JPH0594867A - High frequency oscillator - Google Patents

Abstract

PURPOSE:To lessen the pulsation of double harmonic frequency of high frequency output voltage by providing a transformer which is connected to the output side of an full wave rectifying circuit via a DC cut circuit, while voltage on its secondary side is applied to the grid resistance circuit of an electron tube. CONSTITUTION:The primary voltage of a filament TR3 is inputted to a full wave rectifying circuit 11, so that voltage efd is outputted. Since voltage from which the DC portion of voltage efd is cut off, is inputted to a transformer TR5 from a DC cut circuit 12, voltage eff for double frequency is built up at the secondary side of the transformer. Voltage eff is overlapped to grid bias voltage in such a way that oscillation amplitude is restrained while bias voltage is intensified to the minus side as the amplitude of filament applied voltage in a grid bias circuit 8 is increased. Pulsation can be lessened if the pulsation portion of high frequency output voltage based on change in filament temperature and the pulsation of high frequency output voltage based on bias voltage where voltage eff is overlapped, can be offset each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an industrial high frequency oscillator used for an induction heating device or the like.

[0002]

2. Description of the Related Art A conventional high frequency oscillator in an induction heating device is shown in FIG. In FIG. 5, reference numeral 5 denotes a high-frequency oscillator circuit using the hot cathode electron tube 4 for oscillation. The DC voltage Edc required for oscillation of the electron tube is a three-phase high voltage e ₁ which is a step-down transformer T.
The voltage is reduced to the withstand voltage of the thyristor with R ₁ , the voltage is controlled by the output voltage control thyristor circuit 1, boosted again by the boosting transformer TR ₂ , rectified by the three-phase full-wave rectifier circuit 2, and smoothed by the filter circuit 3. I'm getting it.

Reference numeral 7 denotes a filament circuit of the electron tube 4, which heats the filament of the electron tube by inputting a voltage obtained by stabilizing the single-phase power supply voltage e ₂ by the automatic voltage regulator 6 to the filament transformer TR ₃ . 8 is a grid bias circuit, Ct
₁ and Ct ₂ are tank capacitors, and Cg ₁ and Cg ₂ are feedback capacitors.

[0004]

The high frequency output voltage of the oscillator circuit contains a large amount of pulsation when viewed microscopically. For this reason, a large amount of choke coils and capacitors are added to the filter circuit to improve the pulsation of the DC voltage.

However, when the frequency of pulsation is low and a harmonic wave is used, the filter becomes huge. Further, the control response speed is too slow to control this pulsation with the output voltage adjusting thyristor circuit, which makes control impossible.

Further, the heating of the filament of the electron tube by the single-phase AC voltage affects the thermionic emission and causes the harmonic output voltage fluctuation of several%. Pulsations increase as the load increases.

In the induction heating device, temperature unevenness occurs when the heating member moving at high speed moves 1 mm or more during one cycle of the harmonic wave. Therefore, it cannot be used for higher-grade materials, welding that requires a precise temperature range, and thermal processing.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to reduce the pulsation of the harmonic component of the high frequency output voltage and to reduce the pulsation of high frequency induction heating. An object of the present invention is to provide a high-frequency oscillator capable of reducing the temperature unevenness of the heating member.

[0009]

In order to achieve the above object, a high frequency oscillator according to the present invention is a high frequency oscillator for heating a filament of an oscillating hot cathode electron tube with a single phase alternating current. It is provided with a connected full-wave rectifier circuit and a transformer connected to the output side of the full-wave rectifier circuit via a DC cut circuit to add the secondary side voltage to the grid resistance circuit of the electron tube.

An induction voltage regulator is connected to the single-phase alternating current for heating the filament, and a full-wave rectification circuit is connected to the secondary side of the induction voltage regulator, and the rectification voltage is applied to the grid resistance circuit of the electron tube. May be.

[0011]

When the filament of the electron tube is heated with a single-phase alternating current, the surface temperature of the cathode changes with the harmonic wave, so that the high frequency output pulsates with the harmonic wave.

On the other hand, when the single-phase alternating current for filament is full-wave rectified, the direct current is cut and applied to the transformer, a voltage having a frequency twice that of the single-phase alternating current is obtained on the secondary side. When a voltage of this double frequency is applied to the grid resistance circuit of the electron tube, the grid bias voltage changes, and the high frequency output pulsates with a harmonic wave.

Therefore, by selecting the polarity and magnitude of the voltage from the transformer applied to the grid resistance circuit, the harmonic pulsation of the high frequency output due to the change in the surface temperature of the cathode and the ripple of the DC power supply of the oscillation circuit is canceled. Can be reduced.

When the secondary side voltage of the induction voltage regulator is full-wave rectified and applied to the grid resistance circuit, the grid bias voltage pulsates due to the full-wave rectified wave. In this case, since the grid bias (DC component) voltage changes by the average value of the full-wave rectified wave, if the grid bias (DC component) voltage is added and added to the grid resistor, the transformer is used. Similarly, the harmonic pulsation of the high frequency output can be reduced.

[0015]

First Embodiment FIG. 1 shows a high frequency oscillator circuit according to a first embodiment. In addition,
The same components as those shown in FIG. 4 of the related art are designated by the same reference numerals, and the duplicate description thereof will be omitted.

In FIG. 1, 10 is a frequency doubler circuit, 11 is a full-wave rectifier circuit for full-wave rectifying the primary voltage of the filament transformer TR ₃ , and TR ₅ is connected to this full-wave rectifier circuit. The secondary side of the transformer is connected to the grid resistance Rg circuit of the grid bias circuit 8 of the electron tube 4. Reference numeral 12 is a DC component cut circuit that cuts the primary side DC component of this transformer.

