JP2001015284A - Lighting device of rare gas discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting device for rare gas discharge lamp capable of stabilizing the change in the photo-quantity of discharge lamp after stopping its operation. SOLUTION: A rare gas discharge lamp D is structured so that a pair of band-shaped external electrodes 5 and 6 are arranged on the peripheral surface of an envelope in such a way as isolated from one another, and a lighting device for this discharge lamp is equipped with a high-frequency voltage generating circuit HC including an output transformer TR having a primary coil TRP and secondary coil TRS and a first switching element S1 in series connection with the primary coil and generating a pulse-form high-frequency voltage on the output side of the output transformer on the basis of the switching operation of the element S1 and a DC/DC converter CV having a function to control the output to approx. a constant power. The DC/DC converter is connected with the input side of the high-frequency voltage generating circuit while the rare gas discharge lamp is connected with the output side, and the power on the input side of this circuit in the condition that the lamp is lighted up, is controlled so as to be approx. constant by the constant power generating function of the DC/DC converter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for a rare gas discharge lamp, and more particularly to a rare gas discharge lamp in which a pair of strip-shaped external electrodes are arranged on the outer peripheral surface of a glass bulb having a light emitting layer on the inner surface. The present invention relates to an improvement of a lighting device connected to a circuit.

[0002]

2. Description of the Related Art The applicant has previously proposed a rare gas discharge lamp DL shown in FIG. In the figure, A is a straight tubular envelope which is hermetically sealed by a glass bulb, for example, and a light emitting layer B made of a phosphor such as a rare earth phosphor or a halophosphate phosphor is provided on the inner surface thereof. Is formed. In particular,
In the light emitting layer B, an aperture portion (a portion where the light emitting layer is not formed) Ba having a predetermined opening angle is formed over substantially the entire length. The sealing structure of the envelope A is formed by sealing a disk-shaped sealing glass plate to an end of a glass bulb. It can also be constituted by a top seal. A predetermined amount of a rare gas mainly composed of xenon, which does not contain metal vapor such as mercury, is sealed in the enclosed space of the envelope A. A pair of band-shaped external electrodes C and D made of a metal member are provided on the outer peripheral surface of the envelope A.
Are spaced apart from each other over substantially the entire length of the.

[0003] The rare gas discharge lamp DL is lit by, for example, a lighting device shown in FIG. This lighting device generates, for example, a high frequency voltage (inverter circuit) HA having a frequency of about 30 KHz and a voltage of about 1880 V and an output waveform of substantially a sine wave, and a DC power supply E.
Switching element QA such as a transistor for controlling the supply of DC power from B to inverter circuit HA
And a drive circuit P for supplying a drive signal to the switching element QA. The rare gas discharge lamp DL is provided on the output side of the inverter circuit HA so that a high-frequency voltage is applied to the external electrodes C and D. It is connected to the.

In this lighting device, when a drive signal is applied to and stopped at a predetermined timing from the drive circuit P to the base of the switching element QA, the switching element QA turns on and off at predetermined intervals. During the period in which the switching element QA is on, the high frequency voltage is output by the operation of the inverter circuit HA and applied to the external electrodes C and D of the rare gas discharge lamp DL. Thus, unlike the rare gas discharge lamp DL, which is lit by a single discharge path along the longitudinal direction of the envelope, like a discharge lamp using a hot cathode or a cold cathode, the external electrodes C and D Since a myriad of discharge paths are formed between them (in a direction substantially perpendicular to the longitudinal direction of the envelope A), the light is lit in a striped state. In this state,
The light emitting layer B is excited by a rare gas excitation line to emit light,
Light is mainly emitted outside through the aperture Ba.

[0005] In particular, since no mercury is used in the rare gas discharge lamp DL, the amount of light rises sharply after lighting, and the amount of light reaches almost 100% simultaneously with lighting. ing. For this reason, it is suitable as a light source for document reading of OA equipment such as a facsimile, an image scanner, and a copying machine.

For example, when the rare gas discharge lamp DL is applied to the above-described document irradiating apparatus, the illuminance of the document surface can be reduced by adopting the aperture structure so that the density of the radiated light of the light emitting layer B can be increased. Therefore, the readability of the document can be improved.

However, recently, OA equipment has tended to further increase the document feeding speed in order to increase the processing capacity and increase the efficiency of office work, so that the rare gas discharge lamp DL is used as it is. If applied, the reading accuracy (resolution) of the original document will be impaired. For this reason, a further increase in illuminance is required.

[0008]

SUMMARY OF THE INVENTION Accordingly, the applicant has
Previously, a lighting device for a rare gas discharge lamp shown in FIG. 14 was proposed.
This lighting device is configured such that a rare gas discharge lamp DL is connected to an output side of a high-frequency voltage generating circuit HB that generates a pulsed high-frequency voltage so that a high-frequency voltage is applied to the external electrodes C and D. The high-frequency voltage generation circuit HB includes, for example, an output transformer TR having a primary coil TRa and a secondary coil TRb, and a switching element S1 such as a field effect transistor (FET) connected in series to the primary coil TRa of the output transformer TR. , A capacitor CA connected in parallel to a series circuit of the primary coil TRa and the switching element S1, and a drive circuit PD for applying a substantially square-wave drive signal to the switching element S1.

In particular, a PWM (Pulse Widget) is provided in the drive circuit PD so that the duty ratio of the drive signal can be changed.
th Modulation) function, and the drive timing for turning on the switching element S1 is a rebound period in which the direction of the lamp current Ib flowing through the rare gas discharge lamp DL is reversed within one cycle (T) of a repetitive waveform described later. (T ₂ ).

