US1947218A

US1947218A - Electrical filter system

Info

Publication number: US1947218A
Application number: US360042A
Authority: US
Inventors: Benjamin F Miessner
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1929-05-03
Filing date: 1929-05-03
Publication date: 1934-02-13
Anticipated expiration: 1951-02-13

Description

Feb. 13, 1934. B. F. MIESSNER ELECTRICAL FILTER SYSTEM Filed May 3, 1929 351 Gum/nu 60 grid of tube 8 Patented Feb. 13, 1%34 more STATE 1,947,218 ELECTRICAL FILTER SYSTEM Benjamin F. Miessner, S

y of America, Delaware hort Hills, N. J assignor, mesne assignments, to Radio Corporation New York, N. Y., a corporation of Application May 3, 1929. Serial No. 360,042

17 Claims.

My present invention relates generally to electrical filter systems, and more particularly to a system for filtering or smoothing out the fiuctuations or ripples in a fiuctuating source of uni- 5 directional electrical current supply before delivery to a work circuit or load requiring substantially steady energizing.

One object of my invention is the energizing of the output and input electrodes of three elec trode vacuum tubes in amplifying systems with rectified alternating current from the usual co1nmercially available alternating current sources with little or no resulting hum.

A feature of my invention is the employment 'of the characteristics of a three electrode vacuum tube or its equivalent as an aid in the filter oper ation either independently or in conjunction with its functioning in another usual manner.

The novel features which I believe to be characteristic of my invention are set forth in particularity in the appended claims, the invention itself, however, as to both its organization and method of operation will best be understood by reference to the following description taken in connection with the drawing in which I have indicated diagrammatically several circuit organizations whereby my invention may be carried into effect.

The features of my invention will be well under siood by reference to the figures of the accompanying drawing during the following description thereof, like reference numerals indicating like parts so far as possible in the two figures.

Fig. l diagrammatically illustrates a filter system embodying features of my invention.

Fig. 2 is a modification of the system of Fig. 1 to include a three electrode tube in the dual capacity of filter aiding and amplifying signal current.

In Fig. 1 the full-wave rectifier 6 rectifies alternatiug current from source A. C. with the aid of transformer l and the primary and secondary elements thereof shown, the output of the rectifier being preferably shunted by a storage and filtering condenser '7. The unidirectional current is intended for use in a work circuit 15, which may be for example the plate circuit or circuits of one or more vacuum tubes of a cascaded amplifier. To smooth out the ripples in the rectified current I include a three electrode vacuum tube 8 or its equivalent, the filament of which is heated with the aid of secondary winding 5, so that the filament-to-plate path is in series with the current supply from the rectifier output to the load 15.

By causing the rectified current to pass through the choke coil 9 and resistance 11, both shunted by a ripple governing condenser 10, I can develop such pulsating unidirectional potential on the that the amount of filament-toplate current can be controlled as well as opposing the ripple therein to any desired degree by the pulsations thus introduced on and controlled at the grid. The inclusion of inductance and resistivity in coil 9, resistivity in resistance 11, and capacity in condenser 10, allows for developing the desired degree of grid biasing potential and controlling for the desired amount and phase of the fluctuation potential on the grid to regulate the amount of current flow through load 15 and to eliminate the ripple therein.

In the event the impedance through the space current path and load is such that suificient ripple current cannot be developed on the grid to smooth out the load current ripple to the desired amount the inclusion of a condenser 12 to provide a lesser impedance for the fluctuating component can be used to advantage. A condenser 14 may be employed to prevent actions in the load circuits from being reflected back into the filter system; for example, signal currents, if the load comprises the tubes of a signal current amplifying system.

The system of Fig. 2 differs from that of Fig. 1 in that I employ the tube 8 in the dual capacity of filtering and signal amplifying, as for example the output tube of a cascade system in which the tube 17 is a preceding amplifier or detector. This I accomplish by introducing the signal current output of tube 17 into the grid circuit of tube 8 through transformer 19, tube 17 having a signal current input through transformer or other coupling element 18. The signal current output of tube 8 may be transmitted to a loud speaker or other translating device through transformer 20 and condenser 25.

The plate current of tube 17 forms the load on the filter system, or there may be a plurality of tubes in cascade or otherwise, the filament o-r filaments being heated with the aid of transformer secondary 16. The plate current of tube 1'? is shown to pass through resistance 22 to produce a grid biasing potential for this tube.

In the event the desired grid bias for tube 8 cannot be created by the resistance of coil 9 and shunted resistance 11 in their designs for other purposes, then the inclusion of a resistance 21 will aid in adjusting in the desired manner. Likewise, connection of condenser 12 to an intermediate point 24 of coil 9 may facilitate adjustment for load current ripple elimination.

