JPH02301995A - Electric discharge lamp lighting circuit - Google Patents

Abstract

PURPOSE:To protect a lighting circuit from any overcurrent due to overload appearing at the end of lamp life and also the short circuit of a lamp filament by providing the first and second windings of a detecting transformer having its first winding and its second winding, wherein their winding directions are turned respectively to negate their magnetic fields against each other, and also having its third winding respectively to their relevant preheating current conducting circuits on both sides of an electric discharge lamp, and then providing the third winding to a stopping circuit. CONSTITUTION:The first and second windings 12a, 12b of a detecting transformer 12 having its first winding 12a and its second winding 12b, wherein their winding directions are turned respectively to negate their magnetic fields against each other, and also having third winding 12c are provided respectively to their relevant preheating current conducting circuits on both sides of an electric discharge lamp 1, and the third winding 12c is then provided to a stopping circuit. Whereby the occurrence of an unbalanced preheating current causes the magnetic fields of the first and second windings 12a, 12b not to be negated against each other, and therefore the third winding 12c may induce a voltage exceeding its steady-state voltage for stopping operation of a lighting circuit to protect the lighting circuit from any overcurrent due to overload appearing at the end of lamp life and also the short circuit of a lamp filament by means of a single circuit.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a discharge lamp lighting circuit.

[j I branch of Yorai]

FIG. 3 shows a conventional example of a discharge lamp lighting circuit. Although this circuit could detect the limited lifespan of the discharge lamp 1, it was unable to detect abnormalities due to poor contact of the cap or short circuit of the filament.

In other words, is this circuit between + and -? By turning on the source, the main transistor 4's Hf is supplied from the reactor 2 through the resistor 3, one of the main transistors 4 is turned on, and the oscillation transformer 5 is turned on. Winding 5a and resonance capacitor 6
Oscillation begins at the resonant frequency determined by C. As a result, the preheating windings 5a and I5 on the secondary side of the oscillation transformer 5
A high frequency voltage is generated at the terminal c to preheat the filaments at both ends of the discharge lamp 1, and then the discharge lamp 1 is turned on by the high frequency voltage generated at the secondary winding 5d of the oscillation transformer 5.

During normal lighting, a specified voltage proportional to the number of turns is generated in the detection winding 5e of the oscillation transformer 5. However, when the discharge lamp 1 reaches the end of its life and the load conditions change, the voltage generated in the detection winding 5e also changes, so this is detected by the abnormal voltage detection circuit 7 and the thyristor 8 is activated. , the base current of the main transistor 4 is cut off, and the operation of the lighting circuit is stopped. However, in the case of a poor contact between the base and a short circuit between the filament I and the filament I, the voltage generated in the detection winding 5e does not particularly change, so this cannot be detected. In the figure, 5f is the primary winding of the oscillation transformer 5, 9 is a diode, and 1O is a capacitor.

FIG. 4 shows a conventional example of a circuit that protects only filament short circuits. In this circuit, when the filament of the discharge lamp 1 is short-circuited, a short-circuit current is generated and flows to the preheating windings 5b and 5c of the dragon transformer 5, but at this time, the overcurrent is reduced by the positive characteristic thermistor 11. . Therefore, this circuit does not have a protection function for that pond.

[Problem to be solved by the invention]

The conventional technology described above has the problem that the filament short-circuit protection and lamp life detection functions are configured in separate circuits, making the circuit complicated and expensive.

The present invention has been made in view of the above points, and it is possible to protect the lighting circuit from overload at the end of the lamp life and overcurrent due to filament short circuit with a single circuit, and to prevent short circuit life of the lamp due to poor contact of the lamp base. The object of the present invention is to provide a discharge lamp lighting circuit that makes it possible to operate a discharge lamp.

[Means to solve the problem]

The above purpose is to connect the first and second windings of a detection transformer, which has a first winding, a second winding, and a third winding whose winding directions are such that their magnetic flux cancels out each other, on both sides of the discharge lamp. This is achieved by respectively arranging the preheating current in the energizing circuit and arranging the third winding in the stop circuit.

[Effect]

Since the above means is provided, if an imbalance occurs in the preheating current, the magnetic fluxes in the first and second windings are no longer canceled out, and a voltage higher than the normal voltage is generated in the third winding, causing the lighting circuit to stop. Become so.

[Example]

The present invention will be explained below based on the illustrated embodiments. FIG. 1 shows an embodiment of the invention. Note that parts that are the same as those of the prior art are given the same number 71, and their explanations will be omitted.

In this embodiment, the first winding 12a of a detection transformer 12 includes a first winding 12a, a second winding 12b, and a third winding 12c whose winding directions are such that magnetic fluxes cancel each other out. 2nd winding 1
2a and 12b were respectively disposed in the preheating current supply circuits on both sides of the discharge lamp 1, and the third winding 12c was disposed in the stop circuit.

