JP2008234877A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device improved so that the optical output of a discharge lamp does not unnaturally fluctuate when switching light control methods. <P>SOLUTION: This discharge lamp lighting device is equipped with a DC power supply RDC, an inverter circuit INV, a load circuit LC connected to the output of the inverter circuit while including a resonance circuit RC, a light control means to dimly light the discharge lamp throughout the stable area and astable area of frequency-lamp current characteristics of the discharge lamp, and a control means to perform light control of a frequency control system until the oscillating frequency of the inverter circuit reaches a prescribed upper limit frequency f1, and to perform light control of a pulse control system by forming a driving signal so that the repeating frequency of the driving signal to be supplied to the inverter circuit is set at the upper limit frequency f1, and the inverter circuit outputs a pulsed high frequency voltage Vp having duration corresponding to a light control signal, when the oscillating frequency of the inverter circuit has reached the prescribed upper limit frequency f1 in advance. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a discharge lamp lighting device for dimming and lighting a discharge lamp.

  A discharge lamp lighting device configured to perform dimming of a discharge lamp by superimposing a pulse voltage on the lamp voltage is known (see, for example, Patent Document 1).

  The discharge lamp lighting device described in Patent Document 1 performs dimming so that the output voltage of the inverter circuit changes by changing the output voltage of the DC chopper from the rated lighting to the dimming lower limit, In the vicinity, a pulse voltage is superimposed on the lamp voltage. A DC power supply for rectifying and smoothing the AC power supply voltage is connected to the input end of the DC chopper. The pulse voltage superimposed on the lamp voltage is formed by bringing the oscillation frequency of the inverter circuit close to the resonance frequency of the resonance circuit in the load circuit.

  In the discharge lamp lighting device described in Patent Document 1, the inverter circuit outputs a relatively low-frequency high-frequency voltage during the repetition of the pulse voltage, but this dimming has been widely used in the past. It is none other than width control dimming.

  The discharge lamp lighting device generates a pulse voltage having a high peak value by lowering the oscillation frequency of the inverter circuit to approach the resonance frequency of the resonance circuit. During the repetition of adjacent pulse voltages, the inverter circuit is increased in frequency and away from the resonance frequency of the resonance circuit, so that the inverter circuit continues to operate at a relatively low frequency while the discharge lamp is extinguished. Generating voltage.

JP 2003-197391 A

  However, in the above discharge lamp lighting device, when switching from dimming performed by changing the output voltage of the DC chopper from the rated lighting to the dimming lower limit to dimming by the pulse voltage, the switching frequency of the inverter circuit changes. Since the light output of the discharge lamp changes unnaturally, there is a problem that it is difficult to perform smooth dimming continuously.

  An object of the present invention is to provide an improved discharge lamp lighting device so that the light output of the discharge lamp does not change unnaturally when switching the dimming method.

  The discharge lamp lighting device of the present invention includes: a DC power supply; an inverter circuit that inputs a DC voltage output from the DC power supply and converts the DC voltage into a high-frequency voltage; and a lighting frequency of the discharge lamp that is connected to the output terminal of the inverter circuit. Dimming means for dimming and lighting the discharge lamp by reducing the high-frequency power input to the discharge lamp by controlling the inverter circuit over the stable range and non-stable range caused by the relationship; the oscillation frequency of the inverter circuit is a predetermined upper limit Until the frequency is reached, the oscillation frequency of the drive signal supplied to the inverter circuit is changed in accordance with the dimming signal to perform dimming control of the frequency control method, and when the oscillation frequency of the inverter circuit reaches a predetermined upper limit frequency in advance The repetition frequency of the drive signal supplied to the inverter circuit is the upper limit frequency and the pulse has a duration corresponding to the dimming signal It is characterized in that comprises a; and a control unit performing a dimming control of the pulse control scheme a high-frequency voltage to form a drive signal to the inverter circuit outputs.

  The present invention allows the following aspects.

  [Regarding DC Power Supply] The DC power supply is input supply means viewed from an inverter circuit described later, and outputs a DC voltage. A DC power source, a battery power source, a capacitor, or the like obtained by rectifying an AC voltage may be used.

  The DC power supply is allowed to have a DC voltage conversion function. Although the DC voltage conversion function is not particularly limited in the present invention, for example, a step-up chopper, a step-down chopper, or the like can be used alone or combined and connected in multiple stages.

