Lighting device and luminaire

Abstract

To provide a lighting device and a luminaire capable of interrupting a current flowing through a light source without waiting for detection of an oscillation stop of a converter circuit when an abnormality occurs in the light source.SOLUTION: A lighting device of the present disclosure includes: a converter circuit that generates a voltage for driving a light source from an input voltage; a constant current circuit that includes a switching element connected in series with the light source and maintains a constant current supplied to the light source by changing impedance of the switching element; and a control device that stores a threshold value of an output voltage of the constant current circuit. The control device is configured to execute a process of opening the switching element when the output voltage reaches the threshold value as a trigger.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a lighting device and a lighting fixture. [Background technology]

[0002] In recent years, LEDs have become the norm for lighting fixtures. Compared to incandescent and fluorescent lamps, it is known that the brightness of LEDs is more responsive to changes in input voltage. This poses the problem of the light source appearing to flicker unless the ripple in the voltage supplied to the light source is reduced. To address this issue, an increasing number of two-converter systems are being used, in which the input voltage from an external power source is first boosted to reduce the ripple, and then stepped down to a voltage suitable for the light source in the subsequent stage.

[0003] On the other hand, the two-converter system has the problem of increasing the system size. Therefore, even in the single-converter system, there is a method of reducing ripple by adding a constant current circuit that keeps the current flowing to the light source constant. However, this method has the problem that the output voltage of the constant current circuit rises when an abnormality such as a short circuit occurs in the light source, and unless the current flowing to the light source is cut off, a large power loss occurs in the constant current circuit.

[0004] To address this problem, Patent Document 1 discloses a technology in which, when an oscillation detection circuit detects that an AC-DC chopper circuit, which is a converter circuit, has stopped oscillating, the switching element of the constant current circuit is opened to cut off the current flowing to the light source. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-036663 Summary of the Invention [Problem to be solved by the invention]

[0006] In the above-mentioned method, the trigger for cutting off the current flowing to the light source is set to the cessation of oscillation of the converter circuit. In this case, even if the output voltage of the constant current circuit rises due to an abnormality in the light source, the oscillation of the converter circuit will stop, and the current cannot be cut off until this is detected.

[0007] In order to solve the above-mentioned problems, the present disclosure aims to provide a lighting device and a lighting fixture that can cut off the current flowing to the light source when an abnormality occurs in the light source without waiting for the converter circuit to detect that oscillation has stopped. [Means for solving the problem]

[0008] Aspects of the present disclosure include: a converter circuit that generates a voltage for driving the light source from an input voltage; a constant current circuit having a switching element connected in series with the light source, which changes the impedance of the switching element to keep the current supplied to the light source constant; a control device that stores a threshold value of the output voltage of the constant current circuit; Equipped with The control device Preferably, the lighting device is configured to execute a process of opening the switching element when the output voltage reaches the threshold value. [Effects of the Invention]

[0009] In the present disclosure, the trigger for cutting off the current flowing to the light source is set to when the output voltage of the constant current circuit reaches a threshold value, so that if an abnormality occurs in the light source, the current flowing to the light source can be cut off without waiting for the converter circuit to detect that oscillation has stopped. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a circuit diagram of a lighting fixture according to a first embodiment of the present disclosure. [Figure 2]10 shows time changes in voltage and current in the main circuit element from when an abnormality occurs in the light source until the current flowing through the light source is cut off, according to a comparative example of the first embodiment. [Figure 3] 10 shows time changes in voltage and current in a main circuit element from when an abnormality occurs in a light source until the current flowing through the light source is cut off, according to the first embodiment of the present disclosure. [Figure 4] 10 shows time changes in voltage and current in a main circuit element from when an abnormality occurs in a light source until the light source is turned off, according to a comparative example of the second embodiment. [Figure 5] 10 shows time changes in voltage and current in a main circuit element from when an abnormality occurs in a light source until the light source is turned off, according to the second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Embodiments of the present disclosure will be described with reference to the drawings. The same or corresponding components will be designated by the same reference numerals, and repeated description may be omitted.

[0012] Embodiment 1 1 is a circuit diagram of a lighting fixture 100 according to a first embodiment of the present disclosure. The lighting fixture 100 includes a light source 11 having one or more LED modules, a lighting device 12, and a dimming interface (I / F) circuit 62.

