JP2000021354A - Bulb type fluorescent lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent unexpected thermal deformation or thermal breakage in a fluorescent arc tube even in a final stage of a life of the fluorescent arc tube so as to prevent danger of a fire and the like. SOLUTION: In a final stage of a life of a fluorescent arc tube 14, power supply to the fluorescent arc tube 14 is secured only for a time longer than a prescribed time, in which the fluorescent arc tube 14 is transferred to arc discharge, so that the fluorescent arc tube 14 can be lighted in its life final stage, while within a predetermined time shorter than a time, in which unexpected breakage may be caused in the fluorescent arc tube 14 in its life final stage, a filament electrode (f) and a bulb 14a are positioned so that a hole is bored in a bulb 14a of the fluorescent arc tube 14 by the heat of the filament electrode (f) in the fluorescent arc tube 14. In this way, leakage occurs in the fluorescent arc tube 14, so that an inconvenience such as a fire, which may arise in the case of unexpected breakage occurring in the fluorescent arc tube 14, can be got rid of.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bulb-type fluorescent lamp in which a fluorescent tube and its lighting circuit are housed in a bulb-shaped envelope.

[0002]

2. Description of the Related Art Conventionally, there is a bulb-type fluorescent lamp in which a fluorescent arc tube and its lighting circuit are housed in a bulb-shaped envelope. Such a bulb-type fluorescent lamp has a base that is directly screwed into a socket for setting an incandescent lamp or the like, and a built-in lighting circuit rectifies and smoothes low-frequency alternating current from a commercial power supply by a rectifying and smoothing circuit, The lighting circuit has a structure in which a DC component after smoothing is converted to a high frequency by an inverter circuit and supplied to the fluorescent tube.

Here, a known inverter circuit is known as a complementary switch circuit. Such an inverter circuit has a circuit configuration for generating a high frequency by mutually switching an N-channel FET and a P-channel FET. In a lighting circuit using a complementary switch circuit, a high-frequency secondary voltage is applied to the fluorescent light emitting tube when the fluorescent light emitting tube is started until the fluorescent light emitting tube is turned on.

[0004]

At the end of the life of a fluorescent arc tube, it becomes difficult to light even if a regular lighting voltage is applied. When the fluorescent light emitting tube does not light easily, the lighting current applied to the fluorescent light emitting tube at the time of starting increases. In this case, there is no problem if the lighting circuit side is destroyed due to thermal runaway and power supply to the fluorescent light emitting tube is stopped, but before that, unexpected thermal deformation or unexpected thermal damage is caused to the fluorescent light emitting tube itself. There is a problem. Since such thermal deformation and thermal destruction are unexpected accidents, the fluorescent arc tube emits smoke, mercury vapor jumps out of the fluorescent arc tube, and in some cases, ignites from the fluorescent arc tube or resin parts. This is extremely inconvenient.

It is an object of the present invention to prevent unexpected thermal deformation or thermal destruction of a fluorescent arc tube even at the end of its life, and to avoid danger such as ignition.

[0006]

According to a first aspect of the present invention, there is provided a bulb-type fluorescent lamp comprising: an envelope in which a light-transmitting globe is attached to a base having a base; A fluorescent light tube arranged in a part of the glove; a lighting circuit arranged in a part of the base inside the envelope and having a complementary switch circuit for generating a high frequency for operating the fluorescent light emitting tube; and an inside of the envelope A partition for separating the fluorescent tube and the lighting circuit with the light-emitting tube;
The fluorescent lamp is heated by a secondary voltage that the lighting circuit keeps applying to the fluorescent tube until the fluorescent tube at the start transitions to the arc discharge. Valve destruction means for positioning the filament electrode and the bulb such that the bulb of the fluorescence arc tube is punctured within a predetermined time shorter than the time at which unexpected damage to the fluorescent arc tube at the end of life will occur. I do.

In the first and second aspects of the present invention, the definitions and technical meanings of terms are as follows unless otherwise specified.

The "base" has a size and a shape to be screwed into a socket in which an incandescent lamp or the like is set, for example.

The "substrate" is desirably formed of, for example, resin or plastic and has no light transmitting property or has a very weak light transmitting property. This is to make the lighting circuit invisible to store and hold a “lighting circuit” described later. However, the present invention is not limited to this, and a material having a light transmitting property may be used.

