JP4656117B2 - Discharge lamp equipment - Google Patents

Description

  The present invention relates to a discharge lamp device for lighting a high-pressure discharge lamp, and more particularly to a discharge lamp device suitable for use in a vehicle headlamp.

  Conventionally, after applying a high-pressure discharge lamp (hereinafter referred to as a lamp or bulb) to a vehicle headlamp and increasing the in-vehicle battery voltage with a transformer, the polarity of this high voltage is switched with an inverter circuit, Various types of AC lighting have been proposed (see JP-A-9-180888 and JP-A-8-321389). Here, a switching element for controlling the primary current is provided on the primary side of the transformer, and the switching element is controlled by PWM (pulse width modulation) based on the lamp voltage and the lamp current. The power supply is controlled.

  That is, desired power is supplied to the lamp according to a predetermined control line that defines the relationship between the lamp voltage and the lamp current.

  By the way, the lamp currently applied to the vehicle headlamp has a rating of 35 W, a lamp voltage of 85 V, and a lamp current of 0.41 A. A very small amount of mercury is enclosed in this lamp, and a mercury-free (mercury-free) lamp is desired because of environmental pollution during disposal. In a mercury-free lamp, the stable lamp voltage is about half that of the conventional one. In addition, the lamp voltage in the initial stage of lighting is about 27 V, which is approximately the same voltage as the conventional voltage. In addition, there is a feature that the luminous flux suddenly rises with a slight increase in lamp voltage at the beginning of lighting. For this reason, there is a problem that the lamp power cannot be controlled to a desired level by the conventional lamp power control using the lamp voltage and the lamp current.

  In order to apply a lamp to a vehicle headlamp, it is necessary to quickly start up (brighten quickly) the light beam after turning on the lighting switch. For this reason, a light beam larger than the rated power is applied to the lamp at the beginning of lighting. The rise of the is early. Specifically, in the current 35 W lamp (D2SorD2R bulb), about 70 W is applied to the lamp at the beginning of lighting, and then the power is gradually reduced and controlled to 35 W in a stable state. This control is performed in accordance with a predetermined control line that defines the relationship between the lamp voltage and the lamp current shown in FIG. 11. As is clear from FIG. 11, the lamp voltage at the beginning of lighting is about 27V, and the stable voltage is about 85V. Yes, the lamp power is reduced from 70 W to 35 W in response to the lamp voltage changing from 27 V to 58 V to 58 V.

  Even in a mercury-free lamp, as in the conventional control, after the lighting switch is turned on, it is necessary to start up the light beam quickly (brighten quickly). Therefore, it is necessary to apply a power larger than the rated power to the lamp at the beginning of lighting so that the rise of the luminous flux is accelerated. Specifically, in a mercury-less 35 W lamp, about 90 W is applied to the lamp at the beginning of lighting, After that, it is necessary to gradually reduce the power and control it to 35 W in a stable state. The initial lamp voltage of the mercury-less lamp is about 27 V, which is almost the same as that of the conventional lamp, but the lamp voltage at the time of stability is about 42 V, which is about half of the conventional lamp. If a lamp having such a lamp voltage characteristic is controlled by the control based on the conventional control line shown in FIG. 7, the lamp power is reduced from 90 W to 35 W by 55 W in response to the lamp voltage changing from 27 V to 42 V by 15 V. It will be sufficient to control to. That is, the conventional lamp has a power reduction of 35 W with respect to the voltage change value of 58 V, and the ratio is small. However, the mercury-less lamp has a power reduction of 55 W with respect to the voltage change value of 15 V, and the ratio becomes large. Yes.

  The lamp voltage at the initial stage of lighting is about 27V for both the current lamp and the mercury-less lamp, but ± several V varies. In the current control method, this variation is a variation in lamp power. In particular, in the case of a mercury-free lamp, since the lamp voltage change from the initial lighting to the stable state is as small as about 15V and the ratio is large, the lamp voltage variation at the initial lighting greatly affects the change state of the lamp power, and the stable state is reached. As the lamp voltage varies, the rise characteristic of the luminous flux at the time of lighting varies greatly, and the standard value that defines the rise characteristic of the luminous flux for automobiles cannot be satisfied.

  The present invention has been made as a result of intensive studies on the problems of the mercury-less lamp as described above. The background of the present invention will be described below with reference to FIG.

  FIG. 12A shows a change in the luminous flux corresponding to the elapsed time from the start of lighting.

