JP5010334B2 - Discharge lamp lighting device and lighting apparatus using the same - Google Patents

Description

  The present invention relates to a discharge lamp lighting device and a lighting fixture using the same.

  Conventionally, there has been provided a discharge lamp lighting device capable of dimming control of a discharge lamp such as a fluorescent lamp. With this type of discharge lamp, if the dimming level is low (deep dimming) during dimming or if the ambient temperature decreases, the discharge state may become unstable, causing moving stripes and flickering. Further, if the light control level is further lowered, the discharge may not be maintained and the light may disappear. That is, as the load power supplied to the discharge lamp becomes smaller than the rated value, the load current becomes smaller and the amount of heat generation decreases, so it becomes difficult to maintain a stable discharge state and the light output becomes unstable. Or the problem of disappearing.

  In order to solve the above problems, it is known to detect the load current flowing through the discharge lamp with a current sensor, compare the detected value of the load current with a reference value, and perform feedback control so that the difference is reduced. For example, it is disclosed in Patent Document 1. Hereinafter, a conventional example of a discharge lamp lighting device using such feedback control will be described with reference to the drawings. This conventional example includes an inverter circuit (not shown) that converts a DC voltage into a high-frequency AC voltage and supplies it to a load circuit (not shown) including a discharge lamp (not shown), and a load current flowing through the discharge lamp. And a feedback control circuit 100 including an error amplifier OP as shown in FIG. 5A.

  In the error amplifier OP of the feedback control circuit 100, the discharge lamp load current detection value S1 is input to the inverting input terminal, and the target of the light output of the discharge lamp according to the dimming signal input from the outside to the non-inverting input terminal. The value S2 is input. The output value S3 output from the output terminal of the error amplifier OP is input to a control circuit (not shown) that determines the frequency of the output voltage of the inverter circuit, and when the output value S3 increases, the inverter Feedback control is performed so that the frequency of the inverter circuit increases when the frequency of the circuit decreases and the output value S3 decreases.

  Here, as shown in FIG. 6A, a case is considered where dimming control is performed on a discharge lamp whose load current-load voltage characteristic (hereinafter referred to as “lamp characteristic”) is represented by a curve a in FIG. In the figure, a plurality of vertical curves indicate the output current-output voltage characteristics (hereinafter referred to as “inverter characteristics”) of the inverter circuit at each frequency of the inverter circuit. When the light is dimmed from the maximum light output (50 kHz) in the direction in which the light output decreases, the light is turned on at point A when the frequency of the inverter circuit is 80 kHz. When the light is further adjusted, the load current decreases as the frequency of the inverter circuit increases up to point B (85 kHz). When the frequency of the inverter circuit exceeds 85 kHz, the intersection of the lamp characteristic curve and the inverter characteristic curve. Because there is no lamp, the discharge lamp goes out.

Therefore, when the above feedback control circuit 100 is used, as shown in FIG. 5B, when dimming from the maximum light output to the point B in FIG. 6A, detection is performed as the target value S2 decreases. Although the value S1 and the output value S3 also decrease, if the dimming is performed so that the target value S2 decreases in the vicinity of the point B, the output value S3 decreases, and accordingly, the frequency of the inverter circuit increases and the load current decreases. To do. Then, since the detection value S1 is lower than the target value S2, the output value S3 increases, and conversely, feedback control is performed until the detection value S1 and the target value S2 become equal. Therefore, even if the light is further dimmed from the point B, the discharge lamp does not go out, and the light is dimmed to the point C (80 kHz) as the frequency of the inverter circuit decreases.
JP-A-6-302393

  By the way, a discharge lamp with a high load impedance, such as FHT42 (see FIG. 7A) or FHSD20 (see FIG. 7B) called a compact fluorescent lamp, is used for the discharge lamp lighting device as described above. There is. As shown in FIG. 7C, the FHT 42 and the FHSD 20 have a load current of 20 mA or less and 10 mA or less, respectively, for dimming to less than 10% of the rated light output in an environment where the ambient temperature of the discharge lamp is 25 ° C. In any case, the load impedance is 10 kΩ or more. Further, when the ambient temperature of the discharge lamp is lowered, the load impedance is further increased.

