US2847638A - Voltage regulator - Google Patents

Description

12, 1953 D. A. WILBUR ETAL 2,847,638

VOLTAGE REGULATOR Filed May 27, 1954 2 Sheets-Sheet 1 Fig]. 2

,J VOLTAGE LOAD SOURCE CURRENT In ve r7 tors 0o na/d 14. M/i/buf,

hi/0b H. Peters, Jr.

Aug. 12, 1958 D. A. WILBUR ET AL ,6

VOLTAGE REGULATOR Filed May 27, 1954 2 Sheets-Sheet 2 :7 vomms sat/Rae'- LOAD VOLTAGE LOAD SOURCE VULTH 65 SOURCE II) V en tors: Dona/d A. Wi/bu r, hi/l}? hf Peter; J11,

b 7 4. f eir Attorney- United States Patent VOLTAGE REGULATOR Donald A. Wilbur, Albany and Philip HrPeters, :lrqSchenectady, N. Y., assignors to General Electric Company, a corporation of New York Application May 27, 1954, 'se'rial No. 432;634 Claims. (Cl. 323-29) This invention rel-ates Ito voltage regulators utilizing an oscillator.

Diode devices-are often employed to regulate theciut- :put'volt'age'of a rectifier or other direct current voltage supply and may contain an ionizable gas. The degree of ionization 'varies with the-voltage impressed across the diode so that when the diode is connected across therectifier o'utput terminals, "any tendency of the voltage to increaseuesults in an in'crease'd current flow through the ition, the gaseous type regulator generally requires a startsingvolta'ge higher than the operating voltage o f'the source which it 're'gula'tes.

It is an=object of thi's invention -to. provide an-iinp'roved voltage regulator.

It is a further object of this invention to provide a woltage iregul'ator having a voltage-current characteristic which is stableover wide temperature ranges and with :respeotito a wide range of' ripple frequen'cie's.

.:It is a further object of this invention 'to -provide'an -improved voltage regulator employing a diode discharge device "having a readilyadjus'table voltage regulating level.

in accordancewith' this invention a magnetron oscillator is connected across the terminals'of a voltage sup .ply having :a resistor :in series therewith. Due to the low dynamic resistance 'of the magnetron os'cill'ator When unloaded it operams very effectivelyes adiode regulator. As is well known, the anode tocatho'de voltage required to :start and sustain oscillations is determined by the oscillating frequency, the physical geometry of the magnetron device and'the magnetic fieldstrength. By varying the magnetic field strength or the frequency of oscillatiomthe magnetron operating voltage and hencethe regulating level is readily varied over awide range of values.

The novel features which are believed to be charac'teristic of the invention are set for'th 'With particularity in the appended claims. The invention itself, however, together with "further objec'ts and advantages thereof can best be -understoo'd byreference to the following descripticn taken in connection with the accompanying drawings in which :Figure 1 represents a basic regulating 'circuit incorpora'ting our invention. Figure 2 is a curve of the variation of :direct current voltage as a function of direct current for atraveling Wave magnetron; Figure 3 is aperspe'ctive view of atype of magnetron which may be employed in the circuit'of Figure 1'; Figure 4'illustrat'es a differential connection for magnetron voltage regulators; Figure 5 illustrates a parallel connection for magnetron voltage regulators; Figure 6 illustrat'es a cascade connection fo'rniagnetron voltage regulators; and'Fi'gure 7 illusice trates a modified magnetron voltage regulator circuit "having feedback m'eansfor'varying .the magnetron magnetic field. g Figure lshoivs terminals 1 andlconneeted to direct current voltage source 3. Source 3.rnay be 'a rectifier "subject 'to ripple or other'voltagefluctuations. .-A regusource voltage is divided between resistorjd anc l-load 5.

