US3866088A

US3866088A - Discharge lamp starter device using a backswing voltage booster and characterized by the absence of a preheating function

Info

Publication number: US3866088A
Application number: US353250A
Authority: US
Inventors: Isao Kaneda; Kiyokazu Takeuchi
Original assignee: New Nippon Electric Co Ltd
Current assignee: New Nippon Electric Co Ltd
Priority date: 1971-11-29
Filing date: 1973-04-23
Publication date: 1975-02-11
Anticipated expiration: 1992-02-11

Abstract

A discharge lamp starter device adapted to instantaneously ignite a discharge lamp without preheating the same, in which a backswing voltage booster including a capacitor, a saturable nonlinear inductor and a symmetrical switch in series with the nonlinear inductor is connected across the discharge lamp. The oscillating output of the booster, which is applied to the discharge lamp, can be controlled by bias means for changing magnetic level in the core of the saturable non-linear inductor in the booster. Current limiting means such as a second capacitor can be added to the booster to minimize the rating of the elements required for the booster, thereby reducing the cost of the starter device.

Description

United States Patent 1191 Kaneda et a1.

[ DISCHARGE LAMP STARTER DEVICE USING A BACKSWING VOLTAGE BOOSTER AND CHARACTERIZED BY THE ABSENCE OF A PREHEATING FUNCTION [75] Inventors: Isao Kaneda; Kiyokazu Takeuchi,

both of Osaka, Japan [73] Assignee: New Nippon Electric Company Ltd.,

Osaka, Japan [22] Filed: Apr. 23, 1973 [21] Appl. No.: 353,250

Related US. Application Data [63] Continuation-impart of Ser. No. 202,766, Nov. 29,.

1971, Pat, No. 3,753,037, which is a continuation-in-part of Ser. No. 14,325, Feb. 26, 1970, Pat. No, 3,665,243.

[52] US. Cl 315/105, 315/242, 315/D1G. 2, 3l5/DIG. 5

[51] Int. Cl. H05b 41/00, H 05b 41/14 [58] Field of Search 315/105, 106, 242-244, 315/172, 174, DIG. 2, DIG. 5

[56] References Cited UNITED STATES PATENTS 3.476976 ll/l969 Morita et al. 315/105 X Feb. 11,1975

3,626,243 12/1971 Koyama et a1 315/105 X Primary Examiner-James W. Lawrence Assistant Examiner-Marvin Nussbaum Attorney, Agent, or FirmRoberts & Cohen [57] ABSTRACT A discharge lamp starter device adapted to instantaneously ignite a discharge lamp without preheating the same, in which a backswing voltage booster including a capacitor, a saturable non-linear inductor and a symmetrical switch in series with the non-linear inductor is connected across the discharge lamp. The oscillating output of the booster, which is applied to the discharge lamp, can be controlled by bias means for changing magnetic level in the core of the saturable non-linear inductor in the booster. Current limiting means such as a second capacitor can be added to the booster to minimize the rating of the elements required for the booster, thereby reducing the cost of the starter device.

19 Claims, 23 Drawing Figures PATENTED 1 I975 3,866,088

SHEEI 2 OF 6 FIG.4A 0

FIG.4B o

FIG.5

PATENTEDFEBI 1 1975 3, 866. sum 30F 6 088 DISCHARGE LAMP STARTER DEVICE USING A BACKSWING VOLTAGE BOOSTER AND CHARACTERIZED BY THE ABSENCE OF A PREIIEATING FUNCTION CROSS-REFERENCES TO RELATED APPLICATION This application is a continuation-in-part of our copending application Ser. No. 202,766 filed Nov. 29, 197 I, (now U.S. Pat. No. 3,753,037) entitled Starting Circuit for Discharge Lamps," which is a continuationin-part application based on application Ser. No. l4,325 filed Feb. 26, 1970, and which is now U.S. Pat. No. 3,665,243, all being assigned to the same assignee.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to starting devices characterized by the absence of preheating functions and adapted for rise with discharge lamps ofthe type having filaments but heated from a separate power source, and more particularly to novel and improved and improved discharge lamp starter devices of the type using a backswing voltage booster which produces a higher oscillatory voltage than the associated voltage source and having no preheating function.

2. Description of the Prior Art Discharge-lamp starter devices are generally divided into two groups corresponding to the type of discharge lamp used therewith. The devices of one group are used for lighting the type of discharge lamp having filaments which facilitate ignition upon the supply of heating current thereto and in association with such type of lamp, the starter device provides the heating current as well as the starting voltage during the starting period. This is described in U.S. Pat. No. 3,753,037 of Aug. 14, i973 and U.S. Pat. No. 3,665,243 of May 23, 1972. The other group, which is the group to which this invention is directed, includes starter devices for nonpreheating type discharge lamps or rapid-start type fluorescent lamps in which heating or preheating current of the rapid-start type need not be supplied by a starter device, because it can be supplied from a separate voltage source such as a transformer for the heating of filaments.

Lamps of the first group are generally called hotcathode type discharge lamps and are the normal starting type fluorescent lamps excepting those of the rapid start or instant-start types and the non-filament type of fluorescent lamps. Lamps of the second group are generally called cold-cathode type discharge lamps, which are such as the common mercury and sodium lamps, and include the rapid-start and non-filament types of fluorescent lamps. Some features and differences between the two groups are as follows:

i. As to starter-device function, the second group does not require a filament preheating function but need only supply ignition voltage, whereas the first group is required to preheat filaments.

2. As to abnormal operation of the starter devices, the second group requires the addition of a protective circuit, whereas the first group can utilize an increase of filament resistance as described in U.S. Pat. No. 3,753,037.

3. As to the cost and size of the starter devices, since the second group generally is required to supply a relatively high voltage and energy, its devices are of relatively large size and cost, whereas the devices of the first group are easily in compact form.

4. A drawback of the second group is that it is difficult to control the output thereof when a conventional voltage pulse generator is used. Important problems include the need to control the starting energy and the fact that it is easy to cause sputtering of electrode materials with the application of excess voltage and/or energy.

SUMMARY OF THE INVENTION It is an object of the invention to eliminate the abovenoted and other drawbacks inherent in the prior art and to provide an improved starter device which can be employed for non-preheating type discharge lamps and rapid-start type fluorescent lamps.

Another object of the invention is to provide an improved starting circuit for the above-mentioned discharge lamps, which produces an oscillating voltage according to a backswing voltage generated by a booster including a capacitor, a saturable inductor and a symmetrical switching element.

Still another object of the invention is to provide a discharge lamp operating circuit having a backswing voltage booster, in which the output applied to the discharge lamp can be controlled by bias means for negatively or positively exciting the magnetic field of the core of the saturable non-linear inductor.

