JP2009158171A - Discharge lamp lighting device and illumination apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device which prevents flickering of brightness of a discharge lamp by carrying out appropriately control at the time of transition between target values of a lamp current in one arbitrary period of PWM control, and an illumination apparatus using the same. <P>SOLUTION: The discharge lamp lighting device is equipped with a DC power supply RDC, an inverter circuit INV which converts DC voltage supplied from the DC power supply into AC voltage, a load circuit LC which includes a resonance circuit and is connected to the output end of the inverter circuit and interposed between the inverter circuit and a discharge lamp DL, and a control means CC in which, at the time of lighting control of the discharge lamp by PWM control, at least two different target values are established in one period of the PWM control and a transition period in which the lamp current changes sequentially between the adjoining target value periods is provided, and which carries out light-control lighting of the discharge lamp by carrying out feed-back control during the transition period. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an improvement of a discharge lamp lighting device that performs dimming lighting by PWM control in a deep dimming region and a lighting fixture using the same.

  It is well known that PWM control is suitable for dimming lighting in the deep dimming region of the discharge lamp. As one configuration, the output voltage of the voltage conversion circuit is changed by dimming means to adjust the discharge lamp. Providing frequency control means that can shift light gradually from a frequency in the vicinity of the resonance frequency of the LC resonance circuit to a first frequency higher than the resonance frequency within a predetermined time in the vicinity of the dimming lower limit of the discharge lamp. Is known (see Patent Document 1).

  According to Patent Document 1, the predetermined time is set longer than a transient response time which is generally considered to be about Q (sharpness of resonance) / f1 (operating frequency after change). It is described that di / dt stress generated in the switching element can be suppressed.

  When performing dimming lighting by PWM control in the deep dimming region, it is necessary to apply a high voltage pulse to the discharge lamp when shifting from extinguishing to lighting while repeating intermittent lighting and extinguishing.

JP 2003-197392 A

  However, when a load circuit having a resonance circuit is interposed between the inverter circuit and the discharge lamp, there is a problem that brightness flickers due to variations in the output of the high voltage pulse. In Patent Document 1, in order to suppress di / dt stress generated in the switching element of the inverter circuit, a predetermined time longer than the transient response time is set as the transition period, and the frequency is gradually shifted during the transition period. It is necessary to let

  The present invention relates to a discharge lamp lighting device that prevents flickering of brightness of a discharge lamp by appropriately performing control at the time of transition between target values of a lamp current in an arbitrary one cycle of PWM control, and illumination using the same The purpose is to provide equipment.

  A discharge lamp lighting device according to the present invention includes a DC power source; an inverter circuit that converts a DC voltage supplied from the DC power source into an AC voltage; a resonance circuit that is connected to the output terminal of the inverter circuit, and the inverter circuit and the discharge A load circuit interposed between the lamp and the lamp; when the discharge lamp is dimmed by PWM control, at least two different target values are set in one cycle of the PWM control, and the lamp current between adjacent target value periods And a control means for dimming and lighting the discharge lamp by performing feedback control during the transition period.

  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 and applies it to the inverter circuit as an input voltage. The DC power supply may be a DC power supply, a battery power supply, a capacitor, or the like obtained by rectifying an AC voltage. Further, the DC power supply is allowed to have a DC voltage conversion function and an active filter function. Although the DC voltage conversion function and the active filter function are 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 output from a DC power source into an AC voltage, 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 full bridge type inverter, a half bridge type inverter, a single stone type inverter, or the like can be used.

  [Load Circuit] The load circuit includes a resonance circuit, and is 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 the resonance circuit, it is possible to apply a resonance voltage moderately resonated to the discharge lamp as desired in 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 the 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.

  [Regarding Control Unit] The control unit sets at least two different target values in one cycle of PWM control when the discharge lamp is dimmed by PWM control, and the lamp current is sequentially applied between adjacent target value periods. It is a means for dimming the discharge lamp by providing a changing transition period and performing feedback control during the transition period. In the present invention, PWM control is to control light output as a time average value by controlling the time ratio of each target value with at least two light output values as target values in one cycle of a predetermined period. It means to do.

