Lighting device and illumination device

Abstract

The purpose of the present disclosure is to easily achieve a more streamlined circuit. This lighting device lights a plurality of LED loads (20) having mutually different light emission colors. A control circuit (30) executes periodic switching of a first switching element (Q1) between an ON state and an OFF state such that energy is stored in a primary winding (L1) and the stored energy is transmitted to the secondary side of a transformer (Tr1). The control circuit (30) controls one or more corresponding second switching elements (Q2) among a plurality of second switching elements (Q2) so that, during an OFF period in which the first switching element (Q1) is in the OFF state, a current based on the energy on the secondary side of the transformer (Tr1) flows through one or more secondary-side circuits (B1) among a plurality of secondary-side circuits (B1), thereby turning on / off, or changing the dimming rate of, one or more corresponding LED loads (20) among the plurality of LED loads (20).

Description

Lighting device and illumination device

[0001] This disclosure relates to lighting devices and lighting devices. More specifically, this disclosure relates to a lighting device for lighting a plurality of LED (Light Emitting Diode) loads having different light-emitting colors, and a lighting device equipped with said lighting device.

[0002] Patent Document 1 discloses an invention relating to an LED lighting device. This LED lighting device comprises a power supply circuit, a selector circuit, and a control circuit. The selector circuit sequentially selects one LED load from a plurality of LED loads having red, green, blue, and white light-emitting colors, thereby supplying power to the selected LED load from the power supply circuit. The control circuit controls the selection of the selector circuit so that within the cycle in which the selection of the plurality of LED loads is completed, at least two power supply sections from which power is supplied from the power supply circuit to each of the plurality of LED loads are consecutive. Patent Document 1 describes that the configuration of the LED lighting device can reduce color flicker that tends to occur when the illumination light is dimmed by dimming.

[0003] Japanese Patent Publication No. 2019-204696

[0004] Incidentally, with respect to multiple LED loads having different light-emitting colors (e.g., red, blue, and green), the voltage drop values ​​and current values ​​(required for illumination) differ among the red, blue, and green LED elements. Therefore, it is difficult to control the illumination using the same constant current circuit. In particular, in lighting devices used for stage lighting, the number of LED elements increases, and the same constant current circuit cannot absorb the differences in voltage drop values ​​and current values, which can result in energy being released as heat. In other words, energy loss becomes large, requiring a dedicated constant current circuit for each color, which can lead to increased size and cost. The LED lighting device described in Patent Document 1 uses a selector circuit to control the illumination of multiple LED loads, but similarly, when the number of LED elements increases, there is a problem of increased energy loss. As a result, there is a desire for a more rationalized circuit that can suppress energy loss.

[0005] This disclosure is made in view of the above-mentioned reasons and aims to provide a lighting device and a lighting apparatus that facilitate the realization of a more streamlined circuit.

[0006] A lighting device according to one aspect of the present disclosure lights up a plurality of LED loads having different light-emitting colors. The lighting device comprises a transformer having a primary winding and a plurality of secondary windings, a primary circuit, a plurality of secondary circuits, and a control circuit. The primary circuit has a first switching element connected in series with the primary winding and is electrically connected to a DC power supply. The plurality of secondary circuits each have a plurality of second switching elements and each supplies current to the plurality of LED loads. The control circuit controls the switching operation by individually outputting drive signals to the first switching element and the plurality of second switching elements. The plurality of second switching elements are each connected in series with the plurality of secondary windings. The control circuit periodically switches the first switching element between an on state and an off state so as to store energy in the primary winding using power from the DC power supply and to transmit the stored energy to the secondary side of the transformer. During the off-period when the first switching element is in the off state, the control circuit controls one or more of the multiple second switching elements to control one or more of the multiple second switching elements so that a current based on the energy on the secondary side of the transformer flows to one or more of the multiple secondary circuits, thereby turning on / off or changing the dimming rate of one or more of the multiple LED loads.

[0007] A lighting device according to one aspect of this disclosure comprises the above-described lighting device and the plurality of LED loads.

[0008] Figure 1 is a block diagram of a lighting device equipped with a lighting device according to an embodiment. Figure 2 is a circuit diagram of the LED driver in the lighting device. Figure 3 is a waveform diagram of the drive signal and the current flowing through the LED load based on operation example 1 in the lighting device. Figure 4 is a waveform diagram of the drive signal and the current flowing through the LED load based on operation example 2 in the lighting device. Figure 5 is a waveform diagram of the drive signal and the current flowing through the LED load based on operation example 3 in the lighting device.

[0009] The lighting device and illumination device according to the embodiment will be described below with reference to the drawings.

[0010] (Embodiment) (1) Overview First, an overview of the lighting device 1 and lighting device 100 according to this embodiment will be described with reference to Figures 1 and 2.

[0011] As shown in Figure 1, the lighting device 1 according to this embodiment is configured to light up a light source unit 2. The light source unit 2 includes a plurality of LED loads 20 having different light-emitting colors. In other words, the lighting device 1 lights up a plurality of LED loads 20 having different light-emitting colors.