A still further object of this invention is to provide an economical starter device for the above-mentioned discharge lamps, in which a backswing voltage booster provides reactance means such as a second capacitor to limit current through the booster.

According to the invention, there is provided a discharge-lamp operating apparatus devoid of or having separate heating means: which comprises; a first closed circuit which includes a power source, the linear inductor of an arc discharge stabilizer and a capacitor; a second closed circuit which includes the capacitor mentioned above as being in the first closed circuit, a saturable non-linear inductor and a symmetrical switch element such as a bidirectional diode thyristor connected in series with the non-linear inductor; and a discharge lamp connected in parallel with the capacitor common to the first and second closed circuits.

The starter device in the above apparatus is constituted by a backswing voltage booster comprised by the first and second closed circuits, in which the saturable non-linear inductor is made from coil windings on a core of magnetic and dielectric materials such as ferrite so as to provide a relatively low inductance in the saturated state and a relatively high inductance in the unsaturated state. The output of the booster generally is in the form of an oscillating voltage which is produced by the switching function of the bidirectional diode thyristor together with the functions of compressing a current in the second closed circuir according to the different inductances of the saturable non-linear inductor and inducing a backswing voltage across the saturable non-linear inductor in the unsaturated state, due to the effective capacitance thereof.

In the above starter device, a bias means for changing the magnetic density level of the non-linear inductor is used to control voluntarily the amplitude of voltage and/or the oscillating frequency of the output, for applying the desired starting energy and voltage to discharge lamps. For instance, bias coil windings, the ratio of which to that of the saturable non-linear inductor is preferably about 1/5 to H300, are added to the core of the saturable non-linear inductor. Since the bias coil windings are connected electrically with the first and- /or second closed circuit, the level of the residual magnetic flux density (Br) of the core of the saturable nonlinear inductor is excited by a magnetic field due to commercial-frequency current flowing in the bias coil windings, so that the stored energy of the core and the output voltage may be controlled. Thus, a suitable voltage for starting lamps can be obtained. As to the manner of excitation due to the added magnetic field, there are two ways. There are hereafter designated plus bias for additive magnetization and minus bias for bucking demagnetization with regard to the core.

The addition of bias means is effective in a starter device in the absence of pre-preheating function for a discharge lamp as well as a rapid-start fluorescent lamp. Since the non-preheating discharge lamp requires relatively high power and high voltage for its starting, the use of a plus bias coil is effective particularly at a relatively highoperating temperature to insure lamp igni tion. The plus bias means serves to compensate the decrease of magnetic flux change due to rising temperatures. That is, the maximum magnetic flux density of the high-permeable ferrite core is sharply decreased with respect to that at a relatively low temperature as seen from the fact that the maximum magnetic flux density of a ferrite core at 80 C is onehalf of that at 20 C.

It is another advantage of the invention that the bias means acts as a fail-safe or protective means for abnormal operation in case, for example, the discharge lamp is accidentally removed from its operating apparatus during operation. In such case, the plus bias means serves to change the output voltage to limit the oscillating period, thereby reducing the effective mean value of the oscillating energy of the booster and preventing its self destruction.

The saturable non-linear inductor used in the booster of this invention provides a low inductance in the saturated state and a high inductance in the unsaturated state. This is important for producing high voltage oscillation due to the fact that the rising backswing voltage, induced between the terminals of the saturable non-linear inductor at a moment of turning off of the symmetrical switch, is substantially coincident with the rising of the output voltage which appears across the capactor, and that the non-conduction period of the symmetrical switch is continued for a time due to the impedance function of the unsaturated saturable nonlinear inductor, while the output voltage increases directly up to several times the source voltage.

BRIEF DESCRIPTION OF THE DRAWINGS The principal of a backswing voltage booster is illustrated in FIGS. 1 to and several kinds of discharge lamp starter device in accordance with this invention are shown in FIGS. 11 to 20. More particularly, in the drawing:

FIG. 1 is a schematic circuit diagram of a backswing voltage booster;

FIG. 2 shows a typical V-I characteristic curve of a bidirectional diode thyristor used in the circuit of FIG.

FIG. 3 illustrates waveforms of current and voltage in the circuit of FIG. 1 under operation with DC. source voltage;

FIGS 4 (A) and (B) illustrate waveforms, on enlarged scale, of FIG. 3 for the initial starting period;

FIG. 5 illustrates waveforms on enlarged scale of FIG. 3 for the stable state of oscillation;

FIG. 6 illustrates waveforms of current and voltage in the circuit of FIG. 1 under operation with an A.C. source voltage;

FIG. 7 is a circuit diagram of a backswing voltage booster having a bias means wherein a bias coil is inserted in series with a common capacitor shared by two closed circuits in the booster;

FIG. 8 is a diagram of another circuit wherein a bias coil is inserted in series with a linear inductor in one of the closed circuits;

FIGS. 9 (A) and 9(8) illustrate waveforms of the output voltages produced by the circuits of FIGS. 7 or 8;

FIG. 10 illustrates waveforms of the output voltage produced by the plus bias coil in the circuits of FIGS. 7 or 8;

FIG. 11 is a schematic circuit diagram of a dishcarge lamp starter device according to this invention;

FIG. 12 is a circuit diagram of a starter device of an embodiment of the invention suitable for the igniting of mercury lamps;

FIG. 13 is a modifications of FlG. 12;

FIG. 14 is a circuit diagram of a starter device of another embodiment of the invention suitable for minimizing the ratings of the elements of the starter device;

FIGS. 15 and 16 are circuit diagrams of further embodiments based on the starter device of FIG. 14 suitable for igniting low pressure sodium lamps and fluorescent lamps of the cold-cathode type;

FIG. 17 is a circuit diagram of a starter device of another embodiment of the invention suited for lighting rapid-start type fluorescent lamps having filaments;

FIG. 18 is a circuit diagram of still another embodiment of the invention for a cold-cathode discharge lamp having an auxiliary electrode;

FIGS. 19(A) and 19(B) illustrate waveforms of the limited oscillating voltage applied to the discharge lamp in the circuit of FIG. 18; and

FIG. 20 is a circuitdiagram of a further embodiment of the invention suited for lighting metal-halide discharge lamps.

DETAILED DESCRIPTION The principal of the generation of an oscillating voltage by a backswing voltage booster is next, explained in accordance with its principal circuit waveforms and phenomena as illustrated in FIGS. 1 to 10.

In FIG. 1 is shown a first closed circuit which includes a voltage source E, a linear inductor L and a capacitor. A second closed circuit includes the capacitor C which is common to both closed circuits, a saturable non-linear inductor L and a voltage responsive switch S such as bidirectional diode thyristor or silicon symmetrical switch. A third closed circuit consists of the non-linear inductor in itself characterized by the inducing of a backswing voltage due to its distributed effective parameters of capacitance c and resistance r in the unsaturated state as shown by dotted lines.

