EP2210454A1

EP2210454A1 - Circuit assembly and method for operating a high pressure discharge lamp

Info

Publication number: EP2210454A1
Application number: EP07822542A
Authority: EP
Inventors: Christian Breuer; Andreas Huber; Bernhard Reiter
Original assignee: Osram GmbH
Current assignee: Osram GmbH
Priority date: 2007-11-13
Filing date: 2007-11-13
Publication date: 2010-07-28
Also published as: CN101855945A; KR20100098631A; CN101855945B; JP2011503810A; JP5249342B2; US8593072B2; US20100270934A1; WO2009062542A1; TW200932052A

Abstract

The invention relates to a circuit assembly for operating a high pressure discharge lamp (La), comprising an operating circuit for the high pressure discharge lamp, an input for receiving a switch on/switch off signal for the high pressure discharge lamp (La) and at least one output for supplying an operational signal to the high pressure discharge lamp (La). The operating circuit is designed to lower, after receiving a switch off signal at the input thereof, the power (P) of the operational signal provided at the at least one output. Said operating circuit is also designed to provide the operational signal as an AC signal above a predetermined power threshold value, and as a quasi DC signal below the predetermined power threshold value. The invention also relates to a method for operating a high pressure discharge lamp (La) on said type of circuit assembly.

Description

Confession

Circuit arrangement and method for operating a high-pressure discharge lamp

Technical area

The present invention relates to a circuit ^arrangement for operating a high pressure discharge lamp with an operating circuit for the high pressure discharge lamp having an input for receiving a turn-on / off switching signal for the high-pressure discharge lamp and min ^¬ least one output for providing an operation signal to the high-pressure discharge lamp. It moreover relates to a method for operating a high-pressure discharge lamp on such a circuit arrangement.

State of the art

The present invention particularly relates to the problem ^¬ lematics of the re-ignition of high-pressure discharge lamps, as used in particular in rear-projection TVs and beamers. Such ^{high-pressure} discharge lamps need a cooling period after switching off before they can be successfully re-ignited. As a result, they can not be switched on again as soon as they are switched off, as users of conventional televisions are used to. In the prior art, therefore, such high-pressure discharge lamps are cooled after switching off for a certain time be ^¬ before a new ignition attempt is made. The cooling phase usually lasts between 30 seconds and 3 minutes. Especially with rear projection televisions, this long reignition time is undesirable. From US 2002/0135324 Al a method for operating a dc operated discharge lamp is known. The cited document deals with the problem that when a discharge lamp is switched off, the mercury vaporized during operation condenses on one of the two electrodes of the discharge lamp, thereby increasing the risk of a short circuit with the other electrode. As a solution, the cited document proposes to cool the lamp by reducing the power to ensure that the mercury condenses at a point other than on the electrode.

For further prior art, reference is made to JP 2004-319193 and JP 2003-109845.

Presentation of the invention

The present invention is therefore based on the object of developing a circuit arrangement mentioned at the outset or an initially mentioned method such that a shortened reignition time is made possible as a result.

This object is achieved by a circuit arrangement having the features of patent claim 1 and by a method having the features of patent claim 11.

The present invention is based on the recognition that the solution of this problem is made possible if the lamp is put in a kind of stand-by mode before the actual switch-off. In this standby mode, the discharge lamp is operated at a lower power than in normal operation, whereby the discharge lamp all ^¬ gradually, possibly favors by cooling means of a fan, continues to cool. At the end of stand-by mode, the lamp is preferably cooled to a temperature from ^¬ where they can be re-ignited after an actual shutdown immediately. During the stand-by mode, the lamp can be anytime soon again hochgefah ^¬ ren. Thus, there is ideally no more time at which the lamp can be immediately put into operation ^¬ replaced.

