JP2013247052A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device capable of suppressing abrasion of a lamp electrode by preventing temporary discharge from repeatedly occurring, and efficiently shortening a start and restart time.SOLUTION: An inverter for supplying a rectangular wave AC voltage to a lamp, detection means of a supply voltage of the inverter, and control means for controlling voltage supply of the inverter in accordance with a voltage value and a voltage waveform are provided. The control means has determination means for determining distortion of the voltage waveform, determination means for detecting the existence/absence of a non-load voltage based on the voltage value after determining the distortion, and a counter. The counter executes normal counting when at least a non-load voltage is detected. When the non-load voltage is detected and a distortion in a waveform is detected, the counter executes both normal counting and high-speed counting. Unless at least the non-load voltage is detected, the counter does not execute counting. When the number of the total counting reaches a prescribed value, the supply of a rectangular wave AC voltage is stopped.

Description

  The present invention relates to a discharge lamp lighting device for an HID lamp (high-intensity discharge lamp), and more particularly, to a function capable of reducing the starting time and suppressing wear of a lamp electrode at the time of starting.

  The discharge lamp lighting device generates a high-voltage pulse voltage for starting discharge, that is, for causing dielectric breakdown between lamp electrodes at the time of starting and restarting. Moreover, after lighting, it plays the role which suppresses conduction | electrical_connection of the excess current accompanying the rapid fall of the voltage between lamp electrodes. Furthermore, recently, high-frequency lighting and rectangular wave lighting have been widely used to prevent flickering of the discharge lamp. In order to realize these lighting systems, so-called electronic ballasts equipped with PWM step-down circuits and bridge circuits formed by semiconductor switching elements are widely used, supplying rectangular wave AC voltage alternating with a desired cycle to the lamp It is supposed to be.

  The lighting control mode and restart mode of the conventional lighting device will be briefly described. The discharge lamp lighting device is assumed to be a typical one including a rectifier circuit, a power factor correction circuit, a PWM step-down circuit, a bridge circuit, and a starter circuit. A current-controlled DC voltage is output from the PWM step-down circuit and converted into a rectangular wave voltage by a bridge circuit. In the lighting control mode, the output of the PWM step-down circuit becomes a lighting voltage, is converted into a rectangular wave AC voltage having a predetermined frequency (for example, several tens to several hundreds Hz) by the bridge circuit, and is supplied to the lamp as the lighting voltage. In the lighting control mode, the supply of the rectangular wave AC voltage is always on.

When the lamp goes out during lighting, the discharge lamp lighting device shifts to a restart mode and starts applying a high-pressure pulse for restart. In the restart mode, as shown in the supply pattern of FIG. 6A, the output of the PWM step-down circuit is converted into an intermittent rectangular wave AC voltage by the bridge circuit and then supplied to the lamp. That is, the time for applying the rectangular wave alternating current (supply time T ₁ : also called intermittent on-time) and the time for applying no voltage to the lamp (rest time T ₂ : also called intermittent off-time) are alternately repeated. FIG. 5B also shows an example of the lamp voltage waveform at the supply time T ₁ . Among feed time T ₁ as the voltage waveform, the output of PWM buck circuit becomes no-load voltage. Since the no-load voltage becomes higher than the lighting voltage, a high voltage pulse is induced in the starter circuit. As long as no discharge occurs between the electrodes due to the high-voltage pulse, a no-load voltage alternating at several 10 to several 100 Hz is always supplied. During the supply time T ₁ , a high voltage pulse voltage (also simply referred to as a high voltage pulse) superimposed on each of the continuously supplied rectangular waves is applied to the lamp one after another. In FIG. 6, the waveform of the high voltage pulse superimposed on the rectangular wave voltage is omitted. Following the supply time T ₁ , a pause time T ₂ is initiated when no voltage is applied to the lamp. Thus, the lamp supply voltage and its supply pattern change due to the transition from the lighting control mode to the restart mode, but the frequency of the rectangular wave AC voltage at the supply time T ₁ in the restart mode is the rectangle of the lighting control mode. It is the same as the frequency of wave alternating current (several 10 to several 100 Hz).

In general, restart (hot restart) in a state where the temperature inside the arc tube of the lamp is still high is likely to fail. This is because no discharge occurs even when a high-pressure pulse is repeatedly applied between the electrodes of the arc tube. In order to reliably restart, it is necessary to wait until the temperature inside the arc tube decreases. That is, when no discharge occurs in the supply time T _1, only rectangular wave of the no-load voltage is repeated. Therefore, conventionally, as shown in FIG. 6A, a pause time T ₂ is provided in the restart mode, and a rectangular wave alternating current of no-load voltage is intermittently applied so that the temperature inside the arc tube is increased. It encouraged a drop and was able to restart faster.

The technical content related to this is disclosed in Patent Document 1, for example. Similarly lighting apparatus of Patent Document 1, applying a rectangular wave AC voltage to the lamp to the supply time T _1. Each time the rectangular wave AC voltage is inverted, a high voltage pulse voltage is generated by the starter circuit, and the high voltage pulse superimposed on the rectangular wave AC voltage is repeatedly applied to the lamp. In addition, after the supply time T ₁ of the rectangular wave AC voltage, the rest time T ₂ is provided in common. In any of the methods, the intermittent rectangular wave AC voltage output by the supply time T ₁ and the pause time T _{2 is} continued for a predetermined period, and when lighting is reached, the lighting control mode is entered.

