JP2005071827A - 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 a lower limit of light control of the electrodeless discharge lamp can be set lower. <P>SOLUTION: Although during a period before a PWM signal is switched to H (high) at a time T=t3, a coil voltage Vcoil is previously used to be constant by a voltage Va, because a converter circuit 16 increases an output voltage Vf gradually from the voltage V2 to the voltage V4 (V4<V3), an action frequency finv of an inverter circuit 13 is made to be increased from a frequency f2 to the frequency f4 (f4<f3), and by this, the coil voltage Vcoil is made to be gradually decreased from the voltage Va to Vb (Vb>Voff). <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.

  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 is shown in FIG. That is, as shown in FIG. 17, a period T1 during which a high high-frequency voltage is applied to the induction coil and a period T2 during which a low high-frequency voltage is applied are alternately provided, and a high-frequency voltage applied to the induction coil (hereinafter referred to as coil voltage). ) Are periodically changed, 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.

  FIG. 18 shows a more detailed representation of such changes in coil voltage. FIG. 18A shows the time change of the operating frequency finv of the inverter circuit, and FIG. 18B shows the time change of the coil voltage Vcoil. In FIG. 18B, 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.

  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 Vi applied to the induction coil. When the electrodeless discharge lamp is turned on based on this characteristic, it is different from the starting period (time T = t1 to t2) until the arc discharge state is applied and stabilized (see FIG. 3). In the starting period in which a relatively high voltage (starting voltage) Vi is required, 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. 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. 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 reduced to a desired value. As soon as the discharge lamp is turned on, the operating frequency finv of the inverter circuit is switched from the frequency f1 to the frequency f2 (see FIG. 3, f2> f1). With the above operation, the coil voltage Vcoil becomes the voltage Va. Thereafter, the coil voltage is maintained at a constant value Va by maintaining the operating frequency of the inverter circuit at the frequency f2 until the timing at which the electrodeless discharge lamp is to be extinguished (time T = t3) 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, the coil voltage needs to be increased at the start in consideration of the startability of the electrodeless discharge lamp, but in order to generate the high coil voltage, when 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. When trying to set the lower limit of dimming to a low level, a highly accurate 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 dimming is performed by reducing the average output 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 2002-334797 A

  However, in the time-division dimming control method, the method of lighting the electrodeless discharge lamp while maintaining the voltage of the induction coil at a constant value until the timing at which the electrodeless discharge lamp should be extinguished is reached as described above. There was a limit on the lower limit. That is, if the lighting time is shortened (the extinguishing time is lengthened) in order to reduce the dimming of the electrodeless discharge lamp, the ratio of the starting period to the lighting period increases. When the ratio of the starting period to the lighting period increases, the light output from the electrodeless discharge lamp is conspicuously reflected by human eyes due to the relatively high starting voltage Vi, and the intensity of the light of the electrodeless discharge lamp is human. Therefore, it was difficult to set the lower limit of dimming lower.

  This invention is made | formed in view of such a situation, and it aims at providing the electrodeless discharge lamp lighting device and illuminating device which can set the lower limit of the light control of an electrodeless discharge lamp lower.

  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 the circuit, the power control circuit gradually reduces the voltage applied to the induction coil during the lighting period of the electrodeless discharge lamp. Equipped with a.

  In the above electrodeless discharge lamp lighting device, the power control circuit gradually decreases the high-frequency voltage applied to the induction coil by changing the operating frequency of the switching element.

  In the above electrodeless discharge lamp lighting device, the power control circuit gradually decreases the high-frequency voltage applied to the induction coil by changing the DC voltage of the DC power supply.

  In the above electrodeless discharge lamp lighting device, the power control circuit gradually decreases the high-frequency voltage applied to the induction coil by changing the duty in the on / off operation of the switching element.

  In the above electrodeless discharge lamp lighting device, the power control circuit further includes a period in which the high-frequency voltage applied to the induction coil is gradually increased during the extinguishing period of the electrodeless discharge lamp.

  The power control circuit gradually increases the high-frequency voltage applied to the induction coil by changing the operating frequency of the switching element.

  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 7. An illuminating device comprising a core having a shape and a member made of a heat conductive material and in contact with the core inside the core, wherein the high frequency power supply circuit comprises an electrodeless discharge device according to any one of claims 1 to 6. It is an electric lamp lighting device.

  According to the present invention, since the power control circuit includes a period in which the voltage applied to the induction coil is gradually reduced during the lighting period of the electrodeless discharge lamp, the light emission amount of the electrodeless discharge lamp is reduced. Thereby, the lower limit of the light control of the electrodeless discharge lamp can be set lower.

  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 at the lower end of the large-diameter cylindrical portion, while the peripheral surface of the small-diameter cylindrical portion is in contact with 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 the present embodiment, the electrodeless discharge lamp 2 is turned on and off alternately for a plurality of times in a very short time, and the output of the electrodeless discharge lamp 2 is determined by the ratio between the lighting time and the turn-off time. The split 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 this embodiment, as shown in FIG. 3, by setting the operating frequency finv of the inverter circuit 13 to the frequency f3, the coil voltage Vcoil is less than or equal to the extinguishing voltage Voff. The voltage Vc is set (point a).

