WO1989011160A1

WO1989011160A1 - Low-pressure gas discharge lamp

Info

Publication number: WO1989011160A1
Application number: PCT/CH1989/000080
Authority: WO
Inventors: Jean-Pierre Winkler; Zhi-Yu Gu
Original assignee: Coroplan Ag Im Konkurs
Priority date: 1988-05-05
Filing date: 1989-05-03
Publication date: 1989-11-16

Abstract

A single electronic circuit arrangement (7) lodged in a two-part base housing (18, 19) supplies a high-frequency alternating voltage to two gas-discharge bulbs (2, 21), connected either in series or in parallel. The use of GATs (Gate Associated Transistors) or IGTs (Insulated Gate Transistors) reduces the internal power loss and heat build-up, thereby permitting optimal operation of the gas-discharge bulbs (2, 21) without the need to provide special cooling points or to enlarge the base housing (18, 19). Individual switching means (14, 15, 16) are combined into functional units (8, 9, 10) and pre-cast in housings (11, 12, 13). The low-pressure gas discharge lamp can be manufactured easily and economically, and has a brief stabilization time, a large cos phi and a long service life.

Description

Low pressure gas discharge lamp

Technical field

The invention relates to a low-pressure gas discharge lamp according to the preamble of patent claim 1, a gas discharge vessel according to the preamble of patent claim 9 and a method for producing the gas discharge vessel according to the preamble of patent claim 10.

State of the art

In the compact low-pressure gas discharge lamps, the so-called energy-saving lamps for replacing the incandescent lamps that have been in use for a long time, a current limiting choke, a starter or a heating transformer for heating the electrodes of the gas discharge vessel and a capacitor for compensating the reactive power are installed in the base of the lamp . The current limiting choke and the heating transformer have active power losses and heat up during operation of the gas discharge lamp to about 80 - 90 ° C. The gas discharge vessel arranged in the immediate vicinity of the parts mentioned is usually composed of several U-shaped tube parts, the U-shaped bends of the individual pipe parts have essentially rectangular corners. In the case of gas discharge vessels, the luminous flux output is, among other things, due to the

Mercury vapor determined immediately. Optimal results are achieved if at least one so-called cold spot with a temperature of preferably 45 ° C is present during the operation of the lamp, on which the mercury condenses and determines the vapor pressure. In the case of the above-mentioned gas discharge vessels, which are essentially bent at right angles, the bends form cold spots. However, the condensation of the mercury creates black, non-luminous spots at these points over time. Other embodiments of gas discharge vessels provide specially designed cooling tips in which superfluous mercury vapor condenses in order to maintain an optimal vapor pressure. The discharge vessels with additional cooling tips, which are composed of a plurality of U-shaped tube parts, are complex to manufacture and have the further disadvantage that the luminous layer applied before the individual tube parts are welded together is easily damaged by the welding processes. The 50 Hertz flickering of these lamps is perceptible to the human eye and has a tiring effect. In large rooms where a large number of such larapen are used, care must therefore be taken during installation to ensure that the lamps are distributed evenly over the various phases. The compact low-pressure gas discharge lamps, in which an electronic circuit arrangement for igniting and feeding the gas discharge vessel with a high-frequency alternating voltage is present, made progress in this regard. The 50 Hertz flickering has been eliminated, a steady constant luminous flux is available with these lamps. As a result of the high-frequency supply voltage of the gas discharge vessel, the relatively massive current limiting choke could be replaced by one with smaller dimensions. A compensation of the reactive power with a capacitor is no longer necessary. The base of the lamp, in which the electronic circuit arrangement is housed, has been reduced in size. The high-frequency alternating voltage is generated by means of bipolar power transistors. These heat up due to the rapid switching during operation of the lamp to about 80-90 "C. Also in this embodiment of compact low-pressure gas discharge lamps, the gas discharge vessel suffers from the disadvantages already mentioned.

