EP0759684A1 - Starting device for a high pressure discharge lamp - Google Patents

Abstract

The arrangement includes an ignition control device, including a ballast device (VG) joined to the mains a.c. voltage, an ignition or firing transformer (ZT) in series with the high-pressure discharge lamp (L), an ignition capacitor (CZ) and a spark-gap (FS),for discharging of the ignition capacitor via the ignition or firing transformer (ZT). A circuit element (D4,R10,C12,R11) is therefore connected across a monitored high pressure discharge lamp in order to test its operating voltage, and has a given switching threshold corresp. to the critical restart peak of the high-pressure lamp.

Description

The invention relates to an ignition control device for a high-pressure discharge lamp according to the preamble of claim 1.

Such ignition control devices, with which high-pressure discharge lamps are operated, which allow immediate, automatic re-ignition of the extinguished high-pressure discharge lamp are, for. B. from DE-A-29 38 529 or from EP-B1-0 252 438 known. Due to their function, ignition control devices of this type are basically similar. The phase of an AC mains voltage is connected behind a ballast to the series circuit of an ignition transformer and the operated high-pressure discharge lamp, this lamp load circuit being closed via the neutral conductor of the AC network. Usually, a high-voltage transformer is also provided via a switching network on the primary side at the AC line voltage, the secondary winding of which is connected to an ignition capacitor, optionally also with an auxiliary ignition combination, in order to charge the ignition capacitor, which is connected to the ignition transformer via a spark gap. As soon as the potential rising at the ignition capacitor exceeds the breakdown voltage of the spark gap, the ignition capacitor discharges via this spark gap and generates a high-voltage ignition pulse in the ignition transformer, which initiates the ignited operating state of the high-pressure discharge lamp.

From EP-B1-0 252 438 in particular, it is known to design such ignition control devices in such a way that further ignition attempts are prevented after a very short time when the high-pressure discharge lamp is correctly ignited. If, on the other hand, the high-pressure discharge lamp does not ignite for a predetermined period of time, the high-voltage transformer of the ignition control unit becomes locked; further ignition attempts are then no longer possible. If the high-pressure discharge lamp ignites only briefly, renewed attempts to ignite are permitted, but the circuit is locked if these attempts do not lead to the normal operation of the high-pressure discharge lamp in a predetermined period of time. In order to enable the automatic restart of the ignition of a high-pressure discharge lamp, any locking of the ignition control unit is automatically reset when the mains voltage is interrupted.

The known ignition control devices thus quite meet the requirements in normal operating cases. They protect the ignition control unit from unlimited attempts to ignite a high-pressure discharge lamp that does not ignite and thus protect the ignition control unit itself from thermal overload. They take account of mains voltage interruptions or fluctuations that can cause a burning high-pressure discharge lamp to go out briefly and enable automatic re-ignition. Finally, resetting the power supply, i.e. H. the AC mains voltage to put the ignition control device into a defined idle state, from which normal ignition operation is possible again as soon as the high-pressure discharge lamp is to be put into operation again by switching on the mains AC voltage.

Now, however, high-pressure discharge lamps have the particularly unpleasant property that their operating voltage increases with increasing lamp life at the end of the individual lamp life. This phenomenon can be uncontrolled to extinguish the high-pressure discharge lamp at irregular intervals, e.g. B. result from mains voltage drops. If the aged high-pressure discharge lamp is not yet replaced, the rise in the operating voltage continues to increase, which can lead to the re-ignition voltage of the high-pressure discharge lamp becoming too high and the latter extinguishing. Especially It is unpleasant that this behavior becomes completely uncontrolled at the end of the life of an aged high-pressure discharge lamp and therefore known ignition control devices do not solve this problem satisfactorily and effectively. In order to avoid a damaging reaction of aged high-pressure discharge lamps to the ignition control units, it is currently e.g. B. common in the municipal area in traffic lighting, preventive replacement of such high-pressure discharge lamps after an average service life, which is estimated as a function of the switch-on times, i.e. not fully utilizing the available individual service life of the high-pressure discharge lamp in order to maintain and reduce maintenance costs and costs Keep limits.

The invention is therefore based on the object of developing an ignition control device of the type mentioned in such a way that uncontrolled burning operation in the case of aged high-pressure discharge lamps is reliably avoided at the end of their service life and reaching the end of the service life in an aged high-pressure discharge lamp can be determined with minimal effort .

