US3784781A - Magnetron moding interrupter control circuit - Google Patents

Magnetron moding interrupter control circuit Download PDF

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Publication number
US3784781A
US3784781A US00350270A US3784781DA US3784781A US 3784781 A US3784781 A US 3784781A US 00350270 A US00350270 A US 00350270A US 3784781D A US3784781D A US 3784781DA US 3784781 A US3784781 A US 3784781A
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United States
Prior art keywords
magnetron
energy
generator
sensing
circuit
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Expired - Lifetime
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US00350270A
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English (en)
Inventor
R Foerstner
R Fritts
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Goodman Co LP
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Amana Refrigeration Inc
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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
    • 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

  • a magnetron operating control circuit including means for sensing the commencement of electromagnetic energy radiation and means derived from the sensing means to interrupt the application of line voltages to the magnetron power supply and allow the voltages to decrease for a sufficient time to shift to desired normal operating mode conditions when the supply is reenergized.
  • the circuit incorporates a flexible sensing feature which accommodates the time of the interruption cycle to variations in tubes, line voltages and other circuit parameters, particularly in microwave oven apparatus to substantially reduce the magnetron moding problems.
  • PATENTEDJAN 81974 784'781 sum 2 or z r l l 52' SENSING MAGNETRON INTERRUPTOR ENERGY CONTROL A9 POWER SUPPLY I 60 AND I ELECTRICAL F/G 3 QLL/L JA MAGNETRON MODING INTERRUPTER- CONTROL CIRCUIT BACKGROUND OF THE INVENTION 1.
  • the invention relates to electrical circuits for operating magnetron energy generators in microwave oven apparatus.
  • microwave cooking an energy source commonly employed in the generation of high frequency electromagnetic oscillations is the magnetron energy generator.
  • Such devices employ crossed electric and magnetic fields tranversing-an intraction region between a central cathode and cavity resonators defined by an anode member.
  • the emitted electrons interact in energyexchanging relationship with the electrical energy stored in the cavity resonators and extremely high oscillations are generated, typically, at microwave frequencies of 2450 MHz in the electromagnetic energy spectrum.
  • microwave refers to radiation in that portion of the electromagnetic energy spectrum having wavelengths of from 1 meter to l millimeter.
  • Magnetron tubes are typically operated by a power supply utilizing main line AC voltages which are rectified to provide DC voltages in the region of 4,000 to 6,000 volts.
  • Examples of prior art magnetron power supply circuits are disclosed in U.S. Letters Pat. No. 3,396,342 issued on Aug. 6, 1968 to A.E. Feinberg. Such circuits are especially useful in energizing magnetrons having permanent magnets rather than electromagnets to provide the desired magnetic fields which usually extend parallel to the axis of the cathode member.
  • the circuit disclosed in the referenced patent is of the high leakage reactance transformer type which seeks to substantially minimize any fluctuations in the terruption and the magnetron will oscillate in this DC output voltages due to variations in the AC line voltages.
  • the secondary winding is inductively coupled to the primary winding with full wave rectifying circuit means connected in series with the secondary winding and cathode.
  • magnetron power supplies provide the cathode filament and anode voltages simultaneously and no anode current is drawn until the cathode filament has reached operating temperature'As a result of the initial lack of a load, open circuit transient voltages high as 12 to 15 thousand volts can result when the power supply is energized.
  • the high transient surge currents present a problem in that once the anode voltage rises to the level which allows the magnetron to oscillate the tube may operate at undesirable higher order modes characterized by lower efficiency and high temperatures which shorten tube life.
  • the oscillations therefore, are desired in a particular operating mode, typically the pi mode which is at a lower anode voltage level and provides for stable operation.
  • a mode shift is desirably instituted before the higher order mode oscillations become self-sustaining.
  • One method of coping with the transient voltages surge problem discussed in the prior art includes a separate low voltage filament transformer for preheating the cathode before the main anode voltages are applied. Additional circuitry and components are required for such a separate preheat cycle. In microwave ovens the operator is required to operate the device in separate steps with a preheat period before the main mode.
  • An example of circuits utilizing this principle is found in the copending patent application entitled Magnetron Starting Circuit Ser. No. 185,624 filed Oct. l,'l97l by Donald E. Peterson and assigned to the assignee of the present invention.
