A power supply is provided for an arc discharge lamp which includes a relatively low voltage high current power supply section and a high voltage starter circuit. The low voltage section includes a transformer, rectifier, variable resistor and a bank of capacitors, while the starter circuit comprises several diodes and capacitors connected as a Cockcroft-Walton multiplier. The starting circuit is effectively bypassed when the lamp arc is established and serves to automatically provide a high starting voltage to re-strike the lamp arc if the arc is extinguished by a power interruption

Leighty, Bradley D.

English

NASA Technical Reports Server

United States Patent [191 [11] Patent Number: 4,723,096 
Leighty [45] Date of Patent: Feb. 2, 1988 
Inventor: 
Assignee: 
Appl. No.: 
Filed: 
ARC LAMP POWER SUPPLY USING A 3,849,717 11/1974 Walz et al. ............................ 363/61 
VOLTAGE MULTIPLIER 3,917,975 11/1975 Birkner ................................ 315/205 
4,187,449 2/1980 Knoble ................................ 315/205 
Bradley D. Leighty, Newport News, 4,260,932 4/1981 Johnson .............................. 315/205 
Va. 4,445,166 4/1984 Berglund et al. ..................... 363/61 
The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
879,758 P I  ABSTRACT 
Primary Examiner-David K. Moore 
Assistant Examiner-Michael J. Nickerson 
Attorney, Agent, or Firm-George F. Helfrich; Harold 
W. Adams; John R. Manning 
Jun. 27, 1986 
Int. CI.4 ....................... H02M l/l$ H05B 37/00 
US. C1. .................................... 315/254; 315/276; 
315/277; 315/255; 315/200 R; 315/227 R, 
315/241 R 315/245; 363/59; 363/61 
Field of Search ............... 315/205, 207, 254, 255, 
315/257,276,277, DIG. 5, DIG. 7,200 R, 206, 
227 R, 241 R, 245; 363/59, 61 
References Cited 
U.S. PATENT DOCUMENTS 
2,926,287 2/1960 Bird ..................................... 315/205 
3,665,247 5/1972 Gordon ............................... 315/205 
f 12 
A power supply is provided for an arc discharge lamp 
(38) which includes a relatively low voltage high cur- 
rent power supply section and a high voltage starter 
circuit (10). The low voltage section includes a trans- 
former (15), rectifier (24), variable resistor (26) and a 
bank of capacitors (28), while the starter circuit (10) 
comprises a plurality of diodes (D1 to D12) and capaci- 
tors (C1 to C12) connected as a Cockcroft-Walton mul- 
tiplier. The starting circuit is effectively bypassed when 
the lamp arc is established and serves to automatically 
provide a high starting voltage to re-strike the lamp arc 
if the arc is extinguished by a power interruption. 
5 Claims, 3 Drawing Figures 
23! 18b 
120uf. 350v EACH 
https://ntrs.nasa.gov/search.jsp?R=19880014558 2020-03-23T19:51:11+00:00Z
US. Patent Feb. 2,1988 Sheet 1 of 2 4,723,096 
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US. Patent Feb. 2,1988 
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4.723,096 
1 
ARC LAMP POWER SUPPLY USING A VOLTAGE 
MULTIPLIER 
ORIGIN OF THE INVENTION 
The invention described herein was made by an em- 
ployee of the U.S. Government and may be manufac- 
tured and used by or for the Government for govern- 
mental purposes without the payment of any royalties 
thereon or therefor. 
FIELD OF THE INVENTION 
The present invention relates to power supplies for 
relatively large, e.g., 25 watt, arc discharge lamps. 
