WO2007147722A1

WO2007147722A1 - Device and method for the operation of a high-pressure discharge lamp

Info

Publication number: WO2007147722A1
Application number: PCT/EP2007/055476
Authority: WO
Inventors: Matthias Lau
Original assignee: Osram Gesellschaft mit beschränkter Haftung
Priority date: 2006-06-21
Filing date: 2007-06-04
Publication date: 2007-12-27
Also published as: DE102006028821A1

Abstract

The invention relates to a device and a method for operating a high-pressure discharge lamp (1), said device comprising a voltage transformer (WR) for generating an alternating load current for the high-pressure discharge lamp (1), and a load circuit which is mounted downstream of the voltage transformer (WR) and is provided with terminals (J1, J2) for the high-pressure discharge lamp (1). A low-pass filter (L1, C1), which filters the load current flowing through the high-pressure discharge lamp (1) after the gas discharge is ignited therein when the high-pressure discharge lamp (1) is connected, is disposed in the load circuit, thus preventing the high-pressure discharge lamp (1) from flickering.

Description

Apparatus and method for operating a high pressure discharge lamp

The invention relates to a device for operating a high pressure discharge lamp according to the preamble of claim 1 and a corresponding method for Betrei ^¬ ben a high pressure discharge lamp.

I. PRIOR ART Such a device is described, for example, in EP 0 975 007 A1 and on pages 217 to 218 of the book "Operating Devices and Circuits for Electric Lamps" by CH Sturm and E. Klein, 6th edition of 1992, published by Siemens Company, disclosed.

EP 0 975 007 A1 describes an apparatus for operating a high-pressure discharge lamp, in particular a metal halide high-pressure discharge lamp for a motor vehicle headlight, by means of an inverter.

On pages 217-218 of the aforementioned book, a device is a metal-halide high-pressure discharge lamp with a rectangular Lam ^¬ described penstrom to operate. The discharge path of the high-pressure discharge lamp is connected bridge inverter in the bridge branch of a VoIl- which generates the rechteckförmi ^¬ gen lamp current with alternating polarity.

High-pressure discharge lamps, which are operated on the above-mentioned, generic devices, show a tendency to flicker after prolonged operation, the means, in older high-pressure discharge lamps that have been in use for a long time, there is a tendency to see strong fluctuations in brightness.

II. Presentation of the invention

It is an object of the invention to provide a generic device and a corresponding method for operating a high-pressure discharge lamp, in which a virtually flicker-free lamp operation is made possible.

This object is achieved by the features of claim 1 and 10, respectively. Particularly advantageous from ^¬ guides of the invention are described in the dependent claims.

The inventive device for operating a high-pressure discharge lamp is equipped with a voltage converter for generating an operating current of alternating polarity for the high-pressure discharge lamp and a voltage ^{¬ converter} downstream load circuit, which is provided with terminals for the high-pressure discharge lamp, according to the invention in the load circuit, a low-pass filter is arranged , which, when the high-pressure discharge lamp is connected, after the gas discharge in the high-pressure discharge lamp has been ignited, filters the operating ^current flowing through the high-pressure discharge lamp. The low-pass filter causes in the load circuit a strong attenuation of high-frequency components of the operating current or the operating voltage of the high-pressure discharge lamp. It is assumed that the occurrence of acoustic resonances in the discharge medium of the high pressure Discharge lamp is responsible for the occurrence of brightness variations. By means of the low-pass filter according to the invention, in particular those hochfre ^¬ quent proportions of the lamp current or the lamp voltage are suppressed, which favor the occurrence of the aforementioned acoustic ^¬ resonances in the discharge medium of the high-pressure discharge lamp. A comparison of FIGS. 4 and 5 shows that the brightness fluctuations of the high-pressure discharge lamp during operation by means of the device according to the invention, which has the aforementioned low-pass filter, are markedly reduced in comparison with the operation on the generic device.

Advantageously, the low-pass filter is designed as an LC low-pass filter, which has at least one inductive and at least one capacitive component. In ^comparison with an RC low-pass filter, no ohmic losses can occur in the LC low-pass filter.

Advantageously, a recess formed as part of the apparatus to the invention OF INVENTION ^¬ Zündinduktivität, which serves to produce the required for igniting the gas discharge in the high-pressure discharge lamp ignition voltage is formed as part of the low-pass filter. As a result, the already existing inductance of the ignition circuit for the low-pass filter can be used. According to the preferred embodiment of the invention, the low-pass filter is designed as a so-called T-type low-pass filter, in which in each case one terminal of the at least one inductive component and the at least one kapa ^¬ zitiven component of the low-pass filter and the Zündinduk- tivity are interconnected so that an LCL low pass is formed.

