GB2137829A - Gas Discharge Lamp - Google Patents

Abstract

A gas discharge lamp circuit comprises a lamp tube (13') with at least three electrodes (P'1, P'2, P'3). of which two adjacent electrodes define a set (P'1, P'2), and a ballast formed by flux leakage type core (14) and including primary (15a, 15b) and secondary (16a, 16b) windings. The electrodes are connected to the windings such that adjacent electrodes in a set are of opposite polarity. On starting an arc forms between adjacent electrodes and then spreads throughout the tube. The circuit removes the need for a starter switch. Various lamp shapes and combinations of lamps are disclosed. <IMAGE>

Description

SPECIFICATION Gas Discharge Lamp Background of the Invention This invention relates to gas discharge lamps, and in particular to instant-start gas discharge lamps and the lamp circuits thereof.

The gas discharge lamp is different from the incandescent lamp in which a resistance filament is heated to incandescence by an electric current.

The fluorescent lamp commonly used for iliumination in home and office is one example of gas discharge lamp. For better explanation and understanding, the present invention will be described with the fluorescent lamp as an example. It will be appreciated that the present invention is not limited to the fluorescent lamp and can be applied to other types of gas discharge lamps.

The fluorescent lamp is a gas discharge lamp which produces light by conversion of ultraviolet energy from a low-pressure mercury arc to visible light. The fluorescent lamp consists of a glass tube containing two filament electrodes, a coating of powdered phosphor, and small amounts of mercury and argon gas.

Fig. 1 of the accompanying drawings shows a conventional lamp circuit for fluorescent lamp, which mainly comprises a lamp tube 1, a starter 2 and a ballast 3. The ballast 3 consists of two windings 3a and 3b which are used to raise the voltage from the power source with the effect of an autotransformer.

When the switch SW is turned on, the voltage from the ballast 3 is applied on the starter 2 including a glow tube with one fixed electrode 2a and one bimetallic electrode 2b through the electrodes 4a and 4b of the lamp tube 1. A lowcurrent glow discharge forms in the starter 2 and the heat from this glow expands the bimetallic electrode 2a until it contacts the fixed electrode 2b, forming a short circuit through the starter. The full output voltage of the ballast 3 then causes current to flow through the lamp electrodes 4a and 4b, heating them and causing them to emit electrons. The starter 2 cools because the glow is no longer present, and the contact between the electrodes 2a and 2b opens, impressing full ballast voltage between the lamp electrodes 4a and 4b. If there are enough electrons in the tube 1, the arc is formed; if not, the starting process is repeated.This process may require several repetitions, accounting for the delay and flickering.

Although the above-described lamp circuit has been used for a long time, it still has many drawbacks. The employment of a starter not only increases the cost of the lamp circuit, but also makes it needed to be replaced frequently since it is subjected to glow discharge which readily causes damage. In addition, there must be a time delay between the turning on of the switch and a stable operation of the lamp. This time delay is further increased in the case of an old lamp tube since the mercury pressure changes and the electron emitting ability of the electrodes deteriorates.

The high voltage applied on the lamp tube at the instant when the electrodes of the starter are separated reduces the life of the lamp tube.

Furthermore, flickering results since, under AC voltage operation, the light strength produced is proportional to the instantaneous value of the electric current and pulses twice within each power period.

The prior art has proposed an instant-start circuit to reduce the time delay in starting operation. In the well-known instant-start circuit, a much higher ballast voltage is used in the lamp circuit. Immediately upon energizing the circuit this voltage attracts enough electrons into the tube for the arc. For a given lamp wattage and current, the ballast must absorb a higher voltage and hence the ballast is usually larger and more costly and dissipates greater wattage. Due to the high voltage used, the electrodes of the lamp tube have to withstand higher voltage and thus must be of costly construction and have a shorter life.

This invention is intended to overcome the above problems and thus provides an instant-start gas discharge lamp including novel lamp tube and lamp circuit. The lamp according to this invention eliminates the need of a starter but can be instantly started and obtains the advantages of longer life, even illumination and energy saving.

Summary of the Invention One aspect of the gas discharge lamp according to the present invention comprises a lamp tube with at least four electrodes of which two adjacent electrodes define a set, a ballast formed by flux leakage type core and including primary and secondary windings, the ends of the primary winding are respectively connected to the opposite electrodes in different sets of electrodes, and the ends of the secondary winding are respectively connected to the remaining opposite electrodes in said different sets of electrodes, wherein the connecting manner is that the ends of both windings connected to a same set of electrodes are of different polarity.

