JP2008235085A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device in which occurrence of brightness flickering resulting from optical output at the time of re-ignition caused by a pulse state high frequency voltage impression of a thermionic cathode type discharge lamp is suppressed. <P>SOLUTION: The discharge lamp lighting device is equipped with a direct current power source RDC, an inverter circuit INV in which a direct current voltage that is output from a direct current power source is input and converted into a high frequency voltage, a light control means in which the high frequency current that is connected from the inverter circuit to an output edge of the inverter circuit and input into a discharge lamp DL is reduced and the discharge lamp is lighted and controlled, and a control means CC in which the light control means is controlled, so that the discharge lamp is lighted at a light control level in conformity with a light control signal, and that at least at a deep light dimmer time light control of a pulse state high frequency voltage is repeated to a thermionic cathode discharge lamp by intermittently impressing at frequency of 1 kHz or more, and in which a lamp current is interrupted during the period of the high frequency voltage of pulse state and the high frequency voltage of the pulse state. <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 by adjusting the output voltage of the DC chopper from the rated lighting to the dimming lower limit so that the effective value of the output voltage of the inverter circuit changes. In the vicinity of the lower limit of light, 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 switching frequency of the inverter circuit close to the resonance frequency of the resonance circuit in the load circuit. On the other hand, the discharge lamp is extinguished during the repetition of the adjacent pulse voltage, but the inverter circuit can be operated even while the discharge lamp is extinguished by increasing the oscillation frequency of the inverter circuit and keeping it away from the resonance frequency of the resonance circuit. A relatively low-frequency high-frequency voltage is continuously generated.

  In the discharge lamp lighting device described in Patent Document 1, the inverter circuit outputs a relatively low-frequency high-frequency voltage even during repetition of the pulse voltage, but basically, a pulse that has been widely used in the past. It corresponds to dimming of width control.

JP 2003-197391 A

  However, it has been found that the above-described conventional discharge lamp lighting device described in Patent Document 1 is likely to cause flickering of brightness particularly during deep light control.

As a result of investigation of the cause of the flickering by the present inventor, it has been found that a strong light output is generated at the time of re-ignition that occurs each time a pulsed high-frequency voltage is applied. As a result of further investigation and examination, the following was found.
(1) The time from the moment when the pulsed high-frequency voltage is applied to the re-ignition varies.
(2) As the dimming degree increases, the ratio of the amount of light generated upon re-ignition with respect to the total amount of light generated with the application of the pulsed high-frequency voltage increases, and flickering becomes more conspicuous.
(3) When the re-ignition voltage decreases and the difference from the lamp voltage during lighting decreases, the intensity of light output generated during re-ignition decreases.
(4) A hot cathode discharge lamp such as a fluorescent lamp has a large difference between a re-ignition voltage and a lamp voltage during lighting. For this reason, the intensity of the light output generated at the time of re-ignition increases, and the flicker of brightness tends to occur frequently.
(5) The re-ignition voltage of the hot cathode discharge lamp varies depending on the repetition frequency of the pulsed high-frequency voltage, and when the repetition frequency is 1 kHz or higher, the re-ignition voltage is lowered.

  The present invention has been made based on the above findings.

  The present invention provides a discharge lamp lighting device in which the re-ignition voltage of a hot cathode discharge lamp is lowered to suppress the occurrence of brightness flicker caused by light output during re-ignition due to application of a pulsed high-frequency voltage. For the purpose.

  A discharge lamp lighting device according to 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 reduces high-frequency power output from the inverter circuit and input to the discharge lamp. Dimming means for dimming and lighting the discharge lamp; and controlling the dimming means so that the discharge lamp is lit at a dimming level corresponding to the dimming signal, and at least in the case of deep dimming, the hot cathode discharge lamp is pulsed Control means for intermittently applying a high-frequency voltage at a repetition frequency of 1 kHz or more to perform dimming control in a pulse control system and cutting off the lamp current during the period between the pulse-shaped high-frequency voltage and the pulse-shaped high-frequency voltage; It is characterized by that.