When the inside of the arc tube is ready for restarting, as shown in FIG. 6 (C), transition to arc discharge (also referred to as lighting discharge) within the supply time T ₁ , and arc discharge is repeatedly generated. Lights up. FIG. 3C shows the transition of the lamp voltage waveform when starting normally. The arc discharge generated by the fourth high-pressure pulse application from the start during the supply time T ₁ then repeatedly occurs, and the lighting by arc discharge is maintained. Like this lamp voltage waveform, the lamp voltage at the time of transition to arc discharge once decreases due to dielectric breakdown between the electrodes, and then gradually recovers to the lighting voltage. If the transition to arc discharge can be confirmed by grasping such a change in the lamp voltage, the control circuit continues to supply the rectangular wave AC voltage and shifts to the lighting control mode. One cycle of the alternating voltage after the transition to arc discharge is the same as one cycle of the output voltage of the bridge circuit. As a result of stable re-ignition between the electrodes, the lamp voltage is A simple waveform is repeatedly shown.

Japanese Patent Laying-Open No. 2005-108800 (FIGS. 4 and 5)

However, when the lamp voltage waveform at the rectangular wave alternating current supply time T ₁ is examined, there is rarely a case where a waveform of a no-load voltage alternately alternating as shown in FIG. In reality, a temporary discharge (arc discharge or glow discharge) phenomenon occurs within the supply time T _{1 due} to the continuous application of high-pressure pulses. Since the temporary discharge phenomenon does not lead to continuous arc discharge, the lamp voltage waveform has an irregular shape. A typical example of such a voltage waveform is shown in FIG.

For example, as in the periods a and b shown in FIG. 6D, a temporary arc discharge may occur once or several times, but the arc discharge is not repeated any more. Then, the voltage waveform that has once become a low voltage returns to a high no-load voltage. This case can occur regardless of the direction of the voltage load to be reversed.
In addition, as shown in period c of FIG. 6, after a temporary arc discharge occurs, the glow discharge changes to a smaller current than the arc discharge, and a temporary glow discharge may occur only once or several times. is there. The lamp voltage during the glow discharge is a voltage approximately between the no-load voltage and the arc discharge voltage. When the glow discharge stops, the lamp voltage returns to the high no-load voltage again.
In addition, as in the period d in the figure, glow discharge may temporarily occur without going through arc discharge. Also in this case, when the glow discharge stops, the lamp voltage returns from an intermediate level to a high no-load voltage.
Here, temporary discharge (arc discharge, glow discharge) means that the discharge occurs only once or several times.

  As described above, when the normal arc discharge is not reached and the glow discharge is temporarily generated (periods c and d), the burden on the electrode in the arc tube is increased. Glow discharge tends to wear electrodes due to its nature. Therefore, if the lamp current continues to flow due to frequent occurrence of temporary glow discharge despite the fact that normal arc discharge has not been reached, the electrode will be extremely worn. This phenomenon is often observed in restart (hot restart) in a state where the temperature inside the arc tube is high, but such a phenomenon can also occur during normal startup.

As described above, the startability is improved by intermittently applying the continuous high voltage pulse during the supply time T ₁ every pause time T ₂ , but the supply pattern shown in FIG. As described above, there is a possibility that the application of the no-load voltage is repeated many times every supply time T ₁ until the continuous arc discharge is maintained. Moreover, since in its supply time T ₁ is a temporary glow discharge would occur frequently, occurs more than necessary wear of the discharge tube of the electrodes.

Furthermore, repeated discharge (periods a to d) during the supply time T ₁ while the temperature in the arc tube is still high prevents a smooth decrease in the temperature in the arc tube. Therefore, the time required for starting is not shortened as expected.

  The present invention has been made in view of the above-described prior art, and can prevent the glow discharge from being repeatedly generated at the time of starting the lamp, thereby suppressing the wear of the lamp electrode, and the light emission by the temporary repetition of the discharge. It is an object of the present invention to provide a discharge lamp lighting device that can suppress the rise in tube temperature as much as possible and efficiently shorten the starting time to obtain a good starting property.

The inventor monitors the output waveform of the supply voltage or the supply current to the discharge lamp during the output of the intermittent rectangular wave AC voltage until the start of the discharge lamp, that is, in the start (restart) mode. A control circuit is provided to determine whether the waveform has “distortion”. If the output waveform is distorted, it is determined whether the discharge lamp is in the no-load state at that time, and the supply time T ₁ is completed early on the condition that the no-load state is detected. As a result, the above-mentioned problems were solved and the present invention was completed.

