JP5842956B2 - Discharge lamp lighting device - Google Patents

Description

  The invention of this application relates to a discharge lamp lighting device for supplying electric power to a discharge lamp such as an ultra-high pressure mercury lamp or a xenon short arc lamp, and in particular, discharge lamp lighting having a function to cope with a power failure for a very short time. It relates to the device.

  Discharge lamps that generate light emission using gas discharge are used in various applications. Of these, discharge lamps such as various mercury lamps and xenon short arc lamps are used for manufacturing processes and light processing applications that require a particularly high luminous flux or light with a specific spectrum (wavelength). It is used a lot.

The discharge lamp is used together with a device (lighting device) that appropriately converts and supplies power from a commercial power source. The lighting device includes a circuit that starts discharge to generate light emission or stabilize discharge. Generally, a discharge lamp lighting device is a converter that converts an input voltage from a commercial power source into a voltage suitable for the lamp, a current controller that stabilizes a discharge by controlling a current flowing through the lamp, and starts lighting the lamp. It includes an igniter circuit that operates at the time (at the time of discharge start).
Such a discharge lamp lighting device will be described with reference to FIG. 6 using a lighting device for an ultra-high pressure mercury lamp as an example. FIG. 6 is a schematic view of a conventional discharge lamp lighting device.

As shown in FIG. 6, the lighting device includes a first rectifying / smoothing circuit 1 connected to a commercial power supply CP, a transformer 2 provided so that an output of the first rectifying / smoothing circuit 1 is on the primary side, A second rectifying / smoothing circuit 4 provided on the secondary side of the transformer 2, which includes an inverter circuit 3 including a switching circuit provided between the first rectifying / smoothing circuit 1 and the transformer 2, a lamp The electrodes (anode and cathode) of the discharge lamp L are connected through the measurement circuit 5, the igniter circuit 7 and the like.
A lamp control unit 6 that controls the lighting state of the discharge lamp L is provided, and the lamp control unit 6 includes a lighting control circuit 61. The output of the lamp measurement circuit 5 is input to the lighting control circuit 61, and the output of the lighting control circuit 61 is input to the inverter circuit 3.

  The first rectifying / smoothing circuit 1 includes a full-wave rectifying circuit (diode bridge) 11 and a smoothing capacitor 12 connected to the output side thereof. The inverter circuit 3 switches a voltage that has been rectified and smoothed to become a direct current to obtain a high-frequency voltage (on / off voltage) that changes with a predetermined duty. The transformer 2 is for high frequency, and the high frequency voltage applied to the primary side winding is converted and transmitted to the secondary side, returned to direct current by the second rectifying and smoothing circuit 4, and applied to the lamp electrode. The The frequency of the high frequency generated by the inverter circuit 3 is about 20 kHz to 100 kHz, and the current flowing to the lamp via the transformer 2 is changed by changing the period and pulse width based on the control signal from the lighting control circuit 61. This controls the power supply.

JP 2007-294267 A JP 2011-29096 A JP 2011-154856 A

  As described above, the discharge lamp that is lit by such a lighting device is used in various manufacturing processes, optical processing, and the like. In such an application, particularly high reliability is required for the lighting state of the lamp. For example, an ultra-high pressure mercury lamp is frequently used in a semiconductor process or a liquid crystal process as a light source for exposure in photolithography. In the ultra-high pressure mercury lamp used for exposure, when the lighting state becomes unstable and the output temporarily decreases, the exposure becomes insufficient. As a result, performance of products such as integrated circuits and displays is deteriorated. For this reason, high reliability is required for the stability of the lighting state of the discharge lamp.

  An external factor that cannot be avoided in terms of the stability of the lighting state of the discharge lamp is a power failure. Discharge lamps are used not only in regions with good power conditions but also in factories in regions where power conditions are not good. Power outages can also be triggered by natural phenomena such as lightning even in areas with good power conditions. In addition, a system that consumes a very large amount of power is deployed in a factory, and when the system starts operation, a voltage drop close to a power failure may occur temporarily due to the influence.

  In this specification, the term “power failure” is used in a broader sense than usual. In terms of instability of commercial power, the term “instantaneous voltage drop (instantaneous drop)” may be used in addition to “power failure”. The instantaneous drop means a decrease in power supply voltage in a short time, for example, up to about 100 ms. The “power failure” in this specification includes the case where the voltage drops from the rated value, such as a momentary drop, even if it does not reach complete zero.

  For power outages that may occur due to various factors as described above, it is desirable to minimize the impact on production. Depending on the production site, an emergency power supply (backup power supply) may be provided in consideration of a power failure. However, if there is a time lag in switching to the emergency power supply, it will be in a power outage state during that time, and if the emergency power supply is used up, it will be in a power outage state thereafter. In addition, many discharge lamps used in semiconductor processes and liquid crystal processes are used with a large power consumption of several kW to several tens of kW, and it is necessary to supply the power to the lighting device. An emergency power supply that supplements a large amount of power becomes a very expensive and large device, which makes installation difficult. Therefore, it is desirable to be able to cope with a power outage for a certain amount of time without requiring an emergency power supply.

  A particular consideration regarding the discharge lamp in connection with such a power failure is relighting when the power failure ends and is restored (when power is restored). Since the discharge lamp is a lamp that emits light by gas discharge in the arc tube, dielectric breakdown is required for lighting, and an igniter circuit that temporarily applies a high voltage is provided as described above.

  When the discharge lamp is turned off, the arc tube is often in a high temperature state immediately after that. A high-temperature state means that the gas pressure is high. When the gas pressure is high, it is generally difficult for dielectric breakdown to occur. For this reason, it is often impossible to light even if a high voltage is applied by an igniter circuit. Generally, the discharge lamp is air-cooled in order to keep the temperature constant while the time has elapsed since the start of lighting and is stably lit, and is air-cooled in order to lower the temperature for a certain period after the lamp is turned off. Therefore, in order to light up again, it is necessary to wait until the temperature of the arc tube drops to a temperature at which the arc tube can be turned on. Depending on the apparatus, there is a sequence in which the igniter circuit does not operate and the discharge lamp cannot be started until sufficient cooling is completed. The above sequence may be executed not by the lighting device itself but by a host device such as an exposure device that controls the lighting device.