  • the interrupt time period is selected as a compromise considering the variations in magnetron tubes, domestic line voltages and other circuit parameters to select the optimum average time period. since it is desirable to provide fast, low cost equipment, improvements in power supply circuits for simultaneously applying the anode and cathode filament voltages and operating of the magnetron in the proper operating mode are continually being explored.
  • a magnetron operating control circuit for utilization in microwave oven apparatus embodiment which is based on the sensing of the commencement of electromagnetic energy radiation to derive control signals to interrupt the application of the full anode line voltages for a sufficient time to assure that continued operation of the magnetron generator will be in the normal operating mode frequency.
  • the sensing means control the interruption of the application of the simultaneous voltages rather than rigid delay timer means which represent an approximate compromise of the individual tube performance variables as well as circuit variations.
  • the disclosed magnetron control circuit provides for a customized operation to assure that the proper magnetron operating mode frequency is achieved.
  • FIG. 1 is a schematic diagram of the electrical circuit of the invention
  • FIG. 2 is an isometric view of a microwave oven apparatus embodying the invention with a portion of the outer casing and waveguide launching means broken away to reveal internal structure;
  • FIG. 3 is avertical cross-sectional view-of the microwave oven apparatus illustrated in FIG. 2.
  • a control panel member 26 adjacent to the door assembly provides for the mounting of timers 28 and 30 as well as the start, stop and light buttons 32, 34 and 36.
  • the magnetron energy generator provides the electromagnetic energy for radiation within the enclosure 20.
  • Magnetrons are considered to be well-known in the art and additional information may be obtained from the Microwave Magnetrons, Radiation Laboratory Series, Vol. 6, by G. B. Collins, McGraw-Hill Book Company, Inc., 1948, as well as the referenced copending application.
  • the high voltage power supply and all electrical circuits are indicated by'box 40.
  • the electromagnetic energy is The waveguide is closed at oneend by a terminating 8 wall 48 having perforations 50 which are utilized for the detection of any electromagnetic energy radiation once the magnetron generator commences to oscillate.
  • the antenna member 42 is spaced from the terminating wall 48 approximately 1/4 of a wavelength at the operating frequency of the apparatus for optimum directivity.
  • Distributionof the energy in a plurality of modes is accomplished by any of the well-known means including, for example, a mode stirrer 52 comprising a plurality of paddles 54 supported by a shaft 56 which is actuated by motor 58 supported on top wall 14.
  • a dielectric plate 60 spans the indentation in the bottom wall 16 and supports the articles to be cooked or heated within the enclosure 20.
  • the microwave energy utilized in such apparatus operates at the F.C.C. assigned frequency of 2450 MHz.
  • the magnetron moding interrupter control circuit commences with electromagnetic energy radiation sensing means such as, for example, a semiconductor diode 62.
  • electromagnetic energy radiation sensing means such as, for example, a semiconductor diode 62.
  • Such devices typically are unidirectional and comprise a chip of silicon or germanium and an electrode.
  • the novel circuit incorporates the diode sensing means 62 in close proximity to the perforations 50 in the back terminating wall 48 of the waveguide launching section 46 near antenna 42.
  • FIG. 1 a schematic of the radiation sensing and interrupter magnetron operating control circuit will now be described.
  • the details of the high voltage magnetron power supply circuit including the DC rectification means and transformer have been omitted in order that attention may be focused on the interrupter circuit.
  • An example of a magnetron power supply circuit under consideration may be had by referring to the aforereferenced copending patent application of Donald A. Peterson as well as the power supply circuit disclosed in U.S. Pat. No. 3,396,342 issued to A. E. Feinberg.
  • both the filament power and anode voltages are applied simultaneously to the magnetron 38 through the power supply 40 from a conventional domestic AC line voltage source 64, typically 'l 15-120 volts by means of electrical leads 66 and 68.
  • the novel circuit comprises, first, primary AC line voltage source 64, power relay 70 and semiconductor diode 72.
  • Diode 72 rectifies the line voltage which is filtered through resistor R1 and capacitor C1 to the gate of the silican controlled rectifier SCRl and a diode bridge 76.
  • the current flows through SCRl closing relay 70 and results in the application of voltages to magnetron 38 through power supply 40. As the magnetron filament heats emission starts and the magnetron anode voltage simultaneously rises until the magnetron operates at either the adjacent or the normal operating mode.
  • the commencement of the the oscillations results in generation of electromagnetic energy which is detected by the sensing diode 62 in close proximity to the antenna 42.