Disclosure of the invention

It is the object of the present invention to reduce the power loss generated in the electronic circuit arrangement in such a way that less heat is generated during the operation of the lamp and that, among other things, the gas discharge vessel is easier and less expensive to manufacture, and the above ¬ not mentioned disadvantages.

This object is achieved by the features in the characterizing parts of claims 1, 9 and 10.

Further advantageous features of the present invention are characterized in the dependent claims.

Brief description of the drawings

A low-pressure gas discharge lamp according to the invention is described in more detail, for example, with reference to figures. Show it

Fig. 1 is a view drawing with partial sections of the low-pressure gas discharge lamp according to the invention,

2 shows a circuit diagram of an electronic circuit arrangement for igniting and feeding the gas discharge vessels of the gas discharge lamp, FIG. 3 shows two gas discharge vessels connected in parallel with the preheating and current limiting means,

4 shows two gas discharge vessels connected in series with the preheating means and the common current limiting means, FIG. 5 shows a gas discharge vessel for the low-pressure gas discharge lamp according to the invention,

Fig. 6 representation of the bending process of the glass tube for the gas discharge vessel and

Fig. 7 is a graphical representation of the viscosity of the glass as a function of temperature.

Best way to carry out the invention

1 shows the construction of the low-pressure gas discharge lamp 1 according to the invention. An electronic circuit arrangement 7 for igniting and feeding the gas discharge vessels 2, 21 comprises a printed circuit board 17 and electronic components 14, 15, 16. The individual electronic components 14, 15 , 16 are combined into functional units 8, 9, 10. One or more of the functional units 8, 9, 10 formed are cast in one or more housings 11, 12, 13 with a casting compound, for example an epoxy resin or a silicone rubber compound. On the circuit board 17 facing side electrical connections from said Funk¬ are tional units 8, 9, 10, the latter for mounting on SSL ^~ the circuit board 17, led out. Each of the U-shaped curved discharge vessels 2, 21 each have a fused electrode 4, 5 at the ends of its legs. Each of the electrodes 4, 5 is equipped with a heating coil for preheating the electrodes in the ignition phase of the low-pressure gas discharge lamp. Each of the electrodes πa-gerr melted into the gas discharge vessels 2, 21. j ^* e two connecting wires 23, 24 out of the glass tube 3, 22 'and are connected to the printed circuit board 17 on the side opposite the functional units 8, 9, 10. The assembly sequence of the low-pressure gas discharge lamp is provided, for example, in such a way that the gas discharge vessels 2, 21 are guided into a part 19 of the two-part base housing through openings which are not specifically shown and are fastened by means of an adhesive. The printed circuit board 17 which is equipped with the functional units 8, 9, 10 and has prepared openings for receiving the connecting wires 23, 24 of each of the electrodes 4, 5 of the two gas discharge vessels 2, 21 is inserted into the part 19 of the base housing from the side opposite the gas discharge vessels placed. The connecting wires 23, 24 are guided through the openings of the printed circuit board 17 and soldered to the conductor tracks (not shown) on the printed circuit board. A lamp cap 20 made of plastic or glass is placed over the discharge vessels 2, 21 and centered by an attachment provided on the first part 19 of the base housing. The calotte 20 has at its open end a bead 25 which extends over the entire circumference and points outwards. Two further connecting wires 26, 27 connected to the printed circuit board 17 are previously screwed onto the other part 18 of the base housing with the known from the incandescent lamps Lamp socket 28 soldered. This other part 18 of the base housing _r, which has an indentation at its open end, which also extends over the entire circumference and corresponds to the bead 25 of the cap 20, is now pushed over one part 19 of the base housing and snaps over the bead 25 of the spherical cap 20. This simple process means that the individual parts of the low-pressure gas discharge lamp are mounted without additional fastening means. The circuit board 17 is clamped between the two parts of the base housing 18, 19.

As described in more detail below with reference to FIGS. 2, 3 and 4, the electronic circuit arrangement 7 is designed in such a way that two gas discharge vessels 2, 21 can be ignited and fed.

