JP2023172238A - light source device - Google Patents

Abstract

To provide a light source device with which, even when a discharge lamp that emits an ultraviolet ray is turn-on controlled with low output, it is possible to detect the discharge lamp going out in the middle with good accuracy.SOLUTION: The light source device includes a turn-on circuit for a discharge lamp that emits an ultraviolet ray. The turn-on circuit comprises a transformer that includes a primary winding that is connected to a DC power supply and a secondary winding that is connected to the discharge lamp, a switching element that is connected between the primary winding and the DC power supply, and a control unit that controls electrical continuity of the switching element. The control unit is constituted to exercise turn-on detection control during execution of a dimming operation control mode, to raise primary electric power inputted to the primary winding by temporarily changing the ON/OFF frequency and/or the ON/OFF duty cycle of the switching element in a turn-on detection period that is set within a 100 ms to 30 sec range.SELECTED DRAWING: Figure 1

Description

The present invention relates to a light source device, and particularly to a light source device including an ultraviolet discharge lamp and a lighting circuit thereof.

In recent years, development of technology that utilizes ultraviolet light has been progressing for the purpose of inactivating bacteria or viruses. The present applicant has developed a technique for inactivating bacteria or viruses using an excimer lamp, which is a type of ultraviolet discharge lamp (for example, see Patent Document 1 below).

JP 2019-115525 Publication Japanese Patent Application Publication No. 2010-062157

When lighting an ultraviolet discharge lamp (hereinafter sometimes abbreviated as "discharge lamp") to emit ultraviolet rays to inactivate bacteria or viruses, there are circumstances in which it may be necessary to adjust the illuminance of the ultraviolet rays depending on the usage. There are cases where Note that in this specification, "inactivation" refers to a concept that encompasses killing bacteria or viruses and causing them to lose infectivity or toxicity. Moreover, in this specification, "bacteria" refers to microorganisms such as bacteria and fungi (mold).

Various locations are envisaged for installing a light source device including a discharge lamp. Depending on the location where the discharge lamp is installed, there may be cases where ultraviolet rays with high illuminance are required, or conversely, cases where ultraviolet rays with low illuminance are required in view of the effects on the human body. As an example, it is assumed that bacteria or viruses that may exist in a space or on the surface of an object are inactivated by irradiating ultraviolet rays downward from a light source device installed on the ceiling. In this case, when the height of the ceiling on which the light source device is installed changes, the intensity of ultraviolet rays in the space or on the surface of the object changes. In other words, it may be necessary to adjust the light output depending on the installation location of the light source device.

At the time of filing this application, it is recommended that the cumulative amount of ultraviolet rays irradiated to the human body be within the regulatory values set by ACGIH (American Conference of Governmental Industrial Hygienists). . Therefore, when using the light source device in an environment where humans may be present, the discharge lamp should be operated at low output in order to keep the cumulative amount of ultraviolet rays irradiated to the human body within the above ACGIH regulation value. There are circumstances that make you want to. As a typical example, there is a need to continuously light a discharge lamp at a low light output for a long period of time.

Note that in this specification, adjusting the light output of the discharge lamp may be referred to as "dimming".

In order to adjust (dimming) the light output of a discharge lamp, it is necessary to control the power supplied to the discharge lamp. However, due to the characteristics of discharge lamps, if the power supplied to the discharge lamp is reduced, there is a concern that a phenomenon called "fading out" may occur in which a lit discharge lamp stops lighting (see Patent Document 2 above).

The applicant of the present application is currently developing a light source device for inactivation equipped with a particularly small ultraviolet lamp. Small UV lamps have relatively low rated output. Therefore, if such an ultraviolet lamp is operated at a low output such as 50% or 30% of the rated output, the power supplied to the ultraviolet lamp will be extremely low, and as a result, it is expected that the probability of the above-mentioned extinguishment occurring will increase. .

It is also assumed that a light source device used for the purpose of inactivation is used in an environment where no humans are present. In this case, if the ultraviolet lamp goes out and is not lit, the inactivation performance against bacteria or viruses that may exist in the environment will be lower than the desired level.

It is known that ultraviolet rays with a main peak wavelength of 200 nm to 240 nm have an extremely low effect on the human body, unlike ultraviolet rays emitted from low-pressure mercury lamps that include a component with a wavelength of 254 nm. For this reason, a light source device equipped with a discharge lamp that emits ultraviolet light in the above wavelength range (for example, an excimer lamp containing KrCl or KrBr as a luminescent gas) can be used for inactivation purposes even during times when there are people around. It is assumed that it will be used in However, unlike visible light, ultraviolet rays in the above wavelength range cannot be visually recognized, so it is difficult for people nearby to detect whether the excimer lamp is turned off or not. In other words, even if a light source device is used in an environment where there may be people around, if the ultraviolet lamp is turned off and is not lit, it will not be able to inactivate bacteria or viruses that may exist in the environment. However, the result is lower than the desired level.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a light source device that can accurately detect whether a discharge lamp that emits ultraviolet rays goes out even when lighting is controlled at low output.

A light source device according to the present invention includes a discharge lamp that emits ultraviolet rays, and a lighting circuit for lighting the discharge lamp,
The lighting circuit is
DC power supply and
a transformer that includes a primary winding connected to the DC power supply and a secondary winding connected to the discharge lamp, and boosts the voltage applied to the primary winding;
a switching element connected between the primary winding and the DC power supply;
and a control section that controls conduction of the switching element.

When the control unit receives a dimming command signal indicating that the light output of the discharge lamp is lower than the reference light output, the control unit executes a reference operation control mode in which the discharge lamp is turned on under the reference light output. A dimming operation in which at least one of the ON/OFF frequency and ON/OFF duty ratio of the switching element is changed to reduce the secondary power output from the secondary winding compared to the current time. This is a configuration that executes control mode.

Furthermore, during execution of the dimming operation control mode, the control section temporarily controls the ON/OFF frequency and ON/OFF of the switching element within a lighting detection period set within a range of 100 msec to 30 seconds. This configuration executes lighting detection control that increases the secondary side power by changing at least one of the duty ratios.

One way to determine whether a discharge lamp that was in a lit state has stopped lighting, that is, whether it has gone out is to detect the amount of current flowing through a node connected to the discharge lamp. . When the discharge lamp is on, a high current flows through the node, while when the discharge lamp is off, the current flowing through the node decreases. For this reason, it seems possible at first glance to set a threshold value as a criterion for determination in advance, and to determine that a blackout has occurred if the detected amount of current is below this threshold value. Seem.

However, if the above method is applied when the discharge lamp is lit at low output, that is, while a dimming operation is being performed, there is a possibility that the occurrence of extinguishing will be falsely detected. The reason for this is as follows.

In order to detect the current flowing through a node connected to the discharge lamp, a current detection resistor is generally connected to the node. Increasing the value of this resistance increases Joule heat, leading to unnecessary power consumption and temperature rise. Therefore, the current detection resistor is required to exhibit a small resistance value regardless of whether the discharge lamp is always lit at the rated output or in a dimmed state. Specifically, the resistance for current detection is preferably 0.5Ω or less, more preferably 0.1Ω or less, and particularly preferably 0.05Ω or less. Note that this current detection resistor is preferably 0.01Ω or more from the viewpoint of sufficiently exhibiting current value detection performance.

