JP2005071828A - Electrodeless discharge lamp lighting device and illumination device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrodeless discharge lamp lighting device and an illumination device wherein noise can be reduced to the smallest level to the utmost during a lighting period under time sharing light control. <P>SOLUTION: When the electrodeless discharge lamp starts lighting (reaches a state of arc discharge), and a coil voltage Vcoil drops from a voltage Vi, while a conventional converter circuit would raise an action frequency finv of an inverter circuit from a frequency f1 to the frequency f2 momentarily by raising an output voltage Vf from the voltage V1 to the voltage V2 momentarily, in this lighting device. But, the action frequency finv of the inverter circuit is maintained at the frequency f1 by permitting the converter circuit to maintain the output voltage Vf constant at the voltage V1. By this, the noise emitted from the electrodeless discharge lamp and a discharge lamp lighting circuit can be limited mainly to the noise having a component of the frequency f1 only, and the occurrence of the noise having the component of the frequency f2 can be prevented, and furthermore. Further, no switching from the frequency f1 to the frequency f2 is carried out, and hereby the occurrence of the noise due to the switching is also made to be prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrodeless discharge lamp lighting device and an illumination device for lighting an electrodeless discharge lamp that outputs light by applying a high frequency electromagnetic field to a discharge gas sealed in a bulb.

  Conventionally, a discharge gas sealed in a bulb and an induction coil to which a high-frequency voltage is supplied are provided, and the discharge gas is ionized and excited by an electromagnetic field generated in the induction coil by the supply of the high-frequency voltage. In addition, an electrodeless discharge lamp using light generated by excitation as a light source is known (for example, Patent Document 1 below).

  The discharge lamp lighting circuit for controlling the lighting operation of this electrodeless discharge lamp is, for example, a DC power supply circuit that converts an AC voltage output from an AC power supply into a DC voltage, and an output of the DC power supply circuit is converted into a high-frequency voltage, The inverter circuit is configured to supply this high-frequency voltage to the induction coil of the electrodeless discharge lamp, and a resonance circuit disposed between the induction coil and the inverter circuit.

  As one method of dimming (adjusting the amount of emitted light) of the electrodeless discharge lamp by the discharge lamp lighting circuit having such a configuration, there is a method as shown in FIG. FIG. 12 is a diagram illustrating waveforms of the operating frequency finv and the coil voltage Vcoil of the inverter circuit 13. In the waveform of the coil voltage Vcoil in FIG. 12, the portion drawn in the black and white stripe pattern indicates the waveform of the high frequency voltage, and the line connecting the peaks of the waveform of the high frequency voltage indicates the change in amplitude.

  As shown in FIG. 12, the period T1 during which the high frequency voltage is applied to the induction coil and the period T2 during which the high frequency voltage is not applied are alternately provided, and the high frequency voltage (hereinafter referred to as coil voltage) applied to the induction coil is periodically Thus, the electrodeless discharge lamp repeats a lighting operation (when a high coil voltage is applied) and a light-off operation (when a low coil voltage is applied). Thus, the electrodeless discharge lamp has a light emission amount corresponding to the ratio between the lighting period and the extinguishing period.

  Further, the characteristics of the coil voltage Vcoil with respect to the operating frequency finv of the inverter circuit include the lighting period (time T = t2 to t3) in which the discharge gas of the electrodeless discharge lamp is stably in an arc-like discharge state, and the starting voltage applied to the induction coil. It becomes different in the starting period (time T = t1 to t2) from when Vi is applied until the arc discharge state is stabilized (see FIG. 3). In the starting period in which a relatively high voltage (starting voltage) Vi is required at the beginning, the operating frequency finv of the inverter circuit is set to the frequency f1, and the coil voltage Vcoil is set to the voltage Vi (voltage corresponding to the point a in FIG. 3). And In general, the starting voltage Vi is set to a value larger than the minimum voltage Vst (see FIG. 3) necessary for lighting the electrodeless discharge lamp. When the electrodeless discharge lamp is turned on, the coil voltage Vcoil decreases from the voltage Vi to the voltage Vs (voltage corresponding to the point b in FIG. 3). At this time, if the operating frequency finv of the inverter circuit is maintained at the frequency f1 even after the electrodeless discharge lamp is turned on, the light emission quantity of the electrodeless discharge lamp may not be a desired value. Then, the operating frequency finv of the inverter circuit is immediately switched from the frequency f1 to the frequency f2 (f2> f1), and the coil voltage Vcoil is set to the voltage Va (voltage corresponding to the point c in FIG. 3). Thereafter, the coil voltage Vcoil is maintained at a constant value Va by maintaining the operating frequency finv of the inverter circuit at the frequency f2 until the timing (time T = t4) at which the electrodeless discharge lamp is to be extinguished is reached.

  The dimming method for dimming the electrodeless discharge lamp by changing the time ratio between the lighting period and the extinguishing period is called the time-division dimming control method, and it boosts and lowers the output voltage of the DC power supply circuit. Compared to the DC voltage dimming control method for dimming electrodeless discharge lamps and the frequency dimming control method for dimming electrodeless discharge lamps by controlling the frequency of the switching element of the inverter circuit It has characteristics.

  That is, in the range of dimming of the electrodeless discharge lamp, in particular, when reducing the amount of light emitted by the electrodeless discharge lamp, the lower the dimming lower limit, the higher the performance as the electrodeless discharge lamp is. In order to widen the range, it is desired that the lower limit of dimming can be set lower. When the DC voltage dimming control method is adopted in response to such demands, if the output voltage of the DC power supply circuit is lowered in order to perform dimming of the electrodeless discharge lamp, the input current starts from around the peak voltage of the AC power supply. Therefore, it is difficult to set the lower limit of dimming low, and the dimming range may be narrowed. In addition, as described above, it is necessary to increase the coil voltage at the start in consideration of the startability of the electrodeless discharge lamp, but in order to generate the high coil voltage, if the resonance sharpness Q of the resonance circuit is set high, When the frequency dimming control method is adopted, the voltage at both ends of the induction coil changes greatly even with minute changes in frequency, and high accuracy is required when setting the lower limit of dimming to a low level. Frequency adjustment technology is required. In this way, it is very difficult to accurately adjust the frequency in consideration of variations in characteristics of various electronic components constituting the electrodeless discharge lamp and the discharge lamp lighting circuit.

On the other hand, when the above-described time-division dimming control method is adopted, the electrodeless discharge lamps are alternately turned on and off, and the dimming is achieved by reducing the average amount of light emitted from the electrodeless discharge lamp. Therefore, the above-mentioned problem that occurs in the case of the DC voltage dimming control method and the frequency dimming control method does not occur, and the lower limit of dimming can be set low.
JP 2002-324696 A

  However, taking into account that if the operating frequency of the inverter circuit is maintained at the starting frequency f1 even after the electrodeless discharge lamp is turned on, the amount of light emitted from the electrodeless discharge lamp may not be reduced to a desired value. Thus, when the operating frequency of the inverter circuit is instantaneously increased from the frequency f1 to the frequency f2, the coil voltage Vcoil is lowered, and when the amount of light emitted from the electrodeless discharge lamp is reduced, the light is emitted from the electrodeless discharge lamp or the like. The noise includes two types of noise, noise having a frequency f1 component and noise having a frequency f2 component. Further, when switching from the frequency f1 to the frequency f2, noise due to the switching is also generated.