The resistor4 may'also be considered tofin clude the internal resistance of the 'voltage'source. The regulator fiis a traveling wave magnetron having an elongated thermionic cathode 7 "connected to the negative terminal 1 and'a split'a'node 8 eonn'ectedto'the positive terminal 2. Forsirnplicity of illustration, the magnetron anode 8 is sem i scheniatically illustrated 'as having two segments Which'surround "cathode 7 to form a cylindricalspace charge chamber. An 'iinloaded resonant output circuit 9'is connected between the anode segments. Solenoid ;"10 provides an axially directed magnetic field through -the space chargefichamber. Theterminals .of solenoid 10 are connected to an adjustable direct current ivoltage source "11. A suitable source 'of "heater current1 2 is connected to cathode 7. I v

The magnetroni's operated 'as a conventionaltitraveli-ng wave type with the'direct current radialelectric fielda-nd the axial magnetic field in the space charge chamber acting upon the-electronic space chargeso thatitassumes an average angular velocity about the cathode. When the electronst'ravers'ing a gap'between adjacent anode segments are in'phase with the fringing .alternatingelee tric field between the segments they reinforce the oscilbut the resonant outputcircuit, beinggunloaded.;substantiaIly'fiXe's the'ope'rating frequency so that once the oscillations established by the initial excitation .of the tuned circuit 9'by giving up part of their kinetic energy to the alternating "electric field. Upon losing some of their energy the electrons move toward the anode ,to regain energy, being eventually collectedthere. In this Way the space'charge envelopeis caused to assume a spoke-shaped form, each spoke corresponding to a region of insphase electrons having aniaverage angul'ar'velocity synchronous with the;high frequency electric field of the anode assembly. This is customarily terr'ned 1r mode e utitation.

An increase 'inthe applied radial electricifield tends to increase the average angular velocity 'abovei synchronisin,

lation threshold is reached, a 'further increase in the applied voltage between the anode-and cathode results only'ina larger electron directcur'rntbeing collected at the anode.

Atypical characteristic curve of direct current voltage as a function of direct "current for a traveling wave type magnetron 'is shown in Figure 2 as substantially flat for currentvalues above 'the knee of the operating curve. The voltage drop across the magnetron is substaiitially constant over a wide range of c urrentthrough the magnetron so that whenop'erating above the knee of the curve the dynamicres'istance of themagnetron diode may be'consider'ed to be very low. The dynamic resistance of a device ma be defined'as the quotientcf an incremental change in volitage across the device divided by theresulting incremental change .incurrent through the device and may also be defined by'the ex pression .Dynamic resistanc The magnetron is designed, as is conventional, so as not to be emission limited Since the oscillation threshold occurs at the knee of the curve and is dependent upon the ratio of the radial electric field mine axial 3 magnetic field, the magnetic field density may be adjusted by varying the voltage of the source 11 to adjust the magnetron operating level. The operating voltage may also be varied by changing the resonant frequency of the output'circuit 9. In orderto maintain a low value ofdynamic resistance; the output circuit 9 is tuned and broadening of its tuning is prevented by maintaining a the output circuit unloaded It may beseen, by referring to Figure 1, that when the voltage of the source 3 tends to rise to a value above the knee of the curve of Figure 2, the magnetron current increases very rapidly, thereby increasing the current through the resistor 4. The increased current through resistor 4 increases the voltage drop across resistor 4 and tends to maintain a nearly constant voltage across terminals 1 and 2. Since the magnetron oscillation frequency is in the order of megacycles, the magnetron dynamic resistance remains essentially constant 'over a frequency range from zero cycles per second up to frequenciesin the order of megacycles per second. At high frequencies the sharpness of tuning of the output circuit no longer will allow the anode current to build up in the same ratio to the anode voltage as it does at lower ripple frequencies so that the curve of Figure 2 is no longer substantially flat. In this respect, the magnetron voltage regulator is superior to the conventional :gas diode in which the dynamic resistance usually increases rapidly to a very high value at only a few hundred cycles per second. Therefore, no bypass arrangements are necessary to accoimmodate high fre quency voltage source changes.