The first closed circuit charges the capacitor C through the linear inductor L, giving a constant-current function and the others act alternately to generate a high-amplitude oscillating voltage across the capacitor C; i.e., the third one checks the conducting of the switch S for a given time by inducing the backswing voltage and the subsequent saturating characteristic thereof while the switch S is turning off. Thus, the output voltage across the capacitor C is boosted to about times the source voltage. The output can be further controlled by adding bias means as mentioned hereinafter.

Actually, the circuit of FIG. 1 includes a resistance r in the first closed circuit and a resistance r in the second closed circuit, so that the closed circuits are respectively constituted by elements Er,L CE for the first circuit, elements C-L r SC for the second circuit and elements L 0 and r in parallel for the third circuit wherein the saturable non-linear inductor L has inductance In in the unsaturated state and small inductance ls in the saturated state, and the switch S has a voltage-current (V-I) characteristic curve as shown in FIG. 2. Switch S moreover is characterized by a breakover voltage V against impressed voltage, a breakover current I a holding current I a turn off time 1,, and a breakover voltage V,,,,' against high frequency impressed voltage.

In the above circuit, when a DC. voltage e is applied as the voltage source E under appropriate circuit conditions, the oscillation commences and is developed as shwon in FIG. 3 in which the output voltage v across the capacitor C is significantly raised to about five times as much as the DC. source voltage e when the stable state is reached.

In FIG. 3, the input current i shows a constant increase with passing time, and the variation of input voltage v shows a voltage boost at its peak with an increasing frequency thereof in accordance with the increase of i In the initial starting stage, the waveforms of input current i capacitor current i output voltage v and indicator voltage v across the non-linear inductor L are illustrated in FIG. 4 which has an enlarged time-base with respect to FIG. 3, wherein the output voltage v gradually reaches the level of v by the connection of source voltage 2 at a time t== t and is reversed in polarity by a discharging of the electric charge due to conduction by the switch S at a time t= t and is elevated to a level higher than V,,,, by repeated charging after termination of discharge at time t t These charging and discharging steps are repeated to elevate the peaks step by step. At the same time, the input current I, also increases.

FIG. 5 illustrates each waveform with an enlargement of the time-base with respect to the stable oscillating state of FIG. 3. The input current i is substantially constant and the voltages v, and v are in substantially accord. The terminal voltage v of the non-linear inductor is divided into three periods. The first period T is equivalent to the period for inducing the backswing voltage v,, in which the switch S keeps its nonconducting state in spite of being subjected to a higher impressed voltage than V,,,, by reason of the fact that the difference voltage between v, and v is maintained below V,,,, by the induction of backswing voltage v,,. The second period T is such that the switch S maintains its non-conducting state due to the saturation time of L although the difference voltage exceeds V,,,,. The third period T relates to the saturation state of L by turning on the switch S.

The boosting mechanism is a discontinuous phenomenon, as described above, and therefore explanation is given hereunder in detail for each period of operation of the above-mentioned D.C. operating circuit.

1. Operation of the First Closed Circuit before Switch S Conducts Initially (corresponding to the period between t= 0 and t= I, in FIG. 4(A)):

According to the operation of the first closed circut, the following equation is valid:

L r11 l/C J 8 The output voltage v across the capacitor C possibly rises to two times the source voltage e at the inherent frequency of the first closed circuit. However, the actual fluctuation of v, is negative and of DC. form.

On the other hand, since the saturation voltage v, of the non-linear inductor L is proportional to the frequency of the impressed voltage, the value of v, is so small that the switch S falls into conducting state at time t= t and v V,,,, without any obstruction being caused by v,.

2. Initial Conduction of the Switch S (corresponding to the period between t t and t= The second closed circuit is established by the turning-on of the switch S so that the capacitor C discharges its discharge current i At the same time, another closed circuit E--r,L L -r SE is simultaneously established so that the input current i, flows continuously. The saturable non-linear inductor L stores energy in its equivalent capacitance element due to the electric charges caused by the voltage v applied across the terminal of the non-linear inductor L during conduction of the switch S.

For consideration of changing of the polarity of output voltage, equation (2) holds true for the second closed circuit when the switch S conducts.

L di /dt r i l/c f dr =0 Since the saturable non-linear inductor L provides a very small value of saturated inductance 1,, the peak value of i becomes very large as shown in FIG. 4(A), and the output voltage v reverses its polarity during the second half cycle of i If r is not zero, the absolute value of v after reversing polarity is somewhat lower than before reversing.

Simultaneously, the extra closed circuit E-n-L- L -r SE is established, and if capacitor C is negligibly small under the condition of L 1 and further r is negligibly small under the condition of r, r the formula of i, is simplified as below.

This is so-called transient DC. current and also the constant-current function of the linear inductor L, and is significant concerning the voltage elevation function as hereinafter decribed.

When the second and the extra circuit are established, the current i i +11) flows into the series circuit including the saturable non-linear inductor L and the switch S. This is oscillatory current since i As a result of the excitation during times between t,

and t the non-linear inductor L stores energy en as below:

At the moment of the turning-off of the switch S, i goes down below I and near zero. Therefore, energy 6 n is approximately stored in the equivalent capacitance c of the non-linear inductor L When the composed current i diminishes from its peak and to a magnitude below the holding current I of the switch S, the switch becomes non-conducting at least onece. At the start of the non-conducting state, the capacitor C has completed its discharging step already and commences a charging step because of the D.C.-like 1' This is called the energy storing function of the saturable non-linear inductor L 3. Initial Boosting by the First Closed Circuit (corresponding to the period between t= t and 2 t in FIG. 4(A):

In this period, the input current i flows into the first closed circuit, and the output voltage v is boosted by reason of the fact that the input current 1' maintains its value after checking of the switch S by the constantcurrent function of L 4. Conduction Checking Function of the Non-Linear Inductor (corresponding to the period between t t and t= 1 in FIG. 4(A):

If the differential voltage v V isnt checked by any means, the switch S falls into the conducting state again and one cannot actually utilize theboosting function even though v is able to be boosted above the level of V The non-linear inductor L has the function of checking characteristics against the differential voltage.

In the operating period between t t and t i in FIG. 4(A), the saturable non-linear inductor L returns to the unsaturated state as soon as the switch S turns off, and starts to induce the voltage oscillation v called the backswing in the third closed circuit including the inductance 1,, at unsaturated state and the distributed effective capacitance c and resistance r in parallel relationship. The voltage v,, is based on the release of energy stored due to excitation current in the preceding step. This keeps the switch S in non-conduction state for awhile. Switch S is a symmetrical switch such as, for example, a bidirectional diode thyrister called SIDAC, manufactured by Sindengen Electric Mfg, Co. of Japan.

