Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Patent
1983-05-03
1985-05-14
Beha, Jr., William H.
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
363 90, 323263, H02M 3335
Patent
active
045176337
DESCRIPTION:
BRIEF SUMMARY
The present invention refers to a power supply working after the chopper principle and which belongs to the kind named in the introductory part of claim 1.
A special class of power supplies is in its different modifications called "switched mode regulator", "switched mode power supply", "chopper power supply", "dc-dc converter", "ac-dc converter". They are commonly characterized in that a first direct voltage, which generally is neither stable nor regulated, is switched on and off at a frequency of 20 to 300 kc, thereby energizing an electric circuit at this frequency. This said electric circuit comprises means for smoothing the voltage being storage elements at the same time, hence chokes and condensers. The output voltage is compared with a reference voltage by means of a comparator which is controlling the keying ratio of the switched first direct voltage by means of further circuitry as to obtain the required output voltage. In case the desired voltage ist to be derived from the voltage of a public network, it is generally required to have no resistive coupling between the primary and the secondary circuits of such a power supply. In such case, the circuit chopping the first direct voltage is energizing the primary coil of a transformer.
One distinguishes between forward converters and flyback converters depending on the secondary circuitry.
A state-of-the-art description of switched mode power supplies with one regulated outlet is in "Schaltnetzteile" by J. Wustenhube (Editor), Expert Edition, Grafenau/VDE-Edition, Berlin, GDR. In switched mode power supplies with no resistive coupling, a change in output power causes a change of the keying ratio between the two states of the switching element energizing the primary coil of the isolation transformer. In case the isolation transformer of a switched mode power supply has a multitude of secondary coils each feeding an individual outlet, without special measures only the one outlet will have a stable output voltage from which the actual value/setpoint value difference is obtained (from now on called main circuit); the voltages of the other outlets (hence the secondary circuits) are influenced within wide boundaries by the load.
The diagramm of a circuit with a multitude of controlled secondary circuits has been published in the November/December, 1980, issue of the magazine "Powerconversion International", where, as FIG. 18, the state of the art of such circuitry is shown. There the output voltages E.sub.02 to E.sub.0M are preregulated by inductive coupling of the chokes L.sub.2 to L.sub.M, the final regulation is obtained by conventional series regulation. Such a circuit is rather sumptuous concerning number and size of the required elements and has--due to the series regulation--a relatively low efficiency, as shown in the quoted litterature.
Hence a great share of the input power is to be dissipated as heat. The goal of the invention is a power supply of the kind named in the introductory part of claim 1 which overcomes the mentioned disadvantages and is characterized in claim 1.
By means of the drawings the idea of the invention is exemplified. They show:
FIG. 1 a forward converter, partly as block diagram, as an embodiment of the invention,
FIG. 2 a detail drawing of a forward converter as an embodiment of the invention,
FIG. 3 the voltage response at a given point of the circuit diagram according to FIG. 2,
FIG. 4 a flyback converter, partly as block diagram, as a further embodiment of the invention,
FIG. 5 a secondary circuit of the embodiment shown in FIG. 4 in a detail drawing,
FIG. 6 a dc-dc converter with resistive coupling as a further embodiment of the invention,
FIG. 7 a forward converter as a further embodiment of the invention at which two secondary circuits are connected by resistive coupling, thereby one secondary circuit energizing the other one with dc,
FIG. 8 a push-pull forward converter as a further embodiment of the invention.
The forward converter according to FIG. 1 comprises an isolation transformer 4 with a primary coil 1. It i
REFERENCES:
patent: 4055740 (1977-10-01), Nakamura et al.
patent: 4447866 (1984-05-01), Reeves
IBM Technical Disclosure Bulletin, "Low-Insertion-Loss Class A Precision Regulator", J. S. Contino et al., vol. 21, No. 12, May 1979, pp. 4906-4908.
Ault Anita M.
Beha Jr. William H.
Ostfeld David
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