  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 b). When the electrodeless discharge lamp 2 is turned on (the discharge gas is in an arc-like discharge state), the characteristic of the coil voltage Vcoil shifts to the characteristic indicated by the resonance curve L2, and when the frequency is maintained at f1, The voltage Vcoil drops to a voltage corresponding to the point c.

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, in the present embodiment, the range of adjustment of the amount of emitted light (hereinafter referred to as dimming) of the electrodeless discharge lamp 2 is expanded, and in particular, the lower limit of dimming is set lower (the electrodeless discharge lamp 2). The coil voltage Vcoil during the lighting period of the electrodeless discharge lamp 2 is controlled by changing the operating frequency finv of the inverter circuit 13. 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.

  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 switches from H (high) to L (low) at time T = t1, the conversion circuit 16 instantaneously lowers the output voltage Vf from V3 to V1, thereby causing the inverter circuit 13 to The operating frequency finv is instantaneously lowered from the frequency f3 to the frequency f1. As a result, the coil voltage Vcoil becomes a voltage Vi that is equal to or higher than the aforementioned voltage Vst (see FIG. 3). The frequencies f1 and f3 and the voltage Vi correspond to “f1”, “f3”, and “Vi” shown in FIG.

  At time T = t2, when the electrodeless discharge lamp 2 starts lighting (enters an arc-like discharge state), the coil voltage Vcoil decreases, and the conversion circuit 16 that detects this decreases the output voltage Vf instantaneously. Thus, by raising the voltage V1 to the voltage V2 (V2 <V3), the operating frequency finv of the inverter circuit 13 is instantaneously raised from the frequency f1 to the frequency f2 (f2 <f3). As a result, the voltage Va is smaller than the aforementioned starting voltage Vst and larger than the extinguishing voltage Voff (see FIG. 3). The frequency f2 corresponds to “f2” shown in FIG.

  Next, during the period until the PWM signal switches to H (high) at time T = t3, conventionally, the coil voltage Vcoil was kept constant at the voltage Va. In the present embodiment, the conversion circuit 16 outputs the output voltage Vf. Is increased from the voltage V2 to the voltage V4 (V4 <V3), thereby increasing the operating frequency finv of the inverter circuit 13 from the frequency f2 to the frequency f4 (f4 <f3). As a result, the coil voltage Vcoil decreases from the voltage Va to the voltage Vb (Vb> Voff). A period from time T = t1 to T = t3 is a lighting period Ton of the electrodeless discharge lamp 2.

  Thereafter, when the PWM signal is switched from L (low) to H (high) at time T = t3, the conversion circuit 16 instantaneously raises the output voltage Vf from V4 to V3, thereby operating frequency of the inverter circuit 13. Finv is instantaneously increased from the frequency f4 to the frequency f3. As a result, the coil voltage Vcoil becomes a voltage Vc equal to or lower than the extinguishing voltage Voff, and the electrodeless discharge lamp 2 is extinguished. The voltage Vc corresponds to “Vc” shown in FIG. Further, a period from time T = t3 to time T = t4 when the PWM signal Vpwm is next switched from H (high) to L (low) is a turn-off period Toff of the electrodeless discharge lamp 2.

  Thereafter, by repeating the operation from time T = t1 to time T = t4, the electrodeless discharge lamp 2 is repeatedly turned on and off, and the amount of light corresponding to the ratio of the lighting period Ton and the extinguishing period Toff is not applied. Output from the discharge lamp 2.

  Thus, since the coil voltage Vcoil is gradually decreased in the lighting period Ton of the electrodeless discharge lamp 2, the lower limit of dimming can be set lower than in the conventional case. As a result, even when the dimming of the electrodeless discharge lamp 2 is performed within a relatively small amount of emitted light, the output (the amount of emitted light) of the electrodeless discharge lamp 2 can be brought close to a desired output.

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

  In the present embodiment, only the control of the coil voltage Vcoil in the lighting period Ton of the electrodeless discharge lamp 2 is different from the first embodiment, and other points including the discharge lamp lighting circuit 3 are the first implementation. Since it is substantially the same as the form, only the differences will be described.

  5A is a diagram showing the PWM signal Vpwm, FIG. 5B is a diagram showing the output voltage Vf of the conversion circuit 16, and FIG. 5C is a diagram showing the operating frequency finv of the inverter circuit 13. FIG. 5D shows a waveform of the coil voltage Vcoil.

  In the first embodiment, the coil voltage Vcoil is controlled to be gradually decreased during the lighting period Ton of the electrodeless discharge lamp 2.

  On the other hand, in this embodiment, as shown in FIG. 5, the conversion circuit 16 increases the output voltage Vf (from the voltage V2) only during the period from the time T = t2 to the time T = t5 in the lighting period Ton. By increasing the voltage V5), the operating frequency finv of the inverter circuit 13 is increased from the frequency f2 to the frequency f5. As a result, the coil voltage Vcoil decreases from the voltage Vd to the voltage Ve.

  Further, during a period from time T = t5 to time T = t3 when the PWM signal switches from L (low) to H (high), the conversion circuit 16 maintains the output voltage Vf at a constant voltage V5. The operating frequency finv of the inverter circuit 13 is maintained at the frequency f5. As a result, the coil voltage Vcoil is maintained at a constant voltage value Ve.

