JP2013246974A - Lighting device and lighting system using the same - Google Patents

Abstract

Provided are a small and low-cost lighting device and lighting fixture capable of dimming a wide range while suppressing interference with a screen of video equipment.
A control unit 4 performs light control by adjusting an output of a step-down chopper unit 3 in accordance with light control signals S1 and S2 input from a light control signal output unit 6. In the first dimming range, dimming is performed by the first dimming method that adjusts the direct current value of the current flowing from the step-down chopper unit 3 to the light emitting diode LD1, and in the second dimming range that is darker than the first dimming range, Dimming is performed by combining the first dimming method and the second dimming method of adjusting the average value of the current flowing through the light emitting diode LD1 by intermittently operating the step-down chopper unit 3. Whether the dimming signal output unit 6 sets the lower limit of dimming by the second dimming method to the lower limit level of the second dimming range based on a control command input from the wireless transmitter 20 according to a user operation. Alternatively, it is switched whether the predetermined level is brighter than the lower limit level within the second dimming range.
[Selection] Figure 1

Description

  The present invention relates to a lighting device for lighting a solid light source and a lighting fixture using the same.

  Conventionally, there has been proposed a lighting device that performs dimming control by causing a current to flow intermittently through a light emitting diode (see, for example, Patent Document 1).

JP 2011-70966 A

  As described above, a lighting device having a circuit configuration as shown in FIG. 5 has been proposed as a lighting device that performs dimming control by intermittently passing a current through a light emitting diode. Note that a dimming method that performs dimming by causing an electric current to flow intermittently through the light emitting diode is called a burst dimming method.

  The lighting device 1 includes an AC-DC converter unit 2 that rectifies and smoothes an AC voltage from an AC power source AC, a step-down chopper unit 3 that steps down the output of the AC-DC converter unit 2, and a control unit 4. The light emitting diode LD1 connected between the output terminals of the step-down chopper unit 3 is turned on.

  The step-down chopper unit 3 includes a diode 11, an N-channel field effect transistor (hereinafter abbreviated as FET) 12, a current detection resistor 13, a smoothing electrolytic capacitor 14, and a choke coil 15. . The cathode of the diode 11 is connected to the high voltage side output terminal of the AC-DC converter unit 2, and the FET 12 and the current detection resistor 13 are connected between the anode of the diode 11 and the low voltage side output terminal of the AC-DC converter unit 2. Connected in series. A series circuit of a capacitor 14 and a choke coil 15 is connected between both ends of the diode 11, and a plurality of light emitting diodes LD <b> 1 are connected in series between both ends of the capacitor 14.

  The control unit 4 is composed of a microcomputer. A dimming signal S1 is input from the outside to the input terminal P1, and a voltage across the current detection resistor 13 is input to the input terminal P3. The output terminal P4 of the control unit 4 is connected to the gate electrode of the FET 12, and the drive signal S3 is input from the output terminal P4 to the gate electrode.

  FIG. 6A is a waveform diagram of each part in the fully lit state, and is a waveform diagram of the dimming signal S1, the drive signal S3, the drain current I1 of the FET 12, and the output current I2 flowing through the light emitting diode LD1 in order from the top.

  A rectangular wave dimming signal S1 with an adjusted duty ratio is input to the input terminal P1 of the control unit 4. In the fully lit state, the duty ratio of the dimming signal S1 is 100%, and the voltage signal is a constant voltage value.

  Here, in a period in which the signal level of the dimming signal S1 is L level, the control unit 4 turns off the FET 12 and stops the switching operation of the step-down chopper unit 3.

  On the other hand, during the period when the signal level of the dimming signal S1 is H level, the control unit 4 performs PWM control of the FET 12, and supplies an output current corresponding to the duty ratio of the dimming signal S1 to the light emitting diode LD1. That is, when the signal level of the dimming signal S1 is switched to the H level, the control unit 4 switches the signal level of the drive signal S3 output from the output terminal P4 to the H level and turns on the FET 12. When the FET 12 is turned on, the drain current I1 starts to flow through the FET 12, and the drain current I1 gradually increases. The control unit 4 monitors the drain current I1 from the voltage input to the input terminal P3. When the drain current I1 reaches a predetermined threshold current Ith, the signal level of the drive signal S3 is switched to L level, and the FET 12 Turn off. The controller 4 turns off the FET 12 and then turns on the FET 12 at a predetermined frequency, or turns on the FET 12 when a certain off time has elapsed. During the period when the signal level of the dimming signal S1 is H level, the control unit 4 repeats the above operation, whereby the drain current I1 having a triangular waveform as shown in FIGS. 6A and 6B is supplied to the FET 12. The

  As shown in FIG. 6A, the duty ratio of the dimming signal S1 is 100% in the fully lit state, and the switching operation of the step-down chopper unit 3 is continuously performed. Therefore, a substantially constant DC current is applied to the light emitting diode LD1. I2 flows and the light emitting diode LD1 is fully lit. On the other hand, as shown in FIG. 6B, at 50% dimming, the duty ratio of the dimming signal S1 is 50%, and the step-down chopper unit 3 performs the switching operation when the signal level of the dimming signal S1 is L level. To stop. Therefore, the current I2 flowing through the light emitting diode LD1 has a current waveform such that the peak value is substantially the same as when all the lights are on, the bottom value is substantially zero, and an average brightness of about 50% is obtained.

