JP2003007493A - Electric discharge lamp lighting equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide electric discharge lamp lighting equipment, which can maintain stabilized operation even if making load current decrease, by suppressing enlargement and a cost rise of parts of an inverter circuit. SOLUTION: The electric discharge lamp lighting equipment consists of a power supply circuit 1 which rectifies/smoothes an alternate-current power supply Vs, an inverter circuit 2, which converts this output into a high frequency output, a control circuit 4, which controls these, and a dimmer circuit part 5 which determines the degree of the dimmer of an electric discharge lamp 3 according to the signal inputted into a signal input part 6, and transmits it to the control circuit 4. In the electric-discharge-lamp lighting equipment, which makes an light output of the electric discharge lamp 3 can be switched gradually or continuously, while lighting the electric discharge lamp 3 by the high frequency output of the inverter circuit 2, by making the operation frequency of the inverter circuit 2 or the output of the power supply circuit 1 change continuously by the dimmer circuit part 5 and the control circuit 4, it is made so that the current, which flows the control circuit 4, may increase as the light output of the electric discharge lamp 3 decreases.

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 for converting a commercial power source into a high frequency output to light a discharge lamp, and more particularly to a dimming technique for a discharge lamp.

[0002]

2. Description of the Related Art Dimming control has been conventionally performed in which the light output of a discharge lamp is changed to a desired output by changing the output when the discharge lamp is lit in a stepwise or continuous manner. By controlling the operating frequency of the inverter circuit stepwise or continuously, the load current flowing through the discharge lamp is suppressed and the light output is reduced.

Each discharge lamp has a rated light output and a rated current / rated voltage, and the operating frequency of the discharge lamp lighting device is usually set so as to satisfy these output characteristics. Here, the light output of the discharge lamp correlates with the load current flowing through the discharge lamp, so when dimming the discharge lamp, set the load current value such that the target discharge lamp has the desired light output. Then, the operating frequency of the inverter circuit is adjusted by using the control circuit included in the discharge lamp lighting device so that the load current of the discharge lamp becomes substantially equal to this value.

When the discharge lamp is lit at a high frequency using an inverter, it is necessary that the load characteristics of the discharge lamp itself and the output characteristics determined by the constants of the components of the inverter circuit match. The load curve of the discharge lamp and the output curve of the inverter circuit are shown in FIG. In FIG. 2, A is the load curve of the discharge lamp, B is the output curve of the inverter circuit during rated lighting, C is the output curve of the inverter circuit during dimming lighting, and D is
Indicates an unlit state. The point where the load curve A of the discharge lamp itself and the output curve of the inverter circuit intersect is the state where the discharge lamp is actually lit.

However, when the constants of the components of the inverter circuit are set so as to be optimum for lighting at the rated output of the discharge lamp (FIG. 2B), the load current of the discharge lamp is reduced as described above. As it goes, it becomes difficult for the load curve of the discharge lamp and the output curve of the inverter circuit to intersect (Fig.
C), the lighting state of the discharge lamp becomes unstable. When the load current is further reduced, there is no intersection and the discharge is stopped (Fig. 2D).

In order to prevent this, it is necessary to change the inductance of the inductor and the capacitance of the capacitor that form the inverter circuit so that the load curve and the output curve have an intersection even when the load current is small. Since it is necessary to increase the inductance of the inductor, which leads to an increase in the size of parts and an increase in cost, it becomes a major problem in the inverter circuit configuration.

[0007]

Therefore, in the conventional dimmable inverter circuit, when the size and cost of the circuit are limited, the load current should be reduced only to a certain current value. It was necessary to suppress the increase in the size of parts and the increase in cost. Also, if the load current is reduced without changing the component constants, the lighting state becomes unstable as described above, and as a result, it is stable against noise such as radiation noise from the outside and fluctuations in the power supply voltage. May deteriorate, and problems such as flicker of the discharge lamp and occurrence of extinction may occur. Further, in the capacitor preheating method, when the load current is reduced, the constant preheating current flowing through the filament of the discharge lamp through the preheating capacitor increases. If an excessive current continues to flow through the filament, the blackening phenomenon near the filament of the discharge lamp is likely to occur.

