JPH08167399A - High pressure discharge lamp - Google Patents

Abstract

PURPOSE: To obtain a high pressure discharge lamp of excellent safety by providing the high pressure discharge lamp to attenuate or stop the pulse voltage when the lamp is not started by some cause. CONSTITUTION: The resistance of a PTC thermistor is increased through the self heat generation by continuously applying the voltage to a starting unit 8 when a discharge tube does not start the discharge of the lamp by some cause though the pulse voltage is generated. The current flowing in a ballast 12 when a glow tube 4 is closed is reduced therewith. The ratio of change di /dt of the current flowing in the ballast 12 when the glow tube 4 is opened becomes smaller, and as a result, the pulse voltage is attenuated or stopped. The high pressure discharge lamp of excellent safety can be thereby obtained.

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 order to improve the efficiency of a high-pressure discharge lamp, for example, a high-pressure sodium lamp, there is a lamp in which xenon gas is used as a rare gas for starting and the filling pressure thereof is increased. Such a high-pressure sodium lamp has a high starting voltage, and in order to light it with a ballast for a mercury lamp, as shown in FIG. 5, a starting unit 20 composed of a series body of a bimetal switch 18 and a resistor 19 is used as a discharge tube. There is one provided in the outer sphere 9 in parallel with 1. This starting unit 2
When 0, the resistor 19 heats red and heats the bimetal switch 18 to open it, and suddenly interrupts the current flowing through the ballast 12 to generate a pulse voltage.

[0003]

However, in such a starting unit 20, a pulse voltage is generated because the voltage is continuously applied to the starting unit 20 when the discharge lamp does not start due to some cause, for example, 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 series body of a switching means and a current limiting means having a positive characteristic having a non-linear resistance characteristic with respect to temperature is connected in parallel with the discharge tube, and the series connection is made. The body and the discharge tube are housed in an envelope composed of an outer bulb and a base.

[0006]

With this configuration, when the lamp does not start for some reason, the resistance value of the current limiting means increases due to self-heating as the voltage is continuously applied to the series body of the switching means and the current limiting means having the above characteristics. To go. Along with that, the current flowing through the ballast when the switching means is closed decreases. Therefore, when the switching means is opened, the rate of change of the current flowing in the ballast di / dt
Becomes smaller and the pulse voltage decays.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, in a high pressure sodium lamp which is an embodiment of the present invention, one electrode 1a of a discharge tube 1 and a starting auxiliary conductor 3 are connected via a starting auxiliary bimetal switch 2. The starting auxiliary conductor 3 is provided close to the discharge tube 1 along the outer surface of the discharge tube 1. The switching means is a series body in which the glow tube 4 and the bimetal switch 7 are connected in series. In this series,
Current limiting means, for example, positive temperature coefficient thermistor having non-linear resistance characteristics with respect to temperature (hereinafter referred to as PTC thermistor)
5 are connected in series. Bimetal switch 7
It has a function of cutting off the electrical connection between the glow tube 4 and the series body 6 of the PTC thermistor 5 after the lamp is started.

A starting unit 8 composed of a series body of a series body 6 and a bimetal switch 7 has electrodes 1 at both ends of a discharge tube 1.
a and 1b, respectively, and thus are connected in parallel with the discharge tube 1.

The discharge tube 1, the PTC thermistor 5, and the starting unit 8 including the series body 6 are housed in an outer bulb 9 having a base 10 to form a high pressure sodium lamp.

Next, the operation when the high-pressure sodium lamp is lit by the power source 13 via the ballast 12 having an inductive property will be described.

First, a current flows through the starting unit 8 through the ballast 12 to open the glow tube 4. At that moment, the current flowing in the ballast 12 is suddenly cut off, so that a pulse voltage is induced in the ballast 12. And
The discharge tube 1 starts to discharge due to the pulse voltage and the starting auxiliary effect of the starting auxiliary conductor 3 provided on the outer surface of the discharge tube 1. After the start of the discharge, the heat from the discharge tube 1 opens the starting auxiliary bimetal switch 2 and the bimetal switch 7, and the voltage application to the starting auxiliary conductor 3 and the starting unit 8 is stopped.

In the high-pressure sodium lamp according to one embodiment of the present invention, when the discharge tube 1 does not start discharging due to some cause even if the pulse voltage is generated, the voltage to the starting unit 8 is increased. If the application continues, P
The resistance value of the TC thermistor 5 increases due to self-heating. Along with that, the current flowing through the ballast 12 when the glow tube 4 is closed decreases. Therefore, the rate of change di / dt of the current flowing through the ballast 12 when the glow tube 4 is opened is reduced, and as a result, the pulse voltage is attenuated.

The PTC thermistor 5 has a function of limiting the current flowing through the starting unit 8 to protect the glow tube 4 as a switching means, in addition to the above-mentioned function.

FIG. 2 shows a high pressure sodium lamp according to another embodiment of the present invention, in which a PTC thermistor 5 is housed in a base 10.

Next, a high pressure sodium lamp which is another 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 14 is different from the structure of the starting unit 8 of the above embodiment. That is, the starting unit 14
Is a bimetal switch 15 as a switching means.
And a resistor 16 that is a heating element that functions to heat and open it, and a PTC thermistor 5 that has a nonlinear resistance characteristic with respect to temperature. The bimetal switch 15 and the resistor 16 are connected in series to form a series body 17, and the PTC thermistor 5 is connected to the series body 17.

When the power source 13 is connected to the high-pressure sodium lamp via the inductive ballast 12, first, the ballast 12
A current flows through the starting unit 14 through the resistor 16 and the resistor 16 is red-heated. The red metal of the resistor 16 heats and opens the bimetal switch 15, and at that moment, the ballast 1
The pulse voltage is generated by suddenly interrupting the current flowing in the No. 2 circuit. Then, the discharge voltage is started by the discharge tube 1 due to the pulse voltage and the starting auxiliary effect of the starting auxiliary conductor 3.
After the start of the discharge, the heat from the discharge tube 1 opens the bimetal switch 2 and the bimetal switch 15 for starting assistance, and the voltage application to the starting assistance conductor 3 and the starting unit 14 is stopped.

In this high-pressure discharge lamp, if 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 14 and the resistance of the PTC thermistor 5 is increased. As the value increases, the current flowing through the ballast 12 when the bimetal switch 15 is closed decreases and the pulse voltage attenuates. Then, since the heating effect of the resistor 16 is reduced due to the decrease in the current flowing through the starting unit 14 and the bimetal switch 15 is not opened, the generation of the pulse voltage can be stopped.

FIG. 4 shows another embodiment of the present invention, in which the PTC thermistor 5 is housed in the base 10.

[0020]

As described above, according to the present invention, the series body of the switching means and the positive current limiting means having the non-linear resistance characteristic with respect to temperature is connected in parallel with the discharge tube.
Since the series body and the discharge tube are housed in the envelope composed of the outer bulb and the base, the pulse voltage can be attenuated or stopped when the lamp does not start for some reason, and therefore, the lamp replacement is required. In such a case, it is possible to provide a high-safety high-pressure discharge lamp that is free from the risk of electric shock.

[Brief description of drawings]

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

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

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

FIG. 4 is a circuit diagram of a high pressure discharge lamp which is another 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 PTC Thermistor 9 Outer Sphere 10 Base 11 Envelope

Claims (4)

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