JPH08273860A - Lighting device for discharge lamp, discharge lamp lighting device and lighting system - Google Patents

Abstract

PURPOSE: To prevent a rush to a phase advanced mode of an inverter circuit by effectively utilizing the existing constitution when DC voltage substantially drops on a discharge lamp which is dimmed and lit with DC voltage indicating a dimming level. CONSTITUTION: A detecting means 7 which is set so that when a value of DC voltage VDC input through a supply line 1 drops than a specified value, operation stops, detects no-fixing of a discharge lamp 5 based on the DC voltage VDC. Oscillation operation of an inverter circuit 3 is stopped with a latching means 9 based on detected output of the detecting means 7. Thereby, a rush into a phase advanced mode of the inverter circuit 3 when voltage of a power supply unit drops is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device, a discharge lamp lighting device and a lighting system.

[0002]

2. Description of the Related Art In recent years, some lighting devices for lighting a discharge lamp are provided with a dimming function in order to enhance their commercial value. There are various methods for dimming the discharge lamp, but in any case,
A dedicated dimming line for sending a dimming level signal is wired to an inverter circuit for dimming the discharge lamp. The dimming level is set for each discharge lamp (each inverter circuit) and the dimming lighting is performed.

However, when considering the facility lighting in a store or the like, since a large number of discharge lamps are handled, it is not preferable that a dedicated dimming line is required for each discharge lamp because it is wasteful on wiring and it is not preferable. The operation of the light lighting control becomes troublesome.
In particular, for dimming lighting in stores, etc., use dark light (deep dimming level) for rows on the window side that are bright due to outside light, and light dimming (shallow dimming level) for rows on the back side. Considering good points, it is troublesome to perform a dimming operation for each individual discharge lamp.

In consideration of such a point, by using a collective DC power source and outputting a DC voltage corresponding to the dimming level to the DC output line, the inverter of the discharge lamp lighting device connected to the DC output line. A lighting system has been proposed in which a DC voltage is detected in a circuit and dimming control is performed according to the DC voltage to turn on a discharge lamp. That is,
From the viewpoint of the inverter circuit side, the value of the supplied DC voltage itself includes the dimming level information, and feedback control is performed so that the drain current of the switching element in the inverter circuit, for example, the FET becomes constant. , Constant power control is performed. In the example of the store mentioned above, the batch DC power supply is for the window side row, the back side row,
Prepared as for the middle row. According to this, it suffices to connect the discharge lamp lighting device for lighting at the same dimming level to the DC output line of the common collective DC power source, and the dedicated dimming line can be eliminated.

[0005]

In this type of inverter circuit, it is necessary to prevent the oscillating operation from operating in the phase advance mode. This is because when operating in the phase advance mode, the reactive current increases and the switching element is more likely to be thermally destroyed. Therefore, when the DC voltage that is supplied from the batch DC power supply side and indicates the dimming level drops to a value below a preset constant value, the inverter circuit is subjected to feedback control to enter the phase advance mode. There is a possibility that it will happen, and countermeasures are required.

Therefore, the present invention relates to a discharge lamp which is dimmed and turned on the basis of a direct current voltage indicating a dimming level, and when the direct current voltage is greatly reduced, the inverter circuit enters the phase advance mode. It is an object of the present invention to provide a discharge lamp lighting device, a discharge lamp lighting device, and an illumination system using the same, which can effectively prevent the existing configuration from being used.

[0007]

According to another aspect of the present invention, there is provided a lighting device for a discharge lamp, which is connected to a DC voltage supply line indicating a dimming level and supplies AC power to the discharge lamp by an oscillating operation. And an inverter circuit for dimming and lighting; a detection for detecting that a discharge lamp is not installed based on the DC voltage, which is set to be inoperative when the value of the DC voltage input by the supply line falls below a certain value. And latch means for operating based on the detection output of the detection means to stop the oscillation operation of the inverter circuit.

The discharge lamp lighting device according to the second aspect of the present invention is connected to a DC voltage supply line indicating a dimming level, and supplies AC power to the discharge lamp by an oscillating operation to perform dimming lighting. Inverter circuit; non-installation detection function that detects whether the discharge lamp is not installed based on the DC voltage that is input from the supply line, and power supply drop detection function that detects a power supply drop that is less than a certain value of the DC voltage that is input to the supply line And a latching unit that operates based on the detection output of the detecting unit to stop the oscillation operation of the inverter circuit.

