JP2018195503A - Lighting device, luminaire, and signboard - Google Patents

Abstract

To provide a lighting device having a function of visible light communication, which can inhibit a circuit element from being broken even if abnormality such as a connection failure of a light-emitting element occurs.SOLUTION: A lighting device 10 comprises: a constant current source 11; an overvoltage detection circuit 12 which stops operation of the constant current source 11 when detecting an output voltage of the constant current source 11 exceeding a first predetermined value; a capacitor C1 connected to an output terminal of the constant current source 11; a series circuit including a load wiring line 15 connected in series with an LED unit 14 and a transistor Q1; and a modulation-abnormality detector part 13 having a function as a modulation circuit which turns the transistor Q1 on/off based on signals for visible light communication, and a function as an abnormality detection circuit which turns the transistor Q1 off for first prescribed time or longer on detection of an abnormal state. When the abnormality detection circuit turns the transistor Q1 off for the first prescribed time or longer, the constant current source 11 increases the output voltage until it exceeds the first predetermined value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a lighting device that applies a current to a light emitting element such as an LED, a lighting fixture that includes the lighting device, and a signboard that includes the lighting fixture, and particularly relates to a lighting device that includes a modulation circuit for visible light communication.

  In recent years, a lighting device that applies a current to a light emitting element such as an LED has been proposed that includes a modulation circuit for visible light communication (see, for example, Patent Document 1). With such a lighting device, the lighting device also becomes a data communication device, and a convenient wireless environment is constructed.

  According to the lighting device of Patent Document 1, a visible light communication switch element is connected in series with an LED, and a resistor is connected in parallel with the switch element. Thus, even when the switch element is off, no load is applied, so that the output voltage of the constant current source is stabilized.

JP 2013-110634 A

  However, in the lighting device disclosed in Patent Document 1, when the output path of the constant current source is disconnected due to poor connection between the lighting device and the LED, the output voltage of the constant current source rises to the maximum, and the modulation circuit And excessive voltage stress is applied to the LED. As a result, the circuit elements constituting the lighting device may be destroyed. Furthermore, in this state, if the LED is reconnected to the lighting device (that is, removed), an excessive current is applied to the LED due to discharge from the smoothing capacitor connected to the output terminal of the constant current source. There is also a possibility that the LED will be destroyed when applied.

  Therefore, the present invention has been made in view of the above problems, and is a lighting device having a function of visible light communication, and even when an abnormality such as a connection failure of a light emitting element occurs, a circuit element is An object of the present invention is to provide a lighting device or the like that is prevented from being destroyed.

  In order to achieve the above object, a lighting device according to an aspect of the present invention is a lighting device that applies a current to a light-emitting element, and includes a constant current source, a capacitor connected to an output terminal of the constant current source, A series circuit including a load wiring and a switch element connected in parallel with the capacitor and connected in series with the light emitting element, and a modulation circuit for turning on and off the switch element based on a signal for visible light communication, An overvoltage detection circuit that performs output suppression control to stop the operation of the constant current source or reduce the current output from the constant current source when detecting that the output voltage of the constant current source exceeds a first predetermined value; When an abnormal state that is at least one of an abnormality of a light emitting element, an abnormality of the load wiring, an abnormality of the modulation circuit, and an overload of the switch element is detected, the switch is operated for a first predetermined time or more. An abnormality detection circuit for turning off the child, and the constant current source increases the output voltage until the first predetermined value is exceeded when the switch element is turned off for the first predetermined time or more by the abnormality detection circuit. Let

  In order to achieve the above object, a lighting fixture according to one embodiment of the present invention includes a light emitting element and the lighting device that applies a current to the light emitting element.

  In order to achieve the above object, a signboard according to an embodiment of the present invention is illuminated with a light emitting element, the lighting device for applying a current to the light emitting element, and at least one of a character and a figure. The display board shown is provided.

  According to the present invention, there is provided a lighting device having a visible light communication function, in which even when an abnormality such as a connection failure occurs, a lighting device or the like in which circuit elements are prevented from being destroyed is provided.

Circuit diagram of lighting device according to Embodiment 1 Timing chart showing operation of lighting device according to Embodiment 1 Circuit diagram of lighting device according to Embodiment 2 Timing chart showing operation of lighting device according to Embodiment 2 External view of lighting apparatus according to application example of embodiment 3 External view of signboard according to application example of embodiment 3

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that each of the embodiments described below shows a specific example of the present invention. The numerical values, shapes, materials, constituent elements, arrangement positions and connection forms of the constituent elements, operation timings, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept of the present invention are described as optional constituent elements. Also, the drawings are not necessarily shown strictly. In each figure, substantially the same configuration is denoted by the same reference numeral, and redundant description is omitted or simplified.

(Embodiment 1)
First, the lighting device according to Embodiment 1 will be described.

