JPH01115097A - Electric discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of acoustic resonance phenomena without problems of radio noise by composing a lamp current wave form of a high frequency supplied to an electric discharge lamp with a fundamental wave component and a second high frequency component to the fundamental wave. CONSTITUTION:When a AC power source 1 is turned on, DC voltage is generated on both ends of a starting circuit 4 with a rectifier 2 and a smoothing circuit 3, when the DC voltage becomes above a given value, the circuit 4 operates and also a drive circuit 5 begins action to flow a base current to a transistor 6 and the transistor 6 becomes an ON state. When the transistor 6 becomes an ON state, voltage is generated between terminals of a main winding 8 of a transformer 7, and an electric discharge lamp 13 is actuated and lit. The voltage between terminals of the winding 7 of the transformer 7 becomes a positive/negative asymmetrical wave form, and a main component of frequency components of the wave form is a fundamental wave and its second high frequency. Consequently, a high bright electric discharge lamp can be satiafactorily lit with problems such as acoustic resonance phenomena, colour separation, short life etc., eleminated by setting and adjusting a component ratio of the second high frequency and a DC component to the fundamental frequency component.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a discharge lamp lighting device that lights a discharge lamp using high frequency waves obtained by converting direct current using an inverter device.

[Conventional technology]

In conventional discharge lamp lighting devices, lighting of the discharge lamp using high frequency is widely practiced in order to reduce size, weight, and loss, and to increase the luminous efficiency of the discharge lamp itself. However, when high-intensity discharge lamps such as high-pressure mercury lamps, high-pressure sodium lamps, and metal halide lamps are lit at high frequencies, a so-called acoustic resonance phenomenon may occur in which the discharge arc fluctuates or sometimes goes out. Therefore, several methods have been proposed to eliminate this phenomenon.

FIG. 6 is a schematic block diagram of a conventional high-frequency discharge lamp lighting device. In Fig. 6, l is an AC power supply, 2 is a rectifier, 21 is a high frequency converter composed of semiconductor switching elements, and 13 is a discharge lamp. This device converts AC into DC with the rectifier 2, and then converts the DC into High frequency converter 2
1 converts it into high-frequency alternating current and supplies it to the discharge lamp 13.

Hereinafter, a conventional method for removing the acoustic resonance phenomenon will be explained with reference to FIG.

First, there is a method of lighting the discharge lamp 13 in a high frequency band in which no acoustic resonance phenomenon occurs.

However, this method increases the switching loss generated in the semiconductor switching elements constituting the high frequency converter 21, which not only poses a problem in terms of reliability of the device, but also increases the frequency of radio noise, which is undesirable.

Therefore, the next method was devised to light the discharge lamp 13 using a waveform in which a third harmonic was superimposed on the fundamental wave. FIG. 7 is a diagram showing the waveform. FIG. 7(a) shows the waveform of the fundamental wave, FIG. 7(b) shows the waveform of the third harmonic with respect to the fundamental wave, and FIG. 7(C) shows the waveform of the third harmonic superimposed on the fundamental wave. This method involves superimposing a third harmonic component above a certain value set in a region where acoustic resonance does not occur on a fundamental frequency set in a frequency band where acoustic resonance occurs.
This is intended to prevent acoustic resonance phenomena. According to this method, the switching frequency of the semiconductor switching element used in the high frequency converter 21 becomes equal to the frequency of the fundamental wave, so that switching loss can be reduced.

[Problem that the invention seeks to solve]

However, the method of superimposing the third harmonic has the following problems in selecting the fundamental frequency. Generally, the intensity of the acoustic resonance phenomenon in a high-intensity discharge lamp (the degree of swinging of the arc and the ease with which it goes out) tends to weaken as the frequency of the alternating current voltage for lighting the discharge lamp 13 increases.

This tendency is the same for metal halide lamps, high pressure mercury lamps, and high pressure sodium lamps.

FIG. 8 is a diagram showing the relationship between the acoustic resonance phenomenon and the lighting frequency in a 100W metal halide lamp, which is an example of this. In FIG. 8, the solid color frequency band represents the stable lighting region, and the arc instability increases in the order of the hatched region, the mesh region, and the black region, and as a result of the experiment,
It was found that the discharge arc disappears in the black region. Incidentally, among high-intensity discharge lamps, metal halide lamps have a wider frequency band in which they exhibit an acoustic resonance phenomenon than high-pressure mercury lamps and high-pressure sodium lamps.

For example, some commercially available small metal halide lamps even exhibit an almost continuous acoustic resonance phenomenon from about 10 KHz to about 200 KHz.

For this reason, even with third harmonic superimposed lighting, if the fundamental frequency is not selected in a resonant frequency band where the intensity of the acoustic resonance phenomenon is relatively weak, even if the third harmonic exceeds the frequency band where the acoustic resonance phenomenon occurs, Even if you choose a suitable location, it may not be possible to prevent acoustic resonance phenomena due to variations depending on the discharge lamp. In addition, depending on the discharge lamp, the resonant frequency band appears intermittently, and there are some that have stable lighting areas scattered here and there, but the resonant frequency band also varies depending on the individual differences of the discharge lamp, the power at the time of lighting, the lighting posture, etc. Therefore, when mass producing lighting devices, it is difficult to set the fundamental frequency to a stable frequency band sandwiched between the resonance frequency bands. Therefore, the fundamental frequency must be set in a relatively high frequency band of the resonant frequency band.
However, if the fundamental wave frequency is made high, the third harmonic will inevitably be in the high frequency region (for example, in the medium radio frequency band).
This may cause problems with radio noise. especially,
This phenomenon is noticeable in discharge lamps such as metal halide lamps, which have dispersion in their resonance frequency bands. As described above, the method of superimposing the third harmonic has the disadvantage that the setting of the fundamental wave frequency is limited by the frequency of the third harmonic.

The present invention has been made based on the above circumstances, and can prevent the occurrence of acoustic resonance phenomena without causing problems with radio noise, and moreover, the fundamental frequency can be set at a third frequency.
It is an object of the present invention to provide a discharge lamp lighting device that is not limited by harmonics.

[Means for solving problems]

To achieve the above object, the present invention provides a discharge lamp lighting device that lights a discharge lamp using a high frequency wave obtained by converting a direct current, in which a lamp current waveform obtained by converting the direct current into a high frequency wave mainly has a fundamental wave component. and a second harmonic component.

[Effect]

As described above, the present invention lights up a discharge lamp using a lamp current in which the second harmonic component is mainly superimposed on the fundamental wave component, so that it is possible not only to prevent the occurrence of acoustic resonance phenomena, but also to prevent the occurrence of acoustic resonance phenomena. Radio noise due to harmonics can be easily removed.

〔Example〕

A first embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. 1 is a diagram showing a first embodiment of a discharge lamp lighting circuit according to the present invention. In FIG. 1, 1 is an AC power supply, 2 is a rectifier, 3 is a smoothing circuit, 4 is a starting circuit that operates when the DC voltage exceeds a certain value, 5 is a drive circuit, and 6
is a transistor, 7 is a transformer, 8 is the main winding of transformer 7,
9 is a limiting winding provided in the transformer 7, 10 is a capacitor, 11 is a diode, 12 is a current limiting reactor, and 13 is a discharge lamp. FIG. 2 is a waveform diagram of current and voltage for explaining the operation of the first embodiment, and FIG. 2(a) is a waveform diagram of the current flowing through the collector of the transistor 6, and FIG.
is a waveform diagram of the voltage between the terminals of the main winding 8 of the transformer 7, t1 to t
3 is a symbol indicating the passage of time. FIG. 3 is a current waveform diagram of the discharge lamp 13 when a 70W metal halide lamp is stably lit with the discharge lamp lighting device of the first embodiment, and a waveform diagram showing the principle of the present invention. is the current (voltage) waveform between the terminals of the discharge lamp 13 when lit, (b) is the waveform of the fundamental wave, (C) is the waveform of the second harmonic with respect to the fundamental wave, and (d) is the waveform of the second harmonic with respect to the fundamental wave. The fundamental wave shown in the same figure (b) and the same figure (C
) is a waveform that is a composite of the second harmonics shown in FIG.

Note that a DC power source may be used instead of the AC power source 1 in FIG. 1. Fig. 4 shows a circuit diagram when using a DC power supply. In Fig. 4, 14 is a DC power supply,
The rest is the same as the first embodiment shown in FIG. In this case, the rectifier 2 and smoothing circuit 3 shown in FIG. 1 become unnecessary.