According to a third aspect of the present invention, there is provided the discharge lamp lighting device according to the first or second aspect, wherein a constant value of the DC voltage is
This is a configuration in which the boundary value between the slow phase mode and the advanced phase mode in the oscillation operation of the inverter circuit is used.

The invention according to claim 4 is the invention according to claims 1 to 3.
The lighting device for a discharge lamp according to any one of claims 1 to 4, wherein an inverter circuit is connected between filament electrodes of the discharge lamp.
It is a modified half-bridge type having two preheating capacitors and a common line set; the detection means is provided on the non-common side with respect to the discharge lamp.

The invention according to a fifth aspect is the first to the fourth aspects.
The lighting device for a discharge lamp according to any one of items 1 to 4, wherein the inverter circuit includes an inductive ballast. That is, the inverter circuit is usually configured to include a ballast, and the ballast may be a capacitive ballast, but in the present invention, it is an inductive ballast.

The discharge lamp lighting device according to the invention of claim 6 is
A discharge lamp lighting device according to any one of claims 1 to 5; and a discharge lamp that is energized by the discharge lamp lighting device.

A lighting system according to a seventh aspect of the present invention includes a collective DC power source for outputting a DC voltage indicating a dimming level to a supply line; and a discharge lamp lighting according to the sixth aspect, which is connected to the supply line of the collective DC power source. And a device. In the present invention, the collective DC power source may be one that outputs a DC voltage according to the dimming level, and may be configured as a boost chopper system, for example.

[0014]

According to the first and second aspects of the invention, when the discharge lamp is not mounted, that is, when the filament electrode is detached, it is provided to detect the non-mounting and stop the oscillation operation of the inverter circuit. When the detecting means is in such a state that the direct current voltage indicating the dimming level drops below a certain value, it becomes inoperative. Due to the inactive state of the detection means, the power supply drop monitoring function is substantially exerted, and the oscillation operation of the inverter circuit is stopped via the latch means, so that the inverter circuit enters the phase advance mode and operates. There is no.

In the third aspect of the invention, since the constant value of the DC voltage at which the detecting means is inoperative is the boundary value between the lag mode and the lead mode, the lag mode operates. It is possible to reliably prevent the inverter circuit from entering the phase advance mode due to a decrease in the DC voltage serving as the power supply voltage.

According to the fourth aspect of the present invention, the detecting means is provided on the non-common side of the modified half-bridge type inverter circuit. It is easy to have and.

According to the fifth aspect of the invention, the inverter circuit including the inductive ballast is prevented from entering the phase advance mode.

According to the invention of claim 6, claim 1
Since the discharge lamp lighting device according to any one of 1 to 5 is used, the discharge lamp can be safely lit by the inverter circuit that does not enter the phase advance mode due to the decrease in the DC voltage that is the power supply voltage. it can.

In the invention described in claim 7, claim 6 is provided.
Since the discharge lamp lighting device described above is used together with the collective DC power supply, even if the collective DC power supply that outputs the DC voltage indicating the dimming level has a voltage drop for some reason, it is connected to this collective DC power supply. The inverter circuit of the electric lighting device does not enter the phase advance mode, and the lighting system is safe.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a discharge lamp lighting device and a discharge lamp lighting device according to the present invention will be described with reference to FIGS. FIG.
Is a block diagram showing a schematic configuration, and FIG. 2 is a circuit diagram showing a specific configuration.

First, there is provided a DC power supply 2 in which the value of the DC voltage V _DC output to the supply line 1 is variable according to the dimming level. A discharge lamp lighting device 4 mainly including an inverter circuit 3 is connected to a supply line 1 of the DC power supply 2. Here, as the inverter circuit 3, for example, a capacitor preheating type and a modified half bridge type inverter circuit is used, and the discharge lamp 5 is connected to the output side of the inverter circuit 3. The modified half-bridge type inverter circuit 3 has a pair of switching elements, for example, FETs Q ₁ and Q _2, and one preheating capacitor C ₁ connected between the filament electrodes 5 a and 5 b of the discharge lamp 5. And then FE
A DC cut capacitor C ₂ and an inductive ballast L ₂ are connected between the connection midpoint of T Q ₁ and Q ₂ and the filament electrode 5a on the non-common side. here,
The pair of FETs Q ₁ and Q ₂ are alternately turned on / off by a drive control circuit 6 having a voltage / frequency conversion function to oscillate at a predetermined frequency to turn on the discharge lamp 5. At this time, since the value of the DC voltage V _DC supplied from the DC power supply 2 includes the dimming level information, a voltage detection circuit is provided as in a specific configuration example described later, and the value of the detected DC voltage V _DC is included. The drive control circuit 6 according to the
Controls the operation of Q ₁ and Q ₂ . In such a modified half-bridge type inverter circuit 3, the filament electrode 5a side is the non-common side, and the filament electrode 5b side is the common side that determines the ground potential.

