HU195056B - Series circuit for high-pressure discharge lamps, preferably for sodium-vapour lamps - Google Patents

Abstract

The present invention relates to a ballast circuit for high-pressure discharge lamps, in particular sodium lamps, having a pulse generator (10) with an operating frequency greater than 1 kHz connected to a source of a DC voltage of at least 150 V, a first pulse transformer (18) arranged thereon, and a pulse generator connected in series with a high pressure discharge lamp (10). 10) an ignition circuit fed from the outlet (20) of the pulse generator (10) to the output (20, 21) of the pulse generator (10) and the pulse generator (10) in series with the condenser (25) mounted in parallel with the high pressure discharge lamp (6). it includes a serial oscillating circuit tuned to its idle frequency while an inductive member is inserted between the high pressure discharge lamp (6) and the throttle (24). The essence of this is that the pulse generator (10) is designed for the high-pressure discharge lamp (6) to provide a nominal burning voltage of less than 35% of the direct voltage, and the first pulse transformer (18) arranged therein is formed as an auto transformer or a spreading transformer having a primary coil (22). ) an intermediate junction (27) for the output (21) of the pulse generator (10) is provided. -1-

Description

BACKGROUND OF THE INVENTION The present invention relates to a ballast for high-pressure discharge lamps, in particular sodium lamps having a pulse generator having an operating frequency greater than 1 kHz connected to a source providing a voltage of at least 150 V, and having a ballast inserted in the pulse generator output chokes in series with it, with the capacitor in parallel with the high-pressure discharge lamp installed, the pulse generator includes tuned idle frequency series resonant circuit, and is interposed inductive member between the high-pressure discharge lamp and the choke, which auxiliary primary winding of the pulse generator output by connecting the second pulse transformer secondary and the first pulse transformer is a primary winding preferably a disconnecting capacitor is connected in series.

It is known that the operation of gas-filled high-pressure discharge lamps, including sodium lamps, requires, on the one hand, an ignition voltage higher than the operating voltage and, on the other hand, a current limiting ballast due to the negative current characteristic of the lamp. It is a thermal problem that the lamp reaches its rated luminous efficacy only after a certain warm-up time (usually a few minutes). The increased ignition voltage required for safe ignition means increased electrical stress on the batteries used.

Many types of ballast circuits for the operation of high-pressure discharge lamps are known. Of these, the most advanced types at the present state of the art are the high frequency pulse voltage excitation types, which exhibit about 10 to 15% increase in luminous efficiency compared to the mains frequency supply, and the non-volatile effect caused by non-volatile arc extinguishing.

When designing ballast circuits, small dimensions and small losses are a top priority. The circuits to be used must contain as few components as possible to minimize losses and must meet the factory-specified conditions for operating the lamps.

The properties, operating parameters and requirements of high-pressure discharge lamps can be found in publications of manufacturers such as TUNGSRAM RT. These typically describe ballast circuits fed from 50 or 60 Hz networks, since the application is primarily powered by mains power. When selecting the operating point for the operation of the discharge lamp, it is considered important that the burn voltage be set to a value slightly higher than half the supply voltage (mains voltage). The in-service change of the discharge lamp operating point is an inevitable process that accompanies the aging of high-pressure discharge lamps as the burn voltage increases slowly over time.

It is also known that high-pressure discharge lamps have lower lifetime voltages, for example, where the rated burn voltage is around 50 volts, have a higher lifetime compared to 100-110 volts, and have a lower ignition voltage requirement. These types of lamps are primarily designed for use in countries where the mains voltage is around 110 to 120 V, because the inductive ballast can easily set the reference stable working point. Where the mains voltage is 220V or more, there is a problem with the economical operation of such lamps. Such a reduction in voltage would only require the use of separate circuits (transformers, possibly AC-AC converters), and the resulting efficiency gains and cost increases would outweigh the benefits of increased life.

Considering the above requirements, there are also voltage limits for the 220 V supply. The voltage of the 220 V full-wave rectifier is given, and the AC voltage obtained from the DC voltage thus obtained is also specified. For example, by using two series-connected, countercurrent-controlled semiconductor switching devices in a pulse generator for rectangular voltage, rectangular signals of approximately 80% of the mains AC voltage are obtained. Controlling low-voltage lamps from this level is still not economically feasible.