Next, the operation of this embodiment will be described with reference to FIGS.
Will be described.

Since the primary voltage of the filament TR ₃ (FIG. 2 (a)) is input to the full-wave rectifier circuit 11, its output voltage e _fd is as shown in FIG. 2 (b). Since a voltage obtained by cutting the DC component of the output voltage e _fd is input to the transformer TR ₅ from the DC cut circuit 12, the voltage e of the frequency doubled as shown in FIG. 2C is input to the secondary side of the transformer. _ff occurs.

This voltage e _ff is superposed on the grid bias voltage so that the bias voltage becomes deeper to the negative side when the filament applied voltage amplitude increases via the grid resistance Rg of the grid bias circuit 8 to suppress the oscillation amplitude. It

When an electron tube filament is heated by alternating current, (1) on average, the amount of heat per unit time (J / sec = W) charged into the filament and the amount of heat released per radiant heat are about 1900 ° K. In equilibrium.

(2) Microscopically, the filament is 19
The amount of heat to bring the temperature to 00 ° K Q ₁₉₀₀ (Joul) of f × 2 cycles

[0022]

[Equation 1]

Is added. Wrms = W in steady state
It becomes rad.

Since the amount of heat input is determined by R _if ² (R: filament resistance, _if : filament current), _{if a} single-phase voltage e _f is applied to the filament, the filament temperature T is doubled as shown in FIG. Pulsates.

However, if the pulsation of the high frequency output voltage based on the filament temperature change in FIG. 3 and the pulsation of the high frequency output voltage based on the bias voltage on which the voltage e _ff are superimposed are canceled, a single-phase AC It is possible to reduce the pulsation of the high frequency output voltage due to the filament heating.
Further, it is possible to reduce the harmonic pulsation of the high frequency output voltage based on the rectification ripple of the DC power supply circuit. The voltage from the transformer TR ₅ may be adjusted by a variable voltage dividing resistor or the like and applied to the grid resistance.

However, by generating the former pulsation so as to be opposite to the latter pulsation, the harmonic pulsation of the high frequency output can be reduced.

Second Embodiment FIG. 4 shows an oscillator circuit according to a second embodiment. In addition, the same components as those shown in FIG. 1 are designated by the same reference numerals, and the duplicate description thereof will be omitted.

In FIG. 4, reference numeral 13 is a voltage regulator which uses the filament circuit voltage e _f as a power source, and the single-phase full-wave rectifier 11 is connected to the secondary side thereof. Rg ₁ and Rg ₂ are grid resistors forming a grid resistor Rg, and the single-phase full-wave rectified voltage e _fd ′ of the rectifier 11 is applied to both terminals of the resistor Rg ₂ . Also in this embodiment, since the voltage of the frequency twice the filament applied voltage can be adjusted and superimposed on the grid bias voltage, the harmonic pulsation of the high frequency output voltage can be reduced.

[0029]

Since the present invention is configured as described above, it has the following effects.

(1) The pulsation of the harmonic component of the high frequency output voltage can be reduced.

(2) As a result, it is possible to reduce the temperature unevenness of the heating material that moves at high speed and is heated by, for example, high frequency output.

(3) The quality of heat processing (welding quality, heat treatment quality) due to temperature unevenness can be greatly improved.

(4) Since the allowable amounts of other factors that change the quality are increased, stable operation becomes possible.

(5) Therefore, productivity, operating rate, yield, labor saving, cost reduction can be realized, or higher quality can be put to practical use, which can contribute to realization of new products.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a high-frequency oscillator according to a first practical example.

FIG. 2 is a waveform diagram showing the voltage of each part of the harmonic suppression circuit.

FIG. 3 is a waveform diagram showing the relationship between filament voltage and filament temperature.

FIG. 4 is a block circuit diagram showing a high frequency oscillator according to a second embodiment.

FIG. 5 is a block circuit diagram showing a conventional high frequency oscillator.

[Explanation of symbols]

1 ... Output control thyristor circuit, 2 ... 3-phase full-wave rectifier circuit, 3 ... Smoothing filter, 4 ... Hot cathode electron tube, 5 ... High frequency oscillation circuit, 6 ... Automatic voltage regulator, 7 ... Filament circuit, 8 ... Grid Bias circuit, 10 ... Double harmonic suppression circuit, 11 ... Single-phase full-wave rectification circuit, 12 ... DC component cut circuit, 13 ... Induction voltage regulator.

Claims (2)

[Claims] 1. A high-frequency oscillator for heating a filament of an oscillating hot cathode electron tube with a single-phase alternating current, comprising: a full-wave rectification circuit connected to the single-phase alternating current for heating the filament; and an output side of the full-wave rectification circuit. A high-frequency oscillator, characterized in that a transformer connected to the direct-current cut circuit to apply the secondary voltage to the grid resistance circuit of the electron tube is provided to reduce the harmonic pulsation generated in the high-frequency output. 2. A high-frequency oscillator for heating a filament of an oscillating hot cathode electron tube with a single-phase alternating current, an induction voltage regulator connected to the single-phase alternating current for heating the filament, and a secondary side of the induction voltage regulator. A high-frequency oscillator, comprising: a full-wave rectification circuit that applies full-wave rectification of a voltage and applies the rectified voltage to a grid resistance circuit of the electron tube to reduce a harmonic pulsation generated in a high-frequency output.