US3325682A

US3325682A - Variable power supply

Info

Publication number: US3325682A
Application number: US245227A
Authority: US
Inventors: Jr Andrew Byron Elliott
Original assignee: Jefferson Electric Co
Current assignee: MAGNTEK Inc A CORP OF; Jefferson Electric Co
Priority date: 1962-12-17
Filing date: 1962-12-17
Publication date: 1967-06-13
Anticipated expiration: 1984-06-13

Description

2 Sheets-Sheet 1 A. B. ELLIOTT, JR

VARIABLE POWER SUPPLY June 13, 1967 Filed Dec. 17, 1962 June 13, 1967 A. B. El l |o'rr, JR

VARIABLE POWER SUPPLY 2 Sheets-Sheet 2 Filed DSC. 17, 1962 United States Patent O 3,325,682 VARIABLE POWER SUPPLY Andrew Byron Elliott, Jr., River Forest, El., assigner to Jefferson Electric Company, Bellwood, Ill., a corporation of Delaware Filed Dec. 17, 1962, Ser. No. 245,227 7 Claims. (Cl. 315-97) This invention relates to a variable power supply for gaseous discharge devices, and in particular for uorescent lamps of the continuously heated ilament type, otherwise known as rapid start lamps.

It has been proposed to control the luminosity of a gaseous discharge device by regulating the power supplied to the arc by means of a phase control device connected in series with the arc. However, such phase control arrangements cannot satisfactorily be applied to a solid state circuit due to the irregular voltage wave shape developed across the control device due to larnp operation, which produces discontinuities in the response and consequently results in a jump dimming action.

It is an object of my invention to provide a solid state dimming arrangement which has an exceedingly wide range of variation between the points of minimum and maximum luminosity.

Another object of my invention is to provide an arrangement which permit-s smooth dimming, in the sense that sudden jumps in or increments ot luminosity are avoided as the cont-rol is operated from dim to bright or vice versa.

According to my invention I provide a solid state phase control device in which that which is controlled is the sinusoidal voltage of the supply line, thus providing an improved and less costly variable power supply, as compared with prior art arrangements.

Another object of my invention is to provide an improved variable power supply which includes a ballast suitable for operating rapid start lamps.

The characteristic of rapid start lamps is that two sources of power are required, one for energizing the arc, and one for energizing the filaments. In the usual ballast, the arc and the filaments are customarily energized from a common primary winding by means of separate secondary circuits, the one for energizing the arc being known as the operating circuit, and those for energizing the larnents 'being known as the filament circuits.

The present invention provides a supply line type of phase control for energizing the arc while at the same time the power supplied to the lamp laments is constant.

Another object is to provide an improved dimming `arrangement which will ignite the lamps at the point of lowest luminosity. In other words, the lamps do not have to be ignited at a point of high luminosity and then the control turned down to a low luminosity point.

A still further object is to provide a variable power supply which is operative for uniformly controlling the luminosity of a great number of lamps, to the end that a single rheostat or dimmer control mechanism can be utilized to control all of the ballasts of a particular installation, irrespective of whether the ballasts comprise a single branch circuit or a number of branch circuits.

With reference now to the drawings in which like reference numerals designate like parts:

FIG. l is a circuit diagram showing a preferred embodiment of my invention;

FIG. 2 is a circuit diagram showing the bridge connection of the phase control device shown in FIG. 1;

FIG. 3 shows a modified system;

FIG. 4 is a diagram of the phase control device of FIG. 3;

Patented June 13, 1967 FIG. 5 shows a modified type of phase control device; and

FIG. 6 shows a modiiied arc supply transformer.

In FIG. 1, leads 1G and 11 are provided for connection to a suitable AC source, such as a 60 cycle, 118 volt line. Connected in parallel across the

leads

10 and 11 are a plurality of ballasts 12 for energizing gaseous discharge devices 13, such as fluorescent lamps.

Disposed in series circuit with all of the ballasts 12 is a phase control device 14, this being connected in the lead 10 ahead of the first ballast 12.

Each ballast comprises an arc supply transformer 15 for energizing the lamp 13, and a lament transformer 16 for energizing the lamp filaments.