  In the present invention, the dimming of the discharge lamp may be performed by PWM control over the entire region from full light lighting to deep dimming, or only the deep dimming region may be PWM control, and the other regions may be AM control. Good. Note that the PWM control means dimming using a pulse width control method. The AM control means amplitude control method dimming.

  In one cycle of the PWM control, the output value of the inverter circuit is supplied to the discharge lamp, that is, the target value that the discharge lamp is substantially turned on, and the output that is not supplied is OFF, that is, the target value that the discharge lamp is substantially turned off. The target values for the two controls are included at least. Further, as the control target value, ON is divided into a plurality of level values, and three or more target values can be set as a whole. Each target value period is provided in one cycle of PWM control. In the present invention, in addition to the above, a transition period is provided between two adjacent target value periods. However, it can also be recognized that the transition period is a part of two target value periods that are adjacent in the actual aspect. The PWM frequency is generally set to 100 Hz to several kHz.

  In the transition period, the lamp current is sequentially changed from the adjacent target value preceding in time toward the next target value. At that time, the control means performs feedback control. The object of this feedback control is the voltage supplied to the discharge lamp and / or the lamp current. In this case, it is preferable that the lamp voltage is feedback-controlled before the discharge lamp is lit, that is, at the start, and the lamp current is feedback-controlled after the discharge lamp is started and lit. In the lamp voltage feedback control, a high starting voltage can be maintained constant, and in the lamp current feedback control, the lamp current can be increased and decreased in a stable and sequential manner toward the next adjacent target value.

  Means for sequentially increasing or decreasing the lamp current during the transition period is not particularly limited in the present invention. For example, the oscillation frequency of the inverter circuit is fixed and the resonance frequency of the load circuit is changed. This changes the position of the oscillation frequency on the resonance characteristic curve of the load circuit, so that the lamp current supplied to the discharge lamp can be increased or decreased. Further, the oscillation frequency of the inverter circuit may be changed, or the input voltage of the inverter circuit may be changed. In the latter case, the input voltage can be made variable by using a variable voltage DC power supply.

  Further, the control means sets the length of the target value period, that is, the time width during which the discharge lamp is substantially lit in one cycle of PWM control, that is, the integrated value of the variable proportional to the light emission amount of the discharge lamp during the period. Can be configured to switch to a target value period that is OFF, that is, substantially extinguished. Here, the variable proportional to the light emission amount of the discharge lamp means detection data of illuminance formed by lighting of the discharge lamp, and the electric variable means lamp power data or lamp current data. The predetermined value is an integrated value of a variable corresponding to the target value for dimming.

  In the above aspect, when the light output of the discharge lamp in one cycle of the PWM control reaches the target value, the ON period is ended at that time and the process proceeds to the OFF period, so that dimming control with stable light output is realized. . Particularly in the deep light control region, the effect that a slight variation in the lighting start timing of the discharge lamp during one PWM control cycle causes a flickering of the brightness of the light output of the discharge lamp becomes relatively significant. It is effective for suppressing the above-mentioned influence. The above aspect is effective when the control means performs the feedback control of the lamp voltage until the discharge lamp starts and lights up, and the lamp current feedback control is performed after the lighting.

  Further, it is effective that the control means shortens the feedback control cycle so as to synchronize with one oscillation cycle of the inverter circuit. As a result, the response of the feedback control becomes faster, the shift to the target value can be made earlier, and the dimming control in the deep dimming region is stabilized. As a result, it is possible to stably perform deep dimming up to a dimming degree close to 0%.

Next, other modes that can be permitted by 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. As a result, the above-described control can be finely executed. According to this aspect, in addition to finely and accurately performing dimming control, it is possible to incorporate various control means other than the dimming control described below.
2. The control means includes storage means for storing the output frequency of the inverter circuit.
3. The control means generates a drive signal for the inverter circuit.
4). The control means has a feedback control function to maintain the output of the inverter circuit at a predetermined value or to change it as desired.
5. The control means performs protective operations such as end-of-life determination of the discharge lamp and determination of whether or not the discharge lamp is mounted. Along with this, known circuit means such as a lamp voltage and lamp current detection circuit can be added to the discharge lamp lighting circuit.

