US3039043A

US3039043A - Variable a.c. transducer

Info

Publication number: US3039043A
Application number: US811237A
Authority: US
Inventors: Raymond A Macmillan
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-05-05
Filing date: 1959-05-05
Publication date: 1962-06-12
Anticipated expiration: 1979-06-12

Description

R. A. M MILLAN VARIABLE TRANSDUCER June 12, 1962 3,039,043

Filed May 5, 1959 IN VEN TOR.

264mm AMAWLM United States Patent 3,039,043 VAREABJLE A.C. TRANSDUCER Raymond A. MacMillan, Greenwood, Mass., assignor to the United States of America as represented by the Secretary of the Air Force Filed May 5, 1959, Ser. No. 811,237

4 Claims. (Cl. 323-66) (Granted under Title 35, [1.5. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the United States Government for governmental purposes without payment to me of any royalty thereon.

This invention relates to a circuit for controlling large alternating current signals, and more particularly a circuit wherein a direct current potential is utilized to control aforesaid alternating current signals.

In accordance with the present invention, a novel circuit is provided that varies the apparent A.C. resistance of aforesaid current from a few ohms to several megohms. The apparent A.C. resistance is automatically controlled by a direct current potential. In addition to the foregoing features, an AC. signal may be modulated by applying a proper D.C. modulating potential in place of the D.C. control potential.

An object of the present invention is to provide a novel circuit responsive to a D.C. potential for controlling alternating signals.

Yet another object of the present invention is to provide a novel circuit wherein a smooth control of an alternating current signal is obtained in response to a direct current potential.

Still another object of the present invention is to provide a novel circuit wherein an apparent'alternating current resistance is controlled in response to a direct current potential.

A further object of the present invention is to provide a unique circuit wherein an alternating current signal is modulated by a varying direct current potential.

Further objects, features and advantages of this invention will suggest themselves to those skilled in the art and will become apparent from the following description of the invention taken in connection with the accompanying drawing.

In the single figure of the drawing, there is shown transformer 1 having a single ended primary Winding and a center tapped secondary winding. The primary winding is adapted to receive an alteranting current signal at terminals 2. The center tapped secondary Winding has terminals 3, '4, and 5. Full wave dry rectifier bridge 6 is supplied at point 8 with an alternating signal from terminal 3 by way of adjustable resistor 7 and at terminal 9 directly from terminal 5. The alternating current signal at terminal 8 is 180 out of phase with that at point 9. Positive terminal 10 of rectifier bridge 6 is connected to anode 13 of electron discharge device 12. Negative terminal 11 of rectifier bridge 6 is connected to cathode 14 of electron discharge device 12. Control grid 15 of electron discharge device 12 is returned to cathode 14 by way of resistor 16.

An alternating current flows from center tapped terminal 4 of transformer 1 through external load 21 by way of output terminal 19 and then to output terminal 2%. Load 21 may be any external circuit or device being supplied an alternating current signal being controlled by a D.C. potential. From output terminal 20, the alternating current flows through rectifier bridge 6 by way of terminal 8 and terminal 9 and thence to terminal of transformer 1.

The magnitude of the aforementioned alternating current is primarily determined by the unbiased resistance 3,039,043 Patented June 12, 1962 "ice of electron discharge device 12. In the normal operation of electron discharge devices complete cutoff is not obtained and a small residual current would flow. Under this condition, a current of opposite phase is applied to rectifier bridge 6 from terminal 3 of transformer 1 by way of adjustable resistor 7. By adjusting the value of resistor 7, current in external load 21 can be made zero for approximate cut-off of electron discharge dew'ce 12. With the aforesaid approximate cut-off existing in electron discharge device 12, currents of a small magnitude continue to flow so that the aforesaid adjusting of the value of resistor 7 permits the voltage drop thereacross to be equal to the voltage drop across terminals 8 and 9 of rectifier bridge 6 and hence there can be no current flow in .load 21. The negative potential necessary to control electron discharge device 12 may be applied to terminals 17 and 18, obviously any value between full conduction and approximate cut-off can be obtained by varying the D.C. control potential applied to terminals 17 and 18. The magnitude of the alternating current flow is then determined precisely and in direct proportion to the magnitude of the D.C. potential applied to electron discharge device 12 by way of terminals 17 and 18. Thus, there is provided a precise control of relatively large alternating current and/or power by means of a novel circuit responsive to D.C. potentials.

