JPH0282498A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To enable high voltage at no-load to be restrained by connecting capacitors in parallel with individual discharge lamps through filaments on the connection sides of two discharge lamps in series, and connecting other capacitor in parallel with the two discharge lamps through filaments on the other sides. CONSTITUTION:A capacitor 16 is connected through filaments 4a and 5b, and capacitors 14 and 15 are connected in series through filaments 4a and 4b, and 5a and 5b. And the series composite capacity value of the capacitor 14 and the capacitor 15 is made almost equal to the capacity value of a capacitor 16. Hereby, in case that fluorescent lamps 4 and 5 are not connected, as the capacitor 16 and the choke do not resonate in LC series, high voltage is never applied to the capacitor 16. Also, preheating currents which flow to each filament at the time of starting-up can be balanced by selecting the capacity of the capacitor 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a two-light series discharge lamp lighting device using series resonance, and particularly to a discharge lamp connection mode suitable for improving safety.

[Conventional technology]

Examples of conventional two-shot series connection methods are shown in FIGS. 2 and 3. In the figure, 4 and 5 are discharge lamps, 1 and 15 are capacitors in parallel with the individual discharge lamps 4 and 5, 16 is a capacitor in parallel with the two lamps, and 17 is a choke coil.

[Problem to be solved by the invention]

The above conventional technology has the following problems.

In Fig. 2, even when the discharge lamps 4 and 5 are not connected, the choke 17 and the capacitor 16 cause LC series resonance, and a high voltage (several times the AC power supply voltage) is applied across the capacitor 16, making it safe. Sexually undesirable. To prevent this, a protection device is required to detect that the discharge lamp 4.5 is not connected and prevent the inverter from stopping oscillation.

In FIG. 3, a connection method that solves the above problem is shown. There is a problem that an imbalance occurs in the residual heat current at the time of δ starting.

That is, filaments 4b and 5b are filaments) 4a
, 4b, the residual heat current becomes larger.

[Means to solve the problem]

The above purpose is to connect the capacitor 15 to the filaments 4a and 5b.
The solution is to connect the capacitors 14, 15 in series via the filaments 4b, 5a.

This is achieved by setting the capacitance values of the capacitors 14, 15, and 16 so as to have the following relationship. That is, the series combined capacitance value of capacitor 14 and capacitor 15 is made approximately equal to the capacitance value of capacitor 16.

[Effect]

If fluorescent lamps 4 and 5 are not connected, capacitor 16
Since there is no LC series resonance between the choke 17 and the choke 17, no high voltage is applied to the capacitor 16.

Furthermore, according to equation (1), the residual heat current flowing through each filament at startup can be balanced by selecting the capacity of the capacitor 16.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows an example of a half-blip circuit, in which high-frequency voltage is supplied to the discharge lamps 4 and 5 by alternately turning on and off cascade-connected transistors 6 and 7. Oscillator 11, transistor 9. A circuit consisting of 10 and a transformer 8 is a drive circuit for a transistor 6.7, and the excavation frequency is determined by a capacitor 12 and a resistor 13 of an oscillator 11.

The discharge lamps 4 and 5 are started using a choke 17 and a capacitor 14.
This is done by 15 LC series resonances. Also, capacitor 1
6 provides a boosting effect even while the discharge lamp 4.5 is on, and improves the fluctuation characteristics due to fluctuations in the electric R voltage.

Here, the effect of the capacitor 16 will be explained. When the effective value voltage of AC type R1 is E, and the voltage V1 of capacitor 2.3 is completely smoothed, it is expressed by the following equation.

V = 2E - (2) On the other hand, since the inverter is a half bridge, the voltage Vjl between A and 8 is expressed by the following equation.

VA, = V, = 2E - (3) Here, if the tube voltage of the discharge lamp 4.5 is VL4゜vLs, then if there is no capacitor 16, VAB >
Unless VL4 + Vt, s - (4) is satisfied, the discharge lamps 4 and 5 cannot be kept lit.

Therefore, under the condition that formula (4) is satisfied, the capacitor 16 is not necessary, but in this embodiment, VAll ≦
This is effective when using a discharge lamp with VL4 + VLs - (5).

That is, the role of the capacitor 16 is to resonate in series with the choke 17 and the capacitor 16 even while the discharge lamps 4 and 5 are on, thereby increasing the voltage applied to the two discharge lamps 4 and 5, thereby stably discharging them.

Conventional methods for connecting the capacitor 16 are shown in FIGS. 2 and 3, but these methods have the same problems as described above.

Therefore, the capacitor 16 is connected to the filament 4a of the discharge lamp 4.
, are connected via the filament 5b of the discharge lamp 5. Further, the capacitors 14 and 15 are connected in series via the filament 4b of the discharge lamp 4 and the filament 5a of the discharge lamp 5, respectively.

As a result, even if the AC power is turned on in a state where the discharge lamp 4.5 is not present, the capacitor 16 becomes open and the A
The voltage between -C increases only to the value (3).

Further, by setting the relationship between the capacitors 14, 15, and 16 as (1), the preheating currents at the time of starting the fluorescent lamps 4 and 5 are kept balanced.

According to experiments, the following formula is more preferable for (1) in terms of the lifespan of the discharge lamp.

Series combined capacitance value of capacitor 14 and capacitor 15 = (
0.9 to 1.1) effective.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIGS. 2 and 3 are circuit diagrams of main parts of conventional examples. 1... Exchange 1! Source, 2.3... Capacitor, 4.5
...Discharge lamp, 6,5...Transistor, 8...Drive transformer, 9.10...Transistor, 11.
...Oscillator, 12...Capacitor, 13...Resistor, 14゜15゜16...Capacitor diagram diagram

Claims (1)

[Claims] 1. In a two-lamp series lighting device that uses series resonance, a capacitor is connected in parallel to each discharge lamp through the filament on the connection side of the two discharge lamps in series,
A discharge lamp lighting device characterized in that another capacitor is connected in parallel with the two discharge lamps via a filament on the other side.