The arc supply transformer 15 is a high reactance transformer comprising a primary winding 17 and a secondary winding 18 which are loosely coupled to each -other by a suitable core structure. For instance, as diagrammatically shown with respect to one of the ballasts, the windings 17 and 18 may be mounted in end to end relationship on a winding leg 19 of a suitable core structure so as to provide a ilux leakage path therebetween, the latter being designated by the conventional symbol 20.

The primary 17 is connected across the

leads

10 and 11, the transformer having suitable output or

secondary leads

21 and 22 across which the lamp 13 is connected to provide the operating circuit. The windings 17 and 18 may either be isolated, or connected in autotransformer relationship, as shown.

Thus the primaries 17 are connected in parallel with each other across the

leads

10 and 11, and in series circuit with the phase control device 14.

The iilarnent transformer 16 is a tightly coupled transformer comprising a primary winding 23 and two

secondary windings

24 and 25, which are connected by suitable conductors to the lament-s 24a and 25a of the lamp 13.

A branch lead 26 is connected at point 27 to the lead 1li, the point 27 being ahead of the phase control device 14. The primary windings 23 are each connected Abetween the branch lead 26 and the lead 11, all of the primaries 23 being connected in parallel relationship with each other. Thus the iilament transformers 16 are not affected by the operation of the phase control device 14.

As shown in FIG. l, the phase control device 14 comprises a bridge network 29 having a rectier diode 30 in each of its lfour legs, and having -a bridge connection 31 across the

midpoint terminals

32 and 33.

The bridge connection 31 is shown in FIG. 2, and comprises an SCR (silicon controlled rectiiier) 34 having a gate 35.

A suitable trigger circuit is provided for the gate 35 of SCR 34, which includes a relaxation oscillator 36 connected in parallel with a zener diode 37 across

junction points

38 and 39. A dropping resistor 4t) is connected between point 38 and the terminal 32, and point 39 is connected to terminal 33.

The relaxation oscillator 36 includes a unijunction transistor 41 connected between

points

38 and 39 and having a base-two 42, a `base-one 43, and an emitter 44. The base-one 43 is connected to the lgate 35, and the emitter 44 is connected to a junction point 45 in an RC charging circuit, the latter comprising series resistances 46-47 and a capacitor 48.

The capacitor 48 is charged at -a rate determined by the series resistance 46-47. When the emitter bre-ak-over voltage is reached, the condenser 48 discharges through a resistance 49 which is connected between the ybase-one, 43 and the junction point 39. Thus, a pulse is -applied to the gate 35 which is positive with respect to the cathode of the SCR and triggers the SCR into a conductive state.

As an example of suitable quantities, the Zener 37 may lbe a 22 volt Zener, and the dropping resistor 40 may be 18,000 ohms. A 330 ohm resistance 50 is connected between the base-two 42 and the junction point 38. The resistance 49 is 47 ohms. Also, -a 10,000 ohm resistance, not shown, may preferably be connected in parallel across the Zener 37 to dampen the rate of voltage buildup with respect to the reference point 3S. In the RC charging circuit, the resistance 46 may be 3000 ohms, the resistance 47 may be a 70,000 ohm variable resistance, and the condenser 48 is .12 mfd.

Regulation of the variable resistance 47 controls the point in each half cycle at which the SCR 34 switches from the blocking to the conducting state, and thus controls the area under the wattage half cycle curve.

In operation, the power which is supplied to the operating circuit is controlled by regulation of the variable lresistance 47 of the phase control device 14, with the result that the luminosity of the lamps 13 may be regulated. Howe-ver, such regulation does not affect the power supplied to the lamp filaments 24a and 25a with the result that the minimum arc sustaining voltage is not increased over the rated operating voltage of the lamp.

The arrangement shown has been found to supply adequate voltage in the operating circuit for operating the lamps at all degrees of luminosity. Since the power supply to the lamp filaments is not reduced by the operation of the phase control device, it is possible to start the lamps at almost the point of lowest luminosity.

One advantage of placing the phase control device in the primary circuit is that lower voltage components can be used than when placed in the secondary circuit, thus reducing materially the cost of the phase control device.

A further advantage of the present arrangement is that the operation of the trigger means is not adversely affected by the irregular voltage wave shape of the operating circuit for the reason that the trigger circuit draws on the line voltage which is substantially sinusoidal. According to the FIG. 2 embodiment the supply voltage for the trigger circuit is the voltage which is developed across the SCR during blocking, land this is the line voltage.

