Electrical transmission or interconnection systems – Plural supply circuits or sources – One source floats across or compensates for other source
Patent
1996-01-11
1997-12-16
Shoop, Jr., William M.
Electrical transmission or interconnection systems
Plural supply circuits or sources
One source floats across or compensates for other source
307 43, 307 71, 307 87, 307141, H02J 338
Patent
active
056989083
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The method relates to a DC power supply system in which a principal power source is buffered by an auxiliary power source by providing that in the event of failure of the principal power source the auxiliary power source takes over the supply of energy.
In a known form of the buffered DC power supply, the mains voltage as the principal power source is rectified and, as an intermediate voltage, feeds a switching voltage transformer which supplies the final consumer. Via a further voltage transformer, the voltage of a battery is brought to a value near the lower limit of the intermediate voltage. The principal voltage and auxiliary voltage are decoupled by diodes and thus alternatively generate the intermediate voltage. Particularly in the case of data processing equipment, a digital signal is required which indicates whether the further power supply is ensured or whether the auxiliary voltage is exhausted after a mains failure. For this purpose, a watchdog module designed as a trigger compares the intermediate voltage with a reference voltage and thus generates a digital mains failure signal.
A disadvantage in this form of intermediate voltage generation is the large tolerance, required by the summation of tolerances, as explained in more detail in the description, of the input voltage for which the consumer of the intermediate voltage, that is to say the switching voltage transformer, must be designed. The latter must be configured for high voltages and, at the same time, for high currents in conjunction with low input voltages, in order to be able to provide the desired power at the output.
German reference DE 33 22 943 C2 demonstrates a power supply system in which an intermediate voltage is used. The rectified mains AC voltage serves as principal voltage source. The auxiliary voltage source is provided by a battery whose output voltage is transformed to the intermediate voltage by a DC-DC converter. A controller monitors the mains voltage and upon undershooting of a reference voltage switches on the DC-DC converter and thus connects the auxiliary voltage source to the intermediate voltage.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a buffered intermediate voltage whose voltage range is not essentially wider than that of the voltage obtained from the mains voltage.
The invention achieves this object by providing that a controlable transformer is used for the auxiliary voltage source and that the control is performed independently of the value of the intermediate voltage.
In particular, the previously existing digital mains failure signal obtained from the intermediate voltage is used in order to switch on the auxiliary voltage. In this case, the auxiliary voltage is initially higher than the reference voltage which leads to the mains failure signal. The result of this is that the mains failure signal oscillates owing to feedback, that is to say there is a rapid succession of switching on and off which initially appears disadvantageous. However, this arrangement achieves the object simply by means of an interposed time-delay element. By means of a further integration element or time-delay element, it is then possible to generate the mains failure signal fed to the consumers, if the oscillating signal is missing for more than one cycle.
In another embodiment, use is made of the fact that the auxiliary voltage source is a DC-DC converter whose output voltage can be controlled by the mains failure controller. Here, as well, it is accepted that the original mains failure signal oscillates and that it is only through a timer that the mains failure signal to be relayed has to be formed. The analog controller switches on the auxiliary voltage at the start of the mains failure signal with a voltage situated above the reference voltage, as a result of which the mains failure signal is virtually immediately deactivated again. However, the controller keeps the auxiliary voltage switched on and rather makes use of the deactivated mains failure signal for the p
REFERENCES:
patent: 3599071 (1971-08-01), Lapuyade et al.
patent: 4866295 (1989-09-01), Leventis et al.
patent: 4890003 (1989-12-01), Seibert et al.
patent: 5461263 (1995-10-01), Helfrich
Pollmeier Werner
Schuck Josef
Weidner Ernst
Paladini Albert W.
Shoop Jr. William M.
Siemens Nixdorf Informationssysteme AG
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