will be described with reference to FIG.

[0043] (4.1) First characteristic First, the first characteristic of the lighting device 10 will be described.

[0044] As Comparative Example 1, a case where the bypass circuit 2 is not connected in parallel to the light source 4 in FIG. 1 is assumed. In this case, the current (output current I3) flowing through the detection resistor R1 is equal to the current (first current I1) flowing through the light source 4. For this reason, for example, when the output current I3 is changed within a range of 100% (upper limit) to 0.5% (lower limit), the dimming control range of the lighting device 100 is also within a range of 100% to 0.5%, similar to the output current I3. Therefore, in this case, the dimming rate of the light source 4 cannot be controlled to 0.5% or less. The dimming rate of 0.5% corresponds to the lower limit of the control range of the output current I3 of the lighting circuit 1.

[0045] In contrast, in the lighting device 10 according to the first embodiment, the bypass circuit 2 is connected in parallel to the light source 4. In this case, the output current I3 is the sum of the first current I1 flowing through the light source 4 and the second current I2 flowing through the bypass circuit 2, as described above. Therefore, the output current I3 varies within a range obtained by adding the second current I2 to the first current I1. In the following description, in order to make the description easier to understand, the target voltage is not increased.

[0046] For example, the reference voltage Vref is set so that the second current I2 flowing through the bypass circuit 2 is 0.5%. That is, the bypass circuit 2 is configured to allow a current (second current I2) equal to the lower limit of the control range of the output current I3 by the control circuit 3 to flow. For example, when the dimming rate (specified dimming rate) of the lighting device 100 is 0.5%, which is the lower limit, the output current I3 of the lighting circuit 1 is 0.5% and the second current I2 flowing through the bypass circuit 2 is m0.5%, so the first current I1 flowing through the light source 4 is 0%. Also, for example, when the dimming rate (specified dimming rate) is 0.6%, the output current I3 is 0.6% and the second current I2 is 0.5%, so the first current I1 is 0.1%. That is, in the first embodiment, when the output current I3 is changed within a range of 100% to 0.5%, the dimming control range of the lighting device 100 is a range of 100% to 0%. In this way, the lighting device 10 according to the first embodiment makes it possible to light the light source 4 at a dimming rate equal to or lower than the lower dimming limit (e.g., 0.5%) of conventional lighting devices. In short, the lighting device 10 according to the first embodiment makes it possible to achieve deeper dimming.

[0047] (4.2) Second characteristic Next, the second characteristic of the lighting device 10 will be described.

[0048] As Comparative Example 2, a case is assumed in which the second current I2 flowing through the bypass circuit 2 is set to the above-mentioned lower limit (e.g., dimming rate of 0.5%) (i.e., the set value of the second current I2 is the above-mentioned lower limit). In this case, taking into consideration the variation in the second current I2 due to individual differences in the lighting device 10, when the designated dimming rate is a deeper dimming rate (e.g., 1%), the light source 4 may be turned off.

[0049] 2, when the set value I2_typ of the second current I2 is set to the lower limit, the second current I2 flowing through the bypass circuit 2 varies within a range from a maximum second current I2_max (e.g., dimming rate of 0.6%) to a minimum second current I2_min (e.g., dimming rate of 0.4%) due to individual differences in the lighting device 10. Note that the maximum second current I2_max is larger than the set value I2_typ, and the minimum second current I2_min is smaller than the set value I2_typ.

[0050] Therefore, as shown in Fig. 3, taking into consideration the above-mentioned variation in the second current I2, the first current I1 (=output current I3-second current I2) flowing through the light source 4 varies within a range from the maximum first current I1_max (=output current I3-minimum second current I2_min) to the minimum first current I1_min (=output current I3-maximum second current I2_max). The set first current I1_typ in Fig. 3 is the first current I1 when the second current I2 is the set value I2_typ.

[0051] More specifically, when the second current I2 is the set value I2_typ (i.e., when there is no variation in the second current I2), the first current I1 flowing through the light source 4 becomes the set first current (set first current) I1_typ (=output current I3-set value I2_typ). In this case, when the specified dimming rate is 0%, the set first current I1_typ becomes exactly 0%. That is, the set first current I1_typ becomes a straight line passing through the origin 0 in FIG. 3.

[0052] Furthermore, when the second current I2 is the minimum second current I2_min (i.e., when the variation in the second current I2 is minimal), the first current I1 flowing through the light source 4 becomes the maximum first current I1_max (=output current I3-minimum second current I2_min). When the specified dimming rate is 0%, the maximum first current I1_max becomes a predetermined current α1 (e.g., a current at a dimming rate of 1%) that is greater than zero. That is, the maximum first current I1_max becomes a straight line passing through the predetermined current α1 (e.g., a current at a dimming rate of 1%) on the vertical axis of FIG. 3.

[0053] Furthermore, when the second current I2 is the maximum second current I2_max (i.e., when the variation in the second current I2 is maximum), the first current I1 flowing through the light source 4 becomes the minimum first current I1_min (=output current I3-maximum second current I2_max). The minimum first current I1_min is always 0% when the designated dimming rate is equal to or lower than a predetermined dimming rate β1 (e.g., 1%). That is, the minimum first current I1_min becomes a straight line passing through the predetermined dimming rate β1 (e.g., 0.1%) on the horizontal axis of FIG. 3.

[0054] In this way, when the above-mentioned variation in the second current I2 is taken into consideration, the first current I1 varies within a range from the maximum first current I1_max to the minimum first current I1_min. Then, when the designated dimming ratio is equal to or less than the predetermined dimming ratio β1, a problem occurs in that the minimum first current I1_min is always 0.

[0055] On the other hand, in the lighting device 10, in order to solve the above problem, the second current I2 is limited to a current less than the lower limit value as described above. In the following description, the lower limit value is set to the lower limit value γ1. That is, the maximum second current I2_max is limited to less than the lower limit value γ1 (see FIG. 4). As a result, as shown in FIG. 5, the minimum first current I1_min (=output current I3-maximum second current I2_max) becomes almost 0% (more precisely, a value slightly greater than 0%) when the designated dimming rate is 0%. That is, the minimum first current I1_min becomes a straight line passing through the origin 0 in FIG. 5. Therefore, the maximum first current I1_max and the set first current I1_typ also become 0% or more when the designated dimming rate is 0%. This makes it possible to prevent the light source 4 from turning off without emitting light at the designated dimming rate due to the variation in the second current I2 caused by the individual difference of the lighting device 10.

[0056] (4.3) Third characteristic Next, a third characteristic of the lighting device 10 will be described.

[0057] As a comparative example 3, a case where a detection resistor R1 is connected between the cathode of the light source 4 and the second end of the capacitor C1 in FIG. 1 is assumed. In this case, the output power of the lighting circuit 1 is charged to the capacitor C1, and the charging current of the capacitor C1 flows through the detection resistor R1. Therefore, the control circuit 3 detects the current flowing due to the charging and discharging of the capacitor C1, not the current output from the lighting circuit 1. Therefore, in this case, there is a possibility that a delay occurs in the feedback control. Also, in this case, there is a possibility that an overshoot occurs in the first current I1 flowing through the light source 4.

[0058] In contrast, in the lighting device 10, as shown in FIG. 1, the control circuit 3 detects the current I4 flowing through the inductor L1 as the output current I3. Specifically, the control circuit 3 detects the voltage V2 across the detection resistor R1 connected between the lighting circuit 1 and the capacitor C1 as the current I4 flowing through the inductor L1. The current I4 flowing through the inductor L1 is the output current of the lighting circuit 1 before being smoothed by the capacitor C1. The control circuit 3 detects the output current I3 of the lighting circuit 1 from the current I4 flowing through the inductor L1, and feedback controls the lighting circuit 1 based on this output current I3. This makes it possible to suppress delays in feedback control due to charging and discharging the capacitor C1. It also makes it possible to suppress overshoots of the first current I1. In particular, since overshoots during low dimming are easily noticeable, this is effective in feedback control during low dimming.

[0059] (5) Effects A lighting device 10 according to the first embodiment includes a lighting circuit 1, a bypass circuit 2, and a control circuit 3. The lighting circuit 1 supplies lighting power to a light source 4. The bypass circuit 2 is connected in parallel with the light source 4. The control circuit 3 controls the lighting circuit 1 so that an output current I3 of the lighting circuit 1, which is the sum of a first current I1 flowing through the light source 4 and a second current I2 flowing through the bypass circuit 2, matches a target value. The second current I2 flowing through the bypass circuit 2 is a current less than a lower limit value in a control range of the output current I3 of the lighting circuit 1 by the control circuit 3.

[0060] According to this configuration, the second current I2 flowing through the bypass circuit 2 is a current less than the lower limit of the control range of the output current of the lighting circuit 1 by the control circuit 3. Therefore, when the output current I3 of the lighting circuit 1 is controlled to a current with a deeper dimming ratio, it is possible to prevent the light source 4 from being turned off without emitting light at the specified dimming ratio due to variations in the second current I2 caused by individual differences in the lighting device 10.

