JP2010055838A - Metal halide lamp lighting device, and headlight and vehicle using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly reduce the high-frequency noise from a metal halide lamp by promoting production of free iodines in the metal halide lamp. <P>SOLUTION: A lamp electric potential control part 6 has a cumulative lighting time measuring part 61 for measuring a cumulative lighting time of the metal halide lamp La, and a bias control part 62 for applying bias voltage between an adjacent conductor Rf disposed adjacently to an arc tube of the metal halide lamp La and the metal halide lamp La and controlling the bias voltage, in response to a measurement result in the cumulative lighting time measuring part 61. In the bias control part 62, during an aging period, from when the cumulative lighting time is zero until a certain time is reached, operation is carried out in a positive electric potential mode, with the adjacent conductor Rf set as a reference electric potential and an electrode side of the metal halide lamp La as a positive electric potential, and during a regular use period after the aging period, operation is carried out in a negative-potential mode considering the adjacent conductor Rf as a reference electrical potential and the electrode side of the metal halide lamp La as a negative potential. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a metal halide lamp lighting device for lighting a metal halide lamp, a headlamp using the same, and a vehicle.

  Conventionally, as a metal halide lamp lighting device for lighting a metal halide lamp that is a kind of high-intensity discharge lamp used for spotlights, projector light sources, vehicle headlamps, etc., avoiding acoustic resonance, etc. For this purpose, it is known that a metal halide lamp is lit by a low-frequency rectangular wave.

  This type of metal halide lamp lighting device includes a main circuit that generates a lamp voltage that has a rectangular wave shape and reverse polarity, and the lamp is output by applying the lamp voltage output from the main circuit to the metal halide lamp. .

However, in the method of lighting a metal halide lamp with a rectangular wave in this way, the current that flows through the metal halide lamp (hereinafter referred to as the lamp current) instantaneously becomes zero when the polarity of the lamp voltage is reversed. There is a problem that high-frequency noise is generated during the process. In order to reduce this high-frequency noise, there is an experimental result that it is effective to raise the electrode temperature in order to facilitate re-ignition. FIG. 12 shows the lamp current waveform with the horizontal axis as the time axis. Thus, a countermeasure is considered in which the lamp current is temporarily increased before polarity inversion (FIG. 12A) and before and after polarity inversion (FIGS. 12B to 12D) (for example, Patent Document 1, 2). For example, when the lamp current is increased before polarity inversion as shown in FIG. 12A, it is confirmed that the electrode temperature at the time of polarity inversion can be kept high, and high frequency noise generated from the metal halide lamp at the time of polarity inversion can be reduced. ing.
Japanese National Patent Publication No. 10-501919 JP 2002-110392 A

  However, if the control is performed to increase the lamp current when the polarity of the lamp voltage is inverted as described above, the light output of the metal halide lamp varies instantaneously while the lamp current is increasing. As a result, if the metal halide lamp itself is stationary, the increase or decrease of the light output will not be recognized, but if the metal halide lamp itself moves at high speed, such as in a car, it will cause flickering etc. It becomes. As another means of reducing high frequency noise generated from a metal halide lamp, it is conceivable to suppress the temperature drop of the electrode by increasing the speed of polarity reversal, but in this case, the increase in noise generated from the main circuit or As a result, the burden on the circuit elements increases and the reliability of the main circuit cannot be ensured.

  By the way, it has been found that the high frequency noise generated when the polarity of the lamp voltage is reversed is reduced as the cumulative lighting time of the metal halide lamp elapses. FIG. 13 is considered to be caused by the polarity inversion of the lamp voltage for three types of in-vehicle metal halide lamps (lamp 1 to lamp 3) in which sodium iodide (NaI) is sealed in the arc tube as a metal halide (metal halide). It shows an example of a time-dependent change of high-frequency noise (about 400 kHz), and shows that the noise peak value (vertical axis) decreases as the cumulative lighting time (horizontal axis) elapses. Such a decrease in noise level is released with the progress of the reaction between the metal halide (here, sodium iodide) and the glass forming the arc tube in the arc tube of the metal halide lamp as the cumulative lighting time elapses. Due to an event that iodine (hereinafter referred to as free iodine) increases, the arc generated in the arc tube becomes thinner, the hot spot (bright spot) formed on the cathode side electrode becomes smaller, and the spot temperature rises Presumed to be. That is, when free iodine increases, the electrode temperature increases, so that hot spots are likely to be formed during polarity reversal, and high-frequency noise is reduced.

