Discharge lamp lighting device and vehicle illumination device

Abstract

To provide a lighting device for discharge lamp capable of suppressing an out-of-resonance state even in a case where a change of an environmental temperature is considerable, and an irradiation device for vehicle.SOLUTION: A lighting device for discharge lamp applies a drive voltage in a predetermined operation frequency to a discharge lamp. The lighting device for discharge lamp comprises: a switching output circuit which includes a switching element and converts a DC voltage into an AC voltage in the operation frequency; a control circuit where the primary-side coil is electrically connected with the switching output circuit via a capacitor for resonance and the secondary-side coil is electrically connected with a transformer electrically connected with the discharge lamp and the switching output circuit and which generates a drive signal of the switching element; and an operation frequency setting circuit which is electrically connected with the control circuit and includes a resistor and a temperature sensitive element connected in series with the resistor. A resistance value of the temperature sensitive element is reduced when a temperature rises. The control circuit sets the operation frequency based on a value of combined resistance of the resistor and the temperature sensitive element.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] FIELD An embodiment of the present invention relates to a discharge lamp lighting device and a vehicle illumination device. [Background technology]

[0002] There are lighting devices that light discharge lamps. For example, lighting devices that include an LLC resonant circuit that has a switching element, a resonant capacitor, a transformer, etc. The output voltage of the LLC resonant circuit varies depending on the operating frequency, so the operating frequency is preset.

[0003] However, the transformers used in LLC resonant circuits have temperature characteristics. For example, when the ambient temperature is high, the inductance value of the transformer decreases, resulting in a higher resonant frequency. On the other hand, when the ambient temperature is low, the inductance value of the transformer increases, resulting in a lower resonant frequency.

[0004] Therefore, for example, when the ambient temperature rises, the set operating frequency may become smaller than the resonant frequency, which causes a so-called out-of-resonance state, making it impossible to start the discharge lamp and causing it to not light up. Alternatively, when the ambient temperature drops, the set operating frequency may become higher than the resonant frequency, which may make it difficult to maintain the desired output voltage. Here, the lighting device may be used in a vehicle illumination device. The vehicle illumination device installed in an automobile or the like is required to operate normally even in an environment of, for example, -40°C to 85°C. Therefore, when the lighting device is used in a vehicle illumination device, it is likely to be in an off-resonance state, and the discharge lamp cannot be started and is likely to not light. Alternatively, it may become difficult to maintain a desired output voltage.

[0005] Therefore, even if the environmental temperature changes significantly, Proper lighting of discharge lamps There was a need to develop a technology that could do this. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5949968 Summary of the Invention [Problem to be solved by the invention]

[0007] The problem to be solved by the present invention is that even when the environmental temperature changes greatly, Proper lighting of discharge lamps The present invention provides a discharge lamp lighting device and a vehicle illumination device that can achieve this. [Means for solving the problem]

[0008] A discharge lamp lighting device according to an embodiment applies a drive voltage of a predetermined operating frequency to a discharge lamp. The discharge lamp lighting device includes: a switching output circuit having a switching element and converting a DC voltage into an AC voltage of the operating frequency; a transformer having a primary winding electrically connected to the switching output circuit via a resonance capacitor and a secondary winding electrically connected to the discharge lamp, the transformer having an inductance value with temperature characteristics; a control circuit electrically connected to the switching output circuit and generating a drive signal for the switching element; and an operating frequency setting circuit electrically connected to the control circuit and having a resistor and a temperature-sensitive element connected in series with the resistor. The control circuit sets the operating frequency based on a combined resistance of the resistor and the temperature sensitive element, and the combined resistance is set so that the operating frequency set by the control circuit is greater than the resonant frequency of the resonant capacitor and the transformer at a predetermined ambient temperature. The temperature-sensitive element is The environment When the temperature rises, the resistance value decreases. If Depending on the amount of reduction in the resistance, The set The value of the operating frequency is increased. environment When the temperature drops, the resistance value increases. If Depending on the increase in resistance, The set The value of the operating frequency is reduced. [Effects of the Invention]

