JP5440298B2 - lighting equipment - Google Patents

Description

  The present invention relates to a luminaire including an LED light source.

  A light-emitting diode lighting device including a step-down chopper is known (see, for example, Patent Document 1). In the light-emitting diode lighting device including the step-down chopper described in FIG. 2 of Patent Document 1, a resistance element 61 having a small resistance value is connected between the FET 5 serving as the first switching element and the first inductor 7. The resistor element 61 is connected between the base and emitter of the bipolar transistor 21 which is the second switching element. The collector of the transistor 21 is connected to the gate terminal of the FET 5, and the emitter is connected to the connection point between the resistance element 61 and the first inductor 7.

  When the FET 5 is turned on, a current flows through the resistance element 61 and the first inductor 7 and this current gradually increases. When the voltage across the resistance element 61 reaches a bias for operating the transistor 21, the transistor 21 The FET 5 is turned on, whereby the FET 5 is turned off. The voltage across the resistor element 61 is used as the base bias of the transistor 21. When this voltage reaches a predetermined voltage, the transistor 21 is turned on to turn off the FET 5, so that the turn-off timing is set to the second inductor. 12 can always be accurately taken without being influenced by the voltage value induced in the circuit 12. That is, the FET 5 can always be switched accurately.

  In addition, the base bias for turning on the transistor 21 is as low as 0.5 V in the case of a silicon transistor. Therefore, there is almost no power consumption in the resistance element 61, and wasteful power consumption can be prevented as much as possible.

  On the other hand, in FIG. 2 of Patent Document 1, a phototransistor 24T of a photocoupler 24 is connected between the collector and base of the transistor 21, and the phototransistor 24T is connected to a light-emitting diode of the photocoupler 24 corresponding to a PWM dimming signal. When it is turned on at a low frequency via 24D, the step-down chopper operates intermittently as shown in FIG.

Japanese Patent No. 4123886

  However, there is a demand for further reducing the power loss of the resistance element connected in series with the first switching element in the light-emitting diode lighting device of Patent Document 1. In addition, the temperature characteristic is determined by the temperature characteristic of the transistor 21, and there is a problem that it is difficult to provide a desired temperature characteristic.

  Further, in the case of the dimming control described in Patent Document 1, the dimming signal is a PWM system, and the low-frequency PWM dimming signal has an intermittent waveform (see FIG. 4A). Operates intermittently in response to the PWM dimming signal. Therefore, it is necessary to start the step-down chopper every time the operation is started, and the self-excited oscillation operation tends to become unstable and the circuit efficiency is lowered.

  In the present invention, the self-oscillation type constant current control operation during dimming is stable, the power loss of the impedance means for current feedback can be further reduced, the temperature characteristics are good, and the output current varies. It aims at providing the lighting fixture which equipped with few LED lighting devices.

  The luminaire of the present invention includes: a luminaire main body; and an LED lighting device disposed inside the luminaire main body; the LED lighting device includes a DC power source, an input terminal connected to the DC power source, and a load. A first circuit including an output terminal to be connected, a switching element, impedance means and an inductor in series and connected between the input terminal and the output terminal, and a second circuit including an inductor and a free wheel diode in series and connected to the output terminal A step-down chopper, an LED light source connected to the output end of the step-down chopper, a drive winding is magnetically coupled to the inductor of the step-down chopper, and a voltage induced in the drive winding is applied as a drive signal to the control terminal of the switching element The voltage of the drive signal generation circuit that maintains the switching element in the ON state and the impedance means of the step-down chopper is detected. A turn-off circuit having a switching element that is turned on by the output of the comparison means that outputs when the detected voltage exceeds a reference value and the output of the comparison means to short-circuit the output terminal of the drive signal generation circuit and to turn off the switching element; The reference value of the comparison means is formed by a voltage dividing circuit having a variable resistor by dividing the voltage of the reference voltage source and the reference voltage source, and the LED light source is dimmed by changing the reference value by operating the variable resistor And a dimming means in which the operation portion of the variable resistor is operatively exposed to the outside of the luminaire main body.

  The present invention allows the following aspects.

  A lighting fixture is a device that uses a light emitting diode as a light source. The luminaire main body refers to the remaining part excluding the LED lighting device from the luminaire.

  The LED lighting device includes a DC power supply, a step-down chopper, an LED light source, a drive signal generation circuit, a turn-off circuit, and a dimming unit.