  The present invention has been made in view of the above reasons, and a metal halide lamp lighting device capable of promptly reducing high-frequency noise from a metal halide lamp by promoting the generation of free iodine in the metal halide lamp and the use thereof. The purpose is to provide a headlamp and a vehicle.

  According to the first aspect of the present invention, a main circuit for lighting a metal halide lamp by applying a lamp voltage to the metal halide lamp so that directions of currents flowing between a pair of electrodes of the metal halide lamp are alternately reversed, and an arc tube of the metal halide lamp A lamp potential control unit for applying a bias voltage between a proximity conductor made of a conductive material and a metal halide lamp disposed in proximity to each other, and the lamp potential control unit is enclosed in an arc tube of the metal halide lamp. The bias voltage can be controlled so that an attractive force acts between the metal component of the metal halide and the adjacent conductor.

  According to this configuration, the lamp potential control unit applies a bias voltage between the proximity conductor made of a conductive material disposed close to the arc tube of the metal halide lamp and one electrode of the metal halide lamp. During the application of free iodine, the generation of free iodine can be accelerated in the arc tube of the metal halide lamp. That is, when the metal component of the metal halide sealed in the arc tube is sodium, since the sodium is positively ionized in the arc tube, the proximity conductor is located between the proximity conductor disposed in proximity to the metal halide lamp and the metal halide lamp. When a bias voltage with a low potential is applied and an electric field is applied, an attraction force acts between the sodium atom and the adjacent conductor outside the arc tube due to the electric field, and the sodium atom is forcibly extracted. Sometimes the iodine remaining in the arc tube becomes free iodine, so that the production of free iodine can be accelerated. As a result, it is possible to quickly reduce the noise level of the high frequency noise generated when the polarity of the lamp voltage is reversed.

  According to a second aspect of the present invention, in the first aspect of the present invention, the lamp potential control unit sets the positive potential mode in which the metal halide lamp side is a positive potential and the metal halide lamp side is a negative potential with the proximity conductor as a reference potential. There are two operation modes, ie, a negative potential mode, and the positive potential mode is switched to the negative potential mode at a predetermined timing.

  According to this configuration, during operation in the positive potential mode, free iodine is generated by forcibly extracting sodium atoms to the adjacent conductor outside the arc tube by an electric field acting between the adjacent conductor and the metal halide lamp. Can be expedited. On the other hand, after switching to the negative potential mode, there is an advantage that sodium atoms are not extracted and it is possible to avoid excessive generation of free iodine in the arc tube.

  According to a third aspect of the present invention, in the first aspect of the present invention, the lamp potential control unit applies the bias voltage with the proximity conductor as a reference potential and the metal halide lamp side as a positive potential, and the bias voltage at a predetermined timing. It is characterized in that the size of is reduced.

  According to this structure, until the magnitude of the bias voltage is decreased, sodium atoms are forcibly extracted to the adjacent conductor outside the arc tube by the electric field acting between the adjacent conductor and the metal halide lamp, thereby Generation can be accelerated. On the other hand, after the bias voltage is reduced, the escape of sodium atoms can be suppressed, and the generation of free iodine in the arc tube can be avoided. In addition, since the lamp potential control unit only needs to switch the magnitude of the bias voltage, the configuration can be simplified as compared with the case where the polarity of the bias voltage is reversed.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the lamp potential control unit includes a cumulative lighting time measuring unit that measures a cumulative lighting time of the metal halide lamp, and a cumulative lighting time measuring unit. A bias control unit that variably controls the bias voltage in accordance with the cumulative lighting time measured in step (b), and the bias control unit includes the proximity conductor during an aging period until the cumulative lighting time reaches a predetermined time from zero. Is a positive potential on the metal halide lamp side, and the bias voltage is controlled so that the relative potential of the metal halide lamp with respect to the adjacent conductor becomes higher than the normal period after the aging period ends.

  According to this configuration, the bias control unit sets the metal halide lamp side as a positive potential with the adjacent conductor as a reference potential during the aging period until the cumulative lighting time of the metal halide lamp reaches a certain time from zero, and the aging period ends. Since the bias voltage is controlled so that the relative potential of the metal halide lamp with respect to the adjacent conductor becomes higher than the subsequent normal period, the generation of free iodine is promoted in the arc tube of the metal halide lamp during the aging period. As a result, the noise level of the high frequency noise generated at the time of reversing the polarity of the lamp voltage can be quickly reduced during the aging period, and the high frequency noise can be maintained at a low level during the subsequent normal period.