  The burst dimming method as described above is a dimming method that adjusts the visual brightness by intermittently passing a current through the light emitting diode LD1, and is bright or dark or blinks at a cycle that is not perceived by human eyes. Is repeated. In this dimming method, only the ratio of the period during which current is passed through the light emitting diode LD1 and the period during which no current is passed is adjusted, so that a wide dimming range can be obtained relatively easily.

  However, when such a lighting device or its illumination space is photographed with an imaging device such as a video camera, the illuminance changes appear as light and dark stripes on the screen, depending on the shutter speed and exposure time of the imaging device. There was a problem of flickering. Further, depending on the period of burst dimming, there is a problem that the luminaire itself can flicker visually, or that a strobe effect in which an afterimage remains when a fast moving object is viewed under the illumination.

  As a dimming method for solving such problems, a switching power supply generates a direct current having a substantially constant current value and supplies it to the light emitting diode, and adjusts the current value of the direct current to control the light emitting diode. There is an optical system (so-called DC dimming).

  When burst dimming is not performed in the circuit of FIG. 5 described above and the output of the step-down chopper unit 3 is smoothed by a smoothing capacitor, a direct current having a substantially constant current value is supplied to the light emitting diode LD1. When the threshold current Ith of the drain current I1 is changed according to the dimming level, the value of the current flowing through the light emitting diode LD1 changes, so that the light emitting diode LD1 can be dimmed. In this dimming method, since a direct current with a smoothed current value is supplied to the light emitting diode, it is possible to reduce flickering of light and dark. However, as the dimming level is lowered, the threshold current Ith of the drain current I1 is lowered and the on-time of the FET 12 is shortened. Therefore, there is a problem that the control frequency deteriorates because the oscillation frequency of the FET 12 becomes too high or each time of the switching operation becomes too short. Even when the dimming control is performed only by the direct current dimming, the problem occurs. To do.

  Therefore, it is conceivable to reduce the difference between light and dark by connecting a smoothing capacitor between the output terminals of the step-down chopper unit 3 in the circuit shown in FIG. 5 and supplying the current smoothed by the smoothing capacitor to the light emitting diode LD1. . 7A to 7C show changes in the output current waveform when the capacitance value of the smoothing capacitor connected between the output terminals of the step-down chopper unit 3 is changed. FIG. 7A shows the capacitance value. FIG. 7C shows the output current waveform when the capacitance value is the maximum. As described above, even when the same dimming operation is performed, by increasing the capacitance value of the smoothing capacitor, the peak-to-bottom ratio of the output current, that is, the difference in brightness of the light emission is reduced. It can improve the problem of light and dark stripes appearing on the screen and flickering on the screen. However, since a large-capacity smoothing capacitor is required, there is a problem that the lighting device is increased in size and cost.

  It is also conceivable to suppress interference with the video equipment by setting the frequency of the burst dimming method to a frequency sufficiently higher than the shutter speed of the video equipment. However, there is a problem that the dimming range is narrowed because the control frequency deteriorates because the oscillation frequency becomes too high or each time of the switching operation becomes too short.

  The present invention has been made in view of the above problems, and its object is to provide a small and low-cost lighting device capable of dimming a wide range while suppressing interference with the screen of a video device, and the same It is in providing the used lighting fixture.

  A lighting device of the present invention is a lighting device for a semiconductor light emitting element that emits light when a current flows in a forward direction, and adjusts an output of the lighting circuit unit that supplies current to the semiconductor light emitting element, and the lighting circuit unit Thus, a dimming control unit that performs dimming control and a dimming range limiting unit are provided. The dimming control unit performs dimming by combining the first dimming method and the second dimming method. In the first dimming method, dimming is performed by adjusting the direct current value of the current flowing from the lighting circuit portion to the semiconductor light emitting element. In the second dimming method, dimming is performed by operating the lighting circuit section intermittently and adjusting the average value of the current flowing through the semiconductor light emitting element. The dimming control unit performs dimming control only by the first dimming method in the relatively bright first dimming range, and the first dimming range is darker than the first dimming range. Dimming control is performed by both the dimming method and the second dimming method. The dimming range limiting unit sets at least a dimming lower limit by the second dimming method as a lower limit level of the second dimming range or within the second dimming range according to a user operation. Switching between a predetermined level brighter than the lower limit level is switched.

  The lighting device preferably further includes a wireless signal receiving unit that receives a wireless signal transmitted from a wireless transmitter that transmits a control command according to a user operation using a wireless signal. The dimming restriction unit switches whether the dimming lower limit is set to the lower limit level or the predetermined level according to a control command received by the wireless signal receiving unit.

