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Патент USA US2403487

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July 9, 1946.
A. v. BEDFORD
2,403,487
CATHODE RAY DEFLECTION CIRCUIT
Filed July 50, 1941
ÍÍG.1.Í `
C4
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16
MII"
-Iwlß l
- ßnventor
,
Alda, ïzßedford
Y
(Ittomeg
l
'
»
8B .y
` ` l~
2,403,481
Patented July 9, 1946
UNITED .STATES :PATE
- oFFica
2.403,4'si ,
cA'rHonE-nsr DaFLEc'noN omctn'r
Aida V. Bedford, Collingswood, N. J., assignor to
Radio Corporation of America, a corporation of
Delaware
'
Application July an, 194i, serial No. 404.613 '
s claims.
1
(ci. sis-21)
.
My invention relates to cathode ray deilection
circuits and particularly to circuits employing
electromagnetic deiiection.
One of the more diñicult problems in design
ing a deflecting circuit is that of obtaining the
desired deñecting current wave shape'. It is es
pecially difiicult in cases where the defñecting
coils have a substantial amount of. distributed
capacity and where either the deilecting coil re
sistance itself, or the coil resistance together with 10
8
.
"
^
An object of the present invention is to pro
vide an improved method of and means for pro
ducing a ñow of deflecting current of the desired
wave shape.
'
A further object oi’ the invention is to provide
an improved electromagnetic deiiecting circuit for
use with deilecting coils having `a substantial
'
plied to a cathode ray deilecting circuit compris- -
`
älilehresistance of a cable or the like, is _rather
2
Referring to Fig. 1, the invention is shown ap
ing deiiecting coils I0 which are supplied through
a cable I2 withdei‘lecting current from an out
put tube I I. The output circuit of tube II may
include a conventional choke coil I3 and block
ing condenser Il.
.
,
_
„
'
-
vOne oi' the voltage wave components applied
to the grid ofthe output tube II consists of the.
usual sawtooth wave combined with a rectangu
lar pulse. This portion ofthe wave is produced
by a capacitor C comprising condensers CI and
C2 in series -with each other and in series with
a “peaking” resistor R. The- capacitor C is
'charged comparatively slowly ¿thrown a plate re-.
_sistor I8 and is discharged rapidly through a'
discharge tube I.'l in responsel to the applicationoi'a positive pulse I8 to the grid thereof..
The pulses I8 may be supplied to the discharge
amount of resistnce and distributed capacity.
20 tube I1 from any suitablejsource s_uch as a
A still further object 'of the invention isv to
blocking oscillator indicated at I0. " '
»
provide an improved deiiecting circuit for passing
The combined sawtooth-puise wave across
a sawtooth current through deñecting coils hav
C-R is impressed across a potentiometer cir
ing a substantial amount of resistance eiïectively
cuit comprising a blocking _ condenser vCI- and
'in series therewith and a substantial amount of 25 the resistors R2 and R3, all connected in series.
capacity effectively in shunt thereto.
The voltage across resistor R2, which has 4a low
In one embodiment of the invention. a vspecial
resistance compared with that oi' R2, is applied
network preceding the deñecting circuitl output
to the grid of the output tube llvthrough the
- tube adds voltages from two circuit branches to
usual coupling condenser 2|. _ The potentiometer
supply to the grid of this tube (l) a voltage that 30 circuit does not appreciably load the capacitor C
would give the desired sawtooth current in the
since _the resistance of R2 is made great enough
absence of capacity across the deiiect-ing coil
to give R2-C a time constant that is long com
and (2) an additional voltage that supplies the
pared with a deflection cycle. current taken by the capacity, this additional
In accordance with my invention, another volt-~
voltage being given a wave shape which takes into 35 age
wave is added to the above-mentioned saw
consideration the deñecting coil resistance and/or
tooth-pulse wave by” means of a condenser C3'
cable resistance or the like in series with the coil.
connectedbetween the Junction point ofcou
In a preferred embodiment, there is a network
densers CI and C2 and the Junction point of re
preceding the output tube which simulates the
sistors R2 and RI. This connects C3 and R8
output circuit of said tube, this network includ 40 across condenser C2 . and peaking resistor R
ing a condenser corresponding to distributed ca
whereby a voltage that is the differential of _the
pacity and being itself preceded by a wave shap
voltage across C2---RI appears across R2 anais
ing means for producing current of the proper `
added to the other voltage wave, that is. to the
wave shape through the said network.
combined sawtooth-pulse wave. ‘ .
.
The invention will be better understood from 45 The> above described differentiation is obtained
the following description 'taken in connection
since the impedance of R3 is low compared with
with the accompanying drawing, in which
that oi.' C! -whereby the current ilow through CI
Fig. 1 is a circuit diagram of a deiiecting cir
(and through R2) is given by the `equation
cuit embodying my invention,
Fig. 2 is a diagram of an equivalent'circuit for 50
.
E
te:
a portion of the circuit in Fig. 1, and
Fig. 3 is a circuit diagram of a preferred em
where C is the capacity of condenser _Cl and E
bodiment of the invention.
is the voltage across C2and R.
.
Corresponding parts in the several iigures are
The circuit operation will be understood by
indicated by like reference characters.
55
referring to Fig. 2 where Rip represents the cath
v
2,403,487
4
3
The network voltage is applied to the grid of
tube I! through an amplifier 42 for reversing `its
polarity, it being preferred that the tube || be
ode-plate resistance of the output tube II, R4
represents the deñecting coil resistance and any
other resistance in series therewith, such as all
or part of the resistance of the cable I2, L rep
driven towards plate current cutoii? during the
return-line time as is well known in the art. The
tube II functions,Á however, as a substantially
linear amplifier.
Considering the function of the above-described
network more in detail, it will be apparent that
resents the inductance of the de?lectlng coils I0,
and Cd represents the distributed capacity of the
coils l0 and any additional capacity across them
such as the capacity of the cable I2.
The circuit operation of Fig. 1 may be analyzed
as follows:
10 the sawtooth voltage component applied to the
The combined sawtooth-pulse voltage across
C-R consists of a sawtooth voltage across Cl,
another sawtooth voltage across C2 and a pulse
voltage across R. The voltages across CI and C2v
are those required to drive a sawtooth current 15
through Rp and through R4, respectively, and
thev voltage across R is that required to drive a
grid of tube v33 produces a voltage pulse across
coil 40 and a voltage sawtooth across the resistors
38 and 39. In the absence of capacity across the
deflecting coils this would produce a straight saw
tooth current in the deflecting coils.
The value of the resistor 32 with respect to the
condenser 3| is such‘ that the voltage wave ap
plied to the differentiating condenser 31, is the
same shape as the voltage which would exist
sawtooth current‘through the inductance L. No
other voltage at the grid of tube | I would be re
quired if the distributed capacity Cd were absent. 20 across Cd, when a straight sawtooth current ñows
through R11 and L. Hence, the current through
However, there is the capacity Cd across R4 and
condenser 31 corresponds to the current through
L which will draw current. I provide this cur
Cd and generates a component of IR drop in re
rent by the additional differentiated voltage ob
sistor 34 which causes a similar component of
tained by the circuit C3-R3 -connected across
C24-R. It will be apparent that the voltage 25 current to ñow into the network 38, 39, 4D and 4|.
across C2-R is a sawtooth wave plus a pulse, just
as the voltage across R4 and L is a sawtooth wave
The ñow of this component of current then re
vention which corrects more exactly for the ca
pacitor and a resistor .in series, means -for pro
ance L of coils I0, and a condenser 4I corre
resistor and across at least one but not all of said
condensers, means for adding said diiîerentiated
‘sults in a voltage component being applied to th'e
grid of tube 42 (and then to the grid of tube II)
plus a pulse. Therefore, the differentiated volt
which is correct to cause tube II to supply the
age appearing across R3 is the voltage required
to supply current to the distributed capacity Cd 30 desired capacity component of current to its actu
al output circuit. Therefore, the voltage appear
for the assumed desired condition of a straight
ing across the network 38, 39, 40 and 4| when
or undistorted sawtooth current ñowing through
applied to the grid of the output tube causes th'e
the inductance L, that is, through the deiiecting
desired undistorted sawtoothl current to iiow
coils I0.
It may be noted that the operation of that por 35 through the deflecting coils.
I claim as my invention:
`
-tion of the above circuit for supplying the ca
1. A cathode ray de?lecting circuit comprising
pacity. current for Cd is based on the assumption
deflecting coils having distributed capacity there
that thel output tube feeds into a pure resistive
across and having resistance effectively in series
load so far as the grid voltage vs. plate current
characteristic is concerned. This assumption, of di) therewith, a vacuum tube having a grid circuit
and having a-plate circuit coupled to said coils
course, is not strictly true.
to supply defiecting current therethrough, a ca
Fig. 3 shows a preferred embodiment of the in
ducing a sawtooth voltage wave across said ca
pacity across the deflecting coils I0. In the out
put circuit of the tube I'I there is a condenser 3| 45 pacitor and a Voltage pulse -across said resistor,
means comprising a branch circuit connected
across which a sawtooth Voltage appears and a
across said capacitor and resistor for differentin
resistor 32 across which a pulse voltage appears.
ating the voltage appearing across said resistor
'A potentiometer comprising resistors 33 and 34
and at least a portion of the voltage appearing
is connected across condenser 3|, and the input
said capacitor, means for adding said »dif
electrodes of an amplifier tube 35 are connected 60 across
ferentiated voltage to at least a portion of the
across resistor 34.
voltage appearing across said capacitor, and
The combined sawtooth' and pulse voltage ap
means for impressing said added voltages upon
pearing across the condenser 3| and the resistor
said grid circuit.