  [Inverter Circuit] The inverter circuit is means for converting a DC voltage including a power supply ripple output from a DC power source into a high frequency, and includes at least one switching element. In the present invention, the circuit system of the inverter circuit is not particularly limited. For example, a half bridge type inverter, a full bridge type inverter, a single stone type inverter, or the like can be used.

  Further, the inverter circuit can be configured to have a variable oscillation frequency. Note that by making the frequency variable, the high-frequency output can be made constant or dimming as described later.

  Further, the inverter circuit is allowed to include an insulated or non-insulated output transformer as desired.

  [Regarding Dimming Means] The dimming means is means for dimming and lighting the discharge lamp according to the dimming signal, and operates the inverter circuit in the following manner for dimming.

  1. A mode of performing frequency control type dimming. That is, when the frequency of the high frequency voltage applied to the resonance circuit of the load circuit is changed, the operating point on the resonance characteristic of the load circuit of the discharge lamp moves and the degree of resonance changes, so the high frequency voltage applied to the discharge lamp is changed. The discharge lamp can be dimmed by changing the dimming signal. For example, in the slow phase region where the frequency is higher than the resonance point of the resonance characteristic curve, the discharge lamp power decreases as the frequency increases, and the dimming degree increases.

2. A mode in which a pulsed high-frequency voltage is repeatedly applied. That is, the discharge lamp can be dimmed by repeatedly applying the pulsed high-frequency voltage to the discharge lamp, in other words, by intermittently applying the high-frequency voltage. Any of the following states may be selected between repetitions of adjacent pulsed high-frequency voltages.
(1) A state in which continuous lighting is performed by continuously applying a high frequency voltage that is relatively low but capable of sustaining arc discharge between the pulsed high frequency voltage and the pulsed high frequency voltage.
(2) A state in which the arc discharge does not last but the weak discharge lasts between the pulsed high-frequency voltage. In such a state, the re-ignition voltage becomes low.
(3) A state in which no voltage is substantially applied to the discharge lamp between the pulsed high-frequency voltage and the pulsed high-frequency voltage. Therefore, neither lighting nor weak discharge continues. This form includes stopping the oscillation of the inverter circuit.

  In this aspect, the dimming degree can be changed by changing the duty of the pulsed high-frequency voltage or changing the repetition frequency of the pulsed high-frequency voltage while fixing the duration of the high-frequency voltage. In short, the duty ratio of the pulsed high frequency voltage may be changed.

  In order to form a pulsed high-frequency voltage, control may be performed to increase the DC voltage output of the DC power supply or to bring the oscillation frequency of the inverter circuit closer to the resonance point side of the load circuit.

  Among the modes for dimming listed above, one mode is applied during a frequency f0-f1 in a relatively moderate stable lighting region in the frequency-lamp current characteristic curve of the discharge lamp shown in FIG. . The frequency f1 is a frequency at which the discharge lamp can be started or re-ignited.

  On the other hand, 1 is applied over the stable lighting region and the unstable lighting region between the frequencies f1 and f3 in the frequency-lamp current characteristic curve of the discharge lamp shown in FIG. That is, this is a mode suitable for application at least during deep light control.

  2. In this aspect, in order to change the dimming degree, the duty of the pulsed high-frequency voltage may be changed, or the duration of the high-frequency voltage may be fixed and the repetition frequency of the pulsed high-frequency voltage may be changed. In short, the duty ratio of the pulsed high frequency voltage may be changed.

  The oscillation frequency of the inverter circuit in the pulsed high frequency voltage is a predetermined frequency (f1). On the other hand, during the period between the adjacent pulsed high-frequency voltages, the oscillation frequency of the inverter circuit is selected from the range of f2-f3 or controlled by the control means described later as an oscillation product.

  [Regarding Control Unit] The control unit is a unit that controls the dimming unit to dimm and light the discharge lamp. In order to dimm the discharge lamp, the control from the rated lighting of the discharge lamp to the so-called dimming lower limit and the control at the time of deep dimming are managed. Note that deep light control is deep light control whose degree of light control is further advanced from the above-described so-called light control lower limit, and is generally 20% or less, preferably 3% or less, and more desirably infinitely up to 0%. Light approaching. Therefore, the present invention intends to provide a discharge lamp lighting device capable of dimming up to deep dimming.