[0013] The lighting device 12 includes an input filter circuit 1, a converter circuit 3, a constant current circuit 4 that keeps the current flowing through the light source 11 constant, and a control device 50.

[0014] An external power supply is connected to the input filter circuit 1, which receives an input voltage from the external power supply. The input filter circuit 1 includes a fuse 25 for overcurrent protection, an AC capacitor 26, and a diode bridge 27 that full-wave rectifies the AC voltage from the external power supply and converts it to a DC voltage. The high-potential side of the output of the diode bridge 27 is connected to the converter circuit 3, and the low-potential side is connected to a ground terminal (not shown).

[0015] The converter circuit 3 includes an isolated flyback circuit including a transformer 14 and a switching element 15 , and converts the DC voltage received from the input filter circuit 1 into a voltage suitable for driving the light source 11 .

[0016] The converter circuit 3 includes an input voltage detection unit including resistors 16 and 17 connected in series, and divides the input voltage to the converter circuit 3. The voltage division value (first voltage) of resistors 16 and 17 is detected by the control device 50. This enables the control device 50 to detect the input voltage of the external power supply.

[0017] Capacitor 10 is connected in parallel with the output of diode bridge 27. This reduces ripples that occur during full-wave rectification by diode bridge 27 and switching by switching element 15, which will be described later. A control power supply generating circuit 19 and one end of the primary side of transformer 14 are connected to the positive electrode of capacitor 10.

[0018] A first terminal of a switching element 15 is connected in series to the other end of the primary side of the transformer 14.

[0019] The switching element 15 has a first terminal connected to the transformer 14, a second terminal connected to the negative electrode and the ground terminal of the capacitor 10, and a control terminal connected to the control device 50. The switching element 15 is, for example, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). When the switching element 15 is a MOSFET, the first terminal is a drain terminal, the second terminal is a source terminal, and the control terminal is a gate terminal.

[0020] The anode of a diode 20 is connected to one end of the flyback winding on the secondary side of the transformer 14. The diode 20 is provided to transmit a stable voltage to the output side. The cathode of the diode 20 is connected to the positive electrode of an electrolytic capacitor 21. The negative electrode of the electrolytic capacitor 21 is connected to a ground terminal.

[0021] An output voltage detection unit including resistors 22 and 23 connected in series is connected in parallel to electrolytic capacitor 21. The voltage division value (second voltage) of resistors 22 and 23 is input to control device 50. This enables control device 50 to detect the output voltage of converter circuit 3.

[0022] The light source 11 has a structure in which a plurality of LED modules are connected in series. Although a plurality of LED modules are shown in the figure, it is sufficient that there is one or more LED modules.

[0023] The constant current circuit 4 is a regulator circuit including a switching element 41 connected in series to the light source 11, a resistor 43 for detecting the current (Io) flowing through the light source, and a comparator 42. The constant current circuit 4 keeps the current supplied to the light source 11 constant by changing the impedance of the switching element 41.

[0024] The input side of the comparator 42 is connected to the resistor 43 and the control device 50. The output side of the comparator 42 is connected to the control terminal of the switching element 41. The comparator 42 amplifies and outputs a voltage so that the voltage applied to the resistor 43 matches the voltage supplied from the control device 50 and suitable for the light source 11, and changes the voltage (Vg) applied to the control terminal of the switching element 41.

[0025] A first terminal of the switching element 41 is connected to the cathode of the light source 11, a second terminal is connected to a resistor 43, and a control terminal is connected to a comparator 42. The switching element 41 is, for example, a MOSFET. When the switching element 41 is a MOSFET, the first terminal is a drain terminal, the second terminal is a source terminal, and the control terminal is a gate terminal. Depending on the voltage (Vg) applied to the control terminal, the switching element 41 brings the first and second terminals into a short-circuit state, an open state, or a state connected with a finite impedance. As the impedance of the switching element 41 changes, the current (Io) flowing through the light source 11 also changes.

[0026] One end of the resistor 43 is connected to the second terminal of the switching element 41 and the input side of the comparator 42. The other end of the resistor 43 is connected to a ground terminal. By adjusting the impedance of the switching element 41, a voltage based on the current (Io) flowing through the light source 11 is generated across the resistor 43. By using the generated voltage as the input to the comparator 42, feedback control can be performed to keep the current (Io) flowing through the light source 11 constant.