  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 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.

  The inverter circuit is preferably a separately excited type that receives a drive signal from a control means described later. By doing so, the oscillation frequency can be varied by changing the repetition frequency of the drive signal. 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 in accordance with the dimming signal, and causes either or both of the DC power supply and the inverter circuit to act for dimming. Is included. That is, one or both of the DC power supply and the inverter circuit constitute at least a part of the dimming means when they are used for dimming. The main modes in such cases are listed below.

  1. A mode of a voltage control system in which dimming is performed by modulating the amplitude of a lamp current by reducing the effective value of a DC voltage output from a 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. This voltage control can be used when a high-frequency voltage is generated in the form of pulses in a pulse control method to be described later.

  2. A mode of a frequency control system that performs dimming by changing the oscillation frequency of the inverter circuit. That is, when the oscillation 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 connected to the discharge lamp is moved and the degree of resonance is changed, so that it is applied to the discharge lamp. The discharge lamp can be dimmed by changing the effective value of the high-frequency voltage in accordance with 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 voltage applied to the discharge lamp decreases as the frequency increases, and the dimming degree increases.

  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). A mode of a pulse control system in which a pulsed high-frequency voltage is repeatedly applied. That is, in this aspect, the discharge lamp can be dimmed by intermittently applying to the discharge lamp a high pulsed high-frequency voltage that has a relatively high peak value and can be re-ignited by the discharge lamp. it can.

  Among the modes of operation of the DC power supply and the inverter circuit for dimming listed above, ~ 3. This mode is suitable for application in a stable lighting region where the characteristic curve between the frequencies f0 to f2 is relatively gentle in the frequency-lamp current characteristic curve of the discharge lamp. That is, this is a mode suitable for application at the time of dimming up to the so-called dimming lower limit.

  In contrast, 4. This mode is suitable for application in the unstable lighting region described later in the frequency-lamp current characteristic curve of the discharge lamp. That is, 4. This mode is a mode suitable for application during deep light control. However, 4. This aspect is an aspect that can also be applied to the above-described stable lighting region. In the present invention, at least during deep light control, this mode is adopted to perform light control of the discharge lamp.

  [Regarding Control Unit] The control unit is a unit that controls the dimming unit to dimm and light the discharge lamp. That is, the control means controls from the rated lighting of the discharge lamp to the so-called dimming lower limit and the control at the time of deep dimming in order to dim the discharge lamp. 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. The present invention is intended to provide a discharge lamp lighting device capable of dimming up to deep dimming.

  In the present invention, dimming control by the pulse control method is performed at least during deep dimming, and the repetition frequency of the pulsed high-frequency voltage at that time is set to 1 kHz or more. If the repetitive frequency is less than 1 kHz, the re-ignition voltage maintains a high value, and thus flickering of brightness due to re-ignition cannot be reduced.

  When the repetition frequency of the pulsed high-frequency voltage is 1 kHz or more, the difference between the re-ignition voltage and the lamp voltage during lighting becomes small. If it does so, the intensity | strength of the strong light which generate | occur | produces in the case of re-ignition will become small, and will cause the flicker of brightness.

  Furthermore, as the repetition frequency of the pulsed high-frequency voltage is increased, the re-ignition voltage decreases, but when it decreases to a certain extent, the re-ignition voltage finally stops at a constant value, which is less than the lamp voltage at the rated lighting. Never go down. According to the inventor's investigation, it has been found that it is optimal to set the repetition frequency to a pulsed high-frequency voltage when the re-ignition voltage is about 20% higher than the final fixed value. It was. Under such conditions, the flickering of brightness is effectively suppressed, and the range in which deep light control is possible becomes even wider. In addition, no burden is imposed on the discharge lamp, and therefore, deterioration of the characteristics of the discharge lamp is reduced.