The same applies when the discharge lamp is turned off due to a power failure.Even if it is possible to turn it on again by power recovery, the temperature of the arc tube is first detected, and if the temperature exceeds the specified temperature, the cooling mechanism is activated. To cool the arc tube. Then, after confirming that the temperature of the arc tube has dropped to a predetermined value or less, the igniter circuit is operated to light up again. Alternatively, the relationship between the cooling intensity and the arc tube temperature is grasped in advance, and after the predetermined cooling is performed for a predetermined time, the igniter circuit is operated to light up again. Hereinafter, this cooling operation is referred to as after-cooling.
The after-cooling time varies depending on the type of lamp and usage conditions, but is generally in the range of 10 to 20 minutes. In addition, it takes about 15 to 30 minutes for a lamp having a large heat capacity to return to the state before turning off (power / illuminance) after relighting.
Since the discharge lamp relights in such a sequence, it generally takes time to relight. For this reason, in the case of a discharge lamp used at a production site, since there is a time required for relighting in addition to the operation stop due to a power failure, the influence on productivity is great.

  On the other hand, the discharge lamp lighting device as shown in FIG. 6 is configured to maintain a normal lighting state for a very short time even when a power failure occurs and there is no commercial power input. Specifically, in the configuration shown in FIG. 6, the smoothing capacitor 12 included in the first rectifying and smoothing circuit 1 has this function. Although this capacitor is for smoothing, it stores a considerable amount of charge in the normal lighting state. When a power failure occurs and the commercial power supply input becomes zero, the smoothing capacitor 12 is discharged (discharges electric charge), and the resulting voltage is similarly applied to the inverter circuit 3, the transformer 2, and the second rectifying and smoothing on the secondary side. The voltage is applied to the lamp electrode via the circuit 4. For this reason, even if a power failure occurs, light emission is maintained for a very short time. This time is normally about 10 ms (milliseconds) to 50 ms. For example, 20 ms is a standard value, and the capacity of the smoothing capacitor 12 is designed in consideration of this.

  Therefore, even if a power failure occurs, if power is restored within the time until the discharge of the smoothing capacitor 12, the light emission is maintained (the ionization state has not been eliminated). It is possible to continue lighting. However, this time is as short as about 20 ms as described above, and cannot cope with a power failure exceeding this time. For example, even if an emergency power supply is provided, if the time lag until switching to it exceeds 20 ms, the lamp is turned off, and it cannot be turned on again unless a sequence including after cooling is executed.

In order to shorten the time required for relighting after power recovery, it is conceivable to increase the capacity of the smoothing capacitor 12 and lengthen the time during which lighting can be maintained without input of commercial power. However, increasing the capacity means increasing the size of the smoothing capacitor 12, and the lighting device itself must be large. In addition, an increase in the size of the smoothing capacitor 12 means that the device cost increases accordingly.
The invention of this application has been made in consideration of the above problems, and maintains the ionization state for a long time during a power failure without using an emergency power source or increasing the capacity of the smoothing capacitor, and recovers the power. After power is turned on, it quickly returns to the lighting state (normal mode) before the occurrence of a power failure, so that the lamp loses time due to a power failure and the subsequent re-lighting causes a loss of time, and the electrodes are consumed by repeatedly turning the lamp off and on again. It is an object of the present invention to provide a discharge lamp lighting device that solves the problem.

In order to solve the above problems, the invention according to claim 1 of the present application includes a rectifying and smoothing circuit connected to a commercial power source,
A DC / DC conversion circuit that includes an inverter circuit, converts the output of the rectifying and smoothing circuit to an arbitrary direct current by the inverter circuit, and supplies the direct current to the discharge lamp;
A lamp measurement circuit for measuring the power supplied to the discharge lamp or the current flowing through the discharge lamp;
A discharge lamp lighting device that includes a lighting control unit that controls the inverter circuit according to a measurement result in the lamp measurement circuit, and that supplies power to the discharge lamp connected to the output side of the DC / DC conversion circuit,
The inverter circuit is a circuit that can be controlled in the normal mode. In the normal mode, the power or current of the discharge lamp becomes a normal value by switching the output of the rectifying and smoothing circuit according to the measurement result of the lamp measurement circuit. Control mode,
further,
It has a power failure continuation detection means that detects that a commercial power failure has continued beyond the set normal lighting maintenance condition range,
The rectifying / smoothing circuit includes a smoothing capacitor,
The set normal lighting maintenance condition is a condition determined as a condition that normal lighting can be maintained by the accumulated charge of the smoothing capacitor after a power failure of the commercial power supply.
The lighting control unit can control the inverter circuit in the ionization maintenance mode in addition to the normal mode. In the ionization maintenance mode, the discharge lamp power or current is lower than the normal value and discharged. In this mode, the inverter circuit is controlled so that the ionization maintenance target value, which is the value of power or current that can maintain the ionization state in the arc tube of the lamp, is obtained.
The power failure continuation detection means is a means for detecting that the power failure detected by the power failure sensor has continued beyond the set normal lighting maintenance condition range, provided with a power failure sensor for detecting a commercial power failure.
The lighting control unit switches the control in the inverter circuit from the normal mode to the ionization maintaining mode when the power failure continuation detecting means detects that the power failure of the commercial power source has continued beyond the range of the set normal lighting maintenance condition. It has the structure of.
In order to solve the above-mentioned problem, the invention according to claim 2 is the configuration according to claim 1, wherein the set normal lighting maintenance condition is that normal lighting can be maintained by the accumulated charge of the smoothing capacitor after a power failure of the commercial power supply. It has a configuration that is a time set as time.
Moreover, in order to solve the said subject, invention of Claim 3 is the rectification smoothing circuit connected to a commercial power supply,
A DC / DC conversion circuit that includes an inverter circuit, converts the output of the rectifying and smoothing circuit to an arbitrary direct current by the inverter circuit, and supplies the direct current to the discharge lamp;
A lamp measurement circuit for measuring the power supplied to the discharge lamp or the current flowing through the discharge lamp;
A lighting control unit for controlling the inverter circuit according to the measurement result in the lamp measurement circuit;
A discharge lamp lighting device for supplying power to a discharge lamp connected to the output side of the DC / DC conversion circuit,
The inverter circuit is a circuit that can be controlled in the normal mode. In the normal mode, the power or current of the discharge lamp becomes a normal value by switching the output of the rectifying and smoothing circuit according to the measurement result of the lamp measurement circuit. Control mode,
further,
It has a power failure continuation detection means that detects that a commercial power failure has continued beyond the set normal lighting maintenance condition range,
The rectifying / smoothing circuit includes a smoothing capacitor,
The set normal lighting maintenance condition is a condition that is set as a condition that allows normal lighting to be maintained by the accumulated charge of the smoothing capacitor after a power failure of the commercial power supply, and the lower limit of the voltage across the smoothing capacitor remaining charge that can maintain normal lighting Value,
The lighting control unit can control the inverter circuit in the ionization maintenance mode in addition to the normal mode. In the ionization maintenance mode, the discharge lamp power or current is lower than the normal value and discharged. In this mode, the inverter circuit is controlled so that the ionization maintenance target value, which is the value of power or current that can maintain the ionization state in the arc tube of the lamp, is obtained.
When the power failure continuation detecting means detects that the power failure has continued until the voltage across the smoothing capacitor falls below the lower limit after a power failure of the commercial power supply, the lighting control unit switches the control in the inverter circuit from the normal mode to the ionization mode. It has the structure of switching to the maintenance mode .
In order to solve the above problem, the invention according to claim 4 is the configuration according to claim 1, 2, or 3, wherein the lighting control unit is switched from the normal mode to the ionization maintenance mode, and then the ionization maintenance target. The inverter circuit is controlled by increasing the value periodically or gradually.
In order to solve the above problem, the invention according to claim 5 is the configuration according to claim 4, wherein the lighting control unit periodically changes the ionization maintenance target value after switching from the normal mode to the ionization maintenance mode. The inverter circuit is controlled at a high value, and the lowest value in each cycle is zero.
In order to solve the above-mentioned problem, the invention according to claim 6 has a structure in which the rated power of the discharge lamp is 1 kW or more in the structure according to any one of claims 1 to 5.

