Lighting device and luminaire

Abstract

To provide a lighting device and a luminaire capable of reducing the number of ports of a processing circuit.SOLUTION: A lighting device according to a disclosure includes a lighting circuit, a processing circuit, a first detection circuit that detects a voltage corresponding to a state of the lighting circuit and outputs the voltage as a first detection voltage, a second detection circuit that outputs a High signal as a second detection voltage when a voltage or a current of the lighting circuit is larger than a predetermined first threshold, and outputs a Low signal as a second detection voltage when an output voltage of the lighting circuit is smaller than the first threshold, and a selection circuit that inputs a higher one of the first detection voltage and the second detection voltage to the processing circuit. The voltage of the High signal is set in advance to be larger than a variation range of the first detection voltage according to a state of the lighting circuit, and the processing circuit controls the lighting circuit according to the first detection voltage when the first detection voltage is input, and stops an operation of a switching element when the second detection voltage is input.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a lighting device that prevents the continued application of overpower to an LED array in a predetermined failure mode. This lighting device includes a boost chopper circuit including an inductor, a switching element, and a drive control unit that switches the switching element. The lighting device also includes a buck chopper circuit including an inductor and a switching element connected in series to the LED array. A thyristor is inserted and connected in the main current path of the boost chopper circuit. A resistive element is connected in parallel to the thyristor. An auxiliary winding is provided on the inductor of the boost chopper circuit. A trigger circuit supplies a trigger current to the thyristor based on the voltage generated in the auxiliary winding. Furthermore, a protection circuit causes the drive control unit to stop the switching operation of the switching element when a detection voltage generated in response to the switching operation of the switching element falls below a predetermined value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-120697 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, as shown in Patent Document 1, lighting devices are sometimes equipped with multiple protection circuits. For example, suppose an LED becomes detached from the output terminal of a DC-DC conversion circuit that performs constant current control due to unintentional poor contact or vibration. In this case, the DC-DC conversion circuit attempts to continue to pass current, causing the output voltage of the DC-DC conversion circuit to increase. This may result in a voltage exceeding the allowable voltage applied to electronic components such as the lighting device's smoothing capacitor, potentially causing the DC-DC conversion circuit to malfunction. Therefore, some lighting devices are equipped with an overvoltage protection function that detects the output voltage of the DC-DC conversion circuit and shuts down the DC-DC conversion circuit if the output voltage exceeds a predetermined voltage.

[0005] Typically, this function is realized by a detection circuit that detects the output voltage of the DC-DC conversion circuit, and a control unit that reads the detection signal output from the detection circuit, determines whether it is an overvoltage, and stops the operation of the DC-DC conversion circuit depending on the result of the determination. The control unit's function is generally realized by a processing circuit such as a microcomputer reading and determining the detection signal. Such a microcomputer has an A / D (analog-to-digital) conversion port, converts the analog detection signal input through the A / D port into a digital value, and then performs overvoltage determination using a program or the like.

[0006] In addition, various detection signals are generally input to the A / D port of a microcomputer. For example, detection signals such as the DC output voltage of a power factor correction circuit and the LED current of a DC / DC converter are input to the A / D port. Furthermore, if a lighting device is equipped with a temperature detection circuit and has a function to limit the LED current according to the temperature of a specific component or the ambient temperature, a temperature detection signal may also be input to the A / D port. As such, particularly when a lighting device drives and controls both a power factor correction circuit and a DC / DC converter, many detection signals are required, which may require multiple ports on the microcomputer. Therefore, there is a risk of a shortage of ports. Furthermore, as microcomputers become larger, circuit boards also become larger, which could increase the cost of lighting devices.

[0007] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a lighting device and a lighting fixture that can reduce the number of ports in a processing circuit. [Means for solving the problem]

[0008] A lighting device according to the present disclosure includes a lighting circuit that lights a light source by turning a switching element on and off; a processing circuit that controls the lighting circuit; a first detection circuit that detects a voltage according to the state of the lighting circuit and outputs the voltage as a first detection voltage; a second detection circuit that outputs a High signal as a second detection voltage when the voltage or current of the lighting circuit is greater than a predetermined first threshold, and outputs a Low signal as the second detection voltage when the voltage or current of the lighting circuit is smaller than the first threshold; and a selection circuit that inputs the higher of the first detection voltage and the second detection voltage to the processing circuit, wherein the voltage of the High signal is set to be large relative to the range of fluctuation of the first detection voltage according to the state of the lighting circuit, and the processing circuit controls the lighting circuit according to the first detection voltage when the first detection voltage is input, and stops the switching operation of the switching element when the second detection voltage is input. [Effects of the Invention]

[0009] In the lighting device according to the present disclosure, the higher of the first and second detection voltages is input to a processing circuit, and the processing circuit controls the lighting circuit according to the first detection voltage when the first detection voltage is input, and stops the switching operation of the switching element when the second detection voltage is input, thereby reducing the number of ports of the processing circuit. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a circuit block diagram of a lighting fixture according to a first embodiment. [Figure 2] FIG. 4 is a diagram illustrating a temperature protection operation according to the first embodiment. [Figure 3] 10A and 10B are diagrams illustrating a temperature protection operation according to a modification of the first embodiment. [Figure 4] 5A and 5B are diagrams illustrating an overvoltage protection operation according to the first embodiment. [Figure 5] 4 is a diagram illustrating a signal voltage range input to a port of the processing circuit according to the first embodiment. FIG. [Figure 6] FIG. 10 is a circuit block diagram of a lighting fixture according to a modified example of the first embodiment. [Figure 7] FIG. 10 is a circuit block diagram of a lighting fixture according to a second embodiment. [Figure 8] 10 is a diagram illustrating a signal voltage range input to a port of a processing circuit according to a second embodiment. FIG. [Figure 9] FIG. 10 is a circuit block diagram of a lighting fixture according to a third embodiment. [Figure 10] 10 is a diagram illustrating a signal voltage range input to a port of a processing circuit according to a third embodiment. FIG. [Figure 11] FIG. 10 is a circuit block diagram of a lighting fixture according to a fourth embodiment. [Figure 12] 10 is a diagram illustrating a signal voltage range input to a port of a processing circuit according to a fourth embodiment. FIG. [Figure 13] FIG. 10 is a cross-sectional view of a lighting fixture according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] A lighting device and a lighting fixture according to the present embodiment will be described with reference to the drawings. The same or corresponding components are designated by the same reference numerals, and repeated description may be omitted.

[0012] Embodiment 1 FIG. 1 is a circuit block diagram of a lighting fixture 100 according to a first embodiment. The lighting fixture 100 includes a lighting device 10 and a light source 2, which serves as a load. The lighting device 10 receives power from an AC power source 1 to light the light source 2. The light source 2 is, for example, an LED lamp that uses an LED (Light Emitting Diode) as a light-emitting element. The light-emitting element may be an organic electroluminescence (EL) element, for example.

[0013] The lighting device 10 includes a rectifier circuit 3, a power factor correction circuit 4, a DC-DC conversion circuit 5, and a control circuit 6. The rectifier circuit 3, the power factor correction circuit 4, and the DC-DC conversion circuit 5 correspond to a lighting circuit that lights the light source 2 by turning on and off switching elements.