[0009] According to an embodiment of the present invention, even when the environmental temperature changes significantly, Proper lighting of discharge lamps It is possible to provide a discharge lamp lighting device and a vehicle illumination device that can achieve this. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic perspective view illustrating an illumination device for a vehicle according to an embodiment of the present invention; [Figure 2] 2 is a schematic cross-sectional view of the vehicle irradiation device in FIG. 1 taken along line AA. FIG. [Figure 3] FIG. 1 is a circuit diagram illustrating a lighting device. [Figure 4] 10 is a graph illustrating the relationship between the frequency value and the step-up / step-down ratio; [Figure 5] 10 is a graph illustrating the relationship between the environmental temperature and the value of the resonance frequency. [Figure 6] 10 is a graph illustrating the setting of the value of the operating frequency; DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments will be illustrated with reference to the drawings. In the drawings, like components are designated by like reference numerals and detailed descriptions thereof will be omitted where appropriate. The discharge lamp lighting device according to the present embodiment can be used in a lighting device or an irradiation device that is installed in an environment where temperature changes are large. For example, the discharge lamp lighting device according to the present embodiment can be suitably used in a vehicle irradiation device that is installed in a vehicle such as an automobile or a train. Therefore, in the following, as an example, a case where the discharge lamp lighting device is used in an illumination device for a vehicle will be described.

[0012] The vehicle irradiation device can be installed, for example, in the cabin or trunk of an automobile, or in the cabin of a railway vehicle, etc. However, the installation location of the vehicle irradiation device is not limited to those exemplified.

[0013] FIG. 1 is a schematic perspective view illustrating an illumination device 100 for a vehicle according to this embodiment. FIG. 2 is a schematic cross-sectional view of the vehicle illumination device 100 in FIG. 1 taken along the line AA. As shown in FIGS. 1 and 2, the vehicle illumination device 100 includes, for example, a lighting device 1, a housing 2, a substrate 3, a discharge lamp 4, a lamp cover 5, wiring 6, a window 7, and a shield 8.

[0014] First, a lighting device 1 according to the present embodiment will be illustrated. As shown in FIG. 2, for example, the lighting device 1 can be provided inside the housing 2. The lighting device 1 is provided, for example, on the surface of the substrate 3 on which the discharge lamp 4 is provided. If the discharge lamp 4 and the lighting device 1 are provided on the same surface of the substrate 3, it becomes easy to reduce the thickness dimension T of the housing 2. The lighting device 1 is electrically connected to a pair of terminal holders 41 to which the discharge lamp 4 is attached, using wiring members such as a wiring cord or a metal plate. Therefore, by attaching the discharge lamp 4 to the pair of terminal holders 41, the lighting device 1 and the discharge lamp 4 can be electrically connected.

[0015] The lighting device 1 applies a drive voltage of a predetermined frequency to the discharge lamp 4. The lighting device 1 also controls the value of the frequency (operating frequency) of the drive voltage applied to the discharge lamp 4. When the drive voltage is applied to the discharge lamp 4, for example, a discharge occurs between a pair of electrodes provided on the discharge lamp 4, and light such as ultraviolet light is emitted from the discharge lamp 4.

[0016] FIG. 3 is a circuit diagram illustrating the lighting device 1. As shown in FIG. As shown in FIG. 3, the lighting device 1 includes, for example, a switching output circuit 11, a transformer 12, a resonance capacitor 13, a control circuit 14, and an operating frequency setting circuit 15.

[0017] The switching output circuit 11 is electrically connected to the primary winding of the transformer 12 via a resonant capacitor 13. The switching output circuit 11 converts a DC voltage into an AC voltage of a predetermined frequency. For example, the switching output circuit 11 converts a DC voltage from a DC power supply 200 into an AC voltage of a predetermined frequency, such as a pseudo-sine wave voltage. The DC power supply 200 is, for example, a battery or a battery mounted on a vehicle such as an automobile.

[0018] The switching output circuit 11 illustrated in Fig. 3 is a half-bridge circuit, and includes, for example, a switching element 11a and a switching element 11b.