  The DC power supply supplies power for rectifying an AC power supply, for example, a commercial AC power supply voltage to light the light emitting diode, in a DC mode to a step-down chopper described later. The mode of rectification is not particularly limited, but full wave rectification is preferable. However, not only a rectified DC power supply but also a DC power supply including a battery or the like may be used. Further, when the DC power supply is a rectified DC power supply, a smoothing capacitor can be connected between the output terminals to smooth the DC output voltage.

  The step-down chopper includes a first circuit and a second circuit, and a switching element and a first inductor are connected in series to an input end, and a first inductor and a free wheel diode are connected in series to an output end. It is a chopper circuit, an impedance means is connected in series with the switching element of the step-down chopper, a turn-off circuit described later is operated, and the LED light source is turned on by self-excited oscillation type constant current control for turning off the switching element.

  The LED light source includes a light emitting diode as a light source, is connected as a load to the output terminal of the step-down chopper, and is lit by being energized by the output current of the step-down chopper. The LED light source connected to the output terminal of the step-down chopper may be a series circuit in which a plurality of light emitting diodes are connected in series, or may be a single circuit. A plurality of these may be connected in parallel to constitute a load circuit. In addition, since the light emitting diode is not particularly limited in its light emission characteristics, package mode, and the like, various known light emission characteristics, package modes, ratings, and the like can be appropriately selected and used.

  The drive signal generation circuit includes a drive winding magnetically coupled to the inductor of the step-down chopper, applies a voltage induced in the drive winding to the control terminal of the switching element, and maintains the switching element in the on state. If desired, an impedance element such as a series circuit of a capacitor and a resistor can be interposed between the drive winding and the control terminal.

  The turn-off circuit includes comparison means and a switch element, detects the voltage of the impedance means of the step-down chopper, and turns on the switch element with the output of the comparison means generated when the detected voltage exceeds a reference value. The switch element short-circuits the output end of the drive signal generation circuit. The switching element of the step-down chopper is turned off by this short circuit.

  The comparison means can configure the turn-off circuit with a switch element, for example, a transistor, and set the input voltage to a voltage that is clearly lower than the base-emitter voltage when the switch element is turned on, for example, 0.3 V or less. . Thereby, the impedance of the impedance means can be reduced to a small value that can reduce the power loss generated there.

  Further, by interposing the comparison means between the impedance means and the switch element so that the switch element is turned on by the output voltage of the comparison means, the temperature characteristic of the step-down chopper turn-off is accompanied by the presence of the comparison means. Unaffected. As a result, the temperature characteristics of the LED lighting device are improved. That is, the comparison means compares the input voltage with a reference voltage set inside, and amplifies the input voltage to a high voltage and outputs it when the input voltage exceeds the reference voltage.

  Further, the reference voltage for comparison with the input voltage in the comparison means is generally set using a Zener diode. Since the temperature characteristic of the comparison means is substantially determined by the temperature characteristic of the Zener diode that sets the reference voltage, it is not possible to select a Zener diode having a slightly negative characteristic or a flat temperature characteristic that is suitable as the temperature characteristic of the turn-off circuit. Easy.

  Furthermore, since the turn-off control of the switching element of the step-down chopper is performed through the operation of the comparison means, the variation management of the output current of the step-down chopper is easy and the variation is reduced.

  In the present invention, the turn-off circuit including the comparison means and the switch element can be configured mainly by a voltage comparator using an operational amplifier, that is, a comparator. In this case, either the first mode in which the turn-off circuit is configured by the comparator and the switch element that is turned on by the output voltage, or the second mode in which the turn-off circuit is configured by only the comparator having a relatively large sink current capacity. May be. In the second mode, since the comparator itself has a relatively large sink current capacity, it exhibits the function of a switch element, so that a separate switch element is unnecessary.

  Next, the light control means will be described. The reference value input to the comparison means of the turn-off circuit is formed by a voltage dividing circuit including a reference voltage source and a variable resistor. Then, the reference value can be changed by operating the variable resistor, and when the reference value changes to a value smaller than that of the total light of the LED light source, the peak value of the current value flowing through the first circuit of the step-down chopper As a result, the output current of the step-down chopper is reduced, so that the LED light source is dimmed.

