JPH0689791A - Electrodeless discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To supply high frequency power to a lamp stably with a high efficiency and make the light-output constant. CONSTITUTION:A lamp lighting device includes a DC power supply part, an inverter part to invert a DC power supplied thereby into a high frequency power, a lamp body 11 in which at least a discharging gas or vapor is encapsulated in a lamp tube, a lighting coil 9 installed in the neighborhood of or within the lamp body and, supplied with a high frequency power from the inverter, and a matching circuit at least composed of a series capacitor for resonance in series connection with the lighting coil and a parallel capacitor 9 for resonance in parallel connection with the lighting coil. The high frequency power is fed to the lamp body through a plasma ring within the lamp body coupled magnetically with the lighting coil, and thereby this discharge lamp of electrodeless type is lighted up. The parallel capacitor 9 is formed by sandwiching a dielectric body 14 having a negative temp. coefficient between two electrode plates 13a, 13a situated opposingly, and it is made possible to reduce the electrostatic capacitance of this capacitor 9 with increase of the temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrodeless discharge lamp for lighting a lamp by inputting high-frequency power from a lighting coil wound around the lamp body to a plasma ring in the lamp body which is magnetically coupled. The present invention relates to a lighting device, and more particularly to a lighting device capable of supplying high-frequency power to a lamp with high efficiency.

[0002]

2. Description of the Related Art In an electrodeless discharge lamp, a main tube of a lamp body made of quartz glass is formed into a spherical shape, and for example, krypton gas or a luminescent metal which is vaporized when excited is enclosed in the main tube. In this electrodeless discharge lamp, a lighting coil is wound around the lamp body for several turns (about 1 to 3 turns), and a short-wave band of several MHz or more is applied to the lighting coil from the inverter through a matching circuit. By passing the high frequency current of
The discharge gas or vapor in the lamp body is excited to form a plasma ring that is magnetically coupled to the coil. As a result, high-frequency power is supplied from the lighting coil to the plasma ring in the lamp body that is magnetically coupled, and the electrodeless discharge lamp is lit at high frequency. Such an electrodeless discharge lamp has excellent characteristics such as high efficiency, high brightness, high color rendering, and long life.

By the way, in order to improve the efficiency of such a lighting system, it is necessary to increase the generation efficiency of high frequency power. For this purpose, for example, a means of forming an inverter unit by a class D half bridge circuit using MOSFET as a switching element is adopted. In this case, by adjusting the phase so that the zero cross point of the current phase matches the zero cross point of the voltage phase in the inverter section, it is possible to switch in the state of zero volt, and the charging time of the switching element becomes zero. Thereby, the efficiency can be increased to 90% or more.

[0004]

However, the resonance circuit including the matching circuit connected to the inverter section and the lighting coil has a sharpness of resonance because it is necessary to efficiently supply a large amount of power for excitation to the lighting coil. (Q factor) is 300
The value is set to a very high value of up to 500, and even if the value of the capacitor forming the matching circuit or the inductance of the lighting coil slightly changes, the lighting output greatly changes. This variation in the inductance of the lighting coil causes the coil to reach a high temperature (200
To about 300 ° C.), and variations in the capacitance of the series resonance capacitor and the parallel resonance capacitor of the matching circuit are also due to the conduction heat from the heated lighting coil.

The present invention has been proposed in order to solve the problems of the prior art, and it is possible to stably and stably supply high-frequency power to the lamp with high efficiency and make the light output constant. An object of the present invention is to provide an electrodeless discharge lamp lighting device.

[0006]

In order to achieve this object, the present invention provides a DC power source section, an inverter section for converting the DC power source from the DC power source section into a high frequency power source, and at least a discharge characteristic in the lamp tube. A lamp main body filled with gas or vapor, a lighting coil arranged near or within the lamp main body, to which high-frequency power is supplied from the inverter unit, and a resonance coil connected in series to the lighting coil. A matching circuit composed at least of a series capacitor and a parallel capacitor for resonance connected in parallel to the lighting coil, and high-frequency power is supplied via a plasma ring in the lamp body magnetically coupled to the lighting coil. By inputting into this lamp body, in a lighting device that lights an electrodeless discharge lamp, a negative temperature is generated between opposing electrodes. Constitute the parallel capacitor by sandwiching a dielectric with a number, we are so used to reduce the electrostatic capacitance of the parallel capacitor with increasing temperature.
The temperature coefficient of this dielectric is preferably 100 ppm / K or more.