[0019] The switching elements 11a and 11b are, for example, MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors). If the switching elements 11a and 11b are MOSFETs, which are voltage-driven elements, it is possible to reduce power loss in the circuit. Furthermore, if the switching elements 11a and 11b are MOSFETs, it is possible to increase the switching speed and reduce switching loss. Although the switching output circuit 11 is a half-bridge circuit in the above example, the switching output circuit 11 may be, for example, a full-bridge circuit.

[0020] The primary winding of the transformer 12 is electrically connected to the switching output circuit 11 via a resonance capacitor 13. The secondary winding of the transformer 12 is electrically connected to a pair of electrodes provided on the discharge lamp 4.

[0021] Since the LLC resonant circuit is used, circuit efficiency can be improved, which reduces the amount of heat generated by circuit components and allows the lighting device 1 to be made smaller. If the lighting device 1 is made smaller, the vehicle illumination device 100 in which the lighting device 1 is installed can also be made smaller. The vehicle illumination device 100 is often installed in a narrow space such as the interior of a vehicle. Therefore, if the lighting device 1 can be made smaller, the installation of the vehicle illumination device 100 will be easier.

[0022] The control circuit 14 is electrically connected to the switching output circuit 11 . The control circuit 14 sets the value of the operating frequency based on the resistance value of the operating frequency setting circuit 15 (the combined resistance value of the resistor 15a and the temperature sensitive element 15b).

[0023] Control circuit 14 increases the value of the operating frequency according to the amount of decrease in the resistance value of operating frequency setting circuit 15, and decreases the value of the operating frequency according to the amount of increase in the resistance value of operating frequency setting circuit 15. The relationship between the resistance value of operating frequency setting circuit 15 and the set value of the operating frequency can be found in advance by conducting experiments or simulations. The resistance value of the operating frequency setting circuit 15 (the combined resistance value of the resistor 15a and the temperature sensitive element 15b) will be described in detail later.

[0024] Based on the generated signal, the control circuit 14 alternately switches between applying a voltage to the gate electrode of the switching element 11a and applying a voltage to the gate electrode of the switching element 11b, thereby converting the DC voltage from the DC power supply 200 into an AC voltage of a predetermined operating frequency. For example, the operating frequency is about 100 kHz to 300 kHz.

[0025] Furthermore, by operating the LLC resonant circuit having the switching output circuit 11, the transformer 12, and the resonant capacitor 13 intermittently using the control circuit 14, the peak value of the drive voltage applied to the discharge lamp 4 can be maintained, thereby enabling stable dimming.

[0026] Here, in the LLC resonant circuit, the step-up / step-down ratio, and therefore the output voltage, varies depending on the value of the operating frequency. FIG. 4 is a graph illustrating the relationship between the frequency value and the step-up / step-down ratio. As can be seen from Figure 4, the higher the set value of the operating frequency is relative to the resonant frequency, the lower the step-up / step-down ratio becomes. If the set value of the operating frequency is lower than the resonant frequency, the step-up / step-down ratio becomes higher than when the set value of the operating frequency is higher than the resonant frequency. The region where the set value of the operating frequency is lower than the resonant frequency is the so-called off-resonance region. In the off-resonance region, the discharge lamp 4 cannot be started, and therefore the discharge lamp 4 does not light. Therefore, in the case of a typical LLC resonant circuit, an operating frequency greater than the resonant frequency is preset.

[0027] However, the transformer 12 used in the LLC resonant circuit has temperature characteristics, so the value of the resonant frequency changes with changes in the environmental temperature. FIG. 5 is a graph illustrating the relationship between the environmental temperature and the value of the resonant frequency. When the ambient temperature increases, the inductance value L of the transformer 12 decreases, and the resonant frequency (1 / (2π√(L×C))) increases, as shown in Figure 5. On the other hand, when the ambient temperature decreases, the inductance value L of the transformer 12 increases, and the resonant frequency decreases.