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

  Also in the present embodiment, the control of the coil voltage Vcoil in the lighting period Ton of the electrodeless discharge lamp 2 is different from that of the first embodiment, and other points including the discharge lamp lighting circuit 3 are the first implementation. Since it is substantially the same as the form, only the differences will be described.

  6A is a diagram illustrating the PWM signal Vprm, 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. FIG. 6D shows a waveform of the coil voltage Vcoil.

  In the second embodiment, when the electrodeless discharge lamp 2 starts to be lit, the coil voltage Vcoil is gradually decreased until a time during the lighting period Ton (time T = t5), and then the coil voltage Vcoil is set to a constant value. Controlled to maintain.

  On the other hand, in the present embodiment, as shown in FIG. 6, during the period from time T = t2 to halfway time T = t6 in the lighting period Ton, the conversion circuit 16 changes the output voltage Vf to a constant voltage V6. By maintaining the above, the operating frequency finv of the inverter circuit 13 is maintained at the frequency f6. As a result, the coil voltage Vcoil is maintained at a constant voltage value Vg.

  Further, during a period from time T = t6 to time T = t3 when the PWM signal switches from L (low) to H (high), the conversion circuit 16 increases the output voltage Vf from the voltage V2 to the voltage V6. The operating frequency finv of the inverter circuit 13 is increased from the frequency f2 to the frequency f6. Thereby, the coil voltage Vcoil is gradually decreased from the voltage Vg to the voltage Vh.

  As in the second and third embodiments, the control can be performed by providing the lighting period Ton of the electrodeless discharge lamp 2 with an arbitrary ratio between a period during which the coil voltage Vcoil is gradually decreased and a period during which the coil voltage Vcoil is maintained constant. As in the first embodiment, the lower limit of dimming can be set lower, and the output (light emission) of the electrodeless discharge lamp 2 can be adjusted even when the electrodeless discharge lamp 2 is dimmed within a relatively small amount of emitted light. Light amount) can be made close to a desired output.

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

  Also in the present embodiment, the control of the coil voltage Vcoil in the lighting period Ton of the electrodeless discharge lamp 2 is different from that of the first embodiment, and other points including the discharge lamp lighting circuit 3 are the first implementation. Since it is substantially the same as the form, only the differences will be described.

  7A is a diagram illustrating the PWM signal Vpwm, FIG. 7B is a diagram illustrating the output voltage Vf of the conversion circuit 16, and FIG. 7C is a diagram illustrating the operating frequency finv of the inverter circuit 13. FIG. 7D shows a waveform of the coil voltage Vcoil.

  In the first embodiment, the coil voltage Vcoil is controlled to be gradually decreased during the lighting period Ton of the electrodeless discharge lamp 2.

  In contrast, in the present embodiment, as shown in FIG. 7, the coil voltage Vcoil is decreased stepwise during the lighting period Ton of the electrodeless discharge lamp 2.

  That is, in FIG. 7, in the lighting period Ton of the electrodeless discharge lamp 2, the time T = t7 and t8 at which the coil voltage Vcoil is switched halfway are set, and the period from the time T = t2 to the time T = t7 is converted. 16 maintains the output voltage Vf at V2, thereby maintaining the operating frequency finv of the inverter circuit 13 at the frequency f2. As a result, the coil voltage Vcoil is maintained at a constant voltage Vj.

  In the period from time T = t7 to time T = t8, the conversion circuit 16 raises the output voltage Vf from the voltage V2 to the voltage V6 (V6 <V3), so that the operating frequency finv of the inverter circuit 13 is changed from the frequency f2 to the frequency f2. Raise to f6. As a result, the coil voltage Vcoil is lowered from the voltage Vj to the voltage Vk.

  Further, during the period from time T = t8 to time T = t3, the conversion circuit 16 raises the output voltage Vf from the voltage V6 to the voltage V7 (V7 <V3), thereby changing the operating frequency finv of the inverter circuit 13 from the frequency f6 to the frequency f6. Increase to f7 (f7 <f3). As a result, the coil voltage Vcoil is lowered from the voltage Vk to the voltage Vm.

  As described above, the control for lowering the coil voltage Vcoil in a stepwise manner during the lighting period Ton can set the lower limit of dimming lower as in the first embodiment, and the light emission amount is relatively small. Even when the light control of the electrodeless discharge lamp 2 is performed, the output (light quantity) of the electrodeless discharge lamp 2 can be brought close to a desired output.

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

  The present embodiment is different from the discharge lamp lighting circuit 3 in the first to fourth embodiments described above in that a conversion circuit 16 and a control circuit 19 are further connected. Since it is substantially the same as the illuminating device in 1st-4th embodiment, only a different point is demonstrated.

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

As shown in FIG. 8, in the present embodiment, the conversion circuit 16 and the control circuit 19 are connected as described above, and the frequency (or duty) of the switching operation by the switching element Q1 is controlled via the control circuit 19. Thus, the output voltage V _DC of the DC power supply circuit 12 is configured to be controllable, and in the first embodiment, the coil voltage Vcoil is controlled by controlling the output voltage Vf from the conversion circuit 16 to the drive circuit 15. However, in the present embodiment, the coil voltage Vcoil is controlled by controlling the output voltage V _DC of the DC power supply circuit 12.