The gas discharge vessels 2, 21 no longer consist of multiple bent glass tubes, but only have a single bending point. The welding of the individual, pre-bent glass tubes into a unit, which is usually to be carried out after the luminescent layer has been applied, which is complex and has a destructive effect on the luminescent layers already applied, is eliminated. As a result of the plurality of gas discharge vessels, there is an increase in the amount of melted-in electrodes. As production studies have shown, this additional effort compared to the profit by eliminating the above-mentioned difficulties in welding, especially in large-scale production, is easily tolerable.

FIG. 2, together with FIG. 3, shows a first embodiment in which the two gas discharge vessels 2, 21 are connected in parallel, and FIG. 2, together with FIG. 4, shows a second embodiment. exemplary embodiment for the case in which the two gas discharge vessels 2, 21 are connected in series. The circuit shown in FIG. 2 has many known features which are not described in detail below.

The mains alternating voltage of, for example, 220 volts is fed to the feed points 53 and 54. In principle, these two points correspond to the connecting wires 26, 27 connected to the lamp socket 28. A filter formed from the resistor R1, the capacitor C2 and the coil L is constructed in a known manner and is used to keep mains disturbances away from the circuit arrangement. The thermistor R2 serves as a so-called soft start component for limiting the inrush current. Serve a bridge rectifier BR and a downstream Lade¬ capacitor Cl ^'the rectifying and smoothing the Netzweckselspannung. The resistor R3 arranged in the plus line and the downstream capacitor C3 located between the plus and minus lines serve to suppress interference in the circuit arrangement. Significantly, the radio interference suppression devices R3, C3 are arranged on the high-frequency side of the circuit arrangement, as is the case with known other circuits. A resistor R4 is also arranged in series with a capacitor C4 between the plus path and the minus path. With the connection point of these two elements R4, C4, a trigger diode diac is connected to one connection. The other connection of the trigger diode leads to the control connection 41a of the one transistor 41. This circuit, which is formed from the resistor R4, the capacitor C4 and the trigger diode Diac, is in known embodiments of electronic circuit arrangements. gene also exists and serves to excite the means for generating the high-frequency AC voltage after switching on the AC mains voltage. The capacitor C4 is charged positively via the resistor R3 until the trigger voltage of the trigger diode Diac is reached. The trigger diode switches from a high-ohmic state to a low-ohmic state. The capacitor C4 can discharge via the trigger diode Diac via the resistor R7 and the fourth winding 42d of the transformer 42 connected in series with the resistor R7. The control input 41a of the transistor 41 becomes positive with respect to the source 41b of this transistor and the transistor 41 is conductive. In the following, let us first consider the embodiment variant with the discharge vessels 2, 21 connected in parallel according to FIG. 3 in combination with FIG. 2 to explain the processes that are now taking place. The reference point 47 in FIG. 2 is said to be 3 with reference point 49 in FIG. 3 and reference point 48 in FIG. 2 with reference point 50 in FIG. The third winding 42c of the transformer 42, the inductors 33, 33 'each serving as current limiting means, before the transistor 41 is conducted via the resistors R4, R5, which are in the order of magnitude of a few 100 kOhms, the heating windings of the

25 electrodes 5, 5 ', the means for preheating the electrodes 30, 31, 32, 30', 31 "F 32 * as well as the capacitor C6 charged via the heating windings of the electrodes 4, 4 'can now be via the circuit and the are now in the low-resistance, conductive state

3.0: Discharge transistor 41 via the sink 41c to the source 41b and via the low-resistance resistor R9 connected in series to the source after the minus path. The one through the third winding 42c of the transformer 42 current pulse flowing through the transistor 41 generates a voltage in the first winding 42a of the transformer which applies a positive voltage to the control input 40a of the transistor 40, so that the latter has a positive voltage between it

