US2707766A - Cold cathode voltage regulator - Google Patents

Description

y 3, 1955 c. R. WILLIAMS 2,707,766

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Patented May 3, 1955 CULD CATHQDE VOLTAGE REGULATOR Charies R. Widliams, Hawthorne, Califl, assignor to Northrop Aircraft, 112e,, Hawthorne, Calii, a corporation oi California Appiication August 18, 1950, Serial No. 189,256

4 Claims. (Cl. 323-22) The present invention relates to voltage regulators, and more particularly to a voltage regulator utilizing a cold cathode glow tube.

An object of the present invention is to provide a voltage regulator of the cold cathode glow tube type for which the supply voltage to be regulated need not be high for the purpose of igniting the tube.

it is another object of the invention to provide a voltage regulator having an output voltage current characteristic such that capacitance loading of the output will not cause oscillation.

It is another object of the invention to provide a voltage regulator utilizing a three electrode cold cathode glow tube.

at is still another object of the invention to provide a positive peak clipping circuit for alternating currents.

in brief, the present invention utilizes a glow tube having two anodes and a cold cathode of the kind described in the co-pending application Serial No. 156,659 of Glenn E. Hagen et al., and which utilizes a cathode of open construction. Means are provided to maintain a continuous glow discharge between one anode and the cold cathode. The voltage source to be regulated is connected to the other anode through a resistance to cause a second glow discharge from the second anode to the cathode; the value of this resistor and that of the source to be regulated being chosen so that the second glow discharge operates on a fiat portion of the voltage-current curve during fluctuation of the source being regulated, and during fluctuation of the load resistance. The load is then connected directly to the second anode. By operating the tube on a sloping portion of the voltage-current curve, the same circuit will operate as positive peak clipping device for A. C. waves.

The invention will be more fully understood by reference to the drawings in which:

Figure 1 is a wiring diagram of a preferred circuit embodying the present invention.

Figure 2 is a voltage-current curve of a conventional two electrode voltage regulating glow tube.

Figure 3 is a voltage-current curve taken at the regulating anode of a three electrode glow tube used in the circuit of Figure 1. v

Figure 4 is a circuit diagram showing how tubes acting as voltage regulators or peak clippers can be paralleled.

In Figure 1 a three electrode glow tube 1 is provided with an envelope in, containing a cathode 2 of open construction, a relatively small sustaining anode 3, and a relatively large regulating anode 4.

To operate the tube 1 as an efiicient voltage regulator, as shown in Figure l, the sustaining anode 3 is connected to the cathode 2 (via ground) through a sustaining anode resistor 1t) and a sustaining source 11 having a voltage higher than the striking voltage of the tube 1. Resistance is valued to cause the tube to glow with a stable discharge between the sustaining anode 3 and the cathode 2.

The regulating anode 4- is connected to a source to be regulated through a regulating resistance 12, and a load circuit 13 is provided between regulating anode 4 and cathode 2 (via ground).

The conventional two electrode voltage regulating glow tube usually has a hollow cylinder cathode and a centrally supported wire or rod anode. When the tube is in operation, the cathode glow forms on the inside of the cylinder. The large cathode area, all parts of which are nearly equidistant from the anode, obtains a large range of cathode cur ent with very little change in cathode to anode voltage, as shown in Figure 2. In this figure, B to C is the useable current range. At point C the inside of the cathode is completely covered with glow, higher voltage is required to force more current through the tube. Below point B the negative slope of the characteristic tends to cause oscillation, especially if the tube is loaded with a parallel capacitance. Point A represents the igniting potential. The supply voltage to be regulated must have at least this value in order to start and maintain glow in the tube.

It should be noted that the voltage-current curve between points B and C in Figure 2 has been exaggerated in order to explain the operation. Actually the voltage differential between points B and C is only on the order of a few volts.

In conventional tubes various means are employed to lower the igniting potential; for example, a small quantity of radio active material may be included in the tube to supply a continuous source of ions.

In the present invention ionization is supplied by the sustained discharge from the sustaining anode 3 to the common cathode 2 which is of open construction. This ionization is suh'icient to convert the negative slope portion of the regulating anode voltage-current characteristic curve into a positive slope curve, as shown in Figure 3. No potential higher than the burning potential is required on the regulating anode for the purpose of ignition.

In operation, a change in the D. C. voltage from the source to be regulated will cause a corresponding change in the current through the resistor 12. The resistor 1'2. potential drop thus varies, but even though the glow current between the regulator anode 4 and the cathode 2 varies, either because of the fluctuation in the D. C. source voltage or the load demand, the voltage drop across the regulator anode 4 and the cathode 2 remains substantially constant, as shown in Figure 3.

The tube circuit of the present invention can also be used for a positive peak clipping circuit when an A. C. supply is fed into resistor 12. For this latter operation the tube is normally operated on the knee of the voltagecurrent curve of Figure 3, such as point D for example. If the load is of low impedance, an A. C. voltage supplied from the source to be regulated would cause a swing toward the right and left of point D. Thus, positive going wave changes of A. C. are effectively eliminated by the drop across resistor 12, while negative going changes of A. C. are passed to the output.

If currents larger than can be obtained with one tube are desired, the sustaining anodes 3 and the cathodes 2 of several tubes can be connected in parallel to one sustaining source 11. The load circuit then is connected in parallel with all of the regulating anodes 4 and the cathodes 2, as shown in Figure 4.

From the above description it wii be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute, the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise a preferred form of putting the invention into effect, and the invention is, therefore, claimed in any of its forms or modifications Within the legitimate and valid scope of the appended claims.

What is clairncd is:

1. In a cold cathode voltage regulating circuit having a glow tube provided with two anodes and a common cathode; an open cathode structure; a D. Q voltage supply and a resistance operatively connected in series with one anode to provide a first continuous and ionizing discharge between a first anode and the cathode; means operatively connected for producing a second and simultaneous discharge with said first discharge out connected between the second anode said cathode; and a load circuit connected in parallel with said second anode and cathode and regulated by said second discharge, said load circuit including a pair of output terminals.

2. A circuit in accordance with claim 1 wherein said means for producing said second glow discharge between said regulating anode and said cathode comprises a second D. C. voltage source and a regulating resistance connected in series with the parallel combination of said load circuit and the path of said second glow discharge, whereby a regulated D. C. voltage can be initiated and maintained across a load connected to said output terminals without first raising said second D. C. voltage source above normal operating value.

3. A circuit in accordance with claim 2 wherein said regulating resistance has a value cooperating with the other components to operate said regulating anode and cathode circuit over a substantially flat portion of the voltage-current curve of said anode-cathode circuit.

4. A voltage regulating circuit comprising a glow tube having an envelope containing an anode operated solely as a continuously sustaining anode, a regulating anode, a cold cathode of open structure, and a filling of ionizable gas at glow discharge pressure, means operatively connected to maintain a first continuous ioniz ng discharge between said sustainiing anode and said cathode, a D. C. voltage source and a regulating resistance connected in series with said regulating anode and said cathode, and a load circuit connected in parallel with said regulating anode and said cathode, said load circuit including a pair of output terminals.

References Cited in the file of this patent UNiTED STATES PATENTS OTHER REFERENCES Publication entitled Beschrecbung des Glimmrelais, March 17, 1930.

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