JP2008181814A - High pressure discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress flickers without increasing circuit stress throughout the entire period of a lamp life. <P>SOLUTION: A control circuit 11 computes a proper lamp current from a detected lamp voltage and target power. The control circuit 11 provides a projecting portion in timing immediately before inversion of the proper current. In accordance with the accumulated lighting time of a lamp, the level of the projecting portion is heightened and the level of a flat portion is lowered. Thereby, the level of the projecting portion is comparatively low at the beginning of a lamp life, small lamp currents are superimposed, the temperature of a lamp electrode is not unnecessarily increased, and the life can be prevented from being shortened. In addition, a problem undesirable from a view point of global environments such as deterioration of circuit efficiency caused by superimposing excessive lamp currents, a large amount of heat generated, and increase of current consumption, can be prevented from arising. In this way, the flickers can be reduced while suppressing stress of the circuit. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a lighting device for a high pressure discharge lamp that reduces flicker of the high pressure discharge lamp.

  Conventionally, high pressure discharge lamps such as metal halide lamps have high efficiency and high brightness, so they are used for outdoor lighting such as road lighting or for light sources of projection devices such as DLP (digital light processing) and liquid crystal projectors. As such, it has come to be used in various ways.

  In a conventional high pressure discharge lamp lighting device for lighting such a high pressure discharge lamp, for example, a starter having a high pressure pulse generation circuit is used. A power supply voltage obtained from a commercial AC power supply is applied to the starter through a ballast. The high voltage pulse generation circuit is supplied with a DC voltage from the ballast and generates a high voltage pulse (thousands to tens of thousands of volts) for starting the high pressure discharge lamp. When the high-pressure discharge lamp is lit by this high-pressure pulse, the generation of the high-pressure pulse is stopped, and thereafter the lighting is maintained by constant power control by rectangular low-frequency alternating current.

  By the way, when a high pressure discharge lamp is lit at a rectangular low frequency, a discharge delay may occur immediately after polarity reversal and flicker may occur. Therefore, Patent Document 1 discloses a technique for superimposing a pulsed current on a lamp current.

In Patent Document 1, the electrode temperature is temporarily increased by superimposing a pulsed current on the lamp current immediately before the polarity reversal, and the re-ignition energy after zero crossing is suppressed to a minimum, thereby reducing flickering. It is designed to avoid it.
Special table 10-501919

  By the way, in general, in the high-pressure discharge lamp, the lamp voltage increases as the lamp life approaches, and the lamp current decreases due to the constant power control. For this reason, the electrode temperature tends to decrease at the end of the lamp life, and flickering is likely to occur due to the decrease in the electrode temperature, and the extinction may occur.

  In order to sufficiently suppress flicker even at the end of the lamp life using the technique of Patent Document 1, it is necessary to set the pulsed current value superimposed immediately before polarity inversion to be extremely large. As a result, a large lamp current is superposed even in the initial stage of the lamp, which unnecessarily increases the lamp electrode temperature and significantly shortens the service life. In addition, there is a problem from the viewpoint of the global environment that the circuit efficiency is lowered due to the superposition of the excessive lamp current, the heat generation is increased, and the current consumption is increased.

  The present invention provides a lighting device for a high-pressure discharge lamp that can extend the life of a lamp to the maximum and can suppress flicker sufficiently over the entire life of the lamp and with a minimum necessary energy consumption. The purpose is to provide.

  A lighting device for a high-pressure discharge lamp according to the present invention includes a DC / DC converter circuit that boosts or lowers a DC voltage, a DC / AC inverter circuit that converts an output voltage of the DC / DC converter circuit into a low-frequency alternating current, And a control means for controlling the DC / DC converter circuit and the DC / AC inverter circuit, wherein the control means controls an output amount of the DC / DC converter circuit and an operation timing of the DC / AC inverter circuit. Immediately before the polarity inversion of the low-frequency alternating current, the output amount of the DC / DC converter circuit is increased to generate an output current having a substantially rectangular wave shape having a protruding portion, and the low-frequency alternating current The level of the protruding portion relative to the level of the flat portion is changed according to the degree of deterioration of the high-pressure discharge lamp.