[0061] Furthermore, in the lighting device 10 according to the first embodiment, the maximum second current I2_max is the maximum value of the range of variation in the second current I2 due to individual differences in the lighting device 10. The maximum second current I2_max is a current less than the above-mentioned lower limit.

[0062] According to this configuration, when the output current I3 of the lighting circuit 1 is controlled to a current with a deeper dimming ratio, it is possible to further prevent the light source 4 from being turned off without emitting light at the specified dimming ratio due to variations in the second current I2 caused by individual differences in the lighting device 10.

[0063] In the lighting device 10 according to the first embodiment, the lighting circuit 1 includes a switching element Q1 and an inductor L1. The control circuit 3 detects a current I4 flowing through the inductor L1 as an output current I3.

[0064] According to this embodiment, it is possible to suppress overshoot of the first current I1 during startup and during steady state.

[0065] Moreover, the lighting device 10 according to the first embodiment further includes a capacitor C1 and a detection resistor R1. The capacitor C1 is connected between the output terminals of the lighting circuit 1 and between the lighting circuit 1 and the light source 4. The detection resistor R1 is connected between the lighting circuit 1 and the capacitor C1, and detects an output current I3. The control circuit 3 detects, as the output current I3, a current corresponding to a voltage V2 across the detection resistor R1.

[0066] According to this embodiment, it is possible to detect the output current I3 of the lighting circuit 1 by detecting the current corresponding to the voltage V2 across the detection resistor R1.

[0067] Moreover, in the lighting device 10 according to the first embodiment, the bypass circuit 2 includes a resistor R2 and an operational amplifier OP1. The resistor R2 is connected between the output terminals of the lighting circuit 1. The operational amplifier OP1 performs feedback control so that a reference voltage Vref input to a non-inverting input terminal and a voltage V3 across the resistor R2 input to an inverting input terminal match each other.

[0068] According to this embodiment, regardless of the specifications of the light source 4, it is possible to pass a constant current (the second current I2) in parallel with the light source 4.

[0069] In the lighting device 10 according to the first embodiment, the light source 4 includes at least one LED 41. The forward voltage of the light source 4 is applied to the bypass circuit 2.

[0070] According to this embodiment, it is possible to apply a voltage equal to the forward voltage of the light source 4 to the bypass circuit 2.

[0071] Moreover, the illumination device 100 according to the first embodiment includes a lighting device 10 and a light source 4. The light source 4 has at least one LED 41.

[0072] According to this embodiment, for example, even if the specifications of the light source 4 are changed, a constant current (second current I2) can be caused to flow by the bypass circuit 2, and therefore there is an advantage that no circuit change is required.

[0073] (Embodiment 2) A lighting device 10A and an illumination device 100A according to the second embodiment will be described with reference to Fig. 6 to Fig. 8. Regarding the lighting device 10A and the illumination device 100A according to the second embodiment, the same components as those of the lighting device 10 and the illumination device 100 according to the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

[0074] (1) Composition 6, the lighting device 100A according to the second embodiment further includes a light source 4A that emits light of a different color from the light source 4, a lighting circuit 1A, a bypass circuit 2A, a detection resistor R21, and a capacitor C21 in the lighting device 100 according to the first embodiment. Also, the lighting device 10A according to the second embodiment further includes a lighting circuit 1A, a bypass circuit 2A, a detection resistor R21, and a capacitor C21 in the lighting device 10 according to the first embodiment.

[0075] The light source 4, the lighting circuit 1, the bypass circuit 2, the detection resistor R1, and the capacitor C1 correspond to one another. The light source 4A, the lighting circuit 1A, the bypass circuit 2A, the detection resistor R21, and the capacitor C21 correspond to one another.

[0076] The light source 4, the lighting circuit 1, the bypass circuit 2, the detection resistor R1, and the capacitor C1 shown in Fig. 6 are configured similarly to the light source 4, the lighting circuit 1, the bypass circuit 2, the detection resistor R1, and the capacitor C1 of embodiment 1. For this reason, detailed description of the light source 4, the lighting circuit 1, the bypass circuit 2, the detection resistor R1, and the capacitor C1 shown in Fig. 6 will be omitted.

[0077] The light source 4A is configured similarly to the light source 4, and has a plurality of light emitting elements 41A. The light source 4A emits light of a different color from the light color emitted by the light source 4. That is, the plurality of light sources 4, 4A emit light of different colors. The light source 4 emits, for example, warm light, and the light source 4A emits, for example, white light. The plurality of light sources 4, 4A are connected in parallel to each other and connected to a DC power source 5.

[0078] The lighting circuit 1A supplies lighting power to the light source 4A. The lighting circuit 1A is configured similarly to the lighting circuit 1. The lighting circuits 1, 1A are connected between a DC power source 5 and the corresponding light sources 4, 4A. The lighting circuits 1, 1A are connected in parallel to each other and connected to the DC power source 5.

[0079] The lighting circuit 1A includes a switching element Q21, an inductor L21, a diode D21, a first output terminal T21, and a second output terminal T22. The switching element Q21 includes a first terminal, a second terminal, and a control terminal. The first terminal of the switching element Q21 is connected to the positive electrode of the DC power supply 5. The second terminal of the switching element Q21 is connected to the cathode of the diode D21 and to the first terminal of the inductor L21. The control terminal of the switching element Q21 is connected to the control circuit 3. The first terminal of the inductor L21 is connected to the second terminal of the switching element Q21 and to the cathode of the diode D21. The first terminal of the inductor L21 is connected to the positive electrode of the DC power supply 5 via the switching element Q21. The second terminal of the inductor L21 is connected to the first output terminal T21. The cathode of the diode D21 is connected to the second terminal of the switching element Q21 and to the first terminal of the inductor L21. The anode of the diode D21 is connected to the second output terminal T22. The anode of the diode D21 is connected to the negative electrode of the DC power supply 5 via the second output terminal T22.

[0080] The bypass circuit 2A is connected in parallel to the light source 4A. The bypass circuit 2A is configured similarly to the bypass circuit 2, and includes a transistor Tr21, an operational amplifier OP21, and resistors R22 and R23.

[0081] The collector terminal of the transistor Tr21 is connected to the first output terminal T21 on the high potential side of the lighting circuit 1A. The emitter terminal of the transistor Tr21 is connected to the second output terminal T22 on the low potential side of the lighting circuit 1A via a resistor R22. The base terminal of the transistor Tr21 is connected to the output terminal of the operational amplifier OP21 via a resistor R23. A reference voltage Vref is applied (input) to the non-inverting input terminal of the operational amplifier OP21. The inverting input terminal of the operational amplifier OP21 is connected to a connection point P21 between the emitter terminal of the transistor Tr21 and the resistor R22. The output terminal of the operational amplifier OP21 is connected to the base terminal of the transistor Tr21 via the resistor R23. The operational amplifier OP21 compares the voltage across the resistor R22 with the reference voltage Vref, and performs feedback control so that the two match.

[0082] A first terminal of the capacitor C21 is connected to the first output terminal T21 on the high potential side of the lighting circuit 1A. A second terminal of the capacitor C21 is connected to the second terminal of the detection resistor R21. In this manner, the capacitor C21 is connected between the output terminals (first output terminal T21, second output terminal T22) of the lighting circuit 1A between the lighting circuit 1A and the light source 4A. The capacitor C21 has a function of smoothing the output current I3A of the lighting circuit 1A.

[0083] The detection resistor R21 is a resistor for detecting the output current I3A of the lighting circuit 1A. A first terminal of the detection resistor R21 is connected to the second output terminal T22 on the low potential side of the lighting circuit 1A. A second terminal of the detection resistor R21 is connected to the second terminal of the capacitor C21. That is, the detection resistor R21 is connected between the lighting circuit 1A and the capacitor C21. The voltage generated across the detection resistor R21 is a voltage corresponding to the output current I3A.

[0084] In the lighting device 10A, the lighting circuit 1 outputs an output current I3, the second current I2 flows through the bypass circuit 2, and the first current I1 flows through the light source 4. The output current I3 is the sum of the first current I1 and the second current I2. Moreover, the lighting circuit 1A outputs an output current I3A, the second current I2A flows through the bypass circuit 2A, and the first current I1A flows through the light source 4A. The output current I3A is the sum of the first current I1A and the second current I2A.

[0085] The second currents I2, I2A flowing through the bypass circuits 2, 2A are currents less than the lower limit of the control range of the output currents I3, I3A of the corresponding lighting circuits 1, 1A by the control circuit 3. In other words, if the maximum value of the range of variations in the second currents I2, I2A due to individual differences in the lighting devices 10A is the maximum second current, the maximum second current of the second currents I2, I2A is a current less than the above-mentioned lower limit. In the second embodiment, the multiple second currents I2, I2A flowing through the multiple bypass circuits 2, 2A are different from each other. In other words, the set values ​​of the multiple second currents I2, I2A are different from each other.