  The present invention has been made in view of such circumstances, and provides an electrodeless discharge lamp lighting device and a lighting device capable of reducing noise as much as possible during a lighting period during time-division dimming control. The purpose is to do.

  In order to achieve the above object, an electrodeless discharge lamp lighting device according to the first means of the present invention is an electrodeless discharge lamp lighting device that outputs a high frequency voltage to be applied to an induction coil of an electrodeless discharge lamp. A DC power source, a power conversion circuit connected to the DC power source and converting a DC voltage of the DC power source into a high frequency voltage by an on / off operation of a switching element, and an induction coil of an electrodeless discharge lamp connected to the power conversion circuit A resonance circuit that generates a high-frequency voltage applied to the power supply and a power control that causes the electrodeless discharge lamp to periodically turn on and off by periodically turning on and off the high-frequency voltage applied to the induction coil In the electrodeless discharge lamp lighting device comprising a circuit, the power conversion circuit calculates a frequency of a high-frequency voltage applied to the induction coil during a lighting period of the electrodeless discharge lamp. The constant frequency of the on-off operation by the switching element that generates a high frequency voltage of the voltage value required to initiate the lighting of the electrodeless discharge lamp.

  In the above electrodeless discharge lamp lighting device, the DC power supply adjusts the high frequency voltage applied to the induction coil by reducing the DC voltage during the lighting period of the electrodeless discharge lamp.

  Further, in the electrodeless discharge lamp lighting device described above, the power conversion circuit is configured such that the high-frequency voltage applied to the induction coil by reducing a duty period of the on / off operation by the switching element during the lighting period of the electrodeless discharge lamp. Adjust.

  An illumination device according to a first means of the present invention includes a discharge gas containing at least mercury and a rare gas, a bulb for sealing the discharge gas, a high-frequency power circuit for generating a high-frequency voltage, and a cross section provided in the bulb. An induction coil that is disposed in a concave cavity and supplies a high-frequency electromagnetic field to the discharge gas by a high-frequency voltage supplied from the high-frequency power circuit, and a cylinder made of a magnetic material and wound around the induction coil 5. A lighting device comprising a core having a shape and a member made of a thermally conductive material and in contact with the core inside the core, wherein the high-frequency power supply circuit includes an electrodeless discharge device according to claim 1. It is an electric lamp lighting device.

  According to the present invention, the power conversion circuit converts the frequency of the high-frequency voltage applied to the induction coil during the lighting period of the electrodeless discharge lamp to the high-frequency voltage of a voltage value necessary to start lighting of the electrodeless discharge lamp. Since the frequency of the on / off operation by the switching element to be generated is made constant, it is possible to prevent the occurrence of noise having a component of the frequency f2 in the related art and the frequency is not switched. Generation | occurrence | production can also be prevented and, thereby, noise can be reduced compared with the past.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of a lighting device according to the invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of a lighting device. As shown in FIG. 1, the lighting device 1 includes an electrodeless discharge lamp 2 and a discharge lamp lighting circuit 3 that controls the lighting operation of the electrodeless discharge lamp 2.

  FIG. 2 is a cross-sectional view of the electrodeless discharge lamp 2. As shown in FIG. 2, the electrodeless discharge lamp 2 includes a bulb 4, an induction coil 5, a core 6, a heat conductor 7, and a base 8.

  The bulb 4 is a member formed of a light-transmitting material such as quartz glass and having a substantially spherical peripheral surface and a hollow portion 9 having a concave cross section inside. Inside the bulb 4, a discharge gas containing at least a metal vapor (for example, mercury vapor) and a rare gas is enclosed. A fluorescent material 10 and a protective film 11 are applied to the inner wall of the bulb 4.

  The phosphor 10 converts ultraviolet rays emitted from mercury into visible light, and is composed of calcium halophosphate, red phosphor (Y, Gd) BO3: Eu, green phosphor CaPO4, and blue phosphor. Some material such as BaMgAll4O23: Eu is used. The protective film 11 is for suppressing the reaction between mercury vapor and quartz glass (the material of the bulb 4) to improve the luminous flux maintenance factor of the bulb 4, and is made of alumina (Al2O3), silica (SiO2), titania. Fine particles such as (TiO2), ceria (CeO2), yttria (Y2O3), and magnesia (MgO) are used. The protective film 11 is a thin film compared to the phosphor 10 in order to improve the transmittance of the bulb 4.

  The induction coil 5 is formed by winding a strip made of copper or a copper alloy a predetermined number of times. The induction coil 5 has a wound portion fitted on the core 6, and an end thereof is connected to an output terminal of the discharge lamp lighting circuit 3 (resonance circuit 14 described later). A high frequency electromagnetic field is oscillated at a predetermined frequency (for example, 13.56 kHz) by the high frequency voltage supplied from, and the high frequency electromagnetic field is applied to the discharge gas sealed inside the bulb 4. Note that the frequency of the high frequency electromagnetic field applied to the discharge gas is not limited to 13.56 MHz, and any other frequency may be used as long as the frequency is about 2.6 MHz to 15 MHz that can reduce the adverse effect of radiation noise on other electrical devices.

  Here, the principle of light emission of the electrodeless discharge lamp 2 will be described. When a high-frequency electromagnetic field is generated around the induction coil 5 by the supply of a high-frequency voltage from the discharge lamp lighting circuit 3, the electrons in the bulb 4 are accelerated by this high-frequency electromagnetic field and collide with the atoms of the discharge gas. The gas is ionized and new electrons are generated. The generated electrons receive energy by the high-frequency electromagnetic field and collide with the atoms of the discharge gas to give energy. As a result of ionization or excitation of energized atoms, plasma is generated and light is emitted when the excited atoms return to the ground state. The electrodeless discharge lamp 2 uses this light as a light source.

  The core 6 is a member formed in a cylindrical shape, and the other end is fixedly erected on the base 8 so that one end faces the inside of the hollow portion 9. The core 6 is made of a material such as nickel zinc (NiZn) phyllite, which is a soft magnetic material having a magnetic permeability of about 150, but any material containing a soft magnetic metal such as manganese zinc (Mn—Zn) ferrite can be used. It may be anything. A soft magnetic metal alone may be used as the material of the core 6. The soft magnetic material has a coercive force Hc in the bulk state of about 100 e or less.

  The heat conductor 7 is a long member having a substantially convex cross section having cylindrical portions having different diameters. The heat conductor 7 is supported by the base 8 at the lower end of the large-diameter cylindrical portion, while the peripheral surface of the small-diameter cylindrical portion contacts the inner peripheral surface of the core 6.

  The base 8 is a bottomed substantially cylindrical member formed by aluminum die casting and having an opening on the upper surface.

