JP2008293930A - Electrodeless discharge lamp lighting device and luminaire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: an electrodeless discharge lamp lighting device capable of suppressing increase of noise due to resonance of a coupler while employing a dimming method of lighting an electrodeless discharge lamp with dimming by periodically changing over a lighting period to a non-lighting period; and a luminaire. <P>SOLUTION: The electrodeless discharge lamp lighting device 1 includes: a high-frequency power circuit 4 outputting high-frequency power; the coupler 3 arranged adjacently to the electrodeless discharge lamp 2 and supplied with the high-frequency power from the high-frequency power circuit 4 to cause a high-frequency electromagnetic field to act on a discharge gas of the electrodeless discharge lamp 2; and a dimming control circuit 5 controlling the high-frequency power circuit 4 to alternately change over, at a changeover frequency, a lighting period in which the high-frequency power supplied to the coupler 3 is set to a value allowing the electrodeless discharge lamp 2 to be lit, and a non-lighting period in which the high-frequency power is set to a value without lighting the electrodeless discharge lamp. The dimming control circuit 5 sets the changeover frequency to the high-frequency side relative to the natural frequency of the coupler 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrodeless discharge lamp lighting device and a lighting fixture that employ a dimming method in which an electrodeless discharge lamp is dimmed by periodically repeating a lighting period and a non-lighting period.

  Conventionally, an electrodeless discharge lamp lighting device for lighting an electrodeless discharge lamp having a bulb (airtight container) filled with a discharge gas has been provided. This electrodeless discharge lamp lighting device includes a power coupler (hereinafter referred to as a coupler) that is inserted into a hollow portion that is recessed in a bulb of the electrodeless discharge lamp, and supplies high frequency power to the coupler. Turn on the electrode discharge lamp.

  Below, the structure of this kind of electrodeless discharge lamp lighting device is demonstrated easily with reference to FIG. 2 which shows embodiment of this invention. The coupler 3 of the electrodeless discharge lamp lighting device includes an induction coil 6 that generates a high-frequency electromagnetic field when high-frequency power is supplied to excite a discharge gas, and is formed in a substantially cylindrical shape from a soft magnetic material and is guided to the outer periphery. A core (ferrite core) 7 around which a coil 6 is wound is provided (see, for example, Patent Document 1).

  In addition, as a dimming method for such an electrodeless discharge lamp 2, a lighting period t1 for setting the high frequency power supplied to the induction coil 6 to a size at which the electrodeless discharge lamp 2 is lit as shown in FIG. It is common to perform dimming of the electrodeless discharge lamp 2 by periodically switching between the non-lighting periods t2 set to a size that does not light up and adjusting the ratio of the lighting period t1 in one cycle. (For example, refer to Patent Document 2). However, when dimming (flashing dimming) is performed using this dimming method, it is necessary to apply a high voltage to the induction coil 6 at the time of re-ignition (at the time of transition from the non-lighting period t2 to the lighting period t1). For this reason, the core 7 may be vibrated due to distortion in the core 7 caused by the transient current flowing in the induction coil 6. Here, the switching frequency (the switching frequency between the lighting period t1 and the non-lighting period t2) is usually in the range of several hundred Hz to several kHz (audible range), and as a result, noise is generated by the vibration of the core 7. Is concerned.

Therefore, as means for suppressing noise, the induction coil is adjusted during re-ignition by adjusting the switching frequency so that the non-lighting period t2 during dimming is within a predetermined period during which ions in the electrodeless discharge lamp 2 remain. An invention that eliminates the need to apply a high voltage to 6 has been proposed (see, for example, Patent Document 3). That is, according to the invention described in Patent Document 3, the ions generated in the electrodeless discharge lamp 2 during the lighting period t1 decrease during the non-lighting period t2, but are re-pointed within the predetermined period during which the ions remain. Since the arc is performed, it is not necessary to apply a high voltage at the time of re-ignition, and the transient current that flows through the induction coil 6 at the time of re-ignition is suppressed. As a result, the vibration of the core 7 is suppressed and the noise is reduced. Can do.
Special table 2003-515898 gazette JP 2000-353600 A JP 2006-155961 A