  FIG. 12B shows a change in the lamp voltage corresponding to the elapsed time from the start of lighting. The variation of the lamp is represented by three valves (lamps) of a valve a, a valve b, and a valve c. ing. Note that the time axes of FIG. 12A and FIG.

  When a constant power of about 90 W is applied to the lamp in order to quickly raise the luminous flux after the start of lighting, as shown in FIG. 12 (A), the luminous flux that was about 50% immediately after lighting is gradually increased over time. When the constant power continues to be applied thereafter, overshoot occurs as shown by the broken line in the figure. In addition, the lamp voltage at the beginning of lighting of each bulb a, b, c increases while having different voltage values as shown in FIG. In the change in the lamp voltage of the bulb at the initial stage of lighting, the inventors have changed the lamp voltage when the luminous flux reaches about 80% to 100% (timing E shown in FIG. 12B). It has been found that ΔVL (first change value ΔVL1) becomes a substantially constant value in the bulbs a, b, and c having different lamp voltages at the beginning of lighting, that is, ΔVLa1≈ΔVLb1≈ΔVLc1. Regardless of which bulb is used, the control of reducing the lamp applied power is started when the lamp voltage change value ΔVL increases to the first change value ΔVL1, thereby preventing overshoot of the luminous flux. I found that I can do it.

  Furthermore, the present inventors have found that ΔVL is the first change value ΔVL1 (ΔVLa1, ΔVLb1) for power control after the lamp voltage change value ΔVL increases to the first change value ΔVL1 (ΔVLa1, ΔVLb1, ΔVLc1). , ΔVLc 1) to reach the second change value ΔVL 2 (ΔVLa 2, ΔVLb 2, ΔVLc 2), the lamp applied power is controlled according to the change in ΔVL, so that variations in lamp voltage due to individual lamp differences can be absorbed. It was found that even if the voltage varies, overshoot and undershoot of the light beam can be suppressed, and the light beam can be smoothly converged to 100%. In FIG. 12, A represents a period during which 90 W is applied to the lamp, and B, C, and D represent periods during which lamp power is controlled according to ΔVL in each of the bulbs a, b, and c.

  According to the first aspect of the present invention, there is provided a mercury-less lamp lighting control device for detecting a current lamp voltage or an equivalent signal voltage for detecting a current lamp voltage or an equivalent signal voltage, and detecting and storing a lamp voltage or an equivalent signal voltage at the beginning of lamp lighting. Storage means, and ΔVL detection means for obtaining a lamp voltage change value (ΔVL) which is a change value from the lamp voltage or equivalent signal voltage stored in the storage means to the current lamp voltage or equivalent signal voltage, The lamp applied power is gradually reduced according to the elapsed time from when the ΔVL obtained by the ΔVL detection means reaches a predetermined value or more, and the process proceeds to stable lamp applied power control. This is based on the fact that ΔVL has a predetermined value (first change value ΔVL1) that is substantially constant even when the bulbs have different lamp voltages at the beginning of lighting. Therefore, by performing such control, it is possible to prevent light beam overshoot.

  According to a second aspect of the present invention, the lamp voltage or equivalent signal voltage at the initial stage of lamp operation, which becomes the reference value of the lamp voltage change value ΔVL, is the same value as ΔVL with respect to the current lamp voltage or equivalent signal voltage as the value is lower. The use of a large value of ΔVL makes it easy to control the lamp power, and the time when the phenomenon in which the lamp voltage becomes the minimum voltage appears, that is, the phenomenon in which the luminous flux becomes the minimum. The lamp voltage or the equivalent signal voltage in the time zone where it appears is stored as a reference value.

  The third aspect is based on the fact that the time zone in which the luminous flux is lowest is within 6 seconds from the start of normal lighting.

  According to the fourth aspect of the present invention, the lamp voltage control can be easily performed as described above by storing the minimum voltage value in the time period as the lamp voltage or the equivalent signal voltage.

  According to the fifth aspect of the present invention, the mercury-less lamp lighting control device detects the current lamp voltage or the equivalent signal voltage, detects the current lamp voltage or the equivalent signal voltage, and detects and stores the lamp voltage or the equivalent signal voltage at the beginning of the lamp lighting. Storage means, a ΔVL detection means for obtaining a lamp voltage change value (ΔVL) which is a change value from the lamp voltage or equivalent signal voltage stored in the storage means to the current lamp voltage or equivalent signal voltage, and after lighting The lamp application power is controlled in accordance with the elapsed time, and the lamp application power is gradually reduced in accordance with the elapsed time from the time when ΔVL obtained by the ΔVL detection means reaches a predetermined value or more. Transition to control.

