WO1998017081A2

WO1998017081A2 - Direct current gas discharge lamp starter and direct current gas discharge lamp instant start ballast

Info

Publication number: WO1998017081A2
Application number: PCT/EP1997/005741
Authority: WO
Inventors: Richard Izycki
Original assignee: Bischl Electronic Gmbh
Priority date: 1996-10-17
Filing date: 1997-10-17
Publication date: 1998-04-23
Also published as: DE19642947A1; DE29624405U1; WO1998017081A3

Abstract

A starter (10) for a gas discharge lamp operated by direct current can be series connected to incandescent electrodes located therein. The starter (10) comprises a switching device (24) which, when in closed position conductively connects incandescent electrodes, thereby enabling a heating phase. When in open position said device enables induction of a voltage pulse, resulting in ignition of gas discharge lamp. Switching device (24) is formed by a semiconductor switching element.

Description

Direct current gas discharge lamp starter and direct current ballast for a gas discharge lamp

description

The present invention relates to a direct current gas discharge lamp starter for igniting a gas discharge lamp to be operated with direct current, the gas discharge lamp comprising a first glow electrode, the first connection of which can be connected to a direct current source for supplying / removing current and the second connection of which can be connected to a first connection of the starter and comprises a second glow electrode, the first connection of which can be connected to the direct current source for current dissipation / power supply and the second connection of which can be connected to a second connection of the starter, the starter comprising a switch element which can be switched between a conductive and a non-conductive state for optionally conducting Connecting the first and the second connection of the same in an electrode heating phase in such a way that in the heating phase an electrical current through the first glow electrode via the starter to the second glow electrode or in the opposite direction flows, and to interrupt the conductive connection of the first and the second connection of the same for igniting a gas discharge lamp and during an operating phase of a gas discharge lamp, further comprising control means for switching the switch element between the conductive and the non-conductive state.

The use of AC gas discharge lamps is widespread these days. However, it has been recognized that gas discharge lamps, when they are operated in an AC mode, have fluctuations in intensity with the frequency of the mains voltage, that is to say approximately 50 Hz, which are perceived as unpleasant, especially when working under such lighting. It has therefore already been proposed to use direct current gas discharge lamps supply, so as to eliminate the flickering in the operation of such gas discharge lamps. However, conventional starters can no longer be used in such DC-operated gas discharge lamps. Such starters include a bimetal switch as the switch element, which closes when heated and opens again when it cools down. For control purposes, a glow lamp is connected in parallel to the bimetallic switch, which leads to heating of the bimetallic switch when energized, which then closes and thus initiates the heating phase of the lamp, since after the

Switch element current flows through both glow electrodes. When the switch is closed, however, the glow lamp is bypassed, so that practically no current flows through it and the switch is no longer heated by it. The result of this is that after a predetermined period of time during which the glow electrodes are heated, the switch opens again and thus supplies the ignition pulse for the gas discharge lamps in cooperation with a choke coil.

If such an AC starter is now operated in a DC mode, the following problem arises. If the bimetallic switch is closed by the glow lamp and then opened again after the heating phase has ended, an arc is drawn between the two moving contacts when the switch is opened. However, since there is no polarity reversal of the voltage, as is the case in AC operation, but the voltage applied to the switch remains almost the same, the length of time and the distance over which the arc is drawn is significantly increased compared to AC operation . On the one hand, this leads to the switching time of the starter being shifted, as a result of which the ignition characteristic of the gas discharge lamp is adversely affected must become. In order to eliminate this disadvantage and to be able to operate gas discharge lamps in a direct current mode, a ballast for gas discharge lamps is known, for example, from German patent DE-36 07 109-C, in which each connection of each of the two glow electrodes via a switch element with the positive or is connected to the negative connection of an energy source. The switches are used, on the one hand, to heat the two glow electrodes in a state in which all four switches are closed and then to generate ignition pulses by periodically opening and closing two of the four switches. The switches are under the control of a control device which, depending on the operating mode, periodically opens and closes two of the four switches or keeps them open for longer periods in order to supply the gas discharge lamp with a pulsed direct current.

Furthermore, a ballast for the direct current operation of gas discharge lamps is known from the German patent application DE-44 01 630-A, in which current is in turn supplied via four switch elements of the gas discharge lamp, ie the two glow electrodes of the gas discharge lamp. For this purpose, one of the connections of the glow electrodes is conductively connected to the switch elements. The two other connections of the glow electrodes are connected to one another via a resistor and a capacitor. An ignition coil is arranged between one of the connections of the glow electrodes, which is connected to the switch elements, and the associated switch element. The ignition coil thus forms an oscillating circuit together with the resistor and the capacitor. If a high-frequency current is now supplied via a control unit, the resonant circuit can be set in resonance in order to generate the required ignition voltage. In order to be able to generate this resonance, the control device traverses a large frequency spectrum in the range from 80 kHz down to 20 kHz to ignite the gas discharge lamp in order to deliver that the resonant frequency of the resonant circuit is hit.

