WO2011061180A1

WO2011061180A1 - Method and device for starting hid lamp, and ballast

Info

Publication number: WO2011061180A1
Application number: PCT/EP2010/067559
Authority: WO
Inventors: Martin Brueckel; Matthias Morkel; Haixiang He; Wanchun Jiang
Original assignee: Osram Gesellschaft mit beschränkter Haftung
Priority date: 2009-11-20
Filing date: 2010-11-16
Publication date: 2011-05-26
Also published as: CN102076156A

Abstract

A device (10) for starting a high intensity discharge lamp, comprising: a driving device (102), a resonance circuit (104) and a control device (106), wherein the driving device (102) obtains energy from a power source (100), and applies a voltage with a certain frequency to the resonance circuit (104) under a control of the control device (106), the resonance circuit (104) applies an output voltage thereof to the high intensity discharge lamp (108), wherein the control device (106) is configured to control an output voltage frequency of the driving device (102), so that the output voltage frequency is decreased gradually from a resonance frequency (f_Res) of the resonance circuit (104). Further, the present invention also discloses a ballast comprising the device for starting the high intensity discharge lamp as well as a method for starting the high intensity discharge lamp.

Description

METHOD AND DEVICE FOR STARTING HID LAMP, AND BALLAST

Field of the Invention

[0001] The present invention relates to a method for starting a high intensity discharge (HID) 5 lamp, a device for starting the HID lamp, and a ballast having such device.

Background of the Invention

[0002] The process from the starting of the HID lamp to the HID lamp entering a stable operation includes three stages. In the first stage, a high voltage is applied to the HID lamp, so 10 as to cause a breakdown of a dielectric medium contained in the HID lamp. The high voltage is generally generated via a resonance circuit, hi the second stage, a preheating voltage is applied to the HID lamp, so as to perform preheating on electrodes of the HID lamp. After that, in the third stage, a normal operation voltage is applied to the HID lamp, so that the lamp enters the stable operation.

15 [0003] In a typical method in the prior art, a high frequency voltage with a first frequency near the resonance frequency of the resonance circuit is applied to the resonance circuit in the first stage, so as to generate the high voltage for causing the breakdown of the HID lamp, and then a voltage with a second frequency is applied to preheat the electrodes of the lamp when the breakdown of the lamp is detected.

10 [0004] The above method has following drawbacks: after the breakdown of the lamp, the voltage with the second frequency is directly applied to the electrodes of the lamp, thus conducting components in the lamp and relevant circuit suffer an impact caused by a current jump. Further, an excessively high thermal stress caused by the jumping preheating current may lead to a damage of the electrode system of the lamp, such as the damage of the electrode tip,

25 film or welding connection part, so that the service life of the lamp may be shortened.

Summary of the Invention

[0005] The object of the present invention is to provide a method and device for starting a lamp. The defects in the prior art may be reduced with such method and device. Further, the 30 present invention provides a ballast including the device for starting the lamp.

i [0006] According to the invention, there is provided a device for starting a HID lamp, including: a driving device, a resonance circuit and a control device, wherein the driving device obtains energy from a power source and applies a voltage with a certain frequency to the resonance circuit under a control of the control device, the resonance circuit applies an output voltage thereof to the HID lamp, wherein the control device is configured to control an output voltage frequency of the driving device, so that the output voltage frequency is decreased gradually from a resonance frequency of the resonance circuit.

[0007] Further, according to the present invention, there is provided a ballast, which comprises the above device for starting the HID lamp.

[0008] Further, according to the present invention, there is provided a method for starting the HID lamp, comprising: applying a voltage with a resonance frequency of a resonance circuit to the resonance circuit, so as to generate a high voltage for breaking down the HID lamp; decreasing a frequency of the voltage gradually until an optimal preheating frequency of the HID lamp, so as to preheat the HID lamp; and the high intensity discharge lamp entering a stable operation stage after a completion of the preheating.

