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Aprll 11, 1950
F. KERKHOF
CIRCUIT-ARRANGEMENT FOR GENERATING A
'
2,503,745
SAW-TOOTH CURRENT IN A COIL
Filed Dec. 26, 1947
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INVENTOR.
Faaosm K KERKHOF
Patented Apr. 11, 1950
UNITED STATES PATENT OFFICE
2,503,745
CIRCUIT ARRANGEMENT FOR GENERATING
A SAW-TOOTH CURRENT IN A COIL‘
Frederik Kerkhof, Eindhoven, Netherlands, as
signor to Hartford National Bank and Trust
Company, Hartford, Conn., as trustee
Application December 26, 1947, Serial No. 794,031
In the Netherlands January 14, 1947‘
6 Claims.
(C1. 315-—-27)
2
1
tery ‘l, the diode is conductive during the whole
The invention relates to a circuit-arrangement
for generating a saw-tooth current in a coil hav
ing a self-induction L and a resistance R, which
current is derived from the voltage set up across
an inductance coil at least part of which is
included in the anode circuit of a discharge tube,
of the sweep of the saw-tooth current due to the
induced voltage in the Winding l which makes the
cathode of the diode more negative than the
anode thereof. The consequence thereof is that
with the circuit-arrangement according to Fig. 1
during the whole of the sweep the voltage across
the total Winding i is limited by the diode to a
value substantially equal to the voltage E of the
whilst a diode is included in a circuit which is
connected in parallel to at least part of this
anode circuit in such manner that during the
sweep of the saw-tooth current the diode is con
ductive.
It is the object of the invention to provide a
circuit arrangement for generating a saw-tooth
sweep current having a high degree of linearity.
A speci?c object of the invention is to provide
an inductive type saw-tooth current generator
of the above referred to type in which non
linearities of the generated sweep current are
corrected.
In accordance with the invention, these ob
jects are achieved by including in the inductive
circuit of the generator a further inductive ele
ment which varies in value proportional to the
amplitude of the generated current.
The invention will be described in greater detail
with reference to the appended drawing in which:
Figs. 1 and 2 are schematic diagrams of saw
tooth current generators of the type to which
the invention applies.
10
battery '1, whereas with the circuit-arrangement
according to Fig. 2, the voltage across the whole
of the winding l is similarly limited to a value
substantially equal to the voltage across the por
tion p of the battery ‘I.
In the circuit-‘arrangement according to Fig. 1
15
the effect of the coil 6 may be referred to the
primary side of the transformer 2, in which event
during the sweep of the saw-tooth current the
equivalent circuit according to Fig. 3 obtains,
20 wherein L1 represents the transposed self-induc
tion L of the coil 6 and r is the resistance of the
diode increased by the transposed resistance R of
the coil 6 and by the resistance of the winding I.
In this circuit we have:
25
If 1- is suf?ciently small, its effect is negligible
so that the current i varies linearly with the time
1.‘. If r is not su?lciently small, the current 2' varies
Fig. 3 is a schematic diagram of the equivalent 30 exponentially with time.
circuit of the generator of Fig. 1,
The circuit-arrangement according to Fig. 4
Fig. 4 is a schematic diagram of a saw-tooth
obviates the above noted disadvantages and ex
current generator according to the invention.
hibits the feature that the coil 6 has connected
In the ?gures similar parts are denoted by the
in series with it a second coil 8, the self-induction
same numbers.
35 of which decreases, upon increase of the intensity
In the circuit-arrangement according to Fig. 1
of the saw-tooth current traversing this coil, in
the primary winding I of a transformer 2 has a
portion thereof included in the anode circuit of
a discharge tube 3 and the remainder thereof
forms part of a circuit comprising a diode 4.
Impulses are supplied to a control grid of tube 3
by means of a saw-tooth generator of conven
tional form.
such manner that during the sweep this current
increases linearly or substantially linearly with
time.
If the inductance coil 8 has a self-induction
value
A coil 6 which in practice constitutes the de?ecé
(Lo being a constant value, 1- being the trans
tion coil of a cathode ray tube, is connected to 45 formed resistance of the coil 6, which is required
the secondary winding 5 of the transformer 2.
to be corrected, and
In the circuit-arrangement according to Fig. 2
the whole of the primary winding l of the trans
former is included in the anode circuit of the
tube 3. However, in this arrangement the anode 50 being constant), it has proved possible to obtain
a sweep of the saw-tooth current which increases
of the diode 4, instead of being connected to the
linearly with time.
negative terminal of a battery ‘I, is connected
In that case we have:
to a point of higher potential.
The operation of both circuit-arrangements is
well-known but it is of importance to point out 55
that with the circuit-arrangement according to
Fig. 1 owing to the fact that only part of the
primary winding I is included in the anode circuit
Due to the variable self -induction, a voltage
of tube 3 and with the circuit-arrangement ac
-z'r, which exactly neutralizes the disturbing term
cording to Fig. 2 owing to the fact that the anode
'+ir, is set up across the coil 8.
