Discharge lamp lighting device and vehicle illumination device

Abstract

To provide a lighting device for a discharge lamp capable of improving circuit efficiency, and an irradiation device for a vehicle.SOLUTION: A lighting device for a discharge lamp is configured to apply a drive voltage of predetermined frequency to a discharge lamp. The lighting device comprises: a first transformer which is electrically connected to one electrode of the discharge lamp; a second transformer which is electrically connected to the other electrode of the discharge lamp; and a switching output circuit which is electrically connected to a primary-side coil of the first transformer and a primary-side coil of the second transformer through a capacitor for resonance, and converts a DC voltage into an AC voltage of a predetermined frequency under PWM control.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 with pulse lighting circuits have been proposed as lighting devices for lighting dielectric barrier discharge lamps such as excimer lamps. By using a pulse lighting circuit, it is possible to provide a pause section in the current waveform of the discharge lamp during lighting, thereby improving the luminous efficiency of the discharge lamp. To further improve the luminous efficiency of discharge lamps, pulse lighting circuits using flyback circuits have also been proposed. However, typical pulse lighting circuits have a problem of poor circuit efficiency due to large power losses in the transformer and switching elements. Furthermore, poor circuit efficiency leads to increased heat generation from circuit components, making it difficult to miniaturize the lighting device. Therefore, there has been a demand for the development of a technology that can improve circuit efficiency. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-200690 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a discharge lamp lighting device and a vehicle illumination device that can improve circuit efficiency. [Means for solving the problem]

[0005] A discharge lamp lighting device according to an embodiment applies a drive voltage of a predetermined frequency to a discharge lamp, and includes: a first transformer electrically connected to one electrode of the discharge lamp; a second transformer electrically connected to the other electrode of the discharge lamp; a switching output circuit electrically connected to the primary winding of the first transformer and the primary winding of the second transformer via a resonance capacitor, and converting a DC voltage into an AC voltage of a predetermined frequency by PWM control; a detector that detects an output state of at least one of the first transformer and the second transformer; a comparator that compares the output state detected by the detector with a reference value to detect a fluctuation in the drive voltage caused by fluctuations in the DC voltage; and an LLC control circuit that inputs a PWM signal used for the PWM control to the switching output circuit; It is equipped with: The LLC control circuit changes the duty cycle of the PWM signal based on the amount of fluctuation in the drive voltage detected by the comparator. The detection unit is an auxiliary winding provided on at least one of the first transformer and the second transformer. [Effects of the Invention]

[0006] According to the embodiments of the present invention, it is possible to provide a discharge lamp lighting device and a vehicle illumination device that can improve circuit efficiency. [Brief explanation of the drawings]

[0007] [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] FIG. 10 is a circuit diagram illustrating a lighting device according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments will be illustrated with reference to the drawings. In each drawing, like components are designated by like reference numerals and detailed descriptions thereof will be omitted where appropriate. Although there is no particular limitation on the use of the discharge lamp lighting device according to the present embodiment, it can be used, for example, as a vehicle illumination device provided in vehicles such as automobiles, trains, etc. Therefore, the following will explain, as an example, a case where the discharge lamp lighting device is provided in a vehicle illumination device.

[0009] 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.

[0010] 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.

[0011] First, a lighting device 1 according to the present embodiment will be illustrated. As shown in FIG. 2, the lighting device 1 is 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.

[0012] 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 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.

[0013] 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 (which corresponds to an example of a first transformer and a second transformer), a resonance capacitor 13, a detection unit 14, and a control circuit 15.

[0014] The switching output circuit 11 is electrically connected to the primary windings of the two transformers 12 via a resonant capacitor 13. The switching output circuit 11 converts a DC voltage into an AC voltage of a predetermined frequency by PWM (Pulse Width Modulation) control. 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 switching output circuit 11 also changes the voltage applied to the primary windings of the transformers 12. The DC power supply 200 is, for example, a battery or a battery mounted on a vehicle such as an automobile.

[0015] The switching output circuit 11 illustrated in Fig. 3 is a half-bridge circuit, and includes, for example, a switching element 11a, a switching element 11b, and a drive circuit 11c.

[0016] 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.

[0017] The drive circuit 11c converts the DC voltage from the DC power supply 200 into an AC voltage of a predetermined frequency by alternately switching 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, for example, based on a control signal (PWM signal) from the control circuit 15. For example, the frequency is about 100 kHz to 300 kHz. Furthermore, the drive circuit 11c can change the output voltage (the voltage applied to the primary winding of the transformer 12) by changing the duty ratio based on the PWM signal from the control circuit 15. 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.

