JP2002203695A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent abnormal heating of the filament and base part of the discharge lamp when one of the filaments of the hot cathode type discharge lamp in which resonance capacitor is connected in parallel is broken. SOLUTION: The discharge lamp lighting device comprises an inverter circuit INV of half-bridge type that converts the DC power source output obtained from the AC power source AC into a high frequency output and supplies to the discharge lamp La. An impedance element Z is connected in series with a resonance capacitor C2 on non-power source side of the filament f1, f2 of the discharge lamp La made of a fluorescent lamp. Even when one of the filaments f1 or f2 of the discharge lamp La is broken, and the charged electric charge of the capacitor C2 is rapidly discharged through the discharge lamp La, the impedance element Z becomes a current limiting factor and the pulse current is suppressed. Thereby, the abnormal heating of the filament f1 or f2 or base part of the discharge lamp La can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting apparatus for lighting a hot cathode discharge lamp by converting a DC voltage to a high frequency voltage.

[0002]

2. Description of the Related Art In recent years, as a discharge lamp lighting device for lighting a discharge lamp such as a fluorescent lamp, a DC voltage generated from an AC power supply such as a commercial power supply is converted into a high frequency voltage by an inverter circuit, and the discharge lamp is lit at a high frequency. Discharge lamp lighting devices are rapidly spreading. There are various types of fluorescent lamps, such as straight tube fluorescent lamps and ring-shaped fluorescent lamps. From the viewpoint of resource saving and energy saving, the size and weight of lighting fixtures and the efficiency of discharge lamps are improved. For this purpose, there is a growing demand for a fluorescent lamp dedicated to high-frequency lighting having a smaller tube diameter than usual. In addition, as a fluorescent lamp with further miniaturization, a so-called single-ended fluorescent lamp (compact fluorescent lamp), in which a glass tube having filaments disposed at both ends thereof is bent so that both filaments are adjacent to one side, has also become widespread. It is getting. As such a single-necked fluorescent lamp, for example, 2
Main type (P type) FPL (Trade name: Twin 1 fluorescent lamp),
4-tube (D-type) FDL (trade name: twin 2 fluorescent lamp), 4-tube (M-type) FML (trade name: twin 2 parallel fluorescent lamp), 6-tube FHT (trade name) : Twin 3
Fluorescent lights) are commercially available. In these single-base fluorescent lamps, the base is formed of synthetic resin.

[0003] There are two types of fluorescent lamps, a hot cathode type and a cold cathode type. For applications such as home use, facility use, and store use, hot cathode type fluorescent lamps are used from the viewpoint of lamp life. Commonly used. Hereinafter, a hot cathode fluorescent lamp will be described.
The fluorescent lamp refers to a hot cathode fluorescent lamp.

[0004] The basic principle of such a fluorescent lamp is to cause a fluorescent substance applied on the inner wall of the glass tube to emit light by a discharge phenomenon between filaments arranged at both ends of the glass tube. The filament is formed mainly of tungsten, and the surface is coated with a thermionic emitting material (emitter). The discharge is maintained by emitting a thermoelectron from the emitter by applying a current to the filament. .

[0005]

By the way, the emitter applied to the filament gradually decreases due to consumption (or evaporation) or scattering with the lighting of the fluorescent lamp, and the emitter is exhausted at the end of the life of the fluorescent lamp. It is well-known that the state becomes a so-called Emiless state. In such an Emiless state, it is difficult to emit thermoelectrons from the filament having no emitter, and the so-called half-wave discharge mode (or the half-wave lighting mode) discharges by thermionic emission from the filament where the emitter remains. ). In this half-wave discharge mode, power is concentrated on a portion near the filament due to an increase in the resistance value of the filament in the Emiless state and an increase in the cathode drop. As a result, the filament is abnormally heated, so that the glass near the filament is abnormally heated. The heat is conducted to the tube, and the base near the filament may be discolored or thermally deformed by the heat. In particular, it has recently been found that when the filament breaks due to abnormal heating, the vicinity of the filament is further abnormally heated.