  When the lamp electrode is turned on again after the lamp is extinguished (hereinafter referred to as “hot start”), the lamp voltage immediately after lighting is higher than the lamp voltage immediately after lighting when the lamp is cold. Accordingly, ΔVL becomes a low value, and the time until ΔVL reaches a predetermined value becomes long, so that power reduction is delayed, and as a result, overshoot of the luminous flux occurs.

  According to the sixth aspect of the present invention, the power applied to the lamp is reduced regardless of ΔVL after a predetermined time set according to the turn-off time before the lamp is turned on. It becomes possible to perform accurate power control.

  According to a seventh aspect of the present invention, the elapsed time from when the ΔVL obtained by the ΔVL detection means reaches a predetermined value or more, or when the lamp voltage VL reaches the predetermined value or more, whichever comes first. In response to this, the lamp applied power is gradually reduced, and the lamp applied power control is shifted to a stable state. For this reason, for example, when lighting starts with the lamp being completely cooled (hereinafter referred to as a cold start), power is reduced when ΔVL first reaches a predetermined value. On the other hand, during a hot start, the lamp voltage is reduced. First reaches a predetermined value and the timer circuit reduces the power. This is because ΔVL is high because the lamp voltage at the beginning of lighting at cold start is lower than the lamp voltage at the beginning of lighting at hot start, whereas the lamp voltage immediately after lighting at the hot start is cold start. This is because the lamp voltage is higher than the lamp voltage immediately after lighting at time, and the lamp voltage further increases with time. The lamp applied power is gradually reduced according to the elapsed time from when the ΔVL reaches the predetermined value or when the lamp voltage reaches the predetermined value, whichever comes first. Since the transition to the lamp power control is performed, variations in the lamp voltage due to individual lamp differences can be absorbed, the overshoot and undershoot of the light beam can be suppressed, and the light beam can be smoothly converged to 100%.

  According to the discharge lamp device of the present invention, variations in lamp voltage due to individual differences among lamps, particularly mercury-free lamps, can be absorbed, overshooting and undershooting of the light flux can be suppressed, and the light flux can be smoothly converged to 100%.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an overall configuration when a discharge lamp device according to an embodiment is applied to a vehicle headlamp.

  In FIG. 1, reference numeral 1 denotes an in-vehicle battery as a DC power source, 2 denotes a lamp (high pressure discharge lamp) which is a vehicle headlamp, and 3 denotes a lighting switch of the lamp 2.

  The discharge lamp device has circuit function units such as a DC power supply circuit (DC-DC converter) 4, a takeover circuit 5, an inverter circuit 6, and a starting circuit 7.

  The DC-DC converter 4 includes a flyback transformer 41 having a primary winding 41a disposed on the battery 1 side and a secondary winding 41b disposed on the lamp 2 side, and a MOS connected to the primary winding 41a. The transistor 42, the rectifying diode 43 connected to the secondary winding 41b, and the smoothing capacitor 44 are configured to output a boosted voltage obtained by boosting the battery voltage VB. That is, when the MOS transistor 42 is turned on, a current flows through the primary winding 41a and energy is stored in the primary winding 41a. When the MOS transistor 42 is turned off, the energy of the primary winding 41a is changed to the secondary winding 41b. To be supplied. By repeating such an operation, a high voltage is output from the connection point between the diode 43 and the capacitor 44.

  The takeover circuit 5 is composed of a capacitor 51 and a resistor 52, and the capacitor 51 is charged after the lighting switch 3 is turned on, so that the lamp 2 is promptly shifted to the arc discharge from the dielectric breakdown between the electrodes.

  The inverter circuit 6 turns on the lamp 2 with alternating current, and includes an H bridge circuit 61 and bridge drive circuits 62 and 63. The H bridge circuit 61 includes MOS transistors 61a to 61d that form semiconductor switching elements arranged in an H bridge shape. The bridge drive circuits 62 and 63 alternately turn on and off the MOS transistors 61a and 61d and the MOS transistors 61b and 61c in accordance with a signal from the H bridge control circuit 400 described later. As a result, the direction of the discharge current of the lamp 2 is alternately switched, the polarity of the applied voltage (discharge voltage) of the lamp 2 is reversed, and the lamp 2 is turned on by alternating current. The starting circuit 7 is installed between the midpoint potential point of the H-bridge circuit 61 and the negative terminal of the battery 1, and includes a transformer 71 having a primary winding 71a and a secondary winding 71b, diodes 72 and 73, and a resistor 74. , A capacitor 75 and a thyristor 76, and starts lighting the lamp 2. That is, when the lighting switch 3 is turned on, the capacitor 75 starts charging, and thereafter, when the thyristor 76 is turned on, the capacitor 75 starts discharging, and a high voltage is applied to the lamp 2 through the transformer 71. As a result, the lamp 2 is turned on with dielectric breakdown between the electrodes.

