US2709757A - Eerroresonant flip-flops - Google Patents

Description

May 31, 1955 w. E. TRIEST FERRORESONANT FLIP-FLOPS 2 Sheets-Sheet 1 Filed Aug. 25, 1953 FIG! CURRENT -L|NEAR EMPEDANCE TRIGGER FIG. 3

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-/-v5/vr0, By WILLIAM E. TR/EST JOHN ALDEN HALL A TTO/QNEV y 31, 1955 w. E. TRIEST 2,709,757

FERRORESONANT FLIP-FLOPS Filed Aug. 25, 1953 2 Sheets-Sheet 2 1 M i l h F/G,4 EB n fl A A A A A A A 3 70m 50 KC.

SOURCE OF TRIGGER PU LSES INVENTOR By WILL MM 5 TR/ES T J'OHN ALDEN HALL ATTOENE 3 United States Patent O FERRORESONANT FLIP-.FLOPS Wiliiam E. Triest, Hyde Park, N. Y., assignor to International B s e achi es orporat on, New k, N. Y., a corporation of New York Application August 25, 1953, Serial No. 376,490

7 m (CL 0 -8 This invention relates to electronic switching means and particularly to means for selecting and enabling paths for the transmission of electrical pulses.

In the art of electronic control where exceptionally high speed operations are essential, information is transmitted by pulses and where different steady state current conditions are to be established this is accomplished by triggering electronic tubes into operation. Static devices are employed since any mechanical movements as the operation of switches, manual or power driven or the operation of relays are not within the speed requirements for such electronic switching.

The object of the present invention is the provision of a flip-flop device having a sufiicient speed of operation for use in an electronic switching system. The term flip-flop is commonly used in the electronic art to desigs nate a device which on alternate operations will successively condition or enable two outgoing paths. For prior art descriptions of such devices reference is made to Electronics, April 1952, page 121, and, in the computer art to the Williams Patent 2,502,360, column 6, lines 50 et seq.

In accordance with the present invention a peculiar phenomenon observed in electrical circuits carrying alternating current and including therein iron core coils is employed. This is spoken of as the jumping phenomena in ferroresonance, for an application of which, reference is made to the prior art disclosures in the Stacy and Krom Patent 1,725,022, August 20, 1929. In the observation of these circuits it has been noted that as the voltage applied to the circuit is steadily increased so does the current steadily increase until a point is reached where the current suddenly leaves its steady advance and jumps to a much greater value. Also, when from this greater value the voltage is then steadily decreased so does the current steadily decrease until a point is reached where F the current suddenly jumps to a much lower value.

The object of the present invention is to improve the operation of devices depending on the principle of this phenomenon by providing circuit means to exaggerate the effect so as to provide a great margin in the commer-. cial tolerances of the electrical components going into the construction of such devices.

A feature of the invention is the use of a circuit having a pair of parallel circuits each including a ferroresonant element, constructed and arranged to be mutually controlling whereby a circuit disturbance will cause the current flow in both of said parallel circuits to jump, one in one direction and one in the other, and whereby the change in current value in each of said circuits will fortify the change in the other.

The extent to which the current change in one circuit fortifies the change in the other is a measure of the speed of operation of the circuit. Where a plurality of these flip-flops are interconnected to provide a frequency divider, the speed of operation of each is a cont-rolling factor in the limits of frequency values that may be applied. Operations within kilocycle ranges are possible of ferroresonance.

2,709,757 Patented May 31, 1955 with prior art devices and it would be useful if the same operations could be extended into the megacycle ranges but this requires smaller and smaller impedance values in the circuit components so that regenerative or fortifying means have to be employed.

A feature of the invention is the use of selected magnetic material in the ferroresonant components of the circuits which have certain magnetic characteristics tending to increase the rapidity of magnetic changes. Certain magnetic materials are known which have what may be described graphically as a substantially square hysteresis loop or one in which the change from magnetic energigation in one direction to corresponding energization in the other is practically instantaneous. The rapidity of this change is a factor in the value of the potential induced in a coil wound about such magnetic material and therefore is a controlling factor in the tolerances that may be allowed in the practical construction of the device.

Another feature of the invention is the use of cross coupling means in the said two parallel ferroresonant circuits. Thus when a circuit disturbance is effected as by a triggering pulse in an associated magnetic element coil, the current in one branch will increase and the current in the other branch will decrease. If the coils carrying these branch currents are cross coupled, then the total current or total magnetomotive force generated in one magnetic element will be increased by the natural increase in cur rent in its principal winding and also increased by the natural decrease in current in the other circuit by a cross coupling coil on the said magnetic element. By the same token the magnetomotive force generated in the other magnetic element will be decreased by the natural decrease in current in its principal winding and also decreased by the natural inrease in current in the other circuit by a cross coupling coil on the said magnetic element. This is analogous to a regenerative effect since the efiect operates to fortify itself whereby the speed of operation is greatly increased.