The present invention has been made in view of the above problems, and an object thereof is to stabilize even when the load current is reduced while suppressing the size increase and cost increase of the components of the inverter circuit as much as possible. An object of the present invention is to provide a discharge lamp lighting device capable of performing an operation, preventing an unstable operation in advance, and maintaining a stable operation. In addition to this, it is an object of the present invention to provide a discharge lamp lighting device capable of limiting the constant preheating current, which increases when the load current is decreased, so as not to exceed the necessary current.

[0009]

As shown in FIG. 1, a discharge lamp lighting device according to a first aspect of the present invention includes a power supply circuit 1 for rectifying and smoothing an AC power supply Vs, and an output of the power supply circuit 1. An inverter circuit 2 for converting into a high frequency output, a discharge lamp 3 which is turned on by the high frequency output of the inverter circuit 2,
A control circuit 4 for controlling the operation of the power supply circuit 1 and the inverter circuit 2, a signal input section 6 for inputting a signal from the outside, and a discharge lamp 3 of the discharge lamp 3 according to a signal input to the signal input section 6. And a dimming circuit section 5 for determining the dimming degree and transmitting the dimming degree to the control circuit 4. The dimming circuit unit 5 determines the dimming degree of the discharge lamp 3 according to the input external signal, and transmits it to the control circuit 4. The control circuit 4
Controls the output Vdc of the power supply circuit 1 and the operating frequency of the inverter circuit 2 according to the signal from the dimming circuit unit 5. The control circuit 4 is configured such that the amount of current flowing through the control circuit 4 and the output of the inverter circuit 2 change, and the output of the inverter circuit 2 decreases when the amount of current increases. The dimming circuit unit 5 receives an external signal and smoothes it. Further, the dimming circuit section 5 is connected to the control circuit 4, and a current is supplied to the control circuit 4 in proportion to a DC voltage obtained by smoothing an external signal. In order to reduce the light output of the discharge lamp 3, the input level of the external signal is increased and the dimming circuit unit 5
This is performed by increasing the amount of current flowing from the control circuit 4 to the control circuit 4. As a result, as the light output of the discharge lamp 3 is reduced, the amount of current flowing through the control circuit 4 increases,
The resistance to external noise can be improved.

As shown in FIG. 6, the discharge lamp lighting device according to the third and fourth aspects of the present invention includes a power supply circuit 1 for rectifying and smoothing the AC power supply Vs, and an inverter for converting the output of the power supply circuit 1 into a high frequency output. A circuit 2, a discharge lamp 3 that is lit by the high frequency output of the inverter circuit 2, and the power supply circuit 1
A control circuit 4 for controlling the operation of the inverter circuit 2, a signal input section 6 for inputting a signal from the outside, and a dimming degree of the discharge lamp 3 according to the signal input to the signal input section 6. A dimming circuit section 5 which determines and transmits to the control circuit 4,
The load current detector 7 detects the load current flowing through the discharge lamp 3, generates a detection level that changes in proportion to the load current, and compares it with a predetermined value. The dimming circuit unit 5 determines the dimming degree of the discharge lamp 3 according to the input external signal, and transmits it to the control circuit 4. The control circuit 4
Controls the output of the power supply circuit 1 and the operating frequency of the inverter circuit 2 according to the signal from the dimming circuit section 5. The load current detecting means 7 previously generates a direct current voltage as a reference voltage when the load current is reduced to the lower limit of dimming, that is, just before unstable operation, and outputs the load current generated by the detecting means. Compare with a DC voltage that changes proportionally. When the load current of the discharge lamp 3 is reduced by an external signal input and the DC voltage in the load current detecting means 7 becomes substantially equal to the reference voltage, the dimming circuit section 5
In step 2, the dimming degree at that time is maintained, and control is performed so that the load current is not further reduced even if the external signal input changes to further decrease the load current. As a result, the load current does not fall below the preset dimming lower limit, so that it is possible to prevent the lighting state of the discharge lamp 3 from becoming unstable.

