Патент USA US2571133

Oct.16, 1951
A_ s, HARRls
2,571,131
SWEEP CIRCUIT
Filed Jan. 21, 1946
INPUT
F
COURTPEN
VGORLITD.
FIG.3
INVENTOR
ALBERT S. HARRIS
ATTORNEY
?Patenfecl: Oct.
2,571,131
1U N l TED " S TATES
2,571,131
:Sv'vE'EP omoUrr
. AlberttS. LHarris,IF.0rt Wayne; lndugaswsignorgby
.;mesnej assignments,» ‘to 5 Farnsvvvqrwth ;;R.e_search
Corporation», a..~corporation of Indiana
Application’alannary 21, 1946~,-Serial‘ No.~6f12,477
" 5 Claims
(c1. 257M277)
‘1
.
.1-2
'
.413118 retrace-interval..untilstheisawtooth waveihas
invention relates to sweep ‘:circuits; and
more particularly relates to. a ‘sweep circuit .ar
‘ ranged for-developing-a periodic .sawto'othcur
. reachedv substantially a. minimum.
Preferably,
.. the pulses ofthe voltage wave applied to.the:=input
_ electrodes have a time‘: duration effective to ;_bias
> rent wave which is utilized to produce an electro
.~.the..tube ,to substantially .cutg-off fromithelbegin
.ning .0£..the retrace interval..until..the.sawtooth
waveds tangent tmitstrace iportion. .Theopoint
magnetic ?eld-for de?ecting an electron. beam.
It is conventional practice to.- deflect i'th'e ielec
--tron~beam developedlin a cathode ray .-'tube-by
means of a periodic ielectric or magnetic .de?ec
where the sawtooth wave is tangentqtogits ‘trace
...portionis veryclosato:theminimum. ofrthe wave.
ing a. sawtooth= current :wave. for. themagnetic 10
For. a better .understandingpf .the invention,
tion ?eld. Sweep’ circuits arranged for develop
de?ection of‘ an electron .beam are used, “for. ex
\ together. with. other.~ and afurtherobjects. thereof,
ample, in television picture signal generating and
reproducing tubes. Great difficulties- have. been
“taken. in uconnectimlewith . the .zaccompanying
1 reference. is. madatqgthe. followmggdescription.
vdrawing, and itsscODQ wi11.;-be; pointed out :;in
experienced - in' conventional : sweep circuits ar
ranged’ for developinga sawtoothcurrent wave 15 .;the
prevent'thelintroduction of transients, particu
the
Wave. ~ The sawtooth .. current...waves.,.are
..
. Fig. 1. is atcircuitodiagramjof. a..-sw.eep circuit
.emhodvinethe present invention;
,
larly at the beginning ofllthe traceintervalaof
caused to flow through. an. inductance element
which may be the electron beam. de?ecting. coil.
appendedclaims.
a .In the. accompanying drawmgr
because-it has not been-.possibleheretofore.to
_'Eig-.. 2 illustrates“ thecinput eveltage -andcthe
20a .outuutcurrentrotavacuum tubefqrmine nart'of
.; thesweep circuitp?he invention; and... c.
An inductance elementinherently has distributed
. 121g. 3, is. acircu
iagrampff.
,
.medi?edemeep
and stray-capacitances which,.together withthe
‘inductance of the coil, :form .an oscillatory;.sys
tem. The abruptchang-es of. theifirstéderivative
-. of thesawtooth current waveintroduce tran
sients, particularly. at the 'beginningpf thetrace
. interval. The portion of the trace interval upon
which . transients; .are superimposed , {can: not the
.used for de?ecting the ielectronlbeamhthus ‘de
.creasing .the;.usetul._time duration ofithe .trace
interval.
.
:-It_is the principalrcbject of theipresentginven
tion, therefore,..to. provide a-sweep circuit for
. developing a periodic sawtoothcurrent wave sub
cathode. lmmnnige
35
stantially without introducing transients ‘at the
beginning of the trace .iinterval, therebytqin
.crease'the useful time duration _-.of the tracepor
,cated
stray capacitanceE
atB+-. Elle;.1nductance~element
iributed. cavaciiané
8 includ
.ing. theinterelectrqdeigapecitencég?i T édeil‘clid
thecapacitance otthede'ads of coil 8, is indicated
tion of the Wave.
A further object of the invention is to provide 40
. a scanning circuit__including a vacuum tubev for
developing a sawtooth current wave of larger
sweep amplitude with a given averagecurrent
through the ‘tube than‘ has been possible in prior
. art circuits.
