JP2006185807A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a lighting device of a discharge lamp capable of lighting stably, without causing generation of flickering of light throughout all the period from the start of lighting till reaching regular lighting of a high luminance discharge lamp. <P>SOLUTION: A lighting frequency determination circuit 6 which specifies a stable lighting frequency band corresponding to a voltage detected by a lamp voltage detection circuit 4 by reference to a relationship between a lamp voltage stored in the memory 2 and a stable lighting frequency band is installed, and the HID lamp 1 is lighted by the lighting frequency in the range of the stable lighting frequency band specified by the lighting frequency determination circuit 6 from the start of lighting till reaching the regular lighting of the HID lamp 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a discharge lamp lighting device that stably lights a high-intensity discharge lamp (HID lamp: High Intensity Discharge Lamp) such as a metal halide lamp used as a light source for an automobile headlight or the like.

In recent years, since HID lamps have characteristics such as high efficiency, long life, and high color rendering properties, they are becoming widely used in indoor and outdoor lighting, video equipment light sources, vehicle headlight light sources, and the like.
Inside the arc tube of the metal halide lamp, a high pressure xenon or mercury used as a starting gas is enclosed in addition to a metal halide in which several kinds of metals such as sodium and scandium are combined with a halogen such as iodine.

In the light emission of a metal halide lamp, first, discharge is started with xenon, which is a gas at room temperature, and when the inside of the arc tube becomes hot due to arc discharge of xenon, mercury vaporizes as the temperature rises, leading to arc discharge. Becomes hot.
As the temperature in the tube further increases, the metal halide evaporates and reaches arc discharge, and light emission with high luminous efficiency and high color temperature is obtained.
Mercury plays a role as a link between the discharge of xenon and the discharge of metal halide, but in recent years, metal halide lamps in which mercury is not enclosed have also been provided.

When the metal halide lamp is turned on, it is required to maintain the discharge so that the discharge does not go off according to the state inside the arc tube. That is, a lighting method and a lighting device (ballast) are required to control the discharge following the load characteristics of the changing lamp.
Also, when the metal halide lamp is turned on, light flickering due to fluctuations in the discharge arc caused by the relative relationship between the force due to standing waves generated by acoustic resonance and the force due to convection in the tube due to gravity is observed. There is a unique requirement to light at a lighting frequency that is not.

A conventional metal halide lamp lighting device employs, for example, the following lighting method.
In order to steadily turn on the metal halide lamp during the entire period from the start of discharge to steady lighting, the frequency immediately after lighting is set to a frequency higher than the stable lighting frequency of steady lighting, and the lamp impedance is maintained until steady lighting. Accordingly, a method of gradually lowering the lighting frequency is adopted (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 9-63783 (paragraph numbers [0019] to [0024], FIG. 1)

  Since the conventional discharge lamp lighting device is configured as described above, in the initial lighting state immediately after the start of lighting of the metal halide lamp, in the period in which the rare gas (for example, xenon gas) discharge in the tube is dominant, the discharge arc There was a problem that fluctuations occurred and the metal halide lamp could not be lit stably.

  The present invention has been made to solve the above-described problems, and allows stable lighting without causing light flicker over the entire period from the start of lighting of a high-intensity discharge lamp to steady lighting. It is an object of the present invention to obtain a discharge lamp lighting device that can be used.

  The discharge lamp lighting device according to the present invention uses the lamp state determined by the characteristics of the high-intensity discharge lamp and the relationship between the stable lighting frequency band or means for specifying the relationship, and the lamp state detected by the lamp state detection means. Stable lighting frequency band specifying means for specifying the stable lighting frequency band corresponding to the state is provided, and from the start of lighting of the high-intensity discharge lamp to steady lighting, the stable lighting frequency band specified by the stable lighting frequency band specifying means is provided. The high-intensity discharge lamp is lit at a lighting frequency within the range.

  According to the present invention, the relationship between the lamp state determined by the characteristics of the high-intensity discharge lamp and the stable lighting frequency band, or the means for specifying the relationship is used, and the state of the lamp detected by the lamp state detection unit is handled. Stable lighting frequency band specifying means for specifying the stable lighting frequency band is provided, and lighting within the range of the stable lighting frequency band specified by the stable lighting frequency band specifying means from the start of lighting of the high-intensity discharge lamp to steady lighting Since the high-intensity discharge lamp is lit at a frequency, it can be stably lit without causing light flickering over the entire period from the start of lighting of the high-intensity discharge lamp to steady lighting. effective.