  Dimming control from the rated lighting of the discharge lamp until the oscillation frequency of the inverter circuit reaches a predetermined value is performed by a frequency control method. The frequency control method is the same as described in 1. It is controlling so that it may become the aspect described in (1). That is, the predetermined oscillation frequency is the frequency-lamp current characteristic curve of the discharge lamp shown in FIG. 1, and the high frequency voltage applied to the discharge lamp in the stable lighting region where the characteristic curve is relatively gentle starts the discharge lamp. Alternatively, the frequency f1 that can be re-ignited is selected. For reference, the frequency f1 in the resonance characteristic curve of the load circuit is shown in FIG. In FIGS. 1 and 2, the symbol f0 is the resonance frequency, f3 is the frequency at which the lamp current is 0, and f2 is the boundary frequency between the stable lighting region and the unstable lighting region.

  Dimming control in the range from when the oscillation frequency of the inverter circuit reaches the predetermined value (f1) through the start of dimming from the rated lighting state to the time of deep dimming is performed by a pulse control method. In the pulse control method, 2. The dimming control is performed so as to achieve the mode described in (1). The pulsed high frequency voltage has an oscillation frequency of a predetermined value (f1). Further, during the period between adjacent pulsed high-frequency voltages, if the oscillation frequency is higher than a predetermined value (f1) and the discharge lamp cannot be kept on and the frequency f3 is set to weak discharge, a low-frequency high-frequency voltage is generated. To do. Note that if the drive signal is suspended during the period between adjacent pulsed high-frequency voltages of the drive signal, the discharge lamp is turned off and no weak discharge occurs. Further, during the period between adjacent pulsed high-frequency voltages, the discharge is sustained, but if the frequency f2 is higher than a predetermined frequency, a low high-frequency voltage is generated and the discharge lamp continues when the pulsed high-frequency voltage is applied. And sustain the discharge. Therefore, any one of the above-described aspects can be adopted as desired.

  In order to control the oscillation frequency of the inverter circuit by the control means, the repetition frequency of the drive signal formed by the control means is changed. The repetition frequency of the drive signal is equal to the oscillation frequency of the inverter circuit.

  Next, other aspects of the control means will be described.

  1. The control means is mainly composed of a digital device such as a microcomputer and a DSP (digital signal processor) and an analog IC. This enables fine control.

  And according to this aspect, dimming control can be performed finely and accurately. Further, various control means other than the dimming control can be incorporated together.

  2. The control means includes storage means for storing a desired frequency such as a frequency (f2 or f3) during a period between the predetermined frequency (f1) and the adjacent pulsed high-frequency voltage.

  The specific mode of the frequency stored in the storage means is not particularly limited. For example, as a mode for storing the predetermined frequency (f1), one of the following two means can be adopted.

  The first means stores the repetition frequency of the drive signal at the start of the discharge lamp and stores the frequency at the start of discharge as a predetermined frequency (f1) in the storage means each time or when the discharge lamp is mounted. In this case, a lamp current detection circuit for detecting the start of discharge can be provided. The predetermined frequency (f1) can be accurately stored for each discharge lamp even if there are variations in the discharge lamps and the types.

  The second means stores in the storage means a predetermined frequency (f1) as a frequency set in advance as the frequency at which discharge starts. This means simplifies the configuration.

  Thus, according to this aspect, the dimming control is facilitated and accurate dimming control can be performed.

  3. The control means includes drive signal correction means for obtaining a direct current component in the lamp current flowing by the pulsed high frequency voltage and correcting the drive signal of the inverter circuit so as to cancel the direct current component. When the dimming degree increases and the half wave number of the high frequency voltage included in the pulsed high frequency voltage decreases and the half wave number becomes an odd number, the direct current component in the lamp current flowing by the pulsed high frequency voltage increases. As a result, a cataphoresis phenomenon occurs.

  In order to cancel the DC component by the drive signal correcting means, for example, the repetition frequency of the drive signal is changed for each half wave of the high-frequency voltage, or a DC having a polarity opposite to the detected DC component is superimposed on the discharge lamp. can do. In order to obtain the DC component in the lamp current, for example, the voltage of the load circuit may be detected at both ends of the DC cut capacitor of the load circuit, and the detection locations may be compared.