Valley 40c and its source 40b becomes low-resistance. At the same time, a voltage is induced in the fourth winding 42d in such a way that a negative potential is present at the control input 41a with respect to the source 41b of the transistor 41, so that the resistance between its sink 41c and its source 41b becomes high-resistance. A current now flows from the positive connection point via the resistor R3, the transistor 40, the low-resistance resistor R8 via the second winding 42b of the transformer 42 via the current-limiting means 33, 33 ', the heating windings of the electrodes 5, 5' Means for preheating the electrodes 30, 31, 32, 30 *, 31 ', 32' as well as via the windings for heating the electrodes 4, 4 'and the capacitor C6 after the minus path. The capacitor C6 is recharged. Due to the current flow in the second winding 42b of the transformer 42, the transistor 40 is blocked again and the transistor 41 is again conductive due to the voltages induced in the other windings 42a, c, d. The capacitor C6 discharges again on the current path described. These switching processes are subsequently maintained during the operation of the low-pressure gas discharge lamp. The heating windings of the electrodes 4, 5, 4 '5' are heated by these processes, as are the two PTC thermistors 31, 31 * of the preheating circuits 30, 31, 32, 30 ', 31', 32 *. The heating of the two PTC thermistors 31, 31 'increases their resistance and consequently the voltage between the electrodes 4, 5 and 4 ', 5' of the two gas discharge vessels 2, 21. The preheating circuits are dimensioned such that a gas discharge occurs after a maximum of 0.4 s after the low-pressure gas discharge lamp is switched on. After the ignition, the voltage between the electrodes 4, 5 and 4 ', 5' of the gas discharge vessels drops. The current which increases as a result of the now low-resistance gas discharge vessels is limited by the chokes 33, 33 '. 3 in that for each of the two gas discharge vessels 2, 21 there is a choke 33, 33 'as a current limiting means in

Is connected in series, it is possible that each of the gas discharge vessels can ignite as a result of tolerances in the components and in the gas discharge vessel itself at different times. Let us assume that the gas discharge vessel 2 ignited in front of the gas discharge vessel 21. Despite the breakdown of the voltage between the electrodes 4 and 5 of the gas discharge vessel 2, the voltage between the connection points 49, 50 remains high enough due to the series-connected choke 33 that the second gas discharge vessel 21 can also ignite after a certain time. Laboratory tests have clearly shown that by shortening the preheating time to a maximum of 0.4 s, the life of the lamp can be considerably increased compared to known designs with a preheating time of approximately 0.8 s. The switching frequency of the transistors 40, 41 is mainly dependent on the dimensions of the transformer 42 and the capacitor C6, which together form a resonance circuit in principle. The diodes D2, D3, which are essentially connected in parallel to the drain-source paths of the transistors 40, 41, serve to prevent any overvoltages that occur when one of the two transistor ren can occur as a result of induction voltages of the transformer 42. Compared to known circuit arrangements, the transformer 42 present in the exemplary embodiment described has four individual windings 42a, 42b, 42c and 42d. Compared to the transformers used today with only three windings, this type of transformer has the advantage that the individual transistors 40, 41 are blocked more securely, so that the transistors 40, 41 are not destroyed by a short simultaneous conduction. The mode of operation is as follows: If, for example, a current flows through the third winding 42c when the capacitor C6 is discharged, a voltage is induced in the second winding 42b which briefly counteracts the sink-source voltage of the transistor 40. In the other switching phase, when the transistor 40 is conductive and a charging current flows through the second transformer winding 42b to the capacitor C6, a voltage is initially induced in the third winding 42c which counteracts the sink source voltage of the transistor 41.

These opposing voltages additionally prevent simultaneous conduction of the two transistors.