  In the present invention, the DC / AC inverter circuit is supplied with a DC voltage from the DC / DC converter circuit and supplies a lamp voltage to the high-pressure discharge lamp. The control means controls the output amount of the DC / DC converter circuit and the operation timing of the DC / AC inverter circuit. In this case, the control means increases the output amount of the DC / DC converter circuit immediately before the polarity inversion of the low-frequency alternating current to generate a substantially rectangular wave-shaped output current having a protruding portion, The level of the protruding portion with respect to the level of the flat portion of the low frequency is changed according to the degree of deterioration of the high pressure discharge lamp.

  According to the present invention, it is possible to prolong the life of the lamp to the maximum, and to suppress flicker sufficiently over the entire lamp life and with the minimum necessary energy consumption.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a circuit diagram showing a lighting device for a high pressure discharge lamp according to a first embodiment of the present invention.

  In FIG. 1, the power supply voltage from the power supply unit 1 is supplied to the smoothing capacitor C <b> 1 through the switch 2. A DC voltage appearing between the positive terminal and the negative terminal of the capacitor C <b> 1 is supplied to the DC / DC converter circuit 3 and the PWM control circuit 4.

  The DC / DC converter circuit 3 as a voltage generator is configured by connecting a primary winding of a transformer T and a switching transistor Q1 in series between a positive terminal and a negative terminal. A series circuit of a diode D1 and a capacitor C2 is connected in parallel to the secondary winding of the transformer T.

  The PWM control circuit 4 is controlled by a differential amplifier circuit 14 to be described later, and controls on / off of the switching transistor Q1. Since the switching transistor Q1 is PWM-controlled by the PWM control circuit 4, the level of the DC voltage appearing in the secondary winding of the transformer T can be controlled. The voltage appearing at the secondary winding of the transformer T is smoothed by the diode D1 and the capacitor C2. The voltage appearing between the positive terminal and the negative terminal of the capacitor C2 is supplied to the DC / AC inverter circuit 7 as the output voltage of the DC / DC converter circuit 3.

  The DC / AC inverter circuit 7 has a bridge circuit that converts the supplied DC voltage into, for example, a rectangular wave. That is, the positive output terminal of the DC / DC converter circuit 3 is connected to the drains of the transistors Q2 and Q4 constituting the bridge circuit, and the negative output terminal is connected to the sources of the transistors Q3 and Q5.

  The source of the transistor Q2 and the drain of the transistor Q3 are connected in common, and this connection point is connected to one input terminal of the high voltage generation circuit 8. The other input terminal of the high voltage generation circuit 8 is connected to a common connection point between the source of the transistor Q4 and the drain of the transistor Q5. A high pressure discharge lamp 9 is connected to the output terminal of the high pressure generation circuit 8. Power is supplied to the high-pressure discharge lamp 9 by the bridge circuit constituted by the transistors Q2 to Q5 and the high-pressure generation circuit 8.

  The transistors Q2 to Q5 are on / off controlled by the control circuit 11. The control circuit 11 supplies the drive signal to the gates of the transistors Q3 and Q4 via the amplifier B1, and supplies the drive signal to the gates of the transistors Q2 and Q5 via the inverting amplifier B2. For example, the control circuit 11 has a rectangular low frequency oscillation circuit (not shown) and can output a rectangular low frequency drive signal. The amplifiers B1 and B2 give mutually inverted drive signals to the gates of the transistors Q2 and Q5 and the gates of the transistors Q3 and Q4.

  Thereby, the transistors Q2 and Q5 constituting the bridge circuit are simultaneously turned on and off, and the transistors Q3 and Q4 are also simultaneously turned on and off. When the transistors Q2 and Q5 are on, the transistors Q3 and Q4 are off, and when the transistors Q2 and Q5 are off, the transistors Q3 and Q4 are on.

  When the transistors Q2 and Q5 are turned on, a lamp current flows from the positive output terminal of the DC / DC converter circuit 3 to the negative output terminal via the transistor Q2, the high pressure generation circuit 8, the high pressure discharge lamp 9, and the transistor Q5. Flowing. On the other hand, when the transistors Q3 and Q4 are on, the DC / DC converter circuit 3 is connected to the negative output terminal via the transistor Q4, the high pressure discharge lamp 9, the high voltage generation circuit 8, and the transistor Q3. Lamp current flows. By switching on and off the transistors Q2 and Q5 and the transistors Q3 and Q4 by a rectangular low-frequency drive signal from the control circuit 11, the high-pressure discharge lamp 9 can be driven by a rectangular wave voltage.

  At the time of starting, the high-pressure discharge lamp 9 can be turned on by generating a high-pressure pulse by the high-pressure generation circuit 8. Further, the high-pressure discharge lamp 9 can be driven stably by controlling the power supplied by the DC / DC converter circuit 3.

