JPS60150592A - Device for firing discharge lamp - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a discharge lamp lighting device for lighting a high pressure discharge lamp at high frequency.

[Background technology]

BACKGROUND ART There has been a strong desire for discharge lamp lighting devices to be smaller, lighter, and have lower loss. However, in conventional general discharge lamp lighting devices, choke coils, transformers, capacitors, etc. are used singly or in combination, so that they are large in size and weight. In particular, high-pressure discharge lamps are smaller in size than fluorescent lamps, so when considering incorporating a lighting device into a lighting device, there is a problem in that the storage space is too large and cannot be used properly. For fluorescent lamps, high-frequency lighting devices using switching transistors and the like have been put into practical use with the aim of reducing the size and weight of lighting devices, reducing loss, and improving luminous efficiency. Such a high-frequency lighting device has the same effect as a fluorescent lamp even when applied to a high-pressure discharge lamp, and its practical application is eagerly awaited.

However, during high frequency lighting of high pressure discharge lamps,
It has been known that arc instability (fluctuation, extinction, arc tube destruction, etc.) is caused by acoustic resonance (Journal of Applied Phys.
sics-49(5), may 1978p2680
~2683 and its references) 0 Various methods are known to prevent this, such as rectangular wave lighting and frequency limitation (for example, IES TRANSACTION
DECEMBERI'? 6'? ”In1tialCha
Racteristics of High Inte
Discharge Lamps on H
i-gh Frequency Power'').

The formation mechanism of arc instability that occurs during high-frequency lighting of a high-pressure discharge lamp as described above is thought to be as follows. That is, first a high frequency fluctuation of the electrical input occurs, which causes a pressure change in the gas inside the arc tube, a standing pressure wave is generated at the same wave number, and the pressure amplitude exceeds the limit, causing instability of the arc. occurs. Here, the "special same wave number" is the so-called acoustic resonance frequency, which is determined by the dimension of the arc (actually, the shape of the arc tube) and the sound speed inside the arc tube, and is the same as the above. The speed of sound is determined when the average molecular weight and ion temperature of the gas inside the tube are determined.
Once you know those values, you can set them relatively easily. -The question of the acoustic resonance frequency at which the above-mentioned "arc instability due to pressure amplitude exceeding the limit" occurs is a problem in the nonlinear domain, and cannot be answered simply. It is something.

However, in the process of studying high-frequency lighting of high-pressure discharge lamps, the present inventor discovered that the following technical problems existed. In other words, even if the design is such that arc instability due to acoustic resonance does not occur at rated lighting during steady lighting (this can be achieved, for example, by limiting the same wave number of lighting), the power supply voltage Considering the case of fluctuation, there is a strong possibility that arc instability will occur. It is presumed that such a problem occurs for the following reasons. In other words, when the power supply voltage fluctuates, the state of the arc changes compared to when the rated lighting is applied, and therefore the above-mentioned "special same wave number"
That is, the acoustic resonance isofrequency, and the above-mentioned “
Both the pressure amplitude exceeding the limit, that is, the susceptibility to arc instability, are both changing, so even if a lighting frequency design is implemented to avoid acoustic resonance at rated lighting, the power supply When the voltage fluctuates, arc instability occurs due to the reasons listed in L, and in the end, it is extremely difficult to design a stable lighting frequency when fluctuations in the power supply voltage are taken into consideration. Figure 1 is a specific characteristic diagram for explaining the above state.
is used to show the evaluation of arc stability for combinations of various lighting frequencies and various tube powers, with the O symbol representing stability and the X symbol representing instability. As is clear from the figure, the stable frequency range during rated power lighting does not completely match the stable lighting same wave number range for changes in tube power that would occur due to the power supply type pressure change, and The lighting frequency range becomes narrower as the frequency decreases. At the same time, at the same lighting frequency, arc instability is likely to occur if the tube power fluctuation is on the decreasing side by 1 to the rated tube power.