For example, the conventional discharge lamp lighting device shown in FIG. 8 is a DC power supply that obtains a DC voltage from an AC power supply AC that is a commercial power supply, and a discharge lamp (fluorescent lamp) that converts the output of the DC power supply into a high-frequency output. A so-called half-bridge type inverter circuit INV for supplying La. Here, the DC power supply includes a filter circuit F for removing harmonic noise from an output of the AC power supply AC, a rectifier circuit DB including a diode bridge for full-wave rectifying the AC power supply AC via the filter circuit F, and a rectifier circuit DB. And a smoothing capacitor C0 for smoothing the pulsating flow output of. The inverter circuit INV has a pair of switching elements Q1 and Q2 composed of MOSFETs connected in series to both ends of a smoothing capacitor C0, and a resonance inductor L, a discharge lamp La and a resonance capacitor connected to both ends of a low-side switching element Q2. C2
Are connected via a DC cut capacitor C1. Note that the inductor L is connected to the power supply side of one filament f1 of the discharge lamp La, and the capacitor C2 is connected to the non-power supply side of both filaments f1 and f2. Further, the inverter circuit INV includes a control circuit CNT that supplies a drive signal to the gates of the switching elements Q1 and Q2. In this configuration, the pair of switching elements Q1 and Q2 are alternately turned on and off at a high frequency by the control circuit CNT, so that the inductor L and the capacitor C2 resonate to generate a resonance voltage at both ends of the capacitor C2. A high-frequency alternating current is supplied to start and discharge the discharge lamp La at a high frequency.

Here, in the above conventional example, one filament (for example, f2) of the discharge lamp La as shown in FIG.
Is in the Emiless state, the discharge lamp La
A lamp current I _La having a waveform as shown in FIG. 7A flows, and a charging voltage (resonance voltage) V _C2 as shown in FIG. 7B is applied to the resonance capacitor _C2 . That is, when the filament f2 enters the emiless state, the lamp current I _La flows from the filament f2 to the filament f1 in the discharge lamp La, and the capacitor C2 is charged with electric charge in a direction in which the filament f1 has a high potential. Further, when the filament f2 is broken, as shown in FIG. 11, a substance such as an emitter scattered in the glass tube or tungsten forming the filament f2 is deposited on the lead wires 10 supporting the filament f2. The deposited material 11 causes a short circuit between the two lead wires 10, 10 via a resistor, and a discharge spot is formed on the lead wire 10 supporting the broken filament f2 due to the discharge spot at the time of disconnection. A phenomenon in which the discharge continues between f1 and f1 (hereinafter, referred to as a “discharge continuation phenomenon”) rarely occurs. When the discharge continuation phenomenon occurs, FIG.
As shown in FIG. 2 (b), the voltage V _C2 across the capacitor C2 further increases, and finally, the charge of the capacitor C2 is rapidly discharged via the discharge lamp La, and as shown in FIG. In some cases, a pulse current having a high peak value flows as the lamp current I _La . In actual measurement, although it varies depending on conditions, a pulse current having a peak value of several tens of amperes may flow. When a pulse current having a very high peak value flows between the filament f1 and the lead wire 10 as described above, the lead wire 10 is abnormally heated, and the stem and the base are abnormally heated through the lead wire 10. Here, the base portion is formed of a resin material that does not cause discoloration or thermal deformation due to a rise in temperature during normal lighting. Discoloration and thermal deformation may occur.

By the way, the above phenomenon is not limited to the case where the resonance capacitor is connected to the power supply side of the filament of the discharge lamp, but the filament f1 of the discharge lamp La as in the conventional example shown in FIG. This may also occur when a resonance capacitor C2 is connected to the non-power supply side of f2. That is, the above phenomenon does not occur if the electrical connection between the discharge lamp La and the capacitor C2 is cut due to the disconnection of the filament f2. However, in general, the high frequency operation of the discharge lamp La is performed at a higher frequency than the ionization frequency. Since plasma always exists in the glass tube of the discharge lamp La, the plasma is often electrically connected to the capacitor C2 through the plasma. Therefore, in a circuit configuration in which the capacitor C2 is connected in parallel with the filaments f1 and f2 of the hot cathode discharge lamp La, if the filament f1 or f2 on one side breaks, the above-described phenomenon always occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method in which one filament of a hot cathode discharge lamp having a resonance capacitor connected in parallel is broken. An object of the present invention is to provide a discharge lamp lighting device in which a filament or a base of a discharge lamp is prevented from being abnormally heated.

[0010]

According to a first aspect of the present invention, a DC power supply, one or more switching elements, a resonance inductor and a capacitor, and an output of the DC power supply having a high frequency are provided. An inverter circuit for converting the output to a hot cathode type discharge lamp, and connecting a resonance capacitor between filaments of the discharge lamp. It is characterized in that a current limiting impedance element is provided in a closed circuit, one of the filaments of the discharge lamp is broken, and the discharge continuation phenomenon described in the prior art occurs, and the resonance capacitor is charged via the discharge lamp. Even when the electric charge is suddenly discharged, the pulse current is suppressed by the impedance element connected in series with the capacitor as a current limiting element. Therefore, it is possible to prevent the filament and the base of the discharge lamp from being abnormally heated when one of the filaments of the hot cathode discharge lamp to which the resonance capacitor is connected in parallel is broken.

According to a second aspect of the present invention, in the first aspect, a resonance capacitor is connected to a power supply side of the filament, and a power supply for preheating the filament is provided without passing through the capacitor. This has the same effect as the first aspect of the present invention.

A third aspect of the present invention is characterized in that, in the first aspect of the present invention, the resonance capacitor is connected to the non-power supply side of the filament, and has the same effect as the first aspect of the present invention.

[0013] The invention of claim 4 is the invention of claim 1 or 2 or 3.
2. The invention according to claim 1, wherein the DC power supply comprises: an AC power supply; a rectifier circuit for rectifying the AC power supply; and a chopper circuit for intermittently connecting the rectified output of the rectifier circuit to obtain a desired DC output. Or, the same effect as the second or third invention is exerted.

According to a fifth aspect of the present invention, in the second aspect, the preheating power source comprises a secondary winding and a tertiary winding provided on the resonance inductor, and a secondary winding and a tertiary winding. It comprises a DC cut capacitor connected between the filaments, and has the same effect as the second aspect of the present invention.

According to a sixth aspect of the present invention, a DC power supply, one or more switching elements, an inductor for resonance, and a capacitor are provided. A discharge lamp lighting device comprising an inverter circuit for supplying a cathode-type discharge lamp and a resonance capacitor connected between filaments of the discharge lamp, a detection for detecting a current flowing through the filament via the resonance capacitor. Means, determining means for determining whether the current level detected by the detecting means exceeds a predetermined threshold, and performing switching control of the switching element when the determining means determines that the current level exceeds the threshold. Control means for lowering or stopping the output of the inverter circuit, and one of the filaments of the discharge lamp is disconnected. When the discharge continuation phenomenon described in the paragraph (1) occurs and the charge of the resonance capacitor is rapidly discharged via the discharge lamp, the peak value of the pulse current due to this discharge is detected by the detecting means, and the threshold value is determined by the determining means. If it is determined that the output voltage exceeds the threshold value, the control means performs switching control of the switching element to reduce or stop the output of the inverter circuit. Therefore, the pulse current is suppressed by reducing or stopping the output of the inverter circuit. When one of the filaments of a hot-cathode type discharge lamp connected in parallel with a capacitor for use in a discharge lamp breaks, it is possible to prevent the filament and the base of the discharge lamp from being abnormally heated.

According to a seventh aspect of the present invention, in the sixth aspect, the resonance capacitor is connected to the non-power supply side of the filament and the detecting means is connected in series to the ground side of the resonance capacitor. The same operation as that of the sixth aspect is achieved.

According to an eighth aspect of the present invention, in the sixth aspect, the resonance capacitor is connected to the power supply side of the filament, and the detecting means is connected in series to the ground side of the resonance capacitor. The same effect as the invention of Item 6 is exerted.

[0018]

(Embodiment 1) A discharge lamp lighting device according to the present embodiment shown in FIG.
The same circuit configuration as the conventional example including a DC power supply that obtains a DC voltage by C and a half-bridge type inverter circuit that converts the output of the DC power supply into a high-frequency output and supplies the output to the discharge lamp La, includes a fluorescent lamp. The resonance capacitor C2 is connected to the non-power supply side of the filaments f1 and f2 of the discharge lamp La.
It is characterized in that an impedance element Z is connected in series with the above. The same components as those of the conventional example are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, the discharge lamp La
When one of the filaments f1 or f2 is disconnected, the discharge continuation phenomenon described in the related art occurs, and the charge of the capacitor C2 is rapidly discharged via the discharge lamp La,
The impedance element Z connected in series with the capacitor C2 serves as a current limiting element to suppress the pulse current. For this reason, when one of the filaments f1 or f2 of the hot-cathode discharge lamp La to which the resonance capacitor C2 is connected in parallel is broken, the filament f1 or f2 of the discharge lamp La and the base are abnormally heated. In particular, it is possible to prevent discoloration and deformation of the base portion due to heat in a single-base fluorescent lamp in which the base portion is formed of a synthetic resin.

By the way, as shown in FIG.
A boost chopper circuit CH may be provided between and the smoothing capacitor C0. This step-up chopper circuit CH has a conventionally well-known configuration, and includes a series circuit of a choke coil L0 and a diode D1 between an output terminal on the high potential side of a rectifier circuit DB and one end on a high potential side of a smoothing capacitor C0. A switching element Q3 composed of a MOSFET is connected between the anode of the diode D1 and the output terminal on the low potential side of the rectifier circuit DB, and the chopper control circuit 1 turns the switching element Q3 on and off at a high frequency. The DC voltage obtained by boosting the power supply voltage of the AC power supply AC is supplied to both ends of the smoothing capacitor C0. Also in such a circuit configuration, the impedance element Z serves as a current limiting element, so that a pulse current when a discharge continuation phenomenon occurs can be suppressed.

(Embodiment 2) The discharge lamp lighting device according to the present embodiment shown in FIG. 3 includes a series circuit of a resonance capacitor C2 and an impedance element Z, and a filament f of the discharge lamp La.
1, f2, and a preheating power supply 2,
2 is characterized in that the filaments f1 and f2 are preheated, and the other configurations are common to the conventional example and the first embodiment. Therefore, common components are denoted by the same reference numerals. Is omitted.

As described in the prior art, in the circuit configuration in which the resonance capacitor C2 is connected to the power supply side of the filaments f1 and f2, the filaments f1 and f2 of the discharge lamp La are used.
The discharge continuation phenomenon is more likely to occur when one of the filaments f1 or f2 of the discharge lamp La is disconnected than the circuit configuration in which the capacitor C2 is connected to the non-power supply side of the discharge lamp La. Thus, also in the present embodiment, as in the first embodiment, the impedance element Z connected in series with the capacitor C2 serves as a current limiting element to suppress the pulse current, so that one filament f1 of the discharge lamp La is used. Or, when the wire f2 is disconnected, it is possible to prevent the filament f1 or f2 of the discharge lamp La and the base from being abnormally heated.

(Embodiment 3) In the discharge lamp lighting device of this embodiment shown in FIG. 4, a secondary winding n2 and a tertiary winding n3 provided in a resonance inductor L are connected to a DC cut capacitor C.
It is characterized in that the preheating power supplies 2 and 2 are configured by connecting in series to the filaments f1 and f2 via C3 and C4, and the other configuration is common to the conventional example and the second embodiment. The same reference numerals are given to the same constituent elements, and the description is omitted.

In the present embodiment, a high-frequency voltage is induced in the secondary winding n2 and the tertiary winding n3 by the resonance current flowing through the inductor L, and the preheating current flows through the filaments f1 and f2 with the high-frequency voltage. Is preheating. In this embodiment, as in the second embodiment, the impedance element Z connected in series with the capacitor C2 serves as a current limiting element to suppress the pulse current.
When one of the filaments f1 or f2 is disconnected, it is possible to prevent the filament f1 or f2 of the discharge lamp La and the base from being abnormally heated.

As shown in FIG. 5, a resonance circuit composed of a series circuit of a capacitor C5 and an inductor L2 is connected in parallel with the capacitor C1 and the switching element Q2, and a secondary winding n2 and a tertiary winding provided on the inductor L2. The preheating power supplies 2 and 2 may be configured by connecting the line n3 in series to the filaments f1 and f2 via the DC cut capacitors C3 and C4.

(Embodiment 4) The discharge lamp lighting device of the present embodiment shown in FIG.
And a detection circuit 3 connected in series to the ground side of the resonance capacitor C2 on the non-power supply side of the device for detecting the level of the current flowing through the capacitor C2, and determining whether the current level detected by the detection circuit 3 exceeds a predetermined threshold. And if a current exceeding the threshold value flows, the control circuit C of the inverter circuit INV
A determination circuit 4 for outputting an abnormality detection signal to the NT, and when the abnormality detection signal is input from the determination circuit 4, the control circuit CNT suppresses the pulse current when the inverter circuit I
It is characterized by controlling NV. The same components as those of the conventional example are denoted by the same reference numerals, and description thereof will be omitted.

When one of the filaments f1 or f2 of the discharge lamp La breaks and the discharge continuation phenomenon described in the related art occurs, the charge of the capacitor C2 is rapidly discharged through the discharge lamp La. The peak value of the pulse current due to this discharge is detected by the detection circuit 3 and compared with the threshold value by the determination circuit 4. Here, the threshold value is set to a value sufficiently higher than the detection level of the current flowing through the capacitor C2 at the time of steady lighting or normal preheating, and lower than the detection level of the current flowing by discharging the capacitor C2 at the time of occurrence of the discharge continuation phenomenon. . Therefore, the discrimination circuit 4 outputs an abnormality detection signal to the control circuit CNT when the detection level of the pulse current due to the discharge exceeds the threshold value. In the control circuit CNT receiving this abnormality detection signal, the switching elements Q1, Q2
The switching frequency of the inverter circuit IN
V output or switching element Q
1, the switching of Q2 is stopped and the inverter circuit IN
The output of V is stopped. As a result, the inverter circuit INV
Is reduced or stopped, the pulse current is suppressed, and when one of the filaments f1 or f2 of the hot-cathode discharge lamp La connected in parallel with the resonance capacitor C2 is disconnected, the filament of the discharge lamp La is disconnected. f1 or f2
And the base portion can be prevented from being abnormally heated.

(Embodiment 5) A discharge lamp lighting device according to the present embodiment shown in FIG. 7 is different from the circuit configuration of Embodiment 3 in that the detection circuit 3 and the discrimination circuit 4 in Embodiment 4 are provided instead of the impedance element Z. There is a feature in this point, and other configurations are common to the third and fourth embodiments. Therefore, common components are denoted by the same reference numerals and description thereof is omitted.

Thus, in the present embodiment, the fourth embodiment
Similarly, one of the filaments f1 or f1 of the discharge lamp La
2 is disconnected, the discharge continuation phenomenon described in the related art occurs, and the charge of the capacitor C2 is rapidly discharged through the discharge lamp La, the pulse current due to this discharge is detected by the detection circuit 3, and the determination circuit 3 In 4, when the detection level of the pulse current exceeds the threshold value, an abnormality detection signal is output to the control circuit CNT. The control circuit C receiving this abnormality detection signal
In NT, the output of the inverter circuit INV is reduced by changing the switching frequency of the switching elements Q1 and Q2, or the switching of the switching elements Q1 and Q2 is stopped to stop the output of the inverter circuit INV. As a result, the pulse current is suppressed by the output of the inverter circuit INV being reduced or stopped, and the hot-cathode discharge lamp La to which the resonance capacitor C2 is connected in parallel.
When one of the filaments f1 or f2 is disconnected, it is possible to prevent the filament f1 or f2 of the discharge lamp La and the base from being abnormally heated.

The circuit configuration for preheating the inverter circuit INV and the filaments f1 and f2 in the first to fifth embodiments is merely an example, and the technical concept of the present invention can be applied to other circuit configurations. Further, the present invention, when using an inverter circuit corresponding to a plurality of types of discharge lamps having the same filament characteristics and different rated power, without being particularly affected by the lamp characteristics,
The above-described abnormal pulse current can be suppressed.

[0031]

According to a first aspect of the present invention, there is provided a hot cathode type discharge lamp including a DC power supply, one or more switching elements, a resonance inductor and a capacitor, and converting the output of the DC power supply into a high frequency output. And an inverter circuit for supplying
In a discharge lamp lighting device in which a capacitor for resonance is connected between filaments of a discharge lamp, an impedance element for current limiting is provided in a closed circuit between the capacitor for resonance and the discharge lamp. Is disconnected, the discharge continuation phenomenon described in the prior art occurs, and even if the charge of the resonance capacitor is rapidly discharged via the discharge lamp, the impedance element connected in series with the capacitor is a current limiting element. As a result, the pulse current is suppressed to prevent abnormal heating of the discharge lamp filament and the base when one of the filaments of the hot cathode discharge lamp connected in parallel with the resonance capacitor is broken. There is an effect that can be.

According to a second aspect of the present invention, in the first aspect, a resonance capacitor is connected to a power supply side of the filament, and a preheating power supply for preheating the filament without passing through the capacitor is provided. The same effect as that of the first invention is exerted.

According to a third aspect of the present invention, since the resonance capacitor is connected to the non-power supply side of the filament in the first aspect of the invention, the same effect as the first aspect of the invention can be obtained.

The invention of claim 4 is the invention of claim 1 or 2 or 3
Since the DC power supply includes an AC power supply, a rectifier circuit for rectifying the AC power supply, and a chopper circuit for intermittently outputting the rectified output of the rectifier circuit to obtain a desired DC output, the DC power supply according to claim 1 or 2 or The same effect as that of the third invention is exerted.

According to a fifth aspect of the present invention, in the second aspect, the preheating power source comprises a secondary winding and a tertiary winding, a secondary winding and a tertiary winding provided on a resonance inductor. Since the DC cut capacitor is connected between the filaments, the same effect as that of the second aspect of the invention can be obtained.

According to a sixth aspect of the present invention, there is provided a DC power source, one or more switching elements, a resonance inductor and a capacitor, and the output of the DC power source is converted into a high-frequency output and supplied to a hot cathode type discharge lamp. In a discharge lamp lighting device comprising an inverter circuit and a resonance capacitor connected between filaments of the discharge lamp, a detection means for detecting a current flowing through the filament via the resonance capacitor,
Determining means for determining whether or not the current level detected by the detecting means exceeds a predetermined threshold; and performing inverter control by performing switching control of the switching element when the determining means determines that the current level exceeds the threshold. Control means for reducing or stopping the output of the discharge lamp, one of the filaments of the discharge lamp is broken, the discharge continuation phenomenon described in the related art occurs, and the charge of the resonance capacitor is discharged through the discharge lamp. In the case of a sudden discharge, the peak value of the pulse current due to this discharge is detected by the detecting means, and when it is determined that the threshold value is exceeded by the determining means, the controlling means performs switching control of the switching element to perform the inverter circuit. In order to reduce or stop the output of the inverter circuit, the output of the inverter circuit is reduced or stopped, whereby the pulse current is suppressed, and the capacitor for resonance is not provided. There is an effect that it is possible filaments or the base part of the discharge lamp when one of the filament of the discharge lamp connected hot-cathode is broken is prevented from abnormal heating.

According to a seventh aspect of the present invention, in the sixth aspect, the resonance capacitor is connected to the non-power supply side of the filament and the detecting means is connected in series to the ground side of the resonance capacitor. The same effect as that of the invention is achieved.

According to an eighth aspect of the present invention, in the sixth aspect, the resonance capacitor is connected to the power supply side of the filament and the detecting means is connected in series to the ground side of the resonance capacitor. The same effects as those of the present invention can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic circuit configuration diagram of a first embodiment.

FIG. 2 is a schematic circuit configuration diagram showing another configuration of the above.

FIG. 3 is a schematic circuit configuration diagram of a second embodiment.

FIG. 4 is a schematic circuit configuration diagram of a third embodiment.

FIG. 5 is a schematic circuit configuration diagram showing another configuration of the above.

FIG. 6 is a schematic circuit configuration diagram of a fourth embodiment.

FIG. 7 is a schematic circuit configuration diagram of a fifth embodiment.

FIG. 8 is a schematic circuit configuration diagram of a conventional example.

FIG. 9 is an explanatory diagram of a half-wave discharge mode according to the embodiment.

FIG. 10A is a waveform chart showing a lamp current in the half-wave discharge mode of the above, and FIG. 10B is a waveform chart showing a voltage across the resonance capacitor in the half-wave discharge mode of the above.

FIG. 11 is an explanatory view when the filament is disconnected.

12A is a waveform chart showing a lamp current when the filament is broken, and FIG. 12B is a waveform chart showing a voltage across the resonance capacitor when the filament is broken. FIG.

[Explanation of symbols]

 AC AC power supply DB Rectifier circuit C0 Smoothing capacitor INV Inverter circuit La Discharge lamp L Resonance inductor C2 Resonance capacitor Z Impedance element

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Wataru Noda 1048 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Works, Ltd. (reference) 3K072 AA02 BA03 BA05 BB01 BC01 BC03 CA16 DB03 DB04 DD04 EA03 EB05 GA03 GB12 GC04 HA06

Claims (8)

[Claims] 1. A power supply comprising: a DC power supply; and an inverter circuit including one or more switching elements, a resonance inductor and a capacitor, converting an output of the DC power supply into a high-frequency output and supplying the RF power to a hot cathode discharge lamp. A discharge lamp lighting device comprising a resonance capacitor connected between filaments of the discharge lamp, wherein a current limiting impedance element is provided in a closed circuit between the resonance capacitor and the discharge lamp. Lighting device. 2. The discharge lamp lighting device according to claim 1, further comprising a preheating power source for preheating the filament without connecting the capacitor for resonance to a power supply side of the filament. 3. The discharge lamp lighting device according to claim 1, wherein a resonance capacitor is connected to a non-power supply side of the filament. 4. The DC power supply comprises: an AC power supply; a rectifier circuit for rectifying the AC power supply; and a chopper circuit for intermittently rectifying the rectified output of the rectifier circuit to obtain a desired DC output. 4. The discharge lamp lighting device according to 1, 2, or 3. 5. A preheating power supply includes a secondary winding and a tertiary winding provided on a resonance inductor, and a DC cutoff connected between the secondary winding and the tertiary winding and each filament. 3. The discharge lamp lighting device according to claim 2, comprising a capacitor. 6. A direct current power supply, and an inverter circuit including one or more switching elements, a resonance inductor and a capacitor, converting an output of the direct current power supply to a high frequency output, and supplying the high frequency output to a hot cathode type discharge lamp. A discharge lamp lighting device having a resonance capacitor connected between filaments of a discharge lamp, a detection unit for detecting a current flowing through the filament via the resonance capacitor, and a current level detected by the detection unit being a predetermined level. Determining means for determining whether or not the threshold value is exceeded; and control means for performing switching control of the switching element to reduce or stop the output of the inverter circuit when the determining means determines that the current level exceeds the threshold value. A discharge lamp lighting device comprising: 7. The discharge lamp lighting device according to claim 6, wherein a resonance capacitor is connected to the non-power supply side of the filament and detection means is connected in series to the ground side of the resonance capacitor. 8. The resonance capacitor is connected to the power supply side of the filament, and the detection means is connected in series to the ground side of the resonance capacitor.
The discharge lamp lighting device as described in the above.