JP2010055828A - Discharge lamp lighting device, and headlight and vehicle using the same - Google Patents

Abstract

Disclosed is a discharge lamp lighting device, a headlamp using the same, and a vehicle that reduce the high-frequency noise when the lamp is lit while extending the life of the lamp.
A discharge lamp lighting device includes a DC-DC converter unit 1, an inverter unit 2 that converts an output of the DC-DC converter 1 into an AC voltage of a rectangular wave and supplies it to a metal halide lamp La, and a DC-DC converter. The control part 6 which controls the output of the part 1 and the inverter part 2 is provided. The control unit 6 includes a cumulative lighting time measuring unit 63 that measures the cumulative lighting time of the metal halide lamp La, and a current target increasing unit 65 that increases the output power of the inverter unit 2 by increasing the lamp current in synchronization with polarity inversion. The current target increasing unit 65 increases the increase in output power at the beginning of lighting according to the measurement result of the cumulative lighting time and decreases the increase in output power as the cumulative lighting time elapses. This reduces the noise reduction effect.
[Selection] Figure 1

Description

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

  In recent years, high-intensity discharge lamps such as metal halide lamps have been used as light sources for automobile headlamps and projectors. Discharge lamp lighting devices that use metal halide lamps as the light source employ a rectangular wave lighting system to prevent the occurrence of acoustic resonance, but the rectangular wave lighting system has a moment when the lamp current becomes zero when the polarity is reversed. For this reason, the discharge state becomes unstable, flickering of the metal halide lamp may occur, and extinction may occur in the worst case. In addition, even when there is no extinction, the metal halide lamp is once extinguished and then re-ignited, resulting in an increase in noise generated from the metal halide lamp at the time of polarity reversal. Note that when the polarity of the rectangular wave output is reversed, the lamp current becomes zero and the metal halide lamp is once extinguished, and then the opposite polarity voltage rises. At this time, a bright spot is formed on the electrode serving as the cathode. Takes time, and only a low current flows during that time. After that, when a bright spot is formed on the cathode, the lamp impedance decreases, the current increases, and the current keeps the bright spot stable, but after the bright spot disappears, the bright spot again It is considered that noise is generated due to a steep fluctuation in the lamp voltage before it is formed.

Here, if it is easy to form a bright spot after the metal halide lamp is once extinguished at the time of polarity reversal, it is considered that noise generated at the time of polarity reversal can be reduced. Therefore, as shown in FIG. Increasing the lamp current before the current is reversed, or increasing the lamp current before and after the lamp current is reversed as shown in FIGS. In the past, a discharge lamp lighting device has been proposed which prevents the occurrence of flickering and flickering (see, for example, Patent Documents 1 and 2).
Japanese National Patent Publication No. 10-501919 JP 2002-110392 A

  In the above-described discharge lamp lighting device, the electrode temperature is increased by increasing the lamp current before the polarity of the lamp current is reversed, so that the electrode temperature at the time of polarity reversal can be maintained at a high temperature state, thereby It became possible to stabilize the discharge state at the time of reversing the polarity of the lamp current and immediately after the reversal. Moreover, by stabilizing the discharge state at the time of polarity reversal and immediately after the reversal, the effect of reducing the high frequency noise generated by the metal halide lamp at the time of polarity reversal was confirmed. As a result, the life of the metal halide lamp may be shortened due to evaporation or melting.

  By the way, the present inventors have confirmed that the high frequency noise generated from the metal halide lamp when the polarity of the lamp current is reversed decreases as the cumulative lighting time increases. Fig. 20 shows the measurement of the relationship between the peak value of noise (frequency is about 400 kHz) and the cumulative lighting time, which seems to be caused by the high frequency noise generated by the metal halide lamp when the polarity is reversed, for a vehicle headlamp using a metal halide lamp. The results show that the noise level decreases as the cumulative lighting time elapses for any of the lamps A to C.

  This phenomenon is considered to occur for the following reasons. As the cumulative lighting time elapses, the metal halide (metal halide) sealed in the lamp reacts with the glass forming the lamp tube to generate free iodine in the lamp. This free iodine is affected by the arc discharge, and the hot spot formed on the electrode is reduced and the spot temperature rises. It is estimated that the level will decrease.

  As described above, when the temperature of the electrode spot rises as the cumulative lighting time elapses, the high-frequency noise generated when the metal halide lamp is re-ignited decreases, but the operation increases the electrode temperature to reduce the noise. If the operation is continued, the electrode temperature rises excessively, causing deformation due to evaporation or melting of the electrode, which may shorten the life of the metal halide lamp. In order to reduce high frequency noise from the metal halide lamp, it may be possible to provide a noise filter or an electromagnetic shield, but there is also a problem in that the cost is increased.

  The present invention has been made in view of the above problems, and its object is to provide a low-cost discharge lamp lighting device that reduces the high-frequency noise during lamp lighting and extends the life of the lamp, and It is to provide a headlamp and a vehicle using the same.

  In order to achieve the above object, the invention according to claim 1 is directed to a power converter that converts an input power source into a DC voltage having a voltage value necessary for lighting a metal halide lamp, and an output of the power converter is converted to a rectangular wave alternating voltage. An inverter unit that converts and supplies the metal halide lamp, and a noise reduction unit that reduces noise generated from the metal halide lamp when the polarity of the output of the inverter unit is inverted by adjusting the output of the inverter unit, and a cumulative lighting period becomes longer And a control unit that reduces the noise reduction effect of the noise reduction unit.

  According to a second aspect of the present invention, in the first aspect of the invention, the noise reduction unit has time adjusting means for adjusting a polarity inversion time required for inverting the polarity of the output of the inverter unit, and the control unit is configured to perform cumulative lighting. The polarity inversion time is increased by the time adjusting means as time elapses.

  According to a third aspect of the present invention, in the first aspect of the present invention, the noise reduction unit has output adjusting means for increasing the output power of the inverter unit in synchronization with the polarity inversion of the output of the inverter unit. As the lighting time elapses, the increase in the output power by the output adjusting means is reduced.