  However, even in the invention described in Patent Document 3, it has been confirmed that the noise increases depending on the size of the coupler 3 (particularly when the coupler 3 is downsized). Here, the natural frequency of the coupler 3 (measurement of the natural frequency of the coupler 3 is performed by vibration analysis when the coupler 3 is hit with an impact hammer). As a result of examining the relationship between fc and the switching frequency fdim, the natural frequency is obtained. Since fc has a higher relationship than the switching frequency fdim (that is, fc> fdim), the inventors relate to the above phenomenon in which the noise level increases due to resonance of the coupler 3 due to the natural frequency of the coupler 3. I got the knowledge that it is. That is, even if the switching frequency fdim itself does not match the natural frequency fc of the coupler 3, if the frequency that is an integral multiple of the switching frequency fdim (that is, the harmonic frequency) matches the natural frequency fc of the coupler 3, the induction coil There is a problem that resonance occurs in the coupler 3 due to the harmonics of the current waveform of the switching frequency flowing through 6, and the vibration of the coupler 3 increases to increase the noise level.

  The present invention has been made in view of the above circumstances, and adopts a dimming method for dimming and lighting an electrodeless discharge lamp by periodically switching between a lighting period and a non-lighting period, and the resonance of the coupler. An object of the present invention is to provide an electrodeless discharge lamp lighting device and a lighting fixture that can suppress an increase in noise caused by the above.

  According to the first aspect of the present invention, a high-frequency power supply circuit that outputs high-frequency power and an electrodeless discharge lamp comprising a bulb in which a discharge gas is enclosed is disposed close to the high-frequency electromagnetic field received from the high-frequency power supply circuit. The switching frequency is used to alternate between a coupler having an induction coil that operates, and a lighting period in which the high-frequency power supplied to the coupler is set to a size that the electrodeless discharge lamp is lit and a non-lighting period that is set to a size that does not light And a dimming control circuit for controlling the high-frequency power supply circuit so that the switching frequency is set to a higher frequency than the natural frequency of the coupler.

  According to this configuration, since the dimming control circuit sets the switching frequency higher than the natural frequency of the coupler, the frequency that is an integral multiple of the switching frequency matches the natural frequency of the coupler. Therefore, the coupler does not resonate due to harmonics of the current waveform of the switching frequency flowing through the induction coil. As a result, an increase in noise due to resonance of the coupler can be suppressed. When the coupler has a plurality of natural frequencies, the switching frequency may be set so as to be higher than at least one natural frequency, so that the switching frequency is higher than any natural frequency. Compared to the configuration set on the low frequency side, the coupler is less likely to resonate, and an increase in noise can be suppressed.

  According to a second aspect of the present invention, in the first aspect of the present invention, the coupler is made of a soft magnetic material and the core around which the induction coil is wound, and is formed in a cylindrical shape and thermally coupled to the core. A heat conductor that dissipates the heat of the heat, and the heat conductor is formed with a slit extending along the axial direction so as to reduce the natural frequency of the coupler. .

  According to this configuration, it is possible to prevent an excessive temperature rise of the core by radiating the heat of the core by the heat conductor. Moreover, since the slit extended in the axial direction is formed in the heat conductor, the spring constant of the heat conductor is smaller and the natural frequency of the coupler is lower than in the configuration without the slit. Therefore, the switching frequency set higher than the natural frequency of the coupler can also be set lower as the natural frequency becomes lower, and as a result, the circuit due to the higher switching frequency. It is possible to provide a highly reliable electrodeless discharge lamp lighting device with reduced component stress.

  According to a third aspect of the invention, there is provided the electrodeless discharge lamp lighting device according to the first or second aspect, and an electrodeless discharge lamp comprising a bulb in which a discharge gas is sealed.

  According to this configuration, it is possible to provide a luminaire that can suppress an increase in noise due to resonance of the coupler of the electrodeless discharge lamp when the electrodeless discharge lamp is dimmed.