  In this lighting device, it is preferable that the dimming restriction unit further includes a storage unit that stores whether the dimming lower limit is switched to the lower limit level or the predetermined level. The dimming limiter switches the dimming lower limit to the same level as before the light extinction based on the stored contents of the storage unit at the time of relighting after the light is turned off.

  In this lighting device, it is preferable that the dimming control unit has an automatic dimming function for automatically controlling the light output according to the ambient brightness or the current time.

  In this lighting device, the dimming control unit sets a ratio of the minimum value to the maximum value of the current flowing through the semiconductor light emitting element in a state where the dimming restriction unit switches the dimming lower limit to the predetermined level. It is also preferable to control to% or more.

  The lighting fixture of this invention is equipped with one of the lighting devices mentioned above, and the semiconductor light-emitting element lighted by the said lighting device, It is characterized by the above-mentioned.

  According to the present invention, the dimming control unit performs dimming control in both the first dimming method and the second dimming method in the second dimming range that is darker than the first dimming range. Controllability is more stable than when dimming only with the first dimming method, and dimming control is possible in a wider dimming range. Thus, since the dimming control is performed in both the first dimming method and the second dimming method in the second dimming range, the dimming control can be performed in a wider dimming range. Since light is dimmed by the optical method, when the dimming level becomes dark, the period during which no current flows through the semiconductor light emitting element becomes long. For this reason, when shooting with an imaging device, the illuminance change may appear as bright and dark stripes on the screen, or the screen may appear to flicker. Even in such a case, a period in which no current flows in the semiconductor light-emitting element is provided by switching the dimming lower limit by at least the second dimming method to a predetermined level brighter than the lower limit level within the second dimming range by the user's operation. Therefore, the difference in light output brightness can be reduced. Therefore, it is possible to reduce changes in illuminance appearing as bright and dark stripes on the screen or flickering when the image is captured by the imaging device. In addition, since a large-capacity smoothing capacitor is not required to smooth the current flowing through the semiconductor light-emitting element, a small and low-cost lighting device and a lighting fixture using the same can be realized.

It is a schematic block diagram of the lighting device of this embodiment. (A) is an operation waveform diagram of each part in a fully lit state, (b) is an operation waveform diagram of each part in a dimming state by the first dimming method, and (c) is a first dimming method and a second dimming method. It is an operation | movement waveform diagram of each part in the light control state by combination. It is explanatory drawing explaining the dimming control method same as the above. It is an external view of the wireless transmitter used for the same as the above. It is a schematic block diagram of the conventional lighting device. (A) is an operation waveform diagram of each part in the full lighting state, (b) is an operation waveform diagram of each part in the dimming lighting state. (A)-(c) is an output current waveform figure at the time of changing the capacitance value of the smoothing capacitor connected to the output terminal of a pressure | voltage fall chopper part.

  Embodiments in which the present invention is applied to a light-emitting diode lighting device and a lighting fixture using the same will be described below with reference to the drawings.

  FIG. 1 is a schematic circuit diagram showing a circuit configuration of a lighting fixture. This luminaire includes a lighting device 1, a light emitting diode LD <b> 1 that is turned on by the lighting device 1, and a wireless transmitter 20 that is used by a user to remotely operate the lighting device 1. The lighting fixture includes, for example, a fixture main body (not shown) installed on a ceiling surface or a wall surface, and the lighting device 1 and the light emitting diode LD1 are held on the fixture main body. In this embodiment, the case where the semiconductor light emitting element as the light source is the light emitting diode LD1 will be described, but the light source is not limited to the light emitting diode. For example, a semiconductor light emitting element such as an EL (Electro Luminescence) element may be used as a light source as long as it emits light when a current flows in the forward direction.

  First, the wireless transmitter 20 will be described with reference to FIG. FIG. 4 is an external view of the wireless transmitter 20, and the body 20a of the wireless transmitter 20 is formed separately from the fixture body of the lighting fixture. The container body 20a has a rectangular parallelepiped shape and is formed to have a portable size. A plurality of operation buttons 21 to 26 are arranged on the surface of the container body 20a. A housing (not shown) for transmitting a wireless signal (for example, an optical signal such as an infrared ray) including a control command corresponding to the operation of the operation buttons 21 to 26 is accommodated in the body 20a. .

