US2750555A

US2750555A - Voltage regulating apparatus

Info

Publication number: US2750555A
Application number: US279476A
Authority: US
Inventors: Kather Erich Nevin; Thomas A O Gross
Original assignee: Raytheon Manufacturing Co
Current assignee: Raytheon Co
Priority date: 1952-03-29
Filing date: 1952-03-29
Publication date: 1956-06-12
Anticipated expiration: 1973-06-12

Description

2 Sheets-Sheet 1 June 12, 1956 E. N. KATHER ETAL I VOLTAGE REGULATING APPARATUS Filed March 29, 1952 5R 6 Y mum 5 HA N 4 m M M .3 a WWW F A 4 I fl 0 7 W IIIL 0 L a h w 2 2 a a A m m y P F Y Q A Y M mm au 5 June 12, 1956 E. N. KATHER ET AL VOLTAGE REGULATING APPARATUS Filed. March 29, 1952 2 Sheets-Sheet 2 MAGNE TIC FIELD DE/VS/ T Y B ,w A a a |||l||l| lllJfill' fl w u T G l. g s D D 8 m I m N I F a M W w m l m M E A g Fr lllllllj/ a 55 s 0 w ANODE CURRENT I INVENTORS 5/2/0 NEV/N KATA/El? THOMAS A. o. GROSS;

BY AT ORNEV Ba 3b 3c MAGNET/C FIELD DENSITY B 2,750,555 Patented June 12, 1956 VOLTAGE REGULATING APPARATUS Erich Nevin Kather and Thomas A. 0. Gross, South LincohaMasn, a'sslgnors to Raytheon Manufacturing Company, Newton, Mass, a corporation of Delaware Application March 29, 1952, Serial No. 279,476 5 Claims. (Cl. 323-22) This invention relates to a means for deriving a substantially constant voltage from a source of electrical energy which is subject to variations in voltage and current and, more particularly, relates to an electron discharge device having a magnetic field associated therewith for producing a constant voltage.

Among the most widely used voltage regulators are cold cathode gas-filled diodes, such as neon glow discharge tubes. These tubes have certain disadvantages which detract from their performance as voltage regulating devices. Such tubes have a relatively poor response to transients so that the output'voltage will not remain constant if the power supply voltage varies rapidly. Furthermore, these regulator tubes are characterized by comparatively large hysteresis owing, principally, to the relative immobility of the heavy gas ions as compared with electrons whose masses are extremely small; because of this hysteresis, the voltage drop across the tube will vary with the direction of fluctuation in voltage and the response of the tube to rapidly increasing and decreasing voltage is relatively poor. Another disadvantage of such tubes is that the voltage required to ignite the glow tube when the circuit is first energized is higher than the normal operating terminal voltage. It is necessary, therefore, to

supply a voltage equal to or higher than the starting or,

ignition voltage, which, in conventional glow discharge voltage regulators, is approximately thirty per cent greater than the normal operating voltage; in addition to the requirements for high source voltages, the regulation of transients is poor when high-starting voltages are re-,

quired.

An additional disadvantage of gas discharge regulators is that life is relatively short because of absorption of gases by the electrodes. Since gas pressure and gaseous content are voltage-determining parameters in tubes of this type, an absorption of gas results in instability which increases as the tube ages. Finally, the voltage and ourrent range in such tubes is severely limited. For example,

typical gaseous regulator tubes, such as tube type 0A3, are designed to operate within a range of only approximately five milliamperes to thirty milliamperes. These tubes will regulate at only one fixed value of voltage, such as 150 volts; such tubes, therefore, are inflexible. Where the voltage to be regulated is higher than approximately 150 volts, resort must be hadto two or more of such tubes in series. It is evident, therefore, that the number of tubes necessary for regulation of high voltages becomes prohibitive.

Pursuant to this invention, the voltage regulator com-v prises a diode electron discharge device including an evacuated substantially gas-free envelope containing concentrically positioned cylindrical electrodes and a means for producing a magnetic field to control the current between said electrodes. By making the strength of the magnetic field equal to or substantially equal to the cut-0E value corresponding to the value of voltage to be regulated, the electron discharge device has a voltage-current characteristic which is substantially flat over a very wide range of current. This device, ftherefore, serves as an excellent voltage regulator over a wide current range.

The strength of the magnetic field may be readily varied, as by varying the current flow in an electromagnet surrounding said discharge device, to the cut-oif value corresponding to any voltage. In this way the regulator is capable of regulating satisfactorily over a wide range of voltages.