Further, detection means 7 for detecting whether or not such a discharge lamp 5 is mounted in a socket is provided for the filament electrode 5a on the non-common side. First, the filament electrode 5a is connected to the line of the DC voltage V _DC of the DC power source 2 via the resistor R _1, and the voltage dividing resistors R ₂ and R ₃ are connected between the filament electrode 5a and the common line. ing. These voltage dividing resistors R ₂ ,
The detection unit 8 is connected to the connection midpoint of R ₃ . That is,
By detecting the level of the potential generated at the connection midpoint of the voltage dividing resistors R ₂ and R ₃ with the detection unit 8, the filament electrode 5a
It is detected whether or not is attached. In the state where the filament electrode 5a is attached, the current based on the DC voltage V _DC is changed to resistance R ₁ → filament electrode 5a →
Since the voltage dividing resistors R ₂ and R ₃ flow in the path of the common line, a voltage dividing potential is generated, so that the potential becomes H level. On the other hand, the current dividing resistor R _2, R ₃ does not flow in a state where the filament electrode 5a is not mounted, does not occur a divided potential, and L level potential. In this way, whether or not the discharge lamp 5 is not attached is detected based on the DC voltage V _DC .

As described above, between the detection section 8 of the detection means 7 for detecting the non-mounting of the discharge lamp 5 and the drive control circuit 6,
Latch means 9 is provided which acts to stop the oscillating operation of the FETs Q ₁ and Q ₂ based on the unattached detection signal. The latch means 9 is configured so that the latch is released when the detection signal of the detector 8 becomes H level (when the discharge lamp 5 is mounted).

In addition to the original function of detecting the discharge lamp non-attachment, the above-mentioned detecting means 7 is provided when the value of the DC voltage V _DC drops to a value below a certain value such that it is below the minimum dimming level. Is configured to have a power drop detection function that detects this as a power drop. This is realized by making the detecting means 7 substantially inoperative when the value of the DC voltage V _DC input from the DC power supply 2 falls below a certain value. Considering the correspondence with the discharge lamp non-attachment detection function, when the value of the DC voltage V _DC is higher than a certain value, the detection unit 8 detects it as an H level, but when it falls below a certain value, the detection unit 8 is detected. Is set to be detected as L level.

Therefore, even when the detection means 7 detects the power supply drop, the latch means 9 is latched and the inverter circuit 3
Will stop the oscillation operation. That is, DC power supply 2
When the value of the DC voltage V _DC supplied from the inverter circuit 3 to the inverter circuit 3 falls below a certain value, the inverter circuit 3 is subjected to constant power control under the feedback control by the drive control circuit 6, so if it is left as it is, it will be delayed. It is not desirable because it will enter the phase advance mode from the phase mode. However, since the oscillating operation of the inverter circuit 3 is forcibly stopped as described above, the FETs Q ₁ , Q _{2 and the} like are protected without entering the phase advance mode. For this purpose as well, it is sufficient to use the detecting means 7 for detecting that the discharge lamp is not mounted, which is indispensable in this type of device, so that the structure can be simplified.

Next, a concrete configuration example will be described with reference to FIG. It has an input terminal 11 connected to the supply line 1. The discharge lamp 5 is connected between the voltage lines of the input terminal 11 via the inverter circuit 3. FET
A resistor R _D for controlling the drain current is connected to the drain side of Q ₂ . Also, these FETs
A driving IC 12 for controlling on / off operation is connected to the gate side of Q ₁ and Q ₂ . This inverter circuit 3
The output is variable by variably controlling the oscillation frequency, and a control IC 13 for controlling the operation of the drive IC 12 is provided. The drive control circuit 6 is composed of these ICs 12 and 13, and the control IC 13 is structured to include a latch means 9.