Particularly, from the viewpoint of downsizing a light source device including a discharge lamp, the size of components is also subject to certain restrictions. Also from this point of view, it is preferable to use a resistor with a small resistance value as described above as a resistor for current detection.

However, if a current detection resistor with a small resistance value is connected to a node, the potential difference generated across the resistor will inevitably become small. Therefore, if you want to accurately detect the onset of fading by comparing it with a reference value based on this potential difference, the voltage detected by the resistor is amplified by an amplifier (typically an operational amplifier) and then compared to the reference value. It is necessary to compare it with the base value. From the viewpoint of ensuring a difference from the reference value to be compared and accurately determining the comparison result, it is necessary to increase the amplification factor of the amplifier when the voltage detected by the resistor is small. However, as the amplification factor of the amplifier increases, the amount of superimposed noise also increases, making it easier for errors to occur. In other words, as a result of the superimposed noise being amplified even though fading has occurred, there is a concern that it will be erroneously determined that fading has not occurred because it exceeds the threshold value. In addition, if the standard threshold value is raised to eliminate this concern, it is also possible that the value will fall below the threshold even though no fading has occurred, resulting in a false determination that no fading has occurred. It will be done.

On the other hand, according to the light source device having the above configuration, in the mode in which the light output is turned on with the light output being lower than the reference light output, that is, during the execution of the dimming operation control mode, within the range of 100 msec to 30 seconds. Control is performed to temporarily increase the secondary power supplied to the discharge lamp within the set lighting detection period. In other words, even if the light is lit at a low output during execution of the dimming operation control mode, high secondary power is temporarily output from the secondary winding of the transformer during an extremely short lighting detection period. By detecting the current flowing within this period, comparison with the threshold value can be made without using an amplifier with an extremely high amplification factor.

When the above-mentioned control is executed, the light output temporarily increases for a short period of time even during the dimming operation, if no fading has occurred. However, since the above-mentioned light source device is equipped with an ultraviolet lamp, the temporary increase in light output during the dimming operation is not visually recognized by surrounding people. For this reason, the lighting detection period is a period of time during which flickering due to a temporary increase in the light output of a lamp that emits visible light is not visible, specifically an extremely short period of 20 msec or less, typically about 1 msec. There is no need to set it to . By setting the lighting detection period to a relatively long time within the range of 100 msec to 30 seconds, the time required to perform processing to avoid errors due to noise superimposition, such as moving average processing and smoothing processing using a capacitor, can be set. can be secured.

When performing the above detection, the current flowing through the node connected to the discharge lamp (secondary current) may be detected, or the current flowing through the node connected to the primary winding of the transformer (primary current) may be detected. It may also be a device that detects side current).

That is, the light source device includes a first current detection unit that detects a primary current flowing through the primary winding or a secondary current flowing through the secondary winding and outputs a detection result to the control unit. Prepare,
The control unit determines that the discharge lamp is in a non-lighting state if a value based on a detection result by the first current detection unit is lower than a predetermined first threshold value during execution of the lighting detection control. It does not matter if it is something to judge.

When a lighting command signal for lighting the discharge lamp is input together with the dimming command signal, the control unit controls the secondary side power to execute the reference operation control mode within a starting period that is an initial stage of lighting operation. After controlling the conduction of the switching element so that it is equal to or higher than the time, the secondary side power is controlled to be equal to or higher than when executing the dimming operation control mode within a steady period after the end of the starting period. A configuration for controlling conduction of the switching element,
The control unit may be configured to execute the lighting detection control within the steady period.

When turning on a discharge lamp that has been turned off, an operation (starting operation) for starting discharge is required. Specifically, a process is performed in which the voltage applied to the discharge lamp is increased and, if necessary, a light source (such as an LED light source) for lighting assistance is turned on. In this specification, a period during which processing for starting lighting of a discharge lamp in an extinguished state is performed is referred to as a "starting period." Moreover, in this specification, after the starting period ends and the discharge lamp is in the lighting state, the period during which the lighting state continues is referred to as a "steady period".

The state in which the lighting command signal is input to the control unit together with the dimming command signal corresponds to, for example, a state in which an instruction to turn on a discharge lamp in an off state at 50% dimming is given. In this case, higher power is supplied to the discharge lamp during the starting period than during the steady-state period. Once discharge begins, the power supplied to the discharge lamp is reduced to continue lighting at 50% light output. According to the above configuration, during the period when the light is turned on in such a dimmed state, that is, during the steady period, high secondary side power is temporarily generated from the secondary winding of the transformer during the lighting detection period. This makes it possible to determine whether the signal has faded or not.

The light source device includes:
a first current detection unit that detects a primary current flowing through the primary winding and outputs a detection result to the control unit;
a second current detection unit that detects a secondary current flowing through the secondary winding and outputs a detection result to the control unit,
The control unit determines that the discharge lamp is in an unlit state if a value based on a detection result by the first current detection unit is less than the first threshold value during execution of the lighting detection control. death,
When the control unit is configured to perform a process in which a value based on a detection result by the second current detection unit is below a second threshold value that is lower than the first threshold value while executing the reference operation control mode or the dimming operation control mode, In this case, it may be determined that the secondary winding is in an open, no-load state.

In addition to the above-mentioned "turning off" as a cause of the discharge lamp not lighting up, there is also a faulty electrical connection between the lighting circuit and the discharge lamp. This electrical connection failure may occur due to a disconnection of a connection line, a physical connection failure, or the like. When such an electrical connection failure occurs, the secondary winding of the transformer becomes open and unloaded. When the node connected to the secondary winding of the transformer (hereinafter referred to as the "secondary circuit") is opened, the resistance value maximizes, the secondary side of the transformer becomes high voltage, and the transformer's The voltage value on the primary side also increases. As a result, an excessive voltage is applied to the switching element, and there is a fear that the switching element may be damaged in some cases.

If it is detected that a discharge lamp is not lit, the measures that can be taken after that will differ depending on whether the cause of the discharge lamp's failure is due to the lamp going out or due to no load. It is assumed that In the case of non-lighting due to turning off, for example, the administrator or the system side may issue a command to restart the light source device to return it to the lighting state. On the other hand, in the case of non-lighting due to no load, a maintenance worker needs to inspect the inside of the light source device.

When the secondary circuit of a transformer is unloaded, substantially no current flows through the secondary winding of the transformer. Therefore, the second current detection unit detects the current flowing through the secondary winding (secondary current), and if the detection result is lower than the threshold (second threshold) set to an extremely low value, , it can be determined that the secondary circuit of the transformer is in a no-load state.

On the other hand, when the discharge lamp is extinguished, a higher current flows than when the secondary circuit of the transformer is under no load. As mentioned above, the light source device is equipped with a transformer that boosts the voltage applied to the primary winding. The current (primary current) flowing through the secondary current is higher than the secondary current.

