US3702969A - Power supply circuit for continuous-wave magnetron - Google Patents

Power supply circuit for continuous-wave magnetron Download PDF

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Publication number
US3702969A
US3702969A US179384A US3702969DA US3702969A US 3702969 A US3702969 A US 3702969A US 179384 A US179384 A US 179384A US 3702969D A US3702969D A US 3702969DA US 3702969 A US3702969 A US 3702969A
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Prior art keywords
coil
magnetron
voltage
alternating current
source
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US179384A
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Jean Paul Maillot
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Alcatel Lucent NV
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International Standard Electric Corp
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Assigned to ALCATEL N.V., DE LAIRESSESTRAAT 153, 1075 HK AMSTERDAM, THE NETHERLANDS, A CORP OF THE NETHERLANDS reassignment ALCATEL N.V., DE LAIRESSESTRAAT 153, 1075 HK AMSTERDAM, THE NETHERLANDS, A CORP OF THE NETHERLANDS ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: INTERNATIONAL STANDARD ELECTRIC CORPORATION, A CORP OF DE
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/66—Circuits
    • H05B6/666—Safety circuits
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
    • H02M7/02—Conversion of AC power input into DC power output without possibility of reversal
    • H02M7/04—Conversion of AC power input into DC power output without possibility of reversal by static converters
    • H02M7/06—Conversion of AC power input into DC power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B9/00—Generation of oscillations using transit-time effects
    • H03B9/01—Generation of oscillations using transit-time effects using discharge tubes
    • H03B9/10—Generation of oscillations using transit-time effects using discharge tubes using a magnetron