The magnetron reaches its operating voltage smoothly without requiring a breakdown from a higher voltage. The long time stability of the magnetron regulator is also superior since, as a high vacuum device, it is not subject to changes of gas conditions as may occur in gaseous regulators or is it sensitive to temperature variations. Furthermore, the regulating level can easily be adjusted over a wide range by changing the density of the axial magnetic field.

Figure 3 shows a miniature type low cost magnetron which may be suitably employed as the magnetron 6 of Figure 1. This magnetron is of the interdigital type having two interleaved sets of anode vanes which are connected by an inductive metal loop. The loop and any vane-to-vane capacity form an internal tank circuit. For details of constructional features of small low cost magnetrons of this general type, reference is made to U. S. Patent 2,617,956, issued November 11, 1952 to L. U. Hamvas and assigned to the assignee of the present invention.

metal disks or rings 16 and 17 spaced in parallel planes along a common axis transverse with the lengthwise axis of the tubular envelope. Each of the annular disks or rings has a similar plurality of digital projections which are bent to extend in an axial direction towards the opening in the opposite anode ring. In the example shown, the anode ring 16 has a set of four such equally spaced projections 19 which are interleaved with but spaced from the corresponding set of four projections 18 integral with the other anode ring 17. These projections are the anode vanes or segments and define a substantially cylindrical space charge chamber between their inner surfaces. An insulating spacer disk 20, constructed of a suitable insulating material such as mica, is secured to the outer surface of the anode ring 16, preferably by 4 tabs, and is apertured to receive and support the free ends of the vanes 18 extending from the opposite anode ring 17. A similar disk 21 is secured to the anode ring 17 and is similarly apertured to receive and support the ends of the anode segments 19. This construction permits the desired equal spacings between the adjacent anode segments to be maintained.

A cylindrical cathode sleeve 22 is axially positioned in insulating relation with the anode segments 18 and 19 by central openings in the spacer disks 20 and 21 through which the cathode ends extend. The cathode sleeve, which is suitably made of nickel, is coated with a thermionically emissive substance, such as barium oxide, which emits electrons when heated by element 23 positioned within the cathode sleeve to provide the magnetron space charge. The right-hand end of the cathode sleeve is preferably closed to reduce heat losses by radlation and is conductively supported by a lead-in conductor 24. The ends of the heater are brought out through the open left-hand end of the cathode sleeve and are suitably welded to the internal ends of lead-in conductors 25 and 26.

The resonant output circuit for the magnetron is provided by a conductive loop 27 having its ends attached to the anode end rings 16 and 17. In the device of Figure 3, this loop is positioned within the envelope and made of a relatively stiff conductor extending toward the base of the device. A lead-in conductor 28 is welded or otherwise firmly secured to the midpoint of loop 27 to support the electrode assembly and provide a direct current anode connection. No high frequency anode coupling means or terminals are required since the output circuit is preferably unloaded to keep the dynamic resistance between the anode and cathode at a minimum value. It is to be understood that while the loop 27 has a small inductance, which is all that is needed for the high operating frequencies for which magnetrons of this type are customarily designed, the output circuit may be provided with additional turns for greater inductance as may be desired for lower frequency operation or with means for varying the inductance.

The device is conventionally evacuated and sealed. An inductive loop including a strip 29 is supported from one of the lead-in conductors. A suitable getter such as barium is placed on strip 29. After the final evacuation and sealing of, the envelope, the loop may be excited by induced high frequency energy to heat and vaporize the getter material and thus absorb any residual gases remaining in the envelope.

Also shown in Figure 3 is an annular permanent magnet 30 surrounding the envelope 13, the magnet being notched and magnetized to define the dissimilar poles poles facing opposite ends of the space charge chamber. Electromagnetic means may, of course, be alternatively or additionally provided for establishing the axial magnetic field in the space charge chamber.