  In the present invention, the change range of the reference value, and therefore the dimming range, can be set within a range of 20 to 100% with respect to the output current of the high-voltage chopper at the time of all light from the LED light source. If the lower limit of the dimming range is less than 20%, the feedback amount by the drive winding is reduced, and the self-excited current control operation of the step-down chopper tends to become unstable, so care must be taken. On the other hand, if it exceeds 100%, the LED light source performs overload lighting, and the temperature rise of the LED light source increases and the life is likely to be shortened. In addition, the said light control range is 25 to 100%, and if it is this range, more stable lighting will be performed near the light control lower limit.

  For the above reasons, if the dimming range is set in a desired manner within the above range, the step-down chopper can dimm the LED light source while stably performing the self-excited current control operation. For example, dimming can be performed continuously or stepwise within the above range, or can be set continuously or stepwise within a range narrower than the range of 30 to 100%. In the case of setting in stages, it is preferable that the dimming range can be selected in at least three stages.

  For the dimming operation, the operation part of the variable resistor is exposed from the luminaire body to the outside. Thereby, a desired light control level can be selected by manually operating the operation unit.

  According to the present invention, the turn-off circuit that turns off the switching element of the step-down chopper includes a switching element that short-circuits the output terminal of the drive signal generation circuit that supplies a driving signal to the switching element, and impedance means in series with the switching element of the step-down chopper And a comparison means interposed between the switch elements, and the reference value of the comparison means is divided by a voltage dividing circuit having a variable resistor by dividing the reference voltage source and the voltage of the reference voltage source. Not only can the LED light source be dimmed while the chopper performs a stable self-excited current control operation, the impedance of the impedance means can be further reduced to further reduce the power loss of the impedance means, and temperature characteristics With good output and less variation in output current It is possible to provide a lighting device for lighting the LED light source D lighting device.

It is a figure which shows the spotlight as one form for implementing the lighting fixture of this invention. It is a circuit diagram which similarly shows an LED lighting device. It is a circuit diagram which shows the detail of the circuit part which similarly makes a reference value variable.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  As shown in (a) front view and (b) perspective view of FIG. 1, the luminaire 10 of the present invention includes a luminaire main body 1 and an LED lighting device 2, for example, in a distribution duct installed indoors. It is configured to be mounted and receive power.

  The luminaire main body 1 includes a base body part 11, a support part 12, and a lamp body part 13 in this embodiment.

  The base body 11 is mainly composed of a rectangular case. As shown by a dotted line in FIG. 1A, the LED lighting device 2 to be described later is housed inside, and a power receiving plug 11a is provided at one end in the longitudinal direction. Similarly, support plugs 11b are disposed on the other end side. Since the base body part 11 is supported by the power distribution duct by the power receiving plug 11a and the supporting plug 11b, the luminaire main body 1 can be securely attached. In addition, an operation portion K of a variable resistor, which will be described later, which is housed in the base body 11, that is, a light control knob, is exposed from an end surface of the base body 11 opposite to the lamp body 13 in the longitudinal direction.

  The support portion 12 is disposed at a position deviated to one end side in the longitudinal direction of the base portion 11, has a bifurcated shape, and supports the bifurcated central axis so as to be rotatable in a horizontal plane by a pivot P1, A lamp body 13, which will be described later, is supported in a vertical plane so as to be able to be received by a pivot P2 disposed at the tip of the forked arm. As a result, the light projecting direction from the lamp body 13 can be adjusted over three dimensions.

  The lamp body 13 includes a light projecting surface 13a on the front surface and a heat radiating portion 13b on the rear surface. The light projecting surface portion 13a includes an LED light source LED. The LED light source LED has a plurality of light emitting diodes arranged in a distributed manner. The heat dissipating part 13b includes heat dissipating fins so as to dissipate heat generated from the LED light source LED to the back. In addition, in FIG.1 (b), the lamp | ramp part 13 has shown the state which faced the horizontal direction right side in the figure, and the state which faced the upper side.

  As shown in FIG. 2, the LED lighting device 2 includes a DC power source DC, a step-down chopper SDC, an LED light source LED, a drive signal generation circuit DSG, a turn-off circuit TOF, a dimming means DM, and an overvoltage protection circuit OVP. ing. In addition to the above components, a startup circuit ST and an overvoltage protection circuit OVP are additionally provided.

  The DC power source DC includes a full-wave rectifier circuit DB and a capacitor C1 whose input ends are connected to the AC power source AC. Capacitor C1 may be either a high frequency cut capacitor or a smoothing capacitor. And it connects between the output ends of full wave rectifier circuit DB. Note that a noise prevention capacitor C2 is connected between the input terminals of the full-wave rectifier circuit DB.