[0009] With the present invention, the current impact occurring during the start of the lamp can be weakened, the thermal stress of the electrode system during the start can be reduced, so that the service life of the lamp can be prolonged. Brief Description of the Drawings

[0010] The present invention may be better understood by referring to the description hereinafter in combination with the drawings, wherein in the drawings, the same or similar referenee signs are used to indicate the same or similar components. All the drawings and the detailed description are included in the specification and constitute a part of the specification, and are used to further present examples to illustrate the preferred embodiments of t!ie invention and explain the principles and advantages of the invention. Wherein:

[0011] Figure 1 shows a block diagram of a device for starting an HID lamp according to an embodiment of the invention.

[0012] Figure 2 shows a block diagram of the device for starting the HID lamp according to another embodiment of the invention.

[0013] Figure 3 shows a circuit diagram of the device for starting the HID lamp according to an embodiment of the invention.

[0014] Figure 4 shows a flow chart of a method for starting the HID lamp according to an embodiment of the invention.

[0015] Figure 5 shows a flow chart of the method for starting the HID lamp according to another embodiment of the invention.

[0016] In the drawings, the same reference signs are used for the same or corresponding components.

Detailed Description of the Embodiments

[0017] Hereinafter, the embodiments of the present invention will be described in combination with the drawings. In view of clearness and conciseness, not all the features of the practical embodiments are described in the description. However, it should be understood that many decisions specific to the embodiments need to be made during the development of any practical embodiments, so as to achieve the specific objects of the developer, and these decisions may vary to some extent according to different embodiments. Further, it should be understood that although the developing work may be rather complicated and time-consuming, it is only a routine job for those skilled in the art who benefit from the disclosure of the present invention.

[0018] It should be further pointed out here that in the drawings, only the device structure closely related to the solution of the present invention is illustrated in the drawings, and other details having little relation with the present invention is omitted, so as to avoid making the present invention unclear due to unnecessary details.

[0019] The inventor notices that with respect to an inductor, the impedance thereof is relevant to an AC voltage applied on the inductor. The higher the frequency of the voltage is, the larger the impedance is, and thus the smaller the current flowing through the inductor is. When the frequency of the voltage is decreased, the current flowing through the inductor becomes larger. By utilizing this principle, it can be realized to reduce the current impact suffered by the lamp when the HID lamp is started.

[0020] Figure 1 shows a block diagram of a device 10 for starting an HID lamp according to an embodiment of the invention. The device 10 includes: a driving device 102, a resonance circuit 104 and a control device 106. The driving device 102 obtains energy from a power source 100, and applies a voltage with a certain frequency to the resonance circuit 104 under the control of the control device 106. The resonance circuit 104 applies an output voltage thereof to the HID lamp 108. Wherein, the control device 106 is configured to control the output voltage frequency of the driving device 102, so that the output voltage frequency is decreased gradually from the resonance frequency fkes of the resonance circuit 104. Because the initial output voltage frequency of the driving device 102 is the resonance frequency f_Res of the resonance circuit 104, a high voltage can be output by the resonance circuit 104 to break down the HID lamp. At this time, because the voltage has a high frequency, the inductor in the resonance circuit shows a high impedance, so that the current flowing through the HID lamp is relatively small. After that, because the output voltage frequency of the driving device 102 is decreased gradually through the control device 106, the impedance of the inductance in the resonance circuit is decreased gradually, so that the current flowing through the HID lamp is increased gradually. Thus, it is avoided to a great extent the impact on the lamp caused by the current jump from the first stage of breakdown of the HID lamp to the second stage of preheating the HID lamp, and the thermal stress endured by the electrode system of the lamp is reduced, so that the service life of the lamp is advantageously prolonged.

[0021] It should be noted that the aforementioned output voltage frequency is not strictly required to be decreased exactly from the resonance frequency f_Res. The output voltage frequency can also be decreased from a value near the resonance frequency, as long as the frequency can make the resonance circuit to generate a voltage that is high enough to break down the lamp. For example, the output voltage frequency can be decreased from a frequency higher than the resonance frequency f_Res.

