WO2009027921A2

WO2009027921A2 - Ignition unit for igniting a discharge lamp

Info

Publication number: WO2009027921A2
Application number: PCT/IB2008/053398
Authority: WO
Inventors: Pavel Pekarski; Carsten Deppe
Original assignee: Philips Intellectual Property & Standards Gmbh; Koninklijke Philips Electronics N. V.
Priority date: 2007-08-29
Filing date: 2008-08-25
Publication date: 2009-03-05
Also published as: WO2009027921A3

Abstract

An ignition unit (3) for igniting a discharge lamp (1), especially a high intensity discharge (HID) lamp or an ultra high intensity discharge (UHP) lamp, and a switch unit, which especially can be manually operated by a user, for switching on a discharge lamp is disclosed. Furthermore, a circuit arrangement for operating such a discharge lamp (1) comprising a lamp driver (21) and an ignition unit (3), and a discharge lamp unit comprising a discharge lamp (1) or lamp burner, preferably a reflector and such a circuit arrangement is described, which advantageously can be used due to a small volume and a small weight for example in ultra bright torches like Ujoy® torches or Ujoy® lamps or Ujoy® projection systems.

Description

IGNITION UNIT FOR IGNITING A DISCHARGE LAMP

FIELD OF THE INVENTION

The invention relates to an ignition unit for igniting a discharge lamp, especially a high intensity discharge (HID) lamp or an ultra high intensity discharge (UHP) lamp, and a switch unit, which especially can be manually operated by a user, for switching on a discharge lamp. Furthermore, the invention relates to a circuit arrangement or a lamp driver comprising an ignitor, for operating (i.e. igniting and driving) a discharge lamp, and a discharge lamp unit comprising a discharge lamp or lamp burner, preferably together with a reflector, and such a circuit arrangement or lamp driver, as used for example in ultra bright torches like Ujoy® torches or Ujoy® lamps or Ujoy® projection systems.

BACKGROUND OF THE INVENTION

For igniting HID or UHP lamps, usually ignition units are used which comprise bulky, heavy and/or costly components like an inductive ignition transformer and high voltage capacitors. It is obvious that such ignition units are disadvantageous especially when designing small discharge lamp units. Furthermore, the required high level of the ignition voltage sets limitations on the minimal isolation distances within a related lamp unit. This is as well disadvantageous especially when small dimensions of a discharge lamp unit are desired as for example for use in a torch. One possibility to decrease size (and costs) of an ignition unit (i.e. the ignition related parts and components) is to reduce the required ignition voltage by introducing ignition aids like an antenna and an UV enhancer. However, a negative effect of a reduced ignition voltage is an increase in time delay needed for hot ignition, so that the lamp cannot be switched on immediately after it has been switched off. Finally, even for ignition voltages as low as 2.5 kV, the ignition related parts and components usually take about 30% of the volume of the whole lamp driver.

As an alternative to an inductive ignition transformer, a piezoelectric transformer can be used as for example disclosed in WO 99/12389. Generally, a piezoelectric transformer uses the principle of double energy conversion. Electrical energy which is applied at the input of the piezoelectric transformer is converted to mechanical vibrations. These mechanical vibrations are converted to electric energy on the output of the piezoelectric transformer. Maximal conversion efficiency is achieved if the frequency of the electrical energy on the input corresponds to the mechanical resonance frequency of the piezoelectric transformer. However, it is often difficult to use piezoelectric transformers within known lamp driver topologies.

SUMMARY OF THE INVENTION

A first object underlying the invention is to provide an ignition unit for igniting a discharge lamp, or to provide a circuit arrangement or lamp driver comprising an ignitor, for igniting and driving (i.e. operating) a discharge lamp or a discharge lamp unit as mentioned in the introductory paragraph above, by which at least one of the above mentioned disadvantages of known ignition units or ignitors like bulky volume, heavy weight, costly components, restrictions with respect to small isolation distances, can be diminished or avoided.

A second object underlying the invention is to provide a switch unit for manually switching on a discharge lamp or lamp unit, which has a very simple construction and which can be operated by a user in a very easy and simple manner.

The first object is solved according to claim 1 by an ignition unit for igniting a discharge lamp, especially a HID or UHP lamp, which comprises (or is provided in the form of) an ignitor in the form of a mechanical piezoignitor for creating an ignition voltage for igniting the discharge lamp upon a mechanical actuation of the piezoignitor.

Furthermore, the first object is solved according to claim 5 by a lamp driver for driving a discharge lamp comprising such an ignitor, and according to claim 6 by a circuit arrangement for operating a discharge lamp, comprising a lamp driver for generating a lamp current, and such an ignitor.