Embodiment 1 FIG.
1 is a block diagram showing a discharge lamp lighting device according to Embodiment 1 of the present invention. FIG. 1 shows an example of lighting a high-intensity discharge lamp (hereinafter referred to as HID lamp 1) such as a metal halide lamp. .
In the figure, the memory 2 shows the relationship between the lamp state determined by the characteristics of the HID lamp 1 and the stable lighting frequency band, that is, the relationship between the lamp voltage and the stable lighting frequency band, or the relationship between the lamp voltage and the stable lighting frequency band. Means for specifying is stored.

The lamp current detection circuit 3 detects the current flowing through the HID lamp 1. The lamp voltage detection circuit 4 detects the voltage applied to the HID lamp 1 as indicating the state of the HID lamp 1. The lamp voltage detection circuit 4 constitutes lamp state detection means.
The lamp power determination circuit 5 determines the power that needs to be supplied to the HID lamp 1 according to the current detected by the lamp current detection circuit 3 and the voltage detected by the lamp voltage detection circuit 4.
The lighting frequency determination circuit 6 refers to the relationship between the lamp voltage stored in the memory 2 and the stable lighting frequency band, or uses means for specifying the relationship between the lamp voltage stored in the memory 2 and the stable lighting frequency band. Thus, the stable lighting frequency band corresponding to the voltage detected by the lamp voltage detection circuit 4 is specified. The lighting frequency determination circuit 6 constitutes a stable lighting frequency band specifying unit.

The power source 7 supplies power to the lighting waveform supply circuit 8. The lighting waveform supply circuit 8 operates by receiving power from the power supply 7 and generates a lighting waveform for supplying the power determined by the lamp power determination circuit 5. However, when the lighting waveform supply circuit 8 generates the lighting waveform, the HID lamp has a lighting frequency within the range of the stable lighting frequency band specified by the lighting frequency determination circuit 6 from the lighting start of the HID lamp 1 to the steady lighting. A lighting waveform such that 1 is lit is generated, and the lighting waveform is supplied to the lamp starting circuit 9.
The lamp starting circuit 9 lights the HID lamp 1 according to the lighting waveform supplied from the lighting waveform supply circuit 8.
The power source 7, the lighting waveform supply circuit 8, and the lamp starting circuit 9 constitute lamp lighting means.

Next, the operation will be described.
FIG. 2 is an explanatory diagram showing a change in lamp impedance when the HID lamp 1 is lit and the state of the lamp at each impedance. In FIG. 2, the change in the tube temperature depends on the input energy from the start of discharge. For this reason, the horizontal axis of FIG. 2 is the same as the time range.
The lighting of the HID lamp 1 is divided into four periods according to the state of the lamp.
That is, the discharge waiting period A, breakdown B, luminous flux rising period C, and steady discharge period D. Hereinafter, the phenomenon in each discharge period and the state of the lamp will be briefly described.

A. Discharge standby period In the discharge standby period, the load state of the lamp is equivalent to that of the capacitor, and the lamp impedance is as large as several MΩ to several tens MΩ. During this period, the lighting device boosts the lamp to a voltage at which breakdown occurs.
B. When the breakdown lamp voltage reaches the breakdown voltage, breakdown occurs, current flows through the lamp, and discharge begins.

C. Luminous flux rising period When arc discharge starts after breakdown, the luminous flux rising period is reached. In the luminous flux rising period, the lamp is raised to a predetermined luminous flux. In particular, when used as an in-vehicle headlamp, it is necessary to rapidly raise the luminous flux, and power with a rated power of 35 W or more (for example, about 70 W) is input to the lamp.
Since the in-pipe state of the lamp changes significantly during this period, the description will be divided into three periods C1 to C3.

C1. Low Impedance Period In a period where the temperature in the tube is relatively low for a few seconds after the discharge is started, the discharge of the rare gas in the tube (for example, xenon) is dominant, and the impedance of the lamp is relatively low.
C2. Equilibrium period The temperature in the tube rises and the vaporization of mercury is promoted, and the pressure ratio between the rare gas and mercury in the tube is almost the same. By promoting the vaporization of mercury, the pressure in the tube increases, and the impedance of the lamp gradually increases.
C3. High impedance period The temperature inside the tube rises, and the discharge by mercury becomes dominant. The lamp impedance is further increased compared to the equilibrium period of C2.
D. Steady discharge period The metal halide, which is a substance enclosed in the tube, evaporates, and the luminous flux, the temperature in the tube, and the lamp impedance reach an equilibrium state.

In order to stably light the HID lamp 1 in each period from A to D, it is necessary to light with a waveform corresponding to the lamp state in each period.
When the HID lamp 1 is lit at a high frequency, depending on the lighting frequency, the discharge arc is curved due to the relative relationship between the force caused by the standing wave generated by the acoustic resonance phenomenon and the force caused by convection in the tube caused by gravity. In some cases, a fluctuation phenomenon may occur.
When the phenomenon that the discharge arc fluctuates occurs, the lamp light flickers and is visually observed, making it difficult to use as illumination. In order to light the lamp light without flickering, it is necessary to maintain the discharge without changing the shape of the discharge arc.