[0022] Further, it should be noted that the decrease of the output voltage frequency of the driving device 102 can be implemented in various modes according to requirements. For example, the output voltage frequency can be linearly decreased gradually, or can be non-linearly decreased gradually. Further, it is also possible that the output voltage frequency remains unchanged for a certain time near the resonance frequency, so as to break down the HID lamp more reliably, and then the output voltage frequency is decreased gradually. These solutions can be conceived by those skilled in the art according to the idea put forward by the present invention.

[0023] The control device 106 can be an embedded mono-chip computer or the like commonly used in the art. Such control device generally can be programmed according to requirements, so as to control the driving circuit to output the voltage of the required frequency, or to change the frequency according to the required manner (changing rate, linearity, non-linearity, etc.). This is a technology known by those skilled in the art and will not be further illustrated here.

[0024] Preferably, parameters of the resonance circuit and the lamp system are designed so that the resonance frequency f_Res of the resonance circuit is higher than the ideal preheating frequency f_pre of the HID lamp, and the control device 106 is configured to control the output voltage frequency of the driving device 102, so that the output voltage frequency is decreased gradually from the resonance frequency of the resonance circuit 104 until the ideal preheating frequency f_pre of the HID lamp, and maintains this ideal preheating frequency until the end of the preheating stage. The ideal preheating frequency f_pre here refers to that the current flowing through the lamp electrode generated under this frequency can achieve the best preheating effect.

[0025] Figure 2 shows a block diagram of the device 10' for starting the HID lamp according to another embodiment of the invention. The device 10' basically corresponds to the device 10 shown in Figure 1. The difference is that the device 10 further comprises a detecting device 110 for detecting the state of the lamp. For example, the detecting device 110 detects the current flowing through the HID lamp and the resonance circuit. If the current is higher than a preset value, it is detennined that the HID lamp is broken down. Otherwise, the HID lamp is not broken down. When the detecting device 110 determines that the lamp is broken down, the control device 106 controls the output voltage frequency of the driving device 102 to be decreased according to the signal from the detecting device 110. When the detecting device 110 determines that the lamp is not broken down, the aforementioned step is repeated, i.e., the output voltage frequency of the driving device 102 is made to be decreased gradually again from the resonance frequency f_Res of the resonance circuit 104. The detection of the detecting device 110 can be implemented after the entire preheating process is completed, or can be implemented after the breakdown process and before the start of the preheating process, or can be implemented during the preheating process. It should be noted that the wording of after the preheating process, before the start of the preheating process or during the preheating process refers to a state that the control circuit and the driving circuit operate according to the preheating mode, and does not mean whether the lamp is actually broken down.

[0026] The detecting device 110 can also be an embedded mono-chip computer or the like commonly used in the art. The detecting device can output the corresponding signal according to the input current. This is the technology known by those skilled in the art and will not be further illustrated here.

[0027] In Figure 2, the detecting device is illustrated as been arranged separately from the control device. However, those skilled in the art can understand that the detecting device 110 can also be integrated in the control device 106. For example, the detecting device 110 and the control device 106 are the same embedded mono-chip computer which can be programmed to implement the functions of both detection and control. Due to the detecting device 110, the control device can start to decrease (or continue decreasing) the output voltage frequency of the driving device 102 after the confirmation of the breakdown of the HID lamp, or can provide (or continue providing) the voltage for enabling the lamp to enter the stable operation after the confirmation of the breakdown of the HID lamp, so that the operation reliability of the device 10' is improved.

[0028] Figure 3 shows a circuit diagram of the device for starting the HID lamp according to an embodiment of the invention. It should be noted that the circuit diagram is only schematic, and the purpose thereof is to illustrate the idea of the present invention. Those skilled in the art can further modify the circuit for the practical object. For example, an additional capacitor can be connected in parallel for protecting the switching elements. Such modification does not affect the essential of the present invention.