Another set of requirements for ballast circuits is the safe generation of ignition pulses and the reliability of the necessary circuits. The production of ignition pulses of about 1000-2000 (possibly 4000) V requires the production of components rated for this voltage, and this high electrical insulation strength increases the difficulty, dimensions and weight of the components, particularly the serial choke. The high voltage signals and their transients must be protected from the semiconductor elements used in the pulse generator.

A circuit for igniting multiple fluorescent tubes by means of a vibrating circuit is described in U.S. Patent No. 1,556,292. GB. The teachings contained herein are not applicable to high-pressure discharge lamps, since the resonant ignition itself is not capable of solving the high-voltage ignition tasks that occur with the latter type of lamp.

-2195056

DE-A-27 05 170 discloses a ballast circuit for supplying a high-pressure discharge lamp from a DC battery or other source of rectified voltage. The proposed circuit comprises a pulse generator, which is connected as a high frequency DC / AC converter directly to one pole of the capacitor connected parallel to the corners of the high pressure discharge lamp and directly to the other pole of the capacitor. The pulse generator has two switching semiconductor circuits led to a pulse transformer and a resistor divider. The disadvantage of this ballast circuit is that it generates high voltage ignition pulses as a single firing signal, so that each component in the firing circuit must be sized to a high voltage across the entire firing signal.

It is an object of the present invention to provide a ballast circuit for high-pressure discharge lamps which, on the one hand, consist of components that are significantly reduced in voltage compared to prior art and can be scaled to lower voltage strengths, on the other hand. efficient, reliable operation.

The invention is based on the discovery that for operating a high-pressure discharge lamp, it is sufficient to provide an arrangement at the output of a pulse generator which supplies power under normal operating conditions and which is connected to the pulse generator by a high-frequency

In order to solve this problem, that is, for the ignition and power supply of high-pressure discharge lamps, especially sodium lamps, which are significantly lower than the mains AC voltage, and an ignition circuit in series connected to the high-pressure discharge lamp, the output of the pulse generator being provided, wherein the ignition circuit comprises a capacitor connected to the output of the pulse generator; an inductive member is inserted between which an imp a second pulse transformer connected to the output of the pulse generator is provided as a secondary coil, and a capacitor disconnected in series with the primary pulse of the first pulse transformer, and according to the invention, the pulse generator is the first pulse transformer arranged therein is designed as an autotransformer or a spray transformer, the primary winding of which has an intermediate branch to the output of the pulse generator. A great advantage of the proposed solution is that it can be formed from a relatively small number of ballast circuits whose high-voltage transients generated on the serial oscillator circuit capacitor together with the auxiliary pulse generator signals provide a reliable ignition of the lamp.

Significant circuit savings also result from the branching of the first impulse transformer, which is designed as a jet transformer, directly or via a reduced inductance choke to the capacitor and at least in part the inductance of the pulse transformer is at least partially represented by the inductance of the pulse transformer.

By incorporating a ballast circuit according to the invention, low-voltage high-pressure discharge lamps can also be supplied from higher-voltage networks, the circuit is simple, has low loss in efficiency and, due to the serial oscillation circuit, fires more safely and inductive coils.

The ballast circuit according to the invention will now be described in more detail with reference to the drawings. In the drawing it is

1 is a schematic diagram of an exemplary embodiment of a ballast according to the invention,

Figure 2 is a diagram illustrating a distinctive detail of the embodiment of Figure 1, while

Fig. 3 is a circuit diagram illustrating an exemplary internal configuration of the pulse generator 10 shown in Fig. 1.

The ballast circuit according to the invention (Fig. 1), for example, has a pulse generator 10 connected between a full-wave rectifier DC terminal 4, 5 connected to a 220 V mains voltage via terminals 1, 2 and a high-pressure discharge lamp 6 connected to the two outputs cap is provided with auxiliary pulse generator 7.