That is, in order to achieve the object, the discharge lamp lighting device of the present invention is
An inverter that converts the input DC voltage into a rectangular wave AC voltage and supplies it to the discharge lamp;
Detecting means for detecting a supply voltage from the inverter;
Control means for controlling the voltage supply of the inverter in accordance with a detection voltage value of the detection means and a voltage waveform obtained from the detection voltage value.
The control means includes
Distortion determining means for determining the presence or absence of distortion of the voltage waveform obtained from the detected voltage value;
After the distortion determination means determines the presence or absence of distortion, no-load voltage determination means for determining whether or not the discharge lamp is discharged by detecting the presence or absence of no-load voltage based on the detected voltage value;
And a counter for measuring the supply time (T ₁ ) of the inverter.
The counter executes a normal count at least when the no-load voltage discriminating means detects no-load voltage regardless of the distortion of the voltage waveform.
Further, when the distortion determination unit detects a distortion of the voltage waveform and the no-load voltage determination unit detects a no-load voltage, the counter executes both a normal count and a high-speed count.
Alternatively, the counter does not execute any counting at least when the no-load voltage determining means does not detect the no-load voltage regardless of the distortion of the voltage waveform.
Then, when the total count of the counter reaches a predetermined value, the measurement of the supply time (T ₁ ) is completed, and the supply of the rectangular wave AC voltage to the discharge lamp is stopped.

In the present invention, the distortion determination means uses a voltage lower limit value determined to be a no-load voltage as a reference value (V ₀ ), and when the detected voltage value is less than the reference value (V ₀ ). It is preferable to determine that the voltage waveform has distortion. If such a criterion is used, both the case where the voltage between the electrodes of the discharge lamp is a voltage at an intermediate level corresponding to glow discharge and the case where the voltage is a short circuit voltage corresponding to arc discharge, Will be detected. In the present invention, a voltage range that is larger than the short-circuit voltage during arc discharge and smaller than the no-load voltage is referred to as an intermediate level voltage.

In the present invention, the control unit further includes a counter for downtime count is to count the pause time (T ₂₎ by reaches a value predetermined, timed pause time (T ₂₎ has been completed Sometimes it is preferable to restart the supply of the rectangular wave AC voltage to the discharge lamp. With such a configuration, it is possible to intermittently supply the rectangular wave AC voltage at the time of starting and restarting.

  In the present invention, it is preferable that the detection means detects a DC voltage before AC conversion by the inverter. Since the detection target is not an AC voltage but a DC voltage, the detection voltage value can be easily processed, and waveform distortion and no-load voltage can be detected instantaneously and accurately.

The discharge lamp lighting device of the present invention includes an inverter that converts an input DC voltage into a rectangular wave AC voltage and supplies the square wave AC voltage to the discharge lamp;
Detecting means for detecting a supply current from the inverter;
Control means for controlling the voltage supply of the inverter according to the detected current value of the detecting means and the current waveform obtained from the detected current value.
The control means includes
Distortion determining means for determining the presence or absence of distortion of the current waveform obtained from the detected current value;
A supply current determination means for determining whether the discharge lamp is discharged by detecting the presence or absence of a supply current based on a detected current value after the distortion determination means determines the presence or absence of distortion;
And a counter for measuring the supply time (T ₁ ) of the inverter.
Then, at least when the supply current discriminating means does not detect the supply current regardless of the distortion of the current waveform, the counter executes a normal count.
Further, when the distortion determination unit detects a distortion of the current waveform and the supply current determination unit does not detect the supply current, the counter executes both a normal count and a high-speed count.
Alternatively, the counter does not execute any count at least when the supply current discriminating means detects the supply current regardless of the distortion of the current waveform.
Then, when the total count of the counter reaches a predetermined value, the measurement of the supply time (T ₁ ) is completed, and the supply of the rectangular wave AC voltage to the discharge lamp is stopped.

As described above, the discharge lamp lighting device according to the present invention includes a distortion determination unit, a no-load voltage determination unit, and a control unit having a counter, and performs the following two-step operation. That is, in the first step, the control means looks at the output waveform of the detection means and determines whether or not the output waveform is distorted. In the second step, when the control means determines that there is distortion, after the determination, the detection voltage is again checked to determine whether or not there is a no-load voltage. When it is determined that there is distortion and there is no load voltage, the counter is caused to execute both normal count and high-speed count, and the inverter supply time (T ₁ ) is counted quickly. As a result, if a temporary discharge phenomenon (temporary arc discharge or glow discharge) occurs when supplying a rectangular wave alternating current of no-load voltage to the discharge lamp, the supply time will be counted faster. The voltage supply to the discharge lamp by the inverter can be stopped early.

  For example, the case where the counter used in the present invention is set as follows will be described. When the total count of the counter reaches the threshold value, the supply time is counted and this threshold value is set to 30. It is assumed that the count number increases by 1 when the normal count is executed, and the count number increases by 1 even when the high-speed count is executed. Assume that the determination of the presence or absence of waveform distortion or no-load voltage is executed once per second. When there is no waveform distortion, the counter executes only a normal count, so the count increases by 1 every second and reaches the threshold value in 30 seconds. On the other hand, if the waveform continues to be distorted, the counter executes both a normal count and a high-speed count, so the count increases by (1 + 1 =) 2 every second, and the threshold value reaches 15 seconds. Will be reached. Actually, distortion occurs or does not repeat until the threshold value is reached, so that the count number per second becomes 1 or 2 each time. That is, the time until the total count reaches the threshold is determined according to the waveform distortion occurrence rate.

