US1954784A - Automatic voltage regulator - Google Patents

Description

April 17, 1934. R, A. BRADEN AUTOMATIC VOLTAGE REGULATOR Filed April 7, 1930 INVENTOR RENE A BR DEN BY 7%@ ATTORNEY Patented Apr. 17, 1934 PATENT OFFICE AUTOMATIC VOLTAGE REGULATOR Rene A. Braden, Merchantville, N. Radio Corporation of America.

Delaware J., assigner to a. corporation of Application April 7, 1930, Serial No. 442,239

4 Claims.

My present invention relates to voltage regulators, and more particularly to an automatic voltage regulator for electron discharge devices.

In operating a socket-power radio receiver, it may practically prove expensive to accept the usual 110 volt lighting current at its face value. In many sections the usual lighting current measures anywhere from 90 to 130 volts. In some sections the voltage may drop as low as 80, while in other sections the voltage may rise as high as 140. The natural consequence of such fluctuation, particularly where the fluctuation rises above rated voltage, is prematurely burned out radio tubes.

The disadvantages that arise at excessive line voltage and insuicient line voltage, are similar in their disturbing influence. With excessive line voltage the set may operate with greater power, but the electron discharge tubes may be under 'constant strain. The radio tubes may burn out in short order, resulting in costly operation.r In case there is insufficient line voltage, the radio set operates usually with weak volume and poor tonal quality. Accordingly, it can be seen that if line voltages were constantly high or low,

the problem could be solved by various expediencies. Instead, however, line voltages usually fluctuate from high to low throughout the day and at indefinite intervals. For example, within a few minutes there may be an enormous difference in line voltage, with consequent disastrous effects on tubes.

Now, I have discovered, and devised means for utilizing a method for maintaining a feeding voltage to the tubes within a slight percentage of radio tube guaranties. According to my present invention a circuit is arranged, and associated with the power transformer of the lighting current supply, for maintaining constant filament current in the electron discharge devices, particularly of a radio receiver, in spite of varying line voltage. Briefly, the present method utilizes an auxiliary circuit coupled to the power transformer, which auxiliary circuit is employed for producing in the circuits of the filaments to be protected, a regulating voltage which constantly opposes and substantially balances out, the increment of voltage created by the abnormal line voltage increase or decrease.

Accordingly, it is one of the main objects of my present invention to provide a method of, and employ means for, maintaining constant filament current flow in electron discharge devices, particularly employed in radio receivers, with varying line voltage, the method consisting in providing an additional circuit, in the power transformer circuit, for producing a voltage constantly preventing disturbances caused by voltages greater or less than a predetermined, desired line voltage.

Another important object of the present invention is to provide in a radio receiver employing one or more electron discharge devices, which radio receiver is operated by socket-power from the usual 110 volt lighting current source, a circuit associated with the power transformer, and including an element, the resistance of which falls proportionally with increased applied voltage, and which circuit is coupled to the filament circuit of the electron discharge device in such a manner that voltages above or below 110 volts in the filament circuit are prevented by a regulating voltage produced by the said auxiliary circuit.

Other objects of the invention are to improve generally the simplicity and efficiency of automatic voltage regulators for radio receivers, and to provide an automatic line voltage regulator which is not only durable and reliable in operation, but economically arranged in a radio receiver.

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.

In the drawing,

Fig. 1 diagrammatically shows a circuit embodying the invention,

Fig. 2 graphically shows the operation of the invention,

Fig. 3 represents graphically the ideal and the actual carbon filament lamp characteristics,

Fig. 4 diagrammatically shows a modified form of the invention,

Fig. 5 graphically presents the characteristics of the modification shown in Fig. 4.

Referring to the accompanying drawing there is shown an electron discharge device 1 including the usual control electrode, cathode and anode. It is of course understood that the electron discharge device can be a tetrode or even a pentode tube. It is further pointed out that the device canbe of the type wherein an indirectly heated cathode is employed, it being only essential to the sok -9 also being in series with the winding 6.

present invention that the iilament 2 be energized and heated from a source of current 3, the latter in this case being the usual 110 volt alternating current source utilized for lighting current.

As is well known to those skilled in the art the source 3 is connected to the filament of each tube through a power transformer 4, the primary 5 of which is directly connected to the source 3, and the secondary 6, of which device, is connected to the filament circuit of the tube or tubes. In the drawing I have only shown one electron discharge device, the circuit between the grid and filament of the device being termed input, While the circuit between the anode and filament is termed output.

