US2480385A

US2480385A - Electronic switch

Info

Publication number: US2480385A
Application number: US583763A
Authority: US
Inventors: Paul B Sebring
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1945-03-20
Filing date: 1945-03-20
Publication date: 1949-08-30
Anticipated expiration: 1966-08-30

Description

Aug. 30, 1949. P. at SEBRING I ELECTRONIC SWIFTCH Filed March 20, 1945 $525 big Paul 5. 5

Patented Aug. 30, 1949 UNITED STATES PATENT OFFICE:

2,480,385 ELECTRONIC swrron Paul B. Sebring. Cambridge, Mass, assignor to the United States of America as represented by the Secretary of the Navy Application March 20, 1945, Serial No. 583,763 3 Claims. (Cl. 250-27) This invention relates to an electronic circuit closing device and has for its primary object the provision of a device of this character which operates to open and close a circuit between two points without directly affecting either of the points.

Another object of the invention is to provide an electronic switch which can be made as effective as a set of contacts in interrupting current from voltages of the order of 100 volts regardless of the polarity of the voltage, but which overcomes the disadvantages of a relay in that no moving parts, or parts subject to corrosion are employed.

Other objects and advantages of the invention will become apparent from the following specification taken in connection with the accompanying schematic diagram which shows one application of the present invention.

Referring to the schematic diagram, the switch of the present invention is shown applied to control the circuit between points A and B. In the application shown it is desired to close the circuit between these points for a definite time interval following the completion of a keying cycle in another device such as an underwater echo ranging system. Only the keying circuit of the echo ranging system is shown, since only this much is necessary for an understanding of the present invention. The keying circuit involves simply a generator in series with which are various relay coils and a key, manually or automatically operated.

The electronic switch of the present invention is connected into the keying system at point X and includes oscillator Ill of any suitable design and operating at any desired frequency sufiiciently removed from the operating frequency of the echo ranging system. For example, if the echo ranging system operates at 20 kilocycles, 100 kilocycles has been found satisfactory as the operating frequency for the oscillator I0.

The oscillator l includes a triode I I the grid of which is connected to point K through a capacitor l2 having a discharge path to ground through resistor l3. The time constant of the RC connecting circuit so formed determines the period of closure of the switch as will be hereinafter explained. I

The oscillator circuit shown is a conventional Hartley circuit, but it is obvious that oscillators of other types may be used. Such oscillators include the colpitts, the ultraudion, and other circuits which are well known to those skilled in the art.

A part of the tank circuit of oscillator I0 is constituted by a coil l5 which acts as the primary of two transformers the secondaries of which are coils H and IS. The secondaries are preferably wound on the same toroidal form as the primary IS. The output of each secondary coil is rectified and filtered and applied to the grid of a triode as a controlling bias. Rectification of the transformer output takes place in diodes 2| and 22 and the'associated filter circuits are designated generally 23 and 24, while the controlled triodes are numbered 25 and 26 in the schematic. The output of the oscillator is such that when the oscillator is operating, suficient voltage is induced in coils I! and I9 to completely block the

triodes

25 and 26 so that there is effectively an open circuit between points A and B.

The filter units 23 and 24 operate at the frequency Of the oscillatorlll, and may be quite small because of the high frequency. It is desirable that the shunt capacitors of these filters discharge quickly so as not to introduce an appreciable time delay. The shunt resistance should be made as low as possible without unduly reducing the output voltage of the filter.

It will be seen that the

triodes

25 and 26 are oppositely connected so that the polarity of the voltage presented to the switch is of no importance in the action of the switch, which will conduct in either direction when closed.

The triodes 2| and 22 may, of course, be replaced by other types of rectifiers such as the copper oxide rectifier or the germanium rectifier.

The operation of the device may be summarized by considering a, typical cycle of an associated echo ranging system in which a short pulse of sound is emitted, followed by a period in which it is desired to close a switch for a predetermined interval. A relay could be used with a proper time delay but such apparatus has numerous objections which are unimportant here. It is desired that all connections remain undisturbed and also that the switch be completely free of ground so that the grid of each

triode

25 and 26 must be biased oif with respect to its own cathode whenever the switch is to be opened. In the present invention the isolation from ground is accomplished by using the voltage from secondaries l1 and I9 as bias voltages as above stated. Having made closure of the switch dependent solely on the conducting condition of

triodes

25 and 26 and hence the voltage in secondaries I! and I9, it remains only to control the oscillator I0 in order to control the switch.

, If the oscillator is operating, a voltage is induced in each of the secondaries i1 and I9 and the switch, as above stated, is open, while if, for any reason, the oscillator should be cut off or its action stopped, the bias Voltage on the grids of

triodes

25 and 26 will disappear. The tubes then conduct and the switch would be in its closed state permitting current flow between points A and B.

