JP2001273984A - Lighting method and lighting device of high voltage discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting method of a high voltage discharge lamp in which a stress on electrodes at start-up is small, in which electrode melting to cause devitrification is hard to be generated, and which has a good starting capacity. SOLUTION: This is operated with a supply of direct current during the period of less than 5 seconds after the lamp is started, controlled at a substantially constant current after changing feed current into a alternating current successively, and controlled at a substantially constant power while the lamp is lighted in a stable condition. The value of alternating current when controlled at a nearly constant current is equal to or less than twice as much as the current value that can supply a constant power in a specified minimum voltage while the lamp is lighted in a stable condition and, after the lamp is started, the value of direct current is more than 0.5 times and less than 0.9 times as much as alternating current value when controlled at the constant current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting method and a lighting device for a high-pressure discharge lamp, and more particularly to a method in which the stress applied to the electrodes during startup is small, the electrodes are less likely to melt to cause devitrification, and the startup performance is improved. Regarding good things.

[0002]

2. Description of the Related Art A method for operating a high-pressure discharge lamp is known with respect to power control, for example from US Pat. No. 4,240,009.

That is, as described in the claim "1. (d)", a constant current is supplied at the time of lamp startup, and then a constant power is supplied at the time of stable lighting.

Further, this kind of lamp is started by a high-voltage pulse voltage. In the case of a square-wave lamp current, the current is interrupted at the moment when the polarity of the square wave is switched.

[0005] For this reason, commutation mistakes occur in the initial stage of cold start in which the electrode temperature is low, making it difficult to shift from glow to arc, causing blackening of the lamp.

In order to solve such a problem, it has been conceived to start with a DC output for an appropriate period immediately after the start, to prevent commutation until the electrode temperature rises, and to facilitate the transition to an arc. .

However, starting with a DC output puts a heavy burden on the lamp electrode on the positive electrode side, and has a problem that the lamp life is affected.

In particular, in recent years, ultra-high pressure water root lamps with high brightness and long life have been actively developed, and the burden on the positive electrode side due to this DC start cannot be ignored.

That is, when the electrode is slightly melted, an impure alkali component such as potassium contained in the tungsten electrode appears in the lamp, which causes a chemical reaction with quartz glass to cause crystallization of the glass and devitrification. It causes the life to be shortened.

[0010] This electrode melting phenomenon is particularly remarkable in hot start. This is because a large load is applied to the electrode by the DC start even while the temperature of the electrode is still high.

As one means for reducing the load on the electrode, the DC period may be shortened (less than 0.5 seconds). However, before the electrode temperature rises appropriately, the operation shifts to AC lighting and the commutation error occurs. Is liable to occur.

As another means for reducing the load on the electrode, there is a case where the constant current value at the time of starting is sufficiently reduced to such an extent that the electrode does not melt.

In this case, even if the DC period is somewhat longer (0.5
〜5 seconds) Although electrode melting is less likely to occur, the rising time tends to be longer due to insufficient power at lamp startup.

Further, depending on the air-cooled state of the lamp, the lamp may not reach the stable lighting region within the DC period. Furthermore, when the voltage is low due to the variation of the lamp voltage, a problem arises in that the specified constant power cannot be supplied due to insufficient current.

In particular, these problems are short arc (less than 2 mm)
This is remarkable in the high-pressure discharge lamps.

[Test of Conventional Example] In order to confirm the problems of the above-mentioned conventional lighting method, as an example, in a 150 W ultra-high pressure mercury discharge lamp, a bulb outer diameter of 11 mm, an arc length of 1.3 mm,
A prototype lamp with an internal pressure of 180 atm during lighting was prototyped, and lighting was attempted by supplying a square-wave alternating current of approximately 100 Hz.

FIGS. 2A and 2B are diagrams for explaining power control characteristics according to a conventional lighting method. FIG. 2A shows a lamp current characteristic with respect to a lamp voltage, and FIG. 2B shows a lamp power characteristic with respect to a lamp voltage. .

FIG. 3 is a diagram showing a waveform for explaining a lamp current at the time of starting according to a conventional lighting method.

Experimentally, even if the rise of the lamp is long, it is possible to reach the stable lighting region without any problem, there is no commutation error in terms of startability, and the melting point of the electrode is 2.4 A at a constant current value. Was a compromise. At this time, the period of the DC output could be set to about 2 seconds as appropriate.

A curve B in FIG. 5 shows a state of the rising of the lamp at this time, and the time when the light amount is 50% is about 90 seconds.