BACKGROUND OF THE INVENTION 
Large (2-watt and up concentrated arc lamps find 
widespread application in scientific fields and elsewhere 
including use as light sources for Schlieren, shadow- 
graph and other flow visualization techniques. A seri- 
ous drawback in the operation of such lamps is the 
intermittent or otherwise unreliable performance of the 
associated power supplies. Such lamps make very sub- 
stantial demands on their power supplies in that a start- 
ing voltage of in excess of lo00 volts is required 
whereas, when the arc is stabilized, the voltage drop 
across the lamp is approximately 20 volts. Conventional 
operating techniques involve supplying the lamp from a 
constant voltage in excess of 50 volts, with a series 
resistance being used to limit the current to about 1.25 
amperes. This series resistance also serves to eliminate 
the effect of the negative resistance of the lamp arc. The 
starting voltage for the lamp is conventionally provided 
by a relay-choke combination which produces a high 
voltage spike by inductive kickback. This technique for 
generation of the starting voltage is the weakest feature 
of such conventional power supplies. 
There are, of course, many different designs for 
power supplies for many different applications. Patents 
of interest in this general field include U.S. Pat. Nos. 
3,544,840 (Saiger); 3,629,647 (Lake) 3,665,247 (Gor- 
don); and 3,849,717 (Walz et al). The Walz et al patent 
discloses a circuit for gas discharge lamps wherein both 
supply and firing voltages are provided by a voltage 
multiplier comprising a plurality of voltage doubler 
circuits. The Saiger patent discloses a supply circuit for 
a gas discharge lamp such as a xenon tube which em- 
ploys a transformerless multiplier of the capacitor-rec- 
tifier type in combination with a pulse trigger circuit. 
The Lake patent discloses a voltage doubling starting 
circuit for a gas discharge lamp comprising a pair of 
diodes and a pair of capacitors connected in a voltage 
doubling configuration in combination with a bleeder 
resistor. The Gordon patent discloses a power regulat- 
ing circuit for light amplifier tubes which includes a 
voltage multiplier formed by capacitors and diodes. 
Other patents of more general interest include U.S. 
Pat. Nos. 3,911,191 (Patrick et 1); 4,241,360 (Hambor et 
al); and 4,389,703 (Morel et al). These patents relate to 
voltage multiplier circuits employing capacitors and 
diodes, with the Petrick et a1 patent being concerned 
with a Cockcroft-Walton cascade circuit. 
SUMMARY OF THE INVENTION 
In accordance with the invention, an improved 
power supply for high voltage (25 watt) arc discharge 
lamps is provided which overcomes many of the disad- 
vantages of the prior art. The power supply of the in- 
5 
10 
15 
20 
25 
30 
35 
40 
45 
50 
55 
60 
65 
2 
vention includes, inter alia, a solid state starter circuit 
which replaces the electromechanical components of 
the prior art. The invention eliminates problems associ- 
ated with the prior art when used with aged lamps and, 
in this regard, provides reserve capacity to permit the 
use of such older lamps (which have higher starting 
voltage requirements), thus extending the useful life 
over which the lamps can be employed. The power 
supply of the invention also possesses an automatic 
restart capability so that if a lamp is extinguished due to 
a power interruption, the power supply circuit will 
automatically restart the lamp after power is restored. 
Further, the power supply of the invention does not 
require an operator to be in attendance. 
In accordance with a preferred embodiment thereof, 
the present invention comprises, in combination, at least 
one high arc discharge lamp and a power supply circuit 
for the lamp, the power supply circuit comprising a 
relatively low voltage, high current power supply sec- 
tion and a high-voltage multiplier circuit connected 
between the low voltage section and the lamp. The low 
voltage power supply comprises a voltage transformer 
adapted to be connected to an A.C. source, a rectifier 
bridge circuit for rectifying the output of the voltage 
transformer, and a variable resistance device for limit- 
ing the current to the lamp, while the multiplier circuit 
comprises a plurality of diodes and capacitors con- 
nected in a series multiplier configuration for generating 
a high voltage, under no load conditions, so as to estab- . 
lish the lamp arc. The values of the capacitors employed 
are such that when the lamp arc is established, the di- 
odes are biased into conduction and provide a very low 
resistance series current path through the multiplier 
circuit so that the multiplier circuit is bypassed and so 
that the supply voltage for the lamp is provided by the 
low voltage power supply section. The multiplier cir- 
cuit acts, responsive to interruption of the lamp arc, to 
re-generating the high voltage so as to re-establish the 
The circuit configuration of the multiplier circuit is 
preferably that of a Cockcroft-Walton multiplier. Ad- 
vantageously, the multiplier includes a fmt input pro- 
vided by an isolating winding of the voltage trans- 
former and a second input connected through a bank of 
parallel-connected capacitors to the variable resistance 
device of the low voltage supply section. 
