Electric power conversion systems – Current conversion – Including an a.c.-d.c.-a.c. converter
Reexamination Certificate
1989-10-02
2001-05-08
Berhane, Adolf Deneke (Department: 2838)
Electric power conversion systems
Current conversion
Including an a.c.-d.c.-a.c. converter
C363S132000, C315S2090SC
Reexamination Certificate
active
06229718
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to self-oscillating transistor full-bridge inverters, particularly of a type that provides sinusoidal output voltage.
2. Description of Prior Art
Although self-oscillating transistor inverters providing their output in the form of sinusoidal voltage do presently exist —as for instance described in U.S. Pat. Nos. 4,370,600 and 4,392,087 to Zansky, or in U.S. Pat. No. 4,277,726 to Burke —full-bridge inverters of that type do not presently exist. Yet, full-bridge inverters have several significant advantages as compared with half-bridge or regular push-pull inverters, especially in terms of voltage, current and/or power handling capabilities.
SUMMARY OF THE INVENTION
Objects of the Invention
A first object of the present invention is that of providing a self-oscillating full-bridge transistor inverter with substantially sinusoidal output voltage.
A second object is that of providing a full-bridge inverter powered from a center-tapped DC voltage source and having its own output center-tapped.
A third object is that of providing an inverter that is particularly cost-effective, efficient and versatile in use.
These, as well as other important objects and advantages of the present invention will become apparent from the following description.
Brief Description
In its preferred embodiment, subject invention is a full-bridge inverter comprising four switching transistors and being symmetrically powered from a center-tapped DC voltage source through an inductor means having two windings on a single magnetic core—with one winding positioned in each leg of the DC source. This full-bridge inverter has a center-tapped parallel-resonant L-C circuit connected across its output, and is made to self-oscillate by way of two positive feedback current-transformers, each connected in series with the center-tapped L-C circuit and any load connected thereto.
The outputs from the current-transformers are applied to the control terminals of the four switching transistors, thereby providing load-proportional drive to these transistors.
The center-tapped DC voltage source, the inductor means and the full-bridge inverter circuit with its two feedback current-transformers are connected together in symmetrical fashion; which provides for the center-tap of the inverter output to be at the same potential as the center-tap of the DC voltage source. Thus, since the center-tap of the DC source is grounded, the center-tap of the inverter's output is grounded as well; which, in turn, implies that any load connected to the inverter's output is symmetrically referenced to ground.
The feedback current-transformers are saturable and so designed as to saturate approximately at the time the inverter's output voltage reaches zero magnitude.
A Zener-type voltage-limiting device is connected directly between the inverter's DC power input terminals, thereby to protect the transistors from voltage transients of excessive magnitude.
REFERENCES:
patent: 2965856 (1960-12-01), Roesel
patent: 3155875 (1964-11-01), Wenrich et al.
patent: 3868561 (1975-02-01), Matthes
patent: 4184128 (1980-01-01), Nilssen
patent: 4277726 (1981-07-01), Burke
patent: 4307353 (1981-12-01), Nilssen
patent: 4346332 (1982-08-01), Walden
patent: 4469988 (1984-09-01), Cronin
patent: 4504895 (1985-03-01), Steigerwald
patent: 135689 (1982-08-01), None
patent: 153473 (1984-09-01), None
Baker, “High Freq. Pwr.Conv. with FET—Contr. Res. Charge Transfer”, PCI Apr. 1983 Proceedings, pp. 130-133.*
No Author, “Buck-Regulator and H-Inverter”, Elekt. -Applikation, vol. 13, No. 1, pp. 28, 29, 1981.
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