[0014] The rectifier circuit 3 is a diode bridge circuit consisting of four diodes. The rectifier circuit 3 full-wave rectifies the AC voltage input from the AC power source 1. This full-wave rectified voltage is not smoothed while the power factor correction circuit 4 is in operation, and becomes a pulsating voltage with twice the frequency of the AC power source 1. In other words, the filter capacitor C1 connected to the DC output side of the rectifier circuit 3 does not smooth the full-wave rectified voltage. The filter capacitor C1 is a small-capacity capacitor that is sufficient to remove switching ripples from the power factor correction circuit 4.

[0015] The power factor correction circuit 4 is, for example, a boost chopper circuit. The power factor correction circuit 4 includes an inductor L1, a switching element Q1, a diode D1, and a smoothing capacitor C2. The switching element Q1 is, for example, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The smoothing capacitor C2 is provided to smooth the output voltage of the boost chopper circuit. The smoothing capacitor C2 is, for example, an electrolytic capacitor, and has a larger capacity than the filter capacitor C1.

[0016] The DC-DC conversion circuit 5 is, for example, a step-down chopper circuit. The DC-DC conversion circuit 5 includes a switching element Q2, a diode D2, an inductor L2, and a smoothing capacitor C3. The switching element Q2 is, for example, a MOSFET. As described above, the lighting circuit includes the power factor correction circuit 4, which is a constant voltage circuit, and the DC-DC conversion circuit 5, which is a constant current circuit that receives power from the constant voltage circuit and supplies current to the light source 2.

[0017] The switching element Q1 of the power factor correction circuit 4 and the switching element Q2 of the DC-DC conversion circuit 5 are both driven and controlled by a control circuit 6. The control circuit 6 includes a processing circuit 6a that controls the lighting circuit. As will be described later, the processing circuit 6a reads signals detected from various components, performs calculations, and generates drive signals for the switching elements Q1 and Q2 based on the calculation results.

[0018] The processing circuit 6a is, for example, a microcomputer. For example, the processing circuit 6a realizes its functions by executing a program stored in a built-in memory using an arithmetic circuit 6d such as a built-in processor. The functions of the processing circuit 6a may be realized by multiple arithmetic circuits 6d. The control circuit 6 also includes a drive circuit 6b that converts the drive signal generated by the processing circuit 6a into a voltage signal suitable for driving the switching elements Q1 and Q2. The drive signal is, for example, a PWM (Pulse Width Modulation) signal.

[0019] The power factor correction circuit 4 charges and discharges energy using the inductor L1 and smoothing capacitor C2 by turning on and off the switching element Q1. As a result, the power factor correction circuit 4 boosts the voltage full-wave rectified by the rectifier circuit 3 and converts it into a predetermined DC voltage. At this time, the processing circuit 6a detects and reads the voltage of the smoothing capacitor C2 using voltage detection resistors R1 and R2. As a result, the processing circuit 6a adjusts the on time of the switching element Q1 so that the DC voltage output by the power factor correction circuit 4 approaches the desired voltage. Furthermore, the power factor correction circuit 4 controls the switching element Q1 to correct the power factor so that the input current waveform of the AC power source 1 becomes sinusoidal and is approximately in phase with the voltage of the AC power source 1.

[0020] The DC-DC conversion circuit 5 charges and discharges energy in the inductor L2 and smoothing capacitor C3 by turning on and off the switching element Q2. In this way, the DC-DC conversion circuit 5 converts the DC voltage input from the power factor correction circuit 4 and supplies a desired DC current to the light source 2. The processing circuit 6a detects and reads the current flowing through the light source 2 using the current detection resistor R3. In response, the processing circuit 6a adjusts the on time of the switching element Q2 so that the DC current output by the DC-DC conversion circuit 5 approaches the desired current.

[0021] In this way, the processing circuit 6a receives the analog voltage signals output from the voltage detection resistors R1 and R2 and the current detection resistor R3. The processing circuit 6a preferably includes multiple A / D converters 6c that convert the input analog signals into digital signals. By inputting the analog signals output from the voltage detection resistors R1 and R2 or the current detection resistor R3 to a port equipped with the A / D converter 6c, the detected values ​​can be directly received by the processing circuit 6a. This allows, for example, an arithmetic circuit 6d included in the processing circuit 6a to compare the target signal value with the detected signal value in a software program and control the detected signal value so that it matches the target signal value.

[0022] Next, the protection functions will be described. The lighting device 10 of this embodiment has an overvoltage protection function and a temperature protection function. First, the overvoltage protection function will be described. Even if the light source 2 becomes detached from the output terminal of the DC-DC conversion circuit 5 due to poor contact, vibration, or the like, the DC-DC conversion circuit 5 attempts to continue to pass current. As a result, the output voltage of the DC-DC conversion circuit 5 increases. At this time, a voltage exceeding the withstand voltage may be applied to electronic components constituting the lighting device 10, such as the smoothing capacitor C3, which may cause the DC-DC conversion circuit 5 to malfunction. Therefore, as an overvoltage protection function, the control circuit 6 detects the output voltage of the DC-DC conversion circuit 5 and stops operation of the DC-DC conversion circuit 5 when the voltage exceeds a predetermined value.

[0023] Next, the temperature protection function will be described. For example, a thermistor Rth is provided as a temperature detection element on a circuit board constituting the lighting device 10. The processing circuit 6a detects changes in the ambient temperature or the temperature of a specific component from changes in the resistance value of the thermistor Rth. When the ambient temperature or the temperature of a specific component reaches a preset temperature, the control circuit 6 reduces or cuts off the current supplied to the light source 2. This prevents the temperature of the light source 2 or the components constituting the lighting device 10 from rising and keeps them below their heat-resistant temperature. This prevents malfunctions in the lighting device 10 or the light source 2, improving reliability.

[0024] Next, the configuration and operation of the control circuit 6 that realizes the overvoltage protection function and temperature protection function will be described. The control circuit 6 has voltage-dividing resistors R4 and R5 that detect the output voltage of the DC-DC conversion circuit 5, an overvoltage protection threshold voltage E1, and a comparator circuit Comp as circuits that realize the overvoltage detection function. The output of the comparator circuit Comp is connected to a port having an A / D converter 6c of the processing circuit 6a via a diode OR circuit Dor and resistor R6.

[0025] The voltage-dividing resistors R4 and R5, the overvoltage protection threshold voltage E1, and the comparator circuit Comp correspond to a second detection circuit. The second detection circuit outputs a High signal as the detection voltage Vh when the output voltage of the lighting circuit is greater than a predetermined first threshold, and outputs a Low signal as the detection voltage Vh when the output voltage of the lighting circuit is smaller than the first threshold. Here, the output voltage of the lighting circuit means the output voltage of the DC-DC conversion circuit 5.

[0026] The control circuit 6 includes a resistor R7 and a thermistor Rth connected in series with the resistor R7 as a circuit for realizing a temperature protection function. A control power supply Vcc is applied across both ends of the resistor R7 and thermistor Rth. The voltage at the connection point between the resistor R7 and thermistor Rth is connected to a port of the processing circuit 6a having an A / D converter 6c via a diode OR circuit Dor and resistor R6. The resistor R7 and the thermistor Rth connected in series with the resistor R7 correspond to a first detection circuit that detects a voltage corresponding to the state of the lighting circuit and outputs it as a detection voltage Vt. In other words, the first detection circuit of this embodiment detects the temperature as a detection voltage Vt.

[0027] The thermistor Rth may be installed in close contact with or in close proximity to a component (not shown) or other object whose temperature is to be measured. The thermistor Rth may also be installed within the space (not shown) that is the object of measurement. For example, the thermistor Rth may be installed within the internal space of a housing (not shown) that houses the lighting device 10.

