JP2009158323A - Discharge lamp lighting device - Google Patents

Abstract

Disclosed is a discharge lamp lighting device capable of maintaining high-quality light emission without flicker.
A DC / DC converter 3 for converting an output voltage of a DC power source, a DC / AC inverter 4 for converting an output of the DC / DC converter into a rectangular wave AC, and a high voltage pulse at an output of the DC / AC inverter. , An igniter 5 that supplies the discharge lamp 6 that does not use mercury, an output waveform detector that detects the output waveform of the DC / DC converter, and a waveform in which the output waveform detected by the output waveform detector is preset. When the flicker occurs, the DC / DC converter and the DC / AC inverter are set so that a predetermined power is added to the lighting power supplied to the discharge lamp and output when the flicker occurs. The control part 9 to control is provided.
[Selection] Figure 1

Description

  The present invention relates to a discharge lamp lighting device suitable for lighting a discharge lamp that does not use mercury, and more particularly to a technique for reducing flickering of the discharge lamp.

  In recent vehicles, a headlamp incorporating a discharge lamp as a high-intensity light source capable of obtaining a bright field of view has become widespread. A discharge lamp lighting device for lighting a headlamp incorporating such a discharge lamp is always required to be downsized, highly efficient, and inexpensive. It is desired to eliminate mercury as a constituent material of a discharge lamp.

  A conventional discharge lamp (hereinafter referred to as “conventional bulb”) in which mercury is enclosed in addition to a metal iodide (metal halide) such as sodium iodide or scandium iodide is a discharge lamp voltage (rated voltage) during steady lighting. ) Is 85V, and the current (rated current) is 0.41A. Therefore, since a comparatively thin electrode can be used as the electrode of the discharge lamp, the tip temperature of the electrode can be easily maintained at an appropriate temperature, and arc discharge can be easily maintained.

  In contrast, a discharge lamp that does not use mercury (hereinafter referred to as “Hg free bulb”) having a rated voltage of 42 V and a rated current of 0.83 A has a resistance so that the loss does not increase even if the energizing current increases. Since it is necessary to reduce the size, an electrode having a large diameter is used. Therefore, the temperature of the contact part with the arc discharge where the electrons at the tip of the electrode radiate or land is easy to be transmitted to the glass sphere (easy to cool), and keeping the temperature of the contact part stable, that is, maintaining the arc discharge stably is It is not good at conventional valves.

  Therefore, the Hg-free valve that is lit by the rectangular wave alternating current is structurally more susceptible to current interruption when switching the current polarity than the conventional bulb, and flickering due to this phenomenon is likely to occur. The flicker caused by the current interruption at the time of switching the current polarity is a phenomenon that can occur even in the conventional valve although the frequency is low. Techniques for reducing such flickering are disclosed in the following documents.

  For example, Patent Document 1 is a discharge lamp lighting device that lights a discharge lamp by a rectangular wave alternating current, and particularly when the current is zero-crossed when switching the polarity of a rectangular wave that is likely to occur when a discharge lamp that is approaching the end of its life is turned on. Disclosed is a discharge lamp lighting device in which 60% of power is applied after 20 to 50 μs after passing through a current zero crossing point of polarity switching or 80% after 50 to 100 μs in order to prevent disappearance due to a phenomenon in which generated current is interrupted. ing.

  According to this discharge lamp lighting device, it is possible to shorten the period in which the current is interrupted immediately after switching the current polarity, to prevent flicker that occurs from that timing, and to extend the time until the discharge lamp needs to be replaced. be able to. In addition, if a new discharge lamp has a low frequency of occurrence and is configured to supply the electric power after detecting a phenomenon in which the current is interrupted and the frequency of occurrence increases as it approaches the end of its lifetime, it will be excessive for the brand new discharge lamp. Without supplying power, the discharge lamp near the end of its life is supplied with higher power to prevent flickering, so the life of the new discharge lamp is extended without deteriorating due to excessive power. be able to.