The lighting device thus configured operates as follows. First, when the DC power supply EB is connected to the input side of the high frequency high voltage generation circuit HB, the capacitor CA is charged. In this state, when the square wave drive signal shown in FIG. 15A is applied from the drive circuit PD to the gate of the switching element S1, the switching element S1 is turned on at the point in time as shown in FIG. 15B and FIG. On, off operations are performed at t ₁ , t ₂ , t ₃ . When the switching element S1 is turned on, a current (coil current Ic) flows from the capacitor CA and the DC power supply EB to the primary coil TRa of the output transformer TR as shown in FIG. Accumulates electromagnetic energy. Next, when the switching element S1 is turned off, the secondary coil TRb based on the action of the stored electromagnetic energy.
Generates a pulsed high-frequency voltage, and the rare gas discharge lamp DL
Is applied to the external electrodes C and D, a discharge is generated between the external electrodes, and the rare gas discharge lamp DL is turned on. As shown in FIGS. The current Ib flows. The lamp current Ib, with flow in the period T ₁ of the first half of each one period of the repetition period (T), the recoil period T ₂ as a stored charge lamp current Ib to rare gas discharge lamp DL, the period T ₁
Flows in the direction opposite to the direction of. When applying a driving signal between the recoil period T ₂ to the switching element S1, as shown in FIG. 15 (c), the time t _1, t ₃ ···
, A pulse current flows through the coil current Ic. In relation to this current, the lamp current Ibj indicated by oblique lines in FIGS. 15D and 16B is included in the lamp current Ib.
Flow is superimposed on the lamp current flowing in the period T _2. still,
Delaying applying timing of the drive signal to the switching element S1 outside the bounce period T _2, the lamp current I
b is merely a damped oscillation, and the lamp current Ib indicated by oblique lines
j stops flowing. As a result, the rare gas discharge lamp DL emits light (φ) as shown in FIG.
In response to the increase in bj, the brightness φ is also indicated by oblique lines (φ
j). The switching element S
As earlier applied timing of the driving signals is rebound period T ₂ of the to 1, without increasing the input to the lighting device deliberately can increase the lamp current Ibj the shaded effectively.

According to this lighting device, the rare gas discharge lamp DL
Of the lighting state, for the direction of the lamp current Ib flowing in the period T ₁ of the post-OFF operation of the switching element S1 is a switching element S1 is turned on in the rebound period T ₂ for inverting, high-frequency voltage generating circuit HB without increasing the input current deliberately, it is possible to increase the lamp current flowing through the rebound period T ₂ by Ibj min,
Along with this, the brightness (light amount) φ can be increased by φj. Therefore, when applied to a document irradiating device of an OA device, the illuminance of the document surface can be increased, and it is possible to cope with an increase in the document feeding speed.

However, when the input voltage (voltage on the primary coil TRa side of the output transformer TR) Vcc of the high-frequency voltage generating circuit HB increases in the operating state due to power fluctuations, the coil current Ic is indicated by a dotted line in FIG. current value at time t ₂ as shown is high. Along with this, the lamp current Ib and the light amount φ are also shown in FIGS.
, As shown by the dotted line. Therefore, if the power supply fluctuates during the operation of the OA equipment, there arises a problem that the reproduction quality is impaired.

Also, since this lighting device is excellent in the rising property of the amount of light after the rare gas discharge lamp DL is turned on, when it is applied to a document irradiation device of an OA device, a document is read almost simultaneously with the operation of the OA device. Although the operation can be performed, for example, the illuminance after operating for about 5 minutes is reduced by about 5% as compared with the illuminance immediately after lighting, so that the reading accuracy changes over time,
There is also a problem that reproduction quality is impaired.

Specifically, in the rare gas discharge lamp DL, a discharge is generated between the external electrodes via the envelope (glass bulb) A by applying a high-frequency voltage to the external electrodes C and D as described above. At this time, the temperature of the glass bulb rises to, for example, about 100 ° C. due to electric discharge or the like. For this reason, the light-emitting characteristics of the light-emitting layer B are impaired or the characteristics of the high-frequency voltage generating circuit HB are affected, and the illuminance is reduced by about 5%. Therefore, there is a demand for stabilization of the light amount of the rare gas discharge lamp DL after the operation of the lighting device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rare gas discharge lamp lighting device capable of stabilizing the light quantity fluctuation of the rare gas discharge lamp after operation.

[0016]

SUMMARY OF THE INVENTION Accordingly, in order to achieve the above-mentioned object, the present invention provides a metal member on an outer peripheral surface of an envelope having a light emitting layer on an inner surface and a rare gas sealed in an inner space. A rare gas discharge lamp having a pair of band-shaped external electrodes spaced apart from each other over substantially the entire length of an envelope, an output transformer having a primary coil and a secondary coil, and a primary coil thereof. A high-frequency voltage generating circuit that includes a first switching element that is electrically connected, and that generates a pulsed high-frequency voltage on the secondary coil side of the output transformer based on the switching operation of the first switching element; A DC / DC converter having a function of controlling power, and a DC / DC converter provided on the input side of the high-frequency voltage generation circuit.
The DC converter is connected to the rare gas discharge lamp on the output side, and the power on the input side of the high frequency voltage generating circuit in the lighting state of the rare gas discharge lamp is made substantially constant by the constant power function of the DC / DC converter. Is controlled.

According to a second aspect of the present invention, a pair of band-shaped external electrodes made of a metal member are provided on the outer peripheral surface of an envelope having a light emitting layer on the inner surface and a rare gas sealed in the inner space, A rare gas discharge lamp, which is arranged so as to be separated from each other over substantially the entire length of the envelope, and a translucent insulating member is mounted on the outer peripheral surface of the envelope so as to cover the external electrodes, Primary coil,
An output transformer having a secondary coil, a first switching element connected in series to the primary coil thereof, and a first drive circuit for applying a drive signal having a constant frequency and duty ratio to the first switching element; A high-frequency voltage generating circuit for generating a pulsed high-frequency voltage on the secondary coil side of the output transformer based on the switching operation of the first switching element, and a DC / DC converter having a function of controlling the output to a substantially constant power A DC / DC converter is connected to the input side of the high-frequency voltage generation circuit, and a rare gas discharge lamp is connected to the output side, and the power on the input side of the high-frequency voltage generation circuit when the rare gas discharge lamp is turned on is connected. ,
The DC / DC converter is controlled so as to be substantially constant by a constant power function.

Further, the third invention of the present invention relates to the DC / D
The C converter includes at least a series circuit of a coil and a diode connected between the input and the output, a second switching element that controls switching of a current flowing through the coil,
A current detection circuit for detecting a current flowing through the second switching element, a second driving circuit for applying a PWM-controlled drive signal to the second switching element, and accumulating energy stored in the coil via a diode And controlling the current flowing through the second switching element to have a substantially constant peak value by feeding back the current detected by the current detection circuit to the second drive circuit. The invention of Claim 4 is the DC / DC
The converter is a boost converter,
A fifth invention is characterized in that the duty ratio of the drive signal output from the first drive circuit is set to 60% or more.

