EP1843645B1 - Switching assembly for high pressure gas discharge lamps - Google Patents

Description

The invention relates to a circuit arrangement for igniting a high-pressure gas discharge lamp, which is connected on the input side to a magnetic ballast for providing an AC supply to the lamp, according to the preamble of claim 1 and a method for operating a high pressure gas discharge lamp with an ignition circuit.

Conventional circuit arrangements for igniting a high-pressure gas discharge lamp are often designed as a superposition ignition circuit. This has an ignition transformer, which is connected on the primary side with a Zündauslöseschaltung and secondary side between the ballast and the lamp for transmitting an ignition pulse is arranged on the lamp. The circuit arrangement has a surge capacitor and a first switch means. In this case, a series connection of at least the first switching means and a primary winding of the ignition transformer is connected in parallel to the surge capacitor. If a primary-side ignition pulse is now generated after the charging of the surge capacitor by the closing of the first switch means in the ignition triggering circuit, the ignition transformer transmits this ignition pulse to the supply circuit of the lamp. In order to obtain a sufficiently high secondary-side ignition pulse, the transmission ratio of the Zündübertragers is designed accordingly. Once the lamp has ignited, usually the circuit arrangement for igniting the lamp is turned off.

Such a generic circuit arrangement is for example in the German Offenlegungsschrift DE 195 31 622 A1 and the DE 195 31 623 A1 described.

Due to the high electrical and thermal load, in particular at the electrodes of the high-pressure gas discharge lamp, the latter have a limited life, which leads to malfunction at the end of use. Typical is, for example, a so-called cycling operation in which the lamps extinguish after a short burning time, are restarted by the ignition circuit, etc. Furthermore, there is the problem that due to the aging process in particular at the electrodes of the lamp high power losses are generated, which ultimately can lead to a short circuit or even to a bursting of the glass vessel of the lamp. Such effects can also lead to the fact that the ballast is damaged by the heat and must be replaced together with the defective lamp.

Known in the art is the use of a thermal switch in the supply circuit of the lamp, which interrupts the AC supply to the lamp when heat buildup occurs when the associated temperature sensor detects exceeding a predetermined temperature. Such a thermal switch can be designed, for example, as a fuse, which responds after the occurrence of an elevated temperature in the vicinity of the ballast or the high-pressure gas discharge lamp. The use of such a thermal switch is relatively uncertain, since such a temperature sensor can detect the fault in the lamp only delayed in time, because the heat loss must be transferred via heat conduction only from the place of origin of electrical power loss to the sensor. For this reason, it may be despite the provision of such a thermal switch during operation of a high-pressure gas discharge lamp that in the case of aging of the lamp such a strong Heat is caused that the holder of the lamp, the ballast and / or the ignition circuit is damaged.

In this respect, the object of the invention is to at least partially avoid the described disadvantages of circuit arrangements of the prior art.

This object is achieved in a surprisingly simple manner by a circuit arrangement for igniting a high-pressure gas discharge lamp, which is connected on the input side to a magnetic ballast for providing an AC supply to the lamp, with the features of claim 1. Thereafter, the circuit arrangement according to the invention on an ignition transformer, which may be formed for example as a pulse transformer, which is connected on the primary side with a Zündauslöseschaltung and secondary side between the ballast and the lamp for transmitting an ignition pulse is arranged on the lamp. The circuit arrangement further comprises a surge capacitor and a first switch element, wherein in the Zündauslöseschaltung a series circuit, comprising at least the first switch element and a primary winding of the Zündübertragers the shock capacitor is connected in parallel. The circuit arrangement according to the invention is characterized in that a series connection, which has at least one controllable second switch means, the lamp for extinguishing the same is connected in parallel and a means for detecting the degree of asymmetry of the lamp voltage is provided and a control device for extinguishing the lamp by the Driving the second switch means in response to the detected unbalance of the lamp operating voltage.

The fact that the circuit arrangement according to the invention is designed to determine the degree of asymmetry of the lamp operating voltage, the Aging condition of the gas discharge lamp can be determined before malfunction or damage to the ballast or the circuit arrangement occur. This effect is due to the fact that such aging of a high-pressure gas discharge lamp as a rule is due to an asymmetry of the cathode drop voltage at the two electrodes, which in turn is caused by a difference in the work function of the electrons at the two electrodes.