By doing this, you can preheat N? If an imbalance occurs in m, the first. The magnetic flux of the second winding & 112a, 12b is no longer canceled out, and a voltage higher than the steady state is generated in the third winding 12c, and the lighting circuit is stopped, causing an overload in one circuit at the end of the lamp life. And ci lighting circuit from overcurrent due to filament short circuit! It is possible to obtain a discharge lamp lighting circuit that protects the lamp base and prevents short lamp life due to poor contact of the lamp cap.

That is, during normal lighting, the first winding 12a and the second winding 12b of the detection transformer 12 inserted in the middle of the preheating windings 5b and 5c are set so that their magnetic fluxes cancel each other out, and the third winding &I Almost no voltage is generated at 12c.

At the end of the life of the discharge lamp l, the preheating current changes due to the one-sided emitterless state of the filament, disconnection, short circuit, etc., so a voltage higher than the normal voltage is generated in the third winding 12c of the detection transformer 12. In addition, when the discharge lamp l is attached, due to poor contact with the base, etc., the preheating current becomes unbalanced even when the -blade side preheating current is not energized, and the detection transformer 12
The magnetic flux generated in the first winding 12a and the second winding 12b is no longer canceled out, and a voltage is generated in the third winding 12c. This abnormal voltage is detected by the abnormal voltage detection circuit 7 and the transistor 13 is operated to cut off the Hase current of the main transistor 4 and stop the operation of the lighting circuit. By doing so, the lighting circuit is protected from overload conditions during the lifetime of the discharge lamp 1 and overcurrent when the filament is short-circuited, and short life phenomena due to poor contact with the base of the discharge lamp 1 are prevented. Be able to do it.

As described above, according to this embodiment, the lighting circuit can be protected by stopping the lighting circuit when the discharge lamp is short-lived or when the filament is short-circuited. Furthermore, in the event of poor contact with the lamp cap or disconnection of the lamp filament, the lighting circuit is stopped and the abnormality is notified, thereby preventing troubles such as a short life of the discharge lamp.

Another implementation of the invention is shown in FIG.

In this embodiment, when an abnormal voltage is detected in the third @ line 12c of the detection transformer 12, the abnormal voltage detection circuit 7 operates the transistor 13, drives the relay 14, and switches from the contact 14a to the contact 14b. It is designed to cut off the power supply. In this case as well, the same effects as in the above case can be achieved.

In addition, in each of the above embodiments, by providing the abnormal voltage detection circuit 7 with a recovery function and stopping the operation of the transistor 1 after a predetermined time, the lighting circuit can be operated again and the lighting circuit can be turned off. Instead, the discharge lamp 1 may be blinked to indicate an abnormality.

〔Effect of the invention〕

As mentioned in E, the present invention makes it possible to protect the lighting circuit from overload during lamp life and overcurrent due to filament I-short circuit with one circuit, and also to prevent short lamp life due to accidental touching of the lamp base. This is a discharge lamp lighting circuit that eliminates overload during lamp life and overcurrent due to filament short circuit with a single circuit, and also prevents short lamp life due to poor contact of the lamp base. can be obtained.

[Brief explanation of drawings]

1 and 2 are circuit diagrams showing different embodiments of the discharge lamp lighting circuit of the present invention, FIG. 3 is a circuit diagram for detecting the end of life U of a conventional discharge lamp lighting circuit, and FIG. 4 is the same. <Conventional lamp filament short circuit 1/8 diagram. 1... Discharge lamp, 12... Detection transformer, 12a...
・First winding, 12b...second winding, 12c...third
Winding, 15...Lighting circuit. Patent applicant Hitachi 0? Mei Co., Ltd. $ 1 Figure

Claims (1)

[Scope of Claims] 1. A discharge lamp lighting circuit which is provided on both sides of the discharge lamp and has a preheating current supply circuit for preheating the filament of the discharge lamp and a stop circuit for stopping the lighting of the discharge lamp. The first and second windings of the detection transformer, which includes a first winding, a second winding, and a third winding whose magnetic fluxes cancel each other out, are connected to a preheating current energizing circuit on both sides of the discharge lamp. A discharge lamp lighting circuit characterized in that the third winding is disposed in the stop circuit. 2. The discharge lamp lighting circuit detects a difference in the preheating current of the filament occurring between the first and second windings of the detection transformer in the third winding of the detection transformer, and stops the operation of the lighting circuit. A discharge lamp lighting circuit according to claim 1, which is adapted to do the following. 3. The discharge lamp lighting circuit detects, in the third winding of the detection transformer, a difference in the preheating current of the filament occurring between the first and second windings of the detection transformer, and controls the operation of the lighting circuit. A discharge lamp lighting circuit according to claim 1, wherein the discharge lamp lighting circuit is configured to intermittently stop the lamp and display an abnormality.