  On the other hand, in the hot cathode discharge lamp, there is a variation in the time delay from the application of the pulsed high-frequency voltage to the re-ignition, and due to this variation, the amount of light generated when the pulsed high-frequency voltage is applied varies. Arise. This phenomenon is one of the causes of brightness flickering. The time delay until re-ignition also tends to decrease as the pulse repetition frequency of the pulsed high-frequency voltage increases. If the repetition frequency is 1 kHz or more, the influence of the time delay on the brightness flicker may be reduced. found.

  By the way, in order to form a pulsed high-frequency voltage, the above-mentioned 1. 2. Voltage control method of the above and 3. Any of these frequency control methods can be used. In the case of the voltage control method, the DC voltage output from the DC power supply is intermittently increased to a required level. Then, the high frequency voltage output of the inverter circuit is correspondingly increased. In the case of the frequency control method, the oscillation frequency of the inverter circuit is intermittently lowered. If it does so, since it will approach the resonant frequency of a load circuit, the high frequency voltage will become high by resonance in the meantime.

  In the pulse control method, in order to change the dimming degree, the repetition period is fixed and the duty which is the duration of the pulsed high-frequency voltage is changed, or the high-frequency voltage duration is fixed and the pulsed What is necessary is just to change the repetition period of a high frequency voltage. In short, the duty ratio, which is the ratio of the time width of the pulsed high-frequency voltage to the repetition period, may be changed.

  On the other hand, when changing the oscillation frequency of the inverter circuit by the control means, the frequency of the drive signal formed by the control means is changed. The frequency of the drive signal is equal to the oscillation frequency of the inverter circuit.

  In the dimming control of the pulse control system, in order to control the dimming degree continuously and smoothly, the frequency of the drive signal supplied from the control means to the inverter circuit, and hence the oscillation frequency of the inverter circuit, is f, When the pulse repetition frequency for intermittently generating the high-frequency voltage is F, the ratio f / F between them is preferably set to at least about 10 or more. If it is less than about 10, the number of periods of the high-frequency voltage contained in one pulsed high-frequency voltage becomes too small, and it becomes difficult to perform fine dimming control.

  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. 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. (Regarding 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 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.

  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.

  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 the control by the pulse control method, by setting the repetition frequency of the pulsed high-frequency voltage to 1 kHz or more, the re-ignition voltage is reduced and the difference from the lamp voltage during lighting is reduced. It is possible to provide a discharge lamp lighting device in which light output generated when a pulsed high-frequency voltage is applied and the discharge lamp is re-ignited is reduced, and accordingly, flickering of brightness is reduced.

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

  1 to 4 show an 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. FIG. 4 is a graph showing the lamp current characteristics, and FIG. 4 is a waveform diagram of the drive signal voltage and the lamp current.

  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 control means CC, a lamp voltage detection circuit V1D, a lamp current detection circuit ID, and a filament heating circuit FHC. It has. 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 that is the output end of the boost chopper BUC. 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 corresponds to the dimming signal generating means DM and maintains the lamp power at a value corresponding to the dimming degree based on detection outputs of a lamp voltage detection circuit V1D and a lamp current detection circuit ILD described later. Perform feedback control.

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

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

  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 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 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 corresponding to the oscillation 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, a description will be given of a case where dimming is performed by a frequency control method when the dimming degree is increased from a state where the discharge lamp DL is started and lit in a rated state, for example.

  The control means CC sequentially increases the repetition frequency of the drive signal corresponding to the dimming signal. At this time, the repetition frequency of the drive signal is controlled as follows. That is, since the starting voltage is applied to the discharge lamp DL when the oscillation frequency of the inverter circuit INV is a frequency relatively close to the resonance frequency f0 in FIG. 2, 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 increased after the discharge lamp DL is lit, the voltage applied to the discharge lamp DL is reduced due to the resonance characteristics of the load circuit, so that the light output level of the discharge lamp DL is increased. The dimming degree is increased by reducing. In addition, when the voltage which can be started, for example, the voltage which can be started reaches frequency f1 applied to the discharge lamp DL beforehand, it can be comprised so that it may transfer to dimming control of a pulse control system.

