JP2011103310A5 - - Google Patents

Description

  FIG. 3 is a block diagram illustrating a configuration of the discharge lamp driving device 200. The discharge lamp driving device 200 includes a drive control unit 210 and a lighting circuit 220. The drive control unit 210 is a computer including a CPU 610, a ROM 620, a RAM 630, a timer 640, an output port 650 that outputs a control signal to the lighting circuit 220, and an input port 660 that acquires a signal from the lighting circuit 220. It is configured. The CPU 610 of the drive control unit 210 executes a program stored in the ROM 620 based on output signals from the timer 640 and the input port 660. Thereby, the CPU 610 realizes functions as the drive frequency modulation unit 612 and the modulation pattern setting unit 614. The functions of the drive frequency modulation unit 612 and the modulation pattern setting unit 614 realized by the CPU 610 will be described later.

The lighting circuit 220 includes an inverter 222 that generates an AC pulse current. The lighting circuit 220 controls the inverter 222 based on a control signal supplied from the drive control unit 210 via the output port 650. Specifically, the lighting circuit 220 causes the inverter 222 to generate an AC pulse current corresponding to a power supply condition (for example, the frequency or pulse waveform of the AC pulse current) specified by the control signal. As an alternating current supply unit , the inverter 222 generates a constant power (for example, 200 W) alternating current pulse current supplied to the discharge lamp 500 according to the power supply conditions specified by the lighting circuit 220, and the generated alternating current pulse current is discharged to the discharge lamp. 500.

  The lighting circuit 220 is also configured to detect a voltage (lamp voltage) between the electrodes 532 and 542 when a constant power AC pulse current is supplied to the discharge lamp 500. In general, when the discharge lamp 500 is turned on, the electrodes 532 and 542 are consumed and the tips thereof are flattened. When the tips of the electrodes 532 and 542 are flattened, the distance between the electrodes 532 and 542 increases. Therefore, when the discharge lamp 500 deteriorates and the electrode 532 is consumed, the voltage (lamp voltage) between the electrodes 532 and 542 required for constant power driving of the discharge lamp 500 increases. Therefore, the deterioration state of the discharge lamp 500 can be detected by detecting the lamp voltage. When the electrodes 532 and 542 are consumed and the tip is flattened, the arc is generated with the random position of the flattened portion as a base point. Therefore, when the tips of the electrodes 532 and 542 are flattened, a so-called arc jump occurs in which the arc generation position moves.

The drive frequency modulation unit 612 of the drive control unit 210 sets the frequency (drive frequency) fd of the AC pulse current output from the lighting circuit 220 according to the modulation pattern set by the modulation pattern setting unit 614. As described above, the drive frequency of the discharge lamp 500 is switched between the drive frequency modulation unit 612 and the modulation pattern setting unit 614. Therefore, the drive frequency modulation section 612 and the modulation pattern setting section 614 together may also be referred to as a "frequency switching section." The modulation pattern setting unit 614 changes the modulation pattern to be set according to the lamp voltage, as will be described later.

  When the lamp voltage Vp decreases, the modulation range of the drive frequency fd is narrowed to suppress the growth of the protrusions 538 and 548, thereby suppressing the increase in the lamp current Ip due to the further decrease in the lamp voltage Vp. Therefore, blackening inside the discharge lamp 500 due to the increase in the lamp current Ip can be suppressed. Further, by suppressing the increase in the lamp current Ip, it is possible to reduce the thermal load of the ballast circuit constituting the inverter 220. In the modulation pattern shown in FIG. 8 as well, protrusions caused by continuous low-frequency driving can be obtained by monotonously changing the driving frequency fd in the intermediate frequency period between the lowest frequency period Tl2 and the highest frequency period Th2. Disappearance and generation of minute protrusions by continuously driving at high frequency can be suppressed, and the formed protrusions can be maintained in a preferable shape.

By suppressing the growth of the protrusions 538 and 548 using the modulation pattern shown in FIG. 8, the lamp voltage Vp increases with the use of the discharge lamp 500. When the lamp voltage Vp becomes equal to or higher than a predetermined lower threshold ( 70 V in this embodiment ) , the modulation pattern shown in FIG. 7 is set. Thereby, the growth of the protrusions 538 and 548 is promoted, and the increase in the lamp voltage Vp due to the consumption of the electrodes 532 and 542 is suppressed.

  Note that non-monotonically changing means that when changing the frequency from the frequency of the maximum frequency period (highest frequency) to the frequency of the lowest frequency period (lowest frequency), or from the lowest frequency to the highest frequency, Says to change in the opposite direction. For example, the drive frequency fd can be changed non-monotonously by changing the order of two or more intermediate frequency periods when the drive frequency fd is changed stepwise in one direction. Non-monotonic is a state where the sum of changes in a specific direction when changing from the highest frequency to the lowest frequency or from the lowest frequency to the highest frequency is larger than the difference between the highest frequency and the lowest frequency. Can also be expressed. The modulation pattern for changing the drive frequency fd non-monotonically is a basic waveform (triangular wave in the example of FIG. 7) that connects the temporal center points of each period defining the modulation pattern with a higher frequency than the basic waveform. It is good also as what prescribes | regulates by the waveform which superimposed the waveform. In this case, the superimposed high-frequency waveform may be a noise waveform such as white noise or blue noise. Also, the modulation pattern may be defined by a waveform having 1 / f fluctuation characteristics.