As will be described below, according to the invention described in each claim of the present application, the inverter circuit can operate in the ionization maintenance mode in addition to the normal mode, the commercial power supply fails, and the power failure satisfies the set normal lighting maintenance condition. Since the control in the inverter circuit is switched from the normal mode to the ionization maintaining mode when continuing beyond the range, the ionization state in the arc tube is maintained using the residual charge in the smoothing capacitor. Therefore, when power is restored in the ionization maintaining state, the discharge lamp can be returned to the normal lighting state without performing the after cooling sequence. For this reason, the time required to return the discharge lamp to the state before the occurrence of the power failure (normal mode) is shortened, and productivity deterioration due to the power failure is minimized. In addition, since the ionization maintenance target value is lower than the target value during normal lighting, the charge reduction of the smoothing capacitor is slow, the time during which ionization can be maintained is long, and the power failure time that can be restored to normal lighting without after-cooling is longer Become. For this reason, it becomes possible to deal more widely with power outages that may occur due to various factors, and it becomes a discharge lamp lighting device that is particularly suitable when used in areas where power conditions are not good.
According to the invention of claim 4, in addition to the above effect, the ionization maintenance target value is periodically or gradually increased after switching from the normal mode to the ionization maintenance mode. The rise to the extent that it cannot be controlled is suppressed.
According to the fifth aspect of the present invention, in addition to the above effect, since the lowest value in each period in the periodic ionization maintenance target value is zero, the lamp voltage rises while saving the residual charge of the smoothing capacitor. The suppression effect can be obtained.
In addition, according to the invention described in claim 6, since the rated power of the discharge lamp is 1 kW or more, there are many cases in which after-cooling must be performed when the ionization state is eliminated, and each of the above effects is obtained. Significant significance.

It is the schematic of the discharge lamp lighting device which is embodiment of invention of this application. It is a figure for demonstrating the lighting device of embodiment, Comprising: It is the schematic which showed about the relationship between setting normal lighting maintenance time and the selection of the capacity | capacitance of the smoothing capacitor | condenser 12, and the smoothing capacitor | condenser 12 at the time of a power failure It is the schematic which showed the change of the amount of stored charges. It is the schematic shown about the power recovery in ionization maintenance mode. It is the timing chart shown about the control sequence in the discharge lamp lighting device of an embodiment. It is the schematic shown about the control pattern in ionization maintenance mode. It is the schematic of the discharge lamp lighting device of a prior art example.

Next, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described.
Drawing 1 is a schematic diagram of a discharge lamp lighting device of an embodiment. The lighting device shown in FIG. 1 includes a first rectifying / smoothing circuit 1 connected to a commercial power supply CP, a transformer 2 provided so that the output of the first rectifying / smoothing circuit 1 is on the primary side, An inverter circuit 3 provided between the rectifying / smoothing circuit 1 and the transformer 2 for controlling the power supplied to the discharge lamp L; a second rectifying / smoothing circuit 4 provided on the secondary side of the transformer 2; And a lamp measuring circuit 5 for measuring the power supplied to the lamp L.

  The commercial power supply CP means a power supply source sold by a power company. However, when the apparatus of the embodiment is used in a factory or the like, it may have a private power generation facility. It's a little broader. That is, the commercial power supply CP means a power supply (external power supply) that supplies power to the lighting device. The apparatus according to the embodiment has a function to cope with such a power failure.

The first rectifying / smoothing circuit 1 includes a diode bridge (full-wave rectifying circuit) 11 as a rectifying circuit and a smoothing capacitor 12.
In this embodiment, the inverter circuit 3 is formed of a full bridge inverter circuit composed of four semiconductor switching elements (transistors, FETs, IGBTs, etc.). By turning on two switching elements alternately, the output (direct current) of the rectifying and smoothing circuit is converted into a rectangular wave. Such a switching circuit 3 is disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-39390, and can be referred to. The output of the inverter circuit 3 is a high frequency of about 20 kHz to 100 kHz, and the transformer 2 is a high frequency insulating transformer.

