JP2008277149A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device which can be set up at a desired lighting-control level by using a delayed phase zone of resonant characteristics of a load circuit and is suitable for lighting control, especially at a middle luminance range. <P>SOLUTION: The discharge lamp lighting device includes a direct current power source RDC, an inverter circuit INV for converting direct current voltage output from the direct current power source into high-frequency voltage, the load circuit LC connected with an output end and having a resonant circuit RC and making a discharge lamp DL connect, and a lighting adjustment control means CC for light-adjusting and lighting the discharge lamp by adjusting high-frequency power entered into the discharge lamp, in that a frequency switching cycle is formed by a first frequency period in a delayed phase zone of the resonant characteristics of resonant frequency f0 and a second frequency period in a delayed phase zone of the resonant characteristics of the resonant frequency f0 at respective delayed phase zones of two resonant characteristics in the range of the resonant characteristics of the resonant frequency f0 and the resonant frequency of resonant frequency f0/n (n: an odd number). <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 in which the operating frequency of the inverter circuit is set within a range of f0 / 3 to f0 / 2 with respect to the resonance frequency f0 of the load circuit when the discharge lamp is fully lit, and higher than f0 when dimming. The lighting device is known (see Patent Document 1).

  According to the discharge lamp lighting device described in Patent Document 1, the lighting state can be switched to all-light lighting or dimming while preventing the switching element of the inverter circuit from performing the phase advance operation.

Japanese Patent Laid-Open No. 10-294193

  However, the discharge lamp lighting device described in Patent Document 1 has no problem when the dimming lighting is step dimming, but is not suitable because it cannot secure a sufficient operating frequency change range for a wide range of continuous dimming. is there.

  An object of the present invention is to provide a discharge lamp lighting device that can be set to a desired dimming level by using a slow phase region of a resonance characteristic of a load circuit, and is particularly suitable for dimming in a middle luminance region. .

  Another object of the present invention is to provide a discharge lamp lighting device suitable for continuous dimming over a wide range.

  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 resonance circuit that is connected to the output terminal of the inverter circuit; A load circuit connected to the discharge lamp; between the respective slow-phase regions of the two resonance characteristics in the range of the resonance characteristic of the resonance frequency f0 of the load circuit and the resonance characteristic of the resonance frequency f0 / n (n: odd number); A frequency switching period is formed between a period of the first frequency in the slow phase region of the resonance characteristic of the resonance frequency f0 / n and a period of the second frequency in the slow phase region of the resonance characteristic of the resonance frequency f0. And dimming control means for dimming and lighting the discharge lamp by adjusting the high-frequency power input to the discharge lamp.

  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.

  Further, when the value of the DC voltage output of the DC power supply is changed, the high frequency voltage of the inverter circuit changes, so that the discharge lamp that is lit when this high frequency voltage is applied can be dimmed. Changing the value of the DC voltage output of the DC power supply can be easily realized by providing a chopper circuit in the DC power supply, for example.

  [Inverter Circuit] The inverter circuit is a means for converting a DC voltage 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.

  The inverter circuit is preferably a separately excited type that receives a drive signal from a control means described later. Therefore, for example, it is possible to change the operating frequency of the inverter circuit by changing the oscillation frequency by configuring so as to output a drive signal from the control means. Note that by making the frequency variable, the high-frequency output voltage can be made constant or dimmed as described later.

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

  [Load Circuit] The load circuit includes a resonance circuit and is connected to the output terminal of the inverter circuit. The discharge lamp is connected to a load circuit. The resonance circuit has a resonance frequency f0 resonance characteristic or a resonance characteristic of resonance frequency f0 / n (n: odd number). The resonance circuit is preferably a series resonance circuit, and the discharge lamp is connected to a position to which a resonance voltage on resonance characteristics corresponding to the oscillation frequency of the inverter circuit is applied.