[0086] The illumination light of the lighting device 100A is composed of a composite light of the lights emitted from the multiple light sources 4, 4A. In the second embodiment, it is possible to adjust the dimming rate and color temperature of the illumination light. In this case, the dimmer 6 outputs a dimming signal specifying a desired dimming rate of the illumination light and a color temperature signal specifying a desired color temperature of the illumination light to the control circuit 3. The control circuit 3 determines the dimming rate (individual dimming rate) of each light source 4, 4A based on the dimming rate specified by the dimming signal and the color temperature specified by the color temperature signal. More specifically, the control circuit 3 is set with a correspondence relationship between the dimming rate and color temperature of the illumination light and the individual dimming rate of each light source 4, 4A. The control circuit 3 determines the individual dimming rate of each light source 4, 4A corresponding to the specified dimming rate and color temperature based on this correspondence relationship. Then, the control circuit 3 controls the output currents I3, I3A of each lighting circuit 1, 1A so that each light source 4, 4A emits light at the determined individual dimming rate.

[0087] More specifically, the control circuit 3 of embodiment 2, like the control circuit 3 of embodiment 1, detects the output currents I3, I3A of the corresponding lighting circuits 1, 1A based on the voltage across the detection resistors R1, R21, and controls the corresponding lighting circuits 1, 1A so that the detected output currents I3, I3A match the target values ​​(target currents).

[0088] In the second embodiment, similarly to the first embodiment, the dimming rate of the illumination light of the lighting device 100A may be referred to as a "dimming rate", and the dimming rate of each of the light sources 4, 4A may be referred to as an "individual dimming rate". In addition, the "desired dimming rate" may be referred to as a "specified dimming rate", and the "desired color temperature" may be referred to as a "specified color temperature".

[0089] (2) Characteristics of the lighting device Next, characteristics of the lighting device 10A according to the second embodiment will be described with reference to FIG.

[0090] As Comparative Example 4, a case is assumed in which the set values ​​of the second currents I2, I2A flowing through the bypass circuits 2, 2A are set exactly to the lower limit (e.g., dimming rate of 0.5%) of the control range of the output currents I3, I3A of the corresponding lighting circuits 1, 1A by the control circuit 3. In this case, taking into consideration the variation in the second currents I2, I2A due to individual differences in the lighting devices 10A, when the specified dimming rate is a deeper dimming rate (e.g., 1%), one of the multiple light sources 4, 4A may be turned off.

[0091] 7, consider a case in which the designated color temperature of the illumination light is gradually changed from the light color of the light source 4 (warm color: 2700K) to the light color of the light source 4A (white color: 6500K) in Comparative Example 4. That is, the state is changed from one state where only the light source 4 emits light (i.e., the designated color temperature of the illumination light is warm color of 2700K) to the other state where only the light source 4A emits light (i.e., the designated color temperature of the illumination light is white color of 6500K) by gradually decreasing the first current I1 flowing through the light source 4 and gradually increasing the first current I1A flowing through the light source 4A.

[0092] In this case, as described above, the set value of the second current I2 flowing through the bypass circuit 2 is set exactly to the above-mentioned lower limit value. Therefore, due to the variation in the second current I2 caused by the individual differences of the lighting device 10A, the first current I1 may always have a dimming rate of 0% within a certain range W2 around 6500K. Also, as described above, the set value of the second current I2A flowing through the bypass circuit 2A is also set exactly to the above-mentioned lower limit value. Therefore, due to the variation in the second current I2A caused by the individual differences of the lighting device 10A, the first current I1A may always have a dimming rate of 0% within a certain range W1 around 2700K.

[0093] Here, consider a case where the designated color temperature of the illumination light is changed from 2700K to 6500K in a state where the designated dimming rate of the illumination light is controlled to a deeper dimming rate (for example, 1%). In this case, when the designated color temperature of the illumination light is within a certain range W1 around 2700K, the first current I1A is always a current with a dimming rate of 0%, and the light source 4A is turned off. Therefore, even if the designated color temperature of the illumination light is changed within the certain range W1, the light source 4A does not emit light, and only the light source 4 emits light, so that the designated color temperature of the illumination light remains at a warm 2700K. Similarly, when the designated color temperature of the illumination light is within a certain range W2 around 6500K, the first current I1 is always a current with a dimming rate of 0%, and the light source 4 is turned off. Therefore, even if the designated color temperature of the illumination light is changed within the certain range W2, the light source 4 does not emit light, and only the light source 4A emits light, so that the color temperature of the illumination light remains at a white 6500K. For this reason, when the specified dimming rate of the illumination light is a deeper dimming rate, if the specified color temperature of the illumination light is changed within the certain ranges W1, W2, a difference will occur between the specified color temperature of the illumination light and the actual color temperature of the illumination light, causing the user to feel uncomfortable.

[0094] In contrast, in the lighting device 10A, the set values ​​of the second currents I2, I2A flowing through the bypass circuits 2, 2A are set to be less than the lower limit value of the control range of the output currents I3, I3A of the corresponding lighting circuits 1, 1A by the control circuit 3. Therefore, as shown in FIG. 8, even if there is a variation in the second current I2 due to the fixed difference of the lighting device 10A, the first current I1 does not have a dimming rate of 0% within a certain range W2 around 6500K. Similarly, the first current I1A does not have a dimming rate of 0% within a certain range W1 around 2700K. In the example of FIG. 8, the first current I1 becomes a current with a dimming rate δ1 that is slightly larger than the dimming rate of 0% when the designated color temperature of the illumination light is 6500K. The first current I1A becomes a current with a dimming rate δ2 that is slightly larger than the dimming rate of 0% when the designated color temperature of the illumination light is 2700K. The dimming rates δ1, δ2 may be the same value or may be different values.

[0095] Therefore, in the lighting device 10A, when the designated color temperature of the illumination light is changed from 2700K to 6500K, the first current I1A gradually increases from the current with the dimming rate δ1. Therefore, due to the above-mentioned variation in the second current I2A, the first current I1A does not become a current with a dimming rate of 0% within a certain range W1 around 2700K (i.e., the light source 4A does not turn off). Also, when the designated color temperature of the illumination light is changed from 2700K to 6500K, the first current I1 gradually decreases from a current with a dimming rate of 1.1% to a current with a dimming rate δ2. Therefore, due to the above-mentioned variation in the second current I2A, the first current I1 does not become a current with a dimming rate of 0% within a certain range W2 around 6500K (i.e., the light source 4 does not turn off). Therefore, it is possible to suppress the occurrence of a difference between the designated color temperature of the illumination light and the actual color temperature of the illumination light. As a result, it is possible to suppress the user from feeling uncomfortable.

[0096] (3) Effects In the lighting device 10A according to the second embodiment, the light source 4 is included in a plurality of light sources 4, 4A that emit light of different colors. The lighting device 10A includes a plurality of lighting circuits 1, 1A and a plurality of bypass circuits 2, 2A. The plurality of lighting circuits 1, 1A include a lighting circuit 1, correspond to the plurality of light sources 4, 4A, and supply lighting power to the corresponding light sources. The plurality of bypass circuits 2, 2A include a bypass circuit 2, correspond to the plurality of light sources 4, 4A, and are connected in parallel with the corresponding light sources. A certain light source among the plurality of light sources 4, 4A, a certain lighting circuit among the plurality of lighting circuits 1, 1A, and a certain bypass circuit among the plurality of bypass circuits 2, 2A correspond to each other. The control circuit 3 controls the plurality of lighting circuits 1, 1A so that the output current I3, I3A of the certain lighting circuit, which is the sum of the first current I1, I1A flowing through the certain light source and the second current I2, I2A flowing through the bypass circuit 2, 2A, matches a target value.

[0097] According to this configuration, in the lighting device 10A that lights up the multiple light sources 4, 4A, when the output current I3, I3A of any one of the multiple lighting circuits 1, 1A is controlled to a current with a deeper dimming rate, it is possible to prevent the corresponding light source 4, 4A from being turned off without emitting light at the designated dimming rate due to variations in the second current I2, I2A caused by individual differences in the lighting device 10A. This makes it possible to prevent the actual color temperature of the illumination light formed of light emitted from the multiple light sources 4, 4A from becoming a color temperature different from the designated color temperature when the illumination light is controlled to a deeper dimming rate.

[0098] Furthermore, in the lighting device 10A according to the second embodiment, the multiple bypass circuits 2, 2A include a first bypass circuit 2 and a second bypass circuit 2A. The second current I2 flowing through the first bypass circuit 2 is different from the second current I2A flowing through the second bypass circuit 2A.

[0099] According to this configuration, the second currents I2, I2A of the multiple bypass circuits 2, 2A can be made different from each other.

[0100] (4) Variations Modifications of the second embodiment will be described. In the following description, the same components as those of the lighting device 10 and the illumination device 100 according to the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted. In addition, the following modifications may be implemented in combination.

[0101] (4.1) Variation 1 In the second embodiment, when two lighting circuits 1, 1A, two light sources 4, 4A, and two bypass circuits 2, 2A are provided, the set values ​​of the two second currents I2, I2A flowing through the two bypass circuits 2, 2A are different from each other. However, when three or more lighting circuits, three or more light sources 4, 4A, and three or more bypass circuits are provided, the set value of at least one of the three or more second currents flowing through the three or more bypass circuits may be different from the set value of the remaining second currents. For example, when three lighting circuits, three light sources, and three bypass circuits are provided, the lower limit values ​​of the three lighting circuits are respectively 2 mA, 3 mA, and 3 mA. In this case, the set values ​​of the three second currents flowing through the three bypass circuits may be, for example, 1.5 mA, 2.5 mA, and 2.5 mA, respectively.