A discharge lamp lighting device according to a fifth aspect of the present invention is shown in FIG.
As shown in, the frequency setting section 43 is provided in the control circuit 4, and the control circuit 4 is configured so that the operating frequency is determined in proportion to the current flowing through the frequency setting section 43. An upper limit value of the current flowing through the frequency setting unit 43 is set, and when the output of the inverter circuit 2 is decreased by the dimming circuit unit 5, the frequency setting unit 43 flows to increase the operating frequency. Even if the current increases, a limit is set so that a current exceeding the upper limit of the current does not flow, and control is performed so that the operating frequency does not exceed the upper limit. As a result, the load current never falls below the preset dimming lower limit,
Therefore, it is possible to prevent the lighting state of the discharge lamp 3 from becoming unstable. Further, in the discharge lamp lighting device according to the invention of claim 6, instead of the frequency setting unit 43, the power supply circuit output control unit 42 is controlled by the dimming circuit unit 5 as shown in FIG. The output voltage is controlled so that it does not exceed the lower limit.

The discharge lamp lighting device according to the invention of claim 7 is as shown in FIG.
As shown in FIG. 1, a power supply circuit 1 that rectifies and smoothes the AC power supply Vs, an inverter circuit 2 that converts the output of the power supply circuit 1 into a high frequency output, and the operations of the power supply circuit 1 and the inverter circuit 2 are controlled. A control circuit 4, a signal input section 6 for inputting a signal from the outside, and a dimming degree for deciding the dimming degree of the discharge lamp 3 according to the signal inputted to the signal input section 6 and transmitting it to the control circuit 4. A circuit unit 5, a lamp filament preheating circuit using a capacitor C3, and a means 8 for detecting the voltage across the lamp filament are provided. For the filament both-ends voltage detecting means 8, a DC voltage substantially equal to the voltage across the filaments when the constant preheating current just before the blackening phenomenon in the vicinity of the filament of the discharge lamp 3 tends to occur due to the influence of the constant preheating current is used as a reference. The voltage is preset in the dimming lower limit setting unit 44, and the voltage detected by the filament both-ends voltage detection means 8 is compared with the reference voltage generated in advance. When the load current of the discharge lamp 3 is reduced by the external signal input and the DC voltage at the filament both-ends voltage detection means 8 becomes substantially equal to the reference voltage, the dimming degree at that time is maintained and the external signal input becomes Even if the load current is changed to a lower value, the load current is controlled so as not to decrease further. As a result, the constant preheating current does not exceed a preset current value at which blackening is likely to occur, and therefore blackening is less likely to occur near the filament of the discharge lamp 3.

Further, in the discharge lamp lighting device according to the invention of claim 8, instead of the above-mentioned filament end voltage detecting means 8, as shown in FIG. 12, there is a current between the filament of the discharge lamp 3 and the preheating capacitor C3. A winding for detection is provided, and the level of the constant preheating current detected by the constant preheating current detecting means 9 connected to the output of the winding is compared with a preset upper limit value of the constant preheating current, and the load is loaded in the same manner as above. It limits the current.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION (Embodiment 1) Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a discharge lamp lighting device with a light control function, which is one embodiment of the present invention. In FIG. 1, the power supply circuit 1 includes a rectifying circuit DB that rectifies the AC power supply Vs and a smoothing circuit that smoothes the rectified voltage, and converts the AC power supply Vs into a DC voltage Vdc and outputs the DC voltage Vdc. Smoothing circuit is inductor L
1 is a step-up chopper circuit composed of a switching element Q1, a diode D1, and an electrolytic capacitor C1. The inverter circuit 2 alternately turns on and off the switching elements Q2 and Q3, converts the output of the power supply circuit 1 into a high frequency, and lights the discharge lamp 3. C2 is a capacitor for cutting direct current, L2 is an inductor for resonance, and C3 is a capacitor for resonance and filament preheating.