By the way, when a discharge lamp is lit at a high frequency, it is generally desired to light it at a lighting frequency of 20 KH2 or higher (a frequency exceeding the audible frequency range), for example, but if it exceeds -10,000'OOKuz 2, the electric number Since problems such as an increase in radiation noise from electric lights and an increase in the switching frequency of switching semiconductors occur, the lighting frequency must be higher than a certain frequency (e.g. 20 kHz or higher) and 1 o OK.
It is said that it is desirable to set the frequency within a range that does not significantly exceed Hz. However, in the case of four high-voltage lamps, if the lighting frequency becomes 50 KHz or less, the acoustic problem as explained in Figure 1 above may occur. There is a problem that the probability of arc instability due to resonance is extremely high, and for this reason, setting the lighting frequency is currently an extremely difficult design point. [Object of the Invention] The present invention was made in view of the above points,
The purpose of this is to maintain low levels of radiation noise, power supply feedback noise, switching semiconductors, etc. from the discharge lamp in high-frequency lighting devices for high-pressure discharge lamps, and to prevent arc failure. To provide a discharge lamp lighting device 1'fr in which stability can be solved by E taking into account even the drop in power supply voltage.

[Disclosure of the invention]

(Construction) The present invention has been made based on the discovery of technical problems made during the above-mentioned study regarding high-frequency lighting of high-pressure discharge lamps, and it is a method for high-frequency lighting of high-pressure discharge lamps. When a lamp is lit, approximately the lowest frequency in the frequency range in which arc instability does not occur due to acoustic resonance when the lamp is lit at the rated power (in the case of M 25 o L/Bu mentioned above, approximately gO
KHz) at the same time as lighting the discharge lamp at the rated power.
Stable lighting of the discharge lamp by controlling the tube power to be approximately equal to the rated value or slightly higher than the rated value in response to possible power supply voltage fluctuations, especially when the power supply voltage drops. It is an attempt to obtain.

(Embodiment) Fig. 2 is a circuit diagram of an embodiment for realizing the contents of the present invention described above in a circuit manner. is a diode, Lt is a choke coil, C1 is a capacitor, I
The NV inverter and DL are high pressure discharge lamps. The circuit block including transistor Q1, choke coil LL, capacitor C1 and diode D2 forms a switching regulator circuit, and transistor Q
1 is controlled by the switching control unit A2 and the voltage detection unit A+ of the AC power source v1. When the transistor QI is turned on, a voltage obtained by rectifying the alternating current source V and the n alternating current voltage by the diode bridge DB+ is applied to the choke coil L via the diode D+ and the transistor QtIk. In addition, when transistor Q17 is off, the back electromotive force generated across the choke coil L+ is charged to capacitor C1 through diode l'''D2, and this capacitor C+(r) is charged with a charging voltage of Inno S-YIN.
V is driven to light the high pressure discharge lamp DL.

In the above circuit configuration, the power of the discharge lamp DLO tube can be made variable by making the voltage of the capacitor C1, which is the input voltage of the inverter INV, variable. It can be changed by That is, AC power supply Vs
When the voltage of ff is the rated voltage, high-pressure discharge ff
The voltage of capacitor C+, which is the input voltage of inverter INV, is connected to transistor Q, so that DL becomes the rated tube power.
The switching state of the transistor Qr is set so that even if the voltage of the AC power supply v1 drops below the rated voltage, the voltage of the capacitor CI remains approximately constant or increases slightly. It is possible to keep the high-pressure discharge lamp DLO tube power approximately constant or to increase it slightly. That is, at least when the voltage of the AC power supply v1 drops below the rated voltage, the voltage detection section A1 detects this state, and the switching control section A2 controls the transistor Q and t in a direction to reduce the non-conducting period of the transistor Q1. This makes it possible to keep the voltage of the capacitor C1 substantially constant or increase it to a certain extent, so that the power of the high-pressure discharge lamp DLD tube does not drop below at least the rated power supply voltage. In the embodiment shown in FIG. 2, the inter-ignition frequency of the e-J converter INV is an abbreviation of the frequency range in which arc instability due to acoustic resonance does not occur when the high-pressure discharge lamp DL is lit at the rated power as described above. Figure 3 is a circuit diagram of another embodiment for realizing the above-mentioned content of the present invention in a circuit manner, and in the wooden embodiment, the input voltage to the inverter INV is The waveform is different from that of the embodiment shown in FIG. 4 In Figure 3, the same elements as those in the embodiment in Figure 2 are designated by the same reference numerals and explanations are omitted.D
Further, Cz and Cm are capacitors, D, ~I)S are diodes, and Q2 is a transistor.