Further, the sixth invention of the present invention provides the DC / D
The C converter includes at least a series circuit of a third switching element, a coil, and a first diode connected between an input and an output, and a second circuit connected in an opposite direction between an output side of the third switching element and ground. A second switching element for controlling the switching of the current flowing through the coil, a current detecting circuit for detecting the current flowing to the second switching element, and a second switching element for controlling the current flowing through the coil. , A third switching element, PW
A second drive circuit for providing a drive signal under M control, and a polarity of the drive signal from the second drive circuit connected between the second drive circuit and the second switching element or the third switching element And a capacitor for storing the electromagnetic energy stored in the coil via the first and second diodes. The third switching element is used for the switching operation of the second switching element. And performing a switching operation in response thereto, and controlling the current detected by the current detection circuit to be fed back to the second drive circuit so that the peak value of the current flowing through the second switching element becomes substantially constant.
A seventh invention is characterized in that the DC / DC converter is a buck-boost converter.

An eighth invention of the present invention is directed to the above-mentioned DC / D
The C converter includes at least a coil having a primary coil and a secondary coil, a second switching element connected in series to the primary coil of the coil, a current detection circuit connected in series to the second switching element, A second switching element for applying a PWM-controlled drive signal to the second switching element;
And a diode connected between the secondary coil of the coil and the high-frequency voltage generating circuit, and a capacitor that stores the electromagnetic energy stored in the coil via the diode. The current is fed back to the second drive circuit so that the peak value of the current flowing through the second switching element is controlled to be substantially constant.

Further, a ninth invention of the present invention is the above-mentioned second invention.
Is at least set by an oscillator that outputs a signal having a substantially constant frequency, a comparison circuit that outputs a high-level signal when an input signal reaches a reference voltage, and an output signal from the oscillator and the comparison circuit. And a flip-flop circuit to be reset, and when the voltage based on the current detected by the current detection circuit reaches a reference voltage, the second switching element is controlled to be turned off by a signal output from the comparison circuit. Wherein the peak value of the current flowing through the second switching element is made substantially constant,
In a tenth aspect of the present invention, the off-period of the first switching element is controlled by a free oscillation of a lamp current generated by an effective inductance on the secondary coil side of the output transformer and an effective capacitance when the rare gas discharge lamp is turned on. Is set within the first one cycle of.

[0022]

Next, a first embodiment of a lighting device for a rare gas discharge lamp according to the present invention will be described with reference to FIGS. The same parts as those in the prior art shown in FIGS. 12 to 16 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, DL is a rare gas discharge lamp, which is constructed as follows. That is, reference numeral 1 denotes a straight tubular envelope which is hermetically constituted by a glass bulb, for example, and a light emitting layer 2 made of a phosphor such as a rare earth phosphor or a halophosphate phosphor is formed on the inner surface thereof. ing. In particular,
The light emitting layer 2 has an aperture 2 having a predetermined opening angle.
a is formed over substantially the entire length. The sealing structure of the envelope 1 is configured by sealing a disk-shaped sealing glass plate to an end of a glass bulb. It can also be constituted by a top seal. A predetermined amount of a rare gas containing xenon as a main component which does not contain a metal vapor such as mercury is sealed in the closed space of the envelope 1 as described later.

A sheet structure 3 is wound around the outer peripheral surface of the envelope 1 so as to be in close contact therewith. This seat structure 3
For example, an insulative translucent sheet 4 having substantially the same length as the entire length of the envelope 1 and a metal bonded to one surface of the translucent sheet 4 at a predetermined interval from each other. A pair of band-shaped external electrodes 5 and 6 made of a member, terminals 51 and 61 extending from ends of the external electrodes 5 and 6, one surface of the light transmitting sheet 4 and one of the external electrodes 5 and 6 And an adhesive layer 9 provided on the surface of the substrate. When the seat structure 3 is attached to the envelope 1, the external electrodes 5,
6, a first opening 7 is formed between one side edge and a second opening 8 is formed between the other side edge, and light from the light emitting layer 2 mainly emits the aperture 2a. From the outside through the first opening 7.

The above-mentioned sheet structure 3 is mounted (wound) on the outer peripheral surface of the envelope 1 so that the external electrodes 5 and 6 are located between the envelope 1 and the light-transmitting sheet 4. . The attachment of the seat structure 3 to the envelope 1 is performed, for example, as shown in FIG. First, the sheet structure 3 is arranged on the stage 10 in a developed state. Next, the envelope 1 is disposed at one end 4a of the translucent sheet 4 in the sheet structure 3, and the envelope 1 is moved by the pair of driven rollers 11, 11.
Stage so that it can be pressed against
Is slightly moved in the M direction, and then moved in the N direction. Then, the envelope 1 relatively rolls on the translucent sheet 4, and the outer peripheral surface of the envelope 1 is wound with the sheet structure 3 to be mounted. In the sheet structure 3, the external electrodes 5 and 6 are adhered to the outer peripheral surface of the envelope 1 by using an adhesive layer 9 formed on the surface, and the light-transmitting sheet 4
Is adhered to the outer peripheral surface of the envelope 1 at the time of winding by using the adhesive layer 9 formed on one side thereof, and the respective ends 4a and 4b are overlapped by the second opening 8 and adhered. Have been.

As a constituent member of the envelope 1 of the rare gas discharge lamp DL, for example, lead having a volume resistivity of 1 × 10 ⁹ Ωcm or more at 150 ° C. and containing silicon oxide and boron oxide as main components is used. A borosilicate glass-based material (hereinafter, referred to as BFK glass for convenience) is preferable. The BFK glass is made of, for example, silicon oxide (67.6%), alumina (4
%), Boron oxide (18%), sodium oxide (1%),
It is composed of potassium oxide (8%), lithium oxide (1%), titanium oxide (0.4%) and the like. In addition, lead glass, barium glass, or the like can be used. This barium glass is made of, for example, an oxide of silicic acid, alumina, boric acid, potassium, barium, calcium, or the like. The thickness of these glasses is 0.2-0.7mm
(Preferably in the range of 0.4 to 0.7 mm). However, when the wall thickness is less than 0.4 mm, especially less than 0.2 mm, the mechanical strength of the envelope 1 is extremely reduced, and the defect rate due to glass breakage in the production process by mass production equipment increases. And conversely,
When the thickness exceeds 0.7 mm, a striped discharge state is visually observed, and the light emitted from the aperture portion 2a may flicker. Therefore, it is desirable to set the thickness of the envelope 1 within the above range. In some cases, the wall thickness of the envelope 1 can be set outside the upper limit thereof.