The second rectifying / smoothing circuit 4 is for rectifying and smoothing the high frequency converted by the transformer 2 into a direct current and supplying it to the lamp electrode. As shown in FIG. 1, the second rectifying / smoothing circuit 4 includes a diode bridge 41 as a rectifying circuit, a choke coil 42 as a smoothing circuit, a capacitor 43, and the like.
In the discharge lamp lighting device of FIG. 1, the inverter circuit 3, the transformer 2, and the second rectifying / smoothing circuit constitute a DC / DC conversion circuit for supplying specified power or current to the discharge lamp.
In this embodiment, the lamp measurement circuit 5 measures the power supplied to the discharge lamp L, measures the voltage at both ends of the discharge lamp L and the current flowing through the discharge lamp L, and outputs the power value. It is supposed to be.

  The lighting device of the embodiment includes a lamp control unit 6 that controls the lighting state of the discharge lamp L, and the lamp control unit 6 includes a lighting control circuit 61 that controls the switching circuit 3. As shown in FIG. 1, the lamp measurement circuit 5 is connected to a lighting control circuit 61. The lighting control circuit 61 controls each switching element in the inverter circuit 3 in accordance with the output of the lamp measurement circuit 5, and performs PWM control and PFM control so that the duty ratio of the rectangular wave becomes a predetermined value.

Such a lighting device includes an input terminal connected to the commercial power supply CP, and the input terminal is connected to the first rectifying and smoothing circuit 1. When an AC voltage from the commercial power supply CP is applied to the first rectifying / smoothing circuit 1 via the input terminal, the first rectifying / smoothing circuit 1 smoothes the DC voltage, and then the inverter circuit 3 It is converted to a high frequency voltage with a duty ratio. The high-frequency voltage is transformed by the transformer 2 and then returned to direct current by the second rectifying and smoothing circuit 4 and applied between the lamp electrodes. Thereby, the steady lighting of the discharge lamp L is maintained.
At the start of lighting of the discharge lamp L, the igniter circuit 7 operates, and a high voltage is applied between the lamp electrodes to break down the inside of the arc tube and start discharge. After the discharge starts, the current flowing between the lamp electrodes is adjusted, and a stable lighting state is entered.
Although omitted in FIG. 1, it is preferable to insert a choke coil for power factor improvement before the diode bridge 11.

Further, the lighting control circuit 61 includes a power target value setting unit (not shown) in which a target value of power supplied to the discharge lamp L is set. In many cases, the power target value is a rated power, but the target value may be appropriately changed in consideration of parameters such as the required illuminance on the irradiation surface and the integrated lighting time of the discharge lamp L. . The lamp measurement circuit 5 and the lighting control circuit 61 constitute a feedback control system, and feedback control is performed so that the set power is obtained.
A mode in which the above control is performed by the lighting control circuit 61 is hereinafter referred to as a normal mode. The normal mode means a control mode in a normal state where no abnormal state of power failure has occurred.

  In such a discharge lamp lighting device, a power failure of the commercial power supply CP can occur as described above. The lighting device of the embodiment has a special configuration in consideration of this point. That is, first, the capacity of the smoothing capacitor 12 is determined so that a normal lighting state can be maintained if a power failure occurs for a short time. The capacity for this varies depending on the type of the discharge lamp L, the rated power, and the time during which the normal lighting state is maintained. For example, when the discharge lamp L has a rated power of 1 kW or more, the capacity of the smoothing capacitor 12 is about 1000 μF to 5000 μF. More specifically, when the rated power of the discharge lamp L is about 10 to 15 kW (for example, 13.5 kW), the capacity of the smoothing capacitor 12 is about 10000 μF to 100000 μF.

Moreover, the lighting device of the embodiment is controlled in the inverter circuit 3 according to the detection result of the power failure continuation detecting means 8 and the power failure continuation detecting means 8 for detecting that the commercial power source CP exceeds the set normal lighting maintenance condition range. And switching means for switching between.
In this embodiment, the set normal lighting maintenance condition is a time (hereinafter referred to as a set normal lighting maintenance time) set as a time during which normal lighting can be maintained by the accumulated charge of the smoothing capacitor after a power failure of the commercial power supply. The power failure continuation detection means 8 includes a power failure sensor 81 and a determination unit that determines whether or not a power failure has continued for a time equal to or longer than a set normal lighting maintenance time by an output from the power failure sensor 81. As the power failure detection means 8, for example, a power failure detector S87A sold by OMRON Corporation can be used.

  The power failure sensor 81 may be connected to the input terminal of the commercial power supply CP. The power failure sensor 81 is a sensor that outputs a power failure occurrence when the voltage of the commercial power supply CP drops below a limit. For example, when the commercial power source CP is a three-phase alternating current and the rated value is 200 V, the power failure sensor 81 outputs a signal to the timer circuit 82 as a power failure when the power failure sensor 81 becomes 150 V or less. The output from the power failure sensor 81 continues while a power failure occurs. The determination unit is a timer circuit 82 and outputs a time-up notification signal that becomes active when the timer is turned on as will be described later. Note that the reference value that the power failure sensor 81 determines as a power failure can be arbitrarily changed in addition to 150V.

The set normal lighting maintenance time and the capacity of the smoothing capacitor 12 will be described with reference to FIG. FIG. 2 is a schematic diagram showing the relationship between the set normal lighting maintenance time and the selection of the capacity of the smoothing capacitor 12 in the lighting device of the embodiment, and shows the accumulated charge amount of the smoothing capacitor 12 when a power failure occurs. It is the schematic which showed the change.
When the discharge lamp L is normally lit, the smoothing capacitor 12 operates literally to perform a smoothing action, and the smoothing capacitor 12 is fully charged. The amount of charge, and _{Q 0} in FIG. For example, a power failure the voltage falls below a predetermined value occurs in the commercial power supply CP, to the time and t _0.

Since the time t ₀ the voltage of the commercial power supply CP falls below a predetermined value, a smoothing capacitor 12 starts to discharge from time t _0, power supply to the discharge lamp L is continued while using the stored charge. Therefore, the amount of charges stored in the smoothing capacitor 12 from the time t ₀ starts to decrease. Although the lighting of the discharge lamp L by the stored charge of the smoothing capacitor 12 as described above is maintained, it decreased gradually accumulated charge amount with the passage of time, at time t _1, the limit capable of supplying electric power that can be sustaining It falls below the amount of charge Q _1. Therefore, the discharge lamp L in the time t ₁ is turned off. When selecting the capacitance of the smoothing capacitor 12, the capacitance of the smoothing capacitor 12 so that the time slightly before the time t ₂ than the time t ₁ by a margin becomes set normal lighting maintenance time is selected.

