A Filament Current Control Device of Frequency Conversion Microwave Generating Source

Abstract

The invention discloses a filament current control device of a variable-frequency microwave generation source, and relates to the technical field of variable-frequency microwave power supplies. The device comprises a field-effect tube, a first diode, a high-voltage isolation driving module and a microwave variable-frequency circuit. The high-voltage isolation driving module is connected with the field-effect tube and is used for controlling opening and closing of the field-effect tube; and the microwave frequency conversion circuit comprises a magnetron and a filament winding unit of a main transformer. The field-effect tube and the first diode are connected in series to form a series branch which is connected with the filament winding unit in parallel. The filament winding unit is connected with the magnetron, and the field-effect tube is used for adjusting a current at two ends of a filament in the magnetron. The filament winding unit is an output winding of the main transformer. Thedevice provided in the invention can realize quick start of the magnetron.

Description

technical field [0001] The invention relates to the technical field of frequency-variable microwave power supplies, in particular to a filament current control device for frequency-variable microwave generators. Background technique [0002] In order to flexibly control the filament current, the high-power microwave variable frequency power supply above 1.5KW is designed to independently supply power to the filament at the cathode high voltage end, which can easily adjust the filament current. [0003] In order to save cost and compact structure, the low-power microwave frequency conversion power supply below 1.5KW takes the filament power supply from a winding of the cathode high-voltage transformer, that is to say, there are two windings on the secondary side of the high-voltage transformer, one is to provide high voltage for the cathode, and the other To supply power to the filament, this will cause a congenital deficiency of the low-power microwave frequency conversion p...

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Problems solved by technology

[0003] In order to save cost and compact structure, the low-power microwave frequency conversion power supply below 1.5KW takes the filament power supply from a winding of the cathode high-voltage transformer, that is to say, there are two windings on the secondary side of the high-voltage transformer, one is to provide high voltage for the cathode, and the other To supply power to the filament, this will cause a congenital deficiency of the low-power microwave frequency conversion power supply: when starting up, in order to make the filament heat up quickly and reach the temperature of emitting electrons, it is necessary to increase the power output of the transformer to provide sufficient current for the filament, and at this time the magnetic control The tube does not start up, and the cathode high voltage is equivalent to an open circuit, causing the high voltage output to be very high, even close to the breakdown voltage of the magnetron. Every time it is started, it will damage the magnetron; The current of the filament will be too small, because after the magnetron works, the magnetron will heat up, even if cooling measures are taken, the temperature of the magnetron will still reach more than 80 or 90 degrees, and its impedance characteristic is negative temperature. Characteristics, the higher the temperature of the magnetron, the lower the impedance, in order to keep the power of the magnetron constant, according to the power formula P=U 2 / Z, when Z becomes smaller, the variable frequency power supply needs to increase the frequency, increase the internal resistance of the main transformer, reduce the high voltage output, that is, U becomes smaller to keep the power constant, because the two windings of high voltage and filament power supply are wound on a transformer , the power supply reduces the output of U, and the filament current is passively reduced. In this way, as the magnetron works for a long time, its temperature continues to rise slowly and the cathode impedance gradually decreases. The variable frequency power supply controls the main transformer to continuously increase the internal resistance, reduce the output voltage, and the filament The current is continuously reduced passively, and the temperature of the cathode generated will drop to the critical state of electron emission, prompting the discontinuous emission of electrons, the microwave output changes from continuous wave to discontinuous wave, and even fault phenomena such as magnetron mode hopping occur.

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