  According to a fifth aspect of the present invention, the lamp potential control unit according to any one of the first to third aspects of the present invention, wherein the electric potential that changes in relation to the cumulative lighting time of the metal halide lamp among the electric characteristics of the metal halide lamp. And a bias control unit that variably controls the bias voltage according to the cumulative lighting time determined by the cumulative lighting time determination unit. In the aging period until the cumulative lighting time reaches a certain time from zero, the bias control unit sets the adjacent conductor as a reference potential and sets the metal halide lamp side to a positive potential, and compared with the normal period after the aging period ends. The bias voltage is controlled so that the relative potential of the metal halide lamp to the adjacent conductor is increased.

  According to this configuration, the bias control unit sets the metal halide lamp side as a positive potential with the adjacent conductor as a reference potential during the aging period until the cumulative lighting time of the metal halide lamp reaches a certain time from zero, and the aging period ends. Since the bias voltage is controlled so that the relative potential of the metal halide lamp with respect to the adjacent conductor is higher than in the subsequent normal period, the generation of free iodine is promoted in the arc tube of the metal halide lamp during the aging period. As a result, the noise level of the high-frequency noise generated when the polarity of the lamp voltage is inverted can be quickly reduced during the aging period, and the high-frequency noise can be maintained at a low level during the subsequent normal period. In addition, since the cumulative lighting time is determined from the monitoring result of the electrical characteristics of the metal halide lamp, the cumulative lighting time is reset when replacing the lamp without providing a function for resetting the cumulative lighting time, thereby simplifying the circuit. be able to.

  The invention of claim 6 includes the metal halide lamp lighting device according to any one of claims 1 to 5, a metal halide lamp that is turned on when a lamp voltage is applied from the metal halide lamp lighting device, and a metal halide lamp. And a lamp body to be held.

  According to this configuration, in the headlamp, high-frequency noise from the metal halide lamp can be quickly reduced by promoting the generation of free iodine in the metal halide lamp, so that the lamp current at the time of polarity reversal of the lamp voltage can be reduced. There is no problem that the light output of the metal halide lamp fluctuates and flickers during running as in the conventional example in which the high frequency noise is reduced by increasing.

  The invention according to claim 7 is characterized in that the headlamp according to claim 6 is provided in a vehicle main body.

  According to this configuration, in the vehicle, high-frequency noise from the metal halide lamp can be quickly reduced by promoting the generation of free iodine in the metal halide lamp, so that the lamp current at the time of reversing the polarity of the lamp voltage is increased. Thus, unlike the conventional example in which high frequency noise is reduced, there is no problem that the light output of the metal halide lamp fluctuates and flickering is felt during traveling.

  In the present invention, the lamp potential control unit applies a bias voltage between a proximity conductor made of a conductive material disposed close to the arc tube of the metal halide lamp and one electrode of the metal halide lamp. Inside, the generation of free iodine can be accelerated in the arc tube of a metal halide lamp. As a result, there is an advantage that the noise level of the high frequency noise generated when the polarity of the lamp voltage is reversed can be quickly reduced.

(Embodiment 1)
A metal halide lamp lighting device (hereinafter simply referred to as “lighting device”) A according to the present embodiment converts a DC voltage from a DC power source 1 into a magnitude required by the metal halide lamp La, as shown in FIG. DC-DC converter 2, inverter circuit 3 that converts the output (DC voltage) of DC-DC converter 2 into a low-frequency rectangular wave lamp voltage, and an igniter that generates a voltage of several tens of kV when the metal halide lamp La is started The main circuit includes a circuit 4 and a drive unit 5 that monitors the output voltage (lamp voltage) and output current (lamp current) of the inverter circuit 3 and controls the DC-DC converter 2 so that the output power becomes the target power. ing.

  Here, the DC-DC converter 2 is a flyback converter, and a series circuit of the primary winding P1 of the transformer T1 and the switching element Q1 is connected between both ends of the DC power source 1, and the secondary winding of the transformer T1. A series circuit of a diode D1 and a smoothing capacitor C1 is connected between both ends of the line S1. The diode D1 prevents the current generated in the secondary winding S1 of the transformer T1 from flowing into the smoothing capacitor C1 when the switching element Q1 is turned on and a voltage is applied to the primary winding P1 of the transformer T1. Inserted in the direction.