  Here, the lamp characteristics and the frequency characteristics when the ambient temperature of the FHT 42 is changed are shown in FIGS. As shown in FIG. 8A, the load impedance at the time of low luminous flux dimming is the lowest when the ambient temperature is 50 ° C. and the highest when the ambient temperature is 0 ° C. When the ambient temperature is 25 ° C. or less, the frequency characteristic curve of the inverter circuit having a frequency of 80 kHz and the lamp characteristic curve intersect at two points. Further, as shown in FIG. 8B, when the ambient temperature is 50 ° C., the frequency of the inverter circuit at the lower limit of the dimming level is about 85 kHz, and the frequency also increases at the lower limit of the dimming level. I keep doing it. When the ambient temperature is 25 ° C., the frequency of the inverter circuit at the lower limit of the dimming level does not change at about 81 kHz. When the ambient temperature is 0 ° C., dimming in the direction of lowering the light output of the discharge lamp, the frequency decreases from the time when the frequency of the inverter circuit reaches about 82 kHz, and the frequency decreases to about 77 kHz. This is because the feedback control circuit 100 is operated to prevent the discharge lamp from extinguishing, and the intersection of the lamp characteristic curve and the inverter characteristic curve is maintained.

  However, in the above conventional example, when a discharge lamp having a high load impedance is used at the time of low beam dimming such as FHT42 and FHSD20, a region Z as shown in FIGS. 6B and 8B (FIG. 6). If flickering occurs in the discharge lamp due to the ambient temperature of the discharge lamp decreasing (between points B and C in (a)), the frequency of the inverter circuit is reduced by the feedback control circuit 100, and the load current is reduced. By increasing the frequency, the flickering of the discharge lamp can be avoided. However, when the frequency of the inverter circuit is decreased in the region Z, the load current decreases, and feedback control is performed in the direction in which the discharge lamp goes out. It was. In order to solve the above problem, for example, a method of obtaining the constant current characteristic of the inverter circuit by setting the frequency of the inverter circuit when dimming with a low luminous flux near the no-load resonance frequency of the resonance circuit is conceivable. It is necessary to increase the value of the resonance inductance of the resonance circuit and lower the output voltage of the inverter circuit, and the core that forms the resonance inductance becomes larger and the startability is likely to deteriorate. There was also a problem that it became an unrealistic design.

  The present invention has been made in view of the above points, and flickering and extinguishing of the discharge lamp can be avoided even when dimming is performed to reduce the light output of the discharge lamp having a high load impedance. It aims at providing a discharge lamp lighting device and a lighting fixture using the same.

In order to achieve the above object, the invention according to claim 1 is an inverter circuit that converts a DC voltage into a high-frequency AC voltage and supplies it to a load circuit including a discharge lamp, and an output-related value that reflects the light output of the discharge lamp. Output from the first detection circuit, the target value setting circuit for setting the target value of the light output of the discharge lamp according to the dimming signal input from the outside, and the target value and the first detection circuit A feedback control circuit having a first comparator for comparing with a detected value and performing feedback control by varying the frequency of the output voltage of the inverter circuit according to the output of the first comparator so that the detected value is maintained at a target value And detecting that the feedback control circuit changes the frequency of the output voltage of the inverter circuit in the direction of increasing the light output of the discharge lamp in a state where the dimming signal is changed in the direction of decreasing the light output of the discharge lamp. Second detection time With the door, the target value setting circuit detects a change in the frequency in the second detection circuit to secure the target value, the output-related value, a load current flowing through the discharge lamp, the second detection circuit , A second comparator for comparing the output value of the first comparator and the target value, and the increase / decrease relationship of the difference between the output value of the first comparator and the target value is inverted, so that the frequency It is characterized by detecting a change .