9A is a diagram showing the PWM signal Vpwm, FIG. 9B is a diagram showing the output voltage Vt from the conversion circuit 16 to the control circuit 19 (or the output voltage V _DC of the DC power supply circuit 12), FIG. 9 (c) is a diagram showing the operating frequency finv of the inverter circuit 13, and FIG. 9 (d) is a diagram showing the waveform of the coil voltage Vcoil.

  First, when the PWM signal Vpwm switches from H (high) to L (low) at time T = t1, as in the first embodiment, the conversion circuit 16 instantaneously changes the output voltage Vf from the voltage V3 to the voltage V3. By lowering to V1 (see FIG. 4B), the operating frequency finv of the inverter circuit 13 is instantaneously lowered from the frequency f3 to the frequency f1. As a result, the coil voltage Vcoil becomes a voltage Vi that is equal to or higher than the aforementioned voltage Vst.

When the electrodeless discharge lamp 2 starts lighting at time T = t2 (enters an arc-like discharge state), the coil voltage Vcoil decreases, and the conversion circuit 16 that detects this decreases the output voltage Vf instantaneously. By raising the voltage V1 to the voltage V2 (V2 <V3) (see FIG. 4), the operating frequency finv of the inverter circuit 13 is instantaneously raised from the frequency f1 to the frequency f2. As a result, the voltage Va is smaller than the aforementioned starting voltage Vst and larger than the extinguishing voltage Voff (see FIG. 3). Until time T = t2, the output voltage Vt from the conversion circuit 16 to the control circuit 19 is maintained at Vt1, so that the output voltage V _DC of the DC power supply circuit 12 is maintained at the voltage V _DC1 .

Next, in the period until the PWM signal switches to H (high) at time T = t3, in the first embodiment, the output voltage Vf from the conversion circuit 16 to the drive circuit 15 is increased to increase the coil voltage. In this embodiment, the output voltage Vf is maintained at the voltage V2, and instead, the output voltage Vt from the conversion circuit 16 to the control circuit 19 is gradually decreased from the voltage Vt1 to the voltage Vt2. As a result, the output voltage V _DC of the DC power supply circuit 12 is gradually decreased from the voltage V _DC1 to the voltage V _DC2 . Thereby, the coil voltage Vcoil decreases from the voltage Va to the voltage Vb. Note that since the conversion circuit 16 maintains the output voltage Vf at the voltage V2, the operating frequency finv of the inverter circuit 13 is maintained at a constant frequency f2.

Thereafter, when the PWM signal is switched from L (low) to H (high) at time T = t3, the conversion circuit 16 instantaneously increases the output voltage Vf to the drive circuit 15 from the voltage V2 to the voltage V3. The output voltage Vt to the control circuit 19 is instantaneously increased from the voltage Vt2 to the voltage Vt1. As a result, the operating frequency finv of the inverter circuit 13 instantaneously increases from the frequency f2 to the frequency f3, and the output voltage V _DC of the DC power supply circuit 12 instantaneously increases from the voltage V _DC2 to the voltage V _DC1 . As a result, the coil voltage Vcoil becomes equal to or lower than the extinguishing voltage Voff, and the electrodeless discharge lamp 2 is extinguished.

Thus, by controlling the coil voltage Vcoil by controlling the output voltage V _DC of the DC power supply circuit 12, the lower limit of dimming can be set lower as in the first embodiment, Even when light control of the electrodeless discharge lamp 2 is performed in a range where the amount of emitted light is relatively small, the output (the amount of emitted light) of the electrodeless discharge lamp 2 can be brought close to a desired output.

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

  In this embodiment, the conversion circuit 16 generates an output voltage Vp in addition to the output voltage Vf in the first to fourth embodiments, and outputs these two types of output voltages Vf and Vp to the drive circuit 15. The other points are substantially the same as those of the discharge lamp lighting circuit 3 in the first to fourth embodiments, and only the differences will be described.

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

As shown in FIG. 10, in the present 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 is lowered and the electrodeless discharge lamp 2 Output 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 output of the electrodeless discharge lamp 2 is lowered. Note that the duty of the switching operation by the switching elements Q3 and Q4 is the time during which the gate-source voltages V _{GS (Q3)} and V _{GS (Q4)} of the switching elements Q2 and Q3 are at the H (high) level for one cycle. It can be controlled by changing the ratio.

  11A shows the PWM signal Vpwm, FIG. 11B shows the output voltage Vp to the drive circuit 15 of the conversion circuit 16 (or the duty DUTY of the switching elements Q3 and Q4), and FIG. (C) is a figure which shows the operating frequency finv of the inverter circuit 13, and FIG.11 (d) is a figure which shows the waveform of the coil voltage Vcoil.

  First, when the PWM signal Vpwm switches from H (high) to L (low) at time T = t1, the conversion circuit 16 lowers the output voltage Vf from the voltage V3 to the voltage V1 as in the first embodiment ( 4), the operating frequency finv of the inverter circuit 13 is instantaneously lowered from the frequency f3 to the frequency f1. As a result, the coil voltage Vcoil becomes a voltage Vi equal to or higher than the voltage Vst.