  Patent Documents 2 and 3 disclose a discharge lamp lighting device that avoids flickering of a discharge lamp used in a projector. In the lighting of the Hg-free bulb for an in-vehicle headlamp, the flicker that the discharge lamp lighting device disclosed in Patent Document 1 described above whose brightness changes is to be avoided is clearly recognized, and the quality as a light source is reduced. Therefore, it is necessary to suppress the occurrence. However, the flicker that the discharge lamp lighting device disclosed in Patent Document 2 and Patent Document 3 tries to avoid is not accompanied by a large brightness change just by moving the luminous point on the tip of the electrode. This is not a problem because it is not recognized in the field of view illuminated by the headlamp. The means for avoiding the flickering of the discharge lamp lighting device disclosed in Patent Literature 2 and Patent Literature 3 will be described below as a reference example, with the difference being completely different from the discharge lamp lighting device according to the present invention.

  The flicker to be avoided by the discharge lamp lighting device disclosed in Patent Document 1 is flicker caused by short-time extinction due to current interruption immediately after current polarity switching in rectangular wave AC lighting of the discharge lamp. The flicker that the discharge lamp lighting device disclosed in Japanese Patent No. 2 and Patent Document 3 tries to avoid is light emission (brightness) caused by movement of the starting point of arc discharge of the electrode (specifically, the position of the electrode where electrons are emitted or landed). This is due to the movement of the point, and the flickers to be avoided by the two are completely different in the generation mechanism.

  The discharge lamp lighting device disclosed in Patent Document 2 is a discharge lamp lighting device that lights a discharge lamp by rectangular wave alternating current, and prevents flickering due to arc movement that is likely to occur at a current zero crossing point when switching the polarity of the rectangular wave. For this purpose, flicker detection means is provided, and when the flicker occurrence is detected by the detection means, higher electric power is output to the discharge lamp so that the discharge lamp is kept at a temperature at which flicker does not occur.

  The arc discharge in the discharge lamp starts from a small protrusion on the surface of the electrode, and this protrusion is generated by a halogen cycle generated inside the discharge lamp that is lit at an appropriate temperature. In other words, if the discharge lamp is kept at an appropriate temperature and lit, a protrusion serving as a starting point of arc discharge is generated on the tip surface of the electrode. Therefore, the discharge lamp lighting device disclosed in Patent Document 2 generates and fixes the starting point of arc discharge, and lights up with power exceeding the rated power so as not to cause flicker.

  Similarly to the discharge lamp lighting device disclosed in Patent Document 2 described above, the discharge lamp lighting device disclosed in Patent Document 3 has the same rating in order to prevent flicker (flicker) due to arc movement. It is configured to keep the discharge lamp at a temperature that does not flicker by lighting the discharge lamp with a deformed rectangular wave that increases power when the discharge lamp with high voltage is turned on or when the ambient temperature is low Yes.

  The discharge lamp lighting device disclosed in Patent Document 3 suppresses the occurrence of flickering in the same way as the discharge lamp lighting device disclosed in Patent Document 2 described above, but is disclosed in Patent Document 2. While the discharge lamp lighting device is lit by a square wave with a simple increase in power, a deformed rectangular wave with a high peak value or a changed period causes the discharge lamp lighting temperature to be low or the voltage to increase. It responds by supplying power exceeding the rated power to the discharge lamp.

  Further, the discharge lamp lighting device disclosed in Patent Document 4 is flicker caused by the movement of arc similar to the discharge lamp lighting devices disclosed in Patent Document 2 and Patent Document 3, which are generated in an in-vehicle Hg-free valve. In order to prevent this, the output voltage of the DC / DC converter is increased to 1.5 times or more before and after the current polarity switching timing in the case of lighting with a rectangular wave.

  In the discharge lamp lighting device disclosed in Patent Document 4, flickers that the discharge lamp lighting devices disclosed in Patent Document 2 and Patent Document 3 described above try to avoid in the lighting of an Hg-free bulb for an in-vehicle headlamp. Although it was invented in view of problems, as described above, this flicker does not pose a problem when used as a light source for a headlamp. In addition, 1.5 times or more, which is the amount of power increase at the time of switching the current polarity performed by the discharge lamp lighting device disclosed in Patent Document 4, is 60% which is a feature of the discharge lamp lighting device disclosed in Patent Document 1. Or it has the same meaning as an 80% increase in power.

