US3912969A

US3912969A - Discharge lamp lighting apparatus

Info

Publication number: US3912969A
Application number: US460019A
Authority: US
Inventors: Kenichi Nakai; Hiroshi Nishimura
Original assignee: Matsushita Electric Works Ltd
Current assignee: Panasonic Electric Works Co Ltd
Priority date: 1973-04-13
Filing date: 1974-04-11
Publication date: 1975-10-14
Anticipated expiration: 1992-10-14
Also published as: DE2417593B2; GB1464879A; NL7404869A; DE2417593A1

Abstract

A discharge lamp lighting apparatus wherein a discharge lamp circuit is provided on the secondary side of a leakage transformer, the leakage transformer being arranged to produce a secondary voltage which is lower than the ordinary starting voltage of the discharge lamp. An auxiliary winding magnetically coupled with at least the secondary side winding of the leakage transformer is wound on an iron core, and a phase advancing current circuit is coupled to the auxiliary winding for raising the lamp voltage at turn-on to a level exceeding the starting voltage.

Description

United States Patent Nakai et al.

DISCHARGE LAMP LIGHTING APPARATUS lnventorsz' Kenichi Nakai, Osaka; Hiroshi Nishimura, Kyoto, both of Japan Matsushita Electric Works, Ltd., Osaka, Japan Filed: Apr. 11, 1974 Appl. No.: 460,019

Assignee:

Foreign Application Priority Data Apr. 13, 1973 Japan.... 48-42362 Apr. 13, 1973 Japan 48-42364 us. Cl. 315/278; 315/239; 315/254; 315/289; 315/010. 5

1m. (:1. H05B 41/16; 1-105B 41/232 Field of Search 315 239, 244, 246, 247, 315/254, 260, 276, 278, 289, DIG. 5

References Cited UNITED STATES PATENTS 12/1942 Fries 315/278 X [451 Oct. 14, 1975 2,443,490 6/1948 Yates 315/254 X 2,791,726 5/1957 Feinberg 3,125,705 3/1964 Feinberg et a1... 3,792,310 2/1974 Crawford Primary Examiner-James W. Lawrence Assistant Examiner-E. R. LaRoche Attorney, Agent, or FirmWolfe, Hubbard, Leydig, Voit & Osann, Ltd.

[ ABSTRACT 5 Claims, 8 Drawing Figures US. Patent Oct. 14, 1975 Sheet 1 of4 3,912,969

/P o ART Fig. 2 A g 3 r 8 1 T US. Patent Oct. 14, 1975 Sheet 2 of4 3,912,969

VOLTAGE US. Patent 05: 14, 1975 Sheet3 of4 3,912,969

DISCHARGE LAMP LIGHTING APPARATUS This invention relates to discharge lamp lighting apparatus.

A circuit diagram of a conventional typical discharge lamp lighting apparatus is shown in FIG. 1 in which an alternating current source 1 is connected to the primary side of a leakage transformer 2 and a discharge lamp, such as a fluorescent lamp, is connected, to the secondary side of the leakage transformer 2. In such case, it is necessary that the secondary voltage V of the leakage transformer 2 be set above the voltage value which can start the discharge lamp 3. Therefore, when the current source I is switched on, the discharge lamp 3 will be started by the voltage V and will shift to normal lighting wherein the voltage across the discharge lamp 3 will decrease to a level lower than the starting voltage. In such apparatus, the leakage transformer 2 must be provided with a high secondary no-load voltage which can start the discharge lamp 3, and a current capacity capable of passing a current sufficient to normally light the discharge lamp 3. Therefore, the windings between A and B of the transformer 2 are required to be of a wire size having a current capacity sufficient to pass the normal current. As a result the leakage transformer 2 is large, the entire discharge lamp lighting apparatus is large, the weight is high and the price is also high.