[0102] (4.2) Variation 2 In the second embodiment, the set values ​​of the multiple (e.g., two) second currents I2, I2A flowing through the multiple (e.g., two) bypass circuits 2, 2A are different from each other. However, the set values ​​of the multiple second currents I2, I2A may be the same as each other.

[0103] (Embodiment 3) A lighting device 10B and an illumination device 100B according to the third embodiment will be described with reference to Fig. 9 to Fig. 12. Regarding the lighting device 10B and the illumination device 100B according to the third embodiment, the same components as those of the lighting devices 10, 10A and the illumination devices 100, 100A according to the first and second embodiments will be denoted by the same reference numerals, and the description thereof will be omitted in some cases.

[0104] (1) Composition 9, the lighting device 100B according to the third embodiment further includes a light source 4B that emits light of a different color from the light sources 4 and 4A, a lighting circuit 1B, a bypass circuit 2B, a detection resistor R31, and a capacitor C31 in the lighting device 100A according to the second embodiment. Also, the lighting device 10B according to the third embodiment further includes a lighting circuit 1B, a bypass circuit 2B, a detection resistor R31, and a capacitor C31 in the lighting device 10A according to the second embodiment.

[0105] The light source 4, the lighting circuit 1, the bypass circuit 2, the detection resistor R1, and the capacitor C1 correspond to one another. The light source 4A, the lighting circuit 1A, the bypass circuit 2A, the detection resistor R21, and the capacitor C21 correspond to one another. The light source 4B, the lighting circuit 1B, the bypass circuit 2B, the detection resistor R31, and the capacitor C31 correspond to one another.

[0106] The light sources 4, 4A, the lighting circuits 1, 1A, the bypass circuits 2, 2A, the detection resistors R1, R21, and the capacitors C1, C21 shown in Fig. 9 are configured similarly to the light sources 4, 4A, the lighting circuits 1, 1A, the bypass circuits 2, 2A, the detection resistors R1, R21, and the capacitors C1, C21 of embodiment 2. For this reason, detailed description of the light sources 4, 4A, the lighting circuits 1, 1A, the bypass circuits 2, 2A, the detection resistors R1, R21, and the capacitors C1, C21 shown in Fig. 9 will be omitted.

[0107] The light source 4B is configured similarly to the light sources 4 and 4A, and has a plurality of light emitting elements 41B. The light source 4B emits light of a different color from the light emitted by the light sources 4 and 4A. That is, the plurality of light sources 4, 4A, and 4B emit light of different colors. The light source 4 emits light of, for example, red light, the light source 4A emits light of, for example, green light, and the light source 4B emits light of, for example, blue light. The plurality of light sources 4, 4A, and 4B are connected in parallel to each other and connected to a DC power source 5.

[0108] The lighting circuit 1B supplies lighting power to the light source 4B. The lighting circuit 1B is configured similarly to the lighting circuits 1, 1B. The lighting circuits 1, 1A, 1B are connected between a DC power source 5 and the corresponding light sources 4, 4A, 4B. The multiple lighting circuits 1, 1A, 1B are connected in parallel to each other and connected to the DC power source 5.

[0109] The lighting circuit 1B includes a switching element Q31, an inductor L31, a diode D31, a first output terminal T31, and a second output terminal T32. The switching element Q31 includes a first terminal, a second terminal, and a control terminal. The first terminal of the switching element Q31 is connected to the positive electrode of the DC power supply 5. The second terminal of the switching element Q31 is connected to the cathode of the diode D31 and to the first terminal of the inductor L31. The control terminal of the switching element Q31 is connected to the control circuit 3. The first terminal of the inductor L31 is connected to the second terminal of the switching element Q31 and to the cathode of the diode D31. The first terminal of the inductor L31 is connected to the positive electrode of the DC power supply 5 via the switching element Q31. The second terminal of the inductor L31 is connected to the first output terminal T31. The cathode of the diode D31 is connected to the second terminal of the switching element Q31 and to the first terminal of the inductor L31. The anode of the diode D31 is connected to the second output terminal T32. The anode of the diode D31 is connected to the negative electrode of the DC power supply 5 via the second output terminal T32.

[0110] The bypass circuit 2B is connected in parallel to the light source 4B. The bypass circuit 2B is configured similarly to the bypass circuits 2 and 2A, and includes a transistor Tr31, an operational amplifier OP31, and resistors R32 and R33.

[0111] The collector terminal of the transistor Tr31 is connected to the first output terminal T31 on the high potential side of the lighting circuit 1B. The emitter terminal of the transistor Tr31 is connected to the second output terminal T32 on the low potential side of the lighting circuit 1B via a resistor R32. The base terminal of the transistor Tr31 is connected to the output terminal of the operational amplifier OP31 via a resistor R33. A reference voltage Vref is applied (input) to the non-inverting input terminal of the operational amplifier OP31. The inverting input terminal of the operational amplifier OP31 is connected to a connection point P31 between the emitter terminal of the transistor Tr31 and the resistor R32. The output terminal of the operational amplifier OP31 is connected to the base terminal of the transistor Tr31 via the resistor R33. The operational amplifier OP31 compares the voltage across the resistor R32 with the reference voltage Vref, and performs feedback control so that the two match.

[0112] A first terminal of the capacitor C31 is connected to the first output terminal T31 on the high potential side of the lighting circuit 1B. A second terminal of the capacitor C31 is connected to the second terminal of the detection resistor R31. In this manner, the capacitor C31 is connected between the output terminals (first output terminal T31, second output terminal T32) of the lighting circuit 1B between the lighting circuit 1B and the light source 4B. The capacitor C31 has a function of smoothing the output current I3B of the lighting circuit 1B.

[0113] The detection resistor R31 is a resistor for detecting the output current I3B of the lighting circuit 1B. A first terminal of the detection resistor R31 is connected to the second output terminal T32 on the low potential side of the lighting circuit 1B. A second terminal of the detection resistor R31 is connected to the second terminal of the capacitor C31. That is, the detection resistor R31 is connected between the lighting circuit 1B and the capacitor C31. The voltage generated across the detection resistor R31 is a voltage corresponding to the output current I3B.

[0114] In the lighting device 10B, the lighting circuit 1 outputs an output current I3, the second current I2 flows through the bypass circuit 2, and the first current I1 flows through the light source 4. The output current I3 is the sum of the first current I1 and the second current I2. Moreover, the lighting circuit 1A outputs an output current I3A, the second current I2A flows through the bypass circuit 2A, and the first current I1A flows through the light source 4A. The output current I3A is the sum of the first current I1A and the second current I2A. Moreover, the lighting circuit 1B outputs an output current I3B, the second current I2B flows through the bypass circuit 2B, and the first current I1B flows through the light source 4B. The output current I3B is the sum of the first current I1B and the second current I2B.

[0115] In the third embodiment, the second currents I2 and I2A are currents less than the lower limit of the control range of the output currents I3 and I3A of the corresponding lighting circuits 1 and 1A by the control circuit 3, as in the second embodiment. Unlike the second currents I2 and I2A, the second current I2B is a current equal to or greater than the lower limit of the control range of the output current I3B of the corresponding lighting circuit 1B by the control circuit 3. That is, if the minimum value of the range of variation of the second current I2B due to the individual difference of the lighting device 10B is the minimum second current, the minimum second current is a current equal to or greater than the above-mentioned lower limit. For example, when the above-mentioned lower limits of the three lighting circuits 1, 1A, and 1B are 3 mA, 3 mA, and 2 mA, respectively, the three second currents I2, I2A, and I2B are, for example, 2.5 mA, 2.5 mA, and 2.5 mA, respectively.

[0116] The illumination light of the illumination device 100B is composed of a composite light of the lights (i.e., red light, green light, and blue light) emitted from the multiple light sources 4, 4A, and 4B. In the third embodiment, it is possible to adjust the dimming rate and color temperature of the illumination light. In this case, the dimmer 6 outputs a dimming signal specifying a desired dimming rate of the illumination light and a color temperature signal specifying a desired color temperature of the illumination light to the control circuit 3. The control circuit 3 determines the dimming rate (individual dimming rate) of each light source 4, 4A, and 4B based on the dimming rate specified by the dimming signal and the color temperature specified by the color temperature signal. More specifically, the control circuit 3 is set with a correspondence relationship between the dimming rate and color temperature of the illumination light and the individual dimming rate of each light source 4, 4A, and 4B. The control circuit 3 determines the individual dimming rate of each light source 4, 4A, and 4B corresponding to the specified dimming rate and color temperature based on this correspondence relationship. Then, the control circuit 3 controls the output currents I3, I3A, I3B of the lighting circuits 1, 1A, 1B so that the light sources 4, 4A, 4B emit light at the determined individual dimming rates.

