JP2001076897A - Microwave oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave oscillator using a magnetron, improving in stability and startup property by connecting a plurality of MOS-FETs in series to allow the use of a bias voltage to be supplied to the magnetron as a substitute for a vacuum tube. SOLUTION: A microwave oscillator comprises a high voltage power supply 11 capable of generating a DC high voltage of few kilovolts (3 KV or so), a constant voltage generation part 12A for applying the DC high voltage of few kilovolts partially to a plurality of MOS-FETs connected in series to generate a bias voltage (2.5 KV or so) to be supplied to a magnetron 14, the magnetron 14 for generating microwaves in accordance with the bias voltage and a cavity resonator 15 for generating a plasma in accordance with the microwaves.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oscillator using a magnetron, and more particularly to a microwave oscillator for stabilizing a device voltage supplied to the magnetron.

[0002]

2. Description of the Related Art Microwave oscillators in the prior art are:
As shown in FIG. 2, a high voltage power supply 11 for outputting a high voltage of about 3 KV, a constant voltage generator 12 for generating a bias voltage to be applied to the magnetron based on the high voltage of 3 KV, and a constant voltage generator And a magnetron 1 for generating microwaves.
4 and a cavity resonator 15 that resonates with the microwave to excite plasma.

The constant voltage generator 12 comprises a pentode 16 and a control transistor Tr for controlling the current of a control grid G1 of the pentode 16. The control transistor Tr is controlled by an external current command input unit 13. A bias voltage to be supplied to the magnetron 14 is generated by controlling the current of the control grid of the pentode 16. The pentode 16 has a structure including a control grid G1, a shielding grid G2, and a suppression grid G3 between the anode P and the cathode K.

A microwave oscillator having such a configuration is first provided with a magnetron 14 from a high voltage power supply 11 of about 3 KV through a constant voltage generator 12 using a pentode 16.
To generate a bias voltage for biasing. At this time, the anode side of the magnetron 14 is grounded.
A negative high voltage of about 2.5 KV is applied. Further, a heater power supply 17 is connected to the cathode which also functions as a heater. At this time, the magnetron 14 outputs a microwave having a substantially constant frequency substantially proportional to the current. Constant voltage generator 1
The command value of 2 is externally changed by the current command input and is used for adjusting the microwave output power. The microwave output is guided to the cavity 15, and the plasma is excited at a point where the energy in the cavity 15 is concentrated.

[0005]

However, when a magnetron is used in an electronic cooker or the like, a commercial power supply is operated by using a pulsating voltage that has been boosted by a leakage transformer, half-wave rectified or full-wave rectified. In this case, the current is determined by the characteristics of the leakage transformer.

However, since the plasma used for the analyzer is required to always have the same temperature and density, the microwave is also required to always have a constant output. Since a high DC voltage of about 2.5 KV is required for the bias voltage of the magnetron, the high voltage power source needs to be capable of supplying a high voltage of about 3 KV. There is no single element having a sufficiently safe operation area at such a high voltage. For this reason, vacuum tubes that are robust against relatively excessive voltages have been widely used. However, most of the vacuum tubes have been discontinued, and even if they are currently produced, there are many problems in availability and quality. In addition, there is a problem that a so-called preheating time is required, that is, it is necessary to wait for a long time after the power is turned on until a stable operation is performed.

Therefore, by using a switching element which does not require a preheating time and has good characteristics, in particular, a MOS-FET,
There is a problem that a bias voltage of a DC high voltage of about 2.5 KV can be generated and a circuit configuration that can withstand a supply of about 3 KV of a high-voltage power supply must be solved.

[0008]

In order to solve the above-mentioned problems, a microwave oscillator according to the present invention comprises a high voltage power supply capable of generating a DC high voltage of several kilovolts, and a DC high voltage of several kilovolts. Is applied to a plurality of switching elements connected in series to generate a bias voltage to be supplied to a magnetron; a magnetron that generates a microwave based on the bias voltage; And a cavity resonator for generating plasma based on the waves.

The switching element is a MOS-F
ET; the high voltage of several kilovolts is approximately 3 KV of DC voltage, and the bias voltage is approximately 2.5 KV of DC voltage.