Other features will appear hereinafter.

The drawings consist of two sheets having six figures, as follows:

Fig. 1 is a graph showing the relation between voltage and current in an alternating current ferroresonant circuit;

Fig. 2 is a schematic circuit diagram of a conventional ferroresonant flip-flop device used for purposes of explanation;

Fig. 3 is an idealized graph used in the description of the circuit of Fig. 2;

Fig. 4 is a representation of wave forms in different branches of the circuit of Fig. 2;

Fig. 5 is a schematic circuit diagram of the arrangement of the elements of the present invention, showing particularly the cross coupling coils employed in the manner about to be explained; and

Fig. 6 is a schematic circuit diagram showing how several ferroresonant flip-flop circuits may be connected in cascade as in a frequency divider.

Ferroresonance is a phenomenon which has been observed in alternating current circuits having resistance, capacity and inductance characterized by non-linearity of inductance values generally produced by a coil inter-. linked with a magnetic circuit. Fig. 1 shows the relation between voltage and current in such a circuit and indicates what has been termed the jumping phenomenon This figure indicates that as the voltage increases, the current likewise increases to a point a where the current suddenly increases to the value at point I). Thereafter the current increases as the voltage increases toward the direction of point e. If, while the circuit is in the stable condition indicated by the curve from the point a through b toward 0, the voltage, or the current is decreased the point (I will be reached Where suddenly the current value will be reduced to the value at e. Such a circuit therefore shows a rising value e a b c and a falling value c b d e 0 and has two stable states 0 e and b c under any and all conditions, and stable states 0 e a and b c under rising values and c b d and e 0 under diminishing values.

The jumping phenomenon of ferroresonance has been employed in circuit operators known as ferroresonant flip-flops.

A flip-flop is a bistable circuit device which may be employed as a scale of two means, that is by a first pulse it may be driven from one stable state to another and by a succeeding pulse it may be driven back to the first stable state. It is a device finding use, by way of example, in the circuitry of chain and ring counters and in frequency dividers. Very high speed flip-flops are essential in the circuitry of electronic computers.

Fig. 2 illustrates the principle of operation of a ferroresonant flip-flop. The voltage E is any alternating current source including a high frequency source such as one generating radio frequency power. The load consists of a common impedance 1 connected in series with two circuits 2 and 3 connected in parallel relation with each other and each containing a saturable core inductor, 4 and 5 respectively, and a capacity element, 6 and 7 respectively. Each saturable core inductor is provided with an additional coil, 8 and 9 respectively, by means of which the circuits may be triggered. Each of these two branch circuits is capable of exhibiting ferroresonance as shown in Fig. 3. If voltage E and common impedance 1 are properly chosen, E1 will be at a value Ex and one of the LC branches will be at state (2) with high current and consequent high capacitor voltage, While the other branch will be in state (1) with low current and low capacitor voltage. The high current in one resonant branch causes a voltage drop across the Z impedance 1 which reduces the voltage across the L-C branches to Ex- Only one branch can be in ferroresonance, since ferroresonance in both would produce an excessive drop in Z1 and the voltage across L-C would be below the critical voltage E01.

Assume initially that branch 2 is in state (1) and branch 3 is in state (2). Next assume a pulse signal to be transmitted over trigger A through coil 8. The inductance LA of coil 4 will decrease, and this branch will tend toward the ferroresonant condition. The increased voltage drop cross the Z impedance 1, due to higher current in branch 2, will reduce E1 below E01 and branch 3 will drop from state (2) to state (1). Simultaneously, branch 2 will be driven further into ferroresonance and will go to state (2). Branch 2 will then remain in state (2) and branch 3 will remain in state (1) until a signal appears at the trigger B terminal.

Any conventional means, such as a crystal diode and a simple filter circuit, may be used to obtain direct current levels from the EA tap 10 and the EB tap 11.

By way of example, a circuit in the form of Fig. 3 might have Z in the form of a resistor of 100 ohms, CAXCB each of .005 mfd. and coils 4 and 5 each 180 turns of wire on a core 1D constructed of 5 convolutions of .0007 inch tape wide of a magnetic material of high retentivity and displaying a particularly square hysteresis loop. The power source E may be 100 kc. If the power source is applied, starting at E=0, it may be increased until one of the branches becomes ferroresonant and then advanced just beyond this voltage when the circuit becomes stable. Trigger pulses of about 7 microseconds will flip the state of the circuit and if the two coils 8 and 9 are connected to a single trigger conductor successive trigger pulses applied thereto would successively change the state of the two coils in the fashion of a scale of two device.