[0117] More specifically, the control circuit 3 of embodiment 3, like the control circuit 3 of embodiment 2, detects the output currents I3, I3A, I3B of the corresponding lighting circuits 1, 1A, 1B based on the voltages across the detection resistors R1, R21, R31, and controls the corresponding lighting circuits 1, 1A, 1B so that the detected output currents I3, I3A, I3B match target values ​​(target currents).

[0118] In the third embodiment, similarly to the first and second embodiments, the dimming rate of the illumination light of the lighting device 100B may be referred to as a "dimming rate", and the dimming rate of each of the light sources 4, 4A, and 4B may be referred to as an "individual dimming rate". In addition, the "desired dimming rate" may be referred to as a "specified dimming rate", and the "desired color temperature" may be referred to as a "specified color temperature".

[0119] (2) Characteristics of the lighting device Next, characteristics of the lighting device 10B according to the third embodiment will be described with reference to FIGS.

[0120] As Comparative Example 5, a case is assumed in which the set values ​​of the second currents I2, I2A, I2B flowing through the bypass circuits 2, 2A, 2B are set exactly to the lower limit (e.g., dimming rate 0.5%) in the control range of the output currents I3, I3A, I3B of the corresponding lighting circuits 1, 1A, 1B by the control circuit 3. In Comparative Example 5, a case is considered in which the designated dimming rate of the illumination light is a deeper dimming rate (e.g., 1%) and the designated color temperature of the illumination light is changed from 2000K to 4000K. In this case, the ideal change of the first currents I1, I1A, I1B flowing through each light source 4, 4A, 4B is as shown in FIG. 10. That is, the first current I1 flowing through the light source 4 emitting red light monotonically decreases from an individual dimming rate of 0.9% to an individual dimming rate of 0.5% when the designated color temperature of the illumination light is in the range from 2000K to 4000K. The first current I1A flowing through the light source 4A emitting green light increases monotonically from an individual dimming rate of 0.3 to an individual dimming rate of 0.8 when the designated color temperature of the illumination light is in the range from 2000 K to 4000 K. The first current I1B flowing through the light source 4B emitting blue light has an individual dimming rate of 0% when the designated color temperature of the illumination light is in a certain range W3 from 2000 K to a predetermined color temperature M1, and increases monotonically from an individual dimming rate of 0% to an individual dimming rate of 0.4% when the color temperature is in the range from M1 to 4000 K.

[0121] As Comparative Example 6, a case is assumed in which all of the set values ​​of the second currents I2, I2A flowing through the bypass circuits 2, 2A, 2B are set to less than the lower limit value in the control range of the output currents I3, I3A, I3B of the corresponding lighting circuits 1, 1A, 1B by the control circuit 3, as in the cases of the first and second embodiments. In Comparative Example 6, as in Comparative Example 5, a case is considered in which the designated color temperature of the illumination light is changed from 2000K to 4000K. In this case, as shown in FIG. 11, the first current I1B flowing through the light source 4B emitting blue light has an individual dimming rate of 0% from 2000K to a certain range W3 of the predetermined color temperature M1, and then increases monotonically after suddenly increasing with a gap G1 at the color temperature M1. That is, in the first current I1B, which starts to increase monotonically after the state of the individual dimming rate of 0% continues for a certain range W3, if the set value of the corresponding second current I2B is set to less than the lower limit value as described above, when the first current I1B starts to increase monotonically from the state of the individual dimming rate of 0% which continues for a certain range W3, it suddenly increases with a gap G1 and then starts to increase monotonically. Therefore, the gap G1 of the second current I2B makes the light source 4B suddenly bright. As a result, there is a problem that the color temperature of the illumination light changes significantly due to the gap G1 of the second current I2B.

[0122] In contrast, in the lighting device 10A, the set values ​​of the second currents I2 and I2A at which the gap G1 does not occur in Comparative Example 6 are set to less than the lower limit value of the control range of the output currents I3 and I3A of the corresponding lighting circuits 1 and 1A by the control circuit 3, as in the first and second embodiments. The set value of the second current I2B at which the gap G1 occurs in Comparative Example 6 is set to equal to or greater than the lower limit value of the control range of the output current I3B of the corresponding lighting circuit 1B by the control circuit 3. In this case, as shown in FIG. 12, in the first current I1B at which the state of the individual dimming rate of 0% continues for a certain range W3 and then starts to increase monotonically, as described above, the set value of the corresponding second current I2B is set to equal to or greater than the lower limit value, so that when the first current I1B starts to increase monotonically from the state of the individual dimming rate of 0% that continues for a certain range W3, it starts to increase smoothly and monotonically without the gap G1. Therefore, in the lighting device 100B, it is possible to suppress a large change in the color temperature of the illumination light due to the gap G1.

[0123] (3) Effects In the lighting device 10B according to the third embodiment, of the multiple bypass circuits 2, 2A, 2B, in the bypass circuit 2, 2A, the second current I2, I2A flowing through the bypass circuit 2, 2A is a current that is equal to or greater than the lower limit of the control range of the output current I3, I3A of the corresponding lighting circuit 1, 1A by the control circuit 3. Of the multiple bypass circuits 2, 2A, 2B, in the bypass circuit 2B, the second current I2B flowing through the bypass circuit 2B is a current that is equal to or greater than the lower limit of the control range of the output current I3B of the lighting circuit 1B by the control circuit 3.

[0124] According to this configuration, in illumination light composed of light emitted from a plurality of light sources 4, 4A, 4B, when the color temperature of the illumination light is changed at a deeper dimming rate, it is possible to prevent the light emitted from the light source 4B corresponding to the bypass circuit 2B from suddenly becoming brighter.

[0125] (Embodiment 4) A lighting device 10C and an illumination device 100C according to the fourth embodiment will be described with reference to Fig. 13. Regarding the lighting device 10C and the illumination device 100C according to the fourth embodiment, the same components as those of the lighting device 10 and the illumination device 100 according to the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted.

[0126] (1) Composition 13, the lighting device 100C according to the fourth embodiment differs from the lighting device 100A according to the second embodiment in that the lighting circuit 1A, the detection resistor R21, and the capacitor C21 are omitted, and the lighting circuit 1, the detection resistor R1, and the capacitor C1 are shared between the multiple light sources 4, 4A. Also, the lighting device 100C according to the fourth embodiment differs from the lighting device 100A according to the second embodiment in that the lighting device 100C according to the fourth embodiment further includes multiple switching elements Q2, Q22. Other than these points, the lighting device 100C according to the fourth embodiment is configured similarly to the lighting device 100A according to the second embodiment.

[0127] Therefore, the lighting device 100C includes a plurality of light sources 4, 4A that emit light of different colors, a lighting circuit 1, a detection resistor R1, a capacitor C1, a plurality of bypass circuits 2, 2A, and a plurality of switching elements Q2, Q22.

[0128] 13 are configured similarly to the light source 4, the lighting circuit 1, the bypass circuit 2, the detection resistor R1, and the capacitor C1 of embodiment 2. For this reason, detailed descriptions of the light source 4, the lighting circuit 1, the bypass circuit 2, the detection resistor R1, and the capacitor C1 will be omitted.

[0129] The light source 4A is configured similarly to the light source 4A of the embodiment 2. The anode of the light source 4A is connected to the first output terminal T1 of the lighting circuit 1. The cathode of the light source 4A is connected to the second output terminal T2 of the lighting circuit 1 via the detection resistor R1. That is, the multiple light sources 4, 4A are connected in parallel with each other and connected to the rear stage of the lighting circuit 1.

[0130] The bypass circuit 2A is configured similarly to the bypass circuit 2A of the second embodiment, and is connected in parallel to the light source 4A.

[0131] The switching elements Q2, Q22 correspond to the light sources 4, 4A. The switching elements Q2, Q22 correspond to the bypass circuits 2, 2A. The switching elements Q2, Q22 control the first currents I1, I1A flowing through the corresponding light sources 4, 4A to individually control the turning on and off of the corresponding light sources 4, 4A. In the fourth embodiment, the switching elements Q2, Q22 PWM-control the first currents I1, I1A flowing through the corresponding light sources 4, 4A. The switching elements Q2, Q22 are connected in series to the corresponding light sources 4, 4A. The switching elements Q2, Q22 are also connected in series to the corresponding bypass circuits 2, 2A. The switching elements Q2, Q22 are provided, for example, downstream of the corresponding light sources 4, 4A. The switching elements Q2, Q22 may be provided upstream of the corresponding light sources 4, 4A.

[0132] More specifically, the switching elements Q2, Q22 are, for example, MOSFETs. The switching elements Q2, Q22 have a first terminal, a second terminal, and a control terminal. In the fourth embodiment, since the switching elements Q2, Q22 are MOSFETs, the first terminal is a drain, the second terminal is a source, and the control terminal is a gate. The first terminals of the switching elements Q2, Q22 are connected to the cathodes of the corresponding light sources 4, 4A. The second terminals of the switching elements Q2, Q22 are connected to the second output terminal T2 of the lighting circuit 1 via the detection resistor R1. The control terminals of the switching elements Q2, Q22 are connected to the control circuit 3.