  Hereinafter, as an example of the control means, a method using a digital circuit as a main calculation for power control and an analog circuit as a feedback system will be described as an example.

  The constant power control of the DC / DC converter circuit 3 is performed by feeding back the detection result of the lamp voltage and the lamp current. Between the positive output terminal and the negative output terminal of the DC / DC converter circuit 3, resistors R2 and R3 constituting the output voltage detection circuit 5 are connected in series. The connection point of the resistors R2 and R3 is connected to the input terminal of the A / D converter 10, and the output voltage of the DC / DC converter circuit 3 is divided by the resistors R2 and R3 and supplied to the A / D converter 10. It has come to be. The A / D converter 10 converts the input voltage into a digital signal and supplies it to the control circuit 11.

  The control circuit 11 outputs an output from the A / D converter 10, that is, a digital value corresponding to the lamp voltage. For example, the control circuit 11 calculates a lamp current (hereinafter referred to as an appropriate lamp current) necessary for constant power control of the high pressure discharge lamp 9 with respect to the detected lamp voltage. The control circuit 11 sends the calculated appropriate lamp current value as an analog voltage to the inverting input terminal of the differential amplifier circuit 14 via the D / A converter 13.

  On the other hand, a resistor R4 constituting the output current detection circuit 6 is connected to the negative output terminal of the DC / DC converter circuit 3, and the output current detection circuit 6 provides a voltage proportional to the lamp current flowing through the resistor R4. The signal is sent to the non-inverting terminal of the dynamic amplifier circuit 14.

  The differential amplifier circuit 14 differentially amplifies the voltage corresponding to the appropriate lamp current value and the output voltage of the output current detection circuit 6 corresponding to the actually flowing lamp current, and sends the output voltage to the PWM control circuit 4. Is done. As a result, the PWM duty ratio increases when the lamp current actually flowing is smaller than the proper lamp current, and conversely, when the lamp current is larger than the proper lamp current, the duty ratio decreases. As a result, a feedback loop is formed to control the amount of power generated in the secondary winding of the transformer T by controlling on / off of the transistor Q1.

  By this feedback loop, control is performed so that the difference between the appropriate lamp current and the detected lamp current becomes zero. That is, the actual lamp current is controlled according to the appropriate lamp current waveform, and the control circuit 11 can control the lighting of the high-pressure discharge lamp 9 with a desired constant power. For example, even when the lamp voltage rises at the end of the life of the high-pressure discharge lamp 9, constant power control is performed on the high-pressure discharge lamp 9 by generating an appropriate lamp current waveform corresponding to the lamp voltage detected by the control circuit 11. Can do.

  The control circuit 11 is configured to generate a projection-like waveform portion having a higher level than the other portions in the proper lamp current waveform at a timing immediately before the polarity of the rectangular proper lamp current waveform is reversed. Thereby, as described in Patent Document 1 described above, the occurrence of flicker can be suppressed.

  In the present embodiment, the control circuit 11 controls the level in a period (hereinafter referred to as a protruding period) in which a protruding waveform portion (hereinafter referred to as a protruding part) is superimposed on the appropriate lamp current waveform and other than the protruding period. The level of a waveform portion (hereinafter referred to as a flat portion) in a period (hereinafter referred to as a flat period) is controlled according to, for example, the degree of lamp deterioration. In this case, the control circuit 11 increases the level of the projection period of the appropriate lamp current waveform and decreases the level of the flat period as the deterioration degree of the lamp progresses, for example, at the end of the lamp life. . That is, the ratio between the level of the protruding portion and the level of the flat portion is increased as the end of the lamp life is reached. In addition, the control circuit 11 sets the level of the projecting period and the level of the flat period so that the power represented by the area surrounded by the appropriate lamp current waveform is constant over the entire lamp life. It comes to control. As the protruding period, for example, a period sufficiently shorter than the cycle of the appropriate lamp current waveform is set.