  The inverter circuit 3 is a full bridge circuit configured by connecting a series circuit of switching elements Q2 and Q4 and a series circuit of switching elements Q3 and Q5 in parallel between both ends of the smoothing capacitor C1 of the DC-DC converter 2. Consists of. Thus, by alternately turning on the group of switching elements Q2 and Q5 and the group of switching elements Q3 and Q4, an alternating voltage is generated between the connection point of switching elements Q2 and Q4 and the connection point of switching elements Q3 and Q5. (Lamp voltage) is generated. However, before starting the metal halide lamp La, the switching elements Q2 and Q5 are fixed to the on state and the switching elements Q3 and Q4 are fixed to the off state.

  The igniter circuit 4 includes a transformer T2, a spark gap SG1 connected in series with the primary winding P2 of the transformer T2, and a capacitor Cs. The igniter circuit 4 is connected between the output terminals of the inverter circuit 3 (the switching elements Q2 and Q4). A series circuit of the primary winding P2 of the transformer T2 and the spark gap SG1 and the capacitor Cs are connected in parallel between the connection point and the connection point of the switching elements Q3 and Q5. Here, the secondary winding S <b> 2 of the transformer T <b> 2 is connected in series with the metal halide lamp La, and is connected between the output ends of the inverter circuit 3.

  Next, the basic operation of the lighting device A configured as described above will be described.

  When the lighting device A is turned on and the switching element Q1 of the DC-DC converter 2 is turned on, a current flows through a series circuit of the primary winding P1 of the transformer T1 and the switching element Q1. At this time, since the current that attempts to flow through the secondary winding S1 of the transformer T1 is blocked by the diode D1, the energy generated by the current flowing through the primary winding P1 is stored in the transformer T1. Next, when the switching element Q1 is turned off, a current flows through the path of the secondary winding S1, the smoothing capacitor C1, and the diode D1 of the transformer T1, and the energy stored in the transformer T1 is transferred to the smoothing capacitor C1.

  Here, since the metal halide lamp La is in an open state before the metal halide lamp La is started (before discharge is started), the output voltage of the DC-DC converter 2 (the voltage across the smoothing capacitor C1) is obtained by repeating the above operation. Gradually rises. At this time, since the switching elements Q2 and Q5 are fixed in the inverter circuit 3 and the switching elements Q3 and Q4 are turned off, the voltage across the capacitor Cs also increases. When the voltage across the capacitor Cs reaches the breakdown voltage of the spark gap SG1, the spark gap SG1 breaks down, a voltage is instantaneously applied to the primary winding P2 of the transformer T2, and the secondary winding S2 of the transformer T2 Therefore, a high voltage obtained by multiplying the above voltage by the turns ratio of the transformer T2 is generated. This high voltage (about several tens of kV) causes the metal halide lamp La to break down. At that moment, a current flows from the DC-DC converter 2 to the metal halide lamp La via the inverter circuit 3, and the metal halide lamp La shifts to arc discharge.

  By the way, the lighting device A of the present embodiment applies a bias voltage between the metal halide lamp La and the proximity conductor Rf made of a conductive member arranged in proximity to the arc tube (not shown) of the metal halide lamp La, and As shown in FIG. 2, a lamp potential controller 6 that variably controls the bias voltage according to the cumulative lighting time of the metal halide lamp La is provided. In the present embodiment, a metal reflecting mirror that exists around the arc tube of the metal halide lamp La and reflects the output light of the metal halide lamp La is used as the proximity conductor Rf.

  The lamp potential control unit 6 measures a cumulative lighting time measurement unit 61 that measures the cumulative lighting time of the metal halide lamp La, and bias control that controls a bias voltage according to a measurement result (cumulative lighting time) in the cumulative lighting time measurement unit 61. And a reset switch 63 for resetting the cumulative lighting time measured by the cumulative lighting time measuring unit 61 to zero when the metal halide lamp La is replaced. Here, the cumulative lighting time measuring unit 61 monitors the operating time of the inverter circuit 2 and measures the cumulative lighting time on the assumption that the cumulative value is equal to the cumulative lighting time of the metal halide lamp La.

  Here, the proximity conductor Rf is grounded to a circuit ground common to the lighting device A, and the bias control unit 62 applies a DC bias voltage between the circuit ground and one electrode of the metal halide lamp La. Configured. Thereby, a bias voltage is applied between the adjacent conductor Rf and one electrode of the metal halide lamp La, and if the potential of the adjacent conductor Rf (that is, the potential of the circuit ground) is set to the reference potential (0 V), the metal halide lamp La The potential of one of the electrodes is charged to a potential corresponding to the bias voltage.

  In the present embodiment, the bias control unit 62 includes a positive potential mode in which the proximity conductor Rf is set to the reference potential (0V), the electrode side of the metal halide lamp La is set to a positive potential (> 0V), and the proximity conductor Rf is set to the reference potential (0V). There are two operation modes: a negative potential mode in which the electrode side of the metal halide lamp La is a negative potential (<0V). Then, as shown in FIG. 2, the bias control unit 62 operates in the positive potential mode during a period until the cumulative lighting time reaches a certain time from zero (hereinafter referred to as an aging period t1), and when the certain time is reached. The polarity of the bias voltage is reversed, and the operation is performed in the negative potential mode in the subsequent period (hereinafter referred to as the regular period t2).

  Thereby, in the aging period t1, the metal halide lamp La side becomes a positive potential when the proximity conductor Rf is set to the reference potential, and the metal halide lamp La is relatively relative to the proximity conductor Rf as compared with the normal period t2 after the aging period t1 ends. As the potential increases, sodium, which is a substance enclosed in the metal halide lamp La, is extracted from the arc tube of the metal halide lamp La, and free iodine (hereinafter referred to as free iodine) is generated at an accelerated rate. At this time, as shown in FIG. 3, the lamp voltage rises steeply as free iodine is rapidly generated, and during the subsequent normal period t2, it rises equivalent to the rated lighting when no bias voltage is applied. The rate rises relatively slowly.

  Here, the noise level of the high frequency noise generated in the metal halide lamp La at the time of reversing the polarity of the lamp voltage rapidly decreases during the aging period t1 set at the beginning of lighting as shown in FIG. 4, and during the subsequent regular period t2. It has been confirmed that a low noise level is maintained. After the low noise state is realized in this way, the polarity of the bias voltage is reversed in order to avoid excessive generation of free iodine, so that a practical problem can be avoided.

  The reason why high frequency noise is reduced by applying a bias voltage will be described below.

  That is, since the sodium sealed in the arc tube of the metal halide lamp La is positively ionized in the arc tube, a bias voltage is applied between the adjacent conductor Rf existing around the arc tube and the metal halide lamp La. When an electric field having a positive potential on the metal halide lamp La side is applied, an attraction force is generated between the adjacent conductor Rf by the electric field and is forcibly drawn to the outside of the arc tube (on the adjacent conductor Rf side). These sodium atoms are sufficiently small, and can pass through the tube wall (quartz glass) of the arc tube that has become hot due to lighting.

  FIG. 5 shows the time change of the lamp voltage when the adjacent conductor Rf is set to the reference potential (0 V) and the metal halide lamp La is charged with a positive potential (hereinafter referred to as positive potential lighting). The horizontal axis represents the time axis, and the vertical axis represents the lamp voltage. In the example of FIG. 5, a bias voltage is applied between one electrode of the metal halide lamp La and the adjacent conductor Rf so that the metal halide lamp La is charged to a positive potential of 630 V when the adjacent conductor Rf is set to the reference potential. Shows the change in lamp voltage. In such a high level positive potential lighting, the lamp voltage rises by about 2 V after 10 hours of lighting.

  On the other hand, FIG. 6 is a graph showing the relationship between the rise value (horizontal axis) of the lamp voltage caused by extracting sodium from the arc tube and the noise level (vertical axis) of the high frequency noise generated from the metal halide lamp La. As is apparent from this figure, when sodium is removed from the arc tube, the high frequency noise rapidly decreases in a certain range (here, the voltage increase value is 5 V or less). Such a decrease in the noise level is caused by the fact that only sodium is taken out from sodium iodide sealed in the arc tube and iodine remains as free iodine in the arc tube. In the arc tube shown in FIG. This is considered to be a phenomenon similar to a decrease in noise level caused by an increase in free iodine due to a reaction between a metal halide (here, sodium iodide) and glass. In other words, when free iodine increases, the arc generated in the arc tube becomes thinner, the hot spot (bright spot) formed on the cathode side electrode becomes smaller and the spot temperature rises, so a hot spot is formed during polarity reversal. It is considered that high frequency noise is reduced by being easily performed.