However, the design of these systems for the direct current operation of gas discharge lamps known from the prior art are not suitable for being combined with conventional, already installed gas discharge lamps which have previously been operated in an alternating current mode. This would require structural modifications to the gas discharge lamps, in which the ignition is generated in a conventional manner via the AC starter described above in cooperation with an upstream choke coil.

It is therefore the object of the present invention to provide a simple and inexpensive possibility of being able to convert conventional gas discharge lamp lighting systems to direct current operation or to be able to train them for direct current operation ex works.

To achieve this object, according to a first aspect of the present invention, a direct current gas discharge lamp starter is provided for igniting a gas discharge lamp to be operated with direct current, the gas discharge lamp comprising a first glow electrode, the first connection of which can be connected to a direct current source for supplying / removing current and the second connection thereof is connectable to a first connection of the starter, and comprises a second glow electrode, the first connection of which can be connected to the direct current source for current dissipation / power supply and the second connection of which can be connected to a second connection of the starter, the starter being between a conductive and a Switchable non-conductive state switch element for selectively conductive connection of the first and the second terminal thereof in an electrode heating phase such that in the heating phase an electrical current through the first glow electrode via the star ter to the second glow electrode or flows in the reverse direction, and to interrupt the conductive connection of the first and the second connection thereof for igniting a gas discharge lamp and during an operating phase of a gas discharge lamp, further comprising control means for switching the switch element between the conductive and the non-conductive state. According to the invention, it is provided that the switch element comprises a semiconductor switch element with a first connection connected to the first connection of the starter and a second connection connected to the second connection of the starter and with a control connection connected to the control means for supplying a switching signal.

In the starter according to the invention, the switching process is therefore not carried out by a mechanical switch, i.e. a switch with approaching and spaced-apart contact areas, but switched by a semiconductor switching element. The occurrence of an arc and the problems associated therewith can be eliminated, so that a starter which can be installed in a conventional gas discharge lamp lighting system is provided. The starter has essentially the same switching characteristics as a conventional AC starter, so that in addition to the fact that no additional mechanical, i.e.. in terms of circuitry, changes to lighting systems that have already been installed or are intended to be installed, the operating characteristics of such lighting systems are also not impaired.

It can be provided, for example, that the switch element comprises a transistor, in particular a field effect transistor. Such switch elements are simple and inexpensive to manufacture, and power-free switching can be achieved in particular when using field effect transistors. For example, it can be provided that the switch element is in a non-conductive state when a switching signal is not applied to the control connection.

Conventional starters have two contacts of identical design, which are connected to counter-contacts on gas discharge lamps. This means that these starters can be combined with the gas discharge lamp in two different positions. In direct current operation, however, this would mean that, depending on the installation position, the direction of current supply to the starter according to the invention would be different. In addition, in a manner known per se, the direction of the current is reversed at intervals of approximately 15-30 minutes in order to avoid cataphoresis effects in gas-discharge lamps operated with direct current. This would also result in the direction of the current supply being changed at periodic intervals. In order to be able to ensure that the components of the starter according to the invention are always supplied with current of a defined flow direction, it can further be provided in the starter according to the invention that the first and the second connection of the starter with the first and the second connection of the Switch element are connected via voltage rectifier means.

As already mentioned at the beginning, a glow lamp is provided in conventional AC starters, which essentially takes over the timing of the bimetal switch. In order to be able to provide a corresponding function in the starter according to the invention, the starter according to the invention can further comprise a capacitive element connected in parallel to the switch element, in particular a capacitor which can be charged to a first switching voltage by a voltage applied between the first and the second connection of the starter is. By suitable selection of the capacitance of the capacitive element, time-dependent variables can be generated, which can be used to control the switch element. In direct current operation of gas discharge lamps, it is generally provided that a voltage of approximately 150 V is applied to the gas discharge lamp, and thus the starter, in the ignition phase, whereas only approximately 50 V are present in the operating phase. Since the capacitive element is only intended to generate parameters required to control the switch in the ignition phase, it can be provided that the capacitive element can only be charged if the voltage present between the first and the second connection of the starter is higher than a first predetermined threshold voltage . This can be done, for example, in such a way that a first blocking element, in particular a Zener diode, is arranged in series with the capacitive element, which is conductive when the first threshold voltage is exceeded and otherwise blocks the flow of current.