In order to generate a DC high voltage as described above,
By dividing the DC high voltage, it becomes possible to generate a bias voltage using a switching element, for example, a MOS-FET, which is distributed on the general market.

[0011]

Next, an embodiment of a microwave oscillator according to the present invention will be described with reference to the drawings.
The same components as those in the prior art will be described with the same reference numerals.

As shown in FIG. 1, the microwave oscillator according to the present invention supplies a high voltage power supply 11 for outputting a high DC voltage of approximately 3 KV and a magnetron 14 based on the DC high voltage 3 KV. Constant voltage generator 12A that generates a bias voltage to be applied, a current command input unit 13 that commands the current of the constant voltage generator 12A, a magnetron 14 that generates a microwave, and resonates with the microwave to excite plasma. And a cavity resonator 15. The control transistor Tr is connected to an external current command input unit 13.
And supplies the magnetron 14 with approximately 2.
The bias voltage, which is a high voltage of 5 KV, is controlled.

The constant voltage generator 12A is provided with a high voltage from the high voltage power supply 11 (in the embodiment, a DC high voltage of approximately 3 KV).
A resistance group A and a control resistance group B connected in series to divide and apply a voltage are provided in parallel, and a plurality of switching elements are connected in series between the resistance groups A and B.
The OS-FET 18 is provided. Specifically, the gate G of the MOS-FET 18 has a control resistor group B
And a resistor R2 for dividing the voltage of the pressurizing resistor group A is connected to the drain D side, and this resistor R2
Is connected to the source S side. As described above, when the n MOS-FETs 18 are connected in series, the value of the power supply voltage to be supplied (3 KV in the embodiment)
The number of MOS-FETs 18 that can be divided to a withstand voltage that can be withstood by the MOS-FETs 18 may be arranged to generate a desired device voltage (2.5 KV in the embodiment).

The microwave oscillator having the above-mentioned configuration is firstly constituted by a constant voltage generator 12A composed of a MOS-FET 18 connected in series from a high voltage power supply 11 of about 3 KV.
To generate a bias voltage for biasing the magnetron 14. At this time, since the anode side of the magnetron 14 is grounded, a negative high voltage of about -2.5 KV is applied to the cathode. Further, a heater power supply 17 is provided for the cathode also serving as a heater.
Is connected. At this time, from the magnetron 14,
A microwave having a substantially constant frequency that is substantially proportional to the current is output. The command value of the constant voltage generator 12A is externally changed by the current command input, and is used for adjusting the microwave output power. The microwave output is guided to the cavity resonator 15,
The plasma is excited at the point where energy is concentrated in the cavity resonator 15.

[0015]

As described above, a plurality of MOS-FETs in which a voltage obtained by dividing a DC high voltage is connected in series
, It is possible to generate a desired device voltage with a voltage corresponding to the withstand voltage of each MOS-FET. Therefore, a switching regulator that is mass-produced can be used, so that inexpensive and stable quality can be ensured, and a MOS-FET with a very good start-up characteristic is used. There is an effect that the operation can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic circuit diagram of a microwave oscillator using a MOS-FET according to the present invention.

FIG. 2 is a schematic circuit diagram of a microwave oscillator using a pentode according to the related art.

[Explanation of symbols]

11; high-voltage power supply; 12A; constant voltage generator; 13; current command input unit; 14; magnetron;
16; heater power supply, 18; MOS-FET

Claims (3)

[Claims] 1. A high-voltage power supply capable of generating a DC high voltage of several kilovolts, and said DC high voltage of several kilovolts is divided and applied to a plurality of switching elements connected in series, and is applied to a magnetron. A microwave oscillator comprising: a constant voltage generator for generating a bias voltage to be supplied; a magnetron for generating a microwave based on the bias voltage; and a cavity resonator for generating a plasma based on the microwave. 2. The microwave oscillator according to claim 1, wherein said switching element is a MOS-FET. 3. The microwave oscillator according to claim 1, wherein the high voltage of several kilovolts is a DC high voltage of about 3 KV, and the device voltage is a DC high voltage of about 2.5 KV.