Current and voltage regulator system

Feb. 12, 1946. r. m. bowie 2,394,891

CURRENT AND VOLTAGE REGULATOR SYSTEM

Filed Feb. 5, 1943

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INVENTOR

Robert M 3ow/e

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Patented Feb. 12, 1946

2,394,891

UNITED STATES PATENT OFFICE

2,394,891

CURRENT AND VOLTAGE REGULATOR SYSTEM

Robert M. Bowie, Emporium, Pa., assignor to Sylvania Electric Products Inc., Emporium, Pa., a corporation of Massachusetts

Application February 5, 1943, Serial No. 474,800

Claims. (Cl. 171—312)

This invention relates to current regulators and to voltage regulators and more particularly to regulators employing electronic tubes.

A principal object of the invention is to provide an electronic system for controlling closely the current flowing through a load, and substantially independently of reasonable variations in input voltage and load impedance.

Another object relates to a regulating system employing grid-controlled electron tubes wherein separate batteries for biassing the control grid of the regulator tube or tubes, is obviated.

Another object relates to a regulating system employing a plurality of grid-controlled electron tubes wherein the effect of changes in the heater power supply to the electron-emitting cathodes, is substantially compensated for by using a special symmetric connection of the tubes.

A feature of the invention relates to a regulating system employing at least one grid-controlled amplifier tube which tests the current to be regulated, and whose control grid is self-biassed above ground potential by a cathode resistor. The effect of negative feedback which normally tends to take place through such a cathode resistor is partially compensated for by another symmetrically connected tube having the same cathode resistor but with its grid held at a constant grid voltage.

Regulators may be divided as follows:

1. Hot wire ballast lamp type.

2. An electronic amplifier circuit which controls a series resistor tube, the amplifier circuit being controlled by the saturated emission from a diode filament which is heated under control of the current to be regulated.

3. An electronic amplifier circuit controlling a series resistor tube in which the amplifier is actuated by the voltage drop caused by the current to be controlled flowing through a fixed resistor. In this circuit, some source of fixed potential must be provided against which the voltage drop is compared.

4. The mu bridge.

Accordingly, it is another feature of this invention to provide an improved regulator of the third of the above classes.

Other features and advantages not specifically enumerated will be apparent after a consideration of the following detailed descriptions and the appended claims. In the drawing which represents certain preferred embodiments,

Fig. 1 Is a schematic wiring diagram of a current regulator according to the invention and having a single amplifier stage.

Fig. 2 is a diagram of a system similar to Fig. 1 but employing two amplifier stages.

Many regulators of the third class above mentioned have the disadvantage that a battery or special power supply must be provided to produce the bias on the first stage of the amplifier. Furthermore, since the amplifier is usually of the

D. C. type, its output is influenced by the filament or heater voltage. The systems as shown in Figs. 1 and 2 require no separate battery for bias purposes and provide automatic compensation for any voltage variations applied to the heater or filament of the cathode.

Referring to Fig. 1, the terminals “B-f-” and IB are the terminals to which the input voltage is applied. The terminals 13 and 14 are those across which the load is to be connected and through which the current must be closely regulated so as to be substantially independent of the voltage across B+ and 15, and so as to be substantially independent of variations in the actual load impedance. For simplicity, the load is represented in the drawing by resistor I i. Resistor (A which is connected in series with the load and ground is a sampling resistor which develops voltage drops under control of the load current. Also connected in series with the load is a grid-controlled tube i 0 whose plate resistance is automatically varied under control of the amplifier tubes B and 6 so as to keep the load current constant.

The plates of amplifier tubes 5 and 6 are symmetrically connected through their individual plate resistors 3 and 4 and common resistor 9 to the terminal B+. The cathodes of amplifier tubes B and 6 are connected to ground through the common adjustable bias resistor 7. Preferably, the grid bias of tube 5 is adjusted by means of the potentiometer 2 and its sliding contact so that it is substantially the same as the grid bias of tube 6. The plate potential for tubes 5 and 6 and the grid potential for tube 6 is maintained substantially constant by any well-known form of glow discharge type voltage regulator tube I, connected across resistor 2.

If the voltage applied to B-f- should increase, it would tend to produce an increase in voltage across resistor 12. The latter increase would then change the bias on grid 21 to cause an increase in plate current of tube 6 and a greater drop across resistor 7. Normally the negative feedback resulting from resistor T would substantially annul the effect of the increase in potential on grid 21. However, the increasing drop across resistor 7 tends to increase the bias on tube 5 thereby reducing its plate current. As a result, the plate

3,394,891 current through tube 6 increases approximately one-half as much as might have been expected had the cathode been at constant potential. Hovewer, the actual increase of plate current in tube 6 is many times that which would take place without the tube 5 and the common bias resister 7. The increased plate current of tube 6 flowing through resistor 4 causes the grid potential of tube 10 to be reduced, resulting in a reduction of voltage across the load 11, and hence reducing tendency of current variation through said load.

In the event that the impedance of the load varies while the input potential B+ is constant, for example if the load resistance decreased, an increased current would tend to flow in such a way as to increase the potential of the control grid 21. In this condition, the same sequence of events would take place as above described to cause a depression of the potential on the grid of tube 10 thereby compensating for the reduction in the load impedance.

Since tubes 5 and 6 are symmetrically connected through the common cathode bias resistor 7, any increase in emission from the cathodes or filaments of these tubes due for example to increased heater power, results in increased current through cathode resistor 7 thereby providing the same negative feedback to both tubes which substantially compensates for the increase in cathode emission. >

In many cases, it is desirable to achieve a much higher degree of constancy than is obtained by a single stage of amplification. An arrangement for accomplishing this, with plural stages of symmetric amplification is shown in Fig. 2. In this figure, those parts which correspond to similar parts in Fig. 1 bear the same designation numerals. In the system of Fig. 2, any increase in potential of the grid of tube β causes a corresponding decrease in the potential of tube 5. The decreased plate current in tube 5 produces an increase in the potential of the grid of amplifier tube 19: Similarly, the potential of the grid of tube 20 is decreased. The potentials on the grids of tubes 19 and 20 are amplified by the respective tubes so that the potentials affecting the individual plate resistors 17 and 18 are much greater than can be obtained from a single stage of amplification. Since tube 20 inverts the phase of the voltage applied to its grid, it is necessary to derive the control voltage for tube i0 from tube 19. Like the system of Fig. 1, this system employs the common cathode resistor 7 for the two amplifier tubes 5 and 6 and the common cathode resistor 22 for the amplifier tubes 19 and 20 and any increase in cathode emissivity resulting from increase in the heater power of the tubes is substantially compensated for.

While in the drawing the grid potential of tube 5 (Fig. 1 or Fig. 2) is fixed under control of the gas voltage regulator tube I, it will be un derstood that this fixed potential for the grid of tube 5 may be provided from any other source. Furthermore, the system of Fig. 1 as well as that of Fig. 2, may be used for voltage regulation by connecting the load between terminals 13 and 15 and by employing a fixed resistor 11, and with the load connected between terminals il and U. It is therefore a further object of the invention to produce an improved voltage regulating system of the type characterized by the objects set forth in page 1 and hereof in connection with current regulators.

Various changes and modifications may be made in the disclosed embodiments without departing from the spirit and scope of the invention.