  FIG. 1 is a circuit diagram of a lighting device 10 according to the first embodiment. This lighting device 10 is a device having a function of applying current (that is, lighting) to the LED unit 14 and a function of visible light communication, and includes a constant current source 11, an overvoltage detection circuit 12, and modulation / abnormality detection. The unit 13 is provided.

  The LED unit 14 is an example of a light emitting element serving as a load of the lighting device 10. Here, the LED unit 14 is connected to the lighting device 10 by a load wiring 15 and includes a plurality of LEDs 1 to 5 connected in series. In addition, a light emitting element is not restricted to LED, Other light emitting elements, such as organic EL and inorganic EL, may be sufficient. Further, the LED unit 14 is not limited to a plurality of LEDs connected in series, and may be configured by one LED, may be configured by a plurality of LEDs connected in parallel, or connected in series. A plurality of LED sets may be connected in parallel.

  The constant current source 11 is a power source that applies a constant current to the LED unit 14 that is a load. The constant current source 11 increases the output voltage to the maximum voltage when the load is disconnected. For example, when the transistor Q1 is turned off for a first predetermined time (for example, 10 msec) or longer, the constant current source 11 increases the output voltage until the first predetermined value is exceeded. For example, when the forward voltage of the LED unit 14 is 15V to 78V, the first predetermined value is a value of 86V or more.

  When the overvoltage detection circuit 12 detects that the output voltage of the constant current source 11 exceeds the first predetermined value, the overvoltage detection circuit 12 performs an output suppression control for stopping the operation of the constant current source 11 or reducing the current output by the constant current source 11. Circuit. The overvoltage detection circuit 12 compares, for example, a resistance voltage dividing circuit that detects an output voltage, a constant voltage diode that determines the first predetermined value, a voltage obtained by the resistance voltage dividing circuit and a voltage obtained by the constant voltage diode. Comparator etc. In addition, the overvoltage detection circuit 12 receives the third voltage when the output voltage falls below a third predetermined value that is equal to or lower than the first predetermined value after exceeding the first predetermined value, or after the output voltage exceeds the first predetermined value. When the predetermined time has elapsed, the output suppression control is canceled. Thereby, the constant current source 11 returns to normal operation. The third predetermined value is a threshold voltage, for example, 3 V or less, at which the modulation / abnormality detection unit 13 (particularly, the microcomputer MCU1) can be reset and restarted. The third predetermined time is a time from when the constant current source 11 exceeds the first predetermined value and the operation of the constant current source 11 is stopped by the overvoltage detection circuit 12 until the voltage across the capacitor C1 becomes approximately 0V. For example, 1 sec.

  The modulation / abnormality detection unit 13 functions as a modulation circuit that turns on and off the transistor Q1 that is a switching element based on a signal for visible light communication, and an abnormality detection that turns off the transistor Q1 for a first predetermined time or more when an abnormal state is detected. It is a circuit that has both circuit functions. Specifically, the modulation / abnormality detection unit 13 includes a constant voltage regulator REG1, a microcomputer (microcomputer) MCU1, capacitors C1 and C2, diodes D1, constant voltage diodes ZD1, transistors Q1 to Q4, and resistors R1 to R6. The

  The capacitor C1 is a smoothing capacitor connected to the output terminal of the constant current source 11 (that is, between the two output terminals). In the modulation / abnormality detection unit 13, a transistor Q1 is provided as a switching element for visible light communication, and the transistor Q1 is periodically turned on and off. The transistor Q1 is, for example, a MOSFET. In the off period of the transistor Q1, since the current path is interrupted, the output voltage of the constant current source 11 increases. In order to suppress the amount of increase, a capacitor C1 is provided. The capacitance of the capacitor C1 is desirably a value at which the output voltage increase ΔVF during the off period of the transistor Q1 is 30% or less of the forward voltage VF of the LED unit 14, for example. Specifically, when the off period Toff is 208 μsec, the output current Iout is 0.7 A, and the forward voltage VF is 15 V, the increase amount ΔVF is 4.5 V from ΔVF = 15 V × 0.3 = 4.5 V. It becomes. Therefore, the minimum capacitance C1min of the capacitor C1 is 32.4 μF from C1min = Toff × Iout / ΔVF = 208 μsec × 0.7 A / 4.5 V≈32.4 μF. Accordingly, the capacitance of the capacitor C1 is set to 33 μF or more, for example.

  The constant voltage regulator REG1 is a circuit module that generates a constant power supply voltage for operating the circuit inside the modulation / abnormality detection unit 13 from the output voltage of the constant current source 11. The constant voltage regulator REG1 is, for example, a small switching regulator or a series regulator that outputs a power supply voltage of 5V.