  When the electrodeless discharge lamp 2 starts to be lit at time T = t2, the coil voltage Vcoil decreases, and the conversion circuit 16 that detects this decreases the output voltage Vf from the voltage V1 to the voltage V2 (V2 <V3). By instantaneously increasing (see FIG. 4), the operating frequency finv of the inverter circuit 13 is instantaneously increased from the frequency f1 to the frequency f2. As a result, the coil voltage Vcoil becomes a voltage Va which is smaller than the starting voltage Vst and larger than the extinguishing voltage Voff.

  Next, in the period until the PWM signal switches to H (high) at time T = t3, in the first embodiment, the output voltage Vf from the conversion circuit 16 to the drive circuit 15 is increased to increase the coil voltage. In this embodiment, the output voltage Vf is maintained at the voltage V2, and instead the output voltage Vp is decreased from the voltage Vp1 to the voltage Vp2. As a result, the duty DUTY of the switching operation by the switching elements Q2 and Q3 decreases from DUTY1 to DUTY2, and as a result, the coil voltage Vcoil decreases from the voltage Va to the voltage Vb. Note that since the conversion circuit 16 maintains the output voltage Vf at the voltage V2, the operating frequency finv of the inverter circuit 13 is maintained at a constant frequency f2.

  Thereafter, when the PWM signal is switched from L (low) to H (high) at time T = t3, the conversion circuit 16 instantaneously raises the output voltage Vf from the voltage V2 to the voltage V3, while instantaneously raising the output voltage Vp. Thus, the voltage Vp2 is raised to the voltage Vp1. As a result, the operating frequency finv of the inverter circuit 13 instantaneously increases from the frequency f2 to the frequency f3, and the duty DUTY of the switching operation by the switching elements Q2 and Q3 instantaneously increases from DUTY2 to DUTY1. As a result, the coil voltage Vcoil becomes a voltage Vc lower than the extinguishing voltage Voff, and the electrodeless discharge lamp 2 is extinguished.

  In this way, by controlling the coil voltage Vcoil by changing the duty DUTY of the switching operation by the switching elements Q2 and Q3, the lower limit of dimming can be set lower as in the first embodiment. Even when the dimming of the electrodeless discharge lamp 2 is performed within a relatively small amount of emitted light, the output (the amount of emitted light) of the electrodeless discharge lamp 2 can be brought close to a desired output.

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

  In the present embodiment, the control method of the coil voltage Vcoil is different from the illumination devices of the first to fourth embodiments described above, and the other configurations including the discharge lamp lighting circuit 3 and the electrodeless discharge lamp 2 are the first. Since this is substantially the same as the first to fourth embodiments, only the differences will be described.

  In the present embodiment, in order to improve the startability of the electrodeless discharge lamp 2 (to make an arc discharge state as quickly as possible), the coil voltage Vcoil is set to a predetermined value before the start voltage Vi is applied to the coil voltage Vcoil. The voltage is gradually increased to

  12A shows the PWM signal Vpwm, FIG. 12B shows the output voltage Vf from the conversion circuit 16 to the drive circuit 15, and FIG. 12C shows the operating frequency of the inverter circuit 13. FIG. 12D is a diagram showing the waveform of the coil voltage Vcoil.

  As shown in FIG. 12A, when the PWM signal Vpwm switches from H (high) to L (low) at time T = t1, the conversion circuit 16 converts the output voltage Vf to the voltage V6 (V1 <V2 <V6). The operating frequency finv of the inverter circuit 13 is instantaneously lowered from the frequency f6 to the frequency f1 (f1 <f2 <f6 <f4 <f3) by lowering from <V4 <V3) to the voltage V1. As a result, the coil voltage Vcoil becomes a voltage Vi equal to or higher than the voltage Vst.

  At time T = t2, when the electrodeless discharge lamp 2 starts lighting (enters an arc-like discharge state), the coil voltage Vcoil decreases, and the conversion circuit 16 that detects this decreases the output voltage Vf instantaneously. By raising V1 to V2 (V2 <V3), the operating frequency finv of the inverter circuit 13 is instantaneously raised from frequency f1 to f2 (f2 <f3). As a result, the coil voltage Vcoil becomes a voltage Va that is smaller than the aforementioned starting voltage Vst and larger than the extinguishing voltage Voff (see FIG. 3).

  Next, during a period until the PWM signal switches to H (high) at time T = t3, the conversion circuit 16 increases the output voltage Vf, thereby changing the operating frequency finv of the inverter circuit 13 from frequencies f2 to f4 ( Increase to f4 <f3). As a result, the coil voltage Vcoil decreases from the voltage Va to the voltage Vb.

  Thereafter, when the PWM signal is switched from L (low) to H (high) at time T = t3, the conversion circuit 16 instantaneously increases the output voltage Vf from V4 to voltage V3, whereby the operation of the inverter circuit 13 is performed. The frequency finv is instantaneously increased from the frequency f4 to the frequency f3. As a result, the coil voltage Vcoil becomes a voltage Vc equal to or lower than the extinguishing voltage Voff, and the electrodeless discharge lamp 2 is extinguished.