  The step-down chopper SDC includes input terminals t1 and t2 connected to a DC power source DC, output terminals t3 and t4 connecting a load, a switching element Q1, an impedance means Z1 and an inductor L1 in series, and the input terminal t1 and the output terminal t3. A first circuit A connected in between, and a second circuit B including a first inductor L1 and a diode D1 connected in series and connected between output terminals t3 and t4 are configured. An output capacitor C3 is connected between the output terminals t3 and t4.

  In this embodiment, the switching element Q1 of the step-down chopper SDC is composed of an FET (field effect transistor), and its drain and source are connected to the first circuit A. Then, the first circuit A forms an electromagnetic energy storage circuit of the inductor L1 via the output capacitor C3 and / or the load circuit LC described later, the second circuit B includes the inductor L1 and the diode D1 and the output capacitor C3. / Or an electromagnetic energy emission circuit of the inductor L1 is formed via a load circuit LC described later. In this embodiment, the impedance means Z1 is a resistor, but an inductor or a capacitor having an appropriate resistance component can be used if desired.

  The desired number of LED light sources LED are connected in series, and connected in series with the output capacitor C3 to form a load circuit LC. The load circuit LC is connected between the output terminals t3 and t4 of the step-down chopper SDC, and is energized and lit. .

  The drive signal generation circuit DSG includes a drive winding DW that is magnetically coupled to the first inductor L1 of the step-down chopper SDC. Then, the voltage induced in the drive winding DW is applied as a drive signal between the control terminal (gate) and one main terminal (drain) of the switching element Q1, and the switching element Q1 is maintained in the ON state. The other end of the drive winding DW is connected to the other main terminal (source) of the switching element Q1 through the impedance means Z1.

  In this embodiment, the drive signal generation circuit DSG includes a capacitor C4 in series between one end of the drive winding DW and the control terminal (gate) of the switching element Q1 in addition to the above configuration. Further, a Zener diode ZD1 is connected between the output terminals of the drive signal generation circuit DSG, and an overvoltage is applied between the control terminal (gate) of the switching element Q1 and one main terminal (drain), and the switching element Q1 is destroyed. An overvoltage protection circuit is formed to prevent this.

  The turn-off circuit TOF includes a comparator CP1, a switch element Q2, and first and second control circuit power supplies ES1 and ES2. The reference value is input to the inverting input terminal of the comparator CP1. The reference value is formed by the light control means DM described later. The voltage of the impedance means Z1 is input to the non-inverting input terminal of the comparator CP1, and the comparator CP1 compares it with a reference value.

  The switch element Q2 is formed of a transistor, and has a collector connected to the control terminal of the first switching element Q1, and an emitter connected to a connection point between the impedance element Z1 and the first inductor L1. Therefore, when the switch element Q2 is turned on, the output terminal of the drive signal generating circuit DSG is short-circuited. Thereby, the switching element Q1 is turned off.

  The first control circuit power supply ES1 is configured by connecting a series circuit of a diode D2 and a capacitor C5 to both ends of the drive winding DW. When the increasing current flows through the inductor L1, the first control circuit power supply ES1 is connected to the drive winding DW. Capacitor C5 is charged via diode D2 by the generated induced voltage, a positive potential is output from the connection point of diode D2 and capacitor C5, and a control voltage is applied to the output terminal of comparator CP1 via resistor R7. It is configured as follows.

  The second control circuit power supply ES2 is configured by connecting a series circuit of a diode D3 and a capacitor C6 across the tertiary winding W3 that is magnetically coupled to the inductor L1, and when a current that decreases from the inductor L1 flows. The capacitor C6 is charged via the diode D3 with the induced voltage generated in the tertiary winding W3, a positive voltage is output from the connection point of the diode D3 and the capacitor C6, and the control voltage is applied to the reference voltage source ZD2. A reference voltage is generated.