[0028] Therefore, for example, if the operating frequency value is set based on the resonant frequency value when the ambient temperature is 25° C., when the ambient temperature reaches 85° C., the set operating frequency value may be smaller than the resonant frequency value at 85° C. As described above, when the set operating frequency value becomes smaller than the resonant frequency value, a so-called off-resonance state occurs, and the discharge lamp 4 cannot be started and does not light.

[0029] In this case, if the operating frequency is set based on the resonant frequency at the highest ambient temperature, it is possible to prevent the discharge lamp 4 from going out of resonance even if the ambient temperature changes. However, this may result in a too small step-up / step-down ratio and therefore an excessively small output voltage, causing the discharge lamp 4 to stop lighting.

[0030] Therefore, the lighting device 1 according to the present embodiment is provided with an operating frequency setting circuit 15. 3, the operating frequency setting circuit 15 is electrically connected to the control circuit 14. The operating frequency setting circuit 15 is electrically connected between a terminal of the control circuit 14 and the ground. The operating frequency setting circuit 15 includes, for example, a resistor 15a, a temperature sensing element 15b, and a clamp element 15c.

[0031] The temperature sensing element 15b is connected in series with the resistor 15a. The resistance value of the temperature sensing element 15b decreases as the temperature increases. The temperature sensing element 15b is, for example, a negative temperature coefficient thermistor (NTC thermistor).

[0032] As described above, the control circuit 14 sets the value of the operating frequency based on the resistance value of the operating frequency setting circuit 15 . FIG. 6 is a graph illustrating the setting of the value of the operating frequency. As shown in FIG. 6, at a predetermined ambient temperature (for example, 25° C.), the value of the combined resistance of resistor 15a and thermosensitive element 15b is adjusted so that the value of the operating frequency is greater than the value of the resonant frequency.

[0033] In this case, since the resistance value of the temperature-sensing element 15b does not change unless the ambient temperature changes, the resistance value of the resistor 15a is adjusted to achieve the desired combined resistance value, and thus the desired operating frequency value. For example, a resistor 15a having an appropriate resistance value may be selected or the resistance value of the variable resistor 15a may be adjusted depending on the resistance value of the temperature-sensing element 15b at a predetermined ambient temperature. Incidentally, multiple resistors 15a may be provided to facilitate adjustment of the resistance value and improve the adjustment accuracy.

[0034] Next, the functions of the resistor 15a and the thermosensitive element 15b will be described. If the ambient temperature becomes higher than the ambient temperature when the resonant frequency value was set (for example, if it becomes 85°C), the resistance value of resistor 15a remains almost unchanged, but the resistance value of temperature-sensitive element 15b decreases. As a result, the combined resistance value of resistor 15a and temperature-sensitive element 15b decreases. As the combined resistance value decreases, the terminal voltage of control circuit 14 decreases. As described above, control circuit 14 increases the operating frequency value in accordance with the amount of decrease in the combined resistance value of resistor 15a and temperature-sensitive element 15b. If the operating frequency value increases, it is possible to prevent an off-resonance state from occurring, even if the resonant frequency value increases as the ambient temperature rises.

[0035] When the ambient temperature drops below the ambient temperature at which the resonant frequency was set, the resistance of resistor 15a remains almost unchanged, but the resistance of temperature-sensitive element 15b increases. Therefore, the combined resistance of resistor 15a and temperature-sensitive element 15b increases. As the combined resistance increases, the terminal voltage of control circuit 14 increases. As described above, control circuit 14 reduces the operating frequency in accordance with the increase in the combined resistance of resistor 15a and temperature-sensitive element 15b. By reducing the operating frequency, the difference between the resonant frequency and the operating frequency can be prevented from increasing, even if the resonant frequency decreases with a drop in ambient temperature. This makes it possible to maintain the desired output voltage.

[0036] If the temperature-sensing element 15b is a negative-temperature-characteristic thermistor, the change in resistance with temperature is not a linear function. Therefore, the resistance of the temperature-sensing element 15b increases rapidly at low temperatures. If the combined resistance increases rapidly, the set operating frequency may fall into the off-resonance range.