A rare gas mainly composed of xenon gas is sealed in the inner space of the envelope 1, and the sealed pressure is set, for example, in the range of 83 to 200 torr. Within this range, the starting characteristics, light output (original surface illuminance),
The effect of improving flicker is obtained. However,
When the filling pressure is less than 83 Torr, the effect of improving the light output becomes insufficient. Conversely, when the filling pressure exceeds 200 Torr, not only the starting characteristics are impaired, but also a striped discharge state is visually observed. The light emitted from the aperture 2a may be flickered. Therefore, it is desirable to set the rare gas charging pressure within the above range. The rare gas charging pressure can be set out of the above range depending on the use and requirements of the rare gas discharge lamp.

Further, the light emitting layer 2 may be composed of only one type of phosphor or a mixture of two or more types depending on the use of the rare gas discharge lamp. For example, in the case of a three-wavelength-band emission type, for example, a europium-activated barium magnesium aluminate phosphor having an emission spectrum in a blue region, a cerium / terbium-activated lanthanum phosphate phosphor having an emission spectrum in a green region, a red region And a mixture of europium-activated yttrium and gadolinium borate phosphors having an emission spectrum, the amount of which is ^{5 to} 30 m / cm ² .
g. In this range, a sufficient amount of light (light output) can be obtained, but if the amount of adhesion is less than 5 mg, the illuminance of the original surface becomes insufficient due to insufficient amount of light. It becomes difficult to form a light emitting layer. Therefore, it is desirable that the amount of the light-emitting layer 2 attached be set within the above range. It is to be noted that the amount of adhesion can be deviated from the above range depending on the use and requirements of the rare gas discharge lamp.

On the other hand, as shown in FIG. 1, the lighting device for lighting the rare gas discharge lamp DL is, for example, a DC power supply E1.
And a high-frequency voltage generating circuit HC connected to the output side of the DC / DC converter CV and generating a pulsed high-frequency voltage. And a rare gas discharge lamp DL connected to the output side of the high frequency voltage generation circuit HC.

In this lighting device, the high-frequency voltage generating circuit HC includes, for example, a primary coil TRp and a secondary coil TRs.
An output transformer TR, a first switching element S1 connected in series to the primary coil TRp of the output transformer TR, and a constant frequency (for example, 50 to 100 KHz) and a constant duty ratio applied to the first switching element S1. (For example, a fixed duty of 60% or more) drive signal V ₁
And a first drive circuit PD for providing the same. The first switching element S1 is configured by, for example, an N-channel field effect transistor (FET). As the first drive circuit PD, for example, a pulse oscillator having a substantially constant frequency and duty ratio is suitable.

In this high-frequency voltage generating circuit HC, the secondary coil TRs of the output transformer TR has a rare gas discharge lamp D
L is connected so that a pulsed high-frequency voltage is applied to the external electrodes 5 and 6, and one of the external electrodes 5 and 6 is grounded. In particular, the state first OFF period of the switching element S1 based on the driving signal V ₁ of the the first driving circuit PD is the effective inductance and a rare gas discharge lamp DL in the secondary coil TRs side of the output transformer TR is turned on within the first period of the free oscillation of the lamp current generated by the effective capacitance, which is preferably set between the recoil period T ₂ in which the direction of the lamp current reverses.

In the lighting device, the DC / DC converter CV includes, for example, a coil L1 and a diode D1 connected between an input (the output side of the DC power supply E1) and an output (the input side of the high-frequency voltage generation circuit HC). And the output side of coil L1 (connection point of coil L1 and diode D1)
, A current detection circuit R connected between the second switching element S2 and the ground, and a drive signal V ₂ connected to the second switching element S2.
And the capacitor C1 in which the electromagnetic energy stored in the coil L1 when the second switching element S2 is turned on is stored (charged) via the diode D1 when the second switching element S2 is turned off. It is configured. This DC / DC converter CV is configured as a boost converter in which an input voltage Vcc and an output voltage Vc have a relationship of Vcc <Vc. The second switching element S2 is constituted by, for example, an N-channel field effect transistor (FET), and the current detection circuit R is constituted by a resistor.

In this DC / DC converter CV,
The second drive circuit CT has a PWM control function. For example, as shown in FIG. 2, an oscillator OSC that outputs a pulse signal VS of a constant frequency and a reference power supply (reference voltage) are connected to an inverting input terminal (-). E2 is a comparison circuit OP in which the output of the current detection circuit R is connected to the non-inverting input terminal (+),
The output terminal of the oscillator OSC is connected to the set terminal S, the flip-flop circuit FF whose output terminal of the comparison circuit OP is connected to the reset terminal R, the input terminal is connected to the output terminal Q of the flip-flop circuit FF, and the output terminal is the second switching element S2. Driver circuits DR connected to respective gates
And 1. Incidentally, the comparison circuit OP is constituted by, for example, an operational amplifier.

The lighting device thus configured operates as follows. First, DC / when DC converter to connect the DC power supply E1 to the input side of the CV, the second driving circuit from the oscillator OSC in CT 7 pulse signal V of constant frequency as shown in (a) _S is the time t _11, are output at t ₁₄ ... and are applied to the set terminal S of the flip-flop circuit FF. Thus from the output terminal Q of the flip-flop circuit FF output signal V _Q to the high level by the rising of the pulse signal V _S as shown in FIG. 5 (b) is, the second switching element via the driver circuit DR1 It is given as a drive signal V ₂ to the gates of S2.

The second switching element S2 granted drive signal V ₂ is turned on at time t ₁₁ as shown in FIG. (C), the second switching element S2 via the coil L1, the current A current I _S2 that increases almost linearly flows through the detection circuit R as shown in FIG. Current detecting circuit terminal voltage of the _{R V R (V R = I} S2 · R) from the resistance value R is constant, increases with increasing current I _S2. When the current I _S2 reaches a certain current value (peak value) I _S2P ,
Terminal voltage V _R becomes V _R = I _S2P · _R. The reference voltage E2 of the comparison circuit OP is set in advance to a voltage value corresponding to the voltage V _R generated when the current I _S2 reaches a certain peak current value I _S2P . Therefore, when the current I _S2 reaches a certain peak current value I _S2P, the terminal voltage V _R reaches the reference voltage E2 of the comparator circuit OP. Thus, from the comparator circuit OP is the output signal V _P of the high level at time t ₁₂ as shown in FIG. (E) is, the flip-flop circuit FF is reset, the signal V _Q of the output terminal Q the drawing goes low at time t ₁₂ as shown in (b), the second switching element S2 is simultaneously turned off at time t ₁₂ as shown in FIG. (c), flowing through the second switching element S2 current I _S2 also not flow at time t ₁₂ as shown in FIG. (d).