  In the present invention, since the switching frequency is set higher than the natural frequency of the coupler, the frequency that is an integral multiple of the switching frequency does not match the natural frequency of the coupler, and therefore the coupler resonates. There is an effect that it is possible to suppress an increase in noise due to the above.

(Embodiment 1)
An electrodeless discharge lamp lighting device (hereinafter abbreviated as a lighting device) 1 according to this embodiment includes a bulb B in which a discharge gas, which is a mixed gas of metal vapor and inert gas, is enclosed, as shown in FIG. A coupler 3 disposed close to the electrodeless discharge lamp 2 is provided, and a high frequency electromagnetic field is applied to the discharge gas in the bulb B from the coupler 3 to turn on the electrodeless discharge lamp 2. In addition, as shown in FIG. 1, a high frequency power supply circuit 4 for supplying high frequency power to the coupler 3, and a dimming control circuit 5 for controlling the output of the high frequency power supply circuit 4 so that the electrodeless discharge lamp 2 is dimmed. It has. As will be described in detail later, the dimming control circuit 5 is set to a lighting period t1 (see FIG. 9) in which the high-frequency power supplied to the coupler 3 is set to a magnitude at which the electrodeless discharge lamp 2 is lit, and a magnitude that is not lit. The electrodeless discharge lamp 2 is dimmed by periodically switching between the non-lighting periods t2 (see FIG. 9) to be set.

  As shown in FIG. 2, the coupler 3 includes a induction coil 6 that generates a high-frequency electromagnetic field by exciting a discharge gas when high-frequency power is supplied, and is formed in a substantially cylindrical shape with the induction coil 6 wound around the outer periphery. The mounted core 7, the substantially cylindrical heat conductor 8 that is thermally connected to the core 7 by being inserted into the internal space of the core 7, and dissipates the heat of the core 7, the core 7 and the induction coil 6, And a coil bobbin 9 interposed therebetween. A winding recess 9a is formed in a portion of the outer peripheral surface of the coil bobbin 9 where the induction coil 6 is wound, and the induction coil 6 is wound, for example, 40 turns in the winding recess 9a.

  The core 7 is formed from a soft magnetic material (for example, Mn—Zn) having good high-frequency magnetic characteristics, and the thermal conductor 8 is formed from a metal material (for example, aluminum, copper, or an alloy thereof) having excellent thermal conductivity. Further, between the core 7 and the heat conductor 8, an elastic resin (for example, silicone rubber) 10 having relatively high heat transfer efficiency is filled. In other words, the core 7 and the heat conductor 8 are bonded and fixed with the elastic resin 10 so that the core 7 and the heat conductor 8 are connected in heat transfer, and the heat of the core is radiated through the heat conductor. By doing so, an excessive temperature rise of the core 7 is prevented. 2, a flange portion 9b having a diameter larger than that of the other portion of the coil bobbin 9 is formed at the lower end portion of the coil bobbin 9, and the heat conductor 8 includes a cylindrical cylinder 8a housed in the coil bobbin 9. 2 has a support base 8b that is tightly fixed to the cylinder 8a so as to surround the lower part of the cylinder 8a in FIG. 2, and a part of the support base 8b protrudes from the lower end surface of the coil bobbin 9 along the lower surface of the flange portion 9b. Has an extended configuration.

  In this embodiment, as a specific example of the electrodeless discharge lamp 2 that is lit by the lighting device 1, mercury and argon gas are enclosed as discharge gas in a substantially incandescent bulb B having a diameter of about 160 mm and a height of 240 mm. In addition, it is considered that the inner surface of the bulb B is coated with a phosphor that converts ultraviolet light into visible light. According to the configuration described above, in the electrodeless discharge lamp 2, when a high frequency electromagnetic field acts on the discharge gas by the induction coil 6, the discharge gas is excited to generate ultraviolet rays, and the phosphor emits light.