  • the energy detected derives a signal which is filtered and amplified by voltage amplifier 78 with the resultant signal further filtered and applied to paired transistors 80 and 82.
  • the amplifier 78 is biased by a 12 volt DC supply 84 and the diode filtering circuit includes resistors R2 and R3 and R4.
  • capacitors C2 and C3 are utilized for the detected electromagnetic energy radiation signal through diode 62.
  • the generated signal is fed into the amplifier 78 through resistors R5 and R6 and resistors R7, R8 and R9 are utilized in the amplifier branch to feed transistors 80 and 82.
  • the amplified signal is conducted by means of resistors R10, R11 and R12 biasing the base of the transistor 82 and capacitor C4 is connected to ground.
  • Transistors 80 and 82 are biased by the 12 volt source 84 through resistor R13.
  • the output of transistor 80 is applied by resistors R14, R15, R16, R17 and R18 and charging capacitor C5 to a unijunction circuit 86.
  • the unijunction circuit 86 controls the firing of the silicon controlled rectifier SCR2 through a gate including resistor R19 circuit with resistor R20 to ground.
  • the firing of the SCR 2 renders transistor 88 conductive with its base electrode biased by resistor R21 with the collector grounded through resistor R22 after the gate of the unijunction reaches a predetermined level.
  • the circuit operates initially when power source 64 activates diode 72.
  • the line voltage is rectified, filtered and applied to gate SCRl on.
  • Current flows through relay 70, and diode bridge 76 to thereby close relay and apply simultaneous voltages to the cathode filament and anode of magnetron 38 through power supply 40.
  • diode 72 Upon commencement of the electromagnetic energy oscillations energy is detected by diode 72, filtered and the resultant signal is applied to amplifier 78 and I the subsequent transistors 80 and 82 with the amplified signal being applied to unijunction circuit 86.
  • Unijunction circuit 86 controls SCR 2 and at a predetermined level transistor 88 becomes conductive.
  • the conductive condition of transistor 88 results in grounding the gate of SCR] and opens to interrupt primary voltage source 64.
  • the relay remains open a period of time determined by charging capacitor C5 whereupon transistor 88 stops conducting thereby allowing the SCRl to becomes conductive and reclose power relay 70 to reapply the voltages to the magnetron through power supply 40 and permit operation of the energy generator in the normal operating mode.
  • SCR2 becomes conductive, the supply voltage to the unijunction circuit 86 is effectively shorted out to thereby prevent subsequent firings except when the main source 64 or electromagnetic energy radiation from the magnetron 38 are turned off. Recycling occurs when the source 64 orradiation are turned on and/or sensed by the disclosed circuit.
  • Diode 62 [N830 Diode 72 IN206 Amplifier 78 No. 709 Voltage Amplifier Transistor 80 2N697 Transistor 82 2N697 R1 33K ohms R2 lK ohms R3 1K ohms R4 500 ohms R5 I ohms R6 e 100 ohms R7 470K ohms R8 4.7K ohms R9 100K ohms R10 2.2K ohms R11 4.7K ohms R12 1K ohms R13 2.2K oh'ms.
  • means for energizing said generator including an Ac voltage source and power supply comprising a transformer power relay and high voltage DC rectification means;
  • means for energizing said voltage source to operate said generator including a power relay and semiconductor means; means for sensing commencement of operation of said generator comprising an energy radiation detector to derive an electrical signal;
  • a filter circuit means including semiconductor means and a charging capacitor to fire said last named means to interrupt operation of said generator for a predetermined period of time determined by storage of electrical energy in said capacitor by opening said power relay.
  • said energizing means comprise a diode rectifier, a first silicon controlled rectifier, and electrical filter means.
  • interrupt circuit means includes a unijunction device and a second silicon controlled rectifier interconnected to said first silicon controlled rectifier by a transistor device having a grounded electrode when in the conductive state to ground said first rectifier and allow said power relay to open deenergizing said voltage source.
  • a microwave oven apparatus comprising:
  • means for energizing said generator including an AC voltage source and power supply comprising a transformer power relay, and high voltage DC rectification means;
  • electrical circuit means for filtering, amplifying and utilizing said derived signal to interrupt operation of said magnetron for a predetermined period of time by opening said power relay.
  • said magnetron includes an output antenna and said energy coupling means comprise a hollow waveguide transmission section with said antenna disposed therein.
  • means for sensing energy radiation comprise a diode rectifier adapted to detect energy radiated from said antenna.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of High-Frequency Heating Circuits (AREA)
  • Microwave Tubes (AREA)
US00350270A 1973-04-11 1973-04-11 Magnetron moding interrupter control circuit Expired - Lifetime US3784781A (en)