Even though the oscillation of v,, is not sufficient in the period of to t the oscillation grows with repetitions of the charging and discharging steps. Thus, the voltage applied to the symmetrical switch S is kept below V by v,,. The backswing voltage is one of the main functions for the generation of a voltage boost. Therefore, the non-linear inductor L is realized by making its core materials from a material such as ferrite that has a suitable dielectric constant and high permeability.

In the operation corresponding to the period between 1 t and I in FIG. 4(A), if the difference voltage between v,. and v reaches V,,,,, the switch S is once permitted to conduct but not completely because of current checking due to the large impedance based on the inductance 1,, in its unsaturated state. The saturable voltage v, of the non-linear inductor L is elevated against an impressed voltage of high frequency.

During this period, the switch S is checked continuously since the leakage current through the series circuit including L and S does not reach the breakover current I of S. Then, the current which starts with a very small value gradually increases and turns the switch S on in its complete conduction state at the given time t t when the saturable non-linear inductor L is finally saturated to have the very small value 1,, in the oscillating operation.

5. Increasing of the Output Voltage v by Steps (corresponding to the operation period after t in FIG. 4(B):

After the time t= 1 operations similar to those mentioned above in the period between r= t and I 1 are repeated. The maximum voltage vflm) across the capacitor C is elevated step by step and the oscillation frequency is also elevated by steps till the equilibrium state is reached. This results firstly because every value v is momentarily elevated due to each increase of the initial condition, and secondly because each terminal voltage v across the non-linear inductor L gradually fits the steeper ascent of each v based on the fact that each stored energy quantity for backswing oscillation is elevated due to each increase of excitation current and each saturable voltage v of inductor L is also elevated incidently in proportional to each increase of oscillation frequency.

At the highest frequency, the backswing voltage v shows a greater ability for checking due to breakover voltage V against the high frequency voltage of the switch S; that is, V is substantially elevated by dV/dt and the oscillation is stabilized at this time.

6. The Equilibrium State of the Oscillation:

Waveforms in the stable state are shown in FIG. 5 wherein the input current i is substantially a constant DC. current. The initial condition for voltage boosting at stable state is expressed by,

i, e/r r Then, assuming the absolute values v before and after voltage boosting are equal, the following equation is obtained within the range of short boosting time t by solving equation (1):

v (max) e/2c(r r (t t /6L C [O p(zero to peak) value] If inductance L of the linear inductor is sufficiently large, the value of v can be boosted many times over the value of source voltage e.

Further, the value of current i, in the charging step is shown by the following, which is just the same as 1' i 2C dv /dt e/r r As to the oscillation periods, they are expressed as T T1 T2 T3 wherein T relates to the polarity changing of v and is expressed by T, 1r V Cl, under the condition of a small r T is a short period after the polarity changing up to the time at which i becomes zero, and approximated as T l /r and T is the period for checking conduction ofthe symmetrical switch S by the function of L hence, T T represents the total period for boosting.

In this circuit, it is noted that the switch S does not always recover its non-conducting state immediately after the end of the period T Boosting will be carried out in such a case only by inducing a backswing voltage except as the current through the switch exceeds the holding current.

In FIG. 1, when an A.C. voltage from the commerical source is used as the voltage source 2, the output voltage v shown in FIG. 6 is obtained. This phenomenon has a practical meaning with regard to the voltage boosting function.

1. Output Voltage of the Oscillating Booster:

In the circuit using the commercial source, an input current i, provides a lag phase angle in a range of 90 to relative to the source voltage e em sin wt, and the amplitude of v, modulated by i shows, for example, the maximum value of five times that of the source voltage as shown in FIG. 6. The oscillation frequency is seen to change corresponding to the variation of i which reaches about 25 KHZ at the maximum.

This is elucidated by the fact that the source frequency is negligibly low in comparison with the oscillation frequency, and by another fact that'each initial condition i for each boosting fluctuates at a rate of the commercial frequency as i e,,,/w i+ r -sin (a)! tan (uh r Therefore, the maximum of the capacitor voltage v proportional to every is approximately as stated below:

2. Output Voltage Control by Bias Means:

The output voltage control of this booster is put into the operation by changing the value 1,, since the backswing voltage v is controlled only by the value of I which is controlled by flux density change AB. Adjustment of AB is generally realized by bias windings situated around the core of L though it might also be done by predetermining the difference between the maximum flux density of saturation B,,, and the residual magnetic flux density B, as for ferrite materials.

FIGS. 7 and 8 show examples of bias circuits using a commercial source, wherein the winding of a bias coil B consists of only one turn because of the high permeability of the ferrite core. Output voltage v is derived from terminals M and N including the bias coil B and the capacitor C in series connection for FIGS. 7 and from terminals P and Q of the capacitor for FIG. 8.

FIGS. 9(A) and (B) show output voltage waveforms, where a slight minus bias is applied for the ferrite core of L at unsaturated state by capacitor charging current i [see FIG. 9(A)] and a slight plus bias is applied for the core of L at unsaturated state [see FIG. 9(B) The output voltage is decreased or increased by bias for the saturable non'linear inductor at unsaturated state, which is arbitrarily controlled despite the fact that the same non-linear inductor is used.

It is also possible to decrease the output voltage due to loss increase by using a higher resistance for r in the second closed circuit.

3. Continuation or Intermission of the Oscillation When a commercial source is applied, the oscillation may be intermittent under certain conditions since the input current i fluctuates momentarily.

The switch S turns off under the condition of as above described, where the current i changes such as in equation (9). If the amplitude of 1', is very small, the oscillation may become intermittent whereby it results that the relation (11) is untrue for phase angles above a certain specific angle (within a right angle) of each half cycle of i and the switch S holds its conducting state after that. Assuming the value of i, to be constant, the oscillation is the more capable of continuing with larger amplitudes of i For larger amplitudes of i it is desirable to increase the capacitance C and/or to decrease the inductance 1 and/or decrease the resistance r It is effective to use bias means for the non-linear inductor L in order to decrease the saturated inductance when complete saturation will not be obtained.

On the other hand, the oscillatory condition of the second closed circuit is expressed as follows:

Therefore, the value of I, is selected to be above C'r /4 for continuous oscillation, and the value I, is selected to be below C-r /4 for intermittent oscillation.

In case a commercial source is applied, each value of I, is gradually decreased corresponding to each increase of i Therefore, in the circuit illustrated in FIG. 7, for example, if a large magnitude minus bias is applied for L at the saturated state, or if a large magni tude plus bias is applied at unsaturated state since the bias current in this connection changes its polarity corresponding to the charging or discharging of the capacitor, intermittent oscillation can be realized over the predetermined value of i due to the complete saturation of L in accordance with the impressed dV/dt voltage applied to the switch S hereinafter described, as shown in FIG. 10.