The "translucent globe" is formed of, for example, glass, but the material is not limited to this.
The shape may be spherical to resemble the shape of an incandescent lamp.

The "fluorescent light emitting tube" is a so-called fluorescent lamp, and its shape is not particularly limited. However, considering that it is housed in a translucent glove, for example, by adopting a U-shaped shape or a continuous shape thereof, a compact shape can be obtained while ensuring brightness.

The "complementary switch circuit" is a circuit for alternately switching between an N-channel FET and a P-channel FET at high speed. That is, the complementary switch circuit generates a high frequency. The high frequency in this case is
For example, it means a frequency of 1000 Hz or more. Such a circuit includes, for example, an N-channel FE
A circuit that supplies the respective required gate voltages commonly to the T and P channel type FETs,
A circuit is applied in which a positive voltage is applied to the N-channel FET to turn it on, and a negative voltage is applied to the P-channel FET to turn it on.

The "lighting circuit" includes a starting circuit. The starting circuit is configured to turn on the N-channel FET at the time of starting. The lighting circuit connects, for example, a current limiting inductance in series with the fluorescent light emitting tube as ballast means in order to compensate for the negative characteristics of the fluorescent light emitting tube serving as a load.

Further, since the "fluorescent light emitting tube" is a fluorescent lamp which is a low-pressure discharge lamp, it is common to use a filament electrode as an electrode and start the hot cathode and turn on the hot cathode of the filament electrode. In such a case,
There are the following two methods for heating the filament electrode at startup.

One is to connect a resonance capacitor in parallel with the discharge lamp via at least one filament electrode at the time of starting. Then, a current flows through the filament electrode via the current-limiting inductance and the resonance capacitor at the time of starting, so that the filament electrode connected in series with these is heated. At the same time, the current-limiting inductance and the resonance capacitor appropriately resonate in series, and the terminal voltage of the resonance capacitor increases, so that the starting of the discharge lamp is promoted.

Second, the filament electrode is heated using a filament heating transformer. The filament heating transformer may be provided separately from the current limiting inductance, but the filament heating winding may be magnetically coupled to the current limiting inductance. This can suppress an increase in the number of circuit components.

Under a predetermined condition, the arrangement of the filament electrode and the bulb such that a hole is formed in the bulb of the fluorescent arc tube by heating the filament electrode of the fluorescent arc tube is because the filament electrode and the bulb are arranged close to each other. Is achieved. Therefore, it is permissible to form the filament electrode so as to be offset from the center of the bulb (Claim 2) or to form the bulb by curving in a direction approaching the filament electrode (Claim 3).

According to the present invention as described above, when the fluorescent light emitting tube reaches the end of its life, power supply to the fluorescent light emitting tube is ensured for a time longer than a specified time for the fluorescent light emitting tube to transition to arc discharge. Therefore, if there is some lighting ability remaining in the fluorescent light emitting tube, the fluorescent light emitting tube can be turned on. Then, the bulb of the fluorescent arc tube is pierced and leaks by heating the filament electrode of the fluorescent arc tube within a predetermined time shorter than the time at which the fluorescent arc tube at the end of life will be unexpectedly damaged. . Since such a breakage of the fluorescent tube is a planned and expected matter,
The risk of ignition and the like is reduced as compared with the case where the fluorescent arc tube is unexpectedly damaged. Therefore, safety is ensured.

[0019]

FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG.

<Circuit Configuration> FIG. 1 is a circuit diagram of a lighting circuit provided in a compact fluorescent lamp according to the present embodiment.

In FIG. 1, 1 is an AC power supply, 2 is an overcurrent fuse, 3 is a noise prevention circuit, 4 is a rectified DC power supply,
N is N-channel type FET, SP is P-channel type FE
T and GC are gate circuits, ST is a starting circuit, PT is gate protection means, and LC is a load circuit.

The AC power supply 1 is a commercial 100 V AC power supply.

The overcurrent fuse 2 is formed of, for example, a pattern fuse integrally formed on a wiring board, and protects the circuit from being burned out when an overcurrent flows and burnt out.

The noise prevention circuit 3 includes an inductance L1 interposed in series between the AC power supply 1 and the rectified DC power supply 4.
And a capacitor C1 connected in parallel with the AC power supply 1 on the AC power supply 1 side of the inductance L1 to form an inverted L-shaped circuit together with the inductance L1. Remove to prevent spill.