The inverter control unit 41 in the control circuit 4 is
A pulse signal for alternately turning on and off the switching elements Q2 and Q3 of the inverter circuit 2 is output, and the oscillation frequency of the inverter circuit 2 is determined by the output frequency of this pulse signal. Then, by changing the output frequency, the light output of the discharge lamp 3 can be adjusted,
When the oscillation frequency is low, the optical output is high, and when the oscillation frequency is high, the optical output is low. In addition, the control circuit 4
The power supply circuit output control section 42 therein outputs a pulse signal for turning on / off the switching element Q1 of the power supply circuit 1 at a high frequency, and the output voltage Vdc of the power supply circuit 1 is determined by the output frequency of this pulse signal. By changing the output voltage Vdc, the light output of the discharge lamp 3 can be adjusted. When the output voltage Vdc is increased, the light output is increased, and when the output voltage Vdc is decreased, the light output is decreased.

The dimming signal input section 6 is used to adjust the light output of the discharge lamp 3 and inputs a pulse or DC voltage signal. The dimming circuit unit 5 determines the dimming degree according to the level of the input dimming signal, and transmits it to the control circuit 4.
In this embodiment, as the current flowing from the control circuit 4 into the dimming circuit section 5 increases, the light output decreases, that is, the current flowing through the control circuit 4 and the light output are inversely proportional to each other. The circuit 4 is configured.

The circuit configuration of the dimming circuit section 5 is shown in FIG. The dimming signal input to the dimming signal input unit 6 is stored in the capacitor C.
4, the current I flowing from the control circuit 4 into the dimming circuit section 5 is increased in accordance with the mirror ratio of the current mirror circuit configured by the transistor Q4 and the resistors R1 and R2. With such a configuration, when a DC voltage is input to the dimming signal input unit 6, the higher the voltage level of the dimming signal, the more the mirror current flowing through the mirror circuit increases, and as a result, control is performed. The current I flowing from the circuit 4 into the dimming circuit section 5 also increases, and the light output decreases.

As described above, since the oscillation frequency is high and the load current is small when the light output of the discharge lamp 3 is small,
Although it is more likely to be affected by noise from the outside, in the present embodiment, the smaller the light output, the more the current flowing from the control circuit 4 to the dimming circuit section 5 increases, and the current increases. By doing so, the resistance of the control circuit 4 to external noise can be improved, and the lighting state can be stabilized even when the light output is small.

(Second Embodiment) FIG. 4 is a circuit diagram of a discharge lamp lighting device with a dimming function according to another embodiment of the present invention. In this embodiment, in addition to the circuit configuration of the first embodiment, a frequency setting unit 43 is provided in the control circuit 4. The frequency setting unit 43 changes the operating frequency of the inverter circuit 2 in proportion to the current I flowing through the frequency setting unit 43. The higher the current I flowing through the frequency setting unit 43, the higher the oscillation frequency. , A circuit that reduces the optical output is configured.

The circuit configuration of the dimming circuit section 5 is shown in FIG. The dimming signal input to the dimming signal input unit 6 is stored in the capacitor C.
4, the current I flowing from the frequency setting section 43 into the dimming circuit section 5 is increased in accordance with the mirror ratio of the current mirror circuit configured by the transistor Q4 and the resistors R1 and R2. With such a configuration, when a direct current voltage is input to the dimming signal input unit 6, the higher the voltage level of the dimming signal, the more the mirror current flowing through the mirror circuit increases. The current I flowing from the setting unit 43 into the dimming circuit unit 5 also increases, and the light output decreases.

In the present embodiment, in addition to the same effects as in the first embodiment, the operating frequency of the inverter circuit 2 is increased from the outside by increasing the current value of the frequency setting section 43 as the light output becomes smaller. There is an effect of preventing instability due to interference of high frequency noise.