JP 2005-101016 A JP 2005-327744 A JP 2006-120654 A JP 2005-340064 A

  The above-described discharge lamp lighting device disclosed in Patent Document 1 has been devised for lighting a conventional bulb, and is configured to increase power only at the time of current polarity switching. There is a limit to stabilizing the arc discharge by keeping the electrode of the Hg free valve having the electrode that is easy to cool because the temperature of the tip is transmitted to the glass bulb, and there is a limit to the current when switching the current polarity when lighting with a square wave It is not enough to reduce the flicker caused by the interruption.

  Similarly, the amount of increase in power performed by the discharge lamp lighting device disclosed in Patent Document 4 is the same amount as that of the discharge lamp lighting device disclosed in Patent Document 1 described above. It is equivalent to the disclosed discharge lamp lighting device, and is insufficient to reduce flicker caused by current interruption when switching the current polarity when lighting with a rectangular wave.

  By the way, arc discharge is discharge in which a thermoelectron radiates | emits from a minus electrode and lands on a plus electrode, Since a thermoelectron is easy to be radiated, so that the electrode temperature is high, stable arc discharge is performed, so that electrode temperature is high . On the contrary, if the electrode temperature is low, thermionic electrons cannot be emitted, and a high voltage (breakdown voltage) is required to start discharge (emit electrons). Therefore, in order to continue the arc discharge (without applying a high voltage) even after passing through the current zero cross point at the time of switching the current polarity, even if the voltage between the electrodes is low, the temperature is increased to a high temperature at which the thermoelectrons are emitted. The electrode needs to be maintained.

  However, as described above, the diameter of the electrode of the Hg-free valve is thicker than that of the conventional valve, and the temperature at the tip of the electrode is easily transmitted to the surrounding glass, so that the electrode is easily cooled. The electrode at the end of the life when the tip portion has been scattered is shortened, the tip of the electrode is close to the glass, and the temperature of the electrode is easy to cool, so the current becomes zero (the current polarity switches). Discharge is easy to stop. As a result, compared to the conventional bulb, the Hg-free bulb cannot be denied that the current is interrupted when the current polarity is switched when the rectangular wave is lit, and that the flicker caused by the current disruption is inferior.

  As described above, the Hg-free valve, which is approaching the end of its life, is not sufficient to suppress the flicker due to the thickness of the electrode diameter, and the increase in power as proposed in Patent Document 1 is insufficient. It is desirable to take measures that make it difficult for the current to be interrupted during switching, in other words, to prevent arc discharge from being interrupted. The discharge lamp lighting device disclosed in Patent Document 4 is used for lighting the Hg-free valve, but the input power is substantially the same as the discharge lamp lighting device disclosed in Patent Document 1, and is described above. Insufficient to meet the request.

  The present invention has been made to meet the above-described demand, and an object thereof is to provide a discharge lamp lighting device capable of maintaining high-quality light emission without flickering.

In order to solve the above problems, a discharge lamp lighting device according to the present invention is a discharge lamp lighting device for lighting a discharge lamp that does not use mercury, a DC / DC converter that converts an output voltage of a DC power source, and a DC DC / AC inverter that converts the output of the DC / DC converter into rectangular alternating current, an igniter that superimposes a high voltage pulse on the output of the DC / AC inverter and supplies the discharge lamp, and the output waveform of the DC / DC converter An output waveform detector to detect;
If the output waveform detected by the output waveform detector is different from the preset waveform, it is determined that flickering has occurred, and the lighting power supplied from the DC / AC inverter to the discharge lamp via the igniter is a predetermined power. Are added to output a control unit for controlling the DC / DC converter and the DC / AC inverter.

  According to the discharge lamp lighting device of the present invention, since the lighting power is increased so that the temperature of the electrode of the discharge lamp is maintained at a temperature at which arc discharge is not interrupted, the current is interrupted when the current polarity is switched. The flicker caused can be eliminated. As a result, high-quality light emission without flicker can be maintained.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
1 is a circuit diagram showing a configuration of a discharge lamp lighting device according to Embodiment 1 of the present invention. The discharge lamp lighting device includes a DC power source 1, a power switch 2, a DC / DC converter 3, a DC / AC inverter 4, an igniter 5, a discharge lamp 6, a voltage detector 7, a current detector 8, and a control unit 9. Yes.