  According to this aspect, even if a pulsed high-frequency voltage direct current component is included, the direct current component is corrected, so that the occurrence of the catalysis phenomenon can be suppressed.

  [Other Configurations] In the present invention, the following configurations can be added as desired.

  1. (Load circuit) The load circuit can be interposed between the inverter circuit and the discharge lamp when the discharge lamp is connected to the output terminal of the inverter circuit. By connecting the discharge lamp to the output terminal of the inverter circuit via a resonance circuit, it is possible to apply a resonance voltage moderately resonated to the discharge lamp as desired by the load circuit. The resonant circuit is preferably a series resonant circuit, and the discharge lamp is connected to a position on the circuit where a resonant voltage is applied.

  Also, the load circuit can provide a current limiting impedance for the discharge lamp connected thereto. The reactance of the resonance circuit can be used as the current limiting impedance.

  2. (Regarding Filament Heating Circuit) The filament heating circuit is means for heating the filament electrode to a required degree when the discharge lamp is of a hot cathode type. The filament heating circuit preferably heats the filament electrode prior to starting the discharge lamp, and changes the heating amount in accordance with the dimming degree.

  According to the present invention, in frequency control method dimming, when the oscillation frequency reaches a predetermined frequency, the control shifts to pulse control method dimming with a pulsed high-frequency voltage of the predetermined frequency. It is possible to provide a discharge lamp lighting device that does not cause an unnatural change in the light output of the discharge lamp when shifting to the dimming method.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 3 is a circuit diagram showing a first mode for carrying out the discharge lamp lighting device of the present invention.

  In this embodiment, the discharge lamp lighting device includes a DC power supply RDC, an inverter circuit INV, a load circuit LC, a control means CC, a lamp current detection circuit IlD, and a filament heating circuit FHC. Reference symbol DL is a discharge lamp, and DM is a dimming signal generating means.

  The DC power supply RDC includes a full-wave rectifier circuit FBR and a boost chopper BUC. The full wave rectifier circuit FBR has an AC input terminal connected to a commercial AC power source AC. The input terminal of the boost chopper BUC is connected to the DC output terminal of the full-wave rectifier circuit FBR.

  The inverter circuit INV is a half-bridge inverter, and includes a pair of switching elements Q1 and Q2 connected in series between both ends of the smoothing capacitor C1, which is the output end of the boost chopper BUC, and between the both ends of the switching element Q2. High frequency voltage is output to In the present embodiment, the inverter circuit INV also serves as the light control means of the present invention.

  The load circuit LC is configured by a DC cut capacitor C2 and a resonance circuit RC forming a series circuit, and is connected to both ends of the switching element Q2 of the inverter circuit INV. The resonance circuit RC includes a series resonance circuit of an inductor L1 and a resonance capacitor C3.

  The control means CC forms a drive signal with the repetition frequency controlled corresponding to the dimming signal and the lamp current detection circuit IlD described later, and supplies the drive signal to the switching elements Q1 and Q2 of the inverter circuit INV. In the dimming from the rated lighting state, the control means CC performs dimming control using a frequency control method. For this reason, a drive signal whose frequency is repeatedly changed according to the dimming degree of the dimming signal is formed and supplied to the inverter circuit INV.

  When the repetition frequency of the drive signal reaches the predetermined frequency f1, the dimming control is changed to the pulse control method thereafter. For this reason, the control means CC intermittently forms a drive signal having a predetermined frequency f1 for the pulse duration corresponding to the dimming signal and supplies it to the inverter circuit INV. Further, during the period between the pulsed high-frequency voltages, a drive signal having a repetition frequency f3 is formed and supplied to the inverter circuit INV.

  Further, the control means CC performs feedback control so that the lamp current is maintained at a value corresponding to the dimming degree based on a detection output of a lamp current detection circuit IlD described later.

  The lamp current detection circuit IlD is a means for detecting the lamp current of the discharge lamp DL as means for detecting the electrical state of the discharge lamp DL. The detected lamp current is control-inputted to the control means CC.

  The filament heating circuit FHC is disposed so as to heat the pair of filament electrodes of the discharge lamp DL as required.

  As the discharge lamp, a hot cathode fluorescent lamp or the like can be used. As fluorescent lamps, various fluorescent lamps for general illumination, high-frequency lighting-only types, compact types, and bulb types are applicable.