Next, when the constant current value is reduced to 2 A, the load on the electrode is reduced, which is desirable from the viewpoint of melting of the electrode. However, the rise time is increased to about 120 seconds as shown by curve C in FIG. May not be able to reach the stable lighting region depending on the variation of the lamp and the air cooling condition of the lamp.

In terms of startability, if the DC period is about 2 seconds, the transition to the arc is good at 2 A or more, but commutation mistakes sometimes occur at the timing of switching to AC.

Next, when the constant current value was increased to 2.8 A, the rising characteristic was improved to about 60 seconds as shown by curve A in FIG.

However, in the hot start (relighting test about 30 seconds after the lamp is turned off), it can be observed that the positive electrode tip clearly melts in the DC period. This can be confirmed by observing the inside of the lamp by enlarging and projecting it with a projection lens or the like.

In the case of an ultra-high pressure discharge lamp, basically, no metal halide other than mercury is contained, and an arc having a high color temperature can be visually observed by enlarged projection of the arc. When the electrode melts, an impure alkali component such as potassium contained in the electrode appears, and it can be visually confirmed that an arc having a low color temperature is generated.

In the life test, crystallization was found on the surface of the glass due to the chemical reaction between the impure alkali component and the quartz glass, so that it was confirmed that the electrodes had melted.

[0027]

SUMMARY OF THE INVENTION According to the present invention, when a high-pressure discharge lamp, particularly a high-pressure discharge lamp having a short arc length of 400 W or less, is operated with a square-wave AC lamp current, stress on the electrodes at the time of starting is small. It is another object of the present invention to provide a lighting method and a lighting device in which electrode melting which causes devitrification hardly occurs and which has good startability.

[0028]

According to a first aspect of the present invention, there is provided a method for lighting a high-pressure discharge lamp, comprising supplying a high-current discharge lamp with a rectangular-wave alternating current and lighting the lamp. For a predetermined period of time, start by supplying a DC current, then switch the supply current to an AC current and control it with a substantially constant current, and then control it with a substantially constant power when the lamp is stably turned on. The value of the AC current is not less than 1 time and not more than 2 times the current value capable of supplying constant power at the specified minimum voltage during stable lighting, and the DC current value after starting the lamp is approximately 0.5% of the AC current value during the constant current control. It is not less than twice and not more than 0.9 times.

According to a second aspect of the present invention, there is provided a method for operating a high pressure discharge lamp in which a rare gas and mercury are sealed in an arc tube, and an arc length of 2 mm or less and a high pressure discharge lamp of 400 W or less are used in a high pressure discharge lamp of 50 to 500 W
This is a method of lighting by supplying a square-wave AC lamp current of Hz, and starting by supplying a DC current within 5 seconds after the lamp is started, and then switching the supplied current to an AC current to substantially constant current. Then, the lamp is controlled at substantially constant power during stable lamp operation, and the value of the AC current during the substantially constant current control is at least one time greater than the current value capable of supplying constant power at the specified minimum voltage during stable lamp operation. The DC current value after starting the lamp is 0.5 times or more and 0.9 times or less the AC current value during the substantially constant current control.

According to these, the DC current value at the initial stage of starting and the AC current value that is subsequently controlled at a substantially constant current are appropriately set separately to prevent the electrode from being melted by the DC current and to obtain a sufficient AC current value. Fast rise can be achieved by the current.

A lighting device for a high-pressure discharge lamp according to a third aspect of the present invention is a DC power supply (1) and a down converter (2) connected to the DC power supply (1) for controlling the power of the high-pressure discharge lamp (5). And a full-bridge inverter (3) connected to the output of the downconverter and composed of two pairs of switching elements, a current detection circuit (6) for detecting a lamp current as a detection voltage, and a A voltage detection circuit (7) for detecting as a detection voltage, an inverting amplifier (16) for inverting and amplifying the detection voltage detected by the voltage detection circuit (7), and a detection voltage detected by the current detection circuit (6). Adder circuit (15) that adds the output of the inverting amplifier (16)
A pulse width modulation circuit (9) for performing pulse width control based on the output of the adder circuit (15); and a full-bridge inverter (3) in a preset starting period immediately after the lamp is started. A timer (20) for fixing the switching element in a conducting state and the other set of switching elements in a blocking state, a voltage limiter circuit (17) connected to an output of the inverting amplifier (16), and a signal of the timer (20). It is characterized by comprising means capable of changing the setting of the voltage limiter circuit (17).