  Further, until the time T = t9 in the middle of the time T = t4 when the PWM signal switches from H (high) to L (low), the conversion circuit 16 keeps the output voltage Vf to the drive circuit 15 constant at the voltage V3. Thus, the operating frequency finv of the inverter circuit 13 is maintained at the frequency f3. Thereby, the coil voltage Vcoil is maintained at the voltage Vc.

  Further, in the present embodiment, during the period from time T = t9 to time T = t4, the conversion circuit 16 reduces the output voltage Vf to the drive circuit 15 from the voltage V3 to the voltage V6, thereby operating the inverter circuit 13. The frequency Vinv decreases from the frequency f3 to the frequency f6. As a result, the coil voltage Vcoil increases from the voltage Vc to the voltage Va. Note that the target value of the coil voltage Vcoil to be raised at this time is not limited to the voltage Va, and can be set as appropriate as long as the voltage is lower than the starting voltage Vi.

  Thus, by raising the coil voltage Vcoil in advance during the extinguishing period Toff, a certain amount of energy before plasma is generated is accumulated in the discharge gas of the electrodeless discharge lamp 2 during the extinguishing period Toff. It becomes. As a result, the starting voltage Vi can be set lower than that in the first embodiment. As a result, the starting performance at the time of starting at a low temperature or in a dark state can be improved, and the starting voltage Vi is low. As much as it can be set, noise generated in the output voltage from the discharge lamp lighting circuit 3 can be reduced.

  Next, an eighth embodiment of the present invention will be described.

  In the present embodiment, the control method of the coil voltage Vcoil is different from that of the lighting device in the first to fourth embodiments described above, and the other configurations including the discharge lamp lighting circuit 3 and the electrodeless discharge lamp 2 are the first. Since this is substantially the same as the first to fourth embodiments, only the differences will be described.

  In this embodiment, for the same purpose as in the seventh embodiment, the coil voltage Vcoil is gradually increased to the starting voltage Vi at a constant rate by using a part of the extinguishing period Toff, and the electrodeless discharge lamp 2 Is turned on.

  13A shows the PWM signal Vpwm, FIG. 13B shows the output voltage Vf from the conversion circuit 16 to the drive circuit 15, and FIG. 13C shows the operating frequency of the inverter circuit 13. FIG. 13 (d) is a diagram showing the waveform of the coil voltage Vcoil.

  First, when the PWM signal is switched from H (high) to L (low) at time T = t10, the conversion circuit 16 supplies the drive circuit 15 to the electrodeless discharge lamp 2 (until time T = t11). By reducing the output voltage Vf from the frequency V3 at a predetermined rate, the operating frequency finv of the inverter circuit 13 is lowered from the frequency f3. As a result, the coil voltage Vcoil increases from the voltage Vc.

  At time T = t12, when the coil voltage Vcoil becomes the starting voltage Vi and the electrodeless discharge lamp 2 starts to be lit (enters an arc discharge state), the coil voltage Vcoil decreases and the electrodeless discharge lamp 2 is lit. Assuming that the output voltage Vf at time T = t12 is the voltage V1 and the operating frequency finv of the inverter circuit 13 is f1, the conversion circuit 16 that detects the start of lighting of the electrodeless discharge lamp 2 By increasing the output voltage Vf to 15 instantaneously from V1 to V2, the operating frequency finv of the inverter circuit 13 is instantaneously increased from the frequency f1 to f2. As a result, the coil voltage Vcoil instantaneously drops to a voltage Va smaller than the starting voltage Vi and larger than the extinguishing voltage Voff.

  Further, during a period from time T = t11 to time T = t12 when the PWM signal switches from L (low) to H (high), the conversion circuit 16 changes the output voltage Vf to the drive circuit 15 from the voltage V2 to the voltage V4 ( By increasing to <V3), the operating frequency finv of the inverter circuit 13 is increased from the frequency f2 to the frequency f4. As a result, the coil voltage Vcoil gradually decreases from the voltage Va to the voltage Vb (Vb> Voff).

  When the PWM signal is switched from L (low) to H (high) at time T = t12, the conversion circuit 16 instantaneously increases the output voltage Vf to the drive circuit 15 from V4 to V3, so that the inverter The operating frequency finv of the circuit 13 is instantaneously increased from the frequency f4 to the frequency f3. As a result, the coil voltage Vcoil becomes a voltage Vc equal to or lower than the extinguishing voltage Voff, and the electrodeless discharge lamp 2 is extinguished.

  Thus, until the coil voltage Vcoil becomes the starting voltage Vi, the coil voltage Vcoil is increased at a constant rate by using a part of the turn-off period Toff. The coil voltage Vcoil is higher than that in the seventh embodiment. Therefore, the voltage Vi can be set lower than that in the seventh embodiment. As a result, the startability at the start in a low temperature or dark state can be improved, and the start voltage Vi can be set lower. The noise generated in the output voltage from the discharge lamp lighting circuit 3 can be reduced by the amount that can be set.