(Embodiment 3) FIG. 6 is a circuit diagram of a discharge lamp lighting device with a dimming function according to another embodiment of the present invention. In FIG. 6, the load current detecting means 7 generates a detection potential that changes in proportion to the value of the load current flowing through the discharge lamp 3. The dimming lower limit setting unit 44 in the control circuit 4 uses the load current immediately before the lighting state of the discharge lamp 3 becomes unstable when the load current of the discharge lamp 3 is reduced to reduce the light output. When operated, the detection potential obtained by the load current detection means 7 is preset and output.

The comparator 45 in the control circuit 4 compares the detection potential obtained by the load current detecting means 7 with the output of the dimming lower limit setting unit 44, and the detected potential is the dimming lower limit setting unit 44. When it becomes substantially equal to the output, it operates so as to maintain the operating frequency of the inverter circuit 2 determined by the inverter control unit 41 at that time. By doing so, even if a signal for further lowering the optical output is input to the dimming signal input unit 6, the optical output does not change and the dimming lower limit level can be maintained.

FIG. 7 is a graph showing the relationship between the load current and the dimming signal. In FIG. 7, when the dimming signal is changed in the direction of decreasing the optical output, the load current is dimmed until the load current reaches a predetermined value, that is, the load current preset by the dimming lower limit setting unit 44. Although it decreases according to the signal, after reaching the predetermined value, the predetermined value is maintained even if the dimming signal further changes. By using the configuration of the present embodiment, the dimming level set as the dimming lower limit is prioritized over the dimming signal input, so that the lighting of the discharge lamp does not become unstable.

(Embodiment 4) Another embodiment will be described with reference to FIG. The basic configuration of this embodiment is the same as that of the third embodiment. In the third embodiment, the load current is maintained at the predetermined value after reaching the predetermined value. However, the present embodiment further changes the dimming signal after the load current reaches the predetermined value. In such a case, the control is performed so as to increase the load current with the predetermined value being the minimum. Figure 8
FIG. 4 shows the relationship between the load current and the dimming signal in the present embodiment. As described above, in the present embodiment, when the dimming signal is continuously changed, the load current continuously changes with the predetermined value being the minimum, and therefore, the lighting of the discharge lamp does not become unstable. Thus, a natural dimming operation can be obtained from a predetermined value to the rated output.

(Embodiment 5) Still another embodiment will be described with reference to FIG. The basic configuration of the present embodiment is the same as that of the second embodiment, but the configuration of the dimming circuit section 5 is as shown in FIG. In FIG. 9, the frequency setting unit 4
The output voltage of 3 is constant (Vz). In this way, when a DC voltage is input as a dimming signal and the voltage is gradually increased, a current flows through the resistors R1 and R2 according to the mirror ratio of the current mirror circuit, and as a result, the frequency setting unit 43
The current I flowing from is increased, the oscillation frequency is increased,
The light output of the discharge lamp 3 becomes smaller.

However, when the voltage of the dimming signal is further increased, the current flowing through the resistor R2 further increases, and the resistor R2
Since the potential Vr at the connection point of 3 and R4 rises and the difference from Vz becomes smaller, the current I flowing from the frequency setting unit 43 begins to decrease. As a result, when the dimming signal becomes higher than a certain voltage, the oscillation frequency decreases, and the light output of the discharge lamp increases again. That is, the oscillation frequency does not exceed the predetermined frequency and is limited to the predetermined value or less.

Therefore, the relationship between the load current and the dimming signal in the present embodiment is the same as that in the fourth embodiment,
Therefore, the same effect as that of the fourth embodiment can be obtained. In the case of the present embodiment, the point at which the load current is the minimum, that is, the maximum value of the oscillation frequency is the resistance R1 and R
It can be freely adjusted by setting 2, R3 and R4.

