Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Patent
1988-03-28
1989-09-05
Beha Jr., William H.
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
363 56, H02M 3335
Patent
active
048644803
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention refers to an electric power supply for a switching regulator. The power supply falls within the class of switching power supplies and more specifically within the subgroup of power converters.
2. History of the Prior Art
The state of the art regarding power converters is presented in the paper: "Schaltnetzteile" (Switching Power Supplies) by Joachim Wustehube (Hrsg), Grafenau/Berlin, Federal Republic of Germany. Supplements to the state of the art are contained in the "Technical Newsletter 3/85," Siemens AG, Munich, Germany.
While existing switching controllers experience no problems under normal operating conditions, difficulties arise for existing switching controllers when they are subjected to extreme conditions and special requirements. Often these problems cannot be resolved at the same time or with the same process. Examples of such extreme conditions are:
short circuit results in an almost complete breakdown of the output voltage V.sub.0 and a marked increase of the current. The short circuit is countered by shutting off the switching controller and then turning it on again with a soft starting circuit.
If the short circuit persists, this procedure is repeated, which allows the current to increase repeatedly in accordance with the threshold characteristics.
no-load operation means known today, conventional solutions to the no-load condition include (1) skippig pulses of increasing size that produce a V.sub.0 <=V.sub.Onominal when a maximum voltage V.sub.0 is reached in fixed frequency operation or (2) operating with the use of a built-in initial load.
sudden, severe load changes
large fluctuations of the input voltage
parallel operation of the switching controller the probability that both will operate exactly in phase is infinitesimal. They will therefore impede each other during an attempt to re-power the system.
limited range of the switching frequency control oscillator that usually oscillates on a fixed frequency. A fixed frequency may be selected to avoid interference with an appliance powered by the regulator (for example, a TV set). In this case, only the keying ratio between turn-on time of the transformer primary winding and the period of the oscillation is variable. If the frequency is kept variable, however, it fluctuates between approximately 200 KHz and a few KHz depending on the operating conditions. The frequency reaches the audible range of the human ear at approximately 16 KHz.
Dimensioning of the input filters is therefore extremely difficult, and the switching controller becomes a source of acoustical interference.
SUMMARY OF THE INVENTION
The object of the invention is the following: Among the latter, the following requirements are pointed out in particular: characteristic. same operating process and the same design is provided for. with the internal phasing of the regulator. facilitate dimensioning and to remain outside the audible range.
The operational process of the invention and the power converter of the invention are characterized by the individual treatment of the output voltage V.sub.0, the maximum average output current I.sub.0, the demagnetization of the transformer via the minimum secondary current, and the maximum input voltage-time integral in monitoring functions and circuit components. The invention is further distinguished because the power converter is separated from the input voltage when the maximum input voltage-time integral has reached a pre-determined value that is established by the apparatus. Reclosing occurs only when V.sub.0 and I.sub.0 have not exceeded their maximum values, and the secondary current remains below its minimum threshold. Process and apparatus also lower the input voltage-time integral that is determined by the apparatus if the normal output current at the voltage level V.sub.0 is not needed. This allows the turn-on time t.sub.0n and the pause duration t.sub.0ff to be shortened, which allows the switching frequency to remain variable within a narrow range.
REFERENCES:
patent: 4146832 (1979-03-01), McConnell
patent: 4504898 (1985-03-01), Pilukaitis
patent: 4612610 (1986-09-01), Farnsworth et al.
Stephens et al., "Flyback Converters for Multirail Switches," New Elec., vol. 14, No. 14, pp. 58-60, 14 Jul. 1981, (363/21).
Beha Jr. William H.
Melcher AG
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