Further, if the increment of the number of counts when high-speed count is executed is set to 2, the count speed in a state where there is waveform distortion becomes three times the normal time, and the supply time (T ₁ ), that is, the intermittent on-time Can be reduced to 10 seconds, which is one third of normal time. Furthermore, by setting the increment at the time of high-speed counting to 3, the count speed is four times that of the normal time, and the intermittent on-time can be shortened to 7.5 seconds.

  Thus, according to the present invention, for example, various lamp voltage waveforms as described with reference to FIG. 6D are determined as “distortion”, and when such a voltage waveform is generated, The voltage supply to the discharge lamp stops at an earlier stage than before. Accordingly, when starting and restarting the discharge lamp, it is possible to prevent the glow discharge from being repeatedly generated, thereby suppressing the wear of the lamp electrode, and to increase the arc tube temperature as much as possible by temporarily repeating the discharge. The start time can be efficiently shortened by suppressing. As a result, it is possible to provide a discharge lamp lighting device that can provide both protection of the lamp electrode and good startability.

In the present invention, not only the waveform of the supply voltage to the discharge lamp but also the time measurement speed of the supply time may be changed based on the distortion of the current waveform of the supply current. That is, the detection means may detect a supply current from the inverter. In this case, the distortion determination unit determines whether or not the current waveform is distorted, and uses a supply current determination unit that determines whether or not the discharge lamp is discharged based on the presence or absence of the supply current, instead of the no-load voltage determination unit. . When the control means determines that there is distortion and no supply current, the control unit causes both the normal count and the high-speed count to be executed, and the inverter supply time (T ₁ ) is counted faster. As a result, the same effect as that based on the distortion of the waveform of the supply voltage described above can be obtained.

It is a figure which shows the circuit schematic diagram of the discharge lamp lighting device of this invention. It is a figure for demonstrating the mechanism which changes the time measuring speed of supply time according to the distortion of a waveform. It is a control flowchart of the said discharge lamp lighting device. The figure for demonstrating the processing route according to a typical voltage waveform based on FIG. The time chart and voltage waveform figure for demonstrating the effect of this invention. It is the time chart which shows the supply pattern of the rectangular wave alternating voltage in the conventional discharge lamp lighting device, and the graph which shows the typical example of a lamp voltage waveform.

Hereinafter, an embodiment of a discharge lamp lighting device according to the present invention will be described with reference to the drawings.
FIG. 1 is a circuit schematic diagram showing an embodiment of a discharge lamp lighting device 10. The main constituent circuits of the discharge lamp lighting device (also simply referred to as a ballast) 10 are a rectifier circuit 14, a power factor correction circuit 16, a PWM step-down circuit 18, a bridge circuit 20, and a starter circuit 46. Among these, the PWM high voltage circuit 18 and the bridge circuit 20 are collectively referred to as an inverter of the present invention.

  The rectifier circuit 14 rectifies the AC current of the commercial AC power supply 12 and converts it to DC. The power factor correction circuit 16 is also called an active filter, and sufficiently boosts the low-voltage direct current output from the rectifier circuit 14 to control the output direct-current voltage to be constant, and reduces harmonic components of the input current. The PWM step-down circuit 18 performs current control by pulse width modulation of the switching element 28. The bridge circuit 20 converts the DC lighting power output from the PWM step-down circuit 18 into rectangular wave AC lighting power by the switching elements 36, 38, 40, and 42 having a full bridge configuration. The starter circuit 46 applies a starting high voltage pulse voltage to the lamp 48.

  Specific circuit configurations of the power factor correction circuit 16 and the PWM step-down circuit 18 are not particularly limited. For example, the power factor correction circuit 16 may be a circuit including the step-up transformer 22, the switching element 24, the diode D1, the output side capacitor C2, and the driver 26 for the switching element as shown in FIG. By the operation control of the switching element 24 by the driver 26, a constant boosted DC voltage is generated between the terminals of the output side capacitor C2.

  The PWM step-down circuit 18 includes a switching element 28 that controls the average current by pulse width modulation, a choke coil 30 that smoothes the modulation current, a diode D2, an output-side capacitor 32, and the like, for example, as shown in FIG. A circuit including a driver 34 for the switching element may be used, and the switching element 28 is controlled by the driver 34.

  The bridge circuit 20 includes bridge-connected switching elements 36, 38, 40, and 42, and a driver 44 that controls ON / OFF of the switching elements, and is generally a rectangular wave alternating current that alternates at several 10 to several 100 Hz. The lighting power of is output.

  As the starter circuit 46, an LC vibration type circuit having a coil connected in series to the lamp 48, a capacitor connected in parallel to the lamp, and the like may be adopted. When starting or restarting, when the output voltage of the bridge circuit 20 reaches a predetermined value (no-load voltage), the electric charge accumulated in the capacitor is discharged all at once, causing LC oscillation, and a high voltage pulse is emitted from the coil. It has become. Thereafter, the capacitor of the starter circuit 46 is recharged to generate the next high-voltage pulse, but the time required for charging can be set variously by changing the coil and capacitor to be used. In this way, the high voltage pulse voltage superimposed on each rectangular wave of the rectangular wave AC voltage is applied to the lamp 48 one after another.