In order to achieve the above object , the invention according to claim 2 is an inverter circuit that converts a DC voltage into a high-frequency AC voltage and supplies it to a load circuit including a discharge lamp, and an output-related value that reflects the light output of the discharge lamp. Output from the first detection circuit, the target value setting circuit for setting the target value of the light output of the discharge lamp according to the dimming signal input from the outside, and the target value and the first detection circuit A feedback control circuit having a first comparator for comparing with a detected value and performing feedback control by varying the frequency of the output voltage of the inverter circuit according to the output of the first comparator so that the detected value is maintained at a target value And detecting that the feedback control circuit changes the frequency of the output voltage of the inverter circuit in the direction of increasing the light output of the discharge lamp in a state where the dimming signal is changed in the direction of decreasing the light output of the discharge lamp. Second detection time The target value setting circuit fixes the target value when the second detection circuit detects the change in the frequency, and the target value setting circuit automatically increases or decreases the target value when the power is turned on. When the change in the frequency is detected in the detection circuit, the target value is increased until it becomes larger than the output value of the first comparator .

According to a third aspect of the present invention, in the first aspect of the invention, the target value setting circuit automatically increases or decreases the target value when the power is turned on, and when the second detection circuit detects the change in the frequency, the target value is changed. It is characterized by increasing until it becomes larger than the output value of one comparator.

According to a fourth aspect of the present invention, in the first aspect of the invention, the target value setting circuit changes the target value from a value corresponding to the maximum light output of the discharge lamp to a value corresponding to the dimming signal when the power is turned on. Features.

  The invention of claim 5 is the invention of any one of claims 1 to 4, wherein the target value setting circuit increases the output value of the first comparator to a predetermined value when the target value is a constant value. Then, the target value is increased.

  The invention of claim 6 is the invention according to any one of claims 1 to 5, wherein the discharge lamp is in a state where the ambient temperature of the discharge lamp is about 25 degrees and the light output is about 10% or less of the rated output. The load impedance is 10 kiloohms or more.

  The invention according to claim 7 is an appliance main body, a socket accommodated in the appliance main body and detachably mounted with the discharge lamp, and electric power is supplied to the discharge lamp through the socket. And a discharge lamp lighting device as described above.

According to the invention of claim 1, the target value setting circuit is configured such that the feedback control circuit changes the light output of the discharge lamp in a state where the dimming signal is changed in the direction of decreasing the light output of the discharge lamp in the second detection circuit. The target value is fixed when it is detected that the frequency of the output voltage of the inverter circuit is changed in the direction of increasing the output voltage. Dimming can be performed within the range in which the control circuit operates effectively, and by detecting that the increase / decrease relationship of the difference between the output value of the first comparator and the target value is reversed, the load impedance can be controlled. Even if dimming is performed in the direction of lowering the light output for a high discharge lamp, dimming can be performed within the range in which the feedback control circuit operates effectively.Therefore, the discharge lamp flickers due to a decrease in ambient temperature or the like. When this happens It is possible to perform a stable dimming without shifting the fading-out by the feedback control circuit.

According to the invention of claim 2, the target value setting circuit is configured such that the feedback control circuit changes the light output of the discharge lamp in a state where the dimming signal is changed in the direction of decreasing the light output of the discharge lamp in the second detection circuit. The target value is fixed when it is detected that the frequency of the output voltage of the inverter circuit is changed in the direction of increasing the output voltage. Dimming can be performed within the range in which the control circuit operates effectively. Therefore, even if flickering occurs in the discharge lamp due to a decrease in ambient temperature, etc., stable dimming can be achieved without going off by the feedback control circuit. It can be carried out. In addition, it is determined whether the feedback control circuit is in a dimming state in which the feedback control circuit operates effectively by automatically increasing / decreasing the target value when the power is turned on, and in the invalid state, the dimming in which the feedback control circuit operates effectively Since the target value is increased until the state is reached, flickering and extinguishing of the discharge lamp can be avoided even when the power is turned on .

  According to the invention of claim 3, it is determined whether or not the feedback control circuit is in a dimming state in which the feedback control circuit operates effectively by automatically increasing or decreasing the target value when the power is turned on. Since the target value is increased until the dimming state in which the lamp operates effectively, flickering and extinction of the discharge lamp can be avoided even when the power is turned on.