If the unbalance of the lamp operating voltage exceeds a predetermined value, the controllable second switch means can short the lamp and thus erase it, thereby preventing the degree of unbalance of the lamp operating voltage from being further increased. In this way, the emergence of a dangerous power loss during operation of the lamp is avoided, since otherwise caused by the asymmetry of the cathode drop voltage at the electrodes despite the AC power rectification effect in the lamp, in which the magnetic ballast, in particular a choke, has no current-limiting effect. The controllable by the controller for shorting the lamp second switch means is part of a series circuit, which is connected in parallel to the lamp and at least this switch means and the connections to the lamp.

In contrast to conventional circuit arrangements, the circuit arrangement according to the invention is accordingly able to terminate the operation of the high-pressure gas discharge lamp early enough before other components can be damaged during further operation of the lamp or other malfunctions can occur. In general, then it is sufficient to replace the aged high-pressure gas discharge lamp to operate the relevant lighting device again.

It may be expedient if the control device of the circuit arrangement according to the invention has a timer circuit for controlling the ignition operation of the circuit arrangement, in particular with a counting device for detecting the number of lamp ignitions and / or a counting device for detecting the past ignition time for a detonation attempt. In this respect, the total ignition time of a Zündversuchs can be detected and compared with a stored value. If this predetermined value is exceeded, it is possible to conclude that the lamp has malfunctioned and, to that extent, to prevent further ignition attempts. The same applies to the exceeding of a predetermined number of lamp ignitions within the ignition operation of the circuit arrangement.

In addition, it may also be expedient to provide a controllable, third switch for switching off and / or blocking the Zündauslöseschaltung, which is connected in parallel, for example, the surge capacitor and insofar short-circuits if necessary.

In order to detect the degree of asymmetry of the lamp operating voltage, a series circuit may be provided which has at least one capacitor and one resistor, wherein this series connection of the lamp is connected in parallel. By this measure it is achieved that the DC voltage component of the lamp operating voltage is reflected in the voltage of this capacitor, which can be determined by a corresponding detection means. For example, for this purpose, the control device having an analog-to-digital converter, with which the indicated capacitor voltage can be digitized for further processing.

It may be expedient if the magnetic ballast is designed as a conventional throttle. In addition, can it may be expedient if the series circuit comprising the second switch means does not comprise this throttle, so that the choke is not loaded by the short circuit caused by the second switch means for extinguishing the lamp.

The method, the above object is achieved by a method for operating a high-pressure gas discharge lamp, which is connected to a magnetic ballast for providing an AC supply voltage, with an ignition circuit, which is switched off after the ignition of the lamp. The inventive method is characterized in that during operation of the lamp, the degree of asymmetry of the lamp operating voltage is detected and this degree is compared with a predetermined value and when exceeding the predetermined value, the lamp is shorted to extinguish the lamp discharge.

As a result, the emergence of a high heat loss during operation of the lamp is avoided, which ultimately a malfunction or damage to the ballast and / or the circuit arrangement can be prevented.

It may be expedient if the lamp is short-circuited over a predetermined time interval and the short-circuit is canceled again after the expiration of this time interval. This time interval may, for example, comprise a few milliseconds sufficient to extinguish the high pressure gas discharge lamp. Thereafter, the short circuit can be canceled again, as far as it is ensured that the lamp is not ignited or subsequent ignition attempts are allowed.

In order to avoid that in particular with a self-controlled first switch such as a Sidac after the detection of the Beyond a predetermined degree of asymmetry of the lamp operating voltage no primary-side ignition pulse is generated in the Zündauslöseschaltung, can be provided according to the invention that simultaneously with or after the short-circuiting of the lamp, the ignition circuit is blocked, for example by shorting the surge capacitor.

To ensure that after replacement of an aged high-pressure gas discharge lamp, the new lamp can be operated with the circuit arrangement, the blockage of the ignition circuit is preferably removed after it is disconnected from the power supply and subsequently reconnected to this.

The detection of the degree of asymmetry of the lamp voltage during operation of the lamp can also be used to determine the time course of this asymmetry, whereby ultimately a prognosis for the remaining operating time of the lamp can be determined. For example, it can be provided that from the course of the unbalance of the lamp operating voltage over a predetermined time interval, for example by linear interpolation, the time duration is determined, which remains until the lamp reaches a predetermined limit of the unbalance of the lamp operating voltage at which the lamp is turned off according to the invention. This determined period of time can be optically displayed or digitally or analogue output at a corresponding port for further processing or display.