  The dimming means DM includes a reference voltage source ZD2 and a voltage dividing circuit VD. The reference voltage source ZD2 is formed of a Zener diode in this embodiment, but may be a series stabilized power supply circuit. The voltage dividing circuit VD is configured as shown in FIG. That is, a series circuit of a resistor R11, a variable resistor R12, a variable resistor R13, and a resistor R14 is connected in parallel to the reference voltage source ZD2, and a connection point between the variable resistor R12 and the variable resistor R13 is a non-inversion of the comparator CP1. The reference value is input to the comparator CP1 by connecting to the input terminal. Then, first, the variable resistor R12 is adjusted to set the total light level of the LED light source LED in the factory. Next, the variable range of the variable resistor R13 is set to be the dimming range. Moreover, the operation part of variable resistor R13 becomes the operation part K exposed to the exterior from the lighting fixture main body 1 in FIG. Therefore, when the operation unit K is operated when the lighting fixture 10 is used, the illumination light emitted from the lamp unit 13 is dimmed to a desired level without the dimming range.

  The overvoltage protection circuit OVP is mainly composed of the second control circuit power supply ES2 and the comparator CP2.

  The comparator CP2 has an inverting input terminal connected to a connection point between the resistor R4 and the resistor R5, and a series circuit of the resistor R4 and the resistor R5 is connected in parallel to the capacitor C6 of the second control circuit power supply ES2. . The resistors R4 and R5 constitute a voltage dividing circuit, and the divided terminal voltage of the resistor R5 is applied to the inverting input terminal. The non-inverting input terminal P7 is connected to the inverting input terminal of the comparator CP1.

  The start-up circuit ST includes a resistor R3 connected between the drain and gate of the first switching element Q1 and a resistor R10 connected in parallel to the capacitor C4. When the DC power source DC is turned on, the resistor R3 and the resistor R10 are connected. A positive starting voltage mainly determined by the resistance ratio is applied to the gate of the first switching element Q1, and the step-down chopper SDC is started.

  Next, circuit operation will be described.

  When the DC power source DC is turned on and the step-down chopper SDC is activated by the activation circuit ST, the switching element Q1 is turned on, and the output capacitor C3 of the load circuit LC and / or the light-emitting diode LED in the first circuit A from the DC power source DC. A linearly increasing current flows out through the. This current induces a voltage that is positive on the capacitor C4 side in the drive winding DW of the drive signal generation circuit DSG, and this induced voltage is applied to the control terminal (gate) of the switching element Q1 via the capacitor C4. Is applied, the switching element Q1 is maintained in the ON state, and an increasing current continues to flow. At the same time, a voltage drop occurs in the impedance means Z1 due to the increasing current, and the drop voltage is applied as an input voltage to the inverting input terminal of the comparator CP1 of the turn-off circuit TOF.

  When the input voltage of the comparator CP1 increases with the increase of the current and exceeds the reference value, which is the output of the dimming means DM, the comparator CP1 operates to generate a positive output voltage. As a result, the switching element Q2 of the turn-off circuit TOF is turned on to short-circuit the output terminal of the drive signal generating circuit DSG, so that the switching element Q1 of the step-down chopper SDC is turned off and the increasing current is cut off.

  When the switching element Q1 is turned off, the increasing current flows through the inductor L1 to release the electromagnetic energy stored therein, and the inside of the second circuit B including the inductor L1 and the diode D1 is passed through the load circuit LC. A decreasing current flows out via the output capacitor C3 and / or the light emitting diode LED. Due to this decreasing current, a voltage that is negative on the capacitor C4 side is induced in the drive winding DW of the drive signal generation circuit DSG, and this induced voltage applies a negative potential to the capacitor C4 via the Zener diode ZD1. Since a negative potential is applied to the control terminal (gate) of the switching element Q1, the switching element Q1 is maintained in the OFF state, and a decreasing current continues to flow.

  When the release of the electromagnetic energy accumulated in the inductor L1 ends and the current that decreases decreases to 0, a counter electromotive force is generated in the inductor L1, the voltage induced in the drive winding DW is reversed, and the capacitor C4 Since the induced voltage is applied again to the gate of the switching element Q1 via the capacitor C4 and the resistor R1, the switching element Q1 is inverted again to the ON state and increases again. Begins to flow.

  Thereafter, the circuit operation similar to the above is repeated, and the increasing current and decreasing current are combined and a triangular load current flows, whereby the LED light source LED of the load circuit LC is turned on.

  In the above circuit operation, the operation of the turn-off circuit TOF is performed by the two-stage operation of the comparator CP1 and the switch element Q2, and the comparator CP1 operates stably and accurately even when the input voltage is 0.3V or less. For this reason, since the resistance value of the impedance means Z1 can be reduced, even if the input voltage in the prior art is 0.5 V, according to the present invention, the power loss of the impedance means Z1 is 40 % Or more can be reduced.