Advantageously, it is at the Zündinduktivi ^¬ ty to the secondary winding of an ignition transformer, which is designed as part of a Impulszündschaltung for the high pressure discharge lamp. Often, the aforementioned secondary winding, which acts on one of the lamp electrodes with the ignition voltage during the ignition phase, integrated into the load circuit so that it is traversed by the operating current of the high pressure discharge lamp after completion of the ignition phase. This secondary winding may therefore be advantageous for the above-described low-pass filter ^¬ be used.

In order in particular to avoid the excitation of the particularly critical longitudinal, that is to say, the acoustic resonances acting in the direction of the discharge gap in the discharge medium of the high-pressure discharge lamp, the low-pass filter is dimensioned such that its cut-off frequency is smaller than the lowest frequency of the longitudinal auditory acoustic resonances, hereinafter referred to as basic frequency for the sake of simplicity. With sufficient strength, the longitudinal acoustic resonances can lead to the discharge arc tearing off and thus to the discharge ceasing. In order to avoid egg ne excitation of longitudinal acoustic resonances in the discharge medium of the aforementioned high pressure discharge lamp, is therefore the low-pass filter preferably dimensioned such that its Grenzfre ^acid sequence a sufficient distance from the aforementioned Fundamental frequency and is preferably less than or equal to 120 kHz.

According to the preferred embodiment of the invention, the voltage converter is the Vorrich- invention tung as a half- or full-bridge inverter formed whose switching means have a switching frequency of klei ^¬ ner or equal to 1 kHz, to Operator Op ben to the high pressure discharge lamp with a current of alternating polarity ^¬, the frequency spectrum is well outside the frequency range of the acoustic resonances of the high pressure discharge lamp.

The low-pass filter of the device according to the invention is preferably connected in the bridge branch of the aforementioned half ^¬ or full-bridge inverter to filter the current flowing through the high-pressure discharge lamp lamp current or operating current.

The inventive method for operating a high-pressure discharge lamp with an electric current of alternating polarity is inventively characterized in that after the ignition of the gas discharge in the high-pressure discharge lamp, the current through the Hochdruckentla ^¬ tion lamp is filtered by means of a low-pass filter. As already explained above, the high-frequency components are filtered out of the operating ^current flowing through the discharge medium, the discharge medium of the high-pressure discharge lamp, by means of the low-pass filter. In particular, those portions of the operating current are also filtered out, which is an excitation of acoustic resonances in the discharge medium of the high pressure discharge lamp could favor. As a comparison of Figures 4 and 5, the brightness variations are determined by the filter action of the lowpass filter fixed ^¬ Lich reduced.

III. Description of the Preferred Embodiment

The invention will be explained in more detail below with reference to a preferred embodiment. Show it:

Figure 1 is a schematic representation of the essential components of the device according to the preferred embodiment of the invention with schlos ^¬ sener high-pressure discharge lamp

FIG. 2 shows a schematic of the circuit arrangement of the embodiment of the device according to the invention shown in FIG

FIG. 3 shows passage curves of the low-pass filter of the device shown in FIGS. 1 and 2 for differently dimensioned capacitances of the low-pass filter

Figure 4 The relative deviation of the light intensity from an average of the intensity of a

High-pressure discharge lamp emitted light, which is operated on a generic device, as a function of time, the

Time scale is divided into number of 420 s each lasting switching cycles

FIG. 5 The relative deviation of the light intensity from an average of the intensity of the light intensity pressure discharge lamp emitted light, which is operated on the device according to the invention, as a function of time, wherein the time scale is divided into the number of 420 s each lasting switching cycles

