US3336501A

US3336501A - Starting apparatus for discharge lamps

Info

Publication number: US3336501A
Application number: US409851A
Authority: US
Inventors: Segawa Yasuo
Original assignee: Tokyo Shibaura Electric Co Ltd
Current assignee: Toshiba Corp
Priority date: 1964-11-09
Filing date: 1964-11-09
Publication date: 1967-08-15
Anticipated expiration: 1984-08-15

Description

ug 15, 1967 YASUO SEGAWA 3,336,501

STARTING APPARATUS FOR DISCHARGE LAMPS Filed Nov. 0, 1964 5 Sheets-Sheet 1 I N VEN TOR.

YASUO SEGAWA STARTING APPARATUS FOR DISCHARGE LAMPS Aug. 15, 1967 3 Sheets-Sheet :2

Filed Nov. 9, 1964 FIG. 2c

5, 1967 YASUO SEGAWA 3,336,501

STARTING APPARATUS FOR DISCHARGE LAMPS Filed Nov. 9, 1964 3 Sheets-Sheet 5 7 FIG. 4 FIG. 5

I NVENTOR.

United States Patent 3,336,501 STARTING APPARATUS FOR DISCHARGE LAMPS Yasuo Segawa, Tokyo, Japan, assignor to Tokyo Shibaura Electric Co., Ltd., Kawasaki-shi, Japan, a corporation of Japan Filed Nov. 9, 1964, Ser. No. 409,851 3 Claims. (Cl. 315105) This invention relates to a starting apparatus, for discharge lamps, and more particularly to one which generates a pulsating voltage at every half cycle of a source voltage and superimposes the pulsating voltage upon the source voltage in order to impress the superimposed voltage on a discharge lamp in order that the discharge lamp can be started and lighted easily and surely.

As well known in the art, there are proposed two systems for starting discharge lamps; i.e., one which is a cold-cathode starting system where a discharge lamp starts in a cold-cathode state by impressing a considerably high voltage, and the other is a hot-cathode starting system where a discharge lamp starts by preheating the filament electrodes. The latter starting system is further classified into two types: i.e., a switch-starting system wherein a filament-preheating current flows for a certain period of time through a glow starter, at thermal starter or a manual starter and the preheating circuit is opened after starting, a rapid starting system wherein a filament-heating coil is provided for a magnetic leakage transformer, or the like, which serves as a filament-preheating transformer. Both of these starting apparatus for a discharge lamp as set forth in the above not only require a considerably high starting voltage or a sufficiently elevated preheat for a filament in order to start a discharge lamp rapidly and steadily, but also in a case of the rapid starting type even require to annex a starting aid to a discharge lamp in order to encourage starting.

Necessarily, a large capacity and size of a stabilizer (viz. a magnetic leakage transformer or a choke coil) serving as a current-controlling element is required to meet the requirements set forth in the above. Accordingly, a rise in cost is incurred and further a special consideration must be given to a lighting equipment in providing a starting aid. Moreover, sometimes conventional discharge lamps have encountered an accident that starting of a discharge lamp can not be effected enough to be rapid and sure.

An object of this invention is to provide a starting apparatus for a discharge lamp which can start and light easily and surely.

Another object of this invention is to provide a starting apparatus for a discharge lamp which generates a pulsating voltage, particularly, at the time of starting, every half cycle of a source voltage and superimposes the pulsating voltage on the source voltage in order to impress the superimposed voltage on the discharge lamp in order that the discharge lamp can be started and lighted easily and steadily.

Still another object of this invention is to provide a starting apparatus for a discharge lamp which pulsates a step-up transformer for a short period of time during a half cycle of a source voltage via said step-up transformer situated between an AC power source and a load, i.e., a discharge lamp to generate a high pulsating voltage and "ice superimposes the high pulsating voltage on the source voltage in order to impress the superimposed voltage on the discharge lamp in order that the discharge lamp can be started and lighted easily and steadily.

Still another object of this invention is to provide a starting apparatus for a discharge lamp as above referred to, which automatically pulsates said step-up transformer or the like for a short period of time during each half cycle of a source voltage at every half. cycle of said source voltage before starting and lighting.

Yet another object of this invention is to provide a starting apparatus for a discharge lamp which has no need of large capacity and size of components and further eliminates condensers for generating pulsating voltage, starting aid, and the like to generate a pulsating voltage, with the result of easy manufacture, a low cost and a small size.

A further object of this invention is to provide a starting apparatus for discharge lamps which has a simple construction and can efliect a momentary starting in an automatic response to a predetermined instantaneous value of a source voltage. I

Other objects and advantages of this invention will become apparent from the following description of the preferred embodiments thereof, reference being had to the accompanying drawings, in which FIG. 1 shows a circuit diagram of one embodiment of this invention;

FIGS. 2a to 2c show wave forms illustrating the operation of the embodiment shown in FIG. 1;

FIGS. 3a, 3b, 3c and 3d, respectively, show examples of switch elements used as component elements; and

FIGS. 4 to 9 inclusive show circuit diagrams of dilferent embodiments of this invention.