  The MOS transistor 42, the bridge drive circuits 62 and 63, and the thyristor 76 described above are controlled by the control circuit 10. The control circuit 10 receives a lamp voltage between the DC-DC converter 4 and the inverter circuit 6 (that is, a voltage applied to the inverter circuit 6), a lamp current IL that flows from the inverter circuit 6 to the negative electrode side, and the like. Has been. The lamp current IL is detected as a voltage by the current detection resistor 8.

  FIG. 2 shows a block configuration of the control circuit 10. The control circuit 10 includes a PWM control circuit 100 that turns on and off the MOS transistor 42 using a PWM signal, a lamp voltage detection circuit 200 that converts a lamp voltage into a signal lamp voltage VL, a lamp voltage VL and a lamp current IL, and lamp power. A lamp power control circuit 300 that controls the lamp to a desired value, an H bridge control circuit 400 that controls the H bridge circuit 61, and a high voltage generation control circuit 500 that turns on the thyristor 76 to generate a high voltage in the lamp 2. Has been.

  Next, the lighting operation of the discharge lamp device having the above configuration will be described.

  When the lighting switch 3 is turned on, power is supplied to each part shown in FIG. The PWM control circuit 100 performs PWM control on the MOS transistor 42. As a result, a voltage obtained by boosting the battery voltage VB is output from the DC-DC converter 4 by the operation of the flyback transformer 41. The H bridge control circuit 400 alternately turns on and off the MOS transistors 61a to 61d in the H bridge circuit 61 in a diagonal relationship. As a result, the high voltage output from the DC-DC converter 4 is supplied to the capacitor 75 of the starting circuit 7 via the H bridge circuit 61, and the capacitor 75 is charged.

  Thereafter, the high voltage generation control circuit 500 outputs a gate drive signal to the thyristor 76 based on a signal notifying the switching timing of the MOS transistors 61a to 61d output from the H bridge control circuit 400, and turns on the thyristor 76. . When the thyristor 76 is turned on, the capacitor 75 is discharged, and a high voltage is applied to the lamp 2 through the transformer 71. As a result, the lamp 2 breaks down between the electrodes and starts lighting.

  Thereafter, the polarity of the discharge voltage to the lamp 2 (the direction of the discharge current) is alternately switched by the H bridge circuit 61 so that the lamp 2 is turned on by alternating current. Further, the lamp power control circuit 300 controls the lamp power so that it becomes a desired value, and the lamp 2 is kept on. The ramp voltage detection circuit 200 receives the voltage applied to the inverter circuit 6 as a ramp voltage, and converts it into a ramp voltage VL that becomes a signal voltage.

  Next, the lamp power control circuit 300 will be described with reference to FIG.

  In the lamp power control circuit 300, the output of the error amplification circuit 301 that generates an output corresponding to the lamp voltage VL, the lamp current IL, or the like, which is a signal indicating the lighting state of the lamp 2, is input to the PWM control circuit 100. ing. The PWM control circuit 100 increases the lamp power by increasing the duty ratio for turning on and off the MOS transistor 42 as the output voltage of the error amplifier circuit 301 increases.

  The lighting initial voltage storage circuit (lighting initial voltage storage means) 320 stores the lamp voltage VL immediately after the start of lamp lighting, and outputs the stored lamp voltage VLs.

  The ΔVL detection circuit (ΔVL detection means) 350 subtracts the lamp voltage VLs stored in the lighting initial voltage storage circuit 320 from the lamp voltage VL, and changes the lamp voltage from the lighting initial voltage (VLs) (lamp voltage change). Value) ΔVL is obtained, and the lamp voltage change value ΔVL is output.

  A reference voltage Vr1 is input to the non-inverting input terminal of the error amplifier circuit 301, and a voltage V1 that is a parameter for controlling lamp power is input to the inverting input terminal. A voltage corresponding to the difference between the voltage Vr1 and the voltage V1 is output. The voltage V1 includes a lamp current IL, a constant current i1, a current i2 set by the first current setting circuit 302, a current i3 set by the second current setting circuit 303, and a third current setting circuit. It is determined based on the current i4 set in 304 and the current i5 set in the fourth current setting circuit 305. The sum of current i1, current i2, current i3, current i4, and current i5 is set sufficiently smaller than lamp current IL.