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Application Number Priority Date Filing Date Title
US35027073A 1973-04-11 1973-04-11

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US3784781A true US3784781A (en) 1974-01-08

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US (1) US3784781A (fr)
JP (1) JPS5240460B2 (fr)
AU (1) AU466564B2 (fr)
BE (1) BE807348A (fr)
CA (1) CA954946A (fr)
CH (1) CH562532A5 (fr)
DE (1) DE2357480A1 (fr)
FR (1) FR2225835B1 (fr)
GB (1) GB1410864A (fr)
IT (1) IT997742B (fr)
NL (1) NL7315823A (fr)
SE (1) SE385348B (fr)
ZA (1) ZA738522B (fr)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3943317A (en) * 1973-07-18 1976-03-09 Matsushita Electric Industrial Company, Ltd. Microwave oven power supply circuit
US3999027A (en) * 1975-05-05 1976-12-21 Chemetron Corporation Electronic microwave oven control system and method of preparing food items therewith
US4115679A (en) * 1973-07-18 1978-09-19 Chemetron Corporation Method for automatically heating variable numbers and sizes of food items or the like, in an electromagnetic oven
US4196332A (en) * 1978-02-09 1980-04-01 Canadian Patents And Development Limited Controlled heating microwave ovens
US4245143A (en) * 1978-04-28 1981-01-13 Hitachi Heating Appliances Co., Ltd. Microwave oven
US4504767A (en) * 1982-09-07 1985-03-12 Litton Systems, Inc. Magnetron mode detector
US4990733A (en) * 1988-02-02 1991-02-05 U.S. Philips Corp. Microwave oven with improved microwave power control
WO1996034512A1 (fr) * 1995-04-27 1996-10-31 Fusion Systems Corporation Alimentation pour un magnetron
US20160323939A1 (en) * 2013-12-23 2016-11-03 Whirlpool Corporation Interrupting circuit for a radio frequency generator
US12009676B2 (en) * 2021-10-14 2024-06-11 Sichuan University Simultaneous wireless information and power transfer device and method based on the modulation of power supply ripple of magnetron

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2459721A1 (fr) * 1979-06-22 1981-01-16 Jacomino Jean Marie Dispositif et procede de controle automatique en continu du processus de reticulation ou de vulcanisation des elastomeres

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3611027A (en) * 1968-02-10 1971-10-05 Tokyo Shibaura Electric Co Magnetron operating circuit
US3752948A (en) * 1971-10-01 1973-08-14 Amana Refrigeration Inc Magnetron starting circuit

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3611027A (en) * 1968-02-10 1971-10-05 Tokyo Shibaura Electric Co Magnetron operating circuit
US3752948A (en) * 1971-10-01 1973-08-14 Amana Refrigeration Inc Magnetron starting circuit

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3943317A (en) * 1973-07-18 1976-03-09 Matsushita Electric Industrial Company, Ltd. Microwave oven power supply circuit
US4115679A (en) * 1973-07-18 1978-09-19 Chemetron Corporation Method for automatically heating variable numbers and sizes of food items or the like, in an electromagnetic oven
US3999027A (en) * 1975-05-05 1976-12-21 Chemetron Corporation Electronic microwave oven control system and method of preparing food items therewith
US4115680A (en) * 1975-05-05 1978-09-19 Chemetron Corporation Apparatus for providing temperature equalization cycles for a microwave oven
US4196332A (en) * 1978-02-09 1980-04-01 Canadian Patents And Development Limited Controlled heating microwave ovens
US4245143A (en) * 1978-04-28 1981-01-13 Hitachi Heating Appliances Co., Ltd. Microwave oven
US4504767A (en) * 1982-09-07 1985-03-12 Litton Systems, Inc. Magnetron mode detector
US4990733A (en) * 1988-02-02 1991-02-05 U.S. Philips Corp. Microwave oven with improved microwave power control
WO1996034512A1 (fr) * 1995-04-27 1996-10-31 Fusion Systems Corporation Alimentation pour un magnetron
US20160323939A1 (en) * 2013-12-23 2016-11-03 Whirlpool Corporation Interrupting circuit for a radio frequency generator
US10993293B2 (en) * 2013-12-23 2021-04-27 Whirlpool Corporation Interrupting circuit for a radio frequency generator
US12009676B2 (en) * 2021-10-14 2024-06-11 Sichuan University Simultaneous wireless information and power transfer device and method based on the modulation of power supply ripple of magnetron

Also Published As

Publication number Publication date
GB1410864A (en) 1975-10-22
AU6226973A (en) 1975-05-08
NL7315823A (fr) 1974-10-15
JPS5240460B2 (fr) 1977-10-12
SE385348B (sv) 1976-06-21
IT997742B (it) 1975-12-30
FR2225835A1 (fr) 1974-11-08
ZA738522B (en) 1974-09-25
CH562532A5 (fr) 1975-05-30
CA954946A (en) 1974-09-17
FR2225835B1 (fr) 1978-08-11
AU466564B2 (en) 1975-10-30
JPS5052646A (fr) 1975-05-10
BE807348A (fr) 1974-03-01
DE2357480A1 (de) 1974-10-31

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