FIG. 3 shows a multple branch circuit installation, in which each of the branch circuits A, B and C are substantially identical to the circuit of FIG.L 1, except for the phase control device 14. Here the various leads 16 and 11 are connected to a common pair of supply leads 8 and 9.

The phase control device 14', as shown in FIG. 4, is a bridge type device similar to that shown in FIG. 1 having an `SCR 34 connected across the midpoint terminals 32' and 33. However, in the FIG. 4 embodiment, a single trigger device 52 is provided for all of the SCRs 34', the coupling being by means of 4suitable pulse transformers 51. As shown in FIG. 4, the secondary of the pulse transformer 51 is connected across the gate 35 and the terminal 33. The primary of the pulse transformer 51 is connected to the trigger device S2 by suitable leads 53, the various primaries being connected in parallel.

The trigger device 52 is energized from the common supply lead lines 8 and 9, and the connection therewith provides suitable means by which the trigger device 52 is synchronized to the proper phase relationship with respect to the supply voltage. Thus all of the branch circuits A, B, and C may be controlled by a suitable variable resistance located in the trigger device 52.

A modified form of phase control device 14 is shown in FIG. 5. This comprises two

SCRs

55 and 56 connected in back to back .relationship and being interposed in the lead 10. The gates of the

SCRs

55 and 56 are separately triggered by a pulse transformer 57, the two secondaries lS, 59 of which are connected between the gate and cathode of each SCR, and the :primary 60 of which may be energized by a suitable trigger device 52.

Although only a single lamp ballast 12 is shown, it will be understood that a two or three lamp ballast may be substituted Ltherefor if desired. For example, a suitable arc supply transformer 15 for Va two lamp ballast is shown in FIG. 6, in which two

secondaries

61 and 62 are provided, each being connected in series with the primary winding 17 and being in parallel connection with each other, and adapted for energizing two lamps, 63 and 64.

In some installations, it may be preferred to'provide a phase control device 14' for each Iballast 12, in which event, the two can be enclosed in a single housing 65, as shown with respect to branch circuit C in FIG. 3, vall of the combined units being controlled from the common trigger device 52.

Although only lprefered embodiments of my invention have been shown and described herein, it will be understood that various modifications and changes may be made -in the constructions shown without departing from the spirit of my invention as pointed out in the appended claims.

I claim:

1. Variable power supply means for starting and operating a plurality of filament type gaseous discharge devices comprising first and second power leads for making a connection to an alternating current source, a plurality of ballasts each including a high reactance :arc supply transformer and a filament transformeneach of said high reactance arc supply transformers comprising a primary winding and a secondary winding, all of said primary windings being connected in parallel across said first and second power leads, a phase control device connected in said first power lead between said primary windings and said alternating current source, a branch power lead connected to said first power lead at a point between said phase control device and said alternating current source, said filament transformers each including a primary winding and a plurality of secondary windings, the primary windings of each of said lament transformers being connected in parallel across said branch power lead and said second power lead, output lead means for each of said arc supply transformers, each of said output lead means being connected to the secondary lwindings of its associated arc supply transformer and having outer ends for making a connection across at least one gaseous discharge device, and output lead means for each of the secondary windings of each of the filament transformers connected at one end to said secondary windings, and hav-ing outer ends for making a connection with the yfilaments of said gaseous discharge devices.

2. Variable power supply means as claimed in claim- 1 in which said phase control device comprisesva full wave rectifier bridge network providing midpoint terminals, and a silicon controlled rectifier connected across said midpoint terminals, and a trigger device for actuating the gate of said silicon controlled rectifier.

3. Variable power supply means as claimed in claim 2 in which said trigger device is connected across said midpoint terminals.

4. Variable power supply means as claimed in claim 2 in which said trigger device is connected across said rst and second power leads at a point between said phase control device and said alternating'current source.

5. Variable power supply means as claimed in claim 1 in which said phase control device comprises Va pair of silicon controlled rectifiers connected back to back, and trigger means for actuating the gates of said silicon controlled rectifier.