  As the DC power source 1, for example, a battery mounted on a vehicle can be used. The output of the DC power supply 1 is supplied to the DC / DC converter 3 when the power switch 2 is closed. The DC / DC converter 3 converts (for example, boosts) the DC voltage supplied from the DC power supply 1 into a predetermined DC voltage V1 by performing a switching operation in accordance with a control signal sent from the control unit 9. The DC voltage V1 output from the DC / DC converter 3 is supplied to the DC / AC inverter 4.

  The DC / AC inverter 4 includes an H bridge circuit in which four switching elements are arranged in an H shape. The DC / AC inverter 4 converts the DC voltage V1 sent from the DC / DC converter 3 into a rectangular AC voltage V2 in response to a control signal sent from the control unit 9. The AC voltage V <b> 2 output from the DC / AC inverter 4 is supplied to the igniter 5.

  The igniter 5 functions as a starting circuit. This igniter 5 superimposes a high voltage pulse V3 for starting generated inside itself on the AC voltage V2 sent from the DC / AC inverter 4 and supplies it to the discharge lamp 6 at the time of startup. After 6 is turned on, the AC voltage V <b> 2 sent from the DC / AC inverter 4 is supplied to the discharge lamp 6.

  The discharge lamp 6 is composed of, for example, an Hg-free bulb with a rated power of 35 W and a rated voltage of 42V. The discharge lamp 6 is subjected to dielectric breakdown between the electrodes when the AC voltage V2 on which the high voltage pulse V3 is superimposed is applied from the igniter 5 and starts discharging. By starting this discharge, a current flows through the discharge lamp 6 and light emission is started.

  The voltage detector 7 detects the output voltage of the DC / DC converter 3. The voltage detected by the voltage detector 7 is sent to the control unit 9 as a detected voltage value. The current detector 8 detects the output current of the DC / DC converter 3. The current detected by the current detector 8 is sent to the control unit 9 as a detected current value.

  The control unit 9 is composed of a microcomputer, for example, and generates a control signal based on the detected voltage value sent from the voltage detector 7 and the detected current value sent from the current detector 8 to generate DC / DC. Send to converter 3 and DC / AC inverter 4. As a result, the DC voltage V1 output from the DC / DC converter 3 and the AC voltage V2 output from the DC / AC inverter 4 are controlled, and thus the lighting power supplied to the discharge lamp 6 is controlled.

  Further, the control unit 9 detects the presence or absence of current interruption at the time of switching the current polarity based on the detected voltage value sent from the voltage detector 7 and the detected current value sent from the current detector 8, and the detection result Check for flickering based on the above. When it is determined that the flicker has occurred, a process of increasing the lighting power supplied to the discharge lamp 6 is performed. Details of the processing performed by the control unit 9 will be described later.

  Next, the operation of the discharge lamp lighting device according to Embodiment 1 of the present invention configured as described above will be described with reference to the timing chart shown in FIG. This timing chart represents temporal changes in the voltage, current, and lighting power of the discharge lamp 6.

  In this discharge lamp lighting device, when the power switch 2 is closed, a DC voltage is supplied from the DC power source 1 to the DC / DC converter 3. The DC / DC converter 3 is switching-controlled by a control signal from the control unit 9, converts a DC voltage supplied from the DC power source 1 into a DC voltage V 1, and supplies the DC voltage to the DC / AC inverter 4. The DC / AC inverter 4 converts the DC voltage V1 supplied from the DC / DC converter 3 into a rectangular wave AC voltage V2 in accordance with a control signal from the control unit 9 and sends it to the igniter 5.

  At startup, the igniter 5 superimposes a high voltage pulse V3 generated inside itself on the AC voltage V2 supplied from the DC / AC inverter 4 and supplies it to the discharge lamp 6. By applying the high voltage pulse V3, the discharge lamp 6 starts a discharge due to dielectric breakdown between the electrodes. When the discharge is started, a current flows through the discharge lamp 6, and appropriate electric power is supplied from the DC / AC inverter 4 via the igniter 5, so that the discharge lamp 6 starts to emit light. The lighting power supplied to the discharge lamp 6 is a lighting power (for example, 75 W) that is larger than the rated power (for example, 35 W) of the discharge lamp 6 immediately after lighting, and then gradually decreases to the rated power and reaches the rated power. Then, the discharge lamp 6 is stably lit with constant power and maintains light emission.