[0036] At time t _12, when the second switching element S2 is turned off, the output side of the coil L1 drawing (f) to a voltage higher than the voltage Vcc of the DC power source E1 as shown V ( electromagnetic energy) generated accumulated in the coil L1, and drops to approximately the voltage Vcc at time t _13, the signal V _S from the oscillator OSC at time t ₁₄
As a result, the second switching element S2 is turned on again, so that the voltage V on the output side of the coil L1 becomes 0 level. On the other hand, the second switching element S2
When turned on at _11, to the coil L1 current I _L1 which increases as substantially linearly shown in FIG. (G) flows, a maximum at time t _12. At this point t _12, the second
When the switching element S2 is turned off, the electromagnetic energy accumulated in the coil L1 causes the diode D
1 is stored (charged) in the capacitor C1 through the time t
_Stops flowing at ₁₃ . Thereby, the capacitor C
1 outputs the voltage Vc to the high-frequency voltage generation circuit HC.

In the state where the voltage Vc is supplied from the DC / DC converter CV to the high-frequency voltage generating circuit HC, the first driving circuit PD supplies a constant voltage at a substantially constant frequency as shown in FIG. When the signal V ₁ of the duty ratio is output, the first switching element S1 is turned on at time t ₁ as shown in FIG. (b). Thereby, the output transformer T is output from the DC / DC converter CV.
Through the primary coil TRp of R, a coil current Ic that increases substantially linearly flows through the first switching element S1 as shown in FIG. Next, FIG when the signal V ₁ is at the low level at time t ₂ as shown in (a), the first switching element S1 point as shown in FIG. (B) t ₂
To turn off.

[0038] When the first switching element S1 is turned off at time t _2, the primary coil T of the output transformer TR
Based on the action of the electromagnetic energy stored in Rp, the secondary coil TRs has a primary coil TRp and a secondary coil TRs.
A high frequency voltage in the form of a pulse is generated according to the winding ratio and applied to the external electrodes 5 and 6 of the rare gas discharge lamp DL. And
A discharge is generated between the external electrodes 5 and 6, and the rare gas discharge lamp D
L becomes lit, the charge in the discharge lamp is accumulated substantially with the lamp current Ib begins to flow from the time t _2, in relation to a rare gas discharge lamp DL form the capacitor as shown in FIG. 8 (d) . When the lamp current Ib becomes 0, the electric charge accumulated in the rare gas discharge lamp DL again flows as the lamp current in a direction opposite to the direction of the first period T ₁ (see FIG. 16). The period (T ₂ ) in the reverse direction is referred to as a bounce period for convenience. Accordingly, the rare gas discharge lamp D
L exhibits light emission (φ) as shown in FIG.

As shown in FIG. 8A, the output signal V ₁ of the first drive circuit PD has a constant frequency and the on-duty ratio is set to a constant value of 60% or more. after becoming a low level at time t _2, again at a high level at time t _3. As a result, the first switching element S
1 is turned on again at time t ₃ as shown in FIG. Thus, the primary coil TRa of the output transformer TR after pulsed manner the coil current at time t ₃ as shown in FIG. 3 (c) flows, increases almost linearly. Since electric power is supplied to the secondary coil TRs of the output transformer TR based on the pulse-like coil current, the lamp current flowing during the rebound period (T ₂ ) is indicated by the hatched lamp current in FIG. In addition to the superimposition of Ibj, the light amount φj indicated by oblique lines in FIG.

In particular, as shown in FIG. 8 (b), the time point t _{3 at} which the first switching element S1 is inverted from the off state to the on state is determined by the effective inductance and the rare gas on the secondary coil TRs side of the output transformer TR. since the discharge lamp DL is set within the first period of the free oscillation of the lamp current generated by the effective capacitance of a state in which lighting (preferably between recoil period T ₂ in which the direction of the lamp current reverses) In addition, the current Ibj indicated by the diagonal lines can be effectively superimposed on the free oscillation component of the lamp current. However, when the duty ratio is less than 60%, the free oscillation component of the lamp current at the time point t ₃ becomes small, so that the effect of superimposing the lamp current cannot be sufficiently obtained. Hereinafter, the same operation and the time point t ₁ ~t ₃ period is also the time t ₃ or later is continuously repeated.

By the way, when the voltage Vcc is
Becomes higher, the current I _S2 flowing through the second switching element S2 becomes the time t ₁₂ as shown by the dotted line in FIG.
At a earlier point in time t _{12X, a} constant peak value I _S2P is reached.
As a result, the voltage VR of the current detection circuit _R becomes equal to the reference voltage E2.
Reached, from comparison circuit OP result signal V _P of the high level at time t _12X as indicated by a dotted line in FIG. (E) is output, the output signal V _Q of the flip-flop circuit FF is drawing (b ), Becomes low level at time t _12X as shown by the dotted line, and the second switching element S2 is turned off at time t _12X as shown by the dotted line in FIG. As a result, a voltage V higher than the voltage Vcc is generated on the output side of the coil L1 as shown by a dotted line in FIG. On the other hand, the second switching element S2
Until is turned off at time t _12X , a current I _L1 that increases almost linearly flows through the coil L1 as shown by the dotted line in FIG. _3G , and reaches a maximum at time t _12X . At this time, when the second switching element S2 is turned off, the electromagnetic energy stored in the coil L1 is stored (charged) in the capacitor C1 via the diode D1.
Is done. As described above, when the voltage Vcc increases, the on-period of the second switching element S2 is shortened. Conversely, when the voltage Vcc decreases, the on-period of the second switching element S2 is controlled to be prolonged. This gives D
The output of the C / DC converter CV is controlled so as to have a substantially constant power.

As described above, the constant power supply to the high-frequency voltage generation circuit HC by the DC / DC converter CV is performed as follows.
This is basically performed by controlling the peak current of the current I _S2 flowing through the second switching element S2 via the coil L1 to a constant value I _S2P . Here, _assuming that the inductance of the coil L1 is L ₁ , the current is I _S2P , and the switching frequency of the second switching element S2 is f, DC / D
Power P output from C converter CV is P = 0.5
L ₁ · I _S2P ² · f This power P is
On the inductance L ₁ of the coil L1 is substantially constant, since it is set to a substantially constant value even switching frequency f, to be dependent on the current I _S2 flowing in the second switching element S2 via the coil L1 Become. Therefore, constant power can be _achieved by controlling the peak current of the current I _S2 so as to always be a constant value I _S2P . For this reason, the brightness of the rare gas discharge lamp DL is maintained substantially constant.