The dividing point 15 of the divider consisting of capacitors 11, 12 and resistors 13, 14 between the terminals 4, 5 forms a virtual center and the pulse generator 10 is formed by the dividing point 15 and the two switching semiconductor circuits 16 and 17 comprising a first impulse transformer 18 for providing a back-phase feedback, the primary winding 22 of which comprises a DC isolator 19

It is connected via a capacitor -3195056 to the dividing point 15 and to the common point of the switching semiconductor circuits 16, 17. The latter point is identical to the 20 outputs.

The first pulse transformer 18 has two secondary windings 8, 9 connected to the switching semiconductor circuit 16, 17. 10 pulse generators are best constructed as blocking oscillators; a schematic diagram of such an arrangement is illustrated in FIG. Components within the switching semiconductor circuit 16,17 are standard designations, and no special disclosure of the circuit is required by those skilled in the art.

Between the outputs 20, 21 of the pulse generator 10 (Fig. 1), there is a series of oscillating circuits consisting of 24 chokes and capacitors 25 tuned to the idle frequency of the pulse generator 10. In parallel to the capacitor 25, a series member consisting of a secondary coil of a second pulse transformer 26 and a high-pressure discharge lamp 6 is provided, while the auxiliary pulse generator 7 is coupled to the primary coil of the second pulse transformer 26. The capacitor 25 is connected to the common point of the secondary coil of the second pulse transformer 26 and the throttle 24.

This simple design is made possible by the fact that the first pulse transformer 18 is an autotransformer or a spray transformer, and that the primary winding 22 has an intermediate branch 27, which also forms the output 21 of the pulse generator 10. The necessary connection between the pulse generator 10 and the ignition circuit can thus be accomplished by proper selection of the intermediate branch 27. With proper sizing and spray-transformer design of the first pulse transformer 18, the function of the throttle 24 is provided by the series-induced frictional inductance transformed into the intermediate branch 27, indicated by a dashed line in FIG. One condition for proper operation is that the pulse generator 10, when idle (i.e., at the oscillation frequency of the high pressure auxiliary lamp 6), forms a serial oscillation circuit of the inductor 24 and of the diffused inductance it represents.

Fig. 2 illustrates a variant of the solution of Fig. 1, in which, for simplicity, the second pulse transformer 26 and the auxiliary pulse generator 7 connected thereto are omitted and the transformed serial reactance 28 formed by the dashed line 27 is used. The capacitor 25 is in series resonance at the idle frequency of the pulse generator 10. The circuits not shown in Figure 2 are completely identical to those of Figure 1.

The ballast circuit according to the invention operates as follows:

After full-wave rectification of the mains voltage between terminals 1 and 2, for example 220 V, a DC voltage of about 0.8-0.9 times the peak voltage 4 is obtained if a capacitor of sufficient capacity is used. The DC filter circuit is not shown separately in the drawing. In the exemplary case, a voltage of about 300 V is displayed between the DC terminals 4 and 5 and half of this voltage can be measured at the dividing point. Switching mode semiconductor circuits 16 and 17 of pulse generator 10 receive this semiconductor voltage as a supply voltage and open and close alternately in an avalanche fashion through 180 ° offset phase feedback. As a result, the primary winding 22 of the first pulse transformer 18 is connected to a pulse series having a peak voltage of about 150 V. When the two branches are symmetrical, the duty cycle of the impulse series is 0.5, i.e. the rectangular voltage is symmetric. The role of the isolating capacitor 19 is to isolate the DC component.

The frequency of the pulse train is preferably in the range of 10 to 30 kHz and, with the proposed training of the pulse generator 10, increases in frequency as the load increases.

An essential function of the ballast circuit according to the invention is the efficient operation of the low-pressure high-pressure discharge lamp 6, in particular the sodium lamp. Small, ie 20-35% of the mains voltage, ie longer lifetime and the same performance for sodium lamps with a rated voltage of approximately 45 to 75 V compared to 90 to 110 V rated for normal operation with 220 V has a smaller discharge tube length and consequently a lower ignition voltage requirement. Taking into account the fact that the lamp voltage of the lamp increases slightly during use, it is necessary to use a series impedance inductive reactance and a voltage that sets the operating voltage of new lamps with a peak voltage higher than the peak of the power-voltage characteristic. . It is a well-known circumstance that the characteristic power has a maximum at half the mains voltage. In the case of low-voltage lamps, this condition is no longer met if the series inductance is increased. Therefore, a supply voltage less than the rectangular voltage available on the primary winding 22 of the first pulse transformer 18 is required to provide a suitable operating point.