' Fig. 4 is a representation of the voltage EA and EB wave forms as the circuit is triggered as indicated by the succession of trigger pulses. These pulses have been shown partly as following one another with regularity and partly in an irregular manner. In some circuits such as a frequency divider, the trigger pulses would follow one another with the greatest regularity, whereas in other circuits, as in a computer, they might be irregularly spaced.

Applicant has found that greatly improved operation may be achieved by making the ratio of EH1 to ELo as great as possible and he has achieved this desirable goal by adding another coil to each saturable core and connecting it to the other circuit as shown in Fig. 5 to provide a degree of cross coupling. By making the coils 12 and 13 of 75 turns each and using in the circuit described the ratio Ear/Era is multiplied by three. In addition, the series R3 resistor may be increased.

It has been determined that the current in the branch in state (1) is a lagging current, characteristic of an inductive load, whereas the current in the branch in state (2) is a leading current characteristic of a capacitive load.

The cross-coupling arrangement of the present device shown in Fig. 5 makes use of the fact that the currents in branches 2 and 3 are of opposite phase. A leading current flows in the ferroresonant branch while a lagging current flows in the other branch as above explained. By Way of example, if branch 2 is ferroresonant, then the high leading current in the L E coil 13 will produce flux in core 15 to induce a voltage in the LB coil 16 that will oppose the lagging current therein. This results in a decrease in the current in branch 3 and an increase in current in branch 2, thus emphasizing the tendencies of the two circuits and widening the gap between the values of the voltage drop across the condensers CA and CB.

Thus conventional ferroresonant flip-flop circuits may be improved in their operation by employing cross coupled coils on the saturable cores.

Fig. 6 is a schematic circuit diagram showing how two circuits of the type of Fig. 5 may be connected in cascade to form a frequency divider. The source of alternating current 17 is shown, merely by way of example, as one having a frequency of 700 kc., while the source of triggering pulses 18 is shown also, merely by way of example. as one having a periodicity of 50 kc. One output lead 19, leads to a second circuit. The periodicity of the output would be one half the input, or 25 kc. An artificial line or balancing network will be connected to the other output 20 and this too would show an output of kc.

The output 21 of the second circuit is indicated as leading to a third circuit where it may be used for further dividing the frequency or for any other purpose.

What is claimed is:

1. An alternating current circuit element having a linear impedance in series with a circuit network comprising two like parallel branches, each said branch including a non-linear impedance element and each said branch having means to control the said non-linear impedance element of the other said branch.

2. An alternating current circuit element having a linear impedance in series with a circuit network com prising two'like parallel branches, each said branch including linear and a non-linear impedance elements and each said branch having means to control the said nonlinear impedance element of the other said branch.

3. An alternating current circuit element having a resistance element in series with a circuit network comprising two like parallel branches, each said branch including a capacitive element in series with an iron cored coil and each said branch also having in series a coil coupled with said iron cored coil of said other branch.

4. An alternating current circuit element having a resistance element in series with a circuit network comprising two like parallel branches, each said branch including a capacitive element in series with a coil magnetically interlinked with an element having magnetic properties characterized by a substantially rectangular hysteresis curve and each said branch having in series another coil magnetically interlinked with the said first coil of said other branch.

5. An alternating current circuit element having a linear impedance in series with a circuit network comprising two like parallel branches each including a linear and a non-linear impedance element and each said branch having means to control said non-linear impedance element of said other branch, and a separate circuit for controlling said non-linear elements concurrently.

6. An alternating current circuit element having a linear impedance element in series with a circuit network comprising two like parallel branches each including a linear and a non-linear impedance element and each said branch having means to control the said non-linear impedance element of the other said branches, said elements being so proportioned that a leading alternating current will flow in one of said branches and a lagging alternating current will flow in the other of said branches, and means for disturbing the said current flow conditions in said two branches whereby the said conditions will become reversed.

7. An alternating current circuit element having a linear impedance element in series with a circuit network comprising two like parallel ferroresonant circuits, whereby unlike currents will flow through said circuits, each having means for controlling the other and means for transmitting pulses simultaneously into each said ferroresonant circuits whereby said unlike current conditions become interchanged responsive to each said pulse.

References Cited in the file of this patent UNITED STATES PATENTS 2,653,254 Spitzer et al Sept. 22, 1953

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