According to the present embodiment, the second drive circuit CT in the DC / DC converter CV includes the current detection circuit R
The peak current of the current I _S2 detected by the current detection circuit R based on the signal fed back from the
PW is applied to the second switching element S2 so as to be _S2P.
For M modulated signal V ₂ is configured to be applied, the voltage fluctuation of the DC power source, without being affected such as variation in the load can be controlled substantially constant power output. Therefore, the amount of light of the rare gas discharge lamp DL can be stabilized.

Since the DC / DC converter CV has a constant power function, the circuit configuration of the high frequency voltage generation circuit HC is changed to the output transformer TR, the first switching element S
1. The first drive circuit PD can be simply configured. In particular, the first driving circuit PD, in relation to the switching frequency of the output signal V _1, the duty ratio is fixed at a constant value, can be configured at low cost simply oscillator, it is possible to reduce the cost of the lighting device .

Further, the lamp current Ib in the lighting state of the rare gas discharge lamp DL is free oscillation due to the effective inductance on the secondary coil TRs side of the output transformer TR and the effective capacitance in the state where the rare gas discharge lamp DL is turned on. Although than is flowing based on, the bounce period T ₂ in which the direction of the lamp current reverses, on the basis of the pulse-like coil current generated when the first switching element S1 is turned on again, hatched in FIG. 8 (d) Is superimposed effectively. For this reason, the lamp current can be substantially increased without further increasing the input current of the high-frequency voltage generation circuit HC, and accordingly, the brightness is also indicated by oblique lines in FIG. Can be further increased. Accordingly, not only the amount of light of the rare gas discharge lamp DL can be increased, but also the efficiency of the lighting device can be increased, and for example, it is possible to cope with an increase in the document feeding speed in the OA equipment.

In particular, the output signal V _{1 of} the first drive circuit PD
ON for duty ratio which is set to 60% or more, it is possible to effectively superimpose the current Ibj flowing based on the pulse-like coil current in the rebound period T ₂ in the lamp current, the rare gas discharge lamp DL The amount of light can be increased. However, It can not be increased to the recoil period T ₂ the lamp current effective in this range, it is no longer possible to expect an increase in light intensity.

FIG. 9 shows a second embodiment of the DC / DC converter CV1 according to the present invention, and the basic configuration is the same as the embodiment shown in FIGS. The difference is that the third switching element S3 is connected in series between the DC power supply E1 and the coil L1, and the output side of the first driver circuit DR1 and the third switching element S3
A second driver circuit DR2 having an inversion function is connected between the third switching element S
That is, the second diode D2 is connected in the opposite direction between the output side of No. 3 and the ground. Note that the DC / DC converter C
V1 is composed of a buck-boost converter, and Vcc
Any operation of <Vc, Vcc> Vc is possible.
Further, the first driver circuit DR1 is connected to the second driver circuit CT1.
Is described outside the block of the second drive circuit CT for convenience. further,
The third switching element S3 is configured by, for example, a P-channel field-effect transistor (FET).

The DC / DC converter CV1 thus configured operates as follows. The basic operation of the DC / DC converter CV1 is the first operation shown in FIGS.
This is almost the same as the embodiment.

First, when the DC power supply E1 is connected to the input side of the DC / DC converter CV1, a pulse signal V _S of a constant frequency is output from the oscillator OSC in the second drive circuit CT as shown in FIG. are output at t ₁₁ , t _14, ... and are applied to the set terminal S of the flip-flop circuit FF. This signal V _Q to the high level by the rising of the pulse signal V _S is outputted from the output terminal Q of the flip-flop circuit FF, the gate to the drive signal of the second switching element S2 via the first driver circuit DR1 At the same time it is given as V _2, to the gate of the third switching element S3 inverted driving signal polarity is applied by the second driver circuit DR2. Thereby, the second and third switching elements S
2, S3 the figure (b), the ON state at time t ₁₁ as shown in (c).

Second and third switching elements S2, S3
Is turned on, the current I _S2 that increases almost linearly through the third switching element S3 and the coil L1 to the second switching element S2 and the current detection circuit R as shown in FIG. When the current reaches a certain peak current value I _S2P , the terminal voltage V _R becomes V _R = I _S2P · R. The reference voltage E2 of the comparison circuit OP is set in advance to a voltage value corresponding to the voltage V _R generated when the current I _S2 reaches a certain peak current value I _S2P . Therefore, when the current I _S2 reaches a certain peak current value I _S2P, the terminal voltage V _R reaches the reference voltage E2 of the comparator circuit OP. Thereby, the comparison circuit O
From P signal V _P of the high level at time t ₁₂ as shown in FIG. (E) is output, the flip-flop circuit FF is reset, the signal V _Q of the output terminal Q and low at time t ₁₂ Become. For this, the second, third switching elements S2, S3 the figure (b), at the same time turned off at time t ₁₂ as shown in (c), the current flowing through the second switching element S2 I _S2 even longer flows at time t ₁₂ as shown in FIG. (d).

[0051] At time t _12, when the second, third switching elements S2, S3 is turned off, the coil L
A voltage V higher than the voltage Vcc of the DC power supply E1 is generated at the output side of the DC power supply E1, and the capacitor C1 is charged via the first diode D1 as shown in FIG. For this, the terminal voltage (output voltage) Vc of the capacitor C1 is charged to the capacitor C1 from time t ₁₂ as shown in FIG. (G) is started at time t ₁₃ to the voltage V approximately 0V level The charging is terminated by falling. By the time t ₁₃ after the power is supplied from the capacitor C1 to the high frequency voltage generating circuit HC, the terminal voltage Vc will be gradually descends.

According to this embodiment, the third switching element S3 is connected between the DC power supply E1 and the coil L1,
Since the switching operation is performed in accordance with the second switching element S2, the third switching element S3 is also turned off when the second switching element S2 is turned off, and FIG. As shown, the voltage Vcc of the DC power supply E1 does not appear as the bias voltage in the voltage V. Therefore, even if the power supply fluctuates in the DC power supply E1, the influence on the voltage V generated on the output side of the coil L1 can be suppressed, and more desirable constant power can be realized.

FIG. 11 shows a third embodiment of the DC / DC converter CV2 according to the present invention. The basic configuration is the same as that of the embodiment shown in FIGS. The difference is that the coil L1 is composed of the primary coil Lp and the secondary coil Ls, that the second switching element S2 is connected to the primary coil Lp of the coil L1 in series,
That is, the secondary coil Ls of the coil L1 is connected to the input side of the high-frequency voltage generation circuit HC via the first diode D1.