In the tree embodiment, transistor Q2 and diode D
The series circuit with 6 is connected to the output of the diode bridge DB+ via capacitors Ct and Cs respectively.The capacitors C2 and C8 each have diodes Da and Daf connected to the diode bridge DBs.
Direct reading is performed in series in the opposite direction to the rectifying direction.

In the circuit shown in Fig. 3, capacitors C and Cs are charged in series from AC power supply vI via diode bridge DB+ by conduction of transistor Q2, and inverter voltage from capacitors Cs and Cs is Discharge to INV is performed in parallel via diodes Ds and D4, respectively. Therefore, inverter I NVf
The input voltage is qualitatively as shown in Figure @4. In the same figure, the broken line is the capacitor C! , Cs% diode D1
．． D4, ) shows the output voltage waveform of the diode bridge DB+ in the absence of transistor Q2. Further, in FIG. 4, voltage VC is the voltage across capacitors CI and C3. Therefore, in the embodiment circuit of FIG. 3, the voltage Vc at the input voltage of the inverter INV as shown in FIG.
By increasing the O value at least when the power supply voltage falls below the rated value, it is possible to prevent the tube power from decreasing when the voltage of the AC power supply vI falls below the rated value. Figure @5 shows an example of how this control is carried out. In the same figure, the solid line is the AC power supply v
I(7) Inverter IN when voltage is rated voltage
The waveform of the D input voltage to V is shown. At this time, the high pressure discharge lamp DLilt is lit at the rated power.

On the other hand, the broken line shows the input voltage waveform to the inverter INV when the voltage of the AC power supply Vt falls below the rated voltage. As can be seen from the voltage waveform of this broken line, when the voltage of the AC power supply V1 falls, the voltage VC rises in the direction of the drop in the power supply voltage. @3
As shown above, the illustrated biography shows the diode bridge D B
The period [1■] which directly drives the inverter INV depending on the output of + and the capacitor C connected to the DC output side of the diode ridge DB+! , the period in which the inverter INV is driven by the charging voltage of the CB is alternately used, but even in such stealing, the high pressure discharge lamp DLO tube power is at least reduced when the AC power supply V+D voltage drops below the rated value It is possible to turn on the light without lowering it below the rated value. In addition, in the example shown in FIG.
The voltage Vck can be made variable as described above by the transistor Q.
2, the conduction period II'I of transistor Q2
This can be easily achieved by controlling as shown in Figure @6. FIG. 6(a) shows the full-wave rectified voltage waveform of the AC power source vlO, in which the solid line is at the rated voltage and the broken line is at the voltage drop. FIG. 6(B) shows the transistor Q! corresponding to the case shown by the solid line in FIG. 6(A). The maximum charging voltage to the series circuit of capacitors C2 and 03 is the voltage value of the AC power supply vltn at [1 or C2]. On the other hand, Figure @6 (C) shows the switching state of transistor Q2 corresponding to the case of the broken line in Figure (A), and the charging voltage to the series circuit of capacitors C2 and Cs is the maximum, C3 or [ This is the voltage value of the AC power supply vlI7') at 4 o'clock. Therefore, in the case of Fig. 6 (0), the charging voltage to the condensers +jc, , c3 is (
In the case of the solid line in Figure 6 (a)), the probability is lower than in the case of Figure 6 (c) (in the case of the broken line in Figure 6 (a)), and as shown in Figure 5 above. This makes it possible to control the voltage Vc.