According to this, by changing the setting of the voltage limiter circuit (17) using the signal of the timer (20), the DC current value immediately after the start of lighting and the subsequent AC current controlled by the substantially constant current are controlled. 2. The method according to claim 1, wherein the current value can be changed.
The described starting method can be implemented.

According to a fourth aspect of the present invention, in the lighting device of the high pressure discharge lamp, the voltage limiter circuit (17) includes a shunt regulator (27), and a signal of the timer (20) is transmitted. Utilizing the shunt regulator (27)
The setting of the voltage limiter circuit (17) can be changed by changing the voltage value input to the reference.

According to this, the shunt regulator (27)
, The setting of the voltage limiter circuit (17) can be easily changed.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to preferred embodiments.

[Embodiment] Similar to the above-mentioned conventional example, in a 150 W ultra-high pressure mercury discharge lamp as an example, the outer diameter of the bulb is
m, an arc length of 1.3 mm, and a lamp with an internal pressure of 180 atm during lighting were prototyped, and lighting was attempted by supplying a rectangular wave alternating current of approximately 100 Hz.

FIG. 1 is a diagram for explaining power control characteristics according to the lighting method of the present invention. In FIG. 1, (A) shows a lamp current characteristic with respect to a lamp voltage, and (B) shows a lamp power characteristic with respect to a lamp voltage. I have. FIG. 4 shows waveforms for explaining the lamp current at the time of starting according to the lighting method of the present invention.

As shown in FIG. 4, the DC period immediately after the start of lighting is set to a minimum possible value, for example, about 2.0 A in consideration of the arc transferability and the load on the electrodes.

The lighting is switched to AC lighting after about 2 seconds, and is set to a maximum possible value, for example, about 2.8 A in consideration of the rising characteristics and the load on the electrodes.

That is, in the case of the conventional lighting method, the DC current value immediately after the start of lighting and the subsequent AC current value are the same, but in the present invention, both current values are set separately, and the AC current value is set separately. The current value is set to be larger than the DC current value.

As a result, the direct current immediately after the start of lighting can secure a sufficient arc transferability and a current value with a small load on the electrode, and the subsequent alternating current can obtain a sufficient rising characteristic, and The current value can be set so as to reduce the load on the electrode. In the case of AC, the load on the electrode is smaller than in the case of DC because the polarity is inverted, so that a higher current value can be set.

In this embodiment, the DC period is set to about 2 seconds.
Since the DC current value is small and the load on the electrodes is small,
It may be longer than seconds. However, according to the experiment, melting was confirmed on the electrode surface when the voltage was applied for more than 5 seconds, so that the DC period is preferably at most 5 seconds.

The constant current value of the alternating current during the lamp rising period is the specified minimum voltage (about 70 in this embodiment) when the lamp is stably operated.
V), it was found that the range from the current value (150W / 70V = 2.14A in this embodiment) that can supply a constant power (150W in this embodiment) to a maximum of twice that value was appropriate (this embodiment). In the example, 2.8 A, which is about 1.3 times, was selected).

If it exceeds twice, the load on both electrodes becomes remarkable even in the case of AC lighting, which causes a reduction in life.

Next, it has been found that it is appropriate to set the current value in the DC period immediately after the start in a range of 0.5 to 0.9 times the constant current value of the AC. (In the embodiment, the DC current value / AC current value = 2.0 A / 2.8 A = 0.714.) When this ratio is less than 0.5 times, commutation mistakes become remarkable in terms of transferability to the arc or startability. . Also, this ratio
If it exceeds 0.9 times, the problem of life degradation due to electrode melting becomes conspicuous.

[Lighting Device] Next, a lighting device according to the present invention will be described.

FIG. 6 shows an embodiment of a lighting device according to the lighting method of the present invention. The DC power supply (1) supplies the required open-circuit voltage at the time of starting the lamp, and is usually 200 V or more.

The DC power supply (1) supplies power to the down converter (2). The down converter (2) is a switching element (1
1), a power diode (12), a choke coil (13), and a smoothing capacitor (14) to form a step-down chopper of a typical switching power supply.

The output of the down-converter (2) includes a voltage detection circuit (7) for detecting an output voltage and a current detection circuit (6) for detecting an output current. ) Is fed back to the switching element (11) via the pulse width modulation circuit (9).