  Here, in order to sufficiently reduce the high-frequency noise generated from the metal halide lamp La when the polarity of the lamp voltage is reversed, it is sufficient to generate free iodine that causes an increase in the lamp voltage of about 2 to 5 V. As described above, when the lamp potential control unit 6 applies the bias voltage, a sufficient high frequency noise reduction effect can be obtained in a relatively short time (about 10 hours in the example of FIG. 5). This effect depends on the potential difference of the metal halide lamp La with respect to the adjacent conductor Rf and the distance from the metal halide lamp La to the adjacent conductor Rf. For example, when the charged potential of the metal halide lamp La is lowered, the generation of free iodine is sufficient. The time required to achieve high frequency noise reduction is increased.

  When the metal halide lamp La is replaced and the reset switch 63 is operated, the accumulated lighting time is reset and counted again from zero, so that the bias voltage control shown in FIG. 2 is repeated. In this embodiment, the cumulative lighting time is reset by the operation of the reset switch 63. However, for example, a means for detecting the attachment / detachment of the metal halide lamp La is provided, and the cumulative lighting time is automatically reset when the lamp is replaced. It is also possible.

  In the present embodiment, the lighting device A for lighting the metal halide lamp La in which sodium iodide (NaI) is enclosed in the arc tube as the metal halide (metal halide) is illustrated, but the present invention is not limited to sodium iodide. The present invention can be applied to a lighting device A used for lighting a metal halide lamp La enclosing various metal halides. Even in the case of using a general metal halide lamp La in which a metal halide other than sodium iodide is enclosed, according to the present invention, a halogen that is released by forcibly extracting metal atoms from the metal halide (free halogen) ) Can be promoted.

(Embodiment 2)
In the lighting device A of the present embodiment, the lamp potential control unit 6 applies a bias voltage that always has a positive potential (> 0 V) on the metal halide lamp La side when the proximity conductor Rf is set to the reference potential (0 V). Is different from the lighting device A of the first embodiment.

  That is, in this embodiment, since it is not necessary to reverse the polarity of the bias voltage as in the first embodiment, the ramp potential control unit 6 has a variable output voltage (bias voltage) as shown in FIG. A simple unipolar DC power supply is employed as the bias controller 62.

  Here, as shown in FIG. 8, the bias control unit 62 sets the bias voltage higher than the specified value Vb during the period until the cumulative lighting time of the metal halide lamp La reaches a certain time from zero (aging period t1). The voltage is set to Vb ′, and when the accumulated lighting time reaches the predetermined time, the bias voltage is lowered, and the bias voltage is maintained at the specified value Vb in the subsequent period (normal period t2). In short, the potential of the metal halide lamp La is on the positive potential side in both the aging period t1 and the regular period t2 with respect to the potential (reference potential) of the adjacent conductor Rf, but in the regular period t2 in the aging period t1. Compared to the reference potential, the relative potential becomes higher.

  As a result, during the aging period t1 in which the metal halide lamp La is set to a high positive potential by the bias voltage, free iodine can be generated at an accelerated rate by extracting sodium from the arc tube as in the first embodiment. On the other hand, in the normal period t2, the metal halide lamp La is charged to a positive potential by the bias voltage, but the potential is controlled to a low level (specified value Vb), so that the sodium escape from the arc tube is substantially eliminated. It can be suppressed to a negligible level. As a result, the noise level of the high-frequency noise generated in the metal halide lamp La is rapidly lowered as free iodine is rapidly generated in the aging period t1 in the early stage of lighting, and thereafter the low noise level can be maintained. Yes (see FIG. 4). The lamp voltage rises sharply as free iodine is rapidly generated during the aging period t1, and during the subsequent normal period t2, the rate of increase is the same as that during rated lighting when no bias voltage is applied. It rises relatively slowly (see FIG. 3).

  In the configuration described above, it is not necessary to use a bipolar power source for the bias control unit 62, and the circuit configuration is simplified compared to the configuration of the first embodiment in which the positive potential mode and the negative potential mode can be switched. be able to.

  Other configurations and functions are the same as those of the first embodiment.