In this Embodiment 1, in order to prevent the occurrence of the flickering of the lamp light described above, the lighting frequency is set so that a standing wave that keeps the shape of the discharge arc constant is generated by an acoustic resonance phenomenon during each lighting period. Is used.
Hereinafter, this method will be specifically described.
The frequency at which the acoustic resonance phenomenon of the HID lamp 1 occurs is generally expressed by the following formula (1).
f = nv / 2L (1)
Where L is the geometric distance from the sound wave source to the reflecting surface, v is the sound velocity in the tube, and n is the order of the resonance frequency.

In Expression (1), L is determined by the individual difference of the HID lamp 1. Therefore, the change in the acoustic resonance frequency when the HID lamp 1 is lit is determined only by the change in the in-tube sound speed.
The in-tube sound speed is generally expressed by the following equation (2).
v = (γRT / M) ^1/2 (2)
Where γ is the specific heat ratio, R is the gas constant, M is the average molecular weight, and T is the tube temperature.
From Equation (2), it can be seen that the acoustic resonance frequency is determined by changes in the tube temperature and the average molecular weight. That is, it can be seen that the acoustic resonance frequency changes with each discharge period.

Here, FIG. 3 is an explanatory view showing the measurement result of the relationship between the lamp impedance and the acoustic resonance frequency.
FIG. 3 shows the lamp impedance that can be stably lit when the HID lamp 1 is lit at each lighting frequency. The hatched area is the region where the acoustic resonance phenomenon that keeps the shape of the discharge arc constant, that is, stable lighting. It is an area.
As the lamp impedance increases, the acoustic resonance frequency tends to increase in the low impedance section of C1, shows a substantially constant tendency in the equilibrium period of C2, and shows a tendency to decrease in the high impedance period of C3. Yes.

The characteristics in FIG. 3 are compared with the phenomena in each period.
In the lamp state in the low impedance period of C1, the change in the average molecular weight M is small because the pressure ratio of the rare gas in the tube is large.
Therefore, since the in-tube sound velocity v increases as the in-tube temperature T increases, the acoustic resonance frequency f increases. However, even during this period, the pressure ratio is small as compared with the rare gas in the tube, but since the mercury vapor exists, the lamp impedance gradually increases.

During the equilibrium period of C2, the vaporization of mercury is gradually promoted, the rate of increase in the tube temperature T and the increase in the average molecular weight M are substantially equal, and the change in the acoustic resonance frequency f is almost eliminated.
In the high impedance period of C3, the rate of increase of the tube temperature T is reduced, and vaporization of mercury and metal halide is further promoted, so that the rate of increase of the average molecular weight M is larger than the rate of increase of the tube temperature T. As a result, the in-tube sound velocity v decreases and the acoustic resonance frequency f decreases.

  As described above, since the acoustic resonance frequency f changes according to the in-tube state of each period from the start of lighting, and further varies depending on the vaporization state of mercury or halide metal in each period, the lamp impedance also increases according to the increase in the in-tube temperature T. Therefore, according to the lamp impedance, the lighting frequency is increased during the low impedance period, the lighting frequency is not changed during the equilibrium period, and the lighting frequency is decreased during the high impedance period. Can be lit without flickering.

Further, the voltage of the HID lamp 1 increases as the lamp impedance increases.
Therefore, in each period, the state of the HID lamp 1 in each period during the luminous flux rising period can be determined from the lamp voltage.
That is, the luminous frequency rises by increasing the lighting frequency during the low impedance period when the lamp voltage is low, decreasing the lighting frequency during the high impedance period when the lamp voltage is relatively high, and keeping the lighting frequency substantially constant during the intermediate equilibrium period. The HID lamp 1 can be lit without flickering throughout the period.
In the lighting period, the equilibrium period may hardly exist in terms of time due to the HID lamp 1.

The above-described stable lighting frequency band depends on the HID lamp 1, but the characteristic that the stable lighting frequency with respect to a change in lamp voltage during lighting increases in a low impedance period and decreases in a high impedance period is the same for each lamp. is there. That is, the HID lamp 1 can be lit without flickering by performing lighting according to the relationship between the lamp voltage and the stable lighting frequency for each lamp.
When the stable lighting frequency changes due to deterioration of the HID lamp 1 or the like, the HID lamp 1 can be lit without flickering by determining the lighting frequency according to the characteristics of the lamp voltage and the stable lighting frequency at that time. .