.
. 32 is diiîerentiated in a circuit comprising a con
2. A cathode ray deñecting circuit comprising
denser 31 and the resistor 34. This differenti 55 deilecting coils having distributed capacity there
ated voltage is added in the resistor 34 to the
across and having resistance eiîectively in series
sawtooth voltage whereby the combined voltage
therewith, a vacuum tube having a grid circuit
Wave is impressed upon the grid of amplifier 36.
and having a plate circuit cou-pled to said coils to
In th'e plate circuit of amplifier 36 there is a
supply deñecting current therethrough, a plu
network which simulates the output circuit of 60 rality of condensers in series with a peaking re
the output tube Il, this output circuit being
sistor, means for producing a sawtooth voltage
shown in equivalent form in Fig. 2. The net
wave across each of condensers and a voltage
work comprises a resistor 38 corresponding to Rp
`pulse across said peaking resistor, means for dif
(Fig. 2), a resistor 39 corresponding to R4, an
inductance coil d0 corresponding to theinduct 65 ferentiating the voltage appearing across said
sponding to distributed capacity Cd. The tube
36 is of a. type having such high plate imped
voltage to the voltage appearing across said peak
ing resistor and said plurality of condensers, and
ance with respect to its plate circuit that the
plate current is closely proportional to the grid 70 means for impressing said added voltages upon
said grid circuit.
voltage. As will be explained, the voltage ap
3. A cathode ray deflecting circuit comprising
pearing across this network is the Voltage which,
deflecting coils having distributed capacity there
when applied to th'e grid of the output tube II
across and having resistance effectively in series
will produce current through the deiiecting coils
75 therewith, an output tube coupled to said coils to
that is a straight sawtooth.
5
2,403,487
supply deflecting current therethrough, a plural
ity of amplifier tubes connected in cascade with
tooth component and a component which is a '
derivative of said sawtooth component and of a
said output tube, each of said ampliñer tubes
voltage pulse.
`
.
having a, grid circuit and a plate circuit, a net
5. A cathode ray deflecting circuit comprising
work in the plate circuit, of one of lsaid tubes
which simulates the output circuit of said output
tube, said network comprising an inductance coil
across and having resistance `effectively in series _
deíiectingV coils having' distributed capacity there
therewith, an output tube coupled to said coils to
supply deflect-ing current therethrough, a plu
and a resistor in series, both shunted by a con
denser representing said distributed capacity to
rality of amplifier tubes connected in cascade with , `
form a parallel combination of elements, and a
resistor connected in series with said parallel
said output tube, each of said amplifier tubes hav
ing a grid circuit and a plate circuit,- a network in
the plate circuit of one of said tubes which simu
combination, and means for applying to the grid
of said one tube a voltage consisting of a sawtooth
lates the output circuit of said output tube, said
component and a component which is a derivative `
network comprising an inductance coilärepresent- '
of said sawtooth component and of a voltage
pulse.
4. A cathode ray deflecting circuit comprising
deflecting coils having distributed capacity there
across and having resistance eñie'ctively in series
therewith, an output tube coupled to said coils
to supply deñecting current therethrough, a plu
rality of ampliñer tubes connected in cascade with
said output tube, each of said amplifier tubes
having a grid circuit and a plate circuit,-.a net
work in the plate circuit of one of said tubes
which simulates the output circuit of said output
tube, said network comprising an inductance coil
representing dei‘lecting coil inductance and a re
sistor in series representing said resistance ef
fectively in series, both shunted by a. condenser
representing said distributed capacity to form a
parallel combination of elements, and a resistor
representing the plate-cathode resistance of said
output tube connected in series with said parallel
it
ing deñecting coil inductance and a resistor in
series representing said resistance effectively in
series, both shunted by a,A condenser represent
ing said distributed capacity to form a parallel
combination of elements, and a resistor repre
senting the plate-cathode resistance of said out
put tube connected in series with said parallel
combination, and means for applying to the grid
of said one tube a voltage consisting of a saw
tooth component for producing the voltage drop Í
across said inductance. coil and a component
which is a derivative of said'sawtooth component
and of a, voltage pulse.
-
6. The invention according to claim 5 wherein
said’last means comprises a resistor and acon
denser in series and means for lproducing a saw
tooth voltage across said condenser and a pulse
voltage across said last resistor, means for ob-`
' taining a derivative of the voltages appearing
across said last mentioned series combination of
combination, said network having an impedance 35 resistor and condenser, and means for vadding
which is proportional to the impedance of the
said last sawtooth voltage and said derivative
load circuit of said output tube, said load cir
voltage and applying them to the grid of said one
cuit including the .plate-cathode resistance of the l tube.
output tube; and means for applying to the grid
ALDA v, BEDFoRn.
of said one tube a voltage consisting of a saw
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