  In order to obtain the usage time of the high-pressure discharge lamp 9, a clock circuit 12 is provided. The clock circuit 12 measures the time during which the high-pressure discharge lamp 9 is lit and outputs information on the lighting time to the control circuit 11. The control circuit 11 includes a storage unit (not shown), accumulates information on the usage time from the clock circuit 12, and obtains the cumulative lighting time of the high-pressure discharge lamp 9. Then, the control circuit 11 controls the level of the protruding period and the level of the flat period according to the obtained accumulated lighting time. For example, the control circuit 11 may continuously change the level of the protruding period and the level of the flat period according to the accumulated lighting time, and the level of the protruding period according to the accumulated lighting time. And the level of the flat period may be changed stepwise. For example, the control circuit 11 may perform control so that the level of the projecting period is increased and the level of the flat period is decreased when the accumulated lighting time exceeds a predetermined threshold. Furthermore, when the cumulative lighting time exceeds a predetermined threshold, the level of the protruding period and the flat period may be controlled thereafter according to the cumulative lighting time. Even in this case, since the control is performed so that the effective value of the lamp current is constant, not only constant power control is performed within a predetermined lighting period, but also constant power control over the entire lamp life period. Is possible.

  Next, the operation of the embodiment configured as described above will be described with reference to FIGS. FIG. 2 is a graph showing the state of the level change with the cumulative lighting time, with the cumulative lighting time on the horizontal axis and the level on the vertical axis. FIG. 2 (a) shows the change of the lamp voltage. FIG. 2B shows the level change of the flat part of the lamp current, and FIG. 2C shows the level change of the protruding part of the lamp current. 2B and 2C do not represent the absolute amount of level change, but merely show the state of change. FIG. 3 is a waveform diagram showing a proper lamp current waveform. FIG. 3A shows a waveform at the beginning of the lamp life, and FIG. 3B shows a waveform at the end of the lamp life. FIG. 4 is a flowchart showing the operation of the control circuit 11.

  When the power supply voltage is supplied, the DC / DC converter circuit 3 generates a DC voltage corresponding to the control of the PWM control circuit 4 between the positive output terminal and the negative output terminal. The DC / AC inverter circuit 7 is supplied with the output voltage of the DC / DC converter circuit 3 and supplies a rectangular wave to the high-pressure discharge lamp 9 via the high-pressure generation circuit 8. At the time of starting, the high pressure discharge lamp 9 is turned on by generating a high pressure pulse by the high pressure generation circuit 8. After the high pressure discharge lamp 9 is lit, the control circuit 11 and the PWM control circuit 4 perform constant power control on the high pressure discharge lamp 9.

  That is, the output voltage detection circuit 5 detects the lamp voltage, and the output current detection circuit 6 detects the detected lamp current. The control circuit 11 obtains an appropriate lamp current based on the detected lamp voltage, and generates an appropriate lamp current waveform corresponding to the appropriate lamp current. The differential amplifier circuit 14 supplies the PWM control circuit 4 with a control signal based on the difference between the appropriate lamp current waveform and the detected lamp current. Thus, the PWM control circuit 4 changes the output voltage (lamp voltage) of the DC / DC converter circuit 3 so that the difference between the detected lamp current and the appropriate lamp current becomes zero.

  In this case, the control circuit 11 and the PWM control circuit 4 supply power sufficiently larger than the rated power immediately after starting, and perform control so as to decrease to the rated power as the luminous efficiency of the lamp increases. You may go.

  The control circuit 11 generates an appropriate lamp current waveform having a protruding portion having a level higher than the level of the flat period in the protruding period. It is assumed that the life of the high-pressure discharge lamp 9 is in the initial stage. FIG. 2A shows the change in lamp voltage over the entire life of the high-pressure discharge lamp 9. The high-pressure discharge lamp 9 tends to increase the lamp voltage as the end of the lamp life is reached. In the constant power control in the prior art such as Patent Document 1, the lamp current is simply reduced as the lamp voltage increases. In contrast, in the present embodiment, constant power control is performed while increasing the ratio of the level of the projecting period and the level of the flat period in accordance with the cumulative lighting time of the lamp.

  The flow of FIG. 4 determines that the end of the lamp life is reached by determining that the cumulative lighting time has exceeded a predetermined threshold, and before and after this determination, the ratio between the level of the projecting period and the level of the flat period An example in which is changed in two stages is shown.

  The control circuit 11 acquires the cumulative lighting time in step S1 of FIG. At the beginning of the lamp life, the result of accumulating the lighting time from the clock circuit 12 is a relatively small value. In this case, the cumulative lighting time has not reached the threshold value, and the control circuit 11 shifts the processing from step S2 in FIG. 4 to step S3 to calculate an appropriate lamp current. That is, the control circuit 11 obtains IF1 as the level of the flat portion and obtains IP1 as the level of the protruding portion. The ratio IP1 / IF1 between the level of the protruding portion and the level of the flat portion is a relatively small value.

  The control circuit 11 operates a timer (not shown) (step S5) and outputs a flat portion (step S6). That is, the control circuit 11 outputs the output of the level IF1 only during the flat period as determined in step S7. If the control circuit 11 determines that the flat period has elapsed according to the count value of the timer, the control circuit 11 proceeds from step S7 to step S8 and restarts the timer. Next, the control circuit 11 outputs the protruding portion (step S9), and determines whether or not the protruding period has elapsed by the determination in step S10. When the control circuit 11 determines that the protruding period has elapsed according to the count value of the timer, the process proceeds from step S10 to step S11, the polarity of the output is inverted, and the process is repeated from step S1. Thereby, for example, an appropriate lamp current waveform shown in FIG. For example, the flat period is set to 1.5 ms, and the projecting period is set to 50 μs.

  Next, it is assumed that the use period of the high-pressure discharge lamp 9 is sufficiently long and the cumulative lighting time exceeds the threshold value. In this case, the control circuit 11 shifts the process from step S2 to step S4, and calculates an appropriate lamp current. In this case, the control circuit 11 increases the level IP2 of the protruding portion to be larger than IP1, and also sets the ratio IP2 / IF2 between the level of the protruding portion and the level of the flat portion so that IP1 / IF1 also increases. Further, the control circuit 11 determines the level IP2 of the protruding portion and the level IF2 of the flat portion so as not to change the effective value of the lamp current according to the area of the shaded portion in FIG.

  Next, the control circuit 11 performs the processing after step S5 using the obtained levels IP2 and IF2. In this way, an appropriate lamp current waveform shown in FIG. 3B is obtained from the control circuit 11, for example. As is clear from the comparison between FIGS. 3A and 3B, when the cumulative lighting time exceeds the threshold at the end of the lamp life, the appropriate lamp current waveform is as compared with the case of the initial lamp life. The level of the flat portion is lowered and the level of the protruding portion is increased.

  In the proper lamp current waveform shown in FIG. 3B, the level of the protruding period is sufficiently larger than the level of the flat period. Therefore, a sufficient lamp current can be passed even at the end of the life of the high-pressure discharge lamp 9, and the occurrence of flicker can be suppressed.

  On the other hand, in the proper lamp current waveform shown in FIG. 3A, the level of the protruding period is relatively smaller than the level of the flat period as compared to the appropriate lamp current waveform shown in FIG. In the initial stage of the lamp, a small lamp current is superimposed, so that the lamp electrode temperature is not unnecessarily increased, and the lifetime can be prevented from being shortened. In addition, it is possible to prevent the occurrence of an unfavorable problem from the viewpoint of the global environment, in which circuit efficiency is reduced due to superposition of an excessive lamp current, heat generation is increased, and current consumption is increased. As described above, the peak value of the lamp current is relatively low, and the stress of the circuit can be sufficiently suppressed, and the decrease in efficiency is suppressed, the heat generation is suppressed, and the increase in power consumption can be prevented. it can.

  Further, the hatched portion in FIG. 3A and the hatched portion in FIG. 3B have the same area, so that the high-pressure discharge lamp 9 can be driven with a constant power throughout the life of the lamp. It becomes possible.

  FIG. 2 shows an example in which the flat portion and the protruding portion of the appropriate lamp current waveform are continuously changed according to the cumulative lighting time. That is, the control circuit 11 increases the ratio between the level of the projecting period and the level of the flat period as the cumulative lighting time of the high-pressure discharge lamp 9 becomes longer. Accordingly, high-efficiency lighting control can be performed while suppressing flicker at the beginning of the lifetime, and lighting control can be performed while reliably suppressing flicker at the end of the lifetime.

  As described above, in the present embodiment, the ratio between the level of the protrusion portion added to the protrusion period immediately before the polarity inversion of the lamp current and the level of the flat period is changed according to the cumulative lighting time of the high pressure discharge lamp. Thus, high-efficiency lighting control is possible over the entire lighting period while suppressing flicker.

  That is, at the initial stage of the lamp life, the level of the protrusion is relatively low, and a small lamp current is superimposed, so that the lamp electrode temperature is not unnecessarily increased and the life is prevented from being shortened. be able to. In addition, it is possible to prevent the occurrence of an unfavorable problem from the viewpoint of the global environment, in which circuit efficiency is reduced due to superposition of an excessive lamp current, heat generation is increased, and current consumption is increased.

