EP2123133B2 - Universal electronic ballast for operating hg-free and hg-containing discharge lamps - Google Patents

Abstract

An electronic ballast for a discharge lamp includes a microcontroller, which is configured to identify the parameters which determine the discharge lamp type. The microcontroller implements an orientation mode program once when the lamp is first switched on, which orientation mode program can be used to determine the type of discharge lamp.

Description

Technical area

The present invention relates to a method for controlling a discharge lamp by means of an electronic ballast (ECG) and an electronic ballast, with which any type of discharge lamps can be operated.

State of the art

Mercury-containing and mercury-free lamps, in particular discharge lamps for use in motor vehicles (so-called D lamps) each have very different properties. This applies in particular to the electrical properties of the two lamp types, which exhibit the same nominal power of 35 watts in stationary operation, but the mercury-free lamp has only about half the operating voltage compared to the mercury-containing lamp. Even during startup, both lamp types are very different from each other to operate in order to achieve the desired requirements, such as sufficiently high instantaneous light with an acceptable life.

Therefore, in the prior art, a separate ECG type is used for each type of lamp (Hg-containing D1 lamp or Hg-free D3 lamp), wherein the respective ECG type individually takes into account the peculiarities of the associated lamp type. Although both ECG types are based on a common hardware and software concept, the detailed requirements of the lamps do not make it possible to interchange the ECGs with each other.

This has the disadvantage that in production between two hard and two software variants must be distinguished, and subsequently both products in sales and the customer must be managed two products, which means on the one hand a double storage, and on the other often leads to confusion.

In order to reduce the possibility of confusion, it has been proposed in the prior art to use different plug codings. However, this has the consequence that in addition to the different electronic ballasts and lamps and different cables are needed.

It is in the patent application EP 0 759 686 A2 a method and a circuit arrangement has been proposed in which the electronic ballast comprises a microprocessor which detects the individual lamp type connected to the electronic ballast and activates the lamp in dependence on the recognized lamp type specification.

For this purpose, arranged on the lamp lamp type individual codes, such as arranged on the lamp base nubs, which form a lamp type-individual coding due to their number and arrangement, detected and the lamp is driven according to previously stored operating parameters for this type of lamp. Another way of detecting the type of lamp is to detect a bar code mounted on the lamp. In addition, it is also possible to draw electrical variables for lamp type detection.

A disadvantage of this prior art, however, is that each time the lamp is turned on there is a delay during which the ECG determines which lamp type it is. Therefore, this procedure is just unsuitable for use in the car, since a particularly fast start-up of the lamp is required here. This is also the reason, therefore, during startup, the lamp power is increased to a multiple of the rated power (so-called power start).

The EP 0 702 508 A1 discloses an electronic ballast for gas discharge lamps with a fuzzy controller that generates a control value of the lamp current for controlling the lamp current depending on an actual value of the lamp current for an inverter for creating the frequency or the duty cycle of the lamp current.

Presentation of the invention

It is therefore an object of the present invention to provide a method and an electronic ballast that can be used universally for discharge lamps, but allows a direct control of the discharge lamps.

This object is achieved by a method according to claim 1 and an electronic ballast according to claim 7.

The parameters detected during the orientation mode are stored and the lamp is operated at all subsequent starts with these stored operating parameters. This has the advantage that on the one hand during the orientation phase, a very accurate determination of the lamp parameters can be performed, and on the other no delay occurs when switching on the lamp, since after a completed orientation mode, the lamp only operated with the operating parameters detected in the orientation mode becomes.

During the orientation mode, the lamp is advantageously operated with the lowest of the permissible lamp currents. This ensures that no lamp is damaged due to over-selected currents or power.

Particularly preferred is an embodiment in which a sensor element detects the burning voltage or a burning voltage increase of a lamp mounted on the ECG, and the lamp type is determined on the basis of the detected values that are characteristic of the lamp type. This is particularly advantageous because burning voltage increase are easily identifiable values and other types of identifying features such as bar codes or lamp-mounted studs need not be used as known in the art.