Therefore, when detecting a power out, the value based on the primary current, which is higher than the secondary current, is compared with a predetermined threshold (first threshold). Detection can be performed with high accuracy. According to this configuration, when the value based on the primary side current is less than the first threshold value, it can be determined that the power out is occurring. On the other hand, if the value based on the secondary current is less than the second threshold, it can be determined that there is no load. This makes it possible to identify the cause of the discharge lamp becoming unlit.

The control unit may increase the secondary side power to a value equivalent to that during execution of the reference operation control mode during execution of the dimming operation control mode and within the lighting detection period.

Here, the reference operation control mode may be a control mode in which the control unit controls conduction of the switching element so that the secondary power supplied to the discharge lamp becomes the rated power of the discharge lamp. do not have.

The control unit calculates a value obtained by subjecting the values continuously detected by the first current detection unit during execution of the lighting detection control to a value obtained by performing a moving average process over a period of 10 msec to 50 msec, and The first threshold value may be compared.

As mentioned above, during the execution of the dimming operation control mode, the lighting detection period during which the secondary side power temporarily increases is 20 msec, which is the upper limit of the time during which humans cannot see it due to changes in the intensity of visible light. It is within the range of 100 msec to 30 seconds, which is sufficiently long compared to the above. Therefore, sufficient time can be secured to perform moving average processing on continuously detected current values. As a result, even if an instantaneous noise current is superimposed, the presence of the noise current can be effectively nullified and compared with the threshold (first threshold), allowing accurate determination of extinction. I can do it.

The first current detection section includes:
a detection resistor connected to the primary winding or the secondary winding;
an amplifier that includes an input side terminal connected to the detection resistor and an output side terminal connected to the control section, and amplifies the voltage detected by the detection resistor and outputs it from the output side terminal;
A noise mitigation capacitor connected to the input side terminal or the output side terminal of the amplifier may be provided.

As mentioned above, the lighting detection period during which the input power is temporarily increased during the execution of the dimming operation control mode is 20 msec, which is the upper limit of the time during which humans cannot see the visible light due to changes in the intensity of visible light. In comparison, it is sufficiently long, within the range of 100 msec to 30 seconds. Therefore, even if an instantaneous noise current is superimposed, sufficient time can be secured to smooth the increase in current amount due to this noise current using a time constant. As a result, even if an instantaneous noise current is superimposed, the presence of this noise can be effectively nullified and compared with the threshold (first threshold), making it possible to accurately determine whether the noise has disappeared. can be done.

According to the light source device of the present invention, even when a discharge lamp that emits ultraviolet rays is controlled to turn on at low output, it is possible to accurately detect the occurrence of extinction.

FIG. 1 is a circuit block diagram schematically showing the configuration of an embodiment of a light source device of the present invention. FIG. 2 is a perspective view schematically showing an example of the appearance of a discharge lamp. 2A is a perspective view schematically showing an example of the appearance of a discharge lamp, and is a drawing with some elements removed from FIG. 2A. FIG. Fig. 2 schematically shows the respective temporal changes of the voltage signal V24 supplied from the drive circuit to the switching element, the primary current I1 of the transformer, the secondary voltage V2 of the transformer, and the secondary current I2 of the transformer. This is a timing chart. During execution of the dimming control operation mode, the primary voltage V1 of the transformer, the lighting command signal Q2, the control signal S1, the secondary voltage V2 of the transformer, the secondary power P2, the control signal S18 for the starting auxiliary light source, 3 is a timing chart schematically showing temporal changes of the determination result signal J20 and the determination result signal J20. 12 is a timing chart schematically showing the behavior of the primary current I1 when the discharge lamp goes out during execution of a dimming operation in a case where a lighting detection period is not provided. The value of the threshold current Ith1 used for determining whether the engine has turned off is set between the current Is flowing during the starting period Tα and the current Ia flowing during the steady period Tβ. 12 is a timing chart schematically showing the behavior of the primary current I1 when the discharge lamp goes out during execution of a dimming operation in a case where a lighting detection period is not provided. The value of the threshold current Ith1 used to determine whether the light has disappeared is set to a value lower than the current Ia flowing during the steady period Tβ. FIG. 2 is a timing chart schematically showing the behavior of the primary current I1 when the discharge lamp goes out during execution of a dimming operation in a case where a lighting detection period is provided. FIG. The value of the threshold current Ith1 used for determining whether the engine has turned off is set between the current Is flowing during the starting period Tα and the current Ia flowing during the steady period Tβ. FIG. 7 is a timing chart schematically showing the behavior of the primary current I1 when the discharge lamp does not go out during execution of the dimming operation in a case where a lighting detection period is provided. FIG. The value of the threshold current Ith1 used for determining whether the engine has turned off is set between the current Is flowing during the starting period Tα and the current Ia flowing during the steady period Tβ. 3 is a schematic drawing for explaining the contents of moving average processing performed in a control unit. 12 is a timing chart schematically showing a first result signal Z31 in which a signal derived from a noise current is superimposed when a noise mitigation capacitor is not provided. 12 is a timing chart schematically showing a first result signal Z31 in which a signal derived from a noise current is superimposed when a noise mitigation capacitor is provided. FIG. 3 is a circuit block diagram schematically showing the configuration of another embodiment of the light source device of the present invention. FIG. 3 is a circuit block diagram schematically showing the configuration of another embodiment of the light source device of the present invention.

Embodiments of a light source device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit block diagram schematically showing the configuration of an embodiment of a light source device according to the present invention. The light source device 1 includes a discharge lamp 10 that emits ultraviolet rays Ry1, and a lighting circuit 2 for driving and lighting the discharge lamp 10. As shown in FIG. 1, the lighting circuit 2 includes a control unit 20, a DC power supply 21, a switching element 22, and a transformer 30. Transformer 30 includes a primary winding L1 and a secondary winding L2. The primary winding L1 is connected to the DC power supply 21 and the switching element 22 to form a primary circuit c1. The secondary winding L2 is connected to the discharge lamp 10 to form a secondary circuit c2.

The discharge lamp 10 included in the light source device 1 of this embodiment is, for example, an excimer lamp, which is a type of dielectric barrier discharge lamp. 2A and 2B are perspective views schematically showing the appearance of the discharge lamp 10. However, the structure of the discharge lamp 10 illustrated in FIGS. 2A and 2B is merely an example. In other words, the discharge lamp 10 included in the light source device 1 according to the present invention can emit ultraviolet rays Ry1 when the secondary voltage V2 output from the secondary winding L2 of the transformer 30 is applied. structure may be adopted.

As shown in FIG. 2A, the discharge lamp 10 includes a lid part 41 having a light extraction surface 43 formed on one surface thereof, and a main body casing part 42. FIG. 2B is a schematic diagram with a portion of the lid portion 41 removed from FIG. 2A. In the example shown in FIG. 2B, the discharge lamp 10 includes a plurality of arc tubes 15 and electrodes (11, 12) for applying voltage to each arc tube 15. The electrodes (11, 12) are connected to power supply lines (44, 45) via connecting portions (44a, 45a), respectively. The power lines (44, 45) are connected to the lighting circuit 2. Although the example shown in FIG. 2B shows a configuration in which the discharge lamp 10 includes a plurality of arc tubes 15, it may include a single arc tube 15.