  According to a fourth aspect of the present invention, in the first aspect of the present invention, the noise reduction unit has a waveform adjusting unit that changes the output waveform of the inverter unit in an asymmetric shape, and changes the output waveform according to the cumulative lighting time. Features.

  According to a fifth aspect of the present invention, in the first aspect of the present invention, the noise reduction unit has a current adjustment unit that changes the output current of the inverter unit, and the control unit is a current adjustment unit according to the elapse of the cumulative lighting time. To reduce the output current.

  A sixth aspect of the invention is characterized in that, in any one of the first to fifth aspects, the control unit detects the cumulative lighting time from the electrical characteristic value of the metal halide.

  A seventh aspect of the invention is a headlamp, comprising the discharge lamp lighting device according to any one of the first to sixth aspects.

  The invention of claim 8 is a vehicle, comprising the discharge lamp lighting device according to any one of claims 1 to 6 or the headlamp according to claim 7. And

  As described above, it has been found that the high-frequency noise generated from the metal halide lamp is reduced as the cumulative lighting time increases. However, according to the invention of claim 1, the control unit responds to the passage of the cumulative lighting time. The noise reduction effect of the noise reduction part is reduced, and the noise reduction effect of the noise reduction part is relatively large in the initial use of the lamp. High frequency noise can be reduced. In addition, the control unit reduces the noise reduction effect of the noise reduction unit as the cumulative lighting time elapses. For example, the control unit increases the current flowing through the lamp and the power supplied to the lamp. When reducing the high frequency noise, the stress applied to the metal halide lamp is reduced by reducing the noise reduction effect of the noise reduction part as the high frequency noise generated from the metal halide lamp decreases as the cumulative lighting time increases. Thus, the life of the lamp can be extended. Furthermore, since a noise filter and an electromagnetic shield are unnecessary, there is an effect that a low-cost discharge lamp lighting device can be realized.

  In addition, the noise generated by the metal halide lamp can be reduced by shortening the polarity inversion time. However, according to the invention of claim 2, the noise reduction unit shortens the polarity inversion time at the beginning of lighting. Therefore, it is possible to reduce noise, and by increasing the polarity inversion time as the cumulative lighting time becomes longer, it is possible to reduce the stress applied to the metal halide lamp and circuit parts and to extend the life of the lamp. it can.

  Further, the noise generated by the metal halide lamp can be reduced by increasing the output power of the inverter unit in synchronism with the polarity inversion. Since the increase in output power increases, noise can be reduced, and the increase in output power decreases as the cumulative lighting time increases, reducing the stress applied to metal halide lamps and circuit components. Thus, the life of the lamp can be extended.

  According to the invention of claim 4, the noise reduction unit adjusts the added value of the lamp current and the polarity reversal time, for example, to reduce the noise by making the output waveform asymmetrical, and the accumulated lighting time is long. As the output waveform changes, the stress applied to the metal halide lamp and circuit components can be reduced.

  In addition, the noise generated by the metal halide lamp can be reduced by increasing the output current of the inverter unit. According to the invention of claim 5, the noise reducing unit increases the output current in the initial stage of lighting. Therefore, it is possible to reduce noise, and by reducing the increase in output current as the cumulative lighting time increases, the stress applied to the metal halide lamp and circuit parts is reduced, and the lamp length is increased. Life can be extended.

  According to the invention of claim 6, since a timer for measuring the cumulative lighting time of the metal halide lamp and a switch for resetting the count value of the timer are not required, the cost can be reduced, and the reset operation is performed when the lamp is replaced. Since there is no need to perform the operation, there is an effect that convenience is improved.

  According to the invention of claim 7, it is possible to provide a low-cost headlamp that extends the life of the metal halide lamp while reducing the noise generated from the metal halide lamp.

  According to the invention of claim 8, it is possible to provide a vehicle equipped with a low-cost discharge lamp lighting device or a headlamp that extends the life of the metal halide lamp while reducing noise generated from the metal halide lamp. .

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
Embodiment 1 of this invention is demonstrated based on FIGS.

  The discharge lamp lighting device of the present embodiment is a lighting device for lighting a metal halide lamp which is a high-intensity discharge lamp. As shown in the circuit diagram of FIG. 1, a DC voltage from a DC power source E is applied to the metal halide lamp La. A DC-DC converter unit 1 (power converter unit) that converts (steps up and down) into a DC voltage having a voltage value necessary for lighting of the LED, and an output of the DC-DC converter unit 1 is converted into a low-frequency rectangular wave alternating voltage. An inverter unit 2 that supplies the metal halide lamp La, an igniter unit 3 that generates a voltage of several tens of kV when the metal halide lamp La is started, and that is applied to the metal halide lamp La, and an output voltage of the DC-DC converter unit 1 are detected. Voltage detection unit 4, current detection unit 5 that detects the output current of DC-DC converter unit 1, and detection of voltage detection unit 4 and current detection unit 5 And a control unit 6 having a function of controlling the operation of the DC-DC converter unit 1 so that the output power becomes a target power based on the results, and a function of periodically inverting (alternating) the output of the inverter unit 2. . The metal halide lamp La is configured by enclosing a metal halide (metal halide) such as sodium iodide (NaI) inside a glass bulb.

  In this discharge lamp lighting device, the DC-DC converter unit 1 converts the DC power source E into a voltage, and the inverter unit 2 converts the output voltage of the DC-DC converter unit 1 into a rectangular wave alternating voltage. Further, an igniter unit 3 is connected to the output of the inverter unit 2, and the metal halide lamp La is started by applying a high starting voltage from the igniter unit 3 to the metal halide lamp La. Although a specific configuration is not illustrated, the voltage detection unit 4 and the current detection unit 5 may be configured using resistors or the like.

  The DC-DC converter unit 1 includes a series circuit of a primary winding n1 of a transformer T1 and a switching element Q1 composed of a MOSFET connected between both ends of a DC power supply E. The DC-DC converter unit 1 includes a secondary winding n2 of the transformer T1. A smoothing capacitor C1 is connected via a diode D1. The diode D1 is connected to such a polarity that the charging current does not flow through the smoothing capacitor C1 when the switching element Q1 is on, and the charging current flows from the winding n1 to the smoothing capacitor C1 when the switching element Q1 is off. That is, the DC-DC converter unit 1 is a flyback type, and the voltage at both ends of the smoothing capacitor C1 is raised and lowered with respect to the terminal voltage of the DC power supply E by controlling the on / off time of the switching element Q1. It is possible.