  [Other Configurations] As other configurations in the present invention, the following can be appropriately adopted as desired.

  1. (Discharge Lamp) In the present invention, the discharge lamp may be either a low pressure discharge lamp or a high pressure discharge lamp. However, it is particularly suitable for low-pressure discharge lamps such as fluorescent lamps. The low-pressure discharge lamp may be either a hot cathode type having a filament electrode or a cold cathode type. The low-pressure discharge lamp is typified by a fluorescent lamp, but may be a black light, a sterilization lamp, or the like.

  2. (Regarding Filament Heating Circuit) The filament heating circuit is a means for heating the filament electrode of the hot cathode discharge lamp by supplying an auxiliary heating current separately from the lamp current to a required level. The filament heating circuit is preferably configured to heat the filament electrode prior to starting the discharge lamp and to heat the filament electrode as required according to the dimming degree even during lighting. For example, if the auxiliary heating current is configured to be adjustable using a switching element, the auxiliary heating current can be adjusted as desired by controlling the switching of the switching element.

  For the power source of the auxiliary heating current, various known circuit systems such as a filament transformer energized by the output of the inverter circuit can be employed. In addition, it is possible to know that a required amount of auxiliary heating current according to the dimming rate is supplied by measuring in advance.

  3. (Regarding Discharge Lamp Operating State Detection Unit) The discharge lamp operating state detection unit is a unit that detects at least one of the lamp voltage and the lamp current, and is effective when used in the aforementioned feedback control. In addition, when detecting at least any one of a lamp voltage and a lamp current, you may detect them directly and you may detect them in the site | part which can detect indirectly in a discharge lamp lighting device.

  The lighting fixture of the present invention includes a lighting fixture body, a discharge lamp, and a discharge lamp lighting device. The luminaire is a concept that includes all means using the light emission of the discharge lamp, and allows a variety depending on the application. The luminaire main body refers to the remaining part of the luminaire excluding the discharge lamp and the discharge lamp lighting device. The discharge lamp is as described above. The discharge lamp lighting device is the discharge lamp lighting device of the present invention described above.

  According to the present invention, when the control means performs dimming by PWM control of the discharge lamp, at least two different target values are set in one cycle of PWM control, and the lamp current is sequentially applied between adjacent target value periods. By providing a transition period that changes and performing feedback control during the transition period, it is possible to appropriately perform control at the time of transition between the target values of the lamp current in any one cycle of PWM control for dimming the discharge lamp. Accordingly, it is possible to provide a discharge lamp lighting device and a lighting apparatus using the same, in which variation in high voltage pulse output at the time of starting is suppressed and flickering of the brightness of the discharge lamp is prevented.

  In addition, during the transition period, the control means performs the feedback control of the lamp voltage before the fluorescent lamp is lit and performs the feedback control of the lamp current after the discharge lamp is lit, thereby sequentially increasing or decreasing the lamp current during the transition period. Regardless of the means used to achieve this, stable target value transition can be performed.

  Further, the control means substantially ends the target value period of lighting when the integrated value of the variable proportional to the light emission amount of the discharge lamp during the period reaches a predetermined value, so that the target of substantially extinguishing the target value period. By switching to the period, dimming control with stable light output is realized. Particularly in the deep light control region, the slight variation in the lighting start timing of the discharge lamp during one PWM control period tends to cause a flicker of brightness on the light output of the discharge lamp. According to the aspect, it is effective for suppressing the influence.

  Furthermore, since the feedback control cycle is synchronized with one cycle of the oscillation of the inverter circuit, the feedback control response becomes faster and the transition to the target value can be made faster, and the deep dimming region Dimming control at is stable.