  In addition, when the impedance when the electrodeless discharge lamp 2 is viewed from the induction coil 5 varies due to the influence of the environment around the electrodeless discharge lamp 2 (the ambient temperature or the structure around the electrodeless discharge lamp 2). Even so, the electrodeless discharge lamp 2 can be stably started.

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

  In the present embodiment, the control method of the coil voltage Vcoil is different from that of the lighting device in the first to fourth embodiments described above, and the other configurations including the discharge lamp lighting circuit 3 and the electrodeless discharge lamp 2 are the first. Since this is substantially the same as the first to fourth embodiments, only the differences will be described.

  In the present embodiment, the coil voltage Vcoil in the extinguishing period Toff of the electrodeless discharge lamp 2 is set to a voltage value very close to the aforementioned extinguishing voltage Voff using a configuration in which the conversion circuit 16 detects the coil voltage Vcoil. I am doing so.

  14A shows the PWM signal Vpwm, FIG. 14B shows the output voltage Vf from the conversion circuit 16 to the drive circuit 15, and FIG. 14C shows the operating frequency of the inverter circuit 13. FIG. 14D is a diagram illustrating the waveform of the coil voltage Vcoil.

  The conversion circuit 16 to the drive circuit 15 from time T = t1 when the PWM signal Vpwm switches from H (high) to L (low) to time T = t3 when the PWM signal switches from L (low) to H (high). Since the output voltage Vf, the change in the operating frequency finv of the inverter circuit 13 and the change in the coil voltage Vcoil are substantially the same as those in the first embodiment, description thereof will be omitted.

  When the PWM signal is switched from L (low) to H (high) at time T = t3, in this embodiment, the conversion circuit 16 instantaneously changes the output voltage Vf to the drive circuit 15 from the voltage V4 to the voltage V4. By raising to V3, the operating frequency finv of the inverter circuit 13 is raised from the frequency f4 to the frequency f8. As a result, the coil voltage Vcoil has a voltage value very close to the extinguishing voltage Voff within a range not exceeding the extinguishing voltage Voff.

  That is, in the first embodiment, in order to surely turn off the electrodeless discharge lamp 2, the operating frequency finv of the inverter circuit 13 is taken into consideration that the characteristics of circuit elements in the lighting device vary from one lighting device to another. Therefore, the coil voltage Vcoil in the extinguishing period Toff is set to a voltage value that is significantly lower than the extinguishing voltage Voff.

  On the other hand, in this embodiment, since the extinction of the electrodeless discharge lamp 2 is detected and the operating frequency finv of the inverter circuit 13 is set, the operation of the inverter circuit 13 is considered in consideration of variations in the characteristics of the circuit elements. There is no need to set the frequency finv higher. As a result, by setting the operating frequency finv of the inverter circuit 13 to an appropriate value (frequency f8) while monitoring the coil voltage Vcoil so as not to exceed the extinguishing voltage Voff, as described above, the electrodeless discharge lamp 2 In the extinguishing period Toff, the coil voltage Vcoil can be set to a voltage value very close to the extinguishing voltage Voff. As a result, similar to the seventh embodiment described above, the starting voltage Vi can be set lower than in the first embodiment, and the starting performance of the electrodeless discharge lamp 2 is improved at a low temperature or in a dark state. can do.

  If the coil voltage Vcoil in the lighting period Ton of the electrodeless discharge lamp 2 is decreased, the coil voltage Vcoil when the electrodeless discharge lamp 2 is turned off can be easily detected, and the coil voltage Vcoil in the turn-off period Toff is turned off. A higher voltage can be set within a range not exceeding the voltage Voff.

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

  In the present embodiment, the illumination device according to the first to ninth embodiments is further provided with the following configuration.

  The lower limit of dimming of the electrodeless discharge lamp 2 can also be set low by reducing the duty of the switching operation by the switching elements Q2 and Q3 (shortening the ON time of the switching elements Q2 and Q3). However, in the lighting devices according to the first to ninth embodiments, the lighting period Ton and the starting time of the output of the electrodeless discharge lamp 2 are substantially reduced by reducing the duty of the switching operation by the switching elements Q2 and Q3. If the output TH of the electrodeless discharge lamp 2 when the two coincide with each other is further reduced (and the lower limit of dimming of the electrodeless discharge lamp 2 is set lower), the lighting time Ton becomes shorter than the starting time, so that the electrodeless The discharge lamp 2 may go out.

  In order to solve this problem, in the present embodiment, as shown in FIG. 15A, in the illumination devices according to the first to ninth embodiments, the output of the electrodeless discharge lamp 2 is changed from the output TH. For further reduction, control is not performed to further reduce the duty of the switching operation by the switching elements Q2 and Q3 from the duty at the time of the output TH. Instead, as shown in FIG. The coil voltage Vcoil is further reduced by increasing the overall operating frequency finv of the inverter circuit 13 during the lighting period Ton according to the difference from the desired output of the electrode discharge lamp 2.