Further, as shown in FIG. 3, the stable lighting frequencies are distributed in a plurality of frequency regions, and when a specific HID lamp 1 is lit, it is in a stable lighting frequency band with respect to the lamp voltage of the HID lamp 1. The stable lighting frequency band of any frequency region may be used, and the HID lamp 1 can be lit without flickering.
Further, in the above-described lighting method, the lighting frequency does not need to be along one stable lighting frequency band, and may transition to a stable lighting frequency band in another frequency region.

That is, it is not necessary to determine the lighting frequency so as to always follow the stable lighting frequency band of (I) from the start of lighting to steady lighting. For example, during the lighting, the stable lighting frequency band of (I) to (II) The stable lighting frequency band to be selected as the lighting frequency may be changed as in the stable lighting frequency band from (II) to (I).
Note that the relationship between the discharge period and the acoustic resonance frequency as described above is completely different from that shown in Patent Document 1, and as shown in Patent Document 1, immediately after the start of lighting. Only by the measure of lowering the lighting frequency from the beginning, the shape of the discharge arc cannot always be maintained without fluctuation.

When the HID lamp 1 is turned on, discharge may start in the middle of each of the discharge periods, depending on the elapsed time from the previous lighting.
When a sufficient time has elapsed since the previous lighting and the discharge shifts as shown in FIG. 2, it is called a cold state.
On the other hand, when a sufficient time has not elapsed since the previous lighting and the pressure of the mercury vapor is still high, the discharge is started from the lamp impedance corresponding to the pressure. Such a lamp state is called a hot state.
That is, compared with the case of the cold state, it is the same from the discharge standby period to breakdown in FIG. 2, but the subsequent discharge is, for example, when the discharge starts from the high impedance period of C3, In some cases, discharge starts from the discharge period.

When lighting is performed from the cold state described above, steady discharge occurs through the lighting periods shown in FIG. 2 in order, so that the lighting frequency increases in the low impedance period where the lamp voltage is low as described above, and the lamp voltage is relatively low. The HID lamp 1 can be lit without flickering by falling during a high high impedance period and being kept almost constant during an intermediate equilibrium period.
In the lighting from the hot state, the lighting starts in the middle of the lighting sequence described above. However, when the lighting method of the first embodiment is used, the stable lighting frequency is determined in order to determine the stable lighting frequency from the lamp voltage. The HID lamp 1 can be turned on without flickering.

The operation of the discharge lamp lighting device according to the first embodiment will be specifically described below.
First, the memory 2 stores specifying means for the relationship between the lamp voltage and the stable lighting frequency band determined by the characteristics of the HID lamp 1 or the relationship between the lamp voltage and the stable lighting frequency.
In the example of FIG. 3, the relationship between the lamp impedance and the stable lighting frequency band is shown. However, the relationship between the lamp voltage and the stable lighting frequency band is almost the same as that in FIG. 3, and as the lamp voltage increases during the period C1. The stable lighting frequency is increased, the stable lighting frequency is maintained substantially constant during the period C2, and the stable lighting frequency is decreased as the lamp voltage is increased during the period C3.
When the power source 7 detects a lighting start signal (not shown), the power source 7 starts supplying power to the lighting waveform supply circuit 8.
As will be described in detail later, the lighting waveform supply circuit 8 operates when power is supplied from the power supply 7, generates a lighting waveform for supplying power determined by the lamp power determination circuit 5 described later, and turns on the lighting waveform. The waveform is supplied to the lamp starting circuit 9.

When the lamp starting circuit 9 receives the lighting waveform from the lighting waveform supply circuit 8, the lamp starting circuit 9 starts the HID lamp 1 according to the lighting waveform.
In this way, when the lamp starting circuit 9 starts the starting operation of the HID lamp 1, the voltage applied to the HID lamp 1 rises, and when the lamp voltage reaches the dielectric breakdown voltage, the HID lamp 1 starts discharging. To do.

The lamp current detection circuit 3 detects a current flowing through the HID lamp 1, and the lamp voltage detection circuit 4 detects a voltage applied to the HID lamp 1.
The lamp power determination circuit 5 determines the power that needs to be supplied to the HID lamp 1 according to the current detected by the lamp current detection circuit 3 and the voltage detected by the lamp voltage detection circuit 4.
That is, since the lamp power determination circuit 5 is preset with power necessary for lighting the HID lamp 1 in each of the above-described periods A to D, the current detected by the lamp current detection circuit 3 and the lamp voltage detection are detected. The power currently supplied to the HID lamp 1 is grasped from the voltage detected by the circuit 4, and a power increase / decrease command is output to the lighting waveform supply circuit 8 so that the power matches the required power.