[0029] It can be seen from Figure 3 that the driving device 102 can comprise four switching elements T1, T2, T3 and T4. The DC voltage input via the input terminals El and E2 is transformed into an AC voltage applied on the LC oscillation circuit 104 through the driving device 102. The output voltage of the LC oscillation circuit 104 is applied to the HID lamp 108. As can be seen from Figure 3, the control terminals of the switching elements T1-T4 are connected to the control device 106. Thus, the on/off of these switching elements can be controlled via the control device, so that the control of the frequency of the voltage output to the resonance circuit 104 by the driving device 102 can be implemented. The specific control maimer is as follows: in the first time period, the control device 106 switches on the switching elements Tl and T4, and switches off T2 and T3; in the subsequent second time period, the control device 106 switches on the switching elements T2 and T3, and switches off Tl and T4. After that, the above processes are repeated again. By controlling the switching elements by turns, an AC voltage is present on the LC oscillation circuit 104. Further, the frequency of the AC voltage can be controlled by controlling the length of the first and the second time period. The control manner and the corresponding control device are familiar to those skilled in the art. and will not be further described here. As described in the above embodiments, tlie control device can be configured to make the output voltage frequency of the driving device 102 to be decreased gradually from the resonance frequency f_Res of the resonance circuit, so as to make the impedance of the inductance in the resonance circuit to be decreased gradually, so that the current flowing through the HID lamp is increased gradually. Thus, it is avoided to a great extent the impact on tlie lamp caused by the current jump from the first stage of breakdown of the HID lamp to the second stage of preheating the HID lamp, and the sendee life of the lamp is advantageously prolonged.

[0030] Further, as can be seen from Figure 3, the control device can obtain the information about the lamp via, for example, terminals II and 12. For example, the control device can detect the magnitude of the current flowing through the HID lamp, so that the control device can start to decrease (or continue decreasing) the output voltage frequency of tlie driving device 102 after the determination of the breakdown of the HID lamp, or can provide (or continue providing) the voltage for enabling the lamp to enter tlie stable operation after the determination of the breakdown of the HID lamp. Thus, the operation reliability of the entire device is improved. It should be noted that Figure 3 corresponds to the situation that the detecting device is integrated in the control device. It will readily occur to those skilled in the art that the detecting device and the control device can also be arranged separately, which does not affect the essential of the present invention. [0031 ] As already mentioned above, the output voltage frequency is not strictly required to be decreased exactly from the resonance frequency f_Res. Further, the decrease of the output voltage frequency of the driving device 102 can be implemented in various modes according to requirements. For example, the output voltage frequency can be linearly decreased gradually, or can be non-linearly decreased gradually. Further, it is also possible that the output voltage frequency remains unchanged for a certain time near the resonance frequency, so as to break down the HID lamp more reliably, and then the output voltage frequency is decreased gradually. These solutions can be conceived by those skilled in the art according to the idea put forward by the invention.

[0032] It is also preferred that the parameters of the resonance circuit and the lamp system are designed so that the resonance frequency f_Res of the resonance circuit is higher than the ideal preheating frequency f_pre of the HID lamp, and the control device 106 is configured to control the output voltage frequency of the driving device 102, so that the output voltage frequency is decreased gradually from the resonance frequency f_Res of the resonance circuit 104 until the ideal preheating frequency f_pre of the HID lamp, and maintains this ideal preheating frequency until the end of the preheating stage.

[0033] in the shown circuit, in order to determine whether the preheating stage is completed, for example, a voltage with a certain frequency can be applied to the resonance circuit 104, so as to output a voltage required by the HID lamp in the stable operation (this voltage is generally lower than the voltage required in the preheating stage), and the current flowing through the lamp 108 is detected. When this current reaches a defined value, it indicates that the lamp can enter the stable operation. Thus, it is deemed that the preheating stage should be terminated. The content of determining whether the preheating stage is completed belongs to the technology known by those skilled in the art, and will not be described again here.

[0034] According to a further embodiment of the present invention, there is provided a ballast comprising the device for starting the HID lamp according to the above embodiments.