The basic operation of the DC / DC converter CV2 is almost the same as that of the embodiment shown in FIGS.
The following operations are different. That is, when the second switching element S2 at time t ₁₂ as shown in FIG. 7 (c) is turned off, based on the action of the electromagnetic energy accumulated in the coil L1, the secondary coil Ls 10 ( As shown in f), a voltage V is generated by the winding ratio between the primary coil Lp and the secondary coil Ls, and is accumulated (charged) in the capacitor C1 via the first diode D1 as shown in FIG. Is to be done.

According to this embodiment, since the coil L1 is constituted by the primary coil Lp and the secondary coil Ls in the form of an insulating transformer, the second switching element S2
Is turned off, the voltage Vcc of the DC power supply E1 does not appear as a bias voltage in the voltage V generated in the secondary coil Ls, as in the second embodiment. Therefore,
Even if the power supply fluctuates in the DC power supply E1, the influence on the voltage V generated in the secondary coil Ls can be suppressed, and more desirable constant power can be realized.

In the DC / DC converter CV2, the input side and the output side are magnetically coupled by the primary coil Lp and the secondary coil Ls of the coil L1, so that the input voltage Vcc and the output voltage Vc And Vcc <V
It can be operated in any state of c, Vcc> Vc.

The present invention is not limited to the above-described embodiment. For example, the first to third switching elements can be transistors other than FETs.
Further, the second driving circuit of the DC / DC converter is not limited to the illustrated example as long as it has a function of controlling the peak value of the current flowing through the second switching element to a constant value. Further, as a driving circuit of the switching element, an appropriate circuit can be applied according to the conductivity type of the switching element. The diode means a unidirectional element, and includes a diode using a transistor or the like as a unidirectional element in addition to a general diode element. Further, in the rare gas discharge lamp incorporated in the lighting device, a heat-shrinkable resin tube other than the translucent sheet may be used as the insulating member attached to the envelope, or may be omitted. Alternatively, the light emitting layer may be formed on the entire inner surface of the envelope without the aperture portion, or a deformed portion such as a sawtooth shape may be formed on the side edge of the external electrode. Further, in the form of the external electrode, the band shape means that the overall shape is a band shape, and includes a shape in which a deformed portion, a hole, or the like exists in a side edge portion or a portion other than the side edge portion. And

[0058]

As described above, according to the present invention, DC / D
The second drive circuit in the C converter applies PWM modulation to the second switching element based on the signal fed back from the current detection circuit so that the peak current of the current detected by the current detection circuit always becomes a constant value. Since the output signal is configured to be applied, the output can be controlled to a substantially constant power without being affected by fluctuations in the voltage of the DC power supply, fluctuations in the load, and the like. Therefore, the amount of light of the rare gas discharge lamp DL can be stabilized.

Further, since the DC / DC converter has a constant power function, the circuit configuration of the high frequency voltage generating circuit can be simply configured by an output transformer, a first switching element, and a first drive circuit. it can. In particular, the first driving circuit can be configured with a simple inexpensive oscillator because the switching frequency and the duty ratio of the output signal are fixed to fixed values, and the cost of the lighting device can be reduced.

Further, the lamp current in the lighting state of the rare gas discharge lamp flows on the basis of free vibration caused by the effective inductance of the secondary coil of the output transformer and the effective capacitance in the lighting state of the rare gas discharge lamp. However, during the bounce period in which the direction of the lamp current is reversed, a current flowing based on a pulsed coil current generated when the first switching element turns on again is superimposed on the lamp current. Therefore, the lamp current can be substantially increased without further increasing the input current of the high-frequency voltage generation circuit, and accordingly, the brightness can be increased. Therefore, not only the amount of light of the rare gas discharge lamp can be increased, but also the efficiency of the lighting device can be increased. For example, it is possible to cope with an increase in the document feeding speed in the OA equipment.

In particular, if the on-duty ratio of the output signal of the first drive circuit in the high-frequency voltage generating circuit is set to 60% or more, the current flowing based on the pulsed coil current during the rebound period can be effectively used as the lamp current. They can be superposed, and the amount of light of the rare gas discharge lamp can be increased.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of a lighting device according to a first embodiment of the present invention.

FIG. 2 is a circuit block diagram of a second driving circuit shown in FIG.

FIG. 3 is a vertical sectional view of the rare gas discharge lamp shown in FIG.

FIG. 4 is a development view of a sheet structure applied to the rare gas discharge lamp shown in FIG.

FIG. 5 is a sectional view taken along line XX of FIG. 4;

FIG. 6 is a longitudinal sectional view for explaining the method for manufacturing the rare gas discharge lamp shown in FIG.

7A and 7B are explanatory diagrams of the operation of the DC / DC converter in FIG. 1, wherein FIG. 7A is an output timing chart of an oscillator in a second drive circuit, and FIG. 7B is an output timing chart of the first driver circuit; FIG. 3C is an operation timing chart of the second switching element, FIG. 4D is a current chart flowing through the second switching element, and FIG. 4E is an output timing chart of the comparison circuit; (F) is a voltage diagram on the output side of the coil, and (g) is a current diagram flowing through the coil.

FIGS. 8A and 8B are explanatory diagrams of the operation of the high-frequency voltage generating circuit in FIG. 1, wherein FIG. 8A is an output timing diagram of a first drive circuit, and FIG. 8B is an operation timing diagram of a first switching element; (C) is a diagram of a coil current flowing through the primary coil of the output transformer, (d) is a diagram of a lamp current, and (e) is a diagram of a light emission waveform.

FIG. 9 is an electric circuit diagram of a DC / DC converter showing a second embodiment of the present invention.

10A and 10B are explanatory diagrams of the operation of the DC / DC converter shown in FIG. 9, wherein FIG. 10A is an output timing chart of an oscillator in a second drive circuit, and FIG. FIG. 9C is an operation timing chart of the third switching element, FIG. 9D is a current chart of the current flowing through the second switching element, and FIG. 9E is an output timing chart of the comparison circuit. FIG. 7F is a voltage diagram on the output side of the coil, and FIG. 7G is a terminal voltage diagram of the capacitor.

FIG. 11 is an electric circuit diagram of a DC / DC converter according to a third embodiment of the present invention.

FIG. 12 is a longitudinal sectional view of a rare gas discharge lamp according to the prior art.

FIG. 13 is an electric circuit diagram of a lighting device for a rare gas discharge lamp according to the prior art.

FIG. 14 is an electric circuit diagram of another rare gas discharge lamp lighting device according to the prior art.