In the drawings:

Fig. l discloses an embodiment of the voltage regulator tube according to the invention;

Fig. 2 illustrates a modification or the field structure of the tube of Fig. 1;

Referring to Fig. i, one form of regulating device embodying the subject invention comprises an electron discharge tube ll having an evacuated glass envelope 10, which may be a miniature envelope, such as the T5% envelope, from which substantially all of the gases have been removed. This tube may include a getter for insuring the absorption of whatever gaseous vapors may still remain inside the envelope after sealing. A cylindrical indirectly-heated thermionic cathode H is positioned within envelope it) with its longitudinal axis coincident with the longitudinal center line of said envelope. The cathode is supported by lead wire 12 soldered at one end of the cathode, as shown in Fig.1. A conventional heater is mounted inside cylindrical cathode Ill, the ends l3 and 13' of said heaterbeing securely fastened to lead wires 14; and N, as shown in Fig. l. A cylindrical anode 16 is concentrically positioned with respect to cathode 11 and is supported, by lead wires 15 and 15 soldered thereto. Mica spacers l7 and 17' serve to properly space the anode and cathode within said tube. These spacers have slits into which tabs 18 on cylindrical anode 116 are inserted. Cathode 11 is inserted in a circular aperture in the center of said spacers. The length of the cathode and anode is dependent in large part upon the dissipation required of the tube. The ratio of the anode radius to the cathode radius should be greater than 2.023. The lead wires are brought out to pins 19 extending through a glass header seal externally of the tube base, as clearly shown in Fig. l.

The tube is adapted to be inserted in a standard sevenprong miniature socket 2d fastened to a chassis or other support Ill by eyelets 22 or any'other appropriate fastening device. Surrounding the electron discharge tube l is a hollow cylindrical permanent magnet 23 which may be made of steel or any other. magnetic material having a high remanence. This magnet is adapted to provide an axial magnetic field parallel to the longitudinal axis of tube 1. Magnet 23 is secured to the chassis or support 21 by screws 24 or byany other fastening means which will mount the magnet in its correct position. The regulator tube 1 may be quite small; for example, for 300 volts, a cathode 0.2 centimeter in diameter and an anode 0.5 centimeter in diameter can be used with a field of 550 gauss. v i

If it is desired to maintain constant a different value of voltage across the tube 1, magnet 23 may readily be replaced by another magnet of diiierent field strength merely by removing screw 24 from the chassis 21.

In Fig. 2, a modification of the magnet in Fig. l is kept constant.

shown. The field-producing means of Fig. 2 is an electromagnet 23 having a core 24 upon which a winding 25 is wound. When weaker fields are satisfactory, portion 24 may be a supporting spool or form made of any desired material upon which coil 25 may be wound.

As is well known in the art, electrons traveling from cathode to anode in a diode having a magnetic field perpendicular to the electric field existing between cathode and anode follow quasi-cycloidal paths in a plane normal to the magnetic field.

If no magnetic fields were present, the electrons would move directly from the cathode to the surrounding anode, as shown in curve a of Fig. 5. As the magnetic field is increased, the electrons proceed to the plate in a curved rather than a direct path, as shown in curve b of Fig. 5. If the magnetic field is sufficiently strong, the electron orbits miss the anode completely and return to the cathode in an epicycloidal path of relatively small diameter. This condition of zero current is illustrated by curve d of Fig. 5. At a critical value of field strength, the electron orbits just reach the anode before returning to the cathode, as shown in curve c of Fig. 1. This critical field is called the cut-off field.

From zero magnetic field to cut-off, the current in the tube is substantially constant, provided the voltage is This substantially constant value of current is determined by the space charge limitation. At

- cut-off the current drops from a substantially constant value to zero and, for fields above cut-off, the current is substantially zero. The variation of current passed between the cylindrical diode at constant voltage as a "function of the magnetic field is shown in Fig. 6. As the voltage is progressively increased from En. to El: and thence to Be, it will be seen from Fig. 6 that the current for a given magnetic field strength B increases.

The variation of current in this diode with voltage at constant magnetic field is also of interest. The curves of Fig. may also be used to explain the effect of voltage on current flow. Assuming a constant magnetic field for small voltages, the electron orbits will all be bent around by the magnetic field and will return to the cathode, as shown in curve at of Fig. 5. The current is therefore zero. As the voltage between anode and cathode increases, a critical or cut-off value is reached at which the electron orbits just reach the anode, as shown in curve c of Fig. 5.

The relationship between the magnetic field at cut-off Be and the voltage Ec between cathode and anode, in terms of cathode and anode radii re and n, respectively,

is given as e r, 5 9 a l -(z) where e is a charge on the electron and m is the electron mass.