Definitions

  • a power supply circuit for a continuous wave magnetron provides selectively adjustable microwave power levels that are stable at each level.
  • the unregulated direct voltage supplied to the magnetron cathode is combined with an additional voltage derived from a common alternating current source to provide a total direct current which passes through the electromagnet coil of the magnetron. Variations in the power source are compensated by the variations of the added current in the coil to provide stable magnetron power at each level.
  • the circuit providing the added current to the coil includes a simple rectifier, filter, zener' diode and series resistor arrangement with a switch for selecting different diode, resistor and voltage combinations.
  • Continuous-wave magnetron operation is in noway different than other pulsedmagnetron operations such as, for example, those used in radar.
  • needs for. obtaining high continuous power under economical conditions require a specific technology and, particularly, a specific mode for generating high voltage and induction fields which control the magnetron current and consequently the microwave power.
  • microwave power which is adjustable and stable for each adjustment.
  • Some presently known power supply devices permit varying the available microwave power in discrete stepped levels, but none provides satisfactory results as far as simplicity, device reliability or power stability. at each level are concerned.
  • I lr(V-bB) 1) in this formula: I is the magnetron current intensity, V is the high voltage,
  • r is the internal dynamic resistancewhich is. of some tens of ohms, and b is very large, which means that a small variation of B causes a large variation on I, V being constant.
  • B may be said to be acting, like the grid voltage in a high slope triode.
  • the applied electric power is:
  • V and/or B will permit adjustment of P, and consequently P,,,, in a predetermined manner.
  • the induction B may be provided by a permanent magnet.
  • B is steady and P,,, canvary only if the high voltage V is varied.
  • the supplied power, for a predetermined adjustment of V, is very sensitive to instabilities of V.
  • V is generated by an ac. source whose current is rectified by well known means.
  • the need for simultaneously being able to adjust Pm by discrete levels and for good regulation of each level generally requires complex and costly power supply devices which often use a saturated-current transformer. This precludes varying V and Pm, in a continuous manner.
  • an electromagnet for generating B, an electromagnet is used which has a. coil traversed by a current I
  • B may be assumed to be proportional to the magnetic field created by the coil, or proportional to the current I
  • the formula (1) may be then written:
  • I 1/r(Vr I V/r-aI (3) Taking into account the rapid variations of I with I r /r a is a coefficient substantially higher than 1.
  • Pm can be adjusted very simply by continuous or stepped variations of the current 1 V being steady). 1 is generated by a source of relatively low voltage V, obtained after having rectified the source of alternating current. If, for a predetermined adjustment, V and V, are subject to the same relative variations, equal to those of anac. source of voltage U, a simple calculation shows that:
  • a part P of the magnetron current I is used as current 1,
  • the properly sized coil is electrically connected between the tube anode and the ground.
  • An adjustable resistor is mounted in parallel across the coil and permits variation of p and consequently of the power Pm within a particularrange.
  • V is constant
  • the power Pm is regulated by variation of p.
  • the maximum power corresponds to the minimum value of p and the minimum power to the value p l. in this last case, a shunt resistor is suppressed.
  • the current 1, will usually be produced by a source of rectified voltage V, supplying a resistor R connected in series with the coil of resistance R
  • the calculation shows that l is given by the formula:
  • V and R are constant, or R with V and V,, being constant, or V, and R simultaneously with V being constant, results in a continuous variation or in discrete levels, of Pm from a maximum value to a very low value.
  • V and V are supplied by an a.c. source after rectification. If, for a predetermined adjustment, they are subject to the same relative variations, still equal to those of an a.c. source of volt-age U, a calculation using the formula (6), shows that:
  • a purpose of the present invention is to provide an additional source of current that is added to the magnetron current in the induction coil, such that for each setting of the voltage of the additional source there is a corresponding value of delivered microwave power which is substantially independent of the instabilities of the common a.c. power source or of the magnetron power supply high voltage and of those of the additional source voltage.
  • the circuits associated with the additional source are designed so that, for each adjustment of the voltage thereof, or of the associated circuits and of the microwave power Pm, the effects of the instabilities of the high power supply voltage V are compensated by those of the instabilities of the additional source to maintain Pm stable.
  • the additional source of voltage V is replaced by a source of voltage V, having an output connected to a non-linear circuit comprising in series an element of very stable counter electromotive force (c.e.m.f.) E and very low internal resistance, a resistor R and the induction coil.
  • V is given by the relation V, V, E,,.
  • the magnetron operating at fixed high voltage V, the c.e.m.f. E the resistor Rand the magnetron current intensity I corresponding to a predetermined adjustment of the delivered microwave power are related by the formula:
  • V is equal to V, E, E,,/2 (l I E being the voltage across the induction coil terminals and I; being the intensity of the current passing through the said coil.
  • the non-linear circuit includes q identical Zener diodes and a series resistor R. Decreasing microwave power levels are obtained by successively short-circuiting one, two, three, (q-l) Zener diodes and by simultaneously lowering the voltage V, of the additional source by e,,/2, e, being the equivalent Zener diode counter electromotive force.
  • the nonlinear circuit includes a single Zener diode and q resistors in series. Increasing microwave power levels are obtained by successively short-circuiting one, two, three, (q-l) resistors while each corresponding voltage V,,' is made to vary linearly with the value of the resistance of the circuit.
  • the additional source voltage V,,' is constant and for each microwave power level a coupling circuit comprising a Zener diode and a resistor R is used.
  • the q resistors are replaced by a rheostat and the a.c. source which generates the voltage V comprises a variable autotransformer with a sliding contact, the movement of the sliding contacts of the rheostat and of the autotransformer being properly coupled.
  • the main advantage of the power supplies of the present invention is the excellent regulation of the microwave power delivered by using a non-stabilized high voltage and an additional voltage source, and consequently a reduced cost from that of power supplies used in the prior art. Only two efiicient low pass filters are required.
  • FIG. 1 shows the family of characteristics I f V, I of a continuous-wave magnetron,
  • FIGS. 3, 4 and 5 show three different embodiments of power supply circuits according to the invention.
  • FIG. 1 shows the characteristic curves of the magnetron current I with the high voltage V for various values of the current I, passing through the magnetron electromagnetic coil.
  • V constant
  • the current I decreases rapidly as I, increases slowly.
  • the applied power P VL varies from a maximum value down to a quasi-null value with a relative increase of 1,, which practically is of about 1 to 2.
  • I V/r a 1 wherein r is the internal dynamic resistor of the magnetron (of about a few tens of ohms) and a is a coefficient of a high value, for example 50 to 100. If, according to the present system, I is the sum of the magnetron current I and of a current I, supplied by an additional source, the current I depending on V and I, is given by the relation:
  • FIG. 2 shows I varying with 1,, V being constant.
  • I must always have the same direction.
  • V/rB is equal to the coil current I, which, when V is constant, remains substantially constant.
  • the selection of the winding readily fulfills this condition.