  The dimming signal generating means DM generates a dimming signal having a desired dimming degree according to the operation and supplies it to the control means CC. The dimming signal generating means DM may be disposed at a position separated from the discharge lamp lighting device, or may be disposed inside the discharge lamp lighting device.

  Next, the circuit operation in the first embodiment will be described.

  The inverter circuit INV operates by a drive signal supplied from the control means CC and outputs a high frequency voltage. That is, the switching elements Q1 and Q2 of the inverter circuit INV alternately perform switching operations according to the drive signal sent from the control means CC, and the inverter circuit INV outputs a high-frequency voltage having an oscillation frequency equal to the repetition frequency of the drive signal. .

  Since the discharge lamp DL is connected to the load circuit LC, the discharge lamp DL is lit by receiving application of a high-frequency voltage determined by the resonance characteristics and the oscillation frequency of the resonance circuit RC. When dimming is started from the rated lighting, the control means CC sequentially increases the repetition frequency of the drive signal corresponding to the dimming signal. That is, the discharge lamp lighting device performs dimming control using a frequency control method.

  The repetition frequency of the drive signal is controlled as follows. First, the case of the frequency control method will be described. Since the starting voltage is applied to the discharge lamp DL when the oscillation frequency of the inverter circuit INV is relatively close to the resonance frequency f0, the discharge lamp DL starts to light. Of course, the filament electrode is preliminarily heated prior to starting.

  When the oscillation frequency of the inverter circuit INV is sequentially decreased after the discharge lamp DL is turned on, the voltage applied to the discharge lamp DL is decreased due to the resonance characteristics of the load circuit, so that the light output level of the discharge lamp DL is increased. Dimming is performed at a reduced level. During this time, the oscillation frequency sequentially changes from a value relatively close to the resonance frequency to a predetermined frequency f1, and the dimming degree increases sequentially from the rated lighting.

  Then, when the repetition frequency of the drive signal reaches the predetermined frequency f1, the control shifts to the dimming control of the pulse control system. In this case, the on-duty of the pulsed high-frequency voltage is controlled, but the oscillation frequency of the inverter circuit INV when generating the pulsed high-frequency voltage shifts to the pulse control method without changing to the predetermined frequency. To do. For this reason, an unnatural light output does not occur when the dimming control method is switched.

  FIG. 4 is a waveform diagram of the voltage applied to the discharge lamp DL, that is, the lamp voltage and the lamp current, in the pulse control system. In the figure, the waveform with the symbol V is the lamp voltage, and the waveform with the symbol I is the lamp current.

  As can be understood from the figure, the pulsed high-frequency voltage Vp is applied to the discharge lamp DL at the oscillation frequency f1, and the main current Ia flows, and the low-frequency high-frequency voltage Vw is applied to the discharge lamp DL at the oscillation frequency f3. Thus, a minute current Iw flows. Even when the minute current Iw flows, the discharge lamp DL is turned off. The symbol T in the figure is the repetition period of the pulsed high-frequency voltage Vp.

  Further, the feedback control is performed so that the lamp current is fixed to a value corresponding to the dimming signal by the operation of the lamp current detection circuit ID and the control means CC through the dimming control of the frequency control system and the pulse control system. , Stable dimming is performed.

  Next, another embodiment of the present invention will be described with reference to FIGS.

  FIG. 5 is a circuit diagram showing a second mode for carrying out the present invention. In the figure, the same parts as those in FIG.

  In the present embodiment, when the pulsed high-frequency voltage is asymmetrically positive and negative and applied to the discharge lamp DL, the direct current component is canceled out. In order to realize this, a DC component detection circuit DCD is provided, and its detection output is controlled and input to the control means.

  Further, the control means CC is provided with drive signal correction means therein. The drive signal correcting means detects and compares the load voltage before and after the DC cut capacitor C2 of the drive signal according to the detection output of the DC component detection circuit DCD. As shown in FIG. 6, when the lamp current flowing by the pulsed high-frequency voltage includes an odd number of half-waves of the lamp current and a direct current component is included, the load voltage difference before and after the direct current cut capacitor C2 Appears, and a detection output is generated in the DC component detection circuit DCD.

  The control means CC gives a difference in the time width of adjacent drive signals according to the detection output of the DC component detection circuit DCD. As a result, the DC component is compensated and canceled out, so that the DC component is removed from the lamp current flowing in the discharge lamp DL as shown in FIG.