(Sixth Embodiment) In the fifth embodiment, instead of the frequency setting section 43, the power supply circuit output control section 4 is used.
FIG. 10 shows the connection of 2 with the dimming circuit section 5. In the present embodiment, if the dimming of the discharge lamp is performed by changing the output voltage Vdc of the power supply circuit 1, the same effect as in the fifth embodiment can be obtained.

In the case of the present embodiment, the point that the load current becomes the minimum is the point that the output voltage Vdc of the power supply circuit 1 becomes the minimum, and the resistor R in FIG.
It can be freely adjusted by setting 1, R2, R3 and R4.

(Embodiment 7) FIG. 11 shows a discharge lamp lighting device according to another embodiment of the present invention. The discharge lamp lighting device of FIG. 11 has a preheating capacitor C as a preheating circuit for the discharge lamp 3.
3 is used. In the preheating capacitor C3, a so-called preheating current always flows through the filament of the discharge lamp 3 even when the discharge lamp 3 is lit. And the discharge lamp 3
When the load current is decreased, the preheating current always increases. However, when the value of the preheating current is always large, excessive energy is supplied to the filament, and the so-called blackening phenomenon is likely to occur, in which the filament is darkened due to scattering of the emitter inside the discharge lamp.

Therefore, in the present embodiment, the filament end voltage detection means 8 is provided to generate the detection potential from the voltage across the filament of the discharge lamp 3. Then, the dimming lower limit setting unit 4 in the control circuit 4 is set as the dimming lower limit with a state in which the maximum constant preheating current that does not cause blackening of the discharge lamp 3 flows.
4, the detection potential of the voltage across the filament when the lower limit of dimming is set in advance as a predetermined value. The comparator circuit 45 in the control circuit 4 compares the detected potential with a predetermined value, and when the detected potential becomes substantially equal to the output of the dimming lower limit setting unit 44, an inverter circuit determined by the inverter control unit 41. The operating frequency of 2 is maintained at that time.

By doing so, even if a signal for further lowering the light output is inputted to the dimming signal input section 6, the light output does not change and the constant preheating current at the dimming lower limit can be maintained. It is possible to prevent a blackening phenomenon due to an excessively large preheating current flowing.

(Embodiment 8) FIG. 12 shows a discharge lamp lighting device according to still another embodiment of the present invention. This is an example in which the constant preheating current detecting means 9 is provided in place of the filament both-ends voltage detecting means 8 in the seventh embodiment, and the detection potential is obtained from the constant preheating current itself by utilizing the winding for current detection. In the present embodiment, a current transformer CT for current detection is inserted between the filament and the preheating capacitor C3 to constantly obtain a detection potential according to the preheating current. Also in the present embodiment, as in the case of the above-described seventh embodiment, by setting the detection potential at the dimming lower limit as a predetermined value in advance, the constant preheating current at the dimming lower limit does not exceed the predetermined value. It can be maintained, and it is possible to prevent the blackening phenomenon due to the excessive constant preheating current flowing.

[0035]

According to the present invention, when the discharge lamp is dimmed, when the load current is reduced and the light output is small, the lighting of the discharge lamp is suppressed while suppressing the enlargement of the circuit parts and the cost increase. It is possible to prevent the state from becoming unstable, and it is possible to obtain a stable lighting state even when the load current decreases and the light output is small. Further, it is possible to improve the resistance to noise from the outside and suppress the occurrence of the blackening phenomenon.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an overall configuration of a discharge lamp lighting device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an output characteristic and a lamp characteristic of a conventional discharge lamp lighting device.

FIG. 3 is a circuit diagram showing a configuration of a dimming circuit unit according to the first embodiment of the present invention.

FIG. 4 is a circuit diagram showing an overall configuration of a discharge lamp lighting device according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram showing a configuration of a dimming circuit unit according to a second embodiment of the present invention.

FIG. 6 is a circuit diagram showing an overall configuration of a discharge lamp lighting device according to a third embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a relationship between a load current and a dimming signal of the discharge lamp lighting device according to the third embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a relationship between a load current and a dimming signal of the discharge lamp lighting device according to the fourth embodiment of the present invention.