6. Variable power Vsupply means for starting and operating a plurality of filament type gaseous discharge devices comprising rst and second power leads for making a connection to an alternating current source, a plurality of ballasts each including a high reactance arc supply transformer and a filament transformer, each of said high reactance arc supply transformers comprising a primary winding and a secondary winding, a phase control device for each of said ballasts, means connecting each phase control device in series circuit with its associated primary winding and across said first and second power leads, said filament transformers each including a primary winding and a plurality of secondary windings, the primary windings of each of said filament transformers lbeing connected in parallel across said first and second power leads, output leads means for each of said arc supply transformers, each of said output lead means being connected to the secondary winding of its associated arc supply transformer and having outer ends for making a connection across at least one gaseous discharge device, a pair of output leads for each of the secondary windings of each of the lament transformers, connected at one end to said secondary windings, and having outer ends for making a connection with the filaments of said gaseous discharge devices, a common trigger device having its output connected to each of said phase control devices, and having its input connected across said rst and second power leads.

7. Variable power supply means for energizing a lament type uorescent lamp comprising a ballast having a first core structure including a winding leg, primary and secondary windings mounted on said winding leg in end to end relationship, said core structure and windings providing a high leakage reactance transformer, and lead means for connecting said secondary winding to a lilament type fluorescent lamp, a phase control device, means providing a series circuit adapted for energization by a source of alternating current and including said primary winding and said phase control device, said ballast also including a second core structure having a primary Winding and a plurality of second windings mounted thereon, lead means adapted for connecting each secondary winding to a filament of said fluorescent lamp, and lead means for connecting the primary winding of said ilament transformer to said source of alternating current.

References Cited UNITED STATES PATENTS 3,089,979 5/1963 Lovinger 315-97 X 3,130,347 4/1964 Harpley 315-98 3,170,085 2/1965 Genuit 315-227 3,205,404 9/1965 Kurata et al. 315-194 JOHN W. HUCKERT, Primary Examiner.

R. F. POLlSSACK, Assistant Examinez.

Claims

1. VARIABLE POWER SUPPLY MEANS FOR STARTING AND OPERATING A PLURALITY OF FILAMENT TYPE GASEOUS DISCHARGE DEVICES COMPRISING FIRST AND SECOND POWER LEADS FOR MAKING A CONNECTION TO AN ALTERNATING CURRENT SOURCE, A PLURALITY OF BALLASTS EACH INCLUDING A HIGH REACTANCE ARC SUPPLY TRANSFORMER AND A FILAMENT TRANSFORMER, EACH OF SAID HIGH REACTANCE ARC SUPPLY TRANSFORMERS COMPRISING A PRIMARY WINDING AND A SECONDARY WINDING, ALL OF SAID PRIMARY WINDINGS BEING CONNECTED IN PARALLEL ACROSS SAID FIRST AND SECOND POWER LEADS, A PHASE CONTROL DEVICE CONNECTED IN SAID FIRST POWER LEAD BETWEEN SAID PRIMARY WINDINGS AND SAID ALTERNATING CURRENT SOURCE, A BRANCH POWER LEAD CONNECTED TO SAID FIRST POWER LEAD AT A POINT BETWEEN SAID PHASE CONTROL DEVICE AND SAID ALTERNATING CURRENT SOURCE, SAID FILAMENT TRANSFORMERS EACH INCLUDING A PRIMARY WINDING AND A PLURALITY OF SECONDARY WINDINGS, THE PRIMARY WINDINGS OF EACH OF SAID FILAMENT TRANSFORMERS BEING CONNECTED IN PARALLEL ACROSS SAID BRANCH POWER LEAD AND SAID SECOND POWER LEAD, OUTPUT LEAD MEANS FOR EACH OF SAID ARC SUPPLY TRANSFORMERS, EACH OF SAID OUTPUT LEAD MEANS BEING CONNECTED TO THE SECONDARY WINDINGS OF ITS ASSOCIATED ARC SUPPLY TRANSFORMER AND HAVING OUTER ENDS FOR MAKING A CONNECTION ACROSS AT LEAST ONE GASEOUS DISCHARGE DEVICE, AND OUTPUT LEAD MEANS FOR EACH OF THE SECONDARY WINDINGS OF EACH OF THE FILAMENT TRANSFORMERS CONNECTED AT ONE END TO SAID SECONDARY WINDINGS, AND HAVING OUTER ENDS FOR MAKING A CONNECTION WITH THE FILAMENTS OF SAID GASEOUS DISCHARGE DEVICES.