As a result of the frequent switching of the transistors 40 and 41 from a blocked state to a conductive state, a power loss occurs in each of the transistors 40, 41, which leads to its heating. In known circuit arrangements equipped with bipolar power transistors, the transistors reach an operating temperature of 80-90 ° C. at an ambient temperature of approximately 20 ° C. It has been found that the use of metal-oxide-silicon Field effect lead Stungtransistors, referred to in the further description with MOS-FET, the power loss can be reduced. An even smaller power loss has been obtained by using gate-associated transistors, hereinafter referred to as GAT. The GAT is a combination of a bipolar transistor with a field-effect transistor and, in addition to a small saturation voltage in the conductive state, has a faster switching time than bipolar transistors. With a construction of the same size as that found in known circuit arrangements, it has been achieved that the transistors only heat up to approximately 45 ° C. at an ambient temperature of approximately 20 ° C. As a result of this significant advantage of reducing the internal heat development, in addition to an improvement in the efficiency of the low-pressure gas discharge lamp according to the invention compared to known designs, a simplification in the manufacture of the gas discharge vessels could also be achieved in that the latter no longer had any specially designed cooling points must be present. Results as good as with GATs are achieved by using insulated gate transistors, abbreviated IGTs.

Another embodiment of the low-pressure gas discharge lamp according to the invention provides for the two gas discharge vessels to be connected in series. This embodiment variant is shown by a combination of FIGS. 2 and 4. The reference point 47 in FIG. 2 is connected to the reference point 51 in FIG. 4 and the reference point 48 in FIG. 2 is connected to the reference point 52 in FIG. 4. The

The circuit works in principle exactly the same as before with the gas discharge devices connected in parallel. has been described. Each of the gas discharge vessels 2, 21 connected in series has means for preheating the electrodes 30, 31, 32, 30 ', 31', 32 '. It is striking that each of the two gas discharge vessels 2, 21 only heats one electrode 4, 4 'each. The other electrode 5 and 5 'is heated by shock ionization at the start of the gas discharge. The Zündvor¬ gait of ^* two gas discharge vessels in the same way as described previously. In contrast to the previous one, this embodiment variant only has a common current limiting means, for example a choke 34 connected in series with the two gas discharge vessels 2, 21. It would also be conceivable to form the current limiting means 34, 33, 33 'in this or in the previously described embodiment variant by a capacitor or by a resistor.

A further advantageous feature with regard to rational fabrication is given by combining individual electronic components into so-called functional units. From the circuit diagram of the in the

The circuit arrangement shown in FIG. 2 shows, for example, the combination of the capacitors C2 to C7 ^* . The low-pressure gas discharge lamp according to the invention further provides, as well as the transistors 40, 41, the resistors R6, R7, R8, R9 and the diodes D2, D3 to form a further functional unit and, as already described, in one Connections provided housing to manufacture as a prefabricated molded part. Due to the high-frequency AC voltage for igniting and feeding the gas discharge vessels, which is between 10 and 150 kHz, but preferably at 30 kHz, and through separating the input filter Rl, L, C2 to keep network interference away from the radio interference suppressors R3, C6 arranged on the high-frequency side of the circuit, the inductivities of the new low-pressure gas discharge lamp could be kept extremely low and the cos increased to over 0-, 95 .. become.

Exx gas discharge vessel 2 for a low-pressure gas discharge lamp according to the invention is shown in FIG. 5. The gas discharge vessel 2 consists of a U-shaped glass tube 3, a special bending method being used to ensure that the inner bending radius Ri is at most 2 mm and that both the outside diameter and the inside diameter of the glass tube 3 are over the entire length of the latter has a substantially constant size. The special bending process is explained in more detail in FIGS. 6 and 7. The glass tube 3 is heated in the region of the bending point before bending. The heating temperature TB on the inside of the bend is greater than the heating temperature TA on the outside of the bend. 7 is the

Heating temperature TB in the border area between viscous and liquid glass and the temperature TA in the border area between viscous and solid glass. Because the ^* ; heated glass tube 3 on the inside of the bend is practically liquid, the accumulations of glass which otherwise occur during bending are avoided at this point, and both the inside diameter and the outside diameter of the glass tube remain practically constant after bending. In known embodiments of discharge vessels, the luminescent layer 6 is slipped on the inside after the glass tube has been bent. In the sense of For rational production, a new method provides that the luminescent layer 6 consisting of powdered material is applied electrostatically to the inner surface of the glass tube 3 using an electric field.