[0028] The detection voltage Vh from the comparison circuit Comp and the detection voltage Vt at the junction of resistor R7 and thermistor Rth, which is a temperature detection signal, are both connected to a common port of the processing circuit 6a via a diode OR circuit Dor. The diode OR circuit Dor serves as a selection circuit that inputs the higher of the detection voltage Vt or the detection voltage Vh to the processing circuit 6a. The diode OR circuit Dor has a diode Dor1, whose anode receives the detection voltage Vh, and a diode Dor2, whose anode receives the detection voltage Vt. The cathodes of diode Dor1 and diode Dor2 are connected to each other. The junction of the cathodes of diode Dor1 and diode Dor2 is connected to a port of the processing circuit 6a.

[0029] Next, we will explain the operation of detecting the detection voltage Vh for overvoltage protection and the detection voltage Vt for temperature protection using one port of the processing circuit 6a that has the A / D converter 6c. First, we will explain the case where the light source 2 is normally lit. When the light source 2 is normally lit, there is no overvoltage state, so the voltage input to the comparator circuit Comp from the junction of the voltage-dividing resistors R4 and R5 is lower than the overvoltage protection threshold voltage E1. In this case, the detection voltage Vh, which is the output voltage of the comparator circuit Comp, is a low signal, i.e., approximately zero volts.

[0030] The resistance values ​​of resistor R7, thermistor Rth, and resistor R6 are selected in advance so that when light source 2 is lit normally, the detection voltage Vt generated at the connection point between resistor R7 and thermistor Rth is higher than zero V, which is a low signal. In this case, the voltage Vt of equation 1 is applied to the port of processing circuit 6a. Vt=Vcc×Rt / (Rt+R7)...Formula 1 Here, Rt = 1 / (1 / Rth + 1 / R6). In other words, Rt represents the combined parallel resistance of Rth and R6. For simplicity, the forward voltage of diode Dor2, which makes up the diode OR circuit Dor, is ignored and assumed to be zero volts.

[0031] If an NTC (negative temperature coefficient) thermistor is used for the thermistor Rth, as the temperature of the object to be measured increases, the resistance of the thermistor Rth decreases, and the detection voltage Vt input to the port of the processing circuit 6a decreases. Furthermore, as the temperature of the object to be measured decreases, the resistance of the thermistor Rth increases, and the detection voltage Vt input to the port of the processing circuit 6a increases. When the light source 2 is on and the temperature of the object to be measured is at its maximum expected temperature, the detection voltage Vt input to the port of the processing circuit 6a becomes minimum. This minimum detection voltage Vt is set to be greater than the low signal output by the comparison circuit Comp. For example, when the low signal output from the comparison circuit Comp is 0.5 V, the minimum detection voltage Vt is set to be greater than 0.5 V.

[0032] Furthermore, when the light source 2 is on and the temperature of the object to be measured is at the lowest possible temperature, the detection voltage Vt input to the port of the processing circuit 6a reaches a maximum. This maximum detection voltage Vt is set to be smaller than the High signal output by the comparison circuit Comp. For example, when the High signal is 5V, the maximum detection voltage Vt is set to be lower than 5V.

[0033] In this way, the voltage of the High signal is preset to be large relative to the fluctuation range of the detection voltage Vt according to the state of the lighting circuit. The fluctuation range of the detection voltage Vt corresponds to the range from the upper limit to the lower limit of the temperature measured by the first detection circuit. As a result, when the light source 2 is normally connected and lit, the port of the processing circuit 6a can always be used as a temperature detection port.

[0034] Thus, when the comparison circuit Comp outputs a low signal rather than an overvoltage state, the processing circuit 6a controls the lighting circuit in response to the detection voltage Vt when the detection voltage Vt is input. The processing circuit 6a can, for example, control the current supplied to the light source 2 in accordance with the operating temperature environment. When room temperatures are high, such as in summer, the temperatures of the light source 2 and the lighting device 10 tend to rise. This shortens the lifespan of the device and increases the risk of breakdown. Therefore, the processing circuit 6a detects the temperature inside the lighting device 10 housing or the light source 2 using, for example, a thermistor Rth. When the processing circuit 6a determines that a predetermined temperature has been reached, it reduces the current supplied to the light source 2. This suppresses temperature increases in the device.

[0035] FIG. 2 is a diagram illustrating the temperature protection operation according to the first embodiment. FIG. 2 shows an example of the detected temperature and the change over time in the current supplied to the light source 2 when the temperature inside the housing of the lighting device 10 is detected by the thermistor Rth. At time t0, the light source 2 is in an off state. At time t1, the light source 2 starts to light up. The DC-DC conversion circuit 5 supplies a predetermined current I1 to the light source 2. As a result, the temperature inside the housing starts to rise from the initial temperature, which is room temperature Tr.

[0036] At time t2, the detected temperature becomes higher than a predetermined threshold temperature Tth. This causes the processing circuit 6a to reduce the current supplied to the light source 2 in accordance with the temperature difference between the threshold temperature Tth and the detected temperature. In other words, the processing circuit 6a performs feedback control of the current value so that the detected temperature approximately matches the threshold temperature. In other words, when the detection voltage Vt is input, the processing circuit 6a controls the lighting circuit so that the detection voltage Vt matches the predetermined threshold. Through this control, in the example of FIG. 2, the current supplied to the light source 2 ultimately decreases from I1 to I2. At this time, the temperature inside the housing is maintained at approximately the upper limit temperature. This minimizes the reduction in the current flowing through the light source 2, thereby minimizing the decrease in brightness of the light source 2 in a high-temperature environment.

[0037] FIG. 3 is a diagram illustrating a temperature protection operation according to a modification of the first embodiment. The method for reducing the current when the detected temperature inside the housing exceeds the threshold temperature Tth is not limited to the feedback control method shown in FIG. 2. For example, as shown in FIG. 3, a simple control may be executed to reduce the current value by a pre-programmed amount I1-I3 when the detected temperature reaches the threshold temperature Tth. That is, when the input detected voltage Vt is greater than a predetermined threshold, the processing circuit 6a reduces the current flowing through the light source 2 more than when the detected voltage Vt is less than the threshold. At this time, if the detected temperature does not fall below the threshold temperature Tth1 after a predetermined time has elapsed, the current value may be further reduced by a predetermined amount. That is, the current may be reduced in stages.

[0038] Furthermore, if the current is increased immediately after the temperature falls below the threshold temperature Tth1 due to a decrease in the current, the detected temperature may rise above the threshold temperature Tth1 again, potentially causing hunting, a periodic fluctuation in the current. This hunting may be perceived by the user as flickering and may be unpleasant to the user. For this reason, it is advisable to use hysteresis control as appropriate.

[0039] Hysteresis control will be explained using Figure 3. First, at time t1, light source 2 is turned on. When the detected temperature reaches threshold temperature Tth1 at time t2, the current flowing through light source 2 is reduced to current I3, which is preset in a program. As a result, the detected temperature drops below threshold temperature Tth1, but the current value does not return to I1 and remains at I3. Next, assume that the detected temperature drops at time t3 due to a drop in room temperature, etc. Then, when the detected temperature drops below threshold temperature Tth2 at time t4, the processing circuit 6a returns the current flowing through light source 2 to I1. This makes it possible to suppress periodic fluctuations in the current flowing through light source 2.