[0007]

According to the above-described structure, even if the inductance of the lighting coil that receives the heat of the lamp increases due to the thermal expansion, the capacitance of the parallel capacitor decreases by that amount.
Impedance fluctuation seen from the inverter section can be suppressed, and the electric power supplied from the inverter section to the lamp can be kept constant.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the electrodeless discharge lamp lighting device according to the present invention will be described in detail below with reference to the drawings. An example of this lighting device is shown in the block diagram of FIG. In this figure, the commercial AC power supply 1 is rectified and smoothed by the DC power supply unit 2, converted into a DC power supply, and sent to the inverter unit 3.
The inverter unit 3 is configured as a class D half-bridge type in which switching elements 4 and 5 composed of MOSFETs or the like are connected in series. By switching these switching elements 4 and 5 by the drive circuit 6, a DC power supply is about 13 MHz. Is converted to a high frequency power supply. The output terminal of the inverter unit 3 is connected to the lighting coil 10 via the matching circuit 7, and high frequency power is input from the lighting coil 10 into the lamp main body 11, whereby the electrodeless discharge lamp is lit at high frequency. It The matching circuit 7 includes a resonance series capacitor 8 connected in series to the lighting coil 10 and a resonance parallel capacitor 9 connected in parallel to the coil 10. A starter circuit 12 is connected in parallel to the lighting coil 10, and a high voltage for starting is applied to the glow capillary 11a of the lamp body 11 by operating the starter circuit 12 only when the lamp is started. , The lamp can be stably switched to the lighting state. The circuit constants of the series capacitor 8 are 340 pF and the parallel capacitor 9 is 500 pF.
The lighting coil 10 is set to about 165 nH.

Next, the structure of the parallel capacitor 9 will be described with reference to FIG. This parallel capacitor 9 has a length of 65
mm, the width is 130 mm, and the thickness is about 2 mm. Rectangular electrode plates 13a and 13b made of a copper plate or the like are overlapped with a gap of 0.2 mm between them. The dielectric 14 having a negative coefficient is closely sandwiched. The temperature coefficient of this dielectric 14 is preferably 100 ppm / K or more. As the dielectric 14, for example, an FEP resin plate or the like is used. The electrode plate 13a is connected to the series capacitor 8 and the electrode plate 13b is grounded. The lighting coil 10 is integrally formed with a metal plate that forms the electrode plates 13a and 13b. This is for shortening the power supply line to minimize high frequency loss and enabling effective power supply to the lighting coil 10.

In the electrodeless discharge lamp lighting device having such a structure, the dielectric 14 having a negative temperature coefficient is provided between the electrode plates 13a and 13b of the parallel capacitor 9 of the matching circuit 7.
Since the lighting coil 10 is sandwiched between the lighting coil 10 and the lighting coil 10 when it receives heat from the lamp and expands thermally, the inductance increases.
The capacitance of the parallel capacitor 9 whose temperature has risen decreases by that amount, and the increase in the inductance of the lighting coil 10 can be canceled. The dielectric 14 also has a function of compensating that the electrode plates 13a and 13b of the parallel capacitor 9 are thermally expanded to increase the capacitance. As a result, the load impedance of the matching circuit 7 and the lighting coil 10 viewed from the inverter unit 3 can be made constant irrespective of the temperature change, and after the lamp is lit as shown by the characteristic curve of G1 in FIG. The fluctuation of the lighting output of can be suppressed. In the figure, G2 is an output characteristic of a conventional lighting device in which a parallel capacitor is constituted by a high-voltage capacitor made of a normal monolithic ceramic.

[0011]

As described above, according to the present invention, the dielectric having a negative temperature coefficient is sandwiched between the electrodes of the parallel resonance capacitor connected to the lighting coil, so that when the heat of the lamp is received. Moreover, the capacitance of the parallel resonance capacitor can be reduced, and the increase in inductance due to the thermal expansion of the lighting coil can be suppressed. As a result, it is possible to suppress the impedance variation seen from the inverter unit,
High frequency power can be efficiently supplied to the lamp from the inverter unit, and the lighting output can be kept substantially constant regardless of the passage of time.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an electrodeless discharge lamp lighting device according to the present invention.

FIG. 2 is a perspective view showing a configuration of a parallel capacitor.

FIG. 3 is a characteristic diagram showing a temporal change of a lighting output in this lighting device.

[Explanation of symbols]

 1 Commercial AC Power Supply 2 DC Power Supply Section 3 Inverter Section 7 Matching Circuit 8 Series Capacitor 9 Parallel Capacitor 10 Lighting Coil 11 Lamp Body 11a Glow Capillary 12 Starter Circuit 13a, 13b Electrode Plate 14 Dielectric

Claims (2)

[Claims] 1. A DC power supply unit, an inverter unit for converting the DC power supply from this DC power supply unit into a high frequency power supply, a lamp body in which at least a discharge gas or vapor is sealed in a lamp tube, and the vicinity of the lamp body. Alternatively, a lighting coil arranged in the lamp body and supplied with high-frequency power from the inverter unit, a series capacitor for resonance serially connected to the lighting coil, and a parallel resonance coil connected in parallel to the lighting coil. A non-electrode discharge lamp is provided by inputting high-frequency power into the lamp body via a plasma ring in the lamp body that is magnetically coupled to the lighting coil, and has a matching circuit that is composed of at least a capacitor. In a lighting device for lighting, a parallel dielectric is formed by sandwiching a dielectric having a negative temperature coefficient between opposing electrodes. Configure, electrodeless discharge lamp lighting apparatus, characterized by being reduced electrostatic capacitance of the parallel capacitor with increasing temperature. 2. The temperature coefficient of the dielectric is 100 ppm /
It is K or more, The electrodeless discharge lamp lighting device of Claim 1 characterized by the above-mentioned.