  The control performed when the current interruption of the discharge lamp 6 occurs after the power switch 2 is closed to the stable lighting will be described with reference to the timing chart shown in FIG. As shown in FIG. 2 (b), if a current interruption 12 in which the current of the discharge lamp 6 becomes 0 A occurs at the time of switching the current polarity performed every 1.25 ms while the discharge lamp 6 is lit, FIG. ), The voltage 11 of the discharge lamp 6, which is switched every 1.25 ms, rises beyond the steady-state voltage (for example, 42V) because the DC / DC converter is no longer loaded, and the arc discharge resumes. Fire and descend. These current interruption and voltage increase appear as flickering of the discharge lamp 6.

  When the control unit 9 detects the current interruption and the voltage increase based on the detected current value sent from the current detector 8 and the detected voltage value sent from the voltage detector 7, it determines that the extinction has occurred. Then, as shown in FIG. 2 (c), a predetermined power Δ is added to the constant power (35W) 10 that has been the target power so far, and this increased power ((35 + Δ) W) 15 is used as a new lighting power. Is supplied to the discharge lamp 6 as a target power, and the lighting is continued.

  When the lighting power is increased, as shown in FIG. 2A, after the arc discharge is performed and the discharge lamp 6 is re-lighted, the voltage 13 and current of the discharge lamp 6 are increased and the temperature of the electrode is increased. As a result, the arc discharge is stabilized and the occurrence of current interruption at the time of switching the current polarity is reduced.

  Note that the flicker detected by the discharge lamp lighting devices disclosed in Patent Document 2 and Patent Document 3 described above is due to the difference in the generation mechanism described above, and the output of the DC / DC converter 3 due to the current interruption. Since the voltage does not increase, electrical detection is difficult, and in this discharge lamp lighting device, the use of an optical sensor is also being studied. On the other hand, the flickering of the discharge lamp lighting device according to Embodiment 1 of the present invention is caused by current interruption, and can be sufficiently detected by the circuit configuration described above.

  As described above, according to the discharge lamp lighting device according to Embodiment 1 of the present invention, it is detected that flickering occurs while the discharge lamp 6 is lit, and the lighting power of the discharge lamp 6 is increased. As a result, it is possible to maintain the tip temperature of the electrode where arc discharge is stable, eliminate flickering due to current interruption when switching the current polarity, or eliminate extinction due to current interruption, and maintain high quality lighting. it can.

  If the discharge lamp 6 is lit with rated power when the discharge lamp 6 is new, the temperature of the electrode is kept high enough to radiate thermoelectrons, so that no special lighting power control is required. It is necessary to increase the lighting power and maintain the electrode temperature when lighting the discharge lamp 6 that has passed a certain lifetime, and it is sufficient to respond after detecting the current interruption during lighting. . Therefore, if the lighting power is controlled after the current interruption is detected, the new discharge lamp 6 is not deteriorated by applying excessive power, and the lifetime is not shortened.

Embodiment 2. FIG.
In the discharge lamp lighting device according to Embodiment 2 of the present invention, the power added to the lighting power supplied to the discharge lamp is changed according to the occurrence frequency of flickering of the discharge lamp. The configuration of the discharge lamp lighting device according to the second embodiment is the same as the configuration of the discharge lamp lighting device according to the first embodiment shown in FIG.

  Next, the operation of the discharge lamp lighting device according to Embodiment 2 will be described. FIG. 3 is a timing chart showing the operation of the discharge lamp lighting device according to the second embodiment. The voltage of the discharge lamp 6 (output voltage of the DC / DC converter 3) and the lighting power of the discharge lamp 6 (control unit 9). Represents the change in the target power) over time. Since the effective voltage of the discharge lamp 6 is substantially equal to the output voltage of the DC / DC converter 3, FIG. 3A shows the output voltage of the DC / DC converter 3 instead of the voltage of the discharge lamp 6. Yes.

  In this discharge lamp lighting device, whenever a flicker due to current interruption occurs, that is, as shown in FIG. 3A, every time the output voltage of the DC / DC converter 3 exceeds a predetermined voltage (for example, 84V), As shown in FIG. 3B, a predetermined power is added to the lighting power of the discharge lamp 6, and thereafter, the lighting power is controlled to be gradually reduced. Therefore, if flickering occurs frequently, the increase in lighting power exceeds the decrease, and the lighting power increases as a whole, so that the discharge lamp 6 is turned on with higher lighting power. This higher lighting power raises the electrode temperature and stabilizes the arc discharge, thereby reducing the occurrence of flickering and realizing stable lighting. On the other hand, if the frequency of flickering decreases as the steady lighting continues, the decrease in the lighting power exceeds the increase, and the lighting power gradually decreases as a whole. Thereby, stable lighting with less lighting power is realized.