As for the detecting means 7 side, the resistance R ₁
Are divided into two resistors. The detection unit 8 is configured to include a rectifying diode D ₁ connected to the connection midpoint of the voltage dividing resistors R ₂ and R ₃ , a capacitor C ₃ and a resistor R ₄ connected to the output side thereof. . Further, a series circuit of a resistor R ₅ and a capacitor C ₄ connected to the voltage detection circuit 14 provided on the input terminal 11 side, a connection midpoint between the resistor R ₅ and the capacitor C _4, and a diode D ₁ . And a diode D ₂ connected in the opposite direction to the diode D ₁ between the _two . The midpoint of connection between the resistor R ₅ and the capacitor C ₄ serves as a detection output terminal for control I.
It is connected to the latch terminal of C13.

Here, the voltage detection circuit 14 includes resistors R _{6 to} R connected between the supply lines 1 by the input terminals 11.
A voltage dividing circuit according to _9, the capacitor C ₅ connected in parallel with the resistor R _8, R _9, and a resistor R _7, transistor Q ₃ having a base connected between R _8, of the transistor Q ₃ emitters, Resistors R ₁₀ and R respectively connected to the collector
₁₁ , a transistor Q ₄ whose base is connected between the resistors R ₈ and R ₉ , and resistors R ₁₂ , R ₁₃ , R ₁₄ and R connected between the collector of the transistor Q ₄ and the positive power supply line.
₁₅ and a Zener diode ZD connected in parallel with the resistor R ₁₅ and the transistor Q ₄ . Transistor Q ₄ will monitor a constant value for detection of brownout.

In such a structure, first, the discharge lamp 5
The non-mounting detection operation of will be described. In the state where the discharge lamp 5 is mounted, the DC voltage V _DC flows in the path of the resistance R ₁ → filament 5a → the voltage dividing resistances R ₂ and R ₃ → the common line and flows between the voltage dividing resistances R ₂ and R ₃ in a predetermined manner. The capacitor C ₃ is charged via the diode D ₁ to generate a divided potential. Therefore, the potential of the capacitor C ₃ becomes H level, and the potential charged in the capacitor C ₄ via the resistor R ₅ does not flow through the diode D ₂ . As a result, the potential between the resistor R ₅ and the capacitor C ₄ becomes H level. Since this H-level signal is given to the control IC 13, it is recognized that the discharge lamp 5 is mounted.

On the other hand, in the state where the discharge lamp 5 is not mounted, the resistor R ₁ and the resistor R ₂ are opened, and a divided potential is not generated between the voltage dividing resistors R ₂ and R ₃ . The potential of the capacitor C ₃ becomes L level. Therefore, the potential charged in the capacitor C ₄ via the resistor R ₅ becomes the diode D ₂
And the potential between the resistor R ₅ and the capacitor C ₄ is L
Level. Since this L level signal is given to the control IC 13, it is recognized that the discharge lamp 5 is not attached,
The oscillation operation of the inverter circuit 3 is stopped.

On the other hand, a power supply drop detecting operation when the discharge lamp 5 is mounted and the inverter circuit 3 is operating will be described. First, basically, a collector current corresponding to the value of the DC voltage V _DC input through the input terminal 11 flows through the transistor Q ₃ , so that the value of the DC voltage V _DC is determined by the control IC 13, and DC voltage V
Driving IC1 so that the dimming level corresponds to the _DC value
The oscillation frequency of the inverter circuit 3 is variably controlled via 2. Thus, if the value of the DC voltage V _DC supplied via the input terminal 11 changes, the oscillation frequency of the inverter circuit 3 is also variably controlled according to the value, and the dimming level of the discharge lamp 5 is changed. Will be. The dimming control in this case is performed, for example, in the range of DC voltage 165V = 50% dimming to DC voltage 220V = 100% dimming (all lights). That is, the normal value of the supplied DC voltage V _DC is set in the range of 165 to 220 V, and the oscillation frequency of the inverter circuit 3 is, for example, 40 kHz at full light of 220 V and deep dimming of 165 V. Sometimes 60 kH
The operation is controlled to be z. Therefore, in the inverter circuit 3 of the present embodiment, if the value of the DC voltage V _DC supplied falls below 165V for some reason, the phase advance mode may be entered under feedback control.