  The microcomputer MCU1 is a microcomputer that operates with the power supply voltage generated by the constant voltage regulator REG1. The microcomputer MCU1 includes, for example, a ROM that holds a program, a RAM as a temporary storage area, a processor that executes the program, an input / output circuit such as an A / D converter and a D / A converter, a counter / timer, and the like. LSI. The microcomputer MCU1 functions as a part of the modulation circuit. Specifically, the microcomputer MCU1 outputs a drive signal for turning on and off the transistor Q1 from the output terminal SIG based on a signal for visible light communication according to a built-in program. The signal for visible light communication is a fixed character string determined by a built-in program or a character string that can change dynamically.

  The resistor R6, the transistor Q5, the resistor R5, and the transistors Q3 and Q4 are drive circuits that drive the gate of the transistor Q1, and constitute a part of the modulation circuit. This drive circuit charges and discharges the gate-source capacitance of the transistor Q1 so as to turn on and off the transistor Q1 in accordance with a drive signal from the microcomputer MCU1. Specifically, when the drive signal from the microcomputer MCU1 is HIGH, the transistor Q5 is turned on, whereby the transistor Q3 is turned off and the transistor Q4 is turned on. As a result, the gate of the transistor Q1 is discharged through the transistor Q4 and the resistor R4, so that the gate potential of the transistor Q1 becomes 0 V and the transistor Q1 is turned off. On the other hand, when the drive signal from the microcomputer MCU1 is LOW, the transistor Q5 is turned off, whereby the transistor Q3 is turned on and the transistor Q4 is turned off. As a result, the gate of the transistor Q1 is charged through the transistor Q3 and the resistor R4, so that the gate potential of the transistor Q1 becomes HIGH and the transistor Q1 is turned on. When the transistor Q1 is turned on / off by the drive signal from the microcomputer MCU1, the digital light code for visible light communication is superimposed on the light emission from the LED unit. The resistor R4 is a resistor that limits the charge / discharge of the gate of the transistor Q1. By adjusting the on / off speed of the transistor Q1 by the resistor R4, noise during switching of the transistor Q1 can be suppressed.

  The microcomputer MCU1 also functions as a part of an abnormality detection circuit that turns off the transistor Q1 for a first predetermined time (for example, 10 msec) or more when an abnormal state in the lighting device 10 is detected. Specifically, the microcomputer MCU1 receives the voltage generated in the resistor R1 by the current flowing through the transistor Q1 (that is, the drain current) through the input terminal CS, and periodically converts it into a digital value by the built-in A / D converter. To do. And it repeats calculating the average value of the digital value in a fixed time. Then, the microcomputer MCU1 determines whether or not an abnormal state has occurred by determining whether or not the calculated average value is outside a predetermined range, and if it is determined that an abnormal state has occurred, the transistor Q1 Is controlled to be turned off for a first predetermined time or longer. The predetermined range is a voltage range that can be generated in the resistor R1 by the current flowing through the transistor Q1 when the lighting device 10 is operating normally.

  The abnormal state detected by the microcomputer MCU1 includes at least one of the abnormality of the LED unit 14, the abnormality of the load wiring 15, the abnormality of the modulation circuit, and the overload of the transistor Q1. The transistor Q1 and the load wiring 15 constitute a series circuit connected in parallel with the capacitor C1 and connected in series with the LED unit 14. Therefore, the abnormality of the LED unit 14, the abnormality of the load wiring 15, and the overload of the transistor Q1 may cause disconnection or short circuit of the current path. The “abnormality” includes not only breakage and failure, but also connection failure, contact failure, desorption (repetition of disconnection and reconnection), current path disconnection, short circuit, and the like.

  The resistor R2 is a resistor for applying a bias voltage to the transistor Q1. With this bias voltage, when the lighting device 10 is turned on, the transistor Q1 is automatically turned on before the microcomputer MCU1 is activated.

  The constant voltage diode ZD1 is a Zener diode for limiting the voltage applied to the gate of the transistor Q1. When a bias voltage is applied to the gate of the transistor Q1 through the resistor R2, if the bias voltage is too high, the gate insulating film of the transistor Q1 is destroyed. In order to prevent this, a constant voltage diode ZD1 is provided. For example, the constant voltage diode ZD1 limits the gate potential of the transistor Q1 to 10V.

  The diode D1 is a diode for preventing backflow. When the transistor Q1 is automatically turned on via the resistor R2, a current may be generated toward the constant voltage regulator REG1 via the resistor R4, the emitter of the transistor Q4, the base of the transistor Q4, and the resistor R5. A diode D1 is provided to block this current. The diode D1 can reliably turn on the transistor Q1 before the constant voltage regulator REG1 is activated.