For example, in order to be able to prevent the capacitive element from being overcharged in the event of malfunctions and voltage peaks, i.e. the voltage generated at this element reaches a value that is too high, it is further proposed according to the present invention that a second blocking element connected in parallel with the capacitive element is provided, in particular a zener diode, which, when the voltage generated at the capacitive element is higher than a second predetermined threshold voltage, is conductive, and otherwise blocks the flow of current, the second predetermined threshold voltage being greater than the first switching voltage.

To control the switching state of the switch element, the control means can be designed, for example, to detect the voltage generated at the capacitive element.

For example, it can be provided that the control means are designed such that when the voltage generated at the capacitive element reaches the first switching voltage, it applies the control signal, in particular one Control voltage, to the control terminal of the switch element to close the switch element. This means that when the first switching voltage is reached, the switch element is closed and thus current can flow through the glow electrodes of a gas discharge lamp on which the starter according to the invention is provided.

In addition, the control means can be designed such that when the voltage generated on the capacitive element has dropped to a second switching voltage after reaching the first switching voltage, it stops the application of the control signal, in particular the control voltage, to the Actuate switch element to open the switch element. After the voltage generated on the capacitive element has dropped to the second switching voltage, the heating of the glow electrodes is ended by interrupting the circuit, which simultaneously leads to the generation of the ignition voltage.

The control means are advantageously designed such that they effect the application of the control signal by applying a control voltage to the control connection of the switch element, which control voltage is preferably generated by voltage division of the voltage generated at the capacitive element. 5

According to a further advantageous embodiment, it can be provided that the control means bring about the termination of the application of the control signal, in particular the control voltage, to the control connection of the switch element by conductive connection of the control connection of the switch element to the first or the second connection thereof. For example, when using a field effect transistor as a switch element, this means that the gate electrode is connected to the source electrode, that is to say it is connected to the same potential 5, and the field effect transistor is thus brought into a non-conductive state. The control means can be designed, for example, in such a way that they detect the voltage generated at the capacitive element, in particular the first and the second switching voltage, by voltage division of the voltage generated at the capacitive element.

If it is provided that the capacitive element forms a source of electrical energy for the control means, then the capacitive element has a dual function which makes the provision of an additional power supply for the control means superfluous. Furthermore, this leads to the fact that the current consumption by the control means leads to a discharge of the capacitive element, i.e. the voltage generated on the capacitive element decreases over time, so that a transition from the first switching voltage to the second switching voltage can take place.

According to a second aspect, the present invention relates to a direct current gas discharge lamp lighting system, comprising a gas discharge lamp, a direct current gas discharge lamp starter and a direct current source for supplying a current of constant current to the gas discharge lamp and one between the first connection of one of the glow electrodes Gas discharge lamp and the DC source arranged inductive element, in particular an induction coil.

In particular, it can be provided that this system further comprises a further gas discharge lamp with an associated direct-current gas discharge lamp starter, a first connection of a first glow electrode of the further gas discharge lamp being connected to the first connection of a glow electrode of the first gas discharge lamp and a first connection of a second glow electrode of the further Gas discharge lamp is connected to the direct current source. The system can be constructed in a particularly simple manner if the direct current source is designed to output the current with a constant value regardless of the operating state of the gas discharge lamp / s. This is possible in particular if the direct current gas discharge lamp starter according to the invention is provided, since then the direct current source does not have to output a pulsed current to generate the ignition voltage, as is required in the prior art.

In order to avoid the occurrence of the cataphoresis effects already mentioned, it is proposed that the direct current source be designed to reverse the direction of current flow after predetermined time intervals.

According to a further aspect, the present invention relates to a DC ballast which is designed to output a current with a constant value, preferably independently of the operating state of a gas discharge lamp which can be connected to the ballast.

For example, it can be provided that a current regulator is already integrated in the ballast for outputting a current with a constant value.

In order to be able to avoid the occurrence of cataphoresis effects, it is further proposed that the ballast further comprise a polarity reversal stage for optionally reversing the polarity of the flow direction of the current to be supplied to a gas discharge lamp.

