US3626243A

US3626243A - Instantaneous starter device for a discharge lamp employing a diode thyristor

Info

Publication number: US3626243A
Application number: US852009A
Authority: US
Inventors: Shigeo Koyama; Masao Yasuda; Toru Takei; Yasutaka Kawai; Takeshi Matsushima
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 1968-08-27
Filing date: 1969-08-21
Publication date: 1971-12-07
Anticipated expiration: 1988-12-07
Also published as: FR2016451A1; BE738004A; NL6913049A; DE1943176B2; DE1943176C3; GB1281358A; DE1943176A1

Abstract

A starter device for a discharge lamp instantaneously lighting a fluorescent discharge tube; connecting in parallel with said fluorescent discharge tube a starter circuit consisting of a pulse transformer, a capacitor, and a symmetrical diode thyristor or a reverse blocking diode thyristor having a breakover voltage VBO lower than the rated power source voltage but higher than the tube voltage of said fluorescent discharge tube.

Description

United States Patent Inventors Shigeo Koyama Neyagawa-shi;

Masao Yasuda, Higashiosaka-shi; Toru Takei, Osaka; Yasutaka Kawai, Higashiosaka-shi; Takeshi Matsushima, Nara-shi, all 01 Japan Aug. 21, 1969 Dec. 7, 1971 Matsushita Electric Industrial Co., Ltd. Kadoma-shi, Osaka, Japan Aug. 27, 1968 Japan Nov. 4, 1968, Japan, No. 43/97146 Appl. No. Filed Patented Assignee Priorities INSTANTANEOUS STARTER DEVICE FOR A DISCHARGE LAMP EMPLOYING A DIODE TIIYRISTOR 4 Claims, 11 Drawing Figs.

U.S.Cl 315/101,

315/105, 315/205, 315/207, 315/239, 15/289, 3 IS/DIG. 5

W2- A r r /5 EL r [51] Int. Cl ..II05b 41/18 [50] Field ofSearch 315/100 U, 100 H, DIG. 2, DIG. 5, 101, 105, 205, 207, 239, 289

[56] References Cited UNITED STATES PATENTS 3,476,976 11/1969 Morita et a1. 315/101 FOREIGN PATENTS 466,135 6/1950 Canada 315/100 H Primary Examiner-Roy Lake Assistant Examiner-Siegfried H. Grimm Attorney-Stevens, Davis, Miller & Mosher ABSTRACT: A starter device for a discharge lamp instantaneously lighting a fluorescent discharge tube; connecting in parallel with said fluorescent discharge tube a starter circuit consisting of a pulse transformer, a capacitor, and a symmetrical diode thyristor or a reverse blocking diode thyristor having a breakover voltage V lower than the rated power source voltage but higher than the tube voltage of said fluorescent discharge tube.

PATENTED DEC 71971 SHEET 2 [IF 5 OFF CHARACTE/FVST/C x RES; mmavil wm PATENIEUDEB Han 3.626243 SHEET 5 OF 5 VOL 7/165 CURRENT INSTANTANEGIJS STARTER DEVICE FOR A DISCHARGE LAMP EMPLOYING A DIODE TIIYIIISTOII The present invention relates to a starter device for a discharge lamp instantaneously lighting a fluorescent discharge tube; connecting in parallel with said fluorescent discharge tube a starter circuit consisting of a pulse transformer, a capacitor, and a symmetrical diode thyristor or a reverse blocking diode thyristor. Detailed explanation of the invention will be made hereinafter with reference to the accompanying drawings, in which;

FIGS. I and 2 are the electric circuit diagrams of prior art starter devices for a discharge tube.

FIG. 3 shows the electric circuit diagram of a starter device for a discharge tube according .to one embodiment of the present invention.

FIG. 4 shows the voltage-current characteristic of a symmetrical diode thyristor used in the present invention.

FIG. shows the voltage waveforms across the terminals A and B of the device shown in FIG. 3 during starting.

FIG. 6 shows the waveforms of the current flowing through the symmetrical diode thyristor or at the point A of the device shown in FIG. 3 during starting.