  The inverter unit 2 is a full bridge circuit in which four switching elements Q2 to Q5 each made of a MOSFET are bridge-connected, and includes a series circuit composed of switching elements Q2 and Q4 and a series circuit composed of switching elements Q3 and Q5. The DC-DC converter unit 1 is connected in parallel to the smoothing capacitor C1 provided at the output end. A metal halide lamp La is connected between the connection point of the switching elements Q2 and Q4 and the connection point of the switching elements Q3 and Q5 via the secondary winding n2 of the transformer T2 provided in the igniter section 3. That is, a series circuit of the secondary winding n2 of the transformer T2 and the metal halide lamp La is connected between the output terminals of the inverter unit 2. The switching elements Q2 to Q5 are controlled to be turned on / off by the control unit 6. In normal control, the switching elements Q2 and Q5 and the switching elements Q3 and Q4 are alternately turned on and off alternately so that a low-frequency rectangular wave alternating voltage is applied to the metal halide lamp La. Is done.

  The igniter unit 3 includes a capacitor C2 connected between the output terminals of the inverter unit 2, a transformer T2 in which one end of the primary winding n1 is connected to one end of the capacitor C2, and other than the primary winding n1 of the transformer T2. And a spark gap SG connected between the end and the other end of the capacitor C2. Accordingly, when the capacitor C2 is charged until the voltage across the capacitor C2 reaches the breakover voltage of the spark gap SG, a current flows from the capacitor C2 to the primary winding n1 of the transformer T2 due to the breakdown of the spark gap SG, and the transformer T2 A high voltage is generated in the secondary winding n2. Since the secondary winding n2 of the transformer T2 is connected to the metal halide lamp La, the high voltage generated in the secondary winding n2 is applied to the metal halide lamp La, and the metal halide lamp La can be started.

  The controller 6 outputs the output voltage (corresponding to the lamp voltage) of the DC-DC converter 1 detected by the voltage detector 4 and the supply current (corresponding to the lamp current) to the inverter 2 detected by the current detector 5. ) To control the on / off of the switching element Q1 so that the output power of the DC-DC converter unit 1 becomes a power target value.

  Hereinafter, the control unit 6 will be described more specifically. The control unit 6 uses a microcomputer (hereinafter abbreviated as “microcomputer”) as a main component, and includes, for example, a power target storage unit 61 that includes a ROM and is preset with a power target value Pd, and a power target storage. A current target calculation unit 62 that sets a target current value Id1 using the power target value Pd stored in the unit 61 and the detected voltage value Vs detected by the voltage detection unit 4, and the operating time of the inverter unit 3 is measured. The cumulative lighting time measuring unit 63 that calculates the cumulative value as the cumulative lighting time of the lamp, and an inversion instruction that inverts the polarity of the output to the inverter unit 2 and the inversion determination that generates the inversion synchronization signal SY at the timing before and after the inversion. The current addition value determined according to the measurement result of the cumulative lighting time measurement unit 63 in synchronization with the input of the inversion synchronization signal SY from the unit 64 and the inversion determination unit 64 is a target current. The target current value Id2 obtained by adding to Id1 is output, and when there is no inversion synchronization signal SY, the target current value Id1 is output as it is as the target current value Id2 as a current target increase unit 65 (noise reduction unit, output adjustment means) ) And the output current detection value Is detected by the current detection unit 5 and the target current value Id2, and an error amplifier 66 that outputs the control signal S2 to the switching element Q1 so as to eliminate the difference therebetween. When the reset switch SW is operated during lamp replacement, the cumulative time measuring unit 63 clears the cumulative lighting time and returns it to zero.

  Here, the operation of the lighting device will be described. When a power switch (not shown) is turned on and power is supplied from the DC power source E to the DC-DC converter unit 1, the DC-DC converter unit 1 in the ON period of the switching element Q1 causes the primary winding n1 of the transformer T1. Current flows through the switching element Q1. However, since the induced voltage generated on the secondary side of the transformer T1 during this period is in the reverse direction of the diode D1, the charging current cannot flow through the smoothing capacitor C1, and the energy of the current flowing through the primary winding n1 is the transformer. Accumulated in T1. Thereafter, when the switching element Q1 is turned off, current flows in the path of the secondary winding n2-smoothing capacitor C1-diode D1-2-secondary winding n2 due to the energy stored in the transformer T1, and is stored in the transformer T1. The stored energy is transferred to the smoothing capacitor C1.

  Since the metal halide lamp La is not conducted before the metal halide lamp La is started, the inverter unit 2 is close to a no-load state, and the DC-DC converter unit 1 is lightly loaded, so that the voltage of the smoothing capacitor C1 increases. Here, if the switching elements Q2 and Q5 of the inverter unit 2 are kept on and the switching elements Q3 and Q4 are kept off, the voltage across the smoothing capacitor C1 is directly reflected in the voltage across the capacitor C2, and the capacitor C2 The voltage at both ends increases. Thereafter, when the voltage across the capacitor C2 reaches the breakover voltage of the spark gap SG, the spark gap SG breaks down, and as described above, current flows instantaneously through the primary winding n1 of the transformer T2, and the transformer T2 A high voltage (about several tens of kV) is induced in the secondary winding n2, and the metal halide lamp La is started. When the metal halide lamp La is started in this way, current flows from the DC-DC converter unit 1 to the metal halide lamp La at that moment, and the metal halide lamp La shifts to arc discharge.

