JP6899548B2 - Lighting devices, lighting fixtures and signboards - Google Patents

Description

The present invention relates to a lighting device for applying an electric current to a light emitting element such as an LED, a lighting device including a lighting device, and a signboard including the lighting device, and more particularly to a lighting device including 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 to include 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 switch element for visible light communication is connected in series with the LED, and a resistor is further connected in parallel with the switch element. As a result, the output voltage of the constant current source is stabilized because the no-load state is not achieved even when the switch element is off.

Japanese Unexamined Patent Publication No. 2013-10634

However, in the lighting device of Patent Document 1, when the output path of the constant current source is disconnected due to a 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 the LED is subjected to excessive voltage stress. As a result, the circuit elements constituting the lighting device may be destroyed. Further, in this state, if the LED is reconnected (that is, detached) to the lighting device, an excessive current is transmitted to the LED due to the discharge from the smoothing capacitor connected to the output terminal of the constant current source. It may be applied and the LED may be destroyed.

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

In order to achieve the above object, the lighting device according to one embodiment of the present invention is a lighting device that applies a current to a light emitting element, and includes a constant current source and 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 the switch element on and off based on a signal for visible light communication. When it is detected that the output voltage of the constant current source exceeds the first predetermined value, the operation of the constant current source is stopped or the output suppression control for reducing the current output by the constant current source is performed, and the overvoltage detection circuit. When an abnormality of the light emitting element, an abnormality of the load wiring, an abnormality of the modulation circuit, and an abnormal state which is at least one of the overload of the switch element are detected, the abnormality of turning off the switch element for the first predetermined time or more. The constant current source includes a detection circuit, and when the switch element is turned off by the abnormality detection circuit for the first predetermined time or longer, the constant current source raises the output voltage until the first predetermined value is exceeded.

In order to achieve the above object, the luminaire according to one embodiment of the present invention includes a light emitting element and the lighting device for applying an electric current to the light emitting element.

In order to achieve the above object, the signboard according to one embodiment of the present invention is illuminated by a light emitting element, the lighting device for applying an electric current to the light emitting element, and at least one of characters and figures. It is provided with a display board for showing.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a lighting device having a function of visible light communication, in which the circuit element is suppressed from being destroyed even when an abnormality such as a connection failure occurs.

Circuit diagram of the lighting device according to the first embodiment Timing chart showing the operation of the lighting device according to the first embodiment Circuit diagram of the lighting device according to the second embodiment Timing chart showing the operation of the lighting device according to the second embodiment External view of the lighting equipment according to the application example of the third embodiment External view of the signboard according to the application example of the third embodiment

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that all of the embodiments described below show a specific example of the present invention. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components, operation timings, and the like shown in the following embodiments are examples, and are not intended to limit the present invention. Further, among the components in the following embodiments, the components not described in the independent claims indicating the highest level concept of the present invention will be described as arbitrary components. Moreover, each figure is not necessarily exactly illustrated. In each figure, substantially the same configuration is designated by the same reference numerals, and duplicate description is omitted or simplified.

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

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

The LED unit 14 is an example of a light emitting element that serves as a load for the lighting device 10. Here, the LED unit 14 is composed of a plurality of LEDs 1 to 5 connected to the lighting device 10 by a load wiring 15 and connected in series. The light emitting element is not limited to the LED, and may be another light emitting element such as an organic EL or an inorganic EL. Further, the LED unit 14 is not limited to a plurality of LEDs connected in series, and may be composed of one LED, a plurality of LEDs connected in parallel, or connected in series. A plurality of LED sets may be connected in parallel to each other.

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

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 stops the operation of the constant current source 11 or performs output suppression control to reduce the current output by the constant current source 11. It is a circuit. The overvoltage detection circuit 12 compares, for example, the voltage obtained by the resistance voltage divider circuit that detects the output voltage, the constant voltage diode that determines the first predetermined value, and the resistance voltage divider circuit with the voltage obtained by the constant voltage diode. It is composed of a comparator and the like. Further, the overvoltage detection circuit 12 is the third when the output voltage exceeds the first predetermined value and then falls below the third predetermined value, which is equal to or less than the first predetermined value, or after the output voltage exceeds the first predetermined value. When the predetermined time elapses, the output suppression control is released. As a result, the constant current source 11 returns to the normal operation. The third predetermined value is a threshold voltage at which the modulation / abnormality detection unit 13 (particularly, the microcomputer MCU1) can be reset and restarted, for example, 3 V or less. The third predetermined time is the 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 has a function of a modulation circuit that turns on / off the transistor Q1 which is a switch 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 longer when an abnormal state is detected. It is a circuit that also has the function of a circuit. Specifically, the modulation / abnormality detection unit 13 is composed of a constant voltage regulator REG1, a microcomputer (microcomputer) MCU1, capacitors C1 and C2, a diode D1, a constant voltage diode ZD1, transistors Q1 to Q4, and resistors R1 to R6. To.