The downconverter (2) operates at a high frequency (several tens kHz
It switches at several hundred kHz), and calculates the detected output voltage and output current to control the pulse width by controlling the pulse width by the pulse width modulation circuit (9) in order to supply a certain amount of power after the lamp is stably turned on. .

The voltage detection circuit (7) can easily output a voltage divided by the resistors (28) and (29), and the current detection circuit (6) generally has a low voltage of, for example, 1 Ω or less. Use resistors.

A smoothing capacitor (14) is connected between the output terminal (positive electrode side) of the choke coil (13) and the reference potential. This is used to reduce the effect of ripples that occur because the downconverter (2) switches at a high frequency (several tens to several hundreds of kHz). Generally, a capacitor having a capacitance of about 0.1 μF to 10 μF is used, and the ripple content is set to 5% or less.

The DC output (potential is equivalent to the lamp voltage) of the down converter is connected to the switching elements Q2 (23) and Q3 (2
4), Q4 (25), and Q5 (26) are supplied to the full-bridge inverter (3).

The down converter (2) choke coil (1)
The output terminal (positive side) of 3) is connected to the drain of Q2 (23) and the drain of Q3 (24).

The reference potential side of the down converter is connected to the sources of Q4 (25) and Q5 (26) via a current detection circuit.

A circuit connecting the source of Q2 (23) and the drain of Q4 (25) and the source of Q3 (24) and the drain of Q5 (26) are connected between the output terminal of the choke coil (13) and the reference potential. The output of the full-bridge inverter (3), that is, Q
A discharge lamp (5) is connected between the sources of 2 (23) and Q3 (24) via an igniter (4).

A pulse generation circuit (21) is provided at each gate of Q2 to Q05.
Is supplied through a full-bridge drive circuit (10). Full bridge drive circuit (10) is an inversion driver
(35), (36), and non-inverting drivers (37), (38) are connected to the gates of Q4 (25), Q3 (24), Q2 (23), and Q5 (26), respectively.

As a result, Q3 (2
4), Q4 (25) and Q2 (23), Q5 (26) are alternately turned on and off alternately, and the lamp is turned on by a rectangular wave AC. The frequency of the pulse generation circuit (21) is usually 50 to 500 Hz.

The operation circuit (8) comprises a voltage detection circuit (7) for detecting an output voltage, a buffer circuit using an operation amplifier, an operation amplifier (18), a reference voltage (22), and resistors (32) and (33). The signal is input to the addition circuit (15) via the inverting amplifier (16), and the signal of the current detection circuit (6) for detecting the output current is added to the addition circuit (1).
The constant power characteristic can be achieved when the lamp is operated stably by inputting to 5).

The substantially constant current characteristic during the ramp rising period can be achieved by adding a voltage limiter circuit (17) to the output of the inverting amplifier (16).

As the voltage limiter circuit (17), a shunt regulator (27) is generally used. A voltage divided by the resistors (30) and (31) is input to a reference of the shunt regulator (27) and a required lamp is supplied. The region below the voltage can be made substantially constant current.

As a result, the AC constant current value (in this embodiment,
2.8A).

In order to set the current value during the DC period at the start of the lamp to a required value (2.0 A in this embodiment), the output of the timer (20) is connected to the diode (39) and an appropriately set resistor. This can be achieved by connecting to the reference of the shunt regulator (27) via the series circuit of (40).

That is, using the timer (20), the voltage value input to the reference of the shunt regulator (27) is changed only during the DC period immediately after the start of starting, and the current value is set to a required value.

After the elapse of the DC period, the resistance is set by the timer (20).
(40) will not work, so shunt regulator (27)
Changes to a constant current value of AC.

FIG. 7 shows the state of the output voltage of the inverting amplifier (16). FIG. 2 shows the output of the limiter when the limiter is opened, the limiter is turned on during AC lighting, and the output of the limiter when the DC is turned on. By controlling the limiter, an output current control characteristic as shown in FIG. 1 can be created.

[0067]

As described above, according to the present invention, when a high-pressure discharge lamp, especially a high-pressure discharge lamp having a short arc length of 400 W or less, is operated with a square-wave AC lamp current, the AC current value at the time of starting is increased. By separately setting the DC current value in the initial stage of starting the lamp, the burden on the electrodes is reduced, and the lamp can be turned on in a short time without impairing the startability while maintaining the original long life of the lamp Can be.

The effect is particularly large for an ultra-high pressure mercury lamp, in which the load on the electrodes affects the life of the lamp delicately.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating power control characteristics according to a lighting method of the present invention.