It is to be understood that the device l is symbolic of all the tubes generally employed in a `i'adio receiver, and that the circuit between the filament of the device 1 of the secondary 6 of the transformer may have in it the filaments of other tubes used in the radio receiver. I have further designated at 7', the potentiometer shunted across the iilament 2 in order to adjust the Voltage on the iilament to obtain a uniform potential drop across the filament. This device is well known in alternating current operated radio receivers, and need not be described in any further details.

An auxiliary circuit, generally designated as A, is provided in the power circuit of the receiver. This auxiliary circuit includes a coil 6 which acts as an independent secondary winding of the power transformer 4. A transformer I is provided between the filament circuit and the aux- -iliary circuit A for coupling the two circuits for a reason to be presently explained. The primary winding 8 of the transformer 7 has connected with it in series the carbon iilament 9 of an incandescent carbon filament lamp 10, the filament The secondary 11 of the transformer 7 is connected in series with the filament 2, and the secondary 6 in the electron discharge lament circuit.

It will be readily seen that the voltage in the primary 5 of the power transformer 4 induces a current I1 in the electron discharge iilamentcircuit, it being assumed to iiow in the direction of the arrow; and, also, a current I2 in the carbon filament circuit, flowing in the direction of the arrow. As the line voltage increases, the current I1 in the electron discharge filament circuit tends to increase. I-Iowever, due to the fact that the resistance cf the carbon lament 9 decreases as the current I2 increases, it will be seen that the current I2 in the auxiliary circuit A increases more rapidly than current I1.

The windings 8, 1l of transformer '7 are so arranged between the auxiliary circuit A and the electron discharge lament circuit that the `voltage E, induced in the electron discharge iilament circuit by the transformer 7, opposes the main voltage in the electron discharge iilament circuit, and consequently prevents most of the change in current I1, the direction of the voltage -E in the electron discharge lament circuit beby plotting the resistance of the filament 9 in ohms against current in amperes.

There is thus obtained a curve representing the relation between Ii, I2 with change of resistance of the filament 9 of the carbon lamp 10 in circuit A.

`These curves are obtained, from actual calculan tions and theoretical considerations of the characteristics of the voltage regulator, from the following table:

, Drop R E I i I 2 across R/ Ohms Volts Ampercs Amperes Volts 100 11. 4 1 10 10 50 1l. 65 1 20 10 2U l2. 5 1 50 10 l0 14. 14 1 l. 0 10 5 18. 0 1 2. 0 10 2 3l. 5 1 5.0 10 l 55.8 1 10.0 10

The symbol R designates the resistance of the filament 9 of the carbon lamp 10; the symbol E represents the voltage from source 3; the symbols I1 and I2 represent the currents flowing respectively in the electron discharge tube iilament circuit and the regulating circuit A; while, the last column indicates values for the voltage drop across the carbon lamp filament 9. The various values in the last two tables were obtained by keeping Ii constant, E and R varying as indicated in the table. It Will be noted that the last two columns of the table show what characteristics are required for the carbon lament lamp l0 in circuit A.

It will be noted that the voltage drop across R is constant. This is the ideal condition, but it cannot be attained in practice. The closer the carbon filament comes to having this characteristie, the more constant the iilament current will be with varying line voltage. These calculations are based on the assumption that the resistance R of lament 2 is constant. If the element R had ideal characteristics, it would not matter whether or not the tube filament resistance R was affected by the current iiowing through it, for the current would be constant. But in an actual circuit, the lament resistance R will increase as the iilament current increases. This dependence of iilament i'esistance on current will cooperate with the change of R in holding I1 nearly constant.

The ideal and the actual carbon lament lamp characteristics Vare plotted, and graphically shown, in Fig. 3. This graph shows filament current in carbon lamp as abscissee and Volts across carbon filament as ordinates, three curves being shown in the graph. The curve in full line is designated as the actual curve; the ideal curve is shown in dotted lines; while the constant resistance line curve is shown in dotted line. Three Values, a, b, c of filament current in the carbon lamp are shown as dotted spaced vertical lines, the value c being designated as the maximum safe current.

Currents below the value a do not heat the iilament peiceptibly, and consequently the resistance is constant. If the current is increased beyond this point, the filament is likely to burn out. If the circuit is adjusted so that, at normal line voltage, the current in the carbon lamp is a,

there will be no effect if the line voltage drops voltage falls to such a value that the carbon lilarnent current drops below the value a, the compensation ceases, and variations of line voltage produce corresponding changes in the vacuum tube filament current. If the line voltage increases suiciently to raise the carbon filament current to c, this lament is likely to burn out, as mentioned above. However, the normal operating point may be put far enough below the danger point to eliminate the possibility of such trouble.