The lighting frequency determination circuit 6 refers to the relationship between the lamp voltage and the stable lighting frequency band stored in the memory 2 or means for specifying the relationship between the lamp voltage and the stable lighting frequency band stored in the memory 2. The stable lighting frequency band corresponding to the voltage detected by the lamp voltage detection circuit 4 is specified.
The lighting waveform supply circuit 8 generates a lighting waveform in accordance with a power increase / decrease command output from the lamp power determination circuit 5.
However, when generating the lighting waveform, the lighting waveform supply circuit 8 performs the lighting frequency within the range of the stable lighting frequency band specified by the lighting frequency determination circuit 6 from the lighting start of the HID lamp 1 to the steady lighting (for example, A lighting waveform is generated so that the HID lamp 1 is lit at the lighting frequency (I) in FIG. 3, and the lighting waveform is supplied to the lamp starting circuit 9. Note that any frequency may be used as long as it is within the range of the stable lighting frequency band. For example, an intermediate value of the stable lighting frequency band may be used.
The lamp starting circuit 9 lights the HID lamp 1 according to the lighting waveform supplied from the lighting waveform supply circuit 8.

FIG. 4 shows the experimental results of the luminous flux change when the HID lamp 1 is turned on at a constant frequency and the luminous flux change when the HID lamp 1 is turned on when the HID lamp 1 is turned on by the lighting method of the first embodiment. .
When the lamp is lit at a constant frequency, flickering of the lamp light is confirmed in several periods from the start of discharge to steady lighting.
On the other hand, when a lighting method that determines the lighting frequency from the relationship between the lamp voltage determined by the lamp characteristics and the stable lighting frequency is used, no flickering of the lamp light is observed from the start of lighting to the steady lighting.

  As apparent from the above, according to the first embodiment, the relationship between the lamp voltage stored in the memory 2 and the stable lighting frequency band is referred to, or the lamp voltage stored in the memory 2 and the stable lighting are A lighting frequency determination circuit 6 for specifying a stable lighting frequency band corresponding to the voltage detected by the lamp voltage detection circuit 4 is provided using means for specifying the relationship between the frequency bands, and the HID lamp 1 is switched from the start of lighting to the steady lighting. Since the HID lamp 1 is lit at a lighting frequency within the range of the stable lighting frequency band specified by the lighting frequency determination circuit 6, the entire period from the start of lighting of the HID lamp 1 to steady lighting is used. There is an effect that it can be lit stably without causing the occurrence of flickering of light.

  That is, in the low impedance period in which the rare gas in the tube (for example, xenon) immediately after the start of discharge is dominant, the lighting waveform for increasing the lighting frequency is determined so that the influence of the stable lighting frequency increases as the lamp voltage increases. After the mercury or metal halide evaporates and the mercury or metal halide pressure becomes dominant, the influence of the stable lighting frequency increases as the lamp voltage increases during the high impedance period until the rated lighting. Since the lighting waveform that reduces the lighting frequency is determined, the shape of the discharge arc can be fixed due to the influence of the acoustic resonance phenomenon. As a result, the flickering of the light over the entire lighting period There is an effect that can be stably lit without causing the occurrence.

  In the first embodiment, the lighting frequency determination circuit 6 specifies a stable lighting frequency band corresponding to the voltage detected by the lamp voltage detection circuit 4, and the lighting waveform supply circuit 8 is specified by the lighting frequency determination circuit 6. In this example, a lighting waveform is generated so that the HID lamp 1 is lit at a lighting frequency within the range of the stable lighting frequency band. The lighting frequency determination circuit 6 corresponds to the voltage detected by the lamp voltage detection circuit 4. A stable lighting frequency (for example, the lighting frequency of (I) in FIG. 3) is specified, and a lighting waveform is generated such that the lighting waveform supply circuit 8 lights the HID lamp 1 at the lighting frequency specified by the lighting frequency determination circuit 6. You may make it do.

Embodiment 2. FIG.
In the first embodiment, means for specifying the relationship between the lamp voltage and the stable lighting frequency band or the relationship between the lamp voltage and the stable lighting frequency band is stored in the memory 2, and the lighting frequency determination circuit 6 is stored in the memory 2. Detected by the lamp voltage detection circuit 4 by referring to the relationship between the lamp voltage and the stable lighting frequency band, or by using means for specifying the relationship between the lamp voltage and the stable lighting frequency band stored in the memory 2 Although it has been shown that the stable lighting frequency band corresponding to the voltage is specified, since the current flowing through the HID lamp 1 also represents the state of the HID lamp 1, the relationship between the lamp current and the stable lighting frequency band, or the lamp current When the means for identifying the relationship between the stable lighting frequency band and the stable lighting frequency band is stored in the memory 2, the lighting frequency determination circuit 6 stores the run frequency stored in the memory 2. Corresponding to the current detected by the lamp current detection circuit 3 by referring to the relationship between the current and the stable lighting frequency band or by using the means for specifying the relationship between the lamp current and the stable lighting frequency band stored in the memory 2 The stable lighting frequency band to be specified may be specified.
In the example of FIG. 3, the relationship between the lamp impedance and the stable lighting frequency band is shown. However, in the relationship between the lamp current and the stable lighting frequency band, the stable lighting frequency is decreased with the decrease of the lamp current in the period C1. In the period of C2, the stable lighting frequency is kept almost constant, and in the period of C3, the stable lighting frequency is lowered as the lamp current is decreased.