  According to the invention of claim 4, since the maximum light output is dimmed to a desired dimming level when the power is turned on, the feedback control circuit does not shift to an invalid state when the power is turned on, and therefore the flickering of the discharge lamp. And disappearance can be avoided.

  According to the invention of claim 5, even if the load impedance of the discharge lamp becomes high due to a decrease in the ambient temperature or the like in the dimming state where the feedback control circuit operates effectively, the feedback control circuit shifts to a state where it becomes invalid. The flickering and extinguishing of the discharge lamp can be avoided without any trouble.

  According to the invention of claim 7, it is possible to realize a lighting fixture that exhibits the effect of any one of claims 1 to 6.

  Hereinafter, a discharge lamp lighting device according to an embodiment of the present invention will be described with reference to the drawings. The discharge lamp used in the present embodiment has a load impedance in a state where the ambient temperature of the discharge lamp is about 25 degrees and the light output is about 10% or less of the rated output, similarly to the discharge lamp used in the conventional example. It shall be 10 kilohms or more.

  In the present embodiment, as shown in FIG. 1, an inverter circuit 1 that converts an output voltage of a DC power source E into a high-frequency AC voltage and supplies it to a load circuit 2 including a discharge lamp La, and a load current flowing through the discharge lamp La A current detection circuit 3 that is a first detection circuit that detects a light source, and a target value setting circuit 4 that sets a target value S2 of the light output of the discharge lamp La according to a dimming signal transmitted from an external dimmer LC And a first comparator OP that compares the target value S2 with the detection value S1 output from the current detection circuit 3, and the first comparator OP so that the detection value S1 is maintained at the target value S2. The feedback control circuit 5 that performs feedback control by varying the frequency of the output voltage of the inverter circuit 1 based on the output of the output, and the second comparator CP that compares the target value S2 and the output value S3 of the first comparator OP. Dimming state detection circuit as second detection circuit Consisting of.

  The DC power supply E includes a rectifier circuit DB1 including a diode bridge that rectifies an AC voltage from the AC power supply VS, and a booster circuit (boost chopper circuit) BC that boosts and smoothes and outputs a pulsating voltage from the rectifier circuit DB1. Consists of. The booster circuit BC is configured by connecting a series circuit of an inductor L2 and a switching element Q3 between output terminals of the rectifier circuit DB1, and connecting a series circuit of a diode D1 and a smoothing capacitor C2 between both ends of the switching element Q3. ing. The switching element Q3 uses a MOSFET and is turned on and off at a high frequency by the second control circuit CC2. The second control circuit CC2 controls the output voltage of the DC power supply E by controlling the on / off duty of the switching element Q3.

  The inverter circuit 1 connects a series circuit of two switching elements Q1 and Q2 between the output terminals of the DC power supply E, and a DC cut capacitor Cd between the connection point of the switching elements Q1 and Q2 and the load circuit 2. Connected. The switching elements Q1 and Q2 use MOSFETs and are alternately turned on and off at high frequency by the first control circuit CC1. During the ON period of the switching element Q1, power is supplied to the load circuit 2 through the switching element Q1 and the capacitor Cd And the power is supplied to the load circuit 2 using the capacitor Cd as a power source during the ON period of the switching element Q2.

  The load circuit 2 includes a series circuit of an inductor L1 and a capacitor C1 connected between the output ends of the inverter circuit 1, and a discharge lamp La is connected between both ends of the capacitor C1. The inductor L1 and the capacitor C1 constitute a resonance circuit 2a, and the resonance frequency of the resonance circuit is set lower than the output frequency of the inverter circuit 2. Thus, by changing the output frequency of the inverter circuit 2, the voltage applied to the discharge lamp La changes, and each control of preheating, starting, lighting, and dimming of the discharge lamp La becomes possible.

  The current detection circuit 3 includes a current transformer CT connected in series to the discharge lamp La, and a parallel circuit of a rectifier DB2 composed of a diode bridge and a resistor R1 is provided between the secondary output ends of the current transformer CT. Is connected. Thus, the load current flowing through the discharge lamp La is supplied as the detection value S1 to the inverting input terminal of the first comparator OP of the feedback control circuit 5 described later.