[0018] Two transformers 12 are provided. As described above, the primary windings of the two transformers 12 are electrically connected to the switching output circuit 11. The secondary winding of one transformer 12 is electrically connected to one electrode of the discharge lamp 4. The secondary winding of the other transformer 12 is electrically connected to the other electrode of the discharge lamp 4. In other words, a double high voltage discharge is formed with the midpoint of the transformer 12 as the ground (reference).

[0019] Here, if the discharge lamp 4 is simply lit with a sine wave AC current, the circuit efficiency will be poor. As a result, the luminous efficiency of the discharge lamp 4 may be reduced. The lighting device 1 according to this embodiment is provided with an LLC resonant circuit having a switching output circuit 11, a transformer 12, and a resonant capacitor 13, which reduces the switching loss of the circuit. This improves the circuit efficiency, thereby improving the total efficiency including the discharge lamp 4 and the circuit.

[0020] Furthermore, since the circuit efficiency can be improved, the amount of heat generated by the circuit components can be reduced and the lighting device 1 can 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 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 becomes easier.

[0021] Here, the DC voltage from the DC power supply 200 may fluctuate significantly. For example, the lighting device 1 provided in the vehicle illumination device 100 is electrically connected to a DC power supply 200 (for example, a battery) provided in a vehicle such as an automobile. Generally, the rated voltage of the DC power supply 200 provided in a vehicle such as an automobile is about 13.5V.

[0022] However, in reality, the voltage of the DC power supply 200 may fluctuate, for example, within a range of 9V to 16V due to factors such as a drop in battery voltage, the operation of the alternator, and circuit influences. If the fluctuation in the voltage input to the lighting device 1 becomes large, the fluctuation in the drive voltage output from the lighting device 1 and applied to the discharge lamp 4 also becomes large. If the fluctuation in the drive voltage becomes large, there is a risk that the amount of light, ultraviolet light, etc. irradiated from the discharge lamp 4 may become unstable.

[0023] Therefore, the lighting device 1 is provided with a detection unit 14 and a control circuit 15. The detector 14 detects the output state of the transformer 12. For example, the detector 14 can be provided in each of the two transformers 12. The detector 14 can be, for example, an auxiliary winding provided in the transformer 12. If the detector 14 is an auxiliary winding, it is possible to detect the current flowing in the secondary winding of the transformer 12 (the output state of the transformer 12) by detecting the current flowing in the auxiliary winding.

[0024] Based on the output state of the transformer 12 detected by the detector 14, the control circuit 15 inputs an appropriate PWM signal to the switching output circuit 11 (drive circuit 11c). The control circuit 15 includes, for example, a PWM control circuit 15a, a comparator 15b, a reference voltage unit 15c, and an LLC control circuit 15d.

[0025] The PWM control circuit 15a generates a PWM signal. The comparator 15b compares the output state of the transformer 12 detected by the detection unit 14 with a reference value from the reference voltage unit 15c to detect the amount of fluctuation in the drive voltage caused by fluctuations in the DC voltage. For example, the comparator 15b compares a voltage based on the current detected by the detection unit 14 with the reference voltage from the reference voltage unit 15c. In this way, it is possible to detect the amount of fluctuation in the drive voltage applied to the discharge lamp 4 caused by voltage fluctuations in the DC power supply 200.

[0026] The LLC control circuit 15d inputs a PWM signal used for PWM control to the switching output circuit 11 (drive circuit 11c). The LLC control circuit 15d changes the duty ratio of the PWM signal generated by the PWM control circuit 15a based on the amount of fluctuation in the drive voltage applied to the discharge lamp 4 detected by the comparator 15b. For example, when the drive voltage applied to the discharge lamp 4 becomes lower than a reference value (when the voltage of the DC power supply 200 decreases), the LLC control circuit 15d increases the duty ratio of the PWM signal in accordance with the amount of decrease in the drive voltage applied to the discharge lamp 4. For example, when the drive voltage applied to the discharge lamp 4 becomes higher than the reference value (when the voltage of the DC power supply 200 increases), the LLC control circuit 15d decreases the duty ratio of the PWM signal in accordance with the amount of increase in the drive voltage applied to the discharge lamp 4. That is, the control circuit 15 performs feedback control of the switching output circuit 11 (drive circuit 11c) based on the output state of the transformer 12 detected by the detection unit 14.

[0027] The lighting device 1 according to this embodiment is provided with the detection unit 14 and the control circuit 15, and therefore, even if the voltage of the DC power supply 200 fluctuates, it is possible to suppress fluctuations in the drive voltage applied to the discharge lamp 4. Therefore, even if the voltage of the DC power supply 200 fluctuates, it is possible to stabilize the amount of light, ultraviolet rays, etc. irradiated from the discharge lamp 4.