[0027] The constant current circuit voltage detection unit, which is composed of resistors 31 and 32 connected in series, has one end connected to the first terminal of the switching element 41 and the other end connected to the low potential side and ground terminal of resistor 43. In other words, the constant current circuit voltage detection unit divides the output voltage (Vd) of the constant current circuit 4. The divided voltage value (third voltage) is input to the control device 50. This allows the control device 50 to detect the output voltage (Vd) of the constant current circuit 4.

[0028] The control device 50 can be configured with a known microcomputer provided as a digital power supply control device, or can be configured with an arithmetic device such as a DSP (Digital Signal Processor). The control device 50 includes a memory unit and a central processing unit (CPU).

[0029] The control device 50 receives the first voltage, the second voltage, and the third voltage described above.

[0030] The storage unit has volatile or nonvolatile memory and stores the calculation program to be executed by the central processing unit and various data used in the calculation. The data stored in the storage unit includes a threshold value (Vth) for the output voltage (Vd) of the constant current circuit 4. The threshold value (Vth) is set to a value higher than the output voltage of the constant current circuit 4 during normal operation. The calculation program here is, for example, a program for causing the converter circuit 3 to perform PFC (Power Factor Correction) operation. The storage unit allows data to be written and read by a computer. The A / D conversion unit converts the voltage value input to the control device 50 into a digital value. The central processing unit performs the calculation processing required for lighting control based on the digitally converted voltage value.

[0031] The control device 50 adjusts the ON time of the switching element 15 based on the third voltage, and performs constant voltage control so that the output voltage (Vd) of the constant current circuit 4 coincides with the target voltage stored in the storage unit.

[0032] The control device 50 also receives a dimming command signal from a dimmer 61 via a dimming interface circuit 62. The command content from the dimmer 61 includes turning on or off the light source, a dimming value, and a fade time. The control device 50 outputs a PWM signal for turning on or off the light source 11 based on the command content included in the dimming command signal.

[0033] Next, a method for cutting off the current (Io) flowing through the light source 11 when an abnormality occurs in the light source 11 will be described for each of a comparative example and the present disclosure.

[0034] Comparative Example 2 shows the time changes in voltage and current in the main circuit element from when an abnormality occurs in light source 11 until the current (Io) flowing through light source 11 is cut off, in a comparative example of embodiment 1. Here, the method of Patent Document 1 is assumed. The horizontal axis of the diagram represents time. The vertical axis represents the output voltage (Vd) of constant current circuit 4, the oscillation voltage (Vpwm) which is the voltage between the first and second terminals of switching element 15, the voltage (Vg) at the control terminal of switching element 41, and the current (Io) flowing through light source 11.

[0035] When the light source 11 is in an abnormal state due to a short circuit failure, the output voltage (Vd) of the constant current circuit 4 rises (step S01).

[0036] While the output voltage (Vd) of the constant current circuit 4 continues to rise, the switching element 15 of the converter circuit 3 continues to oscillate at the oscillation voltage (Vpwm). However, when the output voltage (Vd) of the constant current circuit 4 reaches a preset threshold (Vth), the oscillation of the switching element 15 is stopped by the control device 50 (step S02). As the oscillation stops, the output voltage (Vd) of the constant current circuit 4 stops rising and continues to remain at the stopped voltage value.

[0037] As described above, in the method of Patent Document 1, the trigger for cutting off the current (Io) flowing through the light source 11 is set to the cessation of oscillation of the converter circuit 3. That is, when the control device 50 detects that the oscillation voltage (Vpwm) of the switching element 15 is zero, it sets the voltage input to the comparator 42 to 0 V. As a result, the voltage (Vg) at the control terminal of the switching element 41 becomes 0 V, and the switching element 41 enters an open state with infinite impedance (step S03).

[0038] Since the switching element 41 is opened, the current (Io) flowing through the light source 11 is cut off (step S04).

[0039] After an abnormality occurs in the light source, the output voltage (Vd) of the constant current circuit 4 becomes higher than during normal operation. Therefore, during the time T1 from when the abnormality occurs until the current (Io) flowing through the light source 11 is cut off, the power loss in the constant current circuit 4 becomes large.