[0040] FIG. 4 is a diagram illustrating the overvoltage protection operation according to the first embodiment. Next, the overvoltage protection operation will be described. At time t0, the light source 2 is in a lighting state, and the comparison circuit Comp outputs a Low signal. At time t1, it is assumed that the light source 2 is removed from the lighting device 10 for some reason. At this timing, the current flowing through the light source 2 becomes zero. Meanwhile, because the DC-DC conversion circuit 5 performs constant current control, the output voltage of the DC-DC conversion circuit 5 begins to rise. As a result, the voltage generated across the voltage-dividing resistors R4 and R5 also rises, and the detection voltage input to the positive input terminal of the comparison circuit Comp rises. Then, at time t2, the detection voltage becomes higher than the overvoltage protection threshold voltage E1 connected to the negative input terminal of the comparison circuit Comp. As a result, a High signal is output from the output terminal of the comparison circuit Comp. Hereinafter, the High signal may be referred to as the overvoltage protection signal.

[0041] Here, the voltage level Vhi of the High signal is set to be always higher than the detection voltage Vt generated at the connection point between resistor R7 and thermistor Rth. For example, the voltage level Vhi of the High signal is approximately the same voltage as the voltage of the control power supply Vcc input to the comparison circuit Comp. In the example of Figure 1, the power supply input to the comparison circuit Comp and the power supply applied to the series circuit of resistor R7 and thermistor Rth are shared by the control power supply Vcc. Because the detection voltage Vt, which is the temperature detection signal, is the voltage obtained by dividing the control power supply Vcc by resistor R7 and thermistor Rth, it is always lower than the High signal Vhi of the comparison circuit Comp, which outputs the voltage of the control power supply Vcc as is.

[0042] In this way, the voltage Vhi of the High signal is preset to be large relative to the fluctuation range of the detection voltage Vt, which is the temperature detection signal, so the diode OR circuit Dor inputs the High signal, which is the higher voltage, to the processing circuit 6a. As a result, the port voltage of the processing circuit 6a is the detection voltage Vt from time t0 to t2, and is the High signal Vhi from the comparison circuit Comp from time t2 to t3.

[0043] When the processing circuit 6a receives a High signal Vhi as the detected voltage Vt, it stops the operation of the lighting circuit. That is, the processing circuit 6a determines that the High signal is received from the comparison circuit Comp and immediately stops the operation of the DC-DC conversion circuit 5. This causes the output voltage of the DC-DC conversion circuit 5 to drop.

[0044] 5 is a diagram illustrating the signal voltage range input to the port of the processing circuit 6a according to the first embodiment. In this embodiment, the voltage input to the port of the processing circuit 6a comes in two patterns: the detection voltage Vt, which is a temperature detection signal, and the High signal Vhi of the comparison circuit Comp. As described above, the detection voltage Vt and the High signal Vhi are input in different voltage ranges.

[0045] An overvoltage determination threshold Vth is set in the processing circuit 6a by an internal program. When the voltage input to the port is lower than the overvoltage determination threshold Vth, the processing circuit 6a recognizes the input voltage to the port as a detection voltage Vt, which is a temperature detection signal. At this time, the processing circuit 6a adjusts the current flowing to the light source 2 according to the input voltage level. Furthermore, when the voltage input to the port is higher than the overvoltage determination threshold Vth, the processing circuit 6a recognizes the input voltage as a High signal Vhi, which indicates the occurrence of an overvoltage, and immediately stops the operation of the DC-DC conversion circuit 5. In other words, the switching operation of the switching element Q2 is stopped.

[0046] In this way, when the input voltage, which is the detection voltage Vt or Vh input from the selection circuit, is smaller than the predetermined overvoltage determination threshold Vth, the processing circuit 6a drives and controls the lighting circuit in accordance with the input voltage. On the other hand, when the input voltage is larger than the overvoltage determination threshold Vth, the processing circuit 6a stops the operation of the lighting circuit.

[0047] FIG. 6 is a circuit block diagram of a lighting fixture 110 according to a variation of the first embodiment. The lighting fixture 110 includes a lighting device 11 and a light source 2. The lighting device 11 includes a lighting circuit and a control circuit 16. The lighting fixture 110 differs from the lighting fixture 100 in that the overvoltage protection threshold voltage E1 input to the negative terminal of the comparison circuit Comp can be easily changed. In the lighting fixture 110, a PWM signal output from a PWM output port 6e of the processing circuit 6a is input to the negative terminal of the comparison circuit Comp via a smoothing circuit RC1. In other words, the first threshold for causing the comparison circuit Comp to output a High signal is a voltage obtained by smoothing the PWM signal output by the processing circuit 6a. The PWM signal output from the PWM output port 6e is a signal independent of the PWM signals for controlling the switching elements Q1 and Q2.

[0048] Since the PWM signal is converted to DC through the smoothing circuit RC1, the DC voltage input to the negative terminal of the comparator circuit Comp can be changed by changing the duty ratio of the PWM signal through a program. This makes it easy to change the output voltage of the DC-DC converter circuit 5 that initiates overvoltage protection. This makes it possible to apply light sources 2 with different lighting voltages to the lighting device 10.

[0049] The duty ratio of the PWM signal output from the PWM output port 6e may be changed according to the lighting voltage of the light source 2. By changing the program executed by the processing circuit 6a according to the lighting voltage of the connected light source 2, the voltage at which overvoltage protection starts can be easily set. This allows the number of models of lighting device 10 to be reduced.

[0050] As described above, according to this embodiment, the higher of the detection voltages Vt and Vh is given priority and input to the processing circuit 6a. Furthermore, the detection voltages Vt and Vh are set to different voltage ranges. This allows a common voltage detection port for the temperature protection function and the overvoltage protection function, thereby reducing the number of ports in the processing circuit 6a. This allows the microcomputer to be made smaller. This also allows for a smaller and less expensive lighting fixture 100.

[0051] In this embodiment, the output signal of the comparator circuit Comp for overvoltage protection has two values, a High signal and a Low signal, so that the voltage ranges for the temperature protection function and the overvoltage protection function can be easily set to different values.

[0052] Generally, when an overvoltage occurs, the operation of the DC-DC converter circuit 5 must be stopped immediately. In this embodiment, the voltage of the High signal is high relative to the fluctuation range of the detection voltage Vt, so the overvoltage protection operation always takes priority over the temperature protection operation. In other words, when an overvoltage occurs, the High signal notifying the occurrence of an overvoltage is input to the port with the highest priority, regardless of the detection voltage Vt of the temperature detection signal. This allows the overvoltage protection operation to be performed quickly.

[0053] Furthermore, the diode OR circuit Dor of this embodiment eliminates the need for a switch operation to switch a signal input to a port, for example. This allows the operation of the DC-DC conversion circuit 5 to be stopped in the shortest time possible. This reduces voltage stress on the various components that make up the lighting device 10, preventing breakdowns in the lighting device 10 and improving reliability.

[0054] The comparison circuit Comp may be provided external to the processing circuit 6a, which is a microcomputer, or may be configured as an operational amplifier or comparator built into the microcomputer. The selection circuit, i.e., the A / D converter 6c that converts the analog signal output by the diode OR circuit Dor into a digital signal, may be provided external to or internal to the processing circuit 6a.

[0055] These modifications can be applied as appropriate to the lighting devices and lighting fixtures according to the following embodiments. Note that the lighting devices and lighting fixtures according to the following embodiments have many points in common with embodiment 1, so the following description will focus on the differences from embodiment 1.