In the present invention, the above mentioned problems have been successfully solved by using a so-called magnetism increasing property that, when a condenser is connected with the secondary side of a leakage transformer, the secondary voltage value will rise.

A main object of the present invention is to make a discharge lamp lighting apparatus small and light.

Another object of the present invention is to reduce the cost of a discharge lamp lighting apparatus.

Now an embodiment of the present invention shall be explained with reference to a preferred embodiment shown in accompanying drawings, in which:

FIG. I shows a conventional discharge lamp lighting apparatus;

FIG. 2 shows an embodiment of the discharge lamp lighting apparatus of the present invention;

FIG. 3 shows another embodiment of the present invention;

FIG. 4 is an explanatory view;

FIGS. 5 to 8 show other embodiments of the present invention.

. In FIG. 2, showing an embodiment of the discharge lamp lighting apparatus of the present invention, 1 is a leakage transformer formed of

windings

2, 3 and 4 and having an alternating current source 5 connected to the primary side. A discharge lamp 6 is connected between terminals 0 and B of the transformer l, and a condenser 7 is connected between terminals A and B of the transformer I. The number ofwinding turns between the terminals 0 and B of the transformer l is so selected that the voltage V normally generated between the terminals 0 and B will be lower than the ordinary starting voltage of the discharge lamp 6.

Now the operation shall be explained. When the alternating current source is switched on, due to the voltage generated in the winding 2, a phase advancing current I will flow through the condenser 7 and winding 2, and a magnetic flux will be additionally generated in the iron core of the winding 2. This magnetic flux will be of substantially the same phase as of the magnetic flux generated in the iron core of the winding 3, and will act on the magnetic flux generated in the iron core of the winding 3 to increase the magnetism. As a result, the voltage V between the terminals 0 and B of the leakage transformer 1 will increase to a level higher than the ordinary starting voltage of the discharge lamp 6. Accordingly the discharge lamp 6 will be started by this elevated voltage, and will be driven by the electric power fed from between the terminals 0 and B after it is started to maintain the lighting.

As described above, according to the present invention, when the phase advancing current I is made to flow through the winding 2 and the condenser 7, the voltage V will be increased, the discharge lamp 6 will be started and will be normally lighted. Therefore, the number of windings between the terminals 0 and B of the leakage transformer 1 can be selected so that the voltage V under the condition when there is no phase advancing current I, will be lower than the ordinary starting voltage of the discharge lamp 6. As a result, the number of windings between the terminals 0 and B, through which the greater part of the lamp current is made to flow, can be made less than in the conventional case. Further, the windings between the terminals A and B will act mainly as a means of providing the starting voltage, and will have little effect as a means of providing the electric power for maintaining the lighting of the discharge lamp 6, allowing the use of windings of fine wire diameter. As a result the discharge lamp lighting apparatus can be made small and light and the cost can be reduced.

In the foregoing description, it was noted that the voltage V between the terminals 0 and B will be at a level below the starting voltage required to start the discharge lamp 6. However, if this voltage V is selected to be higher than the restriking voltage required to restrike the discharge lamp 6, in the case of restriking it, as a result of the magnetism increasing action, it will not be necessary to apply an elevated voltage. Therefore, after the discharge lamp 6 is started and lighted, the circuit including the condenser 7 will be cut off the lighting circuit. It is needless to say that, in case the voltage V between the terminals 0 and B is selected to be lower than the restriking voltage but higher than the discharge maintaining voltage required for the discharge lamp 6 to maintain the discharge after the lamp is restruck, in order to restrike the lamp, the circuit including the condenser 7 will not be able to be cut off.

FIG. 3 shows another embodiment of the present invention. The main difference from the embodiment of FIG. 2 is the use of a so-called lead peak type transformer in which the secondary side iron core is partly saturated. FIG. 4 shows a secondary voltage of a lead peak type transformer in which the curve A is of an ordinary transformer and the curve B is of a lead peak type transformer.

In FIG. 3, a leakage transformer 1 has an auxiliary winding 2 wound on a partly saturated iron core, a secondary winding 3 and a current source winding 4 to which an alternating current source 5 is connected. A discharge lamp 6 is connected between terminals 0 and B of the leakage transformer 1 and a starting condenser 7 is connected between terminals A and B. The number of windings between the terminals 0 and B of the leakage transformer I is so selected that the voltage V between the terminals 0 and B will be lower than the ordinary starting voltage of the discharge lamp 6 but higher than the discharge maintaining voltage required to maintain the discharge of the discharge lamp.

In operation, when the alternating current source 5 is switched on, a voltage of basic waves will be produced in the secondary winding 3, a voltage of deformed waves will be produced in the auxiliary winding 2 and a phase advancing current I containing mostly components of third higher harmonics will flow through the starting condenser. The phase advancing current I causes a magnetic flux of a deformed wave form to be additionally generated in the iron core of the winding 2. The basic wave components and third higher harmonic components forming this magnetic flux will be components of substantially the same phase as of the magnetic flux generated in the iron core of the winding 3, and will act on the magnetic flux generated in the iron core of the winding 3 to increase the magnetism. As a result, the voltage V of the secondary winding 3 will be modulated and elevated. That is to say, not only the basic wave voltage but also the higher harmonic voltage will be superimposed on the secondary winding 3 wound on the same iron core as the auxiliary winding 2 so that the voltage V will be elevated. Because of this elevation of voltage, the wave height valve of the voltage V will be increased to a level higher than the ordinary starting voltage of the discharge lamp 6. Accordingly the discharge lamp 6 will start, and will be driven by the electric power fed from the terminals and B after starting to maintain the lighting.

Further, in practicing the present invention, as the magnetic flux of the winding 2 acting on the winding 3 to increase the magnetism is of deformed waves of substantially the same phase as those of the winding 3 and having third higher harmonic components, their wave height valve will be larger than of pure sine waves of the same effective value. Therefore, as compared with the case where the iron core of the auxiliary winding is an ordinary iron core, the wave height value of the modulated and elevated voltage of the winding 3 will be higher, and an enhanced effect for starting the discharge lamp be produced.

FIG. shows another embodiment of the present invention formed to be flickerless for two lamps. In the drawing, a leakage transformer 1 has a magnetically coupled winding 2 of a comparatively high voltage wound on an iron core of a partly saturated characteristic, a winding 3 of a comparatively low voltage and a common current source winding 4 to which an alternating current source 5 is connected. A discharge lamp 6 is connected to the high voltage winding 2 of the leakage transformer through a phase advancing condenser 17 so as to form a phase advancing discharge lamp lighting circuit. A second discharge lamp 8 is connected to the low voltage winding 3, and a starting condenser 19 is connected as illustrated between the noncommon terminals of the high voltage winding 2 and low voltage winding 3. In such case, the voltage Va of the high voltage winding 2 is so set as to be of a voltage value sufficient to start the discharge lamp 6 and the voltage Vb of the low voltage winding 3 is so set as to be lower than the ordinary starting voltage of the discharge lamp 8 but higher than the discharge maintaining voltage required to maintain normal lighting.

In operation, when the alternating current source 5 is switched on, a voltage of deformed waves containing mostly third higher harmonic components will be produced in the winding 2 wound on the iron core of a partly saturated characteristic due to the saturated characteristic. Additionally a voltage of basic waves will be produced in the winding 3 wound on an ordinary iron core. As a result a higher harmonic phase advancing current will flow through a circuit including the

windings

2 and 3 and condenser 19, and a magnetic flux of a deformed wave form will be additionally generated in the iron core of each of the

windings

2 and 3. The basic wave components and third higher harmonic components forming this magnetic flux will be components of substantially the same phase as of the magnetic flux generated in the iron core of the winding 3 and will act on the magnetic flux generated in the iron core of the winding 3 to increase the magnetism. As a result, the voltage Vb of the winding 3 will be modulated and elevated. That is to say, not only the basic waves but also the third higher harmonic voltage will be superimposed on the winding 3 so that the voltage Vb will be elevated. Because of this elevation of voltage, the peak value of the voltage Vb will become larger than the ordinary starting voltage of the discharge lamp 8, the discharge lamp 8 will be started, and will be controlled by the electric power fed from the winding 3 after it is started to maintain the lighting. On the other hand, as the voltage Va of the phase advancing winding 2 is of a value sufficient to start the discharge lamp 6, the discharge lamp 6 will be started by the voltage Va and will maintain the lighting. Further, as the voltage Vb of the phase advancing discharge circuit is selected to be of a value lower than that normally encountered, in order to keep the power factor of the entire apparatus high, it is necessary to reduce the effective value of the voltage Va of the phase advancing discharge circuit. However, in the embodiment in FIG. 5, as a lead peak type is adopted for the winding 2, a wave height value sufficient for the starting will be obtained, the effective secondary voltage will be reduced and therefore a flickerless lighting apparatus of high power factor will be pro vided.

Thus, in the embodiment in FIG. 5, as the voltage Vb of the winding 3 is modulated and elevated by the magnetism increasing action of the phase advancing current of higher harmonics flowing through the circuit including the starting condenser 19, the number of winding turns of the winding 3 will be less than in the conventional case. Therefore the entire leakage transformer 1 will be small and light. Further, as the winding 2 having a partly saturated characteristic is used as a phase advancing circuit, a flickerless lighting apparatus of a high power factor type can be obtained.

In the embodiment illustrated in FIG. 5, if the voltage Vb is selected to be of a value at which the discharge lamp 8 can be restruck, after the discharge lamp 8 is started it will be possible to switch the condenser 19 out .of the circuit. In such case, the mutually interfering currents flowing through the condenser 19 due to the current phase difference between the

discharge lamps

6 and 8 during normal operation is eliminated.

FIG. 6 is of an embodiment of a circuit adapted to attain the above mentioned function, achieved by adding a triac l0 and triac trigger resistance 11 to the circuit shown in FIG. 5.

The operation of the triac shall be explained. The value of the resistance 11 is so selected that the triac will conduct with Vb at its elevated starting voltagelevel but will not conduct with the discharge lamp voltage at the normal lighting level. Before the discharge lamp 8 is started, the triac will conduct with Vb but, after it is started, the voltage across the resistance 11 will be reduced. Therefore the triac 10 will be off and the above mentioned function will be provided.

FIG. 7 shows another embodiment of the present invention. It differs from the embodiment of FIG. 5 mainly in that a condenser 9 for preventing electrical noise is provided in parallel with the discharge lamp 8 so that the noise generated in the

discharge lamps

6 and 8 will be simultaneously prevented. It is also noted that if the condenser 9' for preventing noise coupled in parallel with the discharge lamp 6, the same effect will be achieved. The overall circuit operation is the same as in the embodiment of FIG. 5.

FIG. 8 shows another embodiment of the present invention for lighting three lamps. In the drawing, a leakage transformer I has a first secondary winding 2 wound on an iron core having a partly saturated characteristic, a second secondary winding 3 wound on an ordinary iron core and a common current source winding 4 to which an alternating current source 5 is connected. Two series discharge lamps 6 and 6' are connected to the secondary winding 2 through a phase advancing condenser 17. A discharge lamp 8 is connected to the secondary winding 3 and a starting condenser 19 is connected as illustrated between the

secondary windings

2 and 3. The voltage Va of the secondary winding 2 is so set as to be of a level sufficient to start the two series discharge lamps 6 and 60. The voltage Vb of the secondary winding 3 is so set as to be lower than the ordinary starting voltage of the discharge lamp 8 but higher than the voltage required to maintain the discharge.