  Note that a discharge lamp lighting device using a full-bridge type PWM step-down circuit or a half-bridge type PWM step-down circuit having both functions of the PWM step-down circuit 18 and the bridge circuit 20 may be used. These circuits also correspond to the inverter of the present invention. Further, instead of using a driver as the driving means for the switching element of each circuit, an analog control IC may be used as the driving means.

  The discharge lamp lighting device 10 further includes a control unit 52 using a microcomputer and a voltage detection unit 50 that detects a lighting voltage. The control means 52 gives on / off timing signals to the drivers 26, 34, 44 of the respective switching elements. The voltage detection unit 50 includes, for example, an AD converter that digitally detects the DC output voltage output from the inverter circuit, that is, the PWM step-down circuit 18, as the supply voltage from the inverter. The control means 52 calculates and outputs a timing signal to each driver according to the detected value of the lamp voltage. In this manner, the microcomputer sets the optimum current value, voltage value, and rectangular wave frequency for the lamp 48 to be connected. Based on the timing signal, the drivers 26, 34, and 44 for the switching element apply a driving voltage that is turned on / off at the timing to the gate of the switching element.

  The sampling time of the voltage detecting means 50 is preferably at least equal to or less than the interval at which the bridge circuit 20 alternates the rectangular wave voltage. As a result, the supply voltage at least every half cycle of the rectangular wave AC voltage is detected, the fluctuation of the supply voltage can be detected instantaneously, and the discrimination accuracy of the discrimination means 54 and 56 is improved.

<Time measurement processing of supply time by combining normal count processing and high-speed count processing>
What is characteristic in the present invention is that the control means 52 supplies the voltage of the inverter (the PWM step-down circuit 18 and the bridge circuit 20) according to the detection value of the voltage detection means 50 and the voltage waveform obtained from the detection value. Is to control. That is, the control unit 52 includes a distortion determination unit 54, a no-load voltage determination unit 56, a counter 58, and a pause time counter 62.

The distortion determination means 54 determines the presence or absence of distortion of the voltage waveform obtained from the detected value. Discrimination criterion of the presence or absence of distortion, as the reference value V ₀ of the voltage limit value that is determined to be no-load voltage, when the detection value is less than the reference value V _0, and there distortion of the voltage waveform.

The no-load voltage discriminating means 56 detects the presence or absence of the no-load voltage based on the detected value after the distortion discriminating means 54 discriminates the presence or absence of distortion, and the lamp 48 is discharged when no no-load voltage is detected. If no load voltage is detected, it is determined that the lamp 48 is not discharged. As a criterion for determining whether or not there is a no-load voltage, the reference value V ₀ used by the distortion determining means is used, and when the detected value is equal to or greater than the reference value V ₀ , the no-load voltage is determined.

Counter 58 operates in accordance with a combination of the discrimination result of the distortion determining means 54 and the no-load voltage determining means 56, by combining the normal counting operation and fast counting, counting rate of feed time T ₁ To change. That is, according to the determination result of the determination means 54, 56, by changing the operation of the counter 58, by the total number of counts reaches a predetermined value (threshold), measurement of the supply time of the inverter T ₁ is completed Judge. When the measurement of the supply time T ₁ is completed, the supply of the rectangular wave AC voltage to the lamp 48 is stopped.

Here, the counter 58 may set the count number incremented by one count process to 2 or 3 according to the determination result. That is, the counter 58 may be incremented by 1 in the normal count process, and may be set larger than this in the high-speed count process. The count number in the high-speed count process may be doubled, tripled, or quadrupled with respect to the count number in the normal count process, and the double-speed count process may be executed. Furthermore, if the count number of the counter 58 can be adjusted, the time measuring speed of the supply time T ₁ can be changed according to the type and output of the lamp and the usage time, thereby increasing versatility. In this embodiment, if no discharge occurs between the lamp electrodes during feed time T ₁ of the restart, the supply time T ₁ is for example more than 1 second, so that less than 1 minute, normal counting process of the counter 58 The count number at is set.

Downtime counter 62 starts the operation when the timing of the supply time T ₁ is completed. By count of downtime counter 62 reaches a predetermined value, it is determined that counting of the inverter downtime T ₂ is completed. When the measurement of the pause time T ₂ is completed, the supply of the rectangular wave AC voltage to the lamp 48 is resumed. In the present embodiment, the count number of the pause time counter 62 is adjusted so that the pause time T ₂ is, for example, 10 seconds or more and 10 minutes or less.

<Specific distortion determination method>
Here, a specific method for determining the distortion of the voltage waveform will be described. FIG. 2 shows an example of a voltage waveform based on the detection value from the voltage detection means. This figure corresponds to the voltage waveform between the lamp electrodes shown in FIG. That is, the detected voltage waveform is a waveform of a DC voltage before polarity inversion input to the bridge circuit 20.