FIG. 7 shows the voltage-current characteristic of a reverse blocking diode thyristor used in circuit of FIG. 3 and 8 or I1.

FIG. 8 shows the electric circuit diagram of a starter device for a discharge tube according to another embodiment of the present invention.

FIG. 9 shows the voltage waveforms across the terminals A and B of the device shown in FIG. 8 during starting.

FIG. III shows the waveforms of the symmetrical diode thyristor or current flowing through the reverse blocking diode thyristor or at the point B of the device shown in FIG. 8 during starting.

FIG. Ill shows the practical electric circuit diagram of the circuit shown in FIG. 8.

A conventional starter device as shown in FIGS. 1 and 2 consists of a manual switch 2 or a glow switch 3 connected in parallel with kyv wl[pescent 4ischarge lamp The anual switch is inconvenient because it requires much time before starting while a glow switch has the problem of a short lifetime although the starting time is faster. In these figures, 4 is an AC source, 5 is a power source switch, 6 is a current limiting ballast and 7 is a noise preventing capacitor connected in parallel with the manual switch 2 or the glow switch 3. Generally, in order to instantaneously start a fluorescent discharging tube it is necessary to provide a sufficient preheating current to both cathodes and at the same time a high continuous or a pulse voltage enough to light the tube between the opposite cathodes. In the prior art this is attained by winding a cathode preheating winding or a high-voltage applying winding. However, these methods lead to an increase in the size and weight of the current limiting ballast. The efiiciency is reduced due to an increase in the internal loss. Further, the high cost lowers the commercial advantage.

Therefore, this invention is aimed-at removing the abovementioned defects of theprior art and provides a novel starter device for a discharge tube. An embodiment of this invention will be explained with reference to FIGS. 3 to 7 hereinafter. In FIG. 3, 8 is an AC power source, 9 is a noise preventing capacitor, It is a power source switch, II is a current limiting ballast, I2 is a fluorescent discharge tube, both terminals of which have cathodes l3 and M, I5is a pulse transformer for generating a pulse voltage consisting of a primary winding 16 and a secondary winding I7, 18 is a symmetrical diode thyristor, and I9 is a capacitor for generating a pulse voltage. The symmetrical diode thyristor I8 has a switching characteristic as shown in FIG. 4. Namely, at a certain voltage (breakover voltage V the symmetrical diode thyristor rapidly changes from the cutoff state to the conducting state. In this circuit, the noise preventing capacitor 9 is connected in parallel with the power source 8 through the power source switch I0, one end of the power source 8 being connected to one end of the cathode 13 of the discharge tube I2 through the current limiting ballast Ill while the other end of the power source 8 is connected to the one end of another cathode 14 of the discharge tube I2 through the powersource switch I0. The other end of the cathode I3 is connected to one end of the secondary winding I7 of the pulse transformer 15. The other end of the secondary winding I7 is connected to one end of the primary winding 16 and also to one end of the capacitor 19. The number of turns of the secondary winding 17 is larger than that of the primary winding I6 i.e. at a ratio of about 10:1. The other end of the primary winding I6 of the pulse transformer I5 is connected to one end of the symmetrical diode thyristor I8. The other end of a capacitorI9 is connected to the other end of the symmetrical diode thyristor 18 and connected to the other end of the cathode I4 of the discharge tube 12. Here, it is necessary that the primary and secondary windings I6 and 17 of the pulse transformer 15 be wound in the same direction.

The breakover voltage V of the symmetrical diode thyristor used in the present invention has the characteristic; the rated output voltage of the power source 8 the breakover voltage V the tube voltage of the'discharge tube 12.

Next, the circuit operation will be explained in detail. In the circuit of FIG. 3, when the power source switch I0 is closed and the conducting state is reached, a voltage higher than the breakover voltage V i.e. the rated output voltage of the power source 8 is applied across both terminals of the sym metrical diode thyristor 18. Thus, the symmetrical diode thyristor l8 breaks over to make the circuit conductive. A sufflciently large preheating current flows through the cathodes I3 and I4 of the fluorescent discharge tube 12. In this case the breakover of the symmetrical diode thyristor I8 is determined by the breakover voltage V while the cutoff thereof is determined by a current flowing therethrough. Due to the inductance of the current limiting ballast II the current lags behind the voltage so that the symmetrical diode thyristor becomes conductive over substantially the whole period of the cycle and the power source 8. The voltage waveforms between the points A and B of the cathodes I3 and 14 become as shown in FIG. 5 while the waveforms of the current flowing through the thyristor 18 during preheating becomes as shown in FIG. 6. A high pulse voltage (about 600 V) as shown in FIG. 5 is applied between both terminals of the discharge tube 12 and the preheating of the cathode strikes the discharge of the fluorescent tube 12. Once the discharge tube 12 is lit, the voltage appearing across the symmetrical diode thyristor 18 becomes equal to the tube voltage of the discharge tube 12 so that the symmetrical diode thyristor I8 becomes cutoff. Thus, the discharge tube 12 is maintained in the discharge state. However, during the lighting of the discharge tube 12 the waveform of the tube voltage has high peak values by the influence of the charge and discharge of the capacitor 19. This is enhanced particularly atlow temperatures, and occasionally the peak value of the tube voltage exceedsthe breakover voltage V of the symmetrical diode thyristor 18. Thus, even though the discharge tube I2 is lighted and the symmetrical diode thyristor I8 is cutoff, the thyristor recovers its conducting state. As a result, the discharge tube 12 returns to the preheating state and does not commence lighting. In the practical circuit for the purpose of preventing this inconvenience a resistor (not shown) is connected in parallel with the symmetrical diode thyristor I8 or the capacitor I9. By the insertion of this resistor the discharge voltage of the capacitor at each cycle is absorbed and hence the waveform of the tube voltage during lighting is improved. No reignition phenomenon of the symmetrical diode thyristor 18 takes place at low tempera tures. Although in the above embodiment has been made of a symmetrical diode thyristorhaving the characteristic that the cutoff state rapidly changes to the conducting state at a certain voltage (i.e. breakover voltage V a reverse blocking diode thyristor having a high blocking; power at a negative voltage as shown in FIG. 7 can be used. The breakover voltage V of the reverse blocking diode thyristor used here satisfies the condition; the rated output voltage of the power source breakover voltage V the tube voltage of the discharge tube, whereas the blocking voltage V is sufficiently larger than the rated power source voltage. When this reverse blocking diode thyristor is used, a pulsating current flows only in one direction of the circuit. Since a DC component is superposed on this pulsating current, the magnetic circuit of the current limiting ballast saturates so that the fluorescent discharge tube is preheated enough to be lit. The half wave of the power source blocked by the thyristor is applied across the cathodes of the discharge tube. As a result, the same effect can be obtained as in the case of a symmetrical diode thyristor. Furthermore, in the above embodiment a noise preventing capacitor 9 is inserted between the input side of the current limiting ballast 11 and the output side of the cathode 14 of the fluorescent discharge tube 12, i.e. between the points C and D as shown in FIG. 3 in order to obtain the noise preventing effect. The same effect can be obtained when the capacitor is inserted between the points A and B. The thyristor 18 and capacitor 19 may be replaced by each other.

Next, a modified circuit based on the circuit system of FIG. 3 will be explained with reference to FIGS. 8 to 10. In FIGS. 8, 20 is a power source, 21 is a noise preventing capacitor, 22 is a power source switch, 23 is a current limiting ballast, 24 is a fluorescent discharge