  Returning to FIG. 1, the discharge lamp lighting circuit 3 includes an AC power supply AC, a DC power supply circuit 12, an inverter circuit 13, a resonance circuit 14, a drive circuit 15, and a conversion circuit 16.

  The AC power source AC is a commercial AC power source, and the voltage thereof is, for example, 100V, 200V, or 240V.

The DC power supply circuit 12 includes a rectifier circuit 17 and a boost chopper circuit 18, and converts an AC voltage supplied from an AC power supply AC into a predetermined DC voltage V _DC .

  The rectifier circuit 17 is composed of, for example, a diode bridge or the like, and rectifies an AC voltage output from the AC power supply AC into a pulsed DC voltage and outputs it. When the voltage of the AC power supply AC is 100 V, for example, a voltage doubler rectifier circuit may be used instead of the diode bridge. When the voltage doubler rectifier circuit is used, the voltage of the AC power supply AC can be regarded as substantially equal to 200 V, and the current flowing in the circuit connected after the voltage doubler rectifier circuit is compared with the case where the diode bridge is used. Therefore, the efficiency of the discharge lamp lighting circuit 3 can be increased.

The step-up chopper circuit 18 includes an inductor L1, a switching element Q1, a control circuit 19, a capacitor C1, and a diode D. The inductor L1 is connected to the output terminal of the rectifier circuit 17 and the drain terminal of the switching element Q1, and stores energy when the switching element Q1 is on, and releases the stored energy when the switching element Q1 is off. The switching element Q1 is an element made of, for example, an FET (Field-Effect-Transistor), and has a drain terminal connected to the inductor L1 and a source terminal connected to the output terminal of the rectifier circuit 17. The output of the control circuit 19 is connected to the gate terminal of the switching element Q1, and controls the on / off operation of the switching element. The capacitor C1 is connected to the cathode of the diode D and the circuit ground. The capacitor C1 is charged when the switching element Q1 is off, and is discharged when the switching element Q1 is on, thereby converting the output voltage of the inductor L1 to the DC voltage V _DC. For example, an electrolytic capacitor is used. The diode D has an anode connected to the inductor L1 and a cathode connected to the capacitor C1, and prevents discharge current from the capacitor C1 from flowing to the inductor L1 side (reverse flow).

In the step-up chopper circuit 18 having such a configuration, the DC voltage output from the rectifier circuit 17 is constantly applied to both poles of the capacitor C1. Further, while the switching element Q1 is on, the current supplied from the rectifier circuit 17 flows through the inductor L1 and the switching element Q1, and energy corresponding to the current value is stored in the inductor L1. When the switching element Q1 is turned off, the energy stored in the inductor L1 is given to the capacitor C1. As a result, the voltage due to the energy given by the inductor L1 is applied to both poles of the capacitor C1 so as to be superimposed on the direct current voltage of the rectifier circuit 17, whereby the pulsed direct current output by the rectifier circuit 17 is applied. A DC voltage V _DC whose voltage is boosted is generated.

  In this embodiment, the step-up chopper circuit is used, but a step-down chopper circuit may be used. In short, any circuit configuration may be used as long as a certain DC voltage is converted into another DC voltage and output. Although not shown, a step-down chopper circuit may be further connected to the subsequent stage of the step-up chopper circuit 18, and a direct-current power supply circuit may be configured by the AC power supply AC, the rectifier circuit 17, the step-up chopper circuit 18, and the step-down chopper circuit. When a step-down chopper circuit is connected to the subsequent stage of the step-up chopper circuit 18, for example, a plurality of electrodeless discharge lamps having AC power sources AC of 100V to 242V and different rated power consumptions are turned on by one discharge lamp. This can be handled by a circuit. In other words, the step-up chopper circuit 18 keeps the multi-power supply constant in DC voltage, and the step-down chopper circuit adjusts the power supplied to the electrodeless discharge lamp. An electric lamp lighting circuit can be used.

  The inverter circuit 13 is configured to include a series circuit of a switching element Q2 and a switching element Q3 made of, for example, a field effect transistor, and the switching element Q2 has a drain terminal connected to one electrode (anode) of the capacitor C1. The gate terminal is connected to the Hout terminal of the drive circuit 15 to be described later and the source terminal is connected to the H-GND terminal of the drive circuit 15, while the switching element Q3 has the drain terminal driven to the H-GND terminal and the gate terminal driven. The source terminal is connected to the Lout terminal of the circuit 15 and the other electrode (cathode) of the capacitor C1 of the drive circuit 15. Since the field effect transistor has a diode built in parallel between the source terminal and the drain so that the drain terminal is connected to the cathode of the built-in diode, there is no need to separately attach a diode. . Instead of a field effect transistor, a combination of a transistor and a diode connected in antiparallel to the transistor may be used. In this embodiment, a so-called half-bridge type inverter circuit is used, but a full-bridge type or push-pull type may be used.

The inverter circuit 13 converts the output voltage _VDC of the boost chopper circuit 18 from a high frequency voltage of several tens of kHz to several hundreds of MHz by alternately turning on and off the switching elements Q2 and Q3 at a frequency of several tens of kHz to several hundreds of MHz. Then, by supplying this high frequency voltage to the induction coil 5, a high frequency electromagnetic field is generated in the induction coil 5 and the high frequency voltage is supplied to the electrodeless discharge lamp 2. The inverter circuit 13 constitutes a power conversion circuit in the claims.

  The resonance circuit 14 includes a series resonance circuit in which an inductor Ls and a capacitor Cp are connected in series. The high frequency voltage output from the inverter circuit 13 uses several kV to several tens using the resonance characteristics. A high voltage of kV is generated, and this high voltage is applied to the induction coil 5 to light the electrodeless discharge lamp 2. The resonance circuit 14 includes a capacitor Cs connected in parallel with the capacitor Cp with respect to the inductor Ls. The impedance between the inverter circuit 13 and the induction coil 5 is matched by the capacitor Cs, and a high frequency from the inverter circuit 13 is obtained. It also functions as an impedance matching that efficiently supplies power to the induction coil 5.

  Here, the voltage Vcoil applied to the induction coil 5 with respect to the frequency of the high-frequency voltage supplied from the inverter circuit 13 (frequency of the high-frequency electromagnetic field generated in the induction coil 5, hereinafter referred to as operating frequency) finv (hereinafter referred to as coil voltage Vcoil). ) Will be described with reference to the resonance curve shown in FIG.

  As shown in FIG. 3, the characteristic of the coil voltage Vcoil with respect to the operating frequency finv of the inverter circuit 13 is that a certain amount or more of plasma is rapidly generated in the valve 4 after the application of the high frequency voltage to the induction coil 5 is started. The starting period until the arc-like discharge state is reached differs from the lighting period for maintaining the arc-like discharge state.