In this respect, the present embodiment deals with the power supply drop detection function of the detection means 7. First, 165-2
In the state where the normal DC voltage V _DC between 20V is supplied, the detection unit 8 maintains the H level between the resistor R ₅ and the capacitor C ₄ as in the case of detecting the mounting of the discharge lamp described above. The IC 13 for use recognizes that the power supply voltage is normal. However, when the value of the supplied DC voltage V _DC drops below a certain value (for example, 165 V), the potential generated between the resistors R ₈ and R ₉ also undergoes voltage division by the voltage dividing resistors R _{6 to} R _9. Since it is smaller than the predetermined value, the transistor Q ₄ which is normally on is turned off. The potential applied to the base of the transistor Q ₃ are for greatly reduced a divided potential by the DC voltage V _DC and the resistor R _6, R ₇ and the resistor R _8, the emitter of the transistor Q ₃ (resistor The potential generated on the R ₁₀ side) becomes high. Therefore, in the detection unit 8, the potential charged in the capacitor C ₄ via the resistor R ₅ becomes higher than the potential charged in the capacitor C ₃ side, and the potential of the capacitor C ₄ passes through the diode D ₂ . Flowing. As a result, the potential between the resistor R ₅ and the capacitor C ₄ becomes L level, and the control IC 13 recognizes that the power supply voltage has dropped to below a certain value, and stops the oscillation operation of the inverter circuit 3. Therefore, the inverter circuit 3 does not enter the phase advance mode and continue to operate due to a decrease in the DC voltage V _DC below a certain value, and elements such as the FETs Q ₁ and Q ₂ can be protected. .

An embodiment of the illumination system of the present invention will be described with reference to FIGS. 3 and 4. FIG. 3 is a schematic wiring diagram showing a lighting system, and FIG. 4 is a block diagram showing a collective DC power supply.

In the lighting system 21 of this embodiment,
A collective DC power supply 23 is connected to the commercial AC power supply 22, and a plurality of discharge lamp lighting devices 24A, 24B, 24C, ... Are sequentially connected in parallel to the supply line 1 of the collective DC power supply 23. It is configured. That is, the collective DC power supply 23 is used as the DC power supply 2 shown in FIG. Here, the collective DC power supply 23 is the supply line 1
Has a function of varying the value of the DC voltage V _DC supplied to each of the discharge lamps 5A, 5B, 5C, ... In addition, each discharge lamp lighting device 24A, 24B, 24
Each of C, ... has a configuration as shown in FIG. 1 (specifically, FIG. 2), and has inverter circuits 3A, 3B, 3
Discharge lamp lighting device 4A, 4B, 4 mainly composed of C, ...
, And discharge lamps 5A, 5B, 5C, ..., which are energized by the discharge lamp lighting devices 4A, 4B, 4C ,. Each inverter circuit 3A, 3
B, 3C, ... Specifically include the voltage detection circuit 14 for detecting the value of the DC voltage V _DC of the supply line 1 as described above, and the dimming level according to the value of the detected DC voltage V _DC. Has a dimming function for dimming and lighting each of the discharge lamps 5A, 5B, 5C, ....

Therefore, when the collective DC power supply 23 outputs the DC voltage V _DC corresponding to the dimming level onto the supply line 1, the discharge lamp lighting devices 4A, 4B, 4C, ... Connected to the supply line 1. Then, the voltage detection circuit 14 detects the value of the DC voltage V _DC = dimming level, and the inverter circuits 3A, 3B,
.. are controlled, and the dimming lighting of the discharge lamps 5A, 5B, 5C, ... Connected to the common collective DC power supply 23 is performed at the same level. At this time, when the value of the supplied DC voltage V _DC drops below a certain value due to a failure of the collective DC power supply 23 or the like, each discharge lamp lighting device 4 is operated.
Are detected by the detecting means 7 in A, 4B, 4C, ... And the oscillation operation of each inverter circuit 3A, 3B, 3C ,. Therefore, circuit protection in the system can be achieved.

Next, a configuration example of the collective DC power supply 23 will be described with reference to FIG. The collective DC power supply 23 is, for example, of a step-up chopper type, and has a full-wave rectification circuit 31 that full-wave rectifies the AC voltage from the commercial AC power supply 22 into a DC voltage.
It is composed of a boost chopper circuit 32 connected to the output stage of the full-wave rectifier circuit 31. The step-up chopper circuit 32 includes a step-up transformer 33, a switching transistor 34, a rectifying diode 35, and an output smoothing capacitor 36. For such a boost chopper circuit 32, a chopper control circuit 37 for controlling the switching operation of the transistor 34 to maintain the voltage generated across the capacitor 36 at a constant voltage.
Is connected. As the chopper control circuit 37, for example, a commercially available power factor improving IC called SG3561 manufactured by Silicon General Co. is used. The chopper control circuit 37 is provided with a dimming signal which is set from the outside and indicates a dimming level, and the boost chopper is maintained so as to maintain a constant voltage at a value of a DC voltage according to the dimming signal. It controls the operation of the circuit 32. The output stage of the boost chopper circuit 32 is connected to the supply line 1.