The first pulse transformer 18, which is configured as a spreader or autotransformer, is used to reduce the voltage in the ballast circuit according to the invention, and its intermediate branch 27 is connected in series with the inductive reactance of the primary winding of the choke 24 and the second pulse transformer 26. The location of the intermediate branch 27 is the discharge lamp 6

-4195056 depends on the ignition voltage, while the correct choice of capacitor 25 value is crucial for ignition. When the capacitor 25 is in series resonance with the inductance of the inductor 24 at the frequency corresponding to the idle state of the pulse generator 10, a transient voltage over-voltage impulse is superimposed upon the transient voltage. It follows that the voltage of the auxiliary pulse generator 7 can be chosen to be lower than the ignition voltage, so that the voltage of the inductor 24 and the second pulse transformer 26 will be proportionally lower. When the lamp is lit, the load it represents tones the serial oscillator circuit and so exerts a noticeable voltage increase on it. The lamp current flows through the secondary coil of the second pulse transformer 26, which then acts primarily as a serial choke. From the point of view of the ignition pulse, the second pulse transformer 26 is in a heavily loaded state because the working discharge tube through the capacitor 25 kills the transformer output at high frequency.

The spray-transformer design of the first pulse transformer 18 is also significant in reducing, if not eliminating, inductance 24. In this case, the diffused inductance measured from the intermediate branch 27 with the capacitor 25 fulfills the condition of resonance. The solution illustrated in Fig. 2 is particularly advantageous for lamps with lower wattages, where the lower ignition voltage may also allow the second pulse transformer 26 and the auxiliary pulse generator 7 to be omitted. This is, of course, also due to the fact that the series oscillation circuit with its inductance has an increased goodness factor and thus the capacitor 25 can generate higher voltage ignition pulses.

The advantage of the ballast circuit according to the invention is that the load on each circuit element and the electrical voltage demand are reduced, since, for example, the switching semiconductor circuits 16 and 17 are completely separated from the ignition voltage and only half the full DC voltage.

The main advantage of the ballast circuit according to the invention is the ability to operate lamps with lower rated voltages and longer lifetimes from higher mains voltages (for example 220 V or 380 V) and to reduce the electrical load on the ignition circuits.

Although the exemplary embodiment illustrates an AC mains power supply, the operation of the ballast circuit of the present invention is not affected by directly connecting DC power to the DC terminals 4 and 5 from any available source. The present invention is justified if the rated voltage of the discharge lamp is not more than 35% relative to the DC voltage.

Claims (2)

PATENT CLAIMS 1. A ballast circuit for a high-pressure discharge lamp 20, in particular sodium lamps having a pulse generator having an operating frequency greater than 1 kHz, connected to a source providing a voltage of 150 V or more, and having a first the ignition circuit is connected to the output of the pulse generator, from the throttle and with it in series, Contains a series of oscillating circuits formed from a capacitor installed in parallel with 30 high pressure discharge lamps, tuned to the idle frequency of the pulse generator, while between the high pressure discharge lamp and the inductor An inductive member 35 is provided which is designed as a secondary winding of a second pulse transformer connected to the output of auxiliary pulse generator with a primary coil and a first pulse transformer Preferably, a disconnecting capacitor is provided in series with 40 primary windings, wherein the pulse generator (10) has a nominal voltage of less than 35% of the DC voltage for the high-pressure discharge lamp (6). It is adapted to provide a combustion voltage 45 and the first impulse transformer (18) disposed therein is designed as an autotransformer or a spray transformer having a primary winding An intermediate branch (27) is provided 50 (22) leading to the output (21) of the pulse generator (10). The ballast according to claim 1, wherein the inductor (24) is partially 55 or all of the first pulse transformer (18) is configured as a scattering reactance (28).