  Here, as shown in FIG. 3, the first current setting circuit 302 sets the current i2 larger as the lamp voltage VL becomes higher, and the second current setting circuit 303 sets the lamp voltage VL as shown in FIG. The current i3 is set to zero below the first predetermined value, i3 is set to a constant value when VL is equal to or higher than the second predetermined value, and i3 is set to increase as VL increases when VL is higher than the first predetermined value and lower than the second predetermined value. The third current setting circuit 304 sets the current i4 to a constant value when the change value of the lamp voltage VL with respect to the lamp voltage value at the beginning of lighting, that is, the lamp voltage change value ΔVL is equal to or smaller than the first predetermined value, and less than the second predetermined value. If i4 is a fixed value, greater than or equal to the first predetermined value and less than or equal to the second predetermined value, i4 is set to be larger as ΔVL increases. As shown in FIG. 3, the fourth current setting circuit 304 sets the current i5 to be larger as the elapsed time T after lighting becomes longer, and sets i5 to a constant value after several tens of seconds have elapsed from the start of lighting.

  The lamp power control circuit 300 outputs the voltage according to the elapsed time T after lighting, the lamp voltage VL, the lamp current IL, the lamp voltage change value ΔVL, and the like to control the lamp power. The power is set to a large value (for example, 90 W), the luminous flux from the lamp is quickly raised (lightened quickly), the lamp power is gradually decreased as the luminous flux rises, and when the lamp 2 becomes stable, the lamp power is set to a predetermined value. (For example, 35 W).

  Next, the lighting initial voltage storage circuit 320 and the ΔVL detection circuit 350 will be described with reference to FIG.

  The lighting initial voltage storage circuit 320 includes a sample hold circuit including an operational amplifier 321, a switch 322, and a capacitor 323, a switch control circuit 325 that controls opening and closing of the switch 322, and impedance conversion of the output voltage of the sample hold circuit. And an operational amplifier 324 constituting a voltage follower circuit.

  The lamp voltage VL is input to the non-inverting input terminal of the operational amplifier 321, and the capacitor 323 is controlled to have the same voltage as the lamp voltage VL when the switch 322 is on. When the switch 322 is turned off, the charging voltage of the capacitor 323 is held (stored) at the voltage charged in the capacitor 323 at the time of turning off, and then the voltage is maintained until the switch 322 is turned on.

  The switch control circuit 325 detects the start of lighting, maintains the switch 322 until a predetermined time elapses from the lighting start time, and generates a switch control signal for controlling the switch to the off state after the predetermined time elapses.

  Next, the current setting circuit 305, which is a timer circuit, will be described with reference to FIGS. 5 and 7 showing the specific configuration and FIGS. 6 and 8 showing the operation.

(1) About First Embodiment (FIGS. 5 and 6) In FIG. 5, the comparator 503 compares the ramp voltage change value ΔVL of the terminal 501 with the reference voltage VR1 of the reference voltage source 504, and ΔVL is greater than or equal to VR1. When it becomes high level output. The terminal 502 receives a signal TS that is inverted from a low level to a high level after a predetermined time from the start of lighting. The predetermined time is set according to the turn-off time before turning on, and is set to a long time when the turn-off time is long, that is, a cold start, and to a short time when it is short, that is, a hot start.

  The NOR gate 505 takes the logic of the output of the comparator 503 and the signal TS and drives the transistor 506. A constant voltage is applied to the terminal 517. The voltage Va is input to the non-inverting input of the operational amplifier 509. Va becomes a divided voltage obtained by dividing the constant voltage by the resistors 507 and 508 when the transistor 506 is cut off. On the other hand, when the transistor 506 is turned on, the voltage drop between the collector and the emitter of the transistor 506 is small, so Become. The operational amplifier 509 and the diode 510 constitute a unidirectional buffer circuit, and the output voltage is controlled to be the same voltage value as Va only when the voltage on the cathode side of the diode 510 is lower than Va.

  When the transistor 506 is in the cut-off state, Va becomes a divided voltage as described above, and this divided voltage Va is composed of a resistor 512, a capacitor 513, and a resistor 514 via an operational amplifier 509 and a diode 510. The capacitor 513 is charged via the resistor 512. The charging voltage Vc of the capacitor 513 becomes the same voltage value as Va when a predetermined time determined by the time constant CR using the capacitance C of the capacitor 513 and the resistance value R of the resistor 512 as parameters from the start of charging.

  On the other hand, when the transistor 506 is in a conductive state, Va is substantially 0 V as described above, and the charge charged in the capacitor 513 is discharged through the resistors 512 and 514.