  The capacitor C2, the transistor Q2, and the resistors R3 and R1 constitute a current limiting circuit that limits the current flowing through the transistor Q1. Since the current flowing through the transistor Q1 flows through the resistor R1, a voltage corresponding to the current flowing through the transistor Q1 is generated at both ends of the resistor R1. Since the voltage is applied between the base and emitter of the transistor Q2, the transistor Q2 is turned on when the threshold voltage Vbe of the transistor Q2 is exceeded, and the gate potential of the transistor Q1 is lowered. The capacitor C2 is provided for control phase compensation. In normal times, the value of the resistor R1 is set so that the voltage across the resistor R1 does not exceed the threshold voltage Vbe of the transistor Q2. When a load short circuit during lighting or an overcurrent of the load due to overvoltage occurs, the voltage generated across the resistor R1 increases, thereby increasing the current flowing through the transistor Q2 and forcibly turning off the transistor Q1. It is controlled in the direction to do.

  Next, the operation of the lighting device 10 according to Embodiment 1 configured as described above will be described.

  FIG. 2 is a timing chart showing the operation of the lighting device 10 according to the first embodiment. In this figure, from the top, the output voltage Vdc of the constant current source 11, the current Iout flowing through the LED unit 14, the gate-source voltage Vgs (Q1) of the transistor Q1, the voltage of the input terminal CS of the microcomputer MCU1, Detection result ". The “detection result” is a state in which HIGH detects an abnormal state and LOW does not detect an abnormal state.

  Until time t0, the lighting device 10 is operating normally. The microcomputer MCU1 performs control to periodically turn on and off the transistor Q1 based on a signal for visible light communication (see gate-source voltage Vgs (Q1)). As a result, the current Iout flowing through the LED unit 14 is Intermittent current. The output voltage Vdc is stabilized by the capacitor C1. The voltage at the input terminal CS of the microcomputer MCU1 is also in a normal state.

  It is assumed that the LED unit 14 is disconnected from the lighting device 10 due to poor contact between the load wiring 15 and the LED unit 14 at time t0, and the current path is disconnected. Then, the current Iout flowing through the LED unit 14 becomes zero, and the constant current source 11 increases the output voltage Vdc and charges the capacitor C1. Note that the microcomputer MCU1 continues the control to turn on and off the transistor Q1 (see gate-source voltage Vgs (Q1)).

  At time t1, it is assumed that the LED unit 14 is reconnected to the lighting device 10 due to elimination of a contact failure between the load wiring 15 and the LED unit 14, and the current path is conducted. In this state, since the output voltage Vdc is large and the capacitor C1 is charged, if the current path is conducted, a large current flows through the LED unit 14 when the transistor Q1 is turned on. Thereby, the voltage of the input terminal CS of the microcomputer MCU1 rises. The peak of the gate-source voltage Vgs (Q1) of the transistor Q1 is temporarily lowered to 3 to 4 V by the current limiting circuit including the resistor R1 and the like, and an increase in current flowing through the LED unit 14 is suppressed. The The output voltage Vdc decreases rapidly due to the occurrence of the load current.

  Since the voltage at the input terminal CS of the microcomputer MCU1 rises and reaches an abnormal level from time t1 to t2, the microcomputer MCU1 uses the built-in counter to measure the time when the voltage at the input terminal CS exceeds the abnormal level. To start.

  At time t2, when the microcomputer MCU1 detects that the time during which the voltage at the input terminal CS exceeds the abnormal level has reached a predetermined time, it determines that an abnormal state has occurred and turns off the transistor Q1 for a first predetermined time or more. To control. When the transistor Q1 is turned off, the current Iout flowing through the LED unit 14 becomes zero again, and the increase of the output voltage Vdc by the constant current source 11 is resumed. The first predetermined time is a time necessary for at least the output voltage Vdc to reach a voltage determined by the overvoltage detection circuit 12 to be an overvoltage (that is, a first predetermined value), and is, for example, 10 msec.

  When the output voltage Vdc reaches a first predetermined value (for example, 86V) at time t3, the overvoltage detection circuit 12 determines that an overvoltage has occurred and controls the constant current source 11 to perform output suppression control. . That is, the overvoltage detection circuit 12 controls the constant current source 11 to stop the operation of the constant current source 11 or reduce the current Iout output from the constant current source 11 (here, the operation of the constant current source 11 is reduced). Stop output).

  As described above, the lighting device 10 according to the present embodiment is a device that applies current to the LED unit 14, and the constant current source 11 and the output voltage of the constant current source 11 exceed the first predetermined value. When detected, the operation of the constant current source 11 is stopped, or an overvoltage detection circuit 12 that performs output suppression control for reducing the current Iout output from the constant current source 11, a capacitor C1 connected to the output terminal of the constant current source 11, and a capacitor A series circuit including a load wiring 15 and a transistor Q1 connected in parallel to C1 and connected in series to the LED unit 14, and a function as a modulation circuit for turning on and off the transistor Q1 based on a signal for visible light communication Detecting an abnormal state that is at least one of an abnormality of the LED unit 14, an abnormality of the load wiring 15, an abnormality of the modulation circuit, and an overload of the transistor Q1. Then, a modulation / abnormality detection unit 13 having a function as an abnormality detection circuit for turning off the transistor Q1 for a first predetermined time or longer is provided, and the constant current source 11 is connected to the transistor Q1 by the abnormality detection circuit for a first predetermined time or longer. When turned off, the output voltage is increased until the first predetermined value is exceeded.

  Thus, when an abnormal state is detected by the abnormality detection circuit (that is, the modulation / abnormality detection unit 13), the modulation transistor Q1 is turned off for a first predetermined time or longer, and the output voltage of the constant current source 11 is the first voltage. It exceeds the predetermined value. As a result, this is detected by the overvoltage detection circuit 12, and output suppression control is performed to stop the operation of the constant current source 11 or reduce the current output from the constant current source 11. As described above, even when an abnormality such as a connection failure of the LED unit 14 occurs due to the cooperation between the abnormality detection circuit (that is, the modulation / abnormality detection unit 13) and the overvoltage detection circuit 12, it is caused by that. Thus, destruction of the circuit elements constituting the lighting device 10 is suppressed.

  After time t3, when the output voltage Vdc exceeds the first predetermined value and then falls below a third predetermined value that is equal to or lower than the first predetermined value, or after the output voltage exceeds the first predetermined value, the third time When the predetermined time has elapsed, the overvoltage detection circuit 12 cancels the output suppression control.

  Specifically, when the output voltage Vdc becomes 3 V or less, the power supply voltage supplied from the constant voltage regulator REG1 to the microcomputer MCU1 becomes a reset voltage, and the microcomputer MCU1 restarts. Therefore, after several hundred msec after the output voltage Vdc falls below the third predetermined value of 3V, the overvoltage detection circuit 12 cancels the output suppression control for the constant current source 11. As a result, the constant current source 11 restarts normally again, the constant voltage regulator REG1 outputs a normal power supply voltage (for example, 5V), and the microcomputer MCU1 restarts normally. If the time (for example, 1 sec) from when the output of the constant current source 11 is stopped by the overvoltage detection circuit 12 until the voltage across the capacitor C1 becomes approximately 0 V is known in advance, this time is determined as the third predetermined time. May be set to cancel the output suppression control. That is, the overvoltage detection circuit 12 may cancel the output suppression control when the third predetermined time has elapsed since the output voltage Vdc exceeded the first predetermined value.

  As described above, according to the lighting device 10 according to the present embodiment, the output suppression control by the overvoltage detection circuit 12 is released when the abnormal state is recovered due to a temporary abnormality such as a connection failure. Therefore, the lighting device 10 is automatically restored without turning on the power supply to the lighting device 10.

  In addition, after time t3, the abnormality detection circuit also has a case where the output voltage Vdc falls below the fourth predetermined value that is equal to or lower than the first predetermined value after exceeding the first predetermined value, or the output voltage Vdc is the first predetermined value. The detection of the abnormal state may be canceled when the fourth predetermined time has elapsed after exceeding the value.

  Specifically, the microcomputer MCU1 cancels the abnormality determination when the output voltage Vdc falls below a fourth predetermined value (for example, several V) that is equal to or lower than the first predetermined value after exceeding the first predetermined value, The off control for the transistor Q1 is canceled and normal on / off control is performed. Alternatively, when the fourth predetermined time has elapsed after the output voltage Vdc exceeds the first predetermined value, the microcomputer MCU1 cancels the abnormality determination, cancels the off control for the transistor Q1, and performs normal on / off control. The fourth predetermined time is, for example, the time required for the output voltage Vdc to drop to several V after the constant current source 11 stops outputting after the output voltage Vdc exceeds the first predetermined value. is there.

  As a result, when an abnormal state is recovered due to a temporary abnormality such as a connection failure, the abnormality determination by the abnormality detection circuit (specifically, the microcomputer MCU1) is canceled, so that the lighting device 10 is turned on. The lighting device 10 is automatically restored without being turned off and on.

(Embodiment 2)
Next, the lighting device according to Embodiment 2 will be described.

  FIG. 3 is a circuit diagram of the lighting device 10a according to the second embodiment. As in the first embodiment, the lighting device 10a is a device having a function of applying a current to the LED unit 14 (that is, lighting) and a function of visible light communication. The constant current source 11, an overvoltage detection circuit 12 and a modulation / abnormality detection unit 13a. The lighting device 10a basically has the function of the lighting device 10 according to the first embodiment. However, the modulation / abnormality detection unit 13a further detects a low voltage abnormality (or short circuit abnormality) as an abnormal state. This is different from the first embodiment. Hereinafter, a description will be given focusing on differences from the first embodiment.

  The modulation / abnormality detection unit 13a corresponds to the modulation / abnormality detection unit 13 according to the first embodiment in which an input voltage detection circuit 16 is added and the microcomputer MCU1 is replaced with a microcomputer MCU2 to which a new function is added. To do.

  The input voltage detection circuit 16 is a part of the abnormality detection circuit, and detects that the input voltage of the modulation / abnormality detection unit 13a, that is, the output voltage of the constant current source 11 is in a low voltage state. Specifically, when the input voltage detection circuit 16 detects a state in which the output voltage of the constant current source 11 falls below a second predetermined value that is equal to or lower than a first predetermined value as a low voltage state, a detection signal indicating that is detected. Output to the microcomputer MCU2. The second predetermined value is a threshold for detecting the output voltage when the load of the lighting device 10a is short-circuited, and is, for example, 10V. The input voltage detection circuit 16 includes, for example, a resistance voltage dividing circuit that detects an output voltage, a constant voltage diode that determines a second predetermined value, a voltage obtained by the resistance voltage dividing circuit, and a voltage obtained by the constant voltage diode. It consists of a comparator to compare.

  In addition to the function of the microcomputer MCU1 of the first embodiment, the microcomputer MCU2 functions as a part of the abnormality detection circuit when the detection signal from the input voltage detection circuit 16 continues for a second predetermined time or longer (that is, It has a function to determine that (low voltage abnormality) has occurred. Specifically, the microcomputer MCU2 has an input terminal LVD that receives a detection signal from the input voltage detection circuit 16, and whether or not the state in which the detection signal is input to the input terminal LVD has continued for a second predetermined time or more. The determination is made using a built-in delay detection counter. If it is determined that the input of the detection signal has continued for the second predetermined time or more, the microcomputer MCU2 determines that an abnormal state (that is, a low voltage abnormality) has occurred, and turns off the transistor Q1 for the first predetermined time or longer. To control. The second predetermined time is a minimum duration for confirming that the output voltage continues in a low voltage state due to a load short circuit, and is, for example, 10 msec.

  Next, the operation of the lighting device 10a according to Embodiment 2 configured as described above will be described.

  FIG. 4 is a timing chart showing the operation of the lighting device 10a according to the second embodiment. In this figure, from the top, the output voltage Vdc of the constant current source 11, the current Iout flowing through the LED unit 14, the power supply voltage Vcc output from the constant voltage regulator REG1, and the delay detection counter value of the microcomputer MCU2 are shown. The gate-source voltage Vgs (Q1) of the transistor Q1 and the “detection result” by the microcomputer MCU2 are shown. The “detection result” is a state in which HIGH detects an abnormal state and LOW does not detect an abnormal state.

  At time t0, the constant current source 11 starts outputting.

  From time t0 to t1, the capacitor C1 is charged, and the output voltage Vdc of the constant current source 11 starts to rise. When the output voltage Vdc reaches about 5V, the transistor Q1 is biased via the resistor R2 and turned on. Assume that the load is short-circuited and is in an abnormal state. In this state, when the transistor Q1 is turned on, the current Iout flowing through the transistor Q1 becomes constant at the set value of the constant current source 11. Since the transistor Q1 is a MOSFET, the output voltage Vdc is stabilized at a voltage (for example, 4 V) equal to or higher than the threshold voltage Vth of the transistor Q1. In this state, a loss of current Iout × output voltage Vdc occurs in transistor Q1. For example, when the current Iout = 2A and the output voltage Vdc = 4V, a heat loss of 8 W occurs in the transistor Q1, and if this state continues, there is a possibility that the element of the transistor Q1 is destroyed. At this timing, the constant voltage regulator REG1 starts output at a low power supply voltage Vcc.

  At time t1, the microcomputer MCU2 starts to start. When the constant voltage regulator REG1 is a series regulator, the potential difference between the input and the output of the constant voltage regulator REG1 is 1 to 2V, so that the microcomputer MCU2 starts to start with a power supply voltage of about 2V.

  From time t2 to t3, the microcomputer MCU2 is released from the reset state, and according to a built-in program, as a part of the modulation circuit, a drive signal for periodically turning on and off the transistor Q1 based on a signal for visible light communication is provided. Output from the output terminal SIG. The input voltage detection circuit 16 monitors the output voltage Vdc and detects a state where the output voltage Vdc falls below a second predetermined value which is equal to or lower than the first predetermined value. Output to. As a part of the abnormality detection circuit, the microcomputer MCU2 uses a built-in delay detection circuit to determine whether the detection signal from the input voltage detection circuit 16 input to the input terminal LVD continues for a second predetermined time or more. The delay time is counted by a counter (Delay counter). Note that during this period, switching of the transistor Q1 causes the output voltage Vdc to increase during the off-period of the transistor Q1, so that the average voltage of the output voltage Vdc increases.