That is, the resonance curve L1 in the starting period, the coil voltage Vcoil when the switching frequency finv coincides with the resonance frequency f _Q where the impedance of the resonant circuit 14 is minimized becomes theoretically infinite, as the frequency finv leaves the frequency fp It goes down. On the other hand, since the impedance of the discharge gas is smaller in the lighting period than in the starting period, the resonance curve L2 in the lighting period generally has a lower coil voltage Vcoil than the resonance curve L1 in the starting period. , coil voltage Vcoil is maximized at the resonance frequency f _Q, switching frequency finv is gradually decreased with distance from the frequency fp.

  In this embodiment, the electrodeless discharge lamp 2 is turned on and off alternately for a plurality of times in a very short time, and the amount of light emitted from the electrodeless discharge lamp 2 is determined by the ratio between the lighting time and the turn-off time. Time division dimming method is adopted. That is, the amount of light emitted from the electrodeless discharge lamp 2 increases as the lighting time ratio increases. As will be described later, the ratio between the lighting time and the light-off time is determined by the duty of a PWM signal (dimming signal) input to the conversion circuit 16 described later.

  In order to shift the electrodeless discharge lamp 2 from the lighting state to the extinguishing state, it is necessary to set the voltage applied to the induction coil 5 to a voltage equal to or lower than a predetermined threshold Voff (hereinafter referred to as the extinguishing voltage Voff). In order to perform such control of the coil voltage Vcoil, in the present embodiment, the coil voltage Vcoil is set to 0 by setting the operating frequency finv of the inverter circuit 13 to 0 as shown in FIG.

  In order to change the discharge gas inside the bulb 4 from the extinguished state to the arc-like discharge state, it is necessary to set the coil voltage Vcoil when starting to apply the voltage to the induction coil 5 to a predetermined threshold value Vst or more. . In order to perform such control of the coil voltage Vcoil, as shown in FIG. 3, by setting the operating frequency finv of the inverter circuit 13 when starting application of voltage to the induction coil 5, for example, to the frequency f1, the coil voltage Vcoil is set to a voltage Vi equal to or higher than the threshold value Vst (point a). When the electrodeless discharge lamp 2 is turned on (the discharge gas is in an arc-like discharge state), the coil voltage Vcoil changes to the characteristic indicated by the resonance curve L2, and the coil voltage Vcoil becomes a voltage corresponding to the point b. descend.

Note that in the resonance characteristics shown in FIG. 3, by utilizing the resonance frequency f _Q right region A of the straight line X passing through, namely the slow area A phase is delayed of the current flowing through the induction coil 5 from the phase of the coil voltage Vcoil Te, perform control of the coil voltage Vcoil, when performing the control of the coil voltage Vcoil by utilizing the leading phase region B in the left of the straight line X passing through the resonance frequency f _Q, the switching element Q2, Q3 are simultaneously turned on This is because a very large current may flow through the induction coil 5 due to the occurrence of the timing.

  In addition to the above configuration, when the electrodeless discharge lamp 2 is lit during time-division dimming control, conventionally, the light emission quantity of the electrodeless discharge lamp is instantaneously changed from the operating frequency finv of the inverter circuit 13 to the frequency f1. In the present embodiment, the operating frequency finv of the inverter circuit 13 is maintained at the frequency f1. This point will be described later.

  The conversion circuit 16 is a control signal (output voltage) for controlling the operating frequency finv of the inverter circuit 13 based on the PWM signal (dimming signal) Vpwm and the coil voltage Vcoil output from the PWM control signal generator (not shown). Vf is generated. The output voltage Vf will be described later. The conversion circuit 16 is connected to the terminal of the induction coil 5 and detects the coil voltage Vcoil. In the present embodiment, by detecting the coil voltage Vcoil, it is mainly detected whether or not the discharge gas is in an arc-like discharge state.

  Note that the smaller the frequency of the PWM signal, the smaller the ratio of the starting period in one cycle (lighting period + extinguishing period), and the light emission of the electrodeless discharge lamp 2 due to the coil voltage Vcoil having a large starting period is suppressed. However, if the PWM signal frequency is too small and the extinguishing period becomes long, the human eyes will flicker, so that the balance is considered to be about 120 kHz. Is set.

  The drive circuit 15 has a phase difference of approximately 180 ° between the Hout terminal and the H-GND terminal and between the Lout terminal and the L-GND terminal at a frequency corresponding to the output voltage Vf of the conversion circuit 16. A rectangular-wave drive signal is output. Thereby, switching elements Q2 and Q3 are turned on and off alternately. In this embodiment, the duty of each drive signal output between the Hout terminal and the H-GND terminal and between the Lout terminal and the L-GND terminal is substantially the same.

  4A shows a PWM signal Vpwm, FIG. 4B shows an output voltage Vf of the conversion circuit 16, and FIG. 4C shows an operating frequency finv of the inverter circuit 13. FIG. 4D shows a waveform of the coil voltage Vcoil.

  First, when the PWM signal Vpwm is switched from H (high) to L (low) at time T = t1, the conversion circuit 16 instantaneously increases the output voltage Vf from 0 to V1, thereby causing the inverter circuit 13 to The operating frequency finv is instantaneously increased from 0 to the frequency f1. As a result, the coil voltage Vcoil becomes a starting voltage Vi that is equal to or higher than the above-described voltage Vst (see FIG. 3). The frequency f1 corresponds to “f1” shown in FIG.

  Then, when the electrodeless discharge lamp 2 starts to light (becomes an arc discharge state) and the coil voltage Vcoil decreases from the voltage Vi, conventionally, the conversion circuit 16 instantaneously changes the output voltage Vf from the voltage V1 to the voltage V2. By increasing the operating frequency finv of the inverter circuit 13 instantaneously from the frequency f1 to the frequency f2, in the present embodiment, the conversion circuit 16 makes the output voltage Vf constant at the voltage V1, whereby the inverter circuit The operating frequency finv of 13 is maintained at the frequency f1. Thereby, the coil voltage Vcoil becomes the voltage Vs (the voltage corresponding to the point b in FIG. 3). A period from time T = t1 to T = t2 is a lighting period Ton of the electrodeless discharge lamp 2.

  Thereafter, when the PWM signal Vpwm is switched from L (low) to H (high) at time T = t3, the conversion circuit 16 instantaneously lowers the output voltage Vf from V1 to 0, whereby the operation of the inverter circuit 13 is performed. The frequency finv is instantaneously lowered from the frequency f1 to zero. As a result, the coil voltage Vcoil becomes 0, and the electrodeless discharge lamp 2 is turned off. A period from time T = t2 to T = t3 is a turn-off period Toff of the electrodeless discharge lamp 2.

  Thereafter, by repeating the operation from time T = t1 to time T = t3, the electrodeless discharge lamp 2 repeats lighting and extinguishing, and there is no emission light quantity according to the ratio between the lighting period Ton and the extinguishing period Toff. The electrode discharge lamp 2 emits light.

  As described above, since the operating frequency finv of the inverter circuit 13 is kept constant at the frequency f1 during the lighting period Ton of the electrodeless discharge lamp 2, it is emitted from the electrodeless discharge lamp 2 and the discharge lamp lighting circuit 3. The noise is mainly noise having the component of frequency f1, and the generation of noise having the component of frequency f2 can be prevented and the switching from frequency f1 to frequency f2 is not performed. As a result, noise can be reduced as compared with the prior art.