In the application of the invention shown in'the schematic diagram the oscillator is controlled by the keying circuit in the following manner. If it is considered that the key has been open for some time and the oscillator is oscillating, capacitor it will have a potential across its terminal which is equal to the difference in voltage between the negative supply to the keying circuit, which is shown as the generator'Gen and thecoil marked Relay coil, and the negative voltage built up across resistor 13 due to the grid current of the oscillator. If the key is suddenly closed, point X in the keying circuit instantly assumes ground potential and, since the voltage across capacitor 42 cannot change instantaneously, positive' voltage is fed to the grid oi" the oscillator triode H which merely serves to increase temporarily the grid current of the oscillator but does not stop the oscillation of the circuit, The increased grid current serves also to quickly discharge capacitor !2 so that the potential across this capacitor becomes only that due to grid current of triode l! through resistor I3. If the key is suddenly opened, point X becomes immediately negative to ground by the voltage of the generator. Since again the potential across capacitor !2 cannot change instantly but must build up due to current flow through resistor l3, a high negative voltage, sufiicient to out 0113 the tube, is applied for some time to the grid of triode ii in the oscillator circuit thus blocking the oscillator for a period depending on the time cons nt of the charging circuit of capacitor 12. This time constant, can of course, be set at any desired value so that the on-off period of the oscillator is subject to selection. It will also be noted that the controlling circuit for the oscillator may take any desired form without altering the fact that the real switching between points A and B is accomplished as separately and efliectivcly as could be done by a relay without thedisadvantages attending this type of equipment and without altering in any way the connections between these points.

It is obvious to those skilled in the art that the generator Gen may be replaced by abattery or other suitable source of voltage. It is also obvious that in this application the coil relay coil acts only as a current limiting resistance and may be replaced by resistance of suitable value. The point r is provided as shown with a by-pass condenser of small capacity to keep high frequency current from the oscillator out of the power source and other circuits where it would interfere with proper operation of such circuits.

In the application of the invention to echoranging apparatus it is ordinarily desirable to arrange the switch so that it is either on or off."

second electronic tube having an anode, a cath- 'ode';"and a control grid, means connecting the cathode of said first tube and the anode of secnd tubeto one of said terminals, and means connecting the anode of said first tube and the cathode of said second tube to the other of said terminals; a normally operative electronic oscillator comprising an inductance paralleled by capacitance; a pair of output coils inductively related to said inductanceto each receive therefrom an 'alternatingcurrent voltage of a magnitude exceeding the cutoff bias of the said electronic tubes, a unidirectional conducting device connected with each of said output coils. individualized filter me'ansconnected to said unidirectional conducting device to produce a direct current voltage at the output of each'of said individualized filter means; means for-applying one of said direct current voltages between the grid and the oathode of' said'first electronic tube and means for applying the other of said direct current voltages between thelgrid and the cathode of said other electronic tube, whereby said first and second electronic tubes are rendered non-conducting when said oscillator is operative; and means to render said electronic oscillator non-oscillatory for a predetermined period following the actuation ofsaid means.

2, An electronic switch having a pair of terminals comprising; a first electronic tube having an anode, a cathode, and a control grid, a second electronic tube havin an anode, a cathode, and a control grid, means'connecting the anode of said first electronic tube and the cathode of said second"electronic tube to one'of said terminals, and means connecting the cathode of said first electronic-tube and the anode of said second electronicitube to the other of said terminals; a normallyoperative electronic oscillator comprising a third electronic tube having an anode, a cathode and a grid-and an'inductance paralleled by capacitance electrically associated with said third electronic tube to produce sustained oscillation; a pair of output coils inductively related to said inductance toeach receive therefrom an alternatingcurrent voltage of a magnitude exceeding the cut-'ofi bias'of said electronic tubes, an individualized unidirectional conductin device connected with each-of, said output coils to rectify said alterhating current induced in said coils, individualized filter means connected with said rectifying means to produce a direct current voltage at the output of each filter; means connecting one of said individualized filter means to said first electronic tube to apply said direct current voltage betweeniithegridand the cathode of said first electronictube and means to connect the other of. said individualized'filter means to said second electronic tube to apply said direct voltage between the-grid and the cathode of 'saidsecond electronic tube, whereby said electronic tubes are rendered non-conducting when said oscillator is operative; a'source of direct current voltage, a capacitor-resistance circuit connected to the: grid of said third electronic tube, means for applying a negative bias from said source of direct current through said capacitor-resistor circuit to the grid of said tube to render said oscillator inoperative, said negative bias being applied for a time inter val determined by the charging rate of said capacitor-resistor combination.

3. An electronic switch havin a pair of ter minals, comprising; a first electronic tube having an anode, a cathode, and a control grid, a second electronic tube having an anode, a cathode, and a control grid, means connecting the anode of said first electronic tube and the cathode of said second electronic tube to one of said terminals, and means connecting the cathode of said first electronic tube and the anode of said second electronic tube to the other of said terminals; a normally operative electronic oscillator comprising a third electronic tube having an anode, a cathode, and a grid, and an inductance paralleled by capacitance electrically associated with said third electronic tube to produce sustained oscillation; a pair of output coils inductively related to said inductance to each receive therefrom an alternating current voltage of a magnitude exceeding the cutoff bias of said electronic tubes, an individualized unidirectional conducting device connected with each of said output coils to rectify said alternating current induced in said coils, individualized filter means connected with said rectifying means to produce a direct current voltage at the output of each filter; means connecting one of said in dividualized filter means to said first electronic tube to apply said direct current voltage between 6 the grid and the cathode of said first electronic tube and means to connect the other of said individualized filter means to said second electronic tube to apply said direct voltage between the grid and the cathode of said second electronic tube, whereby said electronic tubes are rendered nonconducting when said oscillator is operative; a tapped grid resistor connected to the grid of said third electronic tube, a source of direct current voltage, a capacitor connected between the tap on said grid resistor and the negative side of said source of direct current voltage whereby said capacitor is normally charged, and means for discharging said capacitor, whereby said negative potential of said source of direct current is applied to the grid of said third electronic tube thus rendering said electronic oscillator non-oscillatory during the chargin time of said capacitor.

PAUL B. SEBRING.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS