DE1080227B - Circuit arrangement for electric discharge lamps - Google Patents

Description

The invention relates to a circuit arrangement for electric discharge lamps with preheated electrodes with PTC resistor and fed by heating current windings in the transformer of a resonance-tuned LC ballast. With such circuits, discharge lamps can be operated without magnetic relays, thermal interrupters or glow starters.

Resonance ignition circuits are known per se. In all of these ignition circuits, the voltage increases over the discharge lamp or lamps depending on the current flowing through the resonance circuit. The resonance current also flows through the electrodes of the directly or indirectly via heating current windings Discharge lamp or lamps and is determined by the electrical values of the resonance circuit, such as inductance, Capacitance and ohmic resistance, determined together on the resonance curve Determine the operating point of the arrangement.

A known arrangement works with a high and a multiple of the operating voltage and resonance voltage that occurs immediately when switching on. With another, the voltage increase generated by a distribution transformer complicating the system.

Finally, it is also known the shift in resonance caused by the ignition of the lamp and the the associated loss of core saturation.

In all known arrangements either an overvoltage far above the ignition voltage is generated, or the ignition voltage cannot be controlled within a certain range. In the first case, the operation involves considerable dangers. In the second case, the premature, undesirable cold start of the lamps makes safe continuous operation more difficult and reduces the service life of the lamps. On the other hand, if you choose the resonance voltage so low that no cold start is to be feared, e.g. B. 265 V, the discharge lamp will not ignite with certainty under all circumstances.

The circuit arrangement according to the invention has the advantage over the known circuits that both reliable ignition and a long service life of the discharge lamp are obtained and a limited and controlled voltage increase is used for this purpose. The new circuit arrangement is intended for electrical discharge lamps with preheatable electrodes that have a resistance dependent on the glow temperature and are fed by the heating current windings in a transformer part of a resonance-tuned inductive-capacitive device for operating the discharge lamp or lamps. The essence of the circuit arrangement
for electric discharge lamps

Applicant:
Lumalanipan Aktiebolag, Stockholm

Representative: Dipl.-Ing. J, Gilliard, patent attorney,
Munich 9, Lindenstr. 21

Claimed priority:
Sweden 21 December 1955

Dr. phil. Gosta Siljeholm, Bromma

and Äke Björkman, Älvsjö (Sweden),

have been named as inventors

Circuit arrangement according to the invention is that the heating current windings with the primary winding are electrically and magnetically firmly coupled with such a translation that the transformed resistance change of the electrodes detunes the resonance circuit so that that of the discharge lamp and lamps supplied resonance voltage due to the resonance detuning of one during the preheating Cold start preventing, low value on the ignition voltage is increased.

For this purpose, a choke is expediently connected in series with the discharge lamp, which is connected to an as Transformer executed, with the capacitor in series-connected resonant choke is bridged. Of the The transformer has two heating current windings for each heatable electrode. This is how it becomes possible to dimension the circuit in such a way that the voltage across the discharge lamp is short has a sufficiently low value after switching on, and as soon as the electrodes get hot, on only then increases to a higher value that is permissible, which ensures reliable ignition under all external conditions guaranteed because the resistance of the electrodes changes from the initial cold state is used up to the hot end state. There can be an approximately tenfold increase in resistance in the case of electrodes of the usual type. The change in resistance influences the electrical process in the oscillating throttle via the heating current windings so that their impedance goes from a lower value when the electrodes are cold to a higher value increases with hot electrodes.

9Oi 787/175

The invention and all illustrated embodiments common is the fact that the resonance of the oscillating circuit (resonance circuit) when switched on with cold glow electrodes shifted to the capacitive side of the resonance for mains frequency is and that with increasing electrode resistance the resonance of the oscillating circuit of the resonance for grid frequency approaches, but does not exceed this.

The circuit arrangement according to the invention will become apparent from the description of some in the drawings specified embodiments explained in more detail.

1 shows a circuit arrangement according to the invention for operating a discharge lamp the in

Figure 2 is a schematic diagram of some data in comparison with the corresponding data of the known one circuits described above is given;

3 shows an arrangement according to the invention for operating two discharge lamps;

Fig. 4 shows a schematic diagram of the arrangement of Fig. 3;

5 shows another arrangement according to the invention for operating two discharge lamps.