  For example, by using the control method for the coil voltage Vcoil in the first embodiment and the control method for reducing the duty of the switching operation by the switching elements Q2 and Q3, the output of the electrodeless discharge lamp 2 is set to the threshold value TH. (The output of the electrodeless discharge lamp 2 is approximately equal to the lighting period Ton and the starting time), and the lower limit of the dimming of the electrodeless discharge lamp 2 is set lower as shown in FIG. If it is desired to reduce the duty of the switching operation by the switching elements Q2 and Q3 to further reduce the output TH, the electrodeless discharge lamp 2 may be extinguished. Therefore, from time T = t2 to time T = in FIG. The operating frequency finv of the inverter circuit 13 at t3 is the amount Δf corresponding to the difference Δx between the output TH and the desired output of the electrodeless discharge lamp 2 Make it bigger overall.

  Thereby, the lower limit of the light control of the electrodeless discharge lamp 2 can be set lower while preventing or suppressing the disappearance of the electrodeless discharge lamp 2.

  Next, an eleventh embodiment of the present invention will be described.

In the tenth embodiment, when the light emission quantity of the electrodeless discharge lamp 2 is further reduced from the output TH, the light is turned on by an amount corresponding to the difference between the output TH and the desired output of the electrodeless discharge lamp 2. The coil voltage Vcoil is further reduced by increasing the operating frequency finv of the inverter circuit 13 in the period Ton as a whole. However, in this embodiment, the lower limit of dimming of the electrodeless discharge lamp 2 is set to the DC power supply. The output voltage V _DC of the circuit 12 is set low by reducing it.

That is, in the present embodiment, as shown in FIG. 16 (a), in the illumination devices according to the first to ninth embodiments, the output of the electrodeless discharge lamp 2 is further reduced from the output TH. Control for further reducing the duty of the switching operation by the switching elements Q2 and Q3 from the duty at the time of the output TH is not performed. Instead, as shown in FIG. 16B, the output TH and the electrodeless discharge lamp 2 The coil voltage Vcoil is further reduced by reducing the overall output voltage V _DC of the DC power supply circuit 12 during the lighting period Ton according to the difference from the desired output.

For example, by using the control method for the coil voltage Vcoil in the first embodiment and the control method for reducing the duty of the switching operation by the switching elements Q2 and Q3, the output of the electrodeless discharge lamp 2 is set to the threshold value TH. 16 (a), when the lower limit of the dimming of the electrodeless discharge lamp 2 is desired to be set lower. As shown in the figure, when the duty of the switching operation by the switching elements Q2 and Q3 is further reduced to reduce the output TH, the electrodeless discharge lamp 2 may be extinguished. Therefore, as shown in FIG. 16 (b), the output voltage V _DC of the DC power supply circuit 12 from time T = t 2 to time T = t 3 in FIG. 4 is expressed as the output TH and the desired output of the electrodeless discharge lamp 2. overall reduced further by the amount [Delta] V _DC corresponding to the difference [Delta] x.

  Thereby, like the said 10th Embodiment, the minimum of the light control of the electrodeless discharge lamp 2 can be set lower, preventing or suppressing the extinction of the electrodeless discharge lamp 2. FIG.

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) 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 a waveform of the coil voltage Vcoil. 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 a waveform of the coil voltage Vcoil. In the third embodiment, (a) is a diagram showing the PWM signal Vprm, (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 a waveform of the coil voltage Vcoil. In the fourth 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 a waveform of the coil voltage Vcoil. It is a figure which shows the structure of the illuminating device which concerns on 5th Embodiment. In the fifth 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 a waveform of the coil voltage Vcoil. It is a figure which shows the structure of the illuminating device which concerns on 6th Embodiment. In the sixth 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 a waveform of the coil voltage Vcoil. In the seventh 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 a waveform of the coil voltage Vcoil. In the eighth 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 a waveform of the coil voltage Vcoil. In the ninth 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 a waveform of the coil voltage Vcoil. It is explanatory drawing of the light control in the illuminating device of the 10th Embodiment of this invention. It is explanatory drawing of the light control in the illuminating device of the 11th Embodiment of this invention. It is explanatory drawing of the light control in the conventional illuminating device. 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

Claims (7)

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 electrodeless discharge lamp lighting device, wherein the power control circuit includes a period in which the voltage applied to the induction coil is gradually reduced during the lighting period of the electrodeless discharge lamp.   2. The electrodeless discharge lamp lighting device according to claim 1, wherein the power control circuit gradually decreases a high-frequency voltage applied to the induction coil by changing an operating frequency of the switching element. 3.   2. The electrodeless discharge lamp lighting device according to claim 1, wherein the power control circuit gradually reduces a high-frequency voltage applied to the induction coil by changing a DC voltage of the DC power source.   2. The electrodeless discharge lamp lighting device according to claim 1, wherein the power control circuit gradually decreases a high-frequency voltage applied to the induction coil by changing a duty in an on / off operation of the switching element. 3.   2. The electrodeless discharge lamp lighting device according to claim 1, wherein the power control circuit further includes a period in which a high-frequency voltage applied to the induction coil is gradually increased during a turn-off period of the electrodeless discharge lamp.   6. The electrodeless discharge lamp lighting device according to claim 5, wherein the power control circuit gradually increases a high-frequency voltage applied to the induction coil by changing an operating frequency of the switching element. 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,
7. The lighting device according to claim 1, wherein the high-frequency power circuit is the electrodeless discharge lamp lighting device according to any one of claims 1 to 6.

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