[0012] In this embodiment, as an example, it is assumed that the multiple LED loads 20 consist of a red LED load 21, a green LED load 22, and a blue LED load 23, each having one of the three primary colors of light: red, green, and blue. In Figure 2, the red LED load 21, green LED load 22, and blue LED load 23 are denoted as "LED-R," "LED-G," and "LED-B," respectively.

[0013] The lighting device 100 according to this embodiment comprises a lighting device 1 and a plurality of LED loads 20. The lighting device 100 equipped with the lighting device 1 can be applied as a lighting device for multi-color lighting in, for example, stores, buildings, bridges, exhibition halls, art museums, museums, stadiums (baseball fields, soccer fields, etc.), concert venues, or event venues.

[0014] Each LED load 20 includes one or more LED elements (connected in series). The number of LED elements in multiple LED loads 20 may be the same, different, or partially the same and partially different. In this embodiment, as an example, assuming that the lighting device 100 is used as a lighting device for multi-color lighting effects, each LED load 20 may include tens to hundreds of LED elements.

[0015] In the following, the LED element of the red LED load 21 may be referred to as the red LED element D1 (see Figure 1), the LED element of the green LED load 22 as the green LED element D2 (see Figure 1), and the LED element of the blue LED load 23 as the blue LED element D3 (see Figure 1).

[0016] The lighting device 1 according to this embodiment (see Figure 1) comprises a transformer Tr1 having a primary winding L1 and a plurality of secondary windings L2, a primary circuit A1, a plurality of secondary circuits B1, and a control circuit 30, as shown in Figure 2. In the example in Figure 2, the number of secondary windings L2 and the number of secondary circuits B1 are three, the same as the number of LED loads 20.

[0017] The primary circuit A1 has a first switching element Q1 connected in series with the primary winding L1, and a DC power supply V ＤＣ It is electrically connected to the DC power supply V ＤＣ The first switching element Q1 is periodically switched between the on and off states so that energy is stored in the primary winding L1 using the power from the transformer Tr1, and the stored energy is transferred to the secondary side of the transformer Tr1.

[0018] During an off period T2 (see FIGS. 3 to 5) in which the first switching element Q1 is in an off state, the control circuit 30 controls one or more corresponding second switching elements Q2 among the plurality of second switching elements Q2 so that a current based on the energy on the secondary side of the transformer Tr1 flows through one or more of the plurality of secondary side circuits B1. By controlling the corresponding one or more second switching elements Q2, the control circuit 30 turns on / off or changes the dimming ratio of the corresponding one or more LED loads 20 among the plurality of LED loads 20.

[0019] According to the configuration of the lighting device 1, for example, by adjusting the ratio of the number of turns of the secondary winding L2 corresponding to each LED load 20 with respect to the number of turns of the primary winding L1, it becomes easier to absorb differences in voltage drop values and current values (required for lighting) between LED elements with different emission colors. Therefore, energy loss can be suppressed. Also, compared to the case of preparing a constant current circuit dedicated to each color, an increase in size and cost can be suppressed. As a result, the lighting device 1 has the advantage of being able to more easily realize a more rationalized circuit.

[0020] Further, by including the lighting device 1, the lighting device 100 can more easily realize a more rationalized circuit.

[0021] (2) Details Next, each component of the lighting device 100 according to the present embodiment will be described with reference to FIGS. 1 and 2.

[0022] As shown in FIG. 1, the lighting device 100 according to the present embodiment includes a lighting device 1 and a light source unit 2. The lighting device 100 further includes a housing that houses the lighting device 1 and the light source unit 2, and a cover member having light transmissivity. The cover member is held by the housing so as to guide the illumination light emitted from the light source unit 2 to the outside of the housing.

[0023] (2.1) Light Source Unit The light source unit 2 includes a red LED load 21, a green LED load 22, and a blue LED load 23 as a plurality of LED loads 20 (LED load group) having different emission colors from each other.

[0024] The red LED load 21 includes, for example, a plurality of red LED elements D1 connected in series. The green LED load 22 includes, for example, a plurality of green LED elements D2 connected in series. The blue LED load 23 includes, for example, a plurality of blue LED elements D3 connected in series. The plurality of LED elements of each LED load 20 are not limited to being connected in series, and may be configured by being combined in parallel or in series-parallel.

[0025] Here, assuming that the lighting device 100 is applied as a lighting device for multi-color stage lighting, each LED load 20 includes about several tens to several hundreds of LED elements. That is, the number of red LED elements D1, green LED elements D2, and blue LED elements D3 is all about several tens to several hundreds. The LED elements of each LED load 20 are, for example, so-called light-emitting diodes. In particular, it is assumed that the LED elements of each LED load 20 are so-called micro LEDs.

[0026] Both ends of each of the red LED load 21, the green LED load 22, and the blue LED load 23 are electrically connected to the LED driver 3 (described later) of the lighting device 1.

[0027] The light source unit 2 further includes one or more mounting substrates (printed wiring boards) on which a plurality of LED elements (D1 to D3) are mounted. In addition, the light source unit 2 may further include a heat dissipation member that releases heat generated by the plurality of LED elements (D1 to D3) to the outside, and a lens block that condenses light from the plurality of LED elements (D1 to D3). The heat dissipation member can be formed of a material with high heat dissipation (for example, a plate material such as aluminum or an aluminum alloy).

[0028] (2.2) Lighting device As shown in FIG. 1, the lighting device 1 includes an LED driver 3, a rectifier circuit 4, a PFC (Power Factor Correction) circuit 5, a smoothing capacitor C1, and a dimming control circuit 6.

[0029] The rectifier circuit 4 is composed of, for example, a diode bridge. As shown in Figure 1, the input terminal of the rectifier circuit 4 is electrically connected to an AC power supply AC1 (for example, commercial power supply), and it full-wave rectifies the AC voltage input from the AC power supply AC1 and outputs the rectified pulsating voltage from its output terminal. An input filter circuit may be provided before the rectifier circuit 4 to remove unwanted frequency components such as noise from the AC power of the AC power supply AC1.

[0030] The PFC circuit 5 is a buck-boost converter, also known as a step-up / step-down chopper, configured to improve the power factor by boosting (or stepping down) the input voltage output from the output terminals of the rectifier circuit 4 to a desired voltage. The PFC circuit 5 includes switching elements, inductors, and diodes. The PFC circuit 5 provides (outputs) DC power to the subsequent LED driver 3.

[0031] The smoothing capacitor C1 is connected in parallel with the PFC circuit 5. Both ends of the smoothing capacitor C1 are electrically connected to the pair of output terminals of the PFC circuit 5. The smoothing capacitor C1 receives the DC voltage (i.e., the DC power supply V) output from the PFC circuit 5. ＤＣ The power (from) is smoothed. As a result, the smoothed DC voltage is input to the LED driver 3.

[0032] The dimming control circuit 6 receives an input signal from an external device, such as a wall switch or dimming controller, via a communication line (which may be wireless), to specify whether to turn the lighting device 100 on or off, or to specify the dimming level. Based on this input signal, the dimming control circuit 6 generates a PWM (Pulse Width Modulation) control signal and outputs it to the LED driver 3.

[0033] The LED driver 3 includes a computer system having one or more processors and memory. At least some of the functions of the LED driver 3 (for example, the functions of the control circuit 30 described later) are realized by the computer system's processor executing a program stored in the computer system's memory. The program may be stored in memory, provided via a telecommunication line such as the Internet, or provided on a non-temporary recording medium such as a memory card.

[0034] The LED driver 3 performs constant current control to light up multiple LED loads 20 (LED load group), namely a red LED load 21, a green LED load 22, and a blue LED load 23.

[0035] As shown in Figure 2, the LED driver 3 comprises a transformer Tr1 having a primary winding L1 and a plurality of secondary windings L2, a primary side circuit A1, a plurality of secondary side circuits B1, and a control circuit 30.

[0036] The primary circuit A1 has a first switching element Q1 (semiconductor switch element) connected in series with the primary winding L1 of the transformer Tr1. The primary circuit A1 is powered by a DC power supply V ＤＣ It is electrically connected to the DC power supply V in Figure 2. ＤＣ As mentioned above, this corresponds to the power supply that provides the DC voltage smoothed by the smoothing capacitor C1 from the PFC circuit 5.

[0037] The primary winding L1 has a first end and a second end. The first end of the primary winding L1 is connected to a DC power supply V ＤＣ It is connected to the high-potential side.

[0038] The first switching element Q1 is, for example, a field-effect transistor and has a gate terminal (control terminal), a source terminal, and a drain terminal. The first switching element Q1 is, for example, an n-channel MOSFET, where the drain terminal is the high-potential terminal and the source terminal is the low-potential terminal.

[0039] The gate terminal (control terminal) of the first switching element Q1 is electrically connected to the control circuit 30. The drain terminal of the first switching element Q1 is electrically connected to the second end of the primary winding L1. The source terminal of the first switching element Q1 is connected to the DC power supply V ＤＣ It is connected to the low-potential side.

[0040] The first switching element Q1 performs switching operations in accordance with the drive signal S1 (see Figure 2) input from the control circuit 30 to the gate terminal. In the primary circuit A1, when the first switching element Q1 is ON, the DC power supply V ＤＣ Due to the DC voltage from the source, energy is stored in the primary winding L1 of transformer Tr1. Then, when the first switching element Q1 is switched to the off state, the stored energy is transferred to the secondary side of transformer Tr1.

[0041] Each of the multiple secondary circuits B1 has a plurality of second switching elements Q2 (semiconductor switching elements). In this embodiment, as an example, the plurality of secondary circuits B1 are composed of three secondary circuits B11, B12, and B13 that correspond one-to-one with a red LED load 21, a green LED load 22, and a blue LED load 23, respectively. The secondary circuits B11, B12, and B13 each have second switching elements Q21, Q22, and Q23, respectively.

[0042] Multiple second switching elements Q2 are each connected in series with multiple secondary windings L2. In this embodiment, as an example, the multiple secondary windings L2 are composed of three secondary windings L21, L22, and L23 that correspond one-to-one with a red LED load 21, a green LED load 22, and a blue LED load 23, respectively.