  Next, a second embodiment of the present invention will be described.

In the present embodiment, whether the discharge lamp lighting circuit 3 in the first embodiment is further in time-division dimming control or is in full lighting control for continuously lighting the electrodeless discharge lamp. In addition to the detection circuit for detecting, the conversion circuit 16 and the control circuit 19 are connected, and the operation of the control circuit 19 is controlled by the conversion circuit 16 according to the detection result of the detection circuit, whereby the output voltage of the DC power supply circuit 12 is The difference is that the _VDC is configured to be controllable, and the rest of the configuration is substantially the same as that of the illumination device in the first to fourth embodiments, so only the differences will be described.

  FIG. 5 is a diagram illustrating a configuration of an illumination device according to the second embodiment.

  As shown in FIG. 5, in the present embodiment, as described above, time-dimming dimming control in which the electrodeless discharge lamp 2 is alternately turned on and off is being performed, or the electrodeless discharge lamp 2 is continuously operated. A detection circuit 20 that detects whether or not all lighting control is in progress is provided, and this detection circuit 20 is connected to the conversion circuit 16 and the drive circuit 15. The detection circuit 20 includes a parallel circuit of a capacitor C2 and an electric resistance R1, and a rectangular wave voltage corresponding to the PWM signal Vpwm is applied to both ends of the capacitor C2. The capacitor C2 is charged during the extinguishing period (period in which the PWM signal Vpwm is H (high)) during the time-division dimming control, and the charged charge in the lighting period (period in which the PWM signal Vpwm is L (low)). Is discharged through the electric resistance R1. In this case, during the full lighting control in which the PWM signal Vpwm is always L (low), the voltage Vd of the capacitor C2 is always smaller than the threshold value Vth, while during the time division dimming control, the voltage Vd of the capacitor C2 is As described above, it is set so that it does not become smaller than the threshold value Vth even if it is discharged. By comparing the magnitude of the voltage Vd and the threshold value Vth, whether the full lighting control or the time-division dimming control is being performed. Is detected.

Further, as described above, the conversion circuit 16 and the control circuit 19 are connected, and the conversion circuit 16 outputs a voltage Vt corresponding to the magnitude of the voltage Vd and the threshold value Vth to the control circuit 19. Is configured such that the output voltage V _DC of the DC power supply circuit 12 can be controlled by causing the switching element Q1 to perform an on / off operation at a frequency (or duty) corresponding to the voltage Vt.

6A is a diagram illustrating the PWM signal Vpwm, FIG. 6B is a diagram illustrating the output voltage Vf of the conversion circuit 16, and FIG. 6C is a diagram illustrating the operating frequency finv of the inverter circuit 13. 6 (d) is a diagram showing the output voltage Vd of the detection circuit 20, FIG. 6 (e) is a diagram showing the output voltage V _DC of the DC power supply circuit 12, and FIG. 6 (f) is a waveform of the coil voltage Vcoil. FIG.

First, full lighting control is performed on the electrodeless discharge lamp 2 until time T = t1 when the PWM signal Vpwm switches from L (low) to H (high). That is, the PWM signal Vpwm is maintained at L (low) and the output voltage Vf of the conversion circuit 16 is maintained at the voltage V2, so that the operating frequency of the inverter circuit 13 is maintained at the frequency f2. At this time, no voltage is generated at both electrodes of the capacitor C2 of the detection circuit 20 (voltage Vd = 0), and the conversion circuit 16 receives this and sets the output voltage Vt to the control circuit 19 to a predetermined output voltage. By doing this (not shown), the output voltage V _DC of the DC power supply circuit 12 is maintained at the voltage V _DC1 . As a result, the coil voltage Va corresponding to the operating frequency f2 of the inverter circuit and the magnitude of the output voltage V _DC1 of the DC power supply circuit 12 is applied.

When the PWM signal Vpwm is switched from L (low) to H (high) at time T = t1 to perform time-division dimming control for the electrodeless discharge lamp 2, the conversion circuit 16 converts the output voltage Vf to the voltage V2. By lowering from 0 to 0, the operating frequency finv of the inverter circuit 13 is lowered from the frequency f2 to 0. Thereby, the electrodeless discharge lamp 2 is turned off. At this time, the voltage Vd of the capacitor C2 of the detection circuit 20 becomes the voltage Vd = Vd1 by the PWM signal Vpwm (H (high) signal), and the conversion circuit 16 receives the output voltage Vd1 of the detection circuit 20 and receives the output voltage Vd1. By setting the output voltage Vt to the predetermined output voltage, the output voltage V _DC of the DC power supply circuit 12 is lowered to the voltage V _DC2 . The reason why the output voltage V _DC of the DC power supply circuit 12 is lowered to the voltage V _DC2 will be described later.

Next, when the PWM signal Vpwm is switched from H (high) to L (low) at time T = t2, the conversion circuit 16 raises the output voltage Vf from 0 to the voltage V1, whereby the operating frequency of the inverter circuit 13 is increased. Finv is increased from 0 to the frequency f1. This frequency f1 corresponds to “f1” shown in FIG. 3. By switching the operating frequency finv of the inverter circuit to the frequency f1, the coil voltage Vcoil becomes a voltage Vi equal to or higher than the voltage Vst, and the electrodeless discharge is performed. When the electric lamp 2 starts discharging and the discharge gas enters an arc-like discharge state, the coil voltage Vcoil decreases. At this time, the voltage Vd of the capacitor C2 of the detection circuit 20 decreases exponentially from the voltage Vd1 due to the discharge of the charge charged from the time T = t1 to the time T = t2. As described above, during the time-division dimming control, the voltage Vd of the capacitor C2 does not become smaller than the threshold value Vth, so that the conversion circuit 16 causes the control circuit 19 to supply the voltage Vt from time T = t1 to time T = t2. Is output to the control circuit 19, whereby the output voltage V _DC of the DC power supply circuit 12 is maintained at the voltage V _DC2 .

  When the discharge gas is in an arc-like discharge state, the conversion circuit 16 conventionally increases the operating frequency finv of the inverter circuit from the frequency f1 to the frequency f2 by increasing the output voltage Vf from the voltage V1 to the voltage V2. In this embodiment, as in the first embodiment, in order to reduce the type of noise, the conversion circuit 16 maintains the output voltage Vf at the voltage V1, thereby changing the operating frequency finv of the inverter circuit to the frequency f1. maintain.