  In this manner, the capacitor 513 is charged and discharged according to the conduction and cutoff of the transistor 506, and the capacitor 513 is charged through the diode 510 and the resistor 512, while the capacitor 513 is discharged through the resistors 512 and 514. Is done through.

  The charging voltage Vc is input to the VI conversion circuit 515, and the VI conversion circuit 515 converts Vc into a current i5 having a current value proportional to the voltage value, and i5 is output from the terminal 516. Note that a terminal 518 is a power supply terminal of the timer circuit 305.

  FIG. 6 shows waveforms at various parts during a cold start and a hot start.

  At the cold start, when the power is supplied to the discharge lamp device at timing t0, the discharge lamp device starts to operate, lighting is started at timing t10, and the lamp voltage VL is greatly reduced instantaneously. After the start of lighting, the lamp voltage change value ΔVL gradually increases as time passes. When ΔVL reaches the reference voltage VR1 at timing t1, the output of the comparator 503 is inverted to a high level, and the transistor 506 is turned off. Switching to the cut-off state, the divided voltage Va is applied to the time constant circuit, and the capacitor 513 starts charging. After the start of charging, the charging voltage Vc gradually increases based on the time constant CR. Note that after the start of charging, the signal TS is inverted to the high level at the timing t2 when the time TD1 has elapsed from the timing t0, but the transistor 506 is still kept in the cut-off state and the capacitor 513 is continuously charged. Vc becomes the same voltage value as Va when a predetermined time determined by the time constant CR has elapsed from the start of charging, and thereafter maintains this voltage value.

  Thus, the charging voltage Vc gradually increases based on the time constant CR from the timing t1 when the lamp voltage change value ΔVL increases to the reference voltage VR1, that is, a predetermined value, and a predetermined time determined by the time constant CR has elapsed. From time to time, it becomes the same voltage value as Va and becomes a constant value. Then, a current i5 proportional to this Vc is output from the terminal 516, and the lamp applied power gradually decreases with time.

  Thereafter, when the power is turned off at timing t3, the discharge lamp device is turned off. When the power is turned off, the capacitor 513 starts discharging through the resistors 512 and 514. The capacitor 513 is discharged based on a time constant CR ′ determined by the capacitance C of the capacitor 513 and the series resistance value R ′ of the resistors 512 and 514.

  When the power is turned on at timing t4 before the discharge of the capacitor 513 is completed, the discharge lamp device starts to be lit as in the cold start.

  At the time of this hot start, the lamp voltage VL immediately after lighting is higher than that at the time of cold start, and VL gradually increases with the passage of time from that state to reach a stable voltage. That is, the increase in VL is moderate as compared to the cold start, and the increase in lamp voltage change value ΔVL is also moderate. Therefore, the time from the start of lighting until the timing t6 when ΔVL reaches the predetermined value VR1 is longer than that at the cold start. On the other hand, the time until the signal TS is inverted to the high level is set according to the Toff time, is set to the long time TD1 at the cold start, and is set to the short time TD2 at the hot start. At time t5 before reaching the predetermined value VR1, the signal TS is inverted to high level. Therefore, the output of the NOR gate 505 is inverted to the low level at the timing t5, the transistor 506 is switched from the conductive state to the cut-off state, the divided voltage Va is applied to the time constant circuit, and the capacitor 513 is charged from the discharge operation. Switch to operation. After the start of charging, the charging voltage Vc gradually increases based on the time constant CR. Vc becomes the same voltage value as Va when a predetermined time determined by the time constant CR has elapsed from the start of charging, and thereafter maintains this voltage value.

  As described above, the charging voltage Vc gradually increases based on the time constant CR from the voltage value at the timing t5 when the signal TS is inverted to the high level, and reaches a value Va when a predetermined time determined by the time constant CR elapses. It becomes the same voltage value and becomes a constant value. Then, a current i5 proportional to this Vc is output from the terminal 516, and the lamp applied power gradually decreases with time.

  Furthermore, after the power is turned off at timing t7 and turned off, the power is turned on again at timing t8, and when the power is turned on again, the Toff time is further shortened and the lamp electrode temperature is hardly lowered. The lamp voltage VL immediately after lighting is a voltage value close to the stable voltage value, and the lamp voltage change value ΔVL does not reach the predetermined value VR1, but the signal TS is inverted to a high level at timing t9 immediately after relighting. Thus, the capacitor 513 starts charging. Since the charging voltage Vc of the capacitor 513 is a voltage value close to a constant value at timing t9, Vc rises to a constant value in a short time.