  For example, the resonance characteristics at the resonance frequency f0 are described as follows. With the resonance frequency f0 as a boundary, a frequency above f0 is a slow phase region, and below f0 is a phase advance region. Similarly, even in the low-order resonance characteristics with a resonance frequency of f0 / n, the region above the resonance frequency is a slow phase and the following region is a phase advance region. Therefore, in the case of the resonance characteristics at the middle of the adjacent resonance characteristics, for example, the resonance characteristics at the resonance frequency f0 and the resonance characteristics at the adjacent resonance frequency f0 / 3, with the middle frequency f0 / 2 as a boundary, the higher is the phase advance region, The range from f0 / 2 to f0 / 3 is the slow phase region.

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

  [Regarding Dimming Control Unit] The dimming control unit is a unit that controls the oscillation frequency of the inverter circuit for dimming and lighting the discharge lamp according to the dimming signal, and at least the oscillation frequency of the inverter circuit is It is means for controlling the inverter circuit for dimming and lighting the discharge lamp by PWM by changing the mode.

  In the present invention, the oscillation frequency of the inverter circuit INV includes an aspect that is switched at least at a predetermined cycle during dimming. That is, the dimming control means supplies a drive signal to the switching element of the inverter circuit, for example, and switches the oscillation frequency of the inverter circuit by periodically changing the frequency of the drive signal as follows. Can do.

  In the above control, one resonance is generated between the respective slow-phase regions of the two resonance characteristics in the range between the resonance characteristic of the resonance frequency f0 of the load circuit and the resonance characteristic of the resonance frequency f0 / n (n: odd number). A frequency switching period T is formed by a period T1 of the first frequency fa in the slow phase region of the characteristic and a period T2 of the second frequency fc in the slow phase region of the other adjacent resonance characteristic.

  In the frequency switching period T, when performing PWM control in which the lower period T1 is the on period and the higher period is the off period of the period T1 of the first frequency fa and the period T2 of the second frequency fc By changing the duty ratio, which is the ratio of the ON period to the period T, the power supplied to the discharge lamp can be adjusted to a desired dimming degree. In order to change the duty ratio, the duty cycle may be constant and the switching period may be changed, the frequency switching period may be constant and the on period may be changed, or both may be changed.

  In setting the frequency for dimming control, it is preferable to select the two resonance characteristics as a resonance characteristic at the resonance frequency f0 and a resonance characteristic at f0 / 3 for the following reason. That is, with this selection, noise is hardly generated and circuit design is facilitated. More specifically, the minimum oscillation frequency of the inverter circuit is usually required to be 45 kHz or higher so as not to interfere with the infrared remote controller. For example, when one of the resonance characteristics is set to a slow phase region of f0 / 5, The value of the frequency f0 becomes considerably high, and electromagnetic noise is likely to be generated. As a result, it becomes troublesome to design so as to suppress the generation of noise. On the other hand, in the case of the resonance characteristic of f0 / 3, since the frequency is considerably lower than the above, it is relatively easy to suppress noise generation.

  Then, as a result of the dimming control by switching the oscillation frequency described above, the electric power supplied to the discharge lamp is adjusted to be lower than when all the lights are turned on, and the discharge lamp is dimmed. Further, when the oscillation frequency of the inverter circuit is the first frequency fa, the main power for PWM control is input to the discharge lamp, and when the oscillation frequency of the inverter circuit is the second frequency fc, the remaining power is input. Alternatively, a minute current that causes a weak discharge to occur in the discharge lamp flows, so that the high electrode temperature can be maintained. For this reason, smooth dimming operation can be performed.

  In the dimming control of the present invention, the reciprocal 1 / T of the frequency switching period T, that is, the switching frequency F is 1/10 of the operating frequency f of the inverter circuit in order to control the dimming degree continuously and smoothly. Below, and preferably 1 kHz or more. If it exceeds 1/10, the number of periods of the high-frequency voltage contained in one pulsed high-frequency voltage becomes too small, making it difficult to perform fine dimming control. Further, if the frequency switching frequency F is less than 1 kHz, the re-ignition voltage maintains a high value, and thus flickering in brightness due to re-ignition cannot be reduced.