  Here, the operation button 21 is an operation button for fully lighting the lighting fixture. When the user operates the operation button 21, a control command for lighting the light emitting diode LD1 at a dimming level of 100% is transmitted from the wireless transmission unit. Is done. The operation button 22 is an operation button for turning off the lighting fixture. When the user operates the operation button 22, a control command for turning off the light emitting diode LD1 is transmitted from the wireless transmission unit. The operation button 23 is a button operated to lighten the dimming level. For example, every time the user operates the operation button 23 once, a control command to brighten the dimming level by a predetermined level is transmitted from the wireless transmission unit. Is done. The operation button 24 is an operation button for dimming the dimming level. For example, every time the user operates the operation button 24 once, a control command for dimming the dimming level by a predetermined level is transmitted from the wireless transmission unit. . The operation button 25 is a button operated to switch to a mode in which the light output of the luminaire is automatically controlled according to ambient brightness or time. When the user operates the operation button 25, a control command for switching to a mode for automatically controlling the light output of the light emitting diode LD1 is transmitted from the wireless transmission unit. The operation button 26 is a button operated when using an imaging apparatus such as a video camera or a digital camera. When the user operates the operation button 26, the lower limit of the dimming control is set to a lower limit level of a second dimming range, which will be described later, or a predetermined level brighter than the lower limit level within the second dimming range. A control command for switching is transmitted from the wireless transmission unit.

  Next, the structure of the lighting device 1 will be described with reference to FIGS. The lighting device 1 includes an AC-DC converter unit 2, a step-down chopper unit 3, a control unit 4, a wireless signal receiving unit 5, a dimming signal output unit 6, a storage unit 7, and a buzzer 8. The circuit configuration of the lighting device 1 is not limited to the circuit configuration shown in FIG. 1 and can be changed as appropriate.

  The AC-DC converter unit 2 includes a full-wave rectifier and a smoothing capacitor, and rectifies and smoothes the AC voltage from the AC power supply AC.

  The step-down chopper unit 3 includes a diode 11, an N-channel field effect transistor (hereinafter abbreviated as FET) 12, a current detection resistor 13, a capacitor 14, and a choke coil 15. The cathode of the diode 11 is connected to the high voltage side output terminal of the AC-DC converter unit 2, and the FET 12 and the current detection resistor 13 are connected between the anode of the diode 11 and the low voltage side output terminal of the AC-DC converter unit 2. Connected in series. A series circuit of a capacitor 14 and a choke coil 15 is connected between both ends of the diode 11, and a plurality of light emitting diodes LD <b> 1 are connected in series between both ends of the capacitor 14. The step-down chopper unit 3 steps down the output voltage of the AC-DC converter unit 2 and supplies the current corresponding to the dimming level to the light-emitting diode LD1, thereby lighting the light-emitting diode LD1.

  The control unit 4 is configured by, for example, a general-purpose IC. The dimming signals S1 and S2 are input from the dimming signal output unit 6 to the input terminals P1 and P2 of the control unit 4, respectively, and the current detection resistor is input to the input terminal P3. The voltage at both ends of 13 is input. The output terminal P4 of the control unit 4 is connected to the gate electrode of the FET 12, and the drive signal S3 is input from the output terminal P4 to the gate electrode.

  The control unit 4 performs dimming control by controlling on / off of the FET 12 based on dimming signals S1 and S2 input to the input terminals P1 and P2, respectively. FIG. 3 shows dimming divisions by the lighting device 1. In the first dimming range A where the dimming level is higher (brighter) than 50% and less than or equal to 100%, the lighting device 1 is a direct current of the current flowing through the light emitting diode LD1. Dimming control is performed by a first dimming method (so-called DC dimming method) that adjusts the current value. In the second dimming range B where the dimming level is 10% or more and 50% or less, the lighting device 1 adjusts the average value of the current by intermittently passing a current through the light emitting diode LD1. Dimming control is performed both in the so-called burst dimming method and the first dimming method described above.

  The wireless signal receiving unit 5 receives a wireless signal (for example, an optical signal such as infrared rays) transmitted from the wireless transmitter 20 and outputs a control command included in the wireless signal to the dimming signal output unit 6.

  The storage unit 7 includes, for example, a nonvolatile memory (for example, EEPROM: Electrically Erasable and Programmable Read-Only Memory).

  The dimming signal output unit 6 generates dimming signals S <b> 1 and S <b> 2 according to the content of the control command based on the control command input from the wireless signal receiving unit 5, and outputs the dimming signal S <b> 1 and S <b> 2 to the control unit 4. Here, if the dimming level represented by the control command is within the first dimming range A, the dimming signal output unit 6 includes the dimming signal S1 including a rectangular wave signal with a duty ratio of 100%, and the dimming level. And a dimming signal S2 composed of a DC voltage having a voltage value corresponding to the output voltage to the control unit 4 (see FIGS. 2A and 2B). If the dimming level represented by the control command is within the second dimming range B, the dimming signal output unit 6 includes the dimming signal S1 that is a PWM signal having a duty ratio corresponding to the dimming level, and the dimming level. The dimming signal S2 fixed to the voltage value when the power is 50% is output to the control unit 4 (see FIG. 2C). In the first dimming range A, the voltage value of the dimming signal S2 gradually decreases as the dimming level decreases from 100% to 50%. In the second dimming range B, as the dimming level decreases from 50% to 10%, the duty ratio of the dimming signal S1 gradually decreases from 100% to 20%.