The curve of voltage as a function of magnetic field at cut-off is a parabola, as shown in Fig. 7. The portion to the left of curve 40 is the region of current flow, while the area to the right of said curve is a cut-off region. If a constant voltage Eb is desired, the magnetic field is adjusted to a value Bb, as shown in curve 40 of Fig. 7, at which current just starts to flow. If the voltage is increased to Be, a stronger field Be will be necessary to obtain the cut-off condition; similarly, the cut-ofi field for a voltage E. is reduced to a value Ba. For operation at or near cut-off, a current-voltage characteristic, as shown in Fig. 8, results. The group of curves shown in Fig. 8 represents the variation of anode current of the electron discharge device 1 with anode voltage for different values of magnetic field intensity. Referring to curve 60, the lower and upper current limits for operation as a voltage regulator are shown as I1 and 1:, respectively. Eificient use of this tube as a voltage at which the characteristic ceases to be linear) be at a minimum and that the change in voltageAE be small for large values of Al.

The actual cut-off voltage E0 is somewht lower than the theoretical or projected cut-off voltage Ep- This results from various causes. For instance, it is impossible to the axis of the tube electrodes. Other causes for the knee of the characteristic of Fig. 8 are divergence or fringing of the field at the ends of the electrode structure and the collision of electrons of unequal velocity moving in different paths. These effects, however, are quite small and may be materially reduced by proper and careful design so that the knee 'of the characteristic, and consequently I1, may be reduced. In Fig. 8, the curve 61 illustrates the relationship between the voltage and current when the cut-off magnetic field Be is higher than the value obtaining for curve 60, while curve 62 illustrates the characteristic for lower values of cut-off magnetic field Be. The ratio for contemporary gaseous regulators, such'as the tube types 0A2, 0A3, 0R2, etc., is approximately five. Ratios of Al to I1 far in excess of present gaseous regulators may be obtained by use of the tube of the subject invention.

Referring to Fig. 3, the regulating device 1 is shown connected between a power supply 50 and a load circuit 51 across whose terminals a constant voltage is .desired. One terminal of power supply 50 is connected by a lead 52 through a series resistor 55 to the anode 16 of tube 1. The negative terminal of power supply 50 is connected directly to cathode ll of tube 1 via lead 53. Resistor 55 may, of course, be connected to lead 53 instead of lead 52, if desired. The terminals of load 51, across which a constant voltage is required, are connected directly across the diode .1, as shown in Fig. 3. If the supply voltage decreases, the regulator tube impedance increases, therebydecreasing the regulator tube current and the voltage drop across resistor 55. Likewise, an

shown in Fig. 4.

One terminal of coil 25 is connected to one end of a potentiometer 30. A source of unidirectional current, such as a battery 31, is connected across the ends of said potentiometer. The cathode 11 and anode 14 are connected to the terminals of power supply 50 in series with a resistor 55, just as in Fig. 3. The load circuit 51 is connected directly across electrodes 11 and 14 of tube 1, as in Fig. 3. A milliammeter 35, connected as shown in Fig. 3, serves to indicate substantially the attainment of the cut-off condition and the tube current during oper' ation.

If it is desired to change the regulated voltage from E. to a higher voltage Eb, as shown in Fig. 7, it is necessary, in order to maintain a condition of cut-off requisite for a fiat voltage-current characteristic, that the field strength B be increased from Ba. to Be. By varying the potentiometer 30, the current flowing in coil 25 and, consequently, the magnetic field strength may be increased to the desired value. If, for example, it is desired to maintain the voltage across load 51 constant at voltage Eb instead of at El, the power supply voltage is boosted and the arm 29 of regulator requires that I! (that is, the current at the point 7 potentiometer 30 is moved until meter 35, connected in the cathode-anode circuit of tube 1, indicates a current somewhere within the range of current 11 to Is, preferably at or near the midpoint of this range. The values I1 and I2 may be determined once the curve of anode voltage versus anode current of the magnetron has been obtained. Such an adjustment permits operation over the linear portion of the anode voltage versus anode current curve of Fig. 8 for all values of power supply voltage ranging from the minimum to the maximum values which may be encountered during voltage deviations of the power supply.

The magnetic-electron regulator tube according to the imention otters several advantages over existing regulator tu es.

Provided the limitations of electron transit time are not exceeded, the response of the regulator tube to rapid fiuc-' tuations or transients is quite rapid. Since this tube is free of gas and the consequent slowly moving ions, the tube has little or no' hysteresis. Because of the rapid response and absence of hysteresis the tube may be accommodated to applications which cannot be handled satisfactorily by gaseous tubes. Among these applications are pulse clipping and peak regulation of voltage transients. This tube may be used as a shunt regulator of power supply voltages to provide a greatly improved'atteriuation of voltage ripple at high frequency, such as 400 cycles or higher.