  Next, the operation of the discharge lamp lighting device for realizing the control shown in FIG. 3 will be described with reference to the flowcharts shown in FIGS. 4 and 5, focusing on the discharge lamp lighting processing performed by the control unit 9. .

  In this discharge lamp lighting process, when the power switch 2 is closed, first, the power immediately after lighting is output (step ST11). That is, in order to quickly heat the discharge lamp 6 immediately after lighting and obtain a desired brightness, the control unit 9 causes the DC / DC converter 3 and the DC / DC converter 3 so that 75 W of lighting power is supplied to the discharge lamp 6. The AC inverter 4 is controlled. In the following description, in order to avoid complicated explanation, a description that the increase / decrease of the lighting power supplied to the discharge lamp 6 is performed by controlling the DC / DC converter 3 and the DC / AC inverter is omitted. . Thereafter, the control unit 9 sequentially reduces the lighting power, finally sets the rated power of 35 W as the target power, and performs control so that stable lighting is maintained by the target power.

  Next, the timer is incremented (step ST12). That is, the control unit 9 increments a timer (not shown) held therein. Note that the contents of this timer are cleared at the start of lighting. Next, it is checked whether or not 1.25 ms has passed (step ST13). That is, the control unit 9 checks whether 1.25 ms has elapsed by referring to the contents of the timer. If it is determined in step ST13 that 1.25 ms has not elapsed, the sequence returns to step ST12, and thereafter, the processes in steps ST12 and ST13 are repeated until 1.25 ms elapses.

  If it is determined in step ST13 that 1.25 ms has elapsed, the timer is then cleared (step ST14). That is, the control unit 9 clears the contents of the timer. Next, a target power correction process is performed (step ST15). With the above processing, the target power correction processing performed in step ST15 is executed every 1.25 ms.

  In the target power correction process, the target power of the lighting power supplied to the discharge lamp 6 is calculated. The details of the target power correction process will be described with reference to the flowchart shown in FIG. In the target power correction process, first, the voltage and current of the discharge lamp 6 are measured (step ST21). That is, the control unit 9 acquires the detected current value sent from the current detector 8 and the detected voltage value sent from the voltage detector 7.

  Next, it is examined whether or not flicker occurs (step ST22). That is, the control unit 9 checks whether or not the detected current value and the detected voltage value acquired in step ST21 indicate current interruption and voltage increase. If it is determined in this step ST22 that flickering occurs, 1/10 W is added to the target power (step ST23). That is, the control unit 9 adds 1/10 W to the target power held in itself and supplies the increased target power to the discharge lamp 6 as lighting power. Thereafter, the process returns from the target power correction process to step ST16 of the discharge lamp lighting process shown in the flowchart of FIG.

  If it is determined in step ST22 that there is no flicker, it is checked whether the current target power is greater than 35 W (step ST24). That is, the control unit 9 checks whether the target power held by itself is larger than 35 W, that is, whether it is larger than the rated power. If it is determined in step ST24 that the current target power is 35 W or less, the process returns from this target power correction process to step ST16 of the discharge lamp lighting process shown in the flowchart of FIG. Thereby, the minimum value of lighting power is fixed to 35W.

  If it is determined in step ST24 that the current target power is greater than 35W, then 1 / 10000W is subtracted from the target power (step ST25). That is, the control unit 9 subtracts 1/10000 W from the target power held in itself, and supplies the reduced target power to the discharge lamp 6 as lighting power. Thereafter, the process returns from the target power correction process to step ST16 of the discharge lamp lighting process shown in the flowchart of FIG. Thereby, the lighting power gradually decreases.

  In step ST16 of the discharge lamp lighting process, it is checked whether or not the target power has been reached. If it is determined in step ST16 that the target power has not been reached, the sequence returns to step ST11 to lower the lighting power, and the above-described processing is repeated thereafter. On the other hand, when it is determined in step ST16 that the target power has been reached, lighting with the target power is performed (step ST17). Thereafter, the sequence returns to step ST12, and the above-described processing is repeated. With the above processing, the function of the discharge lamp 6 that reduces the lighting power sequentially from the lighting with the lighting power of 75 W and finally reaches the stable lighting with the rated power of 35 W is realized.