FIG. 6 A side view of a metal halide high-pressure discharge lamp

The essential components of the preferred exemplary embodiment of the device according to the invention, including the connected high-pressure discharge lamp 1 (cf., FIG. 6), are shown schematically in FIG. The high-pressure discharge lamp 1 illustrated in FIG. 6 is a high-pressure metal halide discharge lamp with a nominal electrical power of 35 W, which is intended for use in a motor vehicle headlight. The device according to the preferred embodiment of the invention is designed as an electronic ballast device for this metal halide high-pressure discharge lamp 1. The discharge vessel 12 of the high-pressure discharge lamp 1 surrounded by an outer bulb 11 is anchored in a lamp base 13. The electrical connections Jl, J2, J3 of the ^{high-pressure} discharge lamp 1 are formed as a bushing which is arranged on a side wall of the lamp cap. 13 In the interior of the discharge vessel 12 xenon and metal halides are arranged as the discharge medium. In the case of mercury over free halogen metal-vapor high-pressure ^discharge lamp is the discharge medium of xenon and the iodides of the metals sodium, scandium, zinc, and indium. In the case of a mercury-containing metal halide High pressure discharge lamp consists of the discharge medium of xenon, mercury and the iodides of sodium and scandium. In the interior of the discharge vessel 12 protrude a first, near the base electrode 14 and a second socially remote electrode 15, between which forms a gas discharge during lamp operation. The distance between the electrodes 14, 15 is 4.2 mm. In the interior of the lamp base 13, a pulse ignition scarf ^¬ tion Z is arranged, which serves for generating the ignition voltage required for igniting the gas discharge in the discharge medium of the high-pressure discharge lamp 1. This Impulszündschaltung Z comprises a Zündinduktivität LS, which supply the first near the base electrode 14 via the power ^¬ 17 during the ignition phase of the high-pressure discharge lamp 1 loaded with the required ignition voltage pulses for igniting the gas discharge. The base remote second electrode 15 is connected via a recirculated to the lamp base 13 current return 16 with a first electrical connection Jl of the high pressure discharge lamp 1. A second electrical connector J2 of the high pressure discharge lamp 1 is connected to a first terminal of an inductor Ll and a first terminal ei ^¬ ner capacitance Cl. The second terminal of Ka ^¬ capacity Cl is connected to a first voltage output of a voltage converter J4 WR and to the first terminal Jl of the high pressure discharge lamp. 1 The second ^¬ At the end of the inductor Ll is connected to a second clamping ^¬ voltage output of the voltage converter J5 WR connected. The third terminal of the high pressure discharge lamp 1 is connected to a DC power supply circuit DC, which also ensures the voltage supply for the voltage transformer WR.

The inductor Ll and the capacitor Cl, and the ignition ^¬ inductance Ls form the ignition circuit Z is a so-called tes t-low-pass filter after completion of the ignition phase of the Hochdruckentladungslampel filters the lamp current and high-frequency components of the lamp current or the lamp attenuates ^¬ voltage.

Details of the circuit arrangement of the operating device shown in FIG. 1 are shown in FIG. The voltage converter WR is a full-bridge inverter WR whose bridge branch is arranged between the node points or voltage outputs J4, J5 of the full-bridge inverter WR. The discharge path of the high pressure discharge lamp 1, the ignition circuit as a pulse ignition circuit formed ^¬ Z and the low pass filter Ll, Cl, LS are connected in the bridge arm of the bridge inverter VoIl- WR. The transistor pairs Tl, T4 and T2, T3 of the full-bridge inverter WR switch alternately, so that flows through the bridge branch and the discharge path of the high-pressure discharge lamp 1, after completion of the ignition phase of the high-pressure discharge lamp 1, a current of alternating polarity. The switching ^¬ frequency of the transistor pairs Tl, T4 and T2, T3, and thus the frequency of the current flowing in the bridge branch current is less than 1 kHz and is typically in the range of 250 Hz to 800 Hz. In the figure 2 are also the terminals or electrical contacts J1, J2, J3 are shown in order to connect the interface between the high-pressure discharge lamp 1 or the lamp base 13 and the show drive device. The components LP, LS, CZ, FS of the pulse ignition circuit Z are completely housed in the interior of the lamp cap 13 of the high-pressure discharge lamp 1. In the DC processing Gleichspannungsversorgungsschal- If it is a DC-DC converter, the riert for Lampenbe ^¬ operating voltages required to power the VoIl- bridge inverter WR and the ignition circuit Z gene ^¬ from the vehicle system voltage of the motor vehicle. In addition, the DC voltage supply circuit DC also includes a power control unit (not shown) for controlling the electrical power consumption of the high pressure discharge lamp 1. The Impulszünd ^¬ circuit Z consists of the ignition transformer LP, LS with a primary winding LP and a secondary winding LS, a firing capacitor CZ and a spark gap FS. During the ignition phase of the high-pressure discharge lamp 1, the pulse ignition circuit Z is supplied by the DC voltage supply circuit DC via the through-connected transistor Tl and the terminals J2, J3 with a DC voltage which charges the ignition capacitor CZ to the breakdown ^¬ voltage of the spark gap FS. Upon reaching this breakdown voltage, the spark gap FS is conductive and the ignition capacitor CZ discharges intermittently on the spark gap FS and the primary winding LP of the ignition transformer LP, LS. In the secondary winding LS of the ignition transformer LP, LS thereby high voltage pulses are induced, with which the sockelnahe Elektro ^¬ de 14 of the high pressure discharge lamp 1 is acted upon. These high voltage pulses ignite the gas discharge in the discharge medium of the high pressure discharge lamp 1. After ignition of the gas discharge in the high pressure discharge 1, the ignition circuit Z or the voltage ^¬ supply of the ignition circuit Z is deactivated and the alternating switching of the transistor pairs Tl, T4 and T2, T3 of the full-bridge inverter WR activated, so that over the discharge path of the high-pressure discharge lamp 1 and through the secondary winding LS and through the Inductance Ll and the capacitance Cl, a current of alternating polarity with a frequency ranging from 250 Hz to about 800 Hz flows. The inductance L1, the capacitance C1 and the secondary winding LS of the ignition transformer LP, LS form a T low-pass filter or LCL low-pass filter which attenuates high-frequency components of the lamp current or the current through the bridge branch of the inverter WR. The capacitance of the capacitor Cl and the inductance of the inductor Ll are coordinated with the inductance of the secondary winding LS that Grenzfre ^acid sequence of the lowpass filter is less than or equal to 120 kHz.

According to the first embodiment of the invention loading the inductance Ll sits a value of 0.56 mH, the capacity Ka ^¬ Cl has a value of 4.7 nF and the secondary winding LS an inductance of 0.47 mH. The cutoff frequency of the low-pass filter Ll, Cl, LS in this case is about 120 kHz. The corresponding transmission curve, i.e., the quotient or ratio of the amplitudes and U_OUT U_IN of output voltage and input voltage of the low-pass filter is provided in Figure 3 as solid line represents ^¬.

According to the second exemplary embodiment of the invention, the inductance L1 has a value of 0.56 mH, the Ka capacitance Cl has a value of 20 nF and the secondary winding LS an inductance value of 0.47 mH. The cutoff frequency of the low-pass filter Ll, Cl, LS in this case is about 51 kHz. The associated transmission curve is shown in Figure 3 as a dashed line.

The illustrated in Figure 3 dashed-dotted line belonging to the transmission curve of a low pass filter with the Capa ^¬ zitätswert of 1.0 nF for the capacitor Cl and the Induk ^¬ tivitätswerten 0.56 mH and 0.47 mH for the inductor Ll and the Secondary winding LS. The so-dimensioned low pass filter is not suitable extension for a sufficient filtering of the lamp current and, therefore, not forming part of OF INVENTION ^¬ due to the too small capacitance value.

In the two-part 4, the relative deviation of the light intensity is shown by the high-pressure ^discharge lamp 1 the emitted light as a function of time for a total period of 400 cycles of a mean value of the intensity of the vertical axis. On the horizontal axis the time is plotted in units of switching cycles. Each switching cycle lasts 420 s and comprises a 180 s lasting on ^¬ switching phase of the high-pressure discharge lamp 1 and a 240 s lasting turn-off or cooling phase of the high-pressure discharge lamp 1. The light intensity was measured by means of photocells. The measurement interval of the minimum and maximum light intensity is 4 ms in each case and the mean value of the light intensity was formed over a period of 100 ms. The high-pressure discharge lamp 1 was used for the measurement shown in FIG. 4 on a conventional Onellen generic device operated without the low-pass filter according to the invention. The light intensity is subject to Figure 4 strong fluctuations in the range of about +20 percent to about -50 percent of the average.

In the two-part 5, the relative deviation of light intensity is shown worth of an agent ^¬ the intensity of light emitted from the high-pressure discharge lamp 1 light as a function of time for egg ^¬ NEN total period of 400 cycles on the vertical axis. On the horizontal axis the time is plotted in units of switching cycles. Each switching cycle lasts 420 seconds and includes a 180 s lasting switch-on of the high pressure discharge lamp 1 ^¬ sen and a 240 s lasting from ^¬ switching phase or cooling phase of the high pressure discharge lamp 1. The light intensity was measured by photocells gemes ^¬. The measuring interval of the minimum and maximum light intensity, respectively ^¬ is 4 ms and the mean value of the light intensity has been formed over a period of 100 ms ge ^¬. The high-pressure discharge lamp 1 was operated for the measurement depicted in FIG. 5 on a device according to the invention with a low-pass filter whose limit frequency was approximately 100 kHz and a capacitance value of 10 nF for the capacitance Cl and inductance values of 0.56 mH and 0.47 mH for the inductance Ll and the secondary winding LS possessed. According to FIG. 5, the fluctuations in the light intensity during operation of the high-pressure discharge lamp 1 on the device according to the invention are less than ± 10 percent of the mean value.