[0133] The lighting circuit 1 of the fourth embodiment outputs an output current I3C. The second current I2 flows through the bypass circuit 2, and the first current I1 flows through the light source 4. The second current I2A flows through the bypass circuit 2A, and the first current I1A flows through the light source 4A. The output current I3C is the sum of the first current I1, the first current I1A, the second current I2, and the second current I2A. The second currents I2 and I2A are currents less than the lower limit of the control range of the output current I3C of the lighting circuit 1 by the control circuit 3, similar to the second currents I2 and I2A of the second embodiment. That is, if the maximum value of the range of variation of the second currents I2 and I2A due to the individual difference of the lighting device 10C is the maximum second current, the maximum second current of the second currents I2 and I2A is a current less than the lower limit. In the fourth embodiment, the multiple second currents I2 and I2A are, for example, currents having the same set value.

[0134] The illumination light of the lighting device 100C is composed of a composite light of the lights emitted from the light sources 4 and 4A. In the fourth embodiment, it is possible to adjust the dimming rate and color temperature of the illumination light. In this case, the dimmer 6 outputs a dimming signal specifying a desired dimming rate of the illumination light and a color temperature signal specifying a desired color temperature of the illumination light to the control circuit 3. The control circuit 3 determines the dimming rate (individual dimming rate) of each light source 4 and 4A based on the dimming rate specified by the dimming signal and the color temperature specified by the color temperature signal. More specifically, the control circuit 3 has a correspondence relationship set between the dimming rate and color temperature of the illumination light and the individual dimming rate of each light source 4 and 4A. The control circuit 3 determines the individual dimming rate of each light source 4 and 4A corresponding to the specified dimming rate and color temperature based on this correspondence relationship. Then, the control circuit 3 controls the output current I3C of the lighting circuit 1 and PWM controls the switching elements Q2 and Q22 so that each light source 4 and 4A emits light at the determined individual dimming rate.

[0135] More specifically, the control circuit 3 of the fourth embodiment detects the output current I3C of the lighting circuit 1 based on the voltage across the detection resistor R1, and controls the corresponding lighting circuit 1 so that the detected output current I3C coincides with a target value (target current). Then, the control circuit 3 PWM-controls the switching elements Q2 and Q22 so that the first currents I1 and I1A each become the determined individual dimming ratio.

[0136] In the fourth embodiment, similarly to the second embodiment, the dimming ratio of the illumination light of the lighting device 100C may be referred to as a "dimming ratio," and the dimming ratio of each of the light sources 4 and 4A may be referred to as an "individual dimming ratio." Furthermore, the "desired dimming ratio" may be referred to as a "specified dimming ratio," and the "desired color temperature" may be referred to as a "specified color temperature."

[0137] (2) Effects In the lighting device 10C according to the fourth embodiment, the light source 4 is included in a plurality of light sources 4, 4A that emit light of different colors. The lighting device 10C includes a plurality of bypass circuits 2, 2A and a plurality of switching elements Q2, Q22. The plurality of bypass circuits 2, 2A include a bypass circuit 2, correspond to the plurality of light sources 4, 4A, and are connected in parallel to the corresponding light sources. The plurality of switching elements Q2, Q22 correspond to the plurality of light sources 4, 4A, are connected in series to the corresponding light sources, and control the current flowing to the corresponding light sources. The lighting circuit 1 supplies lighting power to the plurality of light sources 4, 4A. The control circuit 3 controls the lighting circuit 1 so that the output current I3C of the lighting circuit 1, which is the sum of the plurality of first currents I1, I1A flowing through the plurality of light sources 4, 4A and the plurality of second currents I2, I2A flowing through the plurality of bypass circuits 2, 2A, matches a target value. The control circuit 3 controls the plurality of switching elements Q2, Q22 to individually control the turning on and off of the plurality of light sources 4, 4A.

[0138] According to this configuration, in a configuration including a plurality of light sources 4, 4A, the lighting circuit 1 can be made common to the plurality of light sources 4, 4A.

[0139] (3) Modifications Modifications of the fourth embodiment will be described. In the following description, the same components as those of the lighting device 10A and the illumination device 100A according to the second embodiment will be denoted by the same reference numerals, and the description thereof may be omitted. In addition, the following modifications may be implemented in combination.

[0140] (3.1) Variation 1 In the fourth embodiment, the lighting device 100C includes two light sources 4 and 4A, two bypass circuits 2 and 2A, and two switching elements Q2 and Q22. However, the lighting device 100C may include three or more light sources, three or more bypass circuits, and three or more switching elements.

[0141] (3.2) Variation 2 In the fourth embodiment, the second currents I2, I2A flowing through the multiple bypass circuits 2, 2A are illustrated as having the same set value. However, the second currents I2, I2A flowing through the multiple bypass circuits 2, 2A may have different set values. In addition, when the lighting device 100C includes three or more bypass circuits, it is sufficient that the set value of at least one of the three or more second currents flowing through the three or more bypass circuits is different from the set values ​​of the remaining second currents.

[0142] (3.3) Variation 3 In the fourth embodiment, the case where both of the second currents I2 and I2A are currents less than the lower limit of the control range of the output current I3C of the lighting circuit 1 by the control circuit 3 is illustrated. However, as in the third embodiment, one of the second currents I2 and I2A may be a current less than the lower limit of the control range of the output current I3C of the lighting circuit 1 by the control circuit 3, and the remaining second current may be a current equal to or greater than the lower limit of the control range of the output current I3C of the lighting circuit 1 by the control circuit 3. In addition, when the lighting device 100C includes three or more bypass circuits, at least one of the three or more second currents flowing through the three or more bypass circuits may be a current less than the lower limit of the control range of the output current I3C of the lighting circuit 1 by the control circuit 3, and the remaining second currents may be a current equal to or greater than the lower limit of the control range of the output current I3C of the lighting circuit 1 by the control circuit 3.

[0143] (Embodiment 5) A lighting device 10D and an illumination device 100D according to the fifth embodiment will be described with reference to Fig. 14. Regarding the lighting device 10D and the illumination device 100D according to the fifth embodiment, the same components as those of the lighting device 10 and the illumination device 100 according to the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted.

[0144] A lighting device 10D according to the fifth embodiment differs from the lighting device 10 according to the first embodiment in that a bypass circuit 2D is provided instead of the bypass circuit 2.

[0145] As shown in Fig. 14, the lighting device 100D according to the fifth embodiment includes a lighting device 10D and a light source 4. As shown in Fig. 14, the lighting device 10D includes a lighting circuit 1, a bypass circuit 2D, a control circuit 3, a capacitor C1, and a detection resistor R1.

[0146] The bypass circuit 2D has a Zener diode (constant voltage diode) ZD1, a transistor Tr2, a first resistor R4, and a second resistor (resistor) R5.

[0147] The cathode of the Zener diode ZD1 is connected to the first output terminal T1 on the high potential side of the lighting circuit 1 via the first resistor R4. The anode of the Zener diode ZD1 is connected to the second output terminal T2 on the low potential side of the lighting circuit 1. That is, the series circuit of the Zener diode ZD1 and the first resistor R4 is connected between both ends (the first output terminal T1 and the second output terminal T2) of the lighting circuit 1. In addition, the series circuit of the Zener diode ZD1 and the first resistor R4 is connected in parallel with the light source 4.

[0148] The collector terminal of the transistor Tr1 is connected to the first output terminal T1. The emitter terminal of the transistor Tr2 is connected to the second output terminal T2 via the second resistor R5. That is, the second resistor R5 is connected between the output terminals (the first output terminal T1 and the second output terminal T2) of the lighting circuit 1. More specifically, the second resistor R5 is connected between the output terminals of the lighting circuit 1 via the transistor Tr2. In addition, the base terminal of the transistor Tr2 is connected to a connection point P2 between the cathode of the Zener diode ZD1 and the first resistor R4.

[0149] In the bypass circuit 2D, the Zener diode ZD1 has the function of matching the voltage V3 across the second resistor R5 to a target voltage. The target voltage is the voltage across the Zener diode ZD1 minus the base-emitter voltage of the transistor Tr2. This makes the voltage V3 across the second resistor R5 constant, and as a result, the second current I2 flowing through the bypass circuit 2D is also constant.

[0150] In a lighting device 10D according to the fifth embodiment, a bypass circuit 2D includes a resistor R5 and a Zener diode ZD1. The resistor R5 is connected between output terminals of the lighting circuit 1. The Zener diode ZD1 has a function of matching a voltage V3 across the resistor R5 to a target voltage.

[0151] According to this embodiment, regardless of the specifications of the light source 4, it is possible to pass a constant current (the second current I2) in parallel with the light source 4.

[0152] Also in the lighting device 10D according to the fifth embodiment, a bypass circuit 2D is connected in parallel with the light source 4. Therefore, even if a specification change occurs, such as a change in the number of light-emitting elements 41 constituting the light source 4 or a change in the illuminance of the light-emitting elements 41, a constant current (the second current I2) can be caused to flow by the bypass circuit 2D, which has the advantage of eliminating the need to change the circuit.

[0153] (Modification) The first to fifth embodiments are merely one of various embodiments of the present disclosure. Various modifications of the first to fifth embodiments are possible depending on the design and the like, as long as the object of the present disclosure can be achieved. Common modifications of the first to fifth embodiments are listed below. The modifications described below can be applied in appropriate combination.