Particularly advantageous is an embodiment in which the electronic ballast according to the invention comprises a microcontroller which is designed to control a lamp connected to the ECG in such a way that the lamp is operated once in an orientation mode during the first switch-on, during which the lamp type is detected, and each time the lamp is turned on, the lamp is operated in a normal mode adapted to the lamp.

As a result, delays caused by the respective queries of the lamp type known from the prior art prior to actual startup are avoided.

Furthermore, it is advantageous if the electronic ballast comprises a memory element in which at least a first bit for indicating whether an orientation mode has been performed and a second bit for specifying the lamp type are stored. By reading the memory, the microcontroller can decide immediately whether an orientation mode still needs to be performed, or whether the lamp can be put into operation immediately.

In addition, an embodiment is particularly advantageous in which the ECG also has a communication interface, in particular a LIN bus. By means of this communication point, for example, a check can be made as to whether a lamp type has been recognized correctly. In addition, there is the possibility that during a lamp type change by means of this interface, a reprogramming of the ECG, for example by deleting the first bit, can be done. If the first bit is cleared, the microcontroller of the ECG again performs the orientation mode, whereby the new lamp can be detected. This has the great advantage that it is not necessary to replace the electronic ballast and lamp when replacing a lamp type, but only the lamp itself.

It is particularly advantageous for the method according to the invention or the electronic ballast according to the invention to be used in headlamps for operating mercury-free (Hg-free) or mercury-containing (Hg-containing) metal halide high-pressure discharge lamps for use in motor vehicles, so-called D lamps. Straight Hg-free and Hg-containing lamps are based on a common hardware or software concept, but can only be operated with different electronic ballasts due to their very different electrical properties. On the other hand, the universal ECG according to the invention makes it possible for the ECGs to remain in the car while only the lamp is replaced, making it possible to convert from Hg-containing to Hg-free very quickly and very simply.

Further advantages and advantageous embodiments are defined in the subclaims, the figure and the description.

Short description of the drawing

In the following the invention will be described with reference to a drawing. The drawing shows only an exemplary embodiment, which should not be used to narrow the scope of the invention to the example shown.

The single FIGURE shows a flow chart of a first particularly preferred embodiment of the method according to the invention.

Detailed description of the figures

In principle, the operation of Hg-containing and Hg-free D-lamps by means of a single ECG type without any hardware or software conversion or intervention in the TOE is made possible by the fact that an appropriate dimensioning of the hardware and intelligent software is used. The dimensioning of the hardware is to be interpreted essentially to the Hg-free lamp, since this requires the higher power. The intelligence of the software is that the operating parameters for both lamps are stored in the software and when the ECG lamp combination is switched on for the first time the lamp is operated in a so-called orientation mode, the present type of lamp being recognized and stored in a memory element. Subsequently, and with all further starts of the lamp, the lamp is operated with the specified and adjusted operating parameters. In this case, the first switching on and the operation in the orientation mode can advantageously take place only at the headlight manufacturer in a first functional test of the headlight system. Advantageously, two bits are stored in a memory element in the electronic ballast, which indicate whether, on the one hand, an orientation mode has been carried out and, on the other hand, determine which operating parameters are to be used to operate a lamp.

FIG. 1 shows a flowchart of the method according to the invention, which can be performed by a microcontroller included in an ECG, for example, to operate a discharge lamp according to the invention.

In a first step 1, the microcontroller accesses a memory element arranged in the ECG in order to read out a bit I stored in the memory element. Bit I indicates whether an orientation mode has been traversed (step 2).

If no orientation mode has yet been run, this means that the lamp has been put into operation for the first time, and the microcontroller starts a orientation mode program in a further step 3 during which the lamp type connected to the ECG is to be recognized and the detected lamp type parameters are stored in such a way, so that they are immediately accessible each time the lamp is started.