However, in this case, if the operating frequency finv of the inverter circuit is maintained at the frequency f1, the emitted light quantity of the electrodeless discharge lamp 2 may not be set low. For this reason, the amount of light emitted from the electrodeless discharge lamp 2 can also be reduced by changing the frequency (or duty) of the switching operation by the switching element Q1 to lower the output voltage V _DC of the DC power supply circuit 12, so that conventionally When the discharge gas is in an arc-like discharge state, the amount of light emitted from the electrodeless discharge lamp 2 is reduced by switching the operating frequency finv of the inverter circuit from the frequency f1 to the frequency f2. In the present embodiment, instead of this, The amount of light emitted from the electrodeless discharge lamp 2 is reduced by reducing the output voltage V _DC of the DC power supply circuit 12 from the voltage V _Dc1 to the voltage V _DC2 . In the present embodiment, the output voltage V _DC of the DC power supply circuit 12 is decreased to the voltage V _DC2 from the time T = t1 when the time division dimming control for the electrodeless discharge lamp 2 is started. During the time-division dimming control, the output voltage V _DC of the DC power supply circuit 12 may be lowered to the voltage V _DC2 only during a period in which the L (low) PWM signal Vpwm is output. Thus, during the time-division dimming control, the operation from time T = t1 to time T = t3 is repeatedly performed, and the lighting period Ton and time from time T = t2 to time T = t3. The electrodeless discharge lamp 2 emits light with a light emission amount corresponding to the ratio with the extinguishing period Toff from T = t1 to time T = t2.

Thereafter, when the PWM signal Vpwm is maintained at L (low) at time T = t4 to perform full lighting control of the electrodeless discharge lamp 2, until time T = t5 when the voltage Vd of the capacitor C2 matches the threshold value Vth, The conversion circuit 16 maintains the output voltage Vf at the voltage V1, so that the operating frequency finv of the inverter circuit 13 is maintained at the frequency f1. When the voltage Vd of the capacitor C2 coincides with the threshold value Vth at time T = t5, the conversion circuit 16 raises the output voltage Vf from the voltage V1 to the voltage V2, thereby changing the operating frequency finv of the inverter circuit 13 from the frequency f1. As the frequency f2 is increased, the conversion circuit 16 sets the output voltage Vt to the control circuit 19 to a predetermined output voltage in response to the fact that the voltage Vd of the capacitor C2 coincides with the threshold value Vth. Increase the output voltage V _DC from voltage V _DC2 to voltage V _DC1 . As a result, the coil voltage Va corresponding to the operating frequency f2 of the inverter circuit 13 and the output voltage V _DC1 of the DC power supply circuit 12 is applied.

As described above, since the operation frequency finv of the inverter circuit 13 is kept constant at the frequency f1 during the lighting period Ton of the electrodeless discharge lamp 2 as in the first embodiment, the electrodeless discharge lamp 2 and the discharge lamp Since the noise emitted from the lamp lighting circuit 3 is mainly only noise having a component of frequency f1, noise having a component of frequency f2 can be eliminated, and switching from frequency f1 to frequency f2 is not performed. Generation of noise due to the switching can also be prevented, and thus noise can be reduced as compared with the conventional case. Further, in the lighting period Ton of the electrodeless discharge lamp 2, the operating frequency finv of the inverter circuit 13 is kept constant at the frequency f1, so that the light emission quantity of the electrodeless discharge lamp 2 cannot be set low. it is so arranged compensated by lowering the output voltage V _DC of 12, the lighting period Ton of the electrodeless discharge lamp 2, even keeping the switching frequency finv of the inverter circuit 13 constant at the frequency f1, the electrodeless discharge lamp 2 The amount of emitted light can be set low.

  Although the detection circuit 20 for detecting whether the full lighting control is being performed or the time-division dimming control is being configured by the parallel circuit of the capacitor C2 and the electric resistance R1, the detection circuit 20 is replaced with FIG. As shown in FIG. 2, a detection circuit 20 ′ configured by a series circuit of a capacitor C2 and an electric resistance R1 is provided, and a voltage Ve at both ends of the capacitor C2 (voltage at a connection point T between the capacitor C2 and the electric resistance R1) is converted. The output may be made to the circuit 16 (third embodiment). Also in this case, a rectangular wave voltage corresponding to the PWM signal Vpwm is applied to both poles of the capacitor C2, and the light extinction period during the time-division dimming control (period in which the PWM signal Vpwm is H (high)). Thus, the capacitor C2 is charged, and the charged electric charge is discharged through the electric resistance R1 in the lighting period (period in which the PWM signal Vpwm is L (low)). During the full lighting control, the capacitor voltage Ve is always smaller than the threshold value Vth, while during the time-division dimming control, the voltage Ve is set not to be smaller than the threshold value Vth. Is compared to detect whether full lighting control is being performed or time-division dimming control is being performed.

The time change of the voltage Ve of the capacitor C2 is the same as the voltage Vd of the capacitor C2 described in FIG. Further, the PWM signal Vpwm, the output voltage Vf from the conversion circuit 16 to the drive circuit 15, the operating frequency finv of the inverter circuit 13, the output voltage V _DC of the DC power supply circuit 12 and the coil voltage Vcoil change with time as in FIG. In addition, the relationship between these time changes and the time change of the voltage Ve of the capacitor C2 is the same as that in FIG.

  Next, a fourth embodiment of the present invention will be described.

  In the present embodiment, the conversion circuit 16 further generates an output voltage Vp in addition to the output voltage Vf in the first to fourth embodiments described above with respect to the discharge lamp lighting circuit 3 in the second embodiment described above. The main difference is that these two types of output voltages Vf and Vp are output to the drive circuit 15, and the rest of the configuration is substantially the same as that of the illumination device in the first to fourth embodiments. Therefore, only the differences will be described.

  FIG. 8 is a diagram illustrating a configuration of a lighting device according to the fourth embodiment.

  As shown in FIG. 8, in this embodiment, two types of output voltages Vf and Vp are output from the conversion circuit 16 to the drive circuit 15 as described above, and the two types of output voltages Vf. , Vp, the coil voltage Vcoil is controlled. That is, the output voltage Vf controls the frequency of the switching operation by the switching elements Q2 and Q3. As described above, by increasing this frequency, the coil voltage Vcoil decreases and the electrodeless discharge lamp 2 The amount of emitted light decreases. On the other hand, the output voltage Vp controls the duty of the switching operation by the switching elements Q2 and Q3. By reducing this duty, the coil voltage Vcoil is lowered and the light emission quantity of the electrodeless discharge lamp 2 is lowered. . The duty of the switching operation by the switching elements Q3 and Q4 is controlled by changing the ratio of the time during which the gate-source voltage of the switching elements Q2 and Q3 is at the H (high) level with respect to one cycle.

  9A is a diagram illustrating the PWM signal Vpwm, FIG. 9B is a diagram illustrating the output voltage Vf of the conversion circuit 16, and FIG. 9C is a diagram illustrating the operating frequency finv of the inverter circuit 13. 9D is a diagram showing the output voltage Vd of the detection circuit 20, FIG. 9E is a diagram showing the output voltage Vp of the conversion circuit 16, and FIG. 9F is a diagram showing switching by the switching elements Q2 and Q3. FIG. 9G is a diagram showing the duty DUTY of the operation, and FIG. 9G is a diagram showing the waveform of the coil voltage Vcoil.

