Electric power conversion systems – Current conversion – With condition responsive means to control the output...
Patent
1995-07-26
1997-03-25
Nguyen, Matthew V.
Electric power conversion systems
Current conversion
With condition responsive means to control the output...
323222, H02M 542, G05F 1656
Patent
active
056151004
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention refers to a resonant inverter comprising a resonant circuit, a source, an electronic switch means and a control circuit.
The present invention deals in general with a resonant inverter e.g. in the form of an oscillator or of a self-excited narrowband high-frequency amplifier for driving a purely ohmic load, an ohmic capacitive load or an ohmic inductive load.
DESCRIPTION OF THE PRIOR ART
Inverters and switched-mode mains power supplies normally comprise bipolar components, irrespectively of whether they work with a resonant circuit or are able to operate without such a resonant circuit. One embodiment of such a known inverter is, by way of example, disclosed in the following company publication: S. Lowbridge, M. Maytum, K. Rutgers: Electronic Ballasts for Fluorescent Lamps using BUL 770/791 Transistors (Texas Instruments, 1992). This inverter is a self-excited half-bridge circuit working with bipolar transistors, reverse diodes, a series resonant circuit and inductive base feedback. Such a circuit is also classified as a class D amplifier. Due to the lossy draining of the minority carriers of the bipolar components, such circuits can only be operated up to a specific maximum frequency. Even if minority carrier-free MOS transistors are used, such circuits show the disadvantage of capacitive drain losses, since the switch elements must be switched on under voltage. In addition to the losses and frequency limitations explained hereinbefore, other disadvantages of such inverters exist with regard to the large number of components required as well as with regard to the fact that it is impossible to implement load regulation in a simple manner.
The technical publication N.0. Sokal, A.D. Sokal: Class E --A new Class of High Efficiency Tuned Single-Ended Switching Power Amplifiers (IEEE Journal of Solid-State Circuits, Vol. SC-10, No. 3, June 1975) discloses high-frequency amplifiers of the so-called E class which need only a single switch and which have a high efficiency. Such amplifiers are predominantly used as transmitter amplifiers and are operated by means of an externally generated clock pulse with an on time which is approximately half as long as the period duration. Load regulation is not carried out in connection with such high-frequency amplifiers, since this type of amplifier operates at a fixed frequency and with an approximately constant load.
To sum up, it can be stated that, as far as known inverters are concerned, the inverters in the form of half-bridge circuits which were described at the beginning are not suitable for a so-called single-chip solution, which makes use, for example, of a single vertical DMOS transistor, because they require pairs of transistor circuits, that these inverters do not permit load regulation, necessitate a large number of components and show high power losses. Furthermore, such circuits only operate at comparatively low frequencies so that comparatively large capacitive and inductive components are required.
The class E amplifier described has a fixed predetermined frequency within a narrow frequency tolerance range, the clock pulse with a ratio of on time to period duration of 0.5 being generated externally so as to permit optimum operation of the amplifier.
FIG. 1 of U.S. Pat. No. 4,413,313 discloses a resonant inverter which comprises a resonant circuit, a source, an electronic switch means and a control circuit, said control circuit having the following features: a voltage detection circuit responding to a voltage value of the voltage drop across the electric switch means, a current detection circuit responding if the current flowing through the switch means exceeds a specific value, and a control signal generation circuit connected downstream of said voltage detection circuit and said current detection circuit and used for generating a control signal for the electronic switch means. The current detection circuit produces on its output side a "high" signal as soon as a current flows through the resistor in the direc
REFERENCES:
patent: 3641422 (1972-02-01), Farnsworth et al.
patent: 4413313 (1983-11-01), Robinson
patent: 4442397 (1984-04-01), Ishikawa et al.
patent: 4649334 (1987-03-01), Nakajima
patent: 5032972 (1991-07-01), Erckert
patent: 5179511 (1993-01-01), Trovk et al.
IEEE Journal of Solid-State Circuits, vol. SC-10, No. 3, Jun. 1973, pp. 1176, Nathan O. Sokal and Alan D. Sokal,"Class E--A New Class of High-Efficiency Tuned Single-Ended Switching Power Amplifiers".
Fiedler Horst-Lothar
Radecker Matthias
Fraunhofer-Gesellschaft zur Forderung der Angewanten Forschung e
Nguyen Matthew V.
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