Another reason for the intermittent oscillation is found in the characteristics of the switch S. It can be understood from the inequality l 1) that the oscillation becomes continuous as the holding current 1,, becomes large. Another factor for the stopping of the oscillation relates to the breakover voltage V,,,, as against the high frequency voltage impressed immediately after turning off of the switch. Namely, the switch S may conduct by itself due to a so-called dV/dt effect" when the dV/dt value of the impressed voltage increases. The dV/dt effect generally has a close relation to that of turn off time rq. With a small value of tq, the oscillation will tend to be continuous since the breakover voltage V hardly decreases as against an impressed voltage of high frequency.

Intermittent oscillation further relates to the impeded time of L More particularly, the oscillation stops at small angles of each half cycle, unless the response of the non-linear inductor follows sufficiently closely to the oscillation frequency. The dV/dt effect also has a close relationship with the characteristics of L If the checking characteristic is nearly close to both the backswing induction and the response time, continuous oscillation is obtained since the ascent of dV/dt is absorbed by the non-linear inductor.

In the combination of an oscillating voltage booster in a discharge lamp operating circuit, the booster can be effectively used as a starter device for nonpreheating type discharge lamps, including the rapidstart type fluorescent lamp in which filament current is not supplied from the starter device but from another heating source such as a transformer. The starter device of this invention serves to ignite such discharge lamps without any preheating function. On the contrary, the starter device for a preheating type discharge lamp requires the prior preheating of the filaments to ignite the lamp as disclosed in said US. Pat. No. 3,753,037 of Aug. 14, I973. The application of the booster according to the present invention is therefore distinguished from the starter device of the preheating type discharge lamp. For instance, a fail safe for the starter device for the preheating type lamp may be constituted by the filaments of the lamp, but the circuit of this invention adds a high magnitude plus bias means such as a bias coil, and if necessary with the cooperation of a capacitor for limiting current, in order to limit continuous oscillation. This serves to produce, at a given time, a high voltage and energy suitable for the ignition of a nonpreheating type of discharge lamp.

Reference is next made to FIGS. 11-18 and 20 wherein different types of lamp starter devices of the invention are illustrated.

FIG. 11 shows a fundamental circuit of this invention, which circuit comprises a common operating circuit including an AC. power source 10, a discharge lamp 12 of the nonpreheating type with a pair of

electrodes

13 and 14, a stabilizer 15 of the single-choke type; and a starter device connected in parallel with the discharge lamp 12 and including a capacitor 16, a saturable non-linear inductor l7 and a bidirectional diode thyristor 18.

The starter device utilizes the voltage booster to produce a high magnitude oscillating voltage which has been described herein-before. The saturable non-linear inductor 17 is characterized by exhibiting equivalent distributed effective capacitance C illustrated in phantom line to produce a backswing voltage. The singlechoke type stabilizer 15 which acts as a linear inductor can be replaced by other types of stabilizers such as leading or lagging phase devices, high or low power factor devices, constant power factor devices and leakage transformers. This replacement is also possible in the embodiment of FIGS. 11 to 18 and 20. It is well known in practical circuits to use a leading capacitor connected in series with the linear inductor such as shown in FIGS. 17 and 18.

To prevent damage of the starter device of FIG. 11 caused by ignition of the lamp or by abnormal operation clue to the removal of the lamp accidentally during operation from a common mercury-lamp operating circuit, the improved circuit arrangements of FIGS. 12 and 13 are preferred, particularly in operation with a 1 lO-volt commercial line. These circuits are characterized by the adding of bias means to the voltage booster 20 with a related high magnitude plus biasing of the magnetic level of the non-linear inductor 17. Thus, for instance, a bias coil 21 is inserted in series with the stabilizer 15 in FIG..12, and a bias coil 22 is inserted in series with the capacitor 16 in FIG. 13. The magnetic level of the non-linear inductor 17 in these circuits is biased or increased by the

bias coil

21 or 22. The bias coil 21 makes changing of the magnetic level continuous according to the input current of commercial frequency flowing through the stabilizer 15, whereas the bias coil 22 makes changing discontinuous to expand flux change according to the current flowing through the capacitor 16 due to the oscillation of the voltage booster 20.

In the case of FIG. 12, the capacitor 16 of oscillating voltage booster 20 can be used as noise preventing capacitor during normal operation. On the other hand, though the capacitor 16 of FIG. 13 is insufficient to enable its use as a noise preventing capacitor, an added capacitor 23 for improving the power factor can be used for noise prevention. Therefore, special noise preventing capacitors for these embodiments can be omitted for economical reasons.

As the voltage booster is applied in the above circuits, a compact operating apparatus can be achieved for cold cathode type such as mercury lamps and nonpreheating type discharge lamps. This is because the starter device of this invention has no pre-heating function. It is noted that the relatively high magnitude plus bias elevates the voltage impressed on the lamp and forms intermittent oscillation suited for the starting of such type of discharge lamps.

FIGS. 14 to 16 show other embodiments especially suited for a high-pressure sodium lamp and the like which require higher voltages for the starting device. Usually, the operation of a high-pressure sodium discharge lamp is effected by using a leakage transformer having a large winding ratio, but the structure of such a transformer is of large size and heavy weight and the handling thereof is difficult. However, these defects can be eliminated by applying the oscillating voltage booster shown in FIGS. 14 to 16, wherein a current limiting capacitor is added to the starter device.

In FIG. 14 a parallel circuit of a capacitor 30 and a discharge resistor 31 is added to the voltage booster 20 to limit therethrough. When the capacitor 30 for limiting current is used, the ratings or capacities of the elements in the booster 20 can be lessened so as to produce a more economical starter device. This capacitor 30 may be inserted at any place between the bidirectional diode thyristor 18 and the discharge lamp 12 such as at point P in FIGS. 14 and 16 and the same effect of limiting current is achieved.

FIGS. 15 and 16 show embodiments suited for the cold cathode type of fluorescent lamp or sodium discharge lamp, in which a high magnitude plus bias by which magnetic saturation isachieved is also applied together with a current limiter for the voltage booster to minimize the rating of booster elements such as the non-linear inductor 17 and the bidirectional diode thyristor 18 for providing a compact starter device. In FIGS. 15 and 16, the current limiting capacitor 30 has the advantageous function of elevating the starting voltage according to the superimposing of the power source voltage stored in the capacitor itself. The other elements of FIGS. 15 and 16 are the same as in FIGS. 12 and 13 so that the detailed explanation thereof can be omitted here.

It is important in these embodiments that the starting voltage applied to the lamp is formed of intermittent oscillations and that such intermittent oscillations are superposed on the voltage across the capacitor 30. Thus, the high voltage and energy required for such discharge lampscan be easily derived from these voltage boosters 20. These circuits are also suited to protect against the abnormal operation of a metal halide lamp. In a conventional operating apparatus, are discharge of the lighted lamp sometimes ceases during operation at about 200 C of the arc tube temperature due to an accidental spike voltage. Such voltage is often higher than the source voltage, and, in such case, the circuit of the booster is closed so that the lighted lamp sometimes cuts off. The use of a high-magnitude plus-bias coil prevents such accident because, since large changes of magnetic density level are caused by the plus-bias, magnetic saturation becomes difficult and conduction of the bidirectional diode thyristor is checked.

The starter device of this invention is also adapted for the case of a fluorescent lamp of the rapid-start type, and particularly to use with a long-size and high-output lamp type such as of the 96 inch-long llO-watt or 220- watt type, in which filaments of the lamp are heated from a separate source during operation. FIG. 17 shows an embodiment in such case, wherein the starter device comprises a power source 10, a leakage-transformer 15 of the linear type, a phase-advancing capacitor 25 connected in series with the leakage-transformer, and a booster 20 connected across the fluorescent lamp 42. The booster 20 includes a capacitor 16 for oscillation, a series circuit of a saturable nonlinear inductor 17 and a bidirectional diode thyristor 18, and a current limiting capacitor 30. Discharging

resistors

26 and 31 are generally connected across the

capacitors

25 and 30 respectively as shown in FIG. 17. In the above circuit, a capacitance of the capacitor 16 of about 6,000 pF can be used as a noise preventing capacitor as well as for oscillation, and such small capacitance value of the capacitor 16 is favorable to produce an output voltage for the starting of such a fluorescent lamp.

For

heating filaments

43 and 44 of the fluorescent lamp 42, the leakage-transformer 15 is so arranged that a desired heating voltage derived from the primary winding is applied to the

filaments

43 and 44 by the

secondary windings

48 and 49. Further, if necessary, a capacitor may be used across the power source for radio noise prevention. The above starting device is compactly constituted, since the bias means is also omitted due to the use of the small value of the capacitor l6 and a relatively small value such as O.5,u.F of the current limiting capacitor 30.

It is noted that the current limiting capacitor 30 also serves to control oscillating energy applied to the lamp to keep the best condition for lamp ignition and to prolong the lamp life as well as to prevent the overheating of the leakage-transformer and the bidirectional diode thyristor 18 caused by an abnormal operation. This circuit arrangement is suitably utilized for a lamp on-off display apparatus because of its improved starting characteristics.

The further embodiment of FIG. 18 shows a starting device for a cold-cathode discharge lamp with an auxiliary electrode, such as a metal-halide vapor discharge lamp, and this embodiment resolves the problem of a re-ignition characteristics. For instance, when the power source in the ordinary operating device is accidentally cut off during normal operation, the lamp goes out, and even if the power source is restored immediately thereafter (say, for example, within a quarter of a second) the lamp will not re-ignite because of the existence of a high pressure of mercury vapor in the arc tube of the lamp. Such undesired condition will be accelerated by heating due to a glow discharge between the main and auxiliary electrodes and, as a result, damage of the electrodes is severe and the life thereof may become very short.

To improve the re-ignition characteristics, it has been found that the use of an oscillating voltage booster as shown in FIG. 18 is effective, in which there is the A.C. source 10, a phase-advancing capacitor 25, a choke coil 15 acting as a current limiting means which also may be a leakage-transformer, a cold-cathode discharge lamp 60 with an auxiliary electrode 64, and a voltage booster 20. The discharge lamp 60 includes an arc tube 61 containing metal halides, a pair of main electrodes 62 and 63, and an auxiliary starting electrode 64 adjacent one of the main electrodes 62. A starting resistor 65 is connected between the electrodes through a switching element 66 which opens the starting resistor 65 during normal operation and brings the voltage of the auxiliary electrode 64 to a magnitude equal to that of the main electrode 62. This switching element 66 is preferably a bimetallic switch responsiveto the temperature of the are tube 61.

The voltage booster 20 comprises a closed circuit including capacitor 16, saturable non-linear inductor 17, bidirectional diode thyristor 18 and bias coil 22, which is designed to produce an oscillating voltage such as shown in FIG. 19(A). Current limiting capacitor 30 for minimizing the current through the bidirectional diode thyristor 18 or for supplying additive current is connected in series with the bidirectional diode thyristor l8, and discharging

resistors

31 and 33 are connected in parallel with the

capacitors

16 and 30. Second bidirectional diode thyristor 55 whose operating voltage or breakover voltage V,,,, is less than the peak value of the normal source voltage and is higher than the arc tube voltage of the lamp 60 is connected between the lamp 60 and the above-mentioned closed circuit.

In this arrangement, the bidirectional diode thyristor 18 is operated by the terminal voltage of the capacitor 16, and its operating voltage can be set to be about twice that of the second bidirectional diode thyristor 55. When the source voltage is applied across the discharge lamp 60 and at the same time to the second bidirectional diode thyristor 55 through the capacitor 16, it conducts instantaneously, and the capacitor 16 is charged. Since the bidirectional diode thyristor 55 has operating voltages not quite identical for both directions generally, the capacitor 16 is charged nearly up to the source voltage. On the other hand, the voltage wave-form at the terminals of the capacitor 16 becomes asymmetrical for positive and negative polarities. Thus, when the terminal voltage of the capacitor 16 reaches the breakover voltage of the bidirectional diode thyristor 18, it conducts and the charges in the capacitor 16 discharges rapidly and a high frequency oscillating voltage, as shown in FIG. 19(A), is produced as mentioned hereinbefore. The discharge lamp 60 is ignited by the applying of such oscillating voltages.

When the discharge lamp 60 is turned off by an opening of the power source 10 due to some cause during operation, the discharge lamp 60 will not start again although the starting device is actuated, because of the high temperature of the arc tube of the discharge lamp 60 which leads to a high pressure of the vapor of the filling materials. With the passing of time, a glow discharge occurs and immediately shifts to a main are discharge, when the re-ignition voltage decreases below the output voltage of the voltage booster 20. Since the terminal voltage of the discharge lamp 60 decreases during operation, the second bidirectional diode thyristor 55 does not operate. When an instantaneous pulse voltage higher than V arrives from the outside during the conducting state of the second bidirectional diode thyristor 55, the first bidirectional diode thyristor 18 will not becaused to operate so that the voltage booster 20 will not operate erroneously and the discharge lamp 60 operates stably.

In this way, when oscillating voltage is applied to the discharge lamp, the instantaneous current at starting is not necessarily large even if the peak value of the applied voltage itself is rather low, so that the capacitance of the capacitor 30 can be a practical value which is re markably small, and yet difficulty in re-ignition can be eliminated completely.