[0028] Furthermore, the LLC resonant circuit having the switching output circuit 11, the transformer 12, and the resonant capacitor 13 is operated intermittently by PWM control, so that even if the voltage of the DC power supply 200 fluctuates, the peak value of the drive voltage applied to the discharge lamp 4 can be maintained. Therefore, the amount of light, ultraviolet rays, etc. irradiated from the discharge lamp 4 can be stabilized.

[0029] FIG. 4 is a circuit diagram illustrating a lighting device 1a according to another embodiment. As shown in FIG. 4, the lighting device 1a includes a switching output circuit 11, a transformer 12, a resonance capacitor 13, a detection unit 14, and a control circuit 15, for example. The configuration of lighting device 1a can be the same as the configuration of lighting device 1 described above. However, in the case of lighting device 1 described above, a detector 14 is provided for each of the two transformers 12. In contrast, in the case of lighting device 1a, a detector 14 is provided for one of the two transformers 12. In other words, it is sufficient that detector 14 detects the output state of at least one of the two transformers 12. For example, when the characteristics of the transformers 12 are stable, the above-described feedback control may be performed based on the output state of one transformer 12. In this way, the lighting device 1a can be made smaller and less expensive.

[0030] 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. As shown in FIGS. 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 thickness dimension T of the housing 2 can be smaller than the planar dimension of the housing 2. The vehicle illumination device 100 may be installed in a narrow space such as the interior of a vehicle together with electronic devices used for operating the vehicle. Therefore, if the thickness dimension T of the housing 2 can be reduced, the vehicle illumination device 100 can be easily installed.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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. 1 to 4 show an example in which one discharge lamp 4 is provided, a plurality of discharge lamps 4 may be provided. It is sufficient that at least one discharge lamp 4 is provided.

[0036] 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).

[0037] 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 opening on the side opposite to 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.

[0038] 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.

[0039] 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.

[0040] One end of the wiring is electrically connected to the lighting device 1 inside the housing 2. The other end of the wiring is drawn out to the outside of the housing 2 and electrically connected to a DC power supply 200, for example.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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, for example, on the outer wall of the housing 2. 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.

[0045] 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, the shield 8a can be provided also on the end portion on the opening side of the first portion 21, and the shield 8b can be provided also on the end portion on the opening side of the second portion 22.

[0046] 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.

[0047] 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.

[0048] Therefore, the window 7 is made to have electrical conductivity. For example, the window 7 is made of an electrically conductive material. The electrically conductive material may be the same as the electrically conductive material used for the shield 8. In this case, if the electrically conductive material is a metal, it is possible to increase resistance to ultraviolet rays irradiated from the discharge lamp 4.

[0049] If the window 7 is conductive, the reflection loss at the window 7 can be increased, as in the case of the shield 8 described above, and thus the radiation of electromagnetic waves to the outside of the housing 2 through the window 7 can be suppressed.

[0050] 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.

[0051] 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]

[0052] 1 lighting device, 1a lighting device, 2 housing, 4 discharge lamp, 11 switching output circuit, 11a switching element, 11b switching element, 11c drive circuit, 12 transformer, 13 resonance capacitor, 14 detection unit, 15 control circuit, 15a PWM control circuit, 15b comparator, 15c reference voltage unit, 15d LLC control circuit, 100 vehicle irradiation device, 200 DC power supply

Claims

1. A lighting device that applies a drive voltage of a predetermined frequency to a discharge lamp, a first transformer electrically connected to one electrode of the discharge lamp; a second transformer electrically connected to the other electrode of the discharge lamp; a switching output circuit electrically connected to the primary winding of the first transformer and the primary winding of the second transformer via a resonance capacitor, and configured to convert a DC voltage into an AC voltage of a predetermined frequency by PWM control; a detection unit that detects an output state of at least one of the first transformer and the second transformer; a comparator that compares the output state detected by the detection unit with a reference value to detect the amount of fluctuation in the drive voltage caused by fluctuations in the DC voltage; an LLC control circuit that inputs a PWM signal used for the PWM control to the switching output circuit; Equipped with the LLC control circuit changes the duty ratio of the PWM signal based on the amount of fluctuation in the drive voltage detected by the comparator; The discharge lamp lighting device, wherein the detection unit is an auxiliary winding provided on at least one of the first transformer and the second transformer.

2. 2. The discharge lamp lighting device according to claim 1, wherein the LLC control circuit intermittently controls the switching output circuit.

3. A vehicle illumination device provided in a vehicle; a discharge lamp; a discharge lamp lighting device according to claim 1 or 2, electrically connected to the discharge lamp; A vehicle illumination device equipped with:

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