US3723806A - Adjustable stable power supply for continuous wave magnetron - Google Patents

Adjustable stable power supply for continuous wave magnetron Download PDF

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Publication number
US3723806A
US3723806A US00239529A US3723806DA US3723806A US 3723806 A US3723806 A US 3723806A US 00239529 A US00239529 A US 00239529A US 3723806D A US3723806D A US 3723806DA US 3723806 A US3723806 A US 3723806A
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United States
Prior art keywords
source
current
voltage
magnetron
adjustable
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US00239529A
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English (en)
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M Poussereau
M Denis
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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
    • 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
    • H05B2206/00—Aspects relating to heating by electric, magnetic, or electromagnetic fields covered by group H05B6/00
    • H05B2206/04—Heating using microwaves
    • H05B2206/043—Methods or circuits intended to extend the life of the magnetron

Definitions

  • ABSTRACT A power supply circuit for a continuous wave magnetron provides adjustable stable power levels.
  • a first direct voltage source is connected across the magnetron and a second direct voltage source from a common alternating voltage source is connected across the magnetron coil in series with a direct current amplifier.
  • Current feedback to the input of the amplifier is derived from the magnetron by an adjustable voltage divider connection to the first voltage source.
  • Another portion of the voltage divider provides a third direct voltage connection between the second source and amplifier input, the amplifier input current being the sum of current from the third source and adjustable current from the magnetron.
  • the microwave power supplied to the load is equal to P,,, with: P kP kVI; where k is the magnetron efficiency, and from experience it appears that, if the load is rather well matched, k is substantially constant throughout the useful range of the tube characteristics.
  • I (V/r)aI, (1) where r is the internal magnetron resistance and a is an amplification coefficient of high value.
  • An important purpose of the invention described in the above prior application is to obtain a satisfactory stabilization of P,, by suitably amplifying instabilities of V so as to compensate for instabilities of V.
  • the additional source of voltage V is replaced by a source of voltage V, that supplies a nonlinear circuit comprising serially a counter electromotive force (c.e.m.f.) element E,,, that is very stable and has a very low internal resistance, the resistor R and the coil of resistance R,,. V,,is given by the relation:
  • a stabilization effect is obtained for a fixed high-voltage V when, for each value of I, and therefore of V,,' and/or R, E,,, R and I are associated by the relation (5 E, 2 RI 5
  • a rheostat providing R with a variable autotransformer supplying V it is possible to obtain the preceding relation for each desired value of P,, and in a continuous manner.
  • the phenomenon is unstable and the increase of I is limited only by safety switches or non-linear characteristics of the involved components such as the self-inductance L, Zener diode, magnetron, and rectifiers delivering voltage V
  • the current I increases with a time-constant L/ R. This troublesome phenomenon could be avoided only if the increase of current I, after having applied high-voltage V, would be performed with a time-constant at least equal to L/R.
  • an object of this invention is to provide an additional coil current source of adjustable current such that the value I B is substantially independent of the coil characteristics R and L.
  • Another object ofthe invention is to provide an additional source in such a manner that, when high-voltage power is turned on, no transitory unstable phenomenon occurs.
  • a further object of this invention is to provide an adjustable power supply wherein the sensitivity I/I is substantially lower than a.
  • a still further object of this invention is to provide an additional coil current source in such a manner that, for each adjustment of the coil current I,,, the magnetron current I and the delivered microwave power P,, are not dependent upon instabilities of the magnetron high-voltage V and on an additional source of voltage.
  • coil current intensity 1 is provided at the output of a current amplifier, the dynamic output resistance of which is substantially higher than the coil resistor R
  • amplifier input current is equal to the sum of an adjustable control current I, and of a part q of magnetron current I, I, being lower than coil current I so that when highvoltage V is applied to the magnetron, it induces current I.
  • input current 1, is provided by a low voltage source V, serially mounted with a negative feedback voltage equal to r r being a low value resistor.
  • magnetron current I at constant high-voltage, and consequently microwave power P,,,, may be adjusted by varying V,, and/or r,.
  • the sensitivity I/(l,,) is equal to (r,. r;/ r,), r and r being the amplifier input resistor and the sum of internal resistance of low-voltage source V, and of other resistors possibly serially connected with r respectively.
  • a stable c.e.m.f. source c with very low internal resistance is serially connected with source of low voltage V,,', such that V, V, e e being related to r, and l by the formula: e, 2 r,l.
  • V being constant
  • microwave power P is adjusted between desired limits by varying r, and the power value is given by the very simple formula:
  • the amplifier is a common-emitter power transistor.
  • V low-voltage source
  • V being obtained from V through an adjustable potentiometer divider.
  • FIG. 1 shows a schematic diagram of a power supply circuit. for a continuous-wave magnetron according to this invention.
  • FIG. 2 shows a specific embodiment of a power supply'using a power transistor as an amplifier.
  • a magnetron l is provided with DC high-voltage V from source 2 which is assumed to be made of a first AC current rectifier of a standard type and of filter circuits, not shown.
  • the anode of the magnetron l is connected to ground.
  • Control induction field for the magnetron is provided by coil 3 through which current I is passing; 3 has a resistor value equal to R3.
  • the bottom terminal of 3 is connected to a positive terminal of a source 4 of DC low-voltage V,,' which is assumed to be made of a second AC current rectifier and filter circuits, not shown.
  • the top terminal of 3 is connected to the output of a DC amplifier 5 having an output resistance equal to R,.
  • Input circuit of amplifier 5 comprises serially connected from ground: a resistor 6 of value r through which current I of magnetron 1 passes, the positive terminal of source 2 being connected to the top terminal of 6, a source 7 of adjustable DC low-voltage V, which is assumed to be made of a third AC current rectifier and of filter circuits not shown, a source 8 of c.e.m.f. e, which is very stable and has a very low internal resistance, a resistor 9 of value r,, and the input resistance r, of amplifier 5.
  • sources 2, 4 and 7 have low internal resistances compared to those of the circuits to which they are supplying current; and also, it will be assumed that r r, r
  • a r is very much higher than r r the transconductance becomes approximately l/r, and, consequently, is independent of a; if the sources are stable, current I and microwave power P provided by the magnetron are independent of possible instabilities of static magnetron or amplifier characteristics, such as for example resulting from temperature variations.
  • microwave power delivered by the magnetron is:
  • V, P, For constant high-voltage V, P,, varies within the desired range by adjusting V and/or r,.
  • Source 8 permits stabilization of microwave power P,, when DC voltages of sources 4 and 7 are subjected to relative equal variations, particularly when voltages V, V and V, are produced by rectifying a single source of AC current after suitable filtering.
  • P, For each adjust ment of P and therefore, of V, and/or r as a result of combination of formulas (8) and (9), P,,, remains constant if V and V are subjected to the same relative instabilities: d V 'lV dV/V, when 1, [r (r, r /a)] and e, are bound by the formula
  • P it is necessary only to vary the value of r in accordance with the formula 10).
  • War measures the coil current (1 that precludes magnetron 1 from operating when voltage of source 2 is equal to V; thus
  • the amplifier may include a suitable silicon or germanium power transistor of an NPN type.
  • the c.e.m.f. e of the source 8 may be provided by a Zener diode.
  • the magnetron high-voltage is 5 kV and current intensity providing maximum power (P is 1 A. With an efiiciency ratio 1: of percent, (P,,,) 3.5 kW.
  • the four power levels are obtained for current values 1, 0.75, 0.5 and 0.25 A.
  • the value of (1 is 1.3 A and magnetron figure a is within the range of 35; in other words, current 1,, corresponding to current I equal to 1 A is 1.27 A.
  • Amplifier current gain is about 30.
  • Powertransistor emitter-base resistance r for a base current of 40 mA is lower than 15 ohms. Since this resistance varies in response to temperature changes, it is useful to mask it in the sum (r,, r by having the value of r substantially higher, i.e. ohms.
  • the formula (10) gives e 3 V (a value that is readily provided by a Zener diode) and the formula (12) gives: V,,' 1.5 1.3(/30) 6.5 V.
  • Resistor 6 which in this case must continuously vary from 1.5 to 6 ohms, is made of a rheostat.
  • FIG. shows a detailed circuit embodiment of the invention using a common-emitter power-transistor amplifier of the NPN type having the same reference nu meral 5 as in the FIG. 1.
  • Other like reference numerals will be used for the same components already shown in FIG. 1.
  • Rectifier 10 followed by filter stage 11 provides voltage V that is applied through resistor R, of coil 3 to the collector of transistor 5.
  • Voltage V is produced by means of a voltage divider 12, having a relatively low resistance, serially connected with resistor of rheostat 6, to provide resistor values r suitable for current feedback and stabilization according to the invention. Voltage V, from slide contact of 12 is applied through Zener diode 8 and resistor 9 to the base of transistor 5. Capacitor 13, connected between the transistor base and ground, removes AC signals which remain at the output of filter 11.
  • Divider 12 has a division ratio that is slightly adjustable so as to adjust V at a suitable constant value
  • resistor r is equal to the sum of resistor 9, the divider resistor between the top point and rheostat, and the rheostat resistor.
  • Power diode 16 is connected in parallel with coil 3 in a backward direction with respect to I Its purpose is to avoid damaging transistor 5 in the case of a power supply break-down. If such an event occurs, the magnetic energy stored in coil 3 is dissipated in 16, so as to protect transistor 5.
  • High-voltage V of magnetron 1 is provided by rectifier 14 followed by filter stage 15.
  • Rectifiers and 14 are supplied by a single primary AC source, not shown, that, according to the invention may be a non-stabilized source.
  • a magnetron having an anode and cathode, said anode being connected to a ground reference
  • a third adjustable low direct voltage source connected between said second source and said amplifier input, the amplifier input current being the 3.
  • said first, second and third source voltages are unstabilized and are supplied by a common primary AC source, said first and second sources including respective rectifiers and filters, and a source of counter electromotive force that is stable and has a very low internal resistance connected in series with said third low voltage source.
  • said adjustable resistor being an adjustable potentlometer-connected in series between said third voltage source and ground, and the potentiometer slide contact cluding a power diodeconnected in parallel with said coil, the backward diode direction being that of the coil current.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of High-Frequency Heating Circuits (AREA)
US00239529A 1971-04-07 1972-03-30 Adjustable stable power supply for continuous wave magnetron Expired - Lifetime US3723806A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7112281A FR2133075A6 (enrdf_load_stackoverflow) 1971-04-07 1971-04-07

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FR (1) FR2133075A6 (enrdf_load_stackoverflow)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3302060A (en) * 1963-07-17 1967-01-31 Philips Corp Control system for regulating the current in a magnetron tube
US3344364A (en) * 1965-12-10 1967-09-26 Alford Andrew Amplitude of h.f. oscillator stabilized by rectified output of l.f. osc.

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3302060A (en) * 1963-07-17 1967-01-31 Philips Corp Control system for regulating the current in a magnetron tube
US3344364A (en) * 1965-12-10 1967-09-26 Alford Andrew Amplitude of h.f. oscillator stabilized by rectified output of l.f. osc.

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FR2133075A6 (enrdf_load_stackoverflow) 1972-11-24

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

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:INTERNATIONAL STANDARD ELECTRIC CORPORATION, A CORP OF DE;REEL/FRAME:004718/0023

Effective date: 19870311