Furthermore, it may be expedient to use the detected measure of the unbalance of the lamp operating voltage during operation to establish an allowable number of ignition attempts. After expiration of this determined in dependence on the detected degree of asymmetry of the lamp operating voltage number of ignition attempts can then the ignition circuit be blocked. In the same way, it can be provided according to the invention that the determined degree of asymmetry of the lamp operating voltage is used for determining the permitted ignition time within which ignition attempts may be carried out. For example, the permitted number of ignition attempts or the permitted ignition time can be calculated in proportion to the distance of the detected asymmetry from the permitted asymmetry of the lamp operating voltage. In this case, this allowed unbalance of the lamp operating voltage just corresponds to the degree just before the lamp is extinguished.

Fig. 1

eine erste Ausführungsform einer erfindungsgemäßen Schaltungsanordnung zum Zünden einer Hochdruck-Gasentladungslampe in einer Prinzipskizze und

Fig. 2

eine zweite Ausführungsform einer erfindungsgemäßen Schaltungsanordnung zum Zünden einer Hochdruck-Gasentladungslampe in einer Prinzipskizze

zeigt.The invention will now be elucidated by describing some embodiments with reference to the accompanying drawings, in which: FIG

Fig. 1

a first embodiment of a circuit arrangement according to the invention for igniting a high pressure gas discharge lamp in a schematic diagram and

Fig. 2

A second embodiment of a circuit arrangement according to the invention for igniting a high pressure gas discharge lamp in a schematic diagram

shows.

Fig. 1 shows a circuit arrangement according to the invention, which is designed here as Zündschaltungsanordnung 1. At the output terminals L _P , N, the high-pressure gas discharge lamp 3 is connected, via which a lamp operating voltage U _L drops during operation, the lamp current is indicated by I _L. For AC power supply of the lamp, the ignition circuit 1 is connected via a designed as a throttle 2 magnetic ballast to the mains voltage U _N. The circuit arrangement comprises a triggering circuit, which in the in Fig. 1 shown Embodiment, a surge capacitor 30, the primary-side coil winding 13 of a Zündübertragers 10 and a controllable switch 20 has. In this case, the series connection of the primary-side coil winding 13 and the switch 20 is connected in parallel to the surge capacitor 30. The secondary-side coil winding 11 of the Zündübertragers 10 is disposed in the supply line of the lamp. The surge capacitor 30 is connected in parallel with a capacitor 40 and a resistor 41 in series. This parallel connection serves to charge the surge capacitor 30.

The circuit arrangement shown comprises a controller 50, which has a timer module as a subassembly. The controller 50 actuates the switch S1 for generating a primary-side ignition pulse in the Zündauslöseschaltung, which is superimposed pulse-transformed on the secondary side of the Zündübertragers the AC power supply to the lamp. The switch 20 is e.g. designed as a field effect transistor.

Furthermore, the circuit arrangement has a series connection, which comprises at least the resistor 61 and the capacitor 60 and which is connected to the electrodes of the lamp 3 and insofar as this is connected in parallel. In the example shown, this series connection connected in parallel with the lamp also has the secondary-side coil winding 11. The Con-troller 50 is connected via the connecting lines 54, 55 for power supply. The control line 51 controls the switch 20 of the Zündauslöseschaltkreises. Furthermore, the controller 50 has a sensor line 53 which is at the voltage U _{C of} the capacitor 60. The detected voltage on the line 53 U _C is digitized in the controller via an analog-to-digital converter, not shown, so that the voltage at the capacitor 60 is ready for further processing binary coded in the controller 50.

In addition, the timer 50 in the in Fig. 1 illustrated embodiment, a further control line 52, with which a executed as a field effect transistor second switch 70 is driven. The switch 70, together with the secondary winding 11 of the Zündübertragers 10 a series circuit which is connected in parallel to the lamp 3, so that the switch 70, the lamp can be short-circuited. It should be noted that the second switch can also be designed as a thyristor or triac, for example.

The functioning of in Fig. 1 illustrated Zündschaltungsanordnung invention will be described below. After charging the surge capacitor 30 controls the controller 50 at a time at which the mains voltage is above the lamp voltage, the switch S1 briefly to close and then to open again. As a result, the surge capacitor 30 serving as the input power source for the tripping circuit discharges via the primary-side coil winding 13 of the ignition transformer 10. The magnetization of the primary-side coil winding is transformed via the Zündübertragerkern 12 to the secondary-side coil winding 11 and the mains voltage superimposed. A secondary-side ignition pulse is thus applied to the lamp 3, so that it can ignite. If this does not ignite immediately, a decaying oscillation results on the supply line due to the always existing stray capacitance arranged parallel to the lamp 3, the resonant circuit being closed via the capacitors C2 and C3 so that the lamp choke 2 is not loaded with the ignition voltage. After reopening the switch 20, the capacitor 30 is charged again via the parallel connection of the capacitor 40 and the resistor 41. If the lamp has not ignited after the first ignition pulse and the mains voltage is still above the lamp burning voltage, the switch 20 closed again by the controller 50 in the same half-wave to generate a primary-side ignition pulse and again opened after a period of a few microseconds. This process can be repeated several times until finally the lamp ignites.