The another aspect of the gas discharge lamp according to the present invention comprises a lamp tube with at least three electrodes of which two adjacent electrodes define a set, a ballast formed with flux leakage type core and including primary and secondary windings of which the ends of the primary winding are respectively connected to one of said set of electrodes and the opposite single electrode, and one end of the secondary winding is connected to the another one of said set of electrodes.

Embodiments of the present invention will be described with reference to Figs. 2 to 6 of the accompanying drawings in which, Brief Description of the Drawings Fig. 1 shows the conventional lamp circuit for an ordinary fluorescent lamp; Fig. 2 shows a lamp circuit of an embodiment operating in serial resonant manner according to the present invention; Figs. 3 to 5 illustrate the structures of the lamp tubes according to the teaching of the present invention; and Fig. 6 shows a lamp circuit of an embodiment operating in inductive start manner according to the present invention.

The structure of a preferred embodiment according to this invention is illustrated in Fig. 2.

In Fig. 2, the lamp circuit 10 includes a lamp tube 11 and a ballast 12. This embodiment is operated in a serial resonant start manner.

The lamp tube 11 consists of a glass tube 1 3 containing two sets of electrodes P, to P4. In Fig.

2, the electrodes P1 and P2 provided at the right side of tube 11 are defined as the first set and the electrodes P3 and P4 provided at the left side of tube 11 are defined as the second set. The inner wall of glass tube 13 is coated with powdered phosphor. Small amounts of mercury and Argon gas are sealed within the glass tube 1 3.

The ballast 12 is formed with a flux leakage type core 14 having primary and secondary windings 1 5 and 16. The primary winding 1 5 includes the first and second windings 1 spa and 1 sub connected in series. The secondary winding 16 includes the first and second windings 1 6a and 1 6b connected in series. The turns and properties of the primary and secondary windings are completely identical. The polarity of each winding on the ballast 12 is indicated with a black dot in a conventional manner.

In Fig. 2, the upper and lower ends of the primary winding 1 5 are connected to the electrodes P, and P3 of tube 11, respectively. The lower end of the primary winding 15 is also connected to the power source through switch SW. The connection between the first and second windings 1 spa and 1 sub is connected to the another terminal of the power source.

The upper and lower ends of the secondary winding 1 6 on the ballast 1 2 are connected to the electrodes P2 and P4 of tube 11, respectively. A capacitor 50 is coupled between winding 1 6 and electrode P4.

When the switch SW is turned on, the voltage from the power source is raised to, for example, 220 V, by the primary winding 1 5 and applied between the electrodes P, and P3. The secondary winding 16 produces induced voltage of approximately 220 V due to the stray capacitance between the windings 1 5 and 1 6 of the ballast 12 and applies it between electrodes P2 and P4.

Since the respective ends of the primary and secondary windings connected to a same set of electrodes, i.e., P1 and P2 or P3 and-P4, are of opposite polarity, a voltage of approximately 220 V appears-between electrodes P1 and P2 and electrodes P3 and P4, respectively. This relationship is indicated by the waveforms on electrodes P1 to P4 in Fig. 2. Since the distance between the electrodes in a set is very small, the applied voltage of 220 V induces arcs between electrodes P, and P2 and electrodes P3 and P4, respectively and produces a great number of free electrodes. Therefore, light is firstly produced between electrodes P1 and P2 (P3 and P4).

Simultaneously, since there isa high voltage of 220 V between electrodes P1 and P3 and there are a large number of free electrons within tube 11 due to the actuation between each set of electrodes, the arc is formed between electrodes P, and P3 and the lamp is completely started.

According to the structure of the present invention, the starter conventionally used is eliminated, which not only reduces the cost of the lamp but also prevents the trouble of frequent replacement. In addition, the starting process of this lamp circuit is instant and reliable.

According to the present invention, the lamp tube will not be applied with a high voltage since a synchronized current-limiting effect of the ballast is utilized, and thus the lamp tube will have a longer life. In addition, there is no resistance filament provided at the electrode of the lamp tube and thus the problem of that the ends of the tube blackened by the vaporization of the resistance wire is solved. Furthermore, the lamp of this invention will start instantly after the switch is turned on, which increase the efficiency of use and reduces the time delay before the arc is formed. In other words, energy saving is achieved in this invention.

