JP2004273378A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve the purpose by adding a simple circuit structure to a discharge lamp (a fluorescent lamp) lighting device using an inverter circuit, in order to prevent glass of the discharge lamp from melting at worst when a filament is heated due to overvoltage impressed on it as the filament is in an emitter-less state that may happen at end of life of the discharge lamp. <P>SOLUTION: When the discharge lamp gets in an emitter-less state, a component is connected in parallel with each filament in order to restrain the overvoltage impressed on the filaments at both ends of the discharge lamp. As the component, a capacitor with a capacity with negligible influence of voltage and current on the surrounding circuits or zener diodes reversely connected with each other in series are used having no self-consumption of power at normal lighting. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an inverter-type discharge lamp lighting device for lighting a discharge lamp, which relates to an overvoltage treatment that occurs at the end of the life of the discharge lamp.
[0002]
[Prior art]
The discharge lamp apparatus receives power from a commercial AC power supply 10 as shown in FIG. A high-frequency alternating current is generated, and the discharge lamp 40 is lit at high frequency. When the discharge lamp reaches the end of its life, the emitters, which are the electron-emitting substances of the filaments F1 and F2 of the fluorescent lamp, decrease to be in an emitterless state, and a half-wave discharge occurs. If energization is continued in this half-wave discharge state, an abnormal state may occur in the discharge lamp.Therefore, the voltage and current generated in each part due to the half-wave discharge are detected and the discharge lamp reaches the end of its life. (For example, Patent Document 1) or a method of providing a bypass protection element (for example, Patent Documents 2 and 3). Has been taken.
[0003]
[Patent Document 1]
JP 2002-190396 A [Patent Document 2]
Japanese Patent Publication No. 10-199686 [Patent Document 3]
Japanese Unexamined Patent Publication No. Hei 7-135082
[Problems to be solved by the invention]
When the discharge lamp reaches the end of its life, the emitter of one of the filaments of the lamp decreases, and a half-wave discharge occurs. If the lighting is continued in this state, the state where the load is applied continues, and an abnormal state in which the filament is cut may occur. At this time, an overvoltage is applied to the filament portion, but the gap between the filament leads in the discharge lamp is not completely open due to the adhesion of the evaporated filament or metal powder of the broken filament, and has a certain resistance value. Therefore, current flows and the temperature of the glass tube of the discharge lamp rises. Glass is an insulator by nature, but as the temperature rises, the electrical resistance decreases and it conducts electricity, albeit slightly. As a result, the temperature of the glass tube further rises, and when the temperature reaches the melting point of the worst glass, the glass of the discharge lamp may melt. Since the end-of-life detection circuit applied as a countermeasure has two filaments, there is a problem that the circuit becomes complicated and the number of parts increases to detect that one of the filaments has reached the end of life. . Patent Document 2 discloses that at least one of the elements to be added is a diode. However, when a diode is added to at least one of them, there is no effect when an overvoltage is applied in a direction opposite to the direction in which the diode blocks, and the overvoltage is applied to the filament, so this is not a complete measure. When an abnormal state occurs, it is necessary to prevent an overvoltage from being applied to the filament under any conditions. Patent Literature 3 discloses a technique of connecting a resistor in parallel with a filament. However, even during normal lighting, the resistor self-consumes power, causing a constant loss, resulting in a reduction in efficiency and a reversal of energy saving. . In some cases, heat design of the entire circuit is required in consideration of heat generated by the resistor itself. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a discharge lamp lighting device capable of avoiding an overvoltage to a filament electrode in an abnormal state occurring at the end of life.
[0005]
[Means for Solving the Problems]
Therefore, in order to solve the above problem, the invention according to claim 1 is a discharge lamp lighting device using an inverter circuit, wherein a discharge lamp having two filaments is connected in series to the two filaments. And an element for suppressing an overvoltage applied to the two filaments is connected in parallel to the two filaments.
The invention according to claim 2 is the invention according to claim 1, wherein the discharge lamp is a fluorescent lamp.
[0006]
The invention according to claim 3 is characterized in that, in the invention according to claim 1 or 2, the voltage suppressing element is an element that does not consume energy by itself.
According to a fourth aspect of the present invention, in the second or third aspect, the element for suppressing the overvoltage is a capacitor.