  The dimmer LC outputs a pulse signal generated by pulse width modulation as a dimming signal. The larger the duty ratio, the higher the light output of the discharge lamp La, and the smaller the duty ratio. The light output of the discharge lamp La becomes a low luminous flux. The target value setting circuit 4 converts the dimming signal output from the dimmer LC into a DC signal (target value S2) having a level corresponding to the duty ratio. That is, the target value setting circuit 4 outputs a target value S2 proportional to the increase / decrease of the duty ratio of the dimming signal output from the dimmer LC. The target value S2 is given to a non-inverting input terminal of a first comparator OP of a feedback control circuit 5 described later and an inverting input terminal of a second comparator CP of a dimming state detection circuit 6 described later. Further, the target value setting circuit 4 has a limit function, and when the output value S4 of the second comparator CP of the dimming state detection circuit 6 described later becomes a high level, the target value setting circuit 4 outputs from the dimmer LC. The target value S2 is fixed regardless of the dimming signal.

  The feedback control circuit 5 has a first comparator OP composed of an operational amplifier, and the detected value S1 is input to the non-inverting input terminal via the resistor R−, and the target value S2 is input to the inverting input terminal. Is done. A parallel circuit of a capacitor Cl and a resistor Rp is connected between the output terminal and the inverting input terminal, and is configured to remove a low-frequency ripple component by functioning as an integration circuit.

  The output terminal of the first comparator OP is connected to the connection point between the first control circuit CC1 and the resistor Rf via the diode D2, and the first control circuit CC1 supplies a constant current to the resistor Rf. Output. Thus, when the output value S3 of the first comparator OP increases, the voltage across the resistor Rf increases, so that the first control circuit CC1 controls to decrease the frequency of the inverter circuit 1, and the output value When S3 decreases, the voltage across the resistor Rf decreases, so the first control circuit CC1 controls the frequency of the inverter circuit 1 to increase. That is, by performing feedback control so that the difference between the detection value S1 and the target value S2 is eliminated, the discharge lamp La is dimmed to a constant light output corresponding to the dimming signal from the dimmer LC.

  The dimming state detection circuit 6 includes a series circuit of a resistor R2 and a resistor R3 connected to the output terminal of the first comparator OP, and a second comparator CP composed of an operational amplifier. A divided value S4 obtained by dividing the output value S3 of the first comparator OP by the resistors R2 and R3 is input to the non-inverting input terminal of the second comparator CP, and the target value S2 is input to the inverting input terminal. Entered. The output terminal is connected to the target value setting circuit 4 so that the output value S5 of the second comparator CP is given to the target value setting circuit 4.

  The operation of this embodiment will be described below. First, dimming is performed by the dimmer LC in the direction of lowering the light output of the discharge lamp La, that is, when the target value S2 is reduced, the output of the first comparator OP is reduced as the target value S2 decreases. Since the value S3 decreases, the first control circuit CC1 performs control so as to increase the frequency of the inverter circuit 1. For this reason, load current becomes small and the light output of the discharge lamp La falls. At this time, since the target value S2 is smaller than the divided voltage value S4, the output value S5 of the second comparator CP is at a low level.

  When the target value S2 is further decreased to reach less than 10% of the rated light output, that is, reaches the lower limit of the dimming level (region Z in FIG. 2B), the detection value S1 becomes the target value as described in the conventional example. Since it becomes smaller than S2, the output value S3 of the first comparator OP increases. Then, in the second comparator CP of the dimming state detection circuit 6, since the divided voltage value S4 becomes larger than the target value S2, the output value S5 of the second comparator CP becomes high level and the target value. Given to the setting circuit 4, the target value setting circuit 4 fixes the target value S2. Therefore, as shown in FIG. 2A, the frequency of the inverter circuit 1 becomes constant even if the dimming signal from the dimmer LC increases or decreases in the region Z. For this reason, even if the load current decreases with a decrease in the ambient temperature at the lower limit of the dimming level, feedback control for reducing the frequency of the inverter circuit 1 is not performed. La can be prevented from disappearing.