  At time t3, the microcomputer MCU2 detects that the counter (Delay counter) has reached the threshold value Dcm corresponding to the second predetermined time, determines that a low voltage abnormality has occurred as an abnormal state, and sets the transistor Q1 to the first level. Control to turn off for a predetermined time or more is performed. When the transistor Q1 is turned off, the current Iout flowing through the LED unit 14 becomes zero, and the output voltage Vdc increases. The second predetermined time is a time required for at least the output voltage Vdc to reach a voltage determined by the overvoltage detection circuit 12 to be an overvoltage (that is, a first predetermined value), and is, for example, 10 msec.

  When the output voltage Vdc reaches a first predetermined value (for example, 86 V) at time t4, the overvoltage detection circuit 12 determines that an overvoltage has occurred and controls the constant current source 11 to perform output suppression control. . That is, the overvoltage detection circuit 12 controls the constant current source 11 to stop the operation of the constant current source 11 or reduce the current Iout output from the constant current source 11 (here, the operation of the constant current source 11 is reduced). Stop output).

  As described above, in the lighting device 10a according to the present embodiment, the abnormality detection circuit (that is, the modulation / abnormality detection unit 13a) detects the low voltage abnormality as the abnormal state in addition to the abnormal state of the first embodiment. To do. That is, the modulation / abnormality detection unit 13a detects that the state where the output voltage is lower than the second predetermined value which is equal to or lower than the first predetermined value continues as the abnormal state for the second predetermined time or longer. When an abnormal state is detected, the transistor Q1 is turned off for a first predetermined time or longer.

  Accordingly, when it is detected that the state where the output voltage of the constant current source 11 is lower than the second predetermined value which is equal to or lower than the first predetermined value due to a short circuit of the LED unit 14 or the like continues for the second predetermined time or longer, the transistor Q1 Will continue to be turned off. As a result, the output voltage of the constant current source 11 exceeds the first predetermined value, which is detected by the overvoltage detection circuit 12, and output suppression control is performed. Therefore, even when an abnormal state such as a short circuit of the load occurs, it is possible to suppress the transistor Q1 from being destroyed by the power stress in the incomplete ON state of the transistor Q1.

(Embodiment 3)
Next, as Embodiment 3, an application example of the lighting devices 10 and 10a according to the above embodiment will be described.

  FIG. 5 is an external view of a lighting fixture 20 according to an application example of the third embodiment. The lighting fixture 20 is a spotlight installed on the ceiling, wall, or pillar of a room, and includes a circuit box 21, a lamp body 22, and a wiring 23. The circuit box 21 is a box that houses the lighting device 10 or 10a according to the above embodiment. The lamp body 22 houses an LED bulb as a light emitting element. The wiring 23 is an example of a load wiring that electrically connects the circuit box 21 and the LED bulb housed in the lamp body 22.

  Since such a lighting fixture 20 includes the lighting device 10 or 10a according to the above-described embodiment, illumination and visible light communication are simultaneously performed. In addition, even when an abnormal state occurs in which the LED bulb is attached to or detached from the lamp body 22 during lighting due to poor connection or the like, the circuit elements constituting the lighting devices 10 and 10a are prevented from being destroyed. .

  In addition, in this figure, although the spotlight was shown as the lighting fixture 20, as a lighting fixture which concerns on the application example of the lighting device 10 or 10a, it is not restricted to a spotlight. It may be a chandelier, ceiling light, stand, Japanese-style lighting, bracket, foot light, pendant, base light, down light, kitchen light, bathroom light, exterior light, and the like.

  FIG. 6 is an external view of a signboard 30 according to an application example of the third embodiment. The signboard 30 includes a housing 31 that houses an LED bulb (not shown) as a light-emitting element and the lighting device 10 or 10a (not shown) according to the above-described embodiment that applies current to the LED bulb. The display board 32 is provided. The display board 32 is a display board which is illuminated from the back by an LED bulb and shows at least one of characters and figures, and is, for example, a translucent resin substrate on which characters are engraved.

  Since such a signboard 30 includes the lighting device 10 or 10a according to the above-described embodiment, display of characters and the like on the display board 32 and visible light communication are simultaneously performed. In the visible light communication, for example, data indicating characters displayed on the display board 32 and / or data indicating a place where the signboard 30 is installed are superimposed on the illumination light and transmitted. Moreover, according to such a signboard 30, even when an abnormal state occurs in which the LED bulb and the lighting device 10 or 10 a are disconnected and reconnected during lighting due to poor connection or the like, the lighting device 10. And it is suppressed that the circuit element which comprises 10a will be destroyed.

  In the signboard 30 of FIG. 6, the LED as the light emitting element and the display board 32 are separate, but may be integrated. A plurality of LEDs may be arranged side by side in the housing 31 and the emission colors of the plurality of LEDs may be controlled to display at least one of characters and figures using the plurality of LEDs as a display board.