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

  FIG. 1 is a circuit diagram showing a first embodiment for carrying out the discharge lamp lighting device of the present invention. In this embodiment, the discharge lamp lighting device is configured to include a DC power supply RDC, an inverter circuit INV, a load circuit LC, lamp voltage detection means VID, lamp current detection means ID, and control means CC. In the figure, symbol AC is a low-frequency AC power source, 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 its AC input terminal connected to the low-frequency AC 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 formed of a half-bridge type 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.

  The load circuit LC is configured by a DC cut capacitor C2 and a resonance circuit RC forming a series circuit and connected between the output terminals of the inverter circuit INV. The resonance circuit RC includes a series resonance circuit of an inductor L1 and a resonance capacitor C3. A discharge lamp DL is connected in parallel with the resonant capacitor C3. The discharge lamp DL is a hot cathode fluorescent lamp.

  The lamp voltage detection means VlD is a means for detecting the voltage across the discharge lamp DL. A pair of resistors R1 and R2 are connected between both ends of the discharge lamp DL, and rectified by a diode D1 connected in parallel to the resistor R2 among the AC voltage of the terminal voltage divided by the resistor R2. Thus, only positive polarity voltage is controlled and input to the control means CC described later.

  The lamp current detecting means IlD is inserted in a ground-side power line connecting the discharge lamp DL and the inverter circuit INV, and includes a resistor having a small resistance value, a current transformer, and the like. Is input to control means CC described later.

  The control means CC is composed mainly of a microcomputer, and receives an analog detection signal sent from the lamp voltage detection means V1D and the lamp current detection means ID and converts it into a digital format, and an A / D converter function unit ADC, A calculation / storage function unit PM and a drive signal generation function unit DSG are provided. The A / D converter function unit ADC sends the digitized detection data to the calculation / storage function unit PM. The calculation / storage function unit PM compares the feedback data with the target value data, determines the oscillation frequency of the drive signal, and controls the drive signal generation function unit DSG. The drive signal generated from the drive signal generation function unit DSG is supplied to the switching elements Q1 and Q2 of the inverter circuit INV to be switched.

  When the discharge lamp DL is dimmed by PWM control, the control means performs a control operation in the form described below.

  In the control means CC, as shown in the target value time chart of FIG. 2, two target values Ref.1 and Ref.2 are preset for the lamp current in one cycle of PWM control. The target value Ref. 1 is a target value at which the discharge lamp DL is substantially extinguished. The target value Ref. 2 is a target value at which the discharge lamp DL is substantially turned on.

  In one cycle T of the PWM control, transition periods d3 and d4 are provided in addition to the period d1 of the target value Ref.1 and the period d2 of the target value Ref.2. The transition period d3 is located between the period d1 of the target value Ref.1 and the period d2 of the target value Ref.2. The transition period d4 is located between the period d2 of the target value Ref.2 and the period d1 of the target value Ref.1. In the transition period d3, the lamp current is controlled so as to increase gradually by connecting the lamp current value period d1 of the target value Ref.1 to the lamp current period of the target value Ref.2 in an inclined manner. In the transition period d4, control is performed such that the lamp current is sequentially reduced by connecting the lamp current value period d2 at the target value Ref.2 to the lamp current period d1 at the target value Ref.1 in an inclined manner. Therefore, one period T of the PWM control is constituted by the sum of the periods d1, d3, d2, and d4.

  Further, the control means CC controls the operation of the discharge lamp lighting device in order to increase or decrease the lamp current in the transition periods d3 and d4. In this embodiment, for example, the oscillation frequency of the inverter circuit INV is changed toward the increase / decrease direction of the lamp current.

  Further, the control means CC performs feedback control of the discharge lamp lighting device during the transition periods d3 and d4 as shown in the schematic waveform diagrams of the lamp voltage and lamp current explaining the circuit operation centering on the transition period of FIG. In FIG. 3, (a) is an enlarged view centering on the transition period d3 of the target value time chart, (b) is the lamp voltage of the discharge lamp, and (c) is the lamp current. .