  Incidentally, the target value S2 and the output value S3 of the first comparator OP are normally in a proportional relationship as shown by a region Z2 in FIG. 4, but the load impedance is caused by a decrease in the ambient temperature of the discharge lamp La or the like. When it is high, it is in an inversely proportional relationship as in the region Z1 in FIG. When the area Z1 is lit, if the feedback control is performed as described above, the discharge lamp La is likely to flicker and turn off.

  Therefore, as shown in FIG. 3, the target value setting circuit 4 and the dimming state detection circuit 6 may be configured by a microcomputer IC. The microcomputer IC automatically increases or decreases the target value S2 in the target value setting circuit 4 when the power is turned on in the present embodiment, compares the target value S2 with the output value S3 in the dimming state detection circuit 6, and compares the target value S2. If the output value S3 is inversely proportional, the target value S2 is increased until the target value S2 and the output value S3 are proportional.

  By operating the microcomputer IC as described above, even if the target value S2 is set within the range of the region Z1 in FIG. 4 when the power is turned on, the target value up to the region Z2 where the feedback control by the feedback control circuit 5 is effective. Since S2 is automatically increased, it is possible to avoid flickering and extinguishing of the discharge lamp La when the power is turned on.

  The microcomputer IC is configured so that the target value S2 is set to a value corresponding to the maximum light output of the discharge lamp La when the power is turned on, and the target value S2 is reduced to a value corresponding to the dimming signal from the dimmer LC. May be. In this case, even when the target value S2 corresponding to the dimming signal from the dimmer LC is set within the range of the region Z1 in FIG. 4 when the power is turned on, the discharge lamp La is first lit at the maximum light output. It is possible to avoid flickering and extinguishing of the discharge lamp La when the power is turned on.

  Further, in a state where the dimming level is not changed, that is, the target value S2 is constant, the microcomputer IC may be configured to increase the target value S2 when the output value S3 increases to a predetermined value. . That is, by detecting that the detection value S1 decreases and the output value S3 increases, it is determined that the load impedance has increased due to a decrease in the ambient temperature of the discharge lamp La or the like, and the feedback control by the feedback control circuit 5 is effective. The target value is increased up to the region Z2. With this configuration, even when the load impedance of the discharge lamp La increases due to a decrease in the ambient temperature or the like in a dimming state in which the feedback control circuit 5 operates effectively, the feedback control circuit 5 becomes invalid. It is possible to avoid flickering and extinguishing of the discharge lamp La without shifting.

  In addition, it cannot be overemphasized that this embodiment is applicable to the various instrument main body which accommodated the socket by which the discharge lamp La is detachably mounted. Further, the present invention is not limited to the one that detects the load current and performs feedback control as in the present embodiment, but detects an output-related value that changes according to the light output of the discharge lamp La, and adjusts the frequency of the inverter circuit 1 to change the value. It goes without saying that the same effect as described above can be obtained as long as it shines.

It is a circuit diagram which shows the discharge lamp lighting device of embodiment of this invention. It is a figure which shows an operating characteristic same as the above, (a) is a graph which shows the signal characteristic of a light control state detection circuit, (b) is a graph which shows the correlation with the frequency of a light control signal and the output voltage of an inverter circuit. It is a circuit diagram which shows the case where the above-mentioned target value setting circuit and dimming state detection circuit are comprised by the microcomputer. It is a graph which shows the correlation with the target value same as the above, and the output value of a feedback control circuit. It is a figure which shows the feedback control circuit of the conventional discharge lamp lighting device, (a) is a circuit diagram, (b) is a graph which shows a signal characteristic. It is a figure which shows an operating characteristic same as the above, (a) is a graph which shows the correlation of the load current and load voltage of a discharge lamp, and the frequency of the output voltage of an inverter circuit, (b) is the load current of a discharge lamp and the inverter circuit. It is a graph which shows the correlation with the frequency of an output voltage. It is a figure which shows the discharge lamp used for the same as the above, and its characteristic, (a) is the schematic which shows compact fluorescent lamp FHT42, (b) is the schematic which shows compact fluorescent lamp FHSD20, (c) is the load of a discharge lamp It is a graph which shows the correlation with an electric current and load voltage, (d) is a graph which shows the correlation with the load current and load impedance of a discharge lamp. It is a figure which shows the temperature characteristic of the compact fluorescent lamp FHT42, (a) is a graph which shows the correlation with the frequency of load current and load voltage, and the output voltage of an inverter circuit, (b) is the frequency of the output voltage of an inverter circuit, and It is a graph which shows the correlation with load current.