The rectified DC power supply 4 comprises a bridge type full-wave rectifier circuit 4a and a smoothing circuit 4b.

The bridge type full-wave rectifier circuit 4a has an AC input terminal connected to the AC power supply 1 via the noise prevention circuit 3, and a DC output terminal connected to the smoothing circuit 4b.

The smoothing circuit 4b comprises a series resistor R1 and a smoothing capacitor C2.

The series resistor R1 has a resistance value of several ohms or less, and has a function of reducing a harmonic by making a current waveform gentle when a charging current flows into the smoothing capacitor C2.

The drain of the N-channel FET SN is connected to the positive electrode of the smoothing capacitor C2.

On the other hand, the source of the P-channel FET SP is connected to the saw of the N-channel FET SN, and the drain is connected to the negative electrode of the smoothing capacitor C2.

The gate circuit GC comprises feedback means s, series resonance circuit SR, and gate voltage output means OG.

The feedback means s comprises an auxiliary winding magnetically coupled to a current limiting inductance L2 described later.

The series resonance circuit SR has an inductance L3
And a series circuit of a capacitor C3, both ends of which are connected to both ends of the feedback means s.

The gate voltage output means OG is configured to extract a resonance voltage appearing across the capacitor C3 of the series resonance circuit SR via the capacitor C4. One end of the capacitor C4 is connected to a connection point between the capacitor C3 and the inductance L3, and the other end of the capacitor C4 is connected to an N-channel FET SN and a P-channel F
Connected to each gate of ETSP.

Further, the other end of the capacitor C3 is connected to each FET.
Connected to the source. Thus, the resonance voltage appearing between both ends of the capacitor C3 is applied between the gate and the source of each FET via the gate voltage output means OG.

The starting circuit ST comprises resistors R2, R3 and R
Consists of four.

One end of the resistor R2 has a smoothing capacitor C.
2 and the other end is connected to the gate of the N-channel FET SN, and is connected to one end of the resistor R3 and the output terminal on the gate side of the gate voltage output means OG of the gate circuit GC, that is, the other end of the capacitor C4. Connected.

The other end of the resistor R3 is connected to a connection point between the inductance L3 of the series resonance circuit LC and the feedback means s.

One end of the resistor R4 is connected to each of the FETs SN and SP.
, Ie, the source and gate voltage output means OG is connected to the source-side output terminal, and the other end is connected to the negative electrode of the smoothing capacitor C2.

The gate protection means PT includes a pair of zener diodes connected in series with opposite polarities to form a gate voltage output means O.
Connected to G.

The load circuit LC includes a discharge lamp D as a load.
L, a current limiting inductance L2, a coupling capacitor C5, and a resonance capacitor C6.

As the discharge lamp DL, a fluorescent lamp is used. One electrode of the discharge lamp DL is a coupling capacitor C5.
, And the other end is connected to the drain of a P-channel FET SP.

A filament heating winding wh is connected in parallel with the other electrode.

The filament heating winding wh is magnetically coupled to the current limiting inductance L2 to heat the other filament electrode of the discharge lamp DL. Instead of the filament heating winding wh, the lower terminal in the drawing of the resonance capacitor C6 may be connected to the non-power supply side terminal of the lower filament electrode in the drawing of the discharge lamp DL. In this case, the filament electrode is connected to the resonance capacitor C6.
Is heated by the current flowing through it.

The current limiting inductance L2 has one end connected to the sources of the FETs SN and SP, and the other end connected to the other end of the coupling capacitor C5.

The resonance capacitor C6 is connected in parallel with the discharge lamp DL.

Thus, the load circuit LC includes the current limiting inductance L2, the capacitor C5, and the resonance capacitor C6.
Is formed.

A capacitor C7 is connected between the source and the drain of the P-channel FET SP to reduce the load during the switching period of the P-channel FET SP.

<Structure> FIG. 2 is a front view of the bulb-type fluorescent lamp of the present embodiment, FIG. 3 is a cross-sectional plan view thereof, FIG. 4 is an exploded perspective view, and FIG. It is a front view of a lamp.