Since in the orientation mode is not yet known which lamp is present, no power start of the lamp can take place, as this could otherwise be damaged. Instead, in a step 4, a lamp current is applied to the lamp which is limited to the lowest of the maximum permissible lamp currents. This means, for example, that when using Hg-free or Hg-containing D lamps, the maximum current is limited to that of the Hg-containing lamp, since a much higher current is permitted for the Hg-free lamp. In addition, the start-up and nominal power is limited to the lowest of all permissible. In the case of the Hg-containing and Hg-free D-lamp, although the nominal power with 35 W are identical, the Hg-free lamp is to supply a higher power during the start-up phase (starting power). The stated limitation of currents and powers certainly prevents damage to the lamp during the orientation mode.

In a step 5, a burning voltage or a burning voltage rise of the lamp is then detected, for example, by means of a sensor element arranged in the ECG. Due to these parameters and the time evolution of these parameters after the start of the lamp, it can be decided, for example, which lamp type is concerned. However, it is also conceivable, instead of the steps described in steps 4 and 5, to record other parameters defining the lamp type.

It is crucial that in steps 4 and 5, a method is carried out, with which it is possible to detect the lamp type and identify the associated operating parameters, so that in the subsequent step 6, a setting of the lamp type and thus the lamp operating parameters is enabled.

The operating parameters specifying the lamp type determined in step 6 can, for example, be stored in a further step 7 by writing a bit II into the memory element. If not only two types of lamps are available for selection, in method step 7 it is also possible to write a byte instead of one bit, which indicates the lamp type. By means of the stored in step 7 bits or bytes, the microcontroller can decide which operating parameters he should be read from the memory element, with which then the lamp can be controlled. The storage types used are non-volatile memories, for example EEPROM or flash memory. Even EPROM memory are conceivable, but due to the lack of rewritability, the scope of functions is limited accordingly. In the following, an EEPROM memory is required.

After writing bit II, the orientation mode is ended (step 8), and in step 9, the bit I is changed to indicate that an orientation mode has been passed successfully. This can be done, for example, by shifting the bit I from a state "0" to a state "1". If the orientation mode is successfully completed, the microcontroller reads the lamp-specific parameters defined by the bit / byte II from the memory and in a step 10 controls the lamp in such a way that the lamp is operated with the lamp-specific parameters. This means, for example, if it was detected during the orientation mode that the connected lamp is a Hg-free D-lamp, that the rated current and the starting current and starting power are increased accordingly.

At each subsequent start of the lamp, the microcontroller now determines in step 2 that an orientation mode has been run, whereupon it can directly read the bit / byte II and operate the lamp accordingly (step 11 / step 10).

If no clear assignment to one of the considered lamp types could be made during the orientation phase, different scenarios are possible. In the simplest case the lamp is switched off and the error becomes obvious. Alternatively, the lamp may be operated "flashing", by which the power of the lamp is periodically switched between nominal power and e.g. 80% of rated power is changed. It is also conceivable that the orientation mode is repeated cyclically until the orientation mode has been successfully executed. For this purpose, after each orientation mode the lamp is for a certain time, e.g. 5 minutes off to try again. In all the scenarios described, bit I is only changed when a successful detection of the lamp type has taken place.

If concluding function tests are still to be carried out in the production of the electronic ballast after programming the microcontroller, the orientation mode must not yet be executed. Therefore, a counter is to be provided in the microcontroller which stores the number of turn-on operations. Only after this counter reaches a predetermined value, the orientation mode is started. Which lamp type is used as the basis for the operation of the lamp before the execution of the orientation mode is determined in the microcontroller by means of an additional bit or byte during programming.

In order to be able to influence the bit I stored in the memory element, for example in order not to have to replace the entire electronic ballast during a lamp type change or to check which lamp type has been detected, the electronic ballast advantageously has a communication interface. This can be realized for example by a LIN bus. By means of this communication point, it is possible, for example, to erase the bit I, or to return to the "orientation mode not traversed" state. By means of the communication interface, however, it is not only possible to access the bit I, but also to change the bit / byte II or to store further operating parameters for discharge lamps in the memory element of the TOE. As a result, even with newly developed lamps, the old ECGs can continue to be used, which makes it possible to switch to new lamps very cost-effectively.