  That is, in the first half of the transition period d3, lamp voltage feedback control Vl-FBC is performed to maintain a high voltage at which the lamp voltage can be started at a constant value, and the discharge lamp DL is awaited to start. In the latter half of the lighting start threshold value, the discharge lamp DL is lit, so the lamp current feedback control Il-FBC is switched and the lamp current is gradually increased so as to reach the target value Ref. To go.

  Although not shown in the transition period d4, although feedback control similar to the above is performed, the target value is transitioned from Ref. 2 to Ref. Vice versa.

  FIG. 4 is a waveform diagram of each part for explaining the detection operation of the lamp voltage detection means. (A) is a drive signal waveform of the switching element Q1 of the inverter circuit INV, (b) is an AC lamp voltage waveform detected ( c) is a half-wave rectified feedback voltage waveform that is input to the control means CC. Note that the control means CC performs feedback control by reading the instantaneous value of the lamp voltage at the center position of the drive signal and reading the feedback signal.

  Next, a second embodiment for implementing the discharge lamp lighting device of the present invention will be described with reference to the schematic waveform diagram of FIG. That is, in this embodiment, a variable proportional to the light emission amount of the discharge lamp DL during the period, for example, when the integrated value of the lamp power reaches a predetermined value, the lighting target value period d2 is substantially ended, It is configured to switch to the target period d1 that is substantially extinguished.

  Therefore, in this embodiment, the light emission amount of the discharge lamp DL in each cycle of the PWM control is substantially constant. Therefore, the light output can be stabilized even when the start timing varies. Although the transition period is omitted in FIG. 5, the same is true even in the case where there is the transition period described above.

The circuit diagram which shows the 1st form for implementing the discharge lamp lighting device of this invention Similarly target value time chart Schematic waveform diagram of lamp voltage and lamp current, explaining the circuit operation around the transition period Similarly, the waveform diagram of each part explaining the detection operation of the lamp voltage detection means Schematic waveform diagram illustrating a second embodiment for carrying out the discharge lamp lighting device of the present invention

Explanation of symbols

  ADC ... A / D conversion function unit, BUC ... boost chopper, C1 ... smoothing capacitor, C2 ... DC cut capacitor, C3 ... resonance capacitor, CC ... control means, DL ... discharge lamp, DM ... dimming signal generating means, DSG ... Drive signal generation function unit, FBR: full-wave rectification circuit, ID: lamp current detection means, INV: inverter circuit, L1: inductor, LC: load circuit, PM: calculation / recording function unit, Q1, Q2, Q3, Q4 ... Switching element, RC ... resonance circuit, VLD ... lamp voltage detection means

Claims (5)

DC power supply;
An inverter circuit for converting a DC voltage supplied from a DC power source into an AC voltage;
A load circuit including a resonance circuit and connected to the output terminal of the inverter circuit and interposed between the inverter circuit and the discharge lamp;
When the discharge lamp is dimmed by PWM control, at least two different target values are set in one cycle of PWM control, a transition period in which the lamp current sequentially changes is provided between adjacent target value periods, and Control means for performing dimming lighting of the discharge lamp by performing feedback control during the transition period;
A discharge lamp lighting device comprising:   The control means is set with a target value at which the discharge lamp is substantially extinguished and a target value at which the discharge lamp is substantially lit. In the transition period, feedback control of the lamp voltage is performed before the fluorescent lamp is lit, and discharge is performed. 3. The discharge lamp lighting device according to claim 1, wherein after the lamp is lit, feedback control of the lamp current is performed.   The control means sets a substantially target value period for lighting and a target value period for substantially non-lighting in one cycle of PWM control, and substantially sets the target value period for lighting as the light emission of the discharge lamp during the period. 3. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is terminated when the integrated value of the variable proportional to the amount reaches a predetermined value, and is switched to a target period of substantially extinguishing.   The discharge lamp lighting device according to any one of claims 1 to 3, wherein a period of the feedback control is synchronized with one period of oscillation of the inverter circuit. A lighting fixture body;
A discharge lamp disposed in the luminaire body;
The discharge lamp lighting device according to any one of claims 1 to 3, wherein the discharge lamp is lit.
The lighting fixture characterized by comprising.

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