Explanation of symbols

1 Inverter circuit 2 Load circuit 3 Current detection circuit (first detection circuit)
4 Target value setting circuit 5 Feedback control circuit 6 Dimming state detection circuit (second detection circuit)
E DC power supply La discharge lamp

Claims (7)

An inverter circuit that converts a DC voltage into a high-frequency AC voltage and supplies it to a load circuit including a discharge lamp, a first detection circuit that detects an output-related value that reflects the light output of the discharge lamp, and an external input A target value setting circuit that sets a target value of the light output of the discharge lamp according to the dimming signal, and a first comparator that compares the target value with the detection value output from the first detection circuit. A feedback control circuit that performs feedback control by varying the frequency of the output voltage of the inverter circuit by the output of the first comparator so that the value is maintained at the target value, and a dimming signal in a direction that reduces the light output of the discharge lamp And a second detection circuit for detecting that the feedback control circuit changes the frequency of the output voltage of the inverter circuit in a direction to increase the light output of the discharge lamp in a state where the target value setting circuit is changed. Second detection circuit The target value is fixed upon detecting a change in Oite the frequency, the output-related value is a load current flowing through the discharge lamp, the second detection circuit, an output value and the target value of the first comparator A discharge lamp lighting device comprising: a second comparator for comparison, wherein the change in the frequency is detected by reversing the increase / decrease relationship of the difference between the output value of the first comparator and the target value . An inverter circuit that converts a DC voltage into a high-frequency AC voltage and supplies it to a load circuit including a discharge lamp, a first detection circuit that detects an output-related value that reflects the light output of the discharge lamp, and an external input A target value setting circuit that sets a target value of the light output of the discharge lamp according to the dimming signal, and a first comparator that compares the target value with the detection value output from the first detection circuit. A feedback control circuit that performs feedback control by varying the frequency of the output voltage of the inverter circuit by the output of the first comparator so that the value is maintained at the target value, and a dimming signal in a direction that reduces the light output of the discharge lamp And a second detection circuit for detecting that the feedback control circuit changes the frequency of the output voltage of the inverter circuit in a direction to increase the light output of the discharge lamp in a state where the target value setting circuit is changed. Second detection circuit When the frequency change is detected, the target value is fixed, and the target value setting circuit automatically increases or decreases the target value when the power is turned on, and when the second detection circuit detects the frequency change, the target value is set. lamp lighting device release you, and thereby to increase until greater than the output value of the first comparator. The target value setting circuit automatically increases or decreases the target value when the power is turned on, and when the second detection circuit detects the change in the frequency, the target value is increased until it becomes larger than the output value of the first comparator. The discharge lamp lighting device according to claim 1, wherein: The target value setting circuit, a discharge lamp lighting apparatus according to claim 1, wherein the changing the target value to the maximum light value corresponding to the dimming signal from a value corresponding to the output of the discharge lamp when the power is turned on.   The target value setting circuit increases the target value when the output value of the first comparator increases to a predetermined value when the target value is a constant value. The discharge lamp lighting device according to item.   6. The discharge lamp according to claim 1, wherein the discharge lamp has a load impedance of 10 kilohms or more in a state where the ambient temperature of the discharge lamp is about 25 degrees and the light output is about 10% or less of the rated output. The discharge lamp lighting device according to claim 1.   The discharge lamp lighting device according to any one of claims 1 to 6, wherein a power source is supplied to the discharge lamp through the socket, a socket that is housed in the fixture body and in which the discharge lamp is detachably mounted. A lighting fixture characterized by comprising:

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