The arc tube 15 is made of a dielectric material such as quartz glass, and a predetermined luminescent gas is sealed inside. When a high frequency voltage of, for example, about 1 kHz to 1 MHz is applied to the electrodes (11, 12), the voltage is applied to the luminescent gas via the arc tube 15. At this time, discharge plasma is generated in the discharge space (inside the arc tube 15) in which the luminescent gas is sealed, and the atoms of the luminescent gas are excited and become excimer state. Thereafter, when the atoms in the excimer state transition to the ground state, excimer light emission occurs.

The wavelength of the ultraviolet ray Ry1 emitted from the discharge lamp 10 is determined depending on the substance of the luminescent gas enclosed. For example, when KrCl is included as the luminescent gas, the ultraviolet ray Ry1 emitted from the discharge lamp 10 exhibits a spectrum with a main peak wavelength in the vicinity of 222 nm. When the luminescent gas contains KrBr, the ultraviolet ray Ry1 exhibits a spectrum with a main peak wavelength in the vicinity of 207 nm. However, in the present invention, the type of gas sealed in the arc tube 15 of the discharge lamp 10 is arbitrary, and may be appropriately selected depending on the wavelength of the ultraviolet ray Ry1 to be obtained. Furthermore, a phosphor may be provided on the tube wall or light extraction surface 43 of the arc tube 15 for the purpose of converting the wavelength to a longer wavelength side.

The type of luminescent gas or phosphor sealed in the arc tube 15 is selected so that the main peak wavelength of the ultraviolet rays Ry1 emitted from the discharge lamp 10 is 200 nm to 240 nm, thereby converting the discharge lamp 10 into a low-pressure mercury lamp. This makes it possible to reduce the impact on the human body as much as possible compared to the case where

Returning to FIG. 1, the explanation of the lighting circuit 2 will be continued. The lighting circuit 2 shown in FIG. 1 is a circuit called a flyback type. However, the present invention is not limited to the case where the lighting circuit 2 is of a flyback type, and may be of a full bridge type or a push-pull type.

A DC power supply 21 and a switching element 22 are connected to the primary winding L1 of the transformer 30. The DC power supply 21 may be configured by, for example, an AC/DC converter that converts a commercial power supply (not shown) into AC/DC. In this case, as shown in FIG. 1, the lighting circuit 2 may include a smoothing capacitor 25 for smoothing the voltage waveform output from the DC power supply 21. As another example, the DC power supply 21 may be configured with a battery.

The lighting circuit 2 includes a drive circuit 24. The drive circuit 24 outputs a voltage signal V24 to the switching element 22 for switching ON/OFF of the switching element 22 based on the control signal S1 from the control unit 20.

The light source device 1 of this embodiment is equipped with a function of adjusting the intensity of the ultraviolet ray Ry1 emitted from the discharge lamp 10, that is, a dimming function. Specifically, when the dimming command signal Q1 is input to the control unit 20, the control unit 20 changes the control signal S1 output to the drive circuit 24. The dimming command signal Q1 may be transmitted, for example, from a dimming instruction section (not shown). The drive circuit 24 changes at least one of the ON/OFF frequency and the ON/OFF duty ratio of the switching element 22 based on the control signal S1. For example, the ON/OFF duty ratio of the switching element 22 may be reduced, or the ON/OFF frequency of the switching element 22 may be increased. Further, for example, both the ON/OFF frequency and the ON/OFF duty ratio of the switching element 22 may be changed. As a result, the secondary current I2 decreases, and the value of the secondary power P2 supplied to the discharge lamp 10 decreases. As a result, the optical output of the ultraviolet ray Ry1 decreases. This point will be explained with reference to the timing chart shown in FIG.

FIG. 3 shows the voltage signal V24 supplied from the drive circuit 24 to the switching element 22, the primary current I1 of the transformer 30, the secondary voltage V2 of the transformer 30, and the time of the secondary current I2 of the transformer 30. 5 is a timing chart schematically showing changes. In addition, in FIG. 3, since the dimming command signal Q1 is input to the control unit 20, the ON/OFF duty of the switching element 22 is lower than when executing the standard operation control mode in which lighting is performed under the standard light output. is shown in a state where it is lowered. Further, FIG. 3 shows not a starting period, which is a period in which the discharge lamp 10 that has been in an unlit state starts lighting, but a period in which the discharge lamp 10 continues to be lit (a steady period). The time changes of each of the above voltages or currents are schematically shown.

As shown in FIG. 3, when the voltage signal V24 output from the drive circuit 24 to the switching element 22 changes from Low to High at time t1, the switching element 22 changes from the OFF state to the ON state. As a result, the primary current I1 of the transformer 30 increases over time. Thereafter, when the voltage signal V24 changes from High to Low at time t2, the switching element 22 transitions from the ON state to the OFF state. At this time, a back electromotive force is generated in the secondary winding L2 of the transformer 30, and an impulse-like secondary voltage V2 is generated. This secondary voltage V2 is applied from the pair of electrodes (11, 12) to the arc tube 15 of the discharge lamp 10, and ultraviolet rays Ry1 are emitted. The switching element 22 is switched ON/OFF at high frequency based on a control signal S1 from the control unit 20. As a result, as described above, a high frequency voltage of, for example, about 1 kHz to 1 MHz is applied to the electrodes (11, 12). The transformer 30 is provided to induce a secondary voltage V2 higher than the primary voltage V1 input to the primary winding L1 and apply it to the discharge lamp 10.

When the discharge lamp 10 is a dielectric barrier discharge lamp, the discharge lamp 10 is equipped with a pair of electrodes (11, 12) sandwiching the arc tube 15 made of a dielectric material, so that the discharge lamp 10 equivalently constitutes a capacitor element. (Hereinafter, it will be referred to as "equivalent capacitor C10".) Therefore, by applying the secondary voltage V2 to the discharge lamp 10, the equivalent capacitor C10 configured by the discharge lamp 10 is charged.

A secondary voltage V2 is induced in the secondary winding L2 of the transformer 30, so that a secondary current I2 flows through the secondary winding L2. This secondary current I2 flows while releasing the energy stored in the transformer 30, and therefore approaches a zero value as time passes. When the discharge of the energy stored in the transformer 30 is completed by the secondary current I2, the charge stored in the equivalent capacitor C10 is discharged. Due to this discharge, a current in the opposite direction (secondary current I2) flows through the secondary winding L2 of the transformer 30, and the secondary voltage V2 changes so as to approach zero value.

Even after the discharge of the equivalent capacitor C10 is completed, the secondary winding L2 of the transformer 30 serves as a voltage source and continues to flow the secondary current I2 while charging the equivalent capacitor C10. Thereafter, when the secondary current I2 stops flowing, a primary voltage V1 is induced in the primary winding L1 of the transformer 30. This induced voltage has a polarity opposite to that of the DC power supply 21, and a reverse primary current I1 (regenerative current) flows through the primary winding L1 through a parasitic diode provided in the switching element 22. . The primary current I1 gradually approaches the zero value and reaches the zero value at time t2a. When the switching element 22 is turned ON again at time t3, the value of the primary current I1 continues to increase in the same way as from time t1 to t2. Below, the same phenomenon is repeated.