In an ignition controller of the type mentioned, this object is achieved according to the invention with the features described in the characterizing part of patent claim 1.

In known ignition control devices, it is customary to limit the current flowing in the lamp load circuit during the burning operation by means of a ballast and also to measure the lamp current itself in order to derive a protective function for the high-pressure discharge lamp, but also the ignition control device. In the solution according to the invention, the lamp current is also detected in the burning mode, but the burning voltage is also monitored, this monitoring device being equipped in such a way that the ignition control device is locked before a critical threshold value for the re-ignition peak when the burning voltage rises is exceeded. If the high-pressure discharge lamp goes out after the detection of this critical operating state, the ignition control device, which has already been locked, cannot immediately ignite it again. If the mains AC voltage is switched off, this interlock remains for a predetermined period of time, for example 1 s, and only then does it reset itself.

With this solution, unsuccessful hot ignition attempts in the case of aged lamps that fail during operation and the associated increased ignition device wear are avoided. A thermal overload and a destruction of ignition control devices which may be attributable to this may also not occur. Mechanical destruction of the high-pressure discharge lamp by inadmissibly long or repetitive high voltage is also definitely ruled out, which eliminates the cause of secondary damage within the lamp or the headlight. The solution according to the invention also avoids the known phenomenon that electrodes and burners of aged high-pressure discharge lamps are damaged as a result of the supply of excessive ignition energy, which can lead to so-called abnormal lamp operation. The result of this is that the ballast and ignitor are subjected to high thermal loads due to the longer-lasting flowing lamp current with a high DC component and can ultimately fail.

Another significant advantage of the solution according to the invention is that the latent risk of failure due to an unknown aging condition of the lamp can be eliminated without the need to accept shorter lamp replacement intervals. This increases the availability and reliability of lights or headlights that are operated with such high-pressure discharge lamps, particularly in the field of object protection and emergency lighting. After all, it is of immediate importance to the maintenance service over a simple one To have tools with which the aging condition of a high-pressure discharge lamp can be determined even before its actual end of life. By briefly interrupting the mains voltage, e.g. B. <1 s, a burning high-pressure discharge lamp, the maintenance service can determine whether the lamp ignites properly after the short interruption or goes out and can only be re-ignited after a long disconnection of the voltage, ie> 1 s, when the locking circuit is reset. If the latter is the case, this is an essential indicator of an already impermissibly high operating voltage, ie the approaching end of the service life of the checked high-pressure discharge lamp. Because in this case there is a high probability that the monitoring device for detecting the increased operating voltage had already responded before the AC mains voltage was interrupted and the ignition control device had locked for a predetermined period of time.

Finally, a great advantage of the solution according to the invention is the simple circuit structure, which does not require operational amplifiers or other intermediate amplifiers for the ignition device control, and does not require its own power supplies for the control devices implemented in the ignition control device, as a result of which the fuses which are usually required for this are also eliminated. All of this contributes to the reliability and EMC stability of an ignition control device according to the invention.

Finally, according to the teaching of the invention, essentially all circuit variants of non-automated or partially automated high-voltage ignitors in symmetrical or asymmetrical design can be upgraded in order to reliably implement even the desired functions for controlling irregular faults at the end of the service life of high-pressure discharge lamps.

An embodiment of the invention is described below with reference to the circuit arrangement shown in the single figure of the drawing.

As with ignition device controls known per se, an ignition transformer ZT, which is connected in series with a high-pressure discharge lamp L, together with this forms a lamp load circuit which, via an inductive ballast VG which limits the lamp current of the ignited high-pressure discharge lamp L, to AC line voltage u via a line L leading the phase or a neutral conductor N is connected. With this operating circuit, however, only an already ignited high-pressure discharge lamp L can be operated, but not ignited.

Conventional ignition device controls therefore continue to have a device unit which is referred to as an ignition generator. This comprises a mains-fed high-voltage transformer HT, the primary winding of which, connected in series with a first switching network S1, is connected to mains alternating voltage u. As a controlled switching element, this first switching network S1 has a triac V1, the switching path of which is connected in parallel to a first capacitor C1 and a varistor R1 as overvoltage protection. The series connection of a first fixed resistor R2 and a further capacitor C2 is also connected in parallel with the triac V1. The control input of the triac V1 is connected to their connection point via a second fixed resistor R3. The secondary winding of the high-voltage transformer HT is assigned an analog second switching network S2, in which the components corresponding to the elements of the first switching network S1 are identified in the same way, but additionally with "'". At a connection point between the inductive ballast VG and the primary winding of the ignition transformer ZT, both the secondary winding of the high-voltage transformer HT and the input of the second switching element S2 are connected, the output of which consists of an auxiliary ignition combination from the series connection of a third fixed resistor R4 and a third capacitor C3, to which the neutral conductor N of the mains AC voltage u is connected. Furthermore, the secondary winding of the high-voltage transformer HT is connected in parallel with a high-voltage-resistant ignition capacitor CZ, which is also connected in parallel via a spark gap FS to the primary winding of the ignition transformer ZT. Finally, a capacitor network of high-voltage-resistant charging capacitors C4, C5, C6 of the series connection of ignition transformer ZT and the high-pressure discharge lamp L is connected in parallel, similar to conventional ignition devices.

The function of the ignition generator described so far is known per se. If AC line voltage u is applied, no current flows in the lamp load circuit because the high-pressure discharge lamp L has not yet ignited. At the control inputs of the triacs V1, V1 'of the switching networks S1 and S2, the potential of the control signal rises rapidly, as soon as it reaches the breakdown voltage of the triacs V1, V1', they switch through and charging current flows, with which the ignition capacitor CZ in particular is pumping is charged. As soon as the potential building up at the ignition capacitor CZ exceeds the breakdown voltage of the spark gap FS, the ignition capacitor CZ discharges through it. In this way, an ignition pulse is generated in the ignition transformer ZT, which first triggers a glow discharge in the high-pressure discharge lamp L and thus lowers its ignition voltage, so that the high-pressure discharge lamp ignites and, after a start-up time, switches to normal burning operation. When the high-pressure discharge lamp L is ignited, the triacs V1, V1 'of the switching networks S1 and S2 are deactivated and the ignition generator is thus stopped. In the case of a high-pressure discharge lamp L which does not ignite, the duration of the ignition period is limited by the time constant of the timing element R8, C10, which controls the current flow times of the triacs V1, V1 'of the switching networks S1 and S2 via optocouplers V3, V4.

The normal burning operation of the high-pressure discharge lamp L is monitored by detecting the lamp current. For this purpose, the current flowing through the ballast VG is measured as a voltage drop at the ballast, i. H. tapped at a series circuit of a third fixed resistor R5 connected in parallel with a first full-wave rectifier G1 and rectified. A first electrolytic capacitor C7 and a discharge resistor R6 are connected in parallel to its DC voltage outputs, a first Zener diode D1 is provided in the line branch carrying potential, behind which, in turn parallel to the full-wave rectifier G1, a second electrolytic capacitor C8 and the winding K1 of a relay are connected.

In this way, a DC control voltage is derived from the current in the lamp load circuit and is stored in the first electrolytic capacitor C7. If its charge exceeds the breakdown voltage of the first Zener diode D1, relay current flows. The sensitive relay K1 remains energized as long as the specified amplitude for the current in the lamp load circuit is maintained during normal burning operation. If the high-pressure discharge lamp L goes out, the electrolytic capacitors C7 and C8 discharge and the current monitoring circuit resets itself automatically when the relay K1 drops out.

The relay K1 has a normally open contact k11 which, in the rest position, ie when the relay is not activated, connects the AC line voltage u via the series circuit of a fourth fixed resistor R7 and a coupling capacitor C9 to a second full-wave rectifier G2. Parallel to its two DC voltage outputs are a second Zener diode D2 for protection against overvoltages and the series connection of two further electrolytic capacitors C10 and C11 and two further fixed resistors R8 and R9, which form discharge resistors for the parallel electrolytic capacitors. The potential-carrying direct voltage output of the second full-wave rectifier G2 is via a third Zener diode D3 connected to the signal input of a first optocoupler V3, looped through this and serially analogously through a second optocoupler V4 and fed back to the interconnected connection points of the further electrolytic capacitors C10 and C11 and the further fixed resistors R8 and R9. On the output side, the optocouplers V3 and V4 are each coupled into one of the control signal lines for controlling the triacs V1 and V1 '. With this insertion of the optocouplers V3 and V4 in the control signal lines of the triacs V1 and V1 ', there is the possibility, electrically isolated, of deactivating the switching networks S1 and S2 additionally independently of the facts already described. The manner in which this function is used in particular is explained below.

To monitor the burning voltage of the high-pressure discharge lamp L - in addition to the lamp current - a four-layer diode, a Sidac D4 with a current limiting network in series with it, is provided, which consists of a seventh fixed resistor R10, in series with a further coupling capacitor C12, and one there is another fixed resistor R11, which is connected in parallel as a discharge resistor for this coupling capacitor C12. The Sidac D4 is connected on the one hand in the current path behind the ballast VG and connected to the second full-wave rectifier G2 with its current limiting network R10, C12, R11 via the normally open operation of the high-pressure discharge lamp L of the relay K1 via the normally open contact L11 and connected to the neutral conductor N. . Thus, the Sidac D4 together with its current limiting network R10, C12, R11 is in normal burning operation parallel to the lamp load circuit, i.e. H. the series connection of the ignition transformer ZT and the high-pressure discharge lamp L and monitors their operating voltage.

In the case of an aged high-pressure discharge lamp L, if the burning voltage increases during the burning period, the re-ignition peak becomes critical. The high-pressure discharge lamp L can then z. B. come to an end at irregular intervals as a result of brief drops in the AC line voltage. An unprotected ignition generator then starts the high-pressure discharge lamp L again and, if necessary, at ever shorter intervals if the high-pressure discharge lamp L is not replaced. This continuous load can damage the ignition generator, e.g. B. its spark gap FS or on the ignition transformer ZT, but above all also on the ignition capacitor CZ, so that not only the high-pressure discharge lamp L but also the ignition control unit must be replaced.

With the help of the described monitoring circuit for the operating voltage, the occurrence of this critical operating state at the end of the service life of a high-pressure discharge lamp L is reliably avoided. With regard to its breakdown voltage, the Sidac D4 is dimensioned such that it switches on when the predetermined critical value for the re-ignition peak of the high-pressure discharge lamp L is exceeded. The current flow through the Sidac D4 charges via the second full-wave rectifier G2 the network R8, C10 and R9, C11 connected downstream, which blocks the optocouplers V3 and V4 in the charged state. In this case, the switching networks S1 and S2 are deactivated for renewed ignition attempts after a brief interruption in the power supply or after the high-pressure discharge lamp L has gone out. So-called "pulsating operation", which can occur with normal hot igniters, is thus avoided. If the power supply is interrupted for a period of time beyond short-term faults, e.g. B. for more than 1 s, the electrolytic capacitors C10 and C11 discharge through the parallel resistors R8 and R9 to the extent that the third Zener diode D3 blocks and the switching networks S1, S2 are released again. The monitoring circuit for the burning voltage of the high-pressure discharge lamp L therefore resets itself automatically.

This monitoring circuit offers the further possibility of forcing a brief interruption of the mains AC voltage u to determine whether the high-pressure discharge lamp L then ignites again immediately. This means that, for the maintenance of a lamp equipped with a high-pressure discharge lamp L, a simple means is available to check the aging condition of the lamp. The operated lamps no longer have to be replaced preventively, as is often the case, in good time before a medium lamp life has expired in order to avoid a latent risk of failure. Rather, maintenance and usage costs can be reduced by using the full lamp service life. In terms of circuitry, the solution described for a hot-igniter for operating a high-pressure discharge lamp L has the further advantage of a high level of operational reliability achieved with little effort. In contrast to known hot igniters, the igniter control unit does not require a separate power supply, which is why no separate protection is required. Operational amplifiers and other intermediate amplifier stages, which are conventionally used more frequently, are eliminated. All of this contributes to the reliability and EMC stability of the circuit.

Claims (12)