The above second object is solved according to claim 2 by a switch unit for manually switching on a discharge lamp, comprising a switch for switching on a lamp driver, and a mechanical piezoignitor, which are designed and/or mechanically coupled to each other such that upon an actuation of the switch unit by an operator, at first the switch is released and then after expiration of a predetermined time delay the piezoignitor is actuated.

One advantage of these solutions is the fact, that in most cases, a standard mechanical piezoignitor known from other applications like e.g. ignitors for gas ovens or cigarette lighters can be used as ignitor which has very low costs, a low weight and a small volume.

The dependent claims disclose advantageous embodiments of the invention. Claims 3 and 4 are directed on advantageous embodiments of the switch unit, whereas claims 7 to 11 are directed on a lamp unit comprising a discharge lamp and a circuit arrangement according to claim 6 for operating the discharge lamp, which due to its low volume and low weight can advantageously be used e.g. in ultra bright torches like Ujoy® torches or Ujoy® lamps or Ujoy® projection systems. It will be appreciated that features of the invention are susceptible to being combined in any combination without departing from the scope of the invention as defined by the accompanying claims.

Further details, features and advantages of the invention will become apparent from the following description of preferred and exemplary embodiments of the invention which are given with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 schematically shows a lamp unit with a discharge lamp and a circuit arrangement according to a first embodiment of the invention,

Fig. 2 schematically shows a lamp unit with a discharge lamp and a circuit arrangement according to a second embodiment of the invention, Fig. 3 schematically shows a lamp unit with a discharge lamp and a circuit arrangement according to a third embodiment of the invention, and

Fig. 4 schematically shows substantial parts of an embodiment of a switch unit according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Generally, Figures 1 to 3 schematically show a lamp unit with a discharge lamp or lamp burner 1 and a circuit arrangement for operating the discharge lamp 1, which circuit arrangement comprises a lamp driver 21 for driving the lamp 1 and an ignition unit 3 comprising or being provided in the form of a mechanical piezoignitor according to the invention for igniting the lamp 1. Furthermore, a power supply 20 is indicated which is connected with a ground or earth potential and which is provided for feeding the lamp driver 21 with electrical energy. Alternatively to the configuration as shown in Figures 1 to 3, the ignition unit or piezoignitor 3 can also be integrated into the lamp driver 21, so that the lamp driver 21 is provided for both igniting and driving (i.e. operating) the lamp 1.

The discharge lamp 1 comprises a discharge space or volume 10 enclosing a discharge gas and the tips of a first and a second electrode between which a gas discharge is excited. The electrodes of the lamp 1 are electrically contacted each through related pinches 11, 12 with a first and a second terminal, respectively, for applying an appropriate lamp current which is generated by means of the lamp driver 21 as known in the prior art.

The discharge lamp 1 comprises an antenna, especially an external antenna 13 outside of and preferably adjacent to the discharge space or volume 10 (i.e. at the transition between the discharge space or volume 10 and one of the pinches 11, 12), especially in the form of one or more windings of a wire around one of the pinches 11, 12. Furthermore, the discharge lamp 1 according to Figure 3 is provided in one of its pinches 11, 12 with an UV enhancer in the form of an enhancer chamber 14 as known in the prior art.

The lamp driver 21 preferably is a standard lamp driver 21 which is connected with or comprises the power supply 20 with a connection to a ground or earth potential. The lamp driver 21 is configured for driving the lamp 1, i.e. for generating and supplying an appropriate lamp current to the lamp 1 as known in the prior art.

The ignition unit or piezoignitor 3 is connected with one of its output terminals to the antenna 13 at the first pinch 11 of the discharge lamp 1, whereas the other output terminal is connected either to ground (earth potential) according to Figure 1, or with the second terminal at the second pinch 12 (Figure 2) or with the first terminal at the first pinch 11 (Figure 3) of the discharge lamp 1 as explained in more details below.

According to the invention, the ignitor is preferably provided in the form of a mechanical piezoignitor 3 which directly converts mechanical energy, especially in the form of a mechanical actuation or a mechanical impact onto the piezoignitor 3, into a high voltage at its output terminals.

Such a mechanical piezoignitor 3 is known in different forms for example from cigarette lighters or ignitors for gas ovens.

These mechanical piezoignitors 3 have the advantage, that they have a rather small volume, a low weight and low costs. A preferred embodiment of such a piezoignitor 3 which is suitable for igniting a discharge lamp 1 typically generates voltage peaks of about 4 kV or more with a duration of each voltage peak of a few milliseconds.