When executing the dimming operation control mode, the ON/OFF frequency and ON/OFF duty ratio of the switching element 22 are changed in comparison with a mode (standard operation control mode) in which the output of the ultraviolet ray Ry1 from the discharge lamp 10 is the reference light output. At least one of them changes. For example, if the ON/OFF frequency or ON/OFF duty ratio of the switching element 22 is changed alone, the peak value of the secondary voltage V2 changes. In addition, by changing both the ON/OFF frequency and the ON/OFF duty ratio of the switching element 22, the secondary voltage V2 can be kept almost constant, and the secondary voltage V2 can be changed to the discharge lamp 10 within a unit time. The frequency with which V2 is applied can be varied.

As a result, the frequency with which the secondary voltage V2 is applied to the discharge lamp 10 within a unit time or the peak value of the secondary voltage V2 decreases, so that the voltage supplied to the discharge lamp 10 per unit time decreases. Secondary power P2 decreases. Therefore, when the dimming control mode is executed, the output of the ultraviolet rays Ry1 from the discharge lamp 10 is reduced (dimmed) compared to when the reference operation control mode is executed. Note that when reducing the secondary side power P2, by suppressing fluctuations in the secondary side voltage V2, it is possible to make it more difficult for the discharge lamp 10 to turn off, which is likely to be caused by a decrease in the secondary side voltage V2. You can expect it. Furthermore, by suppressing fluctuations in the secondary voltage V2, the possibility that the secondary voltage V2 will rise is also reduced, which improves the degree of freedom in voltage resistance of components and also reduces restrictions on the insulation distance that must be secured. An additional effect of relaxation can also be obtained.

As described above, the frequency of the secondary voltage V2 is a high frequency of about 1 kHz to 1 MHz. For example, when the frequency of the secondary voltage V2 is 100 kHz, the period of the secondary current I2 shown in FIG. 3, which appears as an impulse-like waveform, is an extremely short time of 0.01 msec, can be considered as a continuous current flowing. Furthermore, although the primary current I1 shows changes over time as shown in FIG. 3, the period is still extremely short, so it can be considered that the current is flowing continuously as well.

As shown in FIG. 1, the light source device 1 of this embodiment includes a first current detection section 31 connected to the primary circuit c1 of the transformer 30, and a first current detection section 31 connected to the secondary circuit c2 of the transformer 30. Two current detection sections 32 are provided. A voltage signal based on the current value detected by the first current detection section 31 is amplified via the amplifier 51 and then input to the control section 20 . A voltage signal based on the current value detected by the second current detection section 32 is amplified via the amplifier 52 and then input to the control section 20 . In this embodiment, capacitors (61, 62) for removing noise current superimposed on the amount of current detected by the first current detection section 31 and the amount of current detected by the second current detection section 32 are used. The lighting circuit 2 includes capacitors (65, 66) for removing noise current superimposed on the lighting circuit 2. The first current detection unit 31 is typically a resistor, and its resistance value is preferably 0.5Ω or less, more preferably 0.1Ω or less, and particularly 0.05Ω or less. preferable. Note that this resistance is preferably 0.01Ω or more from the viewpoint of achieving sufficient current value detection performance. The second current detection section 32 is typically a resistor, and the resistance value thereof may be selected from the same conditions as the first current detection section 31.

The first current detection unit 31 is provided to detect whether or not the discharge lamp 10 has turned off. On the other hand, the second current detection section 32 is provided to detect whether the discharge lamp 10 is electrically connected to the secondary winding L2 of the transformer 30. As described above, while the discharge lamp 10 is lit, it can be assumed that current is continuously flowing through both the primary circuit c1 and the secondary circuit c2. Based on the current value detected by step 32), it is possible to determine whether or not the discharge lamp 10 is not lit.

Hereinafter, based on the timing chart shown in FIG. 4, the operation of the lighting circuit 2 when turning off of the discharge lamp 10 is detected based on the detection result of the first current detection section 31 will be described. For convenience of explanation, FIG. 4 shows an initial stage period (starting period) in which the discharge lamp 10 that is in the unlit state starts lighting, and a period (starting period) in which the lighting state continues after lighting starts ( (steady period) are shown.

When the main power supply (not shown) is turned on, the primary voltage V1 transitions to the High level at time t10. Thereafter, the control unit 20 receives a lighting command signal Q2 from a signal transmitting unit (not shown) of the light source device 1. Note that in FIG. 4, it is assumed that the lighting command signal Q2 is input to the control unit 20 together with the dimming command signal Q1. Further, although FIG. 4 shows a case where the control unit 20 receives the lighting command signal Q2 at time t11 after time t10 when the main power is turned on, time t11 is the same time as time t10. I don't mind.

When the control unit 20 receives the lighting command signal Q2 together with the dimming command signal Q1, the control unit 20 first controls the switching element 22 to make the secondary power P2 within the starting period Tα equal to or higher than that during execution of the reference operation control mode. A control signal S1 is generated and transmitted to the drive circuit 24. Upon receiving the dimming command signal Q1, the control unit 20 recognizes that the discharge lamp 10 is to be dimmed. However, during the period (starting period Tα) in which the discharge lamp 10 that is in the unlit state starts lighting, the voltage is higher than that during execution of the dimming operation control mode in order to cause discharge within the discharge lamp 10. It is necessary to supply the next-side power P2 to the discharge lamp 10. The timing chart of FIG. 4 shows that the value Ps of the secondary power P2 during the starting period Tα is higher than the value Pa of the secondary power P2 during the steady period Tβ during execution of the dimming operation control mode. There is. In FIG. 4, the secondary power P2 temporarily changes to a value higher than Pa (here, Ps) even within the steady period Tβ, but this point will be described later.

At time t11, the control unit 20 generates a control signal S1 for controlling conduction of the switching element 22 so that the value of the secondary side power P2 becomes Ps during the starting period Tα, and outputs it to the drive circuit 24. do. In FIG. 4, the content of this control signal S1 is indicated by the symbol Ss. The drive circuit 24 performs ON/OFF control of the switching element 22 based on the control signal S1 corresponding to the control content Ss. After time t11, when ON/OFF control of the switching element 22 is started, a secondary voltage V2 is induced in the secondary winding L2 of the transformer 30.

The value Ps of the secondary side power P2 in the starting period Tα may be equal to the value of the secondary side power P2 within the steady period when the standard operation control mode is executed, or the value Ps of the secondary side power P2 during the execution of the standard operation control mode. The value may be higher than the value of the secondary power P2 during the steady period in . Typically, the value Ps of the secondary power P2 during the starting period Tα is the rated power of the discharge lamp 10. However, this power value Ps may be a value lower than the rated power of the discharge lamp 10. Conversely, considering that the power value is supplied to the discharge lamp 10 only during the starting period Tα, the value Ps of the secondary side power P2 during the starting period Tα is set as a value higher than the rated power of the discharge lamp 10. I don't mind.

As shown in FIG. 1, the discharge lamp 10 may be provided with a starting aid light source 18. In this case, the control unit 20 outputs a control signal S18 for lighting the starting assist light source 18 within the starting period Tα. The starting assist light source 18 is typically an LED light source, and a control signal S18 is transmitted to a power supply drive circuit (not shown) that performs ON/OFF control of the LED light source. The starting assist light source 18 is supplied with current based on the control signal S18 and is turned on. Light from the starting aid light source 18 is irradiated onto the discharge lamp 10 and functions as a trigger for starting discharge.

