Electric power conversion systems – Current conversion – Using semiconductor-type converter
Patent
1988-06-13
1989-03-07
Wong, Peter S.
Electric power conversion systems
Current conversion
Using semiconductor-type converter
363 98, 323289, 307270, H02M 7537
Patent
active
048111929
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
TECHNICAL FIELD
The present invention relates to an inverter apparatus and, in particular, to an inverter apparatus in which a metal oxide semiconductor (MOS) transistor, broadly speaking, a metal insulator semiconductor (MIS) transistor, is connected in series between an input end of a direct-current voltage and a load, and the MOS transistor is driven by a drive signal of a single frequency, thereby converting the direct-current voltage into an alternating-current voltage corresponding to the single frequency. The apparatus according to the present invention can be utilized, for example, as a high frequency power source for a radio-frequency (RF) excitation-type carbonic acid gas (CO.sub.2) laser equipment.
BACKGROUND ART
In the above-mentioned inverter apparatus, the frequency of an alternating-current output voltage corresponds to the frequency of a drive signal for driving a switching MOS transistor. Accordingly, to gain a stable output voltage having a defined frequency, the MOS transistor must quickly respond to the change in voltage of a drive signal of the defined frequency and carry out the switching operation thereof.
On the other hand, it is generally known that an equivalent input capacitance is exists between a gate and a source of a MOS transistor. Such an input capacitance is determined by the size of the source region, i.e., a diffusion region, and the concentration of impurities therein, a location of the gate and source, and the like, and is parasitically formed when the MOS transistor is formed on a semiconductor substrate.
Accordingly, where an input capacitance (capacitor) exists between the gate and the source of the transistor, a problem arises in that, due to the charging or discharging characteristics of the capacitor, the input voltage of the transistor cannot quickly follow the change in voltage of the aforementioned drive signal. Especially, the higher the frequency of the drive signal, the greater the influence. Accordingly, this problem must be solved, from the viewpoint of acquiring a stable high frequency output voltage. On the other hand, because of the power loss caused by resistors inserted in the input circuit, for compensating the influence of the capacitor, another problem arises in that the efficiency of the power conversion of the whole apparatus is lowered.
Furthermore, it is generally known that an equivalent output capacitance exists between a drain and a source of a MOS transistor. The output capacitance is parasitically formed during the forming of the transistor, as in the aforementioned input capacitance. The existence of the output capacitance (capacitor) causes not only the same problem as that in the aforementioned input capacitor, but also other problems.
The details of the problems arising due to the existence of the parasite input capacitor and parasite output capacitor of the aforementioned MOS transistor will be explained later.
DISCLOSURE OF THE INVENTION
A main object of the present invention is to provide an inverter apparatus capable of gaining a stable output voltage having a desired high frequency.
Another object of the present invention is to provide an inverter apparatus capable of not only decreasing a power loss therein, to increase the efficiency of the power conversion, but also raise the frequency thereof as a power source.
The above objects are attained by providing an inverter apparatus comprising: an input terminal for inputting a direct-current voltage; an output terminal connected to a load; a circuit for generating a drive signal of a single frequency; at least one MIS transistor connected in series between the input terminal and the output terminal, and carrying out a switching operation corresponding to the single frequency in response to the drive signal; and a first inductance element connected between a gate and a source of the MIS transistor and effecting a parallel resonance with an input capacitance of the transistor.
In the inverter apparatus according to the present invention, since an inductance elem
REFERENCES:
patent: 4461966 (1984-07-01), Gebenstreit
patent: 4520438 (1985-05-01), Norton
patent: 4566059 (1986-01-01), Gallios et al.
patent: 4694206 (1987-09-01), Weinberg
Fanuc Ltd.
Wong Peter S.
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