A comparison of FIGS. 4 and 5 clearly shows that during operation of the high-pressure discharge lamp 1 at the invented According to the invention, no appreciable variations in brightness occur, in contrast to the operation of this high-pressure discharge lamp 1 on a conventional device without the low-pass filter according to the invention.

The invention is not limited to the embodiments explained in more detail above. It is possible, for example, the components Ll, Cl of the low pass filter to ^¬ together with the ignition device Z in the interior of the lamp base 13 to accommodate. On the other hand, must, however, the igniter Z need not be arranged in the interior of the lamp base 13, but may tronic ballast be housed together with the components Ll, Cl of the low pass filter in the housing of the Elect ^¬.

Claims

claims

1. Device for operating a high-pressure discharge lamp (1) with a voltage converter (WR) for generating an operating current of alternating polarity for the high-pressure discharge lamp (1) and a voltage converter (WR) downstream load circuit with terminals (Jl, J2) for the Hochdruckent ^¬ Charge lamp (1) is provided, characterized in that in the load circuit, a low-pass filter (Ll, Cl) is arranged, which with connected high-pressure discharge lamp (1), after igniting the gas ^¬ discharge in the high-pressure discharge lamp (1), a filtering caused by the high-pressure discharge lamp (1) operating current.

2. Apparatus according to claim 1, wherein the low-pass filter (L 1, C 1) is designed as an LC low-pass filter with at least one inductive component (L 1) and at least one capacitive component (C 1).

3. Apparatus according to claim 1 or 2, wherein the device has a Zündinduktivität (LS) for generating the igniting the gas discharge in the high-pressure discharge lamp (1) required ignition voltage, and the Zündinduktivität (LS) as Be ^¬ part of the low-pass filter (Ll, Cl ) is trained .

4. Apparatus according to claim 3, wherein the low-pass filter is designed as a T-low-pass filter (Ll, Cl, LS), in each case one terminal of the at least an inductive component (Ll) and the at least one capacitive component (Cl) and the Zündinduktivität (LS) are interconnected.

5. Apparatus according to claim 3 or 4, wherein the ignition inductance is the secondary winding (LS) of a Zünd ^¬ transformer (LP, LS), which is formed as part of a Impulszündschaltung (Z) for the high pressure discharge lamp (1).

6. Device according to one or more of claims 1 to 5, wherein the cutoff frequency of the low pass filter ^¬ TERS (Ll, Cl) is smaller than the fundamental frequency of the longitudinal acoustic resonance frequency of the high pressure discharge lamp (1).

7. Device according to one or more of claims 1 to 6, wherein the cutoff frequency of the low pass filter ^¬ ters (Ll, Cl) is less than or equal to 120 kHz.

8. Device according to one or more of claims 1 to 7, wherein the voltage converter as a half or full bridge inverter (WR) with a switching frequency of its switching means (Tl, T2, T3, T4) of less than or equal to 1 kHz is formed.

9. Device according to one or more of claims 1 to 8, wherein the low-pass filter (Ll, Cl) is connected in the bridge branch of the half or full bridge inverter (WR).

10. A method for operating a high-pressure discharge lamp (1) with an electric current of alternating polarity, characterized in that after the Igniting the gas discharge in the high-pressure discharge lamp (1), the current through the high-pressure discharge ^¬ lamp (1) by means of a low-pass filter (Ll, Cl) is filtered.

11. The method of claim 10, wherein the low-pass filter (Ll, Cl) comprises at least one inductive component (Ll) and at least one capacitive component (Cl).

12. The method according to claim 10 or 11, wherein the Zün- fertilg the gas discharge in the high-pressure discharge lamp (1) by means of a Zündinduktivität (LS) is performed, which is formed as part of the low-pass filter ^¬ (Ll, Cl).

13. The method according to one or more of claims 10 to 12, wherein the cut-off frequency of the low-pass filter

(Ll, Cl) is smaller than the fundamental frequency of the longitudinalen acoustic resonance frequency of the high pressure discharge lamp (1).

14. The method according to one or more of claims 10 to 13, wherein the cutoff frequency of the low-pass filter

(Ll, Cl) is less than or equal to 120 kHz.

15. The method according to one or more of claims 10 to 14, wherein the high-pressure discharge lamp (1) after ignition of the gas discharge in the Hochdruckentla- Dungs-lamp (1) is operated with a current of alternating polarity whose frequency is less than 1 kHz.