[0037] Therefore, the operating frequency setting circuit 15 is provided with a clamp element 15c. As shown in FIG. 3, clamp element 15c is connected in parallel with temperature-sensing element 15b. Clamp element 15c applies a clamp voltage to the terminal of control circuit 14. Clamp element 15c is, for example, a diode. When clamp element 15c is a diode, its anode is electrically connected between resistor 15a and temperature-sensing element 15b, and its cathode is electrically connected to ground. In this way, the forward voltage Vf of the diode can be applied to the terminal of control circuit 14. In this case, the forward voltage Vf serves as the clamp voltage. Therefore, even if the combined resistance value increases suddenly at low temperatures, the terminal voltage of control circuit 14 can be clamped. As a result, the set operating frequency can be prevented from entering the off-resonance region.

[0038] The clamp voltage can be determined appropriately depending on the temperature characteristics of the NTC thermistor, for example, by selecting a diode with an appropriate forward voltage Vf depending on the temperature characteristics of the NTC thermistor.

[0039] In this case, the clamp voltage (forward voltage Vf) can be adjusted by connecting a plurality of diodes in series, in parallel, or in series-parallel. Furthermore, if the clamp voltage is, for example, 2 V or higher, a Zener diode can be used instead of the diode.

[0040] It should be noted that clamp element 15c may be omitted when the lower limit of the ambient temperature is high. However, if clamp element 15c is provided, the range of ambient temperatures that can be handled can be widened. In other words, the versatility of lighting device 1 can be improved.

[0041] Next, returning to FIGS. 1 and 2, the housing 2, the substrate 3, the discharge lamp 4, the lamp cover 5, the wiring 6, the window 7, and the shield 8 provided in the vehicle irradiation device 100 will be illustrated. 1 and 2, the housing 2 is box-shaped and has a space therein for accommodating the substrate 3, the discharge lamp 4, the lamp cover 5, and the lighting device 1. The lighting device 1 can also be provided outside the housing 2. However, if the lighting device 1 is provided inside the housing 2, the installation and handling of the vehicle illumination device 100 becomes easier.

[0042] The thickness dimension T of the housing 2 can be made smaller than the planar dimension of the housing 2. The vehicle illumination device 100 may be installed in a small space such as the inside of a vehicle together with electronic devices used for driving the vehicle. Therefore, if the thickness dimension T of the housing 2 can be made smaller, the vehicle illumination device 100 can be easily installed.

[0043] The housing 2 is divided into a first portion 21 and a second portion 22 in the thickness direction of the housing 2. The first portion 21 can be, for example, a base to which the substrate 3, the discharge lamp 4, the lamp cover 5, and the lighting device 1 are attached. The second portion 22 can be, for example, a cover that covers the opening side of the first portion 21. The second portion 22 can be provided with a hole 22a for emitting ultraviolet rays or light. The hole 22a can be provided in a position facing the discharge lamp 4.

[0044] The second part 22 can be provided so as to be detachable from the first part 21. For example, the first part 21 and the second part 22 are detachably connected by an elastic force generated by fitting their openings together.

[0045] The first portion 21 and the second portion 22 can be formed from, for example, an insulating resin. In this case, the material of the second portion 22 may be the same as or different from the material of the first portion 21. If the first portion 21 and the second portion 22 are insulating, the distance between the inner walls of the first portion 21 and the second portion 22 and the discharge lamp 4, the lighting device 1, etc. can be shortened. This makes it easier to make the housing 2 thinner.

[0046] The substrate 3 has a plate shape. The substrate 3 can be provided on the first portion 21 via, for example, a spacer 31. Instead of the spacer 31, the substrate 3 may be provided on a protrusion provided on the first portion 21.

[0047] The discharge lamp 4 is located between the substrate 3 and the second portion 22. The discharge lamp 4 can be provided at a position facing the hole 22a of the second portion 22. The discharge lamp 4 can be detachably provided on a pair of terminal holders 41. The pair of terminal holders 41 can be provided on the substrate 3, for example. Although FIGS. 2 and 3 show an example in which one discharge lamp 4 is provided, multiple discharge lamps 4 may be provided. It is sufficient that at least one discharge lamp 4 is provided.

