Wave transmission lines and networks – Automatically controlled systems – Impedance matching
Reexamination Certificate
1999-05-12
2001-04-03
Lee, Benny (Department: 2817)
Wave transmission lines and networks
Automatically controlled systems
Impedance matching
C333S032000, C336S155000, C336S184000
Reexamination Certificate
active
06211749
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an impedance matching device for matching the impedance of a high-frequency (radio-frequency) generator with the impedance of a load device.
2. Description of Related Art
If the impedance of the high-frequency generator is not matched with the impedance of the load device while supplying a high-frequency power from the high-frequency generator into the load device, the supply efficiency of the high-frequency power from high-frequency generator to the load device is low.
The impedance value of the high-frequency generator is a fixed value, e.g., 50 (&OHgr;) or 75 (&OHgr;). On the other hand, the impedance value of the load device not only varies widely depending on the structure thereof and its installation condition, but varies widely for a short time depending on a physical change caused inside by the high-frequency power applied to the load device, e.g., a temperature rise and the like, and also depending on a chemical change, e.g., generation of a gas and the like, caused by decomposition of a part of the raw material of the components in the load device.
In order to match the impedance of the high-frequency generator with the impedance of the load device, an impedance matching device is generally provided between the high-frequency generator and the load device.
Next, an earlier developed impedance matching device provided between the high-frequency generator and the load device will be explained with reference to
FIGS. 12A
to
12
H.
FIGS. 12A
to
12
H are views showing circuit constructions of the main part of the earlier developed impedance matching device.
Although
FIGS. 12A
to
12
H show a plurality of circuit constructions, because the fundamental circuit functions of the constructions are substantially the same, only the construction shown in
FIG. 12A
will be explained and the explanation for
FIGS. 12B
to
12
H will be omitted.
Each of the impedance matching device shown in
FIGS. 12A
to
12
H comprises a variable capacitance element VC and a variable inductance element VL.
An end of the variable capacitance element VC is connected to a terminal “a” and the other end thereof is connected to terminals “b” and “d”. An end of the variable inductance element VL is connected to terminals “a” and an end of the variable capacitance element VC, and the other end of the variable inductance element VL is connected to a terminal “c”.
For example, between the terminals “a” and “b”, a high-frequency generator which is not shown is connected; and the terminals “c” and “d”, a load device which is not shown is connected.
In order to match the impedance of the high-frequency generator with the impedance of the load device, the capacitance value of the variable capacitance element VC and the inductance value of the variable inductance element VL are changed.
Although a detailed explanation for the method is omitted, the standing wave between the terminals “a” and “b” is measured, and a voltage standing wave ratio circuit is operated on the basis of the measurement result. Thereafter, the capacitance value of the variable capacitance element VC, and the inductance value of the variable inductance element VL are computed to match the impedance of the high-frequency generator with the impedance of the load device. According to the computation result, the capacitance value of the variable capacitance element VC and the inductance value of the variable inductance element VL are changed.
However, in the above-described earlier developed impedance matching device, because the high-frequency power for industrial use is not less than several tens of watts, a variable capacitor is used as the variable capacitance element VC, and the capacitance value of the variable capacitor is changed by using a motor. The inductance value of a coil which is used as the variable inductance element VL is changed by moving a contact (slider) on the coil by using a motor.
According to the above-described method in which the capacitance value of the variable capacitor used as the variable capacitance element VC and the inductance value of a coil used as the variable inductance element VL are changed by using a motor, a great amount of time is necessary to match the impedance of the high-frequency generator with the impedance of the load device because the speed available to change the capacitance value and the inductance value is restricted by the operating speed of the motor.
There is another problem that when the impedance of the load device has suddenly changed after matching of the impedance of the high-frequency generator and the impedance of the load device was carried out, changing of the capacitance value of the variable capacitor used as the variable capacitance element VC and the inductance value of a coil used as the variable inductance element VL cannot follow the sudden change of the impedance of the load device.
There is a further problem that maintenance operations, e.g., a routine lubrication, a replacement of consumable parts and the like, are required.
SUMMARY OF THE INVENTION
The present invention was developed in view of these problems. It is therefore an object of the present invention to provide an impedance matching device which enables changing the inductance value and the like at a high speed and matching the impedance of the high-frequency generator with the impedance of the load device at a high speed. Another object of the present invention is to provide an impedance matching device which does not require maintenance operations.
In accordance with an aspect of the present invention, the impedance matching device which is provided between a high-frequency generator and a load device, for matching an impedance of the high-frequency generator with an impedance of the load device, comprises; at least a coupled circuit which comprises a core, and a main winding and a control winding which are wound around the core; the coupled circuit changing an impedance of the impedance matching device by changing an inductance value of the main winding which depends on a magnitude of a direct current flowing in the control winding.
According to the invention, because the impedance of the impedance matching device is changed by changing the inductance of the main winding in the coupled circuit by changing the current value which flows in the control winding in the coupled circuit, it is possible to enable matching of the impedance of the device at a higher speed than an earlier developed impedance matching device which performs matching by changing the impedance mechanically by using a motor or the like; and it does not require maintenance operations.
In accordance with another aspect of the present invention, the impedance matching device, which is provided between a high-frequency generator and a load device, for matching an impedance of the high-frequency generator with an impedance of the load device, comprises at least a coupled circuit which includes a first core, a first main winding wound around the first core, a second core, a second main winding wound around the second core, and a control winding wound around the first and second cores, both the first and second cores passing through each turn of the control winding; wherein an impedance of the impedance matching device is changed by changing inductance values of the first and second main windings which depend on a magnitude of a direct current flowing in the control winding.
According to the invention, because the impedance of the impedance matching device is changed by changing the inductance of the first and second main windings by changing the current value which flows in the control winding in the coupled circuit, it is possible to enable matching of the impedance of the device at a higher speed than an earlier developed impedance matching device which performs matching by changing the impedance mechanically by using a motor or the like; and it does not require maintenance operations.
Further, because the high-frequency components generated in
Matsukawa Satoru
Yuzurihara Itsuo
Jones Stephen E.
Kyosan Electric Mfg. Co. Ltd.
Lee Benny
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