JPH03127493A - Two lamp series type lighting device - Google Patents

Abstract

PURPOSE:To reduce a noise by connecting a condenser in parallel to the primary winding of a preheating transformer. CONSTITUTION:By the LC series resonance of a choke coil 8 and a condenser 7, discharge lamps 4 and 5 are started to preheat, a current flows in the primary winding 6a of a preheating transformer 6 through the condenser 7, and by the voltage induced in the secondary winding 6b, a circulation current flows in the filaments 4b and 5a of the discharge lamps 4 and 5 respectively to preheat the filaments 4b and 5a, and the discharge lamps 4 and 5 are lighted all at once. To the winding 6a, a noise preventive condenser 9 is connected in parallel, the transformer 6 is made into the earthing potential of a lighting device through the condenser 7, the filaments 4b and 5a never get a high-frequency potential, and the generation of noise can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-frequency two-lamp series lighting device for discharge lamps that is effective in reducing noise.

[Conventional technology]

In a discharge lamp lighting device with two strokes connected in series using LC series resonance. Only the part where two discharge lamps are connected in series is shown in FIGS. 2 and 3. The circuit portion of the discharge lamp is connected in parallel to the output side of the discharge lamp lighting device. In the conventional example shown in FIG. 2, the resonance system of the circuit differs between when the two discharge lamps 4 and 5 are preheated and immediately after one of the discharge lamps 4 and 5 is lit. For this reason, the discharge lamp 4
In order to start the ゜5 without any trouble, the frequency of the lighting circuit must be changed from the vicinity of = (2π L-C) -' (resonant system in which both lamps are preheated) to = (2πV] in the vicinity of -) - ゛ (1 However, if an attempt is made to obtain a sufficient preheating current in consideration of the lifespan of the discharge lamps 4 and 5, the change in frequency becomes slow.

Therefore, the discharge lamps 4 and 5 are turned on one after another, and it is difficult to turn them on instantly.

Further, the circuit shown in FIG. 3 is an improved example of the conventional example shown in FIG. 2, and there is only one resonance system regardless of whether the discharge lamps 4 and 5 are lit. In the above embodiment, since the discharge lamps 4 and 5 can be preheated and started at a frequency in the vicinity of =(2πV]7 and -)-1, it is relatively easy to light up the two lamps at the same time.

[Problem to be solved by the invention]

However, in the above-mentioned prior art, there was a problem in that the filaments 4b and 5b of the discharge lamps 4 and 5 were charged with a high frequency potential due to the preheating transformer, which increased noise.

SUMMARY OF THE INVENTION An object of the present invention is to obtain a two-plane lighting device that reduces noise by using a preheating transformer.

[Means to solve the problem]

The above purpose is to connect in series the choke coil, the filament on one side of the first discharge lamp, the upper winding of the preheating transformer, the capacitor, and the filament on one side of the second discharge lamp in parallel with the output side of the first lighting device. and the secondary winding of the preheating transformer,
The other filament of the first and second discharge lamps is distantly related to each other by connecting a capacitor in parallel with the primary winding of the preheating transformer in a lighting device configured to form a closed circuit. .

[Effect]

Even while the discharge lamps 4 and 5 are lit, current flows through the primary side of the preheating transformer 6. For this reason, the filaments 4b, 5
A high-frequency current always flows through the discharge lamps 4 and 4.
5 has a high frequency potential. FIG. 4 shows the noise model at this time. In other words, a noise source N exists at the connection point between the discharge lamps 4 and 5, and this noise source causes high-frequency current to leak into the ground impedance Z via the discharge lamps 4 and 5, inducing noise. become. C,, C, is the stray capacitance. Therefore, by connecting a noise prevention capacitor in parallel with the preheating transformer to maintain a stable potential, it is possible to prevent the discharge lamps 4 and 5 from becoming high-frequency potential.

Noise can be reduced.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a di-sided array type lighting device according to the present invention. The embodiment shown in FIG. 1 shows a half-bridge circuit, in which transistors 10 and 11 are connected in series.
By alternately turning on and off the discharge lamps 4 and 5, high frequency power is supplied to the discharge lamps 4 and 5. A circuit consisting of an oscillator 13, transistors 14 and 15, and a transformer 12 is a drive circuit for transistors 10 and 11, and a circuit for driving a capacitor 1 of the oscillator 13.
8 and resistor 19 determine the oscillation frequency.

The preheating start of the discharge lamps 4 and 5 is performed by LC series resonance between the choke coil 8 and the capacitor 7, and the preheating transformer 6 uses the current at this time to preheat the other filaments 4b and 5a of the discharge lamp 4.5. It is. Further, the capacitor 9 in FIG. 1 is a noise prevention capacitor in the present invention.

In the circuit configured as described above, a current flows through the primary winding 6a of the preheating transformer 6 and the capacitor 7 due to the voltage at which the discharge lamp 4.5 is lit.

Therefore, a circulating current flows through the filaments 4b and 5a due to the voltage induced in the secondary winding 6b of the preheating transformer 6, and without the capacitor 9, the filaments 4b and 5a would be charged with a high frequency potential. When a capacitor 9 is connected in parallel with the transformer 6, the preheating transformer 6 becomes the ground potential of the lighting device via the capacitor 7, so that the filament 4a.

5b settles down to a stable potential. Therefore, noise sources between the discharge lamps 4 and 5 can be removed.

It is assumed that the value of the capacitor 9 is larger than the value of the resonance capacitor 7 and does not affect the LC series resonance caused by the choke coil 8 and the capacitor 7. In this manner, the present invention is effective in reducing noise in a two-stroke series lighting system using a preheating transformer.

〔Effect of the invention〕

As described above, the two-plane lighting device according to the present invention includes, in parallel with the output side of the lighting device, a choke coil, one side filament of the I discharge lamp, and the primary winding of the preheating transformer.
The capacitor and the filament on one side of the second discharge lamp are connected in series, and the secondary winding of the preheating transformer and the filament on the other side of the first and second discharge lamps are configured to form a closed circuit. In the lighting device, connecting a capacitor in parallel with the primary winding of the preheating transformer has the effect of preventing an increase in noise generated by the preheating transformer.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of a 2-stroke series lighting device according to the present invention, Fig. 2 is a partial circuit diagram of a conventional 2-stroke series lighting device, and Fig. 3 is a circuit diagram of an improved conventional 2-stroke series lighting device. FIG. 4, a partial circuit diagram of a series lighting device, is a diagram showing a noise model of the conventional circuit shown in FIG. 3 above. 4... Second discharge lamp 5... First discharge lamp 6.
...Preheating transformer 6a...Preheating transformer primary winding 6b...Preheating transformer secondary winding 7...Resonance capacitor 8...Choke coil 9
・・・Noise prevention capacitor

Claims (1)

[Claims] 1. Connect in series a choke coil, one-sided filament of the first discharge lamp, the primary winding of the preheating transformer, a capacitor, and one-sided filament of the second discharge lamp in parallel with the output side of the lighting device. , the secondary winding of the preheating transformer, and the first,
A lighting device configured such that the other filament of the second discharge lamp forms a closed circuit, characterized in that a capacitor is connected in parallel with the primary winding of the preheating transformer. lighting device.