tube having cathode

25 and 26 on both sides thereof, 27 is a pulse transformer for generating a pulse voltage consisting of a primary winding 28 and a secondary winding 29, 30 is a symmetrical diode thyristor, 31 is a capacitor for generating a pulse voltage, and 32 is a diode. The symmetrical diode thyristor 30 has a switching characteristic as shown in FIG. 4. Namely at a certain voltage (breakover voltage V,,,,), the symmetrical diode thyristor rapidly changes from the cutoff state to the conducting state. In this circuit construction the noise preventing capacitor 21 is connected in parallel with the power source20 through the power source switch 22. One end of the power source 20 is connected to one end of the cathode 25 of the discharge tube 24 through the current limiting ballast 23 while the other end of the power source 20 is connected to one end of the other cathode 26 of the discharge tube 24 through the power source switch 22. The other end of the cathode 25 is connected to one end of the secondary winding 29 of the pulse transformer 27. The other end of the secondary winding 29 is connected to the end of the primary winding 28 and together to one end of the capacitor 31. The number of turns of the secondary winding 29 of the pulse transformer 27 is larger than that of the primary winding 28 in the ratio of about :1. One end of the symmetrical diode thyristor 30 is connected to the other end of the primary winding 28 of the pulse transformer 27. The other end of the capacitor 31 is connected to the other end of the symmetrical diode thyristor 30 and the positive electrode side of the diode 32. The negative electrode side of the diode 32 is connected to the other end of the other cathode 26 of the discharge tube 24. Here the diode 32 may be connected in the reverse direction.

The breakover voltage V of the symmetrical diode thyristor 30 used in this invention has the characteristic; the rated output voltage of the power source 20 breakover voltage V the tube voltage of the discharge tube 24. The reverse breakover voltage of the diode 32 is sufficiently larger than the rated output voltage of the power source 20.

Next the circuit operation will be explained in detail. In the electric circuit shown in FIG. 8, when the power source switch 22 is closed and the conducting state is reached, a higher voltage than the breakover voltage V i.e. the rated output voltage of the power source 20, is applied between both terminals of the symmetrical diode thyristor 30. Thus, the symmetrical diode thyristor 30 breaks over to make the circuit conductive. A preheating current from the cathodes half wave rectified by the diode 32 flows through the

cathodes

25 and 26 of the fluorescent discharge tube 24. The voltage waveform applied between the points E and F of the

cathodes

25 and 26 of the fluorescent discharge tube 24 during preheating becomes as shown in FIG. 9 while the waveform of the current flowing through the thyristor 30 during preheating becomes as shown in FIG. 10. A high pulse voltage as shown in FIG. 9 appears between both terminals of the discharge tube 24 i.e. between the

cathodes

25 and 26. So, due to the preheating effect of the

cathodes

25 and 26 the discharge tube 24 is effectively lit. Once the discharge tube 24 is lit, the voltage appearing across the symmetrical diode thyristor 30 becomes cutoff. Therefore, the discharge tube 24 maintains the discharge state. Here even if the peak value of the tube voltage waveform of the discharge tube 24 is extremely high or has a large temperature dependence, the capacitor 31 is charged only in the DC direction by the diode 32. Therefore, the bad influence on the peak value of the discharge tube 24 due to the charge and discharge of the capacitor 31 and on the symmetrical diode thyristor 30 can be prevented.

Although in the above embodiment explanation has been made of the case where one end of the secondary winding 29 of the pulse transformer 27 (i.e. the beginning of the winding) is connected to one end of the cathode 25 of the discharge tube 24 and the other end (i.e. the end of the winding) is connected to one end of the primary winding (i.e. the end of the winding), there is no trouble when the secondary winding is connected in the opposite direction. However, it is necessary that the secondary winding 29 and the primary winding 28 are connected in the same direction. Further, it is allowed that the symmetrical diode thyristor 30 and the capacitor 31 are reversely connected.

Although in the embodiment shown in FIG. 8 explanation has been made of a case where the starting element is a symmetrical diode thyristor, a reverse blocking diode thyristor having the characteristic as shown in FIG. 7 may be employed. The breakover voltage of the reverse blocking diode thyristor satisfied the condition; the rated output voltage of the power source breakover voltage V the tube voltage of the discharge tube, whereas the blocking voltage V is sufficiently larger than the rated power source voltage. The current flowing through the circuit in the case of the reverse blocking diode thyristor is a pulsation current in one direction superposed on a DC current. Therefore, the magnetic circuit of the current limiting ballast becomes saturated and the fluorescent discharge tube is preheated enough to be lit. The half wave of the power source blocked by the thyristor is applied across the cathodes of the discharge tube. As the result, the same effect can be obtained as in the case with the symmetrical diode thyristor. It is needless to say here that the reverse blocking diode thyristor is connected in the same direction as the diode. Furthermore, in the above embodiment the noise preventing capacitor 21 inserted between the input side of the current limiting ballast 23 and the output side of the cathode of the discharge tube 24, i.e. between the points G and H has the effect of preventing the noise.