In the present embodiment, the voltage lower limit value determined to be the no-load voltage is used as the reference value V ₀ , and when the detected value is less than the reference value V _0, it is determined that “distortion exists”. The voltage below the reference value V ₀ generated during the period circled in the figure, that is, the intermediate level voltage when temporary glow discharge occurs, and the short-circuit voltage when temporary arc discharge occurs are detected. If so, it is determined that there is distortion.

Furthermore, when the detection value immediately after determining that there is distortion is the no-load voltage, the counter 58 performs both the normal count processing and the high-speed count processing, and the supply time T Increased the timekeeping speed of ₁ . The difference from the time measuring speed of the supply time T ₁ will be described with reference to FIG. In order to make the explanation easy to understand, the timing of counting is indicated by a point marked above the waveform of FIG. Here, the two count processes of the counter 58, that is, the timing for executing the “normal count process” and the timing for executing the “high-speed count process” will be described separately. It is executed at the timing of the point sequence indicated by A on the graph of the figure. The high-speed count process is executed at the timing indicated by B. When it is determined that the detected value of the supply voltage is a no-load voltage, the counter 58 performs a normal count process. Therefore, the count number increases at the timing of the point sequence indicated by A in FIG. 5 and the count of the supply time T ₁ is completed when the count number reaches a predetermined value. The supply time counted in this case is indicated by T _1A . On the other hand, the counter 58 executes not only the normal count process but also the high-speed count process when the distortion of the waveform is detected and the immediately following detection value is a no-load voltage. Therefore, a high-speed count process is simultaneously performed at the timing of the point sequence indicated by B in FIG. For this reason, when high-speed count processing is executed, the total count number increases rapidly. For example, when the supply time reaches T _1B , the total count number reaches a predetermined value. Thus, if the number of executions of the high-speed count process increases according to the detected value, the supply time T ₁ is timed earlier by that amount.

<Control flow of supply time counting process>
Next, a control flow when starting and restarting the lamp 48 using the discharge lamp lighting device 10 of the present embodiment will be described with reference to FIGS.
In FIG. 3, first, when the inverter starts to supply a rectangular wave AC voltage when the power is turned on or the pause time T ₂ elapses (S1), the voltage detection means 50 detects the supply voltage for every predetermined sampling time (S2). ). Based on the detected value, the distortion determination means determines whether or not the output waveform is distorted (S3). Here, the presence or absence of distortion may be determined each time the voltage detection unit 50 detects, or the detected value is temporarily stored in a data file or the like, and then the stored data is read in accordance with the determination timing to determine the presence or absence of distortion. May be.

Next, the presence / absence of no-load voltage is determined based on the detection value immediately after the determination of the presence / absence of distortion (S4, S5). Although the process is divided into S4 and S5 in the processing flow, the same no-load voltage determination means 56 executes this. If it is determined in step S3 that there is distortion, and no load voltage is detected in the next step S4, the counter 58 executes a high-speed count process (S6), and further executes a normal count process (S7). Thereafter, the next process is executed (S8). A step S8 example, when the total count of the counter 58 has reached a predetermined value (threshold) to suspend voltage supply of the inverter, it starts counting down time T _2. If the total count has not reached the predetermined value, the process returns to step S1 to continue the voltage supply and proceed to the detection of the supply voltage.

  If it is determined in step S3 that there is no distortion, and no load voltage is detected in the next step S5, the counter 58 executes a normal count process (S7) and proceeds to the next process (S8). On the other hand, if no load voltage is detected in step S5, the process proceeds to the next process without performing the counting operation (S8).

  If no load voltage is detected in step S4, the counter 58 proceeds to the next process without executing both the high-speed count process and the normal count process (S8). By using the discrimination criteria shown in the following table, the operation of the above processing flow can be explained. These processing flows are described in terms of the execution pattern of the counting process of the counter 58 according to the combination of the determination results of the distortion determination unit 54 and the no-load voltage determination unit 56 as shown in the following table.

(Table 1)
―――――――――――――――――――――――――――――――――――――――
Waveform distortion No-load voltage → Normal count processing High-speed count processing Processing in Figure 4 ―――――――――――――――――――――――――――――――― ―――――――
Yes Yes → Execute Execute Route 2
Yes No → Do not execute Do not execute Route 3
No Yes → Execute Do not execute Route 1
None None → Do not execute Do not execute Route 4
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  That is, at least when the no-load voltage determination means 56 detects the no-load voltage, the counter 58 advances the count number in the normal count process. In particular, when the no-load voltage discriminating means 56 detects the no-load voltage and the distortion discriminating means 58 detects the distortion of the voltage waveform, the counter 58 counts both the normal count processing and the high-speed count processing. To proceed. On the other hand, when at least the no-load voltage determination means 56 does not detect the no-load voltage, the counter 58 performs neither normal count processing nor high-speed count processing. Here, the case where it is determined that there is distortion and the presence of no-load voltage is, for example, determined as “distortion” once an intermediate level (or short-circuit voltage) voltage is detected. If the detected value immediately after making the determination is seen, the case has already returned to the no-load voltage. Conversely, even if an intermediate level voltage is detected and it is determined that there is “distortion”, if the detected value immediately after the determination remains at the intermediate level voltage and has not returned to the no-load voltage, Since no voltage is detected, no counting process is performed.