  Next, the case of performing voltage control type dimming will be described. In this system, dimming is performed by controlling the DC power supply voltage in the lighting state of the discharge lamp DL similar to the above. That is, the output voltage of the boosting chopper BUC is sequentially decreased by controlling the duty of the drive signal of the boosting chopper BUC according to the dimming degree. Since the high frequency voltage output from the inverter circuit INV decreases in response to this voltage decrease, the dimming degree of the discharge lamp DL increases. Then, when a predetermined dimming degree is reached, the pulse control dimming system is shifted to.

  A stable lighting region and an unstable lighting region of the discharge lamp DL will be described with reference to FIG. That is, in the relationship between the oscillation frequency of the inverter circuit INV and the lamp current of the discharge lamp DL, dimming with stable lighting is possible up to the frequency f2 when the frequency is sequentially increased from the resonance frequency f0. Therefore, the region between f0 and f2 is a stable lighting region. On the other hand, stable lighting cannot be performed during the frequency f3 when the lamp current becomes 0 from the frequency f2. Therefore, the area between f2 and f3 is an unstable lighting area. In the stable lighting range, the dimming method is the same as the above 1. ~ 4. Regardless of the dimming method, the dimming can be performed stably. On the other hand, 4. If the pulse control dimming method is not used, stable dimming cannot be performed.

  Next, light control by the pulse control method will be described.

  In the pulse control system, a pulsed high-frequency voltage having a peak value that can re-ignite the discharge lamp DL is intermittently applied to the discharge lamp DL. The pulse repetition frequency F of the pulsed high-frequency voltage is set to 1 kHz or higher. Then, the duty of the pulsed high-frequency voltage is changed according to the dimming degree. The frequency f1 of the high frequency voltage is preferably set to 40 kHz or higher.

  Then, when a pulsed high-frequency voltage is applied across the discharge lamp DL and the discharge lamp DL is re-ignited, an arc discharge is generated inside the discharge lamp DL and the lamp is turned on. When the application is completed, the arc discharge of the discharge lamp DL is extinguished. Therefore, the discharge lamp DL repeatedly flickers at the pulse repetition frequency F of the pulsed high-frequency voltage during dimming by the pulse control method, but it feels to the human eye to be continuously lit.

  In a preferred mode of the present embodiment, the oscillation frequency of the inverter circuit INV immediately before the discharge lamp DL is shifted to the pulse control method is set to f1, and the oscillation frequency of the pulsed high-frequency voltage when the discharge lamp DL is shifted to the pulse control method is directly set to f1. It is to be. Then, when shifting from the frequency control method or the voltage control method to the pulse control method, it is possible to smoothly shift to avoid an unnatural change in light output.

  FIG. 4 is a waveform diagram of each part in the first embodiment of the present invention, where (a) is a current waveform diagram of the lamp current flowing through the discharge lamp DL in the pulse control system, and (b) is the voltage of the corresponding drive signal. It is a waveform diagram.

  As can be understood from the figure, a drive signal having a repetition frequency f1 is intermittently generated at the pulse repetition frequency F and supplied to the inverter circuit INV. As a result, a pulsed high-frequency voltage (not shown) is generated, and the discharge lamp DL As shown in FIG. 4A, the lamp current flows intermittently when applied to the electrode, but during the period between the pulsed high-frequency voltage and the pulsed high-frequency voltage, that is, during the off period of the pulse repetition frequency F Since the drive signal is paused, there is almost no time delay when the lamp current flowing corresponding to the pulsed high-frequency voltage is cut off. When dimming is performed by such circuit operation, deep dimming up to a dimming degree of 3% or less becomes possible.

  Note that during the period between the pulsed high-frequency voltage, a relatively low-frequency high-frequency voltage having a frequency of f3 in FIG. 3 may be applied. The discharge lamp DL is turned off during the period.