FIG. 11 shows a circuit diagram where winding 23' for increasing the cathode preheating current is employed together with the current limiting ballast 23 of FIG. 8.

In the starter device of the present invention constituted as mentioned above, the addition of such auxiliary means fitted to the starting device to further improve the starting characteristic, i.e. the winding wound around the current limiting ballast for increasing the cathode preheating current shown in FIG. 11 and the existence of the adjacent conductor near the discharge tube, does not needless to say depart from the spirit of this invention.

Thus, the inventive use of the symmetrical diode thyristor or reverse blocking diode thyristor as the starter element for lighting the discharge tube has a semipermanent life due to the semiconductor and a much more miniaturized size compared to the conventional glow starter device. Therefore, the weight can be reduced. Since no large current limiting ballast is used, the internal loss is diminished. In addition, more rapid starting is effected.

What is claimed is:

l. A starter device for a fluorescent discharge lamp having first and second cathodes, each of said cathodes having first and second ends, comprising a. a current limiting ballast connected in series with an electric power source between the first ends of said first and second cathodes,

b. a pulse transformer having primary and secondary and second ends, comprising a. a current limiting ballast connected in series with an electric power source between the first ends of said first and second cathodes,

windings wound in the same direction, each of said 5 b. a pulse transformer having primary and secondary windings having first and second ends, windings wound in the same direction, each of said c. first conductive means coupling a first end of the seconding a ing st and Second ends,

dary winding of said transformer to the second end of said 6- s ndu i ans coupling a first end of the Sec nfirst cathode, the second end of aid e o dar indi dary winding of said transformer to the second end of said being onne ted to the nd d f id primary i d. first cathode, the second end of said secondary winding ing, being connected to the second end of said primary windd. a reverse blocking diode thyristor, g, e. a capacitor coupled in series with said thyristor across the a Symmetrical diode thyrlstofr primary winding of said transformer, and e. a capacitor coupled in series with said thyristor across the f. second conductive means coupling the junction of said P 'f Y g a tran f0rrner, and i thyristor and capacitor to the second end of said second dlode only couplmg the J of said and h d capacitor to the second end of said second cathode. 2 A starter device as d fi d by claim 1 wherein Said 4. A second device as defined by claim 3 wherein said first Second conductive means comprise a diode conductive means comprises an auxiliary winding inductively 3. A starter device for a fluorescent discharge lamp having a Coupled to Sam current hmmng first and second cathodes, each of said cathodes having first

Claims

1. A starter device for a fluorescent discharge lamp having first and second cathodes, each of said cathodes having first and second ends, comprising a. a current limiting ballast connected in series with an electric power source between the first ends of said first and second cathodes, b. a pulse transformer having primary and secondary windings wound in the same direction, each of said windings having first and second ends, c. first conductive means coupling a first end of the secondary winding of said transformer to the second end of said first cathode, the second end of said secondary winding being connected to the second end of said primary winding, d. a reverse blocking diode thyristor, e. a capacitor coupled in series with said thyristor across the primary winding of said transformer, and f. second conductive means coupling the junction of said thyristor and capacitor to the second end of said second cathode.

2. A starter device as defined by claim 1 wherein said second conductive means comprise a diode.

3. A starter device for a fluorescent discharge lamp having a first and second cathodes, each of said cathodes having first and second ends, comprising a. a current limiting ballast connected in series with an electric power source between the first ends of said first and second cathodes, b. a pulse transformer having primary and secondary windings wound in the same direction, each of said windings having first and second ends, c. first conductive means coupling a first end of the secondary winding of said transformer to the second end of said first cathode, the second end of said secondary winding being connected to the second end of said primary winding, d. a symmetrical diode thyristor, e. a capacitor coupled in series with said thyristor across the primary winding of said transformer, and f. a diode only coupling the junction of said thyristor and capacitor to the second end of said second cathode.

4. A second device as defined by claim 3 wherein said first conductive means comprises an auxiliary winding inductively coupled to said current limiting ballast.