The invention further relates to a retrofit set with which alternating current gas discharge lamp lighting systems which have already been installed or are to be installed can be converted in a simple and cost-effective manner for direct current operation. The present invention is described below in detail by means of preferred embodiments with reference to the accompanying drawings. Show it:

1 shows a circuit diagram of a direct current gas discharge lamp starter that can be combined with a gas discharge lamp;

2a and 2b in combination a schematic view of a direct current gas discharge lamp lighting system, wherein FIG. 2a shows a block circuit view of a direct current ballast and FIG. 2b the gas discharge lamps which can be combined with the ballast, with respective ones

DC gas discharge lamp starter shows.

1, a DC starter according to the invention is generally designated 10. The starter 10 includes input or. Output connections 12, 14, which are to be connected to a contact connection of the two glow electrodes of a gas discharge lamp in the manner described below, so that the starter 10 is connected in series to the two glow electrodes of a gas discharge lamp. The connections 12 and 14 lead to a rectifier 16, which ensures that, regardless of the direction of current flow of the supplied current, a predetermined polarity is always provided at its output connections 18, 20, ie the connection 18 corresponds to the positive pole, the connection 20 corresponds to the negative pole. The rectifier 16 therefore always delivers a current or a voltage of predetermined polarity regardless of the direction of the current supply via the connections 12, 14, so that defined operating conditions are created for the components of the starter 10. The drain 22 of a field effect transistor 24 is conductively connected to the connection 18 of the rectifier 16, while the source 26 of the field effect transistor 24 is connected to the connection 20. In the illustrated embodiment, the field effect transistor 24 is an enhancement type n-channel MOSFET.

By supplying a suitable control signal to the gate 28 of the MOSFET 24, this can optionally be brought into a conductive state ιo, so that the input or. Output connections 12, 14 are conductively connected to one another, while in the non-conductive state of the MOSFET 24 the line connection between the connections 12, 14 is interrupted.

15

A series circuit comprising a first Zener diode 30, an electrical resistor 32, a diode 34 and a capacitor 36 is connected in parallel with the MOSFET 24, a second Zener diode 38 being connected in parallel with the capacitor 36. The capacitor 36 has the function of a reference transmitter for the MOSFET 24 in the manner described below due to its time behavior.

The starter 10 further comprises a control device 40, for example a control module 40, which controls the switching of the MOSFET 24. For power supply, the control module 40 is connected to the capacitor 36 via connections 42, 44, so that once the capacitor 36 has charged, as described below, the voltage generated at the capacitor 30 36 serves as the supply voltage for the control module 40. Furthermore, the control module 40 taps off the voltage generated at the capacitor 36 via connections 46, 48 via a voltage divider circuit with resistors 50, 52, 54.

35

The function of the starter 10 shown in FIG. 1 is described below. It is briefly on the 2b, in which the connection of a starter to a gas discharge lamp is shown in principle. 2b shows a series connection of two gas discharge lamps 60, 62. A first connection 66 of a glow electrode 64 of the gas discharge lamp 60 is connected to a current source, a second connection 68 of the glow electrode 64 is connected to the input connection 12 of the starter 10. The, output terminal 14 of the starter 10 is connected to a second terminal 70 of a second glow electrode 72 of the gas discharge lamp 16, and a first connection 74 of the second glow electrode 72 can either directly (via a choke coil) with the provision of only one gas discharge lamp second connection of the power source (shown in dashed lines), or can, as in the illustration of FIG. 2b 5 with solid lines, be connected to the second gas discharge lamp. In this case, the second connection 74 of the glow electrode 72 is connected to a first connection 76 of a glow electrode 78 of the gas discharge lamp 62. The second connection 80 of the glow electrode 78 is connected to the input connection 0 of the starter 10, which is assigned to the gas discharge lamp 62, and the second connection 14 of the starter 10 is connected to a second connection 82 of a further glow electrode 84 of the gas discharge lamp 62. A first connection 86 of the glow electrode 84 of the second gas discharge lamp 62 is connected to the power source via a choke coil 88.

If a gas discharge lamp, for example gas discharge lamp 60, is now to be ignited, a voltage which is in the range of approximately 150 V is applied via an ON switch of the current source. Ie this voltage is then present at the connections 12, 14 of the starter 10 in FIG. 1. In this state, the gate 28 of the MOSFET 24 is short-circuited to the source 26 via a line 56 by the control module 40, so that the MOSFET 24 is in its non-conductive state due to the absence of a potential difference between the source 26 and the gate 28. When the voltage is applied, the capacitor 36 can charge via the diode 34 and the resistor 32. The Zener diode 30 has the function of enabling a current flow or the build-up of a voltage across the capacitor 36 in this switched-on state, in which, as already mentioned, the voltage present is in the range of 150 V. For this purpose, the Zener diode 30 has a reverse voltage that is slightly above 50 V, for example in the range of 55-60 V. The Zener diode 38 connected in parallel with the capacitor 36 has a reverse voltage such that it becomes conductive when a voltage in the range of 15-16 V is generated at the capacitor 36 in order to avoid overloading the capacitor 36.