The embodiment described so far is particularly advantageous for electronic ballasts which are switched on and off by switching their supply voltage. For ECGs that are permanently connected to the supply voltage and are switched to the active operating state, for example, by an additional control line or a communication interface, a particularly simple method for influencing the bit I stored in the memory element is possible:

This influence takes place by switching off the ECG completely, for example by briefly pulling off the plug, which leads the supply voltage to the ECG. As memory types now volatile memory, such as RAM memory can be used. After disconnecting the voltage, either the bit I can already be cleared, so that a passage through the orientation mode is initialized. However, it is also possible that the microcontroller in the event of a voltage loss after the restoration of the voltage starts a program that causes a complete erasure of the stored bits and subsequently restarts the orientation mode, so that also influenced by this way influencing the bits I or II is possible.

Disclosed is a method or ECG that is universally applicable to a plurality of types of discharge lamps that performs an orientation mode for detecting the lamp type once upon first turning on, during which the lamp type is detected.

Claims (17)

1. Method for operating a discharge lamp by means of an electronic ballast, the parameters which determine the type of discharge lamp being identified during operation of the lamp by the electronic ballast (6), the step of identification of the discharge lamp type being performed once when the lamp is first brought into operation in an orientation mode (3), the lamp type being stored by means of values for the parameters in such a way that, each time the lamp is switched on again, said lamp is operated with the values for the parameters which were established in the orientation mode, characterized in that the stored values for the parameters can be influenced via an interface arranged in the electronic ballast.
2. Method according to Claim 1, whether or not an orientation mode has been passed through being stored in the electronic ballast (2).
3. Method according to one of the preceding claims, it being possible for the discharge lamp type to be established using a measurable running voltage and/or a running voltage rise (5).
4. Method according to one of the preceding claims, in the orientation mode the lamp being operated at the lowest of the permissible maximum lamp currents and/or the lowest maximum power (10).
5. Method according to one of the preceding claims, the parameters for the operation of the discharge lamp being stored in the electronic ballast (7).
6. Method according to one of the preceding claims, the method being used for distinguishing between Hg-containing and Hg-free discharge lamps.
7. Electronic ballast for a discharge lamp with a microcontroller, which is designed to identify the parameters which determine the discharge lamp type (6), the microcontroller being designed to implement an orientation mode program once when the lamp is first switched on (3), which orientation mode program can be used to determine the type of discharge lamp, the electronic ballast furthermore having a memory element for storing at least one first bit for indicating the execution of an orientation mode and one second bit for indicating the lamp type, characterized in that the electronic ballast has a communications interface for reading the bits stored in the memory element, the communications interface being designed to influence the bits stored in the memory element.
8. Electronic ballast according to Claim 7, the bits being stored in the memory element during the orientation mode (7).
9. Electronic ballast according to Claim 7, the memory element being a read/write memory.
10. Electronic ballast according to Claim 7, the microcontroller being designed to read the bits from the memory and to operate the discharge lamp with the parameters determined by the second bit if the first bit indicates that the orientation mode has been executed (10).
11. Electronic ballast according to one of Claims 7 to 10, the electronic ballast furthermore being designed to operate Hg-containing and/or Hg-free lamps.
12. Electronic ballast according to Claim 11, the electronic ballast being dimensioned for the operation of Hg-free discharge lamps.
13. Electronic ballast according to one of the preceding claims, the electronic ballast having an apparatus for supplying a supply voltage to the electronic ballast, which supply voltage can be used for zero-voltage switching of the electronic ballast.
14. Electronic ballast according to Claim 13, the apparatus furthermore being designed to influence, in particular to overwrite and/or to delete, the bits stored in the memory element by virtue of complete zero-voltage switching of the electronic ballast.
15. Electronic ballast according to one of Claims 7 to 14, the electronic ballast furthermore having a sensor element, which establishes a running voltage and/or a running voltage rise of the discharge lamp (5).
16. Electronic ballast according to Claim 15, the microcontroller furthermore being designed to identify the type of discharge lamp on the basis of a running voltage established by the sensor and/or a running voltage rise (6).
17. Electronic ballast according to one of Claims 7 to 16, the electronic ballast driving the discharge lamp in the orientation mode with the lowest of the permissible maximum lamp currents and/or the lowest maximum power.

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