  After the metal halide lamp La is started (after lighting), the inversion determination unit 64 of the control unit 6 turns on / off the switching elements Q2 to Q5 of the inverter unit 2 as described above, whereby the output of the inverter unit 2 is predetermined. A rectangular wave alternating voltage is applied to the metal halide lamp La by alternating at time intervals. The current target calculation unit 62 of the control unit 6 obtains the current target value Id1 by dividing the power target value Pd input from the current target storage unit 61 by the detection voltage value Vs of the voltage detection unit 4. When the inversion determination unit 64 outputs the inversion signal, the inversion synchronization signal SY is output to the current target increase unit 65 at the timing before and after the inversion. In the current target increase unit 65 as the output adjustment unit, the inversion synchronization signal SY is output. When input, the addition amount of the target value is determined according to the cumulative lighting time measured by the cumulative lighting time measuring unit 63, and this addition amount is added to the current target value Id1 input from the current target calculation unit 62. Thus, the current target value Id2 is obtained, and this current target value Id2 is output to the error amplifier 66. Note that the current target increase unit 65 outputs the current target value Id1 input from the current target calculation unit 62 to the error amplifier 66 as it is when the inverted synchronization signal SY is not input. The error amplifier 66 compares the output current detection value Is detected by the current detection unit 5 with the target current value Id2, and outputs the control signal S2 to the switching element Q1 so that the difference between the two is eliminated. The output of the DC-DC converter unit 1 is controlled, thereby adjusting the power supplied to the metal halide lamp La. By performing the operation as described above, the control unit 6 can increase the lamp current in synchronization with the timing at which the polarity of the rectangular wave output is inverted, thereby increasing the output power of the inverter unit 2. It is possible to reduce the noise generated from the metal halide lamp La by suppressing the decrease of the electrode temperature.

  Here, the operation of the control unit 6 will be described in detail with reference to the flowchart of FIG. When the power is turned on or when the reset switch SW is operated, the control unit 6 initializes variables of the inversion time and the number of inversions (S1), and executes control at no load before the metal halide lamp La is turned on (S2). Thereafter, the control unit 6 determines whether or not the metal halide lamp La is lit (S3). If the metal halide lamp La is not lit, the control unit 6 returns to S2 and continues the control at no load. On the other hand, when it is determined that the light is turned on in S3, the control unit 6 shifts to the following power control loop.

  In the power control loop, the control unit 6 first reads the lamp voltage Vs of the metal halide lamp La by A / D converting the input from the voltage detection unit 4 (S4), and stores this detection value and a memory (not shown). The lamp voltage is averaged using the past detected values (S5). Note that a moving average method or the like may be used as the averaging processing method. For example, three past detected values are stored, and when the detected values are read next, the above three values are added together. What is necessary is just to obtain | require average value a (Vs) by dividing.

  Next, the current target calculation unit 62 of the control unit 6 reads the power target value Pd at that time from the table stored in the power target storage unit 61 (S6), and calculates the power target value Pd in S5. By dividing by the voltage average value a (Vs), the current target value Id1 (= Pd / a (Vs)) is obtained (S7). The current target increasing unit 65 of the control unit 6 sets a synchronization flag when the inverted synchronization signal SY is input from the inversion control unit 64 in step S17 described later, and whether or not this synchronization flag is set in step S8. Is determined (S8).

  Here, if the synchronization flag is set, the current target increasing unit 65 adds a predetermined current addition value to the target current value Id1 obtained in S7, and a value obtained by the addition is set as the target current value Id2. Processing is performed (S9). Here, the current addition value to be added to the target current value Id1 is determined according to the cumulative lighting time of the metal halide lamp La, and is read from a table stored in the ROM in the microcomputer. For example, the current target increasing unit 65 can obtain a noise reduction effect and a flicker prevention effect by adding a current value about 0.1 to 1 times the rated current value to the target current value Id1. The added amount is set to decrease as the cumulative lighting time elapses. In the case of an automotive mercury-containing HID lamp with a rated current value of 0.4A, 0.04A to 0.4A may be added to the target current value Id1, and the automotive mercury-containing HID with a rated current value of 0.8A. In the case of a lamp, 0.08 A to 0.8 A may be added to the target current value Id1. When the synchronization flag is not set in S8, the current target increasing unit 65 performs the process of setting the target current value Id1 input from the current target calculating unit 62 as it is as the target current value Id2.

  When the target current value Id2 is obtained by performing the above-described processing, the control unit 6 reads the lamp current Ip of the metal halide lamp La by A / D converting the input from the current detection unit 5 (S10), and this detection The average value of the lamp current is obtained by taking, for example, a moving average using the value and a past detection value stored in a memory (not shown) (S11), and a comparison operation between the average value Is and the target current value Id2 is performed. When the error amplifier 66 performs (S12), an output control signal is determined and output to the DC-DC converter unit 1 (S13).

  Next, the inversion determination unit 64 of the control unit 6 determines whether or not the inversion period (inversion frequency is several hundred Hz to several kHzx) has elapsed since the output of the inverter unit 2 was inverted last time ( S14) When the inversion cycle has elapsed, an inversion command is output to the inverter unit 2 to invert the polarity of the output of the inverter unit 2 (S15). Further, the inversion determination unit 64 of the control unit 6 determines whether or not an increase in output power in synchronization with the polarity inversion is necessary (S16). If an increase in inverter output is necessary, a synchronization flag is set (S17). If the inverter output does not need to be increased, the synchronization flag is reset (S18). In the present embodiment, the inversion control unit 64 determines that the polarity is synchronized (that is, the inverter output needs to be increased) from 200 μS before the inversion cycle elapses to 50 μS after the inversion cycle elapses. The period synchronized with the polarity inversion (that is, the period in which the inverter output is increased) is not limited to the above period, and there is no problem as long as the time is about 2% to 30% of the half period of the inversion period. Can be obtained.

  Thereafter, the control unit 6 measures the elapsed time from the polarity inversion of the output of the inverter unit 2 (S19), performs other control operations (S20), returns to the above-described processing of S4, and performs the control operation. It repeats.