In. accordance with ,the present. invention, a
sweepcircuitfor. developing periodic sawtooth
waves having a traceand a retrace intervalcom
. .
.mcted ?g apositiv arlgde r9lia'se source 11(11
brcon?enswl 9.
in dotiedlilcee-
‘"’
Triode I is. arrengedfto ' e .ndrmallr scallio
.tive. fso. thatcurfeni ?ewsirqm thaarlqde. y9lt§liée
source.
triode l~.-..to;ercund.
B+.> throueh?niuctance
-..T..I1ei9utput;¢urr§nt
element? ..
45 .throughninductance; element: 3 .‘;iI1..~ il?lle
.
-11pon;time, is illustrated; .ir.1_.'-.the~11.pper. peril 1210f
Fig. 2. . The.outputcurrent.comprises tracepmf
Utions _. l l. .andretraceportions _; l 2. vyllhen trig‘dev l
prises a vacuum.tube having input and output
beginstoconduct space currentsthe curren
’
electrodes. Areactive output circuitiscoupled' 50
,through
determined
inductance;.element
.by-the. tube ...c.h.aracteri_s_t_ics
8_ increases;0f
at .tricde
_
to the output. electrodes. . Meansareprovided for
applying to. the. input: electrodes a .periodic volt
l and by.the.;iner.tia:0fr>12h§ resonant-systemorep
»agewave .to producethe sawtooth wave inthe
resented by inductance element 8andmnd§nser
~10.
:output circuit. <'I?he.;vo.ltage .wave'includes pulses
e?ective to bias the tube from the beginninggof .55 Upon. .thaarriral, of? a-..:.n.eeativermilse 1J3 rim
2,571,181
pressed upon control grid 3, triode I is biased
beyond cut-o? thus terminating the flow of space
current through triode I. The current through
inductance element 8 now decays due to the
inertia effects of the inductance of element 8 and
the capacitance of condenser III.
This corresponds to the retrace interval of the
sawtooth current wave illustrated by the curved
portion I2 in Fig. 2.
includes cathode 28, control grid 21 and anode 28.
Grid leak resistor 38 is arranged between con
trol grid 24 and ground. Cathode resistor 3| is
connected between both cathodes 23 and 26 and
ground. Coupling condenser 32 connects anode‘
~25 of tube section 2I to control grid 21 of tube
section 22. Adjustable grid leak resistor 33 is
arranged between control grid 21 and cathodes
23 and 26. Grid bias battery 29 is arranged in
In the prior art it has been suggested to make 10 series with grid leak resistor 33 between cathode
2E and grid 21 for grid 21 normally biased to
triode I conductive at a time corresponding to
cutoff. Anode resistors 34 and 35 are provided
point A of sawtooth retrace portion I2. Input >
between suitable anode voltage sources indicated
signal 6 illustrated below sawtooth current wave ‘
II, I2 represents grid voltage impressed upon
. at 3+ and anodes 25 and 28, respectively. An
control grid 3. Input signal 6 includes negative 15 input signal consisting of negative pulses 31 is
impressed upon control grid 24 through coupling
pulses I3 having a leading edge I4 which occurs
at the beginning of retrace portion I2 as illus
trated. When negative pulse I3 is terminated
at the point I5 corresponding to point A on 'saw- '
tooth current retrace (portion I2, the current
through inductance element 8 will over-shoot,
and a few transients or oscillations of damped
waveform indicated in dotted lines at I6 are
superimposed upon the beginning of trace portion
I1. It will be apparent that the beginning of
trace portion II can not be used for deflecting an
electron beam until transients I6 have been suf
?ciently damped.
condenser 38.
Multivibrator 20‘ operates as follows.
Tube
section 2I comprising cathode 23, control grid
24 and anode 25 normally conducts space cur
rent. Tube section 22 comprising cathode 25,
control grid 21 and anode 28 is normally biased
to cut-off due to the action of grid bias battery 29.
Thus tube section 2| normally conducts space
current and continues to be conducting until a
negative pulse 31 is impressed through coupling
condenser 38 upon control grid 24 thus biasing
it beyond cut-oif. Thereupon the voltage of
anode 25 begins to rise, and this positive poten
In accordance with the present invention the
time duration or width of negative pulses I3 30 tial change is impressed upon control grid 21
through coupling condenser 32. Now tube section
impressed upon control grid 3 is accurately con
22 begins to conduct space current, while tube
trolled so that the trailing edge of the pulses oc
section 2I is nonconductive.
curs at the point I8. This corresponds to point
Gradually the positive charge impressed upon
B on retrace portion I2 which is substantially
at or near the minimum of the sawtooth wave. ' coupling condenser 32 is dissipated through ad
Preferably the time duration of negative pulses
justable grid leak resistor 33 until tube section
I3 is such that the pulses are effective to bias
22 ceases to conduct space current. It will be
observed that the time duration of the conduc
tion period of tube section 22 is determined by
the time constant of coupling condenser 32 and
triode I substantially to cut-off from the begin
ning of retrace portion I2 until the sawtooth
wave is tangent to the desired trace portion II.‘
When retrace portion I2 of the sawtooth current
wave has reached its minimum the rate of change
or the ?rst derivative of the wave equals zero.