The invention will be described theoretically and also With respect to the preferred embodiments thereof in the following by referring to the accompanying drawings.

Referring now to FIG. 1, the reference numeral 1 designates a step-up autotransformer. Said transformer 1 has an intermediate tap 2 adapted to impress a proper starting voltage upon a discharge lamp 7 and is divided into two parts, i.e., a low voltage winding t and a high voltage winding 1 Said intermediate tap 2 is connected to one terminal of a power source and a switch element 3 is connected, by the end terminals 3 and 3 thereof between one end of low voltage winding t and the other terminal 5 of the power source and, if desired, a current limiting impedance 4 connected in series therewith. Furthermore, between a junction point A of the above low voltage winding 1 and the switch element 3 and the power input terminal 5, a high impedance element, for instance, consisting of condensers is inserted if so desired, and the power input terminal 5 is connected to the above-mentioned high voltage winding 1 through the discharge lamp 7 and a stabilizing element 8 thereof connected in series in this order.

This invention is composed as above described, and Will be first described as to its operating principle ac cording to the theoretical embodiments as illustrated heretofore and later about its actual embodiments.

The intermediate tap 2 and the input terminal 5 are connected to the A.-C. power source, the switch element 3 is closed for a short period of time during a half cycle of the input voltage.

While the switch element 3 remains open, no voltage will appear across 2 and A, but when it closes for a short period of time, the voltage shape at each part will be shown as in FIGS. 2a, 2b and 2c. Namely, the input voltage Va will be impressed across the terminals 2 and as shown in FIG. 2a, and the switch element 3 connected between one terminal of said low voltage winding and the input terminals 5 are closed for duration of 'r, a pulsating voltage Vb like FIG. 2b will be impressed across 2 and A, that is, the low voltage winding, simultaneously making nearly naught the voltage across A and 5. Then the said pulsating voltage Vb is multiplied n times according to the turn ratio and a step-up pulsating voltage will be generated across the output terminals 9 and 5 of the step-up transformer. Moreover, since the input voltage Va is impressed across the terminals 9 and 5, the pulsating voltage Vp will be superimposed thereon as shown in FIG. 2c, and the superimposed voltage will be impressed across the electrodes of the discharge lamp 7 via the stabilizing element 8. Accordingly, the pulsating voltage Vp will appear only when the switch element S is momentarily closed and will be superimposed on the input voltage Va. With this superimposed voltage impressed, the discharge lamp 7 will start quickly and steadily. It may or may not be necessary to synchronize the switch element 3 with the input voltage, and also the switch element 3 may be closed twice or more for a short period of time during half cycle of source voltage or may be closed intermittently at every half cycle. Moreover, even if the switch element 3 has operated in the same manner as above after the discharge lamp is lighted, the discharge current, i.e. lamp current will induce magnetic fluxes in the iron core of the transformer 1, thereby making negligibly small the pulsating voltage superimposed on the source voltage, and though the pulsating voltage may never have a bad influence upon starting the discharge lamp, the switch element 3 may be left open, if desired, after lighting.

Turning now to actual embodiments of the switch element 3 it may be of a mechanical contact type such as shown in FIG. 3a consisting of moving contacts 11 provided for rotatable contactor revolved in the direction as shown by an arrow by a suitable driving source and a stationary contact 12 corresponding thereto. Alternately an electrically non-contact type such as shown in FIG. 3b consisting of semiconductor controlled rectifier elements SCR 14 and 14' having a single control electrode and connected in anti-parallel, or such as shown in FIG. 3c in which SCR 14 is not connected to the output terminals of the bridge rectifier 13, or such as shown in FIG. 3d composed of a saturable reactor having rectangular hysteresis characteristic and which is simple in construction and whose operation synchronizes easily and surely with a certain instantaneous value of source voltage, may be used.

FIGS. 4 to 9 inclusive illustrate different, practical applications, which will be described hereinunder one by one.

To begin with, FIG. 4 shows the one having a current limiting impedance 4 and a switch element 3 as described above which is connected in series with a low voltage winding t This circuit will have almost the same functional effect as the foregoing actual embodiments and may not need extra description without the fact that it prevents over current from flowing through the switch element.

FIG. 5 shows the one in which the primary winding L of a filament heating transformer 16 is connected in parallel with the series circuit of a switch element 3 as shown in FIGS. 3(a) to 3(a) and a current limiting impedance 4, and the secondary windings L and L for heating, of said transformer are connected to the filaments of a discharge lamp 7, respectively. If the switch element 3 is closed momentarily a pulsating voltage impressed on the low voltage winding t will he stepped up by the high voltage winding t and cause a high pulsating voltage which will start and light on the discharge lamp 7. In this case, when the switch element 3 is closed, the filament heating transformer 16 will be short-circuited, but only for a very short moment, and hence the filament heating action will be never affected ill by thermal inertia of the filaments.