In the arrangement according to FIG. 1 for an alternating current-fed discharge lamp 1, a capacitor is used 2 and the impedances 3 and 4 matched to one another and the mains frequency so that one of the electrode resistance dependent resonance voltage occurs across the lamp and it ignites. The reactor 3 is in series with the lamp, which is a resonant choke 4 connected in series with the capacitor 2 in parallel is. The oscillating throttle is designed as a transformer and carries two heating current windings 5, 6 for feeding the preheatable electrodes 7, 8 of the tube 1.

The tight coupling between the primary and secondary windings of the transformer 4 in Connection to the capacitor in series with the primary winding of the transformer can be independent an ignition voltage suitable for the discharge lamp is selected from the level of the mains voltage and the phases of the partial currents are compensated so far that the current through the discharge lamp and the current through the choke will be the same.

In the following it is assumed that the circuit arrangement according to the invention accordingly 1 for the operation of a 40 W fluorescent lamp is provided. From this example, the necessary conclusions can also be drawn for the application of the Arrangement according to the invention can be drawn in other cases.

If a 220 V voltage is applied to the terminals, a current determined by the geometric sum of the resistances of the elements concerned will flow through the choke 3, the capacitor 2 and the transformer 4, 5, 6. If the choke is the usual one for 40 W lamps, the capacitor and the transformer are dimensioned for resonance so that a maximum of 200 mA can pass the circuit and the voltage drop across these two electrodes when they are cold, i.e. the voltage across the lamp, when switched on is 260 V. The heating current windings of the transformer are dimensioned so that a heating voltage of 10 V is applied to the respective electrode. The total cold resistance of the electrodes is then 2 x 2.5 ohms. When glowing, they have a total resistance of 2 x 25 ohms, and the voltage across the lamp increases to about 300 V. For example, the transformer windings can consist of a primary winding of 2000 turns of 0.22 mm wire and two secondary windings of 120 turns consist of 0.43mm wire on a 20W core. When the lamp ignites, a lamp current passes through the choke, which increases its inductive resistance considerably, shifting the resonance position of the circuit considerably and reducing the current through the primary winding of the transformer to about 30 mA. This current, which is capacitive, generates a constant heating voltage of about 3 V at the respective electrode and has a phase-compensating effect on the current in the choke, so that the mains current is kept at the same value as the lamp current at about 0.42 A. The capacitor, whose capacity is 1.0 to 1.2 μΈ , has 330 V at the start of the ignition process and around 80 V during operation.

The change in the resistance of the electrodes can only be used if the transformer is designed with a fixed coupling. This change can e.g. B. reach 2.5 to 25 ohms. This causes a large difference in the load on the secondary side of the transformer, which fully affects the primary side of the transformer during the periods of time that lie between switching on and igniting the lamp. By appropriately adjusting the size of the components, as can be seen from FIG the temperature of the electrodes rises from room temperature to around 800 ° C. In FIG. 2, the ignition time in seconds (sec) is plotted as the abscissa and the cathode ^{temperature (curve 9) in °} C. or the voltage across the lamp (curve 10) in V as the ordinate. In the circuit arrangement according to the invention, not only is cold ignition prevented, but the large impedance of the transformer also prevents any effect of the capacitor on the curve shape of the lamp current.

The ignition time is indicated in the diagram according to FIG. 2 with point 11, that of an electrode temperature of 700 ° C or more. The voltage across the from a stray field transformer The lamp is constant during the entire heating time, as can be seen from the dashed and dotted line 12. The premature ignition takes place around point 13 of the temperature curve for the temperature that is too low of 500 ° C. However, even less favorable cold starts are possible.

The arrangement according to the invention can also be used for the operation of several discharge lamps will. In FIG. 3, the oscillation impedance 16 is shown with three heating current windings 17, 18, 19 provided, which are all connected to the primary winding 20 so that the change in their self-inductance takes place in the required manner and thus the voltage across the discharge lamps during preheating from a low value that does not cause a cold start to a higher value Ignition safe trigger value increases. It is important that the coupling between the various Windings is regulated to such a value that no undesirable change in the Self-inductance of the primary winding takes place. Such a change can easily occur if the in-

ductance change is so great that the resonance position of the circle is shifted too much. In Fig. 4 shows the curve 21 such an undesirable fall in the voltage across the lamp or lamps and the Curve 22 the desired result with correct dimensioning.