  Thus, the control unit 6 can increase the output power of the inverter unit 2 before and after the output of the inverter unit 2 is inverted by executing the power control loop described above, and a period synchronized with the inversion cycle. In addition, it is possible to realize control for increasing the output power of the inverter unit 2 and control for controlling the output of the inverter unit 2 to a predetermined power during other periods. Here, the waveform of each part is shown in the time chart as shown in FIG. FIG. 3 (a) shows switching elements Q2 and Q5 on / off, and FIG. 3 (b) shows switching elements Q3 and Q4 on / off. A current flows when each switching element Q2 to Q5 is on. It is like that. FIG. 3C shows an inversion signal. When the inversion signal is on, all the switching elements Q2 to Q5 are off (the time width of the inversion signal is, for example, several μS). The polarity of the current is reversed. FIG. 3D shows an output current command value increase signal indicating a period during which the current target increasing unit 65 increases the current target value obtained from the inverted synchronization signal SY, and is supplied to the metal halide lamp La during the ON period of this signal. By increasing the lamp current to be supplied, the power supplied to the lamp is increased. Therefore, as shown in FIG. 3E, the lamp current Ip supplied to the metal halide lamp La increases between a period TI1 immediately after the polarity inversion and a period TI2 just before the polarity inversion, High frequency noise generated by the metal halide lamp La can be reduced by increasing the lamp current in synchronization with polarity reversal in the initial use of the lamp. Note that the sum of the period TI1 and the period TI2 for increasing the lamp current is shorter than the half-cycle time of the inversion cycle, and both the periods TI1 and TI2 are each equal to or less than ¼ cycle time of the inversion cycle. For example, the periods TI1 and TI2 are set to several hundreds μs, respectively.

  Here, FIG. 4 shows a waveform diagram of the lamp current by the present lighting device. In the example of FIG. 4A, the increase amount of the lamp current is a rectangular wave-shaped pulse current. Further, the sum of the current increase period TI1 after polarity inversion and the current increase period TI2 before polarity inversion is shorter than the half cycle time of the inversion cycle, and the periods TI1 and TI2 are each a quarter cycle time of the inversion cycle. It is as follows. As described above, there is a moment when the lamp current becomes substantially zero at the time of polarity reversal, so that it becomes difficult to form a bright spot due to a decrease in electrode temperature. However, as shown in FIG. ) Is increased, the discharge can be stabilized after the polarity reversal until the electrode temperature reaches a steady temperature state. In addition, since the lamp current (inverter output) is also increased during the period TI2 before polarity reversal, the electrode temperature is reduced before polarity reversal, so that the decrease in electrode temperature during polarity reversal can be reduced. The discharge state can be stabilized. Therefore, the noise generated from the metal halide lamp La at the time of polarity reversal is reduced, and the effect of reducing flicker, which is flickering of light perceived visually, can be obtained.

  As shown in FIG. 4B, in the current increase period TI2 before polarity inversion, the current target increase unit 65 may increase the lamp current linearly, and the increase in the period TI2 is in the form of a rectangular pulse. Compared with a certain case, the stress applied to the circuit components and the metal halide lamp La is reduced, and the electrode temperature can be increased efficiently.

  In addition, as shown in FIG. 4C, in the current increase period TI1 after polarity inversion, the current target increase unit 65 may increase the lamp current non-linearly, and the increase in the period TI1 is a pulse of a rectangular wave. Compared with a certain case, the stress applied to the circuit components and the metal halide lamp La is reduced, and the electrode temperature can be increased efficiently.

  Furthermore, as shown in FIG. 4D, the current target increase unit 65 linearly increases the lamp current in the current increase period TI2 before polarity reversal, and the current target increase unit in the current increase period TI1 after polarity reversal. 65 may increase the lamp current in a non-linear manner, and the stress applied to the circuit components and the metal halide lamp La is reduced compared to the case where the increment in each period TI1, TI2 is a pulse of a rectangular wave, and the electrode temperature is reduced. It can be raised efficiently. FIG. 5 shows the measured waveform of the lamp current when the lamp current is increased linearly in the period TI2 and the lamp current is increased non-linearly in the period TI1 for the metal halide lamp La having a rated power of 35 W.

  In the example shown in FIGS. 4 and 5, the increase in lamp current in the current increase period TI1 after polarity inversion is substantially equal to the increase in lamp current in the current increase period TI2 before polarity inversion. If the current target riser 65 sets the increase in the period TI2 before the inversion higher than the increase in the period TI1 after the inversion, the decrease in the electrode temperature at the time of polarity inversion becomes smaller. The discharge state can be further stabilized. As a result, noise generated from the metal halide lamp La at the time of polarity reversal is reduced, and it is possible to improve the effect of reducing flicker, which is flickering of light that can be visually perceived. 4 and 5, the sum of the current increase period TI1 after polarity inversion and the current increase period TI2 before polarity inversion is shorter than the half cycle time of the inversion period, and both periods TI1 and TI2 are inverted. The lamp current is controlled to be substantially constant during the time other than both the periods TI1 and TI2 within one cycle of the inversion cycle. Thus, the control unit 6 can suppress the flickering of the light generated by the change in the lamp output by controlling the lamp current substantially constant. In the control unit 6, the time width of the current increase periods TI1 and TI2 and the increase amount of the lamp current in both periods are set to values that cannot be visually recognized by a person.

  FIG. 6 shows the relationship between the cumulative lighting time of the metal halide lamp La and the added value of the lamp current, considering that the noise generated from the metal halide lamp La decreases as the cumulative lighting time increases. In the ascending portion 65, the current addition value is lowered as the cumulative lighting time becomes longer. In addition, the decrease rate of the current addition value is small in the period from the initial lighting to time t1, and the decrease rate of the current addition value is large in the period after time t1. As described above, in the present lighting device, the current addition value (that is, the increase in output power) is decreased as the cumulative lighting time becomes longer, so that the noise reduction effect by the noise reduction unit is increased according to the passage of the cumulative lighting time. The life of the metal halide lamp La can be extended by reducing the stress applied to the metal halide lamp La and the lighting circuit while reducing the noise generated from the metal halide lamp La. In FIG. 6, the current target increasing unit 65 continuously decreases the lamp current addition (that is, the increase in output power) as the cumulative lighting time elapses. If the voltage is to be reduced, the lamp current addition (output power increase) may be changed stepwise.