In operation, when the alternating current source 5 is switched on, the secondary winding 2 of the leakage transformer l will'operate as a series type lead peak ballast to start and light the discharge lamps 6 and 6'. On the other hand, due to the voltage difference Va Vb, a phase advancing current will flow through the circuit formed of the secondary winding 2, starting winding 19 and secondary condenser 3. As a result of the phase advancing current, a magnetic flux will be additionally generated in the iron core of the winding 2. However, this magnetic flux will be of substantially the same phase as of the magnetic flux generated in the iron core of the winding 3 and will act on the magnetic flux generated in the iron core of the winding 3 to increase the magnetism. As a result, the magnetism of the secondary winding 3 will be increased, and the voltage Vb of the secondary winding 3 will be elevated to a level exceeding the ordinary starting voltage of the discharge lamp 8 causing the discharge lamp 8 to be started and lighted. After the discharge lamp 8 is started, ,it will be controlled by the electric power fed from between the terminals 0 and B to maintain the lighting. Thus, as the starting condenser 19 is connected between the

secondary windings

2 and 3, due to the voltage elevation by the magnetism increasing action of the phase advancing current flowing through the starting condenser 19, the number of windings of the phase delaying winding 3 can be made less than in the conventional case. Therefore the entire lighting apparatus can be made small and light with a corresponding reduction in cost.

With reference to FIG. 8, if a condenser 9 is connected in parallel with the discharge lamp 8 as shown by the dotted lines, the voltage Va will be divided by the condensers 19 and 9' and impressed on the discharge lamp 8, and the magnetism of the iron cores in the parts of the

windings

3 and 4 will be above to be increased by the phase advancing current flowing through the condenser 9' so that the voltage Vb will be elevated even further. It is also possible to use one long discharge lamp instead of the two series discharge lamps 6 and 60'.

If the present invention shown in FIGS. 5 to 7 is applied, for example, to a two-40W lamp flickerless type fluorescent lamp stabilizer, it will be possible to produce a rapid type flickerless stabilizer of a high power factor with the same dimensions as of the conventional two-series-4OW lamp rapid type stabilizer.

What is claimed is:

1. A discharge lamp lighting apparatus comprising a leakage transformer including a secondary winding, an auxiliary winding magnetically coupled with said secondary winding, and a current source winding common to said secondary and auxiliary windings, said auxiliary winding being wound on an iron core having a partly saturated characteristic, a discharge lamp connected in series with said secondary winding, the leakage transformer being wound so that the secondary winding produces a voltage which is lower than the starting voltage of the discharge lamp, and a phase advancing current circuit conductively coupling said auxiliary winding to said discharge lamp for increasing the lamp voltage to a level above said starting voltage to start the lamp.

2. The discharge lamp lighting apparatus as set forth in claim 1 wherein said phase advancing current circuit comprises a condenser.

3. The discharge lamp lighting apparatus as set forth in claim 1 wherein said phase advancing current circuit comprises a condenser conductively coupled between the discharge lamp and the auxiliary winding forming a first series circuit including the condenser and the discharge lamp, said apparatus further including a second series circuit comprising a second condenser and a second discharge lamp, said second series circuit being connected in parallel with the first series circuit.

4. The discharge lamp lighting apparatus as set forth in claim 3 further including a third condenser coupled in parallel with at least one of said first and second discharge lamps thereby to suppress electrical noise.

5. The discharge lamp lighting apparatus as set forth in claim 1 wherein said phase advancing current circuit comprises a condenser conductively coupled between said auxiliary winding and said discharge lamp and forming a first series circuit including the condenser and the discharge lamp, said apparatus further including a second series circuit comprising a second condenser and at least two discharge lamps, said second series circuit being connected in parallel with the first series circuit, said auxiliary winding being adapted to generate a voltage sufficient to start said two discharge lamps in the second series circuit.