Due to the effect of resonant complimentary effect of the ballast, the lamp according to this invention has even illumination and good performance. Furthermore, the resonant complimentary effect automatically adjusts the efficiency factor and hence enhances the efficiency of the electrical power.

The principle of automatically adjusting the efficiency factor by the resonant complimentary effect is well-known in the art and will not be described in detail.

A further advantage of the present invention is that the conventional lamp tube with broken electrodes still can be used in the lamp circuit of this invention and thus the life thereof is extended.

Figs. 3 to 5 show the structures of the lamp tubes according to this invention.

Fig. 3 shows the structure of a combined circular lamp tube. This circular lamp tube includes three concentric circular lamp units 21, 22 and 23 with different diameters. The lamp units 21, 22 and 23 are provided with respective electrode sets 24 and can be worked independently. The lamp units 21,22 and-23 may be operated with independent lamp circuits or with common lamp circuit. In the case of independent operation circuits, an element such as a selecting switch may be. used to control the operation so as to obtain the effect of selective operation.

Fig. 4 shows anotherstructure of the combined lamp tube, which includes two independent lamp units 32 and 33 with respective electrode sets 31. The operation of this lamp is similar to that of the one shown in Fig. 3.

Fig. 5 illustrates a bulb-shaped lamp tube according to the present invention. A lamp plug 44 is provided at the lower part of the glass bulb 41 and the contacts thereon are connected to the electrode sets 42 mounted within the bulb 41 with conductors 43. The conductors 43 are provided with glass insulating sheathes so as to prevent the occurrence of arc between conductors 43. The inside treatment of the inner portion of the bulb is identical to those for the above-mentioned tubes.

Fig. 6 shows an embodment of the present invention operating in an inductive starting mode.

This circuit is substantially similar to that shown in Fig. 2, but it is mainly used for the lamp tube having three electrodes. The identical elements in Figs. 6 and 2 are designated with the same reference numbers and the lamp tube and its parts are designated with the reference numbers of the corresponding elements in Fig. 2 added with a prime.

In Fig. 6, the lamp tube 11' consists of a glass tube 13' and the electrodes P" P2 and P3 provided at the ends of the tube 1 3'. The difference between Figs. 2 and 6 is merely that the connection between electrode P4 and the secondary winding 16 of the ballast 12 is eliminated. During the starting operation, arc firstly results between electrodes P, and P2. Then, an arc results between the electrodes P, and P3 and the lamp is instantly started.

It will be appreciated that the circuit shown in Fig. 6 is not limited for the use of a lamp tube having three electrodes. The lamp tube- having four or more electrodes such as the one shown in Fig. 2 may be used if one electrode, e.g., the electrode P4 of tube 11, is unused.

Though this invention has been described with respect to a preferred embodiment, it can be applied to other gas discharge lamps such as mercury lamps. The variation or modification of this invention without leaving the spirit of this invention should be considered as falling within the scope of this invention.

Claims (6)

1. An instant-start gas discharge lamp comprising a lamp tube with at least four electrodes of which two adjacent electrodes define a set, a ballast formed by flux leakage type core and including primary and secondary windings, of which the ends of the primary winding are respectively connected to the opposite electrodes in different sets of electrodes, and the ends of the secondary winding are respectively connected to the remaining opposite electrodes in said different sets of electrodes, wherein the connecting manner is that the ends of both windings connected to a same set of electrodes are of different polarity.

2. The gas discharge lamp as claimed in claim 1, in which said lamp tube is combined from a plurality of independent lamp units which have respective sets of electrodes and can be operated individually.

3. The gas discharge lamp as claimed in claim 2, in which said lamp units are concentric circular lamp units having different diameters.

4. The gas discharge lamp as claimed in claim 1, in which said lamp tube is of bulb-shaped, said sets of electrodes are provided at the inner wall of said tube and a plug connected to the said electrodes is provided at the bottom of said lamp tube.

5. An instant-start gas discharge lamp comprising a lamp tube with at least three electrodes of which two adjacent electrodes define a set, a ballast formed with flux leakage type core and including primary and secondary windings, of which the ends of the primary winding are respectively connected to one of said set of electrodes and the opposite single electrode, and one end of said secondary winding is connected to the another one of said set of electrodes.

6. An instant-start gas discharge lamp substantially as herein described with reference to the drawings.