US3047820A

US3047820A - Saw-tooth voltage generator utilizing integrator

Info

Publication number: US3047820A
Application number: US10003A
Authority: US
Inventors: John G Lawton
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-02-19
Filing date: 1960-02-19
Publication date: 1962-07-31
Anticipated expiration: 1979-07-31

Description

J. G. LAWTON July 31, 1962 SAW-TOOTH VOLTAGE GENERATOR UTILIZING INTEGRATOR 2 Sheets-Sheet 1 Filed Feb. 19, 1960 mmmm k AQY Re/ay fenin e/e m r) INVENTOR. John G. Lawton Ji @ziw 9 a. a. Q bmvf 3,047,820 Patented July 31, 1962 3,047,820 SAW-TOOTH VOLTAGE GENERATOR UTILIZING INTEGRATOR John G. Lawton, Snyder, N.Y., assignor to the United States of America as represented by the Secretary of the Army Filed Feb. 19, 1960, Ser. No. 10,003 Claims. (Cl. 331143) This invention relates to voltage generators and in particular to an arrangement of components whereby a voltage as a function of time may be fed into an integrator and an integrated voltage output result.

It is a chief object of this invention to provide a sawtooth voltage generator such that the mean level of the output voltage will be subject to adjustment.

It is a further object of this invention to obtain from an electronic system having a minimum number of electronic tubes an output voltage that is an integral function of time, said output voltage being obtained from an input voltage that is a function of time.

Other objects of the invention will become apparent as the description thereof proceeds.

Accordingly, the instant invention will now be described with reference to the accompanying drawings in which:

FIGURE 1 illustrates the wave form of the voltage output;

FIGURE 2 is a block diagram of the device;

FIGURE 3 is a circuit diagram of a practical system; and

FIGURE 4 illustrates the current voltage curve characteristics of back to back connected silicon junction diodes of the type used in the invention.

Referring to FIGURE 1, it is seen that the average out-put voltage to be developed is designated as Eav and that voltage increases in a linear manner as a function of time until a value (Eav-I-Ae) is reached. The slope of the wave form then becomes negative with the voltage decreasing in a linear manner as a function of time until a value Eav-Ae is reached. This cycle is then repeated. The average value of the voltage output Eav can be adjusted and means are herein disclosed for varying the average output voltage as desired.

The system used to generate the output waveform depicted in FIGURE 1 is illustrated in the block diagram of FIGURE 2. A reference voltage e is fed from a potentiometer P into a sensing element S. The sensing element S comprises a 50,000 ohm resistor in series with back to back connected silicon junction diodes. The function of the 50,000 ohm resistor is to serve as a protective device when the equipment is first turned on. The sensing element governs the operation of a relay Ry by energizing an armature in the relay which has two stable positions. The two stable positions of the relay provide for electrical connection to either of two input voltage terminals in the relay e+ and e. The voltage output from the relay is consequently constant at one of two steady voltage levels corresponding to the two positions of the relay, e-lor eas shown in FIGURE 2. The relay output is fed into the integrator I, and more specifically to the grid of a pentode therein, as can be seen in the circuit diagram, FIGURE 3.

The desired sawtooth voltage waveform is obtained at the output of the integrator, designated I. The integrator is so designated that it is characterized by the transfer function: e =kfe,dt, wherein e, represents the input voltage, e represents output voltage, and k represents the integrator gain constant. It is readily apparent from the transfer function that so long as the voltage input from the relay e remains constant, the output voltage e will vary linearly with time. The input voltage is kept continually at one constant value or the other constant value by the sensing element and relay, so that input to the integrator e, is either 2+ or e, as designated in FIG- URE 2. Thus the output of the integrator I, being characterized by the aforesaid equation, is always either linearly increasing or decreasing. The slope of the output voltage, either the positive or negative, is dependent on the integrator gain constant, k, and the magnitude of e+ or e-.

The input voltage to the integrator is kept constant by the side stable relay, R, as seen in FIGURE 2. The operation of the side stable relay is as follows: Positive pulses of coil current move the armature to one contact where it will remain until the advent of a negative pulse, which will return the armature to the other stable position.