  FIG. 4 illustrates the flow of the control flow by dividing the voltage waveform into three representative patterns. As for typical patterns, when a rectangular wave AC voltage is supplied, no discharge occurs between the lamp electrodes (case 1), glow discharge occurs (case 2), and arc discharge. This is the three patterns in the case of occurrence of (case 3). Routes 1 to 3 in FIG. 4 are processing routes corresponding to each case.

(Case 1)
As a case where there is no discharge between the electrodes despite the voltage supply, the temperature in the arc tube is still high, such as after the lamp is extinguished, and it cannot be restarted immediately, and detection of no-load voltage may continue. This also applies to the case where no-load voltage is detected again after a temporary discharge has occurred. In the control flow, it becomes processing route 1. Since the detected value is a no-load voltage, it is determined in step S3 that there is no distortion, and in the next step S5, no-load voltage is detected. In step S7, the counter 58 executes a normal counting process. If this state continues and the normal count process of the counter 58 is repeated, the count number increases at a normal speed and the supply time T ₁ advances.

(Case 2)
As a case where a temporary glow discharge occurs between the lamp electrodes, there is a case where the inside of the arc tube is not sufficiently cooled and the temporary discharge is repeated. In the control flow, it becomes processing route 2. Since the voltage waveform drops from the no-load voltage to the intermediate level voltage, it is determined that there is distortion in step S3. In the next step S4, if the glow discharge has already stopped, the no-load voltage is detected, and the counter 58 executes both the high-speed count process and the normal count process. If Shojire even temporary glow discharge times, processing route 2 is repeated, timed supply time T ₁ is made to be terminated early by the count number went increasing fast.

Note that even if distortion due to glow discharge is detected, if the detection value immediately after that does not return to the no-load voltage, the process of route 3 in FIG. 4 is performed, and the process of the supply time T ₁ does not proceed and the process is performed again. The distortion determination at S3 is executed. Normally, the glow discharge does not continue for a long period of time, but immediately returns to the no-load voltage. Therefore, most of the cases where the glow discharge occurs are processed by the route 2.

(Case 3)
When the arc discharge is continuously generated between the lamp electrodes and the lamp is normally lit, the voltage waveform once decreases to a short circuit voltage (for example, 20 to 30 V instantaneously) as shown in FIG. It rises to the lighting voltage (rated lamp voltage). In the control flow, it becomes processing route 3. Since the voltage waveform once decreases to the short-circuit voltage, it is determined that there is distortion in step S3. If arc discharge is maintained in the next step S4, no load voltage is detected, and the counter 58 proceeds to the next operation without performing any high-speed count processing or normal count processing. Thus, if the arc discharge continues, the process is repeated Route 3, the count number of the supply time T ₁ will remain stopped, never counting the feed time T ₁ is completed. Thus, in normal lighting, the determination of “with distortion” and “no-load voltage detection” continues, so the supply of the rectangular wave AC voltage is continued, and the process automatically shifts to lamp lighting control.

  If the arc discharge is temporary, the no-load voltage is detected in step S4, so that the processing route 2 is performed, and the temporary arc discharge is treated as a temporary discharge in the same manner as the glow discharge. Is done.

According to the present embodiment, if a rectangular discharge with no load voltage is supplied to the lamp 48 at the start / restart, a temporary discharge phenomenon (temporary arc discharge or glow discharge) occurs. For example, the count of the supply time T ₁ proceeds quickly, and the voltage supply to the lamp 48 by the inverter can be stopped at an early stage to enter the stop time T ₂ .

For example, as shown in FIG. 5, when high-speed counting processing is not executed, a voltage waveform without distortion (waveform A in FIG. 5) is also generated with respect to a voltage waveform in which distortion repeatedly occurs (waveform B in FIG. 5). The same supply time T _1A is obtained. On the other hand, the counter 58 performs a combination of high-speed count processing and normal count processing as in the present embodiment, so that the time measurement speed is increased, so that the supply time T _1B is shortened as shown by the waveform C in FIG. Is done.

Further, by adjusting the number of counts in a single count process of the counter 58, the counting rate of the supply time T ₁ may be set to a desired fast. The time for which the specific supply time T ₁ is shortened varies depending on the occurrence rate of waveform distortion. For example, the set value of the supply time T ₁ is 30 seconds. Further, the count number in the high-speed count process is adjusted so that the total count number increases at twice the speed in the case of waveform distortion and no-load voltage detection. Under the condition that the distortion of the voltage waveform is continuously detected during the supply of the intermittent rectangular wave AC voltage, the supply time is reduced to about 15 seconds. In addition, the supply time is shortened to about 20 seconds under the condition that 50% distortion of the voltage waveform is detected during the supply of the intermittent rectangular wave AC voltage.

  Therefore, since the voltage supply to the lamp 48 is stopped at an early stage, it is possible to prevent the glow discharge from being repeatedly generated at the time of starting / restarting and to suppress the wear of the lamp electrode. Furthermore, the start-up time can be shortened efficiently by suppressing as much as possible the rise in arc tube temperature due to the repetition of temporary discharge such as arc discharge or glow discharge. As a result, both protection of the lamp electrode and good startability can be obtained.