Each of the leg ends of the U-shaped glass tube 3 is closed by a fused electrode 4, 5. Each of the electrodes 4, 5 is combined with a heating winding, the connecting wires 23, 24 of which protrude from the glass tube. There is a vacuum point 29 essentially in the center of each leg end. It is striking that the gas discharge vessel 2 does not have any specially designed cooling points, neither in the form of bends which increase the surface area, practically at right angles, nor by pronounced vacuum peaks .

Optimal operation of this simply constructed gas discharge vessel in the low-pressure gas discharge lamp according to the invention is possible thanks to the reduction in the internal power loss without increasing the volume of the base housing.

Claims

1. Low-pressure gas discharge lamp (1) with a gas discharge vessel (2) with a glass tube (3), two electrodes (4, 5) melted therein and one on the inside. Luminous layer (6) applied to the inner surface of the glass tube, and an electronic circuit arrangement (7) for igniting and feeding the gas discharge vessel (2), with means for preheating the electrodes (30, 31, 32), means for limiting the current (33, 34) and means for generating a high-frequency AC voltage (40, 41, 42), characterized in that the means for generating the high-frequency AC voltage (40, 41, 42) at least one metal-oxide-silicon field-effect power transistor (40, 41), a gate associated transistor (40, 41) or an insulated gate transistor (40, 41) and a transformer (42) with four windings (42a, b, c, d) to increase the Include blocking security of the transistor (40, 41).

2. The gas discharge lamp as claimed in claim 1, characterized in that the frequency of the alternating voltage is between 10 kHz and 150 kHz.

3. Gas discharge lamp according to claim 1 and 2, characterized in that the electronic circuit arrangement (7) comprises components (14, 15, 16) which are combined to form at least one functional unit (8, 9, 10) and that one or more of the functional units

(8, 9, 10) are cast in at least one housing (11, 12, 13).

4. Gas discharge lamp according to one of claims 1 to 3, characterized in that at least one further gas discharge vessel (21) is present and connected in parallel to the first parallel or in series and that the discharge vessel (2, 21) by the only electronic circuit arrangement (7) are ignitable and feedable.

5. The gas discharge lamp as claimed in claim 4, characterized in that the means for preheating the electrodes (30, 31, 32; 30 ', 31 *, 32') are provided for each of the gas discharge vessels (2, 21) and that the preheating time is less than 0.4 s.

6. The gas discharge lamp as claimed in claim 4 or 5, characterized in that, in the case of gas discharge vessels (2, 21) connected in parallel, the current limiting means (33, 33 ^f ) is connected in series to each of the gas discharge vessels (2, 21).

7. The gas discharge lamp as claimed in claim 4 or 6, characterized in that in the case of gas discharge vessels (2, 21) connected in series, the current limiting means (34) are present together and are connected in series with the gas discharge vessels.

8. Gas discharge lamp according to claim 6 or 8, characterized in that each of the current limiting means (33, 33 ', 34) is a choke, a capacitor or a resistor.

9. Gas discharge vessel for a Niederdruckgasentla¬ discharge lamp according to one of claims 1 to 10, with a U-shaped curved glass tube (3), characterized in that the inner bending radius is at most 2 mm that - both the outer and the inner diameter above the entire length of the glass tube (3) has an essentially constant size and that there are no specially designed cooling points.

10. The method for producing a gas discharge vessel according to claim 9, characterized in that the

Glass tube (3) is heated in the area of the bending point before bending and that the heating temperature (TB) on the inside of the bend is kept warmer than the heating temperature (TA) on the outside of the bend to avoid glass accumulation during the bending process.

11. The method according to claim 10, characterized in that the substance serving as the luminous layer (6) is applied electrostatically to the inner surface of the glass tube (3) using an electric field.