However, with a discharge lamp which is operated in normal operation with an AC signal, the power can not be lowered arbitrarily far, in particular not on a performance that would lead to such a cooling of the discharge lamp, so that they immediately after a shutdown could be re-ignited. Namely, this is therefore not possible because below a ge ^¬ know power threshold of the lamp arc is extinguished. The present invention is therefore further based on the finding that when operating a discharge lamp with an AC signal to avoid the extinction of the lamp arc both electrodes must remain above the thermal emission temperature. The inventors of the present invention have recognized that operation of the high-pressure discharge lamp without extinguishing the lamp arc is possible up to even lower powers if essentially only one electrode is emitted, that is to say if the AC discharge lamp has a quasi-defined power ^threshold value DC signal is operated. For the purposes of the present invention, a quasi-DC signal is a signal which essentially represents a DC signal, in particular also a pure DC signal, for example. In other words, below a predefinable limit, threshold, the lamp instead of from the AC source, which is intended for normal operation, are fed from a sepa ^{¬ rate} DC source. Particularly elegant and inexpensive, however, is a solution in which the intended for normal operation AC source is caused by appropriate on ^¬ control to provide a quasi-DC signal at its output to the discharge lamp. This signal is effective for the discharge lamp as a DC signal, but certain compromises are allowed in terms of its production from a normally pre-see ^¬ nen to realize an AC source subcircuit.

Thus, the operating circuit may include a bridge circuit having at least a first and a second electronic switch, wherein the operating circuit further comprises a drive circuit for at least the first and the second electronic switch, wherein the drive circuit is adapted to control the at least first and second electronic switch, the bridge circuit provides at least the AC signal at its output. As already mentioned, the loading ^¬ driving circuit may include a DC voltage source where ^¬ is designed for the operating circuit, to couple the output to the DC voltage source under the predetermined power threshold. However, the drive circuit could also be designed to control at least the first and the second electronic switch in such a way that the bridge circuit also provides the quasi-DC signal at its output. In that case, no separate DC voltage source would have to be provided.

Is a bridge circuit, a full bridge used where angeord- at the high pressure discharge lamp in the bridge branch ^¬ is net, diagonal switches are switched simultaneously. The full bridge is fed by a direct voltage source ^¬, in particular of the so genann ^¬ th intermediate circuit voltage. The DC voltage source is coupled by the simultaneous switching of the switches located diagonally with alternating polarity with the ^{high-pressure} discharge lamp. A commutation consists of turning off the diagonal switch and switching on the switches in the other diagonal. Two adjacent switches are connected to the negative pole of the DC voltage source, the other two with the positive pole. As a rule, the negative pole represents the reference potential of the circuit arrangement. The switches coupled to the negative pole are therefore usually easy to control. The coupled with the positive pole switch are referred to as high-level switch and are known to be expensive to control.

The drive circuit accordingly comprises a low-side driver for the switch coupled to the negative pole and a high-side driver for the pole coupled to the positive pole, the low-side driver and the high-side driver each having an output for coupling to the respective switches, each having a control input for coupling to a control device and each having a supply port for coupling to a connector for connecting a supply voltage, wherein the high-side driver, a is condensate ^¬ sator, associated with a charge pump, in particular between the supply terminal and the midpoint between the first and the second electronic switch is coupled. In this case, the charge pump preferably further comprises a diode which is coupled between the capacitor and the supply voltage connection such that a current flow from the capacitor to the supply voltage connection is prevented.

In this case, it is particularly preferred if the Ansteu ^¬ erschaltung is designed to provide the quasi-DC signal by Aus ^{¬ management} of pseudo-commutations. These are two commutations executed in rapid succession, with the first commutation being so short that it is more or less suppressed. In ^¬ example, in a preferred Ausführungsbei ^¬ game turns on a full bridge branch for 5 microseconds, the other for 15 ms. The first short commutation is barely visible in the lamp current, virtually suppressed, since the current due to the output capacitance and inductance of the ignition circuit can not reverse its flow direction so fast. The lamp is thus supplied with a DC signal. However, the short commutation is sufficient to recharge the capacitor of the charge pump. A typical commutation during normal operation takes about 50 microseconds in a preferred Ausführungsbei ^¬ play. The ratio between short and ^long commutation for realizing a quasi-DC signal is preferably in the range between 1: 500 and 1: 10000.