  First, full lighting control is performed on the electrodeless discharge lamp 2 until time T = t1 when the PWM signal Vpwm switches from L (low) to H (high). That is, when the PWM signal Vpwm is maintained at L (low), the output voltage Vf of the conversion circuit 16 is maintained at the voltage V2, and the operating frequency finv of the inverter circuit 13 is maintained at the frequency f2. At this time, no voltage is generated at both poles of the capacitor C2 of the detection circuit 20 ′ (voltage Vd = 0), and the conversion circuit 16 receives this and sets the predetermined output voltage Vp to the voltage Vp1 for switching. The duty DUTY of the switching operation by the elements Q2 and Q3 is maintained at DUTY1. As a result, the coil voltage Va corresponding to the operating frequency f2 of the inverter circuit 13 and the duty DUTY1 of the switching operation by the switching elements Q2, Q3 is applied.

  When the PWM signal Vpwm is switched from L (low) to H (high) at time T = t1 to perform time-division dimming control of the electrodeless discharge lamp 2, the conversion circuit 16 converts the output voltage Vf to the voltage V2. By lowering from 0 to 0, the operating frequency finv of the inverter circuit 13 is lowered from the frequency f2 to 0. Thereby, the electrodeless discharge lamp 2 is turned off. At this time, the voltage Vd of the capacitor C2 of the detection circuit 20 ′ becomes Vd1 by the PWM signal Vpwm (“H” level signal), and the conversion circuit 16 receives the output voltage Vd1 of the detection circuit 20 ′ and outputs an output voltage. By reducing Vp from voltage Vp1 to voltage Vp2, the duty DUTY of the switching operation by switching elements Q2 and Q3 is reduced from DUTY1 to DUTY2. The reason why the duty DUTY of the switching operation by the switching elements Q2 and Q3 is reduced from DUTY1 to DUTY2 will be described later.

  Next, when the PWM signal Vpwm is switched from H (high) to L (low) at time T = t2, the conversion circuit 16 raises the output voltage Vf from 0 to the voltage V1, whereby the operating frequency of the inverter circuit 13 is increased. Finv is increased from 0 to the frequency f1. This frequency f1 corresponds to “f1” shown in FIG. 3. By setting the operating frequency finv of the inverter circuit 13 to the frequency f1, the coil voltage Vcoil becomes a voltage Vi equal to or higher than the voltage Vst. When the electrode discharge lamp 2 starts discharging and the discharge gas enters an arc-like discharge state, the coil voltage Vcoil decreases. At this time, the voltage Vd of the capacitor C2 of the detection circuit 20 ′ decreases exponentially from the voltage Vd1 due to the discharge of the charge charged from the time T = t1 to the time T = t2. As described above, since the voltage Vd of the capacitor C2 does not become smaller than the threshold value Vth, the conversion circuit 16 outputs the same voltage as the output voltage Vp1 to the control circuit 19 from time T = t1 to time T = t2. Thus, the duty DUTY of the switching operation by the switching elements Q2 and Q3 is maintained at DUTY2.

  When the discharge gas is in an arc-like discharge state, the conversion circuit 16 conventionally increases the operating frequency finv of the inverter circuit from the frequency f1 to the frequency f2 by increasing the output voltage Vf from the voltage V1 to the voltage V2. In this embodiment, as in the first embodiment, in order to reduce the type of noise, the conversion circuit 16 maintains the output voltage Vf at the voltage V1, thereby changing the operating frequency finv of the inverter circuit to the frequency f1. maintain.

  However, in this case, if the operating frequency finv of the inverter circuit 13 is maintained at the frequency f1, the emitted light quantity of the electrodeless discharge lamp 2 may not be set low. Therefore, since the light emission quantity of the electrodeless discharge lamp 2 can also be reduced by changing the duty of the switching elements by the switching elements Q2 and Q3, conventionally, when the discharge gas is in an arc-like discharge state, When the operating frequency finv is switched from the frequency f1 to the frequency f2, the light emission amount of the electrodeless discharge lamp 2 is reduced. In this embodiment, instead of this, the duty DUTY of the switching operation by the switching elements Q2 and Q3 is set to DUTY1. By reducing from DUTY2 to DUTY2, the amount of light emitted from the electrodeless discharge lamp is reduced. In this embodiment, the duty DUTY of the switching operation by the switching elements Q2 and Q3 is decreased from DUTY1 to DUTY2 from time T = t1 when the time-division dimming control of the electrodeless discharge lamp 2 is started. However, the duty DUTY of the switching operation by the switching elements Q2, Q3 may be reduced from DUTY1 to DUTY2 only during the period when the L (low) PWM signal Vpwm is output during the time division dimming control. Thus, during the time-division dimming control, the operation from time T = t1 to time T = t3 is repeatedly performed, and the lighting period Ton and time from time T = t2 to time T = t3. The electrodeless discharge lamp 2 emits light with a light emission amount corresponding to the ratio with the extinguishing period Toff from T = t1 to time T = t2.

  Thereafter, when the PWM signal Vpwm is maintained at L (low) at time T = t4 to perform full lighting control of the electrodeless discharge lamp 2, until time T = t5 when the voltage Vd of the capacitor C2 matches the threshold value Vth, The conversion circuit 16 maintains the output voltage Vf at the voltage V1 so that the operating frequency finv of the inverter circuit 13 is maintained at the frequency f1. When the voltage Vd of the capacitor C2 matches the threshold value Vth at time T = t5, the conversion circuit 16 The circuit 16 raises the operating frequency finv of the inverter circuit 13 from the frequency f1 to the frequency f2 by raising the output voltage Vf from the voltage V1 to the voltage V2. Further, the conversion circuit 16 sets the output voltage Vp1 to the control circuit 19 to a predetermined output voltage Vp1 in response to the voltage Vd of the capacitor C2 being equal to the threshold value Vth, so that the switching operation by the switching elements Q2 and Q3 is performed. DUTY is increased from DUTY2 to DUTY1. Thereby, the coil voltage Va according to the operating frequency f2 of the inverter circuit 13 and the duty DUTY2 of the switching operation by the switching elements Q2, Q3 is applied.

As described above, since the operation frequency finv of the inverter circuit 13 is kept constant at the frequency f1 during the lighting period Ton of the electrodeless discharge lamp 2 as in the first embodiment, the electrodeless discharge lamp 2 and the discharge lamp The noise emitted from the lamp lighting circuit 3 is mainly only noise having a component of frequency f1, and generation of noise having a component of frequency f2 can be prevented, and switching from frequency f1 to frequency f2 is not performed. Therefore, generation of noise due to the switching can also be prevented, and thus noise can be reduced as compared with the conventional case. Further, in the lighting period Ton of the electrodeless discharge lamp 2, the operating frequency finv of the inverter circuit 13 is kept constant at the frequency f1, so that the light emission quantity of the electrodeless discharge lamp 2 cannot be set low. it is so arranged compensated by lowering the output voltage V _DC of 12, the lighting period Ton of the electrodeless discharge lamp 2, even keeping the switching frequency finv of the inverter circuit 13 constant at the frequency f1, the electrodeless discharge lamp 2 The amount of emitted light can be set low.