  As described above, according to the discharge lamp lighting device according to the second embodiment, it is detected that flickering has occurred during lighting of the discharge lamp 6, and the lighting power of the discharge lamp is increased according to the frequency of flickering. Since it is configured as described above, higher discharge power can be supplied to the discharge lamp 6 that is likely to flicker, and the tip temperature of the electrode at which arc discharge is stabilized can be maintained. As a result, flickering due to current interruption at the time of switching the current polarity or occurrence of extinction due to current interruption can be eliminated, and high quality lighting can be maintained.

Embodiment 3 FIG.
In the discharge lamp lighting device according to Embodiment 3 of the present invention, the power added to the lighting power supplied to the discharge lamp is changed according to the length of the flicker occurrence period of the discharge lamp. . The configuration of the discharge lamp lighting device according to the third embodiment is the same as the configuration of the discharge lamp lighting device according to the first embodiment shown in FIG.

  Next, the operation of the discharge lamp lighting device according to Embodiment 3 will be described. FIG. 6 is a timing chart showing the operation of the discharge lamp lighting device according to the third embodiment. The voltage of the discharge lamp 6 (output voltage of the DC / DC converter 3) and the lighting power of the discharge lamp 6 (control unit 9). Represents the change in the target power) over time. Since the effective voltage of the discharge lamp 6 is substantially equal to the output voltage of the DC / DC converter 3, FIG. 6A shows the output voltage of the DC / DC converter 3 instead of the voltage of the discharge lamp 6. Yes.

  In this discharge lamp lighting device, when flickering due to current interruption occurs, that is, as shown in FIG. 6A, when the output voltage of the DC / DC converter 3 exceeds a predetermined voltage (42V), FIG. As shown in (), the lighting power of the discharge lamp 6 is increased at a predetermined rate only during the flickering period, and thereafter, the lighting power is controlled to be gradually decreased. Therefore, if the flicker generation period is lengthened, the increase in the lighting power increases and exceeds the decrease, and the lighting power rises as a whole. Therefore, the discharge lamp 6 is lit with higher lighting power. This higher lighting power raises the electrode temperature and stabilizes the arc discharge, thereby reducing the occurrence of flickering and realizing stable lighting. On the other hand, if the flicker generation period is shortened by continuing the stable lighting, the increase in the lighting power becomes small, the decrease in the lighting power exceeds the increase, and the lighting power gradually decreases as a whole. Thereby, stable lighting with less lighting power is realized.

  Next, the operation of the discharge lamp lighting device for realizing the control shown in FIG. 6 will be described with reference to the flowcharts shown in FIGS. 4 and 7, focusing on the discharge lamp lighting processing performed by the control unit 9. . The discharge lamp lighting process shown in FIG. 4 is the same as the process described in the second embodiment except for the target power correction process performed in step ST15, and thus the description thereof will be omitted. Only will be described with reference to the flowchart shown in FIG.

  In the target power correction process, first, the voltage and current of the discharge lamp 6 are measured (step ST31). The process in step ST31 is the same as the process in step ST21 shown in FIG. Next, flickering occurs and it is checked whether or not it continues (step ST32). That is, the control unit 9 checks whether or not the detected current value and the detected voltage value acquired in step ST21 indicate current interruption and voltage increase.

  If it is determined in step ST32 that the flickering continues, 1/100 W is added to the target power (step ST33). That is, the control unit 9 adds 1/100 W to the target power held in itself and supplies the increased target power to the discharge lamp 6 as lighting power. Thereafter, the process returns from the target power correction process to step ST16 of the discharge lamp lighting process shown in the flowchart of FIG.

  If it is determined in step ST22 that the flicker does not continue, it is checked whether or not the current target power is greater than 35 W (step ST34). The process in step ST34 is the same as the process in step ST24 shown in FIG. If it is determined in step ST34 that the current target power is 35 W or less, the process returns from the target power correction process to step ST16 of the discharge lamp lighting process shown in the flowchart of FIG. Thereby, the minimum value of lighting power is fixed to 35W.

  If it is determined in step ST34 that the current target power is greater than 35W, then 1 / 10000W is subtracted from the target power (step ST35). The process in step ST35 is the same as the process in step ST25 shown in FIG. Thereafter, the process returns from the target power correction process to step ST16 of the discharge lamp lighting process shown in the flowchart of FIG. Thereby, the lighting power gradually decreases.

  As described above, according to the discharge lamp lighting device according to the third embodiment, it is detected that the flicker has occurred while the discharge lamp 6 is lit, and the discharge lamp is in accordance with the length of the flicker occurrence period. Since the lighting power of 6 is increased, higher power can be supplied to the discharge lamp having a long flickering generation period to maintain the tip temperature of the electrode at which arc discharge is stabilized. As a result, flickering due to current interruption at the time of switching the current polarity or occurrence of extinction due to current interruption can be eliminated, and high quality lighting can be maintained.

  In the description of the first to third embodiments described above, some specific values are used for easy understanding, but the present invention is limited to the values used for the description. Instead, various values can be used depending on the type of the discharge lamp 6 or the like. Moreover, although the control part 9 was comprised by the digital circuit using a microcomputer, it can also be comprised by an analog circuit.

It is a circuit diagram which shows the structure of the discharge lamp lighting device which concerns on Embodiment 1 of this invention. It is a timing chart for demonstrating operation | movement of the discharge lamp lighting device which concerns on Embodiment 1 of this invention. It is a timing chart for demonstrating operation | movement of the discharge lamp lighting device which concerns on Embodiment 2 of this invention. It is a flowchart which shows the discharge lamp lighting process of the discharge lamp lighting device which concerns on Embodiment 2 of this invention. It is a flowchart which shows the target electric power correction process performed by the discharge lamp lighting process of the discharge lamp lighting device which concerns on Embodiment 2 of this invention. It is a flowchart which shows the discharge lamp lighting process of the discharge lamp lighting device which concerns on Embodiment 3 of this invention. It is a flowchart which shows the target electric power correction process performed by the discharge lamp lighting process of the discharge lamp lighting device which concerns on Embodiment 3 of this invention.

Explanation of symbols

  1 DC power supply, 2 power switch, 3 DC / DC converter, 4 DC / AC inverter, 5 igniter, 6 discharge lamp, 7 voltage detector, 8 current detector, 9 control unit.

Claims (4)

A discharge lamp lighting device for lighting a discharge lamp not using mercury,
A DC / DC converter for converting the output voltage of the DC power supply;
A DC / AC inverter that converts the output of the DC / DC converter into rectangular alternating current;
An igniter that superimposes a high voltage pulse on the output of the DC / AC inverter and supplies it to the discharge lamp;
An output waveform detector for detecting an output waveform of the DC / DC converter;
When the output waveform detected by the output waveform detector is different from a preset waveform, it is determined that flickering occurs, and the lighting power supplied from the DC / AC inverter to the discharge lamp via the igniter is determined. A discharge lamp lighting device comprising: a control unit that controls the DC / DC converter and the DC / AC inverter so as to add and output predetermined power. A discharge lamp lighting device for lighting a discharge lamp not using mercury,
A DC / DC converter for converting the output voltage of the DC power supply;
A DC / AC inverter that converts the output of the DC / DC converter into rectangular alternating current;
An igniter that superimposes a high voltage pulse on the output of the DC / AC inverter and supplies it to the discharge lamp;
A voltage detector for detecting an output voltage of the DC / DC converter;
A current detector for detecting an output current of the DC / DC converter;
Based on the voltage detected by the voltage detector and the current detected by the current detector, the occurrence of flickering is investigated by checking whether or not the discharge lamp flickers due to current interruption at the time of switching the current polarity in the DC / AC inverter. The DC / DC converter and the DC / AC inverter so that a predetermined power is added to the lighting power supplied from the DC / AC inverter to the discharge lamp via the igniter. A discharge lamp lighting device comprising a control unit for controlling. The discharge lamp lighting device according to claim 1 or 2, wherein the control unit increases the power to be added to the lighting power as the frequency of occurrence of flickering increases. The discharge lamp lighting device according to claim 1, wherein the control unit increases the power to be added to the lighting power as the flicker generation period becomes longer.

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