[0056] Embodiment 2 FIG. 7 is a circuit block diagram of a lighting fixture 120 according to a second embodiment. The lighting fixture 120 includes a lighting device 12 and a light source 2. The lighting device 12 includes a lighting circuit and a control circuit 26. In this embodiment, voltage detection resistors R1 and R2 correspond to a first detection circuit that detects a voltage corresponding to the state of the lighting circuit and outputs the detected voltage Vd. In this embodiment, the first detection circuit detects the output voltage of the power factor correction circuit 4, which is a constant voltage circuit, as the detected voltage Vd, and the selection circuit inputs the higher of the detected voltage Vd and the detected voltage Vh to the processing circuit 6a. In other words, the lighting device 12 detects the output voltage Vout of the power factor correction circuit 4 and the overvoltage protection signal at the same port of the processing circuit 6a via the diode OR circuit Dor. The other configurations are the same as those of the first embodiment.

[0057] The detection signal of the output voltage Vout of the power factor correction circuit 4 is input to a port of the processing circuit 6a as a detection voltage Vd determined by the voltage division ratio of the voltage detection resistors R1, R2 and resistor R6. That is, the detection voltage Vd of the output voltage Vout of the power factor correction circuit 4 is expressed by Equation 2. Vd=Vout×Ro / (Ro+R1)...Formula 2 Here, Ro = 1 / (1 / R2 + 1 / R6). In other words, Ro represents the combined parallel resistance of R2 and R6. For simplicity, the forward voltage of diode Dor2, which makes up the diode OR circuit Dor, is ignored and set to zero volts.

[0058] During normal lighting of the light source 2, the voltage input to the comparator circuit Comp from the connection point of the voltage-dividing resistors R4 and R5 is lower than the overvoltage protection threshold voltage E1. Therefore, the output voltage of the comparator circuit Comp is a low signal, i.e., approximately zero volts. That is, during normal lighting, a detection voltage Vd corresponding to the output voltage Vout of the power factor correction circuit 4 is input to a port of the processing circuit 6a. At this time, the processing circuit 6a PWM-controls the switching element Q1 so that the output voltage Vout of the power factor correction circuit 4 becomes a desired voltage. That is, when the detection voltage Vd is input, the processing circuit 6a controls the constant voltage circuit so that the detection voltage Vd matches a predetermined target voltage.

[0059] The resistance values ​​of the voltage detection resistors R1, R2, and resistor R6 are selected in advance so that when the light source 2 is lit normally and a low signal is output from the comparison circuit Comp, the detection voltage Vd is higher than the low signal from the comparison circuit Comp. Note that the circuit for detecting the output voltage Vout of the power factor correction circuit 4 is not limited to this method, and other circuit methods may be used. For example, the output voltage Vout may be divided only by the voltage detection resistor R1 and resistor R6, without using the voltage detection resistor R2.

[0060] Next, we will explain how overvoltage protection works. Suppose that for some reason, the light source 2 becomes detached from the lighting device 12. In this case, the DC-DC conversion circuit 5 performs constant current control, so the output voltage of the DC-DC conversion circuit 5 rises. As a result, the voltage generated across the voltage-dividing resistors R4 and R5 also rises, and the voltage at the positive input terminal of the comparator circuit Comp rises. When the voltage generated across the voltage-dividing resistors R4 and R5 becomes higher than the overvoltage protection threshold voltage E1 connected to the negative input terminal of the comparator circuit Comp, a High signal is output from the output terminal of the comparator circuit Comp.

[0061] Here, the voltage Vhi of the High signal is preset to be large relative to the fluctuation range of the detection voltage Vd, which corresponds to the output voltage Vout of the power factor correction circuit 4. The diode OR circuit Dor inputs the High signal of the comparison circuit Comp to a port of the processing circuit 6a as the higher of the detection voltages Vd and Vh. When the High signal is input, the processing circuit 6a immediately stops operation of the DC-DC conversion circuit 5.

[0062] 8 is a diagram illustrating the range of signal voltages input to ports of the processing circuit 6a according to embodiment 2. The voltages input to the ports of the processing circuit 6a have two patterns: a detection voltage Vd corresponding to the output voltage Vout of the power factor correction circuit 4, and a High signal Vhi that is a higher voltage. The fluctuation range of the detection voltage Vd and the High signal Vhi are set to different voltage ranges.

[0063] An overvoltage determination threshold Vth is set in the processing circuit 6a by an internal program. When the voltage input to the port is lower than the overvoltage determination threshold Vth, the processing circuit 6a recognizes the input voltage to the port as a detection voltage Vd corresponding to the output voltage Vout of the power factor correction circuit 4. At this time, the processing circuit 6a performs constant voltage feedback control of the power factor correction circuit 4 so that the detection voltage Vd matches the target voltage signal Vpfc. When the voltage input to the port is higher than the overvoltage determination threshold Vth, the processing circuit 6a recognizes the input voltage as a High signal Vhi indicating the occurrence of an overvoltage, and immediately stops the operation of the power factor correction circuit 4 and the DC-DC conversion circuit 5. In other words, the switching operation of the switching elements Q1 and Q2 is stopped.

[0064] Note that while the High signal of the comparison circuit Comp is being input to the port of the processing circuit 6a, the processing circuit 6a cannot detect the detection voltage Vd. This prevents the processing circuit 6a from performing feedback control of the output voltage of the power factor correction circuit 4. Therefore, in this embodiment, the operation of the power factor correction circuit 4 is also stopped when an overvoltage is detected.

[0065] 8, the fluctuation range of the detection voltage Vd includes the range from approximately zero V before startup to the overshoot voltage at startup. In other words, the fluctuation range of the detection voltage Vd corresponds to the range from the lower limit voltage when the constant voltage circuit is not operating to the upper limit voltage when the output voltage of the constant voltage circuit is overshooting. The High signal is set to be larger than this fluctuation range.

[0066] As described above, according to this embodiment, the higher of the detection voltages Vd and Vh is given priority and input to the processing circuit 6a. Furthermore, the detection voltages Vd and Vh are set to different voltage ranges. This allows a common port to be used for voltage detection for constant voltage feedback control of the power factor correction circuit 4 and for overvoltage detection, thereby reducing the number of ports in the processing circuit 6a.

[0067] Embodiment 3 FIG. 9 is a circuit block diagram of the lighting fixture 130 according to Embodiment 3. The lighting fixture 130 includes a lighting device 13 and a light source 2. The lighting device 13 includes a lighting circuit and a control circuit 36. In the present embodiment, the current detection resistor R3 corresponds to a first detection circuit that detects a voltage corresponding to the state of the lighting circuit and outputs it as a detection voltage Vi. In the present embodiment, the first detection circuit detects the current flowing through the light source 2 as the detection voltage Vi, and the selection circuit inputs the higher one of the detection voltage Vi and the detection voltage Vh to the processing circuit 6a. That is, the lighting device 13 detects the detection signal of the output current of the DC-DC conversion circuit 5, that is, the supply current to the light source 2, and the overvoltage protection signal, through the diode OR circuit Dor at the same port. Other configurations are the same as those in Embodiment 1.

[0068] The current detection resistor R3 that detects the output current of the DC-DC conversion circuit 5 is connected to the port having the A / D converter 6c of the processing circuit 6a through the diode OR circuit Dor and the resistor R6. The lighting device 13 is configured to convert the current Iled flowing through the light source 2 into a voltage signal by the current detection resistor R3 and read it by the processing circuit 6a in order to supply a desired direct current to the light source 2 by the DC-DC conversion circuit 5. Thereby, the processing circuit 6a adjusts the on-time of the switching element Q2 so that the direct current approaches the desired current. Hereinafter, the current Iled may be referred to as the light source current.

[0069] The detection voltage Vi input to the port of the processing circuit 6a and corresponding to the light source current is expressed by Equation 3. Vi = Iled × R3 ··· Equation 3 However, since R3 << R6, R6 is ignored here. Also, the forward voltage of the diode Dor2 constituting the diode OR circuit Dor is ignored for simplification and set to zero V.

[0070] During normal lighting of the light source 2, the voltage input to the comparator circuit Comp from the connection point of the voltage-dividing resistors R4 and R5 is lower than the overvoltage protection threshold voltage E1. Therefore, the output voltage of the comparator circuit Comp is a low signal, i.e., approximately zero volts. That is, during normal lighting, the light source current detection voltage Vi is input to the port of the processing circuit 6a. The processing circuit 6a PWM-controls the switching element Q2 so that the output current of the DC-DC conversion circuit 5 becomes a desired current. That is, when the detection voltage Vi is input, the processing circuit 6a controls the constant current circuit so that the detection voltage Vi matches a predetermined target value.

[0071] In this way, when the light source 2 is lit normally and a low signal is output from the comparison circuit Comp, the resistance value of the current detection resistor R3 is pre-selected so that the detection voltage Vi corresponding to the light source current is higher than the low signal of the comparison circuit Comp.

[0072] Next, the overvoltage protection operation will be described. Suppose that for some reason the light source 2 becomes detached from the lighting device 13. In this case, the DC-DC conversion circuit 5 performs constant current control, so the output voltage of the DC-DC conversion circuit 5 rises. As a result, the voltage generated across the voltage-dividing resistors R4 and R5 also rises, and the voltage at the positive input terminal of the comparator circuit Comp rises. When the voltage generated across the voltage-dividing resistors R4 and R5 becomes higher than the overvoltage protection threshold voltage E1 connected to the negative input terminal of the comparator circuit Comp, a High signal is output from the output terminal of the comparator circuit Comp.

[0073] Here, the voltage level Vhi of the High signal is set to be higher than the light source current detection voltage Vi. The diode OR circuit Dor inputs the High signal of the comparator circuit Comp to a port of the processing circuit 6a as the higher of the detection voltages Vi and Vh. When the High signal is input, the processing circuit 6a immediately stops the operation of the DC-DC conversion circuit 5. In other words, it stops the switching operation of the switching element Q2.

[0074] 10 is a diagram illustrating the range of signal voltages input to the ports of the processing circuit 6a according to embodiment 3. The voltages input to the ports of the processing circuit 6a have two patterns: a detection voltage Vi of the output current of the DC-DC conversion circuit 5, and a High signal Vhi that is a voltage higher than the fluctuation range of the detection voltage Vi. The detection voltage Vi and the High signal are input in different voltage ranges.

[0075] An overvoltage determination threshold Vth is set in the processing circuit 6a by an internal program. When the voltage input to the port is lower than the overvoltage determination threshold Vth, the processing circuit 6a recognizes the input voltage to the port as the light source current detection voltage Vi. At this time, the processing circuit 6a performs constant current feedback control of the DC-DC conversion circuit 5. When the input voltage to the port is higher than the overvoltage determination threshold Vth, the processing circuit 6a recognizes the input voltage as a High signal indicating the occurrence of an overvoltage, and immediately stops the operation of the DC-DC conversion circuit 5.

[0076] The fluctuation range of the detected voltage Vi of the light source current corresponds to, for example, a dimming control range for setting any brightness of the light source 2. The dimming control range of the light source 2 is, for example, a range from minimum dimming to full brightness.

[0077] As described above, according to this embodiment, the higher of the detection voltages Vi and Vh is given priority and input to the processing circuit 6a. Furthermore, the detection voltages Vi and Vh are set to different voltage ranges. This allows a common port to be used for detecting the light source current for constant current feedback control and for detecting overvoltage, thereby reducing the number of ports in the processing circuit 6a.

[0078] In the first to third embodiments, a temperature detection circuit, a detection circuit for the output voltage of the power factor correction circuit 4, and a detection circuit for the light source current have been described as examples of the first detection circuit. However, the first detection circuit is not limited to these, and any circuit that detects a voltage corresponding to the state of the lighting circuit and outputs the detected voltage can be used. For example, the first detection circuit may be a circuit that outputs an analog signal that changes according to the operation of the AC-DC conversion circuit or the DC-DC conversion circuit.

[0079] Embodiment 4 FIG. 11 is a circuit block diagram of a lighting fixture 140 according to a fourth embodiment. The lighting fixture 140 includes a lighting device 14 and a light source 2. The lighting device 14 includes a lighting circuit and a control circuit 46. In this embodiment, the current detection resistor R8, the overcurrent protection threshold voltage E2, and the comparison circuit Comp correspond to a second detection circuit. The second detection circuit outputs a High signal as the detection voltage Vh when the switching current of the switching element Q1 constituting the power factor correction circuit 4 is greater than a predetermined first threshold. The second detection circuit also outputs a Low signal as the detection voltage Vh when the switching current of the switching element Q1 constituting the power factor correction circuit 4 is less than the predetermined first threshold. Here, the current detection resistor R8 converts the current flowing through the switching element Q1 into a voltage signal based on the resistance value of the current detection resistor R8.

[0080] The first detection circuit, which serves as a circuit for realizing a temperature protection function, includes a resistor R7 and a thermistor Rth connected in series with the resistor R7. The first detection circuit is similar to the first detection circuit in the first embodiment, and detects the temperature as a detection voltage Vt.

[0081] During normal lighting of the light source 2, the voltage input from the current detection resistor R8 to the comparison circuit Comp is lower than the overcurrent protection threshold voltage E2. Therefore, the output voltage of the comparison circuit Comp is a low signal, i.e., approximately zero V. In other words, during normal lighting, the temperature detection voltage Vt is input to the port of the processing circuit 6a. The control of the processing circuit 6a in response to the temperature detection voltage Vt is the same as in the first embodiment.

[0082] In this way, the resistance values ​​of resistor R7, thermistor Rth, and resistor R6 are preset so that when a low signal is output from the comparison circuit Comp, the detection voltage Vt corresponding to the temperature is higher than the low signal of the comparison circuit Comp.

[0083] Next, we will explain how overcurrent protection works. Normally, a triangular-wave switching current flows through the switching element Q1 with each switching operation. This triangular-wave switching current is repeated at high frequency. Normally, the detection voltage of the current detection resistor R8, which corresponds to the peak current value of the triangular wave during each switching operation, does not exceed the overcurrent protection threshold voltage E2. However, suppose that the current flowing through the switching element Q1 becomes excessive due to some cause, such as a load short circuit. In this case, the voltage generated across the current detection resistor R8 increases, causing the voltage at the positive input terminal of the comparator circuit Comp to increase. When the voltage generated across the current detection resistor R8 exceeds the overcurrent protection threshold voltage E2 connected to the negative input terminal of the comparator circuit Comp, the comparator circuit Comp outputs a high signal as the detection voltage Vh.

[0084] Here, the voltage level Vhi of the High signal is set to be higher than the temperature detection voltage Vt. The diode OR circuit Dor inputs the High signal of the comparison circuit Comp to a port of the processing circuit 6a as the higher of the detection voltages Vt and Vh. When the High signal is input, the processing circuit 6a immediately stops the switching operation of the switching element Q1, i.e., turns off the switching element Q1.