FIG. 10 shows a modulation pattern that is set when the lamp voltage Vp further increases and becomes equal to or higher than a predetermined upper threshold (the first upper threshold in the present embodiment is 90 V ) . In the modulation pattern shown in FIG. 10, the modulation cycle Tm4 (11 seconds) is divided into 11 periods each having a length of 1 second. In the modulation pattern of FIG. 10, higher and lower frequencies than a predetermined frequency (150 Hz in the example of FIG. 10) are alternately set in each of the first half and the second half of the modulation period Tm4. As a result, like the modulation pattern of FIG. 9, the drive frequency fd changes non-monotonously in an intermediate frequency period between the lowest frequency period Tl4 and the highest frequency period Th4.

  In the modulation pattern shown in FIG. 10, the change amount of the drive frequency fd is larger than that of the modulation pattern shown in FIG. Therefore, the extension of the protrusion 538b by high frequency driving is further promoted in a state where the meltability of the protrusion 538a is higher. Therefore, the growth of protrusions is further promoted as compared with the case where the modulation pattern of FIG. 9 is set. Also, by providing an intermediate frequency period, it is possible to suppress a state in which the amount of change in the drive frequency fd is large, and to suppress the progress of deterioration such as blackening that may occur when the change in the drive frequency fd is large. can do. Further, by providing the intermediate frequency period, the maximum frequency period Th4 and the minimum frequency period Tl4 in the modulation period Tm4 are shortened, thereby suppressing the generation of minute protrusions formed during high frequency driving and low frequency driving. It is possible to suppress the flicker that is likely to occur at the time.

FIG. 11 shows a modulation pattern that is set when the lamp voltage Vp further increases and becomes equal to or higher than a predetermined upper threshold (the second upper threshold in the present embodiment is 110 V ) . In the modulation pattern of FIG. 11, the modulation period Tm5 (15 seconds) is divided into 15 periods of 1 second in length. The modulation pattern of FIG. 11 is obtained by adding a lower frequency minimum frequency period T15, a higher frequency maximum frequency period Th5, and two intermediate frequency periods before and after these two periods to the modulation pattern of FIG. As a result, the modulation range of the drive frequency fd is expanded. Also in the modulation pattern of FIG. 11, higher and lower frequencies than a predetermined frequency (150 Hz in the example of FIG. 11) are alternately set in each of the first half and the second half of the modulation cycle Tm5. Thereby, similarly to the modulation pattern of FIG. 10, the drive frequency fd changes non-monotonously in the intermediate frequency period between the lowest frequency period T15 and the highest frequency period Th5.

  Thus, in the modulation pattern shown in FIG. 11, the amount of change in the drive frequency fd is larger than that in the modulation pattern shown in FIG. Therefore, the growth of the protrusion is further promoted as compared with the case where the modulation pattern of FIG. 10 is set. Further, similarly to the modulation pattern of FIG. 10, by providing an intermediate frequency period, the progress of deterioration such as blackening is suppressed, the generation of minute protrusions formed during high frequency driving, and the low frequency driving. It is possible to suppress flicker that is likely to occur.

Thus, according to the present embodiment, the modulation pattern is switched according to the lamp voltage Vp. When the lamp voltage Vp becomes equal to or higher than a predetermined reference value (80 V in this embodiment), the drive frequency fd is changed non-monotonously in an intermediate frequency period between the highest frequency period and the lowest frequency period. As a result, the growth of the protrusions 538 and 548 is promoted. Therefore, the increase in the lamp voltage Vp accompanying the consumption of the electrodes 532 and 542 can be suppressed, and the discharge lamp can be used for a longer period.

Claims (4)

A discharge lamp driving device comprising:
An alternating current supply unit for supplying an alternating current between two electrodes of the discharge lamp;
A frequency switching unit that periodically switches the frequency of the alternating current supplied by the alternating current supply unit;
With
The frequency switching unit
Switching the frequency by making the frequency different from each other in a plurality of periods in the switching cycle,
When a lamp voltage, which is a voltage between both electrodes when supplying predetermined power between the two electrodes, exceeds a predetermined reference value, the highest frequency period in which the frequency is highest in the switching period, Changing the frequency non-monotonically between the lowest frequency period in which the frequency is lowest within a switching period ;
The frequency change range when the lamp voltage falls below a predetermined lower threshold value lower than the reference value is made narrower than the frequency change range when the lamp voltage exceeds the lower threshold value. Electric light drive device. The discharge lamp driving device according to claim 1 ,
The frequency switching unit has an amount of change of the frequency when the lamp voltage exceeds a predetermined upper threshold value higher than the reference value, and an amount of change of the frequency when the lamp voltage falls below the upper threshold value. Increase the discharge lamp drive device. A discharge lamp driving device according to claim 1 or 2 ,
The frequency of the highest frequency period when the lamp voltage falls below a predetermined lower threshold that is lower than the reference value is lower than the frequency of the highest frequency period when the lamp voltage exceeds the lower threshold. Yes Discharge lamp drive unit. A discharge lamp driving device according to any one of claims 1 to 3 ,
The discharge lamp driving device, wherein the frequency of the lowest frequency period when the lamp voltage falls below the lower threshold is higher than the frequency of the lowest frequency period when the lamp voltage exceeds the lower threshold .