The control unit 20 receives a signal corresponding to the detection result by the first current detection unit 31 connected to the primary circuit c1 of the transformer 30. Hereinafter, this signal will be referred to as "first result signal Z31" (see FIG. 1).

The control unit 20 compares a value based on the input first result signal Z31 with a predetermined threshold (first threshold Th1). Information regarding the first threshold Th1 is recorded in advance in a storage area such as a memory installed in the control unit 20. At time t11, the discharge lamp 10 has not started discharging, so the secondary power P2 has a zero value. Therefore, the primary current I1 does not flow through the primary circuit c1 compared to when the lamp is discharged. Therefore, between times t11 and t12, the value based on the first result signal Z31 is lower than the first threshold Th1. Based on this comparison result, the control unit 20 determines that the discharge lamp 10 is not lit between times t11 and t12. The control unit 20 outputs a signal related to this determination result (hereinafter referred to as "determination result signal J20"). In FIG. 4, the content of the determination result signal J20 indicating that the discharge lamp 10 is not lit is indicated by the symbol k0.

The determination result signal J20 is transmitted, for example, to a result output section (not shown) included in the light source device 1. As a more specific example, the determination result signal J20 is transmitted via wireless communication to a result output unit located at a location away from the light source device 1. The result output unit outputs information indicating that the discharge lamp 10 is not lit when the determination result signal J20 corresponding to the content k0 is input, for example, between times t11 and t12.

The timing chart of FIG. 4 shows a case where discharge of the discharge lamp 10 is successful at time t12, and lighting of the discharge lamp 10 starts after time t12. That is, after time t12, the value of secondary power P2 supplied to discharge lamp 10 increases to Ps. After time t12, since current flows through the secondary circuit c2, the amount of current flowing through the primary circuit c1 also increases. That is, in this time period, the value based on the first result signal Z31 input to the control unit 20 indicates a value higher than the predetermined threshold (first threshold Th1). Based on this comparison result, the control unit 20 determines that the discharge lamp 10 is in the lighting state between times t12 and t13, and outputs a determination result signal J20. In FIG. 4, the content of the determination result signal J20 indicating that the discharge lamp 10 is in the lighting state is indicated by the symbol k1.

In this way, once the discharge lamp 10 starts lighting, the starting period Tα shifts to the steady period Tβ. In FIG. 4, this transition timing is set to time t13. At time t13 when the starting period Tα transitions to the steady period Tβ, the starting assisting light source 18 transitions to the OFF state. As described above, in this example, the dimming command signal Q1 is input before time t11. Therefore, during the steady period Tβ, the secondary power P2 is adjusted in order to bring the discharge lamp 10 into the lighting state (for example, 50% output, 30% output, etc.) under the output indicated by the dimming command signal Q1. be done.

At time t13, the control unit 20 sends a control signal S1 for the switching element 22 to set the value of the secondary power P2 to the power value Pa to be supplied to the discharge lamp 10 during execution of the dimming operation. It is generated and transmitted to the drive circuit 24. In FIG. 4, the content of this control signal S1 is indicated by the symbol Sa. The drive circuit 24 performs ON/OFF control of the switching element 22 based on the control signal S1 corresponding to the control content Sa. As a result, after time t13, secondary power P2 decreases from Ps to Pa.

The dimming command signal Q1 may include information regarding the ratio at which the output of the discharge lamp 10 should be made with respect to the maximum output of the discharge lamp 10. As another example, if the output during dimming is fixed to one type, information regarding the target output does not necessarily need to be shown in the dimming command signal Q1. In this case, the control unit 20 can control the switching element 22 to reduce the output of the discharge lamp 10 to a predetermined level upon receiving the dimming command signal Q1.

The operation control mode in which the discharge lamp 10 is turned on while the output of the discharge lamp 10 is reduced from the maximum output in this manner is referred to as a "dimming operation control mode."

Between times t13 and t14 when the dimming operation is started and the output of the discharge lamp 10 decreases from Ps to Pa, the control unit 20 cannot clearly determine whether or not the discharge lamp 10 is lit. Can not. The reason for this will be explained later.

Between times t13 and t14, the determination result signal J20 output from the control unit 20 may include content indicating that the dimming operation control mode is being executed. In FIG. 4, the content of the determination result signal J20 indicating that the discharge lamp 10 is executing the dimming operation control mode is indicated by the symbol ka.

The reason why it is not possible to clearly determine whether or not the discharge lamp 10 is lit between times t13 and t14 will be explained with reference to FIGS. 5A to 5D. 5A and 5B are timing charts schematically showing the behavior of the primary side current I1 when the lighting detection period of this embodiment is not provided, and are illustrated for comparative explanation. . 5C to 5D are timing charts schematically showing the behavior of the primary current I1 when the lighting detection period of this embodiment is provided.

As described above, when lighting starts at the starting period time t12, the secondary power P2 corresponding to the value Ps is supplied to the discharge lamp 10. At this time, a primary current I1 corresponding to the value Is flows through the primary circuit c1 (see FIGS. 5A to 5D). Thereafter, at time t13, when the dimming operation is being executed and transitions to a steady period Tβ, the secondary power P2 supplied to the discharge lamp 10 decreases from Ps to Pa (see FIG. 4). As a result, the primary current I1 flowing through the primary circuit c1 also decreases from Is to Ia (see FIGS. 5A to 5D).

Here, as shown in FIG. 5A, if the first threshold Th1 for determining lighting/non-lighting of the discharge lamp 10 is set based on the threshold current Ith1 lower than Is, during the starting period Tα In this case, it can be determined that the discharge lamp 10 is lit when the primary current I1 is higher than the threshold current Ith1. However, in this case, when the primary current I1 decreases from Is to Ia after transitioning to the steady period Tβ, the primary current I1 becomes lower than the threshold current Ith1 as shown in FIG. The discharge lamp 10 is erroneously determined to be in an unlit state.

One possible method for avoiding such erroneous determination is to lower the threshold current Ith1 below the value shown in FIG. 5A (see FIG. 5B). That is, a threshold current Ith1 that is lower than the value Ia of the primary current I1 that is expected to flow during execution of the dimming operation is set in advance. Then, the control unit 20 compares the first threshold Th1 based on the threshold current Ith1 and the first result signal Z31 corresponding to the detection result by the first current detection unit 31. According to this method, it seems that it is possible to determine whether the light has gone out even during execution of the dimming operation.

However, in reality, the noise current Iz flows through the lighting circuit 2 even after the discharge lamp 10 has gone out. 5A and 5B show a case where the discharge lamp 10 goes out at time t50 after time t13. In FIGS. 5A and 5B, the noise current Iz is exaggerated for explanation. However, in reality, depending on the degree of dimming of the discharge lamp 10 (ratio of output to maximum output), the instantaneous value of the noise current Iz flowing when the discharge lamp 10 is turned off may be different from that while the discharge lamp 10 is turned on. The value may be close to the value Ia of the flowing primary side current I1.