During operation of the lamp 3, the controller 50 continuously determines the degree of unbalance of the lamp operating voltage. For this purpose, the series connection of the secondary-side coil winding 11, the resistor 61 and the capacitor 60, which is connected to the electrodes of the lamp 3 is used. In this case, the secondary-side coil winding 11 does not interfere with the detection of this DC voltage component, since the former has a negligible DC resistance.

If the lamp operating voltage is symmetrical to each other in both mains half-waves, the capacitor 60 is symmetrically charged or discharged. As already mentioned, the voltage U _C at the capacitor 60 is digitized by the controller 50 by means of an A / D converter, not shown, whose input is connected to the measuring line 53. In the presence of a symmetrical lamp operating voltage in both half-waves, the controller 50 on the capacitor 60 detects a DC voltage component identical to zero.

As described, high-pressure gas discharge lamps are subject to wear, which ultimately leads to failure of the lamp. In general, this aging process manifests itself in a different cathode drop voltage on both electrodes of the lamp, resulting in a rectifier effect of the lamp. In this case, the controller 50 measures a non-zero DC voltage component of the voltage U _C , which is a measure of the unbalance of the lamp operating voltage and from the controller 50 with a predetermined value is compared. If, during operation of the lamp, this preset value is exceeded, the lamp 3 is switched off in order to avoid consequential damage, which could be caused for example due to excessive temperature development. For this purpose, the controller 50 controls the switch 70 to close via the control line 52. As a result, the lamp 3 is disconnected from the supply voltage, whereby the lamp goes out. After an exemplary time interval of 10 milliseconds, the controller 50 re-directs the switch 70 to open. Since the controller 50 has detected that the lamp is faulty, the control line 51 is blocked, so that the switch 20 in the Zündauslöseschaltung can not be controlled to close and thus not to generate a firing pulse. The controller 50 is set to re-initialize after the power is turned off and then turned on again, and then the switch 20 can again be driven to generate a primary-side firing pulse. It is assumed that after disconnecting the controller from the mains, the lamp replaced and after restarting the network, the new lamp can be operated as described.

As in Fig. 1 As shown, the controller 50 includes a timer device having, in the described embodiment, a count device for detecting the number of lamp firings and a counter for detecting the past ignition timing for a firing attempt. In particular, in the case of an aged high-pressure gas discharge lamp, multiple lamp ignitions are often necessary until the lamp finally burns. For this reason, the number of such necessary lamp ignitions is detected in an ignition test and also the required ignition time. Should it turn out in the course of an ignition attempt that a predetermined number of lamp firings or a predetermined ignition time has been exceeded, the controller 50 will close a faulty lamp and omit further ignition attempts. For this purpose, an unillustrated memory area is provided in the controller 50, in which the permitted number of lamp ignitions or the allowable ignition time for a detonation attempt are stored. In the described ignition device 1 according to the invention is now provided that the allowed number of ignition attempts and / or the allowable ignition time is made in a Zündversuch of the determined measure for the unbalance of the lamp operating voltage. The lower the unbalance of the lamp operating voltage, the higher the number of permitted lamp ignitions or the permitted ignition time. If the measured unbalance of the lamp operating voltage approaches the limit value, the number of permitted ignition attempts or the permitted ignition time is correspondingly reduced in order to damage the magnetic ballast or ignition circuit when the lamp is in "end-of-life" state avoid.

In the in Fig. 1 In the embodiment shown, the circuit arrangement 1 does not comprise the magnetic ballast designed as a choke 2. In another embodiment of the invention, however, it is provided to integrate the ballast and the ignition circuit in a single unit, see Fig. 2 , This shows a second inventively designed circuit arrangement in which the ballast 2 and the ignition circuit are formed as a unit. In the Fig. 2 illustrated embodiment of the circuit arrangement is otherwise very similar to the in Fig. 1 constructed and differs from this otherwise only in the design of Zündauslöseschaltung. Its switch 20 is designed here as a passive, self-controlled switch. In the in Fig. 2 illustrated circuit compares the executed as Sidac or triac switch the voltage applied to it with a switch-internal comparator 21 and turns on exceeding a predetermined voltage value, here about 200 volts. A primary ignition pulse is triggered by the Discharge of the surge capacitor 30 is generated, the switch 20 opens again when its holding current is exceeded. The electrical design of the components is designed in such a way that here too the triggering circuit is set up for generating a plurality of ignition pulses within a network half-cycle.