The control module 40 detects the voltage generated at the capacitor 36 via the voltage divider circuit with the resistors 50, 52, 54 and via the connections 46, 48. If the voltage at the capacitor 36 has risen to a value of approximately 14 V, which is a first switching voltage, the control module 40 detects this via the connection 46, whereupon the control module 40 also carries out the conductive connection of its connection 58 connected to the gate 28 the terminal 56 interrupts and the gate 28 is electrically isolated from the source 26. In this state, the gate 28 is then at a potential with respect to the source 26 defined by resistors 53, 55, so that in the state in which the connections 58 and 56 are electrically separated from one another, the potential present at the gate 28 means that MOSFET 24 is brought into its conductive state. Ie, once a voltage of 14 V is generated at the capacitor 36, the control module 40 brings the MOSFET 24 into its conductive state, so that an electrical current from the input terminal 12 via the terminal 18 of the rectifier 16 through the MOSFET 24, via the Terminal 20 of the rectifier 16 can flow to the output terminal 14 or in the reverse direction. In this state, for example, the two glow electrodes 64, 72 of the gas discharge lamp 60 are electrically connected in series, so that due to the electric current flowing through them, the glow electrodes are heated.

A discharge of the capacitor 36 described below, once it has been charged to a voltage of 14 V, is also detected by the control module 40, the control module 40 via the terminal 48 and the voltage divider circuit 50, 52, 54 detecting when the on Capacitor 36 generated voltage has dropped to a value of approximately 9 V. The value of 9 V thus forms the second switching voltage at which the control module 40 causes its connections 58 and 60 to be conductively connected to one another again and thus an electrical short-circuit connection between the gate 28 and the source 26 is produced again. That After the voltage generated at the capacitor 36 has dropped to a value of approximately 9 V, the MOSFET 24 is switched back to its non-conductive state and the conductive connection between the input terminal 12 and the output terminal 14 is thereby interrupted. This interruption of the current flow through the series-connected glow electrodes leads in a manner known per se to a voltage pulse generated by the choke coil 88, by means of which the gas discharge lamp 60 or 62 is ignited.

After the gas discharge lamp 60 or 62 is ignited, the applied voltage drops to approx. 50 V, i.e. to the operating voltage of such a gas discharge lamp. However, since the Zener diode 30 is dimensioned such that it blocks up to a voltage value of over 50 V, the capacitor 36 can no longer be charged after the gas discharge lamp has been ignited, so that the switching state of the MOSFET 24 no longer changes, ie this remains in its non-conductive state after the ignition of the gas discharge lamp 60 or 62.

After the capacitor 36 has been charged once, that is to say a voltage of 14 V has been generated across it, and the MOSFET 24 has been brought into its conductive state, the capacitor 36, which may have a capacitance of approximately 47 μF (45-50 μF), is discharged on the one hand by the current consumption of the control module 40, as already mentioned at the beginning, on the other hand, discharge through resistors 50, 54 and 53, 55 also occurs. That is to say, by suitable dimensioning of the resistors 50, 54, 53, 55, taking into account the current consumption by the control module 40, a specific temporal discharge characteristic of the capacitor 36 can be generated, in which particular care is taken to ensure that when the 14 V Voltage initiated and after the drop to 9 V ended heating phase is long enough to heat the glow electrodes 64, 72, 78, 82 to a sufficient extent.

The diode 34 has the function of preventing the capacitor 36 from being discharged via the MOSFET 24 when the MOSFET 24 is in the conductive state.

In order to ensure that the voltage peaks occurring when the gas discharge lamps are ignited do not damage the MOSFET 24, the latter should have a dielectric strength of up to 1200 V.

FIGS. 2a and 2b show in combination a direct current gas discharge lamp lighting system with a ballast 100 shown in FIG. 2a and the gas discharge lamps 60, 62 already described above with respective starters 10. With regard to the gas discharge lamps 60, 62 shown in FIG. 2b and their starters 10 is referred to the preceding description.

The ballast 100 of FIG. 2a is designed, as explained in more detail below, to output a constant current regardless of an operating state of the gas discharge lamps 60, 62, ie regardless of whether these lamps are currently in operation or are to be ignited. The ballast 100 has connections 102, 104 which can be connected to the conventional supply connections of an AC network. A connection 106 is also provided, which is used for grounding. The connections 102, 5 104, 106 lead to a line filter 108 for interference decoupling. The filter 108 is followed by a rectifier 110, by means of which the AC voltage or the AC current of the power network is rectified into a DC voltage or a DC current. A capacitor 112 is also provided for smoothing the output direct voltage or direct current.