  Further, in this embodiment, when the reset switch SW is operated, the count value of the cumulative lighting time measuring unit 63 is reset to zero. For example, appropriate attachment / detachment detection means (see FIG. 5) for detecting the attachment / detachment of the metal halide lamp La. (Not shown), and when the attachment / detachment detection means detects the attachment / detachment of the metal halide lamp La, the cumulative lighting time measuring unit 63 may reset the count value to zero.

(Embodiment 2)
A second embodiment of the present invention will be described with reference to FIGS. In addition, since the circuit structure of the discharge lamp lighting device is the same as that of Embodiment 1, the same code | symbol is attached | subjected to a common component and the description is abbreviate | omitted.

  In the first embodiment, the current target increasing unit 65 as the noise reducing unit increases the output power of the inverter unit 2 in synchronization with the polarity reversal, while the noise reduction is achieved. In the present embodiment, the control unit 6 inversion judgment unit 64 (noise reduction unit, time adjustment means) adjusts the polarity inversion time (period in which all switching elements Q2 to Q5 are off) required for inverting the polarity of the output of inverter unit 2. The noise is reduced.

  7A shows the on / off of the switching Q2 and Q5, FIG. 7B shows the on / off of the switching Q3 and Q4, and FIG. 7C shows the output from the inversion judgment unit 64 to the inverter unit 2. Inverted signals are shown respectively. While the inversion signal is output from the inversion determination unit 64, the switching elements Q2 to Q5 are all turned off. When the inversion signal is turned off, the polarity of the output of the inverter unit 2 is inverted. By changing the time width Tr of the inversion signal according to the cumulative lighting time, the polarity inversion time Tr required for polarity inversion is changed.

  Here, the shorter the polarity reversal time Tr, the shorter the time during which the lamp current is zero at the time of polarity reversal, so that the decrease in electrode temperature is reduced and the noise generated from the metal halide lamp La at the time of polarity reversal is reduced. I know it. FIG. 8 shows the relationship between the cumulative lighting time of the metal halide lamp La and the polarity inversion time Tr. In the inversion control unit 64, the polarity at the initial lighting period (period in which the cumulative lighting time is small) is likely to generate noise from the metal halide lamp La. By reducing the inversion time Tr, noise generated from the metal halide lamp La is reduced. However, if the polarity inversion time Tr is shortened, the stress applied to the circuit components of the lighting circuit and the metal halide lamp La increases. Therefore, as the cumulative lighting time increases, the inversion control unit 64 increases the polarity inversion time Tr to increase the circuit. The stress applied to the parts and the metal halide lamp La is reduced. Here, when the cumulative lighting time of the metal halide lamp La is increased, noise generated from the metal halide lamp La tends to be reduced. Therefore, even if the polarity reversal time Tr is increased as the cumulative lighting time elapses, the metal halide lamp La is increased. Thus, the life of the metal halide lamp La can be extended while reducing noise.

  In the example of FIG. 8, the increase rate of the polarity reversal time is small in the period from the initial lighting to time t2, and the increase rate of the current addition value is large in the period after time t2. In the present embodiment, the inversion control unit 64 continuously increases the polarity inversion time as the cumulative lighting time elapses. However, if the polarity inversion time is increased compared to the initial use, the polarity inversion time May be changed stepwise.

(Embodiment 3)
A third embodiment of the present invention will be described with reference to FIGS. In addition, since the circuit structure of the discharge lamp lighting device is the same as that of Embodiment 1, the same code | symbol is attached | subjected to a common component and the description is abbreviate | omitted.

  In the first embodiment, the current target increasing unit 65 as the noise reducing unit increases the output power of the inverter unit 2 in synchronization with the polarity reversal, while the noise reduction is achieved. In the present embodiment, the control unit No. 6 current target increase unit 65 (noise reduction unit, waveform adjustment means) increases the lamp current at the time of polarity reversal and reduces the noise by changing the polarity reversal time.

  FIG. 9 shows a lamp current waveform, and the current target riser 65 provides current rise periods TI2a and TI2b (the lamp current polarity is positive in the period TI2a and the lamp current polarity is negative in the period TI2b) immediately before the polarity inversion. In the period TI2a, the lamp current is increased from Ip1 to Ip2a, and in the period TI2b, the lamp current is increased from Ip2 to Ip2b. Here, as the lamp current increases, the electrode temperature rises and noise generated from the metal halide lamp La during polarity reversal is reduced. However, if the electrode temperature rises too much, evaporation of the electrode is accelerated and the lamp life is shortened. There is a problem of becoming.

  Therefore, in the present embodiment, the current target increasing unit 65 changes the lamp current addition value and the current addition time in each of the periods TI2a and TI2b in accordance with the cumulative lighting time. Increasing the noise reduces noise, and as the accumulated lighting time becomes longer, the lamp current addition value (that is, lamp current values Ip2a and Ip2b) is reduced as shown in FIG. 10, and the current as shown in FIG. By increasing the addition times TI2a and TI2b, the stress applied to the circuit components and the metal halide lamp La is reduced while reducing noise, thereby extending the life. In FIG. 10, A indicates the lamp current value Ip2a, B indicates the lamp current value Ip2b, A in FIG. 11 indicates the current addition period TI2a, and B indicates the current addition period TI2b.

  In this embodiment, the product of the lamp current addition value and the current addition period, that is, the product of the lamp current value and the current addition period (Ip2a × TI2a, Ip2b × TI2b) is set to the same value depending on whether the polarity of the lamp current is positive or negative. Thus, the occurrence of a DC component in the waveform of the lamp current can be prevented, and the phenomenon that the metal halide is biased near one electrode during lighting can be avoided.

  In the present embodiment, the current target raising unit 65 sets the lamp current addition value (that is, the lamp current values Ip2a and Ip2b) and the current addition periods TI2a and TI2b to different values depending on whether the polarity of the lamp current is positive or negative. Yes. In general, the electrode temperature of the metal halide lamp La changes according to the duration Tr of the inversion signal that determines the polarity inversion time and the cumulative lighting time. However, the longer the polarity inversion time, the more noise generated from the metal halide lamp La. It has been found that the noise is suppressed, and at the beginning of lighting (a period in which the cumulative lighting time is small) in which noise from the metal halide lamp La is likely to occur, excessive noise can be suppressed by shortening the polarity inversion time. Can do. However, since the stress applied to the circuit components of the lighting circuit increases when the polarity inversion time is shortened, it is preferable to increase the polarity inversion time as the cumulative lighting time of the metal halide lamp La increases. The added stress can be reduced.