  Therefore, according to this embodiment, the catalysis phenomenon does not occur in the discharge lamp DL. In addition, dimming up to one cycle (two half waves) of the high frequency voltage as the minimum time width of the pulsed high frequency voltage is possible. For this reason, it is possible to smoothly perform deep dimming up to a dimming degree close to 0%.

  8 to 12 show a third embodiment for carrying out the present invention. FIG. 8 is a circuit diagram, FIG. 9 is a dimming method switching, a driving voltage waveform diagram, a dimming signal, and a dimming degree. FIG. 10 is a graph showing the relationship between the voltage-current characteristics of the discharge lamp with the ambient temperature as a parameter and the output characteristics of the inverter circuit, and FIG. 11 is a graph showing the relation of ΔVL / ΔIL with respect to the lamp current. FIG. 12 is a graph showing the relationship of the lamp current to the oscillation frequency. In FIG. 8, the same parts as those in FIG.

  First, the circuit diagram shown in FIG. 8 will be described. In this embodiment, a lamp voltage detection circuit VlD and a lamp current detection circuit IlD are provided as means for detecting the operating state of the discharge lamp DL.

  Therefore, in the control means CC, the lamp power input to the discharge lamp DL can be feedback-controlled so that the lamp power corresponding to the dimming signal can be kept constant. For this reason, the dimming control becomes more accurate.

  Further, in this embodiment, as shown in FIG. 9, in the dimming control of the pulse control system, the drive signal is stopped during the period between the pulsed high-frequency voltage so that no high-frequency voltage is generated. It is configured.

  For this reason, the lamp current does not trail after the drive signal of the pulsed high-frequency voltage disappears, so as shown in the graph in the figure, it is a frequency control method from the rated lighting state to the middle dimming degree, and then the pulse control Although it becomes a system, it becomes possible to control smoothly and accurately up to a dimming level close to 0%.

  Next, the relationship between the voltage-current characteristics of the discharge lamp and the output characteristics of the inverter circuit in this embodiment will be described with reference to FIG. In the figure, the output characteristics of the discharge lamp DL are shown by a solid line when the ambient temperature is 25 ° C., and the dimming degree increases as the frequency is increased from the frequency f0 to f2, so that the dimming is possible. However, when the frequency is f3, the voltage-current characteristic curve of the discharge lamp and the output characteristic curve of the inverter circuit do not intersect, so the discharge lamp cannot be lit. On the other hand, when the ambient temperature becomes 0 ° C., the output characteristic curve of the discharge lamp DL intersects with the output characteristic curve of the frequency f3, but since it intersects at a plurality of positions, lighting becomes unstable.

  10 is common to the data shown in FIG. 1 and will be described with reference to FIG. 1. Since the frequency-lamp current characteristic curve becomes steep from frequency f2 to f3, the unstable lighting range is obtained. I understand that there is. Therefore, even if the light is adjusted at the frequency f3, flickering of brightness occurs in the unstable lighting region. Therefore, if the pulse control method is used, dimming can be performed even in an unstable lighting region in which the frequency between adjacent pulsed high-frequency voltages is f3. Of course, dimming is possible even when the operation of the inverter circuit INV during the above period is stopped as in this embodiment.

  The upper frequency limit in the pulse control method will be described with reference to FIGS.

  FIG. 11 is a graph created by calculating the change rate ΔVL / ΔIl with respect to the lamp current from the lamp current-lamp voltage characteristics of the FPL55 type fluorescent lamp with the rated lamp power 55W.

  FIG. 12 is a graph of frequency-lamp current characteristics created using the lamp current effective value of the FPL55 fluorescent lamp with respect to the oscillation frequency of the inverter circuit INV when the load circuit LC having the resonance frequency f0 = 67 kHz is used.

  As can be understood from FIG. 12, when the oscillation frequency is 80 kHz or more, the change in the lamp current becomes steep.

  Further, as seen in FIG. 11, when the effective value of the lamp current is about 300 mA or more, there is almost no change in ΔVL / ΔIl. In such a region, the light can be stably lit by fixing the oscillation frequency. On the other hand, when the effective value of the lamp current becomes 300 mA or less and the value of ΔVL / ΔIl changes, it is necessary to control the oscillation frequency according to the electrical characteristics of the discharge lamp DL.