  In the timer circuit 305 as described above, the time TD2 from the start of lighting until the signal TS is inverted to a high level at the time of hot start is set as a time corresponding to the length of the extinguishing time Toff before lighting. Since 513 performs the discharge operation within the turn-off time Toff, the charging voltage Vc of the capacitor 513 at the start of lighting is a voltage value corresponding to the turn-off time Toff. Therefore, when Vc at the start of lighting is equal to or greater than a predetermined value, the capacitor 513 may be charged regardless of the lamp voltage change value ΔVL. In this case, at the time of cold start, the capacitor 513 starts charging when ΔVL reaches a predetermined value, and at the time of hot start with a short turn-off time Toff, the capacitor 513 starts charging almost simultaneously with power-on.

(2) Second Example (FIGS. 7 and 8) In the second example, the ramp voltage VL input to the terminal 519 by the comparator 520 and the reference voltage VR2 (reference voltage VR2) of the reference voltage source 521 (instead of the signal TS) The configuration is the same as that of the first embodiment except that a signal indicating whether or not VL is equal to or greater than a predetermined value is used.

  Therefore, the waveforms of the respective parts at the time of cold start and hot start are as shown in FIG. 8, and at the time of hot start, the capacitor 513 switches from the discharge operation to the charge operation at timing t5 when the ramp voltage VL reaches the predetermined value VR2. .

  FIG. 9 shows the waveform of each part. In FIG. 9, VB is a voltage of a power source applied to the apparatus, VL is a lamp voltage, IL is a lamp current, SW is an on / off state of the switch 322, VLs is an output voltage of the lighting initial voltage storage circuit 320, ΔVL represents the output voltage of the ΔVL detection circuit 350.

  When power (VB) is applied to the device, the device begins to operate. Timing A indicates that lighting has started. At timing B after a predetermined time has elapsed from timing A, the switch 322 is switched from the on state to the off state, and at this timing B, VLs is held (stored) as the lighting initial voltage. To do.

The ΔVL detection circuit 350 is a subtraction circuit including an operational amplifier 351 and resistors 352 to 355. Here, if R1 = R3 and R2 = R4,
ΔVL = (VL−VLs) × R2 / R1
Thus, the change voltage value ΔVL from the lighting initial voltage VLs of the lamp voltage is obtained.

  Ideally, the lighting initial voltage VLs is a lamp voltage when the luminous flux is the lowest (dark). Accordingly, the predetermined time until the switch 322 determined by the switch control circuit 325 is turned off is set aiming at the time when the luminous flux is the lowest, and is within 6 seconds from the start of lighting.

  FIG. 10 shows another embodiment of the lighting initial voltage storage circuit 320. In contrast to the lighting initial voltage storage circuit 320 of FIG. 4, the switch 322 and the switch control circuit 325 are abolished, a diode 326 is added, and the connection of the capacitor 323 is changed. The capacitor 323 is connected to the reference power supply Vr2, and the capacitor 323 holds the minimum value of the lamp voltage VL by the diode 326. The lamp voltage VL is the lowest voltage at the beginning of lighting, and the luminous flux is lowest at this time. Thus, the lighting initial voltage may be set by holding the minimum voltage of the lamp voltage VL.

  As described above, the discharge lamp device according to the present embodiment includes the storage means (lighting initial voltage storage circuit 320) for storing the lamp voltage or equivalent signal voltage at the beginning of lamp lighting, and the current lamp voltage or equivalent signal voltage. ΔVL detection means (ΔVL detection circuit 350) that obtains a lamp voltage change value (ΔVL) that is a difference between the lamp voltage immediately after lighting stored in the storage means or an equivalent signal voltage, and based on ΔVL obtained by the ΔVL detection means. And configured to control lamp applied power. For this reason, variations in lamp voltage due to individual differences among lamps can be absorbed, overshoot and undershoot of the light beam can be suppressed, and the light beam can be smoothly converged to 100%.

  The storage means for storing the lamp voltage or the corresponding signal voltage at the beginning of lamp lighting may convert the lamp voltage from an analog value to a digital value and store the digital value by a microcomputer or the like. The ΔVL detection means for subtracting the stored lamp voltage immediately after lighting and obtaining the change voltage value (ΔVL) of the lamp voltage may also be performed by digital calculation using a microcomputer or the like.