A current regulator 114 follows the rectification components 110, 112. The current regulator 114 ensures that, as already mentioned, regardless of the operating state of the downstream gas discharge lamps, a current with a constant value in the range of 0.35 is always present A is delivered.

The current regulator 114 comprises a switching transistor 116 and an inductor 120 connected in series with the drain 115 and source 117 thereof. A current regulator 122 is arranged between the source 117 of the switching transistor 116 and the inductor 120 and is connected to a control device 124 in connection with

25 bond stands. The control device 124 controls the switching state of the transistor 116 via the gate 126. The transistor 116 is preferably again a power-free switchable MOSFET, in particular in the embodiment shown again an n-channel MOSFET of the enhancement type. The tax-

30 device 124 controls the switching state of transistor 116 in accordance with the output of current regulator 122 in such a way that, in cooperation with coil 120, an output current results with the desired value. Inductor 120 serves to interrupt the current conduction path through the transistor

35 116 due to its property of maintaining current flow, in cooperation with a freewheeling diode 128 den To keep current at an almost constant value. A transistor 130 in turn serves to smooth the output current.

The current controller 114 is connected to an output 132 of the ballast 100 via a pole reversal stage 134. The pole reversal stage comprises four switching transistors 136, 138, 140, 142, which can be brought into conductive or non-conductive states via control devices 144 (for transistors 136, 140) and 148 (for transistors 138, 142). In particular, diagonally opposite transistors are always simultaneously in a conductive state or in a non-conductive state during operation, so that depending on whether the transistors 136, 142 or the transistors 140, 138 are in a conductive state, the polarity at output connections

15 150, 152 can be selected. Such a variability of the polarity is to be provided because it has been shown that cataphoresis effects, i.e. galvanic separation of the lamp filling occur. To avoid these effects from time to time

20 times, for example at intervals of 15-30 minutes, the polarity at the output connections 150 and 152 reversed. For this purpose, as already mentioned, the transistors 136, 138, 140, 142 are controlled by the control devices 144, 148, which in turn are under the control of a control device 154.

25 hen, switched.

The ballast 100 further comprises a voltage supply 164 with three mutually separate transformers 166, 168, 170, each of which has a supply voltage in the range from

Supply 30 12 V. The transformer 166 supplies the supply voltage for a section 141 of the control device 148, which controls the transistor 138, the transformer 168 supplies the supply voltage for a section 143 of the control device 144, which controls the transistor 136,

35 and the transformer 170 provides the supply voltage for the current regulator 114 and also for those sections 145, 147 of the control devices 144, 148 which are the transistor 140 or control the transistor 142. A separate voltage or Power supply for the different sections of the control devices 144, 148 is therefore necessary since, for example, there is a voltage difference of approximately 150 V between a current supply line 156 and a current discharge line 158 of the polarity reversal stage 134 in the ignition mode. That is, if the transistors 136, 138 are in their conductive states, then the nodes 160, 162 are practically at the same potential as the supply line 156, for example at 150 V. For wiring the transistors, which in the illustrated embodiment are again n-channel -MOSFETs of the enrichment type are, however, a potential difference between gate and source in the range of 10 V is required. This means that a separate potential above the potential of 150 V of the node points 160, 162 is required for connecting the transistors 136, 138. This potential can be generated within the sections 143, 141 of the control devices 148, 144 which control the transistors 136, 138 with respect to the nodes 160, 162, in each case by means of the separate voltage supplies by the transformers 166, 168.

Connections 170, 172 of the lamp system, which is shown in FIG. 2b, can then be connected to the output connections 150, 152 of the ballast 100, so that the ballast 100 forms a direct current source for the gas discharge lamps 60, 62.

As already mentioned, the ballast 100 supplies a current with a constant value, ie with a value of approx. 0.35 A, the direction of current flow being reversed at periodic intervals of approx. 15-30 minutes in order to avoid the cataphoresis effects. The choke coil 88 which can be seen in FIG. 2b is therefore no longer used as a current limiter in the direct current gas discharge lamp lighting system according to the invention. Rather, it has the function, as already mentioned, of supplying the required ignition voltage when the gas discharge lamps 60, 62 are ignited, such as this is also the case with conventional AC gas discharge lamp lighting systems. Furthermore, the inductor 88 has the function of damping or suppressing current fluctuations which can occur in the direct current operation of gas discharge lamps. It has been shown that current fluctuations with a frequency in the range of 2 kHz and an amplitude in the range of up to 10% of the supplied current can occur in direct current operation in gas discharge lamps. However, it has also been shown that such vibrations can be almost completely damped by the choke coil 88, so that the uniform luminous behavior is practically not impaired by such high-frequency current and thus also intensity fluctuations.

