Magnetron variable power supply with moding prevention
AssigneeFusion Systems Corporation
InventorsChuck Daley, Robert J. Sweetman, Charlie Lenny
Life of this patent
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Abstract
A power supply for a magnetron varies a power output level and prevents moding of the magnetron. To provide a variable power output, a microprocessor senses an anode current and voltage of the magnetron. Based on the sensed signals, the microprocessor adjusts the conduction angle of a thyristor to obtain the desired power level. The microprocessor also monitors the anode voltage for detecting moding of the magnetron. If moding is detected, the microprocessor adjusts the conduction angle of another thyristor to change the current supplied to the filament. By changing the filament current, the microprocessor effectively prevents the moding of the magnetron.
Claims17
A power supply for supplying operating voltages to a magnetron used in a heating process, comprising:
- a DC high voltage source controlled by a first thyristor for producing a direct current for said magnetron which is related to a conduction angle of said first thyristor;
- a source of AC filament voltage for said magnetron controlled by a second thyristor for producing a filament current related to a conduction angle of said second thyristor;
- a first means for detecting an anode current and an anode voltage of said magnetron;
- a second means for detecting a filament current and a filament voltage of said magnetron;
- and
- a microprocessor means connected to said first and second means, which is programmed to:
- determine from a desired power setting, a target current for said anode current,
- control said conduction angle of said first thyristor for generating high voltage which produces said target current,
- monitor said anode voltage of said magnetron for determining moding of said magnetron;
- and
- control said conduction angle of said second thyristor for producing a filament current which eliminates said moding of said magnetron.
A power supply for supplying operating voltages to a magnetron having an anode and a filament, wherein said magnetron is used in a heating process, said power supply comprising:
- a pair of power units in parallel with each other, connected to a plurality of power lines which provide an AC operating voltage, wherein each power unit supplies direct current to said anode and alternating current to said filament, and includes (a) a power control circuitry for varying said direct current in response to a desired power setting, and (b) a filament control circuitry for increasing said alternating current in response to moding of said magnetron.
A power supply for supplying operating voltages to a magnetron used in a heating process, comprising:
- a first thyristor connected to a three-phase AC voltage source for providing a conduction angle to an AC operating voltage;
- a step-up transformer unit connected to said first thyristor, for providing an increased AC voltage from said AC operating voltage;
- a rectifying means coupled to said step-up transformer unit, for converting said increased AC voltage to a DC voltage;
- a magnetron coupled to said rectifying means for generating microwave radiation;
- a lamp electromagnetically coupled to said magnetron via a waveguide, for receiving said microwave radiation for use in said heating process;
- a second thyristor connected to said three-phase AC voltage source via a control transformer;
- a step-down transformer connected between said second thyristor and said filament, for providing a filament current to heat said filament under control of said second thyristor;
- a microprocessor connected between said first and second thyristors, and said magnetron through a digital-to-analog converter means, for controlling said first and second thyristors;
- and
- a first buffer means connected between said microprocessor and said first thyristor, and a second buffer means connected between said microprocessor and said second thyristor, for processing signals of said microprocessor, whereby a desired power setting is obtained by controlling said first thyristor and moding of said magnetron is suppressed by controlling said second thyristor.
A power supply for supplying a filament current to a magnetron, comprising:
- a source of AC filament voltage for said magnetron including a step-down transformer connected to said AC operating voltage through a thyristor for producing a filament current related to a conduction angle of said thyristor;
- and
- a feedforward circuit connected between said filament of said magnetron and said thyristor, including:
- (a) a means for detecting a peak filament current of said magnetron;
- and
- (b) a microprocessor means connected to said means through an analog-to-digital converter means, for detecting moding of said magnetron and controlling said thyristor to reduce said moding.
A method for providing a variable power by a power supply to a magnetron used in a heating process, comprising:
- generating direct current for an anode of said magnetron, which includes connecting a step-up transformer to an AC operating voltage via a thyristor and rectifying a stepped-up AC voltage for said magnetron;
- detecting an anode current and an anode voltage of said magnetron;
- determining from a desired power setting a target current for said anode current;
- and
- controlling alternating current on a primary side of said step-up transformer by adjusting a conduction angle of said thyristor via a microprocessor means, thereby establishing a voltage corresponding to said desired power setting which produces said target current.
A method for preventing moding of a magnetron in a power supply for said magnetron used in a heating process, comprising:
- generating a filament voltage, which includes connecting a step-down transformer to an AC operating voltage via a thyristor;
- detecting a peak anode voltage of said magnetron;
- determining a frequency of transitions of said peak anode voltage above a threshold voltage by monitoring and comparing said peak anode voltage with said threshold voltage;
- and
- reducing said frequency of transitions of said peak anode voltage above a threshold voltage by controlling a conduction angle of said thyristor.
Dependencies are inferred from the claim text.