  Here, when the user presses the operation button 21 of the wireless transmitter 20, the dimming signal output unit 6 controls the dimming signal corresponding to the dimming level of 100% based on the control command from the wireless transmitter 20. S1 and S2 are output to the control unit 4, and the light emitting diode LD1 is fully lit. When the operation button 22 of the wireless transmitter 20 is operated, the dimming signal output unit 6 stops the output of the dimming signals S1 and S2 based on the control command from the wireless transmitter 20, and the step-down chopper unit 3 By stopping the switching operation, the light emitting diode LD1 is turned off. When the operation button 23 of the wireless transmitter 20 is operated, the dimming signal output unit 6 brightens the dimming level by a predetermined level from the previous dimming level based on the control command from the wireless transmitter 20. Control signals S1 and S2 are generated and output to the control unit 4. When the operation button 24 of the wireless transmitter 20 is operated, the dimming signal output unit 6 darkens the dimming level by a predetermined level from the previous dimming level based on the control command from the wireless transmitter 20. Control signals S1 and S2 are generated and output to the control unit 4. When the user continues to press the operation button 23 and reaches the upper limit level (100% in the present embodiment) of the dimming range, the dimming signal output unit 6 sounds the buzzer 8 and the user cannot be further brightened. To inform. When the user continues to press the operation button 24 and reaches the lower limit level (10% in this embodiment) of the dimming range, the dimming signal output unit 6 sounds the buzzer 8 and darkens further as described above. Inform the user that it is not possible.

  When the operation button 26 is operated by the user, the dimming signal output unit 6 sets the lower limit of the dimming control to the lower limit level of the second dimming range B based on the control command from the wireless transmitter 20. Alternatively, it is switched whether the predetermined level is brighter than the lower limit level in the second dimming range B. At this time, the dimming signal output unit 6 causes the storage unit 7 to store whether the lower limit of the dimming control is switched to the lower limit level of the second dimming range B or the predetermined level. In the present embodiment, the lower limit level of the dimming range B is 10%, and the predetermined level is 50%, which is the upper limit level of the dimming range B. Therefore, when the lower limit of the dimming control is switched to 50%, the dimming control is prohibited in the second dimming range B, and eventually the dimming lower limit of the light emitting diode LD1 is limited to 50%. . In the present embodiment, the lower limit of the dimming control by both the first dimming method and the second dimming method is switched according to the operation of the operation button 25, but only the lower dimming control by the second dimming method. May be switched between the lower limit level of the second dimming range B or the predetermined level.

  Next, the dimming lighting operation by the lighting device 1 will be described with reference to the operation waveform diagrams of FIGS. Here, FIG. 2A is an operation waveform diagram of each part in the fully lit state, FIG. 2B is an operation waveform diagram of each part in the 50% dimming state, and FIG. 2C is a 10% adjustment. The operation | movement waveform diagram of each part in a light state is each shown. Further, in each of FIGS. 2A to 2C, waveform diagrams of the dimming signal S1, the dimming signal S2, the drive signal S3, the drain current I1 of the FET 12, and the output current I2 flowing through the light emitting diode LD1 in order from the top. Respectively.

  As described above, in the first dimming range A, the dimming signal output unit 6 outputs the dimming signal S1 composed of a rectangular wave signal with a duty ratio of 100% to the control unit 4, and a voltage corresponding to the dimming level. A dimming signal S2 composed of a direct current voltage is output to the control unit 4.

  The control unit 4 performs dimming control according to the dimming signals S1 and S2 input to the input terminals P1 and P2. In the first dimming range A, the dimming signal S1 input to the input terminal P1. The signal level is always H level. When the signal level of the dimming signal S1 is H level, the control unit 4 switches the signal level of the drive signal S3 output from the output terminal P4 to H level to turn on the FET 12. When the FET 12 is turned on, the drain current I1 starts to flow, and the drain current I1 gradually increases. The controller 4 monitors the drain current I1 from the voltage input to the input terminal P3, and when the drain current I1 reaches the threshold current Ith set based on the dimming signal S2, the signal of the drive signal S3 The level is switched to the L level, and the FET 12 is turned off. The control unit 4 turns on the FET 12 when a certain period elapses after the FET 12 is turned on, or when a certain off time elapses. As the step-down chopper unit 3 repeats the switching operation as described above, a drain current I1 having a triangular waveform as shown in FIG. Then, the direct current I2 smoothed by the smoothing capacitor 14 is supplied to the light emitting diode LD1, and the light emitting diode LD1 is turned on. Note that the control unit 4 may detect the auxiliary winding of the choke coil 15 or the voltage at one end of the choke coil 15 to turn on the FET 12 in the critical mode.