FIG. 9 is a circuit diagram showing a configuration of a dimming circuit unit according to a fifth embodiment of the present invention.

FIG. 10 is a circuit diagram showing a configuration of a dimming circuit unit according to a sixth embodiment of the present invention.

FIG. 11 is a circuit diagram showing an overall configuration of a discharge lamp lighting device according to a seventh embodiment of the present invention.

FIG. 12 is a circuit diagram showing an overall configuration of a discharge lamp lighting device according to an eighth embodiment of the present invention.

[Explanation of symbols]

1 power supply circuit 2 Inverter circuit 3 discharge lamp 4 control circuit 5 Light control circuit

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3K072 AA02 AC02 AC11 BB01 BC01                       CA01 CA03 CB08 CB10 DA02                       DB03 DC01 DC07 DC08 DD04                       DE02 DE06 GA03 GB12 GC04                       HA05 HA06 HA10                 3K098 CC09 CC24 CC26 CC41 CC42                       DD22 DD35 DD36 DD42 DD43                       EE03 EE05 EE06 EE13 EE14                       FF02 FF04 FF14 FF20

Claims (8)

[Claims] 1. A power supply circuit for rectifying and smoothing an AC power supply, an inverter circuit for converting the output of the power supply circuit into a high frequency output, a control circuit for controlling the operation of the power supply circuit and the inverter circuit, and an external circuit. A signal input unit for inputting a signal, and a dimming circuit unit for determining a dimming degree of the discharge lamp and transmitting the dimming degree to a control circuit according to the signal input to the signal input unit, and the high frequency of the inverter circuit The discharge lamp is turned on by the output, and the dimming circuit section and the control circuit change the operating frequency of the inverter circuit or the output of the power supply circuit stepwise or continuously to gradually change the light output of the discharge lamp. Alternatively, in a discharge lamp lighting device capable of continuous switching, the control is performed so that the current flowing through the control circuit increases as the light output of the discharge lamp decreases. A discharge lamp lighting device having a control circuit. 2. The control circuit has an operating frequency setting unit that determines the operating frequency of the inverter circuit, and the current flowing through the operating frequency setting unit increases as the light output of the discharge lamp decreases. The discharge lamp lighting device according to claim 1, wherein the control circuit is configured so as to perform. 3. A power supply circuit for rectifying and smoothing an AC power supply, an inverter circuit for converting the output of the power supply circuit into a high frequency output, a control circuit for controlling the operation of the power supply circuit and the inverter circuit, and an external circuit. A signal input section for inputting a signal, a dimming circuit section for determining the dimming degree of the discharge lamp and transmitting it to the control circuit according to the signal input to the signal input section, and detecting a load current flowing through the discharge lamp And a load current detection unit that generates a detection level that changes in proportion to the load current and compares the detection level with a predetermined value. The discharge lamp is lit by the high frequency output of the inverter circuit, and the dimming circuit unit and the control unit are provided. Depending on the circuit
In a discharge lamp lighting device capable of stepwise or continuously changing the output of the inverter circuit to switch the load current of the discharge lamp stepwise or continuously, an external signal input to the signal input unit When the load current of the discharge lamp is decreased by changing the light control circuit unit, the detection level detected by the load current detection means is compared with a predetermined value so that the detection level does not become less than the predetermined value. In addition, the discharge lamp lighting device is characterized in that the output of the inverter circuit is controlled by the dimming circuit section. 4. The control is performed such that the load current is decreased until the detection level reaches a predetermined value, and when the detection level becomes a predetermined value or less, the load current is increased conversely thereafter. The discharge lamp lighting device according to claim 3. 