  Thus, as a design order, first, the set normal lighting maintenance time is determined, and the capacity of the smoothing capacitor 12 is determined with a margin so as to meet this. The set normal lighting maintenance time responds to the user's request that the normal lighting state should be maintained for a very short power failure, and as described above, about 10 ms (milliseconds) to about 50 ms (for example, 20 ms). It is.

  Note that “maintaining the normal lighting state” in the set normal lighting maintaining time means performing the same control as in the case of maintaining the normal lighting state where no power failure has occurred. Here, if the same control as that before the power failure occurs is continued after the power failure, the switching duty of the inverter circuit 3 is maintained in order to maintain the lamp power at a specified value as the charge amount of the smoothing capacitor 12 is attenuated. The ratio increases gradually. Therefore, if the state is continued as it is, the switching duty ratio eventually reaches the upper limit value, and thereafter, the switching duty ratio sticks to the upper limit value, and the lamp power cannot be maintained.

On the other hand, the lighting device of the embodiment sets a control mode called an ionization maintenance mode separately from the normal mode. The ionization maintenance mode is a mode that assumes an abnormal state of power failure. This mode is a mode for controlling the power value to be a value lower than the normal value and capable of maintaining the ionization state in the arc tube of the discharge lamp L.
The lamp control 6 includes a mode switching unit 62. The mode switching unit 62 is a controller provided for the lighting control circuit 61, and is specifically hardware such as a PLC (Programmable Logic Controller). The controller switches the control in the inverter circuit 3 from the normal mode to the ionization maintenance mode when the power failure occurs for a time longer than the set normal lighting maintenance time based on the signal from the power failure detection means 8, and the ionization maintenance mode period Software that switches from the ionization maintenance mode to the normal mode when power is restored is built in. Hereinafter, the ionization maintenance mode will be described.

  In fact, the discharge lamp can be lit again without executing the above-described sequence including cooling of the arc tube within a very short time immediately after the supply of power is lost. This can be easily understood from the fact that an AC-driven lighting device in which an inverter is provided between the DC / DC conversion circuit and the discharge lamp can also maintain the lighting of the lamp. In a very short time after the light is turned off, the gas in the arc tube is in an ionized state. Therefore, although the temperature and pressure are high, if a voltage is applied, a discharge is easily generated and lighting is resumed. When a certain amount of time passes and the ionization state is eliminated by recombination and the temperature is high and the pressure remains high, dielectric breakdown (reionization) hardly occurs, and a sequence such as cooling is required. The time during which the ionization state after the extinction is maintained includes a state in which light emission continues in a very weak state.

The lighting device of the embodiment pays attention to such characteristics of the discharge lamp and introduces a control mode called an ionization maintenance mode. In the ionization maintenance mode, the control target value (lamp power target value) set by the lighting control circuit 61 is the minimum power value required for ionization maintenance, which is much higher than the target value in the normal mode. Low power value.
Naturally, how much power is supplied to a discharge lamp to maintain ionization depends on the type of lamp (type of gas enclosed, gas pressure, distance between electrodes, etc.) and the rated power of the lamp. . It also varies depending on the use conditions such as the use temperature (atmosphere temperature). Taking these factors into consideration, the control target value of the lamp power in the ionization maintenance mode is determined in advance. Hereinafter, the target value of power control in the ionization maintenance mode is referred to as an ionization maintenance target value.

  Further, in the apparatus of the embodiment, when power is restored during the ionization maintenance mode period, the influence of the power failure is avoided by returning the control mode to the normal mode. Hereinafter, this point will be described with reference to FIG. FIG. 3 is a schematic diagram showing power recovery during the ionization maintenance mode.

As described above, the ionization maintenance mode is a mode in which the ionization state in the arc tube can be maintained even when the power supplied to the discharge lamp is significantly reduced. The ionization maintenance target value is higher than the normal target value. It is set as a power value that is small and can maintain ionization. In FIG. 3, it is assumed that the smoothing capacitor 12 stores Q ₀ charge during normal lighting and a power failure occurs at t ₀ . At time t ₀ , the residual charge starts to decrease, but when there is no ionization maintenance mode (in the case of the conventional configuration), at time t ₁ , the residual charge of the smoothing capacitor 12 is below the minimum amount Q ₁ that can be kept on lighting, Turns off. On the other hand, assume that switching from the normal mode to the ionization maintenance mode is performed at time t ₂ (when the set normal lighting maintenance time has elapsed). The ionization maintaining mode, because power consumption is greatly reduced, as shown in FIG. 3, a decrease in residual charge is suddenly slow and the t ₂ as a boundary.

Even in the ionization maintenance mode, power is consumed for ionization maintenance, so that the residual charge gradually decreases although it is slow. Then, below the ionization sustainable amount of charge Q ₂ to which it supplies a possible ionization maintain power at a certain time t _3. In FIG. 3, t ₀ to t ₃ are the longest time that the ionization state is maintained at the time of a power failure (hereinafter referred to as the longest ionization maintenance time at the time of power failure).

Power failure ionization maintain maximum time may be the extent to which (t ₂ ~t 3 in FIG. _3), is a major element best is that user request. In other words, it is a request for how long a power failure should occur so that it can be turned on again without performing an after-cooling sequence. When a large ionization maintenance target value is selected, the maximum ionization maintenance time during power failure (t ₀ to t 3 in FIG. ₃ ) is shortened, but this time can be increased by reducing the ionization maintenance target value within a range where ionization maintenance is possible. Therefore, the longest ionization maintenance time during a power failure is first selected so as to satisfy the user request, and the capacity of the smoothing capacitor 12 is selected so that the minimum ionization is maintained within this time. For example, the maximum ionization maintenance time during a power failure is set to 500 ms, for example.

In any case, since the ionization maintenance target value is significantly lower than the normal lighting target value, the rate of residual charge consumption for maintaining the ionization state is much smaller than when the normal lighting target value is maintained. . For this reason, the maximum ionization maintenance time during a power failure is significantly extended. That is, ionization if maintaining mode is not performed, the contrast lighting sustainable power failure time is limited to a short time until time t _1, the when implementing the ionization maintenance mode, the time t ₃ to ionizing sustainable time Is extended. In other words, the technical idea is to use the remaining charge at the end of the set normal lighting maintenance time while saving as much as possible and to make the ionization maintenance time as long as possible.