The phase of the alternating current signal at

terminals

19 and 20 may be 0 or 180 and is uniquely determined by the polarity of the D.C. control potential applied to electron discharge device 1 2 by way of terminals 17 and 18, hence the circuit of the present invention also provides a novel phase transducer.

There is also shown an output circuit having frequency selective characteristics. The frequency selective circuit is comprised of transformer 22, with its primary tuned to parallel resonance by capacitor 23. The secondary of transformer 22 feeds a series resonant circuit consisting of inductor 24 and capacitor 25. The preselected frequency is then available at output terminals 26 and 27.

The novel circuit of the present invention produces 1.5 volts R.M.S. for 0.1 volt D.C. input. Power was volts 60 cps. other variations were also utilized, in one instance a 50 watt variation in power was controlled by a D.C. potential. Another application for the present invention resides in a compact and economical unit to use in place of large amplifiers to control large power at line frequencies.

What is claimed is:

1. Apparatus to control alternating current signals comprising a transformer adapted to receive said alternating current signals, said transformer having a center tapped secondary with two outer legs, a full wave bridge rectifier having a pair of alternating current input terminals, and a pair of direct current terminals, an outer leg of said secondary winding being connected to one of said pair of alternating current input terminals by way of an adjustable resistor, the other outer leg being connected to the other of said pair of alternating current input terminals, an electron discharge device having an anode, cathode and control grid, said pair of direct current terminals of said rectifier being connected across said anode and said cathode of said electron discharge device, means to control the rate of conduction of said electron discharge device, and a pair of output terminals for said controlled alternating current signal, one of said output terminals being the center tap of said secondary winding and the other being .one of said terminals said alternating current input terminals.

2. Apparatus to control the rate of flow of alternating current signals comprising a transformer receiving said alternating current signals, said transformer having a center tapped secondary winding, a full wave rectifying bridge having two alternating current input terminals said two terminals being connected across said secondary winding by way of alternating current signal adjusting means, means connected in the direct current path of said full wave bridge rectifier to control the current flow therein, said current flow control means receiving a direct current control potential, and an output circuit for said alternating current signals, said output circuit including said center tap of said secondary winding and one of said two alternating current signal input terminals.

3. Apparatus to control the rate of flow of alternating current signals comprising a transformer adapted to receive said alternating current signals, said transformer having a center tapped secondary winding, a full wave bridge rectifier having two alternating current input terminals, said tWo terminals being connected across said secondary winding by way of alternating current signal adjusting means, an electron discharge device connected in the direct current path of said full wave bridge rectifier, means to apply a direct current potential to said electron discharge device to control the rate of conduction thereof, and an output circuit for said alternating current signals, said output circuit including said center tap of said secondary winding and one of said two alternating current signal input terminals.

4. Apparatus for controlling alternating current signals comprising a transformer adapted to receive said alternating current signals, said transformer having a center tapped secondary winding, a full wave bridge rectifier having tWo alternating current signal input terminals and a pair of direct current output terminals, said secondary winding being connected across said pair of input terminals by way of alternating current signal adjusting means, an electron discharge device having an anode, cathode and control grid, said pair of direct current output terminals being connected across said anode and cathode of said electron discharge device, means to apply a direct current potential to said control grid of said electron discharge device to control the rate of conduction thereof, a pair output terminals for said controlled alternating current signal, said output terminals being said center tap of said secondary winding and one of said two input terminals.

Trucksess -a Nov. 6, 1951 Shrider et al. Oct. 24, 1957