[0048] The discharge lamp 4 can be, for example, a mercury lamp, a metal halide lamp, a dielectric barrier discharge lamp, etc. However, the discharge lamp 4 is not limited to the examples given above, and may be any lamp capable of emitting ultraviolet rays or light (for example, visible light).

[0049] The lamp cover 5 is located between the substrate 3 and the second portion 22. The lamp cover 5 can be provided on the substrate 3, for example. The lamp cover 5 is box-shaped and has an open end opposite the substrate 3. The opening 5a of the lamp cover 5 faces the hole 22a of the second portion 22. The discharge lamp 4 and a pair of terminal holders 41 can be provided inside the lamp cover 5. For example, the lamp cover 5 can be formed from an insulating resin. The material of the lamp cover 5 can be the same as the material of the housing 2, for example. However, since the lamp cover 5 is exposed to ultraviolet rays irradiated from the discharge lamp 4, it is preferable to use a material that is more resistant to ultraviolet rays than the material of the housing 2.

[0050] The lamp cover 5 prevents ultraviolet rays and light emitted from the discharge lamp 4 from entering the inner wall of the housing 2, the substrate 3, and the lighting device 1. This prevents these from being deteriorated by ultraviolet rays and the like.

[0051] The lamp cover 5 can also be given a reflector function. For example, the lamp cover 5 can be made of a resin such as white, a reflective film can be formed on the inner wall of the lamp cover 5, or the inner wall of the lamp cover 5 can be curved. If the lamp cover 5 is given a reflector function, the utilization efficiency of the ultraviolet rays and light emitted from the discharge lamp 4 can be improved.

[0052] One end of the wiring 6 is electrically connected to the lighting device 1 inside the housing 2. The other end of the wiring 6 is drawn out to the outside of the housing 2 and is electrically connected to a DC power supply 200, for example.

[0053] The window 7 is provided in a portion of the housing 2 (second portion 22) where the hole 22a is provided. For example, the window 7 is provided on the inner wall of the second portion 22, and covers the hole 22a. The window 7 transmits ultraviolet rays and light emitted from the discharge lamp 4. The window 7 has, for example, a plurality of openings. The window 7 can be formed by weaving a plurality of wires, or can have a plurality of openings formed by etching, pressing, or the like.

[0054] When the discharge lamp 4 is turned on, if a discharge occurs between the electrodes of the discharge lamp 4, electromagnetic waves may be emitted along with ultraviolet rays and light. Furthermore, when the discharge lamp 4 is turned on, electromagnetic waves may be emitted from the switching elements 11a and 11b provided in the lighting device 1 and the wiring electrically connected to the switching elements 11a and 11b.

[0055] As described above, the vehicular irradiation device 100 may be installed in a small space such as the interior of a vehicle together with electronic devices used for driving the vehicle. In such cases, the distance between the vehicular irradiation device 100 and the electronic devices is likely to be short. Therefore, when electromagnetic waves generated in the discharge lamp 4, the lighting device 1, etc. installed inside the housing 2 are radiated to the outside of the housing 2, the electromagnetic waves may be incident on electronic devices installed near the vehicular irradiation device 100. When the electromagnetic waves are incident on electronic devices, they may become electromagnetic noise, which may cause malfunction of the electronic devices. Therefore, the vehicle irradiation device 100 according to this embodiment is provided with a shield 8.

[0056] The shield 8 prevents electromagnetic waves generated inside the housing 2 from radiating outside the housing 2. The shield 8 is conductive and can be provided on, for example, the outer wall of the housing 2. The shield 8 can be made of, for example, a metal such as aluminum. If the shield 8 is conductive, the reflection loss at the shield 8 can be increased, and therefore, the electromagnetic waves generated inside the housing 2 can be effectively prevented from radiating outside the housing 2.