This embodiment can be modified in such a manner that a parallel circuit for decreasing the current through the bidirectional diode thyristor 18, which consists of capacitor 30 and discharge resistor 31, can be connected to the point P, and that location of the bias coil 22 is substituted by the point Q.

Further, an inductance element 32 such as a linear type inductor for suppressing external pulses from impulses by lightening or the like and for preventing erroneous operation of the second bidirectional diode thyristor 55 can be used. This element 32 is designed to allow the passage of the voltage generated in the voltage booster 20 itself. Further,

capacitors

34 and 58 are added for preventing the erroneous operation of the booster 20 all of which have values which are small.

These capacitors may be used with discharge resistors connected in parallel.

It is also noted that the bias coil 22 is to limit the oscillation. A resistor 39 for regulating the starting voltage of the booster 20 is connected to the first bidirectional diode thyristor 18. This increases the operational quality of the booster 20 and the oscillation is made stable and intensified.

Element 38 is a capacitor having a small capacity for increasing the oscillation frequency as well as for changing the output voltage into the limiting oscillation, as shown in FIG. 19(B). It also stabilizes the voltage of the starting device particularly at the lower side for stabilizing the oscillation. The reason is that the oscillating condition of the starting device is changed by the action of the terminal voltage of capacitor 38. rr-type, T-type, L-type or other types of low-pass filters may be constituted together with the capcitor 16 or non-linear inductor 17. Thus, the erroneous operation of the starting device due to internal or external surge voltages such as caused by lightening can be prevented. By suppressing the oscillation frequency and amplitude at starting below a certain value, noise may be prevented. These additional circuits can selectively be used individually or in combination.

FIG. 20 illustrates a modification of FIG. 18, wherein a lowpass filter of 1r-shaped type is constituted by a pair of capacitors 16, 116 for oscillation and an inductor 72 of the linear type. A capacitor 23 for powerfactor correction is added across the power source 10. Also, a thermistor 59 having negative resistance characteristics is added between the power source 10 and the discharge lamp 60, whereby damage to the lamp 60 caused by large current passing through the lamp 60 during the starting period can be prevented. Practically, the thermistor'59 disposed near the lamp has about 30!) at normal temperature (20 C) before the lamp operation and starting periods, but its value is changed to 0.1!) at normal operating temperature (180 C) so as to limit the starting current to the lamp 60. For other elements of FIG. 20, the same reference numbers is in FIG. 18 are used. Hence, detailed explanation with respect thereto is omitted.

The following values of circuit elements, by way of example, can be used in the apparatus:

Resistor 31: R9, I-watt type Inductor 32: 15 mH (for band-pass) Resistors 33, 33: 50 k0, 2-watt type Resistor 39: I00 kQ, l-watt pe Second bidirectional diode thyristor 55: -250V as V,,,,

Capacitor 58; 3000 pF Thermistor 59: 300 at 20 C and 0.10 at 180 C Discharge lamp 60: 400-watt metal halide type with an auxiliary electrode The type of device described above, according to the present invention, decreases the output voltage of the starting circuit arrangement and is capable of supplying sufficient current by means of oscillation, so that it can re-ignite positively a discharge lamp containing a metal halide and provided with an auxiliary electrode.

The non-linear inductor 17 mentioned above has a characteristic capacitance c of 40 pF at 1 kHz, but the value is significantly changed responsive to the applied frequency. As to the permeability of the inductor, it is, for example, about 1,000 at 20 C.

The inductance range of the above nonlinear inductor 17 in saturated state is between lOOuH and lmI-I; this value is changed by the current It is noted that the complete saturation of the inductor is obtained by using a particular core manufactured by TDK Electronic Company in Japan. In such case, the bias means is mainly adjusted for unsaturated inductance.

The types of discharge lamps applicable to this invention are as follows:

1. Fluorescent Lamps i. Hot-cathode instant-starting ii. Hot-cathode rapid-starting iii. Cold-cathode instant-starting 2. Mercury Vapor Lamps By using this invention, it may be possible to operate with a 100V line or to remove the auxiliary electrode from such lamps.

3. Sodium Lamps i. Low pressure type ii. High pressure type 4. Metal-halide vapor Lamps 5. Short-arc Lamps i. Mercury and mercury xenon ii. Xenon Reference is also made herein to U.S. Pat. No. 3,758,818 of Sept. ll, 1973.

What is claimed is:

1. For igniting a discharge lamp by the use of a booster oscillating voltage; a starting device characterized by the absence of a preheating function for said lamp, said starting device comprising a series circuit including a power source and a linear inductor connected in series, and a booster adapted for generating said booster operating voltage, said series circuit and booster being respectively connected across said lamp, said power source supplying an operating voltage via said inductor to said lamp, said booster including a capacitance element adapted for oscillation, a saturable non-linear inductance element and a symmetrical switching element in series connection with said nonlinear element, said capacitance element being connected across said lamp, said non-linear inductance element and switching element being connected across said lamp, said non-linear inductance element including a core of magnetic and dielectric material to provide characteristic equivalent capacitance (c') and different inductances (1,, and 1,.) respectively in the unsaturated and saturated states thereof, a backswing voltage being induced across the non-linear inductance element when said switching element turns off whereby said booster produces a higher voltage than the voltage of said power source during this starting period.

2. A device as claimed in claim 1 further comprising a capacitance element constituting phase-advancing and/or noise preventing means connected in series with said series circuit and/or in parallel with said booster or said power source.

3. A device as claimed in claim 1 wherein a second capacitance element for limiting current flowing through said switching element is connected in the series connection with said switching element in the booster.

4. A device as claimed in claim 3 wherein said discharge lamp is a fluorescent lamp including filaments adapted for being heated by heating current supplied from a heating source.

5. A device as claimed in claim 4 comprising a heating source constituted by a transformer including a primary coil connected to said power source and a secondary coil connected to said filaments of said lamp.

6. A device as claimed in claim 1 wherein said discharge lamp is of the non-preheating type, said booster further including bias means for changing the magnetic level of said non-linear inductance thereby controlling the output of the booster.

7. A starting device for a discharge lamp of the coldcathode type, said device comprising a power source to supply input current and a starting means to supply igniting voltage. said power source and starting means being connected to each other and across said lamp, said starting means comprising arc discharge stabilizing means including a linear inductor in series with said power source, and a voltage booster including a capacitor, a saturable non-linear inductor including a core of magnetic and dielectric material, and a bidirectional diode thyristor in series with said non-linear inductor,

said starting means further comprising a bias coil operatively associated with and controlling the magnetic level of said non-linear inductor, said booster having an output voltage which can be controlled by changing the magnetic flux of said bias coil, said output voltage being generated at least in part by oscillating current generated in said capacitor under the control of said thyristor.