Such commutations are described in the application PCT / EP2006 / 069665 of applicant of 13.12.2006, the disclosure of which was incorporated into the Offenba ^¬ tion of the present application by this reference, however, in a different context Gänz ^¬ Lich. Preferably, the drive circuit is designed to perform the Pseudo-commutations with a frequency between 50 Hz and 1 kHz, preferably 500 Hz. Thereby, a sufficient energy supply of acting as anode electrode of the high-pressure discharge lamp can be ensured ^¬ one hand, so that the emission temperature is exceeded and the lamp arc is not quenched. On the other hand, a cooling of the lamp can be achieved by the discharge lamp immediately after the turn-off operation of the high pressure, a re-ignition of the ^{high-pressure} discharge ^lamp possible. Finally, a sufficient recharging of the capacitor of the charge pump sicherge ^¬ represents may be such a frequency of pseudo-commutations.

Further preferably, the drive circuit is designed to store the polarity during the last quasi-DC operation when switching off, wherein the drive circuit is further designed to use the other polarity at the next shutdown for the quasi-DC operation. As a result, uniform loading of the electrodes of the lamp can be ensured. Further preferably, the drive circuit comprises a timing device, wherein the drive circuit is further designed, after a predetermined period of time in which the Hochdruckentlä- dungs lamp was operated with a quasi-DC signal of a predetermined power to adjust the operation of Hochdruckentla ^¬ tion lamp, ie the Switch off high pressure ^{discharge ¬} lamp. Alternatively, a temperature measuring device may be used which determines whether the high pressure discharge lamp has cooled to a temperature that allows for immediate reignition. By The time measuring device and / or the temperature measuring device will minimize the phase in which the high-pressure ^discharge lamp is operated at lower power but still consumes energy.

Further advantageous embodiments will become apparent from the dependent claims.

The preferred embodiments presented with reference to a circuit ^arrangement according to the invention and their advantages apply correspondingly, as far as applicable, to the method according to the invention.

Short description of the drawing (s)

In the following, an embodiment of egg ^¬ ner inventive circuit ^arrangement will now be described with reference to the accompanying drawings. Show it :

Fig. 1 in a schematic representation of the structure of a circuit arrangement according to the invention;

FIG. 2 shows the time profile of the power supply of the high-pressure discharge lamp; FIG.

FIG. 3 shows the time profile of the lamp current without pseudo-commutations; FIG. and

4 shows the time profile of the lamp current with Pseudo commutations. Preferred embodiment of the invention

Fig. 1 shows a schematic representation of an embodiment of an inventive Schaltungsanord ^¬ tion. This comprises a first El and a second input terminal E2, between which a DC voltage is to be connected, preferably the so-called intermediate circuit voltage, which is of the order of magnitude of between 300 and 400 V. Between the input terminals El, E2, a DC low-voltage power supply unit 10 is connected, which at a first output Al a DC voltage of 5 V to a microcontroller 12, and at a second output A2 a DC voltage of 15 V to a high-side driver 14 and a low-side driver 16 provides. The microcontroller 12 controls the low-side driver 16 directly, the high-side driver 14 via a potential separation unit 18th

Between the output A2 of the DC low-voltage supply unit 10 and the high-side driver 14, a charge pump is coupled, which comprises a diode Dl and a con ^¬ capacitor C1. The capacitor Cl is connected to an alternating selspannungsquelle illustrating the present Brü ^¬ ckenmittelpunkt BMI a bridge circuit 20th The potential of the bridge center point BM1 is supplied to the high-side driver 14 as a reference potential, while the low-side driver 16 receives the reference potential as the ground potential, which represents the potential at the input ^terminal E2.

The bridge circuit 20 includes four electronic scarf ^¬ ter Sl, S2, S3, S4, wherein currency, S4 known to be opened simultaneously in operation the switches of the diagonal Sl rend the switches of the other diagonal S2, S3 CLOSED ^¬ sen, and vice versa. A high-pressure discharge lamp La is coupled via an ignition circuit, which comprises two inductors L 1, L 2 coupled together and a capacitor C 2, between the two bridge centers BM 1, BM 2.