At this point or in the neighborhood thereof the
sawtooth current wave may be given any desired ' — _
slope, such as that of trace portion II, without in
troducing transients.
Thus by controlling the time duration of grid
pulses I3 in the manner explained the introduc
tion of transients at the beginning of the trace .
interval of the sawtooth current wave is pre
vented. Accordingly, the useful time duration of
trace portion II is increased. Furthermore, the
current through inductance element 8 has a ten
grid leak resistor 33. By adjusting resistor 33
the duration of the conduction period of tube
section 22 may be adjusted. Alternatively grid
bias battery 29 may be adjusted to vary the con
duction period of tube section 22.
In the meantime the negative charge impressed
upon condenser 38 is gradually dissipated through
grid leak resistor 30. When the space current
?owing through tube section 22 is terminated
while tube section 2I is still non-conductive, the
potential of cathode 23 drops to ground Potential
because there is no longer a current ?ow through
cathode resistor 3I.
Accordingly, control grid
24 is now less negative with respect to cathode
23 and space current begins to flow again through
tube section 2I until the next pulse 31 biases con
dency to overshoot from point A to point B on
retrace portion I2. By removing the cut-off bias
from control grid 3 when the sawtooth current
wave has reached the point B, the sweep ampli
trol grid 24 beyond cut-off.
Space current ?owing through tube section 22
tude of the current wave is increased by an
causes a voltage drop across anode resistor 35
amount represented by the difference between 60 which is impressed through coupling condenser
1 upon control grid 3 of triode I. Input signal
arrows D and C shown in Fig. 2. Thus, with
8 then comprises pulses I3 of negative polarity
the same average current ?ow through triode I
as required. It will be seen that leading edge
a. larger sweep amplitude may be obtained than
V I4 of pulses I3 is determined by the leading edge
has been possible with prior art circuits.
As explained hereinabove the time duration or 65 of pulses 31 which control multivibrator 20. This
is so because upon the arrival of a negative pulse
width of negative input pulses I3 should be ad
31 the space current through tube section 2I is
justable. For the purpose of developing negative
terminated, while tube section 22 begins to con
pulses having a controllable width andhaving
duct space current thus causing a voltage drop
leading edges recurring at a predetermined time
interval there may be provided, for example, 70 across anode resistor 35. As pointed out herein
above the time duration of output pulses I3 of
multivibrator 20. Multivibrator 20 comprises
multivibrator 28 is determined by the time con
tube sections 2I and 22 which may be arranged in
stant of coupling condenser 32 and grid leak re
a common envelope in themanner of a duplex
sistor '33 and 'may be varied by adjusting resistor
tube. Tube section 2I comprises cathode 23, con
trol grid 24 and anode 25, while tube section 22‘ it :33: 1 1
2,571,131
5
6
It is to be understood that any conventional
means may be employed for supplying negative
pulses l3 of adjustable time duration and im
pressing them upon control grid 3 of triode l.
comprising a vacuum tube having a cathode, an
input electrode and an output electrode, means
for rendering said tube normally conducting dur
ing said trace intervals, an inductive device
coupled between said cathode and said output
electrode which maintains substantially constant
the rate of change of current in said tube dur
ing trace intervals and which decreases the rate
of change of current during the later portions
of said retrace interval until said saw-tooth wave
becomes tangent to its trace portions, and means
for impressing upon said input electrode a series
of pulses each having an amplitude, polarity and
Inductance element 8 may be utilized as the
de?ecting coil or pair of coils for developing a
magnetic electron beam de?ecting ?eld.
How
ever, as illustrated in Fig. 3 in which like com
ponents are designated by the same reference
numerals as were used in Fig. 1, it is also feasible
to couple an inductance element 40 magnetically
to inductance element 8 which is arranged in
the plate circuit of triode I. In that case a
de?ecting coil 4| or a pair of coils may be con
rangement illustrated in Fig. 3 has certain ad
a duration effective to bias said tube to cutoff
from the beginning of said retrace interval until
said saw-tooth current is tangent to its trace por
vantages because transformer 8, 40 facilitates
tion.
nected across inductance element 40.