[0037]

According to the first and second aspects of the present invention, when the discharge lamp is not mounted, that is, when the filament electrode is detached, this mounting is detected to stop the oscillation operation of the inverter circuit. By using the detection means provided, this detection means is provided with a power supply drop monitoring function.
With a simple configuration, it is possible to avoid the inconvenience that the inverter circuit enters the phase advance mode due to the decrease in the DC voltage serving as the power supply voltage, and the inverter circuit can be protected.

According to the third aspect of the invention, since the constant value of the DC voltage at which the detecting means is inoperative is set to the boundary value between the lag mode and the lag mode, the lag mode operates. It is possible to reliably prevent the existing inverter circuit from entering the phase advance mode due to a decrease in the DC voltage serving as the power supply voltage.

According to the fourth aspect of the present invention, the detecting means is provided on the non-common side of the modified half-bridge type inverter circuit. Can be combined easily without any trouble.

According to the fifth aspect of the invention, it is possible to reliably prevent the inverter circuit including the inductive ballast from entering the phase advance mode.

According to the sixth aspect of the invention, since the discharge lamp lighting device according to any one of the first to fifth aspects is used, the phase advance mode is entered based on the decrease in the DC voltage as the power supply voltage. It is possible to provide a discharge lamp lighting device capable of safely lighting a discharge lamp with an inverter circuit that does not operate.

According to the seventh aspect of the invention, since the discharge lamp lighting device according to the sixth aspect is used together with the collective DC power supply, the voltage drops in the collective DC power supply for outputting the DC voltage indicating the dimming level for some reason. Even if there is, the inverter circuit of the discharge lamp lighting device connected to the collective DC power supply does not enter the phase advance mode, and a safe lighting system can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a discharge lamp lighting device and a discharge lamp lighting device of the present invention.

FIG. 2 is a circuit diagram showing its specific configuration.

FIG. 3 is a schematic wiring diagram showing an embodiment of a lighting system of the present invention.

FIG. 4 is a block diagram showing a collective DC power supply.

[Explanation of symbols]

1 Supply Line 3 Inverter Circuit 4 Discharge Lamp Lighting Device 5 Discharge Lamp 5a, 5b Filament Electrode 7 Detecting Device 9 Latch Means 23 Collective DC Power Supply 24 Discharge Lamp Lighting Device C ₁ Preheating Capacitor L ₂ Inductive Ballast

Claims (7)

[Claims] 1. An inverter circuit connected to a direct current voltage supply line indicating a dimming level to supply alternating current power to a discharge lamp by an oscillating operation to perform dimming lighting; a direct voltage input by a supply line Is set to be inoperative when the value of is below a certain value, and detecting means for detecting non-installation of the discharge lamp based on the DC voltage; and oscillating operation of the inverter circuit by operating based on the detection output of the detecting means. And a latch means for stopping the discharge lamp; 2. An inverter circuit connected to a DC voltage supply line indicating a dimming level, for supplying AC power to a discharge lamp by an oscillating operation to illuminate the lamp dimming; a DC voltage input through the supply line A detection means for detecting whether or not the discharge lamp is not mounted based on the above, and a power supply drop detection function for detecting a power supply drop below a certain value of the DC voltage input by the supply line; A discharge lamp lighting device, comprising: a latch unit that operates based on an output to stop an oscillating operation of an inverter circuit. 3. The lighting device for a discharge lamp according to claim 1, wherein the constant value of the DC voltage is a boundary value between the phase delay mode and the phase advance mode in the oscillation operation of the inverter circuit. 4. The inverter circuit is a modified half-bridge type having a preheating capacitor connected between filament electrodes of a discharge lamp and having a common line set therein; The lighting device for a discharge lamp according to any one of claims 1 to 3, wherein the lighting device is provided on a common side. 5. The lighting device for a discharge lamp according to claim 1, wherein the inverter circuit includes an inductive ballast. 6. A discharge lamp lighting device, comprising: the discharge lamp lighting device according to any one of claims 1 to 5; and a discharge lamp that is energized by the discharge lamp lighting device. 7. The discharge lamp lighting device according to claim 6, further comprising: a collective DC power source for outputting a DC voltage indicating a dimming level to a supply line; and a discharge lamp lighting device according to claim 6, which is connected to the supply line of the collective DC power source. Lighting system.