2 to 5, reference numeral 11 denotes an envelope,
12 is a base, 13 is a partition, 14 is a fluorescent light emitting tube, and 15 is a lighting circuit unit.

The envelope 11 includes a light-transmitting globe 11a and a light-shielding base 11b.

The translucent globe 11a is in the form of a glass bottomed cylinder having a light diffusing coating formed on the inner surface.

The light-shielding substrate 11b has a cup shape made of a synthetic resin, a base 12 is mounted on a base, and a translucent glove 11a is fixed to an open end.

The translucent glove 11a is adhered to the open end of the light-shielding base 11b using a silicone adhesive 16 (see FIG. 5).

The partition 13 is formed by molding a white synthetic resin, and is fixed to the open end of the base 11b of the envelope 11 together with the translucent glove 11a by a silicone adhesive. Thus, the partition 13 divides the inside of the envelope 11 into a light-emitting room A and a circuit storage room B. The partition 13 has a fluorescent tube support hole 13a.

The fluorescent tube 14 includes a bulb 14a, a filament electrode f, a phosphor layer (not shown), and a discharge medium.

The bulb 14a is formed in such a shape that three elongated glass tubes are bent in a U-shape at the center and three are connected.

The filament electrode f of the fluorescent tube 14 is
It is a hot cathode type, and a pair is sealed at both ends of the bulb 14a.

Here, FIG. 6A is a perspective view showing a positional relationship between the bulb 14a and the filament electrode f as one mode of the present embodiment, and FIG. 6B is a plan view thereof.
FIG. 7A is a perspective view showing a positional relationship between the bulb 14a and the filament electrode f as another aspect of the present embodiment, and FIG. 7B is a plan view thereof. In the present embodiment, heating is performed by the secondary voltage that the lighting circuit continues to apply to the fluorescent light emitting tube 14 until the fluorescent light emitting tube 14 at the start transitions to arc discharge, that is, a high resonance voltage appearing at both ends of the resonance capacitor C6. Filament electrode f
However, within a predetermined time longer than the specified time for the fluorescent tube 14 to transition to arc discharge and shorter than the time at which the fluorescent tube 14 will be damaged at the end of life, the bulb 14
The positional relationship is such that a hole can be made in a. Such a positional relationship is simply realized by bringing the filament electrode f close to the bulb 14a. Therefore, in the present embodiment, as one aspect thereof, the valve 14
The filament electrode f is offset from the center of a, and the filament electrode f is brought close to the inner wall of the bulb 14a (see FIG. 6). Alternatively, as another aspect,
A concave portion r is formed in the bulb 14a so as to be curved in the direction of the filament electrode f, and the bulb 14a is brought close to the filament electrode f at this concave portion r. Here, the valve breaking means is configured.

The phosphor layer is formed on the inner side of the bulb 14a.

The discharge medium is composed of a rare gas of several torr, such as mercury and argon, and is sealed in the bulb 14a after exhausting the interior of the bulb 14a.

The fluorescent light emitting tube 14 has both ends inserted into the fluorescent light emitting tube insertion hole 13a of the partition 13 from the light emitting chamber A side, fixed to the partition 13 with a silicone adhesive, supported and supported. It is arranged in the light emitting room A of the vessel 11.

The intermediate portion of the fluorescent light emitting tube 14 is fixed to the partition 13 by a silicone adhesive filled from a silicone adhesive filling hole 13b.

The lighting circuit unit 15 includes a wiring board 15a.
And a circuit component 15b mounted on the wiring board 15a.
Are located in

The lighting circuit unit 15 constitutes the lighting device shown in FIG. 1, and the fluorescent tube 14 corresponds to the discharge lamp DL in FIG.

The base 12 is connected to the input terminal of the lighting circuit unit 15, and the output terminal of the lighting circuit unit 15 is connected to both electrodes (not shown) of the fluorescent tube 14.

Although not shown in FIGS. 2 to 5,
An overcurrent fuse 5 is interposed between the fluorescent tube 14 and its lighting circuit. This overcurrent fuse 5
May be directly connected to the outer lead 17 of the fluorescent tube 14, or may be formed in the form of a pattern fuse on the circuit board 15a of the lighting circuit unit 15.

<Circuit Operation> Next, the circuit operation in the present embodiment will be described.