When operated in parallel with the arrangement of two 40 W fluorescent tubes shown in FIG. 3, the switching elements had the following data in one case: the choke 23 consisted of 1700 turns of 0.43 mm wire, and the air gap of the core was 2.0 mm . The reactor 24 had 1320 turns of 0.43 mm wire and an air gap of 1 mm. The capacitor connected in series had a capacity of 3.7 μ ¥. The capacitor 26 had a value of _1S 2.0 μ, Έ, and the primary winding of the oscillating impedance 16 consisted of 1850 turns of 0.25 mm wire. The secondary windings 18 and 19, which each feed one electrode of the capacitively switched or inductively switched lamps 14, 15, each consisted of 100 turns of 0.35 mm wire, while the secondary winding 17 that feeds the two other electrodes in parallel was made of 110 Turns of 0.40 mm wire. The capacitor 27 between the lamps 14 and 15 had a value of 0.5 ixF.

The arrangement in Fig. 5 relates to a series circuit. The following data can be given as an example of their arrangement for operating two 20 W fluorescent lamps of 220 V: The choke 28 had 1550 turns made of 0.40 mm wire and a 1 mm air gap. The capacitor 29 had a capacitance of 1.8 μΈ, and the primary winding 31 of the oscillating impedance connected in series with it had 1850 turns of 0.25 mm wire on a 20 W core. Of the three secondary windings 32,33,34 of the transformer, two windings 32, 33 each feed one electrode of the two lamps and the third winding 34 feeds the two other electrodes in parallel. The windings 32, 33 consisted of 100 turns each of 0.35 mm wire and the winding 34 consisted of 110 turns of 0.40 mm wire. If one or several electrodes contained in the arrangement provide sufficient control of the voltage across the discharge tube via the associated heating current windings, the remaining heating current windings can be connected to the primary winding of the transformer with looser coupling or even stray field coupling. Thus, in the arrangement according to FIG. 5, the windings 32, 33 of the transformer 30 can be so tightly coupled that the desired voltage profile across the fluorescent lamps (that is, according to curve 22 in FIG. 4) is obtained. The winding 34 can then be coupled very loosely to the primary winding 31. In such an embodiment in multi-tube circuits, one electrode of each individual discharge lamp should expediently contribute to the control of the ignition voltage from a lower to a higher value in the manner described.

Claims (4)

PATENT APPLICANT) CHEr 1. Circuit arrangement for electric discharge lamps with preheated and heating current windings fed in the transformer of a resonance-matched LC ballast Electrodes with PTC resistor, characterized in that the heating current windings (5, 6) are electrically and magnetically permanently coupled to the primary winding (4) with such a translation, that the transformed change in resistance of the glow electrodes detunes the resonance circuit so that the resonance voltage supplied to the discharge lamp or lamps is caused by the resonance detuning, from a low one preventing a cold start during preheating Value is increased to the ignition voltage (Fig. 1). 2. Circuit arrangement according to claim 1 for operating a discharge lamp with chokes and Capacitor, characterized in that a choke coil (3) is provided in a manner known per se the discharge lamp is connected in series with a transformer designed with the capacitor in series-connected resonant choke (4) is bridged, and that the transformer has two glow current windings (5, 6) for each individually heatable glow electrode (7, 8). 3. Circuit arrangement according to claim 1 for the inductive-capacitive operation of two parallel-connected Discharge lamps, characterized in that the inductively switched lamp (14) with an oscillating throttle (16) designed as a transformer and one connected in series with it Capacitor (26) is bridged and that the transformer three is fixed to the primary winding coupled secondary windings (17,18,19), two of which each have an electrode of the two lamps and the third the other electrodes of the lamps together, preferably in parallel connection, dine (Fig. 3). 4., circuit arrangement according to claim 1 for series operation of at least two discharge lamps, characterized in that the lamps are implemented as a transformer (30) Oscillating throttle (31) and a capacitor (29) connected in series with it are bridged and that the transformer has three secondary windings 32, 33 firmly coupled to the primary winding, 34), of which two each have an electrode of the series-connected lamps and the third the the remaining electrodes of the lamps connected in series together, preferably in parallel connection, dine (Fig. 5). Considered publications:
German patent applications A 11062 VIIIc / 21 f (published on July 16, 1953), P 3176 VIIIc / f (published on October 22, 1953);
Swiss Patent No. 208 077;
U.S. Patent No. 2,170,447. 1 sheet of drawings © 909 787/175 4. 60