[0085] 12 is a diagram illustrating the range of signal voltages input to the ports of the processing circuit 6a according to the fourth embodiment. The voltages input to the ports of the processing circuit 6a are two patterns: a temperature detection voltage Vt and a High signal Vhi, which is a voltage higher than the fluctuation range of the detection voltage Vt. The detection voltage Vt and the High signal are input in different voltage ranges.

[0086] An overcurrent determination threshold Vth_i is set in the processing circuit 6a by an internal program. When the voltage input to the port is lower than the overcurrent determination threshold Vth_i, the processing circuit 6a recognizes the input voltage to the port as the temperature detection voltage Vt. At this time, the processing circuit 6a performs the control described in the first embodiment in accordance with the detection voltage Vt. When the input voltage to the port is higher than the overcurrent determination threshold Vth_i, the processing circuit 6a recognizes the input voltage as a High signal indicating that an overcurrent has occurred in the switching element Q1. As a result, the processing circuit 6a immediately stops the switching operation of the switching element Q1 and turns off the switching element Q1.

[0087] As described above, according to this embodiment, the higher of the detection voltages Vt and Vh is given priority and input to the processing circuit 6a. Furthermore, the detection voltages Vt and Vh are set to different voltage ranges. This allows a common port for temperature detection and overcurrent detection, thereby reducing the number of ports in the processing circuit 6a.

[0088] As in the modification of the first embodiment, the overcurrent protection threshold voltage E2 input to the negative terminal of the comparator circuit Comp may be a voltage obtained by smoothing the PWM signal output from the PWM output port 6e of the processing circuit 6a. In other words, the first threshold for causing the comparator circuit Comp to output a High signal may be a voltage obtained by smoothing the PWM signal output by the processing circuit 6a. This makes it easy to change the voltage level of the overcurrent protection threshold voltage E2 and to easily set the current setting value of the switching element Q1 at which overcurrent protection begins.

[0089] The duty ratio of the PWM signal output from the PWM output port 6e may be changed according to the lighting power of the light source 2. This makes it possible to apply light sources 2 with different lighting power to the lighting device 14, thereby reducing the number of models of the lighting device 14.

[0090] In the fourth embodiment, a temperature detection circuit has been described as an example of the first detection circuit, but the first detection circuit is not limited to this, and the detection circuit for the output voltage of the power factor correction circuit 4 or the detection circuit for the light source current described in the second and third embodiments may also be used.

[0091] Embodiment 5 FIG. 13 is a cross-sectional view of a lighting fixture 400 according to the fifth embodiment. The lighting fixture 400 comprises a lighting fixture body 40, a connector 41, a light source board 42, and a lighting device 43. The lighting fixture body 40 is a housing for mounting the lighting device 43 and other components. The connector 41 is a connection part for receiving a supply of power from an AC power source 1 such as a commercial power source. The light source board 42 is a board on which light-emitting elements such as LEDs or organic EL elements are mounted as electric light sources. The light source board 42 corresponds to the light source 2 in the first to fourth embodiments.

[0092] Lighting device 43 corresponds to any of the lighting devices of embodiments 1 to 4. Power is input to lighting device 43 from AC power supply 1 via connector 41 and power supply wiring 44. Lighting device 43 is connected to light source board 42 via output wiring 45. Lighting device 43 converts the input power into power to be supplied to light source board 42, and supplies the converted power to light source board 42. The light sources of light source board 42 are lit by the power supplied from lighting device 43.

[0093] From the above, it is possible to provide lighting fixture 400 that can achieve the same effects as those of embodiments 1 to 4. In other words, ports of processing circuit 6a can be easily shared for various detection signals, which makes it possible to reduce the size of processing circuit 6a, as well as the size and cost of the device.

[0094] The technical features described in each embodiment may be used in appropriate combination.

[0095] Various aspects of the present disclosure are summarized below as appendices. (Appendix 1) a lighting circuit that turns on and off the switching element to light the light source; a processing circuit for controlling the lighting circuit; a first detection circuit that detects a voltage corresponding to the state of the lighting circuit and outputs the detected voltage as a first detection voltage; a second detection circuit that outputs a High signal as a second detection voltage when a voltage or a current of the lighting circuit is greater than a predetermined first threshold, and outputs a Low signal as the second detection voltage when the voltage or the current of the lighting circuit is smaller than the first threshold; a selection circuit that inputs the higher of the first detection voltage and the second detection voltage to the processing circuit; Equipped with The voltage of the High signal is set to be large relative to a fluctuation range of the first detection voltage according to the state of the lighting circuit, The processing circuitry When the first detection voltage is input, the lighting circuit is controlled in accordance with the first detection voltage; A lighting device characterized in that when the second detection voltage is input, the switching operation of the switching element is stopped. (Appendix 2) The selection circuit a first diode having an anode to which the first detection voltage is input; a second diode having an anode to which the second detection voltage is input; and the cathode of the first diode and the cathode of the second diode are connected to each other; 2. The lighting device according to claim 1, wherein a connection point between the cathode of the first diode and the cathode of the second diode is connected to a port of the processing circuit. (Appendix 3) The lighting device according to claim 1 or 2, further comprising an A / D converter that converts the analog signal output by the selection circuit into a digital signal. (Appendix 4) The processing circuitry When an input voltage, which is the first detection voltage or the second detection voltage, input from the selection circuit is smaller than a predetermined second threshold, driving and controlling the lighting circuit in accordance with the input voltage; 4. The lighting device according to claim 1, wherein the operation of the lighting circuit is stopped when the input voltage is greater than the second threshold value. (Appendix 5) 5. The lighting device according to claim 1, wherein the first threshold is a voltage obtained by smoothing the PWM signal output by the processing circuit. (Appendix 6) 6. The lighting device according to claim 1, wherein the first detection circuit detects a temperature as the first detection voltage. (Appendix 7) 7. The lighting device according to claim 6, wherein the fluctuation range of the first detection voltage corresponds to the range from the upper limit to the lower limit of the temperature measured by the first detection circuit. (Appendix 8) The lighting device described in Appendix 6 or Appendix 7, characterized in that the processing circuit controls the lighting circuit so that, when the first detection voltage is input, the first detection voltage coincides with a predetermined third threshold value. (Appendix 9) The lighting device described in Appendix 6 or Appendix 7, characterized in that when the input first detection voltage is greater than a predetermined third threshold, the processing circuit reduces the current flowing to the light source compared to when the first detection voltage is less than the third threshold. (Appendix 10) the lighting circuit includes a constant voltage circuit and a constant current circuit that receives power from the constant voltage circuit and supplies current to the light source; 6. The lighting device according to claim 1, wherein the first detection circuit detects an output voltage of the constant voltage circuit as the first detection voltage. (Appendix 11) The lighting device described in Appendix 10, characterized in that the fluctuation range of the first detection voltage corresponds to a range from a lower limit voltage when the operation of the constant voltage circuit is stopped to an upper limit voltage when the output voltage of the constant voltage circuit is overshooting. (Appendix 12) The lighting device described in Appendix 10 or Appendix 11, characterized in that when the first detection voltage is input, the processing circuit controls the constant voltage circuit so that the first detection voltage matches a predetermined target voltage. (Appendix 13) the lighting circuit includes a constant voltage circuit and a constant current circuit that receives power from the constant voltage circuit and supplies current to the light source; 6. The lighting device according to claim 1, wherein the first detection circuit detects a current flowing through the light source as the first detection voltage. (Appendix 14) 14. The lighting device according to claim 13, wherein the fluctuation range of the first detection voltage corresponds to a dimming control range of the light source. (Appendix 15) The lighting device described in Appendix 13 or Appendix 14, characterized in that when the first detection voltage is input, the processing circuit controls the constant current circuit so that the first detection voltage matches a predetermined target value. (Appendix 16) the lighting circuit includes a constant voltage circuit and a constant current circuit that receives power from the constant voltage circuit and supplies current to the light source; 16. The lighting device according to claim 1, wherein the voltage of the lighting circuit is an output voltage of the constant current circuit. (Appendix 17) the first threshold is a voltage obtained by smoothing the PWM signal output by the processing circuit, 17. The lighting device according to claim 16, wherein a duty ratio of the PWM signal is changed according to a lighting voltage of the light source. (Appendix 18) the lighting circuit includes a constant voltage circuit and a constant current circuit that receives power from the constant voltage circuit and supplies current to the light source; 16. The lighting device according to claim 1, wherein the current of the lighting circuit is a current flowing through the switching element of the constant voltage circuit. (Appendix 19) the first threshold is a voltage obtained by smoothing the PWM signal output by the processing circuit, 19. The lighting device according to claim 18, wherein the duty ratio of the PWM signal is changed according to the lighting power of the light source. (Appendix 20) A lighting device according to any one of claims 1 to 19; the light source; A lighting fixture comprising: [Explanation of symbols]