Embodiment 3 FIG.
In the first embodiment, means for specifying the relationship between the lamp voltage and the stable lighting frequency band or the relationship between the lamp voltage and the stable lighting frequency band is stored in the memory 2, and the lighting frequency determination circuit 6 is stored in the memory 2. Detected by the lamp voltage detection circuit 4 by referring to the relationship between the lamp voltage and the stable lighting frequency band, or by using means for specifying the relationship between the lamp voltage and the stable lighting frequency band stored in the memory 2 Although it has shown about what specifies the stable lighting frequency band corresponding to the voltage, since the impedance of the HID lamp 1 also represents the state of the HID lamp 1, the relationship between the lamp impedance and the stable lighting frequency band, or the lamp impedance and the stable lighting When the means for specifying the relationship between the frequency bands is stored in the memory 2, the lighting frequency determination circuit 6 is connected to the memory 2. A lamp impedance detection circuit (not shown) is used by referring to the relationship between the stored lamp impedance and the stable lighting frequency band or by using means for specifying the relationship between the lamp impedance and the stable lighting frequency band stored in the memory 2. The stable lighting frequency band corresponding to the impedance detected by the above may be specified.

Embodiment 4 FIG.
In the first embodiment, means for specifying the relationship between the lamp voltage and the stable lighting frequency band or the relationship between the lamp voltage and the stable lighting frequency band is stored in the memory 2, and the lighting frequency determination circuit 6 is stored in the memory 2. Detected by the lamp voltage detection circuit 4 by referring to the relationship between the lamp voltage and the stable lighting frequency band, or by using means for specifying the relationship between the lamp voltage and the stable lighting frequency band stored in the memory 2 Although what has been described for specifying the stable lighting frequency band corresponding to the voltage, since the luminous flux of the HID lamp 1 also represents the state of the HID lamp 1, the relationship between the lamp luminous flux and the stable lighting frequency band, or the lamp luminous flux and the stable lighting. When the means for specifying the relationship between the frequency bands is stored in the memory 2, the lighting frequency determination circuit 6 is connected to the lamp luminous flux stored in the memory 2 and Corresponding to the luminous flux detected by a lamp luminous flux detection circuit (not shown) by referring to the relationship of the lighting frequency band or by using means for specifying the relationship between the lamp luminous flux and the stable lighting frequency band stored in the memory 2 A stable lighting frequency band may be specified.
In the example of FIG. 3, the relationship between the lamp impedance and the stable lighting frequency band is shown. However, the relationship between the lamp luminous flux and the stable lighting frequency band is almost the same as in FIG. 3, and the lamp luminous flux increases during the period C1. Along with this, the stable lighting frequency is increased, the stable lighting frequency is kept substantially constant during the period C2, and the stable lighting frequency is decreased as the lamp luminous flux is increased during the period C3.

Embodiment 5. FIG.
In the first to fourth embodiments, the relationship between the lamp state such as the lamp voltage and the stable lighting frequency band or the specifying means of the relationship between the lamp state and the stable lighting frequency band is stored in the memory 2. When the lamp 1 deteriorates, the stable lighting frequency may change. Therefore, when the stable lighting frequency changes, the lamp state such as the lamp voltage stored in the memory 2 and the stable lighting frequency. The band relationship may be updated.
The method for updating the storage contents of the memory 2 is not particularly limited. For example, the storage contents of the memory 2 may be updated by inputting update data from an external terminal (not shown).
According to the first embodiment, even when the HID lamp 1 is deteriorated and the stable lighting frequency is changed, there is an effect that the light can be stably lit without causing light flickering.

Embodiment 6 FIG.
In the first to fifth embodiments, the lighting waveform supply circuit 8 is operated within the range of the stable lighting frequency band specified by the lighting frequency determination circuit 6 from the start of lighting of the HID lamp 1 to the steady lighting (for example, In FIG. 3, the lighting frequency is generated so that the HID lamp 1 is turned on. However, as shown in FIG. 3, when a plurality of stable lighting frequency bands are stored, A lighting waveform in which the HID lamp 1 is lit at a lighting frequency other than (I), for example, a lighting frequency of (II) may be generated.
At this time, during the lighting of the HID lamp 1, for example, the lighting frequency of (I) may be changed to the lighting frequency of (II), or the lighting frequency of (II) is turned on. The frequency may be changed.
Thereby, there exists an effect which can raise the freedom degree of the lighting control in a lighting device.