  When dimming over a wider range beyond the above dimming control range according to the present invention, it is allowed to combine dimming control methods such as the following frequency control method and voltage control method. When the lighting level of the discharge lamp from full lighting, that is, 100% dimming to extinguishing, that is, from 0% dimming, is divided into four areas: high luminance, medium luminance, low luminance, and deep dimming. A dimming range suitable for performing dimming control according to the invention is a medium luminance range. Although the above classification is conceptual and numerically unclear, for example, the dimming degree is 100 to 80% in the high luminance range, the dimming degree is 80 to 50% in the middle luminance range, and the 50 to 20% is in the low luminance range. The deep light control range is 20 to 0%. However, an increase or decrease of about 10% is allowed for these numerical ranges. Further, the dimming in the deep dimming region can be PWM control, which will be described later, different from the present invention.

  Therefore, the following dimming control methods can be combined with the control method of the present invention in accordance with the desired dimming mode in each of the above luminance ranges. For example, when the dimming by the control of the present invention is applied to a medium luminance range, for example, continuous dimming over a high luminance range or low luminance range or continuous dimming between a high luminance range or a deep dimming range is possible. become. Of course, dimming only in a desired specific luminance range may be used. When the oscillation frequency of the inverter circuit is changed by the dimming control means, it is preferable to change the frequency of the drive signal formed by the dimming control means. The frequency of the drive signal is equal to the oscillation frequency of the inverter circuit.

  1. Aspect of frequency control method. In this aspect, dimming is performed by changing the oscillation frequency of the inverter circuit. That is, if the oscillation frequency of the high frequency voltage of the inverter circuit applied to the resonance circuit of the load circuit is changed, the operating point on the resonance characteristic of the load circuit to which the discharge lamp is connected moves and the degree of resonance changes. The discharge lamp can be dimmed by changing the effective value of the applied high-frequency voltage in accordance with the dimming signal. In the case of dimming by this method, it is preferable to perform the dimming in a slow phase region having a frequency higher than the resonance point of the resonance characteristic curve.

  Thus, this aspect is suitable for dimming control in a high luminance region and a low luminance region.

  2. A mode of voltage control system. In this aspect, dimming is performed by modulating the amplitude of the lamp current by reducing the effective value of the DC voltage output from the DC power supply. That is, when the DC voltage output from the DC power supply is reduced, the high-frequency voltage output from the inverter circuit is reduced accordingly. Therefore, when this high-frequency voltage is applied to the discharge lamp, the high-frequency power supplied to the discharge lamp is reduced. Is reduced and the discharge lamp is dimmed. In order to reduce the DC voltage output of the DC power supply according to the dimming signal, a chopper circuit, such as a step-up chopper or a step-down chopper, can be added to the DC power supply. It is preferable to set the oscillation frequency of the high-frequency voltage at the time of voltage control in the slow phase region of the resonance characteristic of the load circuit. The voltage control method can also be combined when generating the high frequency voltage in a pulse form in the PWM control method.

  Thus, this aspect is also suitable for dimming control in a high luminance region and a low luminance region.

  3. Above 1. And 2. The aspect which uses the aspect of this together. That is, the above 1. And 2. It is also possible to perform dimming by using this embodiment together.

  4). Embodiment of PWM control system. This aspect is suitable for deep light control, and the PWM control switching period is formed in a first period in which a high-frequency voltage is applied and a second period in which the application of the high-frequency voltage is cut off. Further, in the case where the light control in the deep light control region is performed in this mode, the frequency of the high frequency voltage applied to the discharge lamp in the first period is set to the frequency fd in the slow phase region of the resonance characteristic of the resonance frequency f0. Is good. Thereby, the lamp current can be reduced by a high frequency. In this aspect, the discharge lamp is lit intermittently.

  Next, the dimming 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. Then, dimming control can be performed finely and accurately. Further, various control means other than the dimming control can be incorporated together.

  [Other Configurations] In the present invention, in addition to the essential configuration requirements described above, for example, the following configurations can be added as desired.