The invention according to claim 5 is the invention according to claim 4, wherein the capacitance value of the capacitor is at least 80 times the capacitance value of the preheating capacitor.
The invention according to claim 6 is characterized in that, in the invention according to claim 2 or 3, the element for suppressing the overvoltage is a Zener diode connected in series and reversely connected to each other.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a first embodiment of the present invention. A DC power supply obtained by rectifying a commercial AC power supply 10 by a rectifier circuit 20 and smoothed by a capacitor (not shown) is connected to an inverter control circuit 30 serving as a discharge lamp lighting means. The inverter control circuit 30 is connected to semiconductor switching elements Q1 and Q2 such as FETs, IGBTs, and bipolar transistors. By alternately turning on and off Q1 and Q2, a high-frequency AC is generated to generate a discharge lamp 40. Is turned on at high frequency. Further, a preheating capacitor C1 is connected in series to two filaments of the discharge lamp, and when the discharge lamp is turned on, power is supplied to preheat the filament. Capacitors C4 and C5 are connected in parallel to the two filaments, respectively, and perform voltage division with C1 so that an overvoltage is not applied to the filament portions. It is required that the role of C1 be dominant in terms of the circuit function with respect to the voltage division, so that capacitors C4 and C5 having a capacity sufficiently larger than that of the preheating capacitor C1 should be used. Required. By connecting this capacitor, when a lamp abnormality occurs and the filament opens and a voltage is applied to both ends of the filament, C4 and C5 reduce the voltage across the filament by the voltage division ratio with C1. Can be. The capacity of C4 and C5 is 80 times or more the capacity of C1. If a capacity greater than this ratio is used, the filament will be applied to the filament when an error occurs, such as when the filament is opened, or when the lamp is disconnected due to the disconnection of the socket connecting the lamp and the inverter or the lead-in wire. The voltage at both ends can be kept close to the normal lighting state, and can be kept at a temperature rise that does not melt the glass. When the capacitors C4 and C5 having such capacities are inserted, the voltage and current do not affect the surroundings of the preheating capacitor C1, the lamp portion, and the like even in normal lighting without lamp abnormality.
[0008]
As a second embodiment, FIG. 2 shows a configuration in which zener diodes ZD1, ZD2 and ZD3, ZD4 are connected in series and reversely connected to respective filaments in parallel. When a voltage exceeding a predetermined voltage is applied, ZD1, ZD2, ZD3, and ZD4 conduct, so that the overvoltage applied to the filament portion can be suppressed to a certain voltage or less, and protection can be performed without passing through the filament portion. Further, in the normal lighting state, ZD1, ZD2, ZD3, and ZD4 are not conducting, so that unnecessary energy is not consumed.
[0009]
【The invention's effect】
According to the present invention, after the filament which may occur at the end of the life of the discharge lamp enters an emitterless state, it is avoided that an overvoltage is applied to the filament portion, and as a result of a rise in the glass temperature of the discharge lamp, heat is generated. Glass can be prevented from melting. In addition, since a special protection circuit function or the like is not used, the number of components can be reduced.
Furthermore, since an element that does not consume energy is used as the voltage control element, energy can be prevented from being wasted.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a first embodiment of the present invention. FIG. 2 is a circuit diagram showing a second embodiment of the present invention. FIG. 3 is a circuit diagram showing an example of a conventional discharge lamp device. Description]
DESCRIPTION OF SYMBOLS 10 Commercial AC power supply 20 Rectifier circuit 30 Inverter control circuit 40 Discharge lamp 50 Protection circuit Q1, Q2 Semiconductor switching element L Reactor C1, C2, C3, C4, C5 Capacitor ZD1, ZD2, ZD3, ZD4 Zener diode F1, F2 Filament

Claims (6)

In a discharge lamp lighting device using an inverter circuit, a discharge lamp having two filaments and a preheating capacitor connected in series to the two filaments are provided to suppress overvoltage applied to the two filaments. A discharge lamp lighting device, wherein an element is connected to each of the two filaments in parallel. The discharge lamp lighting device according to claim 1, wherein the discharge lamp is a fluorescent lamp. The discharge lamp lighting device according to claim 1, wherein the element that suppresses the voltage is an element that does not consume energy by itself. The discharge lamp lighting device according to claim 2, wherein the element that suppresses the overvoltage is a capacitor. The discharge lamp lighting device according to claim 4, wherein the capacitance value of the capacitor is at least 80 times the capacitance value of the preheating capacitor. The discharge lamp lighting device according to claim 2, wherein the element for suppressing the overvoltage is a Zener diode connected in series and reversely connected to each other.

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