  Here, the dimming signal output unit 6 sets the threshold current Ith to a smaller value as the dimming level represented by the control command from the wireless transmitter 20 decreases, and thereby the direct current flowing through the light emitting diode LD1. Since I2 decreases, the light emitting diode LD1 is dimmed. For example, as shown in FIGS. 2A and 2B, the threshold current Ith in the 50% dimming state is set to a current value that is approximately half of the threshold current Ith in the full lighting state. Therefore, at the time of 50% dimming, the output current I2 of the step-down chopper unit 3 is lower than the output current I2 in the fully lit state, and the dimming level of the light emitting diode LD1 is dimmed to 50%. In the first dimming range A, the duty ratio of the dimming signal S1 is set to 100%, and the control unit 4 does not perform dimming control by the second dimming method, but only by the first dimming method. Since the dimming control is performed, the drain current I1 becomes a DC current waveform having a current value corresponding to the dimming level, and illumination light with little difference in brightness is obtained.

  On the other hand, in the second dimming range B in which the dimming level is 10% or more and 50% or less, the lighting device 1 performs dimming control by both the first dimming method and the second dimming method. It is assumed that the lower limit of dimming by the second dimming method is switched to the lower limit level (10%) of the second dimming range B by the user operating the wireless transmitter 20.

  In the second dimming range B, as shown in FIG. 2C, the dimming signal S1 is a rectangular signal having a duty ratio corresponding to the dimming level, and the dimming signal S2 has a dimming level of 50%. It becomes the DC voltage of the voltage value at the time of. A drain current I1 having a triangular waveform flows through the FET 12 when the signal level of the dimming signal S1 is H level, and no drain current I1 flows when the signal level of the dimming signal S1 is L level. Therefore, the current I2 flowing through the light emitting diode LD1 has a peak value that is substantially the same as when 50% is lit, and a bottom value that is substantially zero. The period during which the current I2 flows is determined by the duty ratio of the dimming signal S1, and the current waveform is such that the brightness corresponding to the dimming level of the control command is obtained on average. In the waveform of FIG. 2 (c), the duty ratio of the dimming signal S1 is set to 20%, so that an average brightness of about 10% is obtained.

  As described above, in the first dimming range A, dimming control is performed only by the first dimming method (so-called DC dimming method), and a constant current having a current value corresponding to the dimming level flows through the light emitting diode LD1. Therefore, it is difficult for the illumination light to interfere with the image of the video equipment when the video equipment is photographed. In the second dimming range B, dimming control is performed by both the first dimming method and the second dimming method (so-called burst dimming method), and the current flowing through the light emitting diode LD1 cannot be sensed by human eyes. The frequency is periodically changed. This makes it possible to perform dimming control over a wider dimming range than when dimming only with the first dimming method. Further, by sufficiently increasing the period of the second dimming method, the light output of the light emitting diode LD1 can be dimmed without causing flickering to the human eye. However, when shooting with an imaging device such as a video camera or digital camera, depending on the shutter speed and exposure time of the imaging device, the illuminance change may appear as light and dark stripes on the screen, or the screen may flicker. is there.

  Therefore, in the lighting apparatus of the present embodiment, for example, when the user operates the operation button 26 of the wireless transmitter 20 at the time of shooting of the video equipment, at least the light control lower limit by the second light control method (in the present embodiment, the first light control lower limit). The lower limit of the dimming control by both the first dimming method and the second dimming method can be limited. When the user operates the operation button 26 of the wireless transmitter 20 with the lower limit of the dimming control being switched to the lower limit level of the second dimming range B in the second dimming range B, the dimming range is narrowed. A control command for switching the dimming lower limit in the direction is transmitted from the wireless transmitter 20. In response to this control command, the dimming signal output unit 6 switches the lower limit of the dimming control to the upper limit level (50%) of the second dimming range B. As a result, the light control lower limit of the light emitting diode LD1 is raised to 50%, and light control by the first light control method is performed only in the first light control range A. Therefore, it is possible to reduce the change in illuminance appearing as bright and dark stripes in the image of the imaging device or the screen appearing to flicker. In this state, even if the user operates the operation button 24 of the wireless transmitter 20 to reduce the dimming level from 50%, the dimming lower limit is set to 50%. Sounds the buzzer 8 to inform the user that it can no longer be darkened.

  Further, when the user operates the operation button 26 of the wireless transmitter 20 after the photographing is finished, a control command for switching the dimming lower limit in the direction of expanding the dimming range is transmitted from the wireless transmitter 20. In response to this control command, the dimming signal output unit 6 switches the dimming lower limit of both the first dimming method and the second dimming method to the lower limit level (10%) of the second dimming range B. As a result, the dimming lower limit of the light emitting diode LD1 is lowered to 10%, and the dimming control by both the first dimming method and the second dimming method is performed in the second dimming range B, which is deeper. Dimming is possible up to the dimming level.