The high-side driver 14 is used to control the switches Sl, S3, while the low-side driver 16 is used to control the switches S2, S4.

The bridge center point BMI changes accordingly be Potenzi ^¬ al in dependence of the position of the switches Sl, S2 between 0 V and U _ZW. Recharging the capacitor Cl to supply the high-side driver 14 is made possible when the bridge center point BM1 is at ground potential, ie the switch S2 is closed and the switch S1 is open.

One behind the other in each case two successive commutations by two commutations performed in quick succession, so-called pseudo ^¬ commutations are replaced several times to provide a DC signal to the discharge lamp La. Thereby the lamp La receives a DC signal is supplied, as the lamp current input capacitance due to the off ^¬ and inductance can not change direction fast enough in the firing circuit. It is only a brief break in the amplitude of the lamp current detected.

In one embodiment, not shown, the lamp La is supplied instead of performing pseudo ^¬ commutations a DC signal via a power supply and a rectifier as soon as the lamp is supplied Power has fallen so far that when operating the lamp with an AC signal there is a risk of extinguishing the lamp arch.

Fig. 2 shows a schematic representation of the time course of the power P, which is the high-pressure discharge lamp La is supplied. Between times to and ti, the lamp is operated in normal operation at 100% power ^¬ . At time ti, the operator wants to turn off the projector in which the high-pressure discharge lamp La is mounted. The microcontroller 12 is supplied via a not-shown in Fig. 1 interface ent ^¬ speaking signal, after which the circuit ^arrangement according to the invention begins to down-regulate the power supplied to the lamp La. Between times t ₀ and t ₂ , the high-pressure discharge lamp La is operated with an AC signal. At time t _2, that upon reaching a power threshold at which the risk of gen goes out for a further operation with an AC signal of Lampenbo-, switching from AC operating on quasi-DC operation. For this purpose, the high-pressure discharge lamp La is operated with so-called pseudo-commutations. The power supplied to the lamp power is then further lowered until the time t3, the so-called stand-by mode, it ^¬ ranges is where the lamp is operated with pseudo-commutations of a frequency in the order of 500 Hz, to ensure that the capacitor Cl is sufficiently recharged in order to ensure a ordnungsge ^¬ MAESSEN operation of the high-side driver fourteenth Between times t3 and _t4, the lamp is operated with et- wa 20% of their normal performance. As a result, the lamp cools down further, so that at the time t ₄ , the which is determined by specifying the period ti to t ₄ or Mes ^¬ sen the lamp temperature has reached a temperature that allows an immediate successful re-ignition after a shutdown. Alternatively, the temperature measured, the time t _4, characterized determined that the lamp has cooled to a predetermined temperature Tem ^¬, for example, 350 ⁰ C or less.

Accordingly, the high-pressure discharge lamp La in the time window .DELTA.Ti at any time immediately up to 100% hochgefah ^¬ reindeer, if an operator so wishes. At the time AT ₂ the lamp La can be dergezündet immediately successful as ^¬, if an operator wishes. Accordingly, there is no time when the lamp La could not be turned on again immediately.

FIG. 3 shows the time profile of the lamp current, ^without a pseudo-commutation taking place. The commutations are numbered 1 to 14. UNMit ^¬ directly upstream of a commutation of the lamp current is pulse-shaped increased. This is a measure to reduce flicker phenomena, in particular flicker and bow marks, as described for example in the document WO 95/35645. This measure is independent of the implementation of pseudo-commutations according to one aspect of the present invention. The frequency of the rectangular profile of the current is üb ^¬ SHORT- between 200 Hz and 5 kHz.

4, it can be seen that the commutations 3, 4 and 6, 7 were carried out very briefly by the microcontroller 12. In the present case is a long commutation 15 ms, a short commutation only 5 μs. The latter is difficult to see in the lamp current I _L, because the current can not quickly reverse its flow direction due to output capacitance and inductance of the ignition ^¬ circuit. The lamp is thus supplied with a DC signal. ^¬ all recently enough the short commutation to reload the Kondensa ^¬ tor of the charge pump. A typical ^commutation tion in normal operation, however, takes about 50 microseconds in a Favor ^¬ th embodiment.