  Therefore, the upper frequency limit obtained by conducting an experiment for each discharge lamp in advance is stored in the control means CC as data, or the lamp current-lamp voltage characteristic is detected, and the upper frequency limit is obtained according to the calculated ΔVL / ΔIl. Means.

  FIG. 13 is a graph showing the frequency-lamp voltage characteristics of the load circuit in the fourth embodiment for carrying out the present invention. A circuit diagram will be described with reference to FIG.

  In the present embodiment, the control means CC has a storage means therein. The storage means is configured to store the oscillation frequency Vs when the discharge lamp DL is lit by sweeping the oscillation frequency of the inverter circuit INV at the start of lighting as the predetermined frequency f1.

  Therefore, according to the present embodiment, an optimum predetermined frequency can be automatically set according to the discharge lamp DL connected to the discharge lamp lighting device.

Graph showing frequency-lamp current characteristic curve of discharge lamp Graph showing the relationship between the resonance characteristics of the resonance circuit and the lamp voltage of the discharge lamp The circuit diagram which shows the 1st form for implementing the discharge lamp lighting device of this invention Waveform diagram of voltage applied to discharge lamp DL in the same pulse control system, that is, lamp voltage and lamp current The circuit diagram which shows the 2nd form for implementing the discharge lamp lighting device of this invention Waveform diagram when the direct current component is included in the lamp current flowing by the pulsed high-frequency voltage Waveform diagram of lamp current compensated for DC component in second embodiment The circuit diagram which shows the 3rd form for implementing the discharge lamp lighting device of this invention Similarly, dimming method switching, driving voltage waveform diagram and graph showing the relationship between dimming signal and dimming degree Similarly, a graph showing the voltage-current characteristics of the discharge lamp and the output characteristics of the inverter circuit Similarly, a graph created by calculating the rate of change ΔVL / ΔIl with respect to the lamp current from the lamp current-lamp voltage characteristics of an FPL55 fluorescent lamp with a rated lamp power of 55 W Similarly, a graph of the frequency-lamp current characteristic created using the lamp current effective value of the FPL55 fluorescent lamp with respect to the oscillation frequency of the inverter circuit INV when the load circuit LC having the resonance frequency f0 = 67 kHz is used. The graph which shows the frequency-ramp voltage characteristic of the load circuit in the 4th form for implementing this invention

Explanation of symbols

  BUC: Boost chopper circuit, C1: Smoothing capacitor, C2: DC cut capacitor, C3: Resonance capacitor, CC: Control means, DL: Discharge lamp, DM: Dimming signal generation means, FBR: Full-wave rectifier circuit, FHC: Filament Heating circuit, IDD ... lamp current detection circuit, INV ... inverter circuit, L1 ... inductor, LC ... load circuit, Q1, Q2 ... switching element, RC ... resonance circuit

Claims (3)

DC power supply;
An inverter circuit that inputs a DC voltage output from a DC power source and converts it into a high-frequency voltage;
A load circuit that includes a resonance circuit and is connected to the output terminal of the inverter circuit and connects the discharge lamp;
Control that controls the inverter circuit over the stable range and non-stable range that are connected to the output terminal of the inverter circuit and caused by the tonnage frequency of the discharge lamp, thereby reducing the high-frequency power input to the discharge lamp and dimming the discharge lamp. With light means;
Until the oscillation frequency of the inverter circuit reaches a predetermined upper limit frequency, the oscillation frequency of the drive signal supplied to the inverter circuit is changed according to the dimming signal to perform dimming control of the frequency control method, and the oscillation frequency of the inverter circuit Drive signal is generated so that the inverter circuit outputs the pulsed high-frequency voltage of the duration corresponding to the dimming signal at the upper limit frequency and the oscillation frequency by the drive signal supplied to the inverter circuit when the frequency reaches the predetermined upper limit frequency A control means for performing dimming control of a pulse control system;
A discharge lamp lighting device comprising:   The control means sets the repetition frequency of the drive signal between adjacent pulsed high-frequency voltages to a value higher than a predetermined frequency so that the discharge lamp is extinguished during dimming control of the pulse control method. Item 2. A discharge lamp lighting device according to Item 1.   3. The discharge lamp lighting device according to claim 1, wherein the control means includes storage means for storing the frequency of the drive signal.

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