  As described above, the lighting device 1 of the present embodiment is used for lighting the light emitting diode LD1 (semiconductor light emitting element) that emits light when a current flows in the forward direction. The lighting device 1 includes a lighting circuit unit (consisting of a step-down chopper unit 3) that supplies current to the light emitting diode LD1, a dimming control unit that performs dimming by adjusting the output of the lighting circuit unit, a dimming limiting unit, Is provided. The dimming control unit includes a control unit 4 and a dimming signal output unit 6 and performs dimming control by combining the first dimming method and the second dimming method. The first dimming method is a method of adjusting light by adjusting the direct current value of the current flowing from the step-down chopper unit 3 to the light emitting diode LD1 (so-called direct current dimming). The second dimming method is a method (so-called burst dimming) that performs dimming by intermittently operating the step-down chopper unit 3 and adjusting the average value of the current flowing through the light emitting diode LD1. The dimming control unit performs dimming control only in the first dimming method in the relatively bright first dimming range A, and the first dimming in the second dimming range B that is darker than the first dimming range A. Dimming control is performed by both the method and the second dimming method. The dimming restriction unit (also used by the dimming signal output unit 6) is at least a dimming lower limit by the second dimming method (in the present embodiment, the first dimming method and the second dimming method) according to a user operation. The dimming lower limit) is switched between the lower limit level of the second dimming range B or the predetermined level brighter than the lower limit level within the second dimming range.

  In this way, the dimming control unit performs dimming in both the first dimming method and the second dimming method in the second dimming range B that is darker than the first dimming range A. Compared with the case where dimming is performed only by the method, the controllability is stable, and dimming is possible up to a deeper (darker) dimming level. By the way, the darker the dimming level in the second dimming range B, the longer the period during which no current flows through the light emitting diode LD1, and the illuminance change appears as light and dark stripes on the screen when shooting with an imaging device. The screen may flicker. Even in such a case, if the dimming limiter switches the lower limit of the dimming control to a predetermined level brighter than the lower limit level in the second dimming range B according to the user's operation, a current flows through the light emitting diode LD1. Since the period during which no light is present is limited, the difference in light output brightness can be reduced. Therefore, when imaging with an imaging device, the illuminance change appears as light and dark stripes on the screen or the screen flickers by raising at least the dimming lower limit of the second dimming method to a predetermined level. Can be reduced. Further, since a large-capacity smoothing capacitor is not required to smooth the current flowing through the light emitting diode LD1, a small and low-cost lighting device and a lighting fixture using the same can be realized.

  In the present embodiment, the dimming range of the lighting device 1 is changed to the first dimming range by switching the dimming lower limit of both the first dimming method and the second dimming method to the upper limit level of the second dimming range B. Although the first dimming range A is limited only by the dimming method, the dimming lower limit may be switched to a predetermined level within the second dimming range B. Even in this case, since the dimming control by the second dimming method can be limited in a part of the dimming range (a range darker than the predetermined level) within the second dimming range B, the above-mentioned part of the dimming control is possible. In the light range, it is possible to prevent bright and dark stripes from appearing on the screen of the imaging device and flickering of the screen.

  In the present embodiment, the dimming restriction unit switches the dimming lower limit of both the first dimming method and the second dimming method according to the user's operation, but only the second dimming method is used. The light lower limit may be switched between the upper limit level of the second dimming range B or a predetermined level. Even in this case, since the dimming control by the second dimming method is restricted in a part of the dimming range within the second dimming range B, the screen of the imaging device is not bright or dark in the part of the dimming range. It can suppress the appearance of stripes and flickering on the screen. Further, the dimming control unit may perform dimming control by the first dimming method even if the dimming range is darker than the predetermined level as long as there is no problem in controllability.

  In addition, the dimming control unit (consisting of the control unit 4 and the dimming signal output unit 6) in a state where the dimming restriction unit (comprising the dimming signal output unit 6) switches the lower limit of the dimming control to the predetermined level. It is also preferable to control the ratio of the minimum value to the maximum value of the current I2 flowing through the light emitting diode LD1 to 70% or more.

  As a result of an experiment with an actual lighting fixture, if the ratio of the minimum value to the maximum value of the current I2 flowing through the light emitting diode LD1 is controlled to be 70% or more, the difference in light output is sufficiently small, and the imaging device It was confirmed that the interference with the image taken with the can be reduced. Therefore, by controlling the ratio of the minimum value to the maximum value of the current I2 flowing through the light emitting diode LD1 to be 70% or more, the light output of the light emitting diode LD1 can be prevented from interfering with the image of the imaging device. it can.

  Moreover, the lighting device 1 of the present embodiment includes a wireless signal receiving unit 5 that receives a wireless signal from a wireless transmitter 20 that transmits a control command according to a user operation using a wireless signal. The dimming signal output unit 6 serving as the dimming limiting unit sets at least the dimming lower limit of the second dimming method to the lower limit level of the second dimming range B or within the second dimming range B. Switches between a predetermined level brighter than the lower limit level.

  Thereby, if it is in the transmission range of the wireless transmitter 20, even if it does not go to the installation place of the lighting device 1, the lower limit of dimming control can be switched using the wireless transmitter 20, and the convenience improves. . In the present embodiment, the lower limit of the dimming control is switched using the wireless transmitter 20, but the lower limit of the dimming control is operated by the user operating an operation unit (not shown) provided in the instrument body. May be switched.