The capacitor C1 is a smoothing capacitor connected to the output terminals 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 switch element for visible light communication, and the transistor Q1 is periodically turned on and off. The transistor Q1 is, for example, a MOSFET. During the off period of the transistor Q1, the output voltage of the constant current source 11 rises because the current path is cut off. A capacitor C1 is provided in order to suppress the amount of increase. The capacitance of the capacitor C1 is preferably a value such that the amount of increase ΔVF of the output voltage during the off period of the transistor Q1 is 30% or less of the forward voltage VF of the LED unit 14. Specifically, when the off period Toff is 208 μsec, the output current Iout = 0.7A, and the forward voltage VF = 15V, the amount of increase ΔVF is 4.5V from ΔVF = 15V × 0.3 = 4.5V. 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. Therefore, the capacitance of the capacitor C1 is set to, for example, 33 μF or more.

The constant voltage regulator REG1 is a circuit module that generates a constant voltage 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 5 V.

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

The resistor R6, the transistor Q5, the resistor R5, the transistors Q3 and Q4 are drive circuits for driving the gate of the transistor Q1 and form a part of the modulation circuit. This drive circuit charges and discharges the gate-source capacitance of the transistor Q1 so that the transistor Q1 is turned on and off according to the drive signal from the microcomputer MCU1. Specifically, when the drive signal from the microcomputer MCU1 is HIGH, the transistor Q5 is turned on, so that the transistor Q3 is turned off and the transistor Q4 is turned on. As a result, the gate of the transistor Q1 is discharged via the transistor Q4 and the resistor R4, so that the gate potential of the transistor Q1 becomes 0V 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, so that the transistor Q3 is turned on and the transistor Q4 is turned off. As a result, the gate of the transistor Q1 is charged via 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 and off by the drive signal from the microcomputer MCU1, the digital optical code for visible light communication is superimposed on the light emitted from the LED unit 14. The resistor R4 is a resistor that limits the charging / discharging of the gate of the transistor Q1. By adjusting the on / off speed of the transistor Q1 by the resistor R4, noise at the time of switching of the transistor Q1 can be suppressed.

Further, the microcomputer MCU1 also functions as a part of the abnormality detection circuit that turns off the transistor Q1 for the first predetermined time (for example, 10 msec) or more when the 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) via the input terminal CS, and periodically converts it into a digital value by the built-in A / D converter. To do. Then, the calculation of the average value of the digital values over a certain period of time is repeated. Then, the microcomputer MCU1 determines whether or not an abnormal state has occurred by determining whether or not the calculated average value is out of the predetermined range, and when it is determined that an abnormal state has occurred, the transistor Q1 Is controlled to be turned off for the first predetermined time or longer. The predetermined range is the range of the voltage 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 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. The transistor Q1 and the load wiring 15 form 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 destruction and failure, but also poor connection, poor contact, detachment (repeated disconnection and reconnection), disconnection and short circuit of the current path, and the like.

The resistor R2 is a resistor for applying a bias voltage to the transistor Q1. Due to this bias voltage, when the power is turned on to the lighting device 10, 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 via 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. The constant voltage diode ZD1 limits, for example, 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 for the constant voltage regulator REG1 may be generated 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 ensures that the transistor Q1 can be turned on before the constant voltage regulator REG1 is activated.

The capacitor C2, the transistor Q2, the resistors R3 and R1 form 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 across the resistor R1. Since the voltage is applied between the base and the emitter of the transistor Q2, when the threshold voltage Vbe of the transistor Q2 is exceeded, the transistor Q2 is turned on and the gate potential of the transistor Q1 is lowered. The capacitor C2 is provided for control phase compensation. Normally, 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 the load is short-circuited during lighting or the load is overcurrent due to overvoltage, the voltage generated across the resistor R1 increases, which increases the current flowing through the transistor Q2 and forcibly turns off the transistor Q1. It is controlled in the direction of

Next, the operation of the lighting device 10 according to the first embodiment 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, and the "microcomputer MCU1". "Detection result" is shown. The "detection result" is a state in which HIGH has detected an abnormal state, and LOW has not detected an abnormal state.

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

It is assumed that at time t0, 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, and the current path is disconnected. Then, the current Iout flowing through the LED unit 14 becomes zero, the constant current source 11 raises the output voltage Vdc, and the capacitor C1 is charged. The microcomputer MCU1 continues the control to turn on / off the transistor Q1 (see the gate-source voltage Vgs (Q1)).

It is assumed that at time t1, the LED unit 14 is reconnected to the lighting device 10 and the current path is conducted due to the elimination of poor contact between the load wiring 15 and the LED unit 14. In this state, the output voltage Vdc is large and the capacitor C1 is charged. Therefore, when the current path is conducted, a large current flows through the LED unit 14 when the transistor Q1 is turned on. As a result, the voltage of the input terminal CS of the microcomputer MCU1 rises. The current limiting circuit composed of the resistor R1 or the like temporarily lowers the peak of the gate-source voltage Vgs (Q1) of the transistor Q1 to 3 to 4 V, and suppresses the increase in the current flowing through the LED unit 14. Ru. The output voltage Vdc rapidly decreases due to the occurrence of the load current.

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

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

When the output voltage Vdc reaches the 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 control the output suppression. .. That is, the overvoltage detection circuit 12 stops the operation of the constant current source 11 or reduces the current Iout output by the constant current source 11 by controlling the constant current source 11 (here, the operation of the constant current source 11 is performed. (Stop) Output suppression control is performed.

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

As a result, 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 the first predetermined time or longer, and the output voltage of the constant current source 11 becomes the first. Exceeds the specified 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 by the constant current source 11. In this way, even if an abnormality such as a poor connection 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. It is possible to prevent the circuit elements constituting the lighting device 10 from being destroyed.

After time t3, when the output voltage Vdc exceeds the first predetermined value and then falls below the third predetermined value, which is equal to or less than the first predetermined value, or after the output voltage exceeds the first predetermined value, the third. When the predetermined time has elapsed, the overvoltage detection circuit 12 releases 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 the reset voltage, and the microcomputer MCU1 restarts. Therefore, the overvoltage detection circuit 12 releases the output suppression control for the constant current source 11 several hundreds of msec after the output voltage Vdc falls below the third predetermined value of 3V. As a result, the constant current source 11 restarts normally, the constant voltage regulator REG1 outputs a normal (for example, 5V) power supply voltage, and the microcomputer MCU1 also 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, that time is used as the third predetermined time. It may be set as, and the output suppression control may be canceled. That is, when the third predetermined time elapses after the output voltage Vdc exceeds the first predetermined value, the overvoltage detection circuit 12 may cancel the output suppression control.

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

Further, in the abnormality detection circuit after time t3, when the output voltage Vdc exceeds the first predetermined value and then falls below the fourth predetermined value which is equal to or less than the first predetermined value, or the output voltage Vdc is the first predetermined value. When the fourth predetermined time elapses after the value is exceeded, the detection of the abnormal state may be canceled.

Specifically, the microcomputer MCU1 cancels the abnormality determination when the output voltage Vdc exceeds the first predetermined value and then falls below the fourth predetermined value (for example, several V) which is equal to or less than the first predetermined value. The off control for the transistor Q1 is canceled and the normal on / off control is performed. Alternatively, when the fourth predetermined time elapses 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 the 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 the output after the output voltage Vdc exceeds the first predetermined value, for example, in 1 sec. is there.

As a result, when the 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 power is input to the lighting device 10. The lighting device 10 is automatically restored without turning off and on.

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

FIG. 3 is a circuit diagram of the lighting device 10a according to the second embodiment. The lighting device 10a is a device having a function of applying a current (that is, lighting) to the LED unit 14 and a function of visible light communication, as in the first embodiment, and is a constant current source 11 and an overvoltage detection circuit. 12 and a modulation / abnormality detection unit 13a are provided. The lighting device 10a basically has the function of the lighting device 10 of the first embodiment, but the modulation / abnormality detection unit 13a also detects a low voltage abnormality (or a short circuit abnormality) as an abnormal state. In that respect, it differs from the first embodiment. Hereinafter, the points different from those of the first embodiment will be mainly described.

The modulation / abnormality detection unit 13a corresponds to the modulation / abnormality detection unit 13 of the first embodiment in which the input voltage detection circuit 16 is added and the microcomputer MCU1 is replaced with the 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 is lower than the second predetermined value, which is equal to or less than the first predetermined value, as a low voltage state, a detection signal indicating that is generated. Output to the microcomputer MCU2. The second predetermined value is a threshold value 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 uses, for example, a resistance voltage divider circuit for detecting an output voltage, a constant voltage diode for determining a second predetermined value, a voltage obtained by the resistance voltage divider circuit, and a voltage obtained by the constant voltage diode. It is composed of a comparator and the like for comparison.

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

Next, the operation of the lighting device 10a according to the second embodiment 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 by the constant voltage regulator REG1, and the value of the delay detection counter (Delay counter) of the microcomputer MCU2. , 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 has detected an abnormal state, and LOW has not detected an abnormal state.

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

From time t0 to t1, the capacitor C1 is charged and the output voltage Vdc of the constant current source 11 begins to rise. When the output voltage Vdc reaches about 5V, the transistor Q1 is biased via the resistor R2 and turned on. Now, 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 stable at a voltage equal to or higher than the threshold voltage Vth of the transistor Q1 (for example, 4V). In this state, a loss of current Iout × output voltage Vdc occurs in the transistor Q1. For example, when the current Iout = 2A and the output voltage Vdc = 4V, a heat loss of 8W occurs in the transistor Q1, and if this state continues, the element of the transistor Q1 may be 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 2 V, so that the microcomputer MCU2 starts to start with a power supply voltage of about 2 V.

From time t2 to t3, the microcomputer MCU2 is released from the reset state, and according to the built-in program, as a part of the modulation circuit, a drive signal for periodically turning on / off the transistor Q1 based on the signal for visible light communication is sent. Output from the output terminal SIG. Further, the input voltage detection circuit 16 monitors the output voltage Vdc and detects a state in which the output voltage Vdc is lower than the second predetermined value, which is equal to or less than the first predetermined value. Output to. The microcomputer MCU2 is for built-in delay detection in order to determine whether or not the detection signal from the input voltage detection circuit 16 input to the input terminal LVD continues for a second predetermined time or longer as a part of the abnormality detection circuit. The delay time is counted by the counter (Delay counter) of. In this period, the output voltage Vdc rises during the off period of the transistor Q1 due to the switching of the transistor Q1, so that the average voltage of the output voltage Vdc rises.

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. Control to turn off for a predetermined time or longer. When the transistor Q1 is turned off, the current Iout flowing through the LED unit 14 becomes zero, and the output voltage Vdc rises. The second predetermined time is at least the time required for the output voltage Vdc to reach a voltage (that is, a first predetermined value) determined to be an overvoltage by the overvoltage detection circuit 12, and is, for example, 10 msec.

When the output voltage Vdc reaches the first predetermined value (for example, 86V) at time t4, the overvoltage detection circuit 12 determines that an overvoltage has occurred, and controls the constant current source 11 to control the output suppression. .. That is, the overvoltage detection circuit 12 stops the operation of the constant current source 11 or reduces the current Iout output by the constant current source 11 by controlling the constant current source 11 (here, the operation of the constant current source 11 is performed. (Stop) Output suppression control is performed.

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 a low voltage abnormality as an abnormal state in addition to the abnormal state of the first embodiment. To do. That is, the modulation / abnormality detection unit 13a detects that, as an abnormal state, the state in which the output voltage is lower than the second predetermined value, which is equal to or less than the first predetermined value, continues for the second predetermined time or longer. Then, when an abnormal state is detected, the transistor Q1 is turned off for the first predetermined time or longer.

As a result, when it is detected that the output voltage of the constant current source 11 is below the second predetermined value, which is equal to or less than the first predetermined value, for a second predetermined time or longer due to a short circuit of the LED unit 14, the transistor Q1 Continues 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 the output suppression control is performed. Therefore, even when an abnormal state such as a short circuit of the load occurs, it is possible to prevent the transistor Q1 from being destroyed by the power stress in the incompletely on state of the transistor Q1.

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

FIG. 5 is an external view of the luminaire 20 according to the application example of the third embodiment. The luminaire 20 is a spotlight installed on the ceiling, wall, pillar, or the like of a room, and includes a circuit box 21, a lamp body 22, and 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 embodiment, lighting and visible light communication are performed at the same time. Further, even if an abnormal state such as attachment / detachment of the LED bulb to / from the lamp body 22 occurs during lighting due to poor connection or the like, it is possible to prevent the circuit elements constituting the lighting devices 10 and 10a from being destroyed. ..

In this figure, the spotlight is shown as the luminaire 20, but the luminaire according to the application example of the lighting device 10 or 10a is not limited to the spotlight. It may be a chandelier, a ceiling light, a stand, Japanese-style lighting, a bracket, a foot light, a pendant, a base light, a downlight, a kitchen light, a bathroom light, an exterior light, or the like.