8. A device as claimed in claim 7 wherein said bias coil is electrically connected within a first closed circuit consisting of said power source, linear inductor an discharge lamp so as to change the magnetic level of said non-linear inductor in accordance with the input current.

9. A device as claimed in claim 7 wherein said bias coil is electrically connected within a second closed circuit consisting of said capacitor, non-linear inductor and bidirectional diode thyristor and said bias coil is in series with said capacitor, so as to change the magnetic level of said non-linear inductor in accordance with the oscillating current generated in the capacitor.

10. A device as claimed in claim 7 wherein said bias coil is electrically connected in series with both said linear inductor and said capacitor so as to change the magnetic level of said non-linear inductor in accordance with the sum of the input current and capacitor current.

11. A device as claimed in claim 7 wherein said bias coil is a plus bias coil magnetically coupled with said non-linear inductor.

12. A device as claimed in claim 11 wherein said plug bias coil provides a high magnitude biasing of the magnetic level of said non-linear inductor and the winding ratio of said bias coil to said non-linear inductor is in the range of 1/5 to l/300, so as to produce the output voltage in the form of limited oscillation.

13. A device as claimed in claim 7 wherein said booster includes a further capacitor for limiting current through the bidirectional diode thyristor, said further capacitor being connected in series with said bidirectional diode thyristor whereby the impedance of the booster is increased.

14. A device as claimed in claim 7 wherein said booster further includes a low pass filter for checking abnormal impulse voltages from an external circuit coupled to said power source.

15. A method of operating a discharge lamp of the type which is connected to a power source through a linear inductor and which is ignited by the use of a starting device which is characterized by the absence of a preheating function, said method comprising generating a boosted oscillating voltage across a capacitor while supplying the capacitor with current from said power source, said voltage being generated by the connecting of a non-linear inductor with the capacitor and by the repeated opening and closing of a circuit including said non-linear inductor and capacitor; and controlling the magnitude of said boosted oscillating voltage by biasing said non-linear inductor in accordance with the magnitude of current passing through said linear inductor and/or said capacitor to produce magnetic flux change in said non-linear inductor, the boosted voltage having an oscillating period which is limited in accordance with the amplitude of the magnetic flux change.

16. A method as claimed in claim 15 wherein the biasing of said non-linear inductor is used as a fail-safe boosted voltage is formed at least in part with a backswing voltage induced in the non-linear inductor in the unsaturated state thereof and due, at least in part, to the effective capacitance thereof.

19. A method as claimed in claim 15 wherein the opening of said circuit is extended by the impedance function of said non-linear inductor.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 866 o88 Dated February 11, 1975 flsao Kaneda et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 7 line 3 Change:

a 2 1 2'6 .V' L/2 1 1 C Column 8 line 41 Change:

:'L =e/r 1:

Column 8 line 50 Change: To:

3 3 e/Zc (r r (t-t /6L C) t C ,I

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,866,088

Inventor) Isao Kaneda e1; (11

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 8 line 60 Change: To:

2C dv ,/dt e/r r 2C di /d.t= e

C 2 C r r,, l

Column 9 line 35 Change:

L L e l r2 sin (bit tan 0 l/r -7 U m sin(wt tan 1 fl mm r Column 10 line 35 Change: To:

7 c-r -a s0 7 C'r "-4 O Column 11 line 53 Change: To:

capacitance C' capacitance c' Signed and Sealed this twenty-eight Day Of October 1975 [SEAL] A ttes t:

RUTH C. MASON Arresting Office'r Dated February 11, 1975 Page 2 C. MARSHALL DANN Commissioner ofParents and Trademarks Patent No Inventor(s) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3 866 088 Dated EnhvnnrxrJ'l 107'; v a a I 3 Isao Kaneda at 21 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[SEAL] I. In Column 6, line 10: change Ldi dt+ri +1 S'dt 11 1 /c 1 L dl /dt r 1 l/c glldt 2. In Column 6, line 40: change L (1 (1C dt 10/ r 1 1/8512 to: l -1 /L t Signed and Salad this twenty-third Day of March 1976 Arrest:

RUTH C. MASON Anesting Officer C. MARSHALL DANN Commissioner uflalents and Trademarks

Claims

1. For igniting a discharge lamp by the use of a booster oscillating voltage; a starting device characterized by the absence of a preheating function for said lamp, said starting device comprising a series circuit including a power source and a linear inductor connected in series, and a booster adapted for generating said booster operating voltage, said series circuit and booster being respectively connected across said lamp, said power source supplying an operating voltage via said inductor to said lamp, said booster including a capacitance element adapted for oscillation, a saturable non-linear inductance element and a symmetrical switching element in series connection with said nonlinear element, said capacitance element being connected across said lamp, said non-linear inductance element and switching element being connected across said lamp, said non-linear inductance element including a core of magnetic and dielectric material to provide characteristic equivalent capacitance (c'') and different inductances (lu and ls) respectively in the unsaturated and saturated states thereof, a backswing voltage being induced across the non-linear inductance element when said switching element turns off whereby said booster produces a higher voltage than the voltage of said power source during this starting period.

7. A starting device for a discharge lamp of the cold-cathode type, said device comprising a power source to supply input current and a starting means to supply igniting voltage, said power source and starting means being connected to each other and across said lamp, said starting means comprising arc discharge stabilizing means including a linear inductor in series with said power source, and a voltage booster including a capacitor, a saturable non-linear inductor including a core of magnetic and dielectric material, and a bidirectional diode thyristor in series with said non-linear inductor, said starting means further comprising a bias coil operatively associated with and controlling the magnetic level of said non-linear inductor, said booster having an output voltage which can be controlled by changing the magnetic flux of said bias coil, said output voltage being generated at least in part by oscillating current generated in said capacitor under the control of said thyristor.

12. A device as claimed in claim 11 wherein said plug bias coil provides a high magnitude biasing of the magnetic level of said non-linear inductor and the winding ratio of said bias coil to said non-linear inductor is in the range of 1/5 to 1/300, so as to produce the output voltage in the form of limited oscillation.

16. A method as claimed in claim 15 wherein the biasing of said non-linear inductor is used as a fail-safe protection step and is used to limit said oscillating period and the magnitude of said boosted voltage in the event of inadvertent detachment of said lamp from said power source.

17. A method as claimed in claim 15 wherein the core of said non-linear inductor is used to automatically compensate changes in flux in said non-linear inductor due to temperature changes.

18. A method as claimed in claim 15 wherein the boosted voltage is formed at least in part with a backswing voltage induced in the non-linear inductor in the unsaturated state thereof and due, at least in part, to the effective capacitance thereof.