The ballast shown in FIG. 2a and the DC starter shown in FIG. 1 can be used without further adaptation measures in the case of already installed AC gas discharge lamp lighting systems. The ballast 100 only needs to be connected to the supply connections of an existing lighting system, for example a fluorescent tube or the like, so that the fluorescent tube is supplied with direct current. Furthermore, the already existing alternating current starter can be replaced by the direct current starter according to the invention, so that a fully functional direct current gas discharge lamp lighting system with excellent operating characteristics can be obtained by simply adding the components according to the invention. Since, in particular in conventional AC gas discharge lamp lighting systems, choke coils on the one hand are present as current limiters on the other hand for generating the voltage pulses for igniting the lamp, no action needs to be taken with regard to the choke coil 88.

With the ballast according to the invention and the starter, for example, lamp systems can be operated which are one Have gas discharge lamp with a power of 22 W, or systems that have two series-connected lamps each with power of 15 W or 18 W. However, it goes without saying that in connection with the ballast according to the invention and the DC starter according to the invention, lamp systems can be operated with different output values, regardless of whether the lamp systems contain one or more fluorescent tubes connected in parallel or in series.

With the components according to the invention described above, it is therefore possible in a simple manner to convert already installed AC gas discharge lamp lighting systems to DC operation; Likewise, however, lighting systems to be installed can also be designed for direct current operation right from the start, and in each case already existing gas discharge lamps or sockets can be combined with the components according to the invention without conversion measures.

Claims

claims

1. DC gas discharge lamp starter (10) for igniting a gas discharge lamp (60) to be operated with direct current, the gas discharge lamp (60) comprising a first glow electrode (64), the first connection (66) of which can be connected to a direct current source for supplying / removing current and whose second connection (68) can be connected to a first connection (12) of the starter (10), and comprises a second glow electrode (72), the first connection (74) of which can be connected to the direct current source for current dissipation / supply and the second connection ( 70) can be connected to a second connection (14) of the starter (10), the starter (10) comprising a switch element (24) which can be switched over between a conductive and a non-conductive state, for the optional conductive connection of the first (12) and the second ( 14) connection (12, 14) of the same in an electrode heating phase in such a way that an electrical

Current flows through the first glow electrode (64) via the starter (10) to the second glow electrode (70) or in the opposite direction, and to interrupt the conductive connection of the first (12) and the second (14) connection (12, 14) thereof for igniting a gas discharge lamp (60) and during an operating phase of a gas discharge lamp, further comprising control means (40) for switching the switch element (24) between the conductive and the non-conductive state, characterized in that the switch element (24) comprises a semiconductor switch element (24) with a first connection (22) connected to the first connection (12) of the starter (10), a second connection (26) connected with the second connection (14) of the starter (10) and with one with the

Control means (40) for supplying a switching signal connected control connection (28).

2. Starter according to claim 1, characterized in that the switch element (24) comprises a transistor (24), in particular a field effect transistor (24).

3. Starter according to claim 1 or 2, characterized in that the switch element (24) is in a non-conductive state when a switching signal is not applied to the control connection (28).

4. Starter according to one of the preceding claims, characterized in that the first (12) and the second (14) connection (12, 14) of the starter (10) with the first and the second connection (22, 26) of the switch element (12) are connected via voltage rectifier means (16).

5. Starter according to one of the preceding claims, further comprising a capacitive element (36) connected in parallel with the switch element (24), in particular a capacitor (36), which is connected by a connection between the first (12) and the second (14) (12 , 14) of the starter (10) applied voltage can be charged to a first switching voltage.

6. Starter according to claim 5, characterized in that the capacitive element (36) can only be charged if the voltage present between the first (12) and the second (14) connection (12, 14) of the starter (10) is higher is as a first predetermined threshold voltage.

7. Starter according to claim 6, characterized in that a first blocking element (30), in particular a Zener diode (30), is arranged in series with the capacitive element (36), which is conductive when the first threshold voltage is exceeded and otherwise blocks the flow of electricity.

8. Starter according to one of claims 5 to 7, characterized by a second blocking element (38) connected in parallel to the capacitive element (36), in particular a zener diode (38), which, when the on the capacitive element (36) generated voltage is higher than a second predetermined threshold voltage, is conductive, and otherwise blocks the flow of current, the second predetermined threshold voltage being greater than the first switching voltage.