Figure 7 is a circuit diagram of still another embodiment for realizing the above-mentioned content of the present invention in a circuit manner. In the above-mentioned embodiments in FIG. 2 and FIG. 3, an attempt was made to prevent a drop in tube power when the power supply voltage drops by controlling the input voltage of the inverter INV. On the other hand, in the embodiment shown in FIG. 7, the application of the output voltage of the inverter INV to the high-pressure discharge lamp DL is controlled to prevent the tube power from decreasing when the power supply voltage decreases.
In the circuit shown in FIG. 7, the same elements as those in the circuits shown in FIGS.
4 is a smoothing capacitor, DBz is a diode bridge, Q
s is a transistor. In the tree embodiment, the AC voltage of the AC power supply v1 is charged to the smoothing capacitor C4 via the diode ridge DB+, and the inverter INV is driven by the charged voltage (i). The oscillation output is applied to the high pressure discharge lamp DL via an AC switch circuit consisting of a diode ridge DBs and a transistor Q3.The transistor Q3 connects the output of the inverter INV to the high pressure discharge lamp DL.
This is an element for periodically providing a short pause period 7 in the power supply to the AC power source vI, and by configuring the pause period to be substantially short when the effective voltage value of the AC power source vI is lower than the rated time, This is a book that can maintain the high-pressure discharge lamp DLD tube power at least above the rated value when the power supply voltage drops.In addition, in both the example in Figure 3 and the example in Figure 7, the same wave number of oscillation of the inverter INV is as described above. It is set to approximately the lowest frequency in a frequency range in which instability of the arc due to acoustic resonance does not occur when the high-pressure discharge lamp DL is lit at the rated power. In other words, the high-pressure discharge lamp DL should be lit at the lowest lighting frequency that is higher than the highest lighting frequency at which arc instability occurs due to acoustic resonance when the lamp is lit at the rated power. means. To explain this with a diagram, for example, in the case of the metal halide lamp mentioned above, the present inventors have experimentally confirmed that the high frequency lighting characteristics shown in Figure @8 can be obtained. The shaded area in the figure is the area where arc instability occurs, and the lighting frequency ff: is the minimum point among the lighting wavenumbers higher than the highest lighting wavenumber where such arc instability occurs! This means that if the interval number is set to o (approximately gQKHz), arc instability will not occur.

[Invention effect]

Uninvented 1d It is constructed as described above, and in a discharge lamp lighting device for lighting a high-pressure discharge lamp at high frequency, it operates at approximately the lowest frequency in the frequency range in which instability of the arc due to acoustic resonance does not occur when lighting at 1 rated power. The discharge lamp is lit at the rated power, and when the power supply voltage drops below the rated value, the discharge lamp tube power is controlled so that it is approximately equal to the rated value or slightly higher than the rated value. Because of this, it has the advantage of being able to completely eliminate arc instability, taking into consideration not only when lighting at one rated power but also when the power supply voltage drops, and the lighting frequency is the lowest within the possible range. This has the advantage that radiation noise from the discharge lamp and source feedback noise can be reduced, and switch noise of the switching semiconductor can be reduced.

[Brief explanation of drawings]

@Figure 1 is a characteristic diagram of a conventional high-pressure discharge lamp! Fig. 2 is a circuit diagram of one embodiment of the present invention, Fig. 3 is a circuit diagram of another embodiment of the present invention, Figs. FIG. 8, which is a circuit diagram of still another embodiment, is a diagram showing the lighting frequency in the discharge lamp lighting device of the present invention. DL is a high-pressure discharge lamp, INV is an inverter, Vl is an AC power source, and Q+ to Q3 are transistors. Agent Patent Attorney Ishi 1) Long 7 @ 1 Figure Ct case - 100%) DB+ Figure 4 111ff 5 Figure 6 T3 T4 Figure 7 NV Figure 8) f.

Claims (1)

[Claims] In a discharge lamp lighting device for lighting all il+ high-pressure discharge lamps in a directional wave, the discharge lamp is lit at approximately the lowest frequency in the frequency range in which instability of the arc due to acoustic resonance does not occur during lighting at the rated power, A discharge lamp lighting device which is characterized in that when the power supply voltage drops below the rated value, the discharge lamp tube power is controlled to be approximately equal to the rated value or slightly higher than the rated value. stomach.