[0040] If the response of the converter circuit 3 could be made faster, even if an abnormality occurs in the light source 11, the output voltage of the converter circuit 3 would immediately drop in step S01 and the switching element 15 would essentially be in an open state, thereby suppressing an increase in the output voltage (Vd) of the constant current circuit 4. However, from the perspective of improving the power factor of the alternating current voltage AC, the period of the signal that turns on the switching element 15 must be set to be constant with respect to the cycle of the alternating current voltage AC, and there is a general situation in which the response cannot be made any faster than this.

[0041] In this comparative example, following the method of Patent Document 1, the trigger for stopping the constant current circuit 4 is the stop of oscillation of the switching element 15. However, the same effect can be achieved by the switching element 15 being substantially in an open state due to a drop in the output voltage of the converter circuit 3.

[0042] <This Disclosure> 3 shows the time changes in voltage and current in the main circuit elements from when an abnormality occurs in the light source 11 until the current (Io) flowing through the light source 11 is shut off, according to the first embodiment of the present disclosure. Again, the horizontal axis of the diagram represents time, and the vertical axis represents the output voltage (Vd) of the constant current circuit 4, the voltage (Vg) at the control terminal of the switching element 41, and the current (Io) flowing through the light source 11.

[0043] When the light source 11 goes into an abnormal state, the output voltage (Vd) of the constant current circuit 4 rises (step S11), as in the comparative example. Also, as in the comparative example, while the output voltage (Vd) of the constant current circuit 4 continues to rise, the switching element 15 of the converter circuit 3 continues to oscillate.

[0044] In this embodiment, the control device 50 starts processing to cut off the current (Io) flowing to the light source 11 when the output voltage (Vd) of the constant current circuit 4 reaches the threshold value (Vth). That is, upon detecting that the output voltage (Vd) has reached the threshold value (Vth), the control device 50 sets the voltage input to the comparator 42 to 0 V. As a result, the voltage (Vg) at the control terminal of the switching element 41 becomes 0 V, and the switching element 41 is opened (step S12).

[0045] When the switching element 41 is opened, the current (Io) flowing through the light source 11 is cut off (step S13), similar to the comparative example.

[0046] As described above, in this embodiment, the trigger for cutting off the current (Io) flowing to the light source 11 is set to be when the output voltage (Vd) of the constant current circuit 4 reaches the threshold value (Vth). Because there is no need to stop the oscillation of the switching element 15 and detect it as in the comparative example, the time T2 from when an abnormality occurs to when the current (Io) flowing to the light source 11 is cut off can be made shorter than the time T1 in the comparative example. Therefore, it is possible to provide a lighting device and a lighting fixture that, when an abnormality occurs in the light source, can cut off the current flowing to the light source without waiting for the stop of oscillation of the converter circuit to be detected.

[0047] In this embodiment, the oscillation of the switching element 15 of the converter circuit 3 may be stopped after the switching element 41 is opened.

[0048] Embodiment 2 In this embodiment, the light source 11 is turned off before the converter circuit 3 stops oscillating. The following describes the changes from the first embodiment.

[0049] Comparative Example 4 shows the time changes in voltage and current in the main circuit element from when a dimming command signal instructing the light source 11 to be turned off to when the light source 11 is turned off, in a comparative example of the second embodiment. The method of Patent Document 1 is also assumed here. The horizontal axis of the diagram represents time. The vertical axis represents the voltage (Vm) of the dimming command signal, the oscillation voltage (Vpwm) of the switching element 15, the voltage (Vg) of the control terminal of the switching element 41, and the current (Io) flowing through the light source 11.

[0050] When an operation to command turning off is performed on the dimmer 61, the voltage (Vm) of the dimming command signal changes to a voltage indicative of turning off (step S21).

[0051] Based on the change in the voltage of the dimming command signal, the control device 50 detects that the command is to turn off the lights and stops the oscillation of the switching element 15 of the converter circuit 3 (step S22).

[0052] In the comparative example, the trigger for cutting off the current (Io) flowing through the light source 11 is set to the cessation of oscillation of the converter circuit 3. Even when turning off the light, the control device 50 sets the voltage input to the comparator 42 to 0V only after detecting that the oscillation voltage (Vpwm) is zero. This causes the voltage (Vg) at the control terminal of the switching element 41 to become 0V, and the switching element 41 is opened (step S23). As a result, the current (Io) flowing through the light source 11 is cut off, and the light is turned off (step S24).

[0053] Here, the time T1 is the time from when the control device 50 detects the light-off command until the light source 11 is actually turned off.

[0054] <This Disclosure> 5 shows the changes in voltage and current over time in the main circuit element from when a dimming command signal instructing the light source 11 to be turned off to when the light source 11 is turned off, according to the second embodiment of the present disclosure. The horizontal axis of the diagram represents time, and the vertical axis represents the voltage (Vm) of the dimming command signal, the voltage (Vg) at the control terminal of the switching element 41, and the current (Io) flowing through the light source 11.

[0055] When an operation to command turning off is performed on the dimmer 61, the voltage (Vm) of the dimming command signal changes to a voltage indicating turning off, similarly to the comparative example (step S31).

[0056] In this embodiment, the detection of the command to turn off the light triggers the control device 50 to start processing to cut off the current (Io) flowing through the light source 11. That is, upon detecting that the voltage (Vm) of the dimming command signal has changed to a voltage indicating light-off, the control device 50 sets the voltage input to the comparator 42 to 0 V. This causes the voltage (Vg) at the control terminal of the switching element 41 to become 0 V, and the switching element 41 is opened (step S32). As a result, the light source 11 is turned off (step S33).

[0057] In this embodiment, there is no need to stop the oscillation of the switching element 15 and detect this when turning off the light, as in the comparative example, so the time T2 from when the control device 50 detects the light-off command to when the light source 11 is turned off can be made shorter than the time T1 in the comparative example.

[0058] In this embodiment, too, the oscillation of the switching element 15 of the converter circuit 3 may be stopped after the switching element 41 is opened.

[0059] The present disclosure is not limited to the above-described embodiments, and various modifications can be made in the implementation stage without departing from the spirit of the present disclosure. Furthermore, the embodiments and modifications may be implemented in appropriate combinations, in which case the combined effects can be obtained.

[0060] Various aspects of the present disclosure are summarized below as appendices. (Appendix 1) a converter circuit that generates a voltage for driving the light source from an input voltage; a constant current circuit having a switching element connected in series with the light source, which changes the impedance of the switching element to keep the current supplied to the light source constant; a control device that stores a threshold value of the output voltage of the constant current circuit; Equipped with The control device The lighting device is configured to execute a process of opening the switching element when the output voltage reaches the threshold value. (Appendix 2) A process of receiving a dimming command signal including command content from a dimmer; a process of opening the switching element before stopping the oscillation of the converter circuit, triggered by detecting that the command content is light-off; 2. The lighting device according to claim 1, further comprising: (Appendix 3) 3. The lighting device according to claim 1, further comprising a process of stopping oscillation of the converter circuit after opening the switching element. (Appendix 4) A lighting device according to any one of appendices 1 to 3; the light source; A lighting fixture comprising: [Explanation of symbols]

[0061] 1 input filter circuit, 3 converter circuit, 4 constant current circuit, 10 capacitor, 11 light source, 12 lighting device, 14 transformer, 15 switching element, 16 resistor, 17 resistor, 19 control power generation circuit, 20 diode, 21 electrolytic capacitor, 22 resistor, 23 resistor, 25 fuse, 26 capacitor, 27 diode bridge, 31 resistor, 32 resistor, 41 switching element, 42 comparator, 43 resistor, 50 control device, 61 dimmer, 62 dimming interface (I / F) circuit, 100 lighting fixture

Claims

1. a converter circuit that generates a voltage for driving the light source from an input voltage; a constant current circuit having a switching element connected in series with the light source, which changes the impedance of the switching element to keep the current supplied to the light source constant; a control device that stores a threshold value of the output voltage of the constant current circuit; Equipped with The control device The lighting device is configured to execute a process of opening the switching element when the output voltage reaches the threshold value.

2. A process of receiving a dimming command signal including command content from a dimmer; a process of opening the switching element before stopping the oscillation of the converter circuit, triggered by detecting that the command content is light-off; The lighting device of claim 1 further comprising:

3. The lighting device according to claim 1 , further comprising a process for stopping oscillation of the converter circuit after the switching element is opened.

4. The lighting device according to claim 1 or 2; the light source; A lighting fixture comprising:

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