FIG. 6 is an external view of the signboard 30 according to the 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 a lighting device 10 or 10a (not shown) according to the above embodiment in which a current is applied to the LED bulb. , The display board 32 is provided. The display board 32 is a display board that is illuminated from the back surface by an LED light 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 embodiment, the display of characters and the like on the display board 32 and visible light communication are performed at the same time. In visible light communication, for example, data indicating characters displayed on the display board 32 and / or data indicating the location where the signboard 30 is installed are superimposed on the illumination light and transmitted. Further, according to such a signboard 30, even if an abnormal state occurs in which the LED bulb and the lighting device 10 or 10a are disconnected and reconnected during lighting due to a poor connection or the like, the lighting device 10 is used. And the circuit elements constituting 10a are suppressed from being destroyed.

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

The lighting device, the luminaire, and the signboard according to the present invention have been described above based on the first to third embodiments, but the present invention is not limited to these embodiments. As long as the gist of the present invention is not deviated, various modifications that can be conceived by those skilled in the art are applied to the first to third embodiments, and other embodiments constructed by combining some components of the first to third embodiments are also available. , Included within the scope of the present invention.

For example, in the above embodiment, the microcomputers MCU1 and MCU2 have both a function as a part of the modulation circuit and a function as a part of the abnormality detection circuit. 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 the microcomputer using a comparator or the like.

Further, in the above embodiment, the capacitor C1 is provided in the modulation / abnormality detection units 13 and 13a, but is not limited to this position, and if it is connected between the output terminals of the constant current source 11, it is a constant current. It may be built in the source 11, or may be connected at a position between the constant current source 11 and the modulation / abnormality detection units 13 and 13a.

Further, in the second embodiment, in order to detect the low voltage abnormality, the input voltage detection circuit 16 detects the low voltage state, and the microcomputer MCU2 detects that the low voltage state continues for the second predetermined time or more. However, it is not limited to such a realization 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 changed. It may be detected that the continuation is continued for the second predetermined time or more. Alternatively, the input voltage detection circuit 16 may detect the low voltage state and detect that the low voltage state has continued for a second predetermined time or longer.

Further, in the above embodiment, the stress destruction of the circuit element is avoided, but even if 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. It may be determined that the transistor Q1 is turned off. As a result, it is possible to prevent the wrong modulated signal from being output by visible light communication.

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

Claims (6)

A lighting device that applies an electric current to a light emitting element.
With a constant current source
A capacitor connected to the output terminal of the constant current source and
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 that turns the switch element on and off based on a signal for visible light communication,
When it is detected that the output voltage of the constant current source exceeds the first predetermined value, an overvoltage detection circuit that stops the operation of the constant current source or controls output suppression to reduce the current output by the constant current source, and an overvoltage detection circuit.
When an abnormality of the light emitting element, an abnormality of the load wiring, an abnormality of the modulation circuit, and an abnormal state which is at least one of the overloads of the switch element are detected, the switch element is turned off for the first predetermined time or more. Equipped with an abnormality detection circuit
The constant current source is a lighting device that raises the output voltage until the first predetermined value is exceeded when the switch element is turned off by the abnormality detection circuit for the first predetermined time or longer. The lighting according to claim 1, wherein the abnormality detection circuit further detects that the state in which the output voltage is lower than the second predetermined value, which is equal to or lower than the first predetermined value, continues for the second predetermined time or more as the abnormal state. apparatus. In the overvoltage detection circuit, when the output voltage exceeds the first predetermined value and then falls below the third predetermined value which is equal to or less than the first predetermined value, or when the output voltage reaches the first predetermined value. The lighting device according to claim 1 or 2, wherein the output suppression control is released when a third predetermined time has elapsed since the time exceeded. Further, in the abnormality detection circuit, when the output voltage exceeds the first predetermined value and then falls below the fourth predetermined value which is equal to or less than the first predetermined value, or when the output voltage reaches the first predetermined value. The lighting device according to any one of claims 1 to 3, which cancels the detection of an abnormal state when a fourth predetermined time has elapsed since the time exceeded. Light emitting element and
A lighting fixture comprising the lighting device according to any one of claims 1 to 4, wherein a current is applied to the light emitting element. Light emitting element and
The lighting device according to any one of claims 1 to 4, wherein a current is applied to the light emitting element.
A signboard illuminated by the light emitting element and comprising a display board showing at least one of characters and figures.

Images