9. Starter according to one of claims 5 to 8, characterized in that the control means (40) for Erfr.ssen the voltage generated on the capacitive element (36) are formed.

10. Starter according to claim 9, characterized in that the control means (40) are designed such that when the voltage generated on the capacitive element (36) reaches the first switching voltage, the application of the control signal, in particular a control voltage cause the control terminal (28) of the switch element (24) to close the switch element (24).

11. Starter according to claim 10, characterized in that the control means (40) are designed such that when the voltage generated on the capacitive element (36) has dropped to a second switching voltage after reaching the first switching voltage, the termination cause the control signal, in particular the control voltage, to be applied to the switch element (24) in order to open the switch element (24).

12. Starter according to claim 10 or 11, characterized in that the control means (40) cause the application of the control signal by applying a control voltage to the control connection of the switch element (28), which control voltage is preferably by dividing the voltage voltage generated on the capacitive element (36).

13. Starter according to one of claims 10 to 12, characterized 5 indicates that the control means (40) the termination of

Applying the control signal, in particular the control voltage, to the control connection (28) of the switch element (24) by conductively connecting the control connection (28) of the switch element (24) to the first or the second connection (26) thereof.

14. Starter according to claim 11 and if desired claim 12 or 13, characterized in that the control means (40) on the capacitive element (36) generated voltage

15 voltage, in particular the first and the second switching voltage, by voltage division (50, 52, 54) of the voltage generated on the capacitive element (36).

15. Starter according to one of claims 5 to 14, characterized 0 indicates that the capacitive element (36) forms a source of electrical energy for the control means (40).

16. DC gas discharge lamp lighting system comprising a gas discharge lamp, a direct current gas discharge lamp starter (10) according to one of claims 1 to 15, a direct current source (100), in particular a ballast (100), for supplying a current with a constant current to the gas discharge lamp (60) and a

30 between the first connection (74) of one of the glow electrodes (66, 72) of the gas discharge lamp (60) and the direct current source (100) arranged inductive element (88), in particular an induction coil (88).

35 17. DC gas discharge lamp lighting system according to claim 16, further comprising a further gas discharge lamp (62) with a DC gas discharge lamp Pen starter (10) according to one of claims 1 to 15, wherein a first connection (76) of a first glow electrode (78) of the further gas discharge lamp (62) with the first connection (74) of a glow electrode (72) of the first gas discharge lamp (5 60) is connected and a first connection (86) of a second glow electrode (82) of the further gas discharge lamp (62) is connected to the direct current source (100).

10 18. DC gas discharge lamp lighting system according to claim 16 or 17, characterized in that the DC source (100) is designed to output the current with a constant value regardless of the operating state of the gas discharge lamp (60, 62).

15

19. Direct current gas discharge lamp lighting system according to one of claims 16 to 18, characterized in that the direct current source (100) is designed to change the current flow direction after predetermined time intervals

20 reverse.

20. DC ballast, in particular for a DC gas discharge lamp lighting system according to one of claims 16 to 19, wherein the ballast (100)

25 is designed to output a current of constant value regardless of the operating state of a gas discharge lamp (60, 62) that can be connected to the ballast (100).

30 21. DC ballast according to claim 20, characterized in that the ballast (100) comprises a current regulator (114) for outputting a current with a constant value.

35 22. DC ballast according to claim 20 or 21, characterized in that the ballast (100) comprises a pole reversal stage (134) for optionally reversing the Flow direction of a current to be supplied to a gas discharge lamp (60, 62).

23. retrofit kit, in particular for retrofitting or retrofitting an AC gas discharge lamp lighting system into a DC gas discharge lamp lighting system, the retrofit kit comprising: a DC ballast (100) according to any one of claims 20 to 22, wherein the DC pre - ιo switching device (100) between a power source and at least one gas discharge lamp (60, 62) of the system is switchable, at least one DC gas discharge lamp starter (10) according to one of claims 1 to 15, preferably one starter for each gas discharge lamp (60, 62) of the lighting system to be retrofitted or converted, for replacing an AC starter present in the AC gas discharge lamp lighting system with one

20 DC gas discharge lamp starters (10).

24. Retrofit kit according to claim 23, characterized in that the at least one DC gas discharge lamp starter (10) with connection contacts for connecting to the

25 assigned gas discharge lamp is provided, which correspond to the connection contacts of conventional alternating current starters used in AC gas discharge lamp lighting systems.

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