  Further, a lamp voltage change value ΔVL, which is the difference between the current lamp voltage or equivalent signal voltage and the lamp voltage or equivalent signal voltage at the beginning of lamp operation, is obtained, the lamp applied power is controlled based on this ΔVL, and ΔVL is a predetermined value. The lamp application power is gradually reduced by the timer circuit according to the elapsed time from the point when it reaches the value or more, and the lamp power control at the stable time is shifted, so that the variation in the lamp voltage due to the individual difference of the lamp can be absorbed. It is possible to suppress overshoot and undershoot of the light beam and to smoothly converge the light beam to 100%.

  In addition, regardless of ΔVL, the lamp application power is gradually reduced by a timer circuit after a predetermined time from the start of lighting, and the process proceeds to stable lamp application power control. The lamp voltage variation due to the above can be absorbed, the overshoot and undershoot of the light beam can be suppressed, and the light beam can be smoothly converged to 100%.

  Moreover, since the lamp applied power is reduced by the timer circuit after a predetermined time set according to the turn-off time before the lamp is turned on, accurate power control at the time of re-lighting can be performed without being influenced by the electrode temperature of the lamp. It becomes like this.

  Further, a lamp voltage change value ΔVL which is a difference between the current lamp voltage or equivalent signal voltage and the initial lamp voltage or equivalent signal voltage is obtained, and the lamp applied power is controlled based on the ΔVL, and ΔVL is a predetermined value. The lamp application power is gradually reduced by the timer circuit according to the elapsed time from when the voltage reaches the predetermined value, whichever comes first, or when the lamp voltage reaches the predetermined value or higher. Therefore, it is possible to absorb the lamp voltage variation due to individual lamp differences, suppress the overshoot and undershoot of the light beam, and smoothly converge the light beam to 100%.

It is a whole lineblock diagram at the time of applying a discharge lamp device concerning one embodiment of the present invention to a vehicular headlamp. It is a block block diagram of a control circuit. It is a specific block diagram of a lamp power control circuit. It is a specific block diagram of a lighting initial voltage memory circuit and a ΔVL detection circuit. It is a specific block diagram of a first embodiment of a current setting circuit which is a timer circuit. It is the operation explanatory view. It is a specific block diagram of a second embodiment of a current setting circuit which is a timer circuit. It is the operation explanatory view. It is a wave form diagram of each part in FIG. It is a block diagram which shows other embodiment of a lighting initial voltage memory circuit. It is a control diagram which prescribes | regulates the relationship between the lamp voltage and lamp current for demonstrating the conventional control method. It is a wave form diagram for demonstrating the background of this invention.

Explanation of symbols

320 Memory means (lighting initial voltage memory circuit)
350 ΔVL detection means (ΔVL detection circuit)

Claims (8)

A mercury-less lamp lighting control device,
Current lamp voltage detection means for detecting the current lamp voltage or equivalent signal voltage;
Storage means for detecting and storing the lamp voltage or equivalent signal voltage at the beginning of lamp operation;
ΔVL detection means for obtaining a lamp voltage change value (ΔVL) which is a change value from the lamp voltage or equivalent signal voltage stored in the storage means to the current lamp voltage or equivalent signal voltage, and obtained by the ΔVL detection means. A discharge lamp device characterized by gradually reducing lamp applied power according to the elapsed time from when ΔVL reaches a predetermined value or more, and shifting to stable lamp applied power control.   The discharge lamp device according to claim 1, wherein the storage unit stores a lamp voltage or an equivalent signal voltage after a predetermined time has elapsed from the start of lamp lighting.   The discharge lamp device according to claim 2, wherein the predetermined time is within 6 seconds. 4. The discharge lamp device according to claim 2 , wherein the lamp voltage or the equivalent signal voltage stored by the storage means is a minimum voltage value within the predetermined time.   2. The discharge lamp device according to claim 1, wherein the lamp applied power is controlled to decrease until the second change value ΔVL <b> 2 is reached after the time point when the ΔVL increases to the first change value ΔVL <b> 1. After a predetermined time which is set according to the off time before the lamp lighting, the discharge lamp device according to any one of claims 1 to 5, characterized in that to reduce the applied power of the lamp regardless .DELTA.VL.   Depending on the elapsed time from when the ΔVL obtained by the ΔVL detecting means reaches a predetermined value or more, or when the lamp voltage VL reaches the predetermined value or more, the lamp reaches the predetermined value first. 7. The discharge lamp device according to claim 1, wherein the applied power is gradually reduced and the lamp applied power control is shifted to a stable state. The discharge lamp device according to claim 1, wherein the lamp voltage or the corresponding signal voltage stored by the storage means is a minimum voltage value at the initial stage of lamp lighting.

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