  1. (Discharge lamp) In the present invention, the discharge lamp is not particularly limited. However, a low-pressure discharge lamp is suitable for high-frequency lighting. The low-pressure discharge lamp is suitable for lighting a low-pressure mercury vapor discharge lamp represented by a fluorescent lamp. The low-pressure mercury vapor discharge lamp includes a cold cathode type and a hot cathode type, and any of them may be used.

  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, the resonance frequency f0 is between the respective slow-phase regions of the two resonance characteristics within the range of the resonance characteristic of the resonance frequency f0 of the load circuit and the resonance characteristic of the resonance frequency f0 / n (n: odd number). In the discharge lamp, a switching cycle is formed between the period of the first frequency in the slow phase region of the resonance characteristic of / n and the period of the second frequency in the slow phase region of the resonance characteristic of the resonance frequency f0. The dimming control means is configured to dimm and light the discharge lamp by adjusting the high-frequency power to be input, so that a discharge lamp lighting device capable of dimming at a desired level with less stress on the circuit. Can be provided.

  In addition, a discharge lamp capable of continuous dimming over a wide range with little stress on the circuit by performing dimming by the above control in the middle luminance range and dimming in the high luminance range and low luminance range by the frequency control method. A lighting device can be provided.

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

  1 to 4 show a first embodiment for implementing a discharge lamp lighting device according to the present invention. FIG. 1 is a circuit diagram, FIG. 2 is a graph showing resonance characteristics of a load circuit, and FIG. A graph showing the relationship between the current-voltage characteristics and the operating characteristics of the discharge lamp, and FIG. 4 is a waveform diagram of the lamp current in each luminance region.

  In this embodiment, as shown in FIG. 1, the discharge lamp lighting device includes a DC power supply RDC, an inverter circuit INV, a load circuit LC, a dimming control means CC, a lamp voltage detection circuit VID, a lamp current detection circuit IlD, and a filament heating circuit. It has FHC. In addition, the code | symbol AC is a commercial AC power supply of a low frequency, DL is a discharge lamp, DM is a light control signal generation 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 step-up chopper BUC has an input terminal connected to a DC output terminal of the full-wave rectifier circuit FBR, and a DC output can be obtained from between both ends of the smoothing capacitor C1.

  The inverter circuit INV is a half-bridge inverter, and includes a pair of switching elements Q1 and Q2 connected in series between the output terminals of the boost chopper BUC. The inverter circuit INV performs high-frequency switching of a DC voltage output from the DC power supply RDC, A high frequency voltage is output between both ends of the switching element Q2. 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 that is an output end of the inverter circuit INV. The resonance circuit RC includes a series resonance circuit of an inductor L1 and a resonance capacitor C3.

  Further, the load circuit LC has the resonance characteristics shown in FIG. That is, the resonance frequency of the resonance circuit RC is f0, a high frequency region above f0 is a slow phase region, and a frequency region up to f0 / 2 below f0 is a fast phase region. When the frequency is in the frequency range of f0 / 2 or less, the resonance frequency becomes a slow-phase region again up to the 1/3 lower-order resonance point of f0 / 3, and the frequency region of f0 / 3 or less becomes the fast-advancing region again.

  Further, the load circuit LC has its load characteristics set as shown in FIG. That is, the curve A in the figure is a load characteristic curve at the time of all light, and the curve B is a load characteristic curve at the time of dimming. Curve C is an operating characteristic curve of the discharge lamp DL.

  Thus, the intersection a of the load characteristic curve A in all light and the operation characteristic curve C of the discharge lamp DL is the operation point in all light. Further, the intersection b between the load characteristic curve B during dimming and the operating characteristic curve C of the discharge lamp DL is the operating point during dimming.

  The dimming control means CC functions in correspondence with the dimming signal generating means DM, and the lamp power is a value corresponding to the dimming degree based on detection outputs of a lamp voltage detection circuit VID and a lamp current detection circuit IlD described later. The inverter circuit INV is feedback-controlled so as to maintain the above. The lamp current may be feedback-controlled according to the dimming degree.