In the systems of both Figs. 1 and 2 it is preferable to use a vacuum tube 8 having filament characteristics of the type disclosed in my copending application scrim No. 191,195, filed 13 May 1927, which issued on June 18th, 1929 as U. S. Patent No. 1,718,059, or a so-called indirectly heated type of cathode, this in order to avoid disturbances arising from energizing the filament or cathode with alternating current.

No limitations are intended through the confining of my description and explanation to the specific embodiments of the figures of the drawing other than those imposed by the appended claims.

Having fully described my invention I claim:

1. In an electrical current supply system, the combination of a source of fluctuating unidirectional current, a work circuit adapted to be energized by said source, an electron tube, the filament-plate path of which is series connected between said source and said work circuit, and means for varying the impedance of said filament plate path in consonance with the fiuctuating component of said source, whereby said fluctuating component of said source is isolated from said work circuit, said means consisting of a parallel connected choke coil, condenser and resistance system connected in series between the I filament of said tube and one terminal of said source, the grid of said tube being connected to the source side of said choke coil, and a variable condenser connected between the other terminal of said source and said choke coil.

2. In an electrical system, the combination of a source of pulsating direct current, a work circuit, a filter system connected between said source and said work circuit, said filter system including a multi-electrode tube, the cathode-plate path of said tube being series connected be tween said source and said work circuit, and means including a choke coil and an adjustable capacity in shunt with said coil, in said series connection, and a direct current connection between the control grid of the tube and a point on said means such that a pulsation compensating potential is impressed upon said control grid from said filter system whereby the space current of said tube is maintained sub stantially free from variation due to the variations of said source.

Ii In an electrical system, the combination of a source of pulsating direct current, a work circuit, a filter system connected between said source and said work circuit, said filter system including a three electrode tube, the filament-plate path of said tube being series connected between said source and said work circuit, means for energizing the grid of said tube from said filter system whereby the space current of said tube is maintained substantially free from variation due to the variations of said source, means for impressing signal current variations upon the grid of said tube whereby the space current of said tube is varied in consonance with said signal current variations, and means associated with the plate-filament circuit of said tube for abstracting a portion of the signal component of said space current for the production of audible signals.

4. In an electrical system, the combination of a source of pulsating unidirectional current, a work circuit deriving energy from said source, a choke coil and condenser filter system connected between said source and said work circuit, said filter system inluding a three electrode tube, the filament-plate path of said tube being series related to said choke coil and between said condensers, a variable capacitor in shunt with the coil, and means for energizing said grid from said choke coil whereby the space current of said tube is substantially free from variations in intensity due to the variations of said source.

5. In an electrical system, the combination of a source of pulsating unidirectional current, a Work circuit deriving energy from said source, a

choke coil and condenser filter system connected between said source and said work circuit, said filter system including a three electrode tube, the filament-plate path of said tube being series related to said choke coil and between said condensers, means for energizing said grid from said choke coil whereby the space current of said tube is substantially free from variations in intensity due to the variations of said source, means for impressing signal current variations upon the grid of said tube whereby the space current of said tube is varied in consonance with said signal, and means associated with the plate-filament circuit of said tube for abstracting at least a portion of the signal component of said space current for the production of audible signals.

6. In an electrical system, the combination of a source of pulsating unidirectional current, a work circuit, including at least one amplifier tube deriving energy from said source, a choke coil and condenser filter system connected between said source and said work circuit, said filter system including a three electrode tube, the filament-plate path of said tube being series related to said choke coil and between said condensers, means for energizing said grid from said filter system whereby the space current of said three electrode tube is substantially free of variations in intensity due to said source, means for impressing signal currents upon the input circuit of said amplifier tube, means coupling the output circuit of said amplifier tube to the gridfiiament circuit of said three-electrode vacuiun tube, and means associated with the plate-filanient circuit of said three electrode tube whereby the signal component of the space current of said tube is made audible.

7. In an electrical system including a source of pulsating unidirectional current, a work circuit and a filter system connected between said source and said work circuit, said filter system consisting of the combination of a filter condenser connected across the terminals of said source, a direct connection between one terminal of said source and one terminal of said work circuit, a filter choke coil and a three electrode tube, said choke coil and the filament-plate path of said tube being series related between the other terminal of said source and the other terminal of said work circuit, a condenser connected across the terminals of said work circuit, an adjustable capacitative reactance in shunt with the coil and means for energizing the grid of said tube from said source whereby the potential across the terminals of said work circuit is substantially free of any fluctuating component of said source.

8. In an electrical system including a. source til of pulsating unidirectional current, a work circuit and a filter system of said work circuit, a condenser connected across v the terminals of said work circuit, and means for energizing the grid of said tube from said source whereby the potential across the terminals of said work circuit is substantially free of any fluctuating component of said source, said A means consisting of a condenser connected beconnected between said source and said work circuit, said filter system the terminals of said.

tween a point in said choke removed from the source connection thereof and the other terminal of said source, and a condenser in shunt to said choke.

9. In electrical system including a source of pulsating unidirectional current, a work circuit and a filter system connected between said source and said work circuit, said filter system consisting of the combination of a filter condenser connected across the terminals of said source, a direct connection between one terminal of said source and one terminal of said work circuit, a filter choke coil and a three electrode tube, said choke coil and the filament-plate path or" said tube being series related between the other terminal of source and the other terminal of said work circuit, a condenser connected across the terminals of said work circuit, and means for energizing the grid of said tube from said source whereby the potential across the terminals of said work circuit is substantially free of any fluctuating component of said source, said means consisting of a condenser connected between a point in said choke removed from the source connection thereof and the other terminal of said source, and a condenser and resistance parallel connected in shunt to said choke.

10. In an electrical system the combination of a source of pulsating uni-directional current, an amplifier circuit, a filter system including a multi-electrode tube connected therein so that the amplifier current flows in the cathode to anode path of the tube to said amplifier circuit, means through which said pulsating current flows connected to the grid of said tube for introducing thereon a pulsating potential acting to neutralize in said tube pulsations in the amplifier current passing therethrough, and additional means for coupling the output of said amplifier circuit to the input of said tube.

11. In an electrical system the combination of a source of pulsating uni-directional current, a signal amplifier circuit, a filter system including a multi-electrode tube connected therein with its cathode to anode path in series with said amplifier circuit, conections for developing from said pulsating current controlling pulsating current potentials on the grid of said tube for establishing a non-pulsating current of desired magnitude thereon, signal input and output means associated with said tube, and means for connecting the amplifier output to the signal input of said tube.

12. In an electric current supply system, the combination or" a source of fluctuating unidirectional current, a single amplifier circuit adapted to be energized by said source, a second amplifier series connected between said source and said first amplifier circuit, means for varying the average value of the impedance of said second amplifier and automatically varying said value in consonance with the fluctuating component of said source, and means for coupling the output or" the first amplifier to the input or" the second amplifier.

13. In an electrical current supply system, the combination of a source of fluctuating unidirectional current, an amplifier circuit adapted to be energized by said source, an electron amplifier tube, the cathode to anode path of which is series connected between said source and said amplifier circuit, means for varying the average value of the impedance of said cathode to anode path for automatically varying said value in consonance with the fluctuating component of said source, and means for impressing the output oi said circuit upon the input of said amplifier tube.

14. In combination, a source of uni-directional pulsating current, an electron discharge tube provided with signal input and output circuits, a filter system, including an amplifier tube having its input circuit coupled to said signal output circuit, through which said current flows to said first tube, and means responsive to current pulsations for maintaining said current flow to the first tube free of pulsations.

15. In combination with a source of pulsating direct current, a load circuit, a filter network connecting said load circuit to opposite terminals of said source, the network including at least one capacitor shunted across said source, a tube having its cathode to anode path in series between one side of the load circuit and the negative terminal of the source, a biasing circuit for the grid of said tube connected between the cathode and grid thereof and comprising a choke coil connected between said negative terminal and the said cathode, a capacitor in shunt with the coil, and a resistor in shunt with the capacitor, and an additional capacitor connected between the positive terminal of said source and a point on said grid biasing circuit.

16. In combination with a source of pulsating direct current, a load circuit, a filter network connecting said load circuit to opposite terminals of said source, the network including at least one capacitor shunted across said source, a tube having its cathode to anode path in series between one side of the load circuit and the negative terminal of the source, a biasing circuit for the grid of said tube connected between the oathode and grid thereof and comprising a choke coil connected between said negative terminal "and the said cathode, a capacitor in shunt with the coil, and a resistor in shunt with the capacitor, and an adjustable capacitor connected between the positive terminal of said source and a point on the coil of said grid biasing circuit and a variable resistor in series with the coil.

17. In combination with a source of pulsating direct current, a load circuit, a filter network connecting said load circuit to opposite terminals of said source, the network including at least one capacitor shunted across said source, a tube having its cathode to anode path in series between one side of the load circuit and the negaive terminal of the source, a biasing circuit for the grid of said tube connected between the oathode and grid thereof and comprising a choke coil connected between said negative terminal and the said cathode, a capacitor in shunt with the coil, a resistor in shunt with the capacitor, and an additional capacitor connected between the positive terminal of said source and a point on said grid biasing circuit, said load circuit comprising an amplifier tube having its anode ccnductively connected to the positive terminal of the source and inductively coupled to the grid circuit of said first tube, a direct current connection including a grid bias resistor between the anode of the first tube and the cathode of the amplifier tube, a signal input circuit coupled to the grid of the amplifier tube and the said last resistor, and a signal output circuit coupled to the anode circuit of said first tube.

BENJAMIN F. MIESSNER.