  As described above, in the present embodiment, the current addition value of the lamp current and the polarity inversion time are made different depending on whether the polarity is positive or negative, thereby making the output waveform an asymmetric shape, and by changing the output waveform according to the cumulative lighting time, While reducing noise, lamp life and circuit component life are extended.

(Embodiment 4)
A fourth embodiment of the present invention will be described with reference to FIGS. In addition, since the circuit structure of the discharge lamp lighting device is the same as that of Embodiment 1, the same code | symbol is attached | subjected to a common component and the description is abbreviate | omitted.

  In the first embodiment, the current target increasing unit 65 as the noise reducing unit increases the output power of the inverter unit 2 in synchronization with the polarity reversal, while the noise reduction is achieved. In the present embodiment, the control unit No. 6 current target increase unit 65 (noise reduction unit, current adjustment means) reduces the noise by changing the current level Ip1 of the lamp current.

  There is a correlation between the lamp current and the electrode temperature. The larger the lamp current, the higher the electrode temperature, and it becomes easier to form a bright spot during polarity reversal. Therefore, at the beginning of lighting when the noise generated from the metal halide lamp La is large, the current target ascending unit 65 increases the lamp current to reduce the noise. In general, the lamp voltage often increases as the cumulative lighting time increases, and when the lamp power is controlled to be constant, the lamp current decreases as the cumulative lighting time increases. Then, as shown in FIG. 13, the lamp current is lowered more than keeping the lamp power at a constant value, and the lamp power is also reduced as the cumulative lighting time increases as in FIG. Here, if the lamp current becomes excessive, the electrode temperature becomes too high, which may lead to evaporation and deformation of the electrode, but in this embodiment, the lamp current is decreased as the cumulative lighting time increases, Noise can be reduced without significantly affecting the lamp life.

  In the example of FIG. 13, the reduction rate of the lamp current Ip1 is small in the period from the initial lighting to time t3, and the reduction rate of the lamp current Ip1 is large in the period after time t3. In the present embodiment, the current target increasing unit 65 continuously decreases the lamp current as the cumulative lighting time elapses. However, if the lamp current is decreased compared to the initial use, the polarity inversion time is set. It may be changed in steps.

(Embodiment 5)
A fifth embodiment of the present invention will be described with reference to FIG. In addition, since the circuit structure of the discharge lamp lighting device is substantially the same as that of the first embodiment, common constituent elements are denoted by the same reference numerals and description thereof is omitted.

  In the first embodiment described above, the cumulative lighting time measuring unit 63 measures the operating time of the inverter unit 2 to obtain the cumulative lighting time, whereas in the present embodiment, the electrical characteristic value of the metal halide lamp La is calculated. The detecting means 67 for detecting is provided, and the cumulative lighting time measuring unit 63 detects the cumulative lighting time from the detection value of the detecting means 67. The electrical characteristic value detected by the detection means 67 may be any electrical characteristic value as long as it has a correlation with the cumulative lighting time of the metal halide lamp La. For example, the lamp voltage value or the re-ignition voltage. As an example, the peak value of.

  The detecting means 67 may detect a characteristic value that has a direct correlation with the noise generated by the metal halide lamp La. For example, as shown in FIGS. 15 (a) and 15 (b), immediately after the zero crossing when the polarity of the lamp voltage is reversed. The peak value Vpd of the lamp voltage generated at 1 and the length Td of the low current period of the lamp current generated immediately after the zero cross at the time of polarity reversal as shown in FIGS. 16A and 16B may be detected. . There is a correlation between these characteristic values and the noise level. The larger these characteristic values are, the higher the noise level is. Therefore, when these characteristic values are larger than a predetermined threshold, the noise reduction unit performs noise reduction. The reduction effect is increased.

  In this embodiment, since the accumulated lighting time is detected from the electrical characteristic value of the metal halide lamp La, means for measuring the lighting time of the metal halide lamp La, means for resetting the measurement result of the lighting time, Since there is no need to detect and reset the measurement result of the lighting time, the lighting circuit can be reduced in cost and size, and the operation for resetting the cumulative lighting time is also unnecessary, thereby improving convenience. .

  Further, when the characteristic value directly correlated with the noise generated by the metal halide lamp La is detected by the detection means 67, it is possible to appropriately suppress the noise level regardless of variations among lamps.

  In addition, it cannot be overemphasized that the structure of this embodiment may be applied to Embodiment 2-4, and there can exist an effect similar to the above-mentioned.

(Embodiment 6)
Embodiment 6 of the present invention will be described with reference to FIG. FIG. 17 is a circuit diagram of the discharge lamp lighting device according to the present embodiment. The AC-DC converter unit 7 converts the commercial power source AC into a DC power source having a predetermined voltage value, the DC-DC converter unit 1, and the inverter unit 2. And an igniter unit 3, a voltage detection unit 4, a current detection unit 5, and a control unit 6 as main components. The present embodiment is different from the first embodiment in that the DC voltage obtained by converting the commercial power supply AC by the AC-DC converter unit 7 is used as the input voltage of the DC-DC converter unit 1, and other configurations are the same as those of the first embodiment. 1 are the same as those shown in FIG.

  The AC-DC converter unit 7 includes a rectifier circuit DB that performs full-wave rectification of an AC power source that is input via the noise filter NF, and a boost chopper circuit that boosts the rectified output of the rectifier circuit DB to a desired voltage value. The The step-up chopper circuit has a conventionally known circuit configuration, and a series circuit of an inductor L1 and a switching element Q6 connected between the DC output terminals of the rectifier circuit DB, and a diode D2 connected between both ends of the switching element Q6. And a series circuit of a capacitor C3. The on / off state of the switching element Q6 is controlled by the control unit 6.