  This electrodeless discharge lamp 2 has a hollow portion 2 a that is recessed toward the center of the bulb B in a part of the bulb B. The hollow portion 2a has a cylindrical shape with an inner diameter of 32 mm, and the above-described coupler 3 is disposed close to the electrodeless discharge lamp 2 so as to be inserted into the hollow portion 2a. Here, the flange portion 9b of the coil bobbin 9 and the support base 8b of the heat conductor 8 are arranged outside the cavity portion 2a so that the heat of the core 7 can be radiated to the outside of the cavity portion 2a. A cylindrical exhaust pipe 2b is integrally projected from the bottom of the cavity 2a toward the opening side of the cavity 2a, and the inside of the exhaust pipe 2b communicates with the inside of the valve B. Further, inside the exhaust pipe 2b, an amalgam 2c for controlling the vapor pressure of mercury in the valve B and a pair of cylindrical glass rods 2d for fixing the amalgam 2c sandwich the amalgam 2c between both glass rods 2d. Enclosed in shape. The exhaust pipe 2b is provided with a recess 2e for regulating the position of the amalgam 2c and the glass rod 2d.

  A locking recess 2 f for attaching a base 23 for fixing the coupler 3 is provided in the opening peripheral portion of the hollow portion 2 a in the valve B. The base 23 is formed in a cylindrical shape, and integrally includes a small-diameter portion 23a for fixing the valve B and a large-diameter portion 23b for fixing the coupler 3, and the inner periphery of the small-diameter portion 23a is engaged with the valve B. A locking projection 23c that is locked to the concave portion 2f is provided so as to be engaged with a retaining piece 9c that is provided on the outer peripheral surface of the flange portion 9b of the coil bobbin 9 on the inner peripheral surface of the large-diameter portion 23b. A retaining protrusion 23d that prevents the coupler 3 from coming off from 2a is provided. As a result, the coupler 3 of the lighting device 1 can be coupled to the bulb B of the electrodeless discharge lamp 2.

  On the other hand, the high-frequency power supply circuit 4 is connected between the both ends of the switching element Q2 and a DC power supply part E1 that supplies a DC voltage, a pair of switching elements Q1 and Q2 connected in series between the output terminals of the DC power supply part E1. A series circuit of the inductor Ls and the capacitor Cp, and a capacitor Cs connected between both ends of the capacitor Cp. An induction coil 6 is connected between a load side terminal of the capacitor Cs and a circuit ground side terminal of the capacitor Cp. Therefore, if both switching elements Q1 and Q2 are alternately turned on and off at a high frequency, a high-frequency current flows through the induction coil 6.

  The dimming control circuit 5 has a built-in transmitter, and outputs a rectangular wave switching signal to the control terminals of the switching elements Q1 and Q2, thereby turning on and off a driver 11 that alternately turns on the switching elements Q1 and Q2 at a predetermined switching frequency. It has a main circuit unit 12 and a control unit 13 which will be described later.

The main circuit unit 12 is connected between two input terminals of the driver 11 and circuit ground, and serves as a time constant circuit that determines the oscillation frequency (that is, switching frequency) of the driver 11. And a capacitor R1 connected between the other input terminal and circuit ground, and a series circuit of a resistor R2 connected in parallel with the resistor R1 and a frequency changeover switch Q3. ing. Here, assuming that the resistance value of the resistor R1 is r1, the resistance value of the resistor R2 is r2, and the capacitance value of the capacitor C1 is c1, the switching frequency is as follows when the frequency changeover switch Q3 is off.
f0 = α / (r1 × c1)
On the other hand, when the frequency changeover switch Q3 is on,
f1 = α / [{1 / (1 / r1 + 1 / r2)} × c1]
(Where α is a constant). That is, when the frequency changeover switch Q3 is in the on state, the switching frequency is higher than that in the off state (that is, f0 <f1).

  The driver 11 has two output terminals, and the respective output terminals are connected to the control terminals of the switching elements Q1 and Q2. Switching signals having opposite phases to each other are output from these two output terminals, whereby the switching elements Q1 and Q2 of the high-frequency power supply circuit 4 are alternately turned on every half cycle of the switching signal by the switching signal output from the driver 11. Will be.