‘
of the diode 4 is connected to a tap on the bat
2,503,?45
3
As shown in ‘Fig. '14, the “coil comprising a
‘a secondary winding, 'means to f'couplersaid coil
core 9 which with the aid of the battery 7 is
to said secondary winding, a diode element shunt
premagnetized via a variable resistance it and
iing said primary winding and being poled to be
a choke coil l I in such manner that upon increase
conductive during the current ?ow through said
of the current ?owing in the'circuit ‘which in UK primary winding-and through said discharge tube,
cludes the coil 6, the self-induction of the coil 8
and a second inductance element connected in
decreases. To that end a premagnetisation may
series with said‘coil and said secondary wind
be brought about up to a 'value at which the
ing, said secondrinductance element having an
sweep of the saw-tooth current takes place in
inductance which decreases in value with in
that region of the magnetisation curve of the
creases in the current therethrough.
core material in which the self-induction varies
4. An electrical circuit arrangement for gener
linearly with the current intensity.
ating a saw-tooth sweep current in a coil, com
As the core material may be utilized, for ex
prising a discharge tube having a cathode, a con
ample, a sintered magnetic ferrite. Even at small
trol grid and an anode, means to apply a saw
values of themagnetisation‘current, the differ 15 tooth voltage to said-control grid, an inductance
entiali'of the magnetisationcurve of this material
element interposed between said anode and
has a substantially linear course. It has now
cathode, means to couple said coil to said in
‘been found to be possible to obtain the desired
ductance element, a diode-element shunting said
course by a suitable choice of the core material,
inductance element and being poled to be con
‘adapted to the self-induction variation desired. 20 ductive during the current ?ow through said
The choke coil it serves to prevent the im
inductance element :and through said discharge
pedance of the coil 3 from being'in?uenced by
tube, and a second inductance element connected
the premagnetisation circuit. Instead of the
in series with said coil, said second inductance
choke coil, use may alternatively-be made for this
element comprising a core'of a sintered magnetic
purpose of .a'discharge tube having a high internal
ferrite and a magnetizing winding on said core
resistance.
and having an inductance vwhich decreases in
It may be- observed that for the purpose of
value with increases in the‘current therethrough.
premagnetizing the core it is not necessary to
5. An electrical circuit arrangement for gener
provide on that core a special winding, but that
ating a saw-tooth sweep current in a coil, com
the direct-current circuit may include the wind
prising .a discharge tube having a cathode, a
ing of the 00118.
control grid and an anode, means to apply a
Itwill be evident that the correction coil 8 may
saw-tooth voltage to said control grid, an in
alternatively be included in the primary circuit
ductance element comprising a primary winding
of the transformer ‘2, for example, between the
interposed between :said anode and cathode and
primary winding 1 and the battery 7.
a secondary winding, means to couple said coil
What I claim is:
to said secondary *winding, a vdiode element
1, An electrical circuit arrangement for gener
shunting said primary winding and [being poled to
ating a saw-tooth sweep current in a coil, com
be conductive during the current flow through
prising a discharge tube having a cathode, a con
trol grid and an anode, means to apply a saw
tooth voltage to said control grid, an inductance
element interposed between said anode and cath
ode, means to couple said coil to said inductance
said primary winding'and through said discharge
40 tube, a second inductance element comprising a
core of ferromagnetic material, a'?rst winding
arranged on saidcore and connected in series
with said coil and said secondary winding, and a
element, a diode element shunting said induct- ,
second winding arranged on‘said core, and means
ance element. and being poled to be conductive \. to apply a direct current to said second winding
during the current now through said inductance
to premagnetize said coreand impart to said ?rst
element and through said discharge tube, and a
winding an inductance'which decreases in value
second inductance element connected in series
with increases in the current therethrough.
with said coil, said second inductance element
6. An electrical circuit arrangement for gener
having an inductance ‘which decreases ‘in value 50 ating a saw-tooth sweep current ina coil, com
with increases in the current therethrough.
prising a discharge tube having a cathode, a con
2. An electrical'circuit arrangement for gener
trol grid and an anode, means to apply a saw
ating a saw-tooth ‘sweep current'in a coil, com
tooth voltage :to said control grid, an inductance
prising a discharge tube having acathodaa con
element comprisinga primary winding havinga
trol grid and an‘anodaineans'to‘ apply ‘a saw
tooth voltage to said control grid, an inductance
element interposed between said anode and
cathode, means to "couple said coil to said in
tapping, and a-secondary winding, means to con
nect said tapping ‘to saidanode, means to couple
said coil to said secondary winding, a diode ele
ment‘shunting said primary winding and being
ductance'elem'enu'a diode element shunting said
poled to be conductive ‘during the current flow
inductance‘element and being vpoled to be con 60 through said primaryvwinding and through said
ductive during the current ?ow through said
discharge tube, and-a second inductance element
inductance element and through said discharge
comprising a core of ferromagnetic material, a,
tube, and a second inductance element connected
?rst winding arranged- on said core and con
in series with said coil, saidsecondlinduotance
nected in series with said coil and said secondary
‘element comprising a'corexof ferromagnetiomate 65 vwinding, and a second winding arranged on said
rial and a magnetizing winding on said-coreiand
core, a source of a direct current connected to
having an inductance which decreases .in value
said second winding to premagnetize said core
with increases in the current therethrough.
and impart to said ?rst winding an inductance
3. An electrical circuitarrangement for gener
which ‘decreases in value with increases .in the
ating a saw-tooth sweep current in a coil, com 70 current therethroughand a choke coil interposed
‘prising a dischargentube having a cathode, a
between saidsecond windingand said source.
control grid and an anode, means to apply a
FREDERIK KERKHOF.
saw-tooth voltage to ‘said control grid, an in
ductance element comprising a primary winding
vNo referencescited.
interposed between said‘anode and cathode and 75
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