In other words, as shown in FIG. 5B, even if the value of the threshold current Ith1 is set lower than Is, the first result signal Z31 caused by the noise current Iz flowing after time t50 when extinction actually occurs is received. Therefore, there is a possibility that the control unit 20 will erroneously determine that the discharge lamp 10 is lit. This situation becomes noticeable when the discharge lamp 10 is small, the maximum output (typically the rated output) is about 1 W to 10 W, and the dimming operation is performed. In the case of a small discharge lamp 10 with a low rated output, the value Ia of the primary side current I1 that is expected to flow through the primary side circuit c1 during execution of the dimming operation is extremely low, and is equivalent to the instantaneous value of the noise current Iz. It may indicate the level of

In view of these circumstances, in the light source device 1 of this embodiment, as described above with reference to FIG. 5A, the value of the threshold current Ith1 is set to It is set to a value lower than the value Is of the current I1 and higher than the value Ia of the primary side current I1 that is assumed to flow during the steady period Tβ of the dimming control operation mode (see FIGS. 5C to 5D). In addition, in the light source device 1 of the present embodiment, during the period Tc (hereinafter referred to as "lighting detection period Tc") provided within the steady period Tβ of the dimming operation control mode, the secondary side power P2 Control is performed to temporarily raise the amount (see FIG. 4). In FIG. 4, the periods from time t14 to t15 and from time t16 to t17 correspond to the lighting detection period Tc.

In other words, the control unit 20 sets the value of the secondary power P2 at time t14, which is within the steady period Tβ of the dimming operation control mode, to Ps, which is equivalent to the value during the steady period when the reference operation control mode is executed. A control signal S1 for controlling conduction of the switching element 22 is generated and outputted to the drive circuit 24. In the example of FIG. 4, the switching element 22 is ON/OFF controlled based on the control signal S1 corresponding to the same control content Ss as in the starting period Tα. The ON/OFF switching frequency or ON/OFF duty ratio of the switching element 22 is increased compared to the period from time t13 to time t14. As a result, the secondary power P2 temporarily increases from Pa to Ps between times t14 and t15, even though it is within the steady period Tβ of the dimming operation control mode.

In this case, if the extinction occurs at time t50 within the steady period Tβ, the value of the primary current I1 flowing within the lighting detection period Tc from time t14 to t15 is equal to the threshold It becomes lower than the current Ith1. As described above, the value of the threshold current Ith1 is higher than the noise current Iz that may flow while the discharge lamp 10 is turned off. Therefore, on the control unit 20 side, by comparing the first threshold Th1 based on the threshold current Ith1 and the first result signal Z31 corresponding to the detection result by the first current detection unit 31, the steady state of the dimming operation control mode is determined. It can be determined that the extinction occurs even during the period Tβ.

Furthermore, if the extinction has not occurred at time t50 within the steady period Tβ, as shown in FIG. It becomes higher than the current Ith1. Therefore, on the control unit 20 side, by comparing the first threshold value Th1 based on the threshold current Ith1 and the first result signal Z31 corresponding to the detection result by the first current detection unit 31, the dimming operation control mode is determined. It can be determined that no turning off occurs during the steady period Tβ, and that the light is in the lighting state.

The example in FIG. 4 shows a case where the discharge lamp 10 goes out at time t50, which is after time t15 and before time t16. In this case, during the lighting detection period Tc from time t14 to time t15, the control unit 20 causes the first result signal Z31 corresponding to the detection result by the first current detection unit 31 to be lower than the first threshold Th1 based on the threshold current Ith1. It detects that the discharge lamp 10 is also high, and outputs a determination result signal J20 indicating that the discharge lamp 10 is lit. In the example of FIG. 4, the content of the determination result signal J20 indicating that the discharge lamp 10 is in the lighting state is indicated by the symbol k1.

On the other hand, the control unit 20 detects that the first result signal Z31 is lower than the first threshold Th1 within the lighting detection period Tc from time t16 to t17, which is a time period after the time t50 when the extinction occurred. Detect. Then, the control unit 20 outputs a determination result signal J20 with content k0 indicating that the discharge lamp 10 is in an unlit state to a result output unit (not shown). When this determination result signal J20 is input, the result output unit outputs information indicating that the discharge lamp 10 is not lit (going out) to, for example, a management terminal or server. This makes it possible to detect whether the discharge lamp 10 goes out even during the dimming operation. Further, the control unit 20 may perform the same control operation on the switching element 22 again at the start of the starting period Tα after determining whether the discharge lamp 10 has gone out based on the first result signal Z31. .

Next, the second current detection section 32 will be explained.

When the discharge lamp 10 starts lighting or during the lighting operation, the connection state between the discharge lamp 10 and the secondary winding L2 of the transformer 30 may become defective due to some external factor or the like. If the lighting circuit 2 continues to operate in such a state, the secondary circuit c2 becomes open and in a no-load state, so the secondary voltage V2 of the transformer 30 becomes extremely high. As a result, the primary voltage V1 of the transformer 30 also increases, and there is a concern that the switching element 22 may be damaged.

From this point of view, the light source device 1 includes a second current detection section 32 for determining whether the discharge lamp 10 is correctly connected to the secondary circuit c2. The control unit 20 receives a signal corresponding to the detection result by the second current detection unit 32 connected to the secondary circuit c2 of the transformer 30. Hereinafter, this signal will be referred to as "second result signal Z32" (see FIG. 1).

The control unit 20 compares a value based on the input second result signal Z32 with a predetermined threshold (second threshold Th2). Information regarding this second threshold Th2 is recorded in advance in a storage area such as a memory installed in the control unit 20.

As described above, the second current detection section 32 is provided for the purpose of detecting the electrical connection state between the discharge lamp 10 and the secondary circuit c2. Therefore, if the two are disconnected, the secondary current I2 flowing through the secondary circuit c2 will have a substantially zero value. Therefore, the threshold current serving as a comparison standard can be set to a value lower than the threshold current Ith1 described above with reference to FIGS. 5C to 5D. That is, the second threshold Th2 may be a value lower than the first threshold Th1.

Even if the electrical connection between the discharge lamp 10 and the secondary circuit c2 is defective, that is, even if the secondary circuit c2 is unloaded, the primary side circuit c1 is not loaded. A current I1 flows through the circuit c1. Therefore, when attempting to detect the electrical connection state between the discharge lamp 10 and the secondary circuit c2 on the primary side circuit c1 side, it is possible to determine whether the amount of current has decreased due to the discharge lamp 10 being turned off. It becomes difficult to distinguish whether the amount of current is decreasing because the circuit c2 is in a no-load state.

On the other hand, the amount of current flowing through the secondary circuit c2 of the transformer 30 during lighting is lower than that of the primary circuit c1. For this reason, the range of change in the amount of current that can flow when the lamp is not lit and when it is lit becomes small. As a result, when attempting to detect the current flowing through the secondary circuit c2 to determine whether the current has gone out, it is necessary to increase the amplification factor of the amplifier 52 in order to increase the width of change. However, if the amplification factor of the amplifier 52 is increased, the value of the superimposed noise current Iz will also be amplified, and it is expected that the determination accuracy will decrease.