  The lamp voltage detection circuit V1D is a means for detecting the lamp voltage of the discharge lamp DL as one means for detecting the electrical state of the discharge lamp DL. The detected lamp voltage is control-inputted to the control means CC.

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

  The dimming control means CC is preferably composed mainly of a microcomputer and a DSP, and performs feedback control of the lamp power based on the lamp voltage detection circuit VlD and the lamp current detection circuit IlD to respond to the dimming signal. A drive signal whose frequency is controlled is supplied to the switching elements Q1 and Q2 of the inverter circuit INV.

  The dimming control means CC is configured to dimm the discharge lamp HDL in the middle luminance range by supplying a drive signal having at least a predetermined frequency switching period to the inverter circuit INV. In addition, the drive signal frequency-controlled in the high luminance range and the low frequency range is supplied to the inverter circuit INV to dim the discharge lamp DHL.

  The filament heating circuit FHC is disposed so as to heat the pair of filament electrodes of the discharge lamp DL as required. In addition, a known thing can be suitably employ | adopted for the circuit structure of the filament heating circuit FHC.

  The discharge lamp DL is a hot cathode type, and a hot cathode type fluorescent lamp or the like can be used. As this type of fluorescent lamp, various fluorescent lamps such as a general illumination type, a high frequency lighting type, a compact type and a bulb type 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, circuit operation in this embodiment will be described.

  The inverter circuit INV performs a DC-AC conversion operation by a drive signal supplied from the dimming 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 dimming control means CC, and the inverter circuit INV applies a high-frequency voltage having an operation frequency equal to the oscillation frequency of the drive signal. Output.

  Since the load circuit LC is connected to the output terminal of the inverter circuit INV, the voltage of the resonance circuit RC becomes a value corresponding to the oscillation frequency of the inverter circuit INV, and the discharge lamp DL connected thereto A voltage having a value on the resonance characteristic corresponding to the operating frequency is applied.

  The discharge lamp DL is started and lit by application of the above-described high-frequency voltage determined by the resonance characteristics of the resonance circuit RC and the oscillation frequency.

  Next, the light control operation will be described.

  In this embodiment, the light is continuously dimmable from the all-light state to the high luminance range, the medium-term range, and the low luminance range.

  The dimming in the all-light state and the high luminance range is performed by a frequency control method. In this case, the dimming control means CC changes the frequency fa of the drive signal with respect to the inverter circuit INV within the range of the slow phase region in the resonance characteristics of the frequency f0 / 3 to f0 / 2, that is, the resonance frequency is f0 / 3. To perform dimming control. In dimming in the high luminance range, the frequency of the high-frequency voltage output from the inverter circuit INV is relatively low, so that the lamp current flowing through the discharge lamp DL is relatively large as shown in FIG. It becomes a continuous high frequency current.

  Dimming in the middle luminance range is performed by a PWM control method. In this case, the dimming control means CC supplies a drive signal whose pulse width is controlled to the inverter circuit INV. The drive signal subjected to the pulse width control has a frequency switching period of the frequency f0 / 3 to f0 / 2, that is, the period T1 of the oscillation frequency fa within the range of the slow phase region in the resonance characteristics of the resonance frequency f0 / 3, and continuous thereto. And a period T2 of the frequency fc in the slow phase region in the resonance characteristics of the resonance frequency f0 or higher. And a desired light control degree is obtained by changing the duty of period T1. As a result, the lamp current flowing through the discharge lamp DL has an operating frequency fa as shown in FIG. 4B, a relatively high voltage high frequency current, an operating frequency fc, and a relatively low voltage. A high frequency current repeatedly flows to perform a dimming operation by pulse width control. When this lamp current flows, the main part of the lamp power is input to the discharge lamp DL during the first period T1. The electrode temperature may be maintained at a high temperature by the current flowing in the second period T2.