[0154] In the first to fifth embodiments, the lighting devices 100, 100A, 100B, 100C, and 100D are architectural lighting devices (line lighting devices). However, the lighting devices 100, 100A, 100B, 100C, and 100D are not limited to architectural lighting devices such as stage lighting devices, and may be general lighting devices such as downlights.

[0155] In the first to fifth embodiments, the light source 4 has four light-emitting elements 41, but the light source 4 may have, for example, one, two, or three light-emitting elements 41, or may have five or more light-emitting elements 41. That is, the light source 4 only needs to have at least one LED. In the second and third embodiments, the light source 4A has four light-emitting elements 41A, but the light source 4A may have, for example, one, two, or three light-emitting elements 41A, or may have five or more light-emitting elements 41A. That is, the light source 4A only needs to have at least one LED. In the fourth embodiment, the light source 4B has four light-emitting elements 41B, but the light source 4B may have, for example, one, two, or three light-emitting elements 41B, or may have five or more light-emitting elements 41B. That is, the light source 4B only needs to have at least one LED.

[0156] In the first to fifth embodiments, the four light emitting elements 41 are connected in series, but the four light emitting elements 41 may be connected in parallel or in series-parallel, for example. In the second and third embodiments, the four light emitting elements 41A are connected in series, but the four light emitting elements 41A may be connected in parallel or in series-parallel, for example. In the fourth embodiment, the four light emitting elements 41B are connected in series, but the four light emitting elements 41B may be connected in parallel or in series-parallel, for example.

[0157] In the first to fourth embodiments, the transistor Tr1 as the amplifying element is an NPN transistor, but the transistor Tr1 is not limited to an NPN transistor, and may be, for example, a PNP transistor. Furthermore, the amplifying element may be a MOSFET. In the second and third embodiments, the transistor Tr21 as the amplifying element is an NPN transistor, but the transistor Tr21 is not limited to an NPN transistor, and may be, for example, a PNP transistor. Furthermore, the amplifying element may be a MOSFET. In the third embodiment, the transistor Tr31 as the amplifying element is an NPN transistor, but the transistor Tr31 is not limited to an NPN transistor, and may be, for example, a PNP transistor. Furthermore, the amplifying element may be a MOSFET. In the fifth embodiment, the transistor Tr2 as the amplifying element is not limited to an NPN transistor, and may be, for example, a PNP transistor. Furthermore, the amplifying element may be a MOSFET.

[0158] In the first to fifth embodiments, the detection resistor R1 is connected between the second output terminal T2 of the lighting circuit 1 and the second end of the capacitor C1, but the detection resistor R1 may be connected, for example, between the second end of the capacitor C1 and the cathode of the light source 4. In the second and third embodiments, the detection resistor R21 is connected between the second output terminal T22 of the lighting circuit 1A and the second end of the capacitor C21, but the detection resistor R21 may be connected, for example, between the second end of the capacitor C21 and the cathode of the light source 4A. In the third embodiment, the detection resistor R31 is connected between the second output terminal T32 of the lighting circuit 1B and the second end of the capacitor C31, but the detection resistor R31 may be connected, for example, between the second end of the capacitor C31 and the cathode of the light source 4B. (Aspect) The present specification discloses the following aspects.

[0159] The lighting device (10; 10D) of the first embodiment includes a lighting circuit (1), a bypass circuit (2; 2D), and a control circuit (3). The lighting circuit (1) supplies lighting power to the light source (4). The bypass circuit (2; 2D) is connected in parallel with the light source (4). The control circuit (3) controls the lighting circuit (1) so that an output current (I3) of the lighting circuit (1), which is the sum of a first current (I1) flowing through the light source (4) and a second current (I2) flowing through the bypass circuit (2), matches a target value. The second current (I2) flowing through the bypass circuit (2; 2D) is a current less than a lower limit value in a control range of the output current (I3) of the lighting circuit (1) by the control circuit (3).

[0160] According to this configuration, the second current (I2) flowing through the bypass circuit (2; 2D) is a current less than the lower limit of the control range of the output current of the lighting circuit (1) by the control circuit (3). Therefore, when the output current (I3) of the lighting circuit (1) is controlled to a current with a deeper dimming ratio, it is possible to prevent the light source (4) from being turned off without emitting light at the specified dimming ratio due to variations in the second current (I2) caused by individual differences in the lighting devices (10; 10D).

[0161] In the lighting device (10; 10D) of the second embodiment, the maximum value of the range of variation in the second current (I2:2D) due to individual differences in the lighting device (10) in the first embodiment is set as the maximum second current (I2_max). The maximum second current (I2_max) is a current less than the lower limit value.

[0162] According to this configuration, when the output current (I3) of the lighting circuit (1) is controlled to a current with a deeper dimming ratio, it is possible to further prevent the light source (4) from being turned off without emitting light at the specified dimming ratio due to variations in the second current (I2; 2D) caused by individual differences in the lighting device (10; 10D).

[0163] In the lighting device (10A; 10B) of the third aspect, in the first or second aspect, the light source (4) is included in a plurality of light sources (4, 4A; 4, 4A, 4B) that emit light of different colors. The lighting device (10A; 10B) includes a plurality of lighting circuits (1, 1A; 1, 1A, 1B) and a plurality of bypass circuits (2, 2A; 2, 2A, 2B). The plurality of lighting circuits (1, 1A; 1, 1A, 1B) include a lighting circuit (1), correspond to the plurality of light sources (4, 4A; 4, 4A, 4B), and supply lighting power to the corresponding light sources. The plurality of bypass circuits (2, 2A; 2, 2A, 2B) include a bypass circuit (2), correspond to the plurality of light sources (4, 4A; 4, 4A, 4B), and are connected in parallel with the corresponding light sources. A certain light source among the plurality of light sources (4, 4A; 4, 4A, 4B), a certain lighting circuit among the plurality of lighting circuits (1, 1A; 1, 1A, 1B), and a certain bypass circuit among the plurality of bypass circuits (2, 2A; 2, 2A, 2B) correspond to each other. A control circuit (3) controls the plurality of lighting circuits (1, 1A; 1, 1A, 1B) so that an output current (I3, I3A; I3, I3A, I3B) of the certain lighting circuit, which is a sum of a first current (I1, I1A; I1, I1A, I1B) flowing through the certain light source and a second current (I2, I2A; I2, I2A, I2B) flowing through the certain bypass circuit, matches a target value.

[0164] According to this configuration, in a lighting device (10A, 10B) that lights up a plurality of light sources (4, 4A; 4, 4A, 4B), when the output current (I3, I3A; I3, I3A, I3B) of any one of the lighting circuits (1, 1A; 1, 1A, 1B) is controlled to a current with a deeper dimming ratio, the corresponding light source (4, 4A; 4, 4A, 4B) can be prevented from being turned off without emitting light at the designated dimming ratio due to variations in the second current (I2, I2A; I2, I2A, I2B) due to individual differences in the lighting device (10A, 10B). This makes it possible to prevent the actual color temperature of the illumination light, which is composed of light emitted from the plurality of light sources (4, 4A; 4, 4A, 4B), from becoming a color temperature different from the designated color temperature when the illumination light is controlled to a deeper dimming ratio.

[0165] In the lighting device (10B) of the fourth aspect, the plurality of bypass circuits (2, 2A, 2B) in the third aspect include a bypass circuit (2B). The bypass circuit (2B) is a bypass circuit in which a second current (I2B) flowing through a certain bypass circuit (2B) is equal to or greater than a lower limit of a control range of an output current (I3B) of a certain lighting circuit (1B) by the control circuit (3).

[0166] According to this configuration, in illumination light constituted by light emitted from a plurality of light sources (4, 4A, 4B), when the color temperature of the illumination light is changed in a state of a deeper dimming ratio, it is possible to prevent the light emitted from the light source (4B) corresponding to the bypass circuit (2B) from suddenly becoming brighter.

[0167] In the lighting device (10A) of the fifth aspect, in the third or fourth aspect, the multiple bypass circuits (2, 2A) include a first bypass circuit (2) and a second bypass circuit (2A). A second current (I2) flowing through the first bypass circuit (2) is different from a second current (I2A) flowing through the second bypass circuit (2A).

[0168] According to this configuration, the second currents (I2, I2A) of the multiple bypass circuits (2, 2A) can be made different from each other.

[0169] In a lighting device (10C) of a sixth aspect, in any one of the first to fifth aspects, the light source (4) is included in a plurality of light sources (4, 4A) that emit light of different colors. The lighting device (10C) includes a plurality of bypass circuits (2, 2A) and a plurality of switching elements (Q2, Q22). The plurality of bypass circuits (2, 2A) include a bypass circuit (2), correspond to the plurality of light sources (4, 4A), and are connected in parallel to the corresponding light sources. The plurality of switching elements (Q2, Q22) correspond to the plurality of light sources (4, 4A), are connected in series to the corresponding light sources, and control the current flowing through the corresponding light sources. The lighting circuit (1) supplies lighting power to the plurality of light sources (4, 4A). The control circuit (3) controls the lighting circuit (1) so that an output current (I3C) of the lighting circuit (1), which is the sum of a plurality of first currents (I1, I1A) flowing through the plurality of light sources (4, 4A) and a plurality of second currents (I2, I2A) flowing through the plurality of bypass circuits (2, 2A), matches a target value. The control circuit (3) controls the plurality of switching elements (Q2, Q22) to individually control the turning on and off of the plurality of light sources (4, 4A).