As a modification of the present embodiment, the time measurement speed of the supply time T ₁ may be changed based on the distortion of the current waveform of the supply current instead of the waveform of the supply voltage to the lamp 48. That is, a detecting means for detecting a supply current from the inverter is used instead of the voltage detecting means. In this case, the distortion determination means determines the presence or absence of distortion of the current waveform. For example, when a reference current value of a current value that flows due to the occurrence of discharge is set and a current value equal to or greater than the reference current value is detected, it is determined that “distortion exists”. Further, in place of the no-load voltage determining means, a supply current determining means for determining whether the lamp 48 is discharged based on the presence or absence of the supply current is used.

If at least the supply current is not detected regardless of the distortion of the current waveform, the control means 52 increments the counter 58 by a normal count process. Further, if it is determined that the current waveform is distorted and no supply current is detected, the counter 58 is incremented by both the normal count process and the high-speed count process. On the other hand, the counter 58 is not incremented at least when the supply current is detected regardless of the distortion of the current waveform. As described above, when it is determined that there is distortion and no supply current, the counter 58 can execute both the normal and high-speed two count processes to advance the count of the inverter supply time T ₁ quickly. Therefore, the same effect as the discharge lamp lighting device of this embodiment can be obtained.

DESCRIPTION OF SYMBOLS 10 Discharge lamp lighting device 12 AC power supply 14 Rectifier circuit 16 Power factor improvement circuit 18 PWM step-down circuit 20 Bridge circuit 46 Starter circuit 48 Lamp (discharge lamp)
50 Voltage detection means 52 Control means 54 Distortion discrimination means 56 No-load voltage discrimination means 58 Counter 62 Counter for downtime

Claims (5)

An inverter that converts the input DC voltage into a rectangular wave AC voltage and supplies it to the discharge lamp;
Detecting means for detecting a supply voltage from the inverter;
In a discharge lamp lighting device comprising: a detection voltage value of the detection means; and a control means for controlling the voltage supply of the inverter according to a voltage waveform obtained from the detection voltage value.
The control means includes
Distortion determining means for determining the presence or absence of distortion of the voltage waveform obtained from the detected voltage value;
After the distortion determination means determines the presence or absence of distortion, no-load voltage determination means for determining whether or not the discharge lamp is discharged by detecting the presence or absence of no-load voltage based on the detected voltage value;
A counter for measuring the supply time (T ₁ ) of the inverter,
Regardless of the distortion of the voltage waveform, at least when the no-load voltage determining means detects the no-load voltage, the counter performs a normal count,
When the distortion determination unit detects a distortion of the voltage waveform and the no-load voltage determination unit detects a no-load voltage, the counter executes both a normal count and a high-speed count,
Regardless of the distortion of the voltage waveform, at least when the no-load voltage determining means does not detect the no-load voltage, the counter does not execute any count,
When the total count of the counter reaches a predetermined value, the timing of the supply time (T ₁ ) is completed, and the supply of the rectangular wave AC voltage to the discharge lamp is stopped. apparatus. 2. The discharge lamp lighting device according to claim 1, wherein the distortion determination means uses a voltage lower limit value determined to be a no-load voltage as a reference value (V ₀ ), and a detected voltage value is the reference value (V _0). ), It is determined that there is distortion in the voltage waveform. 3. The discharge lamp lighting device according to claim 1, wherein the control means further includes a pause time counter that counts the pause time (T ₂ ) when the count reaches a predetermined value. A discharge lamp lighting device which restarts the supply of the rectangular wave AC voltage to the discharge lamp when the timing of T ₂ ) is completed.   The discharge lamp lighting device according to any one of claims 1 to 3, wherein the detection means detects a DC voltage before AC conversion by the inverter. An inverter that converts the input DC voltage into a rectangular wave AC voltage and supplies it to the discharge lamp;
Detecting means for detecting a supply current from the inverter;
In a discharge lamp lighting device comprising: a detection current value of the detection means; and a control means for controlling voltage supply of the inverter according to a current waveform obtained from the detection current value.
The control means includes
Distortion determining means for determining the presence or absence of distortion of the current waveform obtained from the detected current value;
A supply current determination means for determining whether the discharge lamp is discharged by detecting the presence or absence of a supply current based on a detected current value after the distortion determination means determines the presence or absence of distortion;
A counter for measuring the supply time (T ₁ ) of the inverter,
Regardless of the distortion of the current waveform, at least when the supply current determination means does not detect the supply current, the counter performs a normal count,
When the distortion determination unit detects a distortion of a current waveform and the supply current determination unit does not detect a supply current, the counter executes both a normal count and a high-speed count,
Regardless of the distortion of the current waveform, at least when the supply current determination means detects the supply current, the counter does not execute any count,
When the total count of the counter reaches a predetermined value, the timing of the supply time (T ₁ ) is completed, and the supply of the rectangular wave AC voltage to the discharge lamp is stopped. apparatus.

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