Another difference of in Fig. 2 shown circuit arrangement in comparison to in Fig. 1 shown is that the controller 50 in Fig. 2 the generation of primary ignition pulses can block that can be controlled via the control line 51, a switch 80 for closing, which is arranged parallel to the surge capacitor 30. The trigger circuit is in turn blocked when, as described above, it has been detected that a predetermined amount of unbalance of the lamp operating voltage has been reached.

LIST OF REFERENCE NUMBERS

1

circuitry

2

throttle

3

High-pressure gas discharge lamp

10

Ignition transformer (pulse transformer)

11

Secondary coil winding / coil

12

Zündübertragerkern

13

Primary coil winding / coil

20

switch

30

pulse capacitor

40

capacitor

41

resistance

50

controller

51, 52

control line

53

Measurement line

54, 55

Power Line

60

capacitor

61

resistance

70

switch

80

switch

Claims (12)

1. Switching assembly for igniting a high-pressure gas discharge lamp which is connected on the input side thereof to a magnetic ballast for providing an alternating current supply of the lamp, the switching assembly comprising:

   - an ignition transformer which is connected on the primary side thereof to an ignition trigger circuit and which is disposed on the secondary side thereof between the ballast and the lamp, for transmitting an ignition pulse to the lamp,

   - a surge capacitor and a first switch means, wherein in said ignition trigger circuit a series connection comprising at least said first switch means and a primary winding of the ignition transformer are connected in parallel with said surge capacitor;

   characterized in that a series connection (70, 11) including a controllable second switch means (70) is connected in parallel with said lamp (3) for extinguishing the lamp and that a means for detecting the level of an unbalance of the lamp operating voltage is provided as well as a control device (50) for extinguishing the lamp by controlling the second switch means in response to said detected unbalance of the lamp operating voltage.
2. Switching arrangement according to claim 1, characterized in that the control device (50) includes a timer circuit for controlling the ignition operation of the switching arrangement (1), with a counting device for detecting the number of lamp ignitions and/or a counting device for detecting the ignition time that has passed for an ignition attempt.
3. Switching arrangement according to claim 1 or 2, characterized in that a series connection (60, 61, 11) comprising at least one capacitor (60) and a resistor (61) is connected in parallel with the lamp and that there is further provided a means for detecting the voltage at the capacitor.
4. Switching arrangement according to claim 1, 2 or 3, characterized in that the magnetic ballast is configured as an inductor (2) and that the series connection including the second switch means (70) and connected in parallel with the lamp (3) does not include said inductor.
5. Switching arrangement according to one of the claims 2 to 4, as far as referred back to claim 2, characterized in that third switch means (80) are connected in parallel with the surge capacitor (3).
6. Method for operating a high-pressure gas discharge lamp that is connected to a magnetic ballast for providing an alternating current supply, with an ignition circuit arrangement that is deactivated after the ignition of the lamp, characterized in that during the operation of the lamp (3) a level for the unbalance of the lamp operating voltage is detected, that this detected level for the unbalance is compared to a predetermined value and that the lamp is short-circuited for extinguishing the lamp discharge when said predetermined value is exceeded.
7. Method according to claim 6, characterized in that the lamp (3) is short-circuited for a predetermined time interval and that said short-circuit is cancelled after the expiration of this predetermined time interval.
8. Method according to claim 6 or 7, characterized in that the lamp ignition ciruit arrangement is blocked simultaneously with or after short-circuiting the lamp (3).
9. Method according to claim 8, characterized in that blocked state of the ignition circuit arrangement is cancelled after the ignition circuit arrangement is separated from the power supply and the ignition circuit arrangement is reconnected to the power supply.
10. Method according to one of the claims 6 to 9, characterized in that a detected level for the unbalance of the lamp operating voltage is memorized.
11. Method according to one of the claims 6 to 10, characterized in that during the ignition of the lamp, a detected level for the unbalance of the lamp operating voltage for fixing an allowable number of ignition attempts is considered before the ignition circuit arrangement is blocked.
12. Method according to one of the claims 6 to 11, characterized in that during the ignition of the lamp, a detected level for the unbalance of the lamp operating voltage for fixing an allowable ignition time is considered before the ignition circuit arrangement is blocked.

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