JPS6141107B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high frequency decompression device, and particularly to an output adjustment device thereof.

Conventionally, high-frequency thawing equipment applies dielectric heating by applying a high-frequency high voltage between parallel flat metal electrodes and sandwiching the object to be thawed between them. It was needed. Also, if the high frequency output is too large,
There were drawbacks such as decreased thawing performance and increased surface temperature. Conventional output adjustment methods have involved changing the DC voltage applied to the oscillation circuit, but the common method has been to change the output by changing the taps on the windings of the high-voltage transformer. however,
Since the tap method adjusts the output in stages, it is difficult to adjust the output to a desired level, and the high-voltage transformer is expensive.

The present invention eliminates the above drawbacks and provides a high frequency decompression device whose output can be adjusted continuously and easily. Embodiments of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, an AC voltage is applied from a low frequency AC power source 1 to a high voltage DC power source 2 and converted into a high DC voltage. High frequency oscillation circuit 3 from high voltage DC power supply 2
A high DC voltage is applied to generate a high frequency voltage.
The high-voltage DC power supply 2 is configured by converting an AC high voltage obtained by a high-voltage transformer 20 into a DC high voltage by a rectifier circuit 21, and connecting an input capacitor 22 to an output terminal of the rectifier circuit 21. The DC+ terminal is grounded and the DC- terminal is connected to the high frequency oscillation circuit 3.
The high frequency oscillation circuit 3 is a self-excited oscillation circuit and has the following configuration. A resonant circuit constituted by a parallel circuit of a resonant coil 31, a heating electrode 32, and a stabilizing capacitor 33 is connected between the plate of the straight tube 30 and the ground. A filter capacitor 34 is connected between the plate of the vacuum tube 30 and the ground, and a fine adjustment variable capacitor 34' is connected in parallel with the filter capacitor 34. The filter capacitor 34 and the variable capacitor 34' serve to bypass the resonance current flowing through the resonance coil 31, the heating electrode 32, and the stabilizing capacitor 33, and the output can be adjusted by changing the capacitance of the variable capacitor 34'. FIG. 2 shows changes in the high frequency output P and the oscillation frequency when the capacitance of the variable capacitor 34' is changed. When the capacitance is increased, the high frequency output increases greatly, but the change in the oscillation frequency f is very small.

A chiyoke coil 35 is connected between one end of the resonance coil 31 and the ground, and DC current is supplied. A grid coil 36 and a bias resistor 37 are connected between the grid and the cathode of the vacuum tube 30, and a bypass capacitor 38 is connected between the connection point between the bias resistor 37 and the grid coil 36 and the ground. The grid coil 36 is electromagnetically coupled to the resonant coil 31, forming a so-called plate-tuned oscillation circuit. The cathode terminal of the vacuum tube 30 is connected to the heater transformer 5 and supplied with heater current.

As described above, the present invention connects a variable capacitor for output fine adjustment in parallel in order to make the capacitance of the filter capacitor through which the bypass current of the tank circuit flows variable. When the filter capacitor capacity is made variable, only the high frequency output changes and the oscillation frequency hardly changes, so continuous fine adjustment is possible. Compared to the conventional method of changing the DC voltage by switching the taps of a high-voltage transformer, this method is less expensive and allows continuous fine adjustment of the output.

[Brief explanation of the drawing]

FIG. 1 shows a circuit diagram of a high frequency decompressing device according to an embodiment of the present invention, and FIG. 2 shows a characteristic diagram of the same output adjustment method. 2...High voltage DC power supply, 3...High frequency oscillation circuit,
31...Resonance coil, 32...Heating electrode, 34
...filter capacitor.

Claims (1)

[Claims] 1 Consisting of a high-voltage DC power supply and a high-frequency oscillation circuit connected to the output terminal of the high-voltage DC power supply, the high-frequency oscillation circuit includes a resonant circuit composed of a resonant coil and a heating electrode that dielectrically heats the object to be thawed; A high-frequency decompression device comprising a self-excited oscillation circuit equipped with a variable-capacity filter capacitor that bypasses circuit current, and changing the high-frequency output by changing the capacitance of the filter capacitor.