[0096] 1 AC power supply, 2 light source, 3 rectifier circuit, 4 power factor correction circuit, 5 DC-DC conversion circuit, 6 control circuit, 6a processing circuit, 6b drive circuit, 6c A / D converter, 6d calculation circuit, 6e PWM output port, 10 lighting device, 11 lighting device, 12 lighting device, 13 lighting device, 14 lighting device, 16 control circuit, 26 control circuit, 36 control circuit, 46 control circuit, 40 lighting fixture body, 41 connector, 42 light source board, 43 lighting device, 44 power supply wiring, 45 output wiring, 100 lighting fixture, 110 lighting fixture, 120 lighting fixture, 130 lighting fixture, 140 lighting fixture, 400 lighting fixture, C1 filter capacitor, C2 smoothing capacitor, C3 smoothing capacitor, Comp comparison circuit, D1 diode, D2 diode, Dor diode OR circuit, Dor1 diode, Dor2 Diode, L1 inductor, L2 inductor, Q1 switching element, Q2 switching element, R1 voltage detection resistor, R2 voltage detection resistor, R3 current detection resistor, R4 voltage dividing resistor, R6 resistor, R7 resistor, R8 current detection resistor, RC1 smoothing circuit, Rth thermistor

Claims

1. a lighting circuit that turns on and off the switching element to light the light source; a processing circuit for controlling the lighting circuit; a first detection circuit that detects a voltage corresponding to a state of the lighting circuit and outputs the detected voltage as a first detection voltage; a second detection circuit that outputs a High signal as a second detection voltage when a voltage or a current of the lighting circuit is greater than a predetermined first threshold, and outputs a Low signal as the second detection voltage when the voltage or the current of the lighting circuit is smaller than the first threshold; a selection circuit that inputs the higher of the first detection voltage and the second detection voltage to the processing circuit; Equipped with a voltage of the High signal is set to be large relative to a fluctuation range of the first detection voltage according to the state of the lighting circuit, The processing circuitry When the first detection voltage is input, the lighting circuit is controlled in accordance with the first detection voltage; The lighting device is characterized in that, when the second detection voltage is input, the switching operation of the switching element is stopped.

2. The selection circuit a first diode having an anode to which the first detection voltage is input; a second diode having an anode to which the second detection voltage is input; and the cathode of the first diode and the cathode of the second diode are connected to each other; 2. The lighting device according to claim 1, wherein a connection point between the cathode of the first diode and the cathode of the second diode is connected to a port of the processing circuit.

3. 3. The lighting device according to claim 1, further comprising an A / D converter that converts the analog signal output by the selection circuit into a digital signal.

4. The processing circuitry When an input voltage, which is the first detection voltage or the second detection voltage, input from the selection circuit is smaller than a predetermined second threshold, driving and controlling the lighting circuit in accordance with the input voltage; 3. The lighting device according to claim 1, wherein the operation of the lighting circuit is stopped when the input voltage is greater than the second threshold value.

5. 3. The lighting device according to claim 1, wherein the first threshold value is a voltage obtained by smoothing the PWM signal output by the processing circuit.

6. 3. The lighting device according to claim 1, wherein the first detection circuit detects a temperature as the first detection voltage.

7. 7. The lighting device according to claim 6, wherein the fluctuation range of the first detection voltage corresponds to a range from an upper limit to a lower limit of a temperature measured by the first detection circuit.

8. 7. The lighting device according to claim 6, wherein the processing circuit controls the lighting circuit when the first detection voltage is input so that the first detection voltage coincides with a predetermined third threshold value.

9. 7. The lighting device according to claim 6, wherein the processing circuit reduces the current flowing through the light source when the input first detection voltage is greater than a predetermined third threshold value compared to when the first detection voltage is less than the third threshold value.

10. the lighting circuit includes a constant voltage circuit and a constant current circuit that receives power from the constant voltage circuit and supplies current to the light source; 3. The lighting device according to claim 1, wherein the first detection circuit detects an output voltage of the constant voltage circuit as the first detection voltage.

11. The lighting device described in claim 10, characterized in that the fluctuation range of the first detection voltage corresponds to a range from a lower limit voltage when the operation of the constant voltage circuit is stopped to an upper limit voltage when the output voltage of the constant voltage circuit is overshooting.

12. 11. The lighting device according to claim 10, wherein when the first detection voltage is input, the processing circuit controls the constant voltage circuit so that the first detection voltage coincides with a predetermined target voltage.

13. the lighting circuit includes a constant voltage circuit and a constant current circuit that receives power from the constant voltage circuit and supplies current to the light source; 3. The lighting device according to claim 1, wherein the first detection circuit detects a current flowing through the light source as the first detection voltage.

14. 14. The lighting device according to claim 13, wherein the fluctuation range of the first detection voltage corresponds to a dimming control range of the light source.

15. 14. The lighting device according to claim 13, wherein when the first detection voltage is input, the processing circuit controls the constant current circuit so that the first detection voltage coincides with a predetermined target value.

16. the lighting circuit includes a constant voltage circuit and a constant current circuit that receives power from the constant voltage circuit and supplies current to the light source; 3. The lighting device according to claim 1, wherein the voltage of the lighting circuit is an output voltage of the constant current circuit.

17. the first threshold is a voltage obtained by smoothing the PWM signal output by the processing circuit, 17. The lighting device according to claim 16, wherein a duty ratio of the PWM signal is changed in accordance with a lighting voltage of the light source.

18. the lighting circuit includes a constant voltage circuit and a constant current circuit that receives power from the constant voltage circuit and supplies current to the light source; 3. The lighting device according to claim 1, wherein the current of the lighting circuit is a current flowing through the switching element of the constant voltage circuit.

19. the first threshold is a voltage obtained by smoothing the PWM signal output by the processing circuit, 19. The lighting device according to claim 18, wherein the duty ratio of the PWM signal is changed in accordance with lighting power of the light source.

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

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