  Then, when a drive signal whose pulse width is controlled is supplied to the inverter circuit INV, the dimming operation is performed in the slow phase region in both the resonance characteristics of the resonance frequency f0 / 3 and the resonance characteristics of the resonance frequency f0. The stress on the circuit is not really a problem.

  Next, dimming in the low luminance region is performed by the frequency control method as in the high luminance region. However, in this case, the dimming control means CC supplies the inverter circuit INV with a drive signal having a frequency equal to or higher than the frequency f0 with respect to the inverter circuit INV. For this reason, in dimming in a low luminance region, the frequency of the high-frequency voltage output from the inverter circuit INV is high, so that the lamp current flowing through the discharge lamp DL is a relatively small continuous high-frequency as shown in FIG. It becomes current.

  5 and 6 show a second embodiment for implementing the discharge lamp lighting device of the present invention. FIG. 5 is a graph showing the relationship between each luminance range of dimming and the dimming control method, and FIG. It is a wave form diagram of a drive signal and a lamp current in a light control range.

  In the present embodiment, the dimming method that is optimal for each luminance region is applied by dividing the entire light-on state to the deep dimming state into four luminance regions.

  That is, the same mode as the first mode is adopted for dimming from the all-lighting to the high luminance range, the middle luminance range, and the low luminance range, but the PWM control method is adopted in the deep dimming range. . However, the PWM control in the deep light control region is performed by supplying the inverter circuit INV with a drive signal whose pulse width is generated intermittently as shown in FIG. The lamp current of the discharge lamp DL at this time has an intermittent waveform as shown in FIG. For this reason, it is possible to reliably perform light control in the deep light control region.

  The dimming areas are as follows.

Full light and high brightness range: dimming degree 100-80%
Medium luminance range: Dimming degree 80-50%
Low luminance range: Dimming degree 20-50%
Deep light control range: 0 to 20% of light control

The circuit diagram which shows the 1st form for implementing the discharge lamp lighting device of this invention Graph showing resonance characteristics of load circuit Similarly, a graph showing the relationship between the current-voltage characteristics of the load circuit and the operating characteristics of the discharge lamp Similarly, a waveform diagram of lamp current in each luminance range Graph showing the frequency-lamp current characteristics of the discharge lamp The graph which shows the relationship between each brightness | luminance area of the light control in 2nd form for implementing the discharge lamp lighting device of this invention, and a light control method Similarly, waveform diagram of drive signal and lamp current in deep dimming range

Explanation of symbols

  BUC: Boost chopper circuit, C1: Smoothing capacitor, C2: DC cut capacitor, C3: Resonance capacitor, CC: Dimming control means, DL: Discharge lamp, DM: Dimming signal generation means, FBR: Full wave rectifier circuit, FHC ... Filament heating circuit, ID ... Lamp current detection circuit, INV ... Inverter circuit, L1 ... Inductor, LC ... Load circuit, Q1, Q2 ... Switching element, RC ... Resonance circuit, VLD ... Lamp voltage detection 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 connected to the output terminal of the inverter circuit, including a resonance circuit, and connected to the discharge lamp;
The resonance characteristic of the resonance frequency f0 / n is between the respective slow-phase regions of the two resonance characteristics in the range of the resonance characteristic of the resonance frequency f0 of the load circuit and the resonance characteristic of the resonance frequency f0 / n (n: odd number). The frequency switching period is formed between the first frequency period in the slow phase region and the second frequency period in the slow phase region of the resonance characteristics of the resonance frequency f0, so that the high frequency power input to the discharge lamp is reduced. Dimming control means for adjusting and lighting the discharge lamp;
A discharge lamp lighting device comprising:   The discharge lamp lighting device according to claim 1, wherein the resonance frequency f0 / n (n: odd number) is f0 / 3.   The dimming control means changes the oscillation frequency of the inverter circuit within the range of the frequency f0 / 3 to f0 / 2 in the high luminance range, and changes within the range of the frequency f0 or higher in the low luminance range. The discharge lamp lighting device according to claim 1, wherein the control specified in claim 1 is performed in the dimming in the frequency range.

Images