FIGS. 6 and 7 show those which utilize magnetic leakage transformers, as a stabilizer, in place of the single winding transformer shown in FIG. 5, thus eliminating the aforementioned stabilizing elements and simplifying the structural design. In the one shown in FIG. 7, the secondary windings L and L of a magnetic leakage transformer and those L and L of the filament heating transformer 16 are connected respectively in series with the filaments of a discharge lamp. The embodiment is most practical, and therewith, the filament heating voltage will drop automatically after lighting and the filaments will be prevented from being damaged.

Further, those shown in FIGS. 8 and 9 differ from the foregoing embodiments in that a magnetic leakage transformer 19, in place of the filament heating transformer 16 is connected in parallel with a switch element 3, thereby providing both a boosting and a stabilizing action of the voltage impressed on a discharge lamp 7, and further the one shown in FIG. 9, is provided with a continuous heating action of the filaments in addition. In these embodiments, pulse voltages are generated in exactly the same manner as heretofore explained, insuring steadier lighting of the discharge lamps. Observed from a standpoint of a half cycle of the source voltage, as described above in details, this invention generates a pulsating voltage by closing a switchelement for a short period of time during a half cycle of the source voltage and then operates a step-up transformer for a short duration, and accordingly the step-up transformer can be of a very small capacity and generate sufficiently high pulsating voltage with a simple construction. For this reason the discharge lamps can be started and lighted quickly and steadily.

Furthermore, in case a non-contact switch such as a silicon controlled rectifier element or a saturable reactor element is used as the switch elements in the aforementioned embodiments, each of said elements is controlled with respect to ignition or continuity thereof at a certain instantaneous value during each half cycle of the source voltage or changes its impedance according to saturation. Accordingly, as either of them starts automatically a switching operation at a time point corresponding to a certain instantaneous value during each half cycle and continues a closing operation for a short period of time, a pulsating voltage will be generated automatically at every half cycle without special closing operation. Accordingly, a discharge lamp can rapidly start and maintain a stable discharge state by impression of synchronized pulse. Further, since the starting apparatus for a discharge lamp of this invention does not require a glow starter, a thermal starter, a starting aid, or the like as seen in conventional one, it is simple in manufacture and economical as well.

It will be appreciated, of course, by those skilled in the art, that the foregoing disclosure relates only to preferred embodiments of the invention whose spirit and scope of the invention is set forth in the appended claims.

What is claimed is:

1. A starting apparatus for a discharge lamp comprising a step-up autotransformer having a low voltage terminal, a high voltage terminal and an intermediate tap terminal, a switch element connected at one end thereof to said low voltage terminal, an AC. power source connected between said' intermediate tap terminal and the other end of saidswitch element, a discharge circuit including a series section consisting of a stabilizer and a discharge lamp'connected between said high voltage terminal and said other end of said switch element, and a transformer for heating of filaments of said discharge lamp, a primary winding of said transformer being connected in parallel with said switch element, wherein a pulsating voltage generated at said step-up transformer by closing said switch element for a short period of time during a half cycle of the source voltage is superimposed on said source voltage and impressed upon said discharge lamp.

2. The starting apparatus for a discharge lamp as claimed in claim 1, wherein said switch element is a noncontact switch closing for a short period of time in response to a certain instantaneous value during a half cycle 6 of said source voltage and generating automatically a pulsating voltage at every half cycle of said source voltage before said discharge lamp starts and lights.

3. The starting apparatus for a discharge lamp as 5 claimed in claim 1, wherein said switch element is a saturable reactor.

References Cited UNITED STATES PATENTS 11/1943 Lord 315--239 DAVID J. GALVIN, Primary Examiner.

Claims

1. A STARTING APPARATUS FOR A DISCHARGE LAMP COMPRISING A STEP-UP AUTOTRANSFORMER HAVING A LOW VOLTAGE TERMINAL, A HIGH VOLTAGE TERMINAL AND AN INTERMEDIATE TAP TERMINAL, A SWITCH ELEMENT CONNECTED AT ONE END THEREOF TO SAID LOW VOLTAGE TERMINAL, AN A.C. POWER SOURCE CONNECTED BETWEEN SAID INTERMEDIATE TAP TERMINAL AND THE OTHER END OF SAID SWITCH ELEMENT, A DISCHARGE CIRCUIT INCLUDING A SERIES SECTION CONSISTING OF A STABILIZER AND A DISCHARGE LAMP CONNECTED BETWEEN SAID HIGH VOLTAGE TERMINAL AND SAID OTHER END OF SAID SWITCH ELEMENT, AND A TRANSFORMER FOR HEATING OF FILAMENTS OF SAID DISCHARGE LAMP, A PRIMARY WINDING OF SAID TRANSFORMER BEING CONNECTED IN PARALLEL WITH SAID SWITCH ELEMENT, WHEREIN A PULSATING VOLTAGE GENERATED AT SAID STEP-UP TRANSFORMER BY CLOSING SAID SWITCH ELEMENT FOR A SHORT PERIOD OF TIME DURING A HALF CYCLE OF THE SOURCE VOLTAGE IS SUPERIMPOSED ON SAID SOURCE VOLTAGE AND IMPRESSED UPON SAID DISCHARGE LAMP.