(Embodiment 3)
As shown in FIG. 9, the lighting device A of the present embodiment includes an electrical characteristic measurement unit 64 that measures electrical characteristics of the metal halide lamp La (hereinafter referred to as lamp electrical characteristics). The difference from the lighting device A of the second embodiment is that a cumulative lighting time discriminating unit 65 that determines the cumulative lighting time of the metal halide lamp La is provided in place of the cumulative lighting time measuring unit 61. The bias controller 62 controls the bias voltage according to the determination value (cumulative lighting time) in the cumulative lighting time determination unit 65.

  Here, the lamp electrical characteristic to be measured by the electrical characteristic measuring unit 64 only needs to be correlated with the cumulative lighting time of the metal halide lamp La. For example, the lamp voltage value or the lamp at the time of re-ignition of the metal halide lamp La is used. An example is the peak value of the voltage. It is also possible to measure electrical characteristics that are directly correlated with a reduction in high-frequency noise from the metal halide lamp La.

  According to the above configuration, the cumulative lighting time of the metal halide lamp La is not actually measured, but the cumulative lighting time is estimated from the lamp electrical characteristics. Therefore, when replacing the lamp, the electrical characteristics of the metal halide lamp La after the replacement are estimated. Accordingly, the cumulative lighting time is reset, and there is an advantage that the operation of the reset switch and the means for detecting the attachment / detachment of the metal halide lamp La become unnecessary.

  Other configurations and functions are the same as those in the first or second embodiment.

(Embodiment 4)
The lighting device A of the present embodiment is different from the lighting device A of the second embodiment in that an AC power source (commercial power source) AC is used as a power source instead of the DC power source 1 as shown in FIG.

  The lighting device A includes an AC-DC converter 7 that converts the output of the AC power source AC into a DC voltage and applies the DC voltage to the DC-DC converter 2. The AC-DC converter 7 connects a parallel circuit of a primary winding P3 of a transformer T3 and a capacitor C2 to an AC power source AC, and an inductor L1 and a capacitor C4 are connected between both ends of the secondary winding S3 of the transformer T3. A series circuit is connected, and the voltage across the capacitor C4 is full-wave rectified by a diode bridge DB, and then boosted by a boost chopper circuit.

  The step-up chopper circuit is connected between the capacitor C5 connected between the output ends of the diode bridge DB, the series circuit of the inductor L2 connected between both ends of the capacitor C5 and the switching element Q6, and both ends of the switching element Q6. A series circuit of a diode D2 and a capacitor C6 is provided, and the voltage across the capacitor C6 is applied to the subsequent DC-DC converter 2 as an output voltage. Further, the DC-DC converter 2 employs a flyback converter in the same manner as in the first embodiment in FIG. 10, but a step-down chopper circuit may be employed instead.

  Here, the present invention in which a bias voltage is applied between the metal halide lamp La and the adjacent conductor Rf is specifically applied to a lighting device that turns on the metal halide lamp La with a rectangular wave and increases the output in synchronization with the rectangular wave. Therefore, the lighting device A of the present embodiment can be expected to have the same effect as that of the first embodiment or the second embodiment. As another circuit configuration, a circuit configuration using both the DC-DC converter 2 and the inverter circuit 3 is also known, and the same effect can be obtained by applying the present invention to such a circuit configuration. it can.

  In each of the above embodiments, a DC power source is used as the bias control unit 62. However, the bias control unit 62 is not limited to the DC power source as long as a similar function can be realized by the configuration of the inverter circuit 2, for example.

  Other configurations and functions are the same as those in the first or second embodiment.

  By the way, the lighting device A of each embodiment mentioned above comprises the vehicle headlamp 8 as shown in FIG. 11 with the metal halide lamp La and the lamp body (not shown) holding the metal halide lamp La, for example. . This headlamp 8 is mounted on the vehicle body of the vehicle 9 as a pair of left and right, and is connected to a headlamp control device 10 provided separately on the left and right, so that a control signal from the low beam switch 11 is sent to the headlamp. Lights up in response to the control device 10.

  In the lighting device A used for this kind of vehicle-mounted metal halide lamp La, there are very strict regulations regarding safety and noise. By adopting the lighting device A of the present invention, noise is reduced. However, since the flicker due to the fluctuation of the light output of the metal halide lamp La can be suppressed as compared with the case where the control for increasing the current at the time of polarity reversal is performed as in the conventional configuration, the headlamp 8 has improved safety. In addition, the vehicle 9 can be realized.