FIGS. 15A and 15B are explanatory diagrams of the operation of FIG. 14, wherein FIG. 15A is an output timing diagram of a drive circuit, FIG. 15B is an operation timing diagram of a switching element, FIG. (D) is a lamp current diagram, and (e) is a light emission waveform diagram.

16 is an enlarged view of FIG. 15, wherein FIG. 16A is an operation timing chart of the switching element, and FIG. 16B is a lamp current chart.

[Explanation of symbols]

 Reference Signs List 1 envelope 2 light emitting layer 2a aperture 3 sheet structure 4 translucent sheet (insulating member) 5, 6 external electrode 7 first opening 8 second opening DL rare gas discharge lamp E1 DC power supply E2 reference power supply (Reference voltage) HC High-frequency voltage generating circuit TR Output transformer TRp Primary coil TRs Secondary coil S1 First switching element S2 Second switching element S3 Third switching element PD First drive circuit CT Second drive circuit CV , CV1, CV2 DC / DC converter R Current detection circuit (resistance) L1 coil Lp Primary coil Ls Secondary coil C1 Capacitor D1, D2 Diode DR1, DR2 Driver circuit OSC oscillator OP Comparison circuit FF Flip-flop circuit

Claims (10)

[Claims] 1. A pair of band-shaped external electrodes made of a metal member is provided on an outer peripheral surface of an envelope having a light emitting layer on an inner surface and a rare gas sealed in an inner space over substantially the entire length of the envelope. A rare gas discharge lamp disposed apart from each other, an output transformer having a primary coil and a secondary coil, and a first switching element connected in series to the primary coil of the output transformer; A high-frequency voltage generating circuit for generating a pulsed high-frequency voltage on the secondary coil side of the output transformer based on a switching operation; and a DC / DC converter having a function of controlling the output to a substantially constant power. DC / D on input side of high frequency voltage generation circuit
The C converter is connected to a rare gas discharge lamp on the output side, and the power on the input side of the high-frequency voltage generating circuit in the lighting state of the rare gas discharge lamp is made substantially constant by the constant power function of the DC / DC converter. A lighting device for a rare gas discharge lamp, characterized in that: 2. A pair of band-shaped external electrodes made of a metal member is provided on an outer peripheral surface of an envelope having a light emitting layer on an inner surface and a rare gas sealed in an inner space over substantially the entire length of the envelope. A rare gas discharge lamp having a light-transmitting insulating member mounted on the outer peripheral surface of the envelope so as to cover the external electrode, and an output having a primary coil and a secondary coil. A first switching element connected in series to a primary coil of a transformer and an output transformer, and a first switching element for applying a drive signal having a constant frequency and a constant duty ratio to the first switching element.
A high frequency voltage generating circuit for generating a pulsed high frequency voltage on the secondary coil side of the output transformer based on the switching operation of the first switching element, and a function of controlling the output to a substantially constant power DC / D with
A DC / DC converter is connected to the input side of the high-frequency voltage generation circuit, and a rare gas discharge lamp is connected to the output side, and the input side of the high-frequency voltage generation circuit when the rare gas discharge lamp is lit is provided. A lighting device for a rare gas discharge lamp, wherein the power is controlled to be substantially constant by a constant power function of a DC / DC converter. 3. The DC / DC converter includes at least a series circuit of a coil and a diode connected between an input and an output, a second switching element for controlling a current flowing through the coil, and a second switching element. A current detection circuit for detecting a current flowing through the second switching element and a second switching element for applying a PWM-controlled drive signal to the second switching element.
And a capacitor that accumulates the energy stored in the coil via a diode, and feeds back the current detected by the current detection circuit to the second drive circuit so that the peak of the current flowing through the second switching element is increased. 3. The lighting device for a rare gas discharge lamp according to claim 1, wherein the value is controlled so as to be substantially constant. 4. The lighting device for a rare gas discharge lamp according to claim 3, wherein the DC / DC converter is a step-up converter. 5. The lighting device for a rare gas discharge lamp according to claim 2, wherein a duty ratio of a drive signal output from the first drive circuit is set to 60% or more. 6. The DC / DC converter includes at least a series circuit of a third switching element, a coil, and a first diode connected between an input and an output, and a circuit between an output side of the third switching element and a ground. Connected in the opposite direction to the second
A second switching element for controlling the switching of the current flowing through the coil, a current detecting circuit for detecting the current flowing to the second switching element, and a second switching element for controlling the current flowing through the coil. , A second driving circuit for applying a PWM-controlled driving signal to the third switching element, and a second driving circuit connected between the second driving circuit and the second switching element or the third switching element. An inverting circuit for inverting the polarity of the drive signal from the drive circuit; and a capacitor for storing the electromagnetic energy stored in the coil via the first and second diodes. The switching operation is performed in accordance with the switching operation of the second switching element, and the current detected by the current detection circuit is fed back to the second drive circuit. Lighting apparatus noble gas discharge lamp according to claim 1 or 2 peak value of the current flowing through the second switching element by clause and controls to be substantially constant. 7. The lighting device for a rare gas discharge lamp according to claim 6, wherein the DC / DC converter is a step-up / step-down converter. 8. The DC / DC converter includes at least a coil having a primary coil and a secondary coil, a second switching element connected in series to the primary coil of the coil, and a serial connection to the second switching element. A current detection circuit connected to the second switching element, a second drive circuit that applies a PWM-controlled drive signal to the second switching element, a diode connected between the secondary coil of the coil and the high-frequency voltage generation circuit, A capacitor that stores the electromagnetic energy stored in the coil via a diode, and feeds back the current detected by the current detection circuit to the second drive circuit so that the peak value of the current flowing through the second switching element is reduced. 3. The lighting device for a rare gas discharge lamp according to claim 1, wherein the lighting device is controlled to be substantially constant. 9. The second driving circuit includes: an oscillator that outputs at least a signal having a substantially constant frequency; a comparison circuit that outputs a high-level signal when an input signal reaches a reference voltage; A flip-flop circuit that is set and reset by an output signal from the comparison circuit. The second switching is performed by a signal output from the comparison circuit when a voltage based on the current detected by the current detection circuit reaches a reference voltage. By controlling the element to the off state, the second
9. The lighting device for a rare gas discharge lamp according to claim 3, wherein a peak value of a current flowing through the switching element is substantially constant. 10. The free oscillation of lamp current generated by the effective inductance of the secondary coil side of the output transformer and the effective capacitance of the rare gas discharge lamp when the off-period of the first switching element is turned on. The lighting device for a rare gas discharge lamp according to claim 1 or 2, wherein the lighting device is set within the first one cycle.