The sensing element S monitors the difference between the output voltage of the integrator and the reference voltage e supplied by a potentiometer P. The sensing element exhibits two characteristic voltage thresholds. When either of these is exceeded, the sensing element causes the relay to reverse so that the sign of the slope of the voltage output of the integrator is reversed. The result is that the slope of the output voltage Waveform of the integrator will change and drive toward the other threshold. Since one terminal of the sensing element S is connected to the potentiometer slider at a voltage lever e it is clear that the output voltage of the integrator is limited to the region e +e and e +e where e and e; are the upper and lower thresholds of the sensing element. See FIGURE 4. Further it is clear that any adjustment of the potentiometer results in a change of the average value of the output waveform. If the characteristics of the sensing element are symmetrical, i.e., if e =e =Ae, then the average voltage, e at the slider of the potentiometer will be equal to the average of the output waveform. FIGURE 4 illustrates the voltage current characteristics of the silicon junction diodes used in the sensing element.

FIGURE 3 is a circuit diagram illustrating a practical embodiment and use of the system. The ideal integrator of the block diagram, FIGURE 2, has been approximated by the electronic circuit consisting of three vacuum tubes and associated components. The selection of components and tubes will determine the gain constant, k, of the integrator. \It is seen that because of the relative arrangernent of the relay and sensing element no current can flow through the relay coils until the difference between the output voltage of the integrator, I, and the voltage e at the slider of the potentiometer P reaches the reverse breakdown or Zener voltage of the appropriate diode. Thereafter, any increase in voltage results in an extremely rapid increase in current causing the relay R to be switched to its other stable position and thus reverse the slope of the output voltage. As pointed out in the foregoing, if two diodes of similar characteristics are chosen for use in the sensing element, the reference voltage 2, will equal the average output voltage e It is clear that by moving the slider of the potentiometer, the average output voltage may be adjusted.

While various modifications of the disclosure may be resorted to and will be apparent to those skilled in the art, and while the instant invention has been described herein in a most practical embodiment, it will be understood that the invention is not to be limited to the preferred form described herein, except as limited by the scope of appended claims.

What is claimed is:

1. A voltage generator having an adjustable mean level output voltage comprising, in combination, a potentiometer having a slidable resistance arm, a coil electrically connected in series with said resistance arm; a relay having voltage input terminals and a reversible quickacting switch actuated by an armature; said armature being disposed so that it is under the influence of currents in said coil; a sensing element in series with said coil comprising back to back connected silicon diodes, said sensing element controlling the current in said coil and thereby controlling the position of the switch in said relay; and an integrator in series with the output current of said relay and said sensing element and having electrical components therein such that the voltage output will remain linear so long as the voltage input to the integrator is at a constant value.

2. A voltage generator as in claim 1 wherein the back to back connected silicon diodes have symmetrical characteristics.

3. A sawtooth voltage generator as in claim 1 wherein a large resistance is in series in the conductor connecting said coil to said diodes thereby acting as a protective device when the equipment is first turned on.

4. A voltage generator having an adjustable mean level output voltage comprising, in combination, a potentiometer having an adjustable resistance means; a coil connected by a conductor in series with said adjustable resistance means; a relay having two voltage input terminals and a reversible quick-acting switch actuated by an armature; said armature being disposed to that it is under the influence of current in said coil; a sensing element in series with said coil comprising back to back connected diodes having Zener voltage characteristics, said sensing element monitoring differences in voltage between the voltage output of the potentiometer and a second voltage, said sensing element controlling the current in said coil and thereby controlling the switch in said relay; and an integrator in series with the sensing element, a pentode in said integrator, and the output voltage of said relay biasing said pentode in said integrator.

5. A sawtooth voltage generator as in claim 4 wherein said integrator has electrical components therein such that the voltage output will remain linear so long as the voltage input to the integrator is at a constant value.

References Cited in the file of this patent UNITED STATES PATENTS 2,561,719 White Sept. 8, 1953 2,734,135 Wagner Feb. 7, 1956 2,887,592 Stout et al. May 19, 1959 FOREIGN PATENTS 580,047 Canada July 21, 1959 OTHER REFERENCES Keonig: Electrical Communication, vol. 36, November 2, 1960, pages 132-138.