[0043] Each of the secondary circuits B11, B12, and B13 supplies current to the corresponding LED load 20. The anode terminal of the red LED load 21 is electrically connected to the high-potential terminal of secondary circuit B11, and the cathode terminal of the red LED load 21 is electrically connected to the low-potential terminal of secondary circuit B11. Similarly, the anode terminal of the green LED load 22 is electrically connected to the high-potential terminal of secondary circuit B12, and the cathode terminal of the green LED load 22 is electrically connected to the low-potential terminal of secondary circuit B12. Furthermore, the anode terminal of the blue LED load 23 is electrically connected to the high-potential terminal of secondary circuit B13, and the cathode terminal of the blue LED load 23 is electrically connected to the low-potential terminal of secondary circuit B13.

[0044] Each second switching element Q2 is, for example, a field-effect transistor and has a gate terminal (control terminal), a source terminal, and a drain terminal. Each second switching element Q2 is, for example, an n-channel MOSFET, with the drain terminal being the high-potential terminal and the source terminal being the low-potential terminal. The gate terminal (control terminal) of each second switching element Q2 is electrically connected to the control circuit 30.

[0045] Each of the secondary windings L21, L22, and L23 has a first end and a second end. The first end of secondary winding L21 is electrically connected to the cathode terminal of the red LED load 21. The first end of secondary winding L22 is electrically connected to the cathode terminal of the green LED load 22. The first end of secondary winding L23 is electrically connected to the cathode terminal of the blue LED load 23. The drain terminal of the second switching element Q21 is electrically connected to the second end of secondary winding L21. The drain terminal of the second switching element Q22 is electrically connected to the second end of secondary winding L22. The drain terminal of the second switching element Q23 is electrically connected to the second end of secondary winding L23.

[0046] The source terminal of the second switching element Q21 is electrically connected to the anode terminal of the red LED load 21. Also, the source terminal of the second switching element Q22 is electrically connected to the anode terminal of the green LED load 22. Also, the source terminal of the second switching element Q23 is electrically connected to the anode terminal of the blue LED load 23.

[0047] The second switching elements Q21, Q22, and Q23 perform switching operations according to drive signals S21, S22, S23 (see FIG. 2) input from the control circuit 30 to their gate terminals. For example, when the first switching element Q1 of the primary circuit A1 switches from the on state to the off state and the energy stored in the primary winding L1 of the transformer Tr1 is released, an induced electromotive force is generated on each secondary winding L2 side. The generated induced electromotive force becomes power according to the ratio of the number of turns of each secondary winding L2 to the number of turns of the primary winding L1. At that time, when any second switching element Q2 of the secondary circuits B11 to B13 switches from the off state to the on state, a current based on the induced electromotive force flows through the corresponding LED load 20. When the second switching element Q21 becomes the on state, a current i Ｒ (see FIG. 2) flows through the red LED load 21. Also, when the second switching element Q22 becomes the on state, a current i Ｇ (see FIG. 2) flows through the green LED load 22. Also, when the second switching element Q23 becomes the on state, a current i Ｂ (see FIG. 2) flows through the blue LED load 23. That is, the DC voltage from the DC power supply V ＤＣ is, for example, stepped down according to the ratio of the number of turns of each secondary winding L2 to the number of turns of the primary winding L1, and a current based on the stepped-down voltage flows through the corresponding LED load 20.

[0048] In short, the primary circuit A1 and each secondary circuit B1 function as, for example, an isolated flyback converter.

[0049] The control circuit 30 controls the switching operation by individually outputting drive signals to the first switching element Q1 and the plurality of second switching elements Q2. In this embodiment, as an example, the control circuit 30 controls the switching operation by individually outputting drive signals S1 and S21 to S23 to the first switching element Q1 and the second switching elements Q21 to Q23.

[0050] The control circuit 30 generates drive signals S1, S21 to S23 based on the PWM control signal input from the dimming control circuit 6 to turn on / off the red LED load 21, green LED load 22, and blue LED load 23, or to change the dimming rate.

[0051] The control circuit 30 stores energy in the primary winding L1 and transmits a drive signal S1 to the first switching element Q1 to transfer the stored energy to the secondary side of the transformer Tr1, thereby periodically switching the first switching element Q1 between the on and off states.

[0052] During the ON period T1 (see Figures 3 to 5) when the first switching element Q1 is ON, the control circuit 30 controls the first switching element Q1 to store energy in the primary winding L1. During the OFF period T2 (see Figures 3 to 5) when the first switching element Q1 is OFF, the control circuit 30 controls one or more corresponding second switching elements Q2 to one or more of the multiple secondary circuits B1 so that a current based on the energy on the secondary side of the transformer Tr1 flows through them. By controlling the one or more corresponding second switching elements Q2, the control circuit 30 turns on / off or changes the dimming rate of one or more corresponding LED loads 20.

[0053] (2.3) Operation Example 1 of the Lighting Device Below, Operation Example 1 of the lighting device 1 will be explained with reference to Figure 3. Operation Example 1 is a basic operation example of the lighting device 1. Operation Examples 2 and 3, which will be described later, are application examples of Operation Example 1.