[0057] In this case, a shield 8a can be provided on the outer wall of the first portion 21, and a shield 8b can be provided on the outer wall of the second portion 22. Then, at the connection portion 2a between the first portion 21 and the second portion 22, the shield 8a provided on the outer wall of the first portion 21 and the shield 8b provided on the outer wall of the second portion 22 can be made to come into contact with each other. For example, a shield 8a can be provided on the end of the first portion 21 on the opening side, and a shield 8b can be provided on the end of the second portion 22 on the opening side.

[0058] In this way, the shield 8a and the shield 8b can be electrically connected to each other, and therefore the shield 8a and the shield 8b can be electrically connected to the ground of the vehicle, which makes it possible to prevent a reduction in the shielding effect.

[0059] As described above, the window 7 has a plurality of openings that transmit ultraviolet rays and light emitted from the discharge lamp 4. Therefore, there is a risk that electromagnetic waves may be emitted to the outside of the housing 2 through the plurality of openings provided in the window 7. In this case, if a shield 8 is provided on the outer surface of the window 7, ultraviolet rays and light will not be irradiated to the outside of the housing 2.

[0060] Therefore, the window 7 is made to have electrical conductivity. The window 7 can be made of a metal such as aluminum.

[0061] If the window 7 is conductive, the reflection loss at the window 7 can be increased, as in the case of the above-described shield 8, and therefore it is possible to prevent electromagnetic waves from being emitted to the outside of the housing 2 through the window 7. Furthermore, if the window 7 is made of metal, it is possible to increase the resistance to ultraviolet rays irradiated from the discharge lamp 4.

[0062] Furthermore, if the window 7 is not electrically connected to the ground of the vehicle, the shielding effect of the window 7 may be reduced. Therefore, the window 7 can be electrically connected to a shield 8 provided on the housing 2.

[0063] Although several embodiments of the present invention have been described above, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, the above-described embodiments can be implemented in combination with each other. [Explanation of symbols]

[0064] 1 lighting device, 2 housing, 4 discharge lamp, 11 switching output circuit, 11a switching element, 11b switching element, 12 transformer, 13 resonance capacitor, 14 control circuit, 15 operating frequency setting circuit, 15a resistor, 15b thermosensitive element, 15c clamp element, 100 vehicle irradiation device, 200 DC power supply

Claims

1. A lighting device that applies a drive voltage of a predetermined operating frequency to a discharge lamp, a switching output circuit having a switching element and converting a DC voltage into an AC voltage at the operating frequency; a transformer having a primary winding electrically connected to the switching output circuit via a resonance capacitor and a secondary winding electrically connected to the discharge lamp, the inductance value of which has temperature characteristics; a control circuit electrically connected to the switching output circuit and generating a drive signal for the switching element; an operating frequency setting circuit electrically connected to the control circuit and having a resistor and a temperature sensing element connected in series with the resistor; Equipped with the control circuit sets the value of the operating frequency based on a value of a combined resistance of the resistor and the temperature sensitive element; a value of the combined resistance is set so that the value of the operating frequency set by the control circuit is greater than the value of a resonance frequency formed by the resonance capacitor and the transformer at a predetermined environmental temperature; The resistance value of the temperature-sensitive element decreases as the environmental temperature increases, the control circuit increases the set value of the operating frequency in accordance with the amount of decrease in the combined resistance. or The resistance value of the temperature-sensitive element increases as the environmental temperature decreases, The control circuit reduces the set value of the operating frequency in accordance with the increase in the combined resistance.

2. 2. The discharge lamp lighting device according to claim 1, wherein the operating frequency setting circuit further comprises a clamping element connected in parallel with the temperature sensitive element and applying a clamping voltage to the control circuit.

3. 3. The discharge lamp lighting device according to claim 2, wherein the clamp element is a diode or a Zener diode.

4. 4. The discharge lamp lighting device according to claim 1, wherein the temperature sensitive element is a negative temperature coefficient thermistor.

5. a discharge lamp; a discharge lamp lighting device according to any one of claims 1 to 4, electrically connected to the discharge lamp; A vehicle illumination device equipped with:

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