When the AC power supply 1 is turned on, a DC voltage smoothed by the rectified DC power supply 4 appears at both ends of the smoothing capacitor C2. Then, a DC voltage is applied between both drains of the N-channel type FET SN and the P-channel type FET SP connected in series. However, both FETs SN, SP
Since no gate voltage is applied to both FETs,
SN and SP remain off.

Since the DC voltage is simultaneously applied to the starting circuit ST, both ends of the resistor R3 are mainly connected with the resistors R2 and R2.
A voltage appears according to a proportional ratio between the resistance values of R3 and R4. The terminal voltage of the resistor R3 is applied as a positive voltage between the gate and the source of each FET. As a result, N
The channel type FET SN is turned on because it is set to exceed the threshold voltage. On the other hand, the voltage applied between the gate and the source of the P-channel FET SP has the opposite polarity to the required gate voltage, and thus remains off.

When the N-channel FET SN is turned on,
A current flows from the rectified DC power supply 4 through the drain / source of the N-channel FET SN, and in series with the load circuit LC, that is, the current-limiting inductance L2, the coupling capacitor C5, and the resonance capacitor C6 in series. The series resonance circuit of the current limiting inductance L2 of the load circuit LC, the coupling capacitor C5, and the resonance capacitor C6 resonates, and the terminal voltage of the resonance capacitor C6 increases.

On the other hand, when a current flows through the current limiting inductance L2, a voltage is induced in the feedback means s and the filament heating winding wh which are magnetically coupled.

The voltage induced in the feedback means s by the above-mentioned current causes the series resonance circuit SR to start series resonance. The series resonance causes a boosted negative voltage to be generated in the capacitor C3. Therefore, the negative voltage is regulated to a constant voltage by the gate protection means PT, and the gates of the P-channel FET SP and the N-channel FET SN are connected via the gate protection means OG. Applied between sources. This allows P
Since the gate of the channel type FET SP exceeds the threshold voltage, it turns on. On the other hand, the N-channel type FET SN which has been turned on until now has the opposite polarity and has no predetermined gate voltage, so it is turned off.

When the P-channel FET SP is turned on,
The electromagnetic energy stored in the current limiting inductance L2 of the load circuit LC and the charge stored in the capacitor C6 are released, and the source / drain of the P-channel FET SP and the N-channel FET in the closed circuit of the load circuit LC.
A current flows in a direction opposite to that when SN is turned on.

On the other hand, an alternating voltage is induced in the filament heating winding wh as a current in the alternating current flows through the current limiting inductance L2, and heats one electrode of the fluorescent tube 14 which is the discharge lamp DL. So the fluorescent tube 14
Electron emission takes place inside.

The fluorescent tube 14 has a high resonance voltage (2) appearing across the resonance capacitor C6 together with the electron emission.
(Second voltage) is applied, so that the lamp starts up and lights up.

The current flowing when the P-channel FET SP is turned on causes a current having the same polarity as the current flowing through the starting circuit ST to flow through the feedback means s. Therefore, the N-channel FET SN is turned on again, and the P-channel FET SP is turned on.
Turns off. Thereafter, the FETs SN and SP are alternately turned on and off, and the fluorescent tube 14 is turned on at high frequency. Here, the N-channel type FET SN and the P-channel type FET SP constitute a complementary switch circuit.

Here, it becomes difficult for the fluorescent luminous tube 14 to be turned on at the end of its life. In the present embodiment, the heating circuit is heated by the secondary voltage that the lighting circuit continues to apply to the fluorescent light emitting tube 14 until the fluorescent light emitting tube 14 at the start transitions to arc discharge, that is, a high resonance voltage appearing at both ends of the resonance capacitor C6. The fluorescent arc tube 1 is
The bulb 1 of the fluorescent light emitting tube 14 is disposed within a predetermined time longer than a prescribed time for which the fluorescent light emitting tube 4 is to be transferred to arc discharge and shorter than a time at which the fluorescent light emitting tube 14 at the end of life will be damaged.
A hole is made in 4a. As a result, the fluorescent tube 14 leaks, and subsequent heat generation is prevented. As described above, according to the present embodiment, when the fluorescent luminous tube 14 is at the end of its life, power supply to the fluorescent luminous tube 14 is ensured for a time longer than the specified time for the fluorescent luminous tube 14 to transition to arc discharge. Therefore, the fluorescent tube 14 can be turned on if the fluorescent tube 14 has some lighting ability. On the other hand, since the filament electrode f punctures the bulb 14a within a predetermined time shorter than the time at which the fluorescent light emitting tube 14 at the end of life will be damaged, when the bulb 14a is unexpectedly damaged, In comparison, since the damaged portion is specified in advance, it is possible to prevent smoke and ignition of the fluorescent arc tube 14 from occurring, and to enhance safety.