According to a first embodiment of the invention shown in Figure 1, the piezoignitor 3 is connected with one of its output terminals with the antenna 13 of the discharge lamp 1 and with the other output terminal to a ground or earth potential. By this, the ignition voltage is applied between one of the tips of the electrodes and the ground or earth potential.

According to a second embodiment of the invention shown in

Figure 2, one output terminal of the piezoignitor 3 is again connected with the antenna 13 at one of the pinches 11 (12) of the discharge lamp 1, and the other output terminal of the piezoignitor 3 is connected with the terminal of the discharge lamp at the other pinch 12 (11) opposite to the pinch 11 (12) which is provided with the antenna 13. By this, the ignition voltage is applied between the tips of the electrodes within the discharge space 10. According to a third embodiment of the invention shown in

Figures 3, the discharge lamp 1 is provided in one pinch 11 with the enhancer chamber 14, wherein the antenna 13 around this pinch 11 is positioned between the enhancer chamber 14 and the discharge volume 10, preferably at the transition between the discharge space or volume 10 and the one pinch 11 or adjacent to the discharge volume 10. One output terminal of the piezoignitor 3 is connected with the antenna 13. The other output terminal of the piezoignitor 3 is connected with the terminal of the discharge lamp 1 at the same pinch 11, in which the enhancer chamber 14 is provided, so that the ignition voltage is applied over the enhancer chamber 14 in order to create a primary discharge within the enhancer chamber 14 by which the (secondary) gas discharge between the tips of the electrodes within the discharge volume 10 is excited.

Tests with a 150W UHP discharge lamp 1 and a known standard lamp driver 21 in which the ignition related parts and components had been substituted by such a mechanical piezoignitor 3 showed a reliable cold ignition of the discharge lamp 1 , wherein the piezoignitor 3 was connected with the discharge lamp 1 according to the first embodiment shown in Figure 1. These tests have shown that an UV enhancer chamber 14 is not needed for cold ignition of the lamp 1, because the voltage peaks created by such a piezoignitor 3 have a high enough level to directly create a discharge spark between the tips of electrodes within the discharge volume 10.

However, depending on the kind of the discharge lamp 1 and/or the configuration of the piezoignitor 3 it can be advantageous to connect the piezoignitor 3 with a discharge lamp 1 according to the second or the third embodiment according to Figures 2 or 3 in order to improve reliability of cold ignition and/or for facilitating hot ignition of the discharge lamp 1 (i.e. shortly after it has been switched off).

Generally, for starting a discharge lamp 1 , two conditions have to be fulfilled. The lamp driver 21 has to provide and apply a voltage with at least a medium level (open loop voltage) to the electrodes of the lamp 1 (for UHP lamps this voltage is about 300V), while an ignition voltage peak which is higher than the medium-level voltage is required to ignite the lamp 1, i.e. to start the gas discharge between the tips of the electrodes. This ignition voltage peak is generated by means of the piezoignitor 3 which is connected to the lamp 1 according to one of the above three embodiments according to Figures 1 to 3 and the explanations above. The medium voltage has to be high enough to maintain the discharge after its ignition.

According to a preferred implementation of the invention these two conditions are obtained by time-sequentially first switching-on the lamp driver 21 and second actuating the piezoignitor 3. The time delay in this sequence is designed to be at least as long as the electronic components of the lamp driver 21 need to build up the open loop voltage with a sufficiently high level over the electrodes of the lamp 1, which is required to maintain the gas discharge between the electrodes after this discharge has been ignited by means of the piezoignitor 3. Figure 4 schematically shows the construction of an embodiment of a switch unit 4 according to the invention for obtaining such a time sequence of switching-on the the lamp driver 21 and actuating the piezoignitor 3 upon one manual actuation of the switch unit 4 by a user or operator.

The switch unit 4 (or switch arrangement) according to Figure 4 comprises an arrangement of a switch 22, preferably in the form of an electrical switch, for switching-on the lamp driver 21, and the piezoignitor 3. Between both, a mechanical connection 41 is provided. This arrangement is enclosed in the form of a stack within a housing 42 with a push button B by which the switch 22 and the piezoignitor 3 can be time-sequentially operated or switched by one manual actuation of the switch unit 4, especially by exerting a pressing force onto the button B of the switch unit 4 in a direction according to the arrow A. In order to obtain the time-sequential switching and actuation, the switch 22 and the piezoignitor 3 are oriented and/or positioned within the housing 41 such that the direction of a force, by which they can be switched and actuated, respectively, is generated by or corresponds with the direction A of the force exerted onto the button B of the housing 42 of the switch unit 4.

The related cable connections for connecting the switch 22 to the lamp driver 21 and the output terminals of the piezoignitor 3 to the lamp 1 are not indicated in this Figure.