  FIG. 5 is a waveform diagram showing a lamp voltage as a voltage applied across the discharge lamp. In the figure, the horizontal axis represents time (μs), and the vertical axis represents lamp voltage (V).

  Application of pulsed high-frequency voltage is started at time 0 (μs), re-ignited at about 32 (μs), and the lamp voltage after lighting appears after a slight time delay. I will show you later. The lamp voltage at the time of re-ignition, that is, the re-ignition voltage is about 100V. The lamp voltage has a peak value of about 20V.

  FIG. 6 is a graph showing the relationship between the pulse repetition frequency and the re-ignition pressure. In the figure, the horizontal axis represents the pulse repetition frequency (kHz), and the vertical axis represents the re-ignition voltage (V).

  As can be understood from the figure, the re-ignition voltage of the hot cathode discharge lamp starts to decrease from the vicinity of 1 kHz and rapidly decreases when the pulse repetition frequency becomes 1 kHz or more. If it is less than 1 kHz, the starting voltage is high. However, the re-ignition voltage cannot be higher than the starting voltage.

  The hot-cathode discharge lamp has a pulse-like shape because when the re-ignition voltage becomes low and the difference from the lamp voltage during operation becomes small, the light intensity of the instantaneous strong light output generated during re-ignition becomes small. It was found that even if the time from application of the high-frequency voltage to re-ignition varies, brightness flickering is reduced. It should be noted that even if the repetition frequency is increased, the pulsed high frequency signal is saturated and the re-ignition voltage finally settles to a constant value, but the re-ignition voltage is about 20% higher than the constant value. It is optimal to set the voltage repetition frequency.

  FIGS. 7 and 8 are waveform diagrams showing the lamp voltage, the lamp current, and the light emission intensity as voltages applied across the discharge lamp, respectively, with the time axis matched, and both are the re-ignition time. Is different.

  In other words, in the case of FIG. 7, the pulse-shaped high-frequency voltage is re-ignited when the high-frequency voltage in the first week period has a negative peak value (approximately 22 μs). The intensity of pulsed light emission at this time is 0.7 in arbitrary units.

  On the other hand, in the example of FIG. 8, re-ignition is performed when the high-frequency voltage in the first week of the pulse-shaped high-frequency voltage approaches almost the end of the positive polarity (about 12 μs). The intensity of the pulsed light emission at this time is about 0.5 in arbitrary units.

  FIG. 9 is a graph showing the relationship between the pulse repetition frequency and the time delay of the re-ignition pressure. In the figure, the horizontal axis represents the pulse repetition frequency (kHz), and the vertical axis represents the time delay (μs).

  As can be understood from the figure, when the pulse repetition frequency is 1 kHz or less, the time delay of the re-ignition pressure is reduced and the flickering of brightness is reduced.

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 frequency-lamp current characteristics of a discharge lamp Similarly, waveform diagram of drive signal voltage and lamp current Waveform diagram showing the lamp voltage as the voltage applied across the discharge lamp Graph showing the relationship between pulse repetition frequency and re-ignition voltage Waveform diagram showing the lamp voltage, lamp current, and light emission intensity as voltages applied across the discharge lamp, with the time axis aligned. Waveform diagram showing the lamp voltage, lamp current, and light emission intensity as voltages applied across the discharge lamp, with the time axis aligned. Graph showing the relationship between pulse repetition frequency and time delay of re-ignition pressure

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, VID ... lamp voltage detection circuit

Claims (1)

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;
Dimming means for dimming and lighting the discharge lamp by reducing high-frequency power output from the inverter circuit and input to the hot cathode discharge lamp;
The dimming means is controlled so that the discharge lamp is lit at a dimming level corresponding to the dimming signal, and at least during deep dimming, a pulsed high-frequency voltage is repeatedly applied to the hot cathode discharge lamp at a frequency of 1 kHz or higher. A control means for performing dimming control in a pulse control system and cutting off the lamp current during a period between the pulsed high-frequency voltage and the pulse-shaped high-frequency voltage;
A discharge lamp lighting device comprising:

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