Embodiment 7 FIG.
In the first to sixth embodiments, the lighting waveform supply circuit 8 is operated within the range of the stable lighting frequency band specified by the lighting frequency determination circuit 6 from the start of lighting of the HID lamp 1 to the steady lighting (for example, 3, the lighting waveform generating circuit that generates the lighting waveform so that the HID lamp 1 is lit is shown. However, as shown in FIG. 5, the lighting waveform supply circuit 8 is specified by the lighting frequency determination circuit 6. The lighting frequency within the range of the stable lighting frequency band thus made may be temporally modulated.
That is, for example, the lighting frequency may be temporally modulated with the lighting frequency shown in FIG. At this time, the modulated lighting frequency may deviate from the range of the stable lighting frequency band specified by the lighting frequency determination circuit 6.

In the example of FIG. 5, the waveform of the lighting frequency is a frequency sweep waveform including a stable lighting frequency.
Thus, when the lighting frequency of the frequency sweep waveform is used, even if the stable lighting frequency changes due to the deterioration of the HID lamp 1, if any of the frequencies of the frequency sweep waveform is the stable lighting frequency, the HID lamp 1 Flickering can be prevented, and an effect of reducing the influence of a change in the stable lighting frequency is achieved.
The frequency modulation period and frequency modulation width of the frequency sweep waveform may be selected in any way, and may be changed during the lighting period.

Embodiment 8 FIG.
FIG. 6 is an explanatory diagram showing the relationship between the lamp voltage after the HID lamp is lit, the lighting waveform, and the change in luminous flux.
In the lighting system according to the eighth embodiment, a frequency sweep waveform that includes a stable lighting frequency in the entire lighting period and modulates the frequency at an arbitrary modulation period is used.
FIG. 7 is an enlarged view showing the change of the frequency in the dotted circle in FIG. 6, and shows the change of the frequency in one modulation period.

In the eighth embodiment, when the HID lamp 1 is turned on by the frequency sweep method, when paying attention to one modulation period, the ratio of the time when the lighting frequency matches the stable lighting frequency is a predetermined value (for example, 20%). I try to be bigger.
In this way, by increasing the proportion of time that the lighting frequency matches the stable lighting frequency, the standing wave generation time due to the acoustic resonance phenomenon that keeps the arc shape constant is lengthened, and the lamp is driven at an unstable frequency. When the lighting period is shortened, the influence of the standing wave that induces stable lighting increases. Thereby, the lamp shape is kept constant, and flickering of the light of the HID lamp 1 can be prevented during the entire lighting period.
Further, when this lighting method is used, even if the relationship between the lamp voltage and the stable lighting frequency changes due to deterioration of the HID lamp 1 or the like, the HID lamp 1 can be lit without flickering.

In this lighting method, the frequency modulation period and the frequency modulation width may be changed during lighting.
Moreover, the stable lighting frequency shown in FIG. 3 may be used in any region of the stable lighting frequency, and the frequency region of the stable lighting frequency to be used may be changed during lighting.

Embodiment 9 FIG.
In the above-described eighth embodiment, when focusing on one modulation period, the ratio of the time when the lighting frequency matches the stable lighting frequency is shown to be larger than a predetermined value. However, when focusing on one modulation period, The lamp power when the lighting frequency matches the stable lighting frequency may be made larger than the lamp power when the lighting frequency does not match the stable lighting frequency.
For example, the influence of a standing wave that induces stable lighting can be increased by making the lamp power when driving at a stable lighting frequency larger than the power (for example, 35 W) when driving at an unstable frequency. it can. Thereby, the HID lamp 1 can be lit without flickering.
It should be noted that the method of increasing the proportion of time for driving at the stable lighting frequency in the eighth embodiment and the method for increasing the power for driving at the stable lighting frequency in the ninth embodiment may be used independently. The HID lamp 1 may be turned on without flickering.

It is a block diagram which shows the discharge lamp lighting device by Embodiment 1 of this invention. It is explanatory drawing which shows the change of the lamp impedance at the time of lighting the HID lamp 1, and the state of the lamp in each impedance. It is explanatory drawing which shows the measurement result of the relationship between a lamp impedance and an acoustic resonance frequency. It is explanatory drawing which shows the experimental result of the light beam change at the time of lighting when the HID lamp 1 is lighted at a fixed frequency, and the light beam change at the time of lighting when the HID lamp 1 is lighted by the lighting method of the first embodiment. It is explanatory drawing which shows the relationship of the light beam change with respect to a lighting frequency and a lamp voltage at the time of modulating a lighting frequency by making a stable lighting frequency into a center frequency. It is explanatory drawing which shows the relationship between the lamp voltage after HID lamp lighting, a lighting waveform, and the change of a light beam. It is an enlarged view which shows the change of the frequency in the dotted line circle in FIG.