The switching stiffness and/or the value of the elastic constant and/or the way of travel of the switch 22 and/or of the piezoignitor 3 before being released and actuated, respectively, are selected or designed such that if a user or an operator presses onto the button B according to the arrow A at a time t₀, at first only the switch 22 is released, so that the lamp driver 21 starts to build up the open loop voltage at a time ti, and then the piezoignitor 3 is actuated at a time t₂, so that the ignition voltage peak is generated. The difference between the time t₂ and the time ti (i.e. the time delay between both) is selected such that it is at least as long as the time duration the lamp driver 21 needs to build up the open loop voltage (medium- level voltage) as explained above. This time sequential switching can be obtained by an increasing force exerted onto the button B by the user and/or by an increasing way or distance of depression of the button B into the housing 41.

In order to safely achieve the above time delay, additionally or alternatively to the selection of the switching stiffnesses or the values of the elastic constants or the ways of travel of the switch 22 and of the piezoignitor 3, the mechanical connection 41 between both can be provided for example in the form of a spring (instead of a stiff or fixed connection) having an accordingly selected spring stiffness, so that the operator has to exert an increased or increasing force onto the button B and/or to press the button B with an additional way into the housing 42 in order to release or actuate the piezoignitor 3.

Experiments have shown that for example with a switch unit 4 in the form of an arrangement or stack of a standard electrical switch 22 for switching the lamp driver 21 and a standard piezoignitor 3 (e.g. a cigarette lighter), the required time delay can be obtained with a stiff mechanical connection 41 between both, because the stiffness of the piezoignitor 3 before being actuated is much higher than that of the electrical switch 22 before being released. A preferred application of the above described circuit arrangement and piezoignitor 3 due to its small volume and low weight is a torch such as an Ujoy® torch. In combination with the above described switch 4, such a torch can be handled very easily.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive, and the invention is not limited to the disclosed embodiments. Variations to embodiments of the invention described in the foregoing are possible without departing from the scope of the invention as defined by the accompanying claims. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Any reference signs in the claims should not be construed as limiting the scope of the invention.

Claims

CLAIMS:

1. Ignition unit for igniting a discharge lamp, especially a HID or UHP lamp, comprising an ignitor in the form of a mechanical piezoignitor (3) for creating an ignition voltage for igniting the discharge lamp upon a mechanical actuation of the piezoignitor (3).

2. Switch unit (4) for manually switching on a discharge lamp, comprising a switch (22) for switching on a lamp driver, and a mechanical piezoignitor (3), which are designed and/or mechanically coupled to each other such that by an actuation of the switch unit (4) by an operator, at first the switch (22) is released and then after expiration of a predetermined time delay the piezoignitor (3) is actuated.

3. Switch unit (4) according to claim 2, which is adapted to a lamp driver to be switched on with respect to the time delay such that it is at least equal to or longer than the time duration which the lamp driver needs for building up an open loop voltage of a discharge lamp to be operated.

4. Switch unit (4) according to claim 2, wherein the time delay is obtained by selecting the switching stiffness and/or the value of the elastic constant and/or the way of travel before being released or actuated, respectively, of the switch (22) and/or of the piezoignitor (3).

5. Lamp driver (21) for driving a discharge lamp comprising an ignitor in the form of a mechanical piezoignitor (3) for creating an ignition voltage for igniting the discharge lamp.

6. Circuit arrangement for operating a discharge lamp, comprising a lamp driver (21) for generating a lamp current, and an ignitor in the form of a mechanical piezoignitor (3) for creating an ignition voltage for igniting the discharge lamp.

7. Lamp unit comprising a discharge lamp (1) and a circuit arrangement according to claim 6 for operating the discharge lamp (1).

8. Lamp unit according to claim 7, wherein the discharge lamp (1) comprises an antenna (13) wound around a first pinch (11) of the discharge lamp (1), and wherein the piezoignitor (3) is connected with its first terminal with the antenna (13) of the discharge lamp (1).

9. Lamp unit according to claim 8, wherein the piezoignitor (3) is connected with its second terminal with a ground or earth potential of the lamp unit.

10. Lamp unit according to claim 8, wherein the piezoignitor (3) is connected with its second terminal with a second lamp terminal at a second pinch (12) of the discharge lamp (1) opposite to the first pinch (11).

11. Lamp unit according to claim 8, wherein the discharge lamp (1) comprises an enhancer chamber (14) within the first pinch (11) between the first lamp terminal and the antenna (13) of the discharge lamp (1), and wherein the piezoignitor (3) is connected with its second terminal with a first lamp terminal at the first pinch (11).

12. Projection system or torch comprising a lamp unit according to claim 7.