A second embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and the description is omitted. In the present embodiment, one filament electrode f is connected in series in a resonance loop formed by the current-limiting inductance L2, the capacitor C5, and the resonance capacitor C6 that form a series resonance circuit. That is, the filament electrode f heated by the high resonance voltage appearing at both ends of the resonance capacitor C6 is longer than the specified time for the fluorescent tube 14 to transition to arc discharge, and the fluorescent tube 14 at the end of its life is damaged. A hole is made in the valve 14a within a predetermined time shorter than the time that would occur.

[0080]

According to the present invention, when the fluorescent arc tube reaches the end of its life, power supply to the fluorescent arc tube is secured for a time longer than a specified time for the fluorescent arc tube to transition to arc discharge. If a certain level of lighting ability remains, the fluorescent tube can be turned on. Then, when the fluorescent light emitting tube reaches the end of its life, the filament tube of the fluorescent light emitting tube is heated by heating the filament electrode of the fluorescent light emitting tube within a predetermined time shorter than a time at which unexpected damage to the fluorescent light emitting tube at the end of life will occur. A hole was made in the bulb of, and the hole of the fluorescent tube was made to leak, so that damage to the fluorescent tube was a planned and expected matter, so if unexpected damage occurred to the fluorescent tube, In comparison, the danger such as ignition can be significantly reduced. Thereby, safety can be ensured.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is an overall front view.

FIG. 3 is a cross-sectional plan view.

FIG. 4 is an exploded perspective view.

FIG. 5 is an enlarged front view showing a part.

FIG. 6A is a perspective view showing one embodiment of the present embodiment relating to a positional relationship between a bulb and a filament electrode, and FIG.
Is a plan view thereof.

FIG. 7A is a perspective view showing another aspect of the present embodiment relating to a positional relationship between a bulb and a filament electrode,
(B) is a plan view thereof.

FIG. 8 is a circuit diagram showing a second embodiment of the present invention.

[Explanation of symbols]

 5: Overcurrent prevention element (overcurrent fuse) 11b: Base 11a: Translucent glove 11: Envelope 12: Base 13: Partition wall 14: Fluorescent tube 14a: Valve 15a: Circuit board 17: Outer lead SN, SP : Complementary switch circuit f: Filament electrode

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tsutomu Araki 4-3-1 Higashishinagawa, Shinagawa-ku, Tokyo F-term in Toshiba Lighting & Technology Corporation (reference) 3K072 AA02 AA06 AC11 BA03 BB01 BC01 BC03 CA16 DB03 EA01 EA03 FA01 GA02 GB12 5C015 EE01

Claims (3)

[Claims] 1. An envelope in which a light-transmitting globe is attached to a base provided with a base; a fluorescent light-emitting tube disposed inside the envelope at a portion of the light-transmitting globe; A lighting circuit disposed on the base portion inside the vessel and including a complementary switch circuit for generating a high frequency for operating the fluorescent light emitting tube; and the fluorescent light emitting tube and the lighting circuit inside the envelope. A partition wall; and a filament electrode of the fluorescent tube, which is heated by a secondary voltage which the lighting circuit keeps applying to the fluorescent tube until the fluorescent tube at the start transitions to arc discharge. A hole is formed in the bulb of the fluorescent tube within a predetermined time longer than a prescribed time for the lamp to transition to arc discharge and shorter than a time at which unexpected damage to the fluorescent tube at the end of life will occur. The said A bulb-type fluorescent lamp, comprising: a filament electrode and a bulb breaking means for positioning the bulb. 2. The bulb-type fluorescent lamp according to claim 1, wherein said bulb breaking means is formed by offsetting said filament electrode from a center of said bulb. 3. The bulb-type fluorescent lamp according to claim 1, wherein said bulb breaking means is formed by bending said bulb in a direction approaching said filament electrode.