Now, when AC power supply 1 is turned on, rectifier 2 and smoothing circuit 3
As a result, a DC voltage is generated across the starting circuit 4. When the DC voltage exceeds a certain value, the starting circuit 4 is activated, and the driving circuit 5 also starts operating, causing a base current to flow through the transistor 6, and the transistor 6 is turned on. When the transistor 6 is turned on, the main winding 8 of the transformer 7 has a second
The current shown in Figure (a) begins to flow. This causes transformer 7
A current flows through the control inlet winding vA9 provided in the transistor 6, and by supplying this to the base of the transistor 6, the transistor 6 operates in a saturated on state. Eventually, at time t in Figure 2,
When this occurs, the drive circuit 5 stops supplying the base current, and the transistor 6 turns off. When the transistor 6 turns off, oscillations occur in the tank circuit formed by the main winding 8 of the transformer 7 and the capacitor 10 connected in parallel with it, and the voltage between the terminals of the main winding 8 of the transformer 7 decreases. has a vibration waveform as shown between t and t8 in FIG. 2(b). Then, at time t, the main winding 8 of the transformer 7
When the voltage between the terminals A exceeds the sum of the voltage between the terminals of the smoothing circuit 3 and the voltage drop in the forward direction of the diode 11,
At that moment, diode 11 is turned on. This state continues as long as the voltage between the terminals of the main winding 8 of the transformer 7 due to vibration is higher than the sum of the voltage between the terminals of the smoothing circuit 3 and the forward voltage of the diode 11, that is, until time t. At time t, when the voltage between the terminals of the main winding 8 of the transformer 7 becomes lower than the sum of the voltage between the terminals of the smoothing circuit 3 and the forward voltage of the diode 11, the diode 11 is turned off. At the same time, the discharge current from the capacitor 10 flows into the main winding 8 of the transformer 7, which causes a current to flow through the control winding 9 to the base of the transistor 6.
is turned on again. Thereafter, the above-mentioned operation is repeated.

As a result of the above operation, a second
A voltage as shown in Figure 2(h) is generated, and the discharge lamp 13 is started and lit.The voltage across the terminals of the main winding wA8 of the transformer 7 has the waveform shown in Figure 2(b), so the discharge lamp 13 starts and lights up. '13
The current flowing between the terminals has a positive and negative asymmetric waveform as shown in FIG. 3(a). As a result of detailed examination of the frequency components of the waveform shown in FIG. 3(a), it was found that the fundamental wave and its second harmonic are the main components. FIG. 3(d) shows the fundamental wave (
This is a waveform obtained by combining the waveform (b) in the same figure and the second harmonic ((c) in the figure).

As a result of experimenting with various frequencies based on the waveform shown in FIG. 3(a) above, we found that the effective value of the fundamental wave component of the lamp current flowing through the discharge lamp 13! , and the effective value I2 of the second harmonic component (I z /I + ) was found to be effective in preventing acoustic resonance phenomena by setting it to 0.2 or more. However, if this I*/IIO value is too large, discharge lamp 1
3, the positive/negative asymmetry of the waveform of the current flowing through the I t
It is necessary to suppress the value of /r+ to 0.5 or less.

Note that since the waveform of the lamp current flowing through the discharge lamp 13 is asymmetric between positive and negative, it is allowed to include a DC component, but if the value of this DC component is too large, it may cause color separation or short life of the discharge lamp. 0 In this example device, the ratio of the DC component value 1M of the discharge lamp current to the effective value ■1 of the fundamental wave component (Inc
/It) is easily possible to reduce I D
The above disadvantages can be prevented by setting the value of c/I to 0.3 or less.

As described above, by setting and adjusting the composition ratio of the second harmonic and DC component to the fundamental frequency component, problems such as acoustic resonance, color separation, and shortened life can be eliminated, and high-intensity discharge lamps can be lit well. In addition, discharge lamp 1
As described above regarding the current waveform in No. 3, since the discharge lamp 13 in the high frequency lighting state can be regarded as a substantially resistive load, the voltage waveform of the discharge lamp 13 is substantially similar to the current waveform.

On the other hand, regarding the prevention of radio noise caused by harmonics of the third order or higher of the fundamental wave, as a result of experiments, it was found that the above-mentioned setting values were satisfied and the ratio of the third harmonic I to the effective value 11 of the fundamental wave was ( 13/II) to 0.2 or less could be easily achieved. At this time, the third harmonic has the largest effective value among the third and higher harmonics, and the total effective value f of the discharge lamp current is the effective value of the third and higher harmonics. , the ratio C1,/I. ) was 0.25 or less. Therefore, stable lighting is maintained by the superimposed waveform of the fundamental wave and the second harmonic, and at the same time, it is possible to eliminate the problem of radio noise caused by the third and higher harmonics. As a result, in the conventional method of superimposing the third harmonic, the setting of the fundamental wave frequency was limited by the third harmonic, but according to the device of this embodiment, as described above, the third harmonic Since it is possible to eliminate the problem of radio noise caused by harmonics of the order or higher, the fundamental frequency can be set in a frequency band (higher frequency band) where the acoustic resonance phenomenon is weaker than in conventional devices.

Further, according to the first embodiment described above, the discharge lamp 1 can be operated by a high frequency wave in which the fundamental wave frequency and the second harmonic wave are superimposed using a simple circuit.
3 can be lit.

Note that the transistor 6 used in the first embodiment is M
The starting circuit 4 may be an OS-FET or other element. Also, the starting circuit 4 is not essential and may be added as needed. Furthermore, although the driving circuit 5 has been described as an automatic type, this is not the case. may be passive.

Next, a second embodiment of the present invention will be described with reference to FIG. In Fig. 5, 1 is an AC power supply, 2 is a rectifier, 13
15 is a discharge lamp; 15 is a first generator that generates a fundamental wave component;
16 is a second generator for generating a second harmonic component, and 17 is a transformer for combining the fundamental wave and the second harmonic. In the second embodiment, a first generator 15 generates a fundamental wave as shown in FIG. 3(b), and a second generator 16 provided separately generates a second harmonic as shown in FIG. 3(C). Both waveforms are superimposed by a transformer 17 and supplied to the discharge lamp 13. According to the device of the second embodiment, the voltage (current) waveform of the discharge lamp 13 becomes a waveform as shown in FIG. 3(d), and a superimposed waveform with no DC component is obtained. There is no problem with the lifespan, and other functions and effects are the same as in the first embodiment.

〔Effect of the invention〕

As explained above, according to the present invention, the high-frequency lamp current waveform supplied to the discharge lamp is composed of a fundamental wave component and a second harmonic component with respect to the fundamental wave, thereby eliminating the problem of radio noise. Therefore, it is possible to provide a discharge lamp lighting device that prevents the occurrence of acoustic resonance phenomena and does not limit the setting of the fundamental wave frequency by the third harmonic.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing the first embodiment of the present invention, Fig. 2 is a current and voltage waveform diagram to explain the operation of the first embodiment, and Fig. 3 is a diagram of the current flowing through the discharge lamp. FIG. 4 is a circuit diagram showing a modification of the first embodiment; FIG. 5 is a circuit diagram showing a second embodiment of the invention;
Figure 6 is a schematic block diagram of a conventional discharge lamp lighting device;
The figure is a waveform diagram showing the principle of third harmonic superimposed lighting, and FIG. 8 is a diagram showing the relationship between the lighting frequency of a 100 W metal halide lamp and the acoustic resonance phenomenon. DESCRIPTION OF SYMBOLS 1... AC power supply, 2... Rectifier, 3... Smoothing circuit, 4... Starting circuit, 5... Drive circuit, 6...
Transistor, 7... Transformer, 8... Main winding, 9.
... IS line, 10... Capacitor, 11... Diode, 12... Current limiting reactor, 13... Discharge lamp, 14... DC power supply, 15... First generator, 16
″...Second generator, 17...Transformer, 21...
High frequency conversion device. Applicant: I-Writing System Co., Ltd. Figure 7

Claims (3)

[Claims] (1) In a discharge lamp lighting device that lights a discharge lamp using a high frequency wave obtained by converting direct current, the lamp current waveform obtained by converting the direct current to high frequency waveform is mainly a fundamental wave component and a second wave component.
A discharge lamp lighting device comprising a harmonic component. (2) The ratio (I_2/I_1) between the effective value 1 of the fundamental wave component and the effective value I_2 of the second harmonic component is 0.2.
The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is within the range of 0.5 to 0.5. (3) The discharge lamp lighting device according to claim 1 or 2, wherein the high frequency conversion means includes a transistor inverter device.