[0054] In Operation Example 1, the control circuit 30 sequentially selects one of the multiple second switching elements Q2 and turns it on at each periodic off-period T2 of the first switching element Q1, thereby sequentially lighting up multiple LED loads 20.

[0055] The upper part of Figure 3 shows the signal waveforms of the drive signals S1 and S21-S23 input to the first switching element Q1 and the second switching elements Q21-Q23, respectively. In Figure 3, to make it easier to identify the corresponding switching elements, the signal waveform of drive signal S1 is labeled "Q1," and the signal waveforms of drive signals S21-S23 are labeled "Q21," "Q22," and "Q23," respectively. Furthermore, when the signal level of the voltages of drive signals S1 and S21-S23 is at a High level, the corresponding switching element is turned on, and when it is at a Low level, the corresponding switching element is turned off, hence the labels "On" and "Off."

[0056] Furthermore, the lower part of Figure 3 shows the current i flowing through the primary circuit A1. ｐ The signal waveform, the current i flowing through the red LED load 21. Ｒ The signal waveform, the current i flowing through the green LED load 22. Ｇ The signal waveform, the current i flowing through the blue LED load 23. Ｂ The signal waveform is shown.

[0057] As shown in Figure 3, the first switching element Q1 periodically performs on / off switching operations based on the drive signal S1 from the control circuit 30. In other words, the first switching element Q1 alternates between an on period T1 and an off period T2.

[0058] For the sake of explanation, the on-period T1 and off-period T2 allocated to correspond to the red LED load 21 will be referred to as on-period T11 and off-period T21. Similarly, the on-period T1 and off-period T2 allocated to correspond to the green LED load 22 will be referred to as on-period T12 and off-period T22. Furthermore, the on-period T1 and off-period T2 allocated to correspond to the blue LED load 23 will be referred to as on-period T13 and off-period T23.

[0059] In other words, during the ON period T11, the ON state of the first switching element Q1 causes current i ｐ A current flows, and energy is stored in the primary winding L1. Then, during the off period T21, the second switching element Q21 corresponding to the red LED load 21 is controlled to switch from the off state to the on state, and a current i based on the energy stored during the on period T11 immediately preceding the off period T21 flows. Ｒ This is supplied to the red LED load 21.

[0060] Next, during the ON period T12, the current i is generated by the ON state of the first switching element Q1. ｐ A current flows, and energy is stored in the primary winding L1. Then, during the off period T22, the second switching element Q22 corresponding to the green LED load 22 is controlled to switch from the off state to the on state, and a current i based on the energy stored during the on period T12 immediately preceding the off period T22 flows. Ｇ This is supplied to the green LED load 22.

[0061] Next, during the ON period T13, the current i is generated by the ON state of the first switching element Q1. ｐ A current flows, and energy is stored in the primary winding L1. Then, during the off period T23, the second switching element Q23 corresponding to the blue LED load 23 is controlled to switch from the off state to the on state, and a current i based on the energy stored during the on period T13 immediately preceding the off period T23 flows. Ｂ This is supplied to the blue LED load 23.

[0062] Then, during the ON period T11, the current i is generated due to the ON state of the first switching element Q1. ｐ As current flows, energy is stored in the primary winding L1, and during the off period T21, current i Ｒ This is supplied to the red LED load 21.

[0063] In this operation example 1, under the control of the control circuit 30, one of the second switching elements Q21 to Q23 is sequentially selected and switched from the off state to the on state at each periodic off period T2 of the first switching element Q1. As a result, the current i is applied to the red LED load 21, the green LED load 22, and the blue LED load 23.Ｒ , current i Ｇ , current i Ｂ The LEDs are supplied and lit sequentially in a cyclical manner. Therefore, lighting control related to on / off or dimming rate can be achieved more efficiently for the red LED load 21, green LED load 22, and blue LED load 23.

[0064] Since the on-period T1 and off-period T2 are relatively short, the illumination from the lighting device 100 operating as in Operation Example 1 may appear to the naked eye as if all three LEDs—red LED load 21, green LED load 22, and blue LED load 23—are continuously lit.

[0065] By the way, in the example in Figure 3, the proportion of time (pulse duration) during which the second switching element Q2 is ON (duty cycle) during the OFF period T2 of the first switching element Q1 is 100%. For example, the dimming rate may be changed by repeatedly switching the second switching element Q2 on and off during the OFF period T2 to make the duty cycle less than 100%.

[0066] (2.4) Operation Example 2 of the Lighting Device Below, Operation Example 2 of the lighting device 1 will be explained with reference to Figure 4. Note that since Operation Example 2 is an application of Operation Example 1, explanations of points common to Operation Example 1 will be omitted as appropriate.

[0067] The upper part of Figure 4 shows the signal waveforms of the drive signals S1 and S21-S23 input to the first switching element Q1 and the second switching elements Q21-Q23, respectively, similar to Figure 3. The lower part of Figure 4 also shows the current i, similar to Figure 3. ｐ , current i Ｒ , current i Ｇ , current i Ｂ The signal waveform is shown.

[0068] In operation example 2, the second switching element Q2 of the secondary circuit B1 corresponding to a certain LED load 20 among the multiple LED loads 20 is assigned to be ON during predetermined off periods T2 that occur sequentially within the periodic off periods T2 of the first switching element Q1. When it is not necessary to supply current to a certain LED load 20, the control circuit 30 maintains the second switching element Q2 in the OFF state during the predetermined off period T2.

[0069] Here, as an example, we assume that "a certain LED load 20" is a green LED load 22, but it is not limited to a green LED load 22; it could also be a red LED load 21 or a blue LED load 23.

[0070] For example, the green LED load 22 corresponding to "a certain LED load 20" is assigned to be ON during sequentially occurring off periods T22 (a predetermined off period T2), as explained in Operation Example 1 (see Figure 3). Based on the PWM control signal from the dimming control circuit 6, the current i to the green LED load 22 is controlled. Ｇ If the supply is not required (i.e., the green LED load 22 does not need to be lit), the control circuit 30 maintains the second switching element Q22 in the off state during the off period T22 (see Figure 4).

[0071] In operation example 2, if it is not necessary to supply current to a certain LED load 20, the control circuit 30 keeps the first switching element Q1 in the off state during the ON period T1 of the first switching element Q1 which was assigned to supply current to the LED load 20, thereby suspending the accumulation of energy in the primary winding L1.

[0072] In other words, in the example in Figure 4, the current i to the green LED load 22 during each off period T22 Ｇ During the ON period T12 immediately preceding the OFF period T22, which was allocated for the supply of current i, the control circuit 30 keeps the first switching element Q1 in the OFF state. Therefore, in each ON period T12, the current i ｐ No current is flowing, and in each off period T22, current i Ｇ It's not flowing.

[0073] In this operation example 2, when it is not necessary to supply current to a certain LED load 20 (for example, a green LED load 22), the control circuit 30 maintains the first switching element Q1 in the off state during the corresponding on period T1. In other words, for an off period T2 in which it is not necessary to light up a certain LED load 20, the control circuit 30 maintains the first switching element Q1 in the off state during the on period T1 immediately preceding the off period T2. As a result, not only is the LED load 20 turned off, but power loss associated with the switching operation of the first switching element Q1 can also be reduced.

[0074] (2.5) Operation Example 3 of the Lighting Device Below, Operation Example 3 of the lighting device 1 will be explained with reference to Figure 5. Note that since Operation Example 3 is an application of Operation Example 1, explanations of points common to Operation Example 1 will be omitted as appropriate.

[0075] The upper part of Figure 5 shows the signal waveforms of the drive signals S1 and S21-S23 input to the first switching element Q1 and the second switching elements Q21-Q23, respectively, similar to Figure 3. The lower part of Figure 5 also shows the current i, similar to Figure 3. ｐ , current i Ｒ , current i Ｇ , current i Ｂ The signal waveform is shown.

[0076] In Operation Example 3, similar to Operation Example 2, the second switching element Q2 of the secondary circuit B1 corresponding to a certain LED load 20 among the multiple LED loads 20 is assigned to be ON during predetermined off periods T2 that occur sequentially within the periodic off periods T2 of the first switching element Q1. When it is not necessary to supply current to a certain LED load 20, the control circuit 30 maintains the second switching element Q2 in the OFF state during the predetermined off period T2.

[0077] Here, as in Operation Example 2, we assume that "a certain LED load 20" is a green LED load 22, but it is not limited to a green LED load 22; it could also be a red LED load 21 or a blue LED load 23.

[0078] For example, the green LED load 22 corresponding to "a certain LED load 20" is assigned to be ON during sequentially occurring off periods T22 (a predetermined off period T2), as explained in operation examples 1 and 2 (see Figure 3). Here, for example, based on the PWM control signal from the dimming control circuit 6, the current i to the green LED load 22 is controlled. Ｇ If the supply is not required, the control circuit 30 maintains the second switching element Q22 in the off state during the off period T22 (see Figure 5).

[0079] However, in operation example 3, unlike operation example 2, the off period T22 is allocated to a period for supplying current to another LED load 20. That is, in operation example 3, if it is not necessary to supply current to a certain LED load 20, the control circuit 30 turns on the second switching element Q2 of the secondary circuit B1 corresponding to that other LED load 20 so that current is supplied to another LED load 20 among the multiple LED loads 20 other than the one in question during the predetermined off period T2.

[0080] In the example shown in Figure 5, the current i supplied to the green LED load 22 during each off period T22 is shown. Ｇ During the ON period T12 immediately preceding the OFF period T22, which was allocated for the supply of current, the control circuit 30 switches the first switching element Q1 to the ON state. In other words, as in operation example 1, energy is stored during each ON period T12. However, the energy stored during the ON period T12 is used during the OFF period T22 to supply current to another LED load 20 (red LED load 21 in the example of Figure 5), rather than the green LED load 22. Therefore, the second switching element Q21 is switched to the ON state not only during each OFF period T21 but also during each OFF period T22. As a result, the current i ｐ A current is flowing, and in each off period T22, the current i Ｇ No current is flowing, but current i Ｒ It's playing.

[0081] Thus, in operation example 3, when it is not necessary to supply current to a certain LED load 20 (for example, a green LED load 22), the corresponding off period T2 is allocated to supplying current to another LED load 20 (for example, a red LED load 21). In other words, the off period T2 during which it is not necessary to light up a certain LED load 20 is allocated to the period during which that other LED load 20 is lit. As a result, the period during which that other LED load 20 is lit increases, meaning that the output pulses based on the switching operation of the first switching element Q1 are used more often to light up that other LED load 20, and the illuminance based on the light emitted by that other LED load 20 can be increased.

[0082] Incidentally, if only one color (for example, only one of red, green, and blue) needs to be lit, then during all off periods T2 from T21 to T23, only the second switching element Q2 corresponding to the single-color LED load 20 may be switched to the ON state. By concentrating all of the output pulses based on the switching operation of the first switching element Q1 on a single color, the illuminance of that single color can be further increased.

[0083] Alternatively, if only a single color needs to be illuminated, the second switching element Q2 corresponding to the single-color LED load 20 may be switched to the ON state only during the OFF period T2 (for example, OFF period T21 for red) among the OFF periods T21 to T23 that are assigned to the single color. In this case, the illuminance of the single color can be reduced.

[0084] (3) Effects According to the lighting device 1 of this embodiment, for example, by adjusting the ratio of the number of turns of the secondary winding L2 corresponding to each LED load 20 of the transformer Tr1 to the number of turns of the primary winding L1 of the transformer Tr1, it becomes easier to absorb differences in voltage drop values ​​and current values ​​(required for lighting). As a result, energy loss can be suppressed. In addition, compared to the case where a constant current circuit dedicated to each color is prepared, the overall size increase and cost increase of the lighting device 1 can be suppressed. As a result, the lighting device 1 has the advantage of making it easier to realize a more rationalized circuit.

[0085] (4) Modifications The embodiments described above are only one of many embodiments of the present disclosure. The embodiments described above can be modified in various ways depending on the design, etc., as long as the objectives of the present disclosure are achieved. Modifications of the embodiments described above are listed below. The modifications described below can be applied in appropriate combination with the embodiments described above, and can also be applied in appropriate combination with each other.

[0086] In the embodiment described above, the plurality of LED loads 20 are composed of a red LED load 21, a green LED load 22, and a blue LED load 23, each having three different light-emitting colors: red, green, and blue. However, the plurality of LED loads 20 may be composed of four or more LED loads, each having four or more different light-emitting colors. For example, the plurality of LED loads 20 may be composed of four LED loads, each having yellow in addition to red, green, and blue.

[0087] In the above-described embodiment, the LED elements of each LED load 20 are light-emitting diodes. However, the LED elements of each LED load 20 are not limited to light-emitting diodes, but may also be solid-state light-emitting elements such as organic light-emitting diodes (OLEDs) or laser light-emitting elements.

[0088] In the above-described embodiment, the first switching element Q1 and each of the second switching elements Q2 are field-effect transistors, for example, n-channel MOSFETs. However, this is not limited to these, and the first switching element Q1 and / or each of the second switching elements Q2 may be bipolar transistors. Also, the first switching element Q1 and / or each of the second switching elements Q2 may be p-channel MOSFETs.

[0089] (Aspects) The following aspects are disclosed in this specification.

[0090] The lighting device (1) according to the first embodiment lights up a plurality of LED loads (20) having different light-emitting colors. The lighting device (1) comprises a transformer (Tr1) having a primary winding (L1) and a plurality of secondary windings (L2), a primary side circuit (A1), a plurality of secondary side circuits (B1), and a control circuit (30). The primary side circuit (A1) has a first switching element (Q1) connected in series with the primary winding (L1), and a DC power supply (V ＤＣ ) is electrically connected to the secondary circuit (B1). Each of the multiple secondary circuits (B1) has multiple second switching elements (Q2) and supplies current to each of the multiple LED loads (20). The control circuit (30) controls the switching operation by individually outputting drive signals to the first switching element (Q1) and the multiple second switching elements (Q2). Each of the multiple second switching elements (Q2) is connected in series to the multiple secondary windings (L2). The control circuit (30) is electrically connected to the DC power supply (V ＤＣ The first switching element (Q1) is periodically switched on / off to store energy in the primary winding (L1) using power from the transformer (Tr1) and to transmit the stored energy to the secondary side of the transformer (Tr1). During the off period (T2) when the first switching element (Q1) is in the off state, the control circuit (30) controls one or more corresponding second switching elements (Q2) among a plurality of second switching elements (Q2) so that a current based on the energy on the secondary side of the transformer (Tr1) flows to one or more of the plurality of secondary circuits (B1), thereby turning on / off or changing the dimming rate of one or more corresponding LED loads (20) among a plurality of LED loads (20).

[0091] According to the above embodiment, for example, by adjusting the number of turns of the secondary winding (L2) corresponding to each LED load (20), it becomes easier to absorb differences in voltage drop and current values, and energy loss can be suppressed. In addition, size and cost increases can be suppressed compared to preparing a dedicated constant current circuit for each color. As a result, the lighting device (1) has the advantage of being able to realize a more rationalized circuit.

[0092] With respect to the lighting device (1) according to the second embodiment, in the first embodiment, the control circuit (30) sequentially selects one of the multiple second switching elements (Q2) in a cyclic manner and turns it on at each periodic off period (T2) of the first switching element (Q1), thereby sequentially lighting up multiple LED loads (20).

[0093] According to the above embodiment, the lighting control of multiple LED loads (20) can be achieved more efficiently.

[0094] With respect to the lighting device (1) according to the third embodiment, in the second embodiment, the second switching element (Q2) of the secondary circuit (B1) corresponding to a certain LED load (20) among the plurality of LED loads (20) is assigned to be on during predetermined off periods (T2) that occur sequentially within the periodic off periods (T2) of the first switching element (Q1). When it is not necessary to supply current to a certain LED load (20), the control circuit (30) maintains the second switching element (Q2) in the off state during the predetermined off period (T2).

[0095] According to the above embodiment, it is possible to efficiently interrupt the supply of current to the LED load (20) mentioned above.

[0096] With respect to the lighting device (1) according to the fourth embodiment, in the third embodiment, if it is not necessary to supply current to a certain LED load (20), the control circuit (30) keeps the first switching element (Q1) in the off state during the on period (T1) of the first switching element (Q1) which was assigned to supply current to a certain LED load (20), thereby suspending the accumulation of energy in the primary winding (L1).

[0097] According to the above embodiment, when it is not necessary to supply current to the LED load (20), power loss associated with the switching operation of the first switching element (Q1) can be reduced.

[0098] With respect to the lighting device (1) according to the fifth embodiment, in the third embodiment, if it is not necessary to supply current to a certain LED load (20), the control circuit (30) turns on the second switching element (Q2) of the secondary circuit (B1) corresponding to the other LED load (20) so that current is supplied to another LED load (20) among the plurality of LED loads (20) other than the one in question during a predetermined off period (T2).

[0099] According to the above embodiment, since it is assigned to lighting up another LED load (20) other than the aforementioned LED load (20), the illuminance based on the light-emitting color of the other LED load (20) can be increased.

[0100] The lighting device (100) according to the sixth embodiment comprises a lighting device (1) according to any one of the first to fifth embodiments and a plurality of LED loads (20).

[0101] According to the above embodiment, a lighting device (100) that facilitates the realization of a more streamlined circuit can be provided.

[0102] The configurations relating to the second to fifth embodiments are not essential to the lighting device (1) relating to the first embodiment and can be omitted as appropriate.

[0103] 100 Lighting device 1 Lighting device 20 LED load 30 Control circuit A1 Primary circuit B1 Secondary circuit L1 Primary winding L2 Secondary winding Q1 First switching element Q2 Second switching element T1 On period T2 Off period Tr1 Transformer V ＤＣ DC power supply

Claims

1. A lighting device for lighting multiple LED loads having different light-emitting colors, comprising: a transformer having a primary winding and multiple secondary windings; a primary-side circuit having a first switching element connected in series with the primary winding and electrically connected to a DC power supply; multiple secondary-side circuits each having multiple second switching elements and supplying current to the multiple LED loads, respectively; and a control circuit that controls the switching operation by individually outputting drive signals to the first switching element and the multiple second switching elements, wherein the multiple second switching elements are each connected in series with the multiple secondary windings, and the control circuit periodically switches the first switching element on / off to store energy in the primary winding using power from the DC power supply and to transmit the stored energy to the secondary side of the transformer. A lighting device that, during the off period when the first switching element is in the off state, controls one or more of the corresponding second switching elements among the plurality of second switching elements so that a current based on the energy on the secondary side of the transformer flows through one or more of the plurality of secondary circuits, thereby turning on / off or changing the dimming rate of one or more of the plurality of LED loads.

2. The lighting device according to claim 1, wherein the control circuit sequentially selects one of the plurality of second switching elements in a cyclic manner and turns it on during each periodic off period of the first switching element, thereby sequentially lighting up the plurality of LED loads.

3. The lighting device according to claim 2, wherein a second switching element of the secondary circuit corresponding to one of the plurality of LED loads is assigned to be on during predetermined off periods that occur sequentially within the periodic off periods of the first switching element, and when it is not necessary to supply current to the LED load, the control circuit maintains the second switching element in the off state during the predetermined off period.

4. When it is not necessary to supply current to a certain LED load, the control circuit maintains the first switching element in an off state during the on period of the first switching element which was assigned to supply current to the certain LED load, thereby suspending the storage of energy in the primary winding, as described in claim 3.

5. When it is not necessary to supply current to a certain LED load, the control circuit turns on a second switching element of the secondary circuit corresponding to another LED load among the plurality of LED loads, so that current is supplied to that other LED load during the predetermined off period, the lighting device according to claim 3.

6. A lighting device comprising: a lighting device according to any one of claims 1 to 5; and the plurality of LED loads.

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