  • n is roughly proportional tO A/a. Consequently, I with other values being unchanged, is approximately proportional to d and the resistance R B varies inversely with a.
  • the additional source of voltage V is replaced by a source of higher voltage V, such that V, V,
  • E is a stable voltage corresponding, for example, to the Zener diode characteristic breakdown voltage or to a gas discharge lamp stabilization voltage.
  • Zener diodes and gas discharge lamps operate with a particular value of current intensity passing through them to provide very stable c.e.m. force sources having very'low and constant internal resistance.
  • the absolute instability AV is equal to the absolute instability AV, but the relative instability AV,/ V, is higher than the relative instability AV,'/ V, and thus than AV/V.
  • AV,'/V,' AV/V By replacing AV, in the relation (7) by AV,', V, by V, E, and AV/ V by AV,'/V,', the result is that E,, I and R verify the relation:
  • V, E E,/2 (1 1 wherein: 1 represents the coil current which is substantially constant when I is varied, and E represents the voltage R, 1, across the terminals of the coil having a resistance R Therefore E is also substantially constant.
  • the value of E is selected within the range of values of the voltage E
  • Many Zener diodes are available which permit a c.e.m. force E,to be obtained within a range of a few volts to tens of volts, and which are substantially stable as soon as the current passing through the diodes is over a predetermined value. It is also possible to connect several similar diodes in series by selecting a common Zener diode having a breakdown voltage of about 6 to 10 volts. Such Zener diodes are known to be particularly insensitive to temperature variations.
  • T1 shows the various values of R and V, for a continuous wave magnetron able to deliver, up a maximum microwave power (Pm),, from 75, 50 or 25 of (Pm all of which are regulated according to the invention.
  • the four power levels will be obtained for currents respectively equal to l, 0.75, 0.5 and 0.25 Amperes.
  • a Zener diode or a series connected Zener diode assembly has been selected having a breakdown voltage E, of about 30 V and needing a minimum current I, of 0.4 A in order to consider the internal dynamic resistance as very low and constant. Under such conditions, 1,, is substantially equal to 1.4 A and, with the resistor R being 28 ohms, E is equal to 40 V.
  • the configuration of the two sources of voltages V and V is substantially simpler than those previously used in power supplies for continuous-wave magnetron.
  • the invention is based on the fact that the two do. sources are both subject to the same relative variations as the ac. source from which they are generated. Thus, it is possible, with a large variation in the common a.c. source, to stabilize the a.c. source to a certain extent by using limited-current transformer.
  • the rectified voltages Vand V are not to be stabilized and only good filtering is necessary to eliminate the residual a.c. voltages.
  • FIG. 3 shows the circuit of an embodiment of a power supply circuit for a continuous-wave magnetron, according to the present invention.
  • the only parts of the magnetron 1 that are shown are the cathode la and the cavity-anode lb which is directly connected to the ground.
  • the negative high voltage applied to the cathode 1a is obtained from an ac. source U and a transformer 3 which is then rectified in a rectifierbridge 4 and filtered in a filter made of an auto-inductance and capacitors 5.
  • the positive terminal of the rectifier-bridge 4 is connected to the ground via the coil 2 of the electromagnet.
  • the positive additional voltage V,,' is obtained from the same a.c. source U and a transformer 6 after having been rectified in a rectifier-bridge 7 and filtered in a filter formed by an autoinductant capacitors 8.
  • the secondary of 6 is provided with several outputs: 6-1, 6-
  • a rotating switch 12 which can make contact with the taps 13-1, 13-2, 13-3 and 13-4 may put into operation, one, two, three or four of the resistors 11 from the right to the left. This provides the connections for the resistors R of the table T1. The movements of the two switches may be coupled in any suitable manner.
  • V is equal to:
  • the table T2 may be deduced as follows:
  • the set of four resistors is replaced by a single resistor 11, instead of a single Zener diode, there are four similar Zener diodes mounted in series (10-1 to 10-4), each one having a breakdown voltage of 15 V, and it is possible to put into operation one, two, three or four diodes from right to left by means of a rotating switch 14.
  • the contact position for both switches 9 and 14 of FIG. 4, at points 64 and 15-4, respectively corresponds to the maximum microwave power level.
  • FIG. 5 which again shows only the part concerning the additional source, operates with a constant voltage V,,'.
  • V constant voltage
  • FIGS. 3 and 4 the transformer 6 is shown, but with a secondary having only two connections to the rectifier-bridge 7 which is also connected to the filter 8.
  • the rotating switch 14 of FIG. has four positions 15-1 to 15-4 which provide a series connection of one, two, three or four Zener diodes -1 to 104, having bend voltages respectively of 18, 14, 10 and 8 volts.
  • a rotating switch 12 with four positions 13-1 to 13-4 permits a series connection of one, two, three or four resistors 1 1-1 to 11-4 of which the values are respectively 25, 3, 4 and 4 ohms in order to obtain the resistances R of Table T3.
  • the position for both the switches indicated at 13-1 and -4 respectively, corresponds to the maximum microwave power level.
  • the position 13-4 and 15-1 corresponds to the minimum power level.
  • the values of the resistors, Le. 25, 3, 4 and 4 ohms, are actually theoretical values. In practice, they have to be corrected to take into account the internal resistances of the Zener diodes which may be not negligible le with respect to 3 or 4 ohms. Thus the value of the resistor 11-1 will be 25 ohms minus the sum of the internal resistances of the four Zener diodes 10-1 to 10-4;
  • the value of the resistor 1 1-2 will be 3 ohms plus the internal resistance of the Zener diode 10-1; that of 11-3 will be 4 ohms plus the internal resistance of 10-2; and that of 11-4 will be 4 ohms plus the internal resistance of 10-3.
  • a continuous wave magnetron power supply circuit comprising:
  • a magnetron tube having an enclosed cathode and anode electrodes and an external electromagnetic coil
  • first direct current supply means including first rectitier and filter means connected between said alternating current power source and said magnetron electrodes and coil for supplying direct current thereto;
  • second direct current supply means connected between said alternating current power source and said magnetron coil for supplying additional direct current to said coil, said second direct current means including second rectifier and filter means and a plurality of series connected circuit elements including a resistor and an electron discharge device having a stable characteristic breakdown voltage;
  • said plurality of series connected circuit elements includes a plurality of resistors and said selectively adjusting means includes means for connecting selected numbers of said resistors in series with said coil.
  • said plurality of series connected circuit elements includes a plurality of zener diodes and said selectively adjusting means includes means for connecting selected numbers of said zener diodes in series with said coil.
  • said selectively adjusting means includes means connected to said source of alternating current power for adjusting the voltage from said alternating current power source connected to said second direct current supply means.
  • said selectively adjusting means includes means connected to said source of alternating current power for adjusting the voltage from said alternating current power source connected to said second direct current supply means.
  • said plurality of series connected circuit elements includes a further plurality of zener diodes and said selectively adjusting means includes means for connecting selected numbers of said zener diodes in series with said resistors and coil.
  • said selectively adjusting means includes means connected to said source of alternating current power for adjusting the voltage from said alternating current power source connected to said second direct current supply means.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of High-Frequency Heating Circuits (AREA)
  • Microwave Tubes (AREA)
US179384A 1970-09-18 1971-09-10 Power supply circuit for continuous-wave magnetron Expired - Lifetime US3702969A (en)