Other features and advantages of the invention will 
be set forth in, or apparent from, a detailed description 
of the preferred embodiment which follows. 
BRIEF DESCRIPTION OF THE DRAWINGS 
FIG. 1 is a schematic circuit diagram, partially in 
FIG. 2 is a schematic circuit diagram of a lamp to 
FIG. 3 is a detailed schematic circuit diagram of the 
arc. 
block form, of the power supply of the invention; 
which the power supply is to be connected; and 
starter circuit of in FIG. 1. 
DESCRIPTION OF THE PREFERRED 
EMBODIMENTS 
Referring to FIG. 1, a power supply for large arc 
discharge lamps is shown. The power supply includes a 
direct current supply section which, in the specific 
embodiment being considered, provides 84 volts D.C. 
and serves to provide power for the stabilized arc, and 
a starter circuit, which is indicated at 10 and is de- 
scribed in more detail below. 
497 
3 
As illustrated, an electrical connector or plug 12 is 
connected through a fuse 14 (typically 1 ampere) and a 
switch 16 to a primary winding 18a of a step-down 
tranformer 18 which is shunted by a series combination 
of an indicator lamp 20 and a resistor 22 (typically 47K 
in a specific example). In a specific embodiment, the 
transformer 18 steps down the 120 volts appearing at 
the winding 18a to 60 volts and further includes a pri- 
mary side isolating winding 186 is and a pair of second- 
ary windings 1& and 18d connected as shown. The 
winding 1& is connected to a diode bridge 24 while the 
winding 18b is separately grounded and provides 120 
volts A.C. via an AC line 23 to the AC input of a starter 
circuit 10. 
The diode bridge 24 is connected through a variable 
resistor 26 to a capacitor filter 28 for filtering the D.C. 
output of the bridge 24. In the specific embodiment 
under consideration, the variable resistor 26 is a 3 ohm, 
25 watt device while the parallel-connected capacitors 
of filter 28 are 120 microfarad, 350 volt capacitors. As 
noted above, this portion of the system, which consti- 
tutes the direct current supply, produces a D.C. voltage 
of 84 volts in the specific example under consideration, 
this voltage being supplied to a second input of the 
starter circuit 10 via a 6'commongs line 30. 
The output of the starter circuit 10 is connected via 
an output line 32 through a resistor 34 (25 ohms, 50 
watts in a specific example) to an output terminal 36 
adapted to be connected to the lamp. The resistor 34 
and the variable resistor 26 limit the circuit current. 
The lamp circuit is shown in FIG. 2 and includes a 
lamp 38 and an associated input terminal 40. As noted 
above and discussed in more detail below, a length of 
cable (not shown) is generally used in connecting the 
terminal 40 of the lamp 38 to the power supply shown 
in FIG. 1. 
Referring to FIG. 3, a schematic circuit diagram of 
the starter circuit 10 is shown. As illustrated, this circuit 
comprises a Cockcroft-Walton multiplier and includes a 
plurality of diodes D1 to D12 connected cathode to 
anode, and two sets of capacitors comprising plurality 
of capacitors C1 to C6 and capacitors C7 to C12. As 
shown, the capacitors C1 to C12 are each connected 
between the junctions between the anodes and cathodes 
of two pairs of diodes. For example, the capacitor C2 is 
connected between the junction between the cathode of 
diode of D1 and the anode of diode D2 and the junction 
between the cathode of diode D3 and the anode of 
diode D4, while capacitor C8 is connected between the 
junction between the cathode of diode D2 and the 
anode of diode D3 and the junction between the cath- 
ode of diode D4 and the anode of diode D5. The values 
of the capacitors C1 to C13 are relatively small and in a 
specific embodiment, the capacitors are 0.01 micro- 
farad, 500 volt capacitors, while the diodes D1 to D12 
are INI204A device's (12 amperes, 400 volts). 