  When the lighting device is used for the light source of the above-described photolithography exposure apparatus, it may be considered that the exposure amount to the work is insufficient when the ionization maintenance mode is entered and then the power is restored. It is done. For this reason, it is desirable that such a lighting device is configured to notify the exposure device of information indicating that fact. At that time, it is more preferable to add information on the duration of the ionization maintenance mode.

The operation of the discharge lamp lighting device of the embodiment having such a configuration will be described with reference to FIG. FIG. 4 is a timing chart showing a control sequence in the discharge lamp lighting device of the embodiment.
In a state where the apparatus is operating normally, a rated voltage (for example, three-phase 200 V) is input from the commercial power source CP. The voltage is rectified and smoothed by the first rectifying and smoothing circuit 1 and converted into a high-frequency voltage having a predetermined duty ratio by the inverter circuit 3. The high-frequency voltage is transformed by the transformer 2 and then returned to direct current by the second rectifying and smoothing circuit 4 and applied between the lamp electrodes. The mode switching unit 62 sends a signal to the inverter circuit 3 so as to perform control in the normal mode, and the inverter circuit 3 is controlled to light at a normal lighting target value (for example, a rated power value).

Assume that a power outage occurs at time t ₀ due to some cause, and the voltage of the commercial power supply CP drops to 150 V or less. The power failure sensor 81 detects this power failure and switches the output from OFF to ON. As a result, the timer circuit 82 in the power failure continuation detecting means 8 starts operating. When the timer circuit 82 becomes the time t ₂ which counts the completion of setting normal lighting maintenance time (e.g. 20 ms), time-up notification signal is output. If the output of the power failure sensor 81 is still ON at this time, the mode switching unit 62 sends a signal to the inverter circuit 3 to change the control mode to the ionization maintenance mode. As a result, the target value of the electric power supplied to the discharge lamp L is set to an ionization maintenance target value that is smaller than the normal lighting target value, and the inverter circuit 3 is controlled to be this value. As a result, as shown in FIG. 4, for example, when 15 kW is the rated power (normal lighting target value), the ionization maintenance target value is reduced to 1 kW.

As shown in FIG. 4, when power is restored in the ionization maintenance mode (time t ₄ ) and the input from the power failure sensor 81 is turned OFF, the mode switching unit 62 outputs a signal to the inverter circuit 3. Then, the control target value is changed to the normal lighting target value. As a result, electric power necessary for normal lighting is supplied to the discharge lamp L, and the normal lighting state is restored. More specifically, since the ionization state (dielectric breakdown state) is maintained in the arc tube, when the voltage applied between the lamp electrodes is increased, the current between the electrodes can be increased, and accordingly the lamp is supplied to the lamp. The supply power increases. When the power increases to about the normal lighting target value, feedback is applied, and the power of the normal lighting target value is maintained, so that the increase in current is settled and light emission is stabilized. In this case, since the lamp is not turned off / on again, the after-cooling sequence is not necessary and is not performed.

  When the input from the power failure sensor 81 is turned off (recovered) during the normal lighting maintenance time, the timer circuit 82 does not output a time-up signal, and a control signal is sent to the inverter circuit 3 in particular. Absent. In the inverter circuit 3, since the power value that is the normal lighting target value remains set, when the input from the commercial power supply CP is input through the first rectifying and smoothing circuit 1, switching is performed in the same manner as before the power failure. A high frequency voltage is generated and supplied to the discharge lamp L through the transformer 2 and the second rectifying and smoothing circuit 4. Accordingly, in this case as well, the discharge lamp L returns to the normal lighting state, or the normal lighting state is maintained.

  According to the lighting device of the above-described embodiment, the inverter circuit 3 is operable in the ionization maintenance mode in addition to the normal mode, and the inverter circuit 3 is operated when the commercial power supply CP has a power failure for a time longer than the set normal lighting maintenance time. Since the control in the circuit 3 is switched from the normal mode to the ionization maintenance mode by the mode switching unit 62, the ionization state in the arc tube is maintained by using the residual charge in the smoothing capacitor 12. Therefore, when the power is restored within the ionization maintenance mode time, the discharge lamp L can be returned to the normal lighting state without performing the after cooling sequence. For this reason, the time required for relighting is shortened, and productivity deterioration due to a power failure is minimized.

  And since an ionization maintenance target value is lower than a normal lighting target value, the power failure time which can return to normal lighting without after-cooling becomes longer. For this reason, it becomes possible to respond more widely to power outages that may occur due to various factors. For this reason, it becomes a discharge lamp lighting device particularly suitable when used in an environment in which an instantaneous drop for a relatively long time is likely to occur.

In the above-described embodiment, there are several suitable patterns for the control in the ionization maintenance mode, and thus will be described supplementarily. FIG. 5 is a schematic diagram showing a control pattern in the ionization maintenance mode. The horizontal axis in FIG. 5 is time, and the vertical axis is the target value for power control.
As described above, the ionization maintenance target value is a value significantly lower than the normal lighting target value, and the power supplied to the discharge lamp L is not less than the minimum power necessary for maintaining ionization, but is very small power. Is done. In this case, the ionization maintenance target value may be fixed at a constant value as shown in FIG. 5 (a), but it may be preferable to change it as shown in FIGS. 5 (b) and 5 (c). .

When the discharge lamp is turned on with power much lower than the rated power as in the ionization maintenance mode, the current tends to decrease, and the voltage tends to increase. This is because the number of electrons and positive ions between the lamp electrodes decreases, and the insulation between the lamp electrodes gradually increases.
When the ionization maintenance mode is started and the power supplied to the discharge lamp L is set to a small power that is an ionization maintenance target value, the lamp current also decreases. If the lamp current is kept low, the number of electrons and positive ions between the lamp electrodes decreases, so that the insulation between the lamp electrodes gradually increases and the voltage between the lamp electrodes rises. When feedback control is performed with a constant power, the voltage further increases in order to further reduce the current to match the voltage increase. If the voltage rises above the limit, it will rise above the voltage that can be controlled by the inverter circuit 3, and the purpose of maintaining ionization by reducing the output power cannot be achieved.