FIG. 2 is a diagram illustrating power control characteristics according to a conventional lighting method.

FIG. 3 is a diagram showing a waveform explaining a lamp current at the time of starting according to a conventional lighting method.

FIG. 4 is a diagram showing a waveform explaining a lamp current at the time of starting according to the lighting method of the present invention.

FIG. 5 is a diagram comparing lamp rises due to differences in current values.

FIG. 6 is a diagram showing an example of a lighting device according to the lighting method of the present invention.

FIG. 7 is a diagram illustrating limiter characteristics of power control according to the lighting method of the present invention.

[Explanation of symbols]

(1) DC power supply (2) Down converter (3) Full bridge inverter (4) Igniter (5) Discharge lamp (6) Current detection circuit (7) Voltage detection circuit (8) Arithmetic circuit (9) Pulse width modulation circuit ( 10) Full-bridge drive circuit (11), (23), (24), (25), (26) Switching element (12) Power diode (13) Choke coil (14) Smoothing capacitor (15) Adder circuit (16 ) Inverting amplifier (17) Voltage limiter circuit (18), (19) Opamp (20) Timer (21) Pulse generator circuit (22) Reference voltage (27) Shunt regulator (28), (29), (30), ( 31), (32), (33), (34), (40) Resistance (35), (36) Inverting driver (37), (38) Non-inverting driver (39) Diode

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Koichi Kotani 703 Takamado, Takamaka, Himeji-shi, Hyogo F-Term in Phoenix Electric Co., Ltd. (Reference) 3K072 AA12 BA02 BA05 CA16 DD02 DE06 EB01 GA03 GB03 GB18 GC04 HA02 3K082 AA00 AA01 AA34 AA43 BA53 BA55 BD03 BD04 BD26 BE04 BE08 CA32

Claims (4)

[Claims] 1. A method for lighting a high-pressure discharge lamp by supplying a lamp current of a rectangular wave AC, wherein the lamp is started by supplying a DC current for a predetermined period after the lamp is started, and then the supply current is converted to an AC current. Switching is performed to control the lamp at a substantially constant current. Subsequently, the lamp is controlled at a substantially constant power during stable lighting, and the value of the AC current during the substantially constant current control is a current value capable of supplying a constant power at a specified minimum voltage during the stable lighting. The lighting method of a high-pressure discharge lamp, wherein the DC current value after starting the lamp is 0.5 times or more and 0.9 times or less the AC current value during the substantially constant current control. 2. A rare gas and mercury are sealed in the arc tube,
Arc length 2mm or less, high pressure discharge lamp of 400W or less 50 to 5
This is a method of lighting by supplying a lamp current of 00Hz square wave alternating current, supplying a direct current for a period of less than 5 seconds after the lamp is started, and then switching the supplied current to an alternating current to substantially constant current. Then, the lamp is controlled at substantially constant power during stable lamp operation, and the value of the AC current during the substantially constant current control is at least one time greater than the current value at which constant power can be supplied at the specified minimum voltage during stable lamp operation. The method for lighting a high-pressure discharge lamp, wherein the DC current value after starting the lamp is 0.5 times or more and 0.9 times or less the AC current value during the substantially constant current control. 3. A full circuit comprising a DC power supply, a down converter connected to the DC power supply for controlling the power of the high-pressure discharge lamp, and a pair of switching elements connected to the output of the down converter and forming a pair. A bridge inverter, a current detection circuit that detects a lamp current as a detection voltage, a voltage detection circuit that detects a lamp voltage as a detection voltage, an inverting amplifier that inverts and amplifies the detection voltage detected by the voltage detection circuit, An addition circuit for adding the detection voltage detected by the current detection circuit and the output of the inverting amplifier; a pulse width modulation circuit for performing pulse width control based on the output of the addition circuit; and a preset start immediately after the lamp is started During one period, one set of switching elements of the full-bridge inverter is in a conductive state, and the other set of switching elements is in a cut-off state. Lighting a high-pressure discharge lamp, comprising: a timer fixed to the output of the inverting amplifier; a voltage limiter circuit connected to an output of the inverting amplifier; and a unit capable of changing a setting of the voltage limiter circuit by a signal of the timer. apparatus. 4. The voltage limiter circuit includes a shunt regulator, and a setting of the voltage limiter circuit can be changed by changing a voltage value input to a reference of the shunt regulator using a signal of a timer. The lighting device for a high-pressure discharge lamp according to claim 3, wherein: