JPH08250072A - High pressure discharge lamp - Google Patents

Abstract

PURPOSE: To provide a high pressure discharge lamp having high safety without receiving an electric shock when replacing a failed lamp, even in the case it does not start by some other cause. CONSTITUTION: One electrode 1a of a discharge tube 1 and a starting auxiliary conductor 3 are connected through a starting auxiliary bimetal switch 2, to provide the starting auxiliary conductor 3 adjacent to the discharge tube 1 along its external surface. A starting unit 9, comprising a parallel circuit 8, resistor 6 and a bimetal switch 7, is respectively connected to electrodes 1a, 1b in both ends of the discharge tube 1. A switching means of the parallel circuit 8 consists of a glow tube 4, and a current limiting means consists of a negative characteristic thermistor 5 having a non-linear resistance characteristic relating to a temperature. The resistor 6 limits a current flowing in the parallel circuit 8, and the bimetal switch 7 stops supplying a current to the parallel circuit 8 after discharging the discharge tube 1 is started.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a high pressure discharge lamp.

[0002]

2. Description of the Related Art Conventionally, in a high-pressure discharge lamp, for example, a high-pressure sodium lamp, in order to improve efficiency, xenon gas is used as a starting rare gas to be filled in the discharge tube, and the filling pressure of the xenon gas is higher than before. Since such a high-pressure sodium lamp has a high starting voltage, as shown in FIG. 5, a starting unit 21 composed of a series body of a bimetal switch 19 and a resistor 20 is connected in parallel with the discharge tube 1 and inside the outer bulb 10. It is provided in. This starting unit 21
When the resistor 20 heats red, the bimetal switch 19 is heated and opened, and the current flowing through the ballast 13 is suddenly cut off to generate a pulse voltage.

[0003]

However, in such a high-pressure sodium lamp, a pulse voltage is generated because the voltage is continuously applied to the starting unit 21 when the discharge lamp does not start due to some cause, such as poor starting. However, there was a risk of electric shock when replacing the unlit lamp.

The present invention has been made in order to solve such a problem, and provides a high-pressure discharge lamp having high safety without fear of electric shock when the lamp does not start for some reason. .

[0005]

In the high pressure discharge lamp of the present invention, a parallel body of a switching means and a current limiting means having a negative characteristic having a non-linear resistance characteristic with respect to temperature is connected in parallel with the discharge tube. The discharge tube and the parallel body are housed in an envelope formed of an outer bulb and a base.

[0006]

With this configuration, when the lamp does not start for some reason, the voltage application to the parallel body of the switching means and the current limiting means having a negative characteristic having a non-linear resistance characteristic with respect to temperature continues, so that the current limiting means is continued. The resistance value of becomes smaller due to self-heating. Along with this, the current flowing through the ballast increases when the switching means is open, so the difference between the current flowing through the ballast when the switching means is closed and when the switching means is open is reduced. . Therefore, the rate of change di / dt of the current flowing through the ballast during the operation of the switching means becomes small, and the pulse voltage attenuates.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a high-pressure sodium lamp according to a first embodiment of the present invention has a discharge tube 1 connected in parallel with a parallel body 8 of switching means and current limiting means. 1 and the parallel body 8 are housed in an envelope 12 including an outer ball 10 and a base 11.

One electrode 1a of the discharge tube 1 and the starting auxiliary conductor 3 are connected via a starting auxiliary bimetal switch 2, and the starting auxiliary conductor 3 is close to the discharge tube 1 along the outer surface of the discharge tube 1. Is provided.

A starting unit 9 including a parallel body 8, a resistor 6 and a bimetal switch 7 is connected to the electrodes 1a and 1b at both ends of the discharge tube 1, respectively. The switching means of the parallel body 8 is composed of the glow tube 4, and the current limiting means is composed of a negative characteristic thermistor (hereinafter referred to as NTC thermistor) 5 having a non-linear resistance characteristic with respect to temperature. The resistor 6 limits the current flowing in the parallel body 8, and the bimetal switch 7 stops the supply of the current to the parallel body 8 after the discharge tube 1 starts to discharge.

Next, the operation of the high-pressure sodium lamp of the present invention when it is turned on by using the ballast 13 and the power source 14 having an inductive property will be described.

First, a current flows through the starting unit 9 via the ballast 13. A voltage is applied to the NTC thermistor 5 at the moment when the glow tube 4 performs the opening operation, so that the current flowing through the ballast 13 is rapidly reduced, and a pulse voltage is induced in the ballast 13. Then, the discharge of the discharge tube 1 is started by this pulse voltage and the start auxiliary effect of the start auxiliary conductor 3 provided on the outer surface of the discharge tube 1. After the discharge is started, the heat from the discharge tube 1 opens the bimetal switch 2 and the bimetal switch 7 for starting assistance, so that the voltage application to the starting auxiliary conductor 3 and the starting unit 9 is stopped.

On the other hand, when the discharge tube 1 does not start discharging for some reason despite the generation of the pulse voltage, the voltage is continuously applied to the starting unit 9 and the resistance value of the NTC thermistor 5 self-heats. Becomes smaller.
Along with that, the current flowing through the starting unit 9 increases while the glow tube 4 is open. Therefore, the difference in the current flowing through the ballast 13 between when the glow tube 4 is open and when it is closed becomes small. Therefore,
The rate of change di / dt of the current flowing through the ballast 13 during the operation of the glow tube 4 becomes small, and the pulse voltage attenuates.

When the resistance value of the NTC thermistor 5 becomes smaller and the voltage applied to the glow tube 4 becomes smaller than the operating voltage of the glow tube 4, the operation of the glow tube 4 is stopped and the pulse voltage of the ballast 13 is stopped. Outbreak is stopped.

FIG. 2 shows a high pressure sodium lamp according to a second embodiment of the present invention, in which an NTC thermistor 5 is housed in a base 11.

Next, a high pressure sodium lamp which is a third embodiment of the present invention will be described with reference to FIG.

In the high pressure sodium lamp of this embodiment,
The structure of the starting unit 18 is the starting unit 9 of the above embodiment.
The configuration is different. That is, the bimetal switch 15 is used as the switching means, and the bimetal switch 1
The resistor 16 is provided in series with the parallel body 17 of the NTC thermistor 5 and the NTC thermistor 5. The resistor 16 is the starting unit 1
It has the function of limiting the current flowing through 8 and heating the bimetal switch 7 to open it.

The operation when the above high-pressure sodium lamp is connected to the power supply 14 via the inductive ballast 13 will be described. First, a current flows through the starting unit 18 through the ballast 13, and the resistor 16 is heated. Resistor 1
A voltage is applied to the NTC thermistor 5 at the moment when the bimetal switch 7 is opened by the heat of 6 so that the current flowing through the ballast 13 is rapidly reduced and a pulse voltage is induced in the ballast 13. Then, the generated pulse voltage and the starting auxiliary conductor 3 provided on the outer surface of the discharge tube 1
The discharge assist of the discharge tube 1 starts the discharge of the discharge tube 1. After the discharge is started, the heat from the discharge tube 1 opens the bimetal switch 2 for starting assistance and the bimetal switch 15, so that the voltage application to the starting auxiliary conductor 3 and the starting unit 18 is stopped.

On the other hand, when the discharge tube 1 does not start the discharge for some reason despite the generation of the pulse voltage, the voltage is continuously applied to the starting unit 18 and the resistance value of the NTC thermistor 5 self-heats. Becomes smaller. Along with this, the current flowing through the starting unit 18 increases while the bimetal switch 15 is open. Therefore, the difference in the current flowing through the ballast 13 when the bimetal switch 15 is open and when it is closed is small. Therefore, the bimetal switch 1
Change rate di / d of the current flowing through the ballast 13 during the operation of No. 5
As t decreases, the pulse voltage attenuates. During this time,
Since a current always flows through the resistor 16 and is in a heating state, the bimetal switch 15 is always open, and the generation of the pulse voltage in the ballast 13 is stopped.

FIG. 4 shows a high pressure sodium lamp according to a fourth embodiment of the present invention, in which the NTC thermistor 5 is housed in a base 11.

[0020]

As described above, according to the present invention, a parallel body of a switching means and a current limiting means having a negative characteristic having a non-linear resistance characteristic with respect to temperature is connected in parallel with the discharge vessel. Further, since the parallel body is housed in the envelope composed of the outer bulb and the base, it is possible to attenuate or stop the pulse voltage which continues to be generated when the discharge tube does not start for some reason, and therefore the lamp. It is possible to provide a high-safety high-pressure discharge lamp that is free from the risk of electric shock during replacement or the like.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a high pressure discharge lamp which is a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a high pressure discharge lamp which is a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a high pressure discharge lamp which is a third embodiment of the present invention.

FIG. 4 is a circuit diagram of a high pressure discharge lamp which is a fourth embodiment of the present invention.

FIG. 5 is a circuit diagram of a conventional high pressure discharge lamp.

[Explanation of symbols]

 1 Discharge tube 4 Glow tube 5 NTC thermistor 6 Resistor 7 Bimetal switch 8 Parallel body 9 Starting unit 10 Outer bulb 11 Base 12 Envelope

Claims (4)

[Claims] 1. A switching means in parallel with the discharge tube,
A parallel body with a current limiting means having a negative characteristic having a non-linear resistance characteristic with respect to temperature is connected, and the discharge tube and the parallel body are housed in an envelope composed of an outer bulb and a base. High-pressure discharge lamp. 2. The high pressure discharge lamp according to claim 1, wherein the switching means comprises a glow tube. 3. The high pressure discharge lamp according to claim 1, wherein the switching means is a bimetal switch, and a heating element is connected in series with the parallel body. 4. The high pressure discharge lamp according to claim 1, wherein the current limiting means comprises a negative characteristic thermistor.