  In the lighting device 1 of the present embodiment, the dimming restriction unit (comprising the dimming signal output unit 6) has at least the second dimming method (in the present embodiment, both the first dimming method and the second dimming method). ) Is stored in the storage unit 7 for storing whether the dimming lower limit is switched to the lower limit level of the second dimming range B or to the predetermined level. Then, the dimming limiter switches the dimming lower limit to the same level as before the extinguishing based on the stored contents of the storage unit 7 at the time of relighting after the extinction.

  Thereby, the setting before turning off is stored in the storage unit, and at the time of turning on again after turning off the light using the wireless transmitter 20 or power-off, at least the dimming lower limit by the second dimming method is the same as before turning off. Since it is set to the level, the setting time can be saved. In the case of a user who frequently shoots using a photographic device, it is not necessary to perform the operation of switching the light control lower limit by the second light control method every time, so that the setting work can be saved.

  In the present embodiment, when the operation button 25 of the wireless transmitter 20 is operated, the dimming control unit (consisting of the control unit 4 and the dimming signal output unit 6) is based on a control command from the wireless transmitter 20. Switch the operation mode to automatic dimming mode, which automatically controls the light output. In the automatic dimming mode, the dimming signal output unit 6 that constitutes the dimming control unit, for example, based on a detection signal from a brightness detection unit 9 (for example, a photodiode) that detects ambient brightness, The light output is automatically controlled by controlling the output of the step-down chopper unit 3 so that the brightness becomes a predetermined reference level.

  Even when the dimming control unit operates in the automatic dimming mode, at least in the dimming range darker than the predetermined level by switching the dimming lower limit by the second dimming method to the predetermined level as described above at least in the same manner as described above. Dimming control by the two dimming method is limited. Therefore, even when photographing under illumination in the automatic light control mode, it is possible to reduce the possibility that bright and dark stripes appear on the screen or flickering occurs. The automatic light control mode is not limited to the one that automatically controls the light output according to the ambient brightness, and may be one that automatically controls the light output according to the current time, for example. .

  In the above embodiment, only the dimming for adjusting the brightness is mentioned, but it is applied to the toning control for adjusting the light output by adjusting the light output of different light colors (cold color, warm color, etc.). Thus, the toning control range may be limited, and the occurrence of light color unevenness on the screen of the imaging device can be reduced.

DESCRIPTION OF SYMBOLS 1 Lighting device 2 AC-DC converter part 3 Step-down chopper part (lighting circuit part)
4 Control unit (dimming control unit)
5 Wireless signal receiving unit 6 Dimming signal output unit (Dimming control unit, Dimming restriction unit)
7 Storage Unit 20 Wireless Transmitter LD1 Light Emitting Diode (Semiconductor Light Emitting Element)

Claims (6)

A lighting device for a semiconductor light emitting element that emits light when a current flows in a forward direction,
A lighting circuit for supplying a current to the semiconductor light emitting element;
A dimming control unit for dimming by adjusting the output of the lighting circuit unit,
The dimming control unit adjusts a direct current value of a current flowing from the lighting circuit unit to the semiconductor light emitting element, and intermittently operates the lighting circuit unit to operate the semiconductor Dimming control is performed in combination with the second dimming method that dimmes by adjusting the average value of the current flowing through the light emitting element,
The dimming control unit performs dimming control only by the first dimming method in the relatively bright first dimming range, and the first dimming range is darker than the first dimming range. Dimming control is performed by both the dimming method and the second dimming method,
Depending on the user's operation, at least the lower limit of dimming by the second dimming method is set as the lower limit level of the second dimming range, or the predetermined dimming is brighter than the lower limit level in the second dimming range A lighting device comprising a dimming restriction unit for switching between levels. A wireless signal receiving unit that receives a wireless signal transmitted from a wireless transmitter that transmits a control command according to a user operation by a wireless signal;
The dimming restriction unit switches whether the dimming lower limit is set to the lower limit level or the predetermined level according to a control command received by the wireless signal receiving unit. The lighting device according to 1. The dimming restriction unit includes a storage unit that stores whether the dimming lower limit is switched to the lower limit level or the predetermined level is switched,
The said dimming restriction | limiting part switches the said dimming lower limit to the same level as before light extinction based on the memory | storage content of the said memory | storage part at the time of re-lighting after light extinction, either of Claim 1 or 2 characterized by the above-mentioned. Lighting device.   4. The light control unit according to claim 1, wherein the light control unit includes an automatic light control function that automatically controls light output according to ambient brightness or current time. 5. Lighting device.   In a state where the dimming restriction unit switches the dimming lower limit to the predetermined level, the dimming control unit controls the ratio of the minimum value to the maximum value of the current flowing through the semiconductor light emitting element to 70% or more. The lighting device according to claim 1, wherein:   A lighting fixture comprising: the lighting device according to any one of claims 1 to 5; and a semiconductor light emitting element that is turned on by the lighting device.

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