In the specific example under consideration, under no 
load conditions, Le., before the lamp arc is struck, the 
output of the starter-multiplier circuit 10 is 2,036 volts. 
After an arc is established, the resultant heavy current 
drain maintains a forward bias on all of the diodes D1  to 
D12 and the starter circuit is then constitutes a straight 
conductor current path providing a voltage drop of 7.2 
volts. 
23,096 
4 
The small values of the capacitors C1 to C12 used in 
the starter-multiplier circuit 10 guarantee that the di- 
odes D1 to D12 will be forward biased when an arc is 
established. It is important to note that if the arc is 
5 interrupted due to a power failure or for some other 
reason, the multiplier 10 will again become functional, 
i.e., will again generate a high voltage for restarting the 
It is noted that adequate ventilation must be main- 
10 tained for the output resistor 34 which typically dissi- 
pates 40 watts in the specific embodiment being consid- 
ered. Further, the length of cable connection between 
the power supply and the lamp 38 should be kept rela- 
tively short so as to reduce distributed capacitance. In 
15 this regard, with a large cable capacitance, the non-lin- 
ear arc produced can form a relaxation oscillator and 
operate in a self-pulsing mode. Cable lengths of four 
feet, using RG59 coaxial cables, present no problem. 
Although the invention has been described relative to 
20 a presently preferred embodiment thereof, it will be 
understood by those skilled in the art that variations and 
modifications can be effected in this preferred embodi- 
ment without departing from the scope and spirit of the 
invention. 
arc. 
25 What is claimed: 
1. An apparatus comprising at least one high voltage 
arc discharge lamp and a power supply circuit for the 
lamp, said power supply circuit comprising a relatively 
low voltage, high current power supply section and a 
30 high-voltage multiplier circuit connected between said 
low voltage section and said at least one lamp, said low 
voltage power supply comprising a voltage transformer 
adapted to be connected to an A.C. source, a rectifier 
bridge circuit for rectifying the output of the voltage 
35 transformer, and a variable resistance device for limit- 
ing the current to the lamp, and said multiplier circuit 
comprising a plurality of diodes and capacitors con- 
nected in a series multiplier configuration for momen- 
tarily generating a high voltage, under no load condi- 
40 tions, suffcient to establish the lamp arc, and the values 
of said capacitors being such that when the lamp arc is 
established, the diodes are biased into conduction to 
provide a low resistance series current path through the 
multiplier circuit to provide a continuous low supply 
45 voltage for the lamp from said low voltage power sup- 
ply section, said multiplier circuit constituting means 
for automatically re-generating said high voltage mo- 
mentarily so as to reestablish the arc after an interrup- 
tion and restoration of power from said A.C. source. 
2. An apparatus as claimed in claim 1 wherein the 
circuit configuration of said multiplier circuit is that of 
a Cockcroft-Walton multiplier. 
3. An apparatus as claimed in claim 1 wherein said at 
least one arc discharge lamp comprises a 25 watt lamp 
55 and a cable connection is provided between the lamp 
and the output of the multiplier circuit. 
4. An apparatus as claimed in claim 1 including a 
winding in said voltage transformer isolated from the 
A.C. source and connected to one input of said multi- 
5. An apparatus as claimed in claim 1 wherein a bank 
of parallel connected capacitors is connected between 
said variable resistance device and one input of said 
multiplier circuit. 
50 
60 plier circuit. 
* * * * *  65 


Arc lamp power supply using a voltage multiplier

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