The ar
'
matching of the output impedance of vacuum
4. A sweep circuit for developing periodic saw
tube l to the impedance of de?ecting coil 4 l . The
tooth waves having a trace and a retrace interval
output current may be stepped up or stepped 20 comprising a vacuum tube having a cathode, an
input electrode and an output electrode, means
down as required through transformer 8, 40. The
for rendering said tube normally conducting dur
ing said trace intervals, an inductive device cou
scribed in connection with Fig. 1 by impressing
pled between said cathode and said output elec
input signal 6 of adjustable pulse width upon
25 trode which maintains substantially constant the
control grid 3 through coupling condenser 1.
rate of change of current in said tube during
While there has been described what is at
trace intervals and which decreases the rate of
present considered the preferred embodiment of
change of current during the later portions of
the invention, it will be obvious to those skilled
said retrace interval until said saw-tooth wave
in the art that various changes and modi?cations
may be made therein without departing from 30 becomes tangent to its trace portions, and means
for impressing between said cathode and said
the invention, and it is, therefore, aimed in the
input electrode a series of pulses each having
appended claims to cover all such changes and
steep leading and trailing edges, a polarity and
modi?cations as fall within the true spirit and
a duration effective to bias said tube to cuto?
scope of the invention.
35 from the beginning of said retrace interval until
What is claimed is:
said saw-tooth current is tangent to its trace por
1. A sweep circuit for developing periodic saw
sweep circuit operates in the same manner as de
tooth waves having a trace and a retrace interval
tion.
’
5. A sweep circuit for developing periodic saw
comprising an electronic tube having a cathode
an input electrode and an output electrode, an
tooth waves having a trace and a retrace interval -
output circuit including an inductance element 40 comprising a vacuum tube having a cathode, an
input electrode and an output electrode, means
coupled between said cathode and said output
for rendering said tube normally conducting dur
electrode which decreases the rate of change
ing said tace intervals, an inductive device cou
of current through said tube during the later
pled between said cathode and said output elec
portions of said retrace intervals until said. saw
tooth wave becomes tangent to its trace portions, 45 trode which maintains substantially constant the
rate of change of current in said tube during trace
and means for applying to said input electrode
intervals and which decreases the rate of change
periodic rectangular voltage pulses of negative
of current during the later portions of said re
polarity to produce a sawtooth current through
trace interval until said saw-tooth wave becomes
said inductance element, said pulses having a
time duration and amplitude effective to bias 50 tangent to its trace portions, and means for im
pressing between said cathode and said input
said tube substantially to cut-01f at the beginning
electrode a voltage wave consisting of pulses of
of said retrace interval until the slope of said
a
polarity and amplitude effective to bias said tube
sawtooth current is tangent to the slope of the
to cutoiT from the beginning of said retrace inter
desired trace portion.
val until said saw-tooth current is tangent to its
2. A sweep circuit for developing periodic saw
trace
portion.
tooth waves having a trace and a retrace interval
ALBERT S. HARRIS.
comprising a triode vacuum tube having a cath~
ode an input electrode and an output electrode,
REFERENCES CITED
a reactive output circuit coupled between said
The
following
references are of record in the
cathode and said output electrode which decreas 00
?le of this patent:
es the rate of change of current through said tri
ode during the later portions of said retrace inUNITED STATES PATENTS
terval until said saw-tooth wave reaches a maxi
mum value, and means for applying between said
cathode and said input electrode periodic rectan
gular voltage pulses of negative polarity to pro
Number
65
' duce s'a'i‘d sawtooth wave in said output circuit,
said pulses having a duration and amplitude ef
fective to bias said tube to cut off from the be
ginning of said retrace interval until said saw 70
tooth wave has reached said minimum.
3. A sweep circuit for developing periodic saw
tooth waves having a trace and a retrace interval
2,177,162
2,224,116
2,227,480
2,244,003
2,264,781
2,280,990
2,300,524
2,302,161
2,344,745
2,396,476
Name
'
Date
Wilson __________ __ Oct. 24,
Schlesinger ________ __ Dec. 3,
Andrieu ___________ __ Jan. 7,
Eagles?eld et al ____ __. June 3,
Wheeler __________ __ Dec. 2,
White ____________ __ Apr. 28,
Roberts ___________ __ Nov. 3,
Woerner __________ __ Nov. 17,
Somers __________ __ Mar. 21,
Schade __________ __ Mar. 12,
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