  As mentioned above, although the lighting device, the lighting fixture, and the signboard which concern on this invention were demonstrated based on Embodiment 1-3, this invention is not limited to these Embodiment. Unless it deviates from the main point of this invention, the various form which those skilled in the art thought is given to Embodiment 1-3, and another form constructed | assembled combining the one part component in Embodiment 1-3 is also possible. Are included within the scope of the present invention.

  For example, in the above embodiment, the microcomputers MCU1 and MCU2 have both the function as a part of the modulation circuit and the function as a part of the abnormality detection circuit. However, as an implementation form of the modulation circuit and the abnormality detection circuit, It is not limited to this. For example, the modulation circuit may be realized by a microcomputer, and the abnormality detection circuit may be realized by a circuit different from a microcomputer using a comparator or the like.

  In the above-described embodiment, the capacitor C1 is provided in the modulation / abnormality detection units 13 and 13a. However, the capacitor C1 is not limited to this position. If the capacitor C1 is connected between the output terminals of the constant current source 11, a constant current is provided. It may be built in the source 11 or may be connected to a position between the constant current source 11 and the modulation / abnormality detection units 13 and 13a.

  In the second embodiment, in order to detect a low voltage abnormality, the input voltage detection circuit 16 detects a low voltage state, and the microcomputer MCU2 detects that the low voltage state has continued for a second predetermined time or more. However, it is not limited to such an implementation method. The input voltage detection circuit 16 divides the output voltage of the constant current source 11, and the microcomputer MCU2 detects the low voltage state by comparing the divided voltage with the second predetermined value, and the low voltage state is You may detect that it continued more than 2nd predetermined time. Alternatively, the input voltage detection circuit 16 may detect a low voltage state and detect that the low voltage state has continued for a second predetermined time or more.

  In the above embodiment, the stress destruction of the circuit element is avoided. However, even when the program stored in the ROM becomes abnormal due to the abnormality of the ROM of the microcomputer, the microcomputer is in an abnormal state. And the transistor Q1 may be turned off. Thereby, it is suppressed that the wrong modulation signal is output by visible light communication.

DESCRIPTION OF SYMBOLS 10, 10a Lighting device 11 Constant current source 12 Overvoltage detection circuit 13, 13a Modulation / abnormality detection part (an example of a modulation circuit and an abnormality detection circuit)
14 LED unit (light emitting device)
15 Load wiring 16 Input voltage detection circuit (another example of abnormality detection circuit)
C1 capacitor Q1 transistor (switch element)
20 Lighting equipment 30 Signboard 32 Display board

Claims (6)

A lighting device for applying a current to a light emitting element,
A constant current source;
A capacitor connected to the output terminal of the constant current source;
A series circuit including a load wiring and a switch element connected in parallel with the capacitor and connected in series with the light emitting element;
A modulation circuit for turning on and off the switch element based on a signal for visible light communication;
An overvoltage detection circuit that, when detecting that the output voltage of the constant current source exceeds a first predetermined value, performs output suppression control that stops the operation of the constant current source or reduces the current output by the constant current source;
When an abnormal state that is at least one of an abnormality of the light emitting element, an abnormality of the load wiring, an abnormality of the modulation circuit, and an overload of the switch element is detected, the switch element is turned off for a first predetermined time or more. An abnormality detection circuit,
The constant current source increases the output voltage until the first predetermined value is exceeded when the switch element is turned off for the first predetermined time or more by the abnormality detection circuit. 2. The lighting according to claim 1, wherein the abnormality detection circuit further detects, as the abnormal state, that a state in which the output voltage is lower than a second predetermined value that is equal to or lower than the first predetermined value continues for a second predetermined time or longer. apparatus. The overvoltage detection circuit further includes a case where the output voltage falls below a third predetermined value which is equal to or less than the first predetermined value after the output voltage exceeds the first predetermined value, or the output voltage falls below the first predetermined value. The lighting device according to claim 1, wherein the output suppression control is canceled when a third predetermined time has elapsed since the time exceeded. The abnormality detection circuit further includes a case where the output voltage falls below a fourth predetermined value which is equal to or lower than the first predetermined value after the output voltage exceeds the first predetermined value, or the output voltage falls below the first predetermined value. The lighting device according to any one of claims 1 to 3, wherein detection of an abnormal state is canceled when a fourth predetermined time has elapsed since the time exceeded. A light emitting element;
A lighting fixture comprising: the lighting device according to claim 1, wherein a current is applied to the light emitting element. A light emitting element;
The lighting device according to any one of claims 1 to 4, wherein a current is applied to the light emitting element.
A signboard comprising: a display board illuminated by the light emitting element and showing at least one of characters and figures.

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