  Further, the DC-DC converter unit 1 is changed from the flyback method described in the first embodiment to the step-down chopper method so that a lamp voltage suitable for lighting the metal halide lamp La can be obtained. It has become. The DC-DC converter unit 1 includes a series circuit of a switching element Q7 and a diode D3 connected between both ends of the capacitor C3, and a series circuit of an inductor L2 and a capacitor C4 connected between both ends of the diode D3. ing. Here, in the present embodiment, the AC-DC converter unit 7 and the DC-DC converter unit 1 constitute a power conversion unit.

  Thus, according to the present embodiment, the noise generated by the metal halide lamp La when the metal halide lamp La is turned on in a rectangular wave and the output is increased in synchronization with the polarity inversion, as in the above-described embodiments. Can be reduced.

  Moreover, although the circuit structure which used the DC-DC converter part 1 and the inverter part 2 which were mentioned above is also known, this circuit structure is used instead of the DC-DC converter part 1 and the inverter part 2 of this embodiment. In the same manner as described above, high frequency noise generated in the metal halide lamp La can be reduced. In the present embodiment, the cumulative lighting time is detected from the operation time of the inverter unit 2 as in the first embodiment. However, as described in the fifth embodiment, the cumulative lighting time is detected from the electrical characteristic value of the metal halide lamp La. You may comprise.

(Embodiment 7)
FIG. 18 shows a headlamp 8 for lighting a metal halide lamp La using the headlamp lighting device 10 composed of the discharge lamp lighting device described in any of the first to sixth embodiments described above, and a vehicle using the same. 9 is a diagram schematically showing 9, and when power is supplied from the low beam switch power supply 11 to the headlamp lighting devices 10 and 10 for the headlamps arranged on the left and right sides, each headlamp lighting device The lighting power is supplied from 10 to the corresponding headlamp 8, and the metal halide lamp La is turned on.

  Here, in the case of an in-vehicle discharge lamp lighting device, there are very strict regulations on safety and noise, but by using any of the discharge lamp lighting devices described in Embodiments 1 to 6, Since high-frequency noise generated in the lamp can be reduced, the headlamp 8 and the vehicle 9 with improved safety can be provided.

1 is a circuit diagram of a discharge lamp lighting device according to Embodiment 1. FIG. It is a flowchart explaining operation | movement same as the above. (A)-(e) is a time chart explaining operation | movement same as the above. (A)-(d) is a wave form diagram which shows a lamp current same as the above. It is an actual measurement waveform figure of a lamp current same as the above. It is a figure which shows the relationship between cumulative lighting time same as the above, and a lamp current addition value. (A)-(c) is a time chart explaining operation | movement of the discharge lamp lighting device of Embodiment 2. FIG. It is a figure which shows the relationship between cumulative lighting time same as the above, and polarity inversion time. It is a wave form diagram which shows the lamp current of the discharge lamp lighting device of Embodiment 3. It is a figure which shows the relationship between cumulative lighting time same as the above and an output electric current value. It is a figure which shows the relationship between the same cumulative lighting time and an output current addition period. It is a wave form diagram which shows the lamp current of the discharge lamp lighting device of Embodiment 4. It is a figure which shows the relationship between cumulative lighting time same as the above and an output electric current value. It is a circuit diagram of the discharge lamp lighting device of Embodiment 5. (A) is a waveform diagram of the lamp voltage, and (b) is a waveform diagram of the lamp voltage displayed by enlarging the time axis at the time of zero crossing. (A) is a waveform diagram of the lamp current, and (b) is a waveform diagram of the lamp current displayed by enlarging the time axis at the time of zero crossing. It is a circuit diagram of the discharge lamp lighting device of Embodiment 6. It is explanatory drawing which showed the vehicle of Embodiment 7 typically. (A)-(d) is a wave form diagram which shows the lamp current of the conventional discharge lamp lighting device. It is a figure which shows the relationship between cumulative lighting time same as the above, and a noise peak value.

Explanation of symbols

1 DC-DC converter (power converter)
2 Inverter unit 6 Control unit 63 Cumulative lighting time measurement unit 65 Current target increase unit (noise reduction unit, output adjustment means)
La metal halide lamp

Claims (8)

  A power converter that converts the input power source to a DC voltage having a voltage value required for lighting the metal halide lamp, an inverter that converts the output of the power converter into an alternating voltage of a rectangular wave, and supplies the alternating voltage to the metal halide lamp; A noise reduction unit that reduces noise generated from the metal halide lamp when the polarity of the output of the inverter unit is inverted by adjusting the output, and a control unit that reduces the noise reduction effect by the noise reduction unit when the cumulative lighting period becomes longer. A discharge lamp lighting device characterized by being provided.   The noise reduction unit includes a time adjustment unit that adjusts a polarity inversion time required to invert the polarity of the output of the inverter unit, and the control unit adjusts the time adjustment unit according to the elapse of a cumulative lighting time. The discharge lamp lighting device according to claim 1, wherein the polarity inversion time is increased by.   The noise reduction unit has output adjustment means for increasing the output power of the inverter unit in synchronization with the polarity inversion of the output of the inverter unit, and the control unit is an output adjustment unit according to the elapse of the cumulative lighting time. The discharge lamp lighting device according to claim 1, wherein an increase in output power due to the light is reduced.   2. The discharge lamp lighting device according to claim 1, wherein the noise reduction unit includes a waveform adjusting unit that changes an output waveform of the inverter unit in an asymmetric shape, and changes the output waveform according to a cumulative lighting time. .   The noise reduction unit includes a current adjustment unit that changes an output current of the inverter unit, and the control unit reduces the output current by the current adjustment unit as the cumulative lighting time elapses. The discharge lamp lighting device according to claim 1.   The discharge lamp lighting device according to any one of claims 1 to 5, wherein the control unit detects a cumulative lighting time from an electrical characteristic value of the metal halide.   A headlamp comprising the discharge lamp lighting device according to any one of claims 1 to 6.   A vehicle comprising either the discharge lamp lighting device according to any one of claims 1 to 6 or the headlamp according to claim 7.

Images