[0170] According to this configuration, in a configuration including a plurality of light sources (4, 4A), the lighting circuit (1) can be made common to the plurality of light sources (4, 4A).

[0171] A lighting device (10; 10A; 10B; 10C: 10D) according to a seventh aspect is any one of the first to sixth aspects, in which the lighting circuit (1; 1, 1A; 1, 1A, 1B) has switching elements (Q1; Q1, Q21; Q1, Q21, Q31) and inductors (L1; L1, L21; L1, L21, L31). The control circuit (3) detects the current (I4) flowing through the inductors (L1; L1, L21; L1, L21, L31) as the output current (I3; I3, I3A; I3, I3A, I3B).

[0172] According to this embodiment, it is possible to suppress overshoot of the first current (I1; I1, I1A; I1, I1A, I1B) during startup and steady state.

[0173] A lighting device (10; 10A; 10B; 10C; 10D) according to an eighth aspect is any one of the first to seventh aspects, and further includes capacitors (C1; C1, C21; C1, C21, C31) and detection resistors (R1; R1, R21; R1, R21, R31). The capacitors (C1; C1, C21; C1, C21, C31) are connected between output terminals of the lighting circuits (1; 1, 1A; 1, 1A, 1B) between the lighting circuits (1; 1, 1A; 1, 1A, 1B) and the light sources (4; 4, 4A; 4, 4A, 4B). The detection resistors (R1; R1, R21; R1, R21, R31) are connected between the lighting circuit (1; 1, 1A; 1, 1A, 1B) and the capacitors (C1; C1, C21; C1, C21, C31) and detect the output currents (I3; I3, I3A; I3, I3A, IB, I3C). The control circuit (3) detects the current corresponding to the voltage (V2) between both ends of the detection resistors (R1; R1, R21; R1, R21, R31) as the output current (I3; I3, I3A; I3, I3A, IB; I3C).

[0174] According to this embodiment, by detecting a current corresponding to the voltage (V2) between both ends of the detection resistor (R1; R1, R21; R1, R21, R31), it is possible to detect the output current (I3; I3, I3A; I3, I3A, IB; I3C) of the lighting circuit (1; 1, 1A; 1, 1A, 1B).

[0175] A lighting device (10; 10A; 10B; 10C) according to a ninth aspect is any one of the first to eighth aspects, and the bypass circuit (2; 2, 2A; 2, 2A, 2B) has resistors (R2; R2, R22; R2, R22, R32) and operational amplifiers (OP1; OP1, OP21; OP1, OP21, OP31). The resistors (R2; R2, R22; R2, R22, R32) are connected between output terminals of the lighting circuit (1). The operational amplifiers (OP1; OP1, OP21; OP1, OP21, OP31) perform feedback control so that a reference voltage (Vref) input to a non-inverting input terminal and a voltage (V3) between both ends of the resistors (R2; R2, R22; R2, R222, R32) input to an inverting input terminal are equal to each other.

[0176] According to this embodiment, it is possible to flow a constant current (second current I2; I2, I2A; I2, I2A, I2B) in parallel with the light source (4; 4, 4A; 4, 4A, 4B) regardless of the specifications of the light source (4; 4, 4A; 4, 4A, 4B).

[0177] A lighting device (10D) according to a tenth aspect is any one of the first to eighth aspects, and the bypass circuit (2D) has a resistor (R5) and a Zener diode (ZD1). The resistor (R5) is connected between output terminals of the lighting circuit (1). The Zener diode (ZD1) has a function of matching a voltage (V3) between both ends of the resistor (R5) with a target voltage.

[0178] According to this embodiment, it is possible to pass a constant current (the second current I2) in parallel with the light source (4) regardless of the specifications of the light source (4).

[0179] A lighting device (10; 10A; 10B; 10C; 10D) according to an eleventh aspect is any one of the first to tenth aspects, in which the light source (4) has at least one LED (41). A forward voltage of the light source (4) is applied to the bypass circuit (2).

[0180] According to this embodiment, it is possible to apply a voltage equal to the forward voltage of the light source (4) to the bypass circuit (2).

[0181] An illumination device (100) according to a twelfth aspect includes the lighting device (10) according to any one of the first to eleventh aspects and a light source (4). The light source (4) has at least one LED (41).

[0182] According to this embodiment, for example, even if the specifications of the light source (4) are changed, a constant current (second current I2) can be caused to flow by the bypass circuit (2), so there is an advantage that no circuit change is required. [Explanation of symbols]

[0183] 1 Lighting circuit 2,2A,2B,2D Bypass circuit 3 Control Circuit 4,4A,4B light source 10, 10A, 10B, 10C, 10D Lighting device C1, C21, C31 capacitors L1, L21, L31 Inductors I1,I1A,I1B 1st current I2,I2A,I2B 2nd current I2_max Maximum 2nd current I3, I3A, I3B, I3C output current I4 current OP1, OP21, OP31 operational amplifiers Q1, Q21, Q31 Switching elements Q2, Q22 switching element R1, R21, R31 Detection resistors R2,R22,R32 resistance R5 resistance Voltage between both ends of V2 and V3 ZD1 Zener diode

Claims

1. A lighting circuit for supplying lighting power to the light source; a bypass circuit connected in parallel with the light source; a control circuit that controls the lighting circuit so that an output current of the lighting circuit, which is a sum of a first current flowing through the light source and a second current flowing through the bypass circuit, coincides with a target value; The second current flowing through the bypass circuit is a current less than a lower limit of a control range of the output current of the lighting circuit by the control circuit. Lighting device.

2. a maximum value of a range of variation in the second current due to individual differences of the lighting device is set as a maximum second current; The maximum second current is a current less than the lower limit value. The lighting device according to claim 1 .

3. The light source is included in a plurality of light sources that emit light of different colors, a plurality of lighting circuits each including the lighting circuit and corresponding to the plurality of light sources, the lighting circuits supplying lighting power to the corresponding light sources; a plurality of bypass circuits including the bypass circuit, corresponding to the plurality of light sources and connected in parallel with the corresponding light sources; a light source among the plurality of light sources, a lighting circuit among the plurality of lighting circuits, and a bypass circuit among the plurality of bypass circuits correspond to each other; the control circuit controls the plurality of lighting circuits so that the output current of the certain lighting circuit, which is the sum of the first current flowing through the certain light source and the second current flowing through the certain bypass circuit, coincides with a target value.

3. The lighting device according to claim 1 or 2.

4. the plurality of bypass circuits include a bypass circuit in which the second current flowing through the certain bypass circuit is a current equal to or greater than a lower limit of a control range of the output current of the certain lighting circuit by the control circuit; The lighting device according to claim 3.

5. the plurality of bypass circuits include a first bypass circuit and a second bypass circuit, the second current flowing through the first bypass circuit is different from the second current flowing through the second bypass circuit; The lighting device according to claim 3.

6. The light source is included in a plurality of light sources that emit light of different colors, a plurality of bypass circuits including the bypass circuit, each of which corresponds to the plurality of light sources and is connected in parallel with the corresponding light sources; a plurality of switching elements corresponding to the plurality of light sources, connected in series to the corresponding light sources, and controlling a current flowing through the corresponding light sources; the lighting circuit supplies lighting power to the plurality of light sources; the control circuit controls the lighting circuit so that the output current of the lighting circuit, which is a sum of a plurality of first currents flowing through the plurality of light sources and a plurality of second currents flowing through the plurality of bypass circuits, coincides with a target value; The control circuit controls the plurality of switching elements to individually control turning on and off the plurality of light sources.

3. The lighting device according to claim 1 or 2.

7. the lighting circuit includes a switching element and an inductor, The control circuit detects a current flowing through the inductor as the output current.

3. The lighting device according to claim 1 or 2.

8. a capacitor connected between the output terminal of the lighting circuit and the light source; a detection resistor connected between the lighting circuit and the capacitor to detect the output current; The control circuit detects, as the output current, a current corresponding to a voltage across the detection resistor.

3. The lighting device according to claim 1 or 2.

9. The bypass circuit includes: A resistor connected between output terminals of the lighting circuit; an operational amplifier that performs feedback control so that a reference voltage input to a non-inverting input terminal and a voltage across the resistor input to an inverting input terminal are equal to each other; 3. The lighting device according to claim 1 or 2.

10. The bypass circuit includes: A resistor connected between output terminals of the lighting circuit; and a Zener diode having a function of matching the voltage across the resistor to a target voltage.

3. The lighting device according to claim 1 or 2.

11. The light source includes at least one LED. A forward voltage of the light source is applied to the bypass circuit.

3. The lighting device according to claim 1 or 2.

12. A lighting device according to claim 1 or 2; The light source, The light source comprises at least one LED. Lighting equipment.

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