[0035] Figure 4 shows a flow chart of a method for starting the HID lamp according to an embodiment of the invention. The method comprises:

[0036] S401 : applying a voltage with a resonance frequency of a resonance circuit to the resonance circuit, so as to generate a high voltage for breaking down the HID lamp;

[0037] S403: decreasing the frequency of the voltage gradually until an optimal preheating frequency of the HID lamp, so as to preheat the HID lamp; and

[0038] S405: the HID lamp entering a stable operation after the completion of the preheating. [0039] It should be noted that the aforementioned voltage with the resonance frequency of the resonance circuit is not strictly required to has a frequency exactly equal to the resonance frequency, but can also be a value near the resonance frequency, as long as the frequency can make the resonance circuit to generate a voltage that is high enough to break down the lamp. For example, this voltage can have a frequency higher than the resonance frequency of the resonance circuit.

[0040] Further, it should be noted that the decrease of the voltage frequency can be implemented in various modes according to requirements. For example, the voltage frequency can be linearly decreased gradually, or can be non-linearly decreased gradually. Further, it is also possible that the voltage frequency remains unchanged for a certain time near the resonance frequency, so as to break down the HID lamp more reliably, and then the voltage frequency is decreased gradually. These solutions can be conceived by those skilled in the art according to the idea put forward by the invention. [0041] With this method, it is avoided to a great extent the impact on the lamp caused by the current jump from the first stage of breakdown of the HID lamp to the second stage of preheating the HID lamp, and the thermal stress endured by the electrode system of the lamp is reduced, so that the service life of the lamp is advantageously prolonged.

[0042] Figure 5 shows a flow chart of the method for starting the HID lamp according to another embodiment of the invention. As can be seen from Figure 5, steps S501 , S503 and S505 correspond to the steps S401, S403 and S405 in Figure 4 and will not be described again here. The difference is that after die application of the voltage with the resonance frequency, a step S502 of detecting whether the lamp is broken down is included. When it is determined that the lamp is broken down, the method proceeds to execute step S503. When it is determined that the lamp is not broken down, step S501 is executed again. In this way, the operation reliability of the method is improved.

[0043] It should be noted that the detecting step can also be executed after the completion of the preheating, i.e., after the step S503 and before the step S505. When it is determined that the lamp is not broken down, the step S501 is executed again. In this way, the object of improving the operation reliability can also be achieved. Further, as described above, the step S502 and step S503 can have a temporal overlapping to various degrees.

[0044] It is also preferred that the parameters of the resonance circuit and the lamp system are designed so that the resonance frequency f_Res of the resonance circuit is higher than the ideal preheating frequency f_Res of the HID lamp, and output voltage frequency of the resonance circuit is decreased gradually from the resonance frequency of the resonance circuit until the ideal preheating frequency f_Res of the HID lamp, and maintains this ideal preheating frequency until the end of the preheating stage.

[0045] Finally, it should be noted that the term "include", "comprise" or any other variations means a non-exclusive inclusion, so that, the process, method, article or device that includes a series of elements includes not only these elements but also other elements that are not explicitly listed, or further includes inherent elements of the process, method, article or device. Moreover, when there is no further limitation, the element defined by die wording "include(s) a ..." does not exclude the case that in the process, method, article or device that includes the element there are other same elements.

[0046] The embodiments of the invention are described in detail in combination with drawings. However, it should be understood that the embodiments described above are only used for illustrating the invention, and do not constitute a limitation of the invention. Various modifications and variations may be made to the above embodiments by those skilled in the art, without departing from the essential and scope of the present invention. Therefore, the scope of the present invention is only defined by the appended claims and the equivalent meanings thereof.

Claims

CLAIMS What is claimed is:

1. A device (10) for starting a high intensity discharge lamp, comprising; a driving device (102), a resonance circuit (104) and a control device (106), wherein the driving device (102) obtains energy from a power source (100), and applies a voltage with a certain frequency to the resonance circuit (104) under a control of the control device (106), the resonance circuit (104) applies an output voltage thereof to the high intensity discharge lamp (108), wherein the control device (106) is configured to control an output voltage frequency of the driving device (102), so that the output voltage frequency is decreased gradually from a resonance frequency (f_Res) of the resonance circuit (104).

2. The device (10) for starting the high intensity discharge lamp according to claim 1 , further comprising a detecting device (110) configured to detect a state of the high intensity discharge lamp after an application of the voltage of the resonance frequency;

when the detecting device (110) determines that the high intensity discharge lamp is broken down, the control device (106) controls the output voltage frequency of the driving device (102) to be decreased or continue to be decreased according to a signal from the detecting device (110), and

when the detecting device (110) determines that the lamp is not broken down, the control device (106) makes the output voltage frequency of the driving device (102) to be decreased gradually again from the resonance frequency (f_Res) of the resonance circuit (104).

3. The device (10) for starting the high intensity discharge lamp according to claim 1 , further comprising a detecting device (110) configured to detect a state of the high intensity discharge lamp after a completion of a preheating stage;

when the detecting device (110) determines that the high intensity discharge lamp is broken down, the control device (106) controls the output voltage frequency of the driving device (102), so that the lamp enters a stable operation; and

when the detecting device (1 10) determines that the lamp is not broken down, the control device (106) makes the output voltage frequency of the driving device (102) to be decreased gradually again from the resonance frequency (f_Res) of the resonance circuit (104).

4. The device ( 10) for starting the high intensity discharge lamp according to any one of claims 1 to 3, wherein parameters of the resonance circuit and the high intensity discharge lamp are designed so that the resonance frequency of the resonance circuit is higher than an ideal preheating frequency (f_pre) of the high intensity discharge lamp, and the control device [106] is configured to control the output voltage frequency of the driving device (102), so that the output voltage frequency is decreased gradually from the resonance frequency (f_Res) of the resonance circuit (104) until the ideal preheating frequency (f_pre) of the high intensity discharge lamp, and maintains this ideal preheating frequency until the end of the preheating stage.

5. The device (10) for starting the high intensity discharge lamp according to any one of claims 1 to 3, wherein the control device (106) controls the driving device (102), so that the output voltage frequency thereof is decreased linearly.

6. A ballast, comprising the device (10) for starting the high intensity discharge lamp according to any one of claims 1 to 5.

7. A method for starting a high intensity discharge lamp, comprising:

applying a voltage with a resonance frequency of a resonance circuit to the resonance circuit, so as to generate a high voltage for breaking down the high intensity discharge lamp; decreasing a frequency of the voltage gradually until an optimal preheating frequency of the high intensity discharge lamp, so as to preheat the high intensity discharge lamp; and

the high intensity discharge lamp entering a stable operation stage after a completion of the preheating.

8. The method for starting the high intensity discharge lamp according to claim 7, further comprising: detecting whether the high intensity discharge lamp is broken down after applying the voltage with the resonance frequency;

when it is determined that the lamp is broken down, continuing preheating the lamp; and when it is determined that the lamp is not broken down, applying the voltage with the resonance frequency again.

9. The method for starting the high intensity discharge lamp according to claim 7, further comprising: detecting whether the high intensity discharge is broken down after a completion of the preheating;

when it is determined that the lamp is broken down, making the high intensity discharge to enter the stable operation stage; and

when it is determined that the lamp is not broken down, applying the voltage with the resonance frequency again,

10. The method for starting the high intensity discharge lamp according to any one of claims 7 to 9, wherein the step of decreasing the frequency of the voltage gradually comprises: designing param eters of the resonance circuit and the high intensity discharge lamp so that the resonance frequency (f_Res) of the resonance circuit is higher than an ideal preheating frequency (f_pre) of the high intensity discharge lamp, decreasing the output voltage frequency gradually from the resonance frequency (f_Res) of the resonance circuit (104) until the ideal preheating frequency (f_pre) of the high intensity discharge lamp, and maintaining this ideal preheating frequency until the end of the preheating stage,

11. The method for starting the high intensity discharge lamp according to any one of claims 7 to 9, wherein the step of decreasing the frequency of the voltage gradually comprises: decreasing the frequency of the voltage linearly.