It is to be understood that various other types of magnetron constructions may be employed in arrangements embodying our invention. For example, a traveling wave magnetron having an anode block with cavity resonators incorporated therein may be employed. The hole and slot type of cavity resonator is a typical arrangement in this type of construction, the anode segments defined between adjacent slots being interconnected by the material of the anode block; therefore, no output coupling means is necessary if a cavity resonator type of magnetron is utilized as a voltage regulator.

While magnetrons may readily be designed for operation at relatively high direct current voltages, it may be more convenient where a low voltage is to be regulated or where the size of available magnetrons does not permit operation at a desired low voltage, to utilize two differentially connected magnetrons. Figure 4 shows a first dropping resistor 4 and magnetron 6, series connected, as in Figure 1, across the output termmal' set the voltage source 3 and a seconddropping resistor 4' and a'second magnetron '6' connected across the outputterminals -ofsource 3. The magn etrons have. different operating characteristics .or are provided with different magnetic field strengths in their space charge chambers so that they have operating voltages differing 'by the desired output voltage.

The'load circuit is connected to the respective output circuits of the two magnetrons for low 'voltage operation. tltirnay also beseenthatrbyavarying the operating voltage of one or .bothmagnetrons, the differential output voltage may not only be reduced 'to zero but its polarity may tbexreversed ..as may be desired for certain applications.

It is to be understood that two or more magnetrons may be operated in parallel so that their combined dynamic impedance or resistance is decreased, thus providing a curve of voltage as a function of current having a lesser slope than the slope of the curve shown in Figure 2. Figure 5 illustrates, by way of example, a circuit arrangement utilizing parallel operated magnetrons. Likewise, a number of magnetron regulators may be operated in cascade, as illustrated in Figure 6, with each cascade unit having its own voltage dropping resistor 4 and 4' respectively. In Figures 5 and 6, components which are similar to those in Figures 1 and 4 are identified by the same reference numerals.

The magnetron regulator may be made more sensitive to changes in the voltage source and to changes in the load by passing the anode current through a solenoid so positioned that it decreases the axial magnetic field in the magnetron as indicated in the circuit of Figure 7. Here, as in Figure 1, a magnetron 6 is connected with its output circuit 9 through a resistor 4 to the terminals of a voltage source 3 to be regulated. The magnetic field provided by a solenoid 10 is adjusted to provide the desired normal magnetron operating voltage. A first auxiliary solenoid winding 31, which is positioned to produce a magnetic field aligned with that produced by the solenoid 10 is connected in series between the magnetron 6 and the voltage source 3. The solenoid 31 is connected so as to decrease the total magnetic field when the anode current increases. The solenoid 31 is connected between the anode output circuit 9 and the dropping resistor 4. A second solenoid 32, also positioned to oppose the flux of the solenoid 10, is connected in series with the load 5, the load circuit being connected across the magnetron but not including the solenoid 31.

Solenoid 31 has the effect of decreasing the slope of the characteristic curve of Figure 2 so that the operating voltage is very little higher at high current values than the voltage at the knee of the curve. Thus, when the voltage of the source 3 increases, as may be caused by a voltage ripple, the magnetron draws more current and increases the voltage drop across the resistor 4. At this high value of current the voltage across the magnetron tends to increase. The increased current through the solenoid 31 results in a decrease in the total magnetic field through the magnetron space charge chamber. Accordingly, a lesser electric field is required for oscillation, and the voltage across the magnetron tends to decrease so that the over-all curve of voltage as a function of current tends to be flatter for current values above the knee of the curve. In a like manner, a change in the load current has a similar effect in that an increase in load current in solenoid 32 lowers the magnetic field and results in a flatter over-all curve of voltage as a function of current.

From the foregoing, it is to be seen that in accordance with our invention a traveling wave type magnetron is very effectively employed as a voltage regulator device in various voltage regulating circuits. It operates very effectively to regulate voltages over a wide frequency range of voltage fluctuations and the regulating characteristics are substantially independent of temperature. The

magnetic field strength can readily be adjusted to change the operating voltage to any desired value over a wide range. 'The changes in-the anode current drawn by the magnetron as a regulator cause very little change in the operating voltage, particularly so long as the magnetron output circuit is unloaded andthe radio frequency power generated bythe magnetron is not externally dissipated.

'Wliile the present inventionhas been described by reference to particular embodiments thereof,it will be-understood that numerous modifications may be made by those skilled in the art without departing from the invention.

What'we claim as new and desire to secure by Letters Patent 'of the United States is:

I. A voltage regulator comprising'a source ofvoltage to be regulated, a magnetron discharge device having a cathode and an anode electrode, a resonant output system including said anode electrode, means for producing a magnetic field along the space between said anode and cathode, an impedance, means coupling said cathode and said anode respectively through said impedance to said voltage source to produce an electric field between said cathode and said anode and operate said magnetron at the resonant frequency of said output system whereby the low dynamic resistance of the magnetron causes a large current change therethrough corresponding to relatively small voltage changes in said source to obtain a regulated voltage across said discharge device having a magnitude determined by the strength of said magnetic field and the resonant frequency of said output system.

2. A voltage regulator comprising a source of voltage to be regulated, a magnetron discharge device having a cathode and an anode, an unloaded resonant output system including said anode, means for producing a magnetic field along the space between the cathode and anode, an impedance, means coupling said cathode and said anode respectively through said impedance to said voltage source to provide an electric field between said cathode and said anode and operate said magnetron at the resonant frequency of said output system whereby the low dynamic resistance of the unloaded oscillating magnetron causes a large current change therethrough corresponding to relatively small voltage changes in said source to obtain a regulated voltage across said discharge device having a'magnitude determined by the strength of said magnetic field and the resonant frequency of said output system.

3. A voltage regulator comprising a source of direct current voltage to be regulated, a magnetron discharge device having a cathode and an anode, an unloaded resonant output system including said anode, means for producing a magnetic field along the space between the cathode and anode, an impedance, means coupling said cathode and said anode respectively through said impedance to said voltage source to provide an electric field between said cathode and said anode and operate said magnetron at the resonant frequency of said output system whereby the low dynamic resistance of the unloaded oscillating magnetron causes a large direct current change therethrough corresponding to relatively small voltage changes in said source to obtain a regulated direct current voltage across said discharge device.

4. Means for regulating the voltage between a pair of terminals comprising a first magnetron oscillator including an anode, a cathode, and a first unloaded resonant output circuit including said anode, a voltage dropping impedance means for coupling a source of direct current energy to be regulated across said first magnetron oscil lator through a voltage dropping impedance to produce an electric field between said cathode and said anode and operate said magnetron oscillator at the resonant frequency of said first output circuit, a second magnetron oscillator including an anode, a cathode and a second unloaded resonant output circuit including said anode, a second voltage dropping impedance, and means for coupling said second magnetron across said first magterminals comprising, a first magnetron oscillator including an anode, a cathode and a resonant output circuit including said anode, means for producing a magnetic field along the space between said anode and cathode, an impedance, means for coupling a source of energy to be regulated to said first magnetron through said impedance to produce an electric field between said cathode and said anode and operate said magnetron at the resonant frequency of said output circuit, a second magnetron oscillator including an anode, a cathode and a resonant output circuit, a second impedance, said second magnetron oscillator being coupled across said first magnetron oscillator through a second impedance to obtain a regulated voltage output.

References Cited in the file of this patent UNITED STATES PATENTS 2,750,555 Kather et al June 12, 1956 FOREIGN PATENTS 169,889 Great Britain Oct. 13, 1921 627,335 Germany Mar. 13, 1936

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