The control unit 13 controls the frequency switch Q3 so that the frequency switch Q3 is alternately turned on and off periodically. Hereinafter, the on / off switching frequency of the frequency switching switch Q3 is referred to as a switching frequency. The control unit 13 receives an external dimming signal (a signal representing a duty ratio corresponding to the dimming level), and outputs an oscillator 14 that outputs a control signal of the switching frequency to the control terminal of the frequency switch Q3. A time constant circuit 15 that is connected between two input terminals of the oscillator 14 and circuit ground and determines the oscillation frequency (that is, switching frequency) of the oscillator 14 is provided. The time constant circuit 15 includes a capacitor C2 connected between one input terminal and the circuit ground, and a resistor R3 connected between the other input terminal and the circuit ground. Here, if the resistance value of the resistor R3 is r3 and the capacitance value of the capacitor C2 is c2, the switching frequency fdim of the control signal output from the oscillator 14 in response to the dimming signal is
fdim = β / (r3 × c2)
(Where β is a constant). Therefore, the switching frequency fdim can be arbitrarily set by the resistance value r3 of the resistor R3 and the capacitance value c2 of the capacitor C2.

  Incidentally, the natural frequency fc of the coupler 3 is measured by vibration analysis when the coupler 3 is hit with an impact hammer. Specifically, the frequency spectrum obtained from the output of the acceleration sensor when an acceleration sensor is attached to a part of the cylinder 8a with members other than the cylinder 8a removed from the coupler 3 and vibration is applied to the cylinder 8a with an impact hammer. The frequency that becomes the maximum in FIG. That is, as shown in FIG. 3, the vibration frequency at which the noise level becomes maximum when the coupler 3 is vibrated is defined as the natural frequency fc. A portion of the cylinder 8a that is hit with an impact hammer when measuring the natural frequency fc of the coupler 3 is a portion to which the core 7 is attached. Note that the upper limit value of the natural frequency fc is 6 kHz, and the frequency that becomes the maximum in the range of 6 kHz or less in the frequency spectrum is the natural frequency fc.

  In this embodiment, as shown in FIG. 4, the resistance value r3 of the resistor R3 and the capacitance value c2 of the capacitor C2 are set so that the switching frequency fdim is set higher than the natural frequency fc of the coupler 3. It is set. In short, the switching frequency fdim is set so that the switching frequency fdim is higher than the natural frequency fc of the coupler 3 (that is, fc <fdim).

  According to the lighting device 1 having the configuration described above, when the electrodeless discharge lamp 2 is fully lit (100% dimming), the dimming control circuit 5 turns on the pair of switching elements Q1 and Q2 alternately by switching signals. Thus, a high frequency voltage of several tens of kHz to several MHz is applied to the induction coil 6 through the inductor Ls, the capacitor Cp, and the capacitor Cs. At this time, the frequency changeover switch Q3 of the dimming control circuit 5 is in the off state, and the switching frequency for turning on and off the switching elements Q1 and Q2 is set to f0. When a high frequency voltage of several tens of kHz to several MHz is applied to the induction coil 6, the discharge gas of the electrodeless discharge lamp 2 is excited by the high frequency electromagnetic field to generate a discharge and the electrodeless discharge lamp 2 is lit. Note that the frequency of the high frequency voltage is in the range of several tens of kHz to several MHz because the frequency of the high frequency voltage is less than several tens of kHz and the number of turns of the induction coil 6 or the volume of the core 7 around which the induction coil 6 is wound. When the frequency of the high frequency voltage exceeds several MHz, the loss of the high frequency power supply circuit 4 increases and the loss of the induction coil 6 also increases due to the skin effect. Because there is.

  When the electrodeless discharge lamp 2 is dimmed, the control unit 13 that has received the dimming signal turns on / off the frequency switch Q3 at a predetermined switching frequency fdim, and switches the switching frequency at the cycle. Here, the switching frequency f0 when the frequency changeover switch Q3 is OFF is set to be close to the resonance frequency of the high-frequency power supply circuit 4 determined by the inductor Ls, the capacitor Cp, and the capacitor Cs. When the frequency changeover switch Q3 is off, the high frequency power supplied to the induction coil 6 is relatively large, and the electrodeless discharge lamp 2 is turned on. On the other hand, the switching frequency f1 when the frequency changeover switch Q3 is on is higher than the switching frequency f0, and is away from the resonance frequency of the high-frequency power supply circuit 4. Therefore, when the frequency changeover switch Q3 is turned on, the high-frequency power supplied to the induction coil 6 decreases, and the electrodeless discharge lamp 2 enters a non-lighting state. That is, the dimming control circuit 5 sets the high frequency power supplied to the coupler 3 to a lighting period (that is, a period of the switching frequency f0) t1 that is set to a magnitude that the electrodeless discharge lamp 2 is lit, and a magnitude that does not light. The high frequency power supply circuit 4 is controlled so that the non-lighting period (that is, the period of the switching frequency f1) t2 is alternately switched at the switching frequency fdim.

  The dimming level of the electrodeless discharge lamp 2 is adjusted by adjusting the ratio of the lighting period t1 in one cycle (that is, the duty ratio of the control signal). The ratio employs a configuration determined by the dimming signal, and therefore the dimming level is set by the dimming signal.

  By the way, in this embodiment, since the switching frequency fdim is set higher than the natural frequency fc of the coupler 3 as described above, a frequency that is an integral multiple of the switching frequency fdim (that is, a harmonic frequency) is set. It does not coincide with the natural frequency fc of the coupler 3, and therefore the coupler 3 does not resonate due to harmonics of the current waveform of the switching frequency fdim flowing through the induction coil 6. As a result, an increase in noise due to resonance of the coupler 3 can be suppressed.

  Further, the natural frequency fc of the coupler 3 is not limited to one and may be plural. For example, as shown in FIG. 5, when the coupler 3 has two natural frequencies fc1 and fc2, the switching frequency fdim may be set higher than at least one natural frequency fc1 (that is, fc1 <fdim). In the example of FIG. 5, the switching frequency fdim is set lower than the other natural frequency fc2 (that is, fc1 <fdim <fc2), but for one natural frequency fc1 of the coupler 3, an integer of the switching frequency fdim. The double frequency (that is, the harmonic frequency) does not match, and therefore, the switching frequency flowing through the induction coil 6 as compared with the configuration in which the switching frequency fdim is set lower than any of the natural frequencies fc1 and fc2. The harmonics of the current waveform of fdim make it difficult for the coupler 3 to resonate, and an increase in noise due to the resonance of the coupler 3 can be suppressed.

  Furthermore, as shown in FIG. 6, the switching frequency fdim may be set so that the switching frequency fdim is higher than any of the natural frequencies fc1 and fc2 of the coupler 3 (that is, fc1 <fc2 <fdim). In this case, the frequency that is an integral multiple of the switching frequency fdim (that is, the harmonic frequency) does not coincide with any of the natural frequencies fc1 and fc2 of the coupler 3, and therefore the switching frequency that flows through the induction coil 6 The coupler 3 does not resonate due to harmonics of the current waveform of fdim. As a result, an increase in noise can be suppressed more reliably than when the switching frequency fdim is set lower than the natural frequency fc2.

  The lighting device 1 of this embodiment comprises the lighting fixture A by being accommodated with the electrodeless discharge lamp 2 in one housing | casing 17, as shown, for example in FIG. A housing 17 shown in FIG. 7 includes a die-cast body 18 formed in a box shape with an opening on the lower surface, and a transparent acrylic cover 19 that closes the lower surface of the body 18, and seals the internal space. By doing so, it is waterproof. Therefore, the luminaire A shown in FIG. 7 is used, for example, as a security light outdoors. Here, the lighting device 1 is divided into a circuit block 16 having a configuration other than the coupler 3 and the coupler 3, and the circuit block 16 and the coupler 3 are connected by a cable 20.

  The noise level shown in FIGS. 3 to 6 may be a value (unit: “dBA”) subjected to A characteristic frequency weighting.

(Embodiment 2)
The lighting device 1 of the present embodiment is different from the lighting device 1 of the first embodiment in that a slit 8c is formed in a cylinder 8a of a heat conductor 8 that is one of the components of the coupler 3.

  As shown in FIG. 8, the slit 8c extends along the axial direction of the cylindrical cylinder 8a, and faces the diametrical direction of the cylinder 8a so that one end of the cylinder 8a in the axial direction has a bifurcated shape. A pair is provided.

  According to the configuration of the present embodiment, the rigidity of the cylinder 8a is reduced and the spring constant is reduced, and the natural frequency fc of the coupler 3 is reduced, compared to a configuration in which the cylinder 8a does not have the slit 8c. Therefore, the switching frequency fdim set higher than the natural frequency of the coupler 3 can also be set lower as the natural frequency fc becomes lower. As a result, the switching frequency fdim becomes a high frequency. As a result, the stress of the circuit components can be reduced, and the lighting device 1 with high reliability can be provided.

  Hereinafter, the configuration of the present embodiment will be described in more detail.

  The length dimension of the slit 8c is set to be larger than the length dimension of the core 7, which has the effect that the natural frequency fc of the coupler 3 can be made as low as possible. The core 7 is formed in a substantially cylindrical shape as a whole by combining a pair of semi-cylindrical split cores 7a so that the opening surfaces face each other, and the slit 8c is a cylinder as shown in FIG. 8a is provided at a position corresponding to the joint of the split core 7a. Accordingly, each divided core 7a is attached to each branch piece 8d which is divided into two by the slit 8c in the cylinder 8a, and as a result, the natural frequency fc of the coupler 3 becomes lower. Further, the core 7 is not disposed within the length of the cylinder 8a, but the cylinder 7a is protruded from one end face in the longitudinal direction of the cylinder 8a as shown in FIG. 8B. On the other hand, the length of the coupler 3 is increased by the protrusion of the core 7 by attaching the core 7 so as to be shifted in the longitudinal direction of the coupler 3. As a result, the overall length of the coupler 3 is increased, and the natural frequency fc of the coupler 3 can be further reduced.

  Other configurations and functions are the same as those of the first embodiment.

It is a schematic circuit diagram which shows the structure of Embodiment 1 of this invention. It is a schematic sectional drawing which shows a structure same as the above. It is explanatory drawing which shows the noise level of a coupler same as the above. It is explanatory drawing which shows the noise level and natural frequency of a coupler same as the above. It is explanatory drawing which shows the noise level and natural frequency of another coupler same as the above. It is explanatory drawing which shows the noise level and natural frequency of another coupler same as the above. It is a schematic perspective view which shows a lighting fixture same as the above. The structure of Embodiment 2 of this invention is shown, (a) is a schematic top view of the principal part, (b) is a schematic sectional drawing of the principal part. It is explanatory drawing which shows operation | movement of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrodeless discharge lamp lighting device 2 Electrodeless discharge lamp 3 Coupler 4 High frequency power supply circuit 5 Dimming control circuit 6 Inductive coil 7 Core 8 Thermal conductor 8c Slit A Lighting fixture B Valve fc Natural frequency fdim Switching frequency t1 Lighting period t2 Non-lighting period

Claims (3)

  A high-frequency power supply circuit that outputs high-frequency power and an induction coil that is placed close to an electrodeless discharge lamp composed of a bulb filled with discharge gas and receives high-frequency power from the high-frequency power supply circuit to cause the high-frequency electromagnetic field to act on the discharge gas. High frequency power supply circuit so that the switching frequency is alternately switched between a lighting period in which the electrodeless discharge lamp is lit and a non-lighting period in which the high frequency power supplied to the coupler is set to a magnitude that does not light. And a dimming control circuit for controlling the switch, wherein the dimming control circuit sets a switching frequency higher than the natural frequency of the coupler.   The coupler includes a core made of a soft magnetic material and on which the induction coil is wound, and a heat conductor that is formed in a cylindrical shape and is thermally coupled to the core to dissipate the heat of the core. 2. The electrodeless discharge lamp lighting device according to claim 1, wherein the heat conductor is formed with a slit extending along the axial direction so as to reduce the natural frequency of the coupler.   3. An illuminating apparatus comprising: the electrodeless discharge lamp lighting device according to claim 1; and an electrodeless discharge lamp including a bulb in which discharge gas is sealed.

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