JP2508175Y2 - Amplifier parallel output combiner for low impedance loads. - Google Patents

Description

[Detailed Description of the Invention] a. Purpose of the invention [Industrial field of application] When high frequency plasma is applied to generate ultra-high temperature plasma and it is used in various fields of science and engineering, it requires a large amount of power. A solid-state amplifier (which is used as an amplifier that does not use a vacuum tube but is substantially synonymous with a simple “amplifier”) requires parallel operation. Also, the plasma impedance of the load is very low compared to the amplifier output impedance. The present invention relates to a suitable output combining circuit used for such a purpose.

[Conventional technology]

As a method of synthesizing the output of the solid-state amplifier, generally, a method using a 3 dB hybrid circuit, a Wilkinson distributor or a modification thereof is used. The 3dB hybrid is a directional coupler with a coupling degree of 3dB, and the latter is also large in the frequency band of several MHz used for plasma excitation in the distributed constant circuit and is difficult to use. Regarding these, for example, in the microwave integrated circuit by Yoshihiro Konishi of Kobo Publishing Co., Ltd.
See pages 79-89 and 217-218. They are
Although suitable for the VHF to EHF band, there is also the circuit 6 of FIG. 2 in which the Wilkinson distributor is composed of a lumped constant circuit. This is MANLEY J.HEAD "Synthesize Lumped Element In-P
hase Power Dividers ", Microwave Journal May 198
0, pp 111-112, but for two circuits,
It is necessary to use an even number of amplifiers, and if there are four or more circuits, they must be connected in series in multiple stages as shown in FIG. Further, a relatively large resistor 5 is required as the absorption resistance.

[Problems to be solved by the invention]

An output of several + kW at several MHz is required for exciting the ultra-high-temperature high-frequency plasma, and 6 or more parallel operations are desired for a fixed amplifier with an output of about 5 kW. Moreover, the output impedance of the amplifier is usually selected to be 50Ω, while the plasma excitation inductive load impedance is about 1Ω.
Impedance conversion of about 1 to 1 is required. Due to these conditions, it is difficult to solve by the conventional method.

An object of the present invention is to provide an output synthesis circuit that solves these problems.

(B) Configuration of the device [Means for solving the problem] The present invention, as shown in FIG. 1, provides the outputs of the amplifiers 1 ₁ to 1 _n with
Impedance transformer circuit for converting to low impedance 2 ₁
~ 2 _n are placed and matched by a second impedance transformer circuit 3 which transforms these outputs back into low impedance to power the load 4. The output impedance of the amplifier is matched to the load impedance by the product (n1 × n2) where n1 is the impedance transformation ratio of the former and n2 is the latter.

[Action]

The connected to each amplifier 1 impedance transformer 2 ₁ -
Each output impedance is stepped down to several Ω by 2n,
After that, the outputs are collectively output by the second impedance transformer 3 to generate a load impedance (in the case of plasma, approximately 1Ω.
Before and after).

In the circuit shown in FIG. 2, even if there is a reflection from the load, the reflection is absorbed by the reflection absorption resistor 5, so that it does not adversely affect each amplifier. The reflections from the output will affect the output of each amplifier.
However, if the load changes suddenly, such as in plasma, the second impedance transformer 3
Since it is used as an automatic matching circuit so as to almost always satisfy the matching, there is no reflection from the load, which is not a problem.

Further, the transformation ratios of the first and second transformers can be arbitrarily selected as long as their products are equal, so that the configuration is easy.

〔Example〕

A 6Ω amplifier with an output of 5.5kW at a frequency of 3MHz and an output impedance of 50Ω is connected to an impedance transformer circuit of 50Ω to 8.3Ω each, and the outputs are grouped together as a circuit that can be automatically matched as a second impedance transformer. It was possible to supply high-frequency power of 30kW to the load coil (load impedance of about 1Ω). As an automatic matching circuit, utility model application publication No. 61-30332 (application October 4, 50, actual application Sho 5
No. 0-135799), but the patent application publication Sho 61
No. 139111 can also be used.

C. Effect of the Invention As described above, excitation of ultra-high temperature and high frequency plasma requires power of several tens of kW at several MHz, and the load impedance is very low, around 1Ω. It can be operated compactly and stably by operating several units in parallel. In addition, by making the second impedance transformation circuit an automatic matching type, it is possible to immediately cope with a sudden load change due to a change in plasma and operate stably for a long time.
There is no problem even if the number of amplifiers is odd.

[Brief description of drawings]

FIG. 1 shows a parallel output synthesis circuit diagram of the present invention, and FIGS. 2 and 3 show an example of a conventional two-circuit synthesis circuit using lumped circuit elements. 1 ₁・₁・₂・ 1 ₃・ 1 ₄・ 1 _n is a solid-state amplifier, 2 ₁・ 2 ₂・ 2 ₃・ 2 _n is a first impedance transformer, 3 is a second impedance transformer, 4 is a load, 5 Is a reflection absorption resistance, and 6 ・ 6 ₁ , 6 ₂・ 6 ₃ is a two-circuit combining circuit using lumped circuit elements.

Claims (1)

(57) [Scope of utility model registration request] 1. In a high-frequency power supply device for generating ultra-high-temperature high-frequency plasma, when a plurality of amplifier outputs are connected in parallel to supply power to a low impedance inductive load, an impedance conversion circuit is placed at each amplifier output and the output thereof is provided. A parallel output combining circuit in which an automatic matching circuit is provided so as to supply power to a low-impedance inductive load of the load, and the power is supplied to the load.