It is a schematic circuit diagram which shows the structure of Embodiment 1 of this invention. It is explanatory drawing which shows the change of the electric potential of a metal halide lamp with respect to a reference electric potential same as the above. It is explanatory drawing which shows the time change of a lamp voltage same as the above. It is explanatory drawing which shows the time change of a lamp current same as the above. It is a graph which shows an example of the time change of a lamp voltage same as the above. It is a graph which shows the change of the noise peak value with respect to a lamp voltage rise value same as the above. It is a schematic circuit diagram which shows the structure of Embodiment 2 of this invention. It is explanatory drawing which shows the change of the electric potential of a metal halide lamp with respect to a reference electric potential same as the above. It is a schematic circuit diagram which shows the structure of Embodiment 3 of this invention. It is a schematic circuit diagram which shows the structure of Embodiment 4 of this invention. It is the schematic which shows the headlamp and vehicle which used the metal halide lamp lighting device of this invention. It is explanatory drawing which shows operation | movement of a prior art example. It is a graph which shows the change of the noise peak value with respect to accumulation lighting time.

Explanation of symbols

6 Lamp Potential Control Unit 8 Headlight 9 Vehicle 61 Cumulative Lighting Time Measurement Unit 62 Bias Control Unit 64 Cumulative Lighting Time Discrimination Unit A Metal Halide Lamp Lighting Device La Metal Halide Lamp Rf Proximity Conductor t1 Aging Period t2 Regular Period

Claims (7)

  A main circuit that turns on the metal halide lamp by applying a lamp voltage to the metal halide lamp so that the direction of the current flowing between the pair of electrodes of the metal halide lamp is alternately reversed, and conductivity that is disposed close to the arc tube of the metal halide lamp. A lamp potential control unit that applies a bias voltage between the adjacent conductor made of material and one electrode of the metal halide lamp, and the lamp potential control unit includes a metal component of the metal halide sealed in the arc tube of the metal halide lamp A metal halide lamp lighting device characterized in that a bias voltage can be controlled so that an attractive force acts between adjacent conductors.   The lamp potential control unit has two operation modes: a positive potential mode in which the adjacent conductor is a reference potential and the metal halide lamp side is a positive potential; and a negative potential mode in which the metal halide lamp side is a negative potential, and a predetermined potential mode. The metal halide lamp lighting device according to claim 1, wherein the positive potential mode is switched to the negative potential mode at the timing of   2. The lamp potential control unit applies the bias voltage having the proximity conductor as a reference potential and a positive potential on the metal halide lamp side, and reduces the magnitude of the bias voltage at a predetermined timing. The metal halide lamp lighting device described.   The lamp potential control unit includes a cumulative lighting time measurement unit that measures the cumulative lighting time of the metal halide lamp, and a bias control unit that variably controls the bias voltage according to the cumulative lighting time measured by the cumulative lighting time measurement unit; The bias control unit has a normal period after the end of the aging period, and in the aging period until the cumulative lighting time reaches zero to a certain time, the adjacent conductor is a reference potential and the metal halide lamp side is a positive potential. The metal halide lamp lighting device according to any one of claims 1 to 3, wherein the bias voltage is controlled so that the relative potential of the metal halide lamp with respect to the adjacent conductor is higher than that of the adjacent conductor.   The lamp potential control unit monitors an electrical characteristic that changes in relation to the cumulative lighting time of the metal halide lamp among the electrical characteristics of the metal halide lamp, and a cumulative lighting time determination unit that determines the cumulative lighting time from the monitoring result; A bias control unit that variably controls the bias voltage according to the cumulative lighting time determined by the cumulative lighting time determination unit, and the bias control unit is an aging period until the cumulative lighting time reaches a certain time from zero The bias voltage is controlled so that the relative potential of the metal halide lamp with respect to the adjacent conductor is higher than that of the normal period after the aging period, and the metal halide lamp side is set to a positive potential with the adjacent conductor as a reference potential. The metal halide lamp point according to any one of claims 1 to 3, wherein Apparatus.   A metal halide lamp lighting device according to any one of claims 1 to 5, a metal halide lamp that is turned on when a lamp voltage is applied from the metal halide lamp lighting device, and a lamp body that holds the metal halide lamp. A headlamp characterized by that.   A vehicle comprising the headlamp according to claim 6 on a vehicle body.

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