  Further, the temperature characteristic of the turn-off circuit TOF is determined on the comparator CP1 side, and a desired good temperature characteristic can be given to the comparator CP1, so that the problem caused by the temperature characteristic of the switch element Q2 as in the prior art is Disappear. Note that the temperature characteristic of the comparator CP1 can be easily selected, for example, as a Zener diode used for the reference voltage source, whose temperature characteristic is slightly negative or flat. It can contribute as a temperature characteristic. Thereby, the light emitting diode lighting device with favorable temperature characteristics can be obtained.

  Further, by providing the comparator CP1 in the turn-off circuit TOF, the switch element Q2 can be operated stably and accurately, so that variations in the output of the light emitting diode lighting device are reduced.

  Next, the light control operation will be described. That is, if the resistance value of the variable resistor R13 of the light control means DM is made smaller than that at the time of all light by operating the operation unit K, it is output from the voltage dividing circuit VD and input to the inverting input terminal of the comparator CP1. Since the reference value is small, the switching element Q1 of the step-down chopper SDC is quickly turned off, and the increasing current is small. As a result, the output current of the step-down chopper SDC is reduced, and the LED light source LED is dimmed.

  Next, the operation of the overvoltage protection circuit OVP will be described. That is, if the light emitting diode LED of the load circuit LC becomes abnormal for some reason during lighting, and the output of the step-down chopper SDC becomes overvoltage, it is magnetically coupled to the inductor L1 and the reduced current flows from the inductor L1. Since the voltage induced in the winding W3 is proportional to the output voltage of the step-down chopper SDC, the terminal voltage of the capacitor C6 of the second control circuit power supply ES2 also increases in proportion. As a result, the terminal voltage of the capacitor C6 is divided by the resistors R4 and R5, and the voltage input to the inverting input terminal P6 of the comparator CP2 exceeds the reference voltage, so that a negative output voltage is output from the output terminal. For this reason, the potential of the control terminal (gate) of the first switching element Q1 becomes negative, the first switching element Q1 is turned off, and the light emitting diode LED is turned off to be protected. After that, it is configured so that it cannot be restarted by setting resistance values of resistors R3 and R10 of the starting circuit ST described later.

  DESCRIPTION OF SYMBOLS 1 ... Lighting fixture body, 2 ... LED lighting device, 10 ... Lighting fixture, A ... 1st circuit, B ... 2nd circuit, C3 ... Output capacitor, CP1, CP2 ... Comparator, DB ... Full wave rectifier circuit, DC ... DC power supply, DM ... light control means, DSG ... drive signal generation circuit, DW ... drive winding, ES1 ... first control circuit power supply, ES2 ... second control circuit power supply, L1 ... inductor, K ... operation unit, LC ... load circuit, LED ... LED light source, Q1 ... switching element, Q2 ... switch element, SDC ... step-down chopper, ST ... start-up circuit, t1, t2 ... input end, t3, t4 ... output end, TOF ... turn-off circuit, Z1 ... Impedance means

Claims (1)

A lighting fixture body;
An LED lighting device which is disposed in the interior of the luminaire body;
Comprising:
The LED lighting device includes a DC power supply, first connected between the input terminal connected to a DC power source, an output terminal for connecting a load, said input end and said output end includes a switching element, the impedance means and the inductor in series a step-down chopper having first circuit, and a second circuit connected to the output end comprises said inductor and the freewheel diode in series, the LED light source connected to the output terminal of the step-down chopper, the step-down chopper magnetically coupling the drive winding to the inductor, the voltage induced in the drive winding is applied as a drive signal to the control terminal of the switching element, a drive signal generation circuit that maintains the switching element in the oN state, the by detecting a voltage of the impedance means of the step-down chopper, out when the detected voltage exceeds a reference value Comparison means and a turn-off circuit having a switching element to turn off the switching element to the output terminal of the drive signal generating circuit is turned on by the output of the comparison means shorted, the reference value of the comparison means is a reference to together are formed by a voltage dividing circuit having a voltage source and dividing the variable resistor a voltage of the reference voltage source, so that the by the variable resistor of the operation is changed the reference value for lighting the LED light source dimming and It is configured, and the operation of the variable resistor is provided with a light control means which is exposed to be operated outside of the luminaire body;
A lighting apparatus characterized by that.

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