Ignition control device for a high-pressure discharge lamp (L) with a ballast (VG) connected to the AC line voltage (u), an ignition transformer (ZT) arranged in series with the high-pressure discharge lamp in the lamp load circuit, an ignition capacitor (CZ) and a spark gap (FS) for discharging of the ignition capacitor via the ignition transformer and with a high-voltage transformer (HT) which can be activated via switching networks (S1, S2) to ignite the high-pressure discharge lamp and is connected to the primary side to the line AC voltage, to which the ignition capacitor is connected on the secondary side, characterized by a for monitoring the operating voltage of the high pressure -Discharge lamp (L) of this circuit arrangement (D4, R10, C12, R11) assigned in parallel with one of the critical re-ignition peak of the high-pressure discharge lamp in accordance with predetermined switching threshold for blocking the switching networks (S1, S2) associated with the high-voltage transformer (HT) for a short time successive ignition attempts as long as the AC mains voltage is present. Ignition control device according to claim 1, characterized in that a device (G1, C7, R6, D1, C8, K1) for monitoring the lamp current of the ignited high-pressure discharge lamp (L) is provided with a controlled switch (K1, k11), the switching path (k11 ) is arranged in the current path of the circuit device (D4, R10, C12, R11) for monitoring the operating voltage of the high-pressure discharge lamp such that the latter can only be activated when the high-pressure discharge lamp is on. Ignition control device according to claim 2, characterized in that the device (G1, C7, R6, D1, C8, K1) for monitoring the lamp current for tapping a signal voltage corresponding to the line-frequency lamp current is connected in parallel to a resistance element (VG) located in the current path of the lamp current , a rectifier (G1) and a storage capacitor (C7) for generating a smoothed, rectified signal voltage and, as a controlled switch, a relay (K1) fed by this rectified signal voltage with a normally open contact (k11), which in the current path of the circuit device (D4, R10, C12, R11) is arranged for monitoring the burning voltage of the high-pressure discharge lamp (L) and closes this current path parallel to the high-pressure discharge lamp in the actuated state. Ignition control device according to Claim 3, characterized in that the device (G1, C7, R6, D1, C8, K1) for monitoring the lamp current has a Z-diode (D1) which is connected upstream of the relay (K1). Ignition control device according to one of claims 1 to 4, characterized in that the circuit device (D4, R10, C12, R11) for monitoring the operating voltage of the high-pressure discharge lamp (L) has a threshold switch (D4) in its current path, the switching threshold of which is dimensioned in this way is that it switches through when a predetermined critical value of the operating voltage of the high-pressure discharge lamp (L) is switched on. Ignition control device according to Claim 5, characterized in that the threshold switch (D4) is designed as a four-layer diode (Sidac) with a predetermined breakdown voltage which is related to the critical value of the operating voltage of the high-pressure discharge lamp (L). Ignition control device according to one of claims 5 or 6, characterized in that a current limiting network (R10, C12, R11) is arranged in the current path of the circuit device (D4, R10, C12, R11) for monitoring the operating voltage of the high-pressure discharge lamp (L). Ignition control device according to claim 7, characterized in that the current limiting network, with the threshold switch (D4) in series, has a fixed resistor (R10) and a capacitor (C12) and a further resistor (R11) is assigned to this capacitor in parallel. Ignition control device according to one of Claims 5 to 8, characterized in that in the current path of the circuit device (D4, R9, C12, R10) for monitoring the operating voltage of the high-pressure discharge lamp (L), an activated in its switched-on state, which can be activated when the current is interrupted according to a predetermined value Duration automatically resetting memory device (G2, R8, C10, R9, C11) is provided and that a switching device (V3, V4) on the output side for blocking the switching networks (S1, S2) of the high-voltage transformer (HT) is connected to this memory device as long as the memory device is activated. Ignition control device according to claim 9, characterized in that the switching device for blocking the switching networks (S1, S2) of the high-voltage transformer (HT) has two optocouplers (V3, V4), the inputs of which to the memory device (G2, R8, C10, R9, C11) are connected and the switching paths of which are looped into a control line of the switching networks (S1 or S2) on the output side, the switching networks being blocked by interrupting these control lines. Ignition control device according to claim 9 or 10, characterized in that the memory device (G2, R8, C10, R9, C11) is located in the current path of the circuit device (D4, R9, C12, R10) for monitoring the operating voltage of the high-pressure discharge lamp (L) Rectifier arrangement (G2), to the DC voltage outputs of which a series connection of two RC elements (R8, C10 or R9, C11) is connected in parallel is, the RC elements themselves are each parallel circuits and are connected to one another at a common connection point and that the rectifier output, which is at high potential, is connected to this common connection point of the RC elements via the inputs of the optocouplers (V3, V4) which are in series with one another in this respect is returned. Ignition control device according to Claim 11, characterized in that a Z-diode (D2) biased in the opposite direction is connected to the rectifier outputs in the memory device (G2, R8, C10, R9, C11) and in that a further Z-diode biased in the opposite direction ( D3) is provided in the line connection between the memory device and the optocouplers (V3, V4).

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