US2394891A - Current and voltage regulator system - Google Patents

Description

I Feb. 12, 1946. R. M. BOWIE I 2,394,891

CURRENT AND VOLTAGE REGULATOR SYSTEM Filed Feb. 5, 1943 I T5. l.

INVENTOR ADOBE/P7" N 50 W/A' Patented Feb. 12, 1946 CURRENT AND VOLTAGE REGULATOR SYST 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

2 Claims.

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 blessing 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 inthe 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-blessed 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 unde 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 fiowing through a fixed resistor. In this circuit, some source or 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

I but employing two amplifier stages.

. thermore, since the amplifier is usually of the 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. Fur- 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 oi the'cathode.

Referring to Fig. l, the terminals B+ and Ii are the terminals to which the input voltage is applied. The terminals l3 and H 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 3+ and I5, 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 Ii. Resistor Ltwhich 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 lfl whose plate resistance is automatically varied under control of the amplifier tubes I and B 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 8+. The cathodes of amplifier tubes 5 and 6 are connected to groundthrough the common adjustable bias resistor 1. Preferably, the grid bias of tube 5 is adjusted by means of the potentiometer 2 and its sliding contact so that it is sub tantially the same as the grid bias of tube l.- 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 13+ should increase. it would tend to produce an increase in voltage across resistor l2. The latter increase would then change the bias on grid 2| to cause an increase in plate current of tube 6 and a greater drop across resistor I. Normally the negative feedback resulting from resistor I would substantially annul the effect of the increase in potential on grid 2i. However, the increasing drop across resistor I tends to increase the bias on tube 5 thereby reduclng its plate current. As a result, the plate 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 5 is many times that which would take place without the tube 5 and the common bias resister 1. The increased plate current of tube 6 fiowing through resistor 4 causes the grid potential of tube ID to be reduced, resulting in a reduction of voltage across the load II, and hence reducing tendency of current variation through said load.

In the event that the impedance of the load varies while the input potential 8+ 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 2|. 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 l thereby compensating for the reduction in the load impedance.

Since tubes and 6 are symmetrically connected through the common cathode bias resistor 1, 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 1 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 6 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 i9. Similarly, the potential of the grid of tube 20 is decreased. The potentials on the grids of tubes I5 and 20 are amplified by the respective tubes so that the potentials affecting the individual plate resistors l1 and ii 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 10 from tube l9. Like the System of Fig. 1, this system employs the common cathode resistor I for the two amplifier tubes 5 and 6 and the common cathode resistor 22 for the amplifier tubes i9 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. l or Fig. 2) is fixed under control of the gas voltage regulator tube I, it will be understood that this fixed potential for the grid of tube 5 may be provided from any other source. Furthermore, the system oi Fig. l as well a that of Fig. 2, may be used for voltage regulation by connecting the load between terminals I3 and i5 and by employing a fixed resistor l I, and with the load connected between terminals I! and II. 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.

What I claim is:

1. A regulating system comprising a, source oi D. C. voltage supply, a D. C. load resistor, a gridcontrolled electron tube connected to act as a variable resistor in series with said load resistor across said supply, a control channel comprising first and second grid-controlled tubes, a resistor connected in common from the cathode of said variable resistor tube and the control grid of said first tube to the negative side of said supply, a single cathode bias resistor connected in common from the cathodes 01' said first and second tubes to said negative side, symmetrical connections from the anodes of said first and second tubes to the positive side of said supply, means to bias the control grid of said second tube at a constant potential so as to compensate for the degenerative amplicatiOn of said first tube which tends to occur when the load voltage increases, and a D. C. connection from the anode of said first tube to the control grid 01' said variable re- Sistance tube.

2. A regulator system comprising a source of D. C. voltage supply, a D. C. load, a grid-controlled electron tube connected as a variable resistor in series with said load across said supply, a control channel for controlling the resistance of said tube and comprising two stages of amplification, each stage including a first and a second grid-controlled tube, a resistor connecting the cathodes of the first and second tube of each stage in common to the negative side of said supply source, means connecting the anodes of the first and second tube of each stage symmetrically through respective resistors to the positive side of said source, means connecting the control grid of the first tube of each stage to the load circuit so that the potential of said grid varies with the load voltage, means to maintain the control grid of the second tube of each stage at a constant potential, and means connecting the anode of the first tube of one of sald stages to the control grid of said variable resistance tube to control the plate resistance of said variable resistance tube.

ROBERT M. BOWIE.

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