  In addition, when the power is very small, the voltage and current may vibrate finely, and the lighting state may become unstable. This is considered to be caused by the fact that the temperature in the arc tube has become lower than when the rated power is turned on. When the temperature is further lowered, the ionization state is eliminated, and the inside of the light emission may be in a completely neutral atmosphere state (insulated state).

  In order to avoid these problems, while reducing the power to the ionization maintenance target value, in order to suppress a rise above the lamp voltage limit and a temperature drop above the limit in the arc tube, the power once lowered should be slightly increased. Is preferred. FIGS. 5B and 5C show such a control pattern. For example, as shown in FIG. 5B, a control pattern in which the ionization maintenance target value is slightly increased periodically may be considered. In this example, a square wave pulse shape is used, but a control pattern with other pulse shapes may be used. The control pattern that is periodically changed may be performed immediately after the transition to the ionization maintenance mode, or the control pattern that is periodically changed may be started after a certain amount of time has elapsed.

In addition to the periodic change, as shown in FIG. 5C, a control pattern in which the ionization maintenance target value is gradually increased from a certain point in time may be used. As indicated by the alternate long and short dash line in FIG. 5C, the timing for starting the control pattern for gradually increasing the ionization maintenance target value can be appropriately selected, either earlier or later. Further, the inclination when gradually increasing is also selected as appropriate.
By adopting such a control pattern, it is possible to suppress the lamp voltage rise and the arc tube temperature drop beyond the limit to such an extent that control is impossible while maintaining low ionization-maintaining power.
Even when the control is performed while changing the ionization maintenance target value in such a pattern, if the power is restored within the ionization maintenance mode time and the output of the power failure sensor is turned on, FIGS. As shown by the two-dot chain line in c), the target value is switched to the normal power target value, and the control shifts to the control in the normal mode.

  Further, in the case of the control pattern as shown in FIGS. 5B and 5C, the residual charge of the smoothing capacitor 12 is often consumed earlier than the control pattern shown in FIG. In some cases, the maximum duration of ionization maintenance during a power failure may be slightly shorter. In the case of the control pattern of FIG. 5B, the minimum value in each cycle may be zero (in this case, zero power) if the time is relatively short. In this case, there is a case where there is no large difference in the charge consumption rate when maintaining a small constant value, and there is a case where the maximum ionization maintenance time during a power failure is not particularly shortened. That is, the inclusion of a zero value is preferable in that the residual charge can be saved and the user's desire to keep the ionization time as long as possible can be satisfied.

In the description of the above embodiment, the lamp control is power control (that is, the direct control target is lamp power), but the lamp current may be controlled. In this case, a normal lighting target value and an ionization maintenance target value are set for the lamp current.
In addition, the state in the arc tube in the ionization maintenance mode is sufficient if the ionization state is maintained, and may not necessarily be called “light emission”. In this respect, the ionization mode in the embodiment is conceptually different from the weak emission state mode.

  The lighting device having the ionization maintaining mode as described above is particularly useful in the case of a discharge lamp having a relatively high power. In the case of a large discharge lamp with a large rated power, the pressure and temperature in the arc tube during lighting are likely to be higher than that of a small discharge lamp. For this reason, if the light is extinguished due to a power failure, it cannot be re-lighted without after-cooling, and the after-cooling itself takes a long time. For this reason, the influence on productivity becomes larger. In general, this tendency is remarkable in the case of a high-power discharge lamp of 1 kW or more, and the use of the lighting device of the embodiment is particularly significant.

  Further, the capacity of the smoothing capacitor is selected as a capacity capable of normal lighting during the set normal lighting maintenance time as described above, but when the discharge lamp is 1 kW or more, this capacity is As described above, it is about 1000 to 100,000 F. With such a capacity, it is possible to maintain normal lighting as it is, for example, for a time of about 10 ms to 50 ms.

  In the lighting device of the above-described embodiment, when power is restored in the ionization maintenance mode, the normal mode is automatically restored. However, there may be a configuration in which the automatic restoration is not performed. When power is restored in the ionization maintenance mode, the smoothing capacitor 12 is charged again. However, in the case of a configuration that does not automatically return, the control with the ionization maintenance target value is continued as it is. That is, the ionization maintenance state is continued. Therefore, in this configuration, when the operator confirms power recovery, the operator manually changes the control signal to the inverter circuit 3 to return to the normal mode. Also in this case, since the ionization state of the discharge lamp L is maintained, the after cooling sequence is unnecessary, and the influence on the productivity is reduced. However, in the case of the above-described embodiment, such a manual operation by the operator is unnecessary, and the productivity is higher in this respect.

In the discharge lamp lighting device of the embodiment described so far, the power failure sensor 81 is connected to the input terminal portion of the commercial power supply CP in order to determine whether or not the power failure has continued for a time longer than the set normal lighting maintenance time. And the timer circuit 82 are configured to constitute the power failure detection means 8 and output the time-up notification signal that prompts the transition to the ionization maintenance mode. However, the power failure detection means in the present invention is limited to this. is not.
As described above, the power failure continuation detecting means is means for detecting whether or not the power failure has exceeded the set normal lighting maintenance condition range. The set normal lighting maintenance condition is a condition determined as a condition that allows normal lighting to be maintained by the stored charge of the smoothing capacitor after the power failure of the commercial power supply. In the above embodiment, the smoothing capacitor 12 of the smoothing capacitor 12 is stopped after the power failure of the commercial power supply. This time was set in advance as a time during which normal lighting can be maintained by the accumulated charge.

Other than the above, the normal lighting maintenance condition may be set, for example, the voltage across the smoothing capacitor 12 after a power failure (voltage due to residual charge) may be set. Specifically, a comparator for monitoring the voltage across the smoothing capacitor 12 is provided, and a time-up notification signal is output when it is detected that this voltage has fallen below a specified threshold voltage. May be. Whatever happens, the voltage across the smoothing capacitor 12 is always kept in proportion to the commercial power input voltage in the absence of a power failure, but if a power failure occurs when the discharge lamp is lit in the normal mode, Since the voltage across the smoothing capacitor 12 decreases depending on both the voltage value and the length of the power failure period, the time for promptly entering the ionization maintenance mode without using a power failure sensor or timer is required. This is because an up notification signal can be generated.
In addition, in the case of the configuration described above, the smaller the power when the discharge lamp is lit in the normal mode, the longer the time from when a power failure occurs until the voltage across the smoothing capacitor falls below the threshold voltage and until the time-up notification signal is output. Therefore, the set normal lighting maintenance time is automatically extended, and there is an advantage that the transition to the ionization maintenance mode is easily avoided.

In the embodiment of FIG. 1 described above, an example in which the DC / DC conversion circuit includes the transformer 2 is shown. However, for example, DC / DC conversion is performed by a circuit that does not include a transformer, such as a step-up chopper circuit or a step-down chopper circuit. The invention of the present application exhibits a good effect even in a lighting device constituting a circuit.
In addition, the present invention exhibits a good effect even in a lighting device in which an inverter configured by, for example, a full bridge circuit is provided between the DC / DC conversion circuit and the discharge lamp, and the lamp is AC driven.
In the above-described embodiment of FIG. 1, a simple capacitor input type rectifying and smoothing circuit including the diode bridge 11 and the smoothing capacitor 12 has been described. However, an active filter type power factor correction circuit (PFC) is provided. The present invention exhibits a good effect even in a lighting device.

DESCRIPTION OF SYMBOLS 1 1st rectification smoothing circuit 11 Diode bridge 12 Smoothing capacitor 2 Transformer 3 Inverter circuit 4 2nd rectification smoothing circuit 5 Lamp measurement circuit 6 Lamp control part 61 Lighting control circuit 62 Mode switching unit 7 Igniter circuit 8 Power failure continuation detection means 81 Power failure sensor 82 Timer circuit

Claims (6)

A rectifying and smoothing circuit connected to a commercial power source;
A DC / DC conversion circuit that includes an inverter circuit, converts the output of the rectifying and smoothing circuit to an arbitrary direct current by the inverter circuit, and supplies the direct current to the discharge lamp;
A lamp measurement circuit for measuring the power supplied to the discharge lamp or the current flowing through the discharge lamp;
A discharge lamp lighting device that includes a lighting control unit that controls the inverter circuit according to a measurement result in the lamp measurement circuit, and that supplies power to the discharge lamp connected to the output side of the DC / DC conversion circuit,
The inverter circuit is a circuit that can be controlled in the normal mode. In the normal mode, the power or current of the discharge lamp becomes a normal value by switching the output of the rectifying and smoothing circuit according to the measurement result of the lamp measurement circuit. Control mode,
further,
It has a power failure continuation detection means that detects that a commercial power failure has continued beyond the set normal lighting maintenance condition range,
The rectifying / smoothing circuit includes a smoothing capacitor,
The set normal lighting maintenance condition is a condition determined as a condition that normal lighting can be maintained by the accumulated charge of the smoothing capacitor after a power failure of the commercial power supply.
The lighting control unit can control the inverter circuit in the ionization maintenance mode in addition to the normal mode. In the ionization maintenance mode, the discharge lamp power or current is lower than the normal value and discharged. In this mode, the inverter circuit is controlled so that the ionization maintenance target value, which is the value of power or current that can maintain the ionization state in the arc tube of the lamp, is obtained.
The power failure continuation detection means is a means for detecting that the power failure detected by the power failure sensor has continued beyond the set normal lighting maintenance condition range, provided with a power failure sensor for detecting a commercial power failure.
The lighting control unit switches the control in the inverter circuit from the normal mode to the ionization maintaining mode when the power failure continuation detecting means detects that the power failure of the commercial power source has continued beyond the range of the set normal lighting maintenance condition. A discharge lamp lighting device characterized by that. The set normal lighting maintenance conditions, the discharge lamp lighting device according to claim 1, characterized in that the stored charge of the smoothing capacitor after the power failure of the commercial power source is a time set as the time for normal lighting can be maintained. A rectifying and smoothing circuit connected to a commercial power source;
  A DC / DC conversion circuit that includes an inverter circuit, converts the output of the rectifying and smoothing circuit to an arbitrary direct current by the inverter circuit, and supplies the direct current to the discharge lamp;
  A lamp measurement circuit for measuring the power supplied to the discharge lamp or the current flowing through the discharge lamp;
  A lighting control unit for controlling the inverter circuit according to the measurement result in the lamp measurement circuit;
A discharge lamp lighting device for supplying power to a discharge lamp connected to the output side of the DC / DC conversion circuit,
  The inverter circuit is a circuit that can be controlled in the normal mode. In the normal mode, the power or current of the discharge lamp becomes a normal value by switching the output of the rectifying and smoothing circuit according to the measurement result of the lamp measurement circuit. Control mode,
  further,
  It has a power failure continuation detection means that detects that a commercial power failure has continued beyond the set normal lighting maintenance condition range,
  The rectifying / smoothing circuit includes a smoothing capacitor,
  The set normal lighting maintenance condition is a condition that is set as a condition that allows normal lighting to be maintained by the accumulated charge of the smoothing capacitor after a power failure of the commercial power supply, and the lower limit of the voltage across the smoothing capacitor remaining charge that can maintain normal lighting Value,
  The lighting control unit can control the inverter circuit in the ionization maintenance mode in addition to the normal mode. In the ionization maintenance mode, the discharge lamp power or current is lower than the normal value and discharged. In this mode, the inverter circuit is controlled so that the ionization maintenance target value, which is the value of power or current that can maintain the ionization state in the arc tube of the lamp, is obtained.
When the power failure continuation detecting means detects that the power failure has continued until the voltage across the smoothing capacitor falls below the lower limit after a power failure of the commercial power supply, the lighting control unit switches the control in the inverter circuit from the normal mode to the ionization mode. A discharge lamp lighting device characterized by switching to a maintenance mode. The lighting control unit, after switching from the normal mode to ionizing maintenance mode, claim, characterized in that said ionizing maintenance target value periodically or gradually increased so as to control the inverter circuit 1 2. The discharge lamp lighting device according to 2 or 3 .   The lighting control unit controls the inverter circuit by periodically increasing the ionization maintenance target value after switching from the normal mode to the ionization maintenance mode, and the lowest value in each cycle is zero. The discharge lamp lighting device according to claim 4.   The discharge lamp lighting device according to any one of claims 1 to 5, wherein the rated power of the discharge lamp is 1 kW or more.

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