According to the above configuration, the second current detection section 32 is arranged specifically for determining the electrical connection between the discharge lamp 10 and the secondary circuit c2, so that the second current detection section 32 has an extremely low value as described above. can be set as the second threshold Th2. Since the light source device 1 is provided with the first current detection section 31 based on the primary current I1 in addition to the second current detection section 32, it is possible to accurately determine whether or not the discharge lamp 10 is extinguished. I can do it.

The control unit 20 performs moving average processing on the values based on the first result signal Z31 that are continuously input within the lighting detection period Tc, and compares this average value with the first threshold Th1. (See Figure 6). For example, as shown in FIG. 6, the average value Ai (A1, A2, A3, . . . It is also possible to determine whether the discharge lamp 10 goes out at every sampling interval ti by calculating the average value Ai and comparing the obtained average value Ai with the first threshold Th1.

By performing such processing, even if a high noise current Iz is instantaneously superimposed during the time when the extinction occurs, the influence of the noise current Iz can be reduced and the first threshold Th1 can be adjusted. Can be compared. Thereby, it is possible to determine the presence or absence of extinction with high accuracy. Such processing can be realized by setting the lighting detection period Tc as a relatively long time such as 100 msec to 30 seconds as described above. In this case, the average processing period τs can be set at a time of 10 msec to 50 msec. An example of the sampling interval ti is 500 μsec to 5 msec.

Furthermore, as shown in FIG. 1, the light source device 1 includes capacitors (61, 62) for reducing the noise current Iz superimposed on the amount of current detected by the first current detection section 31. Thereby, as described above, the effect of suppressing erroneous determination of the lighting state based on the noise current Iz is further enhanced. By providing the capacitors (61, 62), the mode of change in the primary side current I1 appearing in the first result signal Z31 becomes gradual. However, as described above, in the light source device 1, a relatively long time such as 100 msec to 30 seconds is set as the lighting detection period Tc, so the time required for smoothing the signal by the capacitors (61, 62) is It can be provided within the lighting detection period Tc. The capacitance of the capacitors (61, 62) is, for example, 0.01 μF to 0.1 μF.

If the capacitors (61, 62) are not present, a high-level noise signal N1 originating from the noise current Iz may be superimposed on the first result signal Z31 (see FIG. 7A). On the other hand, by providing the capacitors (61, 62), the level of the noise signal N2 superimposed on the first result signal Z31 can be suppressed (see FIG. 7B). As a result, it is possible to accurately determine whether or not the discharge lamp 10 has gone out.

In addition, in FIG. 1, capacitors (65, 66) are also provided before and after the amplifier 52 where the voltage signal based on the current value detected by the second current detection section 32 is amplified. However, in the present invention, it is optional whether or not to include the capacitors (65, 66).

[Another embodiment]
Another embodiment will be described below.

<1> The light source device 1 may be configured to include the first current detection section 31 but not include the second current detection section 32 (see FIG. 8A). In this case, the first current detection section 31 may be connected to the secondary circuit c2 (see FIG. 8B).

<2> The light source device 1 described above with reference to FIG. It was set up. However, a light source device 1 that does not include a noise mitigation capacitor (61, 62) is also within the scope of the present invention.

A light source device 1 that does not include an amplifier 51 is also within the scope of the present invention.

1: Light source device 2: Lighting circuit 10: Discharge lamp 15: Luminous tube 18: Starting aid light source 20: Control unit 21: DC power supply 22: Switching element 24: Drive circuit 25: Smoothing capacitor 30: Transformer 31: First Current detection section 32: Second current detection section 41: Lid section 42: Main body casing section 43: Light extraction surface 51: Amplifier 52: Amplifier c1: Primary side circuit c2: Secondary side circuit

Claims (7)

A light source device comprising a discharge lamp that emits ultraviolet light and a lighting circuit for lighting the discharge lamp,
The lighting circuit is
DC power supply and
a transformer that includes a primary winding connected to the DC power supply and a secondary winding connected to the discharge lamp, and boosts the voltage applied to the primary winding;
a switching element connected between the primary winding and the DC power supply;
and a control unit that controls conduction of the switching element,
When the control unit receives a dimming command signal indicating that the light output of the discharge lamp is lower than the reference light output, the control unit executes a reference operation control mode in which the discharge lamp is turned on under the reference light output. Dimming operation control that reduces the secondary side power output from the secondary side winding by changing at least one of the ON/OFF frequency and ON/OFF duty ratio of the switching element compared to the current time. It is a configuration that runs mode,
During execution of the dimming operation control mode, the control unit temporarily controls the ON/OFF frequency and ON/OFF duty ratio of the switching element within a lighting detection period set within a range of 100 msec to 30 seconds. A light source device, characterized in that the light source device is configured to execute lighting detection control that increases the secondary side power by changing at least one of the two. When a lighting command signal for lighting the discharge lamp is input together with the dimming command signal, the control unit controls the secondary side power to execute the reference operation control mode within a starting period that is an initial stage of lighting operation. After controlling the conduction of the switching element so that it is equal to or higher than the time, the secondary side power is controlled to be equal to or higher than when executing the dimming operation control mode within a steady period after the end of the starting period. A configuration for controlling conduction of the switching element,
The light source device according to claim 1, wherein the control unit is configured to execute the lighting detection control within the steady period. a first current detection unit configured to detect a primary current flowing through the primary winding or a secondary current flowing through the secondary winding and output a detection result to the control unit;
The control unit determines that the discharge lamp is in a non-lighting state if a value based on a detection result by the first current detection unit is lower than a predetermined first threshold value during execution of the lighting detection control. The light source device according to claim 1 or 2, wherein the light source device makes a determination. a first current detection unit that detects a primary current flowing through the primary winding and outputs a detection result to the control unit;
a second current detection unit that detects a secondary current flowing through the secondary winding and outputs a detection result to the control unit,
The control unit determines that the discharge lamp is in an unlit state if a value based on a detection result by the first current detection unit is less than the first threshold value during execution of the lighting detection control. death,
When the control unit is configured to perform a process in which a value based on a detection result by the second current detection unit is below a second threshold value that is lower than the first threshold value while executing the reference operation control mode or the dimming operation control mode, 3. The light source device according to claim 1, wherein the light source device determines that the secondary winding is in an open, no-load state. The control unit is characterized in that, during execution of the dimming operation control mode, the secondary side power is increased to a value equivalent to that during execution of the reference operation control mode within the lighting detection period. Item 2. The light source device according to item 1 or 2. The control unit calculates a value obtained by subjecting the values continuously detected by the first current detection unit during execution of the lighting detection control to a value obtained by performing a moving average process over a period of 10 msec to 50 msec, and The light source device according to claim 3, characterized in that the first threshold value is compared. The first current detection section includes:
a detection resistor connected to the primary winding or the secondary winding;
an amplifier that includes an input side terminal connected to the detection resistor and an output side terminal connected to the control section, and amplifies the voltage detected by the detection resistor and outputs it from the output side terminal;
The light source device according to claim 3, further comprising a noise mitigation capacitor connected to the input side terminal or the output side terminal of the amplifier.

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