In Fig. i there is shown a modified form of the invention, in which a gas-filled discharge tube, such as a neon tube, can be used in place of the carbon ilament lamp. Thus a neon tube 10, conventionally represented, is shown connected in the circuit A in Fig. 4. The circuit is otherwise the same, and therefore is not shown with all the details of Fig. 1, it being understood that the remaining details of the circuit are the same as in l. The neon tube can be of any well known construction, such as the nat-plate neon tube commonly used in television receivers.

The characteristics of a neon lamp are graphically shown in Fig. 5 wherein current through neon lamp as abscissae are plotted against volts across lamp as ordinates. The curve shown in full line in Fig. 5 is the actual curve` while the curve shown in dotted line is the ideal characteristic curve. The striking Voltage of the lamp is represented on the drawing by the arrowheaded vertical line. It will be noted that the actuai characteristic curve is very close `to the ideal curve, and good voltage regulation can be obtained with this type of lamp. To produce regulation, the voltage applied to the neon lamp must be above the striking voltage (i. e. starting voltage) Since the neon lamp may have higher resistance, and carry less current, than a carbon filament lamp, a different transformer to couple the compensating circuit to the vacuum tube circuit may be required. Whichever type of lamp is used, the turns ratio of this transformer are to be adapted to the currents and voltages in the two circuits. Thus, if the vacuum tube filaments carry a large current, and the neon lamp (or carbon niament lamp) carries a small current, the coupling transformer will have a winding of a small number of turns in series with the vacuum tube filaments, and a winding with a larger number of turns in the neon or carbon lamp circuit.

It will therefore be seen that even though the line voltage luotuates from high to low throughout the day and at indefinite intervals, in spite of the fact that in a few minutes there may arise an enormous diierence in line voltage, the auxiliary circuit A nevertheless constantly produces in the electron discharge filament circuit an auxiliary voltage which constantly prevents disturbances produced by voltages in the electron discharge filament circuit above or below a predetermined normal operating line voltage.

It is to be understood that the present method and arrangement is not limited to use with an alternating current supply, but may be employed for any iuctuating current source, the essential feature of the invention residing in the provision of an auxiliary circuit for utilizing an increase or decrease in voltage to produce an additional voltage to prevent disturbance due to the increase or decrease of voltage above or below normal operating voltage.

Again, while I have indicated and described two arrangements for carrying my invention into effect, it will be apparent to one skilled in the art that my invention is by no means limited to the particular organizations shown and described, but that many modications may be made without departing from the scope of my invention as set forth in the appended claims.

What I claim is:

1. In combination with a thermionic discharge device provided with an electron emission element, a source of energizing current, a circuit between said source and said element whereby potential from said source may be applied to said element, an auxiliary circuit connected to said source and including a member whose conductance is directly proportional to flow of current through the circuit, said auxiliary circuit being coupled to said rst circuit in such a manner that changes in potential of said source above or below a predetermined operating potential are substantially balanced out by potential induced in said rst circuit from said auxiliary circuit.

2. In combination with a thermionic discharge device provided with a filament, a source of filament heating current, a circuit between said source and said element and including a transformer, an auxiliary circuit coupled to said transformer and including a. device whose conductance is directly proportional to iloiv of current therethrough, and a transformer coupling said first circuit and auxiliary circuit in such a manner that changes in potential oi said source above or below a predetermined operating potential are substantially eliminated.

3. In combination with a thermionic discharge device provided with a filament, a source of lament heating current, a circuit between said source and said element and including a transformer, an auxiliary circuit coupled to said transformer and including a gaseous discharge tube whose conductance is directly proportional to flow of current therethrough, and a transformer coupling said first circuit and auxiliary circuit in such a manner that changes in potential of said source above or below a predetermined operating potential are substantially eliminated.

4. In combination with a thermionic discharge device provided with a lament, a source of filament heating current, a circuit between said source and said element and including a transformer, an auxiliary circuit coupled to said transformer and including a neon discharge tube whose conductance is directly proportional to flow of current therethrough, and a transformer coupling said first circuit and auxiliary circuit in such a, manner that changes in potential of said source above or below a predetermined operating potential are substantially eliminated.

RENE A. BRADEN.

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