  Next, a fifth embodiment of the present invention will be described.

  In the present embodiment, the discharge lamp lighting circuit 3 in the first embodiment is provided with a detection circuit similar to that in the second embodiment, and the PWM control signal generator and conversion circuit (not shown) are further described. 16 is different from that in FIG. 16 in that a DUTY conversion circuit described later is provided, and the other configuration is substantially the same as that of the illumination device in the first to fourth embodiments, and only the difference will be described.

  FIG. 10 is a diagram illustrating a configuration of a lighting device according to the fifth embodiment.

  As shown in FIG. 10, the present embodiment includes a detection circuit 20 that detects whether full lighting control or time-division dimming control is being performed as described above. Since the configuration and operation of the detection circuit 20 are substantially the same as those of the detection circuit 20 of the second embodiment, description thereof is omitted. Further, a DUTY conversion circuit 21 is connected between the PWM control signal generator (not shown) and the conversion circuit 16, and in the first to fourth embodiments, during the lighting period Ton of the electrodeless discharge lamp 2. The duty of the PWM signal output from the PWM control signal generator is compensated for by making it impossible to set the light emission quantity of the electrodeless discharge lamp 2 low by keeping the operating frequency finv of the inverter circuit 13 constant at the frequency f1. Is converted (smaller).

  FIG. 11 shows a DUTY conversion function by the DUTY conversion circuit 21. As indicated by a straight line L in FIG. 11, the DUTY conversion circuit 21 outputs a PWM signal Vpwm ′ having a duty smaller than the duty of the PWM signal Vpwm output from the PWM control signal generator (not shown).

  Thus, for example, in the second embodiment (see FIG. 6), the lighting time Ton of the electrodeless discharge lamp 2 is shortened. Thus, in the first to fourth embodiments, the operating frequency finv of the inverter circuit 13 is kept constant at the frequency f1 during the lighting period Ton of the electrodeless discharge lamp 2, thereby allowing the electrodeless discharge lamp to emit light. The reason why the light amount cannot be set low is that the duty of the PWM signal Vpwm output from the PWM control signal generator is reduced by the DUTY correction circuit 20 as described above, and the electrodeless discharge lamp 2 is turned on by the signal PWM signal Vpwm ′. Since the time Ton is shortened, the light emission of the electrodeless discharge lamp 2 is maintained even if the operating frequency finv of the inverter circuit 13 is kept constant at the frequency f1 during the lighting period Ton of the electrodeless discharge lamp 2. The amount of light can be set low.

It is a figure which shows the structure of the illuminating device of this invention. It is sectional drawing of an electrodeless discharge lamp. It is a figure which shows the characteristic of the coil voltage Vcoil with respect to the operating frequency finv of an inverter circuit. In the first embodiment, a diagram showing the PWM signal Vpwm, (b) is a diagram showing the output voltage Vf of the conversion circuit, (c) is a diagram showing the operating frequency finv of the inverter circuit, and (d) is a coil It is a figure which shows the waveform of voltage Vcoil. It is a figure which shows the structure of the illuminating device which concerns on 2nd Embodiment. In the second embodiment, (a) is a diagram showing the PWM signal Vpwm, (b) is a diagram showing the output voltage Vf of the conversion circuit, (c) is a diagram showing the operating frequency finv of the inverter circuit, d) is a diagram showing the output voltage Vd of the detection circuit, (e) is a diagram showing the output voltage V _DC of the DC power supply circuit 12, and (f) is a diagram showing the waveform of the coil voltage Vcoil. It is a figure which shows the structure of the illuminating device which concerns on 3rd Embodiment. It is a figure which shows the structure of the illuminating device which concerns on 4th Embodiment. (A) is a diagram showing the PWM signal Vpwm, (b) is a diagram showing the output voltage Vf of the conversion circuit, (c) is a diagram showing the operating frequency finv of the inverter circuit, and (d) is a diagram of the detection circuit. The figure which shows the output voltage Vd, (e) is a figure which shows the output voltage Vp of a conversion circuit, (f) is a figure which shows the duty DUTY of switching operation by switching element Q2, Q3, (g) is coil voltage Vcoil. It is a figure which shows these waveforms. It is a figure which shows the structure of the illuminating device which concerns on 5th Embodiment. It is the figure which showed the DUTY conversion function by a DUTY conversion circuit. It is explanatory drawing of the light control in the conventional illuminating device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Illuminating device 2 Electrodeless discharge lamp 3 Discharge lamp lighting circuit 4 Valve 5 Induction coil 6 Core 7 Thermal conductor 12 DC power supply circuit 13 Inverter circuit 14 Resonance circuit 15 Drive circuit 16 Conversion circuit 17 Rectification circuit 18 Boost chopper circuit 19 Control circuit 20, 20 'detection circuit 21 DUTY conversion circuit

Claims (5)

An electrodeless discharge lamp lighting device that outputs a high-frequency voltage to be applied to an induction coil of an electrodeless discharge lamp, wherein the DC power supply is connected to the DC power supply and the DC voltage of the DC power supply is turned on and off by a switching element. A power conversion circuit for converting to a voltage; a resonance circuit connected to the power conversion circuit for generating a high frequency voltage applied to an induction coil of an electrodeless discharge lamp; and a high frequency voltage applied to the induction coil periodically. In an electrodeless discharge lamp lighting device comprising a power control circuit that periodically turns on and off the electrodeless discharge lamp by turning it on and off,
The power conversion circuit generates a high-frequency voltage having a voltage value necessary to start lighting of the electrodeless discharge lamp with a frequency of a high-frequency voltage applied to the induction coil during a lighting period of the electrodeless discharge lamp. An electrodeless discharge lamp lighting device, wherein the frequency of on / off operation by the switching element is constant.   2. The electrodeless discharge lamp according to claim 1, wherein the DC power supply adjusts a high-frequency voltage applied to the induction coil by reducing the DC voltage during a lighting period of the electrodeless discharge lamp. Lighting device.   The power conversion circuit adjusts a high-frequency voltage applied to the induction coil by reducing a duty of an on / off operation by the switching element during a lighting period of the electrodeless discharge lamp. The electrodeless discharge lamp lighting device described.   The electrodeless discharge lamp lighting device according to claim 1, wherein the power control circuit adjusts a high-frequency voltage applied to the induction coil by shortening a lighting period of the electrodeless discharge lamp. A discharge gas containing at least mercury and a rare gas; a bulb for sealing the discharge gas; a high-frequency power supply circuit for generating a high-frequency voltage; and a high-frequency power supply disposed in a hollow section having a concave cross section provided in the bulb. An induction coil that supplies a high-frequency electromagnetic field to the discharge gas by a high-frequency voltage supplied from a circuit, and a magnetic material, a cylindrical core around which the induction coil is wound, and a thermally conductive material, In a lighting device comprising a member that contacts the core inside the core,
5. The lighting device according to claim 1, wherein the high-frequency power supply circuit is the electrodeless discharge lamp lighting device according to claim 1.

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