Explanation of symbols

  1 HID lamp (high-intensity discharge lamp), 2 memory, 3 lamp current detection circuit, 4 lamp voltage detection circuit (lamp state detection means), 5 lamp power determination circuit, 6 lighting frequency determination circuit (stable lighting frequency band identification means) 7 power supply (lamp lighting means), 8 lighting waveform supply circuit (lamp lighting means), 9 lamp starting circuit (lamp lighting means).

Claims (12)

  Identifies the lamp state detection means for detecting the state of the high-intensity discharge lamp, the relationship between the lamp state determined by the characteristics of the high-intensity discharge lamp and the stable lighting frequency band, or the relationship between the lamp state and the stable lighting frequency band A stable lighting frequency band specifying means for specifying a stable lighting frequency band corresponding to the lamp state detected by the lamp state detecting means, and from the start of lighting of the high-intensity discharge lamp to steady lighting. A discharge lamp lighting device comprising: lamp lighting means for lighting the high-intensity discharge lamp at a lighting frequency within a range of the stable lighting frequency band specified by the stable lighting frequency band specifying means.   The lamp state detection means detects the voltage applied to the high-intensity discharge lamp as the state of the high-intensity discharge lamp, and the stable lighting frequency band specifying means determines the lamp voltage and stable lighting determined by the characteristics of the high-intensity discharge lamp. 2. The discharge lamp lighting device according to claim 1, wherein a stable lighting frequency band corresponding to the voltage detected by the lamp state detecting means is specified using the relationship between the frequency bands.   The lamp state detection means detects the current flowing through the high-intensity discharge lamp as the state of the high-intensity discharge lamp, and the stable lighting frequency band identification means determines the lamp current and the stable lighting frequency determined by the characteristics of the high-intensity discharge lamp. 2. The discharge lamp lighting device according to claim 1, wherein a stable lighting frequency band corresponding to the current detected by the lamp state detecting means is specified using a band relationship.   The lamp state detection means detects the impedance of the high-intensity discharge lamp as the state of the high-intensity discharge lamp, and the stable lighting frequency band identification means determines the relationship between the lamp impedance determined by the characteristics of the high-intensity discharge lamp and the stable lighting frequency band. The discharge lamp lighting device according to claim 1, wherein a stable lighting frequency band corresponding to the impedance detected by the lamp state detecting means is specified by using.   The lamp state detection means detects the luminous flux of the high-intensity discharge lamp as the state of the high-intensity discharge lamp, and the stable lighting frequency band identification means determines the relationship between the lamp luminous flux determined by the characteristics of the high-intensity discharge lamp and the stable lighting frequency band. The discharge lamp lighting device according to claim 1, wherein a stable lighting frequency band corresponding to the light beam detected by the lamp state detecting means is specified.   The lamp lighting means changes the lighting frequency within the range of the stable lighting frequency band during the low impedance period during the luminous flux rising period, and changes the lighting frequency within the range of the stable lighting frequency band during the high impedance period during the luminous flux rising period. The discharge lamp lighting device according to any one of claims 1 to 5, wherein the discharge lamp lighting device is changed in a direction of lowering.   The discharge lamp lighting device according to any one of claims 1 to 6, wherein a relationship between a lamp state determined by characteristics of the high-intensity discharge lamp and a stable lighting frequency band is updated.   The stable lighting frequency band specifying means selects one of the stable lighting frequency bands when there are a plurality of stable lighting frequency bands corresponding to the lamp state. 2. A discharge lamp lighting device according to item 1.   9. The discharge lamp lighting device according to claim 8, wherein the stable lighting frequency band specifying means switches to another stable lighting frequency band after selecting one of the stable lighting frequency bands.   The lamp lighting means temporally modulates the lighting frequency including the range of the stable lighting frequency band specified by the stable lighting frequency band specifying means. The discharge lamp lighting device described.   11. The discharge lamp lighting device according to claim 10, wherein when the lamp lighting means pays attention to one of the modulation cycles, the ratio of the time when the lighting frequency matches the stable lighting frequency is made larger than a predetermined value.   When the lamp lighting means pays attention to one cycle of the modulation cycle, the lamp power when the lighting frequency matches the stable lighting frequency is larger than the lamp power when the lighting frequency does not match the stable lighting frequency. The discharge lamp lighting device according to claim 10.

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