5. A power supply circuit for rectifying and smoothing an AC power supply, an inverter circuit for converting the output of the power supply circuit into a high frequency output, a control circuit for controlling the operation of the power supply circuit and the inverter circuit, and an external circuit. A signal input unit for inputting a signal, and a dimming circuit unit for determining the dimming degree of the discharge lamp and transmitting the dimming degree to a control circuit according to the signal input to the signal input unit, and the high frequency output of the inverter circuit Discharge lamp lighting by which the operating frequency of the inverter circuit is changed stepwise or continuously by the control circuit, and the light output of the discharge lamp can be switched stepwise or continuously. In the device, a frequency setting unit is provided in the control circuit, and the control circuit is configured so that the operating frequency is determined in proportion to the current flowing through the frequency setting unit. The discharge lamp lighting device is characterized in that to limit the range of variation of the light output by setting an upper limit value of the current flowing in the frequency setting unit. 6. A power supply circuit for rectifying and smoothing an AC power supply, an inverter circuit for converting an output of the power supply circuit into a high frequency output, a control circuit for controlling the operation of the power supply circuit and the inverter circuit, and an external circuit. A signal input unit for inputting a signal, and a dimming circuit unit for determining the dimming degree of the discharge lamp and transmitting the dimming degree to a control circuit according to the signal input to the signal input unit, and the high frequency output of the inverter circuit The discharge lamp is turned on by the control circuit and the output voltage of the power supply circuit is changed stepwise or continuously by the control circuit to switch the light output of the discharge lamp stepwise or continuously. In the device, an output voltage setting section of the power supply circuit is provided in the control circuit, and the control circuit is controlled so that the output voltage of the power supply circuit is determined in proportion to the current flowing through the output voltage setting section. Constitute the discharge lamp lighting device being characterized in that to limit the range of variation of the light output by setting the upper limit value of the current flowing through the output voltage setting unit. 7. A power supply circuit for rectifying and smoothing an AC power supply, an inverter circuit for converting the output of the power supply circuit into a high frequency output, a control circuit for controlling the operation of the power supply circuit and the inverter circuit, and an external circuit. A signal input unit for inputting a signal, a dimming circuit unit for determining the dimming degree of the discharge lamp and transmitting it to the control circuit according to the signal input to the signal input unit, and a lamp filament preheating circuit using a capacitor The discharge lamp is preheated by the high frequency output of the inverter circuit.
A discharge lamp that can be turned on and that the output of the inverter circuit can be changed stepwise or continuously by the dimming circuit section and the control circuit to switch the load current of the discharge lamp stepwise or continuously. In the lighting device, a fimento voltage detection means for detecting the lamp filament voltage is provided, and when the light output of the discharge lamp is switched by the control circuit, the voltage detected by the filament voltage detection means is compared with a predetermined value, A discharge lamp lighting device, wherein the dimming circuit section controls the output of the inverter circuit so that the detected potential becomes a predetermined value or less. 8. A power supply circuit for rectifying and smoothing an AC power supply, an inverter circuit for converting the output of the power supply circuit into a high frequency output, a control circuit for controlling the operation of the power supply circuit and the inverter circuit, and an external circuit. A signal input unit for inputting a signal, a dimming circuit unit for determining the dimming degree of the discharge lamp and transmitting it to the control circuit according to the signal input to the signal input unit, and a lamp filament preheating circuit using a capacitor The discharge lamp is preheated by the high frequency output of the inverter circuit.
A discharge lamp that can be turned on and that the output of the inverter circuit can be changed stepwise or continuously by the dimming circuit section and the control circuit to switch the load current of the discharge lamp stepwise or continuously. In the lighting device, a winding for current detection is placed between the lamp filament and the condenser of the lamp filament preheating circuit, and a constant preheating current detection means for detecting the constant preheating current flowing through the preheating circuit when the lamp is lit is provided, and When the light output is switched by the control circuit, the constant preheating current level detected by the constant preheating current detecting means is compared with a predetermined value, and the dimming circuit section drives the inverter so that the constant preheating current level becomes equal to or lower than the predetermined value. A discharge lamp lighting device characterized by controlling the output of a circuit.