Claims

claims

1. A circuit arrangement for operating a high pressure discharge lamp (La) with an operating circuit for the high pressure discharge lamp having an input for receiving a turn-on / turn-off for the high pressure discharge lamp (La) and at least one output for loading ^¬ riding provide an operation signal to the ^{high-pressure} discharge lamp ( La), characterized in that the operating circuit is designed, after receiving a turn-off signal at its input to lower the provided at the at least one output power (P) of the operating signal, wherein the operating ^¬ circuit is further designed, over a predetermined power threshold, the operating signal as AC Signal to provide below the predetermined power ^¬ threshold as a quasi-DC signal.

2. A circuit arrangement according to claim 1, characterized in that the operating circuit comprises a bridge circuit (20) having at least a first (Sl) and a second electronic switch (S2), wherein the

Operation circuit further comprises a drive circuit

(14, 16) for at least the first (Sl) and the second electronic switch (S2), wherein the drive circuit (14, 16)) is designed, the at least first (Sl) and second electronic

Switch (S2) to control such that the

Bridge circuit (20) at its output at least the

AC signal provides.

3. Circuit arrangement according to one of claims 1 or 2, characterized in that the operating circuit comprises a DC voltage source, wherein the operating circuit is designed to couple the output with the DC voltage source below the predetermined power threshold value.

4. A circuit arrangement according to claim 2, characterized in that the drive circuit (14, 16) is further designed to drive at least the first (Sl) and the second electronic switch (S2) such that the bridge circuit (20) at its output and the Quasi-DC signal provides.

5. Circuit arrangement according to claim 4, characterized in that the drive circuit (14, 16) is adapted to the quasi-DC signal by shortening of commutations, i. by so-called pseudo commutations.

6. Circuit arrangement according to one of the preceding claims, characterized in that the drive circuit comprises a low-side driver (16) and a high-side driver (14) for at least the first (Sl) and the second electronic switch (S2) wherein the low-side driver (16) and the high-side driver (14) each have an output for coupling to the respective electronic switch (Sl; S2), each having a control input for coupling to a control device (12) and each having a supply terminal for coupling to a terminal for connecting a supply voltage, wherein the high-side driver (14) is associated with a capacitor (Cl) between the supply terminal and the center point (BMl) between the first (Sl) and the second electronic switch (S2) is coupled.

7. Circuit arrangement according to claim 6, characterized in that the drive circuit (14; 16) further comprises a diode (Dl) which is coupled between the capacitor (Cl) and the supply voltage terminal such that a current flow from the capacitor (Cl) to the supply voltage terminal is prevented.

8. Circuit arrangement according to one of claims 6 or 7, characterized in that the drive circuit (12) is designed to switch off the polarity during the last quasi-DC

Store operation, the drive circuit

(12) is further configured to use the other polarity at the next shutdown for quasi-DC operation.

9. Circuit arrangement according to one of claims 5 to 8, characterized in that the drive circuit (14, 16) is designed to perform the pseudo-commutations with a frequency between 50 Hz and 1 kHz, preferably 500 Hz.

10. Circuit arrangement according to one of the preceding claims, characterized in that the drive circuit (14, 16) further comprises a timing device, wherein the drive circuit (14, 16) is further designed, after a predetermined period of time in which the high-pressure discharge lamp (La) was operated with a quasi-DC signal of a predetermined power, the operation of the high-pressure discharge lamp (La) einzu ^¬ make.

11. A method of operating a high pressure discharge lamp

(La) on a circuit arrangement with an operating circuit for the high-pressure discharge lamp (La) having an input for receiving a start / stop signal for the high-pressure discharge lamp (La) and at least one output for providing an operating signal to the high-pressure discharge lamp (La), characterized by following steps: a) Receipt of a switch - off signal at the input of the

Operating circuit; and b) lowering the power of the operating signal provided at the at least one output of the operating circuit, wherein the operating signal is provided as a quasi-DC signal above a predefinable power threshold value as an AC signal, below the predefinable power threshold value.