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FR7033903A FR2106635A5 (enrdf_load_stackoverflow) 1970-09-18 1970-09-18

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4175246A (en) * 1978-02-27 1979-11-20 Advance Transformer Company Energizing circuit for magnetron using dual transformer secondaries
US4481429A (en) * 1982-05-17 1984-11-06 Rca Corporation Bias supply for A.C. line powered apparatus
WO1997030568A1 (de) * 1996-02-19 1997-08-21 Advanced Ferrite Technology Gmbh Stromversorgungsschaltung für ein magnetron

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2979671A (en) * 1959-02-27 1961-04-11 Raytheon Co Magnetron current control systems

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2979671A (en) * 1959-02-27 1961-04-11 Raytheon Co Magnetron current control systems

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4175246A (en) * 1978-02-27 1979-11-20 Advance Transformer Company Energizing circuit for magnetron using dual transformer secondaries
US4481429A (en) * 1982-05-17 1984-11-06 Rca Corporation Bias supply for A.C. line powered apparatus
WO1997030568A1 (de) * 1996-02-19 1997-08-21 Advanced Ferrite Technology Gmbh Stromversorgungsschaltung für ein magnetron

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FR2106635A5 (enrdf_load_stackoverflow) 1972-05-05

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Owner name: ALCATEL N.V., DE LAIRESSESTRAAT 153, 1075 HK AMSTE

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Effective date: 19870311