  As the end of the lamp life is approached, the level of the protrusion is increased in order to suppress flicker, unnecessary current is not superimposed at the beginning of the lamp life, and stress applied to the circuit is suppressed, and the lamp It is possible to prevent the life from being shortened. Further, when the cumulative lighting time of the lamp is increased, the level of the protruding portion is raised and the level of the flat portion is lowered, and an increase in power can be suppressed while reducing flicker, thereby prolonging the lamp life. it can.

  In addition, although the example which incorporates the timepiece circuit 12 was demonstrated in FIG. 1, you may make it obtain the information of the accumulated lighting time of a high pressure discharge lamp by taking in timepiece information from the outside. Further, when the control circuit 11 is constituted by a microcomputer, a built-in timer may be used as a clock circuit. In addition, the storage unit (not shown) may be installed in the liquid crystal projector main body, for example, and only a cumulative lighting time information may be input to the lighting device.

  Further, the example in which the control circuit 11 controls the appropriate lamp current waveform based on the cumulative lighting time of the high-pressure discharge lamp 9 has been described. However, the control circuit 11 controls the appropriate lamp current waveform based on the number of blinks of the high-pressure discharge lamp 9. May be controlled.

  In the above embodiment, the clock circuit is employed to measure the lamp lighting time. However, the output of the output voltage detection circuit can also be used. As described above, the lamp voltage increases as the lamp lighting time increases. For this reason, the lamp lighting time can be estimated by detecting the lamp voltage. That is, the control circuit 11 acquires the output of the output voltage detection circuit 5 at a predetermined timing. This acquired output value is approximately proportional to the voltage across the lamp. In addition, it is possible to estimate the accumulated lighting time of the lamp by storing the actual value of the initial lamp as a constant in advance and comparing this value with the acquired value.

  In addition, a non-volatile memory is mounted on the control circuit 11, and the initial value of the output voltage detection circuit 5 is stored as an initial lamp voltage at the time of factory shipment, for example, and this voltage and the output voltage detection circuit measured during lighting are stored. By comparing with the output of 5, it is possible to estimate the cumulative lighting time with higher accuracy. Thereby, the cumulative lighting time of the lamp can be estimated.

It is a circuit diagram which shows the lighting device of the high pressure discharge lamp which concerns on the 1st Embodiment of this invention. It is a graph which shows the mode of change accompanying lighting time, with lighting time on the horizontal axis and level on the vertical axis. It is a wave form diagram which shows a proper lamp current waveform. 3 is a flowchart showing the operation of the control circuit 11.

Explanation of symbols

    DESCRIPTION OF SYMBOLS 3 ... DC / DC converter circuit, 4 ... PWM control circuit, 5 ... Output voltage detection circuit, 6 ... Output current detection circuit, 7 ... DC / AC inverter circuit, 9 ... High pressure discharge lamp, 11 ... Control circuit, 12 ... Clock Circuit, 14... Differential amplifier circuit.

Claims (4)

A DC / DC converter circuit for stepping up or stepping down a DC voltage;
A DC / AC inverter circuit for converting the output voltage of the DC / DC converter circuit into a low-frequency alternating current;
Control means for controlling the DC / DC converter circuit and the DC / AC inverter circuit,
The control means controls the output amount of the DC / DC converter circuit and the operation timing of the DC / AC inverter circuit,
Immediately before the polarity inversion of the low frequency alternating current, an output amount of the DC / DC converter circuit is increased to generate an output current having a substantially rectangular wave shape having a protruding portion, and the level of the flat portion of the low frequency is increased. A lighting device for a high pressure discharge lamp, wherein the level of the protruding portion is changed according to the degree of deterioration of the high pressure discharge lamp.   The lighting device for a high-pressure discharge lamp according to claim 1, wherein the control means determines a degree of deterioration of the high-pressure discharge lamp based on a cumulative lighting time of the high-pressure discharge lamp.   The control means includes an output voltage detection circuit that measures an output voltage of the DC / DC converter circuit corresponding to a tube voltage of the high pressure discharge lamp, and the deterioration of the high pressure discharge lamp is measured by measuring the output voltage. The lighting device for a high pressure discharge lamp according to claim 1, wherein the degree is determined.   2. The lighting device for a high pressure discharge lamp according to claim 1, wherein the control means determines the degree of deterioration of the high pressure discharge lamp based on the number of blinks of the high pressure discharge lamp.

Images