This tube does not require ignition and therefore the need for high-source voltages is eliminated. Since the tube is free of gas, the problem of absorption of gases by the tube structure is obviated and the voltage-determining parameters remain substantially constant, thereby insuring long life and stability of operation.

This tube may be designed to operate at less than 100 volts up to as high a voltage as desired. The range in current is limited only at the lower end where difliculty may be experienced in obtaining suitable characteristics in the microampere region.

Over at least some of the voltage-current regionsthe size of this regulator may be made smaller than the present regulators. For example, a 5,000-volt regulator may have an anode diameter of only one centimeter and a cathode diameter of 0.25 centimeter and would require a field of approximately 1,000gauss, while the 300-volt tube would require only 550 gauss for an anode diameter of 0.5 centimeter and a cathode'of 0.2 centimeter.

This invention is not to be limited to the specific tube and circuits shown and described. For example, the use of subminiature tubes is possible over certain voltage ranges. The magnetic field structure may take forms other than shown in the drawing, such as a winding enclosed within said tube envelope. It is also possible to make the envelopes themselves of magnetic materials, thereby considerably rediicing the size of the regulator. The resistor shown in Figs. 3 and 4 of the drawings may be replaced by an impedance, such as a condenser or other desired circuit arrangements. It is also possible to connect two or more regulator tubes in series to provide regulation at higher voltages.

What is claimed is:

1. A voltage regulating apparatus comprising an electron evacuated discharge device including only an electron source comprising an electron emitting electrode and an electron collecting electrode, means associated with said device for-producing an axial magnetic field, a resistor connected to one of said electrodes, a source of voltage applied between said electrodes in series with said resistor, the strength of said magnetic field being substantially equal to the cut-off value for the desired voltage to provide a substantially constant voltage between said electrodes over a wide range of current and voltage, and a load circuit across which said constant voltage is desired connected across said electrodes.

2. A voltage regulating apparatus comprising an electron evacuated discharge device including only an electron source comprising an electron emitting electrode and an electron collecting electrode, electromagnetic means surrounding said discharge device and energized by an adjustable source of unidirectional control voltage for producing an axial magnetic field, an impedance connected to one of said electrodes, a source of voltage applied between said electrodes in series with said impedance, the strength of said magnetic field being substantially equal to the cut-off value for the desired voltage to provide a substantially constant voltage between said electrodes over a wide range of current and voltage, and a load circuit across which said constant voltage is desired connected across said electrodes.

3. A voltage regulating apparatus comprising an electron discharge device including only a cylindrical anode and a cathode concentrically arranged in an evacuated enclosure, means surrounding said device for producing an axial magnetic field, a resistor connected to one of said electrodes, a source of voltage applied between said anode and said cathode in series with said resistor, the strength of said magnetic field being substantially equal to the cut-off value for the desired voltage to provide a substantially constant voltage between said anode and said cathode over a wide range of current and voltage, and a load circuit across which said constant voltage is desired connected across said electrodes.

4. A voltage regulating apparatus comprising an electron discharge device including only a cylindrical anode and a cathode concentrically arranged in an evacuated gas-free enclosure, means surrounding said device for producing an axial magnetic field, a resistor connected to one of said electrodes, a source of voltage applied between said anode and said cathode in series with said resistor, means for adjusting the strength of said magnetic field substantially to the cut-off value for the desired voltage to provide a substantially constant desired voltage between said anode and said cathode over a wide range of current and voltage, and a load circuit across which said constant voltage is desired connected across said electrodes.

5. A voltage regulating apparatus comprising an electron discharge device including only a cylindrical anode and a cathode concentrically arranged in an evacuated gas-free enclosure, an impedance connected to one of said electrodes, a source of voltage applied between said anode and said cathode in series with said impedance, an electromagnet including a coil surrounding said device for producing an axial magnetic field, means for variably energizing said coil to adjust the strength of said magnetic field to the cut-ofi value for the desired voltage to thereby provide a substantially constant voltage between said anode and said cathode over a wide range of current and voltage, and a load circuit across which said constant voltage is desired connected across said electrodes.

References Cited in the file of .this patent I UNITED STATES PATENTS 1,548,952 Mills Aug. 11, 1925 2,352,231 Stratton June 27, 1944 2,624,867 Cobine Jan. 6, 1953 FOREIGN PATENTS 627,335 Germany Mar. 13, 1936